PROCESS FOR PRODUCING PURIFIED SYNTHESIS GAS

摘要

The invention provides a process for producing a purified synthesis gas stream from a feed synthesis gas stream comprising besides the main constituents carbon monoxide and hydrogen also hydrogen sulphide, carbonyl sulphide and/or hydrogen cyanide and optionally ammonia, the process comprising the steps of: (a) contacting the feed synthesis gas stream with a water gas shift catalyst in a shift reactor in the presence of water and/or steam to react at least part of the carbon monoxide to carbon dioxide and hydrogen and at least part of the hydrogen cyanide to ammonia and/or at least part of the carbonyl sulphide to hydrogen sulphide, to obtain a shifted synthesis gas stream enriched in H2S and in CO2 and optionally comprising ammonia; (b) removing H2S and CO2 from the shifted synthesis gas stream by contacting the shifted synthesis gas stream with an absorbing liquid to obtain semi-purified synthesis gas and an absorbing liquid rich in H2S and CO2; (c) heating at least part of the absorbing liquid rich in H2S and CO2 in a heater to obtain heated absorbing liquid rich in H2S and CO2; (d) de-pressurising the heated absorbing liquid rich in H2S and CO2 in a flash vessel, thereby obtaining flash gas rich in CO2 and absorbing liquid rich in H2S; (e) contacting the absorbing liquid rich in H2S at elevated temperature with a stripping gas, thereby transferring H2S to the stripping gas to obtain regenerated absorbing liquid and stripping gas rich in H2S; (f) converting H2S in stripping gas rich in H2S to elemental sulphur; (g) removing H2S from the semi-purified synthesis gas by converting H2S in the semi-purified synthesis gas to elemental sulphur to obtain the purified synthesis gas.