METHOD FOR PRODUCTION OF CARBAMIDE Russian patent published in 1995 - IPC

FIELD: organic chemistry. SUBSTANCE: carbamide is produced from ammonia and carbon dioxide at elevated temperatures and pressures in at least two synthesis zones, the first of which is supplied only with the streams of fresh ammonia and carbon dioxide, forming the streams of the carbamide synthesis fusion cake containing carbamide, water, ammonium carbamate, ammonia and carbon dioxide. Carbamate is decomposed in the streams of the carbamide synthesis fusion cake by delivering heat at several stages at reduced pressure and forming concentrated carbamide and gas streams which are absorbed by aqueous absorbents and form an aqueous solution of carbon-ammonium salts. The latter are recirculated into the zones of synthesis other than the first zone. The molar relation of NH₃CO₂ in the first zone of synthesis is maintained within the range from 2.8 to 4 while in the other synthesis zones, in the range from 4 to 5.6. Preferably, the process shall be conducted in two or three zones of synthesis. EFFECT: higher efficiency. 3 cl, 2 dwg