Concentrated Ammonium Nitrate (NH4NO3) 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 NH4NO3 decomposes into NH3 and HNO3 , which recombines quickly into NH4NO3 mist and is 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 150 mg/m3 to more than 2,000 mg/m3, and with a small particle size, e.g. 1 micron.
PROBLEMS TO SOLVE
Air pollution
Product loss (collected liquid can be recycled within the plant)
DESIGN SOLUTIONS
1st stage irrigated ‘Becoil’ Demister / ‘Becone’ Coalescer in 304 Stainless Steel or special alloy.
Then one of the following :
‘Becoil’ Demister in 304L Stainless Steel or Alloy 904L (this 2 stage mesh pad arrangement is commonly used in Russian technology plants where housings are placed around the top of the Prilling Tower).
BlueFil® meshpads as a single or multiple layer system, using ETFE mesh in a vertical or horizontal orientation, with appropriate spray irrigation. This design is most suitable for CAN Prilling Tower emissions.
Medium Velocity ‘Becofil’ Candle Filters, standing type F, with B12 Glass Fibre elements and 304L or 316L Stainless Steel structure.
High Efficiency, Brownian Diffusion ‘Becofil’ Candle Filters, hanging type HT or standing type F, with TGW15, B14W or B14 Glass Fibre elements and 304L or 316L Stainless Steel structure.
Note: demineralised water spraying of any filter medium is required to dissolve formed crystals and so prevent blockage.
