METHOD FOR SYNTHESIS OF UREA FROM AMMONIA AND CARBON DIOXIDE (OPTIONS) Russian patent published in 2001 - IPC

FIELD: industrial inorganic synthesis. SUBSTANCE: process is carried out in reaction zone at high pressure and elevated temperature. Product is freed of a part of unreacted ammonia and carbon dioxide by evaporation and recycled by ejector into reactor. Evaporation-decomposition zone is operated at essentially the same pressure as in reactor. Subsequent zones operated under middle and/or low pressure conditions serve for purification of urea and simultaneous separation of residual carbon dioxide and part of residual ammonia contained in the stream. Aqueous solution of ammonium carbamate obtained in evaporation stage is completely or partially returned into evaporation zone. In another embodiment of process, in the first decomposition-evaporation zone, gas mixture is separated to be ejected into condensation stage and then into reactor, whereas liquid mixture is conveyed to subsequent decomposition-evaporation stages to yield concentrated urea. When necessary, evaporation agent (carbon dioxide or recycling gas stream from reactor) is used in decomposition-evaporation stage. carbon dioxide-into-urea conversion is superior to 70%. EFFECT: enhanced process efficiency. 21 cl, 2 dwg, 2 ex