Granulation Stage of NPK Fertilizer Production Line

In the NPK compound fertilizer production line, granulation is a crucial link between raw material proportioning and finished product output. It not only gives the fertilizer a regular physical form but also directly affects nutrient release efficiency and ease of application. Granulation requires the fine pretreatment of raw materials. Nitrogen, phosphorus, and potassium fertilizers, along with fillers, which have been crushed and screened, need to be thoroughly mixed according to a preset ratio to ensure that each nutrient is evenly distributed in the mixture. The mixed material needs to be adjusted to a suitable moisture content (usually 10%-15%). This parameter is fundamental to subsequent granulation – excessive moisture can easily lead to granule adhesion and clumping, while insufficient moisture makes it difficult to form a stable structure. At this point, the material is conveyed to the granulation machine, initiating the core step of morphological reshaping.

Currently, the mainstream granulation processes are mainly divided into two categories: rotary drum granulation and extrusion granulation. Rotary drum granulator uses a rotating drum to tumble the material while a binder is sprayed, causing the particles to adhere to each other and gradually grow into round, spherical granules. This process is suitable for large-scale production, producing granules with high strength and good flowability. Extrusion granulators use mechanical pressure to force materials into shape without the need for binders, making them suitable for fertilizers with high purity requirements. The granules are mostly columnar or flaky in shape. Regardless of the process used, strict control of parameters such as temperature, pressure, and rotation speed is necessary to ensure that the particle size is concentrated within the suitable range of 2-4 mm.

After granulation, the wet granules need to undergo post-processing steps including drying, cooling, and sieving. The dryer uses hot air to remove internal moisture from the granules, preventing mold and clumping during storage. The cooler lowers the high-temperature granules to room temperature, preventing moisture re-entry due to temperature differences during subsequent packaging. The sieving machine separates substandard fine powder from large particles using multiple layers of screens. The fine powder is returned to the granulator for regranulation, while the large particles are crushed and recycled, achieving efficient resource recovery.

The granulation process of NPK fertilizer is an organic combination of physical morphology optimization and nutrient efficiency enhancement. By precisely controlling the parameters of each stage, not only can high-quality fertilizers that are easy to store, transport, and apply be produced, but nitrogen, phosphorus, and potassium nutrients can also be released evenly in the soil, providing a solid guarantee for high and stable crop yields and becoming an indispensable key process in modern agricultural production.