PROCESS FOR PRODUCING A PURIFIED SYNTHESIS GAS STREAM

摘要

The invention provides a process for producing a purified synthesis gas stream from a feed synthesis gas stream comprising contacting it with a water gas shift catalyst in a shift reactor to obtain a shifted synthesis gas stream enriched in H2S and in CO2. H2S and CO2 are removed from the shifted synthesis gas stream by contacting it with an absorbing liquid to obtain semi-purified synthesis gas and an absorbing liquid rich in H2S and CO2. At least part of the absorbing liquid rich in H2S and CO2 is heated to obtain heated absorbing liquid rich in H2S and CO2 followed by de-pressurising the heated absorbing liquid rich in H2S and CO2 in a flash vessel to thereby obtain a flash gas rich in CO2 and absorbing liquid rich in H2S. The absorbing liquid rich in H2S is contacted at elevated temperature with a stripping gas to thereby transfer H2S to the stripping gas to obtain regenerated absorbing liquid and stripping gas rich in H2S. The H2S in the stripping gas rich in H2S is converted to elemental sulphur and the H2S from the semi-purified synthesis gas is removed therefrom by contacting this gas stream in a H2S-removal zone with an aqueous alkaline washing liquid to obtain a H2S-depleted synthesis gas stream and a sulphide-comprising aqueous stream. The sulphide-comprising aqueous stream is contacted with sulphide-oxidizing bacteria in the presence of oxygen in a bioreactor to obtain a sulphur slurry and a regenerated aqueous alkaline washing liquid.