Pretreatment of waste water from gas scrubbing - by acid gas stripping, wet oxidn. and ammonia stripping

摘要

Pretreating waste water which is generated in the treatment of crude gas produced by gasifying carbonaceous material and which contains trace components, e.g. H2S, HCN, NH3 and hydrocarbons, scrubbed from the crude gas with water. Process comprises removing the trace components by: (a) stripping the waste water with gas and/or steam in an acid gas stripper to obtain an acid gas overhead stream and an H2S-lean water stream; (b) utilising the energy contained in the acid gas overhead stream; (c) subjecting the H2S-lean water stream to wet oxidn. with oxidising agents to obtain an O2-contg. overhead stream and a NH3-contg. water stream; (d) adding the O2-contg. overhead stream to the acid gas overhead stream; and (e) stripping the NH3-contg. water stream with steam to obtain an NH3-contg. overhead stream and a pretreated water stream, which are both passed on for further use or treatment. ADVANTAGE - Removal of H2S in step (a) reduces the oxidising agent consumption (for conversion of HCN and residual H2S) in step (c).