Around 60% of a cement plant’s CO2 emissions are from the calcination step. Received wisdom in the sector is that such emissions cannot be avoided and reduction of combustion CO2 through dry processing, alternative fuels, waste heat recovery or other advanced solutions has historically been preferred. However, the Direct Separation Reactor from Australian firm Calix, which will be used in the Low Emissions Intensity Lime and Cement (LEILAC) project, will tackle the issue of CO2 emissions from calcination head on. The technology has already been used commercially in the magnesite calcining industry. Peter Edwards spoke to key staff from Calix about the technology and its potential for the cement and lime sectors.
Global Cement (GC): Can you summarise the LEILAC project?
Daniel Rennie, Project Coordinator (DR): The Low Emissions Intensity Lime and Cement (LEILAC) project aims to pilot a breakthrough technology to replace an existing part of the cement and lime making process. The Direct Separation Reactor (DSR) from Calix will enable the capture of unavoidable process CO2 emissions from the calcination step, without significant energy penalty at comparable capital costs to conventional cement and lime production equipment.
The LEILAC project will develop and test a suitably-sized pilot plant to validate the Calix technology and facilitate scale up. It will run at 8t/hr for limestone and 10t/hr for cement. The project started in January 2016 and is due to run until the end of 2020. The Preliminary Front End Engineering Design (Pre-FEED) stage ensured that the project was technically viable and it is currently in the Front End Engineering Design (FEED) phase. This will result in a Final Investment Decision in mid-2017. Following from that, there will be a detailed design and construction phase. The pilot plant should become operational in early 2019. The pilot will be built within the HeidelbergCement plant at Lixhe, Belgium to ensure the most realistic testing environment possible.
GC: What are the objectives of the LEILAC plant?
DR: The pilot unit will run over two years, during which time it will undergo extensive testing in a standard operating environment over a continuous basis for several weeks at a time. The research on the process demands and performance, aims to demonstrate that the technology works sufficiently to begin scale-up planning in the cement sector or provide an immediate CO2 capture option for the lime industry.
GC: Who are the main collaborators and what does each of the major players bring to the table?
DR: The consortium is led by Calix, the Australian company behind the DSR technology itself, and comprises HeidelbergCement, Cemex, Tarmac and Lhoist as industrial partners that provide funding, guidance and technical input. We also have Amec Foster Wheeler on board as the consortium’s engineering and procurement partner, as well as ECN and Imperial College London, which are undertaking key research into the main areas of risk for the project, plus analysis of the results. Process Systems Enterprise (PSE) is carrying out the modelling and techno-economic analysis of the technology, Quantis is looking at Life Cycle Analysis and the Carbon Trust is responsible for public engagement. It is supported by Cembureau, ECRA, and EuLA which form the project’s External Advisory Board. The pilot project is funded by the consortium partners (Euro9m) and the European Commission (Euro11m).
GC: How does the Calix technology work to remove and separate the CO2?
Adam Vincent, Project Manager (AV): The Calix DSR seeks to re-engineer the existing process flows of a traditional cement calciner, by indirectly heating the raw meal via a special steel reactor. This unique system enables pure CO2 to be captured, with the combustion exhaust gases kept separate. This elegant solution requires no additional chemicals or processes for a pure CO2 stream. In principle, the cement manufacturing process is not significantly altered.
There are a variety of ways to separate the gas from the calcined meal to produce a clean CO2 stream. In LEILAC we are utilising an internal reversing axial separator, which has been proven to work effectively in our pilot plant in Australia. This approach has the additional benefit of increasing heat transfer between the CO2 gas and incoming cement meal or limestone, thereby increasing efficiency.
GC: What led to development of the DSR?
AV: The idea was co-invented by Connor Horely, sadly no longer with us, and Mark Sceats (Executive Director and Chief Scientist of Calix) for processing magnesite. Together they founded Calix. The process was successful, so Calix acquired a magnesite mine in South Australia and built the first commercial scale plant at Bacchus Marsh in Victoria. After some development they identified the magnesia (MgO) industry as a likely user. With external heating, the particle temperature is raised up to the calcination temperature gradually and uniformly. As a result, the magnesia produced by the system is highly reactive, with a very high surface area. The micron size particles were found to exhibit the same properties as nano-particles, and we call them ‘nano-active.’
In the early days, Calix actually had a fairly strong focus on the use of magnesium oxides for building products. These types of alternative magnesium-based cements were a popular approach to the problem of CO2 emissions from building materials at that time. It was thought that the products made would work well as a binder. However, we found the building products market to be very difficult to penetrate with new materials. This resulted in a rethink within the business and we subsequently turned our attention to other markets.
GC: Can you expand on Calix’s experience in the magnesite calcining industry?
AV: In 2005, the DSR idea was tested in a batch process. In 2009 a 250kg/hr pilot plant demonstrated that the process could work continuously and in 2012 a 5t/hr commercial reactor was built at Bacchus Marsh, Victoria, Australia. It is operated by Calix and has been online for the past four years.
The Bacchus Marsh plant generates extremely caustic MgO by lowering the temperature of the calcination process to avoid sintering. In fact its reactivity is up to 10 times higher than commercial caustic MgO, which has opened up new applications. Calix sells products to the waste water treatment, biogas enhancement and sewage sectors to prevent corrosion, as well as into aquaculture and agriculture. These are the markets developed from the Calix technology when applied to magnesite.
Later, it was demonstrated that the technology could be used to make lime from limestone in a very similar way. This led to the idea of using the DSR for cement production. Further limestone testing confirmed that the kinetics were sufficiently fast and that the DSR design could be used. However, cement and lime plants are larger than magnesia plants and the temperatures are also higher. These differences and several other differences necessitated a larger pilot plant, the LEILAC plant.
As well as CO2 savings, we anticipate that the DSR could lead to higher reactivity cement and lime products as seen in our magnesite experience. This may offer cement producers the ability to create new products at higher margins.
GC: What happens to the CO2?
Mark Sceats (Executive Director and Chief Scientist): The CO2 liberated from heating minerals is generally very pure, as most of the sulphur and other contaminants in the conventional process come from the combustion process. Thus the clean-up of the CO2 gas stream before compression should not be as challenging as post-combustion capture.
On a small scale the compressed CO2 could be used for a wide range of carbon capture and use (CCU) technologies to generate chemicals, to carbonise waste minerals or for special cements in order to make low CO2 building materials.
For other technologies, such as the growth of algae, there is no need for highly-concentrated CO2. However, if the algae-farm could not be located next to the cement plant, the purified CO2 can be liquefied and transported cost effectively to the algae farm. At the largest scales, carbon capture and storage would most likely be required to handle the large volumes of CO2.
GC: The LEILAC literature says that there is almost no penalty other than compression, but what about transport and other factors?
MS: We expect the CO2 handling to be cost effective compared to other methods as the CO2 will be relatively pure but, ultimately, it will depend on the volumes and fate of the CO2. If it is to be liquefied, for example for shipping, the penalty will be relatively large. It could be compressed to 120bar for transportation by pipeline and injection over a reasonable distance, using commercially available compressors. Factors surrounding this will be investigated in the LEILAC techno-economic assessment and Roadmap, to be produced in 2020. It will detail all of the expected costs for the full-scale application of the technology, CO2 compression and transport.
The LEILAC project will actually represent the highest temperature and volumes that the process is ever likely to have to handle. If everything goes to plan, LEILAC will provide assurance that almost any type of mineral could be processed using a DSR. In fact, we are even looking into retrieving CO2 from combustion itself. This is being investigated by coupling the calciner with a de-carboniser reactor under a separate EU
GC: The DSR has some elements similar to waste heat recovery (WHR) boilers. What do you see the overlap to be and what can be learned from that technology?
AV: We have looked at other technologies like recovery heat exchangers for clues on fouling but the challenges with DSR are unique, given its configuration. Howver, there is a specific programme within LEILAC to look at WHR. For future integration we will use waste heat from the cement plant by feeding pre-heated meal. Waste heat from the DSR’s CO2 will also be recovered during the cleaning and compression steps. There are many opportunities to increase efficiencies and properly integrate the DSR with existing cement plant equipment.
GC: Why was the Lixhe plant selected?
DR: Lixhe was kindly selected by HeidelbergCement and is within a company and region that is supportive of innovation. The plant management is supportive of what we are doing, which is crucial for a project like this as it will represent a significant additional workload for the plant’s staff during construction.
The Lixhe plant is close to the centre of HeidelbergCement’s European operations and easily visited from other plants in the region. It is a ‘typical’ plant, as far as such a thing exists, with fairly typical raw meal. It is also close to the EU in Brussels, from which a lot of the funding comes.
AV: We set up Calix UK as our EU subsidiary precisely to be present in the EU, which is the most forward-thinking region in terms of CCS and CCU technology. It allows us to be part of projects like LEILAC.
GC: How will the technology be physically integrated into the plant?
DR: The raw cement meal will be a slip stream from the Lixhe plant. The calcined cement meal, the CO2 stream and the combustion gas will be reinjected into the Lixhe plant. There is a provision for the plant to process other materials, such a pure limestone and other cement meals from our partners. The plan is to demonstrate 95% capture of the process emissions, which is ~60% of the total.
The funding for the Lixhe plant is limited, so the plant will not initially capture and compress the CO2 stream, but will measure its purity for assessment of its potential utilisation.
GC: It seems strange that the CO2 will not be captured? Will it be analysed?
AV: The CO2 will not be collected as the pilot will only be run intermittently for up to two years to test and prove the concept. As such the volumes collected will be relatively small and would vary depending on the nature of the test run. The CO2 will be tested before it re-enters the main Lixhe cement plant, to prove its quality.
GC: What is the plan for evaluation of the technology at Lixhe?
DR: The pilot is due to be constructed in early 2019, and will run until late 2020. It will undertake a number of tests that prove that the technology can be applied to the cement and lime sectors as expected and that the major scale-up risks have been, or can be, addressed.
The plant will run experimental campaigns for cement meal from the host plant at Lixhe and from other participating cement companies and ensure environmental compliance. There will also be trials for lime production. The project will monitor all the operating parameters of the plant.
The steel reactor tube will be assessed for performance, including corrosion, fouling and creep. Importantly, the project will also demonstrate the quality of the lime and clinker produced by the DSR.As part of LEILAC we have a task to examine the impact of DSR calcined cement meal against conventional meal. This work will be conducted by the industry partners and the research groups.
GC: What do you expect to be the major technical barriers to using the technology in a cement plant?
AV: There are two major technical barriers. Firstly, the temperature is higher. Magnesite is calcined at 750°C, whereas the temperatures required in the DSR for cement and lime production will be >900°C. This places additional demands on the steel used in the reactor. Secondly, cement and lime plants are larger than magnesite calcining plants. This will mean that we have to identify a commercially-viable route to scale up from 10t/hr to about 300t/hr, preferably with a retrofit capability. These issues have been at the forefront in developing the design for the Lixhe plant.
GC: How do you think the technology will handle alternative fuels?
MS: The investigation of alternative fuels is part of the LEILAC programme. The findings will inform the 2020 techno-economic study and Roadmap for the deployment of the technology.
The next steps and commercialisation
GC: What happens post-LEILAC, assuming that the project achieves its aims?
DR: At the conclusion of the project a Cement and Lime industry CCS Roadmap will be developed. This Roadmap will be based on the outcomes of the LEILAC pilot’s construction and test, full-scale techno-economic study, Life Cycle Analysis, and retrofit report.
This roadmap will explore the timing and opportunities for the widespread roll out of this technology. This will be important in informing decision makers and industry of the viability of the widespread deployment of Direct Separation as a means of accelerating the decarbonisation efforts of the industry, based on verified data. Using the European targets for emissions reduction, this should also provide tangible information regarding potential costs for the industry, which has had limited economic deep decarbonisation options until this point.
GC: What about in terms of the technology?
AV: For the lime sector, the Lixhe plant is already at the scale needed for commercial use. The first deployment focus is on obtaining an energy efficiency comparable with the best practice used in the industry. Apart from CO2 emissions reduction, the drivers for the adoption of the technology may be: The use of fines that cannot be processed in conventional lime kilns; The added value of high surface area lime that may be produced; The elimination of impurities arising from combustion, and; Possible use of alternative fuels such as syngas and green electricity.
For cement, the next step could be to add a reactor of the existing size to a plant for generating the CO2 for a commercial CCU-project. This may provide an early commercial application and will mature the long term experience of operating the reactor.
The following step for cement will be to build a demonstrator plant module containing perhaps five DSRs, equivalent to 50t/hr of cement meal. The first large scale demonstrator plant would then use five or more of these modules. At this stage, there are no technical impediments that would limit the potential for adoption in Europe. The ease of adoption will largely depend on the integration of DSRs into the conventional cement production process and a retrofit strategy.
GC: Do you envisage the technology will bear a net cost that offsets rising CO2 prices or will it actually produce a revenue for the plant aside from CO2 credit considerations?
DR: Our aim is to demonstrate that the technology captures CO2 without any substantial additional capital cost or operating costs, other than compression. It is possible that: The application to lime will produce a high surface area product that may sell at a premium; A higher surface area lime in cement meal may allow the development of new cement products for niche markets or; The technology can produce a range of meta-clays, such as metakaolin and very high surface area magnesia and semidolime, for cement additives. The benefits may come to bear in different ways depending on the location and the nature of the producer using the technology.
GC: This is an EU-funded project and as such is relevant to that region. Does this technology have applications outside of environmentally-conscious markets like the EU?
DR: Yes, but we envisage that the drivers to adoption may differ in different regions. We hope that the technology will be adopted in regions with lower environmental requirements than Europe due to the ability for cement producers to provide niche, high-value products. Some areas have very strong emphasis on branding and niche Calix-based cement products could help producers to differentiate themselves.
It could also be that CO2 capture could be the main driver in the EU ETS area at first and then the popularity of niche products will drive adoption of the technology in other regions.
GC: I can see analogies with alternative fuels. These are rarely used simply because they are ‘green’ but rather because they offer savings in fuel costs. Could this be how the technology is perceived outside of emissions trading areas?
AV: Possibly, that is why the EU is attractive at the moment. It provides the highest incentive for adoption of this technology in terms of actually having a CO2 price. It’s low, but it is there, unlike in many other regions.
GC: Do you expect there to be ‘attitude’ barriers from other plant operators?
DR: Critical to the success of the DSR technology is the ability for it to integrate into existing cement and lime plants without major redesign of process flow or operating philosophy. This should allow for a turn-key type of approach to work in many plants.
As such, when applied at full scale, it would be a straight replacement of a cement plant’s calciner tower or a lime kiln. It should be a simple, cost effective and efficient way of capturing unavoidable process emissions and thereby provide options for operating in a CO2-constrained world. We expect minimal challenges from attitudes at plant level due to the similarity of the technology with existing production methods.
One further exciting possibility is that we have looked at electrical sources for driving these types of calciners. This is of interest to the cement operators because instead of needing a fuel, you could run a cement plant on solar power, wind power, hydroelectric power, low energy biogas (via generators), and many other renewable sources.
GC: You mention a turnkey approach in your above answer. What about licensing the DSR out to the major cement plant manufacturers?
AV: In terms of looking at how this will be rolled out, licensing is certainly a strong possibility. There may be differences in how we operate in the lime and cement sectors, as the DSR essentially replaces the entire lime kiln. It is different in the cement sector in that it only replaces part of the line. In both sectors there are lots of options and we are not committed to any one pathway at this point.
GC: We will certainly follow LEILAC’s development with interest, gentlemen. Thank you all for your time.
DR/AV/MS: You are welcome - Thank you!