Solubility phenomena related to CO2 capture and storage

Abstract

Capturing CO2 emissions from energy production and storing it under the ground is a potential CO2 mitigation strategy that currently receives much attention. Both CO2 capture and CO2 storage are solubility problems. This paper reviews some important solubility aspects of CO2 capture and storage that are often overlooked. Until very recently, there was not a single CO2 solubility relationship that was both applicable in a wide temperature range and thermodynamically consistent with the enthalpy of solution of CO2. Furthermore, very often the relationship used for the first acidity constant of carbonic acid as a function of temperature is inconsistent with the relationship used for the solubility constant (or Henry constant) of CO2. The removal of CO2 from a gas stream with amine solutions is usually viewed as a chemical reaction, which leads to the practice of heating to remove the CO2 from the solvent. However, viewing this process as a solubility phenomenon suggests the practice of using vacuum to remove the CO2 from the solvent, a potentially more efficient approach.