Four key considerations for producing organic-inorganic compound fertilizer via disc granulation

Organic-inorganic compound fertilizers combine the soil-improving benefits of organic matter with the rapid nutrient availability of chemical fertilizers. While a disc granulation production line is well-suited for this process, success depends on managing four critical aspects related to the dual nature of these "organic + inorganic" blends.

Proportioning determines the physical properties of the feed. The mixing ratio of organic materials to inorganic fertilizers directly affects the viscosity and flowability of the powder blend. An excessive proportion of organic matter leads to loose granules and a low granulation rate, while an excess of inorganic salts results in fragile granules and a high volume of recycled material (fines). In practice, formulations with an organic matter content of 30%–50% tend to yield the most stable granulation. Additionally, care must be taken with urea and ammonium nitrate, as they are highly hygroscopic; they should not be stored in a mixed state with high-moisture organic materials for extended periods.

Particle fineness must be balanced for both components. Organic materials should be processed through a semi-wet or cage fertilizer crusher to a fineness of 60–100 mesh, while inorganic fertilizers—if initially granular—should also be crushed to at least 80 mesh. A mismatch in fineness between the two can cause stratification within the granulation disc, where heavier components settle at the bottom and lighter ones float, leading to a disrupted material curtain and inconsistent granule quality.

Moisture control is more sensitive than it is for purely organic fertilizers. While the optimal moisture content for disc granulation typically ranges from 15%–25%, the presence of inorganic salts alters the material's sensitivity to water. Formulations with high urea content are highly hygroscopic—excess moisture causes the material to stick to the disc walls—whereas those with high potassium salt content have poor water retention, making granulation difficult if moisture levels are too low. Operators must dynamically adjust moisture based on the specific formulation, aiming for a consistency where the material "forms a clump when squeezed by hand but crumbles under light pressure."

Drying must be managed to prevent nutrient loss. Post-granulation drying is necessary, but excessive temperatures can cause urea to decompose and ammonium nitrogen to volatilize. Drying temperatures should be kept between 80°C and 100°C, avoiding prolonged exposure to high heat. Finally, the granules should be cooled before screening and packaging to prevent moisture absorption and caking.

In short: adjust the mix ratio to control physical properties, ensure fineness for uniformity, regulate moisture content according to the formula, and prevent nutrient loss during drying. By strictly managing these four key aspects, the advantages of the disc granulator—namely its gentle forming process—can be fully leveraged in the production of compound fertilizers.