Desulphurisation of coke oven gas - by ammonia scrubbing and stripping with improved pH control

摘要

In the desulphurisation of coke oven gas, the washed gas is scrubbed with aq NH4OH soln., and the used soln. then stripped of acid gases (including H2S) in a stripper. Improvement is the addn. to the used NH4OH soln. in the stripper of some prim. water-washings of the coke-oven vas, which contain NH4 salts of strong acids e.g. NH4C1, and are conventionally sent to the scrubber instead. These washings raise the PH in the stripper and so aid the thermal breakdown of NH4 salts of weak acids, including NH4HS. The H2S concn. in the coke oven gas after scrubbing is less than from conventional NH3-absorption processes, and is environmentally acceptable.