The finished granule size of a double roller press granulator is regulated by three key factors: the specifications of the mold holes on the roller shells, the gap between the rollers, and the feed pressure. Each adjustment method results in specific changes to granule size; the process is simple and suitable for controlling the size of organic and compound fertilizer granules.

I. Replacing roller shells/mold holes (Major adjustment; changing the base granule size). The base size of the granules is determined by the molding holes on the roller shells, which sets the upper limit for granule size. Standard mold hole specifications range from 2 mm to 8 mm; smaller holes are suitable for specialty fertilizers for cash crops, while larger holes are used for slow-release fertilizers for field crops. To significantly alter the finished granule diameter, the entire set of roller shells must be replaced with ones featuring the desired hole size; this changes both the granule shape and thickness simultaneously. This method offers the widest adjustment range and is ideal for long-term, consistent production of specific product sizes, ensuring uniform granule specifications without size variation.

II. Adjusting the gap between the two rollers of the fertilizer roller press granulator (fine-tuning granule thickness and compactness). Gap adjustment screws are located on both sides of the equipment; rotating these screws alters the distance between the two rollers. Increasing the gap results in thicker, larger, and less dense granules, while decreasing the gap yields thinner, smaller, and denser granules. The gap must be adjusted synchronously on both the left and right sides to ensure the rollers remain parallel, thereby preventing uneven extrusion that could lead to defective or fragmented granules. This method allows for fine-tuning thickness without altering the granule diameter, making it suitable for making minor adjustments to granule size and reducing the volume of recycled fines when using the same die holes.

III. Adjusting feed pressure (Auxiliary control of the molding ratio). The associated screw feeder allows for feed rate adjustments via a variable frequency drive. A high feed rate ensures full mold hole filling, resulting in larger, intact granules; insufficient feeding leads to incomplete filling, often producing small fragments or fines. Controlling raw material moisture content is also crucial: moderate moisture facilitates proper molding, whereas excessively low moisture causes the powder to remain loose, leading to an increase in small granules and fines. IV. Integrated screening to control finished product specifications: Even after adjustment, a small amount of fines is inevitably produced; a downstream rotary screen—fitted with interchangeable mesh sizes—separates compliant granules from the fines. The fines are then recirculated for re-extrusion to ensure uniform final granule dimensions. During routine production, fine-tuning of granule size is primarily achieved by adjusting the roll gap, while significant size changes require replacing the roll shells. Combined with uniform material feeding, these measures stabilize granule specifications and increase the yield of compliant finished products.