Unie Van Kunstmestfabrieken B.v.

Stamicarbon B.v.

Petrus J Kaasenbrood

Johannes D Verstegen

Petrus Jm Van Nassau

An improved process and apparatus for the removal of ammonium carbamate from an aqueous urea solution wherein the aqueous urea solution is introduced into a stripping zone and caused to flow down a heat exchange wall as a thin film while being heated and contacted in counter-current relation with a gaseous stripping agent. The aqueous urea solution, while being stripped, is heated for at most 5 seconds at a temperature in the range of from 180.degree.-195.degree. C. and thereafter cooled to a temperature of from 155.degree.-170.degree. C.

Apparatus for the removal of ammonium carbamate from a urea-synthesis

Unreacted free ammonia and ammonium carbamate are removed from a urea synthesis solution efficiently by first heating the solution up to 205.degree.-250.degree. C and then, in a second, separate step, stripping the heated solution with a stripping gas but under adiabatic conditions to remove the unreacted materials. The process is applied as an integral part of a continuous urea preparation.

Process for preparing urea

A process for urea manufacture is described wherein the molar ratio of unreacted NH.sub.3 to CO.sub.2 (including NH.sub.3 and CO.sub.2 in the form of ammonium carbamate) in the carbamate reaction liquid phase is between 2:1 and 3:1, and the same ratio in the liquid phase in the urea autoclave is maintained between 3:1 and 6:1, control of the process being achieved by analysis of the gas phase and maintaining the NH.sub.3 to CO.sub. 2 molar ratio therein between about 1:1 and 6:1, preferably between about 1.5:1 and 3.5:1, in both the carbamate reactor and the urea autoclave.

Method for controlling the ammonia and CO.sub.2 ratios in a urea

An improved urea synthesis process is disclosed in which carbon dioxide and ammonia are reacted at 210.degree. to 245.degree.C under pressures of 250 to 600 atm., the gross molar NH.sub.3 /CO.sub.2 ratio in the liquid phase in the synthesis zone of the order of 2.5 and 8, the carbon dioxide and ammonia being reacted together in a synthesis zone then the resulting urea synthesis solution being stripped in a stripping zone which is in heat exchange relation with the synthesis zone through a wall, and the gas mixture resulting from the stripping is partially recycled to the synthesis zone.

Process for preparing urea from ammonia and carbon dioxide

Ammonium carbamate is decomposed and removed in the form of its gaseous components by contacting a urea synthesis solution comprising the carbamate with a stripping gas, such as carbon dioxide, the countercurrent stripping conducted at adiabatic conditions in the stripper unit. Urea synthesis solution to be treated is supplied at higher pressures and temperatures, at least 205.degree.C and at a pressure of at least 225 atm. Conveniently, the decomposition of the ammonium carbamate and the removal of the liberated gases are carried out at these temperatures and pressures so that the stripper is operative under the same conditions as well.

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Sittard, Netherlands

Petrus J Kaasenbrood