Although more CO2 is absorbed by the lean solvent when the lean solvent flow rate increasing, the increase of the CO2 is less than that of the NH3 in the solvent, and therefore the CO2 loading of the rich solvent flowing out of the absorber decreases. The lower CO2 loading of the rich solvent flowing into the stripper means more heat supply for regenerating the same amount of CO2, thus leading to a higher regeneration energy.