October 2021
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CONTENTS 03 Comment 05 News REGIONAL REPORT: CANADA 10 On The Path To Zero Carbon Concrete Adam Auer, Cement Association of Canada, outlines the path towards zero carbon concrete and highlights the Canadian cement sector’s role in this journey. LOW CARBON CEMENT TECHNOLOGY 16 Thinking About The Future Of Cement World Cement spoke with Cementir Holding’s Chairman & CEO and experts to discover the company’s plans to abate its environmental impact and guarantee a role for cement in the future of construction. GRINDING & MILLING 21 From Compact To Modular Dr. R. Krammer, W. Kulagin, & T. Thiel, LOESCHE GmbH, explain how compact cement plants were enhanced to become faster, more flexible, and capable of meeting the growing challenges of global cement markets. PREHEATERS & PRECALCINERS 25 Gearing Up For Decarbonisation Tahir Abbas and Michalis Akritopoulos, Cinar Ltd., explore the use of hydrogen fuel as a route to decarbonising cement production.
LUBRICATION 39 Weighing Up The Options Markus Burbach, Klüber Lubrication, reviews advances in open gear lubrication and provides a guide for choosing the right technology to optimise reliability and asset utilisation. AIR POLLUTION CONTROL 45 Getting The Green Light Nathan Schindler, Evonik Corporation, shows how plant operators can clean up cement plant filter performance through the use of an instant baghouse check-up system. 49 Boosting Output With Better Bags Brad Currell, SOLAFT, provides a case study showing how innovative filter bag design and customised solutions can improve cement plant operational efficiency and reduce maintenance costs. 54 Ingenious Solutions To Difficult Solutions Eduardo Sauto, GORCO, reviews dedusting solutions for two common sources of diffuse dust emissions in cement plants. 58 A Breath Of Fresh Air – Air Pollution Control Q&A World Cement spoke to experts in the air pollution control sector to gather their views on a range of topics facing the cement industry. Contributions come from: Evonik Corporation, RD42 Engineering, & W.L. Gore & Associates.
CLINKER COOLING & CONVEYING 29 A New Lease Of Life Jaco Harmzen, SKF, outlines the factors that cement producers should consider when looking to extend the service life of clinker pan conveyor bearings. 35 Just Add Water Armin Möck, Lechler, explains how cement producers could benefit from emergency water injections in the clinker cooler in order to control increased gas temperatures. October 2021
ON THE COVER FUTURECEM™ is an innovative, validated and patented technology which allows for more than 35% of clinker in cement to be replaced by limestone and calcined clay. Utilising their synergy, the combination of materials in FUTURECEM has resulted in a more sustainable and effective cement with a carbon footprint up to 30% lower than Ordinary Portland Cement. Since January 2021, FUTURECEM has been available from Aalborg Portland, placing Cementir Group at the forefront of the market as a leader in sustainable cement. For more information: www.cementirholding.com/futurecem
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October 2021 World Cement
DAVID BIZLEY, EDITOR
I
f you needed any further reminders that climate change remains a core fixture of the current political agenda, in just a few weeks, on 31st October, the UK will begin hosting the 26th UN Climate Change Conference of the Parties or, as it’s more commonly known: COP26. The aim of this two-week long meeting is to enable negotiations between the 197 parties to the United Nations Framework Convention on Climate Change (UNFCCC) and agree on methods for dramatically reducing humanity’s impact on the environment. More specifically, the aim of COP26 is to enable the necessary agreements and frameworks required to achieve the following four goals: 1) Secure global net zero by 2050 and limit global average temperature rises to 1.5˚C. 2) Adapt to protect communities and natural habitats most impacted. 3) Mobilise finance: ensuring that developed nations and international financial institutions play their part in funding change. 4) Work together: finalise the ‘Paris Rulebook’ (the detailed rules that make the Paris Agreement operational) and accelerate action to tackle the climate crisis through collaboration between governments, businesses and civil society. Meeting these challenges will require an essential combination of investment, collaboration, and the widespread deployment of new technologies. A daunting task in its own right. It’s good then to see the cement sector continue to make strides towards reducing its own environmental footprint. One recent example is the news that FLSmidth and Chart Industries will be working together to commercialise carbon capture technology capable of removing more than 90% of CO2 emissions from cement production. The technology in question is Cryogenic Carbon Capture (CCC). CCC uses specialised equipment to capture CO2 from exhaust gas and produce it as a high-purity liquid ready for storage and use. FLSmidth’s role is to use its industry recognition and process knowledge to accelerate commercialisation of the technology and optimise it for use in the cement sector. Indeed, the cement industry has seen a flurry of ‘green’ news stories recently: HeidelbergCement announced a new carbon capture pilot project in Eastern Europe, Hoffman Green Cement Technologies has launched its fourth low-carbon cement (emitting one-sixth of the CO2 produced by OPC), Calix’s LEILAC technology has received a e15 million investment, to list just a few examples. Even our cover story this month, an interview with the CEO and other leaders at Cementir Holding (p. 16), looks at how the cement sector can reduce its environmental impact. For more information on cutting edge technologies in the cement sector, make sure to join us on 9 – 10 November for WCT2021. Featuring live Q&As, a virtual exhibition, and presentations from Lubrilog, Titan Cement, Holcim, FLSmidth, thyssenkrupp and more, this online conference is not to be missed! Register today (for free) at: www.worldcement.com/wct2021 3
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NEWS HeidelbergCement to pilot carbon capture project in Eastern Europe
CEMEX strengthens presence in Guatemala
The further development of CCUS pathways is a central part of HeidelbergCement’s carbon neutrality roadmap. Project ACCSESS has been officially presented by the coordinator Sintef Energi AS from Norway. A consortium of 18 industry partners and research organisations will collaborate in a range of activities to speed up deployment of CCUS and link CO2 emitters from mainland Europe to the storage fields in the Nordics. The programme of €18 million in total was rewarded €15 million out of the EU Horizon 2020 budget. “As part of our participation in ACCSESS, HeidelbergCement will pilot a new carbon capture technology in Poland”, says Dr. Dominik von Achten, Chairman of the Managing Board of HeidelbergCement. “The tests of an enzyme-based capture unit at our Górazdze plant will deliver important insights into how we can further reduce costs in the capture process. “At the same time, it will emphasise our strategy to expand CCUS further into our Eastern European based assets.” The enzyme-based capture unit will allow a broader use of the waste heat and will simplify the control of secondary emissions. For HeidelbergCement, the ACCSESS project comprises three focal points. In addition to testing the separation technology in Poland, HeidelbergCement and its partners will carry out a study to explore the optimal integration of a carbon capture unit at the Hanover plant in Germany. The third pillar focuses on all aspects of transporting CO 2 from sites in mainland Europe to Norway, including all regulatory aspects of cross-border CO 2 transport. The consortium will develop transport systems from the Hanover and Górazdze cement plants to the Northern Lights storage facility in Norway – a joint project by the oil and gas companies Equinor, Shell and TotalEnergies. The ACCSESS project is slated for a duration of 48 months, from May 2021 to April 2025. It is being coordinated by Sintef and other 17 partners from academia and industry.
CEMEX has announced that, as part of its growth strategy, it will increase capacity in Guatemala with the construction of a new cement grinding mill that is expected to be completed in early 2023. This investment is accretive and considers the company’s climate action programme. The facility will be strategically located in the company’s plant in Guatemala. It will rely on modern and efficient processes for cement production and environmental standards. The new grinding mill, which will produce low-carbon cements, will be designed to be one of the most sustainable in the sector and will also be aligned with CEMEX’s Future in Action programme, aimed to reduce its carbon footprint. “This investment reinforces CEMEX’s commitment to Guatemala’s development and reflects our confidence in the favourable outlook of the economy in the country and the region,” said Jesus Gonzalez, President CEMEX South, Central America, and the Caribbean. “We are excited about expanding our offer of products and solutions to the market which contribute to sustainable construction, like Vertua, our family of net-zero and low carbon products.” The total value of the investment is approximately US$25 million. Current grinding capacity at the plant is about 0.5 million metric tpy. Following the completion of the project, production will increase approximately by 0.4 million metric t to 0.9 million metric tpy.
October 2021 World Cement
Hoffmann Green Cement announces launch of fourth low-carbon technology Hoffmann Green Cement has announced the launch of H-IONA, its fourth low-carbon technology. The manufacturing of this new cement is incorporated within the existing production unit and emits six times less CO 2 than traditional Portland cement, with a carbon footprint of less than 150 kg per metric t. Continuing on from the technologies already perfected by the company, and notably H-UKR, Hoffmann Green Cement has developed an innovative 5
NEWS DIARY CEMENTTECH 2021 10 – 12 October, 2021 Jiangxi, China Joannalong@ccpitbm.org www.cementtech.org/eng/dj.asp
CEMBUREAU: Cementing Europe’s Future 12 October, 2021 communications@cembureau.eu www.cembureau.eu/events
BULKEX21 12 – 13 October, 2021 Chesford Grange, Warwickshire, UK secretary@mhea.co.uk www.mhea.co.uk
Innovation In Cement Production 09 – 10 November, 2021 www.worldcement.com/wct2021
SOLIDS & RECYCLINGTECHNIK Dortmund 16 – 17 February, 2022 Dortmund, Germany www.solids-dortmund.de
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specific activation system, enabling it to produce this heating-free technology at its fully automated 4.0 industrial site, while preserving natural resources by recycling co-products produced by industry. This cement primarily consists of ground furnace slag and calcium sulfate. H-IONA is the first low-carbon cement to be granted CE marking. Technically, this fourth technology meets all the mechanical, physical, chemical and durability requirements of the NF EN 15743 standard of June 2015. Distributed in bulk in 1 t big bags, H-IONA is also the first Hoffmann Green cement accessible to the general public, as it will be available in 25 kg bags in specialised retail chains aimed at construction professionals and at individuals. This new cement further enhances the product range developed by Hoffmann Green Cement and allows it to address new markets in perfect complementarity with those already targeted by its other three technologies (H-UKR, H-P2A and H-EVA). H-IONA addresses a large number of applications in construction, including reinforced or non-reinforced concrete, industrial buildings, apartments and individual homes, civil engineering and large-volume projects, agricultural concrete, concrete for water treatment plants and light prefabrication. Julien Blanchard and David Hoffmann, co-founders of Hoffmann Green Cement Technologies, say: “By launching H-IONA, the most low-carbon cement on the European market and suitable for a considerable number of applications, Hoffmann Green Cement is following its continuous innovation approach. Furthermore, this is the first low-carbon cement to have received CE marking. Thanks to this groundbreaking technology, we are democratising access to low-carbon cement, as this is the first time that the public will be able to use Hoffmann Green cement. H-IONA thus represents an amazing opportunity for everyone to participate, on their own level, in the transition towards a more environmentally friendly construction model. The launch of this fourth technology also illustrates our teams’ ability to innovate and their commitment, for which we would like to thank them. We will maintain our efforts with the same objective: To accelerate the decarbonisation of the construction sector as much as we can.”
FLSmidth collaborates with Chart Industries to decarbonise cement via carbon capture technology FLSmidth has signed an agreement with Chart Industries, Inc. to implement advanced carbon capture technology to significantly reduce CO 2 emissions from cement production. Cement production represents 7 – 8% of the global CO2 emission – carbon capture technologies are essential to reduce that number and meet the targets of the Paris Agreement. The new collaboration between FLSmidth and Chart joins the two companies’ efforts to adapt and commercialise Chart’s Cryogenic Carbon Capture TM (CCC) for customers in the World Cement October 2021
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NEWS cement industry. CCC is an advanced post-combustion technology developed by Sustainable Energy Solutions (SES), a Chart company. CCC utilises equipment manufactured by Chart and its affiliates to capture CO 2 from exhaust gas at very high rates and produce it as a high-purity liquid ready for storage and use. Working with Chart, FLSmidth will use its global reach and process knowledge to accelerate the commercialisation of CCC and optimise the design of the technology for the cement industry. The ambition is to reduce over 90% of carbon emissions from industrial sources at half the cost and energy of current carbon capture processes. Carbon capture technology is a cornerstone in FLSmidth’s MissionZero sustainability ambition of providing the solutions needed to move the cement industry towards zero CO2 emission by 2030. Carsten Riisberg Lund, Cement President for FLSmidth said: “The cement industry is pursuing all options to reduce its environmental footprint, and carbon capture is a necessary technology to achieve this goal. Through this agreement with Chart, we lay the foundation for the scale-up and deployment of the CCC technology with our customers. The technology developed by Chart is expected to become the most competitive at scale. We look forward to extending Chart’s CCC technology into the cement industry through our global presence and engineering capabilities. This agreement is a significant leap forward in our joint efforts to enable our customers to reduce their environmental footprint.” Jill Evanko, CEO and President of Chart said: “We are delighted that FLSmidth has entered into this important agreement with Chart to advance our carbon capture technology in the cement industry. FLSmidth’s strong reputation and knowledge of the global cement industry will facilitate our growth and place Chart at the heart of the cement industry’s efforts to reach Net Zero.”
Holcim divests business in Brazil Holcim has signed an agreement with CSN for the divestment of its business in Brazil for 8
an enterprise value of US$1.025 billion. This divestment includes Holcim’s five integrated cement plants, four grinding stations, six aggregates sites and 19 ready-mix concrete facilities. This divestment strengthens the company’s balance sheet, significantly reducing its debt ratio. Advancing its portfolio optimisation, Holcim will use the proceeds to invest in its Solutions & Products business, building on the Firestone acquisition. Jan Jenisch, CEO: “This divestment is another step in our transformation to become the global leader in innovative and sustainable building solutions giving us the flexibility to continue investing in attractive growth opportunities. We are pleased to have found a responsible buyer with CSN that will develop the Brazilian business over the long term.” While Holcim divests its activities in Brazil, Latin America is a core strategic growth region for the company. Building on strong positions in all its markets, Holcim recently invested in an additional clinker line in Malagueno, Argentina, a new grinding station in Yucatan, Mexico, and in the continuous growth of its Disensa retail network. Holcim also introduced its Firestone GacoFlex line in Mexico as the first step in developing its roofing systems business across Latin America.
Bedeschi supplies two apron feeders for Lehigh’s Mitchell Plant Bedeschi has been awarded a new order for the supply of two apron feeders to be placed in the primary and secondary crushing area to replace the old existing machines at Lehigh’s Mitchell Plant; the apron feeders feature super duty design with CAT chains and Bedeschi super duty belt. To provide the best service, Bedeschi applied a 3D scan survey to define the exact room availability in the existing plant. The aprons are sized to handle up to 1300 tph of crushed limestone. They are BED RNSH 1800/6 type. These aprons are going to be added to the other three already ordered by Mitchell in their plant upgrade program for clay crushing and additive dosing. World Cement October 2021
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he impact of the COVID-19 global pandemic will continue to redefine the world in ways unimagined. Few industries or economies have escaped the pandemic’s reach, and the cement sector is no exception. The Canadian cement industry began 2020 with strong demand. Economic forecasts were encouraging, and a new federal government had just been re-elected, painting a familiar business-as-usual outlook. By March 2020, COVID-19 related restrictions and economic impacts began to drive down cement consumption and the economic outlook became far less certain. Unsurprisingly, in an industry with an estimated annual production capacity of over 16 million t, 2020 consumption fell short of 2019 levels.
T
Despite a rollercoaster of tightening and relaxing pandemic restrictions imposed across the country, the cement industry has fortunately remained an essential sector in Canada and is emerging as an industry with a recognised role to play in the country’s ‘green economic recovery.’ In fact, the most important legacy of COVID-19 may be the extent to which much needed post-COVID economic stimulus is leveraged to ‘build back better’ and, specifically, to accelerate Canada’s transition to a net-zero economy. Recent global commitments from the sector, most notably the Global Cement and Concrete Association’s (GCCA) Climate Ambition statement, demonstrate that the pandemic has not dampened the cement sector’s commitment
On the path
TO ZERO CARBON CONCRETE 10
to sustainability and, most importantly, to realising its ambition to deliver zero carbon concrete by 2050. Canadian cement producers are supporting this work by charting a roadmap to zero, including the role of partners in government, the construction industry and other civil society stakeholders in helping lay the groundwork for success. This commitment has not been lost on government decision makers in Canada. In both the 2021 Federal Budget as well as the recently updated national climate strategy (The Healthy Environment, Healthy Economy Plan), the cement sector has been identified as an industry ripe with opportunities to contribute towards Canada’s climate objectives. Notably, Canada has earmarked CA$8 billion for a Net-Zero Accelerator fund to expedite
decarbonisation projects, scale up clean technology, and accelerate Canada’s industrial transformation. It has also introduced additional measures and investments to advance technologies of specific significance to the sector, including Carbon Capture Utilisation and Storage (CCUS) and hydrogen. Seizing the opportunity of this alignment of climate change objectives, and in support of Canada’s goal to reduce GHG emissions by 40 – 45% by 2030, the Canadian cement sector is particularly pleased to have recently formalised a partnership with the Government of Canada to help establish Canada as a global leader in low-carbon cement and to achieve zero carbon concrete by 2050, including a cumulative reduction of 15 Mt of GHGs by 2030.
Adam Auer, Cement Association of Canada, outlines the path towards zero carbon concrete and highlights the Canadian cement sector’s role in this journey. 11
This presents an historic opportunity for the industry – in Canada and beyond – to accelerate a low-carbon transition and position cement and concrete as cornerstone materials in a climate friendly and climate resilient future.
The path to zero – building on achievement and success As federal, provincial and municipal governments have called on Canadians to lead in the fight against climate change, the cement sector has risen to the
challenge, investing CA$100s of millions in laying a strong foundation for zero carbon concrete by 2050. The division of powers among the federal and provincial governments in Canada means that each Canadian province brings a different set of rules and policies and, with them, a unique operating environment. Canadian cement companies have successfully adapted to these regional differences by tailoring their low carbon pathfinding projects and pilots to suit Canada’s different jurisdictions, while also trying to promulgate best practices at a national level.
Alternative low carbon fuels (ALCF) – helping to build the circular economy
Lafarge Canada’s Richmond, BC plant is the home of Project CO2MENT, a CCUS demonstration project now in its second phase.
Lehigh Hanson’s Edmonton, AB plant, is the site for an advanced feasibility study for a full-scale carbon capture system.
In Canada, and globally, the easiest and most economical way to reduce cement manufacturing emissions remains substituting fossil fuels used in the kiln with lower carbon alternatives. A key advantage of cement manufacturing is that its fuel flexibility allows cement producers to be part of the solution to various forms of non-recyclable wastes while supporting a circular economy transition. Canada’s fuel substitution rate has historically been quite low (between 7 – 10%) compared to other regions, where the average can exceed 40% and is often much higher. A major impediment to leveraging the benefits of fuel substitution in Canada has been the difficulty in obtaining provincial permits to use non-traditional fuels. With the exception of British Columbia, ALCF permitting regimes in Canada are cumbersome, usually taking years to approve pilot projects and offering little certainty about a facility’s prospects for securing fuel flexibility. Thankfully, as addressing climate change becomes a priority along with an increased emphasis on ‘circular economy’ solutions to waste management, strong collaboration on policy reform to support low-carbon fuels has been seen, particularly in the province of Ontario, home to six of Canada’s 16 cement facilities. The recycling of revenues from carbon pricing regimes, while also uniquely administered in each province, has likewise benefitted ALCF adoption in some regions of Canada by supporting investments in ALCF supply and facility level infrastructure. This is driving confidence that the Canadian cement sector can reach substitution levels meeting or exceeding best practices – with the potential to reduce the carbon intensity of Canadian cement by some 2 – 3 Mt in the near to mid-term.
Low carbon cement – accelerating uptake In Canada, as globally, the easiest and most economical way to reduce cement manufacturing emissions remains substituting fossil fuels used in the kiln with lower carbon alternatives. 12
Another significant near-term opportunity to reduce the carbon intensity of cement in Canada is the transition to Portland-limestone Cement (PLC), including blended PLCs such as Lehigh Hanson’s EcoCem®Plus. While commonly used in Europe for over 35 years, PLC has yet to achieve its full World Cement October 2021
potential in Canada. Nationally, Canadian adoption of PLC was 25.3% of all cement sales in 2018, which was a sharp rise in adoption from the 2017 level at 11.3% but far short of the ambition to make PLC the default cement in Canada. PLC with up to 15% limestone addition was first introduced in the Canadian Standards Association (CSA) cementitious materials standard in 2008 and concrete materials standard in 2009. At 15% limestone, PLC is a cost-equivalent drop-in substitute for Ordinary Portland Cement (OPC), but with up to 10% less embodied carbon. The ambition to convert the Canadian market to 100% PLC would represent up to 1 million t of avoided GHG emissions annually. Importantly, PLC is complementary to other carbon-reducing strategies in concrete, such as using supplementary cementitious materials (SCMs) like fly ash and slag as well as emerging mineralisation technologies. This makes PLC a foundational component of near-term strategies to achieve carbon-intensity reductions of 30 – 40% in concrete. All of the CAC’s member companies are able to produce PLC and it has been fully recognised in the Canadian Standards Association (CSA) cement standards and building code. While there are no technical barriers to the adoption of PLC, its market penetration has been hindered by resistance to
change, a function of the inherent conservatism in the Canadian construction community. Notwithstanding a political prioritisation of climate change policies at all levels of government, public sector specifiers in particular have yet to adopt strong climate change mandates that would help overcome reluctance to require PLC for their billion-dollar infrastructure programmes and public works projects. Governments are collectively the largest purchaser of concrete for buildings and infrastructure and their reluctance to use PLC is a significant obstacle to transitioning to lower-carbon cements in Canada. An important consideration in the transition to PLC is the limited capacity of independent concrete producers to store both PLC and OPC cements. A significant market conversion is needed for these producers to switch to PLC in their silos. This is another important reason that public sector procurement of PLC is so critical in the successful transition to PLC in Canada. The recent launch by the Canadian government of an updated Greening of Government Strategy with targeted initiatives to adopt lower carbon cements such as PLC in all federal buildings and infrastructure projects is very encouraging in this regard. The industry is focused on supporting, accelerating, and scaling these efforts.
Blended cements – scarcer supply Access to fly ash and slag varies across the country and maintaining access to cost-effective supplies of these SCMs is a priority for the sector. These resources, especially fly ash, are expected to become scarcer as Canada’s few remaining coal-fired utilities are rapidly phased out. The sector is actively engaged with its research community on sourcing alternative SCMs to meet future needs, including harvested fly ash. This challenge also points to the value of PLC and that, in the future, the cement industry will need to look towards increasing the amount of allowable limestone content in Canada, in line with its European colleagues, as part of its decarbonisation roadmap.
Carbon capture – the promise of going beyond zero
Using concrete made with lower carbon cement to build the iconic 52 storey, 600 000 ft2 Vancouver House reduced the tower’s embodied carbon by some 2300 t. Architect: Bjarke Ingels, DIALOG and James K.M. Cheng Architects. 14
One of the most exciting developments in the cement and concrete industry in recent years has been the explosion of carbon capture technologies. Carbon capture offers a complete solution to cement GHG emissions, with the potential to capture virtually 100% of the emissions from both calcination and combustion processes. Captured emissions can then be stored underground or used to make other products like carbon neutral synthetic fuels and aggregates. The latter can replace virgin aggregates used in concrete. Several cement facilities in Canada are well advanced in the implementation of carbon World Cement October 2021
capture systems. For example, Lehigh Hanson has undertaken a CA$3 million advanced feasibility study for a full-scale carbon capture system at its Edmonton, Alberta cement facility. Upon successful completion, it would represent the largest carbon capture system at a cement facility anywhere in the world. Similarly, Lafarge Canada recently completed the installation of a flue gas pre-treatment system at its Richmond, British Columbia facility, paving the way for a full carbon capture system, as well as immediate opportunities to test the use of captured CO2 in concrete products. The long-term success of carbon capture hinges, to a great degree, on its commercial application in the cement sector. This is, in part, because cement kilns produce a high concentration stream of CO2 making it efficient to capture, but also because the captured CO2 can be used as a material input in the concrete manufacturing process. Of note, the two winners of the CA$20 million Carbon XPrize are companies focused on decarbonising concrete, including Canada’s own CarbonCure Technologies. Cement is also a major focus of Canada’s nascent CCUS Strategy, which aims to amplify Canada’s track record of innovation in CCUS by leveraging its ample geologic storage capacity as well as investing in building out a CCUS ecosystem (e.g., CO2 capture and transportation hubs) to foster economic
opportunities for Canada’s carbon management technology upstarts. While CCUS remains expensive, it is widely understood as an essential technology for the decarbonisation of cement and concrete, including the potential to transform concrete into a carbon-negative building material. However, codes and standards processes will need to keep pace and strong supportive policies will need to underpin market acceptance and drive these technologies to scale.
All in this together Canada’s cement industry is committed to the transition to a low carbon economy. This is a journey the country is taking collectively with its global peers, but also with its local government, industry, technology and civil society partners.
About the author Adam has over 20 years’ experience as a sustainability professional. As Vice President of Environment and Sustainability with the Cement Association of Canada, Adam works with government, industry, environmental and other civil society groups to advance concrete’s contribution to Canada’s low-carbon transition. He holds a Master’s in Environmental Studies and a Bachelor’s in Science in Ecology.
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THINKING ABOUT THE FUTURE OF CEMENT World Cement spoke with Cementir Holding’s Chairmain & CEO and other experts to discover the company’s plans to abate its environmental impact and guarantee a role for cement in the future of construction.
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Francesco Caltagirone Jr. Chairman & CEO
World Cement (WCT): How significant is the role of sustainability and decarbonisation in today’s cement industry? Francesco Caltagirone Jr. (FC): The industry is definitely approaching a moment of truth. Covid-19 forced Governments worldwide to put in place restrictions that reduced the human footprint to a level not seen in decades. Months of empty roads, empty skies and sluggish economic activity reduced the year’s global greenhouse gas emissions by an estimated 7%, the sharpest annual fall ever recorded. However, the UN has stated that the impact of the coronavirus lockdown on the climate has lowered 2050 temperature projections by just 0.01˚C and the earth is still on course for a catastrophic 3.2˚C of warming by end of the century.
Most climate experts agree that the world must take urgent action to cut emissions and we cannot deny that cement manufacturing is an energy- and CO2-intensive process. At the same time, cement is an integral part of our everyday lives. Indeed, globally, it is the second most-used product after potable water, and it is applied everywhere to build everything – from houses to strategic infrastructure, thanks to its reliable performance, durability and, in general, lower cost than other building materials. We consider ourselves, and we should consider the cement industry as a whole, to be a responsible member of the community we live in and, as such, our part is to promote initiatives and solutions that bring wellbeing to society. Considering their relevant value to the community, cement and related products should be considered as part of the solution and not an issue for climate change.
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Climate change and the urgent need for decarbonisation require the cement industry to take a proactive role in resetting strategies and approaches, looking at a complete revision of the way to run business. To gain a sort of ‘license to operate’ we are all asked to quickly switch the business paradigms of the industry. To identify the best path towards sustainability, every player should assess digital and technological developments and rethink products, portfolios, partnerships, and construction methods. You could say that Covid-19 accelerated the need for the industry to respond to these structural trends. Dilemmas and trade-offs are, of course, present – in some cases there is no economic rationale to embark on this challenge. The entire construction ecosystem, governments and institutions should therefore move to support industry by incentivising green solutions, and not just in financial terms.
(Left) Michele Di Marino – Chief Sales Marketing & Commercial Development Officer. (Right) Stefano Zampaletta – Corporate Product Development.
CCB – plant Gaurain-Ramecroix in Belgium.
Sustainability and decarbonisation must guide our day-by-day operations, and we want to be in the driver’s seat.
WCT: What is Cementir Holding doing to meet the demands for ‘greener’ cement operations? Does the Group have a sustainability strategy? FC: In the last few years, Cementir has been actively committed to pursuing a programme inspired by the principles of the ‘circular economy’, which envisages a series of initiatives focused on reducing the environmental impact of its operations for less CO2-intensive process as well as on developing low carbon products and solutions. By 2030, we will reduce our direct CO2 emissions to less than 500 kg/t of grey cement produced, while for white cement, which is a specialty product with niche applications and markets (representing just 0.5% of total worldwide cement production), the plan is to reduce CO2 emissions to 800 kg/t. FUTURECEM™ technology will play a pivotal role in the plan, and we will exploit the best available technologies and look at new breakthroughs to mitigate CO2 emission from processes. Our commitment to a low-carbon economy and to transparency around our environmental impact has been also recognised by CDP, the gold standard of environmental reporting. In December 2020, we achieved a ‘B’ rating for climate change. This result puts Cementir amongst the top players in the cement industry, while ranking much higher than the average company, considering the CDP European and Global average rating of ‘C’. In July 2021, the Science Based Targets initiative (SBTi) validated Cementir’s CO2 emission reduction targets, judged to be consistent with the ‘well below 2˚C’ objective, pursuant to the Paris Climate Agreement of 2015. To date, 813 companies around the world have obtained the validation of their targets from SBTi, of which only five are cement producers with a ‘well-below 2˚C’ target. The validation of our CO2 emissions reduction targets by SBTi is another important recognition of Cementir’s decarbonisation path to 2030. Sustainable growth represents a commitment to all our stakeholders and, at the same time, it is a necessity for those who work in this sector.
WCT: What role does Cementir’s commercial strategy play in promoting and meeting sustainability goals?
Aalborg Portland – plant Rørdal in Denmark. 18
Michele Di Marino (MDM): Cementir has gradually prioritised sustainability as the key driver in its overall value proposition, even in its commercial approach. That is to say: World Cement October 2021
sustainability is no longer an addon or extra, but it is at the core of our offer. As climate change pressures increase and sales of traditional cement and concrete face threats, the combination of new thinking, innovation and new business models will be critical. In this direction we are, indeed, looking at the entire value chain with a customer- and application-centric perspective, in order to untap all of the value drivers that could be linked to sustainability. To start, this involves the rethinking of solutions portfolios rather than just products, both in cement and concrete, towards a low-carbon footprint, and any opportunities to improve the overall impact of CO2 in their lifecycle. Such a lifecycle perspective is also very important for supporting our partners further commercially in their green transition. We have been developing and launching a number of strategic initiatives, starting from the most relevant one which undoubtedly is the full commercialisation of the FUTURECEM limestone calcined clay technology. This was first used in the InWhite range of products, ultra-high-performance-concrete premixes in 2019, then as grey cement this year in Denmark, with a clear plan to quickly launch in Western Europe next year. The low carbon transformation in this case is enabled through the use of a solution like FUTURECEM, which preserves the same performance in the products, while reducing CO2 emissions by 30%. We are developing other FUTURECEM-related solutions as well as phasing in and focusing on other blended cements, both grey and white. Within our value chain we are accelerating the conversion from conventional to FUTURECEM as the main, if not only, low-carbon solution in ready mix concrete. Our RMC company Unicon Denmark has a target to switch all of its production to FUTURECEM by the end of 2022.
WCT: What other new technologies is Cementir investing into? MDM: Cementir has decided to take more disruptive action for fighting climate change by defining a 10 year roadmap to maximise the deployment of existing technologies and lay the groundwork for the breakthrough innovations that will lead to the production of ‘net zero emissions’ cement. Lately, Aalborg Portland, a subsidiary of Cementir Group, has entered into Project Greensand 2, a pilot project to capture and store CO2 in thwe subsoil under the North Sea. In the 10 year roadmap, the Group planned the main investment needed until 2030, out of which 107 million is included in the 2021 – 2023 Industrial Plan, approved by the Cementir Board of Directors in February 2021. In the 2021 – 2023 period, the major investments cover: Increased use of alternative fuels and raw October 2021 World Cement
materials; a push on district heating and waste heat recovery; and full production of FUTURECEM.
WCT: Can you tell us more about FUTURECEM, and explain how it helps achieve reduced emissions? Stefano Zampaletta (SZ): FUTURECEM is an innovative, validated and patented technology that allows clinker substitution rates of more than 35% in cement with limestone and calcined clay. Leveraging their synergy, the combination of materials in FUTURECEM has resulted in a more sustainable cement with a carbon footprint that is up to 30% lower compared to Ordinary Portland Cement. A further advantage is that the low-carbon benefits of the technology do not come at the expense of strength or quality. The technology is fully recognised as a solution for clinker ratio reduction in the International Energy Agency’s roadmap for ‘Low Carbon transition in the cement industry’ and is listed under ‘low clinker cements’ in the ‘Cementing the European Green Deal’ – 2020, making Cementir Group a frontrunner in the industry.1 The technology is also formally recognised as referenced in the EN 197-5 European standard for even further clinker substitution with II/C-M cements (up to 50%).
WCT: What are the main applications for a technology like FUTURECEM? SZ: FUTURECEM has been primarily focused on the RMC segment. Customers within this segment exploit the technology’s properties to make concrete better to pump and more stable against variations in consistency, which is usually a challenge with the rather cement-poor concrete used in Denmark. Positive feedback has been recorded when replacing Ordinary Portland Cement, with finishing and final surfaces receiving praise. Along with RMC, several Danish concrete precast producers are implementing FUTURECEM in their production through a complete testing programme on site with positive results. The light-brown colour of the concrete is a visible proof for end customers of the sustainable credentials of their building. FUTURECEM will be used in RMC and concrete elements for the ambitious sustainable building UN17 Village in Ørestad, Copenhagen consisting of more than 500 apartments. When completed in 2024, it will be known as the world’s first housing project, integrating all 17 UN world goals in the same building.
References 1. ‘Lower clinker cements’ – https://cembureau.eu/ about-our-industry/innovation/lower-clinker-cements (accessed 09/09/21). 19
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FROM COMPACT
TO MODULAR Dr. R. Krammer, W. Kulagin, & T. Thiel, LOESCHE GmbH, explain how compact cement plants were enhanced to become faster, more flexible, and capable of meeting the growing challenges of global cement markets.
A
s a rule, time, costs, and project scope are the most important factors in business decisions. Often projects cannot be realised because they require too much time, too great an investment, or generally too much effort. For this reason, LOESCHE developed the Compact Cement Grinding Plant (CCG) several years ago, which has been commissioned or is about to be commissioned in more than 12 plants worldwide since its market launch.
The focus during the development of the CCG was on the smallest possible footprint, rather than on the flexibility of the individual buildings. These plants proved very quickly the advantages of a compact design. With such a plant, cement production can start up in less than a year. This makes it possible to develop existing markets quickly. New markets can be tested with low risk and low investment, as the complete plant can be relocated with little effort.
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However, as a compact grinding plant, the CCG is limited in two areas: it is restricted to mills with an annual production of up to 250 000 t of cement and, due to the small footprint, the flexible design of the individual buildings is limited. Therefore, it was only logical that LOESCHE took a further step in this direction. The company has now consistently developed a compact and modular concept for all mill sizes from the LM 24.2 CS to the LM 72.4+4 CS and for entire grinding plants. The company’s goal was, and still is, to build efficient plants. Efficiency here refers not only to energy efficiency, but also to efficient
tendering and project handling. The concept of ‘Variant Management’ was born.
A new concept LOESCHE’s developers take the expectations of the customer and the requirements of the market into account for each new product. For the development of Variant Management, LOESCHE also defined its own requirements and determined how – from an internal point of view – a successful modular concept should look. The following goals were defined: f A ‘building block system’ was developed for this new concept. All buildings should be modularised but able to be freely combined with each other. This would enable the flexible design of projects and allow special customer requirements to be taken into account despite the modularisation. f Optimised plant planning was intended to ensure more efficient use of resources. f By using the modular concept, LOESCHE would be able to prepare quotations more quickly and substantiate them with reliable data from existing plants during the project phase.
Figure 1. The LOESCHE CCG with a LM 24.2 CS.
In detail, this resulted in the following specifications: f All aspects of plant design relevant to approval, such as escape routes, are already considered in the Variant Management. f LOESCHE’s own and major cement producers’ design criteria serve as the basis for all external equipment. f All cable routes are included in the planning right from the start. f The compact concept offers the following standard solutions for bins, filters, and product silos: » Bunker sizes from 10 to 1000 m3. » Filter sizes from 2220 to 23 700 m2 filter area. » Product silo sizes from 350 to 8500 m3.
Advantages
Figures 2 & 3. 3D-views of a grinding plant according to the LOESCHE Variant Management. 22
The Variant Management concept allows for flexible design of the grinding terminal. For example, the product storage capacity can be individually adapted to each customer’s needs. Also, all given topographies can be optimally utilised. Most of the modules for smaller terminals already include completely World Cement October 2021
pre-assembled container systems (see Figures 4 and 5, containerised feed hoppers), which can also be supplied for large mills depending on their use. LOESCHE attaches importance to fast assembly and good maintenance options, so that safe access is provided to all maintenance points. The shortened assembly and engineering times reduce project throughput times and allow grinding terminals to go into production more quickly. This modular concept is suitable for grinding terminals in greenfield as well as brownfield projects. With this concept, the following advantages can now be offered to the customer: f Variant Management results in a reduction in quotation lead times of up to 40%. f The engineering time can be reduced by up to 30%. f This adds up to a reduction in project lead times of approximately three to four months for EPC-projects. f All topographies can be optimally exploited. f Experiences from the project execution flow back into the planning and thus lead to a continuous further development of the individual modules. f The permanent optimisation of the plant planning leads to an improvement of the specific energy demand.
f An improved maintenance concept offers better accessibility for personnel and reduced maintenance costs. For example, the size of the mobile crane required for maintenance work has been greatly reduced.
Case studies Song Lam Cement JSC, Vietnam In January 2019, LOESCHE signed a contract with the Vietnamese customer, Song Lam Cement JSC for the delivery of a vertical roller mill for Line 4 of a brownfield project. The mill type LM 65.4+4 CS will be used for grinding PCB slag at a fineness of 4500 Blaine and a capacity of ≥ 275 tph. The scope of supply in Song Lam included the equipment for the entire grinding terminal from the feeding tower to the product transport downstream of the filter, the engineering for the entire building, the electrical system, and the automation technology. This was the first time that the new LOESCHE Variant Management was partially used. The resulting change in project planning brought the following advantages: f Due to a separate electrical room, there was no hindrance to the assembly. This allowed
for a reduction of the installation time by approximately eight to ten weeks. f The optimised plant design made it possible to reduce the installation area, which led to savings in steel and civil construction.
f The process gas duct layout was also optimised. f In the execution of this project, a great deal of emphasis was placed on the optimisation of the process gas circuit and a new volume flow measurement. These adjustments allowed LOESCHE to build very compactly and to reduce the pressure loss in the process gas circuit. The diffuser downstream of the mill fan was optimised and baffle plates were installed to optimise the flow in the process gas circuit. These optimisations resulted in a 25% reduction of the specific energy requirement of the mill fan. Despite the global COVID-19 pandemic and the strict lockdown conditions in Vietnam, the hot commissioning phase of the Song Lam grinding plant has already been completed.
Figure 4. LOESCHE’s new containerised feed hopper.
Figure 5. Representation of the feed hopper at a plant.
GCM Industries S.A., Burkina Faso In January 2021, the foundation stone was laid for a new greenfield project in Burkina Faso. For the plant of the customer GCM Industries S.A., LOESCHE will supply a compact grinding plant in EPC scope including silo loading, packing plant, steel construction and foundations. A LOESCHE mill type LM 30.2 CS for clinker and slag grinding will be used. This plant is a consistent further development of the project mentioned above and is the first plant where Variant Management is completely implemented. As a result, considerable savings in terms of time and effort are expected here, which will enable production to start soon. The expected start-up is scheduled for mid-January 2022. Two further CCGs in Tunisia and Liberia have also reached the project execution phase in the meantime.
Summary
Figure 6. The LOESCHE LM 65.4+4 CS in Song Lam, Vietnam. 24
Due to the successes of the CCG and the first promising projects with the new Variant Management, LOESCHE is convinced that it is on the right track. With the modular plant concept, the customer can react flexibly and quickly to the increasing challenges of the global and regional cement markets. World Cement October 2021
GEARING UP FOR
decarbonisation Tahir Abbas and Michalis Akritopoulos, Cinar Ltd., explore the use of hydrogen fuel as a route to decarbonising cement production.
he cement industry is making big strides towards meeting its CO2 reduction targets, to eventually comply with the Paris Agreement and reach zero CO2 emissions by 2050. Over the last 30 years, several cement producers have reported reductions in CO2 emissions of over 30%(against the 1990 baseline), which were achieved through increased energy efficiency and the use of alternative fuels and raw materials. The use of calcined clay (turning natural clays into synthetic pozzolanic materials) may lead to additional 40% reduction in CO2 emissions by replacing similar proportions of clinker in the cement mix. In order to reach net zero CO2 emissions, however, a breakthrough in conventional approaches involving non-fossil fuel thermal input and the use of ‘green power’ is required. Besides implementing O2 and CO2 enrichment methodologies (CCSU), among other options, H2 firing is being considered as it replaces combustion generated CO2 with water vapour (H2O). Despite having a green-house effect with a similar thermal radiative properties to that of CO2, water vapour has a negligible impact on the environment as atmospheric concentrations are controlled by temperature.
T
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A piece of the puzzle
(e.g., under sold-out market conditions). However, hydrogen firing has not been embraced for clinker production, not only due to its higher costs but also additional safety concerns. In small boilers, hydrogen has been mixed with natural gas, at the source, to enhance its H/C ratio for lowering CO2 emissions. Combustion tests have shown that up to of 30% H2 can be mixed with natural gas without having to modify burner nozzles and boiler control parameters. When co-firing H2 with solid fuels (i.e., biomass), e.g., kiln burner modifications are required. When opting for on-site H2 production for higher substitution rates, additional safety issues, its handing, storage, and feeding/auto-shut procedures are to be devised. For future low-carbon kiln operation (as world-wide drive for clean hydrogen economy), hydrogen injection mechanism for the kiln burner and calciner need to be developed, in particular for two aspects, (a) explosion/fire safety and (b) optimisation of the hydrogen flame characteristics for co-firing it with biomass/fossil fuels. The latter part requires extensive research to produce a hydrogen/solid fuel flame of a similar length, shape and thermal profile to that of the existing petcoke/coal fired flame. In the kiln front end, the gas-phase flame temperature slightly increases due to the meal phase change, hence the higher adiabatic temperature of hydrogen becomes of paramount importance. Adiabatic flame temperature refers to a flame temperature without heat loss or gain. The adiabatic temperature of hydrogen is much higher than natural gas (2483˚C and 2236˚C, respectively). Under oxygen-hydrogen combustion conditions, adiabatic flame temperature can increase to 3473˚C. The thermal radiative heat transfer of hydrogen, is almost half that of coal, which is generally preferred fuel for its higher radiative heat transfer properties. This poses a critical thermo-fluid dynamics problem – as ‘thermal heat’ from a hydrogen flame will be retained within the combustion products without being dissipated into the ‘meal’ and thus without being transported away from near burner region, this will cause ‘hard-burning’ conditions (leading to clinker quality issues and higher fuel feed rate). Therefore, when considering H2 co-firing, it is important to first analyse the diffusion and mixing pattern with respect to co-firing fuels’ activation energies and reactivities in order to ensure a compact single flame envelop. Prior to co-firing H2, one must carefully assess the physical and chemical characteristics, i.e., compressibility, auto-ignition, Figure. 1. A schematic of Fuel Switching R&D strategy, 2020 – 2021, and flashback, so that kiln gas coordinated by MPA (financed by BEIS).
Hydrogen, therefore, is going to be an important component of the future fuel and energy supply chain. Currently, most hydrogen is produced via steam reforming of natural gas, with production from water (via electrolysers) accounting for less than 10%. ‘Green hydrogen’ production will, therefore, require the development of inexpensive CO2 sequestration and large-scale electrolyser technologies before it can become part of renewable ‘fuel mix’. As an example, the higher the H/C ratio in the composition of a fuel, the lower the CO2 emissions in combustion products, so switching from petcoke to coal and to natural gas will reduce CO2 emissions (by up to 50%) – substitution of fossil fuels with H2 and biomass, will gradually push the cement sector closer to carbon neutral manufacturing. Green hydrogen can be produced through a number of methods; the most straightforward approach would be to use electrolysers for splitting the waters into two streams comprising of H2 and O2. Thus, there is also a possibility to make use of oxygen as oxidant or for it to be exported to other industries, i.e., steel works or nearby chemical processing units. For every kg of hydrogen produced in an electrolyser 8 kg of oxygen is produced as a by-product. The excess hydrogen produced may also be chemically recombined with CO2 to produce a ‘fuel’ – this becomes more feasible when CO2 recirculation and oxy-combustion concepts are applied (as part of CCSU). There are a number of possibilities (i.e., enhanced oil recovery) which need to be specifically studied for a cement plant, as its location with respect to other industries and CO2 utilisation will play an important role in deciding on the best combination of CO2 reduction technologies. Oxygen enrichment in kilns could be cost-effective when either firing poor quality/hazardous fuels (e.g., in wet kilns) or increasing clinker production
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World Cement October 2021
temperatures and radiative heat transfer similar to existing coal/petcoke firing conditions are maintained for good clinker quality. For co-firing H2 through multichannel kiln burners, it would be safer to introduce hydrogen from specifically designed nozzles, allowing for its compressibility and producing higher velocity jets, located at the central port of the kiln burner. This would ensure that the higher but localised temperatures are shielded and are transmitted to surrounding co-firing fuels. By doing so, the adjacent lower calorific value biomass chips or lower volatile petcoke particles are rapidly heated and ignited to higher temperatures. In this firing configuration, solid fuel particles/chips will also compensate for the lack of radiative heat transfer characteristics of the hydrogen flame, which accounts for about 95% of heat transfer within the near burner region. The higher localised gas temperatures are undesirable for thermal NOx formation and maintaining the coating near the kiln front end, which can also be effectively resolved to some extent by use of lower calorific value biomass fractions. For all possible hydrogen injection arrangements, it is important to calculate through detailed computational models for all possible hydrogen injection configurations’ effect on the clinker formation chemistry, combustion products, NOx
and CO emissions. With kiln optimisation with mathematical modelling, a plant can start firing H2 with minimum burner and kiln modifications, hence substantial savings on the time and plant trials. When firing H2 in calciners, higher gas temperatures and lower radiative heat transfer will be of major concern than its combustion in the main burner, due to complex combustion and calcination reactions taking place over a shorter retention time. It is worth mentioning that tertiary air temperature at the calciner inlet is around 900˚C which, in most cases, is similar to calciner exit temperature. Thus, to avoid hot-spots, H2 can be safely combusted in an integrated combustion chamber so that high temperature combustion products are introduced directly into the tertiary air stream(s), allowing the temperature to reach levels similar to that of kiln backend gases (up to 1200˚C). This approach will substantially reduce the risk of the creation of hot-spots near calciner walls, but will still enhance the meal particles’ calcination rate. The mixing of H2 into tertiary air will also suppress the formation of NOx within the calciner in the event of co-firing higher nitrogen-containing fuels. A second option could be to introduce H2 below to meal splash boxes, so that higher gas temperatures are reduced through endothermic meal calcination reactions. Generally in the calciner, there are flow stratification issues impeding the rate of combustion
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and calcination reactions, which necessitates that these highly non-linear and complex reactions be solved using advanced mineral and combustion interactive computational fluid dynamics models, i.e., MI-CFD.
conditions for a variety and variations of fuels. It is expected that the research results will be completed by the end of 2021, the knowledge base can then be employed at other cement/lime plants gearing up for decarbonisation.
Research & development
Fuel of the future?
As part of its Business Energy and Industry Strategy (BEIS), the UK government has awarded funds to support the development of H2 fuel utilisation within industry. Cinar has been part of these R&D investigations over 2019 – 2021, with a scope of carbon free operation of cement and lime plants ranging from feasibility studies to full-scale plant demonstrations. The aim of the research is to investigate gradual replacement of fossil fuel with zero CO2 emissions fuels through ‘Advanced Fuel Switching’ techniques. Using a mix of 50% hydrogen and 50% biomass in the kiln and 83.3% biomass with 16.7% plasma in the calciner (Figure 1) leads to complete elimination of all fossil fuel based CO2 emissions.1 Cinar’s role has been to assist in designing real plant test conditions for the kiln and the calciner for H2, plasma, and biomass firing using its in-house mineral interactive computational fluid dynamics (MI-CFD) models. The simulated results assist in reducing the plant trial costs as well as aiding burner design modifications and defining co-firing strategies. The data archived will, in turn, be used to validate and improve models for H2 co-firing
Hydrogen firing, may also be considered with oxy-combustion (oxygen and carbon dioxide enrichment), as green hydrogen in future will mostly be produced on-site, using large electrolysers powered by wind and/or solar energies. This will open up additional R&D fields focused on safety and handling measures for H2 and O2, which at present have never been utilised at a cement/lime plant. Separately, oxy-combustion has also been actively studied and with the development of low-cost CO2 sequestration technologies, mineral CO2 emissions can also be harnessed. When these two separately developed technologies are combined, a plant may operate one kiln on oxy-combustion and the other on fuel switching concept, on using both technologies in a kiln or calciner. Future cement plants could use both O2 and H2 streams produced from an onsite electrolyser, achieving the zero CO2 target with substantial reduction in H2 and O2 production costs – a plausible solution to work on for the cement plants of 2050 and beyond.
References 1. MPA report October 2019
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A NEW LEASE O OF LIFE
Jaco Harmzen, SKF, outlines the factors that cement producers should consider when looking to extend the service life of clinker pan conveyor bearings. ften, the bearings on the head shaft of clinker pan conveyors do not reach their desired service life. Premature failures are often caused by surface damage in the bearing that is associated with ingress of contaminants and/or insufficient lubrication. Correct installation of bearings also plays a role in extending bearing life. Premature failures can result in costly unplanned downtime and production losses. If a head shaft is run to failure, secondary damage to components such as shafts, housings, couplings and gearboxes associated in the drive train can cause long delays to the repair as these items may have long lead times for delivery. Cement plants are known for their harsh, invasive, and highly abrasive operating environment. Keeping contaminants out of the bearing is the number one priority when seeking to extend service life. However, in order to achieve optimal bearing life, a combination of actions through the bearing life cycle will be required Factors to consider are correct installation, a good lubrication regime, effective ingress protection and a good condition monitoring programme.
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Investigating bearing failure
Typical pan conveyor drive train showing the contaminated operating environment.
A customer recently experienced unplanned failures on a pan conveyor. Frequent bearing failures occurred. The average mean time between failures was four months. With a performance agreement between SKF and the cement mill, SKF was committed to reducing unplanned downtime and increasing the reliability of the mill’s assets. Performance programmes aim to reduce unplanned downtime with early detection of faults in equipment, but also to reduce recurring failures of problem assets by analysing the root cause of failure. Modification, re-design and upgrading of the asset allows for reduced bearing costs as well as increased up-time and productivity. SKF took a process approach to the problem. Investigation of the bearing failure indicated four factors that contributed to the premature failure of the head shaft bearings in this pan conveyor.
Ingress of contaminants
Images showing the harsh operating environment faced by head shaft bearings.
Labyrinth seal arrangement on drive end bearing.
The labyrinth seal is dry and the grease is heavily contaminated. 30
The original seal arrangement relies heavily on re-lubrication of the bearing to ensure purging of the grease through the labyrinth seal. Upon inspection of the bearings, the labyrinth seal was dry. With no grease filling the space between the labyrinth rings on the shaft and housing cavities, dirt and moisture entered through the seal into the housing and eventually into the bearing. A labyrinth seal does not have any contact seals incorporated into its design. Incorporating a contact seal into the application forms a physical barrier between the bearing and the contaminated environment. Labyrinth seals that incorporate a contact seal are often referred to as a taconite seal. Taconite seals have a number of designs that may include felt seals, V-rings or lip seals. Keeping in mind the harsh and extremely contaminated environment, SKF chose to replace the labyrinth seal arrangement with the SKF ‘TK’ heavy duty taconite seal. This seal uses a rotating ring with fingers oriented axially to allow for a longer labyrinth path. A V-ring is incorporated into the seal in such a way that it allows for purging of grease but prevents the ingress of contaminants. O-ring seals on both the shaft and housing allow for a solid seal against moisture and dirt. Each taconite seal is equipped with a grease fitting to allow re-greasing and purging of each seal individually, making sure the seal is effective, independent of the bearing re-lubrication. Although the taconite seal is a robust seal and quite an improvement on the previous arrangement, it is important to optimise the defence against contamination ingress, especially if a conveyor is washed occasionally with high-pressure water. The taconite seal is the first barrier against contamination. By filling the housing free volume on each side of the bearing with around 80% grease, a dirt trap is created – the second barrier. If dirt or moisture finds World Cement October 2021
its way through the taconite seal (first barrier), the grease between the taconite seal and the bearing will trap the contaminants and delay the migration of contaminants to the bearing. The third barrier is achieved by using a sealed spherical roller bearing. The bearing is supplied with seals that allow re-greasing and purge when additional grease is introduced into the bearing. The bearing is factory filled with a high-quality EP grease. In some cases, the bearing can be viewed as ‘sealed for life’ – this requires no re-lubrication. However, in this harsh environment, SKF selected to periodically re-grease the bearings. The combination of taconite seals, a sealed bearing, and a grease barrier becomes an SKF three-barrier solution. This combination has increased the conveyor bearing service life more than three times compared to when open (unsealed) spherical roller bearings are used.
Lubrication It is hard to confirm the initial grease fill by examining the failed bearings. It appears that the bearings were lubricated during installation, but the labyrinth seals were not provided with an initial grease fill. As the labyrinth seals do not have individual lubrication points, they need to be filled with grease during installation. Re-greasing of the bearing will eventually fill up the
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housing free space to allow for grease to purge through the seal. If the housing free space is not filled with grease during installation, it will take some time for the bearing grease to first fill the housing free space and then purge through the labyrinth seals – giving an opportunity for dirt and moisture to enter the housing through the dry labyrinth of the seal. The lubrication route is adjusted to add two lubrication points, one for each taconite seal, reducing the greasing quantity for the sealed bearing. The amount of grease needed for a sealed bearing is much less than for an unsealed bearing.
Installation Although plant personnel are experienced in installing bearings, contractors are often used to do this. Even if written procedures exist for installation, there is no guarantee that the correct procedures were followed and the correct tools were used. In this case, insufficient drive-up of the bearing caused the bearing and adapter sleeve to be loose on the shaft. Having a consistent installation procedure ensures repeatable mounting results. Repeatable results were obtained using the SKF drive-up method. The start position is clearly defined by reading it from a pressure gauge. When using a different method, it is up to the installers to ‘feel’ where the start point is and what the
bearing clearance reduction is. The drive-up method relies on measurable data making the procedure objective, measurable and repeatable. Axial movement or drive-up is measured using a dial indicator. To secure the lock nut and locking washer, the correct size impact spanner was used. A common bad practice of using a cold chisel to secure the lock washer causes damage to the lock nut and a non-uniform load distribution on its circumference could lead to an ovalised lock nut.
Predictive maintenance Vibration analysis is a vital predictive maintenance tool for monitoring the health of the machine. A large number of failures in clinker pan head shafts are related to surface damage of the raceways and rolling elements of the bearings. Surface damage (abrasive wear, surface distress) causes the removal of material from the raceways or alters the bearing raceway surface finish in a smooth way where no steps or impact are created. These faults SKF taconite seal for heavily contaminated are more difficult to identify compared to a cracked environments. ring or spalled raceway. It is however, possible to identify this type of bearing surface damage through vibration analysis using the SKF acceleration enveloping (gE3) technique. Data is collected monthly on the machine using a portable vibration data collector and a team of expert vibration analysts at the SKF Rotating Equipment Performance Centre performs the analysis. The acceleration enveloping analysis technique can also detect a lack of lubrication in the bearings and detect looseness in the bearings if Sealed spherical roller bearing (left) and housing free space they were not mounted correctly. being filled with grease to create a dirt trap (right). Of course, other problems in the drive train such as misalignment, coupling wear, motor and gearbox faults, worn sprockets or chain issues will also be identified, trended and reported. In this case, vibration data is collected manually, but it is possible to mount the vibration sensors on the housings and wire it to a connector box positioned a distance away from the rotating machinery. This will allow for the safe SKF Taconite seal. 32
World Cement October 2021
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periodic collection of the vibration data. The vibration sensors can also be connected to an on-line system for continuous remote monitoring of the conveyor drive line (pulley, gearbox, motor) by analysts at the SKF Rotating Equipment Performance Centre. At the same time, it is also possible to monitor the bearing temperature if a combined vibration/temperature sensor is used, such as the 1
2
3
3
2
1
SKF CMPT 2310T sensor. This sensor can be permanently mounted on the bearing housings, as well as the gearbox and motor. Early detection of issues allows for the planning of corrective actions before the damage in the bearings becomes critical. Vibration monitoring enables planned downtime if it is necessary to replace bearings or sprockets instead of unplanned downtime when failure happens without warning. It also helps avoid secondary damage to the shaft, housings and seals if the bearings might be run to failure.
Summary
SKF Three-barrier solution for contaminated environment.
Hydraulic pump with pressure gauge and hydraulic nut with dial indicator.
In summary, it is evident that bearing life in a clinker pan conveyor is influenced by many factors. To maximise the life of bearings it is necessary to focus on their complete lifecycle. This includes choosing the correct sealing arrangement for the harsh working environment, using a sealed bearing, ensuring the installation is done correctly, lubricating the assembly during installation and during operation, and monitoring the health of the machine to make corrections before damage escalates. The SKF Three-barrier solution with proper mounting and lubrication has significantly increased the life of the conveyor pulley bearings from four months to over 12 months at the time of writing this article. The bearing arrangement is expected to last at least 36 months. Upgrading to the SKF three-barrier solution leads to reduced maintenance requirements, including reduced number of failures and reduced lubrication requirements, which aligns with the performance agreement of increasing reliability and availability. The health and safety of the plant workers was also improved by reducing the maintenance requirements and by using the vibration monitoring on this equipment. The success with this solution on one clinker pan conveyor led to replication of this sealing arrangement on two other clinker pan conveyor head pulleys as well as three bucket elevators on this site. Considering the fact that approximately 52% of equipment in a cement plant is related to conveying material, the SKF three-barrier solution can be implemented in many other applications to improve bearing service life. Applications such as pan conveyors, belt conveyors, bucket elevators, screw conveyors, drag chain conveyors, and rotary valves should be targeted for improvement.
About the author
Securing a lock nut using an impact spanner. 34
Jaco Harmzen spent his career as an Application Engineer at SKF helping customers solve reliability issues on rotating equipment. During his 19-year tenure, Jaco gained invaluable global experience in heavy industries such as mining and cement in South Africa, Australia, and the United States. World Cement October 2021
JUST ADD Armin Möck, Lechler, explains how cement producers could benefit from emergency water injections in the clinker cooler in order to control increased gas temperatures.
C
linker grate coolers play an essential role in the cement manufacturing process. Cement clinker is made by heating a homogeneous mixture of raw materials, mainly ground lime stone, in a rotary kiln at a high temperature. The products of the chemical reaction aggregate together at their sintering temperature of about 1450˚C. Due to the inclination of the rotary kiln, raw cement is constantly falling out of the lower end of the rotary kiln into the lower laying clinker cooler. Clinker normally forms in lumps or nodules, usually 3 mm (0.12 in) to 25 mm (0.98 in) in diameter. Defined openings in the grates allow ambient air, which is pressurised by ventilators installed below, to flow upwards through the clinker bed to cool down the clinker to an ideal temperature of 100 – 120˚C before it leaves the cooler to be stored in silos until it is ground into the final product: cement.
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Why is cold clinker needed? The final product has to be cold at the end of the manufacturing process. The cooling of the clinker is very important, especially considering that the subsequent grinding of the clinker into cement adds additional thermal energy to the product caused by the grinding friction of the steel balls with the clinker. In addition, high clinker temperatures are disadvantageous for the cement milling process. If the clinker is too hot when entering the cement mill, it will lead to increased cement end temperatures, which can damage paper bags and lead to problems in the concrete mixing process if the cement is used immediately. Furthermore, the cooling of the clinker is important for preventing cost intensive damage to downstream equipment like rubber conveyor belts, ducts, ventilators and dust filtration equipment.
Schematic picture of a clinker cooler. Table 1. Types of nozzles. Full cone nozzle Water pressure (bar)
2 - 10
Droplet distribution
Coarse
Number of installed nozzles
6 – 12
Control concept
Cascade (nozzles on/ off).
Advantages
Low investment costs.
Many lances, inaccurate control, Disadvantages
many openings for lances necessary, nozzles tending to clog, many on/off valves in operation.
Comments
36
Outdated design.
Part of the cooling air leaving the internal space of the clinker cooler (above the clinker bed) with a greatly increased temperature of up to 400˚C goes to the kiln burner as ‘secondary air’ and as ‘mid air’ for other processes like coal milling. The rest of the air is exhaust air which is led to a dust filtration device and then discharged into the environment virtually dust free. In many plants electrostatic precipitators (ESP) for dust filtration are still in use, but due to stricter legal regulations today, state-of-the-art baghouse filters (BHF) are more commonly used. Common gas temperatures to the filter are 200 – 250˚C, sometimes 300˚C, depending on the kind of filter and the material of the bags. This flow of clinker into the clinker cooler and the cooling of the clinker is ideally a permanent process, running normally without large fluctuations. Exit gas temperature peaks occur when the quantity of solids falling into the clinker cooler increases very quickly. This can happen when: f A kiln flash occurs: A blockage of a cyclone in the preheater tower is removed and up to 20 t of hot raw material and clinker flows very quickly through the kiln into the clinker cooler. f At certain temperatures and under certain chemical conditions, clinker that has accumulated on a specific part of the kiln inside wall (causing the clinker to form a ‘ring’) can come away and fall into the clinker cooler.
Then, the exhaust air temperature can increase very rapidly to 500 – 600˚C. One can imagine that this leads to serious damage – Twin-fluid nozzle Spillback nozzle either to the steel shells of the ESPs or to the textile 3-5 35 bags in the BHFs – not to Very fine Fine mention the stress caused on the steel ducts and the 2 – 4 (6) 2 – 4 (6) fans. The replacement of a complete set of destroyed Linear/stepless Linear/stepless, textile bags and a destroyed Turn-down ratio: Turn-down ratio: 15:1. filter could be extremely 12:1. costly. Regulation is very Besides these Regulation is very accurate and fast, short-term emergency accurate and fast, and less are lances gas temperature peaks, and less lances are required, as well as high exit gas temperatures required. the use of only one are a problem that control valve. develops slowly over the Compressed air years, due to extended necessary, higher clinker production rates investment costs, air Higher investment without investment in and water have to be costs. a better performing controlled, and fine clinker cooler. It is not spray is carried to the uncommon for these walls by the gas flow. undersized/overloaded Air increases the Most common clinker coolers to use running costs. system today. water injection outside World Cement October 2021
of emergencies, sometimes with it in permanent operation.
Emergency water injection To prevent very expensive damage, many clinker coolers are equipped with an emergency water injection system. These systems are automatically switched on when thermocouples located in the outgoing gas duct are detecting significantly increased, but not harmful, gas temperatures. Tubes with nozzles on the end, so called nozzle lances, are installed in the cooler. The nozzle lances are connected to a water pump, providing the necessary water pressure. In case of an emergency, the nearby standing pumps are switched on and within 3 – 5 sec. the nozzle lances inject a fine spray into the clinker cooler space between the surface of the clinker bed and the ceiling. The evaporation enthalpy of the water cools down the exiting gas very quickly.
would reduce the binding properties of the cement and therefore its quality. The placement and alignment of the nozzles is a crucial design part of such an injection system. f The spray cones of the nozzles must not interfere with each other. This could lead to an accumulation of water and could generate larger droplets which would need more residence time to evaporate. f The vertical location of the nozzle lances is also a parameter to consider. To prevent built-ups on the ceiling, nozzles are often installed as low as possible. However, it could be that a pile of clinker moving through the clinker cooler could touch/bend/damage the lances. Furthermore, the residence time of the droplets is higher when they are leaving the nozzle at a certain distance above the clinker bed. The general rule while determining the nozzle lance position is to get as much residence time as possible from the nozzle to the exit port of the clinker cooler. The complete evaporation of the water droplets has to be accomplished inside the clinker cooler and not in the outgoing gas duct. When the positions of the nozzles are defined, the location of the nozzle lances has to be fixed. They can be installed in the side walls or in the clinker cooler ceiling. The position of the nozzle lances depends on the width of the clinker cooler and the potential free space above the clinker cooler. This space is needed for the installation of the nozzle lances and the maintenance access.
Placement of nozzle lances The engineering process is based on the decisions made regarding where to place the nozzle lances and is an essential part of the function and reliability of the injection system. Requirements to be considered include: f The secondary air (and the occasionally existing mid air) which leaves the clinker cooler at the opening close to the kiln end has to be as hot as possible to improve the thermal efficiency of the kiln. Therefore, the water spray must not cool down this secondary air. Before the horizontal location of the nozzle lances can be fixed, it has to be known where the ‘separation line’ of the cooling air inside the clinker cooler is. Logically, no nozzle must be installed on the section where the secondary air is present. The OEM of the clinker cooler knows exactly where Side wall installation example: Top view (left) and 3D image (right). the separation line is due to elaborate CFD-studies. In the case of a flexible separation line, the location of the nozzle lances has to be fixed in coordination with the end customer. f The droplets must not reach the clinker bed to prevent the reaction with the cement which Clinker cooler inside with nozzle lances sticking in. World Cement October 2021
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Types of nozzles Many different nozzle types have been installed in clinker coolers over the years, however since the introduction of the water injection into the clinker cooler, only a few nozzle types have proven to be successful. Injection rates and quantity of lances The common range for the injected water quantity is from 3 – 30 m3/h water with 2 – 6 spillback nozzle lances. Higher water quantities in large clinker coolers can be realised. Protection of nozzles Since the nozzles are in operation irregularly but are permanently installed in the hot environment inside
the clinker cooler with a high cement dust load, they have to be protected from built-ups during the off-times. This can be done with a small ventilator (one for all nozzles) providing an air pressure of 50 – 80 mbar and a constant flow of protection air. As soon as the water injection has to go into operation, a three-way-valve closes off the protection air and opens the water flow. After the injection period, the remaining water inside the nozzle lance must be prevented from evaporating in the lance. This would lead to the deposition of the mineral components of the water inside the nozzle lance and nozzle. After a number of these drying sequences, this mineral layer could increase, fall away, and block the nozzles. With a short shot of compressed air after shutting off the injection system, the nozzle lances can be completely drained. This sequence of injecting water, draining and protection air is fully automated. Necessary equipment Nozzle lance f Material: heat resistant stainless steel (up to 1000˚C). f Special design features: » Simple and stable/resistant design. » Thick walled protection tube to withstand mechanical impacts. » Projecting length inside the clinker cooler is adjustable. » Quick release flange allowing easy access. » Lances can be disassembled and maintained during normal cement kiln operation. » Protection air outside the nozzle lance/inside the protection tube.
Spray pattern of a spillback nozzle.
Pump and control skid f Special features: » Will be installed and pressure tested in the workshop. » Short commissioning period. » Information about the injected water quantity is permanently available in the central control room.
About the author
Pump and control skid preassembled.
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Armin Möck has been working at Lechler for over 27 years as a consulting and sales engineer/key account manager, responsible mainly for the applications in the cement industry. On average, Armin visits two cement plants per week in Europe, the US and other countries. Lechler is a family owned company and the oldest ‘nozzle company’ worldwide, having designed and produced nozzles for over 140 years with affiliates and sales offices worldwide.
World Cement October 2021
Markus Burbach, Klüber Lubrication, reviews advances in open gear lubrication and provides a guide for choosing the right technology to optimise reliability and asset utilisation.
O
ver the last 100 years, different lubrication technologies for open gears have emerged, giving today’s operators a wide choice. The variety of technologies and the number of different lubricants offered can make it challenging for operators to see the wood for the trees. As a result, the potential to optimise reliability, total cost of ownership and the lifetime of girth gears and pinions is not always exploited. Until a few years ago, one could divide the lubrication technologies for open gears into three categories: asphaltics, solid containing greases and highly viscous oils. Over the last decade, innovative lubrication concepts have been introduced to the market. Therefore, a
more differentiated categorisation is useful to help operators to identify the right technology for their goals: f Asphaltics f Solid containing greases (black) f High-viscous oils/transparent fluids (based on mineral or synthetic hydrocarbon oils) f Solid containing greases (white) f Ultra-high-viscous oils/transparent fluids (based on Polyglycol oils) Each technology has pros and cons (Figure 1) satisfying different needs operators may have depending on their maintenance strategy and practices. This article offers guidance on when to choose each technology.
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Asphaltics When to choose: The use of asphaltics is strongly discouraged for health and safety reasons and their poor housekeeping properties. Asphaltics are a by-product from the crude oil refining process and are also known as bituminous or residual compound lubricants. Despite considerable disadvantages, they are still used by some operators. The reason for this is that although they are basic formulated lubricants with little performance-improving additives, they can provide good gear protection thanks to their ultra-high viscosity. A high viscosity helps to build sufficient film thickness between tooth flanks, which protects them from wear, scuffing and pitting. However, asphaltics have many weaknesses that outweigh their few strengths and as a result they are unpopular in most parts of the world. They can be carcinogenic and are therefore banned by many countries. Due to their ultra-high viscosity,
they require the use of a diluent to temporarily reduce viscosity in order to spray them onto gears. As a result, they feature a low viscosity at the time of application and seldom reach full viscosity during operation. The reason being, that the time it takes for the diluent to evaporate is far longer than the typical spray intervals. As a result, new diluted product is applied before full viscosity is reached, thus causing the evaporation cycle to start from the beginning. Therefore, the lubricant on the gear never reaches the desired viscosity that is meant to protect the gear. At the same time, the absence or low concentration of additives does not provide enough protection against wear whilst the viscosity is low. Another disadvantage is that diluent continues to evaporate if the equipment is stopped. This can lead to the spray nozzles of the lubrication system becoming clogged, which results in lubricant starvation once production is resumed. It can also lead to a build-up of solidified lubricant in the gear guard and tooth
Figure 1. Technology evolution. 40
World Cement October 2021
roots that are extremely difficult to clean. In light of these disadvantages, many lubricant suppliers specialised in open gear lubrication and OEMs strongly discourage the use of asphaltics.
Solid containing greases (black) When to choose: Operators looking for the lowest price per kg rather than best profit impact. Solid containing greases with a black appearance were developed in an attempt to overcome the disadvantages of asphaltics. Their base oil viscosity is far lower though and, as a result, open gears operate in a so-called boundary friction regime as shown in Figure 2 where metal-to-metal contact is the highest and wear, scuffing and pitting protection is the lowest of all friction regimes. To compensate for their low viscosity, solid lubricants such as graphite or molybdenum disulfide are added to provide additional protection of the gear and which cause the black appearance. Whilst these types of greases can support a satisfactory performance of the open gear (e.g. low vibrations, low temperature differentials across tooth flanks), the lifetime of the gear set will always be a few years shorter compared to
a gear set that is lubricated with higher viscosity lubricants. Due to their low viscosity, these greases require a significantly higher amount of lubricant to be applied on the gear than more advanced and higher viscosity lubricants. Whilst the price per kg may be lower than that of more advanced technologies, the total spend on consumption is typically higher and so is the cost for disposal due to a higher waste volume. This can mislead operators when trying to optimise their maintenance budgets. Just like asphaltics, these greases are black in appearance, which means that it is not possible to meaningfully inspect the condition of the gear tooth surface during operation or without cleaning it during shutdown. As a result, condition monitoring is very challenging and prediction of failures is hard, thus jeopardising reliability and uptime.
High-viscous oils/transparent fluids (based on mineral or synthetic hydrocarbon oils) When to choose: Operators looking for the best value for money. Transparent fluids were introduced to the market in the 1990s with Klüber Lubrication being one
B a g fi l ter s H e a t ex ch an ger s P n eum a tic con v eyin g Com ple te d e dus t in g plan ts
GORCO S.A. LEIOA (Bizkaia) Spain +34 944 635 244 gorco@gorco.es www.gorco.es
of the first lubricant manufactures to launch this technology through the Klüberfluid C-F Ultra Series. The development was driven by the recognition that the cement industry needs to improve equipment reliability and lifetime to reduce total cost of ownership and improve profitability. These lubricants have a much higher viscosity and as a result, a much better load carrying capacity than black greases. They offer better separation of the tooth flanks supported by a thicker lubricant film, both for slow running open gears on kilns or fast running open gears on mills. As a result, the gear flanks operate in a mixed friction regime where metal-to-metal contact is much less than in the boundary friction regime as is common with black greases that have a much lower viscosity. The mixed friction regime as common for transparent fluids results in less wear (Figure 2). Less wear means pinion and girth gears maintain their original shape and mass for longer, leading to a longer life and a reduced risk of lower load carrying capacity, vibrations or localised stress that can result in gear failures. Aside from the improved protection of pinion and girth gear, the transparent nature of these lubricants allows for visual inspection of the tooth flank condition during operation. This allows for better insights into the condition of the gear, and if needed, to take corrective actions much earlier than would be possible if using black greases where one has to wait until shutdown for visual inspection. The better lubricity and higher viscosity of this technology allows operators to reduce consumption by up to 50% compared to black, solid containing greases. It also provides more peace of mind as optimised lubricant consumption leads to less over lubrication.
This often occurs when operators are unsure of adequate volumes and sometimes do not receive guidance and on-site support from their lubrication partners. The optimisation of the consumption usually overcompensates the higher price of this technology and results in an overall lubricant cost reduction of 20 – 25% compared to black greases. The much better gear protection, its impact on gear life and total cost of ownership combined with lower lubricant cost make this technology the preferred choice for operators who are looking for best in class maintenance practices and equipment protection.
Solid containing greases (white) When to choose: Operators experiencing excessive dust contamination of their open gears or wanting to utilise the benefits of a high base oil viscosity combined with next generation solid lubricants. White greases have been introduced to the market over the last ten years. Despite being greases, they utilise a similar concept to transparent fluids and use highly viscous base oils combined with advanced additives for best gear protection from wear, scuffing and pitting. They are also transparent in nature, albeit somewhat less than transparent fluids, and allow for visual condition inspection of gear flanks during operation. Additionally, they contain white solid lubricants, which can give them better performance characteristics in the case of cement dust contamination of the lubricant. The types of solid lubricants used in white greases differs to those used in black greases. Moreover, solid lubricant technologies differ substantially from one lubricant manufacturer to another and a generalisation is difficult.
Figure 2. Relationship between lubricant film thickness, friction and wear. 42
World Cement October 2021
Klüber Lubrication uses a ‘Solid Lube Integrated Base Fluid’ (SLIBF) technology for its Klübersynth OA 98-15000 white open gear grease. In contrast to other white greases, the solids in this product are bound in the base oil, which avoids the undesired side effects commonly associated with solids in powder form, such as clogging of spray nozzles which can lead to unplanned downtime due to lubricant starvation and gear failure or the build-up of lubricant at gear tooth roots. Most importantly, Klübersynth OA 98-15000 provides enhanced gear protection in the case of cement dust ingress.
them an excellent choice for reducing friction in order to avoid wear and scuffing. At the same time, Klübersynth C-PG 17 Ultra offers the highest viscosity available at 100˚C (Figure 3), which is an important indicator for determining the actual viscosity during operation at elevated temperatures. In fact, it provides operators with a higher viscosity at 100˚C than they could obtain from the outdated asphaltic technology whilst benefitting from all the advantages of modern lubricant concepts. This lubricant also works without diluents ensuring that its ultra-high viscosity works from the moment it is applied onto the gear.
High-viscous oils/transparent fluids (based on polyglycol oils)
Barriers to exploiting the potential of modern open gear lubricants
When to choose: Operators looking for the highest lubricant viscosity during operation to achieve enhanced wear, scuffing and pitting protection. This technology represents the most advanced open gear lubrication available and was introduced by Klüber Lubrication in 2020. Polyglycol oils are known to offer the best anti-friction properties, especially when sliding friction is high as in open gears. This makes
Operators may be hesitant to upgrade to advanced lubrication technologies even though they are eager to exploit the benefits associated with them and a need to maximise tooth flank life of pinion and girth gear. A common reason is that they experience a reliable operation of their mill or kiln now, which they do not want to jeopardise. Whilst this allows for stable operation in the short-term, they are likely to risk reliable operation in the medium-term and it will most definitely result in a much shorter gear life.
Understandably, some operators are anxious about making changes to their lubrication set-up. To ensure safe transitions, Klüber Lubrication’s sales and service engineers accompany a changeover of lubricants. This is followed by regular onsite inspections to monitor gear contact and spray system patterns, tooth flank temperatures and vibrations. This provides operators with peace of mind that their gear and pinion are in good condition. In addition, during annual shutdown, the wear speed on the gear flanks can be measured to gauge the lower wear rates leading to an extended gear life resulting from advanced lubrication technologies. An alternative to frequent on-site inspections is continuous remote condition monitoring of the girth gear that Klüber Lubrication offers in exclusive partnership with DALOG, a leader in remote condition monitoring solutions for the cement industry. This joint solution allows operators to define limits for performance indicators such as tooth flank temperatures and vibrations. When indicators reach a
defined limit, operators and, if desired, their Klüber Lubrication service engineer are notified to inspect the equipment manually and take corrective actions. This is not only helpful during the changeover process from one lubricant to another but also when optimising lubricant consumption levels, or for detecting lubrication starvation in case of a spray system failure.
Summary Asphaltics and black greases have served operators well for decades. Advanced open gear lubrication technologies offer operators the possibility of improving equipment reliability whilst significantly extending its lifetime, thus maximising asset utilisation. This allows operations and maintenance to a enter a more reliable and cost-efficient state. Operators do not need to accomplish such a transformation all by themselves. A strong lubrication partner can support them with regular on site presence for inspections, lubricant optimisation, staff training and implementation of digital condition monitoring solutions.
About the author
Figure 3. Specific mass loss (mg/kWh) as tested in FZG scuffing Test A/2.8/50’ – The lower the value, the better.
Markus Burbach is the Global Head of Cement at Klüber Lubrication. Prior to this role, he worked as Head of Marketing & Business Development North America for Klüber Lubrication in the United States where he was responsible for Marketing, Application Engineering, Technical Services and Product Management for the Klüber Lubrication and Summit brands.
Figure 4. Comparison of base oil viscosity of different lubricant technologies at different temperatures. 44
World Cement October 2021
GETTING THE LIGHT Nathan Schindler, Evonik Corporation, shows how plant operators can clean up cement plant filter performance through the use of an instant baghouse check-up system.
I
ndustrial demand for cement in the United States has increased steadily over the past decade as construction and infrastructure needs continue to grow. As reported by The Boston Globe, the United States may have insufficient cement capacity to meet the projected needs associated with the government’s proposed US$2.2 trillion infrastructure plan.1 Further, the National Association of Home Builders has called for lower tariffs on key building materials and higher levels of cement imports to meet higher demand.
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These factors put pressure on US cement plants to operate at capacity, minimise unplanned outages, and reduce operating and maintenance costs. These pressures are further enhanced by the Cement MACT regulations, which have mandated a ten-fold reduction in dust emissions. The US EPA has recently announced that it may further reduce particulate emission limits.2 Key to reducing dust emissions in modern cement plants is the application of multiple filter units, typically pulse-jet baghouse filters (Figure 1).
In addition to their role in efficient dust collection, these filters can also contribute to a reduced total cost of ownership. Central to the plant is the kiln/raw mill filter (#7), where dust from the main kiln exit and raw mill are processed. Clinker cannot be produced if the filter is not operating, and if the filter is operating poorly, it can significantly impact the efficiency of the plant. Other critical filters in cement plants include the clinker cooler (#18), cement mill (#26), coal mill (#16), and alkali bypass (#11).
Online decision support tool
Table 1. Filt-O-Meter assessment and input fields. Application: Cement Grinding Baghouse Assessment
Choices
Assessment
Choices
Maximum operating temperature
<300˚F
Current pressure drop
>10 in. WC
Current baghouse filter media
Polyester
During normal operation, how does the baghouse affect production goals?
Reduced cement output
Number of bags in baghouse
<500
Impact of baghouse shutdown on plant production goals
Plant cement production goals are impacted
Baghouse type
Pulse Jet
Pulse frequency per bag
Constant
Current air-to-cloth ratio
>4:1
Frequency of shutdown for corrective action
Quarterly
Typical bag life
<1 year
Analytical tools can be used to assess a plant’s filtration performance and help identify efficiency improvement opportunities. Filt-O-Meter is a complimentary online instant baghouse check-up tool. Developed by Evonik, this tool assesses baghouse filters to help cement plants avoid various cost impacts:3 1) Production reliability: As production demand increases, the process filter can become a bottleneck, limiting production capacity largely due to unplanned outages.
Figure 1. Common cement plant filters. Image courtesy of Intensiv-Filter Himenviro Technologies GmbH.4 46
World Cement October 2021
Shutdown of a 125 tph kiln over a four-day multiple-choice questions capturing readily period, for example, would result in production available system information. losses of 12 000 t. At US$115/t of clinker, this The input from the multiple-choice responses represents a revenue loss of US$1.4 million. is used by the tool to identify areas that may or 2) Operating costs: Poor filter performance may not need attention: can result in increased electrical costs due f Areas warranting immediate attention are to high pressure drop and frequent pulsing. signalled in red. This affects both fan hp and compressed f Areas needing consideration are signalled air consumption. In many cases, the cost of in yellow. increased pressure drop can be significantly f Areas not in need of attention are signalled more expensive than the cost of filter bags. in green. 3) Maintenance costs: Shortened bag life results in increased bag replacement costs Clinker grinding case study and higher labour costs for installation and As a case assessment, Filt-O-Meter was corrective actions. Moreover, maintenance applied to a cement finish mill filter on a staff required for bag changes are taken away ball mill clinker grinding line (Table 1). This from other necessary projects around the particular filter, containing 480 polyester plant. fibre filter bags and operating at 185˚F, was 4) Energy use: Filters not performing at evaluated after the plant decided to increase highest efficiency can also result in excess its production capacity, resulting in an increase energy use, which translates into higher in air-to-cloth ratio to 4.2 ft/sec. This capacity plant operating costs. For example, for Table 2. Filt-O-Meter output screens. a 125 tph kiln, an increase in pressure Status Maintenance Reliability Operating Energy use drop of 4 in. W.C. over You should five years would increase You should take You should take take immediate You should take energy use by about immediate action immediate action action to immediate action 5000 MWh. to reduce your to meet your reduce fan and to reduce your Assessment tools such labour and filter targets. compressor energy use. as Filt-O-Meter provide bag costs. electricity costs. an overview assessment of reliability, operating costs, maintenance costs and energy use. Each of the five major filter applications noted above – kiln/raw mill, clinker cooler, cement mill, coal mill, and alkali bypass – can be assessed using this tool. The user provides Figure 2. Original cement mill baghouse filter media (left image) and input via responses to upgraded media with P84 Cap (right image). Table 3. Cement mill filter performance for original and upgraded filter media. Performance of original PES filter media
PES filter media with P84 cap
Felt weight
18 oz.yd2 (osy)
18 oz.yd2
Clean air permeability
10 cfm
10 cfm
Operating time
7 months
48 months
Air permeability (as received)
1.5 cfm
2.1 cfm
Air permeability (cleaned)
2.1 cfm
3.8 cfm
Dust permeation
22 osy with corresponding increasing of pressure drop & pulse cycles
8 osy with low and consistent pressure drop and low pulsing frequency throughout life
October 2021 World Cement
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increase came at the expense of higher pressure drop and increased dust emissions. Most notably, the filter bag life dropped from 18 to 7 months. Applying Filt-O-Meter to this case yielded red signals in all four output areas (Table 2). The plant decided to upgrade the baghouse filter media to increase bag life and reduce operating costs. As shown in Figure 2 (left image), the original construction of the filter media was 100% polyester (PES). The filtration surface had already been upgraded by incorporating a fine fibre polyester. The felt media also incorporates a polyester scrim and standard polyester on the clean side. Upgrading the filter bag construction to incorporate a P84® cap overlying the PES fine fibre, as shown in Figure 2 (right image), provides a highly retentive asymmetric construction with the same felt weight (18 osy) and air permeability (10 cfm). At the end of bag life, however, distinct differences between the two felt media can be observed (Table 3). The original polyester bags are at the end of their life after only
seven months, while the filter bags with the P84 cap upgrade are operating like new after 48 months, nearly seven times longer. With the original bags, dust has permeated throughout the felt, increasing pressure drop and pulse cycles. On the other hand, the P84 capped bags still exhibit reasonable permeability, good recovery, and minimal dust incorporation. Figure 3 shows the return on investment by incorporating the upgraded filter bags, with the total cost of ownership reduced by more than 50%, from US$270/bag to US$115/bag. After upgrading the filter media with the P84 cap, re-running the Filt-O-Meter tool provides the results shown in Table 4.
Conclusion In today’s demanding market, cement manufacturers will benefit by continuing to identify and act on opportunities to increase production while reducing dust emissions and costs. Filt-O-Meter provides cement plant operators with a concise, easy-to-use tool to effectively identify and prioritise areas in the plant that can help reduce baghouse filter cost of ownership.
References
Figure 3. 4 Year ROI of P84®+Polyester filter bags. Table 4. Filt-O-Meter output screen for upgraded cement mill filter. Status
Maintenance
Good news! Your labour and filter bag costs meet industry expectations.
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Reliability
Operating
Energy Use
Good job. You are meeting your production targets.
Great job! Your fan and compressor electricity costs meet industry expectations.
Congratulations! Your energy use is low.
1. ‘US May Lack Cement Capacity for Government’s Proposed US$2.2 trillion Infrastructure Plan’, Global Cement, June 2021. 2. ‘EPA to Reexamine Health Standards for Harmful Soot that Previous Administration Left Unchanged,’ June 10, 2021, https://www. epa.gov/newsreleases/ epa-reexamine-healthstandards-harmful-sootprevious-administrationleft-unchanged, accessed 02/09/2021. 3. For additional details and considerations for baghouse cost of ownership, see ‘Uncovering the True Cost,’ World Cement, May 2020. 4. For more information and associated details, please visit: https://www. intensiv-filter.com/en/ geschaeftsfelder/zementkalk-gips/ World Cement October 2021
BOOSTING OUTPUT WITH BETTER BAGS Brad Currell, SOLAFT, provides a case study showing how innovative filter bag design and customised solutions can improve cement plant operational efficiency and reduce maintenance costs.
B
eing innovative is a core value for SOLAFT. The goal behind innovation is to bring results and achieve customer filtration targets in new ways. The company has laboratories in the group dedicated to R&D, alongside pilot-scale equipment installed in its Australian operations and CFD modelling tools under development to assist customers. The company’s team consists of mechanical, textile, material and chemical engineers tasked with developing solutions, from the choice of raw material all the way to how the customer can optimise operation of the equipment and achieve the maximum production whilst focusing on achieving the lowest emission levels possible.
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This innovation is demonstrated through the way problems are approached and through the tangible items offered to customers, such as: f Using new polymers – to meet newer and harsher operating conditions.
f Developing new fabrics – to meet stricter particulate matter emissions levels. f Designing products to suit applications – allowing smarter designs and saving installation time. f Applying product solutions in innovative ways. f Designing new products – allowing more production and savings.
Refining a design When it comes to designing products, SOLAFT is pleased with the results it continues to achieve with StarBag™. This product was first developed in 1994 and has undergone continual design improvements ever since. With a design that significantly increases cloth area, it helps to reduce differential pressure across the baghouse, increasing production, reducing emissions, saving energy (compressed air and fan) and increasing filter bag life. In addition to increasing the filtration area, The StarBag™ design allows for total bag length StarBag’s design also allows for total bag length to be reduced and for the drop out zone to be to be reduced and for the drop out zone to be increased, allowing less dust to be deposited increased, allowing less dust to be deposited on on the surface of the bags and directly reducing the surface of the bags and directly reducing the the pressure drop of the equipment. pressure drop of the equipment. This is also a good solution for bag houses Table 1. System information. that have known recurrent abrasion zones at the bottom of the bags due Parameters System information to high turbulence of gases and solids Fuel mill production target (tph) 16 carry-over from the hopper bag to the bags. Pre StarBag production levels (tph) 13 Deficit in production (tph)
3
Fuel
coal/pet-coke
Material moisture
20% 3
Plant design volumetric flow (Am /h @ 70˚C/158˚F)
49 800
Plant actual volumetric flow (Am3/h @ 70˚C/158˚F)
35 000
Pressure drop (mmwc)
260
Dust load (g/m3)
161
Filters
2
Previous bag material
100% PAN + PTFE Membrane
Previous bag dimensions
Ø 127 x 3540
Bags installed per filter
336 2
2
Total useful filtration area per filter (m | ft ) Calculated air-to-cloth ratio (m3/m2.min | ft3/min) Can velocity (m/s | ft/s) System cleaning pressure (bar) Current bag life 50
453 | 4876 1.83 | 6 1.74 | 5.71 6 3 months
Case study: increased pet coke and coal production in a cement plant SOLAFT was approached by a large cement manufacturer in the Americas to propose a solution to their coal and coke mill baghouses. The system was operating below its nominal capacity with an over pressurised mill limiting site production. The details are outlined in Table 1. As detailed, conditions were far from the nominal system design parameters and production was almost 20% lower than the required target. Extremely high differential pressure in the system reduced the nominal flow from a target of 49 800 to 35 000 cm3/hr. The bags were being over-cleaned to try to overcome this problem without any success which, in turn, lead to a domino effect on the bag life; resulting in an operational life span of only three months. This put significant pressure on the customer’s OPEX budgets. The SOLAFT team evaluated the system, World Cement October 2021
bag houses and full process details in order to propose a solution. The solution It is known that the total filter pressure drop is highly affected by the cake accumulated pressure drop, hence, after careful consideration, the team selected StarBags™ that would allow a 100% area gain to the customer, effectively doubling the filtration area in the equipment, bringing the air-to-cloth ratio down. Table 2 provides a before and after comparison. Laboratory results of the StarBags after six months of service showed that the bags were tracking well. Results The customer was pleased with the results and with the solution that was proposed and implemented in 2018, which has increased reliability from plant usage across the last 3.5 years. The customer initially invested in the StarBag
and StarCage™, and based solely on the bag changing frequency, (materials and labour) the ROI was fast. This solution has also allowed more flexibility for the customer, given that since the start of the project a different mix in fuel (lower calorific value) was used to reduce costs, increasing further the dust load to the filter, without major impacts on overall results. Improvements seen to date are as follows: f Achieved and exceeded production target values: 16.5 tph versus 13 tph before. f Increased filter life to 22 months from the previous three months.
Bottom (left) and side (centre) views of filter with StarBags™. Inner view of StarCage™ & StarBag™ (right).
ENGINEERED DUST COLLECTOR SOLUTIONS FOR CEMENT NFM has solutions that will maximize performance and lower operational costs, from Dust Collector Bags and accessories to complete changeouts and renovations. • Pulse Jet Bags & Cages • StarBags™ • Reverse Air Bags & Accessories • Used Filter Analysis • Pulse Valves & Replacement Parts • On Site Service Work • Bag Change Outs • Inspections Contact us today to schedule a visit from one of our technical experts. 1-866-530-9987, USA Toll-Free or 1-540-773-4780, Direct ĔŷľƳʸſœžʙȃŷƽľƬʀıƉž ǞǞǞʀſœžʙȃŷƽľƬʀıƉž
Table 2. Before and after comparison. Parameters
Before
After
Ø 127 x 3540
Ø 120 x 3500
Bag area (m² | ft )
1.35
2.69
Bag quantity per filter
336
336
Total useful filtration area per filter (m2 | ft2)
453
904
-
100%
49 800
49 800
1.83
0.91
1.74 | 5.71
1.74 | 5.71
60 to 80
60 to 80
End of life pressure drop (mmwc)
260
220 – 230
12 months pressure drop (mmwc)
–
180 – 190
5 sec.
9 sec.
6
4.8 to 6
3 months
22 months
13
16.5
Bag dimensions 2
Increase in filtration area Actual volumetric flow (Am3/h @ 70˚C / 158˚F) Calculated air to cloth ratio (m3/m2.min | ft3/min) Can velocity (m/s) Start-up pressure drop (mmwc)
Cleaning frequency System cleaning pressure (bar) Useful life Total production (tph)
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f Reduced cleaning frequency from one pulse at every 5 seconds to one pulse at every 9 seconds. f Reduced amount of interventions and spot changes to equipment. f Plant is running without unplanned stops. f Selected filter media that is a blend of Polyester and Homopolymer Acrylic, which has a reduced cost per square meter of media as compared to the previous 100% Homopolymer Acrylic. A further improvement to be seen in equipment with variable speed drives installed on the fans is the possibility of energy savings from fan current, due to a reduced total static pressure caused by a reduction in the pressure drop in the bag house.
About the author Brad Currell has more than 30 years in industrial filtration, from OEM design through to textile filter media. Brad’s field service and laboratory expertise with the StarBag design spans two decades.
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Ingenious solutions
TO DIFFICULT PROBLEMS Eduardo Sauto, GORCO, reviews dedusting solutions for two common sources of diffuse dust emissions in cement plants.
I
n cement plants, there are sometimes problems with dust emissions that seem unfeasible or at least very complicated and costly to solve. However, through the development of dedusting engineering, simple and, above all, effective solutions to these problems have been developed. This article will discuss two common sources of diffuse dust emissions in factories – points that are not usually dedusted (and when they are, this is not usually done effectively). The first of these problem areas is the galleries for extracting material from silos. These are usually located
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underground, have a horizontal layout and have little space available. The second problem area is the dumping of trucks or shovels into open hoppers. These are points of discontinuous operation, but produce very high dust emissions when in use.
Galleries The correct dedusting of the different material transport elements is essential for the proper functioning of the plant. In addition to preventing contamination and maintaining a healthy environment, it also allows for easy access and for periodic maintenance work to be carried out safely.
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There are areas where dedusting is particularly important, such as enclosed areas, galleries, etc., where if the dust source is not well attended to, the atmosphere becomes unbreathable and piles of dust and material end up forming that can restrict access. Typical examples of these cases are the belt galleries under the clinker silos. These long galleries are low in height and are encased between concrete walls and ceilings.
Typical layout for fluidised ducts in a silo gallery.
Truck unloading without dust emission. 56
The standard approach to the dedusting of these galleries is both difficult and of very limited use. There are two options: f Dedusting with insertable dust collectors in the belt of discharge, one filter after each silo outlet. f Dedusting with a bag filter outside of the gallery and dedusting ducts from each point inside the gallery. The first case has the problem of space; normally the galleries with a height of just over 2 m and a belt that is more than 1 m above the ground leave very little space – almost nothing to place a bunker filter on it (even if it has sleeves in a horizontal position), with the added problem of its poorer efficiency. The second case has a seemingly unsolvable operating problem, as the suction pipes have to be horizontal and usually very long, so that clogging is constant. These clogs lead to a lack of suction and back to an unbreathable atmosphere inside. This environment means that nobody comes in to conduct maintenance and clean the ducts. As a result, the installation soon returns to the same conditions as before. This situation is common in many plants, where these galleries become a source of dust emissions, which not only makes transit and maintenance of the interior equipment impossible, but also the doors or exits to the outside produce a dust emission effect, generating dirt all around. However, there is an alternative that GORCO has developed to limit and reduce these effects, and that is through the special design of fluidised ducts. Since the layout must be horizontal, or with a minimal inclination, central pipes are designed that run through the gallery in such a way that each suction point is connected to the main collector, which is fluidised. In terms of construction, it is like an airslide, with a lower section through which air is injected and a physical separation between the air chamber and the chamber through which the captured dust flows. It is very important to consider the air that must be injected to fluidise the duct for the resulting internal velocities, so it will be of increasing cross-section as it increases in length. In round silos, with belts crossing the silo completely, it is technically better to distribute the aspirations in two parts, with radial fluidised pipes so that the length of the main collector is the radius of the silo. World Cement October 2021
This avoids going to large sections in the final part, which can complicate the implementation in the gallery. This solution with fluidised pipes requires significant engineering work, and the construction of the pipes themselves is more costly and complicated than conventional ones. However, once installed they do not become a dust plug or a useless installation, but allow the gallery to be dedusted, making it passable and suitable for daily general maintenance work.
Open hoppers Receiving hoppers are sources of high leves of dust emissions. They can receive the material from a loader shovel or directly from an open truck, and the material received is varied, from coal to clinker, including any type of additive, so the dust generated is constant and very voluminous. The classical solution for these hoppers is to place a suction hood on the hopper enclosure and to convey the dust sucked in to a filter which is placed close to the hopper. As large volumes of air are required, the installed filter is large and therefore costly for normal use, as these are not usually installations in continuous operation. In addition, when the filtered dust is classed as ATEX, as in the case of coal dust, the filter must already comply with the corresponding regulations and is considerably more expensive. However, there is a simple, more economical and, more importantly, technically better solution. This is to integrate the bag filter itself into the hopper enclosure. The hopper should be encapsulated at the top, closing the bottom and sides, so that the only opening is the front where it is loaded. This is the normal arrangement of any hopper, even if not yet dusted, to try to mitigate dust emission. With the new configuration, the filter is placed hanging from the top of the enclosure at the rear, making the bag plate of the filter the closing in that section. In this way, when a truck or shovel is unloaded, the hopper is depressed, sucking in the dust generated and returning clean, filtered air through the top of the head. The filtered dust falls gently into the hopper itself, so there is also no new external dust return point.
f More efficient collection compared to a traditional hood. f Dust is returned to the hopper itself, whereas with an external filter there is a valve that must return the dust to a big bag or, by means of a screw conveyor, to any place where the dust is disposed continuously. f No dirty air pipes are required, which is especially important when the filtered material is abrasive, such as clinker, so there are no wear elements subject to costly and expensive repairs. f In the case of explosive dusts, such as coal, this arrangement has only the special sleeves and cages, but constructively does not require more reinforced designs or explosion rupture discs, as the hopper is an open space at the front. f Lower investment as the filter uses the existing walls of the enclosure and does not require a separate housing or hopper.
Conclusion These examples confirm that no matter how difficult or seemingly unsolvable the problem, and if the economic aspect is not prioritised, with a little ingenuity almost any problem related to dust collection in a cement plant can be technically solved, or at least greatly improved.
About the author Eduardo Sauto, Industrial Engineer, has been working in the air pollution control sector since 2001 as a Sales and Technical Manager at GORCO S.A. His constant contact with clients and users across a range of sectors has allowed him to accumulate significant experience in solving dedusting problems.
Advantages The advantages of this arrangement over the traditional one are numerous, including: October 2021 World Cement
Coal hopper with integrated dust collector in the rear. 57
A breath of fresh air AIR POLLUTION CONTROL Q&A
58
World Cement spoke to experts in the air pollution control sector to gather their views on a range of topics facing the cement industry. Contributions come from: Evonik Corporation, RD42 Engineering, & W.L. Gore & Associates. 1) With increasingly stringent environmental regulations around the world, what are the main challenges facing cement plants in terms of air pollution control? RD42 Engineering Compared to 20 years ago, the pressure on the cement manufacturing sector from stakeholders demanding a green industry has greatly increased, which has been reflected in environmental regulations becoming more and more stringent. The use of alternative fuels has complicated the production process and has potentially increased the variety and quantity of pollutants. Control over raw materials, fuels and process is critical for limiting emissions. The methods for reducing single pollutants, once in the gas stream, are generally well known, but the process windows are often narrow, depending on several parameters, the knowledge of which is essential. Regarding dust, the extreme fineness and light density of the particles in potentially acidic conditions, represent a new problem to be foreseen, detected, faced and solved. Additionally, gas cleaning technology is rapidly evolving. Examples include new generations of felts and PTFE membranes for the bag filters and high voltage transformers for ESPs. As a result, the technical limits reachable for the emissions are now one, maybe even two, orders of magnitude lower than allowed by the regulations. The possibility of implementing these technologies on greenfield filters must be carefully evaluated, but it is sometimes also possible on equipment that is 20 years old. Another problem, apparently less urgent, that must be solved in the near future, is that of ‘fugitive emissions’, which could have an environmental impact that is potentially more significant than the process filters. Storages, conveyors, loaders and unloaders, and truck cleaning need new solutions, different from ride-on sweepers, and require the highest level of knowledge and experience. W.L. Gore & Associates The main challenge facing cement plants around the world relative to meeting stringent environmental pollution control regulations is internal organisational pressure to decrease cash flow expenditures.
The challenge is one that plays out daily between the production and maintenance teams at cement plants having one view, and the plant and corporate procurement teams on the other side having a very different view. Although there is a portfolio of pollutants that need to continuously and simultaneously be controlled, there are proven technologies from reliable suppliers to meet all the current environmental regulations while doing so reliably and repeatedly. In many cases, these technologies provide decreased maintenance solutions resulting in the lowest total cost of ownership of the air pollution control system. However, many internal cement group programmes encourage plants to purchase generic technologies from countries with low overall labour costs. Although these products from generic suppliers provide a low initial purchase price, despite any potential warrantees offered, they often lead to increased maintenance costs, logistics, inventory, payment terms, trade considerations, productivity losses and, at times, environmental notices of violation.
2) What are the key factors to consider when designing/installing baghouses and fabric filter systems? Evonik Corporation At Evonik, we frequently work with cement plants operating existing fabric filter units. Over the lifetime of a baghouse, plant operating conditions may change due to increased production, a switch to new and alternative fuels, reduced emission limits and/or the addition of environmental control systems. These changes can negatively impact baghouse cost of ownership. Increased pressure drop across the unit can increase fan energy costs, reduce bag life and increase corrective action. Ultimately, plants experience increased maintenance and labour costs, reduced reliability and a negative impact on production goals, as well as increased overall energy use. Capital expenditures required to increase the baghouse footprint to accommodate changed conditions are expensive and often technically unfeasible. Care should be taken in the design phase to accommodate reasonably likely changes to the plant over the life of the baghouse. However, not all plant changes can be anticipated at the time of construction.
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When conditions change outside the parameters of the baghouse design, a smarter filter media, such as bags made from Evonik’s P84® or P84 HT fibres, can provide relief to the critical air-to-cloth ratio and pressure drop with no need for significant capital expenditures. RD42 Engineering The parameters of the air-to-cloth ratio (gas flow divided by the filtering surface) and ‘Can Velocity’ (upward gas speed referred to the free plan area at the bottom of the bags) are still valid as rules of thumb, but their use has been greatly changed compared to the past. Today it is possible, through the use of CFD models, to give them a significance, instead of being purely average values. The limits of CFD models have also become clear in front of discontinuities, which are rarely modelled during the calculations, to supply fake results. Furthermore, many other factors must be considered, such as: f The water and acid dew points of the gas (RD42 uses a special design for the filter heads, to avoid the cold point inside). f The whole spectrum of granulometry of the dust, its density and the chemical components and their behaviour along the cooling of the gas upstream and inside the filter: the evolution of the processes has complicated the pre-separation phase, the hopper design and the selection of the right filter media, for which the PTFE membranes require very special care. f Protection against possible abrasion in the chutes, the hoppers, and the distribution shields. The conclusion is that there is less and less room for improvisation and inexperienced newcomers. This requires a campaign by the procurement departments of clients against the common idea that the filters are commodities, for which the price is often the only driver, after a light qualification phase. W.L. Gore & Associates Since baghouses are designed for 30 years or more, there should be several aspects of the design that are conservative enough to allow for future plant performance increases. Although baghouse designers often allow for a conservative air-to-cloth ratio, certain suppliers are too aggressive when it comes to lift/can velocity as well as the inlet velocity. As plants perform productivity projects which increase airflow to the baghouse, the lift/can velocity and the inlet velocity quickly elevate to levels which can create performance and maintenance issues. High lift/can velocity leads dust to re-entrain directly back onto the filter bags regardless of how effective the filters are at releasing dust. High inlet velocity levels create excessive ongoing maintenance as well as environmental performance issues due to frequent bag failures. Original equipment manufacturers 60
often supply a starter set of filters which provide a minimally acceptable level of performance. Plants seeking to achieve the lowest total cost of ownership are left to their own initiative to seek out higher performance filters in order to obtain the most optimal performance balancing high airflow, low differential pressure and reliably long filter life with low maintenance.
3) What can be done to ensure the maximum efficiency of electrostatic precipitators (ESPs) in cement plants? RD42 Engineering This question is interesting if applied to existing units. As for new units, the qualified suppliers should propose solutions aligned with current state-of-the-art systems. Keeping an existing ESP at full efficiency or resurrecting them to new life requires a few progressive phases, none of which can be bypassed: f Process analysis: gas flow, chemical components, temperature, humidity, has something changed compared to the original design? If so, the compatibility with the existing equipment must be verified. f Gas distribution: is a dedicated system present in our filter, including the upstream ductwork? f Electrostatic design and components: are the existing electrodes, their pitch, the HV units, the insulators in shape and conformity with the most recent technologies? How is an old design affecting the performance of the ESP and what are possible improvements? f Thermal insulation, pre-heating, pressurisation, steel casing and structures: check the status and the design, the details and possible cold points. f Rapping system: after an analysis of the electrical parameters and visual inspection of the mechanical conditions, check if the present system is adequate or not and, eventually, improve, with new calibration, new sequences or replace. A common mistake to be avoided, is that the above phases can be implemented by mechanical or electrical contractors without a experienced general contractor or consultant involved. Afterwards, the keywords during the lifetime of the single units are: continuous and rigorous maintenance, investigation and solution of all anomalies without delay. In case of corrosion or anomaly, try to eliminate the problem promptly, from the very beginning. RD42 is proposing a system based on Wi-Fi-enabled cameras to be placed inside the ESP, with the high voltage in operation, as a support to detect if any problems with sparks may arise. World Cement October 2021
4) What factors should cement manufacturers consider when choosing between an SCR or SNCR system? Evonik Corporation SCR and SNCR control technologies are well known methods of reducing NOx emissions from combustion sources. They each have pros and cons. If a plant is considering options to reduce emissions, it is almost always least expensive to reduce the NOx emissions generated by upgrading the burner. When these techniques do not meet the requirements, SCR and SNCR can be considered. In cement plants, SNCR has been broadly adopted. The calciner/preheater typically provides a suitable residence time for the SNCR reactions to occur. Kiln operation is relatively consistent, so sharp changes that would cause increased NOx or worse, ammonia slip, are generally accommodated. The capital costs of installation are relatively modest in that only an ammonia injection system is required. However, SNCR is limited in its ability to reduce NOx, generally to around 50%. SCR on the other hand has been proven to reduce NOx emissions in some applications, like gas turbines, by over 99%. This significant reduction improvement comes at a high capital cost of footprint and material for the catalysed elements. For cement kilns, incorporating SCR at an existing facility is a major challenge. The high dust loading coats the ceramic elements, reducing their effectiveness, source materials can produce unwanted molecules that poison the catalyst inhibiting their activity, and reheating the flue gas is often required to effectively reduce NOx further increasing the footprint requirements, operating costs, and complexity. W.L. Gore & Associates When choosing between catalytic DeNOx solutions (such as SCRs or catalytic filter bags) and non-catalytic DeNOx solutions (such as SNCR), a primary consideration must be the total level of NOx reduction required, both now and in the future. SNCRs are a lower capital cost option but are limited in the amount of NOx reduction that can be achieved. By contrast, SCRs and catalytic filter elements are capable of significantly higher NOx removal. SNCRs can be used in combination with downstream catalytic solutions, so an investment in an SNCR solution as a short-term option may still be valuable once tighter regulations drive the need for a catalytic solution. Another consideration is ammonia consumption and ammonia slip. Catalytic systems, especially high-performance catalytic filter bags such as GORE® DeNOx Catalytic Filter Bags are capable
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Finally: a 100% waterproof packaging }ìĊāĮ Ĵď ĴìÐ AROVAC® technology řďķ ÆĊ ďĨĴ åďī ÅæĮ ĴìĴ īÐ Ǡǟǟɦ œĴÐīĨīďďå ĊÌ ÆďĉĨăÐĴÐăř ĮÐăÐÌȘ }ìðĮ ďååÐīĮ řďķ maximum protection ĊÌ carefree transportation ďå řďķī ĨīďÌķÆĴș ÐŒÐĊ œìÐĊ ĮĴďīÐÌ ďķĴĮðÌÐ åďī ăďĊæÐī ĨÐīðďÌĮȘ
of achieving the lowest ammonia consumption for a given NOx reduction as well as achieving the lowest overall ammonia slip.
5) What technologies are available for plants looking to limit their emissions of mercury and/or heavy metals? Evonik Corporation Technology for reducing mercury has been adopted in cement plants across the US. There are three basic methods that can be applied: 1) changing fuel to reduce the mercury available, 2) injecting activated carbon, and 3) adopting bromination techniques to enhance the efficiency of mercury capture. All three of these options can be expensive. Low mercury fuels are generally less expensive but may not provide the heating value needed for clinker production without significant controls and modifications. Activated carbon is expensive to inject without the prior adoption of smart media to allow a longer residence time of the sorbent without a significant increase of pressure drop. Operating activated carbon injection with standard filter media would result in increased dust load on the bags, reduced bag life and increased pressure drop. Bromination can negatively impact fibres, such as PPS used in filter bags and, if not applied correctly, can negatively impact cement product quality. The baghouse serves a critical role in the operation of sorbents, such as activated carbon. At Evonik, we have studied how filter media design and selection reduce mercury emissions. As anticipated by our team, a longer duration between pulses and a permanent dust cake layer incorporating carbon can significantly reduce mercury emissions. Trials with specially constructed P84 filter media in power plants have shown a substantial reduction in mercury, without any additional controls required. Evonik is currently seeking a cement plant partner to conduct trials and demonstrate the cost-effectiveness of a smarter filter media. W.L. Gore & Associates Most heavy metals have very low vapour pressure at baghouse temperatures and therefore exist primarily as particulate matter. In those cases, a membrane-based filter bag designed for high particulate capture while maintaining low pressure drop such as GORE LOW DRAG Filter Bags are well suited. Mercury is a heavy metal with a particularly high vapour pressure meaning it exists primarily in the gas phase in a cement process. As a result, different techniques are required to reduce mercury emissions. One class of technologies involves binding or reacting mercury with a solid powdered sorbent (CKD, activated carbon) and then removing that mercury-containing dust from the process, or dust shuttling it to the finish mill. As another option, Gore has developed a low 62
pressure drop mercury filter that continuously and selectively removes gas phase mercury without introducing any additional dust into the process. As a result, the GORE Mercury Control System has no impact on CKD or clinker quality.
6) Looking ahead – what innovations can we expect to see in the field of air pollution control? What role do you see for digital technologies? Evonik Corporation Air pollution control systems continue to improve, both in cost-effectiveness and efficiency. Modern technologies employed in the United States have had a major impact on the quality of the air we breathe and life-expectancy. Innovations in cement plants that Evonik is exploring include improvements to the efficient use of alternative fuels, further reductions in NOx emissions, and cost-effective measures for carbon dioxide capture. Alternative fuels are increasingly being adopted in European cement plants and the trend will likely increase in the United States. Dealing with lower heating value fuels creates challenges for product quality due to lower combustion temperatures in the baghouse. Incorporating catalyst elements for NOx reduction into filter media in the baghouse has long been known in the emissions control industry. Producing the right combination for a durable product with limited capital expenditure is a challenge we have taken on. Carbon capture is increasingly in the news and becoming part of the anticipated regulatory scheme for cement plants around the world. Evonik is exploring ways to adopt its gas separation technologies to reduce the carbon footprint of the cement industry. RD42 Engineering The possibility for innovation in air pollution control is first based on the capacity of the suppliers to capitalise on the experiences of the past while looking at the technical evolution of both components and processes. RD42 believes that the general tendency of considering gas cleaning as a bundle of mature technologies, approaching it with the attitude of ‘cut and paste’ from the last project, is deeply wrong. Progress in critical components such as filtering bags, HV transformers/rectifiers, catalysts, etc., are continuous, so that the possibility of a ‘zero emission’ stack seems to be just around the corner. The challenge for suppliers is to be able to dominate these technologies in a proper way, always considering the price. Efficiency and reliability of the systems and reduction of the operating cost are fields in which digital technologies are rapidly evolving: f For cleaning of the bag filters: a new generation of pulse jet systems, operated on demand, on World Cement October 2021
a variable frequency mode can have a role for reducing air consumption, increasing the lifetime of the bags, and at the same time increasing the stability of the system. The extensive use of ‘on/off Delta p mode’ will be likely consigned to the past. f For ESPs: high frequency T/R and controllers allow higher levels of energisation of the systems, limiting the spark and arc conditions.
About the authors
The possibility for operators to control the units remotely is already profitably used for monitoring the process units: progress in communications both inside and outside the factories will allow for supervision of all the units, also spread in the most remote location of the plant, for immediate alert in case of failure and optimisation of the consumption. In this period of limited mobility, supervision services based on augmented reality devices have been experimented with mainly for the purposes of construction: we foresee that their future adoption will be extended to activities like maintenance and diagnosis, resulting in prompt and proper interventions. This will entail a deep improvement in the environmental reliability of the units and their operating costs.
RD42 Engineering Giorgio Radaelli, is founder and CEO of RD42 Engineering, formerly in the management of Redecam group. Giorgio has worked as a consultant and process integrator for major international customers in multiple technical domains. He is strongly committed to client satisfaction, innovation for the environment and fair business.
Evonik Corporation Nathan Schindler, JD, B.S. is a Technical Sales Manager, Evonik Corporation. He has more than 20 years of experience in air pollution control technologies and regulatory requirements. He currently manages Evonik’s P84 Fiber business in North America, assisting end users reduce the cost of ownership for baghouses.
W.L. Gore & Associates Chris Polizzi is a Chemical Engineer and started with Gore in 1994. He has worked in the cement air pollution control industry for 27 years. As an application engineer, in addition to implementing baghouse solutions, he has written many technical papers/articles which have been presented at conferences and published in global publications.
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