FIELD: technological processes.
SUBSTANCE: invention relates to a method for the final treatment of urea. Method includes: (a) removing water from the urea aqueous solution by evaporation and condensation in the first section of evaporation and condensation to obtain a urea melt; (b) final processing of at least the first part of the specified urea melt, including the granulation step, in which solid urea and polluted air containing powdered urea and ammonia are obtained as a result of this final treatment; (c) cleaning at least part of said polluted air in at least one cleaning device, cleaning includes cleaning by washing with acid using water and acid and cleaning from dust, and as a result of this cleaning by washing with acid get an aqueous solution containing urea and ammonium salts; (d) evaporating at least a portion of the said aqueous solution containing urea and ammonium salts in the second evaporation section to obtain a liquid stream containing urea and ammonium salts, and a gas stream; (e) condensing said gas stream in the second condensation section to obtain a recycle aqueous stream; (f) using at least a portion of said recycled water stream to flush polluted air, as indicated in (c) above; (g) conversing at least part of the specified liquid stream containing urea and ammonium salts, in solid particles and (h) using the said solid particles as nuclei at said granulation stage. Device for final processing of urea and a method of upgrading the installation for the synthesis of urea is also proposed.
EFFECT: method of final processing of urea allows not to pollute wastewater, to improve the regulation of the granulation process, to reduce the evaporation temperature and to reduce the formation of biuret.
16 cl, 6 dwg
