Reducing CO2 Emissions

What makes Leilac, utilising the Calix Technology, so unique when compared to other carbon capture technologies?

The majority of initiatives to capture carbon are based, or adapted, from processes and techniques developed for the energy and chemical sectors, and are all based on separating gases. For 60 years solvents, such as amines, have been used to strip CO₂ from gases (particularly in refineries and natural gas processing plants), and a lot of work has been recently undertaken to apply them to the cement sector at increasingly lower cost. Sorbents (including calcium looping), membranes, and enhancements are being actively developed to reduce the volumes and/or energy required to separate CO₂ from flue gases. Other approaches, such as oxyfuel, separate gases in air, rather than at the stack. All these approaches are being developed, given the increasing government, investor and stakeholder pressures to decarbonise.

Calix is focused on developing technology solutions for cement, lime processing, ensuring that the relatively pure, unavoidable CO₂ released from the mineral itself (limestone) is not contaminated by either air or flue gases. The Calix Technology solution for cement and lime works within a normal cement and lime plants’ process. It is based on an indirect calcination system, where the limestone is heated in a special steel reactor within the pre-calciner. This unique system enables pure CO₂ to be captured as it is released from the limestone, while furnace exhaust gases are kept separate. Heating or “calcining” raw cement meal or limestone by indirect heating (Leilac) or by contact-heat (conventional calciner) can be done in principle with the same specific energy. The process does not involve any additional processes or chemicals, and simply involves a novel “pre-calciner” design (or new kiln, in the case of a lime plant).

What is the Leilac-1 project, and why was it successful?

The Leilac-1 project involved the construction of a pilot plant at the HeidelbergCement plant in Lixhe, Belgium. Extensive research, development and engineering was necessary to design and construct the first-of-a-kind pilot – involving the dedicated, flexible, and professional inputs from all the project’s partners: Calix, Heidelberg Cement, CEMEX, Tarmac, Lhoist, ECN (part of TNO), Imperial College, Quantis, PSE, Solvay and the Carbon Trust.

This enabled the construction of the pilot on time and on budget in 2019. Additionally, studies examining integration of the plant in different configurations, and confirmation of the sustainability of the process have also been conducted by Imperial, PSE, Quantis and the Carbon Trust.

Several challenges were faced in getting the system to run, particularly the burners, feed and conveying systems. These were gradually overcome, and with system becoming increasingly stable over the latter part of the test run campaign.

The project has successfully demonstrated that both limestone and raw meal can be processed; that the CO₂ is successfully separated; and that (disaggregated from the entire system) the energy penalty for indirect calcination (Leilac) is not higher than direct (conventional) calcination. Other major findings are that there has been no build-up of material on the reactor’s wall; that the reactor (despite the numerous runs) is exhibiting no significant negative operational deterioration; that there have been no negative impacts on the host plant, and no impact on clinker production; and that the pilot is safe and easy to operate, with no safety incidents.

Leilac's plant in Lixhe, Belgium
Thanks go to all the staff at Lixhe, service providers, and consortium members tirelessly working during the massive complications arising from the pandemic.
Leilac-1 opening
Official opening of the Leilac-1 pilot facility in May 2019

So… what happens next?

While a follow-on project – Leilac-2 – has started, awarded with €16m funding from the EU Horizon 2020 program and additional industry contribution, a lot more is still to happen at the Leilac-1 site.

Several steps are currently in train to improve the throughput and calcination rates, including:

Natural gas burners icon

Improvements to the natural gas burners used, enabling the furnace to reach its design capacity;

Improvements icon

Improvements to the natural gas burners used, enabling the furnace to reach its design capacity;

Pre-heat icon

Installation of a pre-heat stack to increase the usable length of reactor for calcination – further improving throughput and calcination rates and replicating integration with a host plant.

Once tested and scaled up, (Leilac Low Emissions Intensity Lime And Cement) technology should provide an option for reducing the costs of carbon capture and accelerate the deployment in both industries, enabling society to continue to benefit from these vital products without negatively impacting the environment.