Regeneration Section of CO₂ Capture Plant by MEA Scrubbing with a Rate-Based Model

Abstract

CO2 capture from exhaust gas of power plants, natural gas and refinery gas can be successfully achieved by chemical absorption with alkanolamines. CO2 capture from exhaust gas is often obtained by absorption with monoethanolamine (MEA) which is the most frequently used solvent for this purpose. Our paper focuses on the regeneration section, where the amine solution is separated from the absorbed CO2 and recirculated to the absorber. Since regeneration is obtained in a stripper or a distillation column, it is the most energy demanding unit of the plant, so a careful modeling is required. Thermodynamics, kinetics and mass transfer influence the chemical absorption process. Acidic gases and amines are weak electrolytes, which partially dissociate in the aqueous phase: the high non-ideality of the liquid phase must be properly taken into account, by employing a ?/f method. Kinetics and mass transfer can be described using two different approaches: the “equilibrium-based stage efficiency” model or the “rate-based” one. ASPEN Plus® uses the rate-based model, but the prediction of mass transfer coefficients is based on the film theory by Lewis and Whitman, while other theories can more conveniently be used, i.e. the Eddy Diffusivity theory. Since ASPEN Plus® simulator is suitable to be user customized, it has been chosen as framework for the model proposed in this work, that was validated by comparing simulation results with experimental data of a pilot plant for the purification of exhaust gas from power plant.