Hydrogen Sulfide Removal/Unisulf Process

Unocal's Unisulf process uses a regenerable, alkaline, aqueous washing solution to desulfurize a hydrogen sulfide-containing gas stream. Hydrogen sulfide is absorbed by the solution and converted to sulfur, and the sulfur is recovered from the solution after the solution is oxidatively regenerated downstream for recycle. The solution is formulated with a vanadate, a salt of anthraquinone disulfonic acid, sodium carbonate, sodium bicarbonate, and additives such as sodium citrate, sodium thiocyanate, and a salt of phenol sulfonic acid. These additives eliminate or minimize the chemical consumption of the disulfonic acid and the conversion of hydrogen sulfide and the product sulfur to sulfates, thiosulfates and polythionates.