The creation of NPK compound fertilizer is a meticulous journey that scientifically integrates nitrogen, phosphorus, and potassium. Each process impacts the nutrient balance and consistent quality of the final product.
The first step in production is raw material pretreatment. Basic raw materials such as nitrogen fertilizer (such as urea), phosphorus fertilizer (such as monoammonium phosphate), and potassium fertilizer (such as potassium chloride) are first finely ground in a chain mill to the desired fineness.
The next step is the mixing phase. According to the target formula, an automatic batching system precisely measures the various raw materials, which are then transported to a horizontal mixer for mixing. A properly timed mixing process ensures a uniform distribution of the three elements.
Granulation is a key step in shaping the compound fertilizer. Two common processes are used. A rotary drum granulator rolls the material within an inclined drum while steam or water is sprayed in as a binder, gradually forming spherical granules. This is suitable for large-scale production. A double roller press granulator, on the other hand, forces the material through a screw extruder, forming cylindrical granules that are then crushed and screened. This granulation yield is high and requires no drying, making it more suitable for small and medium-sized production needs.
After granulation, the wet granules first enter a rotary drum dryer, where hot air at a suitable temperature reduces the moisture content to an appropriate range to prevent clumping during storage. The dried granules are still hot and need to be cooled to room temperature in a cooler to prevent condensation in the packaging bags caused by residual heat.
The final stage is screening and packaging. The cooled granules are then graded by a vibrating screen. The fine particles that are screened are returned to the granulation stage for reuse. Qualified granules enter the film coating machine and are sprayed with an anti-caking agent. They are then weighed on an automatic packaging scale and packed into moisture-proof woven bags for quantitative packaging. Storage should be kept ventilated and dry.
In summary, the NPK compound fertilizer production line is a coherent process consisting of raw material pretreatment, ingredient mixing, granulation and molding, drying and cooling, screening and packaging. Each device performs its own function to accurately convert raw materials such as nitrogen, phosphorus and potassium into qualified fertilizers.