1977 Kaasenbrood The Urea Stripping Process – Stripping Technology, Phase Equilibria and Thermodynamics
The economy of the technical production of urea has been substantially improved through the recycling of unconverted reactants at synthesis pressure. Separation of these reactants from the urea synthesis solution is effected by stripping with carbon dioxide gas. The high pressure of the gases stripped off allows condensation at elevated temperature (150-170 °C). At this high thermal level all of the condensation heat developed can be recovered in the form of steam. The urea containing solution left after the stripping is processed in a low pressure recirculation stage, in which small quantities of ammonia and carbon-dioxide remaining in the solution are expelled, to be dissolved in water and recycled to the synthesis section. The urea solution left after the expansion is subjected to evaporation and granulation (e.g. prilling)….