PURPOSE: To recycle and reuse the gaseous mixture composed mainly of NH3 and CO2, by reacting CO2 with excess NH3 at high temperature and pressure, heating the obtained urea synthesis liquid under specific pressure thereby separating the liquid into the gaseous mixture and urea, etc., and condensing the gaseous mixture in the presence of water.
CONSTITUTION: Urea is prepared by reacting CO2 with excess NH3 at high temperature and pressure. In the above reaction, the reaction liquid composed mainly of NH3, NH2CO2NH4, urea and water is subjected to the thermal decomposition under a pressure nearly equal to the reaction pressure, and separated into a gaseous mixture composed mainly of NH3 and CO2 and an aqueous solution containing urea and unreacted material. The gaseous mixture is condensed under a pressure nearly equal to the reaction pressure in the presence of a small amount of water, and the condensate is recycled to the reaction zone. The recycling operation is carried out with an ejector using a major part of recovered aqueous solution containing NH3 and CO2 obtained by the urea-separation process and a major part of newly supplied liquid NH3 as the pumping fluid, and sucking and compressing the condensation liquid of the gaseous mixture with the ejector.
MORIKAWA HARUYUKI
NAGAHAMA TAKASHI
FUJII HIDETSUGU
MITSUI TOATSU CHEMICALS
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