Next generation post-combustion capture: combined CO2 and SO2 removal

A major consideration for post-combustion CO2 capture is the adverse effect of the presence of SO2 on the absorption desorption process. The most common approach is to remove the SO2 from the flue gases in a flue gas desulfurization (FGD) unit prior the CO2 recovery process. This paper reports the experimental and modeling results of a new process for simultaneous removal of CO2 and SO2 for post-combustion applications. This process is named CASPER (CO 2-capture And Sulphur Precipitation for Enhanced Removal), and is based on the precipitation of K2SO4 for sulphur removal. The selected CO2 absorbing solvent is an amino-acid, preferably a potassium amino-acid salt solution. The presence of potassium leads to the subsequent formation of K2SO4, which solubility in the CO2 loaded aqueous solvent solution changes depending on the applied conditions. The optimal crystallization conditions were first determined by characterization of K2SO4 solubility window and then evaluated in the lab-scale crystallization unit. In the next step the model system based on potassium beta-alanate solutions, also with addition of sulphate, were tested for CO2 absorption and desorption pressures by performing VLE (Vapor Liquid Equilibrium) measurements at 40°C and 120°C, respectively. Obtained values were included in preliminary technical assessment, which showed an energetic improvement of 0.7%-points for the CASPER model solvent system in comparison to the baseline 30wt% MEA case. © 2013 The Author