Patent ID: 8414694

Claim:
A CO 2 recovery unit, which includes a CO 2 absorber that brings flue gas containing CO 2 into contact with a CO 2 absorbent to reduce the CO 2 contained in the flue gas, and a regenerator that reduces CO 2 contained in rich solvent absorbing CO 2 in the CO 2 absorber to regenerate the rich solvent, so that lean solvent from which the CO 2 is reduced in the regenerator is reused in the CO 2 absorber, comprising: a heat exchanger that allows the rich solvent to exchange heat with the lean solvent; and a controller that controls to extract part of the rich solvent to allow the part to bypass the heat exchanger, and to be supplied into an upper section of the regenerator without exchanging heat so as to minimize a sum of an enthalpy that is taken out of the regenerator as CO 2 gas accompanying steam and an enthalpy that is a result of subtracting an enthalpy of the rich solvent before heat exchange in the heat exchanger from an enthalpy of the lean solvent after the heat exchange, wherein the controller includes: a plurality of sensors for detecting at least temperatures provided on a rich solvent supplying line and a lean solvent supplying line respectively; a flow meter provided on a split rich solvent supplying line; and an adjusting valve provided on the split rich solvent supplying line downstream of the flow meter to thereby adjust the amount of the rich solvent to be split under an instruction of the controller by adjusting the adjusting valve based on the information obtained by the plurality of sensors and the flow meter so as to approximate a temperature difference between the rich solvent and the lean solvent at an entering side of the heat exchanger and a temperature difference between the rich solvent and the lean solvent at an exiting side of the heat exchanger.