PURPOSE: In the urea synthesis from carbon dioxide and ammonia, the content of ammonia and ammonium carbamate in the reaction mixture is directly detected at the outlet of the synthesis reaction tubes to keep the molar ratio of the starting materials to the required value and increase the urea yield.
CONSTITUTION: In the urea synthesis tube 1, carbon dioxide and a stoichiometric or excessive amount of ammonia are made to react at a temperature and a pressure for urea synthesis and the resultant reaction mixture is sent through pipe 13 to the stripper 2 at the same pressure where unreacting carbon dioxide and ammonia are separated by heating with steam 23 and/or stripping using carbon dioxide. The remaining solution is taken out of the pipe 14 as a urea aqueous solution. In the meantime, the above stripped gas is absorbed by the absorption solution fed from the previous stage and circulated through pipe 21. In this process, for example, a part of process flow is regularly taken out at the outlet A of the synthesis tube 1 to determine the ammonia and ammonium carbamate and calculate the molar ratio of NH2/CO2.
FUJII HIDETSUGU
INOUE SHIGERU
FUKUI AKITO
| JPS4710226A |