METHOD FOR PRODUCING CARBAMIDE

摘要

Carbamide is produced from ammonia and carbon dioxide under an increased temperature and pressure and with a molar ratio of NH3:CO2=(3.4-3.7):1 in a carbamide synthesis reactor. Gases and a liquid carbamide synthesis melt are discharged separately from the carbamide synthesis reactor. Excess ammonia is separated off from the carbamide synthesis melt by separation under a pressure of 9-12 MPa and a subsequent two-stage distillation of the melt, wherein the first distillation stage is carried out under a pressure of 9-12 MPa in a stream ofСО2 (35-40% of the total quantity thereof introducible into the process), and the second distillation stage is carried out under a low pressure. The gases from the distillation are condensed forming recirculatable ammonium carbonate solutions (AC), wherein the gases of the first distillation stage are condensed in two subsequent zones at the pressure of the first distillation stage. In the first zone, condensation is carried out with a portion of the ammonium carbonate solution, which is produced on condensation of the gases from the second distillation stage, being introduced, and the condensing vapours are cooled with the condensate, which boils under a positive pressure, so as to produce a vapour. 75 - 85% of the gases separated off at the separation stage are introduced into the first zone of condensation of the gases from the first distillation stage, and the remaining quantity of gases separated off at the separation stage are conducted, together with the gases, out of the synthesis reactor and into the second zone of condensation of the gases from the first distillation stage. In the second zone of condensation of the gases from the first distillation stage, the condensing vapours are cooled by return water. The ammonium carbonate solution emerging from the second zone of condensation is directed into the reactor. Gases which are not condensed in the second zone are scrubbed under the same pressure by another portion of the ammonium carbonate solution produced on condensation of the gases from the second distillation stage, and the resulting ammonium carbonate solution is introduced into the second zone of condensation. The technical result is the production, in the first zone of condensation of the gases from the first distillation stage, of a vapour with parameters ensuring the use of said vapour in subsequent stages of the carbamide production process.