Heat Stable Salts

After a period of time treating sour gases that were generated by refinery cracking operations — e.g., cokers, fluid catalytic cracking — trace amounts of acid anion contaminants can build to harmful levels in the solvent. The most commonly found are formate and thiocyanate. They result from the absorption of hydrogen cyanide: formate forms by the hydrolysis of cyanide ion to ammonium formate, thiocyanate forms by dissolved oxygen reacting with H₂S and this is followed by a reaction of the oxysulfur anion with cyanide ions. Thiosulphates generally result from the reaction of  dissolved oxygen with H₂S or from SO₂ reaction with H₂S in tail gas treaters when no HCN is present. Sulfates can be formed either from absorption of sulphuric acid or from further oxidation of thiosulphates.

Their description generally paints a bleak picture of HSS, so we must ask: are they always bad? Exactly how and by what mechanism do they influence the amine treating process? Learn the answers to these questions here.