2026/06/27
The strength of granules produced by double roller press granulators depends primarily on three factors: extrusion pressure, material condition, and feed rate. Excessive strength risks damaging the rollers, while insufficient strength leads to crumbling or pulverization; precise, multi-level adjustments can be made to meet the production requirements for organic and compound fertilizers.
First, adjusting the gap between the two pressure rollers and the extrusion pressure is the most direct method for controlling strength. Synchronously tightening the adjustment screws on both sides of the fertilizer production machine narrows the roller gap and increases extrusion pressure; this ensures the material is more fully compressed within the die holes, significantly enhancing granule compactness and compressive strength. Conversely, loosening the screws widens the gap and reduces pressure, resulting in loose, fragile granules. Adjustments must ensure uniform movement of the left and right screws to prevent uneven roller wear or the production of broken material on one side. Some models feature hydraulic boosting systems; increasing hydraulic pressure can significantly raise extrusion force—suitable for materials with low natural binding properties—though pressure must be increased gradually to avoid overloading and damaging bearings or roller shells.
Second, controlling the feed rate ensures a stable fill level. Using a variable-frequency drive (VFD) for the screw feeder ensures sufficient material supply and complete filling of the die holes, resulting in dense extrusion and higher granule strength. Insufficient feeding leads to incomplete die filling and internal voids, making granules prone to crumbling upon slight impact. Forced overfeeding must be avoided, as it can cause the machine to stall or lead to roller shell cracking due to overload; maintaining a uniform, continuous feed is essential for consistent granule strength.
Third, adjusting the raw material formula and moisture content. If material moisture is too low, the powder lacks a binding medium, resulting in loose, weak granules; adding an appropriate amount of water or binders—such as bentonite, humic soil, or starch—can improve binding strength. Conversely, if moisture is too high, the material becomes soft, tends to stick to the rollers during extrusion, and produces granules that deform easily; for organic fertilizers, maintaining moisture between 22% and 28% yields optimal strength. Adding appropriate amounts of inorganic elemental fertilizers can also increase granule hardness.
Fourth, employing auxiliary post-processing methods for reinforcement. After extrusion, the wet granules enter a low-temperature dryer to remove excess moisture and solidify their internal structure; this significantly enhances the strength of the finished product, making it resistant to crumbling during transport and handling. Production begins with baseline adjustments to roll gaps and hydraulic pressure combined with stable feeding, followed by the optimization of material moisture content and binding additives; this multi-faceted approach yields durable, high-hardness granules that do not easily break.
