METHOD OF INDUSTRIAL SYNTHESIS OF UREA Russian patent published in 1995 - IPC

FIELD: organic chemistry. SUBSTANCE: industrial synthesis of urea from ammonia and carbon dioxide is carried out at high temperature and pressure values. Process involves: reaction between high purity reagents in the main reactor and reaction in additional reactor between less purified reagents which take part repeatedly in synthesis. Reaction in the main reactor with high yield of urea is carried out under high pressure 300-400 kg/сm² and at flesh-stage at lower pressure (by 40% of value in the main reactor) and preferably at 200 kg/сm². Flow of gaseous products obtained at the flesh-stage is used in additional reactor under pressure lower than 200 kg/cm². Flows of liquid products from the flesh-stage and from additional reactor were fed to the site for utilization of condensation heat. The latter involves two stages of carbamate decomposition, and the first decomposition stage is carried out successively under pressure 60-100 kg/сm², preferably, at 50 kg/сm², and the second stage is carried out at 60-100 kg/сm², preferably, at 20 kg/сm². Concentrated carbamate solution from the first step of decomposition is fed to the additional reactor, and less concentrated ammonium carbamate solution from the second decomposition step is combined with vapors from the first decomposition step and distilled. Urea solution from the second decomposition step is subjected for quick evaporation at adiabatic regime at 3-6 kg/сm². Formed vapor-gaseous mixture is condensed, and condensate is distilled at the second stage of carbamate decomposition. Solution of purified urea is concentrated under vacuum. Yield of urea in the main reactor is 80%, and in additional one - 20% using regenerated components. EFFECT: improved method of urea production. 3 cl, 1 dwg, 2 tbl