Verfahren zur Herstellung von Harnstoff aus Kohlendioxyd und Ammoniak

摘要

Urea is produced from carbon dioxide and ammonia by a process according to which the ammonium carbamate appearing in the reaction product passing out of the autoclave is continuously dissociated into ammonia and carbon dioxide under pressure ranging between 50 kilogrammes per square centimetre and the and the synthesis pressure and at a temperature ranging between 80 DEG C. and the temperature of decomposition of urea by the application of heat and simultaneous addition of gaseous ammonia in counter current relationship, especially in which process the ammonia serving for the decomposition of the carbamate is constituted by the ammonia feeding the synthesis reaction increased by the amount which is withdrawn as an aqueous solution with urea from the dissociation zone. The preferred residence time of the reaction products in the reactor is preferably less than 30 seconds or more preferably less than 15 seconds. The invention is described with reference to two figures (not shown) and the example gives a mass balance and reaction condition details which include urea synthesis at 175 DEG C. and 135 kilogrammes per square centimetre, dissociation chamber temperature of 180 DEG C.