Hydrocarbon Engineering - December 2023 by PalladianPublications

December 2023

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CONTENTS December 2023 Volume 28 Number 12 ISSN 1468-9340

03 Comment

32 Careful control valve selection

05 World news 07 Elevating sustainability in the world of refining Miro Cavkov, Euro Petroleum Consultants (EPC), Bulgaria, explains why modern refineries need to adopt a diverse approach on their journey to reaching sustainability goals.

11 Reducing environmental impact Andrew Hubbell, CITGO, Brandon Burns, Shell Energy and Chemicals, and Victor Batarseh, W.R. Grace & Co., explain how the environmental impact of FCCs can be reduced with wet gas scrubbers by implementing SOx additive.

17 Minimising damage, maximising value Juan Gonzalez, Merichem, USA, considers the importance of using technology to eliminate hydrogen sulfide (H2S) from gas streams.

22 Conquering challenges Alexander Emil Mavarez Colmenarez and Hussain Hasan Al-Salman, Kuwait National Petroleum Co., Kuwait, discuss the challenges associated with the implementation and commissioning of advanced process control in the NGL fractionation units of the Mina Al-Ahmadi refinery.

26 Selecting cost-effective MOV actuators Michael Li PanFeng, Wonder Engineering Technologies Ltd, Singapore, explains the importance of motor operated valve (MOV) actuators in process plants and addresses key selection criteria.

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Juha Relander, Valmet, Finland, outlines the importance of selecting the most appropriate severe service control valves.

37 Instantaneous bellows leak detection Adam Attig, Emerson, USA, reveals how new technology can instantly detect leaks in relief valve bellows, eliminating the need for manual rounds and reducing fugitive emissions.

41 New challenges meet new technology Gudjon Thor Olafsson, Michael Winther and Rasmus Gregersen, Svanehøj Danmark, discuss the advantages of new electric submersible fuel pumps for LNG-powered ships.

45 Insights from the second law Thomas G. Lestina and Kevin J. Farrell, Heat Transfer Research Inc. (HTRI), USA, examine how using a second-law approach can help to improve the efficiency and environmental impact of process heat exchangers.

50 Using TDL to acheive process and plant safety Tyler Schertz, Mettler Toledo, Switzerland, considers the intrinsic benefits of tunable diode laser (TDL) spectroscopy, which promote a fast and accurate response to safety events within industrial processes.

53 Methane momentum Mark Naples, Umicore Coating Services Ltd, UK, explains why fixing methane leaks from the oil and gas industry can be a game-changer.

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COMMENT CALLUM O'REILLY SENIOR EDITOR

hen it rains, it pours. Just ask fans of Manchester United – the most successful club in the history of English football. Their team has been struggling on the pitch for over a decade, ever since legendary manager, Sir Alex Ferguson, retired in May 2013. This season has been particularly painful for supporters. Aside from a string of poor results, the club has also been beset by a series of off-field issues. Even the club’s famous stadium, Old Trafford, has a leaky roof that is prone to soaking already-disgruntled fans on rainy match days. The consensus is that the club has been neglected by its current owners. Hope is, however, on the horizon: Sir Jim Ratcliffe, the English billionaire founder and Chairman of INEOS Group, is reportedly close to buying a 25% minority stake in the football club for approximately £1.25 billion. Fans will be hoping that the acquisition will signal the start of a new era for the club, with significant investment in its ageing infrastructure and playing staff to follow. INEOS Group’s impending investment in this British institution has, however, been overshadowed by another of its recent business decisions on UK shores. Petroineos, a joint venture between Ratcliffe’s INEOS Group and China’s state-owned PetroChina, has confirmed that it is preparing to shut down Scotland’s Grangemouth refinery and convert it into a fuels import terminal, putting hundreds of jobs at risk. Petroineos has not yet put a timescale on the transition, but said that it expects the work to take around 18 months to complete, so the 99-year-old refinery is expected to continue operating until spring 2025. Franck Demay, CEO at Petroineos Refining, said: “As the energy transition gathers pace, this is a necessary step in adapting our business to reflect the decline in demand for the type of fuels we produce […] This is the start of a journey to transform our operation from one that manufactures fuel products, into a business that imports finished fuel products for onward distribution to customers.” The future of Grangemouth has been in question for some time, due to its age, and highlights the dilemma that refineries face in light of the low carbon future. At the recent European Refining Technology Conference (ERTC) in Lake Maggiore, Italy, Graeme McMillan, Partner & Associate Director at Boston Consulting Group (BCG), described the energy transition as a “tectonic shift” for the sector. In his presentation, McMillan explained that “doing nothing” is not an option for European refineries. However, he noted that refiners still have several levers to pull. If they intend to maintain operations in the long-term, they can look to take advantage of higher margins and increase their competitive position through initiatives such as utilising advances in digitalisation, developing wider crude slates and responding faster to market changes. Refiners can also look to develop decarbonisation plans to minimise exposure to carbon taxes. Another option is transformation – either partially or fully – to new green businesses, leveraging existing assets where advantageous. Alternatively, refineries can operate to capture shrinking margins until the end of their lifecycle, or convert to storage facilities. Perhaps Manchester United serves as the perfect metaphor for the European refining sector during these times. To stand still is to fall behind.

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WORLD NEWS USA | CLG commissions unit at El Segundo

Refinery

hevron Lummus Global LLC (CLG) has announced the completion and startup of an ISOTERRA unit as part of Chevron’s renewable fuel conversion project at its El Segundo Refinery in Southern California, US. The unit leverages both the refinery’s existing assets and CLG’s proprietary catalyst and reactor internals technology to achieve excellent diesel yields. The conversion from a diesel

hydrotreater (DHT) allowed for a quick turnaround of the existing unit, establishing El Segundo as Chevron’s first petroleum refinery with the flexibility to supply diesel fuel derived entirely from renewable or traditional feedstocks. CLG’s ISOTERRA technology is an all-hydroprocessing route designed specifically for converting lipid-rich feedstocks into ASTM-approved renewable diesel or sustainable aviation fuel (SAF).

Canada | Rolls-Royce successfully completes

100% SAF test programme

olls-Royce has successfully completed compatibility testing of 100% sustainable aviation fuel (SAF) on all of its in-production civil aero engine types. This fulfils a commitment, made in 2021, to demonstrate that there are no engine technology barriers to the use of 100% SAF. A ground test on a BR710 business jet engine at the company’s facility in

Canada, completed the test regime. Other engines tested as part of the programme were: Trent 700, Trent 800, Trent 900, Trent 1000, Trent XWB-84, Trent XWB-97, Trent 7000, BR725, Pearl 700, Pearl 15 and Pearl 10X. Testing has involved a variety of ground and flight tests to replicate in-service conditions. All of the tests confirmed that the use of 100% SAF does not affect engine performance.

Worldwide | Oil and

gas industry faces moment of truth

roducers must choose between contributing to a deepening climate crisis or becoming part of the solution by embracing the shift to clean energy, a special report from the International Energy Agency (IEA) has said. The ‘Oil and Gas Industry in Net Zero Transitions’ report analyses the implications and opportunities for the industry that would arise from stronger international efforts to reach energy and climate targets. Released ahead of the COP28 climate summit in Dubai, UAE, the special report sets out what the global oil and gas sector would need to do to align its operations with the goals of the Paris Agreement. Even under today’s policy settings, global demand for both oil and gas is set to peak by 2030, according to the latest IEA projections. Stronger action to tackle climate change would mean clear declines in demand for both fuels. If governments deliver in full on their national energy and climate pledges, demand would fall 45% below today’s level by 2050.

Worldwide | Record global LNG trade to grow another 25% in five years

lobal trade in LNG hit a record high in 2022 and is expected to grow by another 25% to 500 million tpy in five years, according to a new report by the International Energy Forum (IEF). China overtook Japan to become the world’s largest LNG importer and the US became the top LNG exporter in 2023, according to the report titled ‘Fragile Equilibrium: LNG Trade Dynamics and Market Risks’. It was produced by the IEF and Synmax, a satellite data analytics company.

Geopolitics has become the most significant driver of remapping LNG trade flows and investment, according to the report. Faced with the sudden loss of pipeline gas from Russia, European buyers turned to LNG to fill the void. Europe’s surging demand propelled global LNG prices to unprecedented heights and created a supply squeeze for emerging economies, exacerbating a delicate market situation. In Europe, LNG’s share of gas demand rose from 12% a decade

ago to more than 50%, and Europe’s regasification capacity is expected to grow by another 48% by 2030. Over the medium-term, Southeast Asia is expected to become the new LNG import hotspot, with demand poised to double by the end of the decade, driven by Singapore, Vietnam, and the Philippines, the report says. The US will remain the largest source of LNG supply growth in the future, with export capacity expected to grow by 17% by 2025 and another 43% by 2028.

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December 2023

WORLD NEWS DIARY DATES 30 - 31 January 2024 NARTC Houston, Texas, USA www.worldrefiningassociation.com/event-events/ nartc

26 - 29 February 2024 Laurance Reid Gas Conditioning Conference Norman, Oklahoma, USA pacs.ou.edu/lrgcc

03 - 07 March 2024 AMPP Annual Conference + Expo New Orleans, Louisiana, USA ace.ampp.org

10 - 12 March 2024 AFPM Annual Meeting Grapevine, Texas, USA www.afpm.org/events/AnnualMeeting2024

02 - 04 April 2024 Sulphur World Symposium Charleston, South Carolina, USA www.sulphurinstitute.org/symposium-2024

29 April - 03 May 2024 RefComm Galveston, Texas, USA www.events.crugroup.com/refcomm

14 - 16 May 2024 Asia Turbomachinery & Pump Symposium Kuala Lumpur, Malaysia atps.tamu.edu

10 - 14 June 2024 ACHEMA Frankfurt, Germany www.achema.de/en

Global Energy Show Calgary, Alberta, Canada www.globalenergyshow.com

26 - 27 June 2024 Downstream USA Galveston, Texas, USA events.reutersevents.com/petchem/downstream-usa

20 - 22 August 2024 Turbomachinery & Pump Symposia Houston, Texas, USA tps.tamu.edu

licensing and engineering agreements

ummus Technology and Citroniq Chemicals have signed licensing and engineering agreements for green polypropylene plants in the US. The first plant, scheduled for completion in 2027, will produce 400 000 tpy of bio-polypropylene and will be the first in North America with this production capability. In April 2023, Lummus and Citroniq formed a partnership to develop four green polypropylene plants in North America using Lummus’ VerdeneTM polypropylene technology suite. The licensing and engineering

agreements announced are for the first of the four plants. The Verdene suite includes four Lummus technologies: ethanol to ethylene technology, dimer technology, olefins conversion technology, and polypropylene technology. Romain Lemoine, Chief Business Officer of Polymers and Petrochemicals, Lummus Technology, said: “This agreement demonstrates the progress we continue to make with Citroniq in establishing the first world-scale sustainable bio-polypropylene production process in North America.”

Germany | LyondellBasell to build

industrial-scale advanced recycling plant

yondellBasell has made the final investment decision (FID) to build the company’s first industrial-scale catalytic advanced recycling demonstration plant at its site in Wesseling, Germany. Using LyondellBasell’s proprietary MoReTec technology, this plant will be the first commercial scale, single-train advanced recycling plant to convert post-consumer plastic

waste into feedstock for production of new plastic materials that can be run at net zero greenhouse gas (GHG) emissions. The new plant is expected to have a capacity of 50 000 tpy and is designed to recycle the amount of plastic packaging waste generated by over 1.2 million German citizens per year. Construction is planned to be completed by the end of 2025.

Finland | Neste to introduce solar power to its

11 - 13 June 2024

December 2023

USA | Lummus and Citroniq announce

HYDROCARBON

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Porvoo refinery

este has signed a purchase agreement for solar power supply to its Porvoo refinery in Finland with the renewable energy company CPC Finland Oy. Solar power supply from the Lakari solar plant in Rauma, Finland, is expected to start in spring 2024. Once ready, the plant will be the largest operating solar plant in the country. The total annual volume of the agreement is approximately 24 GWh, which represents 75% of the

annual capacity of the Lakari solar plant. The Porvoo refinery has used 100% renewable electricity since the beginning of 2022. Due to the planned development at Neste’s refinery in Porvoo, the use of electricity is expected to increase over the coming years. With the new agreement on the supply of solar power, Neste aims to ensure that its electricity will continue to be derived from renewable resources.

Miro Cavkov, Euro Petroleum Consultants (EPC), Bulgaria, explains why modern refineries need to adopt a diverse approach on their journey to reaching sustainability goals.

efineries today must operate at unprecedented levels of sustainability and efficiency, driven by a dual commitment to commercial viability and environmental responsibility. This article will delve into the key initiatives that refiners can undertake to elevate their sustainability goals. To begin, sustainability will be defined in the context of the refining industry. A successful refinery must surmount several challenges: producing clean products while minimising energy consumption, ensuring affordability for end-users, and HYDROCARBON

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December 2023

maintaining stable income and margins. All of this must be viewed through the lens of environmental responsibility and emissions reduction. Every existing facility must strike a balance between commercial competitiveness and environmental responsibility. They must also be willing to invest in adaptation to meet the evolving energy market landscape. Currently, transportation fuels, especially diesel, remain in high demand. Despite the disruption in global crude flows, the EU stands as a reliable buyer, importing finished fuel products from various sources and destinations. However, the market is currently facing fluctuations; long-term predictions indicate decreased demand for fossil liquid fuels. Despite the EU’s pledge to ban the sale of internal combustion engine cars by 2035, there will still be decades before the existing fleet is replaced. Consequently, production companies should focus their investments on refinery assets that can effectively adapt to the changing landscape of the energy transition and evolving technological requirements. It is important to note that sustainability is often conflated with renewables, which is not entirely accurate. For example, in some scenarios, utilising lower-carbon fossil feedstocks can be more sustainable than relying on renewable sources which may have higher carbon intensity. To successfully enhance energy efficiency and reduce carbon emissions in petroleum refining, adapting multipronged approaches is crucial. Fortunately, many energy efficiency projects rank among the most cost-effective investments for refineries. These projects not only boost productivity, but also contribute significantly to reducing their carbon footprint.

Sustainability through energy efficiency methods Heat transfer is a fundamental aspect of thermodynamics, playing a crucial role in refining processes. Industrial-sized heat exchangers are the workhorses responsible for this

heat transfer within refineries. These robust units, however, often operate under severe conditions, facing a multitude of operational challenges over their lifespan. Fortunately, several strategies can be employed to enhance heat transfer efficiency and minimise energy losses. This explanation will start with the outer layer, before moving inwards. Surprisingly, the role of insulation is sometimes overlooked, and compensatory measures, such as increasing heat from process furnaces or consuming more fuel, are employed to address perceived issues. However, this approach has its limitations and also brings its negative consequences. Raising temperatures to compensate heat losses can lead to increased fuel consumption, higher emissions, and a substantial spike in refinery utility costs. In a continuous refining processes, the simple act of applying proper insulation can result in energy savings amounting to numerous kilowatts. Moving inwards, heat exchangers often encounter temperature variations along the flow of feedstock. Colder spots may result in non-uniform heating, leading to energy losses, while hot spots can trigger fouling problems. Fortunately, a straightforward solution exists in the form of tube inserts, which significantly enhance heat transfer by ensuring uniform distribution, eliminating laminar flowing. Even under ideal conditions, due to the nature of feedstocks, heat exchangers require maintenance. Neglected units may need to be dismantled and, in some cases, sent to external facilities for manual or jet cleaning procedures. In modern refineries, a well-equipped predictive maintenance and monitoring system is a necessity. While innovative heat exchanger designs, such as spiral configurations, excel at mitigating fouling, there is no one-size-fits-all solution. At some point, all heat exchangers must undergo maintenance procedures. Ideally, a refinery should have the capability to bypass a specific heat exchanger by switching to a backup unit. In cases where multiple units are configured in parallel, the ability to isolate one in need of maintenance, without disrupting downstream processes, is essential for efficient operations. In such situations, non-intrusive methods for chemical decontamination emerge as the preferred option. These methods are favoured because they tend to be gentler on the internal components of heat exchangers. Chemical cleaning reagents can be used at higher concentrations without concerns, as their formulations adhere to international standards for metals. Consequently, they effectively dissolve carbon deposits without causing damage to the metal components.

Implementation of heat pumps Figure 1. By embracing a diverse set of technologies,

adopting holistic strategies, fostering collaboration, and remaining adaptable to industry changes, refineries can embark on a sustainability journey that significantly reduces emissions and ensures long-term competitiveness in a dynamic landscape.

December 2023

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Utilising excess or waste heat sources from refinery streams, heat pumps operating on the Carnot Cycle can be integrated into the refinery’s heat generation systems. Although their temperatures may not exceed 200°C, industrial heat pumps are known for their effective operation within the range of 100 - 200°C. These temperatures, harnessed and concentrated from excess or waste heat sources, are ideal for pre-heat trains.

Let ProTreat® Be Your Guide Implementing heat pumps in this way can significantly reduce energy consumption for the initial heating of feedstock, yielding particularly positive results in the processing of lighter crudes.

Emissions treatment and regeneration Embarking on the path to become sustainable refineries of the future requires a seamless transition to cleaner-burning fuels, decarbonisation, and effective integration with petrochemical production. This integration involves utilising a broad range of feedstocks, including renewables such as hydrogen, solar, wind power, and bio-crops. When examining the sources of emissions in refining, it becomes clear that the vast majority originate from combustion processes that provide the energy needed for process heat generation. Process heat furnaces typically use fuel oil, and the combustion of these fuels results in emissions of carbon dioxide (CO2), water vapour (H2O), nitrous and sulfur dioxides (SNOX), methane (CH4), and particulate matter (PM). Solutions for carbon capture and SNOX treatment emissions have gained momentum in recent years, as they can help reduce the overall environmental impact of refineries while still operating with existing configurations. As an alternative, furnaces can be retrofitted to use lower-carbon fuels such as natural gas or even zero-carbon emission fuels like hydrogen (from a combustion perspective). The first step before implementing alternative and lower-carbon fuels is to optimise the heat furnaces. This involves achieving an ideal balance between fuel and air flows to maximise heat production in both the radiant and convection sections of the furnaces.

The Leading Simulator for CO2 Capture

Solvents: • • • • • • •

Primary, secondary, promoted amines CESAR1 (updated with data from DOE partnership & tested within EU-funded consortium “SCOPE”) Amino acid salts Enzyme catalysed & amine-promoted carbonates Ionic solvents High strength piperazine Chilled ammonia

Applications: • • • •

Stationary power generation CO2 capture from LNG-fueled ships Renewable methane from landfill gas and organic waste Hydrogen production via reforming

Electrification of process heat furnaces The electrification of process furnaces is emerging as a promising solution that can significantly reduce the overall carbon intensity of refineries. One of the key advantages of electric furnaces is their ability to operate without emitting flue gases, making them a cleaner option. Electric furnaces also offer enhanced monitoring and control capabilities due to their simplified design. However, there is a fundamental rule to keep in mind: electric heaters can only be considered environmentally sustainable when powered by clean or renewable sources of electricity. For instance, using electricity generated from coal power plants, often referred to as ‘grey electricity’, would simply relocate emissions from Scope 1 and 2 to different locations. Additionally, transmission losses must be considered when evaluating the overall environmental impact of electrification.

Implementing alternative production The implementation of sustainable alternatives is crucial for maintaining competitiveness in the evolving downstream market. Throughout history, technological advancements and breakthroughs have often been

Ferrybridge Pilot Plant, Ferrybridge, UK, 100 TPD

Reliable: • •

New CESAR1 model updated with cutting edge lab and plant data from DOE partnership Thoroughly tested as part of EU-funded research consortium “SCOPE”

driven by the introduction of new regulations, such as the transition to 10 ppm sulfur diesel fuels, IMO 2020 marine fuels, lead-free gasoline with reduced aromatic content, and the integration of bio-components. Technological evolution has consistently pushed the boundaries of production, necessitating adaptation to changing market conditions, requirements, and demand predictions. Sustainable aviation fuel (SAF), green methanol, and green ammonia are gaining significant traction in the market.

Green methanol and green ammonia

These fuels are produced from green hydrogen and carbon, which in the ideal scenario is the molecule to be sourced from captured carbon emissions. They hold great promise, particularly in the maritime sector, where they are expected to dominate as clean fuels.

SAF

SAF is a highly promising commodity for several reasons. Unlike ground transportation, which can transition to electric drivetrains, the aviation sector is considered as one of the hardest to abate. With significant investments in research and infrastructure, the aviation industry heavily relies on middle distillates. SAF offers a drop-in solution to reduce direct emissions from aircrafts, requiring minimal or no retrofitting of existing assets. The technology landscape for SAF production is continually evolving, expanding the range of feedstocks to include renewable oils, animal fats, solid biomasses, bio alcohols and carbon and hydrogen sources. Technology advancements enable the customisation of SAF production to be based on locally available feedstocks. At its core, SAF production requires three key elements: carbon, hydrogen, and energy.

Adoption of a circular mindset To advance sustainability goals, it is essential to adopt a circular mindset and integrate circular approaches into refinery operations. Several areas can benefit from circularity within a refinery: nn SNOx and carbon emissions: implementing circular approaches to reduce SNOx and carbon emissions is crucial. By capturing and repurposing emissions, refineries can minimise their environmental impact and even turn emissions into valuable resources, i.e. captured SO2 to be utilised as sulfuric acid feedstock. nn Catalysts: the circular use of catalysts is gaining prominence. Instead of discarding end-of-life used catalysts, refineries can explore methods for regeneration or reusing these essential components in various processes. The catalyst handling and precious metal smelting business is currently emerging and brings attention to the producers. nn Waste polymers: the recycling and utilisation of waste polymers, especially plastics, in secondary co-processing can significantly reduce the environmental footprint of refineries. These materials can be transformed into new valuable monomers and products. December 2023 10 HYDROCARBON ENGINEERING

nn Water as a scarce resource: efficiently managing water resources is essential. Refineries can implement advanced wastewater treatment processes to purify and recycle water, reducing water consumption and minimising the release of contaminants into the environment. Additionally, the recovery of valuable chemicals from wastewater, such as bases, acids, and oils from sludge deposits, presents opportunities for reuse and resource optimisation. nn Re-refining of spent motor oils: re-refining spent motor oils is an environmentally responsible approach that can recover high-quality lubricants and extend the life cycle of these valuable products. By integrating circularity into these aspects of refinery operations, refineries can not only enhance their sustainability, but also reduce waste, lower resource consumption, and contribute positively to environmental goals.

New tools and technologies The path to refinery sustainability involves harnessing a variety of innovative tools and technologies. Relying on a single ‘silver bullet’ solution, such as hydrogen production and implementation, may not be sufficient to support the overall sustainablity goals. As a key consideration for implementing these advancements, the following paths should be considered: nn Diverse technological arsenal: while hydrogen is an essential component of decarbonisation, it is not the sole solution. A range of technologies and tools should be explored and applied in tandem to achieve a sustainable future for refineries. nn Holistic approaches: sustainability in refineries is not achieved through isolated efforts. Holistic approaches that encompass various aspects, such as process optimisation, energy efficiency, emissions reduction, and waste management, are critical for success. nn Collaborative efforts: collaboration among industry players, technology providers, research institutions, and regulatory bodies is essential. Together, they can drive innovation, share best practices, and create a supportive ecosystem for sustainable advancements. nn Adapting to change: in rapidly evolving industries, clinging to legacy practices may hinder progress. Refineries must be open to change and willing to adopt new technologies and approaches to remain competitive and reduce emissions effectively. nn Emissions reduction: legacy methods may no longer suffice for emission reduction. New tools and technologies offer more efficient ways to lower emissions, making them essential for meeting sustainability goals. By embracing a diverse set of technologies, adopting holistic strategies, fostering collaboration, and remaining adaptable to industry changes, refineries can embark on a sustainable journey that significantly reduces emissions and ensures long-term competitiveness in a dynamic landscape.

Andrew Hubbell, CITGO, Brandon Burns, Shell Energy and Chemicals, and Victor Batarseh, W.R. Grace & Co., explain how the environmental impact of FCCs can be reduced with wet gas scrubbers by implementing SOx additive.

ver the last 80 years, fluid catalytic cracking (FCC) has played a critical role in the refining industry and continues to adapt to shifting industry conditions. The flexibility of the FCC enables refiners to shift between targeting maximum gasoline, light cycle oil, alkylation unit feed, and petrochemical feedstock. This flexibility will continue to drive the longevity of the FCC in the upcoming decades and through the energy transition. In addition to navigating the dynamic landscape in years to come, many refiners are embarking on, or continuing their sustainability journeys. Grace remains committed to supporting the industry with creative solutions to drive the highest profitability operation while minimising the environmental footprint of FCCs. The case studies included in this article examine Grace’s collaboration with refiners to maintain environmental

compliance for SOx emissions in a more cost effective and sustainable manner. SOx emissions are an undesired byproduct of FCC catalyst regeneration in crude oil refineries. These emissions are proportional to the sulfur content of the combined feed to the FCC unit. End of the pipe solutions, such as wet gas scrubbers (WGSs), are a flexible alternative to reduce the SOx emissions at the stack of FCC units.1 They typically employ a quench and absorber section and make use of an alkaline reagent, typically caustic, to capture the SOx in the form of sodium sulfites/sulfates. To reduce SOx emissions from FCC units, SOx reduction additives were developed in the 1980s and have gained widespread application since then.2 Such additives are typically bifunctional catalysts incorporating SOx capturing functionality

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with the catalytic activity for SO2 oxidation and additive regeneration. SOx reduction additives have long been used in the FCC to limit SOx emissions to the atmosphere in units without WGSs. Units with WGSs typically do not require SOx additives to maintain regulatory compliance. However, inflation in caustic soda pricing often impacts operating expenses for FCCs with

Figure 1. Regression predicted caustic usage (without additive) and actual caustic usage over a base period without additive.

WGSs. For some units, inflation of caustic prices in recent years has resulted in over US$1 million/yr in increased OPEX. In response, Grace collaborated with refiners operating WGSs to implement SOx additive for reducing overall SOx compliance costs in both full and partial burn applications. Further analysis of this activity reveals that the benefits extend far beyond a simple cost savings activity. Balancing SOx additive and WGS caustic is not only economically viable, but also reduces the environmental footprint of the FCC. This is done by reducing Scope 3 emissions and converting the sulfur destined for waste from WGS wastewater plants, over to reactor hydrogen sulfide (H2S), which is converted into elemental sulfur and utilised to produce commodities including sulfuric acid and fertilizers. In 1998, Paul Anastas and John C. Warner published 12 principles to guide chemical product and process design according to green chemistry considerations.3 The American Chemical Society provides reference to the principles on its website. Implementing FCC SOx additive to avoid large amounts of fresh caustic usage and spent caustic treatment closely aligns with two of these principles: preventing waste instead of treating it and catalytic reagents are superior to stoichiometric reagents. This article seeks to quantify the economic and sustainability benefits associated with implementing a combination of additive and WGS caustic for maintaining SOx emissions compliance. The evaluation focuses on two example cases: a full burn FCC at the CITGO Lemont refinery, processing a high sulfur feed, and a deep partial burn FCC at a Shell refinery in the US Gulf Coast region that processes a moderately sour feed. Both of these refiners utilised Grace’s latest SOx additive, EMISSCIANTM, which achieves excellent performance by effectively balancing the functionalities of cerium, vanadium, and magnesium, while dispersing the components evenly throughout the additive particle.

Case 1: full burn unit with high sulfur feed

Figure 2. Generic OPEX savings curve for implementing additive in a unit with a wet gas scrubber using caustic.

Figure 3. Regression predicted caustic usage for operation without additive and actual caustic usage with additive during a period where additive was consistently used.

December 2023 12 HYDROCARBON ENGINEERING

The full burn unit at CITGO Lemont examined in this study typically processes 60 000 bpd of feed with an API of 18 and sulfur content of 2.5 weight %. For this operation, the unit’s WGS consumes ~24.5 dry short tons (dst) of caustic (NaOH) per day. As a starting point for the evaluation, the relationship between feed sulfur and caustic consumption at the WGS without SOx additive was determined. It was found that a simple linear regression utilising the mass flow rate of sulfur in the feed predicted WGS caustic consumption reasonably well over a variety of operating conditions, producing a fit with an R2(adj.) = 77%. Figure 1 shows the actual and predicted caustic usage over the baseline period utilised to develop the regression model. Close alignment between actual and predicted caustic consumption confirms a good fit for the regression model. Utilising a combination of the baseline data and Grace’s SOx additive performance model, an evaluation was conducted to determine the optimal balance between additive usage and WGS caustic required to minimise total emissions compliance operating expenses. This type of analysis demonstrates that there is a wide range of SOx additive rates over which OPEX can be reduced, as shown in the generic analysis in Figure 2.

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The CITGO Lemont refinery leveraged this analysis to help set SOx additive rates throughout the year as caustic pricing, feed quality, and feed rates shifted. The evaluation revealed additive rates ranging from 400 to 700 lb/day maximised the total SOx compliance OPEX savings by appropriately balancing SOx additive and WGS caustic. Figures 3 and 4 show a comparison between actual and predicted caustic usage throughout the year, as well as a quarterly summary of SOx additive performance. In this performance overview, the same regression model utilised to describe caustic usage without additive was compared to the actual caustic usage with SOx additive. The gap between actual and predicted caustic consumption signifies the reduction achieved with the additive. The refinery averaged 510 lb/day of SOx additive usage, and 11.8 dst/day of caustic reduction, realising net SOx control OPEX savings of US$2.5 - US$3.5 million/yr (annualised after excluding a period of unusual operation during turnarounds at other process units).

This was calculated assuming a US$1000/dst caustic price. Performing a sensitivity analysis for this unit, comparing additive cost to OPEX savings, shows that implementing SOx additive continues to be economical over a wide range of caustic prices. Examining this activity from a sustainability perspective reveals lower Scope 3 emissions associated with operating the FCC, in addition to waste avoidance. Operation without SOx additive requires greater amounts of caustic to be produced, then shipped to refiner, and treated as total dissolved solids in wastewater plants. Table 1 summarises data and calculations associated with the lifecycle CO2 changes in the system when considering this switch from caustic to a combination of caustic and SOx additive. Detailed assumptions for the evaluation can be reviewed in the section at the end of this article. This analysis confirms that implementing SOx additive for WGS caustic reduction at at CITGO Lemont’s FCC not only provided OPEX reduction of over US$2 million, but also reduced the carbon emissions associated with operating the FCC and diverted sulfur from a waste stream to the sulfur plant, creating a sellable product. Annualised CO2e reduction totalled over 5900 t, which equates to saving the emissions from combusting 102 100 million Btu or 98.6 million standard ft3 of natural gas.5,6

Case 2: deep partial burn unit with moderate sulfur feed

Figure 4. Quarterly summary of additive usage and caustic reduction (calculated as predicted caustic without additive minus actual caustic with additive). Table 1. Summary of sustainability benefits associated with implementing SOx additive in combination with WGS caustic at the CITGO Lemont FCC SOx additive usage (lb/day)

510

Caustic reduction (dst/day)

11.8

Caustic delivery reduction (deliveries/day)

1.1

SOx additive deliveries (deliveries/day)

0.01

Lifecycle CO2e reduction (tpd)

16.3

Annualised lifecycle CO2e reduction (tpy)

5959

Other impacts Waste sulfur converted into sellable product (tpd)

9.5

Waste sulfur converted into sellable product (tpy)

3461

SOx additive to cement kiln (lb/day)

510

December 2023 14 HYDROCARBON ENGINEERING

The partial burn unit examined here is at a Shell refinery on the US Gulf Coast. The FCC at this refinery is a Shell residual fluid catalytic cracking unit (RFCC) that typically operates at ~100 000 bpd with a 22.5 feed API and sulfur content of 0.7 - 1.1 weight %. This FCC routinely operates with flue gas CO between 5 - 7 vol %. Grace conducted a baseline analysis in this unit to determine caustic usage without SOx additive. This analysis yielded a regression model with an R2(adj.) = 68%. Grace collaborated with Shell, leveraging unit data and Grace’s proprietary model to identify the optimum caustic reduction to minimise SOx emissions compliance OPEX. Due to operation in partial burn and limited oxygen availability for oxidising SO2 to SO3, SOx additive is less effective in this unit than the FCC studied in Case 1. As a result of partial burn operation and other unit parameters, the target caustic reduction for maximising OPEX savings was 20 - 25% at the Shell refinery. Figures 5 and 6 demonstrate that the implementation of 400 lb/day of SOx additive, preblended with fresh catalyst, drove a 21.3% caustic reduction. This resulted in US$0.5 - 1.0 million/yr in savings, assuming a US$1000/dst caustic price. Figure 6 is a control chart that shows the difference between actual caustic usage with additive and predicted caustic usage without additive, by calculating the percent reduction relative to predicted performance. The centre line for each period is the mean and the red lines above and below signify the control range of 3 standard deviation. It can be observed that there is very little overlap in the control bands, and the mean for the period with additive usage lies outside the control band without additive usage, indicating that a statistically significant shift has occurred. Despite the challenges for SOx additive in partial burn, significant sustainability benefits are still realised. These benefits are summarised in Table 2.

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When implemented at the Shell refinery for caustic abatement, Grace’s EMISSCIAN delivered a 2230 tpy reduction in CO2e, which equates to saving the emissions from combusting 38 200 million Btu or 36.9 million standard ft3 of natural gas. Additionally, over 4 tpd of sulfur were diverted from the wastewater treatment plant over to the amine system

where it can be converted into sellable products, while generating only 400 lb/day of incremental material to cement kilns.

Conclusions Evaluation of the activities at the CITGO and the Shell refineries show that implementing SOx additive for WGS caustic abatement has the potential to deliver benefits beyond OPEX reduction. Sustainability benefits associated with this activity include reduction in Scope 3 emissions associated with caustic production and transportation, as well as converting the sulfur destined for waste into a usable product in both full and partial burn FCC units. Implementing Grace’s SOx additive, EMISSCIAN, allows refiners to achieve these benefits while also maximising SOx emissions compliance OPEX savings by delivering the highest flue gas sulfur reduction per pound of additive across a variety of applications.

Note Figure 5. Predicted and actual caustic usage before and during trial period where additive was implemented for caustic reduction.

Figure 6. Control chart showing caustic reduction

from base period during the implementation of SOx additive.

Table 2. Summary of sustainability benefits associated with implementing SOx additive in combination with WGS caustic at Shell SOx additive usage (lb/day)

400

Caustic usage and delivery reduction (%)

21.3

SOx additive deliveries (deliveries/day)

0.01

Lifecycle CO2e reduction (tpd)

6.1

Annualised lifecycle CO2e reduction (tpy)

2230

Below is a list of assumptions that have been made within this article for each case study: nn Carbon intensity for producing NaOH is an average of the life cycle analysis carried out by Hong and the value in the Medina-Martos evaluation.7,8 nn Transportation emissions associated with supplying NaOH to the refinery are calculated using the UK government reporting guidance, assuming: NaOH is transported by truck in 22 short t quantities and delivered in a 50 weight % solution9; the NaOH facility is 100 miles from the CITGO Lemont refinery and 50 miles from the Shell refinery on the Gulf Coast; each truck makes a round trip between the refinery with a full load on one leg and empty on the return journey. nn Transportation emissions associated with supplying SOx additive to the refinery are calculated using the UK government reporting guidance, assuming: additive is transported by truck carrying 22 short t making a roundtrip journey from Grace’s facilities to the refinery, and returning empty. nn Spent catalyst from the refinery is sent to a cement kiln. nn Incremental reactor H2S resulting from SOx additive usage is processed into elemental sulfur, helping to satisfy demand for industrial and agricultural applications. nn Shifting operations at the WGS wastewater treatment plant are not considered in this evaluation.

References 1.

Other impacts

2. 3. 4. 5. 6.

Waste sulfur converted into sellable product (tpd)

4.2

Waste sulfur converted into sellable product (tpy)

1536

SOx additive to cement kiln (lb/day)

400

December 2023 16 HYDROCARBON ENGINEERING

SEXTON, J. A., ‘FCC emission reduction technologies through consent decree implementation: FCC SOx emissions and controls in advances in fluid catalytic cracking: testing, characterization, and environmental regulations’ (2010). YALURIS, G., and DOUGAN., T.; Catalagram Europe, Fall 2006, 8-11. ANASTAS., P., and WARNER., J., ‘Green Chemistry: Theory and Practice’, (1998). https://www.acs.org/greenchemistry/principles/12-principles-ofgreen-chemistry.html. https://www.eia.gov/environment/emissions/co2_vol_mass.php https://www.eia.gov/dnav/ng/ng_cons_heat_a_EPG0_VGTH_btucf_a. htm. HONG et al, ‘Life cycle assessment of caustic soda production: a case study in China’, Journal of Cleaner Production, (2013). MEDINA-MARTOS, et al., ‘Environmental and economic performance of carbon capture with sodium hydroxide’, Journal of CO2 Utilization, (2022). https://www.gov.uk/government/publications/environmentalreporting-guidelines-including-mandatory-greenhouse-gas-emissionsreporting-guidance.

Juan Gonzalez, Merichem, USA, considers the importance of using technology to eliminate hydrogen sulfide (H2S) from gas streams.

ossil-based fuels have been integral to the energy-supply landscape since Colonel Drake’s oil discovery in Pennsylvania in 1859 and since the Spindletop geyser erupted in Beaumont, Texas in 1901, setting the stage for the new petroleum economy. Hydrocarbons disrupted the coal industry and have become the fuels that form the bedrock of today’s energy system.

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The world is once again transitioning away from its current fuel supply. Countries worldwide have developed a plan and pathway to the formidable goal of net zero emissions by 2050. Despite the growing consensus on its importance, major obstacles must be overcome to combat global climate change. With such hurdles to traverse, fossil fuels will continue to contribute a significant share of the energy mix until at least 2050. Despite its affordability and security of supply, continued production and use of oil and gas comes with risks. Besides fluctuating consumer demand, price instabilities, and geopolitical issues, there are hazards associated with the extraction, transport, and refinery processes involved in producing fuel. The availability of light sweet crude is diminishing, and environmental restrictions to reduce emissions are at odds with the increasing drive to process heavy and sour crudes. The hydrogen sulfide (H2S) that occurs naturally in crude oil and sour-gas fields presents safety issues, has detrimental effects on production equipment, and is a significant contributor to atmospheric pollution via the formation of acid rain. Utilising these sour-gas streams requires the removal of H 2S. Any method or technology used to remove H2S must be highly efficient and flexible within a wide range of gas conditions and must minimise environmental damage, while maximising the yield value of end products.

Technology LO-CAT® technology has been used to remove H2S from gas streams since the 1970s. It is a wet scrubbing, liquid redox system that uses a chelated iron solution to convert H 2S to innocuous, elemental sulfur. The catalyst used in the liquid redox process is readily

available, and since it is continuously regenerated in the process, less catalyst is used. LO-CAT does not use any toxic chemicals, nor does it produce any hazardous waste byproducts. The process is applicable to virtually all types of gas streams and can remove over 99.9% of the H2S at ambient to moderate temperature, from low to moderate pressure gas streams. The liquid catalyst adapts easily to variations in flow and concentration. Flexible operation allows 100% turndown in gas flow and H 2S concentrations. Units require minimal operator attention. The ‘sweet’ spot of the technology application ranges from 1 tpd up to 20 tpd of sulfur removed.

The chemistry The process chemistry of the LO-CAT technology is embedded in its name: liquid oxidation catalyst. The system oxidation reaction is as follows: H2S (gas) + ½ O2 (gas)  H 2O + S° The overall reaction is sub-divided into two parts: n n Reduction: H2S gas absorption, ionisation and reaction to make solid sulfur in the liquid solution. n n Oxidation: the liquid solution is then oxidised using air and regenerated for re-use. The reduction/oxidation (REDOX) reaction optimises the process variables that allow for favourable reaction conditions.

Case examples Treating acid gas with lower sulfur content

The Coso Geothermal Field is situated within the China Lake Naval Air Weapons Station (NAWS) in Inyo County, California, US. It has been producing geothermal power continuously since 1987, and is one of the Chemical Addition Flue Gas top three producers of geothermal Wash Water Oxidiser electrical power in the US. In 1993, the Vessel Treated Gas Sulfur Cake first of three LO-CAT units was installed Sulfur Filter to remove H2S. The Coso Geothermal Field comprises Absorber Vessel Filtrate four geothermal power plants with nine Tank Sour Gas 30 MW turbine-generator sets. Between 80 and 90 production wells operate at Filtrate Pump any given time, producing a mass flow rate of more than 14 million lb/hr. The Air Coso field can engage 30 to 40 injection Solution Air Blower wells based on the volume of fluid to be Circulation Pump handled and where pressure support is Sour Gas / Treated Gas Chemicals required. Air, Flue Gas, Water Spent / Regenerated Solution The high fluid temperatures dictated that the power plants employ Figure 1. Merichem’s liquid redox system uses a chelated iron solution double-flash technology for steam to convert dangerous H2S into innocuous, elemental sulfur. It is extraction. The fluids that were produced chemical-based and offers reliable and flexibile treatment, with no had moderate amounts of saline chloride liquid waste streams or waste products. brines with total dissolved solids (TDS)

December 2023 18 HYDROCARBON ENGINEERING

from 7000 - 18 000 ppm. Non-condensable gases accounted for 6% of the gas fraction, with 98% of that from carbon dioxide (CO2). H2S ranged from <10 - 85 ppm. Once the wells were tapped and gathered, the steam wells produced electricity from the renewable geothermal energy source. The steam passes through a set of turbines and generators, and the non-condensable vapours are separated from the condensed steam at low pressure. The brine is then reinjected into the geothermal field. The non-condensable vapours cannot be vented to the atmosphere until the H2S particles are removed. The H 2S-laden vapours were reinjected into the geothermal field with water during the initial facility start-up. Over time, the H 2S abatement method became more costly due to compressor maintenance. After the installation, the non-condensable CO 2 and H2S are flashed, compressed, and routed to the LO-CAT unit for sulfur removal before being emitted into the atmosphere. The process has been removing H2S at the COSO facility for 30 years and has significantly reduced sulfur emission exceedances and operating costs.

quickly proved its turndown capabilities and process flexibility. The sour gas flow rate varied from 1.5 to 5.1 million ft3/d, inlet H2S concentrations varied from 8000 ppm to 15 000 ppm, and sulfur production rates occasionally exceeded the design capacity of the unit. Despite the varying gas flows and sulfur concentration regimes, the unit consistently met the 100 ppmv outlet H 2S specification. Since going online in January 2013, the LO-CAT unit required approximately 25 hours per week of operator attention or about three hours per day on the continuously manned facility, which is somewhat higher than land-based units. The LO-CAT unit consistently exceeded the H 2S removal requirement. Due to the value of the sulfur cake as a fertilizer and fungicide in Italian vineyards, the sulfur byproduct was disposed onshore at no cost.

Cleaning fuel gas

The ExxonMobil Altona Refinery in Victoria, Australia, incorporated a LO-CAT unit to treat very high concentrations of H2S in an acid gas stream. The unit for the Altona facility was designed to treat 93% H 2S by volume, to yield 10 tpd of sulfur at a removal efficiency of 99.9%. The unit provided reliable operation for over 27 years, even as the acid gas flow and composition changed, until ExxonMobil closed the refinery processes in 2022. The facility utilised a sulfur melter to liquify and purify the LO-CAT sulfur to more than 99% for subsequent industrial use.

In 1970, the Clean Air Act (CAA) was passed as a comprehensive federal law that regulates air emissions from stationary and mobile sources. Specifically, the CAA and its amendments require engines and fuels to produce less air pollution. Leaded gasoline was banned, and standards were put in place to reduce toxic air emissions from mobile sources. LO-CAT was quickly recognised as a versatile processing scheme for treating gas streams containing any amount of H2S, which makes it suited for cleaning combustible gases or valuable product gas streams. For this application, the LO-CAT system is designed with separate absorber and oxidiser vessels. The chelated iron catalyst is pumped between the vessels, and the absorber removes the H 2S from the sour gas, converting it to elemental sulfur.

Purification of CO2 with low sulfur content

Midstream and renewables

Treating acid gas with high sulfur content

LO-CAT units have been designed and commissioned throughout North America, South America, Asia, and Europe. They remove H2S mostly from CO2 streams to treat the CO2 for subsequent uses, including food-grade CO 2, which is used to produce carbonated beverages or dry ice. The allowable residual H2S in these streams is very low (<1 ppmv) and requires removal efficiencies greater than 99.9%. The total sulfur content of these streams tends to be low, but the highly selective nature of the LO-CAT process allows for economical operation while minimising product loss.

Floating production, storage and offloading (FPSO)

Floating production, storage and offloading (FPSO) vessels are used in deep waters where currents change, and no existing pipeline infrastructure is available. In 2013, a LO-CAT unit was designed and commissioned onboard the Firenze FPSO, located in West Africa, Gulf of Guinea. The H2S levels exceeded the economic limits of scavengers, so the LO-CAT technology became the most viable option for efficient H 2S removal. The unit December 2023 20 HYDROCARBON ENGINEERING

The Standard LO-CAT® system is a configuration of the LO-CAT sulfur recovery technology, chosen to accommodate some of the more common operating conditions for gas treating, and to improve overall project costs and schedules. The new standard design includes pre-configured options for varying gas flowrates and is easily duplicated where more sulfur removal capacity is required. Standard LO-CAT works well for midstream and renewables markets but can be used anywhere schedule is a constraint, and a standard unit can fit. It can be used to treat lower pressure gas streams of up to approximately 4 million ft3/d and below about 2 long tons per day (ltpd) of sulfur from H2S.

Conclusion The wet scrubbing liquid redox process may seem complex, but it consists of only a two step process for eliminating H2S: the removal and destruction of H2S, followed by catalyst regeneration. Its efficiency and efficacy have been evaluated in numerous situations for a range of streams. Using technology can increase reliability and reduce environmental impact, as well as bring a wide range of operation flexibility.

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Alexander Emil Mavarez Colmenarez and Hussain Hasan Al-Salman, Kuwait National Petroleum Co., Kuwait, discuss the challenges associated with the implementation and commissioning of advanced process control in the NGL fractionation units of the Mina Al-Ahmadi refinery.

December 2023 22 HYDROCARBON ENGINEERING

n 2014, Liquified Petroleum Gas Train 4 (LPG4) was commissioned in the Mina Al-Ahmadi (MAA) refinery as part of Kuwait National Petroleum Co.’s (KNPC) strategic vision to increase the refining capacity and meet national and international LPG products demand and standards. After the successful commissioning and stable operation of the plant, multiple advanced process control (APC) companies were approached to study the plant and provide detailed analysis on how to apply APC in the LPG4 NGL fractionation unit. Based on the analysis of the historical data and dynamic simulations, several key areas were identified where APC could be implemented to improve the plant’s performance. These included the optimisation of the de-methaniser operation to maximise the recovery of ethane from the residual gas, the control of feed and heavy components to improve product quality, and the minimisation of energy consumption.

To ensure the successful implementation of APC, the KNPC team and the vendor collaborated closely throughout the project. Regular meetings and discussions were conducted to review the methodology of the implementation, address any challenges or issues, and finetune the control strategies based on the plant’s behaviour. This led to the modification and development of some control philosophies which will be explained in this article. These changes and enhancements resulted in the increased utilisation of APC and maximised benefits. Nevertheless, multiple challenges were faced during system setup and implementation phases, which will also be discussed.

System setup The first challenge during the server setup was establishing the communication between the distributed control system (DCS) gateway station (231A3C) and APC server

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(DMC3TM online server) as shown in Figure 1. The server provided during the commissioning phase did not meet the minimum AspenTech® requirements. Therefore, a new server was set up from scratch

Figure 1. KNPC MAA LPG-4 APC system architecture.

Figure 2. De-ethaniser column in unit 233.

Figure 3. Steam flow indication and PID’s level controllers.

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in-house to provide server and software compatibility. The FoxBridgeTM software, which allows data to transfer from Level 2 to Level 3, was also installed in-house by KNPC with the setup of dynamic matrix controller (DMC) demo controller as an initial stage. Eventually, connecting the server with the existing KNPC network (Level 4) was carried out in-house. After overcoming all of the obstacles mentioned previously, KNPC was ready to proceed with building the DMC models and launching the DMC controllers. After experiencing the difficulties related to system setup, the next phase involved tackling the obstacles in the fractionation unit. The following paragraphs provide an elucidation of the modifications implemented to attain a seamless implementation of APC in the de-ethaniser column. For a comprehensive understanding of the overall process layout of the de-ethaniser column, Figure 2 can be consulted as a visual aid. Additionally, it is worth mentioning that the design of the de-propaniser and de-butaniser columns exhibits considerable similarities. First starting with the actions undertaken in the pre-step test of the de-ethaniser column, specifically focusing on the tuning of the tray temperature controller to establish and sustain an appropriate column temperature profile through the implementation of a PID control loop. Moreover, the level transmitter indication in a particular reboiler’s condensate pot drums was examined and calibrated to accommodate the prevailing conditions of the unit, subsequently ensuring precise measurements, and addressing the zero-value condition. As shown in Figure 3, the steam flow consumption was reduced by 24.4%, which also led to the stabilisation of levels in both reboilers. Furthermore, a modification was incorporated into the DCS, enabling the implementation of a fallback action to mitigate any undesirable fluctuations (bump less) in the tray temperature controller.

De-propaniser

Table 1. LPG4 DMC3™ controller benefits performance analysis

Unit/ System up A new control scheme controller time (%) (cascade control) was applied on this column 233 100 as part of the base layer de-ethaniser study and pre-step test 233 100 activities, by configuring de-propaniser the steam flow 233 100 controllers on the two de-butaniser column reboilers as Total profit slaves for the tray temperature controller. This facilitated better control and stability of the column due to the non-linear nature of the level controllers. The engineering output units of the LP steam temperature controller were developed to match with the setpoint of the steam flow controllers, where a new cascade control was introduced to the existing design. The control action of the PID tray temperature controller was changed from direct to reverse in order to align with operations requirement.

Operations up time (%)

DMC utilisation index (%)

Net profit (US$/day)

Net profit (US$/ month)

Net profit (US$/year)

100

867

26 010

312 120

100

573

17 190

206 280

100

1387

41 610

499 320

84 810

1 017 720

De-butaniser Lastly, in the de-butaniser column, two challenges were faced: the instability of the column, and the level control valves passing for both reboilers. The first challenge was solved by adjusting the top pressure controller. It was possible to enhance the Figure 4. Top pressure PID controller before and after the tuning. stability of the column profile while simultaneously preserving the tray temperature controller to The DMC3 controller performance indicates a prevent any potential decline in yield quality. The distinguished reduction in variability of key process variables. column temperature profile was regulated by tuning the top Furthermore, a substantial reduction in the consumption of pressure PID controller, as shown in Figure 4. steam flow compared with the baseline has been noted, However, another problem was encountered in regards to especially on the de-methaniser and condensate stripper, the passing issue with the valve level control for both where steam consumption has been reduced by 21.9% and reboilers condensate pot drums. To address this problem, the 14.7%, respectively. This is considered a great achievement, issue was observed and resolved internally as part of a especially when considering that the feed flow has been pre-step test activity. maximised simultaneously. Moreover, there has been an undeniable improvement in the unit’s operational stability Baseline and benefit evaluation after the commissioning of the DMC controller in LPG4 plant. methodology The baseline and the benefit evaluation methodology are summarised from 26 September 2021, 00:00:00 hrs, to Conclusion 29 September 2021, 00:00:00 hrs, where the GT compressor The implementation of APC in the LPG4 NGL fractionation was running in auto mode. Data from 26 November 2021, unit at the MMA refinery was a success. Through close 00:00:00 hrs, to 29 November 2021, 00:00:00 hrs, was collaboration between the KNPC team and the vendor, considered as being after DMC3 implementation to validate advanced control strategies were developed and the APC improvements, where in both cases the gas feed to implemented to improve the plant’s performance in terms of the unit was around 750 million ft3/d. ethane recovery, product quality, and energy consumption. This case study demonstrates the benefits of APC in the The process data collected before and after refining industry and highlights the importance of effective commissioning was used to provide this post audit benefit collaboration between the refinery team and the vendor in report. The APC benefit calculation is achieved by comparing overcoming challenges and achieving successful the DMC3 OFF baseline data set with DMC3 ON controller implementation. running data set. The benefits were estimated based on the satisfactory performance of the DMC controller and an Note uptime factor greater than 95%. The authors would like to recognise the dedication and challenging work performed by experienced KNPC staff, especially the APC commissioning Table 1 reveals the net profit achieved and highlights how team which consists of: Ahmad Majed Al-Shammari, Afnan Basem a 100% operations up time was reached. Al-Darwish, Kanagasabai Rathina Sabapathi and Meshal Nabeel Al-Jaber. HYDROCARBON 25

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Michael Li PanFeng, Wonder Engineering Technologies Ltd, Singapore, explains the importance of motor operated valve (MOV) actuators in process plants and addresses key selection criteria.

electing the right motor operated valve (MOV) actuator for a specific application within a process plant can be a complex task, involving various factors. Many users tend to play it safe by replicating past specifications, but this approach can lead to the plant being locked into a private communication protocol from a single manufacturer, resulting in compatibility issues and increased expenses. This article aims to provide an overview of MOV actuators, highlighting essential selection criteria. It also aims to demystify communication protocols, and explore industry advancements. The goal is to enhance user understanding of MOV actuator selection and empower users to make well-informed decisions.

transforms a control signal into physical movement, allowing the valve to perform actions such as opening, closing, or changing its position. MOV actuators are widely used in industrial processes, heating, ventilation, and air conditioning (HVAC) systems, water treatment facilities, and other scenarios requiring precise control over fluid flow. They automate valve operations, potentially enhancing efficiency, accuracy, and enabling remote control capabilities. Control signals for an actuator can be generated from various sources, including manual switches, programmable logic controllers (PLCs), or distributed control systems (DCS).

An introduction to MOV actuators

Considerations

An MOV actuator is used to control the operation of a valve using an electric motor. The MOV actuator

The optimal MOV actuator, from a user’s perspective, depends on the specific needs and requirements of

December 2023 26 HYDROCARBON ENGINEERING

their application. Besides typical industry certifications, a solid track record and proven reliability, users commonly prioritise the following commercial factors during the selection process: n Budget considerations and cost-effectiveness: an ideal actuator should balance features and performance with associated costs while maintaining quality. n Compatibility and scalability: the actuator should be compatible with the user’s existing control system, communication protocols, and necessary accessories. n Local support and maintenance costs: access to local post-sales support, including technical assistance and on-site troubleshooting, is crucial. Additionally, minimising maintenance expenses during turnarounds is essential for overall cost assessment.

By carefully evaluating these factors, users can navigate the complexities of selecting an MOV actuator that aligns with their operational goals, ultimately improving efficiency and system performance.

Selecting the appropriate MOV actuator Choosing the right MOV actuator requires consideration of several critical technical factors to ensure a suitable match for the intended purpose. For in-kind replacement projects, sharing existing MOV specifications with the vendor may suffice. However, for new installations, the following technical aspects should be considered: n Valve type and application: identify the valve type (e.g., ball valve, gate valve, butterfly valve) and its intended application (on-off control, modulating control, emergency shutdown).

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n Load, torque, and thrust requirements: different valves have varying torques and movement requirements. It is important to consider both standard and extreme conditions to determine the forces or torques needed to operate the valve load in the specific application. This assessment will help users to choose an actuator with the appropriate rating and capacity. nn Speed and response time: evaluate the desired valve operation speed and response time. Some situations require rapid, high-speed action, while others demand precise, controlled movements or closing in stages. nn Communication protocol: identify the communication protocol necessary for seamless integration with your control system, whether it is Modbus, PROFIBUS, DeviceNet, or other private protocols. nn Control system compatibility: ensure the selected actuator aligns with your existing control system, whether it is manual switches, PLCs, DCS, or other setups. nn Integration with accessories: verify compatibility and ease of integration with accessories such as positioners, limit switches, feedback devices, and the coupling adapter with the existing valve stem. nn Power source: verify the required actuator’s power source to fit the site requirements, considering availability and appropriateness. nn Mounting and space: consider available installation space and mounting options tailored to your valve and application specifics, including factors such as handwheel access, LCD screen orientation, and fireproof jacket installation. nn Operating environment: account for environmental conditions where the actuator will operate, including temperature, humidity, dust, and corrosive

Figure 1. Field commissioning of Wonder MOV actuators.

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substances, which influence material selection and actuator construction. By meticulously assessing these factors, the process of selecting an MOV actuator becomes a strategic endeavour, aimed at achieving seamless functionality and optimal performance in process plants.

The myth of actuator selection In industries like oil and gas, tradition often reigns supreme, with a preference for sticking to what is already in place. When it comes to picking MOV actuators, technical engineers often find themselves puzzled by private communication protocols. The traditional private or labelled as ‘proprietary’ protocols are sometimes wrongly believed to be a must-have. Unfortunately, this mindset limits choices to certain dominant manufacturers and drives up costs. In reality, the key to choosing any field instrument, including an MOV actuator, lies in open protocols and compatibility. This approach prevents users being locked into a single manufacturer, where proprietary protocols will force users to rely solely on them for instruments and support, ultimately leading to higher costs and often deteriorated levels of support over time. The confusions surrounding traditional private communication protocols contribute to this issue. Users lack a complete understanding on this matter, leading to conformity to try and avoid issues. In the following discussion, some aspects of the mysterious private protocol used by the MOV actuator will be uncovered. The traditional private protocol for MOV actuators is based on a current loop communication architecture. This approach emerged at a time when advanced bus technologies and high-quality communication cables were yet to be developed. This protocol relies on a current loop to transmit signals and control commands between the control system and MOV actuators. In a current ring loop, each actuator connects to a current loop that carries control signals. The current level in the loop corresponds to a specific setpoint or command for the actuator. While this communication method was common in industrial applications due to its ability to transmit signals over long distances before the development of the digital communication, it has limitations in terms of information capacity and data transmission speed when compared to modern digital communication methods. nn Slow data transmission: compared to modern digital communication methods such as Modbus, current loop communication is relatively slow. It does not support real-time data transmission. A typical current loop operates at a baud rate of only 2400 when connecting fewer than 15 units. If more than 15 units are connected, the baud rate drops to just 1200 to 300. On the other hand, with the Modbus protocol, the typical baud rate is 9600, or rising to 19 200 when connecting within 30 units. The refresh rate is 500 msec. for quantities ranging from 30 to 60 units

per loop. Such speeds are unattainable in current loop communication. nn Scalability and hardware dependency: the viability of current loop communication largely depends on the compatibility of hardware components, including both actuators and control equipment. The ongoing development and evolution of private protocols are entirely at the discretion of the manufacturer. Without consistent investments in development, this protocol inevitably becomes outdated. nn Cost implications: current loop protocols come with added expenses including licensing fees, specialised hardware, and software requirements, which can increase costs, including ongoing maintenance expenses. Notably, the lack of competition in the realm of communication protocol isolation can lead to higher prices. For instance, a typical actuator overhaul by such a manufacturer can cost as much as half the price of a new unit due to limited alternatives with the same communication protocol. Moreover, transitioning to a new protocol or system can prove to be even more complex and costly, necessitating the replacement of existing infrastructure. nn Manufacturer dependency and integration challenges: while new actuator manufacturers have embraced open protocols as the industry standard, traditional manufacturers continue to produce actuators that rely on outdated current loop communication.

Unfortunately, these protocols offer no discernible benefits to end-users. The continued use of current loop-based design limits compatibility with third-party actuators, leading to integration challenges and compatibility issues. Consequently, this fosters a reliance on a single manufacturer for hardware, software, and maintenance support. In reality, all MOV actuators available on the market are able to support open protocols. However, some manufacturers may not actively promote open protocols unless explicitly requested by the user. In some cases, certain manufacturers may try to steer users toward defining current loop protocol as mandatory, potentially positioning themselves as the exclusive vendor. This is a common sales tactic often seen in the MOV actuator market.

Advancements in the industry In recent decades, the industry and technology have made significant progress, bringing about substantial improvements through the adoption of open protocols. This progress is especially evident in bus technologies such as Modbus, Profibus, and Foundation Fieldbus. These advancements have enabled MOV actuators to establish direct connections with DCSs or operate through a master station based on the open Modbus protocol.

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The long-distance communication loop maintains high baud rates of 9600 or 19 200, which is significantly faster than Current Loop communication, operating at slower baud rates of 2400 or 1200. The scanning time for each MOV ranges from 50 msec. to 80 msec., while the response time of the MOV is approximately 50 msec. to 80 msec. after the DCS initiates the command. Cable length has a negligible influence on time, less than 1 msec., making it inconsequential in this type of loop communication.

Signal repeater module and communication board

Figure 2. Field configuration for master station using Modbus RTU (RS-485).

Successful implementations

Wonder Engineering has recently completed successful revamp projects in Malaysia and Singapore. These projects involved replacing existing MOV actuators and adding new ones onto manual valves. Communication was established with various DCSs, including those from Honeywell, Emerson, and Yokogawa, using various protocols such as hardwired connections, Modbus, and FOUNDATION Fieldbus.

Modbus-based master station

The field communication controller for MOV actuators, often called the master station, plays a crucial role in creating a field ring loop with redundancy capability and connecting back to DCS. It is developed based on the Modbus communication protocol, ensuring full compatibility with MOV actuators from different manufacturers using the same Modbus protocol. Communication between the master station and DCS is transmitted through either Ethernet or RS 485. The DCS extracts MOV data from the master station’s real-time database, with the DCS acting as the ‘master’ and the master station as the ‘slave’. Based on project experiences, Wonder established that a single master station, using an open protocol, can connect to either up to four single ring loops or two redundant ring loops. This allows for grouping of MOVs, with quantities reaching up to 120 units per ring loop. This capacity can be expanded to accommodate up to 250 units through software expansion. A redundant master station offers hot-swappable capabilities. Each loop can communicate over a maximum distance of 30 km, thanks to the built-in repeaters in the MOV actuators. These repeaters are recommended for actuators located at distances of 750 m, as communication distances can reach up to 1.2 km for the Modbus protocol. December 2023 30 HYDROCARBON ENGINEERING

Signal repeater modules are plug-and-play units located behind the communication board. Default settings include redundant repeaters. Slave addresses are stored on the main board behind the LCD screen, unaffected by signal repeater swaps. The modular loop communication board employs a three-way connection within each actuator, ensuring that any out-of-service MOVs will not impact communication within the same loop. Access to the communication board(s) is possible online. Additionally, an optional built-to-order field communication connection is available, featuring a plug-and-play interface. For added safety, a separate explosion-proof-rated communication chamber can be provided, complete with matching covers for both the connection head and actuator side.

Conclusion Considering the ongoing advancements in communication and hardware technologies, the complexity of MOV actuators has significantly decreased. Choosing an MOV actuator that adheres to an open protocol is a wise decision. This choice prevents end-users from becoming dependent on a single monopoly manufacturer or brand that operates on a private protocol. By carefully considering the technical aspects and avoiding any private protocols mentioned in an inquiry, it is possible to position oneself as an end-user in control. This approach guarantees a cost-effective solution while maintaining mastery over a system. The role of qualified electrical and instrumentation engineers in today’s industrial sector extends beyond ensuring that the instruments selected for the plant function correctly. It involves continuously studying the overall development of electrical and instrumentation technologies in the industry. This includes gaining a clear understanding of the fundamental technical differences in instrumentation products and being able to discern any traditional, outdated practices and sales misrepresentations by a vendor. The goal is to genuinely assist operation in selecting instruments that are stable, offer high cost-effectiveness, and are suitable for the plant. This prevents plants from falling into the pitfalls of high costs, reliance on a single manufacturer, high maintenance expenses, and low-quality post-sales service.

Juha Relander, Valmet, Finland, outlines the importance of selecting the most appropriate severe service control valves.

ontrol valves are an important part of the refining and chemical industry. The selection of these valves requires considerable understanding of the control valve sizing and selection, trim designs, materials, and a controller device. While there are many so-called standard control valves that are part of the process, there is a certain percentage of valves that are under severe process conditions, meaning they need to be selected more carefully. The valves in these services are subject to challenging conditions that affect their performance. As a result, having knowledge of these challenges and being able to provide informed recommendations for solutions is crucial to ensuring proper functioning of the valve, which in turn leads to improved plant efficiency, life cycle maintenance costs and reliability. Typically, there are three different types of control valves: linear, rotary and axial flow. Selection is based on customer requirements and recommendations based on the experiences of valve vendors. The ideal approach is to select the

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valve based on specific applications, rather than selecting just one type of control valve for all applications.

Cavitation and flashing: challenges in liquid flow control Cavitation is a typical example of a valve duty that is considered to be a severe service. It is a two-phase phenomenon that occurs in certain flow conditions. At the control valve restricting the flow, the pressure of the liquid decreases rapidly. As soon as the liquid’s pressure decreases below the vapour pressure level, the liquid starts to turn into a gas, creating vapour bubbles inside the flowing liquid. Essentially, the liquid boils. However, in this case, it is not due to the increasing temperature, but because of the pressure dropping at the throttling valve. What makes cavitation potentially damaging is what happens right after the valve. The pressure of the flow starts to recover downstream from the so-called ‘vena contracta’, the point of smallest diameter where flow passes. As soon as the flow

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pressure increases above the vapour pressure, the vapour bubbles begin to collapse. The collapse of the bubbles happens rapidly and violently, causing pressure shocks inside the process fluid. Those pressure shocks cause, at best, high noise levels, but may at worst lead to mechanical damages in the valve and the equipment in the pipeline after the valve. On the other hand, when flashing occurs, the pressure never recovers back above the vapour pressure level, so the vapour bubbles never collapse. The gas bubbles then expand due to the recovering pressure. This leads to high flow velocity, which increases the risk of damage that is reminiscent of erosion. The key to avoiding possible damage from either cavitation or flashing lies in thorough and professional valve selection. Taking extra time over the control valve selection can potentially double the lifetime of the equipment. For example, cavitation under high pressure differential duty, combined with corrosive or erosive flow media, may result in visible damage in days or weeks, rather than in years, for cases where the valve selection has been carried out carelessly or with incorrect/incomplete process data. All valve types, designs and styles of construction have different capabilities

when handling cavitation and flashing. Cavitation prevention technology typically relies on pressure staging, which can be achieved with special anti-cavitation trims. With correct valve selection, this cavitation phenomenon can be controlled, and even completely avoided, all while preventing any damage from occurring. Today, valve selection and sizing is carried out in valve sizing software, which can automatically recognise flow conditions where phenomena such as cavitation or flashing may take place. It is important to note that not all cavitation must be prevented. Often incipient or partial cavitation is not harmful and, with some valve types, even choked flow is not dangerous with lower pressure differences. Valve sizing and selection software, such as Valmet’s Neles NelprofTM, can automatically estimate the damage potential and guide the user towards the control valve that is most suitable for the exact process conditions. When flashing occurs, the valve selection cannot prevent the phenomena itself. If outlet pressure is smaller than the vapour pressure, flashing will occur. The ideal next step is to select valve constructions that are optimised to endure the flashing and designed to direct the flow smoothly out of the valve into the middle of the pipe after the valve. Eccentric rotary plug valves and angle globe valves are both examples of valve types that excel in flashing applications. Typically, an expander after a valve is also preferred, allowing more room for the two-phase flow.

Erosive flow: maximising the control valve lifetime

Figure 1. The unique metal matrix composite used in the Neles WearBlock™ Solutions.

Figure 2. An anti-noise trim uses flow division and pressure staging for noise abatement.

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Other typical examples of severe service valve applications are control duties with clearly erosive flow media. These are typically liquid slurries or mixtures of gases with abrasive solid particles. Wear, abrasion and corrosion damage will occur similarly, regardless of whether it is a case of liquid or gas mixes, when the medium carries abrasive particles. This can be a known feature of the application – for example, when moving heavy slurries or controlling the amount of hard catalyst fines in a cracker – but also often unwanted and unknown – for example, when sand particles appear in crude oil or in natural gas lines. Nevertheless, it is an issue that needs to be tackled. Just like cavitation damage, erosion damage can occur rapidly and repairing the inner surfaces of the valve and pipeline is typically very time-consuming and expensive – considering it is even possible. Once again, to prevent erosion damage, the crucial step is making the correct selection. With wide openings and smooth flow channels as well as limited local flow velocity maximums, a lot can already be achieved. However, to significantly increase the lifetime of the valve, material selection is the key to success. Typical solutions include upgrading valve base materials to stronger alloys and applying hard coating at least on the trim parts of the control valve. In many cases this is not sufficient and more innovative ideas are required to keep the process running without unwanted maintenance breaks. Ceramics are not uncommon protective lining elements inside valves and offer excellent erosion resistance. Ceramics do, however, have their limitations in resistance to thermal shocks and

electrical conductivity, which are crucial in demanding processes. Neles WearBlockTM (see Figure 1) bi-metal valves, which use metal matrix composite materials, offer a solution in demanding applications in which wear protection similar to ceramics needs to be combined with, for example, electric conductivity.

Aerodynamic noise Controlling flows of gaseous media is often noisy. Limiting the aerodynamic noise from the process is a standard requirement for health, safety, and environmental reasons. Noise causes direct risks for the health of the personnel running the process and may also need to be controlled carefully so that excessive noise from the process plant itself is avoided. In the worst cases, gas noise can be mechanically damaging to the process equipment. At present, a typical noise limit is still 85 dBA in working environments globally, but stricter limits are not uncommon. Methods of aerodynamic noise abatement in control valves are often divided into two basic techniques. In source treatment, the valve internals, trim and flow path are designed to minimise the generation of excessive noise. In path treatment, the already generated noise is dampened, typically by pipeline insulation or separate silencers. Source treatment can prevent excessive noise emitted from the process, as well as limit or even eliminate the mechanical vibrations that are potentially harmful to the

sensitive process equipment. Examples of source treatment methods in control valve trims include flow division, pressure staging, controlling the shock waves and frictional flow path designs (see Figure 2). Such trims specifically developed for gas noise abatement are widely available, both for rotary and linear globe control valves. Selecting the most suitable noise abatement valve construction and trim is a task that requires expertise. Luckily, the computerised control valve noise prediction methods following internationally recognised IEC standards have been around for decades, and now with the newest software, it is easy to simulate and compare various solutions with just a few clicks. Selecting an optimally sized gas control valve with a suitable anti-noise trim for a particular process not only ensures the best control performance that falls within the noise limits, but also maximises solution efficiency by avoiding the use of static resistors, such as diffusers or fixed resistor plates.

Conclusion Putting some extra time and thought into control valve selection can really make all the difference. Having the correct technology available and the expertise to select and size control valves for mission-critical applications and challenging process conditions enables a safe working environment for personnel and the plant. It also increases process efficiency and ensures operational availability and reliability at all times.

Heater Types

NOX Reduction

CO2 Reduction

Ammonia SMR

12 - 25%

2 - 5%

Crude/Topping/CDU

5 - 15%

2 - 5%

CRU

10 - 20%

5 - 15%

Ethylene

15 - 30%

2 - 5%

Hydrogen SMR

12 - 25%

2 - 5%

Other (e.g., Xylene)

5 - 15%

2 - 5%

Adam Attig, Emerson, USA, reveals how new technology can instantly detect leaks in relief valve bellows, eliminating the need for manual rounds and reducing fugitive emissions.

ressure relief valves (PRVs) are a critical layer of overpressure protection for many industries. Under normal operating conditions, the PRV remains closed, but when there is a process upset, the PRV must instantly open to vent the excess process media and avoid overpressure conditions. When backpressure may be encountered in a relief valve header, a bellows PRV design is often employed. These relief devices work well, but under cycling or corrosive chemical applications, the bellows may be damaged, leaking potentially hazardous media to the environment and

adversely impacting PRV performance. Unfortunately, these leaks can be significant and often go undetected for years. This article discusses an innovative PRV design and technology that immediately detects leaks, alerts plant personnel, and limits leak rates significantly, while allowing the PRV to continue operating as designed despite damage to the bellows.

Conventional vs bellows PRV operation A PRV consists of an inlet nozzle attached to the process, which is contained by a disc held tightly against the nozzle

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seat using a calibrated spring (Figure 1). When the process media pressure reaches the PRV’s set pressure, the applied upward force from the process offsets the downward force of the spring and the disc lifts off the seat to exhaust process media. Eventually the pressure drops to a safe

Figure 1. A pressure relief valve protects equipment

by automatically venting the process media when pressure in the inlet nozzle overcomes the downward force of the spring (set pressure).

Figure 2. Typical PRV discharge piping header system.

Figure 3. A bellows-style PRV incorporates a metal bellows above the seat that allows the PRV to operate at setpoint, even with varying backpressure. Should the bellows leak or fail due to a rupture, the PRV set pressure could be affected, and vent header media may escape to the environment.

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operating level and the PRV spring pushes the seat back down, stopping the release. The conventional PRV design works well, provided there is no backpressure on the discharge header (Figure 1). If pressure does exist in the header, it will push the seat down along with the spring, effectively raising the setpoint of the PRV. Since the header pressure can change, the set pressure of the PRV can also vary, which is potentially dangerous and could result in overpressure of the system. In a typical header system with backpressure (Figure 2), a bellows style PRV is often employed to address this issue. This design is similar to a conventional PRV, but it employs a bellows installed above the disk to block the vent header backpressure from reaching the top of the disc. This allows the bellows PRV to operate at set pressure, regardless of any variable header pressure it might encounter (Figure 3). The bellows PRV design works well, provided the bellows remains intact. However, the metal bellows is prone to fatigue, especially in cycling applications. Should the bellows crack or rupture (Figure 3 right), the protection from variable header backpressure is lost and the PRV will no longer lift at setpoint. In addition, the media will leak through the bonnet vent to atmosphere. Unfortunately, bellows damage is common and can lead to flammable or other hazardous media being released. A recent study of 30 000 bellows-style PRVs across multiple industries and various valve manufacturers found the damage rate to range from 2 - 6%. This has subjected innumerable pieces of process equipment to potential overpressure and generated unknown quantities of fugitive emissions. In addition, the industry standard method of determining if a PRV is damaged and releasing fugitive emissions is by a manual walkdown by plant personnel using a sensor, such as a sniffer. This type of inspection does not reliably detect a failure, provides little to no insight on when a leak started, and gives no information on the volume of process media that escaped to atmosphere.

Bellows PRV backpressure balancing piston A PRV design improvement has addressed the limitations of bellows style PRVs, allowing the bellows PRV to operate at set pressure, despite bellows damage. The design change involves the addition of a balancing piston above the bellows (Figure 4). The piston size matches the size of disc, so even if the bellows fails, the PRV will operate at setpoint despite backpressure, since the downward force of the backpressure on the disc is offset by the upward force of the pressure on the piston. The piston and surrounding adapter are machined to tight tolerances, which significantly reduces the rate of leakage through the bonnet. Testing has shown this technology can reduce typical fugitive emissions from bellows damage by up to 90%. While the balanced piston enhancement allows a damaged bellows PRV to operate at setpoint and limits the leak rate, the damage remains undetected, and may go unnoticed until the PRV is pulled for routine maintenance. A new feature has been incorporated into the balanced bellows that also provides notification of a bellows failure,

improved root cause analysis of a damaged bellows, and information regarding the volume of any release.

New bellows leak detection technology A new bellows leak detection technology adds a wired or wireless pressure instrument to the valve that measures the pressure below the piston (Figure 5). Upon damage to the bellows, the pressure below the piston increases and is immediately detected by the transmitter. The transmitter can provide a timestamp notification of a bellows leak, which can be used in correlation with other process information for more effective root cause analysis and improved operations. It also immediately notifies plant personnel of potential hazardous emissions. This technology is available in an upgrade kit and can easily be added to any existing PRV during a repair or retrofit, and it can also be supplied with new valves. Additionally, the pressure measurement allows the system to determine the fugitive emissions volume based on the process media, internal pressure, and known mechanical clearances within the adapter and balancing piston. Insight into the volume of emissions allows the plant to make an informed decision as to how quickly the repair should be made, and to reduce any exposure risk to personnel. Since the PRV will continue to operate as intended with the leak rate significantly reduced, plant personnel can evaluate the situation to determine the severity of the hazard while they continuously monitor its status.

Figure 4. Installation of a piston above the bellows allows the PRV to still operate at setpoint, even with damage to the bellows.

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Application examples A chemical plant with multiple balanced bellows PRVs installed on a flare system header encountered process instabilities and cycling. One PRV was seeing frequent operation, which led to bellows damage and the venting of a highly flammable process media to atmosphere.

Figure 5. The addition of a wired or wireless pressure transmitter (top left) to a PRV provides instant detection of bellows damage and provides the data required for continuous calculation of the fugitive emission leak rate.

Installing a PRV with the new bellows leak detection technology provides plant personnel with the information required to understand how the valve is operating, as well as the ability to immediately detect a leak if the bellows is damaged. Significantly reduced emission rates will mitigate the hazard, and continuous knowledge of the volume of emissions venting will aid plant personnel in the evaluation of the event so they can schedule repair more efficiently. In another application, a refinery had a balanced bellows PRV installed downstream from a fuel transfer valve. The valve was regulating the process irregularly, so the PRV was cycling frequently, working to protect the system. Eventually the PRV bellow’s failed due to this over cycling, venting undetected fuel gas into the atmosphere, and introducing the risk of hazardous combustion. By installing a PRV with bellows leak detection, plant personnel will be able to detect damage to the bellows the moment it occurs, meaning they can immediately remove the system out of service for repair, or determine if the outage can be safely delayed. If operators are facing PRV bellows damage or fugitive emissions, upgrading PRVs to incorporate new balanced piston and bellows leak detection can help significantly. This new technology can ensure that PRVs continue to operate at setpoint, even with bellows damage, while dramatically reducing fugitive emissions should damage occur. More importantly, the leak detection instrumentation makes a faulty valve instantly apparent, allowing this to be addressed before the emissions pose a threat to personnel or equipment.

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Gudjon Thor Olafsson, Michael Winther and Rasmus Gregersen, Svanehøj Danmark, discuss the advantages of new electric submersible fuel pumps for LNG-powered ships.

NG has been a marine fuel option for decades. However, in the commercial marine fuel market, LNG has not made its mark until recent years. Since 2010, the number of LNG-powered ships has grown consistently by 20 - 40% yearly. By the end of 2022, almost 900 LNG-powered vessels were in operation or on order, and further growth is expected in the coming years. Among LNG-powered ships, there are two different fuel pump technologies: the submersible pump and the deepwell pump. Both pump types are driven by electric motors, and are placed in the tank and on the deck, respectively. The deepwell cryogenic pump has considerable technical advantages but, due to its long shaft and motor base arrangement, it is also more expensive, which is why the submersible pump is the dominant standard in most segments.

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As LNG has become more widely used as a marine fuel, ship operators have experienced certain challenges regarding submersible cryogenic pumps. The motor bearing is a ceramic ball bearing type and is therefore prone to contaminants. To prolong service intervals and avoid short circuits, the liquid that cools the motor and lubricates the bearing must be filtered. Several pump manufacturers use external or internal filtration solutions (or a combination) designed to filter all of the

gas flowing through the pump. However, the filters tend to clog up with impurities in the liquified gas, resulting in unavailable pumps and excessive wear on bearings and motor components. Another issue is the electric submersible induction motor, which is a common design standard in the industry. Several scientific studies have shown that this motor type struggles with low efficiency, small torque density, and extensive heat generation. Extensive heat generation in the motor housing is undesirable, as the liquid gas may become gaseous (boil-off), resulting in poor bearing lubrication and loss of motor cooling, and ultimately degrading performance. In 2021, Svanehøj set out to solve the challenges regarding submersible cryogenic pumps for LNG-powered vessels by designing a new solution, the CS fuel pump, which was launched in autumn 2022.

Self-cleaning LNG filter

Figure 1. The CS fuel pump is designed with a

self-cleaning side flow filter. It is placed in the high-flow velocity of the discharge pipe and provides a filtered secondary flow for cooling and lubrication.

Cryogenic submersible pumps are traditionally designed with a filter through which all of the gas flows. That solution has proven ineffective due to clogging. Svanehøj’s CS fuel pump is designed with a ‘strainer’ that has 3 mm holes on the suction side of the pump to catch loose debris, while only a small fraction of the main gas flow passes through the pump’s LNG filter (4 - 6 l/min, which is necessary for cooling and lubrication). This design feature is complemented by a self-cleaning process that is active while the pump is running. The LNG filter for the pump is a side flow filter element developed by Svanehøj in close cooperation with industry specialists. The filter is constructed by using several small, well-defined rings that, when stacked on top of each other, create several small ‘slits’ that enable the separation of harmful particles. The filter is placed in the discharge pipe where LNG has high velocity, providing a filtered secondary flow for enhanced cooling of the motor and lubrication of the motor bearings (see Figure 1). The unit is designed without moving parts, and is easily accessible for service or interchange. For the design and further development of the LNG filter element, a specialised test stand has been constructed to verify functionality. The tests are carried out in water infused with contaminant particles of controlled size and count.

New motor

Figure 2. The new electric IPM motor performs with an efficiency of 96.8% compared to the industry standard of 84 - 88%. It significantly reduces BOG and thereby risk of damage.

December 2023 42 HYDROCARBON ENGINEERING

An essential aspect of the pump is the electric Interior Permanent Magnet (IPM) motor, which is designed to run fully-submerged in the pumped cryogenic fluid. In cryogenic conditions, the motor performs with an efficiency of 96.8% compared to the industry standard of 84 - 88%. Because of the higher efficiency, significantly more electrical energy is converted into mechanical power, thereby saving energy and avoiding boil-off gas (BOG) caused by heat generation. The IPM motor was developed in collaboration with motor suppliers, and based on extensive research,

development and testing. Engineers analysed two motor types in a preliminary study: the Induction Motor and the Permanent Magnet Motor. The choice of the Permanent Magnet Motor design was based on four main arguments: efficiency, weight and dimensions, gap between the stator and rotor, and future prospects. An Induction Motor uses significant energy to form a magnetic field in the rotor. A Permanent Magnet Motor does not require energy to form a magnetic field, as it is incorporated by the permanent magnets. The Permanent Magnet motor design is stable at low temperatures, with low coercivity, loss of cooling and remanence temperature coefficient. A study of a 20 kW Induction Motor showed an efficiency of 87%, meaning that 13% of the supplied energy converts into heat, thereby increasing the risk of BOG, dry running of bearings, and significant damage. Tests of the IPM e-motor show that just 3% of the supplied energy converts into heat, which significantly reduces BOG and therefore the risk of damage. The 20 kW IPM e-motor from Svanehøj weighs 20 kg, which is nearly half of the aforementioned 20 kW Induction Motor. At the same time, the stator diameter in the IPM e-motor is 148 mm compared to 200 mm in the Induction Motor. The lower weight and smaller size reduce the use of materials. With a gap of just 0.5 mm between the stator and rotor, the Induction Motor requires ball bearings on both sides of the rotor. The IPM e-motor is designed with a gap of 1.5 mm between the stator and rotor, and thus requires just one hybrid ceramic ball bearing. The larger gap improves the stability of the pump. The Permanent Magnet Motor is the solution for future LNG pumps, as there are inherent drawbacks related to the Induction Motor design. A Permanent Magnet Motor design can be made smaller and more efficient and reliable at low temperatures. The Svanehøj IPM e-motor is built with full-face bonded rotor and stator laminates for a stable, rigid and strong lamination pack. The permanent magnets are retained in slots by small springs cut into rotor laminates (see Figure 2). The pump is built with only one media lubricated ceramic ball bearing for taking up axial forces. All other bearings are of the robust radial carbon bearing design. The motor stator is fully potted with a special heat-conductive resin, rated for cryogenic operation, to prevent problems with short-circuiting due to tiny electrically-conductive particles accumulating in the copper windings over time. The potting fully encapsulates the copper windings, preventing any containments or moisture from entering the stator. The IPM e-motor is designed to run fully submerged in the pumped cryogenic fluid. Two prototypes were built and tested in liquid nitrogen (-196°C). The tests confirmed that the IPM e-motor performs well at low temperatures, and the hybrid ceramic bearing withstands very harsh conditions.

Cryogenic conditions require specialised pumps Keeping LNG in its liquid form requires cryogenic conditions of at least -162°C (or with the relative pressure built up). LNG pumps must therefore be highly reliable, durable, and constructed from materials that function optimally under cryogenic conditions. The CS pump (see Figure 3) is designed with: n n Long stay-bolts for maximum elasticity and handling of the variance in thermal expansion between materials under cryogenic temperature. n n A cryogenic collet connection for interlocking the motor and centreless ground pump shaft. n n One hybrid ceramic bearing for taking up all axial forces. n n Carbon journal bearings for radial loads. n n A secondary flow driven by pressure differential over the last pump stage. This principle is verified by computational fluid dynamics (CFD).

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n n Fully closed and cast intermediate chambers, which provide reduced hydraulic loss and lower production costs. n n A double-wear ring with a labyrinth seal design for improved hydraulic performance and reduced leakage. n n Impellers with splitter blades to increase the pressure per stage. n n Impellers with balancing holes to minimise the axial force acting on the main bearing. n n An inducer for increased suction performance. The inducer increases pressure in the first impeller and minimises cavitation. It also secures a lower net positive suction head (NPSH) value.

Conclusion

Figure 3. The CS fuel pump introduces two innovations to the market for submersible LNG pumps: a self-cleaning LNG filter to solve the problem of clogging, and an IPM motor to improve reliability and efficiency.

The energy transition of shipping is picking up pace, and the suppliers of critical components and systems must stay at the forefront of innovation to help facilitate this crucial process. The development of the CS fuel pump is an example of how to address a challenge in the market and solve it through innovation and technology. In order to support the green transition, partnerships comprising companies, institutions, and networks need to form in order to develop the technological solutions that are required to succeed in cutting annual greenhouse gas emissions from international shipping by at least 50% by 2050.

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Thomas G. Lestina and Kevin J. Farrell, Heat Transfer Research Inc. (HTRI), USA, examine how using a second-law approach can help to improve the efficiency and environmental impact of process heat exchangers.

rocess heat exchangers have traditionally been designed using methods based on the zeroth and first law of thermodynamics. First-law efficiencies deviate from unity only as a result of thermal leakages to or from the environment and thus are deficient discriminators among designs. A second-law approach requires quantification of thermodynamic irreversibilities in the design – mainly from heat transfer over a finite temperature difference and frictional pressure drop of the stream(s). The resulting second-law efficiency is a better comparator and informs calculations of environmental

impact and sustainability. This article defines and discusses the value of the approach with an example case study. Energy intensive industries, such as refining, petrochemical, and chemical processors, seek to improve energy efficiency to reduce costs. The current emphasis on sustainability increases the incentive to do so. Energy efficiency studies most often address an entire system, where the interrelated performance of a network of unit operations can be assessed. Heat exchanger performance can be an important part of these studies. HTRI has recently been using some overlooked thermodynamic principles to inform design

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decisions for efficient process heat exchanger operation. The insights from this recent research can be used as an additional tool to improve heat exchanger design. The subject of thermodynamics was developed in the nineteenth century in order to improve the performance of heat engines. The great early thermodynamicists including Carnot, Clausius, and Joule were most interested in conserving fuel and not particularly concerned about pollution or climate change. Now, the growing awareness of environmental impact has stimulated a closer look at the thermodynamic performance of all processes. Although important, the thermodynamic performance is not the sole consideration; an acceptable design solution must address criteria developed from concerns about safety, material selection and availability, geography, radiated noise, sustainability, size, maintenance, and economics, among others.

The laws of thermodynamics Taken together, four fundamental laws of thermodynamics form the basis for the rest of the subject. Current control volume or open system analyses with heat exchanger design tools, such as HTRI’s Xchanger Suite®, rely on the zeroth and first laws of thermodynamics along with conservation of mass. The heat exchanger efficiency that HTRI advocates is based on the second law as well. This requires the tracking of the entropy of the fluids that are exchanging heat and recording the dead state temperature and pressure. Availability, a measure of the maximum work that the stream can do, can then be calculated. The four laws of thermodynamics are stated below, using simple declaratives.

Zeroth law

further diminish the accuracy of these design solutions in actual exchangers with their as-built imperfections. While these thermal performance analysis techniques are based on the zeroth and first law of thermodynamics with the conservation of mass, they do not acknowledge or quantify the irreversibilities due to nonideal performance. Entropy increases in any real process according to the second law, which decreases the quality of the energy. When a system operates irreversibly, it destroys work at a rate that is proportional to the system’s rate of entropy generation – a principle called the Gouy-Stodola theorem. Formally, the irreversibility is: (1) It is possible to monetise the destroyed work in terms of the equivalent carbon dioxide (CO2) produced using an emissions factor for the energy source and locale. This presents an opportunity to reduce the carbon footprint – a ceiling value, as according to the second law, it can never be taken to zero. Heat transfer over a finite temperature difference and pressure drop are the two principal sources of irreversibility in a heat exchanger. Other sources may be unrestrained expansion, mixing, turbulence, chemical reaction, resistive loss in electrical circuits, and interactions with the environment (e.g., heat loss or heat ingress in the case of cryogenic heat exchangers). Unfortunately, design approaches to minimise one irreversibility source typically exacerbate others. Availability is a thermodynamic function that depends on the state of both the environment and the system, and reflects the quality of the energy: **

There is a useful quantity called temperature that reflects thermal equilibrium.

First law

There is a useful quantity called enthalpy in an open system that satisfies . In a heat exchanger, no shaft work is performed, and no heat is exchanged with the environment – only among the streams. Changes in kinetic and potential energy are usually negligible. Therefore, the first law simplifies to an enthalpy balance.

Second law

There is a useful quantity called entropy which satisfies for any real process.

Third law*

There is not a thermodynamic process by which one can attain absolute zero temperature.

(2) Availability represents the maximum useful work that can be obtained from a system by a reversible heat engine operating between the energy source and the environment. The environment is usually the dead state, noted with the 0 subscript, because no useful work can be extracted from the environment. The atmosphere contains a tremendous amount of energy, but it cannot be used for doing work unless there is a lot of wind (kinetic energy). The dead state is typically 25 °C and 1 bar pressure. The quality of energy decreases in every thermodynamic process, including heat transfer. In the open system of a two-stream heat exchanger, availability (but not all of it) moves from the hot fluid to the cold fluid; availability always decreases in the process. This observation allows a simple efficiency law to be formed for a two-stream heat exchanger.

Second-law considerations for process heat exchangers The log mean temperature difference (F-LMTD) method and the effectiveness-NTU ( -NTU) method underlie most thermal rating methods. Either method can solve the exchanger rating or sizing problem and will yield an identical solution. These methods utilise the same assumptions, none of which are ever completely true in an actual design. Nonidealities, such as bypass streams and flow maldistribution, December 2023 46 HYDROCARBON ENGINEERING

2nd, two–stream =

Where: Streams possess availability by virtue of temperature and/or pressure that exceeds that of the dead state.

(3)

Fuel streams have added chemical availability, which is often taken simply as the gross calorific value, as this is the maximum work that could be extracted. A heat exchanger has its own boundary or envelope around it. Material and energy streams cross this boundary. Obviously, the scope and accuracy of any performance estimate of the unit operation is limited to the streams and utilities captured in the control volume and boundaries and the fidelity of the modelling. Clearly, all unit operations that make up the complete process must be analysed, but in considering a single heat exchanger, our knowledge is limited to the control volume boundary and what is inside. The flow of availability through a process can be viewed in a Grassman diagram, as in Figure 1. The streams entering the heat exchanger are to the left of the vertical bar in the middle, and the streams departing the heat exchanger are to the right of the vertical bar. The irreversibility is the portion of the availability entering the exchanger that is destroyed in the heat exchange process. For multi-stream heat exchangers and those with turbomachinery (shaft work) or chemical reactions in the control volume, HTRI suggests an alternative second-law efficiency:

drop for the gas side to ensure that compressor power requirements are not exceeded. Because the gas side has the highest thermal resistance, the design of an intercooler requires a careful balance between heat exchange and pressure drop. A rule of thumb for these applications is to ensure that all allowable pressure drop is used for the gas side. This example shows how fouling and applying this rule of thumb can affect the second-law efficiency, cost of construction, and carbon footprint. Consider a skid-mounted moist air intercooler with an air/water mixture on the shell side and cooling water on the tube side. Table 1 lists design process conditions. The thermal design is performed using HTRI’s shell-and-tube software Xist®, and fabrication costs and associated carbon emissions were determined using Exchanger Optimizer with a 5 times (x) cost factor for the continuous-finned tube vs a plaintube. The operational irreversibilities, – were , monetised to a CO2e emission (reduction opportunity). It is understood that the operational carbon footprint calculated in this way is more properly understood as an upper bound on the CO2e reduction opportunity; it can

(4) Where – is the total availability destruction in the control volume of all sources – flow availability, shaft work, and chemical availability (e.g., combustion). Calculating the net rate of change in availability of all the streams in a heat exchanger allows the calculation of the rate of Figure 1. Grassman diagram for (a) generic two-stream heat exchanger availability destruction or lost work, and (b) air cooler. and thus the rate of irreversibility. The second-law efficiency values depend on the dead state Table 1. Design process conditions for moist air temperature. For high temperature cold streams and a dead intercooler state temperature of 25 °C, higher efficiencies are expected. Parameter Value Similarly, for low dead state temperatures, high efficiencies Shell side – moist air (1.86 % H2O by weight) are also expected to increase to 100% at absolute zero temperature. Second-law efficiencies can most effectively Flow rate (kg/s) 7.0 help compare different designs and operating conditions for Temperature, in/out (K) 431.15 / 311.91 a particular application. For waste heat recovery applications Weight fraction vapour, in/out 1.000 / 0.9995 (feed-effluent exchangers, recuperators, and flue gas Inlet pressure (kPa) 243.80 economisers), differences in efficiencies can be directly Allowable pressure drop (kPa) 5.4 related to energy costs and emissions. For other applications, 2 differences in efficiency can indicate other issues. Fouling, Fouling (m K/W) 0.0001 flow bypassing, and other degradation mechanisms reduce Tube side – cooling water the second-law efficiency. Variations in exchanger Flow rate (kg/s) 37.8 geometries have a more subtle impact, as the following Temperature, in/out (K) 305.15 / 310.69 example case demonstrates.

Example case Intercoolers remove the heat of compression with the purpose of reducing the work input to reach the specified pressure. Intercoolers typically have low allowable pressure

Inlet pressure (kPa)

451.32

Allowable pressure drop (kPa)

Fouling (m2

0.0004

Duty (MW)

K/W)

0.875

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In Figure 2, the relative scale of the three design configurations is compared. Also included are performance parameters of a simulation of the continuous-finned configuration, with no fouling factors on either side in the fourth column of Table 2, in order to quantify the effect of fouling. This simple comparison yields many interesting observations. The plain tube configuration has the highest second-law efficiency by either definition, but it costs approximately 30% more than the others to build and emits nearly three times as much carbon during fabrication. This configuration also carries over 88% of the thermal resistance on the shell side, so enhancements there dramatically reduce the tubecount, the cost to build, and carbon emissions associated with fabrication. The potential to reduce the operational carbon emission varies over 8% among the three design configurations. Application of the long-time rule of thumb to fully utilise available pressure drop motivates the Figure 2. TEMA X-shell-and-tube heat exchanger designs for an intercooler, compact, continuous-finned design, illustrating relative sizes and tube bundle configurations. which actually exacerbates the never be zeroed unless all energy sources are ‘green’ or the second law is violated. Table 2 presents geometry and performance attributes of three designs of a TEMA X-shell-and-tube heat exchanger: a plain tube version, a continuous-finned version, and a compact, continuous-finned version.

Table 2. Comparison of intercooler designs Design

Plain tube

Continuous fin

Continuous fin, no fouling factors

Compact continuous fin

Shell inner diameter (mm)

778

762

610

Tube length (m)

4.267

2.591

2.286

Tube outer diameter (mm)

15.875

Tube pitch ratio

1.26

2.05

1.50

Tubepass

Tubecount

1040

151 U-tubes

Fin density (1/m)

No fins

433.1

Heat transfer area (m2)

190

500

264

Calculated P/ allowable P P, shell side

0.28

0.47

1.00

201 U-tubes

0.158

0.154

0.168

0.150

0.161

0.166

0.156

0.174

0.839

0.834

0.844

0.826

Fabrication price, (US$1000)

133

101

105

CO2e emissions from fabrication (t)

Operational CO2e emission reduction potential (tpy)***

556

573

523

604

Effectiveness (first law),

0.944

0.974

0.944

December 2023 48 HYDROCARBON ENGINEERING

second-law efficiency and has the greatest irreversibility among the three. Interestingly, the three designs have identical effectiveness, , which is a first-law quantity. The column with the label, ‘Continuous fin, no fouling factor’, represents a simulation Xist run of the exchanger, with continuous fins, but with no fouling factors. The result is a 1.0% improvement in and a 9% reduction in the operational carbon, which underscores the clear payback in fouling mitigation. With the fouling factors considered, performance, cost, and overall emissions drive one to the continuous-fin arrangement. The compact continuous-fin arrangement has about the same impact initially, but it is more expensive to operate with the slightly lower second-law efficiency. Clearly, the consideration of irreversibilities is a much better comparator for design options and further motivates the development of accurate models of the complex thermal-hydraulic behaviour within the heat exchanger.

Nomenclature

af = specific flow availability (J/kg) h = specific enthalpy (J/kg) h0 = specific enthalpy at dead state (J/kg) S l = irreversibility rate (W) S l = mass flow rate of cold stream (kg/s) S l = mass flow rate of hot stream (kg/s) S l = heat duty (W) T0 = dead state temperature (K) s = specific entropy (J/kg K) 1 5/9/22 10:56 AM HalfPageBrandAd_Apr2022_final.pdf

= specific entropy at dead state (J/kg K) S l= shaft work rate (W) S l = actual work rate (W) S l = reversible work rate (W) S l = rate of change of flow availability for cold stream (W) S l = change in specific flow availability of cold stream (J) S l = rate of change of flow availability for hot stream (W) S l = change in specific flow availability of hot stream (J) S l = rate of net availability destruction (a positive quantity) (W) S l = rate of kinetic energy change (W) S = rate of potential energy change (W) S = rate of enthalpy energy change (W) S = pressure drop (Pa) S = change in entropy, of both system and surroundings (J/K) Sl = effectiveness S l = second-law efficiency of heat exchanger S l S l = second-law efficiency of two-stream heat exchanger

Reference 1.

HINDERINK, A. P., VAN DER KOOI, H. J., and DE SWAAN ARONS, J., ‘On the efficiency and sustainability of the process industry’, Green Chemistry, pp. 176 – 180, (1999).

Notes

*Interest in the third law is resurging because quantum computers operate near absolute zero temperature. **Some texts use the newer term exergy instead of availability. While defined carefully from Greek and Latin roots, exergy sounds too much like energy and entropy so availability is used here. *** An emissions factor of 0.454 kg CO2e /kWhr was assumed.

ompanies that process hydrocarbons to create marketable products are some of the most significantly at-risk for incurring an accident that can result in property damage, loss of life, environmental damage and, at the very least, loss of revenue if production is interrupted or altered. In the US, the Occupational Safety and Health Administration (OSHA) is the regulating agency that defines safety standards and promulgates said standards through the Code of Federal Regulations (CFR). Typically, these standards regulate the chemical and petrochemical sectors, and 29 CFR 1910.119 is the guiding safety documentation that relates to process safety when working with highly dangerous or potentially destructive chemicals. Compliance with these industry regulations, which are promulgated by governing agencies, requires careful selection of the proper process control measurement technology. This article will address this concern by proposing TDL as a suitable safety-critical measurement technology for such processes.

Implementing process safety The practicality of complying with regulations is not the sole concern of companies; the safety of company employees is also important. Taking correct measurements is one way to improve efficiency and ensure minimal effects on the environment, and the prevention of process upsets. Environmental, social and governance December 2023 50 HYDROCARBON ENGINEERING

(ESG) considerations have been a key aspect of publicly-traded companies over the last decade, providing the structure to demonstrate to shareholders how corporations manage risks related to safety and the environment. For the latter, the concept of net zero energy has emerged as a critical company target. The shareholders’ interest in ESG activities correlates with the stock price in the market. ESG is framed around the mandates and laws according to OSHA; specifically sub-part 29 of the CFR. A key aspect to conforming to this is that a process hazard analysis (PHA) must be performed for each process in a production facility. By definition, PHA “identifies, evaluates and controls the hazards in the process.”1 There are several layers surrounding the PHA that prevent a catastrophic event or loss of life from taking place, as shown in Figure 1. Components such as a safe design and implementing Safety Instrumented Systems (SIS) are key to preventing unfortunate events, such as plant and community responses, should an accident occur. What is essential in Figure 1 is that the devices chosen as a part of the process design work as anticipated, and with maximum uptime and efficiency. Tunable diode laser (TDL) spectrometers have several distinguishing factors that make them suitable for difficult and continuously operating processes where safety is critical. Focused arguments for TDL in SIS applications will be presented later on in this article.

Tyler Schertz, Mettler Toledo, Switzerland, considers the intrinsic benefits of tunable diode laser (TDL) spectroscopy, which promote a fast and accurate response to safety events within industrial processes. Key factors for automated process analysis There are several key factors for choosing devices that fit with the process design and components. The chemical and petrochemical industries employ measurements that range from pH and conductivity for liquid-based processes, to several gas-phase measurements such as paramagnetic, NDIR and TDL, to name a few. Some key factors to consider when choosing a technology are minimised maintenance; aftermarket costs for consumables; accuracy and non-interference; and total uptime (see Figure 2). Ideal attributes during the selection process include fast response with no cross interferences; a design that fits directly into the process and is engineered for harsh conditions; minimised uptime by eliminating moving parts or consumables; and meeting the detection limits for safety. TDL spectroscopy is often the select technology that fits with all of the aforementioned considerations. The laser and measurement is highly specific to the absorption of oxygen; the system has no moving parts or consumables; and the level of detection fits well with lower explosion limits (LEL) measurements for safety reasons.

TDL as SIS Safety Integrity Level (SIL) is at the core of any SIS, and defines the relative risk reduction for measurements in the process. The

most stringent level of SIL is SIL4, and the least stringent is SIL1. The standards for SIL arise from ANSI/ISA 84, IEC 61511 and 61508 standards. SIL ratings also define the probability of failure of electronic components. Each successive level of SIL improves the safety margin by a decade, for the probability of failure on demand. In the process industries, SIL2 is a widely accepted level of safety, and manufacturers of instrumentation commonly carry this rating. The SIL evaluation process is performed after a hazard and operability study (HAZOP), and there are different criteria such as the consequence or outcome of an event; the probability of serious injury or death; demand rate for the analysis; and whether there are other means to avoid an accident. In an SIS, both the severity of an event and demand for measurement will likely require SIL2 compliance to ensure an acceptable safety margin. Continuous improvement for safety margins is also an initiative for entities such as NAMUR2 to develop standards for electromagnetic compatibility of equipment that fit with industrial process and laboratories alike. In particular, NE21 is a set of procedures used to identify whether a device in process control is immune to electrical interference. Coupled with SIL, NE21 helps to ensure that an analyser fits with an SIS. Manufacturers of TDL, with a notable exception of METTLER TOLEDO GPro 500®, have not yet embraced NE21. HYDROCARBON 51

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Practical considerations for TDL in SIS systems

Figure 1. Typical levels of detail involved in process hazard analysis.

Numerous analytical technologies exist for process control and ensuring plant safety. However, there are some inherent disadvantages to current measurements. The next section of this article will consider some of the more commonly employed instruments: paramagnetic for oxygen measurements; chemical sensors; and zirconium oxide (ZrO2) for combustion control and process safety. All technologies have been used extensively in the process industries over many decades but, as per Table 1, the pain points of these technologies can be immediately identified when comparing them against TDL technology. TDLs have a clear advantage. As the technology is based on an absolute measurement, and a comparison against a HITRAN simulation is possible, field calibration is typically unnecessary. Validation and slope adjustment is still an option. In contrast to UV-vis or NDIR analysers, the absorption lines for TDL are very narrow and can be carefully selected for a particular component so that the measurement is specific to the species of interest, even in a complex process stream. Another benefit of TDL is that these analysers are typically solid-state, and no moving parts are required – or consumables. The failing of this type of analyser is the operational lifetime of the laser diode itself, which typically has a lifetime of approximately 10 years. A fast and accurate means to obtain measurements is essential to ensuring safety in the process. The market has several vendors that provide options for making a measurement in situ, as opposed to extractive. The latter suffers greatly when it comes to speed of response, and this creates a critical barrier to the fast determination of leaks or an upset in the process control. Another TDL consideration is that, due to the very narrow absorption lines, the wavelength can be tuned selectively for one analyte in a very complex process stream. Thus, there is no interference that would otherwise affect the accuracy of the measurement.

Conclusion In process industries with safety-critical applications, any condition in the plant that contains excess can lead to risks in the pipeline. Risk is minimised during the HAZOP assessment, but careful selection of the analyser for measurement purposes Figure 2. Factors contributing to the implementation of new is a crucial task. analytical instrumentation. TDL spectroscopy has intrinsic benefits that promote a fast, safe and accurate response in industrial processes, and with a Table 1. A summary of competing technology concerns long operational lifetime and Analysis basis Paramagnetic ZrO2 TDL Electrochemical minimal maintenance, the uptime sensor for the measurement is preserved Calibration Regular Regular No – verification can Yes and safety margins in the plant are be performed met. These factors more than Yes, ZrO2 cells can No – maintain optical Yes Consumables Cells need to be reimburse the initial cost of the cleanliness replaced/sensitive be poisoned by analyser, and considering there is to flooding process no need for consumables or parts, Interference(s) NOx, hydrocarbons Yes, combustibles No Yes the return on investment (ROI) Response Installation 8 - 10 sec. < 2 sec. > 15 sec. makes TDL a favourable choice dependent when implementing SIS. Accuracy

Stream dependent

Stream dependent +/- 1% of reading

Stream dependent

In situ

No – SCS always required

Yes

Lifetime

8 - 10 years

5 - 8 years

Approximately 10 years

Variable

December 2023 52 HYDROCARBON ENGINEERING

Notes 1. 2.

See 29 CFR.119(e)(1), https://www. osha.gov/laws-regs/regulations/ standardnumber/1910/1910.119 See https://www.namur.net/de

Mark Naples, Umicore Coating Services Ltd, UK, explains why fixing methane leaks from the oil and gas industry can be a game-changer.

missions management is a journey. But the path to lowering emissions is fraught with complexities and challenges requiring new skills and a measured approach. Nevertheless, it is a journey vital for future viability. Even though methane (CH4) only makes up 0.00017% (1.7 ppm by volume) of the atmosphere, it traps a significant amount of heat. This means it is one of the most potent greenhouse gases (GHGs) contributing to global warming, responsible for up to 20% of global heating alone. Its power is even greater: this gas is 28 times more warming than CO2 in equal quantities. Its concentrations are constantly rising and have increased by 150% since the pre-industrial revolution. According to the Energy Institute’s (EI) recent report, carbon emissions from energy use, industrial processes, flaring, and methane (in CO2 equivalent terms) increased by 0.8% in 2022, reaching a new high of 39.3 gigatonnes of CO2 equivalent (GtCO2e).1 The Earth’s atmospheric CH4 concentration has increased by about 160% since 1750 – with the overwhelming percentage caused by human activity, accounting for 20% of the total radiative forcing from all the long-lived and globally mixed GHG, according to the 2021 Intergovernmental Panel on Climate Change report.2 Global fossil fuel industry emissions of CH4 increased to a near-record in 2022, prompting a call from the International Energy Agency (IEA) for oil and gas companies to use ‘windfall’ profits to clean up leaks of the potent global warming gas. The IEA states that spending US$75 billion – or 2% of oil and gas companies’ combined annual earnings – on lowering CH4 emissions would cut direct GHG emissions by 15%. CH4 emissions are forcing the climate to change in unprecedented ways, but there are still many options to alleviate the impacts through mitigation and adaptation.

Methane matters Oil and gas company commitments to cut CH4 emissions have increased – and with those commitments come public pressure to demonstrate immediate, transparent, and verifiable action.

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With natural (biogenic) and human-caused (anthropogenic) CH4 emissions accounting for US$19 billion in wasted natural gas, something as simple as a leaking pipe or a poorly-managed wetland has a serious cost to businesses. However, to mitigate this wastage, it must first be identified.

Figure 1. Production of coated lenses is now a refined, scalable process, making sensing technology more accessible than before.

Figure 2. Highly specialised filters and coatings are at the core of IR absorption spectroscopy tools used in a wide range of gas sensing applications.

As a powerful tool for detecting trace gases, laser absorption spectroscopy has been widely used in monitoring atmospheric GHGs, pollution, and respiration processes, including human breath analysis. The detection is based on the light absorption when it propagates through a medium. As interest in air quality has dramatically increased in recent years, major and growing sensor manufacturers are seeking high-performance filters at competitive prices. Owing to recent technological advances, the oil and gas industry, scientists and authorities can tap into a growing set of tools to help them detect and quantify emissions. From specialised handheld cameras that help technicians pinpoint leaks, to space-borne instruments that can quantify regional emissions, these tools are changing understandings of emissions and expanding the available approaches toward target setting, monitoring, and compliance. The detection is based on how light is absorbed through a medium. Emitters within the sensor generate pulses of infrared (IR) light, passing through a sampling chamber containing a filter. The filter blocks the light of a certain wavelength, meaning only the required wavelengths make it past the filter to reach a detector. This detector measures the IR light’s intensity (or attenuation), which can determine the precise concentration of gas that may be present. Different filters allow different wavelengths of light to reach the detector, which can, in turn, be used to detect other gases and distinct particles. As it works using the unique properties of light, this kind of sensing technology offers near-limitless scope. It can analyse the particulate matter in human breath, allowing for a detailed breakdown of the particles that enter and leave our lungs. At the other end of the scale, it can be installed in satellites and sent into orbit to monitor for significant global gas leaks. While both applications require very different systems in size and scope, the principle behind the technology is the same. Newer gas analysis instruments use a laser diode mounted on a thermo-electric cooler to tune a laser’s wavelength to the specific absorption wavelength of a particular molecule. They exploit their high-frequency resolution, which results in enhanced sensitivity – more significant levels of interaction between gas molecules and light in the order of parts per billion – and discrimination, as they are tuned to specific gas compounds. This eliminates the potential for false alarms. By incorporating different filters into a system that allows different wavelengths of light to reach the detector, it is possible to check for multiple other gases using the same compact design. This enables monitoring of almost any harmful gas, from CH4 to CO2.

See it to believe it

Figure 3. Modern sensing technology is highly scalable and available in increasingly small form-factor devices thanks to advances in laser absorption spectroscopy.

December 2023 54 HYDROCARBON ENGINEERING

Despite the many precautionary measures taken, leaks are a fairly common occurrence and a significant contributor to the industry’s overall GHG emissions. According to one report, the leaks from bolted joints contribute 170 million tpy of fugitive GHG.3 For decades, the industry has accepted these leaks and, by extension, their emissions as an unavoidable cost of doing business. To keep emissions as low as possible, quickly detecting leaks became an industry-wide priority. Based on the rise of key enabling technologies – such as miniaturised electronics, advanced algorithms, and low-cost

access to space – and fuelled by increased international awareness, these novel solutions have the potential to improve our ability to identify and address pollution sources greatly. With increasing global regulation around CH4 emissions and reporting, innovative technology, supercharged with CH4 narrow bandpass filters, can help to measure methane leaks at a distance, using a laser and camera system to provide a highly capable solution to various gas detection challenges within emission monitoring. Umicore has extensive experience designing new infrared filters to meet precise technical specifications. The company’s IR narrow bandpass filters, intended to isolate a narrow region of the infrared spectrum, can be used for the early detection of noxious, harmful and/or corrosive gasses in the atmosphere in parts per billion. Such technology is critical to ensuring the health and well-being of the workforce and is integral to a robust preventive maintenance system to ensure the site runs at optimal performance whilst complying with all health and safety policies. Losing just 1 m3 of CH4 per hour will result in a financial loss of around £5000/yr.4 Additionally, there are the environmental and human costs to consider. According to the UN Environment Programme, reducing CH4 emissions is the most powerful lever to mitigate climate change. Through the reduction of fugitive emissions, organisations can do the right thing by proactively – and transparently – responding to the climate change crisis with tangible steps that lead to measurable results for both the environment and the business.

73 EST. 1951

Figure 4. Capturing the significant amount of natural gas, or methane, wasted each year across the oil and gas industry would mean progress for both the climate crisis and the energy crisis. There have been diplomatic efforts to make a difference in this space ahead of COP28, set to be hosted in Dubai, UAE, from 30 November to 12 December 2023. Until then, the oil and gas industry must continue to strive to improve leak detection and quantification technologies.

References 1. 2. 3. 4.

The Energy Institute (EI), 72nd Annual Edition of the Statistical Review of World Energy. Climate Change 2021: The Physical Science Basis (ipcc.ch). ‘Environmental Impact of Bolted Joints’, Cumulus, (cumulusds.com) https://www.sciencedirect.com/science/article/abs/pii/ S0015188220301804.

Learn From Industry Experts at the

74TH ANNUAL LAURANCE REID GAS CONDITIONING CONFERENCE Feb. 26-29, 2024

The Laurance Reid Gas Conditioning Conference is an opportunity for engineers and those new to the gas processing industry to gain valuable knowledge and build relationships with industry experts.

For questions, contact Lily Martinez at lmartinez@ou.edu. The University of Oklahoma is an equal opportunity institution. www.ou.edu/eoo. Printed at no cost to Oklahoma taxpayers.

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| Laurance Reid Gas Conditioning aConference

December 2023 56 HYDROCARBON ENGINEERING

OFC, 31 | WONDER® 15 | W. R. Grace & Co. IFC | Zwick Armaturen GmbH

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