METHOD AND APPARATUS FOR PRODUCING CARBAMIDE AND METHOD OF UPGRADING APPARATUS FOR PRODUCING CARBAMIDE Russian patent published in 2013 - IPC C07C273/04 

FIELD: chemistry.

SUBSTANCE: method involves reacting carbon dioxide and ammonia which is fed in excess, in a synthesis zone at high temperature and pressure to form a carbamide synthesis solution containing carbamide, water, ammonium carbamate, ammonia and carbon dioxide, distilling said solution while supplying heat at multiple pressure steps, including distillation at 1.5-2.5 MPa and 0.2-0.5 MPa, to form aqueous carbamide solution and distillation gases. Further, the distillation gases are condensed/absorbed while cooling, using aqueous absorbents and forming aqueous solutions of ammonium carbon salts, recycling the aqueous solution of ammonium carbon salts from the distillation gas condensation/absorption step at lower pressure to the distillation gas condensation/absorption step at higher pressure and then into the synthesis zone, evaporating the aqueous carbamide solution and further treatment thereof with known methods. The solution stream from the synthesis zone, before feeding to the distillation step at 1.5-2.5 MPa, is subjected to adiabatic separation at pressure of 8-12 MPa, followed by distillation at the same pressure in a current of carbon dioxide which is used in amount of 40-60% of the total amount fed into the process. Condensation/absorption of the separated gases, as well as a portion of adiabatic separation gases, is carried out at the same pressure in contact with the aqueous solution of ammonium carbon salts obtained during condensation/absorption of distillation gases at pressure of 1.5-2.5 MPa and cooling a condensate which boils under excess pressure to form a vapour, condensation/absorption at pressure of 1.5-2.5 MPa of the remaining portion of adiabatic separation gases at pressure of 8-12 MPa together with distillation gases at pressure of 1.5-2.5 MPa. The solution of ammonium carbon salts obtained from condensation/absorption at pressure of 8-12 MPa is recycled into the synthesis zone.

EFFECT: high degree of converting starting reactants in the synthesis zone.

3 cl, 3 dwg, 1 tbl, 5 ex