摘要 |
<p>In the synthesis of urea from ammonia and carbon dioxide at high pressures the off gases are used to prepare ammonium carbamate solution having a decreased water content which is recycled to the urea synthesis. The unchanged ammonium carbamate, ammonia and carbon dioxide are adiabatically expanded, and result in decomposition of part of the ammonium carbamate to yield off gases and liquors containing urea, further unchanged ammonium carbamate. The liquors containing the unchanged ammonium carbamate are separated from the gases and then heated to complete the carbamate decomposition, yielding further off gases which are combined with the previous off gases to give ammonium carbamate in a cooler condenser, the solution being recycled under pressure to the urea synthesis. The process may be repeated on the mother liquors. Specification 930,213 is referred to.ALSO:In the synthesis of urea from ammonia and carbon dioxide at high pressures, the off gases are used to prepare ammonium carbamate solution having a decreased water content which is recycled to the urea synthesis. The unchanged ammonium carbamate, ammonia and carbon dioxide are adiabatically expanded to cause decomposition of part of the ammonium carbamate and to yield off gases and liquors containing further unchanged ammonium carbamate. The liquors containing the unchanged ammonium carbamates are separated from the gases and then heated to complete the carbamate decomposition, yielding further off gases which are combined with the previous off gases to give ammonium carbamate in a cooler condenser, this solution being recycled under pressure to the urea synthesis. The process may be repeated on the mother liquors. Specification 930,213 is referred to.</p> |