Reduction of sulfur concentration in physical scrubbing agents

Abstract

In a low temperature gas scrubbing process with a physical scrubbing solution, e.g., methanol, wherein either the H.sub.2 S containing gas-to-be-scrubbed, e.g., coal gasification gas, has a sufficient concentration of SO SO.sub.2 and/or O.sub.2 or wherein the H.sub.2 S containing scrubbing solution is brought into contact with a second O.sub.2 and/or SO.sub.2 containing gas, e.g. a stripping gas, to form elemental sulfur in the scrubbing solution, and said scrubbing solution is regenerated and then cooled to the scrubbing temperature, the improvement which comprises adding a sufficient amount of cyanides to the scrubbing solution to convert the elemental sulfur to thiocyanate, whereby sulfur is not precipitated in the scrubbing solution which would have otherwise occured, and removing the thiocyanate at least partially from the scrubbing solution. The cyanides may be added to the gas-to-be-scrubbed or the scrubbing solution, or there may be sufficient hydrocyanic acid in the gas-to-be-scrubbed at the outset.

Dependencies are inferred from the claim text.