Complex fertilizers such as NPK, are not well-defined products made by using a standard process.
NPK mixture fertilizers are formulated by agricultural scientists to increase the output of the crops by giving it specific and exclusive blend of plant nutrients like a balanced diet for human.
All the major plant nutrients like Nitrogen, Phosphorus and Potash are mixed in different ratios to make it suitable for specific crops. These specific ratios of NPK & S are called grades.
The product name “NPK” is normally followed by three numbers to indicate the percent of N, P2O5 and K2O which the product contains, e.g. 24–6–12 indicates that this particular grade contains 24% N (nitrogen compounds), 6% P2O5 (phosphorus compounds) and 12% K2O (potassium compounds).
Complex NPK fertilizers are manufactured by producing slurries of ammonium phosphates, to which potassium salts are added prior to granulation or prilling.
The raw materials, in the weight belts conveyors, are weighed and moved to Mixer for producing a homogenous mixture. The material is mixed with the recycle material and taken for granulation in granulation drum where the partial granulation is achieved with very fine jet of water spray. The fine powder gets deposited on small granules. This process can be controlled to produce particle size as per the demand of the customers.