Rotary drum granulation is a mature, stable, and mainstream industrial process for manufacturing NPK compound fertilizers, well-suited for large-scale, continuous production. The production line provided by Huaqiang Heavy Industry is highly adaptable and achieves a high granulation rate, making it widely applicable for the production of compound fertilizers with various nutrient concentrations. The entire process consists of five key stages: batching and mixing, rotary drum granulation, drying and cooling, screening and coating, and final packaging—all of which are fully contained and controllable.

The process begins with batching and pre-mixing. Basic NPK raw materials—such as urea, monoammonium phosphate (MAP), and potassium chloride—are combined with necessary secondary nutrients, micronutrients, and binding agents, using an automated metering system to ensure precise proportions. The raw materials are pulverized to achieve uniform fineness and then fed into a twin-shaft mixer, where they are thoroughly blended to ensure an even distribution of nitrogen, phosphorus, and potassium—laying the groundwork for the subsequent granulation stage. The precision of the batching process directly determines the nutrient content of the final product and serves as the first critical checkpoint for ensuring fertilizer quality.
Rotary drum granulation is the core stage of an NPK fertilizer production line. The blended powder is continuously fed into an inclined rotary drum granulator. As the drum rotates at a low speed, the material inside is subjected to constant tumbling and friction. Saturated steam or atomized water is sprayed into the drum; through capillary action and adhesive forces, the fine powder gradually aggregates into "seed" granules. As these seeds continue to roll, additional powder adheres to them in successive layers, eventually growing into granules 2–4 mm in diameter. During production, a portion of the fine material is recycled back into the process; this stabilizes the granulation conditions and increases the granulation rate, resulting in round, compact granules that are resistant to breakage.
Because the freshly formed, wet granules have a high moisture content, they are passed through a rotary dryer, where hot air removes excess moisture. The drying temperature is strictly controlled to prevent the decomposition or loss of nutrients. Once dried, the hot granules enter a cooling unit to lower their temperature, which helps prevent caking during subsequent storage. After cooling, the material proceeds to the screening stage, where granules meeting the specifications move on to the next process. Oversized clumps and undersized fines are crushed and returned to the granulator, ensuring material recycling. Qualified granules may undergo a coating process—applying an anti-caking agent—to improve the fertilizer's flowability and extend its shelf life.
Finally, once nutrient content is verified to meet standards, the product is automatically weighed, sealed, and packaged as finished NPK compound fertilizer. The drum granulation process offers stable operation and high production capacity; it allows for flexible formula adjustments to produce fertilizers with varying nutrient ratios, catering to the diverse fertilization needs of field crops and cash crops alike. It is a highly regarded production method within the compound fertilizer industry.