Carbon Capture Seems Likely to Play an Important Role in Combatting Climate Change. Here Is a Look Into Ongoing Research and Development Within the European Cement Industry Into This Sometimes-Controversial Technology.
By Jonathan Rowland
|Norcem Brevik cement plant, Norway, part of HeidelbergCement Group.|
|CEMCAP chilled ammonia process (CAP).|
|CEMCAP post-combustion calcium looping (CaL) process.|
|CEMCAP membrane-assisted CO2 liquefaction (MAL) process.|
|IKN oxyfuel clinker cooler.|
|Summary of different capture technologies investigated by CEMCAP project.|
|The LafargeHolcim Retznai plant, along with the Italcementi Colleferro plant, is hosting the ECRA oxyfuel demonstration project.|
|ECRA oxyfuel technology.|
|CALIX Direct Separation process for indirect calcination of limestone.|
Europe has been a center for carbon capture and storage (CCS) and carbon capture and utilization (CCU) research for some time now. This activity has been accelerating in the past few years with several projects either recently completed or currently underway, including one – at Norcem’s Brevik plant in Norway – on the cusp of building a full commercial-scale application.
The Carbon Challenge
Driving the research is the industry’s commitment to reduce the carbon intensity of its product as measured on a net specific emissions per tonne of cementitious material basis. The European industry has already had success in this through more conventional techniques, such as the use of alternative fuels and improving energy efficiency. Norcem parent company, HeidelbergCement, for example, has set a target of reducing its net specific emissions per tonne of cementitious material by 30% compared to 1990 levels by 2030, using conventional means.
HeidelbergCement is not alone: one of the key platforms of the Global Cement and Concrete Association (GCCA) – which includes many of the world’s leading cement producers as members and has now taken over the functions of the WBCSD Cement Sustainability Initiative – is a target-driven commitment to reduce the industry’s contribution to climate change.
More is required, however, if the industry is to meet the ambitious goals set by the Paris Agreement. The cement industry is particularly challenged by such targets because carbon is generated by both the energy used in the process and the calcination process itself. Even if energy-based emissions could be eliminated by switching to carbon-neutral fuels, these process emissions will remain and will need to be captured.
“We know in the cement industry that our emissions are not reduced that easily,” Rob van der Meer, director of public affairs at HeidelbergCement, told Cement Americas. “The process emissions cannot be reduced by optimization and fuel switching. When you look at the scenarios being developed by the International Energy Agency (IEA) or the Intergovernmental Panel on Climate Change (ICCC) it is obvious that, to limit warming to 2°C or even 1.5°C, we need CCS/CCU.”
Developing the Solutions
Calling for CCS/CCU to be used in the cement industry might be easy; its development is far from it. In Europe alone, there are a range of projects, developing various technologies, and all may ultimately be needed, as the unique local circumstances of each cement plant prohibit the use of a one-size-fits-all solution. Moreover, the technologies that can be retrofitted to older plants will likely be different to the technologies used on new builds.
Broadly speaking, the technologies under development can be divided into three types: post-combustion capture, oxyfuel combustion, and indirect calcination. Post-combustion capture technologies can again be divided into absorption technologies, calcium looping, and algae-based systems.
The project at Norcem’s Brevik cement plant, part of a larger project supported by the Norwegian government, has been a leader in post-combustion capture research in Europe. Starting in 2013 in cooperation with the European Cement Research Academy (ECRA), initial investigations saw four post-combustion technologies tested at a small-scale test center at the plant to determine their suitability for implementation on a modern cement kiln.
Based on the result of this study, a feasibility study into an aqueous amine-based absorption technology from Aker Solutions was carried with results published in May 2015. Amine-based absorption is the most advanced carbon capture technology and has already been implemented at commercial scale at the Boundary Dam coal-fired power plant in Saskatchewan, Canada.
Since then, Norcem has received Norwegian government support to study implementation of a full-scale CCS project, receiving funding for the final FEED study in 2018. The FEED study will provide the basis for an investment decision. If successful in securing funds, construction will enter a three-year construction phase and could be operational in 2024. In the first instance, the plant is targeting capture of 400,000 metric tonnes of CO2 per year, about half of that produced at the plant. The final investment decision is expected this year.
“We have done a lot of work in Norway,” van der Meer said. “We started with many questions; most of these seem to have been answered. We have the technology selected and that technology is available now.”
Another major study, recently completed, was CEMCAP. Involving a consortium of cement producers (again including HeidelbergCement and Norcem, as well as another HeidelbergCement subsidiary, Italcementi), technology providers and research institutes, CEMCAP investigated four different carbon capture technologies, three of which were post combustion (the fourth, oxyfuel combustion, will be discussed later): the chilled ammonia process (CAP), calcium looping (CaL) and membrane-assisted CO2 liquefaction (MAL).1
- CAP is proprietary technology from GE Power. Similar to the technology used at Boundary Dam and that could be implemented at Brevik, it uses an ammonia-water solution for CO2 capture instead of an aqueous amine solution.
- In CaL, the CO2 is captured using calcium oxide (CaO) particles in a carbonator to make limestone (CaCO3). The limestone is then calcined to CaO and re-used. Two CaL technologies were investigated a part of the CEMCAP project: tail-end and entrained-flow (integrated).
- MAL comprises two steps: the first involves the bulk separation of CO2 from flue gases using CO2-selective polymeric membranes to create a gas stream of sufficiently high CO2 concentration to enable step two, the separation of liquid CO2 through compression and cooling.
A key element of CEMCAP was to compare and analyze the energy consumption of the various technologies against a reference amine-capture technology (MEA). The project concluded that, “all the technologies perform better in terms of primary energy consumption.” It was also found that the post-combustion technologies were easier to retrofit to existing plant than the “more integrated” technologies (oxyfuel and entrained-flow CaL), “Altogether, there is not one winning capture technology but all CEMCAP technologies have been identified as relevant options for […] cement plants.”3
The CLEANKER project has taken up where CEMCAP left off and is developing an on-site demonstration of entrained-flow CaL at Buzzi Unicem’s 1.3 million metric tonne per year Vernasca cement plant in Piacenza, Italy. The project is targeting CO2 capture efficiency of >90% and negative overall emissions through biomass co-firing, as well as limiting the increase in the cost of cement to <€25 per metric tonne. In addition to Buzzi Unicem, project partners also include Italcementi and German equipment supplier, IKN.
The final technology studied by CEMCAP was oxyfuel combustion, which see combustion take place in a CO2/O2 mix instead of air in the kiln. This results in a particularly high concentration of CO2 in the exhaust stream. As part of the project, a cement burner designed by thyssenkrupp was tested under oxyfuel conditions in a 500-kW rig at the University of Stuttgart, while the calcination reaction under oxyfuel conditions was also studied. In addition, the world’s first successful cooling of clinker under oxyfuel conditions was achieved at HeidelbergCement’s Hannover plant, Germany. The innovative cooler was designed and supplied by IKN.
“As the exhaust gases of oxyfuel combustion will have a high concentration of CO2, initial clinker cooling would have to take place in a CO2-rich atmosphere,” said HeidelbergCement’s van der Meer. “No one had done that before, so no one knew if it was possible. Can you cool the clinker from about 1400°C to about 400°C in a CO2-rich atmosphere without consequences for clinker quality? We tested it on a small prototype cooler and found that the clinker produced could be used as a cement intermediate material. So that means one of the challenges in oxyfuel cement production has been solved.”
Following CEMCAP’s oxyfuel research, ECRA launched a demonstration of the technology at two European cement plants: HeidelbergCement’s Colleferro plant in Italy and LafargeHolcim’s Retznei’s plant in Austria. “The technical feasibility of oxyfuel technology can only be proven in real-scale application, but we have sufficient information from our research to believe that we will obtain a positive result after the trials,” said Daniel Gauthier, ECRA chairman, at the launch of the project.
The final carbon capture technology is indirect calcination, which aims to enable the efficient capture of process emissions in both the lime and cement industries. Developed by CALIX, the technology is currently being tested by the LEILAC project, which is based at HeidelbergCement’s Lixhe cement plant in Belgium.
The CALIX technology, which it calls Direct Separation, changes the process flow of the traditional calciner, indirectly heating the limestone in a special steel vessel. This enables pure CO2 to be captured as it is released from the limestone during calcination, as kiln exhaust gases are kept separate. No additional chemicals or processes are required to capture the CO2 and there is minimal change to the overall process as the Direct Separator simply replaces the calciner.
In July, the LEILAC project announced that it had successfully demonstrated separation of CO2 with more than 95% purity during preliminary testing, albeit not at full design capacity due to issues during commissioning. Test runs are now expected to be run until the end of 2020 to smooth out any remaining longer-term issues, such as equipment health and the robustness of the process. At the same time, planning has started to scale-up the technology.
“While there are still challenges ahead to achieving full design capacity, we have achieved many breakthroughs in key areas of the technology,” said Calix Founder, Chief Scientist and Executive Director Mark Screats. “The carbon capture piece of our technology represents a unique approach to mitigating CO2 emissions from lime and cement manufacturing and has the potential to leapfrog other technologies in terms of both timing and cost.”
So You’ve Captured the Carbon … What Next?
Capturing the carbon is only the first step in solving the problem, however: what you do with it next is an equally valid challenge. The traditional solution has been to store it is appropriate geological formations – often old gas fields, where the carbon can also be used to enhance oil recovery. This is plan for the CO2 captured at Norcem, which will be loaded on ships and then pumped into the geology under the North Sea.
Geological storage can be controversial, however, and for all of its demonization in the press, CO2 is a useful chemical. To back this idea up, HeidelbergCement and others founded CO2 Value Europe to champion the use of captured CO2 in industrial processes.
“You can convert CO2 into many other products,” explained van der Meer. “You can use it to recarbonate concrete, for example. You can also use it to produce methanol or methane for synthetic fuels or in the production of light-weight aggregates that can be used in building materials. CO2 Value Europe aims to promote these technologies and the concept of CCU in Brussels.”
Progress – But on a Bumpy Road
Despite the progress made – and Europe’s reputation as a leader in environmental protection – selling carbon capture to European politicians and public can be an uphill task. Geological storage is particularly disliked. “There are several countries, such as Austria and Germany, where geological storage is banned or nearly impossible at the moment,” said HeidelbergCement’s van der Meer. “There is also opposition from several environmental NGOs. As a result, developments in recent years have been extremely challenging. The research has continued, but implementation has been a struggle.”
There are signs that this might be changing. “The German government has now clearly stated that CCS will be needed, and the concept of geological storage is no longer excluded in German policy,” van der Meer continued.
There also needs to be an increase in financial support for carbon capture innovation at the European level for these technologies to go from interesting side shows to something that changes the entire industry. “It’s not just funding of a single project that is needed,” concluded van der Meer. “You need to look at implementation through the whole industry. And for that, CCS and CCU innovation needs more funding to support their development in the next few, crucial years.”
Jonathan Rowland is the international editor for Cement Americas.
1. Knudsen, B.R., Jordal, K., Ruppertand, J. and Hoenig, V., “CO2 Capture”, World Cement (July 2018).
2. (For Table) Jordal, K., et al., “CEMCAP – making CO2 capture retrofittable to cement plants”, Energy Procedia 114.
3. Jordal, K., et al., “CEMCAP Strategic conclusions – progressing CO2 capture from cement towards demonstration”. Available at: https://zenodo.org/record/2593135#.XVWyFuhKjIV
Algae-Based Carbon Capture
Most discussions of carbon capture focus on the chemical-based technologies discussed in this article. These are not the only options, however, as HeidelbergCement is proving at a cement plant in North Africa.
“We are working on a CCU project in Morocco where the CO2 in the kiln exhaust gas is used to grow algae,” explained HeidelbergCement’s van der Meer. “The kiln gas is an ideal feed for them, containing just the right CO2 concentration and levels of other pollutants. All we do is cool it down slightly and then feed it to the algae, which are suspended in water. The only other food they need is sunlight, which is in plentiful supply in Morocco. It’s a very simple process in principle.”
The algae are then harvested, dried and supplier to the local fishing industry as fish food. “We have a one-hectare plant working in Morocco now and want to increase it to 400 hectares in the end.”