High temperature recovery of CO2 from flue cases using hydrotalcite adsorbent

Experimental and theoretical studies on the high temperature recovery of COP from flue gases are presented. The work employs a potassium promoted hydrotalcite adsorbent, for which CO2 capacities in excess 0.8 mol kg(-1) were measured at temperatures of 481 K and 575 K and in the presence of high concentrations (similar to 30% (v/v)) of water. Elution profiles from a bench-scale adsorption unit also enabled analysis of adsorption and desorption kinetics. A cyclic and multibed process for the continuous and energy efficient recovery of CO2 is proposed. The process involves an integrated energy recovery step for the generation of steam, which is then used for the recovery of CO2 from the adsorbed phase. A mathematical model for the CO2-hydrotalcite system, based on measured equilibria and kinetic data, is used for the preliminary assessment of the process, e.g. in terms of CO2 product purity and steam consumption. Particular attention is given to CO2 recovery from the stack gas of a typical 10 MW coal-fired power plant. The work has application to existing industrial processes in which recovered CO2 (at elevated temperatures) can be used as a feedstock for further catalytic processing, such as dry methane reforming and carbon gasification.