METHOD OF PRODUCING CARBAMIDE Russian patent published in 2014 - IPC C07C273/04 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing carbamide from ammonia and carbon dioxide at high temperature and pressure, molar ratio NH₃:CO₂=(3.4-3.7):1. The method is carried out in a carbamide synthesis reactor from which gases and a carbamide synthesis liquid melt are separately output, followed by separation of excess ammonia from the carbamide synthesis melt at pressure of 9-12 MPa, two-step distillation of the melt, condensation of distillation gases to form recyclable ammonium carbonate solutions. Distillation at the first step is carried out at pressure of 9-12 MPa in a current of carbon dioxide. After distillation, the melt is fed into the second distillation step, which is carried out at low pressure. Gases from the first distillation step are condensed in two successive areas at pressure of the first distillation step into which gases output from the synthesis reactor and excess ammonia from the separation step are also fed. In the first area, condensation is carried out while feeding a portion of the ammonium carbonate solution obtained from condensation of gases from the second distillation step, and the condensed vapour is cooled by a condensate which boils at excess pressure to obtain vapour. In the second condensation area of distillation gases from the first step, the condensed vapour is cooled by recycled water and uncondensed gases at the same pressure are washed by the other portion of the ammonium carbonate solution obtained during condensation of distillation gases from the second step. The formed ammonium carbonate solution is fed into the second condensation area and the ammonium carbonate solution coming out of the second condensation area is fed into the reactor. Distillation at the first step is carried out in a current of carbon dioxide which is used in amount of 35-40% of the total amount thereof fed into the process; 75-85% of gases separated at the separation step are fed into the first condensation area for distillation gases from the first step, and the remaining amount of gases separated at the separation step, along with gases output from the synthesis reactor, is fed into the second condensation area for distillation gases from the first step.

EFFECT: producing vapour with parameters which enable use thereof in the next steps of the carbamide synthesis process in the first condensation area of gases from the first distillation step.

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