Synthetic Studies of Some Chemicals Using Hydrogen Sulfide, Hydrogen Cyanide and Ammonia in Coke Oven Gas (II)

Ammonium Sulfamate from Desulfurization Effluent

Abstract

In the production of coke, substantial volumes of effluent are generated from a liquid redox desulfurization plant of coke oven gas. The effluent typically contains NH4SCN and (NH₄) ₂S₂O₃ in high concentrations, and has generally been converted into H₂SO₄, (NH₄) ₂SO₄ or CaSO₄·2H₂O by means of burning or wet oxygen oxidation under severe conditions.
A method was developed for production of NH4SO3NH2 from the effluent.
1. The effluent is treated with wet oxygen oxidation under mild neutral conditions where (NH₄) ₂S₂O₃ is selectively oxidized to NH₄SO₃NH₂ and (NH₄) ₂SO₄. The ratio of NH₄SO₃NH₂ to (NH₄) ₂SO₄ is changed with the concentration of NH₃ and S₂O₃^2-.
2. The resulting solution is oxidized again under more intensive conditions to transform NH4SCN into (NH₄) ₂SO₄.
3. After the oxidation of effluent, the solution is concentrated to saturation point of NH4SO3NH2 under reduced pressure at 70-80t in order to crystallize (NH₄) ₂SO₄. The crystallized (NH₄) ₂SO₄ is filtered and washed with water at the same temperature.
4. The filtrate is cooled to crystallize NH₄SO₃NH₂, which is separated by filtration.
5. The purity of NH₄SO₃NH₂ obtained is about 97%, and the recovery is about 98%. This process affords a commercial procedure for the preparation of NH₄SO₃NH₂ from the desulfurization effluent.