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 (NH
4)
2S
2O
3 in high concentrations, and has generally been converted into H
2SO
4, (NH
4)
2SO
4 or CaSO
4·2H
2O 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 (NH
4)
2S
2O
3 is selectively oxidized to NH
4SO
3NH
2 and (NH
4)
2SO
4. The ratio of NH
4SO
3NH
2 to (NH
4)
2SO
4 is changed with the concentration of NH
3 and S
2O
32-.
2. The resulting solution is oxidized again under more intensive conditions to transform NH4SCN into (NH
4)
2SO
4.
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 (NH
4)
2SO
4. The crystallized (NH
4)
2SO
4 is filtered and washed with water at the same temperature.
4. The filtrate is cooled to crystallize NH
4SO
3NH
2, which is separated by filtration.
5. The purity of NH
4SO
3NH
2 obtained is about 97%, and the recovery is about 98%. This process affords a commercial procedure for the preparation of NH
4SO
3NH
2 from the desulfurization effluent.
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