2026/07/30
The uneven spherical shape of the granules produced by disc granulators has long been a problem that many organic fertilizer plants have been unable to solve. Pellets that are elongated, uneven in size, or rough-surfaced not only compromise commercial appeal but can also reduce efficiency in downstream drying and screening stages. The root cause often lies in a few seemingly simple adjustment details.
If pellets lack roundness, first check the disc rotation speed. The rotational speed of the disc in a disc granulator determines the trajectory and number of rotations of the material within the disc. Excessive speed (>20 rpm) subjects the material to centrifugal force, flinging it toward the disc edge; this results in insufficient rolling cycles and elongated pellets. Conversely, speeds that are too low (<10 rpm) cause material to accumulate at the bottom, preventing the formation of a continuous material curtain and leading to significant size variations. Dynamic adjustment based on material viscosity is recommended: use low speeds (13–15 rpm) for high-viscosity materials and medium-to-high speeds (16–18 rpm) for low-viscosity materials. Observe the process for 30 minutes after each speed adjustment and lock in the parameters only after pellet roundness improves.
Balancing the disc inclination angle and the liquid spray volume is more critical than adjusting either factor in isolation. The inclination angle determines material residence time, while the spray volume dictates the nucleation rate. A mismatch between the two inevitably leads to poor roundness. A steep angle (>50°) causes rapid material slippage, requiring a higher spray volume to accelerate pellet formation; a shallow angle (<40°) allows for thorough rolling, requiring a reduced spray volume to prevent pellets from becoming oversized. A combination of a shallow angle and low spray volume is recommended; this allows pellets to grow slowly and roll thoroughly within the disc, significantly improving the roundness of the final product.
Misalignment of the scraper blade can lead to uneven pellet quality. If the bottom scraper deviates from the disc center, it creates an asymmetrical material distribution—thick on one side and thin on the other. This subjects the pellets to uneven forces within the disc, resulting in significant variations in the roundness of the discharged pellets. Inspection method: After shutting down the machine, measure the thickness of the residual material on the disc surface. If the variation in material thickness exceeds 3 mm, the scraper position requires readjustment. It is recommended to align the tip of the bottom scraper with a point 10–20 mm outward from the disc center, position the side scraper close to the curved edge of the disc, and arrange the scrapers symmetrically on both sides..
