System and method for recovering gas containing CO

1. A method for recovering a gas containing CO 2 and H 2 S using an absorber and a regenerator which recover CO 2 and H 2 S from an introduction gas containing CO2 and H 2 S, the method comprising:

extracting a part of an absorbent from the vicinity of a middle stage of the absorber as a semi-rich solution which has absorbed a part of CO 2 and H 2 S from the introduction gas to reduce a flow rate of the absorbent flowing down below the absorber, and introducing the semi-rich solution into the vicinity of a middle stage of the regenerator to be regenerated;

extracting the absorbent from a bottom portion of the absorber as a rich solution which has absorbed CO 2 and H 2 S from the introduction gas, and introducing the rich solution into the vicinity of a top portion of the regenerator to be regenerated;

extracting the regenerated absorbent from a bottom of the regenerator as a lean solution which has released CO2 and H2S;

performing heat exchange of the rich solution with the lean solution in a first heat exchanger;

branching the lean solution prior to the heat exchange in the first heat exchanger;

performing heat exchange of the branched lean solution with the semi-rich solution in a second heat exchanger; and

merging the branched lean solution after the heat exchange in the second heat exchanger with the lean solution after the heat exchange in the first heat exchanger, and introducing the merged lean solution into the vicinity of a top portion of the absorber so as to be reused;

wherein a part of the rich solution is introduced into the second heat exchanger through a bypass line during operation of not extracting the semi-rich solution, and is subjected to heat exchange with the branched lean solution in the second heat exchanger.