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Urea Production Process



The urea production uses CO2 gas and NH3 liquid as raw materials supplied from Ammonia plant. Urea production process is divided into six units, they are:

(1) Synthesis Unit

This unit is the most important part of the Urea plant which synthesizes Urea by reacting Liquid NH3 and CO2 gas in the Urea Reactor and liquid recycled carbamat produced by Recovery unit is also coming into this reactor. At Synthesis, the operating pressure is 175 kg/cm 2  G. The Urea Synthesis result is sent to the Purification to detach the ammonium carbamat and its the excessive ammonia after being stripped by CO2

(2) Purification Unit

Unconverted ammonium carbamat and the excessive ammonia at Synthesis Unit are decomposed and separated by pressure and heat in two depressurizing steps; 17kg/cm 2 G and 22.2 kg/cm 2 G. The decomposing result of CO2 gas and NH3 are delivered to the Recovery Unit, and the urea solution is sent to the crystallizer unit.

(3) Chrystallizer Unit

Urea solution from Purification unit is crystallized in this unit on vacuum basis. Then the urea crystal is detached at Centrifuge unit. The heat needed to evaporate water is either taken from the urea solution sensible heat, or crystallized urea heat and heat extracted from Urea Slurry circulation to HP Absorber from the Recovery unit.

(4) Prilling Unit

The crystallized urea from Centrifuge unit is dried to 99.8% weight with hot air, then delivered to the upper part of Prilling Tower to be melted and evenly distributed to all distributors, and from distributor is dropped down while being cooled by air from below and produces urea prill. Urea product is sent to the bulk storage by belt conveyor.

(5) Recovery Unit

Ammonia and CO2 gas detached in purification unit is taken back by 2 absorption steps by using mother liquors part of absorbent, which are then recycled to the synthesis unit.

(6) Condensate Process Treatment Unit

Evaporaing and detached water vapor in crystallizer is cooled down and condensated. Small part of urea, NH3 and CO2 is also condensed, which is then processed and decomposed in stripper and hydrolyzer. The CO2 and NH3 gas is resent to the purification unit to be recovered, while the condensated water is sent to the utility.