Method and system for recovering high-purity CO2 from gasification gas

摘要

To provide a method and a system for recovering CO 2 from gasification gas, the method and the system being capable of preventing the recovered CO 2 from being contaminated with COS, without repeating cooling and heating operations and without increasing the steam consumption, even when the CO 2 recovery ratio is changed in recovering CO 2 from gasification gas. Gasification gas being produced in a gasifier (10) and containing CO, CO 2 , COS and H 2 S is subjected to dust removal in a scrubber (20). Then, a part of the gas is subjected to a CO shift reaction, in which CO is converted into CO 2 , in a CO shift reactor (30). Another part of the gasification gas is not subjected to the CO shift reaction by means of a bypass (34), and is mixed with the gas after the CO shift reaction. Thereby, the temperature of the mixture gas is set at 180°C to 300°C, and COS in the mixture gas is converted into H 2 S in a COS converter (40). The H 2 S is absorbed and removed by a H 2 S absorption apparatus (50). Then, CO 2 is absorbed and removed by a CO 2 absorb apparatus.