The common granulation processes of compound fertilizer include tower granulation, agglomeration granulation, extrusion granulation and spray granulation.
High tower granulation process is mainly used for the production of high concentration nitro compound fertilizer. It can directly use concentrated ammonium nitrate solution, eliminating the links of spraying granulation, and granular compound fertilizer eliminates the process of crushing operation. The granulation rate of fertilizer is high, the granules are easy to dissolve, and there will be no agglomeration, but the cost of granulation in high tower is high.
The agglomeration granulation process is divided into drum granulation production line and disc granulation production line.
Rotary drum granulation process has little restriction on compound fertilizer formulation, high production yield, low investment and fast construction speed. The drum granulation performance is reliable, the operation is stable, the maintenance is convenient, and the production cost is low. Rotary drum granulation production line can produce low, medium and high concentration compound fertilizer, suitable for cold and hot granulation. Rotary drum granulation equipment is favored by investors in small and medium-sized compound fertilizer plants and is widely used in compound fertilizer production.
The main equipment of disc granulation production line are disc granulator, chain crusher, mixer, automatic batching machine, rotary dryer, rotary cooler, packing machine, conveyor, etc. The disc granulator can adjust the inclination angle of the granulator to meet the needs of different particles, and its production capacity is smaller than that of the drum granulator. The raw materials for pelletizing in disc granulating production line are urea, ammonium chloride, ammonium sulfate, ammonium carbonate, common calcium, heavy calcium, monoammonium phosphate, diammonium phosphate, calcium magnesium phosphate fertilizer, potassium chloride, potassium sulfate, etc.
Double roller extrusion granulation production line is mainly used in extrusion granulation process of compound fertilizer. Powdery compound fertilizer enters between two pressing rollers and is extruded into flat spherical particles by counter-rolling. In the double roller press granulation production line, the fine quality of particles can be maintained without or with only a small amount of adhesives in the granulation process. The granulation process can be carried out at room temperature, which can save the consumption of dryer and cooler. The production equipment of double roller extrusion granulation mainly includes chain crusher, batching machine, mixer, conveyor, double roller extrusion granulator, packing machine, etc.
The slurry spraying granulation process uses slurry method. The slurry is sprayed into the equipment by heating and pumping. After the water in the slurry is vaporized and separated, the retained solid is formed into granular compound fertilizer. This process can be used not only to produce NPK compound fertilizer, but also to produce ammonium phosphate compound fertilizer.