PROCESS FOR SEPARATING AND RECOVERING UNREACTED MATERIALS IN UREA SYNTHESIS

摘要

Carbon dioxide is reacted with a stoichiometric excess of ammonia at urea synthesis temperatures and pressures in a urea synthesis zone with the mol ratio of ammonia to carbon dioxide being in the range of from 5:1 to 12:1. The urea synthesis effluent from the urea synthesis zone is pressurized to a pressure higher than the urea synthesis pressure, and heated to a temperature higher than the urea synthesis temperature in a separation zone, wherein unreacted ammonium carbamate and excess ammonia contained in the urea synthesis effluent are separated from urea synthesis effluent in the form of a gaseous mixture of ammonia and carbon dioxide. The thus separated gaseous mixture of ammonia and carbon dioxide is recycled to the urea synthesis zone by means of the pressure difference.