The NPK compound fertilizer production line uses steam to add heat and moisture during rotary drum granulation.
Steam provides the heat and moisture needed for the mixed materials to bind together and form granules. The main stages of production are outlined below:

Raw Material Preparation and Batching

Urea, ammonium phosphate, potassium chloride and any required fillers are first crushed to the appropriate size. The automatic batching system then weighs each material according to the formulation before sending the ingredients to the mixer, where they are blended evenly and prepared for granulation.

Rotary Drum Granulation

The blended material enters the rotary drum granulator while saturated steam is introduced. The steam raises the material temperature, helps dissolve soluble salts and provides the liquid phase needed for granulation. As the drum rotates, the material is continuously rolled and pressed, causing the particles to bind together and form granules with sizes that range from 2 to 4 mm.

Drying, Cooling, Screening and Recycling

Wet granules first pass through a rotary dryer supplied with hot air to remove excess moisture, then enter a rotary cooler to lower the temperature, reduce caking and improve granule strength. After cooling, the material is separated by size in a rotary screen. Granules that are within the required size range continue to the next production stage, while fine particles return directly to the granulator as seed material and oversized granules are crushed before being sent back into the process. The return ratio must be adjusted carefully because it is a key factor in controlling production output.

Coating and Packing

Granules that meet the size requirement enter the coating drum, where anti-caking oil, powder or microbial additives can be applied according to the fertilizer formula. The finished product is then weighed automatically, packed and sent to storage.