The method for separating and causing the not - reacted starting materials in the case of a urea synthesis of ammonia and carbon dioxide

摘要

1,272,873. Urea. SNAM PROGETTI S.p.A. 16 Oct., 1970 [16 Oct., 1969], No. 49366/70. Heading C2C. An aqueous solution of urea is prepared by reacting ammonia and carbon dioxide in a reactor so as to produce an aqueous solution of urea contaminated with ammonium carbamate, passing the contaminated aqueous solution to a decomposer and decomposing therein the majority of the ammonium carbamate into gaseous products, separating the majority of the gaseous products from the aqueous solution of urea and stripping at an elevated temperature in a stripper the aqueous solution of urea from which the majority of the gaseous products have been separated with, as a stripping agent, an inert gas, so as to obtain an aqueous solution of urea, and wherein the separated gaseous products are condensed and the resulting condensate is recycled to the reactor and wherein the stream containing the inert gas and stripped gases, emerging from the stripper, is subjected to condensation, and the condensate of stripped gases is recycled to the reactor and the inert gas (which is not condensed) is washed, compressed and recycled to the stripper. The decomposition of the ammonium carbamate may be either a thermal decomposition or be carried out by means of a countercurrent stream of heated gaseous ammonia. The reactor is suitably operated at a temperature of 150‹ to 300‹ C. and pressure of 50 to 300 atmospheres, the pressures in the reactor, decomposer and stripper being preferably the same.