The NPK fertilizer rotary drum granulator is the core equipment in an NPK fertilizer production line, specifically designed for the production of nitrogen, phosphorus, and potassium compound fertilizers. Its core principle utilizes the centrifugal force, gravity, and friction generated by the rotating drum to gradually form uniform and regular granules from loose dry powder raw materials through wetting, agglomeration, and rolling. The entire process requires no high-pressure extrusion, is simple, and is compatible with various NPK formulas, making it the preferred equipment for small and medium-sized fertilizer plants.

Raw material pretreatment is a prerequisite for granulation and directly determines granulation efficiency and granule quality. NPK raw materials are mostly dry powders such as urea, monoammonium phosphate, and potassium chloride, which require three steps of processing: crushing, mixing, and wetting. The pulverized raw material must have at least 80% pass through a 40-mesh sieve to ensure uniform particle size. During mixing, all raw materials must be precisely stirred according to the formula to avoid nutrient imbalance in the particles. During wetting, appropriate amounts of water, steam, or a small amount of binder must be added to control the material's moisture content at 18%-25%, aiming for a consistency where it "can be formed into a ball when squeezed but does not crumble when lightly pinched," ensuring both the material's stickiness and preventing excessive moisture from causing it to stick to the walls.
The core granulation stage is crucial for the transformation of the raw material and is entirely accomplished by the continuous rotation of the drum. The pre-treated, moistened material is fed into a drum tilted at 3°-5°, rotating at a uniform speed of 5-20 rpm. Lifting plates inside the drum continuously lift and drop the material. Through repeated collisions and tumbling, fine powder particles adhere to each other, forming 1-2mm "seed balls," the starting point for particle formation. As the drum continues to rotate, the seed balls continuously absorb surrounding powder, gradually growing larger during rolling. The rubber lining inside the drum effectively prevents particle sticking and scaling, ensuring rounded particles. When the granules reach the target particle size of 2-6mm, they are discharged from the drum outlet. Unformed fine powder is recycled and reintroduced into the drum for granulation, significantly improving raw material utilization. The freshly discharged granules contain a high moisture content and require drying and cooling to remove excess moisture and lower the temperature, preventing clumping during storage. Finally, unqualified broken and large particles are removed by sieving, and anti-caking agents are added as needed to obtain qualified NPK granular fertilizer.
Throughout the granulation process of the rotary drum granulator, the drum speed, tilt angle, and material moisture content are key control parameters, requiring precise adjustment based on the raw material formula. The rotary drum granulation process is simple, requires low equipment investment, and can flexibly adapt to different NPK raw material ratios. It solves the problems of powdered fertilizers easily clumping and uneven fertilization, while also increasing the added value of fertilizers, providing agricultural production with high-quality compound fertilizers that are nutrient-uniform and easy to store and transport.