NPK is a fertiliser where 27% of the product is N, P or K, made up of 3, 12 and 12%, respectively. Among the filters used in an NPK plant are those for Acidulation and Ammoniation duty, treating the exits from the decomposition of Phosphate rocks by HNO3 and P2O5, then the ammonia stage and the KCl stage reactions.
A second filter system is required after the pelletising spherodiser, generally the same design and specification as the reactors exits system.
HNO3 , P2O5 and some NH4NO3 particles
Load typically 10,000 mg/m3
Intermediate (NH4NO3 solution), & thus final, product loss