METHOD OF CARBAMIDE SYNTHESIS Russian patent published in 1998 - IPC

FIELD: chemical technology. SUBSTANCE: carbamide is synthesized by interaction of ammonia and carbon dioxide in the presence of oxygen at increased temperatures and pressures in the zone synthesis. In obtained melt synthesis of carbamide ammonium carbamate is decomposed at two pressure stages - at 1.7-2.2 MPa and 0.25-0.4 MPa. At the first pressure step decomposition is carried out in two successive zones - at 1.8-2.2 MPa and 150-160 C in the first zone and at 1.7-1.9 MPa and 165-180 C in the second zone. Part of gases evolved in the first zone is separated without their pressure change for carbonate ammonium salts an aqueous solution which is recirculated to the zone synthesis and purified gaseous ammonia. The latter is fluidized and separated from oxygen-containing noncondensed gases which are fed to the second zone of the first decomposition step of ammonium carbonate decomposition. Gases evolved in the second zone are condensed with the other part of gases evolved in the first zone and an aqueous solution of carbonate ammonium salts is formed which is recirculated for the stage of gases separation evolved in the first zone of the first step of ammonium carbonate decomposition. An aqueous solution of carbamide free of carbamide and ammonium carbamate is converted then to solid carbamide. EFFECT: decreased energy consumption. 2 dwg