Concentrated Urea solution comes from the Evaporator and is sprayed downwards from the top of the Prilling Tower. The inlet air draft rising inside the Prilling Tower cools the falling, sprayed solution, which then forms into solid ‘prills’. The prills then continue to fall, to the bottom of the tower for collection.
At the top of the tower, around the sprayer heads, the Urea microprills (100 microns ) and average 1 micron diameter mist are entrained by the air going on up to the roof fans and thus out to atmosphere.
Mist loads can vary greatly according to the design and age of the tower, from 100 mg/m3 to more than 1,000 mg/m3.
Product loss (collected liquid can be recycled within the plant)
Then one of the following :
Note: demineralised water spraying of any filter medium is required to dissolve formed crystals and so prevent blockage.