| 摘要 |
1,214,591. Urea. MITSUI TOATSU CHEMICALS Inc. 4 March, 1969 [19 March, 1968], No. 11467/69. Heading C2C. Urea is synthesized from ammonia and carbon dioxide by (a) reacting ammonia and carbon dioxide in a first urea-synthesis zone, (b) passing the effluent from this zone, which contains urea, water, ammonium carbamate, gaseous ammonia and gaseous carbon dioxide, to a heat-recovery zone wherein heat is removed and an ammonia and carbon dioxide containing condensate is obtained, and (c) reacting the ammonia and carbon dioxide in this condensate in a second urea-synthesis zone. The heat-removal in step (b) may be effected by indirect heat exchange between the effluent from step (a) and a stream of water, steam thereby being generated. The effluent from the urea-synthesis zones may be subjected to a number of distillation and absorption steps to recover the urea and a number of the by-products may be recycled. |
