What are the material requirements for a rotary drum granulator?

As a core piece of equipment in the production of compound fertilizers and organic fertilizers, the rotary drum granulator is widely used in large-scale production due to its simple structure and high capacity. Its granulation effect directly depends on whether the material characteristics meet the standards. To ensure efficient and stable operation of the equipment and produce granules with uniform particle size and qualified strength, the material must meet four core requirements: particle size, moisture content, adhesiveness, and component compatibility. None of these can be neglected.

A reasonable particle size distribution is the foundation of granulation. Rotary drum granulation relies on a "snowball" granulation principle, requiring a scientific ratio of coarse and fine materials. Fine powder (particle size ≤ 0.15mm) should account for 60%-70% to quickly absorb binders and form particle nuclei; coarse powder (particle size 0.15-0.5mm) should account for 30%-40% to fill the gaps between the fine powder and improve particle strength. Too much fine powder can easily generate dust and make the particles too dense; too much coarse powder will make it difficult to bind and form particles, easily resulting in broken particles. Particle size uniformity needs to be adjusted using screening equipment.

Precise moisture control is key to granulation. Suitable humidity allows materials to form stable granule cores. Different materials have different humidity requirements: the moisture content of compound fertilizer raw materials needs to be controlled between 15% and 25%, while that of organic fertilizer raw materials is 25% to 35%. Excessive humidity causes materials to stick to the walls, clump together, and deform the granules; insufficient humidity results in excessive fluidity, making it difficult to bind, and producing small, loose granules. This can be flexibly controlled by adding dry materials or spraying water.

Adequate binding properties are essential for granule formation. The material itself needs to have a certain degree of binding property. For example, well-rotted livestock and poultry manure contains humus and has natural binding properties; raw materials with poor binding properties, such as straw powder and sawdust, require the addition of binders such as bentonite and starch. Insufficient binding properties lead to loose and brittle granules, while excessive binding properties cause agglomeration. The type and amount of binder must be precisely selected based on the characteristics of the raw materials.

Ingredient compatibility is a prerequisite for ensuring product quality. Mixed materials must avoid adverse chemical reactions. For example, mixing acidic and alkaline raw materials can easily produce ammonia, leading to increased granule porosity and nutrient loss. Simultaneously, it is essential to ensure uniform composition. Uneven distribution of nitrogen, phosphorus, and potassium in compound fertilizers can lead to nutrient imbalances in the finished product. Scientific formulation and prior testing for component compatibility are necessary.

In summary, strictly controlling the particle size, moisture content, adhesiveness, and component compatibility of materials, combined with optimized equipment parameters, is crucial to fully leveraging the advantages of rotary drum granulators, reducing losses, increasing production capacity, and producing high-quality granular products.