A theoretical analysis of the energy consumption of post-combustion CO2 capture processes by temperature swing adsorption using solid sorbents

摘要

CO2 capture processes based on dry solid sorbents have been praised as a very attractive alternative to absorption by amine solvents (in particular monoethanolamine) in terms of energy consumption. The present paper critically analyzes these very optimistic predictions. It presents a theoretical analysis of three different temperature swing adsorption (TSA) processes: (i) a fixed bed, (ii) an isothermal fluidized bed and (iii) an adiabatic fluidized bed. The solid sorbent is supposed to be an amine immobilized on a support material. A high-level estimation of the energy consumption of the three processes shows that the fixed bed process would be by far the most interesting option, because the thermodynamic driving force for adsorption is higher in the fixed bed. The performances of both the fixed and fluidized bed process dramatically improve if the adsorption step is operated under close to isothermal conditions. Heat transfer in a fixed bed is much slower than in a fluidized bed. Providing the heat exchange area required for isothermal operation is challenging in the fixed bed, but not impossible according to our rough estimations. The paper also defines the adsorption properties (adsorption constant, adsorption capacity, heat of adsorption) of the optimal solid sorbent