The conventional granulation plant is is central to the Casale NPK process.
The plant includes the following main items:
- A rotary drum granulator, in which the ammonium nitrate solution is sprayed over a bed of recycled product consisting of fines, dusts (collected from equipment cleaning), coarse ground grains, some recycled final products, filler (most often limestone or dolomite) and solid raw material if required (ammonium sulphate or calcium sulphate)
- At the outlet of the drum granulator the granules fall through a chute into a rotary dryer meeting a hot, co-current air flow coming from a dedicated heater. The residence time in the dryer is such to completely dry the AN product, which at the exit contains about 0.2 % H2O
- The product is then sent to a screen where it is divided into three parts: undersize, oversize and on-size product. Oversize granules are crushed, mixed with undersize ones and fed back to the granulator together with a portion of the marketable product in order to maintain a constant recycle flowrate
- On-size product is cooled down in a dedicated cooler. A suitable coating agent is added to prevent caking in the coating drum and then the product is sent to storage
- A dedusting and scrubbing system collects all the gaseous effluents of the plant and recovers ammonia and dust from them to prevent pollution and minimize losses. This scrubbing system is equipped with venturis and one or more cyclonic columns.
The plant takes in a wide range of feedstocks, including ammonium nitrate, urea, ammonium sulphate and ammonia for N; superphosphate (SSP, TSP, USP) and phosphoric acid as source of P; and potassium chloride (MOP) and potassium sulphate (SOP) as source of K.
If phosphoric and/or sulphuric acids are available, Casale Pipe Reactor technology is the preferred choice, with either a single pipe reactor located in the granulator (GPR) or the Dual Pipe Reactors process, with a Pipe Reactor in the granulator (GPR) producing NP slurry and a second one in the dryer (DPR) producing solid ammonium phosphate.