CO2 Stripping Process
In CO2 stripping plants urea is synthesized at 140 bar and 180-185°C, with molar NH3/CO2 ratio of 2.95-3.0 in the reactor. CO2 conversion is 58-60%. The reactor effluent, containing unconverted ammonia and carbon dioxide in the form of liquid ammonium carbamate, is decomposed using the feed CO2 as the stripping agent. The gaseous ammonia and carbon dioxide are then partially condensed and recycled to the reactor. The heat produced by this condensation is used to generate 3.5 bar steam. The unreacted carbamate from the stripping section is thoroughly decomposed in a decomposition stage operating at 3 bar and is subsequently condensed to form a carbamate solution, which is recycled to the 140 bar synthesis section. Further concentration of the urea solution leaving the 3 bar decomposition stage takes place in the evaporation section.