Synthesis of urea
AssigneeMitsui Toatsu Chemicals, Inc.
InventorsHiroshi Ono, Hidetsugu Fujii, Shigeru Inoue
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Abstract
The specification describes a process for synthesizing urea. The process comprises reacting ammonia and carbon dioxide in a molar ratio of 3:1-5:1 and at a pressure of 150-250 Kg/cm.sup.2 G, subjecting the resultant reaction mixture to a stripping step using gaseous carbon dioxide at a pressure substantially equal to the urea synthesis pressure and a temperature of 195.degree.-210.degree. C. to remove unreacted ammonia and unreacted carbon dioxide contained in the reaction mixture so that the content of unreacted ammonia is lowered to 10-15% by weight. This invention ensures a high conversion ratio from carbon dioxide to urea, considerably little formation of biuret during the stripping step, and reduced consumption of high pressure steam.
Claims5
A process for synthesizing urea comprising reacting ammonia and carbon dioxide in a molar ratio of 3:1-5:1 and at a urea synthesis pressure of 150-250 Kg/cm.sup.2 G to form a urea synthesis effluent containing urea, water, unreacted ammonia and unreacted carbon dioxide, subjecting said urea synthesis effluent to a stripping step using gaseous carbon dioxide at a pressure substantially equal to said urea synthesis pressure and at a temperature of 195.degree.-210.degree. C. to separate unreacted ammonia and carbon dioxide therefrom and thereby to obtain a urea solution containing 10-15% by weight of unreacted ammonia, further separating unreacted ammonia and carbon dioxide from the urea solution at a pressure of 10-30 Kg/cm.sup.2 G and a temperature of 150.degree.-170.degree. C. to obtain a urea solution containing 8% by weight or less of unreacted ammonia, and subjecting the latter urea solution to a separation step of unreacted ammonia and carbon dioxide which step is operated at a pressure lower than the latter pressure of 10-30 Kg/cm.sup.2 G.
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