World Cement October 2023

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CONTENTS

manufacturers’ association) provides an update on the state of the Turkish cement sector. Additional cement plant updates added by World Cement staff.

COVER STORY

16 Cleaning Gear Drives On The Fly Rodion Rodionov, Klüber Lubrication, gives operators advice on how to clean open gear drives during operation.

GEARS, DRIVES & MOTORS

21 Protecting Production In Prachovice

T. Rothardt and C. Rüttling, SEW-Eurodrive, discuss the replacement of the girth gears in two ball mills at a Czech cement plant.

26 Problem-Free Prediction

Schaeffler Lifetime Solutions provides insight into the modern options a cement plant has to simplify maintenance by making it predictable and plannable.

SEPARATORS & CLASSIFIERS

32 Separating Success

Olaf Michelswirth, Intercem, explains how upgrading to high efficiency separators can improve grinding performance and product quality.

REFRACTORIES

37 Banishing Buildup

Pankaj Gupta, HASLE Refractories, discusses buildup and coating formation in feed pipes, and showcases how these issues can be addressed with refractory linings having a smooth surface.

43 Progress With Prefired, Precast Bricks

Rudraksh Kulkarni and Divyendu Tripathy, Calderys, consider how precast, prefired castables offer cement plants bespoke solutions for all their refractory needs.

ON THE COVER

AIR POLLUTION CONTROL

53 Formidable Fibres

Nathan Schindler, Evonik Corporation, describes how implementing a high-performance fibre material can help cement plants avoid air pollution and meet EPA standards.

60 SCR Solutions For The Cement Industry

Jeff Shelton, BD Heat and Dracyon, demonstrates why preventing buildup is vital for allowing SCR systems to tackle the cement industry’s NOx emissions.

69 Technology To Trust For Process Gas Analysis

Felix Bartknecht and Sriparthan Sriraman, SICK, illustrate the cutting-edge process gas analysis (PGA) systems that were used to help a French cement producer optimise their combustion efficiency while keeping emissions low.

74 A Breath of Fresh Air

Zhu Linhe & Zhang Wei, Sinoma Overseas Development Co., Ltd, and Wang Lan, China Building Materials Academy, discuss the construction and operation of a medium temperature SCR DeNOx project at the LafargeHolcim Dujiangyan cement plant.

81 Embracing ESP Technology

Steven A. Jaasund, LDX Solutions, Inc., outlines the process of upstream gas conditioning for carbon capture scrubbers with wet electrostatic precipitation technology.

MATERIALS HANDLING

85 Moving On Up!

Gambarotta Gschwendt outlines the key considerations when designing central chain bucket elevators to offer a low-cost and long-life solution for bulk materials transportation.

Klüber Lubrication’s lubricants for the cement industry bring you peace of mind with their high performance in extreme environments and superior protection against wear or machine failure. Klüber Lubrication is a one-stop supplier for all applications where lubricants can optimise reliability and profits.

Find out more about Klüber Lubrication’s OEM-approved lubricant portfolio and unique service offering in this month’s cover story on pg. 16.

WE MOVE INDUSTRIES

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Our components for the cement industry: central chains, link chains, reclaimer chains, sprockets, bucket elevators and clinker conveyors.

MORE THAN

COMMENT

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Fatih Birol, the Executive Director of the International Energy Agency (IEA) and one of the world’s foremost energy economists made headlines recently when he said that the prospects of reaching net zero by 2050 had improved after the “staggering” growth of renewable energy and other green investments around the world.

He was quoted as saying: “Despite the scale of the challenges, I feel more optimistic than I felt two years ago […] Solar photovoltaic installations and electric vehicle sales are perfectly in line with what we said they should be, to be on track to reach net zero by 2050, and thus stay within 1.5˚C. Clean energy investments in the last two years have seen a staggering 40% increase.”

That was certainly refreshing to read; positive news that shows real progress is being made. All too often, the commentary surrounding the world’s race to net zero can come across as cataclysmic fear-mongering, more likely turn people away than it is to inspire them. That’s not to say that we should be complacent – far from it – as Birol points out, climate-altering emissions from many sources remain “stubbornly high” and increasing numbers of extreme weather events show how the climate is changing “at frightening speed.” I suppose the point is that whilst we need to acknowledge that the challenge is great, and that the consequences of failure are grave, it is also a challenge that the world can overcome, and that things are heading in the right direction.

Case in point: progress is even being made towards one of the biggest technology challenges involved in the decarbonisation of cement production – CCUS. According to the GCCA’s 2050 Net Zero Road Map, CCUS technologies will ultimately have to account for 36% of all CO2 emissions from cement production. In order to meet this challenge, CCUS pilot projects are springing up at cement plants around the world, exploring different methodologies and techniques for not just capturing the CO2, but also for the equally complicated tasks of storage and utilisation. To give just a couple of examples (from dozens), they range from: Rohrdorfer & ANDRITZ’s recently completed pilot project which captures 1500 tpd of CO2 and converts it into formic acid for the chemicals industry; to Heidelberg Materials’ Edmonton plant, which is being prepared to capture as much as 1 million tpy of CO2, before transporting it by pipeline for underground storage. And that’s not all. In addition to CCUS, many other technologies and processes (renewable energy, alternative fuels, process optimisation, SCMs, etc.) are being developed, refined and rolled out in the cement industry’s journey to net zero.

Come join us in Lisbon on March 10 – 13, 2024 for World Cement’s first in-person conference and exhibition: EnviroTech. Featuring a 2.5 day technical presentation agenda on the decarbonisation of cement, multiple networking events, and a full exhibition, EnviroTech will allow you to network and share actionable business insights with cement industry peers from around the world.

Register today and secure your place at the gateway to green cement: www.worldcement.com/envirotech2024

I look forward to seeing you in Lisbon.

Deccan Cements Ltd awards KHD with clinker grinding line upgrade

Indian cement producer, Deccan Cements Ltd, has awarded KHD a contract to increase capacity at an existing clinker grinding plant. The upgrade will also allow the company to produce both ordinary Portland and pozzolana Portland cements (OPC and PPC) on the same mill.

The plant currently comprises a single ball mill producing 155 tph of OPC at 2900 Blaine. Following the upgrade, capacity will increase to 310 tph of OPC at 3200 Blaine and 370 tph of PPC at 3600 Blaine. Scope of supply includes a roller press, static V-separator, and SKS VC dynamic separator, as well as other associated auxiliary equipment. We are also providing design, engineering, and supply of electrical & instrumentation (automation) equipment.

“We are pleased to announce this contract with Deccan Cements Ltd, a major cement producer in South India. It represents another vote of confidence in our technology and expertise within the strong Indian Cement Industry. We are now looking forward to working with the group to successfully realise this project,” said Ashok Kumar Dembla, Managing Director of Humboldt Wedag India.

ACC begins production of clinker at Ametha plant in Madhya Pradesh

ACC Limited, the cement and building material company of the diversified Adani Group, proudly announces the momentous commencement of commercial production of clinker at its new cutting-edge Ametha cement plant, nestled in the heart of Katni district of Madhya Pradesh. This historic event marks a significant stride in Adani Group’s unwavering commitment to growth.

The Ametha integrated cement plant has a clinker capacity of 3.3 million tpy and a cement capacity of 1 million tpy. This greenfield integrated project will help in lowest cost production of clinker and cement, which will increase ACC’s overall portfolio to 37 million tpy and aid in the overall improvement in profitability and market share of the company.

The Ametha plant’s strategic location in Madhya Pradesh offers a logistical advantage, which will enhance ACC’s ability to cater to critical markets efficiently. This ESG compliant plant will exemplify ACC’s commitment to environmental responsibility with 16.3 MW of WHRS capacity and up to 15% of AFR potential, exemplifying ACC’s dedication to environmental stewardship.

Mr. Ajay Kapur, CEO, Cement Business, said, “This is a monumental achievement in our relentless pursuit of sustainable growth. This milestone harmoniously aligns with our growth strategy for the cement business, enabling us to meet evolving market demands while upholding our unwavering standards of quality.”

ACC extends its gratitude to the local community, suppliers, and regulatory authorities for their support throughout the project’s development. The company remains dedicated to delivering value to its customers and shareholders while contributing to the nation’s infrastructure development.

Cemex works with UN to progress Sustainable Development Goals

Cemex has reaffirmed its commitment to the UN’s Sustainable Development Goals (SDGs) through a series of collaborative efforts that seek to accelerate progress and inspire others in the private sector.

These efforts include Cemex’s participation in the UN’s Forward Faster initiative as an early mover in the building materials sector and co-leading the UN Global Compact’s Sustainable Supplier Impact Program.

Cemex is among the first companies to join Forward Faster, an initiative that aims to bring businesses together to accelerate their contribution to society in five action areas — gender equality, climate action, living wage, finance & investment, and water resilience. The UN Global Compact focused on these areas where the business sector can uniquely and powerfully drive progress across all 17 SDGs. Participants will each choose public targets in one of the action areas. Cemex was invited to join due to its “leadership on Sustainable Finance, Just Transition, Climate, and

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other issues.” Forward Faster officially launched on 18 September, during the UN General Assembly week.

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“Our company is committed to building a better future, one that is more sustainable, circular, and creates a supportive environment for people to thrive,” said Fernando A. González, CEO of Cemex, who participated in a panel during the UN Private Sector Forum, an event hosted annually by the United Nations Global Compact (UNGC) on behalf of the UN Secretary-General that brings the voice of business to the UN through leading CEOs and investors, heads of states and governments, and civil society representatives. “The SDGs provide a great blueprint to effect this change, but progress is not happening fast enough. The public and private sectors must join to map an equitable transition to the sustainable world of tomorrow.”

Cemex is leading the UNGC Sustainable Supplier Impact Program. The program aims to increase the contribution to sustainable development of small and medium enterprises in Cemex’s supply chain.

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ENVIROTECH

World Cement Conference:

Join cement industry professionals from around the world for World Cement’s first in-person conference and exhibition!

10 – 13 March, 2024

Lisbon, Portugal

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From April to August of this year, over 100 of Cemex’s suppliers came together to learn about the UNGC’s ten principles, identify gaps, and build action plans to close them.

The UN’s SDGs provide “a shared blueprint for peace and prosperity for people and the planet, now and into the future.” Cemex is focused on four priority SDGs: (9) Industry, Innovation, and Infrastructure, (11) Sustainable Cities and Communities, (12) Responsible Consumption and Production, and (13) Climate Action.

Capsol Technologies awarded two new paid CCUS feasibility studies in the EU

Capsol Technologies has been awarded feasibility studies for the CapsolEoP ® (end-of-pipe) carbon capture technology at two large cement plants in the EU with the potential to capture more than 1.5 million t of CO 2 per annum combined. The studies will start in Q3 2023.

“We are receiving firm response from the industry – a strong indication that our CapsolEoP provides highly competitive value propositions for cement.

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CapsolEoP reduces energy consumption by more than 50% compared to competing technologies, resulting in 25% lower costs per ton of CO 2 captured. In addition, the CapsolEoP is safe and not harmful to the local environment,” says Jan Kielland, CEO of Capsol Technologies.

The company owning the two cement plants has operations in more than 10 countries, with total emissions of more than 20 million t of CO 2 in 2022.

These awards are Capsol Technologies’ third and fourth engineering studies for the cement industry. In total, Capsol currently has nine cement projects in sales engineering and

GREEN SIZING SOLUTIONS

Lower costs and increase energy efficiency with MMD Sizer solutions

Since the inception of our patented MMD Sizer over 40 years ago, we have been committed to providing machinery that leads the way on productivity, reliability, safety and efficiency.

The MMD Twin Shaft MINERAL SIZER™ has the ability to process a wide range of materials, from hard shale to soft chalks, either separately or combined. Together with the unique agitating action of the counter-rotating shafts, this makes the MMD Sizer ideal for blending and perfectly suited to the demands of the quarrying and cement industry.

Working closely with customers, our teams of technical specialists have engineered many sizing solutions to deliver new heights of performance, efficiency and safety

engineering studies totalling a potential of about 10 million t of CO 2 to be captured annually.

“We are pleased that our solution is gaining attention as demonstrated by an increasing number of incoming requests for sales engineering and engineering studies and look forward to being a major contributor in the path to net zero for cement,” says Jan Kielland, CEO of Capsol Technologies.

Cement, which is one of Capsol Technologies’ four target segments, is estimated by IEA to account for more than 300 million t of captured CO 2 in 2030, representing 30% of total installed carbon capture capacity. Hence, it represents the largest industry opportunity for carbon capture.

Cemcor signs three-year deal with EAM specialist

Cemcor, one of Northern Ireland’s leading cement production companies, has signed a new three-year deal with class-leading Enterprise Asset Management specialist, Peacock Engineering Ltd.

The move comes as the company looks to further invest in improving processes, sustainability and reducing the carbon footprint of its Cookstown plant.

The partnership with Peacock Engineering has seen Cemcor rapidly migrate its existing SAP system into IBM Maximo Application Suite (MAS). MAS, one of IBM’s sustainability software solutions, offers a single platform for intelligent asset management, monitoring, maintenance, computer vision, safety and reliability, enabling the company to have a 360°, real time view of its asset base, across multiple sites simultaneously, if needed.

Cemcor operates a range of facilities and sites across the region, including the cement plant, which has a production capacity in excess of 450 000 t, and a limestone quarry in Cookstown, a shale quarry in Dungannon and an import and export facility in Belfast Harbour.

The investment in its new Maximo EAM system comes following the announcement

last year of LLC Group, one of Northern Ireland’s largest companies, investing £15 million in the firm.

MAS will enable Cemcor to gain better insight into the assets at the Cookstown plant, supporting in the maintenance programmes and management of its diverse asset base, which includes a wide range of complex machinery and heavy equipment such as dumper trucks, stone crushers, conveyors, stone mills, granulators, and drying kilns.

The new system will help to ensure the company is well placed to resolve its maintenance challenges and optimise its assets, helping to increase the lifespan of essential equipment and improve inefficiencies, including in the procurement and usage of replacement parts.

The new EAM system will also help in reducing downtime and the associated costs, increase profitability, while also enabling it to understand and streamline processes at the plant.

Matt Deadman, Chief Operations Officer of Peacock Engineering, said: “We’re thrilled to be working with Cemcor over the course of the next three years.

We have already completed the first stage of our change programme with the successful delivery of its new EAM system. MAS is one of IBM’s sustainability software solutions, it will provide Cemcor with a clearer view of its assets, which include heavy plant and processing equipment, and help in mitigating the current challenges found in its maintenance programme.”

The project was completed in just a few months by Peacock Engineering, and is one of the first, and quickest, major implementations of IBM Maximo Application Suite (MAS) in the UK.

Matt added: “It’s been a pleasure working with Cemcor. As a specialist in both the technical aspects of engineering and in IT, we have managed the delivery in just two months. We are looking forward to working with Cemcor over the next few years to ensure its EAM solution continues to deliver the service level and efficiencies needed to meet its organisational objectives.”

TÜRKÇİMENTO (the Turkish cement manufacturers’ association) provides an update on the state of the Turkish cement sector. Additional cement plant updates added by World Cement staff.

Meeting the needs of the world

The Turkish cement sector, which includes 77 cement plants (56 integrated and 21 grinding facilities) spread across the country, provides direct employment for 17 500 people. With an annual production capacity of 119 million t, the sector ranks as the world’s fifth-largest and Europe’s leading producer. Simultaneously, it stands as the second-largest exporter globally, servicing over 100 markets in its field.

A year in review

The sector faced challenges in 2022 due to the adverse effects of the pandemic and the Ukraine-Russia conflict. With the contraction in the construction industry, both domestic and international sales experienced a decline in tonnage in 2022.

The sector continues to produce below its installed capacity. Approximately 25.1% of the cement produced in 2022 was exported.

Overall exports decreased by 12%, totalling 27.2 million t. This export comprised 18.7 million t of cement and 8.5 million t of clinker.

After experiencing a 7% contraction in 2022, the sector entered 2023 with an increase in domestic sales and a decrease in exports due to the base effect of January 2022.

2023 onwards

In the January – June period of 2023, TÜRKÇ İ MENTO members’ cement production increased by 7.7% compared to the same period of the previous year, reaching 36.7 million t. Domestic sales also increased by 14.4%, totalling 28 million t. With reconstruction after earthquakes and the transformation of risky housing, an increase in domestic sales is expected in the upcoming period.

Looking at sector exports, the declining trend continued in 2023. In the January – July period of 2023, there was a 32% reduction in tonnage compared to the same period, resulting in the export of 10 million t of cement and 2 million t of clinker, with a total of 12 million t.

With the European Union’s Carbon Border Adjustment Mechanism (CBAM) regulation scheduled for implementation in 2026, a decrease in exports to Europe is anticipated. However, as carbon emissions decrease due to investments in the sector, it is expected that exports to Europe will return to previous levels.

Leading in environmental investments

The Turkish cement sector has become a pioneer in the transformation and adoption of new technologies for low-carbon production in the fight against climate change.

According to Turkey’s National Determined Contributions, carbon emissions are set to be reduced by 41% by 2030. Emissions will peak by 2038 and reach net zero by 2053. The cement sector will play a significant role in achieving Turkey’s 2053 zero-emission target.

TÜRKÇİMENTO closely follows projects by public institutions aimed at reducing carbon emissions and contributes to projects promoting low-carbon production.

TÜRKÇİMENTO believes in the collaboration between public and civil society organisations to implement these priority initiatives for carbon emissions reduction and sector-wide compliance.

Starting from the end of 2022, 16 cement plants in the Turkish cement sector produce their own energy through waste heat recovery, totalling 141.5 MW in installed capacity. This capacity is equivalent to the daily electricity consumption of around 566 000 households.

Moreover, transitioning to low-carbon cement production will not only contribute to environmental preservation but also benefit the

Turkish economy by combatting high energy costs and reducing carbon emissions. This transition will be achieved through the promotion of alternative fuel use and the production of blended cement using alternative raw materials. As a result, the cement sector will play a fundamental role in the carbon-free future envisioned for 2053.

About TÜRKÇİMENTO

Representing 94% of the sector, TÜRKÇ İ MENTO was established in 1957 as a non-governmental organisation. TÜRKÇ İ MENTO successfully undertakes various responsibilities, such as research and development services, education, international collaboration, certification, sectoral data collection, university partnerships, cooperation with civil society organisations, and other related institutions.

Plant news

The following section provides a few brief highlights of recent plant projects and updates from the Turkish cement sector.

KÇS Kipas Çimento

KÇS Kipas Çimento’s Kahramanmaras plant ordered a Pyrorotor alternative fuel combustion reactor from KHD to be installed on production line 1. The reactor should enable the plant to continuously achieve a thermal substitution rate above 90% in the calciner. Simultaneously the system will also help to maintain NOx emissions levels to below 800 mg NO 2/Nm 3

Medcem Cimento

Medcem Cimento’s Madencilik plant was supplied with a waste heat recovery unit by Turboden earlier this year. The unit features a 10 MWe organic Rankine cycle system which will facilitate the recovery of heat exhausted from the clinker cooler of the 10 000 tpd kiln. This system is stated to be the largest ORC unit ever installed in a cement plant. The plant had previously installed an SRC system on its second production line and made the decision to go for an ORC system due to its relative strengths compared to SRC technology.

Kentçim Çimento BEUMER was contracted by Kentçim Çimento to design and supply one heavy-duty belt bucket elevator, seven high-capacity belt bucket elevators, one central chain bucket elevator, four apron conveyors, and 13 silo-discharge gates for the new 4250 tph clinker production line. The new design of the bucket elevator system led to an overall steel weight saving of up to 25% and should provide energy savings for the plant.

ENVIROTECH

World Cement

World Cement is pleased to announce its first in-person conference and exhibition!

EnviroTech will bring together industry leaders, technical experts, analysts,

EnviroTech will bring together industry leaders, technical experts, analysts, and other stakeholders to discuss the latest technologies, processes and policies being deployed at the forefront of the cement industry’s efforts to reach net zero.

BY www.worldcement.com/envirotech2024

For more details and registration:

For more details and registration:

Hotel Cascais Miragem Health & Spa, Lisbon, Portugal

TECHNICAL EXHIBITION

EnviroTech will feature a full exhibition with representatives from leading companies in the cement industry. Taking place just a few meters from the conference hall, this impressive area, with views overlooking the Atlantic, will allow exhibitors to showcase their businesses and network with both new and familiar faces from across the cement sector.

To secure your place, register today at: www.worldcement.com/EnviroTech2024

For sponsorship opportunities please contact:

Rod Hardy Sales Director

Ian Lewis Sales Manager

Executive

Cleaning gear drives on the fly

Rodion Rodionov, Klüber Lubrication, gives operators advice on how to clean open gear drives during operation.

When continuous operation is key, cleaning and maintaining open gear drives becomes a critical part of any operation. In the case of cement or mining plants, the reliability of open gear drives plays a crucial role in enabling the efficient operation of ball mills and rotary kilns. To ensure continuous production, effective lubrication and gear maintenance are vital. Klüber Lubrication has introduced a holistic five-step lubrication concept, offering a comprehensive solution for gear protection and cleaning, increasing the components’ lifetimes, and reducing wear – while also reducing downtime required for maintenance.

Operators of ball mills and rotary kilns in cement factories need to balance several factors in the maintenance of their machines: How much time can operators spend on cleaning, repairs, and mandatory check-ups for insurance companies before the ensuing downtime becomes too costly?

Klüber Lubrication has developed innovative lubricants that are changing this calculation, making machines more productive without sacrificing reliability.

Klübersustain EZ 2-46 is a potent cleaning lubricant. It helps to reduce the time required for open gear cleaning whenever a producer is forced to do it and make this procedure safer. For example, it prepares open gears for nondestructive testing (NDT) without dangerous and time-consuming manual cleaning procedures.

It not only has excellent cleaning properties, but it also works under full load while the machine is in operation, meaning that machines do not have to be stopped during cleaning procedures. The procedure is safe and unnecessary production losses due to mill or kiln downtime can be avoided. This cleaning solution reduces open gear cleaning time drastically from as much as 80 hrs (in case of manual cleaning) to 4 hrs or in some cases even to zero. This is made possible by the high load-carrying

capacity and protection against wear offered by Klübersustain EZ 2-46.

Furthermore, the lubricant is eco-friendly and manufactured with more than 70% renewable raw materials, making cleaning safer for users and the environment alike. As it is a biodegradable product, users will also have fewer worries associated with its disposal.

How the comprehensive lubrication concept works

The Klüber A-B-C-D-E approach contains five steps with different lubricants that fulfil important roles in the operation of a ball mill or rotating kiln driven by open gears. To deal with individual factors like the type of machine, stress, specific uses, and others, a variety of products made by Klüber are available for open gear operation or the cleaning needed for maintenance.

This starts – even before the gears have completed their first turn – with type A lubricants, which protect gears during equipment assembly and provide initial lubrication during start up, preventing damage to the tooth flanks. They also aid in assessing the load-carrying area and serve as a contrast lubricant for evaluating the dynamic contact pattern.

The type B lubricant, e.g. Klüberfluid B-F 2 Ultra, quickly optimises the load-carrying area and surface roughness of new gears, and can also relieve scuffing damage resulting from inadequate lubricant supply during operation. It ensures efficient operation during the running-in process, aiming for a load-carrying area

of at least 80% of the tooth surface. Added special solids have a smoothing effect on the tooth flanks by targeted physical-mechanical material removal. The same principle can be used for gear drives that have been in operation for some time, correcting the roughness of the surfaces to enhance the contact area and to reduce friction in the long term.

A number of different lubricants can be used for stage C, which is actual equipment operation. The type C lubricant is the recommended operating lubricant after the running-in process, and its selection is based on factors such as operating temperature, ambient temperature, and application method. Today, high-viscosity transparent fluids are also used as operating lubricants. Klüber offers several types of synthetic lubricants that can be used for this task, taking advantage of the strengths of this new generation of synthetic fluids. They show good adhesion and the lubricant film has an enormous load-carrying capacity. These characteristics assure the lubricant offers high wear protection and can be used in high-temperature environments.

The type D reconditioning lubricant offers an alternative to mechanical treatments like grinding and milling for damaged tooth flank surfaces if the damage is not too severe. The advantage of this way of reconditioning gears is that it can be carried out during operation and can therefore extend the gear life without causing production losses due to lengthy downtimes for manual treatment.

Open gear cleaning without losing production

The last step in this approach is where innovation meets the needs of operators. Type E, Klübersustain EZ 2-46, is a specially designed lubricating oil for cleaning large open gears found in the mining and cement industries. It has an excellent cleaning effect when applied to highly adhesive open gear lubricants such as asphaltic greases, black graphitecontaining greases, or high-viscosity transparent fluids. It will clean the operating lubricant off the teeth and provide visibility for convenient inspection of the gear wheels without stopping production for an extended period of time due to manual cleaning actions – in order to properly assess possible damage, many operators clean their gears manually, resulting in long downtime periods. It is also hazardous work that can lead to injuries.

This is why cleaning with the help of a special lubricant without production stoppages is well suited for any situation where operators need to have open gears cleaned, including to aid nondestructive testing for the detection of cracks that may have formed.

Klüber Lubrication´s A-B-C-D-E approach at a glance.

FZG results according to DIN 51354-1 (A/8.3/90).

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Gear protection and downtime reduction also under high loads

With Klübersustain EZ 2-46, customers can clean their gears while the machine is in the last hour of operation. After shutdown, the open gear is clean and can be quickly and easily wiped down with a rag to remove any residual lubricant. Now, the nondestructive testing can proceed, taking a shorter period of time overall. This means the ball mill or kiln is back in operation sooner. The timesaving can be significant.

It differs from other products on the market as it protects gears while cleaning them, even under high working loads. Therefore, the load does not need to be reduced during operation, increasing overall productivity of the machine even further.

The lubricant offers versatile applications in addition to gear cleaning for NDT purposes. It can be used to address gear contamination issues, for example immediate emergency cleaning action when the open gear is severely contaminated by dust because of liner bolt failures and inadequate gear guard sealing. Clogging of the lubricant drainage system can also be mitigated. It ensures clean and well-maintained gears, promoting optimal gear performance. This synthetic lubricant is also able to clean the gears to prepare the machine for manual repairs, where spotless tooth flanks are required for proper servicing.

It is also ideal for transitioning from black lubricants to transparent lubricants. Due to its cleaning effect, Klübersustain EZ 2-46 makes the gear surfaces visible and helps operators to benefit from using transparent high-viscosity operational lubricants by providing a clean and visible environment where they are able to quickly evaluate the condition of gears while the mill is running without stoppage. This avoids the need to wait for half a year while transparent operating lubricants replace the black ones over time.

Use the best equipment for the job

To get the best cleaning results, the lubricant needs to be applied while the open gear is in motion. The movement plays a big part in the desired cleaning effect and the product is designed to deal with working loads. It contains a special extreme-pressure

additive and a low-viscosity base oil that provide great solvency to remove hydrocarbons and asphaltic compounds.

The spray system plays an important role in how effectively Klübersustain EZ 2-46 works. High pressure and minimum flow rate yield the best results. This allows operators to use the lubricant economically without jeopardising the cleaning effect. High pressure helps to push dirt and old lubricant out of the gear mesh. The recommended volume of one to four litres per minute depends on the number of pinions and will provide a sufficient protection film to avoid premature wear on the gears. For really large open gear systems it is possible to go as far as five to six litres per minute to properly clean the machine.

Following the recommended cleaning procedure is essential when using Klübersustain EZ 2-46. In cooperation with Graco, Klüber Lubrication offers the right tool for the job: a FireBall portable spraying system that can be adjusted to spray the right amount of lubricant.

A variable nozzle allows the initial wetting of the gear with a large cone or flat pattern to prepare the gear for further cleaning. The system is complemented by an additional, more precise and focused jet, which enables thorough cleaning. Spraying approximately 80% on the girth gear and 20% on the pinions helps distribute the product evenly and effectively.

Summary

Klübersustain EZ 2-46 is an effective lubricating oil that offers a range of benefits for open gear cleaning in the cement and mining industries. Due to its wear protection properties it enables gear cleaning during operation, thus saving time and minimising manual labour.

The cost savings are significant, because operators can reduce equipment downtime for cleaning tremendously. The product’s eco-friendly formulation, with over 70% renewable raw materials, reduces environmental impact.

Furthermore, the effective cleaning without gear stoppage enables prompt servicing of the gears, leading to the longevity and optimal performance of gears, prolonging the life of machines. Optimised maintenance also helps companies to reduce their footprint on the environment because materials and resources that went into these machines are used more efficiently.

When applied in accordance with recommended procedures, this lubricant provides efficient gear cleaning and contributes to the overall efficiency and cost-effectiveness of cement plant operations.

About the author

Rodion Rodionov is Market Development Manager and specialist for Heavy Industry at Klüber Lubrication.

Cleaning result. 200 l of Klübersustain EZ 2-46 for 4 hrs.

Protecting production in Prachovice

T. Rothardt and C. Rüttling, SEW-Eurodrive, discuss the replacement of the girth gears in two ball mills at a Czech cement plant.

Cemex operates the second largest cement plant in the Czech Republic in Prachovice, about 100 km east of Prague.

Up to 5000 tpd of clinker is ground into ready-to-use Portland cement there using two identical ball mills 15 m in length. Each of these ball mills is moved by a girth gear. On each mill, two 2250 kW asynchronous motors transfer power via gear units to two pinions with separate bearings. The pinions engage with the girth gear and apply torque to it. A mounting flange and bolted fixings form the connection between the girth gear and the circumferential surface of the ball mill.

A diagnostic check of the mill drives in spring 2017 revealed that both girth gears and all four pinions were already showing significant signs of wear. Continuing to run a system with weakened gearing

that exhibits an advancing damage pattern can lead to a failure of the drive and thus the entire system. This quickly results in long downtimes, which in turn leads to bottlenecks in delivery and costly production losses.

To ensure the future availability of the cement mills, Cemex opted to replace both girth gears, all four driving pinions, and both girth gear covers. Due to their low level of wear, the gear units were classified as not critical and therefore not replaced.

From the very start of the project, SEW-Eurodrive assisted the cement manufacturers with any unresolved issues. Questions of material selection, design/dimensioning, project planning, lubrication, all the way through to construction and commissioning were discussed as a team. The company has many years of experience using girth gears in a wide

variety of industries. Moreover, the SEW-Eurodrive portfolio covers the entire spectrum of drive technology – from the motor and gear units to drive electronics and controllers. The comprehensive support provided throughout the entire design phase ultimately prompted the Cemex-maintenance management team to continue working with SEW-Eurodrive in the later stages of the project.

Cutting-edge material technology

When manufacturing girth gears, SEW exclusively uses high-strength austempered ductile iron (ADI). The properties of this material are superior to those of traditional girth gear materials, such as cast steel. For instance, the ADI used by SEW has a minimum tensile strength of 1000 MPa and a minimum elongation of 5%. Heat treatment is required to achieve the necessary mechanical properties. This treatment encourages the desired microstructure to form and ensures the material exhibits high permissible strength values. The material’s contact fatigue strength, which comes as a result of its excellent cold work hardening properties, makes the girth gears very durable and practically wear-free, if dimensioned, loaded, and lubricated correctly. Moreover, the girth gear can be designed to be significantly more compact and lighter when using ADI instead of the traditional solution.

Segmented design

Another feature of the SEW girth gear is its segmented design. Traditional girth gears generally consist of two to four segments that are machined when assembled. In this solution, the girth gear is designed in several segments. Depending on the total diameter of the girth gear, each of the segments has a very compact design, ranging from 1 – 2 m. The high initial pitch accuracy of this segmented design (ISO 8 and AGMA 9) results in optimum operating performance. Each segment of the girth gear is individually cast, machined, subjected to heat treatment and finished. This ensures that the quality of the girth gear is always identical, regardless of the diameter – be it 4 m or 16 m.

This segmented design also offers additional benefits with regard to handling and replaceability. The individual segments and component groups are much easier to handle onsite. For instance, installers can either preassemble two girth gear halves from the segments and then install the two halves in the application using conventional methods, or install each segment separately on the drum. The option of installing the individual segments separately is particularly beneficial when space is restricted. Moreover, special transportation arrangements are no longer required. Segmented girth gears can be transported in standard containers. And if, at any point, the gearing of the girth gear is damaged, individual segments can be replaced without having to dismantle the entire ring.

Figure 1. Principle of a ball mill drive.

Figure 2. Driving pinion and girth gear (Photo: Cemex).

Figure 3. Because the segments can be preassembled in two halves, handling onsite is considerably simplified (Photo: Cemex).

Shared success onsite

Work on the first ball mill began in spring 2018. This was preceded by detailed project planning and the selection of drive components, which involved not only the headquarters in Bruchsal

but also SEW’s Czech subsidiary and the girth gear delivery plant in Tianjin, China. SEW’s network of experts was able to draw on its experience with projects completed worldwide. To determine the dimensions of the gearing geometry, a finite element simulation was also carried out in addition to the tooth root and tooth flank calculations to ISO 6336. The local Czech service provider MZP – Montáže Přerov a. s. from Přerov was tasked with the installation work. The installation was supervised and test runs conducted in collaboration with the experts from SEW-Eurodrive.

Both mills are currently running without any problems and are safeguarding production at the Cemex plant in Prachovice for the future.

New technology produces measurable improvements

At around 687 to 785 MPa, the tensile strength of the cast steel previously used for the girth gears and pinions is significantly lower than that of ADI. The improved material properties become apparent, for example, when comparing the old and new girth gear.

The width of the girth gear was reduced from 900 to 300 mm. In addition, the number of teeth was lowered from 238 to 180, and the module was increased to 40. All in all, this meant that much less material had to be used, which drives down both investment costs and maintenance and lubrication costs.

Once the girth gear had been commissioned and radial and axial adjustments had been carried out, a series of tests was performed on the drive train, including vibration measurement. The bearing points exhibited a significant reduction in vibrations throughout the entire system. The high pitch accuracy of the segmented girth gears and the professional alignment work carried out by Montáže Přerov and SEW Eurodrive help ensure that the girth gear and its peripherals are exposed to a lower mechanical load.

The thermal assessment that was also conducted found no excessive heating and confirmed the high accuracy of the overall design and its alignment.

Conclusion

By opting for segmented girth gears from SEW-Eurodrive, Cemex has chosen a technology that is both cost-effective and durable in equal measure.

The technical expertise of Montáže Přerov and SEW’s international network of experts ensured that engineering work was spot on and that onsite installation and commissioning work was carried out to the highest professional standards. That is why Cemex has decided to equip another ball mill with a girth gear from SEW-Eurodrive.

Figure 6. No unacceptable heating was found during the thermal examination of the drive pinion. This confirms the high accuracy of the overall construction and its alignment (Photo: Cemex).

Figure 4. New girth gear made from ADI is only 300 mm wide (Photo: Cemex).

Figure 5. SEW girth gear with protective cover (Photo: Cemex).

Problemfree prediction

Crushing and grinding, blending, drying and heating, cooling and more grinding… The motors, drives, and gearboxes in crushers, kilns, mills, and other machines in cement production are critical equipment that keep cement plants running even in the harshest conditions. They have to withstand heavy loads, some operate within extreme heat, and conditions are always dusty. Maintenance is indispensable for ensuring smooth and efficient production and preventing machine failures which can lead to very costly unplanned shutdowns. When motors fail the stress level rises, especially when the failure comes unexpectedly.

With more than 2000 motors in a cement plant, the number of failures occurring within a year is not to be underestimated. More than 50% of the time bearing failures are the cause – and up to 80% of premature bearing failures are caused by improper lubrication.

The good news is that this means up to 80% of premature bearing failures can be prevented.

With over 2000 motors, the number of lubrication points in a cement plant quickly exceeds 5000. With this high number of lubrication points, traditional lubrication approaches can present a significant challenge and that figure of up to 80% of premature bearing failures being due to lubrication issues is no longer very surprising.

Schaeffler Lifetime Solutions provides insight into the modern options a cement plant has to simplify maintenance by making it predictable and plannable.

Selecting the right lubricant

It all starts with selecting the right lubricant. Correct lubricant selection not only has a crucial impact on the life of the bearing and its energy consumption, but also on the correct functioning of the machine or system into which it is integrated. The most important task of a lubricant is to reduce friction and wear in the bearing through the formation of a lubricant film that separates the surfaces – ideally with no metal-to-metal contact occurring between the rolling element and

raceway surfaces. This effect is comparable with the dreaded ‘hydroplaning’ that can occur when a film of water causes a car’s tyres to lose their grip on the road above a certain speed. Although highly undesirable when driving, this effect is an ideal scenario in lubrication, as it reliably minimises friction and prevents wear. The separating lubricating film is ensured by the right lubricant, or respectively, by the right combination of base oil, thickener, and additives. But there are various other requirements a lubricant might have to meet. If elevated temperatures occur in a machine or system, for instance, oil lubrication can act as a coolant. In many cases, this can have a critical impact on how the machine or system functions. Oil lubrication also has the ability to remove contamination from the system by means of filtration. With standard grease lubrication, grease practically being an ‘immobilised oil’, the lubricant cannot provide any cooling function. The grease must be capable of tolerating the resulting temperatures over longer operating periods. Temperature suitability is, therefore, a key selection criterion for greases. Despite not providing any cooling benefits, grease lubrication does have its advantages in that it requires no or very little special design work. Grease acts as an ‘onsite’ oil reservoir and it provides additional protection against the ingress of contaminants from outside.

Choosing the right lubricant is always a compromise for which the expected operating conditions, such as speed or operating and ambient temperature range and load, should be known. The bearing type matters, too. Ball bearings, for example, tend to be less demanding in terms of wear protection than bearings with line contact, such as tapered or spherical rolling bearings, and require different combinations of oil, thickener, and additives. In truth, a ‘one-size-fits-all’ grease does not exist. With all these specifications governing the selection of a lubricant, expert advice should be obtained from the bearing manufacturer to ensure the right lubricant for the application.

Working smarter

Once a suitable lubricant has been identified, the next step is to ensure the right amount of it gets to the right lubrication point at the right time. Automatic lubricators, or better yet smart automatic lubricators, can make this happen. Automatic lubrication delivers a controlled quantity of lubricant to various lubrication points. This happens while the machine is in operation, thus reducing unnecessary downtime. Inspections are needed less frequently than with manual lubrication. The advantage is precise lubrication, which extends service life, avoids the ingress of dirt and also minimises the risk of accidents. A smart lubrication system does all of the

Causes of improper lubrication.

Incorrect lubrication can result in slippage marks, patchy smearing and surface wrinkling (micro pitting) on the rolling elements and their raceways.

Bearing failure due to unsuitable grease.

above but also automatically informs the user via an intuitive app which lubrication points are insufficiently supplied, and which cartridges need to be refilled or replaced. The advantages are location-independent access to the machine condition and the lubricator status in real time. Lubrication problems will no longer go unnoticed, and respective actions can be undertaken in time and thus damage can be minimised or even prevented. Regular inspection efforts can be significantly reduced and the time saved can be directed toward other, more important tasks. Monitoring remotely also means that staff can be kept out of dangerous environments. All anyone needs to do to check the status of the lubrication points, is to check the app.

Going further

But why stop at monitoring lubrication points, when it is possible to comprehensively monitor the overall statuses of the machines and know their condition at any given moment, too?

Vibration condition monitoring has been available for decades. In the majority of cement plants, it is still performed manually in addition to some isolated wired online vibration measurements for the most critical assets. But with over 2000 motors only a small amount of the total assets are actually continuously monitored in this way. As a result, costly unexpected failures still happen regularly. With today’s technologies, however, this no longer needs to be the case and Schaeffler’s experience shows that a clear digital maintenance strategy can reduce the overall maintenance costs considerably. The game changing technologies that make this possible are mainly low power electronics, wireless technologies, platform technologies, and artificial intelligence. Employing these technologies on a large scale in a cement

plant enables maintenance staff to get reliable information on the asset health of machines and take adequate actions before irreversible damage occurs. Maintenance thus becomes plannable and the overall maintenance costs can be reduced significantly.

To make the economic aspect more tangible, consider the following high-level example of costs for a larger scale vibration condition monitoring system: With 1500 sensors a cement plant can monitor the more critical equipment in a continuous way. Assuming here for the purpose of easy calculation a relatively high-cost figure of US$100 per vibration sensor per year (including hardware, AI, and installation), the annual cost would amount to approximately US$150 000. Looking at improved planning and sourcing capabilities alone, experienced maintenance managers will immediately see the payback. The avoidance of downtime and production losses will lead to an even shorter ROI – generally within a few months after installation.

There is another benefit to consider: in today’s economic environment, cement plants all over the world are competing with other industrial sectors for human talents. Companies that employ modern technologies, setting up modern digital workplaces that allow remote machine assessment and decreasing the time spent in front of running machines and thus being able to plan and perform the maintenance repair work efficiently and safely, will be able to attract the right talents on the labour market in the future.

Summary

Wireless condition monitoring around the world

More and more cement plants around the world make a conscious decision to monitor their machines´ conditions with the modern, comprehensive solutions that are available today: Heidelberg Materials (formerly Lehigh Hanson) and Cemex Polska Sp. Z o.o., for instance, use wireless condition monitoring solutions on various critical equipment in their plants and plan to extend the scope further in the future.

It is clear that condition monitoring, smart lubrication, and other technologies that enhance the lifetime of machines and bearings will evolve further over the next years. The pace of innovation is high. Drivers behind this high pace are on the one hand the continuously new technological advances, and on the other hand the high worldwide adoption rates throughout all industrial sectors. As the pace of innovation is that high and the number of solution providers is rapidly increasing, the challenge of production plants is to keep an overview of the available technologies and to decide which might be the best solution for them. A good piece of advice here could be to look at the continuity and the portfolio range of the solution providers rather than at continuous changing specifications. In the end, producing plants need a sustainable solution partner offering a holistic solution portfolio that includes condition monitoring, lubrication devices, and suitable lubricants.

CM sensor on a fan at a Cemex Polska plant.

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Separating success

Olaf Michelswirth, Intercem, explains how upgrading to high efficiency separators can improve grinding performance and product quality.

The improvement of grinding performance and quality is the target when employing separators in the cement mill circuit. Modern ball mills work in a closed circuit and this fact requires the high efficiency separation of fines and finished product in order to achieve satisfactory cement quality.

The main requirements for modern high efficiency separators are homogeneous grain size distribution and high precision in separation. Moreover, the production of different cement types in one grinding circuit has to be possible.

For Intercem, this market request – continuous quality increases for varying cement types – is very obvious and the company is working on a permanent steady increase of separator efficiency.

To meet these requirements, Intercem has developed a range of different classifier types:

� ICV – high efficiency vertical separator. Inflow of the process air including the mill dedusting air during cement separation via a process filter.

� ICS – high efficiency separator with tangentially-fed airflow and upper and lower bearing, accessible from outside for maintenance. For the separation of

mill discharge material and cement separation via high efficiency cyclones or process filters.

� ICD vertical air separator with an installation example. For the use with (and optimisation of) vertical mills.

Functionality

At the top of the separator, there are two inlet feeding points. Here, the material gets into the separator. The mill discharge material will be fed to the top of the rotating cage and the distribution table, which has a special design that allows an optimised distribution of the separator feed to the separation cone.

The material is led into the zone of dispersion which is situated between the rotor and the louvers. This is supported by the rotation of the cage.

A permanent feeding of the air sealing with confined air prevents oversized particles from entering the fine material flow and keeps the area between the sealing rings nearly clean of material.

In order to achieve the maximum lifetime, the sealing rings and the air sealing are made of wear-resistant material. The wear-resistant design of all internal

separator parts assures a long lifetime without the necessity of maintenance. The sealing application is adjustable, thus enabling the sealing gap over long running operating hours.

With the aim of achieving an efficiency improvement, Intercem modified the system. The coarse cement should stay inside the separation zone as long as possible for the best possible deagglomeration of coarse and fine particles. This is achieved by material retaining devices in the separation zone. The impact against the cone of the wear-protected rotor results in the decomposition of agglomerates and the reduction of the size of bigger particles.

Coarse particles (grit) will be partially accelerated by the rotor, held by the guide vanes and discharged through the collector of the lower part of the separator which is protected by a homogeneous wear protection system.

The fineness of the product is adjusted by the speed of the rotor and the air velocity, whereas the air flow will be kept constant on design capacity for a wide range of cement qualities. Only for very fine qualities will the circulation air flow be reduced according to requirements.

It is of great importance that the width of the separation zone is adapted. The design of the rotating cage in-gate vanes and the air guide vanes of the stationed elements have a major influence as well.

A continuous improvement of the separator efficiency ensures the LTA (latest technology available) is used.

Case studies

By means of two examples, the improvement of grinding performance and quality by the exchange of the separators in existing sites can be demonstrated.

Ciments Jbel Oust, Tunisia

The first example comes from Ciments Jbel Oust (CJO) cement grinding plant in Tunisia. The existing 2 nd generation separator (cyclone air separator) was to be exchanged against a modern Intercem Vertical High Efficiency Separator of the 3 rd generation.

The first step was the measurement of the complete plant, which became necessary because no plans or drawings of the existing buildings were available. The measurements were taken via a state-of-the-art 3D scan, which allows engineering based on ‘as it is’ dimensions to achieve a smooth and trouble-free erection.

Intercem received the order to execute the engineering of the separator and the piping

ICV high efficiency vertical separator.

Left: ICS – high efficiency separator with tangentially-fed airflow and upper and lower bearing, accessible from outside for maintenance. Right: ICD vertical air separator with an installation example. For the use with (and optimisation of) vertical mills.

Intercem ICS high efficiency separator with high efficiency cyclones.

arrangement into the existing building. In the Intercem workshop in Oelde, Germany, the separator key components – rotating cage, V-belt drive, bearings, drive shaft – were manufactured. Some sheet metal parts were produced by local manufacturers according to workshop drawings supplied by Intercem. Besides the supply of the ICV Separator, Intercem was also responsible for the delivery of various mechanical and electrical equipment, the dismantling of the old and the erection of the new equipment, the performance tests and the mechanical and electrical commissioning.

The comparison before/after the optimisation shows the impressive results (Table 1).

On a Tromp curve, it is possible to observe

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The replacement of the existing cyclone air separator of the 2nd generation with an ICS high efficiency separator of the 3rd generation was the task of this project.

After Intercem had measured the complete plant with a 3D Scan, the engineering of the new separator and the associated piping arrangement leading into the existing building was begun. In Intercem’s workshop in Oelde, Germany, the key components – such as rotating cage, bearings,

V-belt drive, guide vanes, drive shaft, etc. – were manufactured, whereas sheet metal parts were produced by local manufacturers in Tunisia. The corresponding workshop drawings were supplied by Intercem. All parts were then assembled and fixed onsite.

The execution of both of these projects was realised in compliance with international standards.

Both customers confirmed the efficiency of the new 3rd generation separators.

The Tromp curve for 3.35 cm2/g acc. to Blaine (analysed by VDZ) and the comparison before/after the optimisation show the same results as presented in the first example.

In both examples, the bypass-rate is of 11% @ 4.5 cm2/g and thus the separator exchange led to completely satisfactory results in terms of improvement of grinding performance and quality.

Conclusion

Cutting-edge 3rd generation can classifiers significantly increase performance when compared to 2nd generation classifiers and, moreover, they can reduce the specific energy consumption.

� Ciments Jbel Oust: Production increase of 23% and a specific energy consumption reduction of 23.8%.

� Les Ciments d’Oum El Kelil: Production increase of 41% and a specific energy consumption reduction of 29.2%.

The practical examples of high efficiency separators operating in older cement plants demonstrate a high optimisation potential that can be achieved with relatively little effort.

About the author

Olaf Michelswirth studied mechanical engineering in Paderborn and obtained a degree as a Graduate Engineer. After years of experience in the cement industry, he became General Manager of Intercem Engineering in 2005, applying his expertise in many projects all over the world.

ICS with raw gas duct upstream. Table

Ciments Jbel Oust, Tunisia – before and after results comparison.

Table 2. Les Ciments d’Oum El Kelil (CIOK), Tunisia – before and after results comparison.

Banishing buildup

Pankaj Gupta, HASLE Refractories, discusses buildup and coating formation in feed pipes, and showcases how these issues can be addressed with refractory linings having a smooth surface.

Acontinuous material flow without any obstruction is a primary requirement for dry-process cement manufacturing, but the accumulation of coating and blockages can hamper a plant’s overall productivity – and ultimately its profitability. Coating formation and buildup reduce the effective operational cross-section area, causing bottlenecks in the process that impact the material flow and operational efficiency. If they become severe enough, flow problems can jam the process and bring production to a complete stop. Consequently, cleaning measures – either manual cleaning or the use of flow aids such as high-speed air cannons – are required to limit downtime and improve productivity, adding costs and time to the maintenance plan along

with potentially increasing complexity in the production process. Additionally, refractory walls can be worn or damaged by tools or cleaning techniques, necessitating more frequent repairs or relining.

Feed pipes pose a particular challenge

The feed pipes play a vital role in delivering a controlled and consistent flow of raw meal

mix into the preheater tower and between its cyclones. But they also pose a special challenge by having a narrow cross-sectional area with a relatively low airspeed of the passing raw meal, catering to a higher risk of deposits sticking to the pipe walls, especially in lower cyclone stages with higher temperatures.

The coating formation and buildup in this area seems to depend heavily on the particular chemical composition of the raw meal mix in the clinker manufacturing process. Some plants have negligible coating issues, while others fight a tough battle to minimise and reduce the buildup. For instance, chlorides may be present in the mined chalk or an elevated percentage of MgO in the limestone, which subsequently can react with other components in the process, resulting in a stickier material mix. Furthermore, the burning of alternative fuels – and hence the introduction of additional corrosives like alkalis, sulfates, and chlorides into the preheating process – can in many cases worsen the coating formation on the refractory surfaces.

Counteracting the sticky material

Manually removing the buildup from the feed pipes requires frequent cleaning. In severe cases, cement plants may face the need to shut down operations to clean the coating and buildup, resulting in significant costs in terms of process time, maintenance hours, and wasted energy during the restart.

Feed pipes pose a special challenge when coating formation and buildup is present in the preheater process. This is due to their inherited small cross-sectional area combined with a relatively low airspeed of the passing raw meal mix.

To avoid the need for manual cleaning and to minimise the associated downtime, several measures can be employed in the process to counteract the potentially sticky raw meal mix in the feed pipes. Flow aids, such as air cannons and blasters, can dislodge accumulated material and facilitate a smoother flow of materials through the pipes. While these flow aids can be beneficial, they may also add complexity to the overall system.

The quality of the refractory lining inside the feed pipes is another crucial factor influencing the deposition of raw meal mix. If the surface of the refractory lining is rough and susceptible to chemical reactions with the passing material, it can promote buildup issues. By creating a smoother surface and utilising high-quality refractory materials, the passing material becomes less likely to stick to the feed pipe walls.

Optimising the refractory surface

Focusing on optimising the refractory lining and its surface can be a cost-effective tool to minimise build up, as no extra complexity is added to the production process.

For instance, a 3000 tpd cement plant in Vietnam, operating solely on coal, encountered

An example of severe coating issues in a lower-stage feed pipe section at a cement plant in India, significantly lowering the throughput and posing a high risk of jamming.

severe coating issues in the feed pipe at the lowest stage cyclone. These issues resulted in reduced efficiency and material flow, necessitating frequent cleaning, and posing the risk of blockages. Moreover, the existing local castable used for the lining of the feed pipes had a lifespan of only 18 months.

The cement plant sought a longer-lasting refractory solution that could effectively address the build-up. Following an onsite inspection, an engineer from HASLE Refractories recommended lining the feed pipe with HASLE D59A, a strong and very dense low-cement castable. Through the use of high-quality virgin materials and an optimised grain size distribution, the lining provides a smooth surface with low open porosity.

Consequently, the lining surface becomes significantly less prone to coating formation. Hence, In 2018 the feed pipes for the lowest-stage cyclone were lined with HASLE D59A. A recent inspection in the spring of 2023 confirmed that the lining remains in excellent condition without any coating problems. Over the past five years, the plant has not encountered any coating issues or jamming in the feed pipes, which is a significant improvement compared to the frequent cleaning of buildup required previously.

Meticulous manufacturing for a smooth surface

As an alternative to traditional in-situ castings, the HASLE precast Modular Lining system is available to achieve even smoother surfaces. The lining system is based on standardised precast shapes, including specialised cylindrical versions for feed pipes.

To achieve the highest quality, all precast elements are made exclusively from virgin materials and manufactured under strict controls at HASLE’s facility in Denmark. Here, specialised casting equipment, such as vibration tables and tailor-made moulds, is used. The green precast bodies subsequently undergo a five-day prefiring process, reaching a peak temperature of 500˚C.

This carefully controlled procedure effectively eliminates all free and chemically-bound water, resulting in an impressively low open porosity of just 8 – 10%, a marked improvement compared to the 15 – 20% typically found in in-situ cast linings.

The outcome is an exceptionally smooth surface of the precast elements, boasting heightened resistance to coating. Further, leveraging the refractory material’s exceptional resistance to chemical attacks from alkali, sulfates, and chlorides, the precast solution effectively minimises build up and corrosion issues.

The precast feed pipe lining is based on curved 25 cm x 25 cm elements, designed for easy handling and installation. With the integrated tongue and groove joints on all four sides, the precast elements securely interlock to form a stable cylinder, eliminating the need for additional anchoring. During installation, the joints are filled with a 2 – 3 mm mortar, effectively reducing the infiltration of hot and corrosive gases into the layers and casing behind the hot face lining.

The lining offers enhanced flexibility, allowing customisation to meet different diameters, heat-transfer requirements, and lining designs. While the standard precast elements have

Dismantling feed pipe: heavy coating after one year of operation since last relining.

Installation of HASLE cylindrical Modular Lining precast elements in feed pipe sections at a cement plant in India.

Grind away while saving energy

If you use high-pressure grinding rolls (HPGR) for their high efficiency, rely on Hägglunds to take it even higher. With shaft-mounted motors and a low moment of inertia, Hägglunds hydraulic direct drives limit torque peaks instead of opening the roll gap – so that you grind the first time and waste less energy reprocessing. Count on flexible power and cost-saving reliability, supplied by a team that’s driven to the core.

Hägglunds is a brand of Rexroth. www.hagglunds.com

a thickness of 70 mm, thinner variants down to 50 mm are available, making them ideal for incorporating an insulation layer behind the precast elements, if desired.

Case study: India

The cylindrical HASLE precast Modular Lining solution for feed pipes was introduced in the mid-2000s, and among the early adopters was an Indian cement group covering numerous plants. It is not uncommon to achieve 6 – 7 years of lifetime with hassle-free operation through this solution.

A recent case is from one of their plants in the Northern part of India. The 10 000 tpd plant has one line with two strings and is mainly running on pet coke, with 5 – 10% alternative fuels. Despite using a silicon carbide (SiC) based low-cement castable, the plant faced heavy coating issues in their lower-stage feed pipes and the lifetime of the lining never surpassed 3 – 4 years. The coating formation significantly hampered the flow of material and subsequently triggered unscheduled stops to remove the buildup.

Following an inspection at site, a tailored HASLE precast Modular Lining was implemented in feed pipes for the stage 5 and 6 cyclones, located in the lowest part of the preheater. The first 20 sections were installed in 2015. Quickly seeing that the coating formation almost vanished and that no jamming issues appeared in that part, the plant opted soon after to fully implement the HASLE precast solution for their feed pipes. So from 2016 onwards, 10 – 20 m of the feed pipes for cyclones 5 and 6 have been relined with the HASLE Precast Modular Lining each year in a rotational scheme. The lining in the pipes now consistently achieves at least six years before relining is needed. Moreover, the standardised, modular precast elements facilitate easy repairs, as worn or damaged parts can be replaced with new

precast elements, extending the lining’s life well beyond 6 years.

The implementation of the precast lining has notably minimised buildup in the feed pipe and eliminated the need for unscheduled stoppages to address coating issues. As a result, the Indian cement plant has experienced improved heat and material flow efficiency, significantly boosting overall production performance.

In Northern Europe, a 4300 tpd cement plant –operating on coal and 40% RDF – faced similar challenges of coating and jamming in the feed pipes at the lowest-stage cyclone. After learning about the successful precast installations in India, the maintenance team approached HASLE to explore the viability of this solution for their plant. In January 2023, 10 individual feed pipe sections were lined with the HASLE precast Modular Lining. A follow-up inspection after six months revealed a significant reduction in buildup compared to previous occurrences, with minimal to no coating sticking to the walls of the feed pipe.

Optimising refractory performance can smoothen operations

Cement plants facing severe coating challenges due to sticky raw meal mix or high percentages of alternative fuels can benefit from HASLE’s precast and castable lining solution for their lowest-stage feed pipes. The operational cross-sectional area inside the feed pipes can be maximised, and a smooth surface facilitates a consistent material flow, reducing the need for frequent manual cleaning or high-pressure air cannons. Additionally, tailored precast lining designs can incorporate backup insulation to minimise thermal losses.

With a longer refractory lifespan as well as enhanced operational and thermal efficiency, cement plants can conserve natural resources and reduce maintenance costs, fostering a more sustainable and efficient operation.

Moreover, the location of the feed pipes at elevated heights makes the process of dismantling and repairing the refractory lining a cumbersome and hazardous task. So by extending the lining lifespan and hence avoiding yearly repairs, the plant safety index can be significantly improved.

About the author

Pankaj Gupta is Business Head at HASLE Refractories and services the Indian, Middle Eastern, and African cement markets. He holds a Bachelor’s Degree in Ceramic Technology & a Master’s Degree in Business Management. Having a rich industrial exposure of more than 17 years, he has extensive theoretical and practical experience from onsite installations and an in-depth understanding of refractory challenges and solutions.

A feed pipe section lined with HASLE precast elements at the cement plant in India after 5 years of operation, with no visible coating.

Progress with precast, prefired bricks

Rudraksh Kulkarni and Divyendu Tripathy, Calderys, consider how precast, prefired castables offer cement plants bespoke solutions for all their refractory needs.

Precast, prefired castables are saving customers time while delivering a better performance and meeting more complex requirements. High-temperature environments rely on heat-resistant castables to protect or repair equipment, such as kilns, boilers, incinerators, or furnaces. Usually, these are cast in place – where the materials are mixed, poured, and set at the customer’s

location. While this is an established process, an alternative approach results in both improvements in performance and reduced downtime. Precast, prefired (PCPF) bricks and refractories are becoming an increasingly attractive proposition. The castables are produced offsite and delivered to the customer’s plant – dried out, shaped to the customer’s requirements, and ready to install.

Calderys creates ready-shaped products for conventional castables, low-cement castables, plastic refractories, and insulating castables. These products are used for all types of workplaces, from high-temperature environments to construction projects such as bridges and buildings.

The company’s ready-shaped products are mixed and set in moulds in a quality-controlled industrial environment, at one of Calderys’ facilities, which means they are more likely to deliver longer and better performance than cast-in-place products. Furthermore, the installation time is more than halved, because there is no dry-out time at the customer’s end. Additionally, the company’s design and technical expertise means that it can cast more complex geometric shapes that cannot be achieved with the standard pressing process without modi fi cations or brick cutting onsite.

Better performance

There are numerous bene fi ts to precast shapes over their cast-in-place counterparts.

Ready-shaped products are manufactured in a controlled environment, which means there is greater assurance to the customer of consistent quality and durability of the material.

Rudraksh Kulkarni, one of Calderys’ precast, pre fi red experts, says “the ready-shaped blocks and shapes are made in our own facility,

overseen by our trained quality supervisors. The physical and mechanical properties are better than regular casting.”

In regular casting, the castable material is mixed and applied in situ. Calderys offers an installation service, but customers can also hire local workers if they prefer.

However, it is becoming increasingly challenging to fi nd workers with the right skills – and, Calderys, being the producers, has real in-house experts who understand and know the material to be mixed and poured well.

“The quantity of water used – the ratio of water to castable – and how the castable solution is poured in place is vital in ensuring the best performance,” says Rudraksh.

With ready-shaped products, the castables are delivered as a fi nished product. They minimise the need for human intervention. The controlled environment of the manufacturing facility protects the properties within the materials – high mechanical strength, thermal conductivity, thermal shock resistance, low abrasion, and resistance to cracking (spalling) – and ensures they mix accurately.

Divyendu Tripathy, Thermal Marketing Director at Calderys says: “With precast shapes, we are attempting to eliminate any uncertainty and address the shortage of skilled labour. Calderys provides engineering and installation services for their precast shapes at customers’ sites. Installation of precast shapes is simple and doesn’t have the same challenges around quality.”

“There is less manpower required for the mix or the pour, which minimises human error. It is very important to follow the installation operations properly, as it can impact the performance of the lining.”

“And, of course, because this process requires less manpower and mechanised operations at the site, there are fewer safety risks.”

Quicker to install

During a shutdown, time is of the essence. Each day that goes by without operation represents a significant dent in income. Precast shapes reduce the installation period, which means customers can restart manufacturing sooner.

Any brick or refractory needs a dry-out period after mixing to remove the moisture from the castable or concrete and reinforce the product, so that in operation it does not crack, explode, or get impacted by steam blasting. For products cast in situ, the dry-out stage after pouring can take three to fi ve days, during which time the customer is unable to use their equipment.

Calderys’ precast shapes at one of the company’s facilities. Copyright: Calderys.

Precast, pre fi red products are already dried out before they get to the customer’s site.

“Calderys’ precast shapes are sent as a fi nished product, dried in one of our kilns, as part of a controlled cycle,” says Divyendu. “There is no need for dry-out at the customer’s site. They can install and restart operations within 24 hours, saving three or four days.”

“There is also less water used onsite and the customer saves the energy they would have spent on the dry-out.”

Ability to create complex shapes

Precast shapes are made to each customer’s specifications. The customer sends mechanical drawings of their equipment and the required thickness of the refractory, and Calderys’ internal design and technical teams make the moulds and shapes. Sometimes – and usually for new plants or green fi eld projects – the blocks need a little grinding or chipping for a smooth fi t in place, but for older operations, where accurate specifications are known, the ready-shaped blocks usually fi t easily.

The company has scanning facilities to create 3D-printed moulds, which enable bespoke and more complicated shapes to be created. This 3D printing equipment cuts down on the lead times for creating these geometrically complex

bricks and refractories. With the precast shapes, the company also provides customised refractory formulations with additives for exceptional process conditions, such as thermal shock.

Ready-shaped products also mean that, post-installation maintenance on bricks and refractories is easier compared to the regular casting process. The damaged block is simply removed and replaced with a new one using the existing mould in less time than cast-in-place. Precast shapes can also be cast and kept in stock for emergencies.

Not only is the actual repair process quicker, but because the quality of the ready-shaped products is superior to cast-in-place cement and offers a longer lifespan, repairs are needed less frequently.

Suitable in critical areas

Ready-shaped products are commonly used in less-critical areas of a plant, such as the tertiary air duct (TAD) damper and smoke chamber, as well as cooler areas.

Through Calderys’ research and development process, the precast shapes have been designed and trialed for use in critical areas in plants that face regular wear and tear, for example nose rings and the cooler bullnose, as well as other exposed, high-temperature areas, like burner pipes.

CALDERYS PRECAST SOLUTIONS AT THE SERVICE OF CEMENT PRODUCERS

• Improved performance and increased life

• Minimal installation time

• Ability to create bespoke, complex geometric shapes

• Less frequent and quicker maintenance and repairs

• Suitable for critical and less-critical areas of site

• Safer working conditions

“The burner pipe operates in an environment of 1600 – 1700˚C,” explains Divyendu. “It deals with alternative fuels, which can cause uncertainty and swings in the performance of the rotary kiln. This can be the weakest point for cement plant operators. It is a small piece of equipment compared to others on a cement plant, but if it fails, operations must stop, so it is essential.”

Not many other companies will be able to offer ready-shaped products for a burner pipe, adds Rudraksh: “That piece of equipment is not a big consumer of refractories and not a typical environment for ready-shaped products. We developed the design and material and trialled the innovation in our plant. We found a new and effective way to resolve a maintenance problem.”

The bene fi ts of Calderys’ precast shapes can be summarised as follows:

� Improved performance and increased life.

� Minimal installation time (no dry-out onsite).

� Able to create bespoke, complex geometric shapes.

� Less frequent and quicker maintenance and repairs.

� Suitable for critical and less-critical areas of the site.

� Safer working conditions (less manpower onsite).

Case study

One of Calderys’ customers had a kiln, running on full capacity, with refractory lining in critical areas exposed to heavy stress.

The customer wanted a more advanced, proven refractory solution with enhanced performance, mainly for the nose ring. They were looking for at least double the life of the refractory lining that they had achieved with existing castable solutions.

The customer was impressed with the design and commercial offer of CALDE ® RDS (the name of Calderys’ precast shapes range in India). Additionally, the manufacture and assembly would take place in Calderys’ facility in India, which was local to the customer, meaning a shorter delivery timescale.

A year after installation, the precast solution was inspected and there was minimal erosion to the kiln in the range of only 50 – 70 mm.

The customer ultimately decided to remove the precast blocks because the kiln shell was being changed.

Upon inspection, these blocks were found to be completely intact, with no loosening, and were expected to perform for another 12 months.

The customer has since placed additional orders for other critical areas.

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An overview of oxycombustion

In response to a global outcry over environmental concerns, the cement industry is setting out plans to reduce CO2 emissions as part of an international drive to cut global greenhouse gas emissions to net zero by 2050. At the recent COP27, many nations renewed their commitments and highlighted both their short and long-term steps towards realising their future air-emission targets. The progress on reducing the use of fossil fuels, though, has been less promising and a cause of concern for many ‘green’ campaigners. The use of fossil fuels may still be justifiable provided carbon capture, utilisation, and storage (CCUS) is effectively rolled out, possibly with some assistance from governments, i.e. tax breaks and or soft loans. Indeed, as far as the cement and lime industries are concerned, CCUS is the only solution, perceived at present, that can help producers meet their decarbonisation targets, but due to the high costs of CCUS, there is not yet a commercial application in operation

Tahir Abbas and Michalis Akritopoulos, Cinar Ltd, and Syed Suhail Akhtar, Holcim, provide an assessment of oxy-combustion as a potential CO2 mitigation technology that could become the leading CO2 enrichment path for CCUS in the future.

either in the cement or lime sectors. However, a recently compiled IEA report quotes, CCUS costs are gradually falling, with ample potential for further reductions over the next 10 years. As per THE Global CCS Institute’s 2022 Status Report, it is emphasised that without CCS, reaching the industry’s shared climate goal is practically impossible and states that the outlook for CCS has never been more positive, which is good news for meeting the CO2 mitigation targets.1 Cement and lime plants have responded to the future CO2 reduction needs and have initiated several research and demonstration CCUS projects worldwide.

CO2 capture technologies

The following are some of the most promising CO2 capture technologies either commercially available or in various stages of development. There are two main categories, the precombustion and post-combustion separation of CO2, the former is more expensive and complex for a cement/lime plant implementation and therefore not included here.

� CO2 capture via absorption

� Adsorption-based CO2 capture

� CO2 Capture through membranes

� Cryogenic separation of CO2

� Calcium looping cycle

� Oxy-combustion

This article will focus on oxy-combustion as a potential pathway to carbon neutrality which would require minimal plant modifications to implement.

Oxy-combustion

In comparison to other CO2 separation technologies, oxy-combustion is an attractive option for the cement industry, involving the enrichment of CO2 via oxygen injection and/or use of H2 as a fuel. This would require minimum alterations to the components of a plant, at least when oxy-combustion is applied to the calciner where over 80% of the CO2 enrichment level can be achieved. In the case of full implementation involving a kiln, more than 95% CO2 enrichment is possible, thereby skipping the CO2 separation step and moving directly to filtering, compressing, and making subsequent use of the CO2. When N2 from air is replaced during oxy-combustion, CO2 recirculation is required in order to ensure similar kiln and calciner temperatures. This will require some clinker cooler modifications due to the reduction in gas flow rate and re-establishing the combustion and calcination zones so that the effect on calcination reactions under a higher partial pressure of CO2 is taken care of. Therefore, the most critical component being the calciner, where the appropriate retention time for effective calcination reactions to be completed within conventional residence time, since CO2 enrichment (gas stream with higher partial pressure of CO2) inhibits the release of CO2 from CaCO3 (calcination). A consortium of European companies and the European Cement Research Academy (ECRA) have been studying this issue as part of its CCUS programme for the

Figure 1. Schematic of CCUS operating under oxy-combustion and CO2 recirculation conditions.

Figure 2. The geometry of a 500 tph scaled-down pilot calciner.

cement industry for over five years.2 The results have so far been encouraging and the programme is seeking funds for a CCUS demonstration cement plant. Currently, a multinational cement company, with the assistance of Scandinavian R&D institutes and Scandinavian industry, have initiated feasibility studies to look at the possibility of capturing over 50% of CO2 at a Scandinavian cement plant. The project objectives are to examine the extent to which excess energy from cement production can be utilised for capturing CO2. A new EU-financed project in Eastern Europe will be the first of its kind to capture all of its CO2 and divert it through a pipeline system with offshore permanent storage under the Black Sea, it could start operating as early as 2028. A schematic of CCUS operating under oxy-combustion and CO2 recirculation conditions is given in Figure 1.

With the possibility of making use of H2 as a fuel in oxy-combustion, the overall process may become more economical provided that the green power is available to produce both oxygen and hydrogen using dedicated electrolyser(s). Hydrogen firing or cofiring with biomass, may also be considered with oxy-combustion (oxygen and carbon dioxide enrichment), as green hydrogen in future will mostly be produced onsite, using large electrolysers powered by wind and/or solar power. This will open up additional R&D fields expressing safety and handling measures of H2 and O2, which at present

Figure 3. Upwards velocity contours for: (a) Case “Without CO2 enrichment” (b) Case “With CO2 enrichment”.

have never been utilised at a cement/lime plant. Separately, oxy-combustion has also been actively studied and with the development of low-cost CO2 sequestration technologies, mineral CO2 emissions can also be harnessed. When these two separately-developed technologies are combined, a plant may operate one kiln on oxy-combustion and the other on a fuel switching concept, or use both technologies in a kiln or calciner. Future cement plants could use both O2 and H2 streams produced from an onsite electrolyser, achieving the zero CO2 target with substantial reduction in H2 and O2 production costs – a plausible solution, in conjunction with CCUS, to work on for the cement plants of 2050 and beyond.

Within the cement industry, due to both technical and financial constraints, CCUS has thus far not

been demonstrated at the full scale. Apart from CO2 storage costs, the main technical challenges relate to the effective use of the oxygen/carbon dioxide mixture, which substitutes the nitrogen in the combustion/cooling air, and the minimisation of air ingression so that a CO2 enrichment in excess of 95% is assured. Two experimental studies, conducted within ECRA Phase IV results have shown no adverse effect on clinker quality, refractory life, or hot spots; however lower levels of calcination were observed due to the higher CO2 concentrations inhibiting the calcination reaction.3

For oxy-combustion, small-scale experiments for stationary particles reveal that an increase in the calcination temperature of about 80˚K can be expected for an increase of the gas-phase CO2 partial pressure of 80%. However, the effect on the gas residence time remains relatively unknown, as the particles/stones were static during the experiments, implying that at full scale, both the calciner exit temperature and meal LOI will be affected under CO2 and O2 enrichment conditions as well as due to flow stratification issues.

Theoretical assessment of oxy-combustion potential using CFD

To optimise a calciner for oxy-combustion and CO2 recirculation conditions, detailed 3D models with both combustion and calcination interactions are needed to account for both the decarbonation and recarbonation reactions of CaCO3 under higher partial pressure of CO2

It becomes more important to calculate the role of reversible chemical reactions with general purpose computational fluid dynamics (CFD) models. In most modern calciners, between 90 – 95% calcination is achieved prior to the hot-meal entering the kiln. Studies at the laboratory-scale have shown that limestone calcination is a strong function of temperature, CO2 partial pressure, total pressure and limestone particle size and to a lesser extent residence time.

The research based on both experimental and calcination model development,2 led to a modified meal-particle reaction model has been implemented in the calcination model which is directly coupled with the computational fluid dynamics. The calciner model accurately predicts the laboratory experimental data which is optimised and validated against over 220 full-scale calciners with different configurations and operating conditions.

Initially, a scaled-down pilot calciner (500 tpd) was simulated in order to assess the behaviour of an integrated calciner operating under CO2-enriched conditions. The selected pilot calciner geometry is a scaled-down version of a typical in-line calciner. Clinker production

Figure 5. Meal split below and above TA: (a) 100% meal below TA, (b) 70% below TA and (c) 50% below TA.

Figure 4. Computational results show contours of CO2, calcination and temperature for (a) Case ‘without CO2 enrichment’ conditions (left) (95% calcination and 904˚C exit temperature) and (b) case ‘with CO2 enrichment’ (right) (89% calcination and 917˚C exit temperature).

of 500 tpd with a calciner and kiln fuel split of 63 – 37%. The calciner has two burners both about 1.5 m below the tertiary air duct and firing in a direction 30˚ downwards, each located on opposing walls and in the same plane as the kiln axis. The meal is introduced just above the burners located on the other two opposed walls in a direction perpendicular to that of the burners (Figure 2). The calciner has a diameter of 1.98 m and a height of 37 m with two small restrictions after 8 m and 11.3 m. Thus, the developed flow in this calciner results in a residence time of approximately 3.5 sec.

The fuel, is injected from two multichannel burners with a transport air velocity of 30 m/s while axial air is introduced through an axial sleeve that injects the primary air/ gas at around 150 m/s. In the CO2 enrichment scenario, the same transport air is utilised but the axial air is replaced by oxygen-enriched primary gas (CO2 47% and O2 54%).

For the case ‘without’ and ‘with CO2 enrichment’, the composition of the gases vary at the different inlets. The kiln gases introduced at 980˚C have a density of 1.4 kg/Nm3 while that density increased to 1.7 kg/Nm3 with CO2 enrichment.

In Figure 3 it is shown that the CO2-rich atmosphere results in a slightly increased gas residence time, from 3.5 to 4 sec., this leads to a corresponding decrease in the upward velocities. The calciner gas velocities drop from 10 – 15 m/s to 8 – 13 m/s with the CO2 enrichment. An increase in the residence time is favourable for the calcination reactions, however in this particular scaled-down calciner having already lower upward velocities, the lower velocities may drop further under lower clinker production – hence a potential risk of lower calciner gas velocities reaching critical upward velocities to entrain and lift the injected meal particles.

In Figure 4 and Figure 5, results show contours of CO 2 , O 2 , and temperature for ‘without’ and ‘with’ CO 2 enrichment conditions. The shown calcination is the total meal calcination obtained at the exit including the calcination that had already taken place prior to meal particles entering the calciner. Computational results show that the calcination drops by 6%,

resulting in a gas temperature increase of 13˚C at the calciner exit.

The effect of meal split was studied as a means of increasing the calcination level under enriched CO2 conditions, when meal is supplied 100% below the tertiary air duct, and then decreased to 70% and 50%, respectively. The results show a slight gain due to the meal particles’ higher dispersion rate.

In Figure 6, the calcination of the meal particles is shown. When more meal is supplied above the TA the temperatures near the burners increase and thus the meal particles that are supplied in the lower level are calcined to a higher degree, and although there has been a slight decrease in the residence time

Figure 7. Comparison of volatiles and fuel burnout for (a) Case ‘without CO2 enrichment’ and (b) Case ‘with CO2 enrichment’.

Figure 6. Full-scale calciner (5000 tpd).

of upper meal particles, a slight increase in the exit calcination level is achieved. The rate of calcination is indicated through colouring meal particle trajectories from blue to red.

For a full-scale demonstration, a 5000 tpd calciner with a 6 sec. residence time was modelled (Figure 6). A comparison of the volatiles remaining between the two cases, as shown in Figure 7, reveals that in ‘without CO2 enrichment’ the fuel volatiles burn slowly due to lower oxygen concentrations of the riser duct gases resulting in being transported upstream where volatiles burn when more oxygen from tertiary air becomes available. This is also indicated through colour-coded coal particle trajectories, which turn from blue to red first for volatile release, and then again from blue to red to exhibit the char burnout.

The case ‘with CO2 enrichment’ using an oxy-burner with axial air O2-enrichment, shows that the coal particles burn much faster due to the pure oxygen that is directly introduced in the fuel stream.

By increasing the earlier ignition of solid fuels, it is possible to release more heat earlier and then transfer that heat to meal particles through both thermal radiation and convection. Since CO2 retains a substantial part of the radiative heat, the higher temperatures achieved due to injecting oxygen near the fuel do not produce hot spots near the calciner refractory walls. In addition, meal particles can also be injected closer to the oxy-fuel burner to accelerate the calcination reactions, without suppressing the combustion reactions. This will enable existing calciners to operate without experiencing adverse effects on the calcination of meal particles under a higher CO2 partial pressure (i.e. CCUS conditions), provided efficient oxy-fuel burners are installed and meal injection location(s) are located/partitioned accordingly.

CO2 separation and utilisation/storage

A plant operating under CCUS would need to monitor carbon dioxide concentrations in addition to oxygen as any ingression of air will dilute the CO2 concentrations with N2 and O2 and hence affecting the CO2 separation efficiency. The enriched CO2 tower gases are diverted through the filtration process for the removal of solids and those species which interfere with the CO2 separation process, if using anything other than the oxy-combustion CO2 capture technique, followed by removal of water vapours through condensation, final purification and compression for its storage or utilisation. As opposed to storage (i.e. EOR or under sea), there are several CO2 utilisation opportunities to be considered some already developed and others in R&D stages. As mentioned earlier, none of the cement plants are operating under CCUS, apart from a handful of

planned demonstration projects to be commissioned within the next few years. The higher CO2 capture costs need some government support at this stage, i.e. amine scrubbing US$100/t of CO2. Among others are indirect heating to release CO2 from CaCO3 in a cement plant, testing to be completed in 2025, and indirect heating by a special steel reactor so the process CO2 can be captured; CO2Ment, in a pilot-scale R&D project, are focusing on capturing CO2 in concrete production. In another initiative, the project aims are to combine CO2 with bypass dust for forming construction aggregates. A major cement producer is developing indirect heating to produce clinker through concentrated solar power. A cement company is developing oxy-fuel operating with a 330 MW electrolyser and in an R&D project, investigation is carried out to combine CO2 with H2 to produce methanol and plastics. Once these CO2 utilisation options are developed it will clarify which CO2 enrichment technique is to be used along with the possibility of integrating H2 firing.

Conclusion

Cement and lime plants, at some stage within next few years, will embrace the new technologies geared towards reducing CO2 emissions with partial and full implementation of CCUS beyond 2030. A number of CO2 separation and utilisation technologies are under development and some CCUS demonstration projects at cement plants are set to start operation within the next few years, therefore paving the way for future developments. Those technologies which will store or utilise CO2 are also rapidly emerging. At present, it is perceived that if green power becomes available and is plentiful, then oxy-combustion and H2 firing will become the leading CO2 enrichment path. However, prior to that partial oxy-combustion in the calciner and/or use of H2 in the kiln as an alternative fuel may be used in conjunction with other CO2 capture technologies, i.e. amine absorption. H2 is gradually finding its way to cement plants, initially, introduced in small amounts as a combustion enhancer, and has shown many benefits at over 20 kilns in Europe.4

References

1. ‘2022 Status Report’, Global CCS Institute, 2022 –https://status22.globalccsinstitute.com/2022-status-report/ introduction/

2. ‘Roadmap To Carbon Neutrality’, Portland Cement Association, 2021 – https://www.cement.org/docs/ default-source/roadmap/pca-roadmap-to-carbonneutrality_10_10_21_final.pdf

3. AKHTAR, S. S., ABBAS, T., and AKRITOPOULOS, M., ‘Adapting calciners operating under CO2 enrichment for CCS’, 2017 IEEE-IAS/PCA Cement Industry Technical Conference, 2017, p. 1-16, doi: 10.1109/ CITCON.2017.7951840.

4. GONZALEZ GAITAN, L., Cemex, Global Cement, November, 2022, p. 28.

Formidable fibres

Nathan Schindler, Evonik Corporation, describes how implementing a high-performance fibre material can help cement plants avoid air pollution and meet EPA standards.

The production of industrial goods, like cement, is necessary for the benefits of modern life: roads, hospitals, bridges, long-lasting buildings, walkable urban cities. One of the critical considerations for operators producing cement is to ensure that the harm to the environment is minimised. Every day, the industry gains new insights into its impact on the environment and ways to resolve those impacts. The US EPA recently proposed new standards that, if adopted, will require future reductions in PM 2.5 emissions. 1 This article will discuss the challenges surrounding the control of fine particle emissions like PM 2.5 with the pulse-jet baghouse, and address the question as to whether operators can count on filter bags made from materials such as P84 ® and P84 HT.

Cement plants are in the business of producing particles in the form of cement. Over the decades, the cement industry has taken many steps to mitigate and reduce the impact of particulate emissions on the environment. In 2015 – 2016, the Portland Cement NESHAP (commonly known as Cement MACT) required all existing US cement plants to reduce particulate matter emissions and control mercury emissions. The most common method implemented by cement plants for controlling these emissions is pulse-jet fabric filters on the kiln effluent and many other locations throughout a cement plant.

In January, the US EPA announced plans to continue its trend to reduce the ambient air quality standard for PM 2.5 particles by lowering the annual ambient PM 2.5 limit from 12 µg/m 3 to between 8 and 11 µg/m 3 . PM 2.5 particulate consists of fine inhalable particles with diameters generally 2.5 µm and smaller. 2 2.5 µm is very fine; it is about 30 times finer than the average human hair. The US EPA has estimated that PM 2.5 emissions cost the US billions of dollars annually in public

health impacts. 3 As plants continue to optimise manufacturing performance and ensure that their product and other particulate is captured effectively, the total cost of ownership of pulse-jet collection systems increases.

The four factors of pulse-jet fabric filter cost of ownership

Pulse-jet fabric filters are widely accepted for use in cement plants. They prevent emissions of particulates into the atmosphere in various applications, from high temperature kiln, raw mill, and clinker cooler streams to lower temperature applications like coal mill, cement grinding, and storage silos. Regardless of the composition of the flue gas stream, all pulse-jets operate with the same basic design. The gas or air is induced under negative pressure into the dirty side of the baghouse. The dust laden gases impact filter bags suspended from a tube sheet. Periodically, a blast of high-pressure air is injected into the clean side of the bag, causing the bag to pop and shed the dust layer into the hopper. The cleaned air then exits the filter unit from the clean side where it is typically released into the atmosphere. When fine particles penetrate the filter media (Figure 1), the pulsing system is unable to effectively remove the particles. Over time, as the bag blinds, the residual pressure drop increases, causing more frequent pulsing. Blinded bags add significantly to the total cost of ownership of operating a filter unit. 4 Selecting the right filter media for an application is critical to the operational success of a plant.

Fine particles have an outsized impact on filter performance

PM 2.5 particulate may be small, but it has a significant impact on the performance of filter media and leads to a significantly higher cost to operate a filter unit. Evonik’s experience handling the impact of fine particles dates back to the fabric filter upgrades at the Eskom power plants in South Africa in the 1990s. During pilot testing at the plant using standard fibres in the filter

Figure 1. Blinded cement grinding mill felt with e-PTFE membrane.

Figure 2. Activated carbon particle size distribution.

media, the filter units repeatedly tripped on high pressure drops. After evaluating the bags, the plant determined that fine, smooth particles penetrated the felt, blinding the bags.

The plant was able to overcome these issues by integrating P84’s irregular multilobal shape as a surface layer. Decades later, the plant continues to benefit from the low pressure drop and long bag life as a result of this filtration solution.

Today, some plants are seeing the impact of fine particles on the operation of their filter units. Some common sources of fine particles in the main baghouse are kiln effluent and clinker cooler fines. Activated carbon, added in many US cement plants recently to control mercury emissions, increases the number of fine particles that the filter media needs to handle. Many plants are also grinding cement to finer and finer grades, like UF-II. Finally, coal mill filters can be impacted by switching to fuel grades, like pet coke, that require finer grinding.

When evaluating the fineness of particles, there are several methods used. The most common in cement is Blaine fineness, which provides a relative particle size when compared to other similar materials but does not provide a distribution of particles. Another method looks at the percent volume of various size particles. This can be useful for evaluating mass loading characteristics, but can be misleading when evaluating filtration performance. A final method evaluates the number or count of particles across a range of sizes. When evaluating very fine materials, this method is more useful in filtration. Take for example commercially available activated carbon (Figure 2). When evaluated on a volume basis, less than 10% of the particles are smaller than 2.5 µm. However, when evaluated on a number basis, more than 95% of particles are smaller than 2.5 µm.

This distinction between number and volume is important in filtration efficiency when dealing with fine particles, because these fine particles are more capable of penetrating into and through filter media than the larger particles.

A common solution to improving filtration performance for applications with fine particles in North America is to apply an e-PTFE membrane to the filtration surface of the bag. The expanded PTFE membrane is a thin, breathable film that is effective in removing particles because it has a

Figure 3. Submicron particles damage e-PTFE membrane.

Figure 4. P84 fibre cross-section.

Figure 5. P84 microfibre cap after VDI test.

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large enough pore structure for gases to pass through, but it is small enough to prevent typical-size particles from passing through. It also releases dust well, so unwanted dust does not build up on the bag surface. These

attributes of e-PTFE membranes are actually detrimental when most particles are fine. The pore structure of a high-quality e-PTFE membrane has openings in the range of 1 – 2 µm. In one recent application, bags made of fibreglass with ePTFE membrane were installed in a filter unit to capture a clay product consisting of 80% (by count) particles finer than 1 µm. The particles passed directly through the membrane, causing the plant to exceed emissions criteria in a matter of days. Figure 3 shows damage to the membrane layer in a cement grinding application, allowing submicron particles to blind the felt.

Shaping a solution

P84 fibre is well-known in the filtration industry for high-temperature applications and for providing excellent filtration performance. Evonik’s P84 fibre product line can handle high temperatures of operation, allowing it to be used in most dry filtration applications. However, what makes P84 really unique is its irregular multilobal shape.

As seen in Figure 4, the cross-section of each P84 fibre is different. This shape allows P84 to build a porous, permanent dust cake on the surface of a bag, preventing particles from penetrating into the felt. 5 P84 micro-fibres (also visible in Figure 4) provide even more surface area preventing the finest particles from being emitted into the atmosphere.

Evonik recently conducted third-party testing to evaluate the performance of filter media constructed with a P84 microfibre cap and an ultra-fine clay product. The well-known VDI test method was utilised to simulate pulse-jet filtration conditions with a high (2 m/min.) air-to-cloth ratio. The rich and porous dust cake formed by the microfibre cap (Figure 5) prevented emissions of the fine clay. PM 2.5 emissions were below the detection limit, while residual pressure drop and pulse cycle times remained in a good range.

Helping cement plants improve filtration

In North America, one cement plant has been using P84 fibres with the microfibre cap to handle fine particles from the kiln and raw mill at high filtration velocities for around 20 years. Particle size distribution testing confirms that the particles in the flue gas are 1.5 µm on average. When analysed by count, over 95% of the particles are finer than 2.5 µm. In some

Figure 6. Kiln dust particle size distribution.

Figure 7. Glass/membrane damage.

Figure 8. P84 microfibre cap after 42 months.

compartments of this unit, the air-to-cloth ratio approaches 2 m/min., which is much higher than the recommended 1 m/min. maximum range.

During the 2000s, the plant conducted tests with various filter media before adopting a P84 microfibre cap.

The plant evaluated a high-quality fibreglass with e-PTFE membrane. The fine particles and high velocity caused significant damage to the membrane, allowing the dust to completely penetration the fabric.

On the other hand, the P84 microfibre cap filter media provided excellent filtration capacity over 48 months. Figure 8 shows the continued prevention of dust penetration into the filter media over the life of the filter bags while avoiding mechanical damage. As a result, the plant has benefitted from lower operating costs, lower maintenance costs, improved productivity, and lower energy use. These same benefits have also been successfully adopted in cement grinding, clinker cooler, and coal grinding filter units.

Conclusion

The team at Evonik welcomes the opportunity to work with plants to help them optimise the right filter media based on their actual operating conditions.

The company is always exploring new ways to improve P84, including the development of P84 HT for higher temperature resistance and new filter media constructions. It has also developed ways to reduce fuel requirements when using their products to deliver oxygen enhanced air onsite at a fraction of the cost of other systems. 6

References

1. Proposed Decision for the Reconsideration of the National Ambient Air Quality Standards for Particulate Matter (PM), January 6, 2023 – https://www.epa.gov/ pm-pollution/proposed-decisionreconsideration-national-ambientair-quality-standards-particulate.

2. Particulate Matter (PM) Basics – https://www. epa.gov/pm-pollution/particulate-matter-pm-basics

3. Proposed Revisions to National Ambient Air Quality Standards for Particulate Matter, January 2023 – https://www.epa.gov/system/ files/documents/2023-01/PM%20NAAQS%20 Reconsideration%20Proposal%20-%20Overview%20 Presentation_0.pdf

4. SCHINDLER, N. and OGILVIE, K., ‘Uncovering the True Cost’, World Cement, May 2020.

5. HARFMANN, P. and ROFF, G., ‘Filter Media Today and for Future Requirements’, Technical Textiles, Feb. 2008.

6. SCHEER, C. and SCHINDLER, N., ‘Pulling a Production Boost out of Thin Air’, World Cement, December 2022.

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SCR solutions for the cement industry

Jeff Shelton, BD Heat and Dracyon, demonstrates why preventing buildup is vital for allowing SCR systems to tackle the cement industry’s NOx emissions.

In today’s world, regardless of the industry, emission regulations are getting stricter. In the cement industry there is a drive to reduce NOx emissions. Plants are now considering the use of a selective catalytic reduction system (SCR) to accomplish this task. When designed and operated properly, an SCR system can reduce NOx emissions by up to 97%.

An SCR system is an add-on device that injects a reagent such as ammonia or urea, into the gas stream with the presence of catalyst to start a chemical reaction. At the right temperature (570 – 750˚F) the reagent and the catalyst convert NOx to nitrogen and water.

Urea + 2NO + ½O2 → 2N2 + 3H2O, or 2NH3 + 2NO + ½O2 → 2N2 + 3H2O

SCR systems have been used successfully in various industries for several years. In the US they are frequently installed in the power, industrial, oil, gas, and petrochemical industries. The use of SCR systems in the US to control NOx emissions in the cement industry is uncommon. In Europe and China, however, SCR systems are more commonly used in cement plants to reduce NOx pollution.

Global push to reduce NOx emissions

Regulations for the harmful pollutant NOx are becoming stricter across the globe. Perhaps the best example is the ‘Good Neighbor Provision’ recently passed in the US. This regulation has set specific goals and targets for stricter NOx emissions in 23 states. This regulation specifically addresses air pollution that crosses state boundaries that affects neighbouring states. It is believed the new stronger emission regulations will increase cement production costs and offer new operational challenges. To meet the new regulations new NOx removal equipment is expected to be required.

The most proven solution is the addition of an SCR system. Many plants have used SNCR systems to combat NOx emissions, but the efficiency will not meet the new regulations. New SCR systems in the cement industry can reduce NOx emissions by 90% and in some cases 97%.

Many of the SCR units installed in the cement industry have suffered from buildup issues which reduces NOx removal and operational time. Buildup has been a challenge which can be overcome.

Buildup like that shown in Figure 1 prevents the reagent from interfacing with the catalyst and has a deep impact on NOx removal and pressure drop across the system. It is not uncommon for plants to be forced into downtime to manually clean the SCR system.

Shown in the top of Figure 1 is a cleaning rake. This system operates continuously and requires a boiler tube bank ahead of the system to

Figure 1. Buildup in an SCR system before air cannon installation.

Figure 2. Compact SCR unit used in cold flue gas (clean side) installation.

heat the air. This is an expensive and unreliable system to operate and in most cases does not clean the catalyst. Indeed, it has proven effective at plugging the catalyst. These types of systems have failed to keep the SCR unit free from buildup and are often the cause of damage to the catalyst. Buildup is one of the greatest challenges in good SCR system operation in cement plants. Buildup that is evenly spaced across a reactor is often a sign that the gas flow velocity is too low. This reactor is located after the baghouse was not expected to suffer from buildup.

Avoiding buildup

In an effort to avoid buildup some cement plants have selected to install the new SCR units in a clean side (low-dust) location. This is a position after the baghouse or ESP. This location has temperature challenges (to be effective, a certain temperature is required). In many low-dust applications, the temperature of the flue gas drops below what is required for an SCR system to be effective and must be heated up. Buildup in this location impacts the operation of the SCR system because cement dust tends to be sticky. This type of buildup is often experienced in other industrial applications and can be controlled with the right gas flow, mixing system, and proper cleaning system with the use of the right amount of catalyst volume.

In general, the benefits of using a SCR system to control NOx includes the following:

� High NOx removal. The SCR system can remove up to 95% of the NOx emissions.

� Can be retrofitted to existing plants.

� Low operational cost and the availability to keep the plant running. The key for any SCR system is that the operational cost remains as low as possible and that it keeps the plant running.

� One of the biggest advantages of a clean-side SCR is that the system can be installed while the kiln is operating. A shut down is

Figure 4. Flue gas modelling of vortex mixers.

Figure 5. Clean SCR system installation.

Figure 3. Sonic horn installation.

only required to finish the tie-ins to the existing ducting. Reducing the amount of downtime reduces lost revenue and profitability for the owner. In addition, the clean side SCR can be designed to be isolated from the kiln permitting cleaning or repairs to be carried out, while the kiln keeps operating.

The key to any successful SCR system application is the SCR unit OEM must address and supply the following.

� Good gas flow and mixing system.

� Proper cleaning system.

� Catalyst that resists buildup and remains buildup-free for years.

Two companies (BD Heat and Dracyon Corp) with years of SCR experience can provide a reliable and efficient SCR system for the cement industry, thus supplying a NOx removal system that remains buildup-free and is highly efficient at NOx removal. BD Heat has been supplying SCR systems in the petrochemical, industrial, and oil and gas markets for years. The company has over a dozen SCR systems installed around the world, with more coming online each year. These systems utilise direct injection of either anhydrous or aqueous ammonia into the flue gas. This is done upstream of the catalyst bed.

The use of flow modulation devices such as vortex-generating mixers allows for an even redistribution of NOx and the reagent within the flue gas, regardless of the complexity of the ducting. The vortex-generating mixer design is well known and used in the high dust environments of in the power industry. This patented system has been proven again and again as a key element to help eliminate buildup in SCR systems and allow high NOx removal. These features help to ensure that the performance of a given unit meets the specific needs of that project, regardless of application or of the reduction requirements of that location. Each component for the system is built to scale. In addition, each component is extensively flow tested to ensure that after installation the unit will perform as designed. Because of this, BD Heat Recovery Division’s SCR system can reach up to 97% efficiency within a single reactor.

In the past, BD heat has used Umicore as their catalyst supplier. Umicore is one of the leading suppliers of catalysts worldwide. Applications include power, petrochemical, industrial, and oil and gas markets and include both low-dust

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cannon (left) and two 4 in. multiplier systems. The stainless steel hose is to compensate for the growth of the SCR versus the platform. The SCR unit has two layers. On the top layer there is a single air cannon with three multipliers while the opposite wall has two multipliers. The second layer is identical to this layout but with two exceptions. The air cannon is connected to the top layer air cannon with a stainless steel hose so that they can share the air tank. The top layer also has a sonic horn installed.

and high-dust applications. In cement applications, in most cases, the catalyst is a fibre-reinforced Vanadium-Tungsten-Titania catalyst. The catalyst is available in a version with a 0.4 mm wall. The DNX-LD catalyst can be optimised to meet the specific operating conditions by varying the active constituents of the catalyst, the pitch size, and the wall thickness to achieve the desired performance.

Umicore’s cement experience, together with extensive laboratory testing, have proven the DNX-LD catalyst activity is maintained over long operation in a wide range of applications.

The combination of the above features of the DNX-LD catalyst ensures a long, trouble-free service life. This translates directly into minimised catalyst and operating costs and thus it ensures excellent value and easy operation. The long service life combined with the low-pressure drop makes the DNX-LD catalyst very economical to operate.

Dracyon Corp has years of experience in the cement industry by working with Air Cannons to solve buildup issues. Company personnel have applied air cannons to eliminate many different types of buildup in the cement industry. These personnel are also responsible for the introduction of air cannons tosolve SCR unit buildup issues in other industries. The personnel with Dracyon Corp have been active in improving operation in many SCR systems in the industry including experience in the cement industry.

The Dracyon Corp approach to cleaning SCRs is as follows:

� Do not allow particles larger than the pitch opening of the catalyst to reach the catalyst. This will block the gas flow.

� These large particles must be stopped by a screen and blasted into smaller pieces with air cannons. These particles must be smaller than the screen opening before being allowed to be introduced to the catalyst. Any particles seeing the catalyst must be smaller than the pitch which will allow it to pass.

� Whenever possible install a sonic horn. The sonic horn produces a high-energy, low-frequency sound wave that causes the particles to vibrate. Sonic horns are a low-cost approach to supplemental cleaning.

Figure 6. SCR buildup prior to air cannon and sonic horn installation.

Figure 7. Air

Conclusion

Buildup will be different at each cement plant SCR system due to the fuel mix utilised by that plant. Close attention must be paid to evaluating the fuel and the resulting particles. The key to success is the BD Heat gas flow and mixing system which has proven to be effective. Once operators get the proper flow they will then need to protect the catalyst from building up. A good cleaning system with the right catalyst is essential.

About the author

Jeff Shelton is the President of Dracyon Corporation, and a former member of the Senior Management Teams at both IGS and Martin Engineering. He has over 40 years of experience in the air cannon and SCR industries. Jeff is known for his development of innovative technology and process applications for both SCR systems and air cannons.

Figure 8. (a, b) Fan Jet Nozzles designed to spread out the air blast and clean a 6 in. area from side to side and an area of 8 in. straight ahead. (c) Perf Plate catalyst screen with an opening area size of 80% of the catalyst pitch. The screen is designed not to allow any particles larger than the catalyst pitch to reach the catalyst. Particles larger than the opening of the screen will be blasted into smaller pieces by the air cannon blast so they can pass through the catalyst without causing buildup.

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Technology to trust for process gas analysis

Felix Bartknecht and Sriparthan Sriraman, SICK, illustrate the cutting-edge process gas analysis (PGA) systems that were used to help a French cement producer optimise their combustion efficiency while keeping emissions low.

In November 2020, Heidelberg Materials’ subsidiary Ciments Calcia presented drafted terms of a large-scale investment and reorganisation programme for several of its production sites in France. The €400 million investment programme was in line with Heidelberg Materials’s strategy to create a sustainable low-carbon and high-performance business throughout the group and even included a new 4000 tpd clinker production line at its Airvault cement plant for further fuel handling and efficiency upgrades, as well as process improvements at its cement production sites in Couvrot and Bussac-Forêt.

The cement industry is one of the most energy-intensive industries in the world, with energy accounting for up to 40% of production costs. As a result, the industry has been actively seeking alternative fuels to reduce its reliance on fossil fuels, which are not only costly but also contribute to greenhouse gas emissions. One of the most popular alternative fuels in the cement industry is waste-derived fuel, which includes materials such as shredded wood, waste paper, plastics, tyres, and waste oil. These materials can be used to replace a large portion of fossil fuels in the production process, reducing costs and fostering decarbonisation at the same time. Overall, the trend towards alternative fuels in the cement industry is driven by a need to reduce costs and emissions while remaining competitive in the global market.

Adapting to alternative fuels

Throughout the industry, it is well known that a large share of alternative fuels increases the risk for

possible cyclone blockages, ring formation, and corrosion issues, which will consequently lead to a pressure loss, increased wear of the kiln sealing, incomplete combustion, and a rise in sulfur and chlorine volatilisation. Furthermore, the restriction of the kiln diameter can lead to poorly granulated clinker and an increase in gas velocities, which can elevate dust formation and even cause local hot spots inside the pyroprocess, damaging the refractory material and outer kiln shell. The usual associated effects are frequent kiln stops, reduced kiln availability, diminished productivity, and reduced clinker quality caused by the periodic breakaway of deposits. This phenomenon, however, can be avoided by monitoring the gas composition inside the pyroprocess and feeding the

information into a closed loop control system to maintain stable and optimised process conditions. Right from the project’s start, the managers at Calcia attached high importance to choosing the correct process gas analysis system for the future growing requirements for process control at upgraded and future plants. Having good experiences with a large installed base of SICK kiln inlet process gas analyser systems not only in France but in many other production sites belonging to the Heidelberg Materials group and following the recommendation of plant operators in various countries, Calcia decided to request SICK to provide its Cement Probe System, SCPS 3300 (Figure 1), for the projects to be executed in France.

The main tasks of kiln inlet process gas analysers in cement plants are:

� Measuring the process gas composition in the rotating part of the kiln.

� Monitoring the excess air rate (O 2) at the kiln inlet.

� Checking for carbon monoxide concentration (CO) and completeness of combustion.

� Monitoring NO and NO 2 concentrations for emission and temperature control.

� Monitoring of sulfur volatiles (SO 2).

� Controlling the measurement values mentioned by providing information for burner controls, fuel and raw material mixture adaption, and flue gas cleaning system controls.

In addition to these functionalities, other customers have benefitted from the capability of the analyser system to give an indication about the internal chlorine cycle by measuring the process gas concentration of hydrogen chloride (HCl), helping plant operators to reduce blockage issues caused by high chlorine volatility. Furthermore, this information can help to limit the bypass gas volume flow and keep HCl emissions at a low level.

Taking measurements

Taking measurements in harsh environments with dust concentrations of up to 2000 g/m 3 and temperatures around 1400˚C is challenging, but the SCP3000 high temperature gas sampling probe (Figure 2) with its water-cooled pipe and highly efficient self-cleaning function is a reliable solution for gas sampling at the kiln inlet. Due to its special design and high-pressure back purge blower, the probe avoids clogging even when operated in high-dust kiln

large

atmospheres containing

Figure 1. SICK SCPS3300 kiln inlet process gas analysis system (1. Retraction unit with carriage; 2. Mounting flange plate with protection tube; 3. Local control cabinet; 4. Water/water cooler; 5. Air/water cooler; 6. PLC cabinet; 7. Instrument air pressure cabinet; 8. Cable & tube support stand; 9. MCS300P HW gas analyser).

Figure 2. SICK`s SCP3000 gas sampling probe for kiln inlets installed at Calcia Couvrot.

amounts of chloride and sulfur compounds. Having the flow-optimised and reinforced gas intake mounted at an angle, averted from the gas stream, direct entrance of dust and particles to the sampling system is reduced to a minimum. Thus, the highly corrosive-resistant probe tube, which comes in different lengths from 2.5 – 4 m, is protected from abrasion and material caking.

Probe cooling is enabled via an external water/water or air/water heat exchanger. Having no mechanical moving parts inside the gas’ path enables the collection of large amounts of gases, while at the same time, effects of thermal stress and blockages are excluded due to the limited attack surface inside the probe. The extracted gas is cleaned by flowing through the heated metal mesh dust filter installed at the probe’s end. To decrease overall maintenance time, the filter, filter chamber, and probe tube are back-purged using pressurised air coming from an integrated shock blower unit. Thereby the cleaning sequence can be initiated automatically or manually. Periodic rotation of the probe by +/-45˚, and the ability to move it 10 cm back and forth during full operation, prevents deposits from sticking and baking on the probe’s outer surface. Consequently, the probe can be extracted at any time. To do so, the system has, besides an electrical retraction unit, an additional pneumatically-driven backup system, which allows the probe to be drawn out of the kiln via a dust resistant spindle drive, even during a power failure. The mechanicallyor pneumatically-operated sealing box prevents hot material flowing from the kiln and protects people and machinery in the external area while ensuring that no false air gets inside the kiln correspondingly. Heated system components reduce the risk of thermal bridges and concomitant problems with condensation of corrosive gases. As a result, a high system availability of over 95% is guaranteed. A control unit and local operating panel allow automated and manual operation of the device via an integrated touch panel.

SICK is one of the only suppliers which offers gas extraction probe and analyser solutions from a single source. Furthermore, the company has experience in offering kiln inlet gas analysers based on the hot/wet measurement technology. Using the MCS300P HW multi-component gas analyser (Figure 3) with its nondispersive infrared (IR) process photometer, cement

producers have the opportunity to measure up to six IR active gas components, plus oxygen. For the application at the kiln inlet, the analyser system is normally configured to measure all combustion-related gas components such as O 2, CO, CH 4 (if natural gas is used), NO, CO 2, and process parameters such as SO 2, HCl, and NH 3. Due to hot/wet technology, the gas path is completely heated from the sampling to the final analysis. Thereby ensuring that the extracted gases are always above the dew point, which reduces the risks of problems associated with condensates like acid corrosion or piping blockages. Since the sample gas is not cooled, even water-soluble components like NH 3, HCl, and SO 2 can be measured with one single cuvette and without any gas treatment or calculation effort. Furthermore, SICK’s

hot/wet technology does not require additional gas coolers, special acid filters, water traps or hydrogen peroxide dosing systems to eliminate the corrosive SO 2 in the process gas. This leads to a reduction of maintenance efforts and consumables.

The combination of the SCP3000 high temperature gas sampling probe and MCS300P HW multi-component gas analyser can handle the challenges of taking gas measurement in the kiln inlet at cement plants, regardless of high gas temperatures, high dust loads, or corrosive gases, without the need for a complex and maintenance-intensive sample conditioning system. The automated selfcleaning and self-adjusting capabilities of the analyser system allow for high availability and result in significantly lower operational costs compared to conventional cold/dry sampling systems, which tend to be very complex and difficult to maintain. Therefore, operational costs for hot/wet technology can be up to 40% lower than cold/dry sampling systems. The system is optimised for usage with difficult fuels with high sulfur content (e.g. pet coke) and alternative fuels (tyres, RDF, oils, woodchips, medical waste etc.) making it reliable even when applied in very aggressive measurement atmospheres.

As the plant conversion at Calcia Couvrot was performed on a very tight schedule, SICK was able to support the shutdown activities by reprioritising the production of the process gas analyser system and coordinating the technical approval and logistics efforts accordingly. Installation and commissioning were handled efficiently with the timely assistance of the site maintenance team in May 2021. Since the installation, maintenance demands are minimal with above-average system availability.

Moving forward

In the future, Calcia plans to implement SICK’s Condition Monitoring Box (Figure 4), which provides a new digital service helping to increase the availability of the process gas analyser system at the kiln inlet. The SICK Condition Monitoring Box is a web-based condition monitoring solution for sensors and machines. The vital data of the connected devices are collected by the gateway, encrypted,

Figure 5. SICK’s web-based condition monitoring solution.

Figure 6. Manual checking and cleaning of the SCP3000’s dust filter is made simple by having easy access from the back side of the probe.

and sent via mobile network, LAN, or Wi-Fi to a secure cloud host for further processing. This collected data can be visualised and evaluated in the Condition Monitoring Box web application. Significant changes in the device status are monitored, thereby enabling timely intervention by the maintenance personnel, and ensuring the availability and productivity of critical device components and machines. In this way, the Condition Monitoring Box improves availability and reliability of the devices, as well as the avoidance of unplanned equipment failures and downtimes. As an option, the connected devices can be monitored by SICK as part of a service agreement too. Condition monitoring keeps an eye on all vital parameters that indicate the health of the overall system – including the gas analyser, the sampling system, as well as all auxiliaries like the cooling system for the water-cooled gas extraction probe tube or the PLC (Figure 5). With this information, problems can be identified before they occur. For plant operators this results in an extended product lifecycle and an increase of return on investment. Furthermore, the solution allows SICK to optimise maintenance and enables immediate troubleshooting, which reduces travel expenses and labour hours for SICK

service engineers. These cost savings are passed on to the cement producer directly. In addition, detailed remote health checks increase the data quality of the analytical systems. These improvements increase overall maintenance efficiency and can extend the lifecycle of the machines and plants.

“The current system design of gas sampling probe and water/water cooler is a big improvement as there are no probe clogging or high temperature alarms. The system needs way less human intervention, just a weekly check. We are very happy with the current availability rate”, says Sergio Tossi, Plant Manager at Calcia Couvrot.

Summary

As a result of the good relationship between SICK and Calcia, as well as many other members of the Heidelberg Materials group globally, not only the plant in Couvrot was equipped with the SCPS3300 kiln inlet process gas analyser system comprising of SCP3000 gas extraction probe and MCS300P hot/wet multi-component gas analyser, the best suitable solution for this demanding and important measurement application. Additionally, this solution will also be installed at the Beaucaire and Airvault sites.

A breath of fresh air

LafargeHolcim Dujiangyan Cement Co., Ltd., founded in early 1999 in Chengdu, China, is the only wholly-owned subsidiary of the multinational cement company Holcim Group in China. It has three advanced production lines with dry precalcining kilns, producing 4.1 million tpy of cement clinker and 5.3 million tpy of cement. Dujiangyan Cement Co., Ltd., is adhering to Holcim Group’s ecological and environmental protection policies involving the most stringent international environmental standards, and is working to become a modern, environmentally friendly plant. It has been listed as one of the first industrial green design demonstration enterprises in China.

Clinker calcination in cement production typically requires the high temperature combustion of coal, resulting in flue gas containing a certain amount of nitrogen oxides (NOx). Taking the 3200 tpd production line of Dujiangyan Cement Co., Ltd. as an example, the field test shows that the original concentration of NOx in flue gas is about 800 mg/Nm3. After adopting staged combustion and SNCR technology, the NOx emission concentration could be controlled below 100 mg/Nm3, but the NH3 escape was as high as 75 mg/Nm3. In order to meet the first level standards of air pollutant emissions in the Chinese cement industry, that is to maintain flue gas NOx emission concentration below

50 mg/Nm3 and NH3 escape below 5 mg/Nm3, and at the same time to determine a feasible DeNOx technology for widespread applications in the near future, Holcim Group decided to integrate medium temperature SCR DeNOx technology solutions in Dujiangyan Cement Co., Ltd.

SCR DeNOx process solutions

The kiln of the 3200 tpd production line of Dujiangyan Cement Co., Ltd. uses a KHD PYROCLON calciner, with an effective furnace capacity of 1300 m3 and the following dimensions: Ø 4.8 m x 52 m. The production line is equipped with a 9 MW waste heat power generation system. The staged combustion

Zhu Linhe & Zhang Wei, Sinoma Overseas Development

Co., Ltd, and Wang Lan, China Building Materials Academy, discuss the construction and operation of a medium temperature SCR DeNOx project at the LafargeHolcim Dujiangyan cement plant.

technology matched with the production line is mainly to add the fuel into the calciner in different stages and form a reduction zone in the cone of the calciner to control the generation of fuel-type NOx. The SNCR process technology injects a certain amount of ammonia into the calciner, causing NOx to be reduced to N2 by the ammonia injected at 850 – 1050˚C. In general, staged combustion technology and SNCR technology can achieve 20% and 50% denitrification efficiency respectively.

The SCR denitrification technology injects a reducing agent (ammonia/urea solution) into the pipelines of the reaction tower and, with a catalyst in the reaction tower, selectively reduces NOx in the 75

flue gas to N2 and H2O. The reaction efficiency of SCR technology is high and can control the ammonia nitrogen mole ratio at about 1:1, to prevent NH3 escaping while reducing NOx.

In fact, depending on the different temperatures of the cement kiln gas, SCR DeNOx technology can operate in both high temperature and medium temperature layouts. Specifically, the SCR reaction tower can be placed in front of, or after the flue gas waste heat boiler; the former reaction temperature window is 320 – 300˚C, while the latter is 220 – 160˚C. The results show that medium temperature layout (Figure 1) has the following advantages: when the flue gas temperature is reduced by about 100˚C, the flue gas volume can be reduced by about 15%, and the amount of catalyst and the size of the reaction tower can also be reduced. Due to the dust collection effect of the waste heat boiler, the dust concentration in the flue gas can be reduced from about 100 g/Nm3 to about 50 g/Nm3, which can reduce the risk of the catalyst being blocked by dust and thus reduce the consumption of compressed air in the reaction tower. More importantly, it will not affect kiln operation and power generation of waste heat boiler, nor will there be any risk of large crusts (discharged from the preheater) falling and blocking the catalyst.

One of the technical keys of SCR DeNOx is the catalyst. Research teams in China have developed a medium-temperature SCR DeNOx catalyst in cement kiln flue gas through long-term basic theoretical research, laboratory analysis tests, and pilot testing under actual conditions; and obtained demonstration application in cement production lines.1 Accordingly, Holcim Group approved the construction of the world’s first medium temperature SCR DeNOx project of cement kiln flue gas in LafargeHolcim Dujiangyan Cement Co., Ltd. The project was constructed by Sinoma Overseas Development Co., Ltd.

SCR DeNOx process design and construction

The design scope of this project includes the SCR reactor and the inlet and outlet pipes, reactor bypass pipes, ammonia metering and injection system, compressed air and soot blowing system, electrical instrument control system, etc. The basic data and design technical indicators of cement clinker production line and SCR DeNOx system are listed in Table 1 and Table 2, respectively. The process flow is shown in Figure 2.

As can be seen from Table 1 and Table 2, the actual production capacity of the cement production line is 3750 tpd, the flue gas flow after the waste heat boiler is 480 000 m3/h, and the flue gas temperature is between 220 – 240˚C, the flue gas dust concentration is about 60g/Nm3, the NOx concentration can be expected below 400 mg/Nm3, but the designed

Figure 1. Medium temperature and medium dust SCR DeNOx layout of cement kiln flue gas.

Figure 2. SCR DeNOx process flow.

Figure 3. Engineering design and actual layout of SCR reactor.

Figure 4. 3D CFD simulation of fluid field and pressure drop in the reactor.

technical indicators require that the NOx emission concentration is less than 50 mg/Nm 3 and the NH 3 escape is less than 5 mg/Nm 3

As shown in Figure 2, the construction of the SCR reaction tower includes the introduction of flue gas from the kiln into the reaction tower from the outlet of the high-temperature fan through the newly built pipelines, and the flue gas after denitrification treatment goes back into the original flue gas main discharging pipelines. The reaction tower contains 4+1 layers of catalyst, which are installed with an acoustic soot blower and a rake soot blower. The air is then supplied by the air compressor outside the tower. Part of the dust in the flue gas is carried out by the flue gas, and part of the dust settles in the hopper at the bottom of the reactor and is transported to the raw meal product conveying system by the bottom screw conveyor.

The ammonia injection system of the reactor includes ammonia storage, metering, and delivery, and the ammonia spray gun is installed at the outlet pipe of the preheater C1 stage outlet duct.

SCR reactor and connecting pipelines

‘SCR reaction tower’ refers to the tower structure with a catalyst installed (Figure 3). The flue gas without denitrification is mixed with NH 3 and passes through the SCR reaction tower. With the catalytic reaction, NOx in the flue gas is reduced with ammonia to generate N 2 and water. The residual ammonia content (NH 3 escape rate) in the flue gas after the reactor will not exceed 5 mg/Nm 3 , the pressure drop of the reactor will not exceed 150 pa per layer, and the overall temperature drop will not exceed 5˚C.

Based on the flue gas flow velocity and catalyst canal flow velocity, 130.64 m 3 of catalyst is used, for 4+1 layers, with each layer being approximately 32.7 m 3 . With the catalyst channel being 13 x 13 m, the flue gas flow velocity is 4.4 m/s, surface velocity is 5.9 m/s. According to catalyst consumption and 4-layer layout requirements, CFD simulation and other methods were used to calculate and ensure the computational fluid dynamics and low-pressure loss, as shown in Figure 4.

Soot cleaning system

As the dust content of the flue gas is approximately 60 g/Nm 3 , to avoid dust deposits and blockages in the reaction tower and catalyst channels, five acoustic soot blowers (staggered on the opposite side) and four compressed air rake soot blowers are set above each catalyst layer. The dust is cleaned regularly through programme control, to ensure stable operation and reduce the maintenance cost of the SCR system.

Figure 5. Diagram of rake soot blower.

Figure 6. Acoustic soot blower and working principle.

Figure 7. Layout, control, ammonia injection amount, metering regulation of ammonia injection system.

Figure 8. Diagram of SCR reaction tower control process.

Layout, parameter, function, and operation control of rake soot blowers

The rake soot blower (Figure 5) is mainly composed of two parts: the rake tube in the reaction tower and the soot tube outside. When starting, the soot blowing pipe (outside the tower) is pushed forward or backward through the mechanical transmission of the reducer. The central pipe of the soot rake in the tower is connected to the soot blowing pipe outside the tower, the central pipe is placed on several branches with special nozzles. By advancing or reversing the soot blowing pipe outside the tower, the air from the nozzle will blow and clean the covered area, without any dust deposits.

Acoustic soot blower

The working principle of the acoustic soot blower (Figure 6) is to input an air source (compressed air or steam) with a certain pressure into the specially-made air chamber of the soot blower, so that the air source oscillates in a specific geometric chamber and stimulates the intense oscillation of the gas in the chamber to emit high intensity sound waves. Sound waves enter the area that may collect dust in the SCR reactor and with the acoustic energy, the air and dust particles in these areas will oscillate, disturbing and preventing the collection of dust particles on the heat exchange surface or between particles, ensuring that it is always in a state of suspended fluidisation, and the flue or gravity can take it away.

Reactor ammonia injection system

The capacity and configuration of the SCR ammonia injection

system (Figure 7) meets the requirements for removing the maximum amount of NOx from the flue gas. In actual operation, the ammonia supply mainly relies on the SNCR ammonia injection system at the front, and the

Table 2. Main design technical indicators.

Table 1. Basic production line and SCR DeNOx system characteristics.

SCR system supplements ammonia injection

to effectively control the NH 3 escape while maintaining the denitrification efficiency of the system.

Automatic control of the full system

This project uses DCS for centralised management and control of the SCR system, and collects pressure, temperature, NOx indicators, equipment operation trends and other data. The DCS system consists of field control and central control.

Field control

Collect all DI and AI signals from the SCR site and output DO and AO signals; complete motor sequence logic control, process parameters detection and monitoring, PID cascade, multivariable complex control, and others.

Central control

The central control consists of the central control room, the existing operator station, and the engineer station. Its functions are:

� Display the process flow diagram of dynamic parameters.

� Display motor start-stop operation and running state.

� Display bar charts.

� Display historical trend curves.

� Display control loop details and parameter corrections.

� Display alarm status.

� Display alarm status and operation reports.

System operation and highlights

Operating data

The SCR system has been formally incorporated into the operation and optimised through commissioning. All data meets the emissions targets.

System highlights

Fluid field optimisation

A baffle is set at the inlet at the top of the SCR system, so that the flue gas entering into the reactor can maintain the airflow distribution and maintain the original state to the maximum, and to avoid the airflow separation and turbulence caused by the change of pipeline section and change of pipeline direction.

Soot removal optimisation of the reactor

The operation logic of the rake soot blower was adjusted, and the operation sequence was modified as follows: from the middle of the reactor to two sides of the reactor, which greatly improve the blowing efficiency of the

soot blower and avoid the soot deposit to the greatest extent.

Optimisation of flue gas desulfurisation process

When SCR technology is not used for denitrification in the production line, the ammonia consumption is large, and the sulfur in the flue gas and NH 3 escapes from the SNCR system form ammonia desulfurisation at the end of the production line, so that the sulfur emission from the chimney outlet can meet the emission standard. After the production line adopts SCR technology for denitrification, the denitrification efficiency increases, the ammonia consumption is low, and the NH 3 escape decreases significantly. During the downtime of the raw mill, the consumption of ammonia desulfurisation cannot be satisfied, resulting in unstable sulfur emission indicators.

After systematic research and tests, a certain proportion of calcium carbide slag (the main component is calcium hydroxide) was added into the raw material and desulfurisation powder was also added at the end of the kiln when the mill is stopped. Such operation can effectively control sulfur emissions and meet the emission indicators without affecting the stable operation of the SCR system.

Result and conclusion

The SCR DeNOx system for No.1 kiln in LafargeHolcim Dujiangyan Cement Co., Ltd has been officially been in operation for nearly one year. Operation indicators are as follows: NOx emission <45 mg/Nm 3 , NH 3 escape <1.0 mg/Nm 3 , overall ammonia consumption <3.1kg/t-cli., system pressure drop <450 Pa, overall power consumption <3.2k Wh/t-cli., all are better than the standard requirements for the first level enterprises in China. The successful implementation and stable operation of the SCR denitrification project in LafargeHolcim Dujiangyan Cement Co., Ltd not only achieved the ultra-low emission goals, but also fully verified that the medium temperature & medium dust SCR DeNOx system is a stable, reliable, and advanced technology for flue gas denitrification, with low operating cost, which is of great significance for air pollution control and environmental protection.

References

1. WANG LAN, Discusses the installation and operation of a moderate temperature SCR reactor, World Cement, 2014, (04): 10 – 15.

2. WANG LAN, ‘NOx emission reduction technology in cement kiln and review’, Cement, 2021. (03):42 – 45.

3. YIN HAIBIN, ‘Research and analysis of DeNOx technology of cement kiln flue gas at medium temperature’, Cement, 2022. (04):13 – 18.

Embracing ESP technology

Steven A. Jaasund, LDX Solutions, Inc., outlines the process of upstream gas conditioning for carbon capture scrubbers with wet electrostatic precipitation technology.

The cement and lime industries are experiencing increased environmental concern regarding carbon dioxide emissions. This will likely drive the installation of CO2 scrubbers at kilns in both sectors. Recent experience with CO2 scrubbers in other industries has demonstrated the importance of the cleanliness of the gases entering a scrubber system. In particular, solid and liquid particles such as sulfuric acid mist will cause problems such as excessive reagent consumption and equipment fouling. This article will describe the potential of wet electrostatic precipitators to significantly reduce the particulate load at the inlet to a CO2 scrubber to minimise reagent consumption and maintenance problems at the downstream scrubber.

Introduction

There is a rapidly growing interest in technologies to abate CO 2 emissions worldwide. Reductions in current rates of carbon dioxide emissions from existing sources are becoming a pillar of the world’s strategy to reduce the greenhouse gas concentration in the atmosphere. This strategy is particularly relevant to the cement industry because of the nature of the process, which involves both the combustion of fossil fuels and the conversion of calcium carbonate to calcium oxide by separating the CO 2 molecule.

Much of the attention directed towards CO 2 emission abatement is focused on CO 2 scrubbing technologies. Such technologies are well developed. Most use amines to absorb CO 2 and then regenerate the amine solution to yield a concentrated stream of nearly pure CO 2 gas which can then be reused or permanently sequestered. Such CO 2 scrubbing systems work best when the incoming gases are free of undesirable impurities. Thus, cleaning the incoming gases is essential to the overall CO 2 emissions control process. This article will address the use of wet electrostatic precipitation systems to affect this inlet gas cleaning step.

Industry background

The cement and lime industries are responsible for about 8% of global CO 2 emissions. In 2021, these industries emitted an estimated 2.9 billion t of CO 2 . This is more than the CO 2 emissions from worldwide aviation or the entire European Union. The primary source of CO 2 emissions from the cement industry is the production of clinker which is the main ingredient in cement; for the lime industry it is the calcination of limestone.

The other primary source of CO 2 emissions from the cement and lime industries is the combustion of fuels to heat the kilns. This accounts for about one-third of the total emissions. There are 99 cement plants in the US. There are 96 operating kilns in the lime

industry, with another 177 lime kilns in the pulp and paper industry. Given these facts, it is no surprise that the cement and lime industries are the second largest CO 2 -emitting industry behind electric power generation. Clearly, the industry faces a significant challenge.

CO2 scrubbers

The most widely applied CO2 scrubbing technology uses an aqueous-monoethanolamine (MEA) solution to absorb dilute CO2 and render it into a concentrated form after desorption. The concentrated CO2 stream is then suitable for sequestration, enhanced oil recovery, or other industrial uses. There are many full-scale CO2 scrubbers of this type in operation, and they have been shown to reduce CO2 emissions from flue gases by more than 90%. While there are also several other processes in various stages of development, the MEA scrubbing process appears to be the most widely accepted. There is little question that this technology is mature and proven effective.

However, while the MEA CO2 scrubbing process is proven, it is also costly to operate. There is much work involved in minimising OPEX for these scrubbers. Still, even under the best conditions, an MEA scrubbing system could consume up to 30% of the power of an upstream coal-fired generating station. One of the main OPEX factors is solvent loss, and a contributing factor to solvent loss is the presence of contaminants in the inlet gas stream.

Reported experience also shows that the cleanliness of the inlet gas stream is essential in minimising maintenance costs. Solid particulate matter in the incoming gas stream can foul equipment such as heat exchangers in the scrubbing system.

These contaminants can be solid and/or liquid particles that form when the inlet gas stream is cooled by saturation before contact with the CO 2 absorbing solution. Of particular concern is the sulfuric acid mist that forms in this way.

Wet electrostatic precipitators

The CO 2 scrubbing process must start with the gas stream in a saturated, wet state. That step may have been accomplished in an existing SO 2 scrubber in applications such as coal-fired boilers. In other applications where fabric filters or dry electrostatic precipitators are employed, a wet quench system would be required before the gas stream could enter the CO 2 scrubber. Regardless, such upstream quench cooling will be necessary. After this quench step, wet electrostatic precipitators (wet ESP) would fit.

Global carbon dioxide emissions by category.

Wet ESPs have several characteristics that make them well-suited for precleaning a gas stream prior to treatment in a CO2 scrubber. First, because they operate in cooled, saturated conditions, they can capture condensables such as acid mist and heavy organics. Additionally, wet ESPs are not sensitive to the chemical makeup of the collected particles, such as dust resistivity, a factor that is very important in dry ESP systems.

Because of these and other factors, wet ESPs are a highly effective solution for collecting fine particles regardless of the chemical makeup. This characteristic is particularly beneficial in applications where most heavy particulate matter has already been removed, but hard-to-clean fine particles remain. Such is the case in cement or lime kilns where fabric filters, dry ESPs, or wet scrubbers play this role.

Examples of where this ability is utilised are applications involving the collection of sulfuric acid mist or other condensable particulates. Both types of emissions are found in the gases emanating from lime and cement kilns.

Wet ESPs are configured in several ways. Most utilise discrete collection tubes in either up or downflow operation. There are also horizontal flow designs that use plates for collection. The various designs have many advantages and disadvantages, but any type will do the job if appropriately sized and operated.

Two concerns are frequently expressed when wet ESPs are considered: water consumption and energy demand. In reality, both are relatively minor issues. First, regarding water consumption, when part of a scrubbing system, a wet ESP will not add to the water demand of the system because any water required by the wet ESP can be reused in the upstream quench process. And second, regarding energy consumption, the pressure drop across a wet ESP is very small, as is the demand for electric power. In summary, wet ESP OPEX is never significant in the overall gas cleaning system.

Finally, wet ESPs are passive devices without moving parts. Because of this and the other features discussed above, wet ESPs are ideal for ‘polishing’ a gas stream before it enters a CO 2 scrubbing system downstream.

The performance of wet ESP technology in controlling fine particle emissions has been demonstrated on hundreds of installations in the USA and thousands worldwide. Both high efficiency and extremely low outlet concentrations on fine particle sources have been demonstrated. A few case-study examples follow:

Plywood veneer dryer

Wet ESPs are commonly used to control fine particle condensable particulate emissions from veneer dryers. In this case, the wet ESP was installed to treat 30 000 ft 3 /min. (51 000 m 3 /hr) emanating from a dryer treating Douglas fir veneer. Inlet and outlet particle size distribution measurements for this installation show that the wet ESP achieved excellent particulate removal over a range of inlet particles, largely in the submicron size range. Overall, the

Veneer dryer wet ESP inlet/outlet particle size distributions.

Before and after installation of wet ESP on a veneer dryer.

average particulate concentration at the outlet of the wet ESP is less than 0.01 grains/scfd (~23 mg/Nm 3 ).

Biomass-fired boiler

A second common application for wet ESPs is downstream of a wet scrubber treating emissions from a biomass-fired boiler. The data shown in the illustration below demonstrates the effectiveness of the wet ESP system in achieving compliance with the US EPA Boiler MACT regulations as implemented in 2013.

Fibreglass forming

Wet ESPs are also used to control emissions from the manufacture of fibreglass. The data shown here clearly demonstrates the ability of a properly designed wet ESP to achieve extremely low outlet particulate concentrations.

Capital costs

Generally, wet ESPs are more costly than other emission control technologies, such as wet scrubbers, dry ESPs, and fabric filters. However, beyond that, it is difficult to provide a more specific CAPEX estimate. This is because the capital costs of wet ESP systems vary significantly depending on many factors. Most important is the construction material. In benign environments with moderate pH and low chloride concentrations, simple 304 or 316 stainless steel is suitable.

If chlorides are a problem, higher-grade alloys such as duplex stainless steel or super austenitic stainless may be required. In very aggressive environments, high nickel alloys may be necessary. In addition, site-specific factors can significantly impact the installation cost and overall CAPEX.

Conclusion

In summary, with the advent of the demand for CO2 emission abatement, the cement and lime industry will have to develop the proper control technologies. The leading candidate today is wet scrubbing with amine solutions. These systems will need contaminant-free inlet gas to ensure this technology operates with the lowest operating and maintenance costs. A proven tool for achieving this goal is wet electrostatic precipitation.

About the author

Steven Jaasund is a registered Chemical Engineer with a BS in Chemical Engineering from Lafayette College and an MS in Engineering from the University of Washington. He has worked in the emission control technology for over 50 years. He is the author of several papers and holds several patents on this subject.

Table 1. Wet ESP emissions from fibreglass forming.

Unit 1 wet ESP.

Unit 2 wet ESP.

Wet ESP outlet concentrations from biomass boiler.

herever vertical transport is required, bucket elevators play an important role. The cement industry has to deal with the issue of raising different types of materials (limestone, pozzolan, chalk, various additives, raw meal, clinker, cement, alternative fuels, ash, and others).

Other than the slow elevators used for lifting large materials (100 – 350 mm) with gravitational discharge, there are two categories of elevators often used in cement plants – belt bucket elevators and chain bucket elevators.

� Belt bucket elevators are suitable for materials with fine or small grain sizes, and with a temperature of less than 120˚C (max 150˚C). They allow high capacities (1800 m3/h and more with bucket filling coefficient < 80%) or high lifting heights (wheelbases up to 150 m and more).

� Chain elevators are suitable for materials with medium grain size (up to 80 –100 mm) and also for high temperatures. However, these elevators are not suitable for high lifting heights (60 – 70 m wheelbases are already exceptional). The limitation of their use for large wheelbases

is due to the weight of the chains, which grows as the breaking load, which becomes vital, increases.

Factors to be considered for chain elevators

Generally speaking, chain drives are characterised by the discrete nature of the pitch of the meshes and the number of teeth ‘Z’ of the wheels (Z is real if the wheel is toothed, or fictitious if the wheel is smooth). This makes the chain drive unique and leads to advantages and disadvantages. The advantages include (in addition to the lower load on the shaft bearings), the certainty of a transmission without slippage between the chain and the wheel, if this is toothed.

The disadvantages are the vibrations and the resultant noise caused by the impact of the teeth on the wheel, and even more from a ‘polygonal action’ phenomenon that occurs due to the fact that the chain, wrapped around the wheel, forms a polygon rather than a circle. This leads to a floating movement of the chain.

While designing a conveyor that uses mechanical chains (mesh formed by pins and

Gambarotta Gschwendt outlines the key considerations when designing central chain bucket elevators to offer a low-cost and long-life solution for bulk materials transportation.

bushes joined by side plates), engineers should consider a fairly long chain pitch (distance between the pivot points) to minimise costs. The chains, in fact, often constitute a very important part of the overall cost of the machine. However, this clashes with the polygonal action, which requires the chain pitch to be reduced.

When the drive wheel of a chain drive works at a constant speed, the speed of the chain itself is not constant but faces periodic fluctuations. This fluctuation, which is caused by the fact that the chain, when wound on a wheel – whether it is toothed or not – forms a polygon rather than a circle, and its movement is known as a ‘polygonal action’; the chain is said to move with a ‘polygonal speed fluctuation’ generating dynamic loads which need to be taken into due consideration.

Many studies show that the dynamic load of the chain due to this ‘polygonal action’ is similar to

that of a simple forced vibration where its intensity increases with increasing speed up to the value of the critical speed.

Higher speeds produce smaller dynamic loads. It should be noted that a bucket elevator’s typical speed is much lower than the critical speed. Nevertheless, operators should take into consideration that the combined chain, bucket, and material weights are considerable and this leads to a natural variation in speed. Should speed change significantly, noise and vibrations occur.

The experimental results show that chain pitch and the number of teeth on the wheel are the main factors that influence the dynamics of the chain, i.e. the polygonal speed fluctuation.

The fluctuation decreases with increases in the number of teeth and reductions in the chain pitch.

The mechanical chain with the shorter pitch works more fluidly, and with less vibration, due to the less polygonal speed fluctuation.

It is understandable why the round steel chain ring elevators, which have a very short wheelbase, are less noisy.

Designers of chain elevators therefore need to identify the geometric parameters of chain pitch and the number of teeth on the wheel that ensure a fair compromise between the cost-effectiveness of the transmission and a transportation system that is as fluid as possible.

Special features of central chain elevators, type ESPC

In recent decades it has been noted that the type of central single-chain elevator, following a strong marketing push from some leading manufacturers, has become the most requested chain elevator.

Gambarotta is following this trend at the expense of the historic EVD and EVR elevators, which use the two round steel chains with oval rings.

Among the many bucket elevators with chains that are part of Gambarotta’s product range, there are ESPC bucket elevators, classified as fast elevators with centrifugal discharge with a single central chain.

The company produces ESPCs with a single row of buckets driven by a single gear wheel.

They are used for medium grain sized materials, <100 mm, and have a maximum lifting capacity of about 600 m3/h. This capability fulfils 80 – 90% of the current market demands.

For higher capacities, Gambarotta uses the ESPLV series of chain elevators. These have buckets connected to the two side chains, driven by two toothed wheels, and reach a lifting capacity up to 2000 m3/h with 1600 mm-wide buckets, at a speed of 1.6 m/s and an 80% filling factor. This is the most compact and cost-effective solution for large lifting capacities.

Figure 1. Drive station of ESPC B.E.

Figure 2. Single sprocket wheel for ESPC B.E.

The ESPC central chain bucket elevator boasts some unique chain and wheel drive characteristics.

The chain

The choice of the chain pitch was made by taking into consideration the technical issues presented earlier in the article, combined with the company’s extensive experience with the supply of chain buckets elevators.

These considerations and experiences led the company to adopt only two types of chain pitch: 1500 mm for smaller equipment, and 180 mm for the larger machinery, which enabled a maximum ascent speed of 1.6 m/s (96 m/min.).

Gambarotta’s goal was to reach the maximum benefit for its customers: achieving a low cost and long service life. The company chose a simple mechanical chain, which follows the standardisation base of the DIN 8167 regulations. It is also workable on machine tools by many manufacturers, to form the three characteristic elements of the chain: plates, pins and bushes.

Various sizes of resistant elements are provided to obtain chains with different breaking loads suitable for the chains of special elevators.

Other manufacturers use chains with special parts and expensive forged materials, which require specific moulds and equipment.

The considerable cost of these chains limits the production to a few models, to perhaps only 3 or 4. This sometimes means that elevators have to be equipped with an exaggerated chain, due to their cost.

Gambarotta Gschwendt determined some important parameters of the chains, including the thickness of the bush and the hardness of the contact surfaces subject to sliding:

� The bush is of the thick type. The hardened peripheral areas (internal and external) are thus separated by a tenacious interposed zone to withstand those dynamic loads, which cause undesired vibrations, due to the polygonal action mentioned above.

� The surfaces in contact between the pin and bush and between the bush and wheel teeth are heat treated in order to gain high hardness, and then wear-resistance for long periods.

To ensure a long service life, the chain is selected by comparing the real safety factor (ratio between breaking load and working load) with a minimum safety factor specifically calculated, according to the situation.

This minimum factor can change from elevator to elevator as required, starting from a common basic value, which is then influenced by the value of wear cyclicity (wear cycles per unit of time). The cyclical wear is due to the ascent rate

and the wheelbase parameters of that precise elevator; directly proportional to the speed and inversely proportional to the wheelbase. In a transmission chain, each link undergoes four wear cycles for each complete devolution: one at the beginning and one at the end of its contact with the upper and lower wheels. The cyclicity value is therefore maximised for low and fast elevators and is minimised for higher, slower elevators.

With this selection and with the geometric dimensions chosen for the chain, the specific contact pressure between pin and bush has low values, generally lower than 30 N/mm2, with a consequent increase in operating life.

Toothed control wheel

Gambarotta elevator chains are manufactured with a control gear, with interchangeable sections. Therefore, ESPC elevators also have a control gear wheel.

The main reason for this choice is that only the gear wheel can guarantee a slip-free transmission for all operating conditions.

It should be noted that the phenomenon of polygonal action happens on smooth wheels as well, where the real teeth are replicated by the points of support of the bushes on the wheel circumference.

During the operation of an elevator, possible slippage between the smooth wheels and the chain can occur.

This may be due to the pulsations caused by the dredging of the material or the possible discontinuous flow of material being fed into the base.

Furthermore, the smooth wheel system requires consistent chain tension to create the friction necessary to guarantee the transmission of motion from the wheel to the chain. This causes an unwelcome chain overload and an undesired increase in the load on the drive shaft bearings.

Some chains designed to work on smooth wheels, in addition to the bushings, also have the edge of the plates that rest, sometimes causing a flexure, which is not suitable for secure resistance.

The plates of a chain wound on a gear wheel, on the other hand, are always subjected to pure traction.

Finally, even the choice of the diameter of the drive wheel has an impact on the wear of the chain since it determines the magnitude of the friction angle between the pin and bushing which occurs at the beginning and end of the rotation of the chain on the wheel. A higher number of teeth, and therefore a larger diameter wheel, corresponds to a lower rotation angle, followed by lower wear intensity.

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NO x Catalyst High-dust Abatement

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