Nathan J. Nicholas

7 – Inorganic salt solutions for post-combustion capture

Carbon dioxide capture, using inorganic salts of weak acids such as potassium carbonate (K2CO3), has been used in many industrial processes. K2CO3 has benefits over traditional amine-based absorption liquids for post-combustion CO2 capture (PCC) as it has lower regeneration energy and is nontoxic, nonvolatile, cheap, and more resistant to absorbent degradation following contact with SOx and NOx. However, K2CO3 has slow reaction kinetics with CO2 leading to the need for large equipment or the addition of rate promoters to achieve desired levels of CO2 removal. In this chapter, the background and commercial history of K2CO3-based processes has been introduced followed by detailed discussion on the chemistry and thermodynamics of K2CO3-based processes for CO2 capture. The absorption kinetics, vapor–liquid equilibrium and solid–liquid equilibrium data and a range of rate promoters have been described. Finally, demonstration projects that have been operated to reduce CO2 emissions from power stations using K2CO3 have been introduced.