Analysis of Hydroxide Sorbents for CO2 Capture from Warm Syngas

Integrated gasification combined cycle (IGCC) with CO2 capture and sequestration (CCS) is a promising technology to efficiently mitigate the emission of CO2. Warm CO2 removal has been predicted to make the CO2 capture process more efficient. Here, we investigate the efficiency penalties associated with CO2 removal via a pressure swing adsorption (PSA) process using metal hydroxide sorbents at elevated temperature. We use numerical models constructed in MATLAB and integrate these with Aspen Plus process simulations. We apply these models to both general metal hydroxides of variable enthalpy of adsorption and real metal hydroxides identified using density functional theory (DFT) calculations. We show that having an enthalpy of adsorption between 15 and 20 kJ/mol results in a PSA process that gives an overall IGCC–CCS efficiency that is competitive with the conventional IGCC–CCS process using (cold) Selexol. An enthalpy of adsorption of 20 kJ/mol is predicted to be the most favorable because it yielded a promising combination of HHV efficiency and higher working capacity. In addition, we identify Fe­(OH)2, Co­(OH)2, Ni­(OH)2, and Zn­(OH)2 as potentially favorable real materials, with IGCC–CCS efficiencies predicted to be within 1% HHV of that of Selexol.