CORA – Separation of CO₂ from air for power-to-X
processes for sector coupling

CO₂ on the conveyor belt

Carbon dioxide and water are sustainable raw materials for power-to-X processes, with the air providing an almost inexhaustible source for the processes at any location. Getting the carbon dioxide (CO₂) out of the air is not an easy task, however, and usually requires electricity and heat for the separation and concentration. The process of separating CO₂ from the air is most interesting for locations with favorable wind and PV conditions where there are plans to make power-to-X products on a grand scale in the future. In the short term, CO₂ consumers who have produced their CO₂ from burning fossil fuels until now can switch their CO₂ supply to a renewable option. In the longer term, the separation of CO₂ from the air can facilitate adherence to the climate targets with negative CO₂ emissions after the fossil CO₂ emissions have been reduced to an unavoidable residual level.

The partners in the joint project “CORA” are facing the challenge of rolling out an effective and easily scalable technology. First, the German Institutes of Textile and Fabric Research (DITF) will develop a fabric/fiber tape for the efficient absorption and desorption of CO₂. This will be accompanied by the development and testing of a belt system at the Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW). This step enables to desorb CO₂ and H₂O in different zones of the running belt with the help of process waste heat such as electrolysis and downstream e-fuel synthesis and to make them available in concentrated form.

The cheapest and most efficient method

Two processes, which can be operated continuously for the separation of CO₂ from the air, have already been developed and demonstrated at the ZSW. Both methods use a scrubbing process for CO₂ absorption. An aqueous sodium hydroxide solution (NaOH) was used to absorb CO₂ in the first instance (2009). In this case, the carbonate solution formed was electrically regenerated through dialysis. The electricity consumption was correspondingly high, with over 5 kilowatt-hours per kilogram CO₂. This is why an aqueous solution of polyethylene imine (PEI) of high molecular weight was used as the CO₂ sorbent in a further variant from 2016 to 2019. This enabled thermal CO₂ desorption, thereby allowing the use of waste heat from downstream power-to-X steps, which significantly reduces the electricity consumption for the CO₂ supply to below 2 kilowatt-hours per kilogram CO₂.

One aim pursued in developing the new process in “CORA” is to decrease electricity consumption by dispensing with large air blowers. Another is to recover water from the process instead of using water, as was previously the case with the air scrubber. The plan is to have a circulating tape of fabric with groups of amines fixed to it for the adsorption of CO₂. That is why the material development process is of great importance. A tape apparatus is being developed at the same time. The design brief, in this case, is to come up with an efficient method of desorbing CO₂ and H₂O and to make them available on a continuous basis.

To ensure that the new process also meets the climate policy targets and is environmentally sound, the Institute for Energy and Environment Reasearch (ifeu) will flank a full life-cycle assessment and evaluation of long-term CO₂ storage.

Pooling expertise for the industrial roll-out

The research team – consisting of the research institutes DITF, ifeu, and ZSW and industrial partner Mercedes-Benz – has the necessary skills to realize the ambitious goals of an efficient CO₂ and H₂O supply for power-to-X processes.

The new “CORA” process aims to reduce the electricity consumption to values below 0.5 kilowatt-hours per
kilogram CO₂ and cut the required process heat. Another aim is to develop a cost-effective CO₂ sorbent based on cellulose fibers and amines in order to lay the foundation for competitive industrial practices and scalable technology. The potential to provide CO₂ and H₂O in parallel makes the new process an ideal raw material supplier for power-to-X processes in remote locations with good PV and wind power conditions.

It is hoped that more industrial partners will come on board to prepare for the next steps in the industrial roll-out and join the pursuit of the large-scale strategy within the project framework.

CORA-Projektblatt zum Download