公开(公告)号：US4207256A

公开(公告)日：1980-06-10

申请号：US651569

申请日：1976-01-22

申请人： Shigeru Inoue ,  Tadao Shirasu ,  Hisashi Miyagawa

发明人： Shigeru Inoue ,  Tadao Shirasu ,  Hisashi Miyagawa

IPC分类号： C02F1/04 ,  C07C67/00 ,  C07C239/00 ,  C07C273/04 ,  C07C273/16 ,  C07C126/02

CPC分类号： C07C273/04

摘要： A process for treating water vapor generated in concentrating an aqueous urea solution wherein a urea synthesis effluent containing urea, unreacted ammonium carbamate and water from a urea synthesis zone is subjected to a plurality of decomposition stages, the pressures of which stages are stepwise reduced to decompose and separate substantially all of the unreacted ammonium carbamate from the aqueous urea solution. The aqueous urea solution which still contains small amounts of ammonia and carbon dioxide is concentrated to obtain crystalline urea or molten urea substantially free of water. The water vapor generated in concentrating said aqueous urea solution which contains small amounts of ammonia and carbon dioxide is cooled for condensation thereby forming a dilute aqueous ammonium carbamate solution which is subjected to rectification under a gauge pressure below 25 kg/cm.sup.2 to distil off a gaseous mixture of water vapor, ammonia and carbon dioxide, introducing the gaseous mixture into the unreacted ammonium carbamate decomposition stage using rectification under substantially the same pressure as the pressure of the rectification for the dilute aqueous ammonium carbamate solution to remove the water vapor from the gaseous mixture, and recovering the resultant ammonia and carbon dioxide together with a gaseous mixture of ammonia and carbon dioxide which is generated in the unreacted ammonium carbamate decomposition stage.

摘要翻译： 一种处理在浓缩尿素水溶液中产生的水蒸汽的方法，其中含有尿素，未反应的氨基甲酸铵和来自尿素合成区的水的尿素合成流出物经受多个分解阶段，其阶段的压力逐步降低以分解 并将基本上所有未反应的氨基甲酸铵与尿素水溶液分离。 将含有少量氨和二氧化碳的尿素水溶液浓缩，得到基本上不含水的结晶性尿素或熔融脲。 将含有少量氨和二氧化碳的所述含尿素水溶液浓缩产生的水蒸气冷却冷凝，从而形成稀释的氨基甲酸铵水溶液，该溶液在表压低于25kg / cm 2下进行精馏以蒸发气体 水蒸气，氨和二氧化碳的混合物，将气体混合物引入未反应的氨基甲酸铵分解阶段，在与稀氨基氨基甲酸铵水溶液的精馏压力基本相同的压力下，使用精馏从气态混合物中除去水蒸汽 并且将所得的氨和二氧化碳与在未反应的氨基甲酸铵分解阶段中产生的氨和二氧化碳的气体混合物一起回收。