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Preparing pure urea solution, useful as reducing agent for selective catalytic reduction of nitrogen oxides, comprises rinsing urea solution in deaerator, separating urea crystals and re-circulating mother liquor enriched with biuret
Preparing pure urea solution, useful as reducing agent for selective catalytic reduction of nitrogen oxides, comprises rinsing urea solution in deaerator, separating urea crystals and re-circulating mother liquor enriched with biuret
Continuously preparing highly pure urea solution from a conventional urea synthesis, comprises producing a circulation quantity ratio of 10-30 kg solution/kg suspension crystals of concentrated urea solution; rinsing in a deaerator containing a tempered air; degassing with ammonia; separating the crystals from the separating apparatus and provided into dissolving container, to form urea solution, which is free of typical impurities and contains ammonia and biuret; and re-circulating the mother liquor enriched with biuret for biuret decomposition through a reactor. Continuous preparation of highly pure urea solution from a conventional urea synthesis, comprises producing a circulation quantity ratio of 10-30 kg solution/kg suspension crystals of concentrated urea solution in a crystallizer under 0.05-0.2 bar; subsequently concentrating in a separating apparatus to a water content of 5-25%; rinsing in a deaerator containing a tempered air in a quantity ratio of 1-3 kg/kg of crystals; degassing with ammonia; separating the crystals from the separating apparatus and provided into highly turbulent dissolving container, in which the crystals are dissolved with a circulation quantity ratio of 10-30 kg solution/kg crystals in vapor condensate that arises in the urea production, to form urea solution (31.8-33.2%), which is free of typical impurities and contains ammonia (lesser than 30 ppm) and biuret (50 ppm); and re-circulating the mother liquor enriched with biuret for biuret decomposition through a reactor.
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