Meeting climate-change goals requires steep reductions in greenhouse-gas emissions from existing power plants and hard-to-abate industry operations. However, the energy required to release captured CO2 from sorbent material is a challenge for the economic viability of these efforts. Also, retrofitting carbon-capture and storage (CCS) systems onto existing plants can be complicated and costly. Now, a CCS technology using electrically driven heat and vacuum pumps is positioned to address both issues, especially in situations where little or no waste heat is available from the host plant.
The technology, known as continuous swing adsorption reactor (CSAR), was developed by researchers at the independent research organization SINTEF (Trondheim, Norway; www.sintef.no), along with collaborators at CCS technology developer Caox AS (Stavanger, Norway; www.caox.no). A successful demonstration using CSAR to capture CO2 from fluegas was recently completed at a waste incineration facility near Bergen, Norway. CSAR represents a novel approach to providing heat for releasing CO2 from sorbent material, and can be cost-effectively retrofitted onto existing facilities because it is powered by electricity rather than steam.
CSAR features two fluidized-bed reactors (diagram), one for adsorbing CO2 from fluegas, and the other for desorption of the gas. As the fluegas enters the first reactor, the CO2 is adsorbed by polyethyleneimine (PEI) sorbent, which circulates between the two reactors. “This binding process occurs at low temperature and generates heat,” says Jan Hendrik Cloete, SINTEF research scientist. The heat is then transferred to the desorption reactor via a heat pump, where it is used to release the CO2 from the sorbent, this time at a higher temperature. “The heat pump is used to transfer the heat between the reactors, while the vacuum pump assists in releasing the CO2,” he explains.
Combined, the two pumps transfer heat efficiently, and consume minimal energy. Because both pumps use conventional electricity, installation on existing plants is straightforward.
The research showed that “CSAR technology competes very well with other [CCS] technologies that utilize heat” [such as temperature-swing adsorption], says Cloete. “This applies in particular if reasonably priced electricity from renewable sources is available,” he says.
Following the successful demonstration at the waste incinerator, SINTEF plans to further test the 100-kg-per-day CO2 pilot plant at a cement factory in Spain in 2026.