INDUSTRY NEWS
INNOVATION
BLAST FURNACES
FURNACE REPAIRS
www.furnaces-international.com September 2017
Contents
Editor: Nadine Bloxsome Tel: +44 (0) 1737 855115 INDUSTRY NEWS
Email:
INNOVATION
FURNACE REPAIRS
BLAST FURNACES
nadinebloxsome@quartzltd.com
2 - News Emission reduction 4 - 3-in-1 approach to dust, SOx and NOx
Production editor: Annie Baker www.furnaces-international.com
Measurement 8 - Accurate temperature measurement improves Holophane furnace
Sales/Advertisement production: Esme Horn Tel: +44 (0) 1737 855136
Environment 10 - An environment-friendly furnace
Email: esmehorn@quartzltd.com
Sales Manager:
Brazing furnace 15 - Lab based brazing simulation
Manuel Martin Quereda Email:
Innovation 18 - Atlas Machines
manuelm@quartzltd.com
Subscriptions: Elizabeth Barford
Furnaces 20 - Putting the efficiency into container glass furnaces
Email: subscriptions@quartzltd.com
Managing Director: Steve Diprose
Blast furnace 24 - Impact of cooling on blast furnace 27 - Powering India’s largest blast furnace
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Chief Executive Officer: Paul Michael
Furnace repairs 28 - Making the most of your furnace
Published by Quartz Business Media Ltd,
Company profile 32 - Veralia completes Euro 46 million VOA
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Quartz House, 20 Clarendon Road,
Health & safety 36 - Substitution of aluminium silicate wool products in the furnace industry
Redhill, Surrey RH1 1QX, UK. Tel: +44 (0)1737 855000. Fax: +44 (0)1737 855034.
Event preview 42 - The Surface Engineering and Heat Treatment Industry Conference & Exhibition
Email: furnaces@quartzltd.com Website:
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www.aluminiumtoday.com/furnaces/
Furnaces International is
Research & development 43 - Themserve commission research and development extrusion-billet casting facility
published quarterly and distributed worldwide digitally
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Š Quartz Business Media Ltd, 2017
Furnaces International September 2017
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Comment and News
SGL Group to sell cathodes, furnace linings and carbon electrodes business SGL Group has signed the sale and purchase agreement to sell its cathodes, furnace linings, and carbon electrodes (CFL/CE) business to funds advised by Triton. The two parties have agreed on an enterprise value (cash and debt free) of 250 million euros, which, after deduction of standard debt-like items (mainly pension provisions) as well as other customary adjustments, results in cash proceeds of more than 230 million euros. The final proceeds will be determined based
on the balance sheet at closing. The transaction is subject to customary closing conditions, mainly relating to antitrust approvals. Closing is expected in Q4 2017. According to SGL, "Triton seeks to invest in and support the positive development of mediumsized businesses headquartered in Europe, focusing on businesses in the industrial, business services and consumer/ health sectors. The 31 companies currently in Triton's portfolio have combined sales of
around 14.4 billion euros and around 89,000 employees. Following the closing of the transaction, approximately 30 employees in Germany and 600 employees in Poland, who are based at the two production facilities in Nowy Sacz and Raciborz, will move from SGL Group to their new owner, says SGL. The sale will result in a book profit of approximately 130 million euros in the current fiscal year of SGL Group.
Ovako opts for systems spray-cooled EAF modernisation plan Swedish steel producer Ovako has awarded Systems Spray-Cooled (SSC) the contract to modernise and increase safety on its Electric Arc Furnace (EAF). It will be the first Spray-Cooled roof in the Nordic region, the company claims, and will be located at Ovako’s bar, billet, tube, and rings facility in Hofors, Sweden. Ovako was first being exposed to SprayCooled technology at the European Electric Steelmaking Conference in Italy and has weighed the new technology against its current pressurised tubular roofs. The main concern
was implementing the technology with its environment (piping); otherwise, Ovako has been highly enthusiastic about the technology and, claims SSC, saw clear advantages for maintenance and safety. Because Spray-Cooled equipment operates at atmospheric pressure, the cooling water is not pumped across the area to be cooled. Therefore, the potential for high pressure, high volume water leaks is eliminated, the company claims. Under the contract, the new roof will be engineered to work with Ovako’s current furnace
set-up, as well as ‘futureproofed’ to integrate with planned furnace upgrades. To alleviate concerns about potential piping issues, the new roof will be engineered using state-of-the-art 3D laser scans of the current furnace and surrounding mill. According to SSC, the 3D laser scan will aid in the design, especially since the available drawings are 25 years old and are said to have discrepancies. It will also allow piping to be designed accurately for easy fitment and should greatly reduce or eliminate unforeseen issues in the process.
Comment
Welcome to the September 2017 issue of Furnaces International. This issue includes a host of features looking at everything from temperature measurement, innovations, energy efficiency, furnace repairs and optimisation. Even though my publishing background has seen my knowledge of industrial manufacturing improve (it’s still not quite up to scratch) it seems there is always something new to learn when it comes to furnaces. The majority of the articles included in this issue focus around furnaces used in the manufacturing of glass, aluminium and steel. However, I’d be interested to include more articles across future issues, which are dedicated to other areas of industry and put furnaces in the spotlight, so please don’t hesitate to get in touch if you’d like to contribute. Nadine Bloxsome Editor, Furnaces International nadinebloxsome@quartzltd.com
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News
NEWS IN BRIEF
Zippe successfully installs batch plant at Mexico’s Industria Vidreria de Coahuila (IVC) Zippe Industrieanlagen has successfully installed a batch plant for a 560tpd furnace at Mexico’s Industria Vidreria de Coahuila (IVC). German company Zippe implemented the project on a turnkey-basis and its scope of supply includes two cullet return systems for the new melting furnaces, F3 and F4. IVC is a joint venture of USbased glass manufacturer Owens-Illinois (O-I) and the brewer, Constellation Brands. The new building site is in the city of Nava, north Mexico, 30km from the Texan border in the USA. The plant will manufacture bottles exclusively for a directly adjacent brewery. Repairs start on Bedlam Furnaces Scaffolding has sprung up around an icon of Shropshire’s World Heritage Site, as a £1.2 million project is launched to save it. The Bedlam Furnaces in Ironbridge has been classed as being “at risk” by Historic England, and work has now begun to protect them for the future. Several severe winters and the exposed nature of the structure have caused the deterioration of the brickwork and hard cappings and the general deterioration in its condition. It is thought to be the last surviving furnace of its kind in the country. While Abraham Darby I came to Coalbrookdale in 1708 or 1709 to begin work perfecting the use of coke to smelt iron, it wasn’t until about two or three decades later that it took off.
Verallia invests €30 million in its largest glass furnace Verallia is investing €30 million on modernising its Azuqueca plant in Spain, to improve its standards of sustainable development. A new furnace and facilities were installed at the plant, including one of the world’s largest glass furnaces. The new equipment was inaugurated in the presence of Verallia’s main customers, suppliers
and local authorities at a ceremony led by Jean-Pierre Floris, President and CEO of Verallia (pictured). This latest-generation furnace is the upgraded plant’s flagship innovation. It is the largest the company has ever installed anywhere in the world. It is also more sustainable, as it emits less CO2 per metric tonne of glass produced.
With this new furnace, Verallia Azuqueca can produce two million containers a day (more than 500 jars a minute). During the event, JeanPierre Floris pointed out that “Verallia is continuing to invest with the longer-term future in mind while aiming to continuously improve quality, flexibility and productivity.”
Diamond Heat Treat acquires vacuum furnace to support IGT and aerospace industries Diamond Heat Treat recently purchased a TITAN® H6 vacuum furnace with 6-bar gas quenching to expand their capabilities and serve additional market sectors, including IGT and Aerospace. While Diamond Heat Treat – acquired by Calvert Street Capital Partners – already has three vacuum furnaces at their Rockford, Illinois, facility, the new furnace’s range of process capabilities allows them to better address key needs for
different markets. According to Mike Sobieski, CEO of the thermal processing strategy, “This addition of technical capabilities is in line with our strategy of partnering with family-owned thermal processing companies and then investing in both people and equipment to enable profitable growth.” One of Ipsen’s modular heat-treating systems, the furnace features a 36” x 48” x 36” (915 mm x 1,220 mm x 915 mm) work zone with a 3,000-pound (1,361 kg)
load capacity. This furnace is also capable of operating at temperatures of 1,000 °F to 2,400 °F (538 °C to 1,316 °C) with ±10 °F (±6 °C) temperature uniformity. Diamond’s purchase is consistent with Calvert Street Capital Partner’s strategy to partner with, support, and develop commercial heat treating manufacturers as described in a March 2017 interview with John Hubbard produced by Heat Treat Radio.
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News
Saudi steelmaker reaps benefits of Tenova DRI technology Hadeed Saudi Iron & Steel Company has signed a final acceptance certificate for the delivery, by Tenova, of a DRI-based furnace optimisation system for the Hadeed plant's Electric Arc Furnace 5. Tenova's i DRI technology project at Hadeed has already demonstrated its performance credentials by achieving a 1.42% yield increase, a 4.1% productivity increase, a 3.23% reduction
on electrical consumption and a 1.6 min reduction on Power on Time (PON). "As applied to the DRI process, the models are responsible to calculate the most important parameters used by the i EAF®control modules”, says Tenova, an international engineering company based in Italy. Working alongside the plant PLC, system performance was achieved through validation of
several fundamental outputs, including off-gas measurements using EFSOP technology; a downstream analyser; temperature and off-gas flow sensors; furnace and auxiliary service automation; process modelling for real-time mass and energy balance; chemical energy control and optimisation of oxygen lances; and DRI feed rate control.
Hotwork success in South East Asia Hotwork International has successfully completed a furnace project in Indonesia. The Swiss group completed furnace glass draining, furnace heat up and a cullet fill with expansion control at both PT Muliaglass’ float and container furnaces. A similar project with NSG Float Glass in Vietnam has also been completed.
A number of furnace heat-ups, furnace draining and other service projects in South East Asia were
completed by the group between Q4 of last year and this year’s first quarter.
Atmosphere and vacuum furnaces shipped Fifteen atmosphere and vacuum furnaces were shipped to customers in aerospace, commercial heat treating and MIM industries around the world during the second quarter of 2017, including China, Hong Kong, India, Japan, Saudi Arabia, and the United States. The shipments included:
� Two large, vertical (bottom-loading) MetalMaster® vacuum furnaces, each with a 120” (3 m) diameter work zone and 10,000-pound (4,500 kg) load capacity � Five standard TITAN® vacuum furnaces complete with PdMetrics® � Debind and sinter vacuum furnaces for the MIM industry
� ATLAS integral quench atmosphere furnace, which was delivered six weeks after order placement
In addition to these transactions, Ipsen USA of Cherry Valley, Illinois, delivered several custombuilt vacuum furnaces that will process parts for the aerospace industry.
NEWS IN BRIEF Oxy-fuel burner restores airfuel regenerative furnaces to full production Engineers at Air Products have commercialised an improved version of the company’s Cleanfire ThruPort oxy-fuel burner for avoiding downtime during repairs and extending the lifetime of air-fuel regenerative furnaces in glassmaking plants. The company’s original Cleanfire ThruPort burner was designed to introduce oxy-fuel combustion (using pure oxygen as the oxidant, rather than air) in air-fuel-fired regenerative glass-melting furnaces. The water-cooled ThruPort burners have a unique design (photo) in which two “nested” lances deliver oxyfuel (top lance) and staged oxygen (bottom lance) are controlled by a mechanism to control the proportion of oxygen between the two. “By separating (staging) a portion of the oxygen away from the main oxy-fuel flame, we can control the rate of mixing between fuel and oxygen in the flame,” says Mark D’Agostini, senior research associate at Air Products. “This leads to flame lengths that can be optimally tailored to the width of the furnace combustion space, and is also a mechanism for reducing NOx emissions.”
Primary fuel oxygen lance Tilt mechanism
Secondary staged oxygen lance
Air Products
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Emission reduction
Figure 1. Ceramic candle filter, 2m long.
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Emission reduction
3-in-1 approach to dust, SOx and NOx Matthias Hagen* discusses how the Ecopure CCF, a new combined DeDust, DeSOx and DeNOx process, has been used by a Chinese glassware manufacturer to combat excess emissions from its furnace. The technology means the glass manufacturer can confidently face today’s emission targets, as well as stricter goals that will be introduced in the future.
Dürr first deployed the Ecopure CCF technology for Libbey Glaswware (China) Co., a Chinese glassware manufacturer. It enables the company to comply with low emission limits. Another strength of this space-saving technology is its suitability for both new installations and retrofits. Due to TA-Luft 2017 – the new air pollution control regulations – this technology is also of particular interest to industrial companies in Germany. The draft bill of the new air pollution control regulations (Technische Anleitung zur Reinhaltung der Luft, or TA-Luft) is currently under discussion in Germany, and new emission limits are being formulated as recommendations. It may seem that these are only marginal changes to the systems, but for many industries the new limit values represent the starting point for considering acquiring additional equipment or implementing completely new exhaust air purification processes. The glass industry, among other industries, now needs to review the longterm suitability of existing technologies such as electrostatic precipitators. Industrial growth in China continues to outpace that of Germany. Many firms, including those in the West, are investing in new production sites. Although GDP is no longer heading skyward at astronomical speed, the rate of growth is still three times higher than in Germany. Pollution control in China cannot always keep up with such a fast paced
GDP growth – and it has not been able to do so yet, which is evident when one takes a closer look at the current practices of many permit authorities in China. These days it is difficult to operate production facilities without an exhaust gas treatment system, especially in highly industrialised regions. This was the case for Libbey Glaswware (China) Co., which was threatened with the closure of its plant in the greater Beijing area. Consequently, it was forced to install a suitable exhaust air purification system within a short period of time.
Technology selection In glass manufacturing, furnaces are used when the glass, made from various raw materials including cullet, is melted. These furnaces are heated by burners, which, despite a high level of energy recovery, still need large amounts of fuel (oil or gas). Because of the high temperatures in the glass tank, the exhaust gas flow contains high levels of nitrogen oxides (NOx), sulfur oxides (SOx), and dust. When planning the system, it was important to reliably comply with current limit values and preferably take future tightening of limits into account as well. Firstly, a solution using conventional technology was considered. This consists of an electrostatic precipitator followed by a catalytic NOx abatement system employing a selective catalytic reduction (SCR) catalyst. While this SCR process would meet current limits, it would not
meet future stricter dust emission limits. As an alternative, Dürr looked at using a filter with fabric hoses in combination with an Ecopure SCR. Since this type of filter can only be operated at a maximum temperature of 220°C due to the filter media used, the raw gas, which is hotter than 350°C, has to be cooled. For the subsequent DeNOx process however, the optimal temperature is around 350°C, which means the gas has to be heated again. The high investment and operating costs of a heat displacement system, that is the cooling/ heating option, represented an excessive overall additional cost, so this technology was rejected.
Solution Dürr’s Ecopure Catalytic Candle Filter (CCF) technology makes it possible not only to comply with emission limits without additional cooling or heating processes, but it actually keeps emissions at less than 50% below limit values. As a result, the Chinese manufacturer now considers itself well equipped for future tighter limits. With this technology from Dürr, three pollutants are eliminated simultaneously in one system, which translates into economic operating costs savings.
DeDust Filtering exhaust gases at high temperatures was already an available option for many years. Ceramic candle
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Emission reduction
Furnace off gas
NOx
NH2
NOx
NH2
H2O NOx NOx
NOx
N2 DeNOx
NH2
H 2O N2
Clean air
H 2O
Catalytic filter (CCF)
Figure 2. NOx conversion principle.
CaSO4/CaSO3 H 2O
SOx SOx Furnace off gas
DeSOx
SOx SOx
H2O
Clean air
H2O
SOx Catalytic filter (CCF)
Figure 3. Separation principle for acidic constituents in the gas, using SOx as an example.
filters were used ten years ago in an exhaust air purification system at a hazardous waste incineration plant. These candles are made from ceramic fibres that can withstand temperatures of up to 900°C (Figure 1). Since the filter wall is much thicker in comparison to fabrics, these filters are rigid. This results in a long service life, as the deformation during cleaning, via a burst of compressed air which causes wear in fabric filters, does not occur. The filter’s rigidity means that a permanent filter cake forms on its surface. This contributes to better filter performance and much lower cleaned gas values, especially for superfine particulates.
DeNOx
In the established SCR process, nitrogen oxides are removed via a reaction between injected urea or aqueous ammonia with NOx. Because of the catalyst, this reaction takes place at a relatively low temperature of 350°C. Ecopure CCF filters are coated with this catalyst material. The candles therefore perform the same function as the coated ceramic honeycomb in an Ecopure SCR, another Dürr exhaust air purification system. The doping of the fibres with catalytically active centres on their surface proves to be advantageous in this case. Unlike in conventional catalyst honeycombs, the omission of the gas phase helps to improve the filter’s performance (Figure 2). The catalyst thereby is located on the
inside of the filter wall where it is dustprotected. The usual aging due to the clogging of pores and reduction of active surface area doesn’t happen.
allows space-saving installation within existing production facilities (Figure 4). The high efficiency of the individual processes delivers maximum separation efficiencies for all types of pollutants, meeting the latest requirements of the forthcoming TA-Luft 2017 regulations particularly in respect of dust and nitrogen oxides. Integrating the three individual processes into the Ecopure CCF system means lower maintenance costs and reduced space requirements, which results in lower operating costs. The 3-in-1 technology has been well received, particularly in overseas markets, and now it has been included in the official draft of the VDI 2578 standard in Germany.
Contact *Global Customer Director, Dürr Systems, Germany www.durr-cleantechnology.com
DeSOx
Sulphur in many processes exists mainly as SO2, which may be separated using wet or dry processes. With low pollutant concentrations, dry processes have become the preferred choice over highly efficient wet processes, due to their lower life-cycle costs. This technology is based on the reactivity of a sorbent such as calcium hydroxide (Ca(OH)2) with acidic constituents in the exhaust gas such as SO2, HCl and HF. In many applications, the technology described above has proven effective both with electrostatic precipitators and with fabric filters. For the desulphurisation process to achieve good separation efficiency, a temperature of up to 180°C and sufficient moisture are required (Figure 3). At higher temperatures, however, the reactivity of the calcium hydroxide decreases at first, before rising sharply again from about 300°C upwards. This selective temperaturedependent behaviour makes the use of calcium hydroxide particularly suitable for separating acidic constituents from exhaust gas in a temperature range that is favourable for the Ecopure SCR DeNOx process mentioned earlier.
3-in-1 technology As all three processes are combined in one unit, the setup is compact and
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Emission reduction
Figure 4. Ecopure CCF for a glass manufacturer.
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Measurement
Accurate temperature measurement i
French glass lighting solutions provider Holophane has implemented Ametek Land’s Near Infrared Borescope (NIR-B) Glass, a thermal imager, at its plant in northern France. It is reaping the benefits by accurately measuring the temperature within its glass melt tank, reports Mark Bennett*. Holophane has produced and transformed glass for technical applications, specifically glass optical components for automotive lighting since 1921. When the company rebuilt the 33m², 85-tonne, end-fired regenerative furnace in 2014 at its Les Andelys plant in northern France, Holophane wanted to replace its existing visual camera system with new thermal imaging technology to provide continuous on-line temperature measurement. Ametek Land recommended its Near Infrared Borescope (NIR-B) Glass with an auto retraction system, which can operate
at extremely high ambient temperatures adjacent to the glass melt tank, while providing real-time thermal images and temperature data from inside the tank (Figures 1 and 2).
Demanding environment The NIR-B Glass was developed specifically to operate in the demanding environment of a glass melt furnace. It features an integral cooling system as well as a specially designed air purge that keeps the 90° lens clear of contaminants to provide 24/7 data to the plant. Even at high furnace temperatures, it
delivers high-definition (656 x 494 pixel) thermal images to generate accurate, traceable temperature measurements in the 1000 to 1800°C (1832 to 3272°F) range. This solution is suitable for float, container, borosilicate, fibre and speciality glass furnaces. At the Les Andelys plant, the NIR-B Glass was installed above the throat of the tank in a location with a high ambient temperature of more than 60°C. Ametek Land recommended a heat shield below the borescope for this installation to reduce the heat coming directly from the throat.
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Measurement
ent improves Holophane furnace
Figures. 1 (left) and 2 (right): The Ametek Land NIR-B Glass, installed on Holophane’s 85 tonne furnace for speciality glass.
The solution also incorporated an autoretract mechanism that provides the instrument with additional protection with instantaneous automatic retraction from the furnace wall in the event of a failure of air purge, water cooling and mains power or if there is an overtemperature condition detected at the borescope tip. Among the borescope’s major benefits to Holophane is its ability to provide a 90-degree wide-angle thermal image with clear visual definition, combined with a continuous temperature readout. This helps the operators maintain furnace control and therefore optimise productivity. The NIR-B Glass has been used to continuously monitor the optical profile (temperature profile) along the furnace walls to optimise the location of hotspots and to monitor areas of the crown for high temperature with alarms to prevent overheating. Ametek Land’s Cyclops optical pyrometer was used as the basis for the technology incorporated into the
NIR-B Glass – hence the reliability of the temperature measurement. With more than 324,000 available temperature measurement points in the field of view, the borescope can also be used to monitor for drift in crown roof thermocouples by assigning emissivity values for a specific or range of data points. The wide-angle thermal image provided by the NIR-B Glass has helped operators at Holophane to monitor glass batch line and batch flow from the charging end up to the throat. With configurable outputs, it is possible to create an alarm if the batch crosses the desired melt line. By using an area function in the Land Image Processing Software (LIPS) Holophane can monitor foam.
Alerts The NIR-B Glass also alerts the operator to any air leakage or ratholes/cracks in the melt tank as well as corrosion areas near the chargers or burners. The instrument gives an operator the option to see the difference in temperature gradients when the burners do not operate correctly, which may be an indication that the burner needs to be cleaned, re-aligned or air-to-gas ratio adjusted. Emmanuel Declerck, Industrial Director at Holophane said: “The borescope helps greatly to maintain the right quality
flames with good turbulence and shape, therefore optimising the quality of our end products along with our energy usage. The images provided by the instrument are particularly important at the exit, near the throat, where temperature profiles are routinely monitored by operators.” Combing video images with continuous real-time temperature data, has allowed the NIR-B Glass to replace Holophane’s traditional CCTV cameras and provide a full optical profile. The NIR-B Glass solution offers Holophane’s plant operators the ability to see cold spots from air leaks in the structural refractory, making it easier to detect cracks and enable prompt repair. Its operators can also visualise flames to optimise the flame patterns and thermal efficiency and overlay thermal profiles across the crown and along the melt for more accurate batch line control, production throughput optimisation and batch transit time recording. “We are confident that as a direct result of implementing Ametek Land’s solution, we are achieving significant savings in energy usage,” added Mr Declerck.
Contact *Glass Sector Manager, Ametek Land, Dronfield, UK www.landinst.com 9
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Environment
An environment-friendly furnace ArcelorMittal Hamburg’s decision to choose an environmentally friendly, high performance/low emissions walking beam furnace for 16.5 m special steel billets could offer up the benchmark for quality and operational costs in long products heating systems. By A Biliotti* and D Garassino** A Danieli Centro Combustion (DCC) furnace equipped with a control system supplied by Danieli Automation has been chosen by ArcelorMittal Hamburg. The furnace has been designed for safe and reliable operation and offers a thermal profile that achieves optimum heating efficiency thanks to improved convective heat exchange in the furnace’s unfired zone. Proprietary flameless burners, supplied by DCC, reduce the environmental impact of the equipment. The ‘state-of-the-art’ equipment, coupled with Danieli Automation’s fully automatic control logic, will allow the most flexible reheating practices to match production mix requirements at the plant for low and medium carbon, bearing, spring and cold heading steel. During the next shutdown period, the existing mill will be connected to the new furnace and this will allow the steelmaker to increase the weight of coil to 2 tonnes and improve productivity and efficiency at the special steel wire rod mill on-site.
A walking beam furnace for billets The walking beam furnace supplied by DCC guarantees a production rate of 175 tonnes/hr at a discharging temperature of 1,250°C. The furnace can achieve a 235 tonnes/hr production capacity meaning that ArcelorMittal Hamburg can increase production going forward by acting on the installed thermal power. The furnace can process a wide range of products including 140x140 mm billets with lengths ranging from 9m to 16.5 m. Products are charged into the furnace in a single row with processed steel grades ranging from low carbon to more valuable metals such as 100Cr6, 34CrMo4, 42CrMoS4, 30NiCrMo3. The furnace has six combustion control zones which include two types of burners (frontal for the walls and
radiant for the roof designed using Ultra Low NOx technology) with different heating capacities according to zone requirements. This configuration ensures the best heating quality and the fastest response time when a change in production is required. Frontal MAB burners (Multi Air Burners) are designed to operate with PHL (Proportional High Low) control logic to create optimal conditions at all operating levels. This is achieved by cyclically turning the burners on and off to reduce thermal flow according to requirements. This results in higher process heating quality and easier furnace management. MAB and radiant burners rely upon flameless technology to reduce NOx emissions, while offering a more uniform heating in all burner areas. DCC will supply ArcelorMittal Hamburg with all the necessary handling equipment upstream and downstream of the furnace from billet charging on the stock yard to the first stand of the rolling mill, including pawl tables, transfer devices, weighing and measuring systems, reject devices, diverter and pinch roll.
To minimise material and energy loss, DCC’s and DA’s combined technology ensures that no billet is rejected in the case of mill cobles: along the 90-metre long rollerway between furnace and pinch roll, machines and logics have been designed to have constant control of billet temperature, and in case of mill stoppage, up to two billets can be charged back in the furnace.
Flameless burners New burner design has been greatly influenced by national and international norms and regulations concerning environmental protection: a modern burner guarantees optimal efficiency while complying with ever-decreasing limits on pollutant concentrations in waste gas exhausts. Furnace efficiency is generally increased by pre-heating combustion, a technique that recovers part of the heat from the exhaust fumes, while increasing flame temperature. Unfortunately, combustion temperature amplifies NOx emissions. For this reason, over the past few years innovative combustion technologies
Figure 1. Discharging of a billet
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Environment
have been developed, with the aim of maintaining high burner efficiency and reducing polluting emissions into the environment. Two of these technologies are “staged combustion” and “flameless combustion”. DCC’s R&D department has been particularly active in this field, with theoretical simulations and experimental campaigns (research furnace exclusively dedicated to burner testing), which have enabled a complete range of highperformance burners to be developed. The main advantages of flameless combustion are: • Significant reduction of polluting emissions • Uniformity of flame temperature, therefore higher product quality • Increased furnace efficiency • Reduction of combustion noise. DCC has developed a new generation
staged combustion (below self-ignition temperature) and flameless combustion (above self-ignition temperature). The fundamental concept, which is common to both techniques, is to minimise temperature peaks and oxygen presence in the combustion reaction by diluting the reacting gases with those that have already been combusted. Staged combustion is performed by injecting combustion air in different steps, thereby obtaining a primary combustion zone which is rich in fuel (reducing zone), and a secondary combustion zone rich in air (oxidising zone), however highly diluted by fume recirculation; this allows a gradual and complete combustion, avoiding the coincidence of high oxygen content and high reaction temperature. The system is based on the specific geometry of the air diffuser inside the burner, which leads the primary and secondary air flows to
Figure 2. General Overview of a walking beam furnace
length (Figure 3). Once the furnace temperature is above the self-ignition temperature, the flameless combustion mode can be activated, by switching gas entry to a separate gas lance while keeping the same air feeding. The special fluid-dynamic design and the high gas and air speeds further increase flue gas recirculation and cause an expansion of the reaction process to a larger volume; the low oxygen content in the reaction ensures a diluted combustion that makes the flame invisible (Figure 4).
Burner performances Figure 5 shows experimental measurements of NOx emissions as a function of furnace temperature and air excess (evaluated in terms of O2 content in the fumes); the three curves in the upper left refer to the staged combustion mode, while the three curves in the lower right refer to the flameless mode. The best NOx performance is obtained by operating the burner in the green areas: staged combustion is used for heating up the furnace, and in pre-heating zones working at low temperature; at higher temperatures the burner is switched to flameless combustion, which cuts emissions by 50%. Another advantage of the DCC flameless burner is increased uniformity of furnace temperature. This implies an improved temperature uniformity in the furnace charge, and higher quality final products. The burner has proven to be extremely flexible and can be used either with high calorific value fuels (such as natural gas) or with low calorific value fuels; combustion air can be pre-heated to temperatures in excess of 500°C, in order to increase combustion efficiency and overall furnace performance.
Optimisation model
Figure 3. Staged combustion; semi-visible flame
burner that guarantees extremely low NOx emissions and uniformity over the entire operational range and for any temperature of the furnace chamber. This is achieved by using two different combustion techniques:
Figure 4. Flameless combustion; invisible flame
the different combustion zones, with the appropriate speed and angle. This type of staged combustion permits a substantial reduction in NOx emissions and the high recirculation factor reduces the temperature gradient along the flame
Danieli Automation (DA) Furnace Level 2 is a software package consisting of several modules that work in real time in order to optimise the reheating process. They can be grouped into the following tasks: • Material tracking and communication with other systems • Process Models • Process Control • User interface The use of instruments to measure billet temperature in a furnace has always been debated. As the noisy environment
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Environment
120 NOx [ppm] Semivisible flame Double air staging combustion 60
Visible flame Flameless combustion 0 800
9800
Standard 1% O2
Standard 2% O2
1000
1100
Standard 3% O2
Flameless 1% O2
1200 Flameless 2% O2
1300 Flameless 3% O2
Figure 5. NOx emissions (ppm), measured with natural gas firing
Figure 6.Level 2 architecture Communications
Continuous emissions monitoring
Models - Product - Chamber - Metallurgical
- Other automation systems
- Entry area - Exit area - Furnace area
Control loops - Static - Dynamic
User interfaces
Tracking Level 2
state of the furnace is not observable until the end of the process, when it is too late to get any correcting action. The first aim of MPC is to automatically calculate furnace set points in order to minimise the difference between the mean product temperature and their heating practice. Heating practices describe the heating rules for each product and are open to process engineers, who can manage them in order to achieve the desired results, like fuel consumption saving or following special heating strategies (low decarburisation, alloyed steels, …).
- Workstation - Mobile - Web
A dedicated system for combustion monitoring installed in the chimney provides online fumes Typical monitored emissions are nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2) and sulfure oxides (SOx). These values can be stored by a trending system (Danieli Automation HMI server and/or Danieli Automation Fast Data Analyser) and can be used for certification according to the regulation in force.
Quantity, quality and quickness DA’s design concept is based on the Q3 formula: • Quantity • Quality • Quickness
Figure 7. Typical online overview page of Level 2 client application
makes a direct measurement very difficult, a mathematical model of the heating process is used as a virtual sensor and, in the same time, it is applied in the set-up of the control strategy as explained below. It is based on a finite difference model in order to evaluate material bulk temperature and uniformity. All the relevant thermo-physical characteristics of steels and interactions within the furnace chamber and among billets are considered for the calculation of temperatures when the mathematical
model is used as virtual sensor. The furnace model is used for the control strategy based on a Model Predictive Control (MPC) technique. It uses a feed-forward algorithm to estimate furnace behaviour from its actual condition and evaluates the proper actions needed to get the desired product output, while fulfilling constraints and optimising furnace performances. In fact the heating process is slow and requires the right amount of energy and time to be given to the products. In addition the
Such an approach, fully in line with the Industry 4.0 paradigm, introduces the data-driven philosophy exploiting the hidden value of the usual parameters for process control. In fact, even if obtaining a quantitative estimation of consumption savings is immediate, additional constraints can be addressed by applying online and real time multiobjective techniques. In this context, DA’s online control system maximises furnace efficiency and directly acts on environmental impact and other aspects. Proper combustion ensures that emission limits are met and production yield is increased as a consequence of reduced weight loss due to scale formation. Quality is commonly considered a competitive factor. Danieli Automataion Level 2 focuses on achieving the temperature and uniformity required by a rolling mill. This is the first step that is necessary to obtain the desired mechanical properties at the end of the overall process. Quality assurance is made possible by
12 Furnaces International September 2017
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Environment
a reporting system that provides all the necessary data for periodical evaluation of the furnace, such as fuel-specific consumption, temperatures, ratios, and analysis. The combination of adaptive mathematical models and the feedforward strategy allows the MPC to maintain consistent behaviour during stationary conditions and a quick reaction to transitory productions. In the first instance it allows the steel maker to balance furnace loads according to installed heating power. In the latter case, it anticipates furnace behaviour according to the incoming production, optimising transitions of productivity (full to slow production and back), product geometry, charging temperature and steel quality.
Fumes
Trends & monitoring (PC/server)
Probes
Figure 8. Continuous emission monitoring system.
Analyser
Acquisition (PLC)
Figure 9. An example of furnace consumptions in the long run
Getting value from data
Conclusions DCC has proposed a new generation of furnaces that integrate the sharp edge of combustion technology with the integrated design of both the process and environmental aspects. In this context, the staged/flameless burner is yet another example of DCC’s focus on innovation. The company’s chief objective is to provide leading-edge technology, allowing high product quality, lower
30 Specific consumption [Sm3/t]
From the 1960s automation systems and equipment gained in popularity in the steel industry. Today all steel plants are equipped with a series of complex systems that monitor relevant data and control processes automatically. Danieli Automation Q3 Intelligence, a business intelligence platform dedicated to the metallurgical production process, can improve things further by merging, storing, processing and evaluating data from, say, Danieli Automation Furnace Level 2, and transforming it into knowledge. In a scenario where smart systems are applied more and more to industry, Q3 Intelligence Analytics allows exploration and investigation of past process performances to gain insight and drive process design and planning, via advanced statistical methods and predictive modeling. Q3 Intelligence Analytics can help answer questions such as “why is this happening?”, “what if these trends continue?”, “what will happen in the future?” (predictions), “what is the best that can happen?” (optimisation).
25 20 15 10 5
Fe 55
0 0/100 101/200 101/200 201/300 301/400 401/500 501/600 601/700
Fe 41
Fe 50 Fe 45 Fe 41st
Fe 37 Fe 34 >701
Steel grade
Charging temperature [°C]
Carbon steel
T-disch T-target
RM lastpass
Figure 10. An example of correlation between furnace target, model temperature and measured temperature at rolling mill
operating costs, trouble-free operation and ever-increasing environmental friendliness. Danieli Automation Level 2 is a robust control system which allows users of the DCC furnace to achieve uniform operation, process cost savings and product quality. A careful analysis of its performance indicators can also lead to
product flow optimisation and improved performance of the entire plant.
Contact * Danieli Centro Combustion, process engineer ** Danieli Automation, design engineer – process Control Systems 13
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Furnaces International September 2017
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, Tomorrow s Technology Today
E L E C T R H I G I C D H F U S H V Q H R R N P F O L A C O R D E T E I B U E H R L B B E A N E L E R T E S R S H C Y S M O M T T E D E A R M L L O E N I N U G G B I N O E E I R O I N T S G T 1
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Why bother scrabbling around for a solution? GLASS SERVICE
A Division of Glass Service
Brazing Furnace
Lab based brazing simulation Aluminium is the preferred material for both engine cooling and air conditioning in cars. This is due to its unique combination of strength, corrosion resistance and recyclability. Of course, it plays an important part in vehicle lightweighting too. As a result, there have been numerous developments in the aluminium brazing process, the flux chemistry and in system design to make its use more cost-effective. Adam Nadin* explains
Figure 1. Innoval’s laboratory brazing furnace
Controlled atmosphere brazing (CAB) is the primary process for manufacturing aluminium heat exchangers. Consequently it is undergoing continuous development to meet the challenges of today’s OEM’s. The CAB process requires accurate control of the thermal cycle from room temperature to >600°C in an inert gas atmosphere. However, the continuous industrial CAB furnaces are not suitable for running trials to optimise the process conditions for new materials and designs. Innoval does a lot of work for aluminium heat exchanger manufacturers and their suppliers. This is either an R&D project or an investigation to get to the bottom of a production problem. To do this we’ve developed several techniques to establish the surface condition of sheet products. For clad products, oxide film thickness and carbon residue are two key factors in
brazeability. We are able to measure both of these using our FTIR and Leco carbon analyser. However, we have found that relating these to brazing performance with a practical method is crucial to understanding the balancing act between oxide, carbon and flux levels. After reviewing all ‘off-the-shelf’ options for an aluminium brazing furnace suitable for experiments in the lab, we
decided to manufacture our own, Figure 1. We wanted a glass tube furnace that would meet our experimental needs for characterising and testing brazeability.
Table-top aluminium brazing furnace Our brazing furnace bridges the gap between the theoretical brazeability based on oxide and carbon results, and
Figure 2. Example of a post brazed angle-on-coupon sample with full fillet formation
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Furnaces International September 2017
Aluminium International Today Directory
Glass International Directory
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07/09/2017 12:20
Brazing Furnace
Figure 3. First image shows a uniform ‘good’ braze. The second shows over braze resulting in localised core erosion (arrowed)
industrial trials. We can program it to run an almost infinite number of braze profiles in an inert gas environment. We use nitrogen gas with certified levels of oxygen as a contaminant. We can also use it to assess the impact of metallurgical properties like microstructure and grain structure on the brazing process. We do this using a simple angle-on-coupon test specimen. It’s also possible to evaluate other material parameters such as the cladding alloy chemistry, clad ratio and surface condition of the clad alloy, together with flux type and flux load. The tube furnace has a viewing window for in-situ video monitoring of the clad melting and fillet formation process. This provides an insight into the critical events which occur during the brazing cycle.
How we use our furnace During brazing, the balancing act between time and temperature is critical to achieving a good brazed product, assuming the surface chemistry is favourable. For example, it may seem possible to reduce the number of rejects by using a longer dwell time at the peak temperature of the braze cycle. The example in Figure 3 shows two identical AoC samples of a tubestock prepared with the same flux load. Both
If the over brazing shown here had occurred on a heat exchanger, the manufacturer could expect to see a significant reduction in the strength of the tubes due to the reduction in the cross sectional area. There could also be a reduction in corrosion resistance depending on the alloys used. The image on the left shows a good uniform brown band** region which is typical of long life alloys. However, the image on the right has no perceptible
The test pieces During brazing we use an angle-oncoupon (AoC) test piece as a standard, Fig ure 2. This compromises a clad product as the coupon and a 3003 alloy for the angle, which represents the tube and fin found in heat exchangers. These are, of course, customer dependant and we can vary both. The coupon is usually coated with flux. We raise the angle with stainless steel wire to make it harder to form a complete fillet.
experienced the same temperatures during a braze cycle. However, the sample on the right had an extended dwell time at peak temperature. This has resulted in severe erosion of the core alloy of the tubestock, and has eroded a great deal of the 3003 angle.
brown band formation, and would therefore have decreased resistance to corrosion.
Contact *Materials Technologist, Innoval Technology Limited, UK
**The ‘brown band’ forms during brazing. It consists of densely precipitated particles containing Al, Mn and Si. This band is typically a few tens of microns thick at the surface of the core adjacent to the cladding layer. The brown band is responsible for corrosion resistance of the clad side of the brazed product.
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Innovation
18 Furnaces International September 2017
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Innovation
Improving steel mill furnace rolls reliability US-based Atlas Machine & Supply presented ESTAD delegates with new methods for improving the reliability of steel mill furnace rolls utilised in the manufacturing process. The third annual European Steel Technology & Application Days (ESTAD) convention held in Vienna, Austria, 26-29 June. Making the presentation on behalf of Atlas was Jeremy Rydberg, vice president of the company’s corporate development group and a recognised authority on advance welding and inspection techniques. The inspection and welding process, developed at Atlas and claimed to be unique, significantly increases the life of industrial rolls by utilising proprietary welding and phased array ultrasonic testing methods. The advanced techniques produce a level of weld quality and consistency that was previously unobtainable, according to Rydberg. According to Atlas, achieving such a high-quality result is seen as crucial to keep industries in production. The process significantly reduces the risk of unplanned outages caused by failed rolls that can easily cost a manufacturer in excess of $750,000, it is claimed. Atlas’ advanced process for increasing the life of steel furnace rolls is also transferable to other industries, according to Rydberg. “This is an advanced welding and inspection technique that can be used in any industrial application that utilises temperature-resistant stainless steel,” he said. The process can also be utilised by power generation, nuclear, oil and gas, and petro-chemical companies. For further information, log on to www.atlasmachine.com
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Furnaces
Putting the efficiency into container
Container glass furnaces are fundamentally inefficient, believes Richard van Breda*, with half of the energy supplied to a furnace being wasted. Here he discusses how there needs to be a focus on optimising energy, with the answer being smaller, more agile and efficient furnaces rather than the huge furnaces currently in fashion with the industry.
The heart of a container glassmaking plant is the furnace. It is where glass is created and is where the magical transformation happens where silica sand is converted into glass through the addition of vast quantities of heat energy. In the world of container glass, the furnace is the area where a large part of the costs of making glass bottles is concentrated. Firstly, there is the large capital cost of the furnace complex, which is the single most expensive part of a container glass plant. Secondly there are the running costs. Energy is a major cost driver in container glass and most of the energy is used in the furnace.
It appears certain that energy costs are going to rise. Forbes reports that “The International Energy Agency (IEA) projects a 75% increase in oil prices by 2020�. This is a commonly held view among the energy commenters and forecasters. So what does this mean for operators of container glass furnaces fuelled with traditional oil and gas derivative fuels? When one examines the cost drivers in container glass, energy quickly appears near the top of the list, commanding between 12 to 20% of the cost structure. In some very high energy cost regions this amount can reach the 25% mark. The
cost of glass containers is heavily linked to energy costs and prices. Glass containers will always be regarded as the premium packaging medium, and as a result at the high-end market level there will always be a demand for a fancy glass bottle for a premium product. However, in the mass market where there is signiďŹ cant price sensitivity and price pressure, glass has to compete with other lower cost packaging solutions such as PET and cans. While both of these products also have cost structures linked to energy, they come under less pressure from increased energy costs when compared with glass.
20 Furnaces International September 2017
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Furnaces
r glass furnaces
certainty, stability and predictability for a period into the future. This makes setting pricing and achieving budgets possible. It would be reckless to view hedging energy costs in the glass industry as a way to make money. Hedging smooths out the long-term price change trends, but does not mitigate the overall price trends in the long run.
Improved furnace efficiency The second option of using less energy per tonne of glass produced appears to be obvious. Furnace designers and builders have invested significant efforts in designing furnaces that are more fuel efficient. This has been achieved by improved heat recycling through regenerators or recouperators. The quality of the furnace refractories and insulation has improved over time, however as the quality improves generally so too does the capital cost increase. The size and the scale has increased, which has made the furnaces more efficient. Today large furnaces of around 400 to 450 MT of glass per day offer some of the most efficient sizes. Larger furnaces means more efficient glass melting and hence lower production costs, but it can mean reduced flexibility. Think of a scenario where a glass plant installs three 450 MT per day furnaces, one for amber, one for flint and another for green glass. The resulting output is in the region of 440 kMT per annum of good glass. There are not many regions in the world that can economically support glass installations of that scale. So, while the desire for energy efficiency calls for larger furnaces, the demand flexibility insists on smaller for flexible furnaces – and herein lies the paradox.
Alternative energy sources Energy price pressure
Energy hedging
Glassmakers are very conscious of the energy price trends and it is a subject that keeps them up at night. The focus quickly moves on to how to control energy costs, as this is a major driver of the overall cost structure of glass containers. There are three obvious solutions: the first is controlling the costs through financial hedging; the second is to simply reduce the amount of energy used per tonne of glass produced; and the third is to find an alternative source of energy which is not expected to rise.
Financial energy hedging is a well-used methodology that has been used for many years by both the glassmakers and the large glass container buyers to set and lock the price of energy. This methodology provides the ability to fix the price of energy for a fixed period of time – but this privilege comes at a cost. From time to time the hedge may beat the market. When this happens it is usually more luck than skill. Over the long-run a well-executed hedging programme is likely to follow the market rather than beat it. Therefore, hedging should be seen as a methodology of providing price
Decades ago when there were still pockets in the world where electricity was available in abundant supply and at cheap rates, it was common to find electrical glass furnaces in place for large scale production. South Africa was a good example. Electrical furnaces are still seen, but mainly for small installations. Electricity has become expensive and its use has been substituted by furnace oil and natural gas, which offer lower cost primary fuel solutions, although it is also true that the use of electrical boosting is commonplace to optimise the gas and oil fired furnaces. Oxy fuel furnaces have made their debut in some regions with high cost energy
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Furnaces
Typical energy flows in a container glass furnace. Fuel source (6.5 to 7 GJ) Heat air 1.4 to 1.5 GJ Energy input (4.8 to 5.0 GJ)
Lehrs 0.35 GJ Forehearts 0.35 GJ Compressors, Fans etc 1.2 to 1.3 GJ
Furnace (6.2 to 6.5 GJ)
Stack 1.1 to 1.3 GJ
Hot waste gas (2.5 to 2.7 GJ) Furnace losses 1.2 to 1.3 GJ Regeneration Melting glass 2.5 GJ
costs such as Italy. But their application is limited and requires complex and expensive oxygen processing plants. These furnaces also have the additional advantage of lower emissions. With the advent of renewable electricity generation, solar and wind, combined with the improvement in energy storage and battery technology, could we see the return of electrical furnaces?
Inefficient Container glass furnaces are fundamentally inefficient. In the container glass industry it is accepted that to make glass bottles it requires between 6 and 7 GJ of energy per metric tonne of glass produced. Of this, only half of this energy is actually used for a useful outcome and the remaining energy is lost and wasted. However, when one looks at the real useful energy that is used in the process, one realises how inefficient a glass furnace really is. Chemistry dictates that about 2.6 GJ. of energy is required to melt batch and create glass. We also know that about 0.35 GJ is required for the forehearths and lehrs respectively. A further 1.2 GJ is lost as heat from the furnace. Approximately 2.5 GJ of energy is then pumped out of the furnace as hot exhaust gas. Fortunately, just over half of this heat (1.4 GJ) is recaptured in the regenerator or recouperator and sent back into the furnace. The other 1.1 GJ of energy is pumped into the atmosphere via the stack. Therefore, of the 4.5 to 5 GJ of energy that is supplied to the furnace, less than half is used to melt glass. The remaining energy is lost and wasted.
Given the high energy cost and the fact that the majority of the energy is wasted, surely there needs to be a focus on optimising this?
Possibilities for improved furnace performance The obvious place to start is to use the low grade heat expelled through the stack to generate steam, electricity generation and even desalination of water. However, this comes with substantial capital investment. The use of new techniques such as submerged combustion may hold some opportunity to optimise the combustion and the amount of energy required for the processes. Fundamentally, is it possible to reduce the amount of lost heat?
Furnace life Apart from the high energy costs associated with the furnace, the furnace is also an expensive piece of capital equipment. A new large container glass furnace can cost upwards of $10 million. The life of the furnace is limited and companies are glad if they get 10 to 12 years life out of the furnace. This leads to a large depreciation charge. The glass markets are calling for more bespoke bottles, with a wider range of colours and more complexity. All this calls for smaller and more agile furnaces that can support short runs and faster colour changes. Innovations such as forehearth colouring, and post process firing and conditioning go some way to achieving increased flexibility. However, the associated costs constantly inhibit their
wider commercialisation. The industry has focused on making larger furnaces, chasing the increased efficiency of larger furnaces. But the market is calling for smaller and flexible furnaces. Many markets in the world simply cannot support the large furnace configuration. In pretty much every country in the world there is a market for beverage or food production requiring the use of glass bottles. However, there are many countries where the glass market simply cannot support the scale of the new modern day efficient glass furnaces – a 450 MT per day furnace produces more than 100 kMT of glass per year. Therefore, it is little wonder that many countries in the world simply do not have local container glass manufacturing. Surely there is a need to develop a more agile, smaller scale efficient glass furnaces, that will allow for the proliferation of glassmaking facilities locally. This will have the effect of creating more flexibility, lower cost glass, and importantly more accessibility. This will ensure that glass remains relevant in the mass market as the packing solution of choice. Richard van Breda has extensive experience in the container glass world, manufacturing, recycling and buying container glass. He operates as an independent consultant to the packaging industry and is based in Switzerland.
Contact Richard van Breda, Independent Consultant, Switzerland Email: richard@richardvanbreda.com
22 Furnaces International September 2017
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, Tomorrow s Technology Today
E L E C T R H I G I C D H F U S H V Q H R R N P F O L A C O R D E T E I B U E H R L B B E A N E L E R T E S R S H C Y S M O M T T E D E A R M L L O E N I N U G G B I N I C O E E U K I R O L T I N S D G T 1
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When FIC can supply all of your glass needs
All-electric furnaces Electric boosting Electrode holders - High 'Q' - Maxi 'Q' Bubbler systems
www.fic-uk.com +44 (0) 1736 366 962 , The World s Number One in Furnace Technology
FIC (UK) Limited Long Rock Industrial Estate Penzance Cornwall TR20 8HX United Kingdom
GLASS SERVICE
A Division of Glass Service
Blast Furnaces
Impact of cooling on blast furnaces The life of the refractory lining, and the type of cooling system employed, in a blast furnace has a major influence on campaign life. By improving the method of cooling the lining life can be prolonged which leads to increases in campaign life and so a reduction of down-time for furnace repair, so improving productivity and, therefore, decreasing the unit cost of the hot metal. By S Sudhir, RR Kumar, RK Singh, VK Jha, BK Das and A Arora*
Lining life, cooling system and operating practice all have a major influence on the campaign life of a blast furnace. By improving the method of cooling, lining life can be prolonged, which will lead to an increase in the campaign life of the furnace. This facilitates a reduction of down-time of the furnace leading to a decrease in hot metal cost. The improved process efficiency in blast furnace operations combined with ever larger furnaces has increased the heat flux with a consequent requirement for greater levels of cooling to ensure a long shelf life. The heat flux has a major influence on blast furnace operation, optimum heat flux being required for smooth furnace operation. Heat flux is thus used as a tool to set the burden distribution to optimise the use of the furnace gas. The traditional function of the cooling elements and water cooling circuits is the protection of the shell. To achieve this goal the cooling system must remove sufficient heat from the refractory lining. The cooling water circuit must also keep the wall temperature of the cooling elements, plates or staves, within prescribed limits to optimise campaign life. By recording the thermal status when the furnace is running in an optimum condition, heat loss may be minimised by optimising the quality of water, its thermal conductivity and that of its cooling materials. A small rise in water temperature is preferred which may be achieved by adjusting water flow and
Figure 1. Installed cooling plate
Figure 2. Uneven wear of plates
selecting materials of desired thermal conductivity. Any reduction of the heat load/loss will influence production costs.
and 90s gave birth to copper stave coolers. To support the advancements in cooling elements, the cooling water system has likewise seen an evolution from raw water ‘once through’ to sophisticated soft/ demineralised water closed loop circuits.
Evolution of cooling Blast furnace cooling systems have been developing since 1884. Until the late 1920s, cooling was applied to the hearth and bosh areas only. Cooling for the stack region was developed between 1930 and1940. External cooling methods such as shower and jacket cooling of the furnace shell were tried. This method relied on extracting the heat through the furnace shell to the cooling medium which generated high thermal stresses and hence reduced the life and integrity of the shell. This problem was later eliminated by the use of plate coolers and stave coolers in which heat is extracted from the furnace before it reaches the furnace shell. The development of various generations of cast iron stave coolers continued until the late 1980s. Further development of stave coolers in the 80s
Types of cooling Cooling systems are often compared based on their maximum heat flux capability. Selection of cooler type must be made on the basis of equilibrium heat flux (load) in the specific region of the furnace. External spray cooling was the earliest development and is still extensively used to protect the hearth shell and in some cases bosh. Spray or shower cooling is simply the addition of a water spray or curtain down the outer shell of the furnace. The advantages include low cost, easy repair, minimal refractory consumption and no chance of water leakage inside the furnace. High wear areas such as the slag zone can be cooled using spray or shower cooling at very low
24 Furnaces International September 2017
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s
Blast Furnaces
investment. The main disadvantages are high thermal stresses on the furnace shell along with lower rates of heat removal. An additional drawback is that the heat transfer decreases with time due to scaling and deposition of dust and microbiological impurities on the surface of the furnace shell. External spray cooling also has problems counteracting hot spot formation over large areas, since boiling of the film of water may occur away from the zones of impingement.
Plate cooling Plate coolers are located inside the furnace shell in the refractory (Figure 1) and are normally made of copper or cast iron, thus providing intensive cooling while withstanding high heat fluxes inside the furnace. Furnace cooling intensity can be increased in regions of high heat load, such as the bosh, belly and lower stack by varying the spacing between the coolers. It is also observed that relatively few plate coolers use copper resulting in lower costs when compared to other coolers, such as copper staves. The limitations are that the plates take a greater width on the refractory which reduces the working volume of the furnace and installation requires large openings in the furnace shell. Also, cooling can be non-uniform (Figure 2) which leads to uneven refractory wear and disruption of the flow of the process gases in the furnace. Moreover, it is also often difficult to mount or replace coolers in the tuyere zone of the furnace.
1st generation stave
2nd generation stave
3rd generation stave
4th generation stave
Figure 3. Generations of staves with enhanced cooling
Stave cooling Stave coolers are generally used in the bosh and stack region of the furnace. These are large water-cooled blocks of metals, usually with refractory inserts between them and the hot face. Initially they were constructed of cast iron with steel pipes cast inside for water to circulate through. Copper is now generally used to improve the cooling performance and to allow the formation of a freeze layer to provide extra protection. The advantages of stave coolers are uniform cooling, the possibility of directly inspect the furnace shell for hot spots, long life, and the copper from end-of-life stave coolers can be recovered. The limitations are: Difficult to replace during furnace operation and expensive as a large amount of copper is required in the designs. Hence some stave coolers are still made of grey cast iron or SG cast iron. Four generations of staves have now evolved (Figure 3):
Figure 4. Close loop cooling water circuit
Expansion tank with pressure Secondary cooling water
and level control
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Blast Furnaces
• Generation I – Staves are deficient in corner cooling; • Generation II – Staves have improved corner cooling; • Generation III – Staves are better developed to provide refractory support by providing a nose above the straight stave face. Serpentine pipes for nose and additional zig-zag pipe arrangement provide better cooling; • Generation IV – These have edge cooling at top and bottom, ledge cooling and serpentine pipe behind the primary vertical part. The front face of the stave is provided with slots for fixing refractory blocks.
Cooling medium and circuit There are four main types of water circuits for furnace cooling systems in use around the globe: a. Once through cooling water: Requires a very large volume of water usually pumped from a natural source. The disadvantages include difficulty to control of chemical composition of discharge water, which is environmentally hazardous and a large volume of water is also discharged. b. Open re-circulating with cooling tower: Here water is heated as it cools the shell of the furnace and then passes to a hot sump. Pumps are installed to transfer the hot water to the cooling tower and cooled water is then held in a cold sump from where it is recirculated. c. Open re-circulating with indirect cooling: In the case of an open recirculating system with indirect cooling, the heat is removed from the water by means of heat exchangers, either to air or to water. There is no direct contact between the circuit water and secondary cooling. d. Closed loop cooling water (Figure 4): In this system there is no chance of atmospheric contamination of the cooling water. This will prevent scaling/ corrosion of these coolers, in the long run, leading to lower thermal conductivity or water leaking into the furnace - major reason for damage to the refractory.
Heat loss in blast furnace The heat load is given by the formula: Heat Flux = V d S ∆t where V = flow rate of water, S = specific heat of the cooling medium, d = density of cooling medium and ∆t = temperature difference between outlet and inlet. In general, the heat losses in a blast
BF
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volume (t/d/M3)
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Prod.
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HBT
Energy
Type
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rate
wind
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of cooling
circuit
(kg/tHM)
(Nm3/tHM)
(Gcal)/tHM
member
BSP #1
886
1.91
474
1290
924
4.19
CI Staves
Open
BSP #2
886
1.37
485
1641
896
4.37
CI Staves
Open
BSP #3
886
1.45
485
1484
905
4.33
CI Staves
Open
BSP #4
1491
1.14
489
1543
655
4.25
C Staves
Open
BSP#5 1491 1.70 462 1391 943 4.14 CI Staves Open BSP#6 1491 1.81 468 1271 941 4.14 C Staves Open BSP#7 2105 1.71 471 1384 904 4.19 CI Staves Close BSL#2 2250 1.64 491 1392 974 4.38 CI Staves Close BSL#3 1758 1.55 486 1534 781 4.28 CI Staves Open BSL#4 1758 1.45 501 1629 834 4.46 CI Staves Open BSL#5 1758 1.81 473 1270 936 4.18 CI Staves Open RSP#3 996 1.28 501 1487 929 4.47 Cu plate Open RSP#4 1448 1.48 498 1390 939 4.42 CI Staves Open RSP#5
3470
1.90
458
906
1149
4.01
ISP#5
3551
0.98
452
1405
1205
4.18
Cu Plate & CI Staves Close CU & CI Staves
Close
DSP#2 1204 1.62 460 1381 978 4.13 CI Staves Open DSP#3 1204 1.84 457 1235 999 4.07 CI Staves Open DSP#4 1539 1.68 466 1225 894 4.09 CI Staves Open
Table 1. Blast furnaces operating in SAIL plants
furnace are 3-6% through the cooling circuit and 2-5% through the top gas. Therefore, the total heat loss is 5-10%. Within this total, around 50-60% of the heat loss takes place in the stave/plate coolers, around 25-30% from the tuyeres, about 10-12% in the hot blast valve and about 5-7 % from the hearth area.
Results An effective cooling system keeps the hot face temperature of the refractory linings at a sufficiently low temperature to form a skull on the inside lining. The lower the hot face temperature, the greater tendency to form a stable skull. The temperature of the hot face depends on the rate of heat extraction from the lining refractory. This skull formation acts as a thermal barrier and protects the refractory lining from some of the attack mechanism such as alkali and chemical attack, oxidation by CO2, H2O and O2 and abrasion / erosion. The cooling system counters some of the attack mechanisms on the refractory face, for example, heat load and temperature fluctuations. A rough estimate indicates that reducing cooling loss through the tuyere by 5% would result in saving of 0.7-1kg coke/tHM. In conclusion, an efficient cooling system contributes significantly to a longer campaign life, higher productivity and safe operation of a blast furnace. Quantification of the thermal load is necessary to design the cooling system and requires calculation of water flow rates for different zones to optimise water flow in each cooler thereby ensuring
increased life and minimising the use of excessive water.
Bibliography 1.
PCH Zonneveld , RJ van Laar , Danieli
Corus BV, The NETHERLANDS ‘21st Century Blast Furnace Design in India’ ,Steel Tech proceedings September 2010 (p 4) 2.
Martin Smith, Mike Eden and Alex
Hancock, Siemens VAI, Stockton-on-Tees, UK ‘Design and Erection of Large Blast Furnace’ Steel Tech proceedings September 2010 p42 3
http://ispatguru.com/blast-furnace-
cooling-system/ 4.
Lecture 6/page 26-36, 22nd McMaster
University
Blast
Furnace
Iron
Making
Course-2012 5.
L Vroman, SIDMAR ‘Longer campaign
life through lining and cooling system at SIDMAR Blast Furnace’, McMaster Symposium No. 10, May, 1982 ‘Optimization of Furnace Lining Life’ 6.
RK Verma, RDCIS,SAIL ‘Blast Furnace
Cooling System & Campaign Life’, Technology Awareness Programme ,28-31 August 2007 7.
Hugo Joubert ‘Analysis of blast furnace
lining /Cooling System using CFD’ Rand Afrikaans University November 1997 8.
www.paulwurth.com/Our-Activities/.../
Furnace-Lining-Cooling 9.
Karel Verscheure, Andrew K Kyllo,
Andreas Filzwieser, Bart Blanpain, Patrick Wollants ‘Furnace Cooling Technology in Pyrometallurgical Processes’ 10.
M P Smith, J Fletcher, R W Harvey, R
Horwood, Primetals Technologies, Stocktonon-Tees, TS17 6ER, UK ‘Blast Furnace Cooling Stave Design’
26 Furnaces International September 2017
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Blast Furnaces
Powering India’s largest blast furnace ABB’s electrification and automation solutions ensure reliable performance of the four million ton per annum blast furnace. As part of its Make in India vision, the government of India recently announced its ambition to become the world’s second largest producer of steel by 2030. This will involve trebling the capacity of crude steel production to 300 million tones (MT) and investing more in capacity building. This isn’t a distant dream. The industry has reported healthy growth in recent years – expanding capacity and footprint of steel mills across the country. ABB has been helping many steel producers in the country and delivering turnkey projects and advanced services covering instrumentation, controls and electricals for the country’s leading iron and steel manufacturers – making high-quality steel reliably and helping shape India’s infrastructure. This includes the recent 10+ million ton per annum (MTPA) integrated steel plant which is also home to country’s largest blast furnace and sinter plant of 4 MTPA capacity. ABB India provided sophisticated solutions at this modern blast furnace that keep the plant up and running smoothly. At any plant, the quality of the steel produced depends on the chemical reactions occurring in a blast furnace that continuously operates at dynamic heat conditions with temperatures ranging from 800°C up to 1250°C as hot as molten lava. Any variations in the blast furnace or the sinter plant can lead to the disruption of the entire steel-making process and cause huge losses. Know-how and know-why of the complexity and criticality of steel making, helped ABB India deploy a comprehensive electrification solution including switchboards, power distribution panels, HT panels and transformer to ensure reliable, efficient and uninterrupted power during this steel-making process. Also, ABB’s energy efficient and low maintenance
synchronous motors provided smooth start blast furnace blowers. The blower is critical to maintain the air flow within the furnace, and maintain optimal
pressure. The ABB solution of sync motor and drives help the blowers start reliably within the shortest possible time, without any current spike or mains voltage dip.
POWERING INDIA’S LARGEST BLAST FURNACE
Can produce 6 million tons of steel annually (821 Eiffer towers can be built with that much!)
Contains five 26MW blower fans (each fan has as much power as 14,445 hairdryers combined!)
Set up at Angul, Odisha (Famous for its steel plants)
Has a volume of 4,554 cu. metre (equivalent to ~167 buses)
Produces a hot blast of temperature 1250°C (That’s about one quarter the temperature of the sun surface of the sun!)
The blast furnace is 34.2m tall (Almost the height of Rashtrapathi Bhavan)
The drives that power the blower fans were provided by ABB. ABB also handled the supply, erection and commissioning of the electrical parts. 27
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Furnaces International September 2017
Furnace Repairs
Making the most of your furna The glass industry is challenged with high capital requirements for furnace repairs towards and at the end of the campaign life. Furnace repairs are costly, not only in capital expenditure but in downtime. Lost sales and lack of fixed cost absorption during idle repair periods reduces the overall profitability for glass manufacturers. James Uhlik* discusses how engineers at the TECO Group provide their experience for high quality engineering and design for quick repairs. TECO aims to supply its customers with furnaces and technology that will exceed their expectations for quality, performance and life. 28 Furnaces International September 2017
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Furnace Repairs
The TECO Group began as Toledo Engineering Co. Inc. (TECO) in 1927 with its roots in the glass container industry. Some 90 years later TECO supports all sectors of glass manufacturing: float, fibre, tableware, solar and speciality, while continuing to support the container industry. Focused on the long-term financial performance of glass melting systems, TECO is proud to say that there are hundreds of TECO-designed furnaces operating in these various glass manufacturing industries worldwide. The group has amassed expertise that brings vast industry know-how to the forefront of its designs and engineering. TECO knows not only how to build furnaces, but uses the latest Computation Fluid Dynamics (CFD) modeling and has more than 600 years of collective industry experience to assure design and operational excellence. The TECO Group includes forehearth design and operation from Zedtec, electric boosting equipment from KTG Systems, and more recently, custom control systems from EAE Tech. These capabilities provide support to glass companies with a complete spectrum of value-added services that optimise their operations through offerings that complement the process. At the same time these capabilities provide training opportunities to improve energy and productivity metrics. Figure 1. Encirc furnace installation
ace
Encirc In 2003 Tecoglas, as part of the TECO group, was approached by Encirc to assist it in evaluating the design and installation of two large furnaces with capabilities to produce multiple colours of glass for the industry (Figure 1). It was at this time that TECO took the opportunity to adapt the group’s knowledge and modeling capability of high tonnage production into the design and construction of these large side port natural gas-fired furnaces. TECO used its technology and know-how to bring to life the largest side port furnaces designed for use in the glass container industry. The machine configuration was designed to provide a stable platform, which allowed the furnace to achieve pulls well above industry norms. These benefits resulted in increased furnace life, increased furnace pull, stable melting with improved quality, energy efficiency per tonne pulled, minimal disruption during job changes, and efficient tonnes/square metre over the life of the furnace.
The first furnace was commissioned in mid 2005 and is being prepared for a repair in 2018, at which time it will have pulled in excess of 16,000 tonnes/square metre over the campaign (a key metric of capital efficiency). Adrian Curry, Managing Director of Encirc, said: “Encirc has built its reputation on providing customers with a quality product. We make more than 2.5 billion glass containers a year for some of the world’s leading brands, so having welldesigned and efficient furnaces has been crucial. I am pleased to say that to date our furnaces have given us the flexibility, the quality and most importantly of all the reliability that we require as a business to be successful.” Encirc continued with its second TECO furnace and today enjoys these same performance standards. The furnace staff at the facility have done an excellent job of continually inspecting, applying proper maintenance and operating the furnaces with care. The preplanning, engineering, machine configuration and diligence of the Encirc team have resulted in a high utilisation of the assets without compromising glass quality and the life of the furnaces, resulting in extended life and maximum use of the capital investments.
From art to science The TECO Group respects the need for proper auditing, maintenance and ongoing performance monitoring to assure the long life of a furnace. Its predictive modeling uses multiple furnace modeling software programmes and has become a value added service for not only design, but also troubleshooting (Figure 2). The art of glassmaking is becoming more of a science as we refine the use of these tools in our interactions with customers. “Modeling has allowed us to investigate the inner workings of what has been a closed box in the past,” stated Chris Hoyle, Vice President – Technical Director, TECO Group. “The science of modeling along with our industry know-how and experience has shown us through operational data that in most modern furnaces fining is the bottleneck to meeting operational flexibility or production requirements, whether it is increased pull or glass quality”, he said. The resulting optimised design incorporates a flat bottom with a submerged throat. TECO data shows that fining is both improved and more predictable
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Furnaces International September 2017
Feature
Figure 2. An example of a CFD modeling diagram.
(Figure 3) and the collateral benefits are improved operational flexibility and glass consistency, reduced energy consumption and longer campaign life. This is the design being recommended for the glass container industry on new projects. Park Cam Greenfield construction has come along
infrequently over the last few decades, so TECO is proud to have been selected to participate in the most recent greenfield installations at Park Cam in Turkey. TECO used its experience to design, engineer, build and commission the largest endport furnaces in its history. TECO engineers used their extensive experience in container, float and other
glass industries to produce a highly efficient design in conjunction with CFD modeling. This project has been a success, rapidly exceeding the guaranteed pack to melt ratio and continuing to maintain that standard. In operation, both energy efficiency and glass quality have also proved to be consistently above expectations.
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Feature
Figure 4. Park Cam facility
Park Cam has continued to grow its business, completing the second phase of its long-term plan with the installation and commissioning of a second furnace in 2016. This furnace has the same design as the original with the exception of some minor design enhancements focused on additional energy savings, improved access for future maintenance and life extension (Figure 4). The glass industry has a long history and the TECO Group is honoured to be such a large part of it. Proper deployment and maximisation of capital is our job. TECO works hard with our customers to ensure a product that exceeds their expectations and continues to invest in the latest technologies available to improve our ability to design accurately
from the beginning. Also, investing in people allows TECO to stay up to date with shop floor needs for auditing and operational excellence. It is the firm belief of the company that designing a furnace or a plant correctly from the start; employing a rigorous audit programme; employing appropriate upgrades and keeping up on preventive maintenance; and training of key personnel are critical to the long life of these capital intensive assets, and assist in the preservation of life and optimisation of the investments.
100
% Refining
90 80 70 60 50 TECO Group Endport Convective Flow Technology
40
Other Endport Technology
30 20 10
Residence time
*Director of Technical Services, Toledo Engineering Co, Inc. Toledo, Ohio, USA.
sales@teco.com www.teco.com
Figure 3. Diagram showing TECO data for optimum furnace conditions.
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Furnaces International September 2017
Company profile: Verallia
Verallia completes €46 million VOA Since becoming a standalone company in 2015, Verallia has invested more than €46m in modernising VOA’s (Verrerie d’Albi) two furnaces as well as its cold end equipment. The investments allow the plant to offer flexible and shorter runs to its customers.
VOA’s furnace no.1 and its three production lines underwent a complete re-build at the end of 2015 and came into service at the beginning of 2016. It is dedicated to the production of flint and extra-flint glass. Following on from that investment, VOA’s furnace no. 2 has been fully refurbished and produces green, deadleaf and cannelle-coloured bottles. A match lighting ceremony was recently held at the plant to celebrate the re-start of furnace number 2. Benoît Chatillon, Managing Director of VOA, stated: “The modernisation of furnace no.2 and all its manufacturing lines concludes an investment programme that is historically high for our site. “Today, our plant is newly equipped with industry-standard tools. This is a key competitive strength that will help us to grow our presence on the market, support our differentiation strategy and ensure our customers are delivered an exemplary level of performance and service.” The new installations will enable the VOA plant to extend its partnerships with customers who have expressed a preference for extra-flint glass, such as Bacardi and the Perrin family. VOA’s furnace n°1 is one of two Verallia France furnaces that specialises in producing extra-flint glass (the other is located in Cognac). Another investment was the colouration feeder, which enables certain colours to be obtained with-out having to colour the glass bath in the furnace, notably extra-black. The modernisation of furnace no. 1 cost €24m, took two months of construction work, and required more than a hundred subcontractors. More than 800 people
were involved in the project, all in all. With improved combustion and by using special refractories, furnace n°1 now consumes less energy and emits less CO2, sulphur oxides (SOx) and nitrogen oxides (NOx). For the same glass furnace pull, it generates between 5% and 10% less waste than its predecessor. According to Glass Global consulting company, both furnaces at the site have a capacity of 250 tonnes a day. Furnace n°1 feeds three production lines on which three IS machines form 350,000 bottles a day. Today two of these lines, compared to one in the past, are equipped with Flex Line technology, making it possible to produce several products simultaneously. The set-ups also contribute to this flexibility, with VOA’s team able to do up to four a day, which equates to two thirds of production. Investments were also made further down the line, with a heat recovery system installed on the annealing lehrs. The whole cold end sector has also been revamped, notably with the acquisition of two packaging robots co-developed with CRITT, a small Albi-based company. These palletiser robots continuously pack the small runs of the Flex Line lines. All settings are memorised by the machine and applied instantly whenever the same bottle is made. Safety and workstation ergonomics have also been improved. In the hot end the cabins have been enlarged and acoustically insulated. Some cabins will also be installed in the cold end for the first time. The building’s lighting has been reviewed and VOA has also invested in hoists to carry moulds, thus minimising the loads lifted during set-ups.
32 Furnaces International September 2017
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Company profile: Verallia
A modernisation
Pierrette Marty and Simon Duran, two VOA retirees, light the matchstick at the furnace reopening event
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Furnaces International September 2017
Company profile: Verallia
VOA is also fully involved in its region’s environmental chain. The plant receives all the household glass collected in the Midi-Pyrenees region, where it is then sorted and reprocessed: it is totally recycled in one of the plant’s two furnaces.
VOA’s business Located in the middle of southern Europe’s major vineyards, VOA predominantly serves this wine market, which represents around 60% of its sales. It also makes bottles for spirits and nonalcoholic beverages. In 2015 it had a turnover of €105 million and is based on a 23 hectare site. Part of its production is dedicated to Selective Line, Verallia’s premium brand for still and sparkling wines, spirits and soft drinks. VOA mainly serves the wine regions south of the Loire River. Stretching from west to east, its geographic presence covers the following wine appellations: Bordeaux, Côtes de Gascogne, du Lot, du Gaillacois, du Languedoc, Côtes du Rhône and Coteaux Varois. It is also present in Burgundy. VOA is part of Verallia’s manufacturing base in France, which consists of seven glassmaking plants, a decorating facility and two design centres. It employs 300 staff.
VOA Chairman, Emmanuel Auberger, said: Over the past few years the plant has focused on the high end market. Its design and engineering office creates tailored models and part of VOA’s production is reserved for Selective Line.” Significant projects for VOA include it partnering with the Perrin family to develop the Miraval bottle, named after Brad Pitt and Angelina Jolie’s family estate. The estate owners were won over by the design proposed by VOA and based on an old Burgundy-style bottle in extra-flint. Since then, this rosé wine is grow-ing fast, sold in a number of countries. Since 2014, VOA has produced fluorescent glass bottles. Completely transparent in daylight, they turn fluorescent blue when exposed to black light in bars or nightclubs. VOA also produced a new bottle for the Federation of Châteauneuf-duPape Producers’ Unions. Conserving its original 1937 shape, this embossed bottle now meets eco-value criteria. Its weight has been reduced from 650 grams to 610 grams. VOA manufactures bottles for producers of appetizers and spirits, and its long-time customers such as Ricard or Bacardi are often geographically close to Albi. Today, these historic key accounts have been
joined by customers such as Moët Hennessy, which have opted for VOA’s high-end products in extra-flint or extra black glass to serve their flourishing markets. VOA, Albi, France
www.verallia.com www.voaglassbottles. com
34 Furnaces International September 2017
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Company profile: Verallia
VOA in figures: � 120 year history. � 300 employees. � First private company in the Albi region. � Two non-stop manufacturing furnaces and six production lines. � 4000 machines and engines in the factory. � 800,000 bottles made each day, including 350,000 bottles made of extra flint, and 350 different models each year. � 1000 customers in France and in 20 countries. � Design and engineering office. Its design centre produces 80 creations a year.
The plant produces 800,000 items a day.
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Furnaces International September 2017
Health & Safety
Substitution of aluminium silicate wo In addition to solving technical challenges, it is the constant task of the industrial furnace manufacturers, applying all the know how to limit the health risk of their employees and users of their furnace technology to a minimum. The Technical Rules for Hazardous Substances (TRGS) reflect the state of the art of occupational medicine and occupational hygiene and other proven knowledge about activities involving hazardous substances including their classification and labelling. These rules specify requirements of the Hazardous Substances Act within its scope of application. With the complete substitution of aluminium silicate wool in its
product range, Nabertherm GmbH was successfully able to comply in total with the requirements of the TRGS 619 setting new standards in the furnace industry.
Scope of application The TRGS 619 explains the substitution possibilities of amorphous aluminium silicate wool products, which are primarily used for thermal insulation in furnace and incinerator construction, heating systems and exhaust systems for
motor vehicles, especially for application temperatures above 900ยบC. The substitution is following the goal to eliminate or reduce to a minimum the hazard entailed in activities when dealing with hazardous substances.
Definitions Aluminium silicate wool, previously also known as ceramic fibers (Refractory Ceramic Fiber = RCF), consists of amorphous fibers produced by melting
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Health & Safety
HT 160/18 DB200 with pneumatically driven and parallel lift door
ool products in the furnace industry a combination of Al2O3 and SiO2, usually in a 50:50 weight ratio (see also VDI 3469 Sheet 1 and Sheet 5 and TRGS 558). They can additionally include ZrO2. Aluminium silicate wool products are mainly used at temperatures > 900 ºC and primarily in equipment that operates intermittently or under intermittent application conditions. AES wools (alkaline earth silicate wools = high-temperature glass wools) consist of amorphous fibers produced by melting a combination of CaO, MgO and SiO2 and are intended for hightemperature applications. AES wool products are generally used at application temperatures of up to max. 1200°C and in continuously operating equipment and domestic appliances.
Polycrystalline wools (PCWs) consist of fibers with an Al2O3 content > 63 wt. percentage and a SiO2 content < 37 wt. percentage; they are produced from aqueous spinning solutions in the “sol-gel method”. The water-soluble green fibers formed initially as a precursor are then crystallized by means of heat treatment. Polycrystalline wools are generally used at application temperatures > 1300ºC and in critical chemical and physical application conditions.
Determination of substitution possibilities The employer is obliged to check always what hazards can arise during the use of refractory products. The substitution solution must achieve an overall reduction
in the hazards posed by hazardous substances at the workplace. At the same time, it should not lead to an increase in other hazards at the workplace or to an increased impairment of other goods to be protected (e.g. fire and explosion hazards, furnace breakouts accompanied by the escape of molten materials). Hazardous properties of fibrous dusts from high-temperature wools and resulting hazards for workers Elongated particles have a carcinogenic effect if they are sufficiently long, thin and biostable. Fibers that meet the TRGS 619 criteria under number 2 paragraph 2 are deemed to be sufficiently long and thin (critical fibers). Potentially carcinogenic fibrous dusts can be released during activities
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Health & Safety
Fully automatic drop-bottom furnace plant, consisting of two drop-bottom furnaces, movable water bath and several loading and unloading positions
38 Furnaces International September 2017
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Health & Safety
High-temperature lift-top furnace HT 2600/16 LT DB200 for production
39 Furnaces International September 2017
Health & Safety
involving aluminium silicate wools and polycrystalline wools. According to current scientific knowledge, a risk of cancer cannot be ruled out in the event of inhalation of these fibrous dusts. The fibrous dusts released are assessed as a category 2 or category 3 carcinogens in accordance with TRGS 905 “List of substances that are carcinogenic, mutagenic or toxic for reproduction”. Accordingly, fibrous dusts from aluminium silicate wools (ASWs) are to be assessed as category 2 carcinogens (substances that are to be regarded as carcinogenic for people. There are sufficient indications for the assumption that exposure of a human to the substance may cause cancer). Within the meaning of TRGS 905, under the term “all other inorganic fiber dusts” (number 2.3 para. 6 of TRGS 905), fibrous dusts of polycrystalline wools (PCW) are to be assessed as category 3 carcinogens (substances that are of concern because of a possible carcinogenic effect on people, but about which there is insufficient information for a satisfactory evaluation). Fibrous dusts from AES wools are not classified as carcinogenic.
TRGS 558 “Activities involving hightemperature wool” describes protective measures for activities involving hightemperature wools.
Substitution principles Employers are obliged to ensure that any risk posed to the health and safety of employees by a hazardous material at the workplace is eliminated or minimised by the measures defined in the risk assessment. To meet this obligation, the employer should preferably arrange for the substitution of the hazardous material. In particular, the employer should avoid activities involving hazardous materials or should substitute hazardous materials with substances, mixtures, products or processes that are not hazardous or less hazardous to the health and safety of employees in the respective application conditions. As a matter of priority, the employer must check whether a substitution is technically possible for products made of aluminium silicate wool (RCF). A substitution should be examined within the framework of an overall assessment based on the entire lifecycle of the possible products used. Products made of aluminium silicate wool must always be substituted if: 1. The technical properties (application temperatures, thermalinsulation properties, long-term behaviour and service life) are equivalent and 2. Lower overall health risks exist for employees throughout the entire life cycle. WB 3360/14 for reducing firing of porcelain
40 Furnaces International September 2017
Further reasons for considering the use of substitute solutions can include costs, environmental-protection aspects and energy and resource efficiency. It must be emphasized, however, that higher costs incurred for a substitute solution do not automatically result in a “do not use” assessment. In particular, if the substances to be substituted pose a high risk, greater weight must be attributed to the reduction of risk. The result of the substitute selection must be documented in the risk assessment and disclosed to the competent authorities on request. Products that do not contain fibers classified as category 1 or 2 carcinogens while satisfying the requirements with regard to application temperature and other application conditions can be used as fibrous substitutes with a lower health risk. Implementation of the substitution of aluminium silicate wool products in industrial furnace design Due to their good insulation ability aluminium silicate wool fibers (RCF) were typically used for operating temperatures ranging between 900°C and 1400°C for many years. By classifying these fiber materials in category 2, it is mandatory to examine the possibilities of substitution and to initiate, where it is technically possible. As described above, only the argument of higher costs is not sufficient to continue to hold on to RCF. AES-fiber materials, which are classified as non-critical, can often not be used as the only substitute for aluminium silicate wool due to their product characteristics. PCW fiber materials are the technical
Health & Safety
alternative in many cases. However, the significantly higher procurement costs of these high-temperature fibers complicate the transition. The TRGS 619 in adapted interpretation has been applied in many European countries and outside Europe. In countries like France or the US State of California huge company groups have not allowed the use of carcinogenic fiber materials for many years already. After the revision of the TRGS 619 in 2013 manufacturers of insulating materials have responded and widened their product portfolio by mixing fibers (e.g. from PCW- and AESmaterials) to close this gap. However, until now the international furnace industry has hesitated to make use of these substitution alternatives partially for technical but mainly for cost reasons. The Nabertherm GmbH as one of the largest manufacturers of industrial furnaces with the unique broadest product range in the market has â&#x20AC;&#x201C; from right in the beginning - intensively analysed the possible substitution of aluminium silicate wool by suitable alternative materials.
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Already in 2015 the first kiln series were delivered RCF-free from the Nabertherm GmbH. Successively, substitution possibilities were determined for all furnace families by the Nabertherm design team with 65 engineers. Almost every furnace model was touched and structurally modified so that RCF fibers are used neither in the hot side nor as rear insulation. Now, Nabertherm can proudly report that the entire furnace range has been changed in close cooperation with leading international fiber suppliers. Today, almost no standard furnace, which is delivered to customers, is insulated with aluminium silicate wool (RCF-fiber material) anymore. Through alternative design solutions, substituting in most cases could be performed almost cost neutral. At least, costs are no reason, not to use non-carcinogenic fibers in the future. Only for very few applications, where no alternative to RCF-fibers is existing, classified fibers must be used. However, these are handled very restrictively and will be mutually agreed together with the customer.
The Nabertherm GmbH employs more than 450 employees at their manufacturing plant in Lilienthal/ Bremen in Northern Germany. Every year, more than 7,500 kilns and furnaces for Arts & Crafts, Laboratory, Dental, Thermal Process Technology, Advanced Materials, Glass and Foundry with working temperatures between 30°C and 3000°C are produced and delivered. As manufacturer of high-quality products - Made in Germany - and market leader in this segment, Nabertherm GmbH feels obliged, particularly in health-related issues, to position itself at the top of the industry and offer leading products with respect to quality and safety.
Contact Nabertherm GmbH contact@nabertherm.de
Text sources: abstracts from the German TRGS 619, Edition May 2013
13/09/2017 12:25:49
Furnaces International September 2017
41
Research & Development
Thermserve commission research and development extrusion-billet ca Thermserve have recently completed the commissioning into service a research and development facility at BCAST, Brunel University, UK.
The supply consisted of a complete melting and DC casting system, gas fired billet heating furnace, an offline taper heater and an rapid quench. Alongside the main items Thermserve also provided all the required mechanical handling from, melting and DC casting to billet loading at the furnace through to delivering the billet to the press. Situated at Brunel Centre for Advanced Solidification Technology (BCAST) the plant aims to deliver optimum control over the heating, and in some cases cooling of aluminium billets prior to extrusion. Thermserve has over a decade of experience in the production of extrusion equipment, however the stringent performance criteria enforced by BCAST offered an enviable technical challenge.
Single Strand DC Billet Caster and Furnace Thermserve designed and supplied an electrically heated crucible furnace and DC billet caster. This enabled Brunel to make and cast their own alloy specification and cast the appropriate billet. The DC caster is single strand and casts up to 3m length and a 6-inch billet. The Hot Top casting method is employed here and produces very satisfactory segregation. The system is fully automatic with PLC casting control, designed in-house by Thermserve along with the complete water cooling and recirculation system.
Billet Heating Furnace The three-zone billet heating furnace is a conventional gas fired billet heating furnace equipped an EN746-2 compliant combustion system. The system employs
42 Furnaces International September 2017
a gas/air mixing system developed by Thermserve, the system was developed as a result of the lack of satisfactory mixing systems available on the open market. Temperature is controlled by an in
house derived algorithm offering high levels of accuracy, the temperature is measured by duplex thermocouples in each of the three zones fitted to low impact reciprocating carriages.
Research & Development
asting facility
Billets are loaded in to the furnace via a pneumatically driven ramp and are pushed through via a chain driven electromechanical drive. Billets roll over KINTNER supplied stainless steel rollers throughout the length of the furnace. The furnace is lined with precast refractory sections fixed in the hearth and with low thermal mass lined clam shells. The refectory was selected after both thermal and mechanical modelling had been completed. The accuracy required by the process meant that this element of the design was critical. At the exit of the furnace a guillotine style door is fitted prior to a set of acceleration rolls with conveys the billet to the taper heater.
Taper Heater A key component of the supply was a billet taper heating furnace capable of raising the preheated billet to temperatures up to in excess of 600C. Trials were carried out at Thermserveâ&#x20AC;&#x2122;s factory in Telford to establish the limits of certain alloys prior to the final design of the mechanical handling elements of the system, due to the elevated temperatures it was necessary to engineer out excessive loads which could deform the billet and render it un-extrudable. The two zone furnace is fitted with duplex thermocouples, however due to the elevated temperatures involved utilise different materials of construction, further the cooling operates at higher pressures. A typical cycle time in the furnace is less than 40 seconds; hence significant thermal power was required to achieve the
duty. Numerous interlocks are engineered into the controls to mitigate the risk of overheating.
Billet Quench After the billet has reached itâ&#x20AC;&#x2122;s set temperature it is ejected from the taper heater and is conveyed to the billet quench, the transfer time is critical to the process and is loaded into the quench within 30 seconds. The quench is constructed entirely of stainless steel and is equipped with 3 individually controlled quench spray ring. The process was validated prior to shipping with numerous site visits by the client. Critical to the process were spray angle and spray velocity, and whist despite significant development work was carried out at the design stage a great deal was learnt during site trials. The quench rate is derived via a flow / time based calculation which was refined during production trials. An optical pyrometer is positioned at the exit of the quench which coupled with a high accuracy positional controller offers a snap shot of the surface temperature along the length of the billet, this acts as a final check prior to dispatching the billet to the press. Now fully commissioned the equipment is being used to assist with the development of high strength alloys for use in the automotive sector. The Engineering and Physical Sciences Research Council (EPSRC) and Brunel University jointly fund the new centre at BCAST with the support of Jaguar Land Rover and Constellium.
Contact www.thermserve.com 43 Furnaces International September 2017
Event Preview
The Surface Engineering and Heat Treatment Industry Conference & Exhibition Co-sponsored by the UK’s Contract Heat Treatment Association (CHTA), the Surface Engineering Association and Wolfson Heat Treatment Centre, the event takes place on 13th October at historic Kenilworth’s Chesford Grange, UK.
Chaired by CHTA’s Alan J Hick, the emphasis of the international heat treatment sessions is on practical developments aimed at reducing costs and increasing productivity whilst enhancing quality, efficiency and environmental aspects:
Lightweight Jigs and Fixtures: Process and Quality Improvements with Oxide Fibre Ceramics in Heat Treatment Furnace Applications Mathias Kunz, WPX Faserkeramik GmbH, Germany Lightweight Jigs and Fixtures: Carbon Composites in Controlled-atmosphere Furnaces with Oil Quenching Florian Heck, GTD Graphit Technologie GmbH, Germany Efficient Radiant-tube Gas Heating of
Industrial Heat Treatment Furnaces with “Flameless Oxidation” Lee Rabe, WS Wärmeprozesstechnik GmbH, Germany Reducing Operating Costs with EndoInjector™ and ExoInjector™ Daniel Panny, Atmosphere Engineering Company, Germany Operating Experience with Modular Controlled-atmosphere Heat Treatment Systems Philippe Warter (Codere, Switzerland) Operating-cost Reduction with ZeroFlow® Nitriding Leszek Małdzinski, Poznan University / Seco/Warwick, Poland Technology of Vacuum-furnace Cooling-rate Control with Gas (and Oil) Quenching
Philippe Lebigot, BMI, France The Practical Use of Ipsen’s PdMetrics™ Software Platform for Predictive Maintenance Oliver Obladen, Ipsen, Germany, and Mike Long, Vacuum & Atmosphere Services, UK The Industrial Internet of Things (Industry 4.0) and the Heat Treater Peter Sherwin, Eurotherm by Schneider Electric, USA
The heat treatment sessions will be staged alongside presentations for metal finishers and an exhibition featuring some 25 of the major suppliers to the heat treatment sector, including industry sponsors Bodycote, Control Energy Costs, Hauck Heat Treatment, Vacuum & Atmosphere Services / Ipsen and Wallwork Heat Treatment.
Full details of the event appear at www.sea.org.uk/industry-conference/. 44 Furnaces International September 2017
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Furnace Optimisation
Focus on: Online measurement From front to back: Continuous online measurement of material properties for optimisation of the furnace model in the SEGAL hot-dip galvanising line
Strip cooling Furnace
EMG IMPOC EMG IMPOC
Zinc pot
Todayâ&#x20AC;&#x2122;s advances in flat steel production are predominantly driven by the significant increase in the demand for high-strength steels (Advanced High Strength Steels - AHSS). Furthermore, the high quality standards of the automotive market have resulted in significantly more stringent requirements for steel manufacturers. In this context, EMG started collaborating on a development project with the EMG IMPOC system on the Segal hot-dip galvanising line in Liege/ Belgium in 2013 in collaboration with partners the SMS group, Drever and Tata Steel. The objective of this project is, on the one hand, to improve (homogenise) the material qualities of higher-strength materials, such as dual-phase steels, while on the other hand increasing productivity and simultaneously reducing energy costs. An IMPOC system has been installed near the outlet of the continuous annealing furnace of the Segal hot-dip galvanising line since as early as 2014. The SMS group and Drever, the manufacturer of the continuous annealing furnace, continuously adapted the parameters of the mathematical furnace model by using the measuring results from the IMPOC
system. The resulting adjustments made to the operation of the furnace with regard to temperatures, cooling rates and speeds in the various sections of the furnace, not only led to an increase in the quality of the material produced - IMPOC is used as an additional system for material release - but also to an overall increase in production throughput by 15%. This outstanding result naturally instilled a desire for more. Another IMPOC system is currently being tested at a location upstream of the continuous furnace. The objective here is to determine faster and more favourable parameter settings for the mathematical model and thus for the continuous annealing process. A difficulty facing this line is caused by the input material. Due to the upstream manufacturing process, the structures in the material are irregular rather than homogenous. If these inhomogeneities are known - therefore enabling use of the IMPOC system upstream of the furnace - the mathematical furnace models can take these into account. As a result, there is potential to enhance the quality and yield even further. Continuous measurement of material properties with the EMG IMPOC system upstream and downstream of the
annealing furnace at the Segal hot-dip galvanising line (principle diagram). However, the Segal hot-dip galvanising line is not an isolated case. The coupling of the microstructure model for the annealing process (SMS group), the furnace model (Drever) and the IMPOC system was also implemented in the spring of 2017 for the Universal hot-dip galvanising and annealing line, which the SMS group is currently constructing for Big River Steel in the USA. This socalled iFurnace approach is becoming established and is set to ensure optimal quality results as well as high production throughput.
Conclusion The continuous online measurement of material properties by EMGâ&#x20AC;&#x2122;s IMPOC system, combined with the physical and mathematical models for the annealing process and furnace operation (iFurnace approach), provides the ideal prerequisites for high production throughput while simultaneously ensuring high product quality.
Contact www.emg-automation.com 45
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Furnaces International September 2017