| 摘要 |
1423977 Urea I MAVROVIC 14 May 1974 [13 June 1973] 21384/74 Heading C2C Urea is synthesized from ammonia and carbon dioxide in a process in which a first aqueous urea solution comprising urea, ammonium carbonate, ammonia and water is produced at elevated temperature and pressure, the process comprising (a) reducing the pressure and heating the first aqueous urea solution in a first carbamate decomposing zone to decompose from 10 to 60% by weight of the ammonium carbamate therein to ammonia and carbon dioxide, (b) heating the first aqueous urea solution in a second carbamate decomposing zone to decompose additional ammonium carbamate to ammonia and carbon dioxide and to produce a liquid phase comprising urea, water, residual ammonium carbamate and residual excess ammonia, and a gaseous phase comprising carbon dioxide, ammonia and water, (c) separating the gaseous phase and the liquid phase, and (d) contacting this gaseous phase, urea and fresh carbon dioxide to form ammonium carbonate in indirect heat exchange with the first aqueous urea solution, the quantity of urea so contacted being such that the reaction product has a urea to water weight ratio of 0À1 : 1 to 1À6 : 1. |
