7. Tail gas treatment

On leaving the Claus unit, after conversion of the H ₂ S in the acid gas into sulfur, the gas cannot be released into the atmosphere or sent to the incinerator without additional treatment, due to the residual H ₂ S content and the presence of SO ₂ from the first stage of the Claus reaction, which converts H ₂ S into SO ₂ by oxidation. H ₂ S and SO ₂ contents are a few hundred ppmv, although these can be reduced by implementing Superclaus-type technology. The standard relating to the limitation of discharges into the atmosphere imposes a limit value of 35 mg/m ^...