Aspen HYSYS Simulation of CO2 Removal by Amine Absorption from the Flue Gas of a Coal-Fired Power Plant

This paper reports the preliminary modelling results of a project examining the optimization of Post Combustion Carbon Capture. A simplified MEA (monoethanolamine) based CO2 removal process has been modelled in the process simulation tool Aspen HYSYS. The sour gas treated is a typical flue gas from a coal-fired power plant but has been simplified by the exclusion of any SOx, NOx or other trace elements which may be found in such gases. The thermodynamic properties of the simulation are calculated using the Li-Mather aqueous amine model which is available in Aspen HYSYS. A series of modifications to a base case scenario are examined with reference to CO2 removal and steam consumption at the stripper column. Changes are made to the amine flow rate, number of absorber column trays, flue gas temperature and amine concentration whilst the specification of the stripper column remains consistent with 10 stages and a reflux ratio of 0.3. The purified CO2 product from the stripper is specified to a minimum concentration of 98 mole.% as such high purities may be necessary for efficient downstream processes. Preliminary modelling results show that increasing amine flow rate increases CO2 capture in the absorber, but also increases heat consumption in the regeneration column. Increasing the number of trays in the absorber leads to increases in the CO2 capture in the absorber and decreases in heat consumption in the stripper column. Variance of the flue gas temperature across the range 25-55°C has little impact upon CO2 removal in the absorber or the steam consumption in the stripper column. The variation of MEA concentration is examined within the allowable range in Aspen HYSYS (0 - 30 mass% amine), showing increased CO2 removal and reduced heat consumption in the stripper at higher MEA concentrations. With CO2 removal of 88%, the steam consumption in the regeneration column is calculated as 2.5MJ/kg CO2 removed.