| 摘要 |
<p>waste gases, esp. gases from the synthesis of melamine from urea, are introduced into a urea-synthesis plant by a procedure comprising a high-pressure part for the reaction of CO2 and NH3 to give NH4 carbamate and the partial conversion of this into urea, and a depressurising part with several stages of decreasing pressure for the recovery of unreacted NH3 and CO2 and their recycle in the form of an aqs. carbamate soln. to the high-pressure part, the CO2-contg. gas being absorbed in the carbamate soln. in a zone connected to the high-pressure part, where the NH3 CO2 wt. ratio is regulated at 0.78-1.25:1, the pressure is 15-60 atm. and the temp. is 120-165 degrees C.</p> |
