Process Flow Diagram (video)

[Audio] Process Flow Diagram for Urea Production with Full Liquid Recycling Carbon dioxide from the gas tank having previously passed through Compressor (2) is supplied to Mixer (8) at a pressure of 200 bar and a temperature of 35 degrees celsius. To prevent corrosion of the apparatus carbon dioxide is mixed with oxygen in an amount of 0.6-1 volume %. Liquid ammonia from the warehouse under a pressure of 25 bar is supplied by Pump (4) to the Liquid Ammonia Collector (5) which also receives return liquid ammonia from Condenser (21) through Receiver (22). From the collector liquid ammonia is pumped under a pressure of 200 bar and sent through Heater (7) to Mixer (8). Liquid ammonia carbon dioxide and water are supplied to the mixer in a molar ratio of 4.5:1:0.5. The mixer is designed to thoroughly combine all three components resulting in the formation of ammonium carbamate. From the mixer the melt enters the Synthesis Column (9) where urea is formed at 200 degrees celsius and 200 bar. The residence time of the reaction mixture in the synthesis column is 45 minutes. Under these conditions the degree of conversion of ammonium carbamate to urea is 65%. The urea melt formed in the synthesis column is throttled from 200 bar to 20 bar and sent to the first-stage distillation unit. The distillation unit consists of a Rectification Tower (13) a Heater (14) and a Separator (15). Before the melt enters the Rectification Tower of the first-stage distillation it is heated to 140 degrees celsius by gases from Separator (15) which are used to evaporate part of the ammonia from the melt. The liquid phase from the distillation column goes to Heater (14) where the steam is heated to 160 degrees celsius. From the heater the vapor-liquid mixture enters Separator (15) where the gas and liquid phases are separated. The liquid phase from Separator (15) is sent to a similar second-stage distillation unit and the gaseous phase flows down the Rectification Tower (13). In the rectification tower the gas phase is mixed with gaseous ammonia released from the melt during throttling and sent to Washing Tower (16). The washing tower is irrigated with liquid ammonia which is supplied to the washing column for temperature regulation. Pure gaseous ammonia from the washing column at a temperature of 50°C enters the First-Stage Condenser (26) where it is condensed and discharged into the Ammonia Collector (5) for return to the cycle. The liquid phase from the washing column which is a solution of ammonium salts concentrated at a temperature of 105°C enters Plunger Pump (17) and is supplied to the mixer under a pressure of 200 bar. Gases with a small ammonia content that are not condensed in the condensers of the first and second stages are sent to Absorber (30) and then to Desorber (36) for purification before being released into the atmosphere. The liquid phase is a 70-72% urea solution and is sent for processing into the finished product. The liquid phase from the Second-Stage Separator (22) enters the Vacuum Evaporator (38) where due to selfevaporation it condenses to 74-76%. Then in film-type Evaporators (42) and (43) the solution is evaporated to 97-98.5%. The melt is then sent to the Granulation Tower (45) and subsequently to packaging..