How to use double roller granulator to make fertilizer pellets

Introduction to Double Roller Granulation

A double roller granulator is a type of machinery widely used in the agro-industry to produce fertilizer pellets. It is favored for its ability to process powdered materials into granules without the need for additional binders or moisture. This method is particularly well-suited for making compound fertilizer pellets, as it can create a uniform and dense product that is easy to handle and apply.

The Basic Mechanics of a Double Roller Granulator

Principle of Operation

A double roller granulator operates on the principle of extrusion. It consists of two opposing rotating rollers with a series of mold cavities carved into the surface. As the powdered material is fed into the machine, it is compressed between the rollers and forced into the mold cavities, where it is shaped into pellets.

Roller Configuration

The rollers are the heart of the granulator, and their configuration is critical to the process. They are typically made of high-strength materials to withstand the pressure of granulation and may have a variety of surface patterns depending on the desired pellet size and shape.

Preparing the Fertilizer Material

Formulating the Fertilizer

Before granulation, the raw materials for the fertilizer must be carefully formulated and mixed. The mixture typically includes nitrogen (N), phosphorus (P), and potassium (K), as well as other micronutrients tailored to specific crop needs.

Powder Preparation

The materials are then ground into a fine powder. This powder must have the correct particle size to ensure that it can be properly compacted into pellets by the granulator.

The Granulation Process

Feeding the Material

The powdered fertilizer is fed into the hopper of the double roller granulator. A conveying device, usually a screw conveyor, ensures that the material is consistently fed into the space between the rollers.

Roller Compression

As the rollers rotate, the material is pulled into the gap between them. The pressure exerted on the material as it passes through this gap compacts it into a dense, sheet-like form.

Pellet Formation

The compacted material then enters the mold cavities where it is shaped into ball pellets. The intense pressure within the molds ensures that the pellets are solid and durable.

Post-Granulation Processing

Sizing and Separation

Once the pellets are formed, they may need to be sized to ensure uniformity. Oversized or undersized pellets can be separated and either recirculated into the process or discarded.

Quality Control in Pellet Production

Testing Pellet Integrity

Regular quality checks are essential to ensure that the pellets meet the required standards. Tests are carried out to assess the integrity, size, and nutrient content of the pellets.

Adjusting Machine Parameters

If the pellets do not meet the desired specifications, adjustments are made to the machine parameters. This might involve changing the roller speed, pressure, or the particle size of the powder.

Packaging and Storage

Packaging the Fertilizer Pellets

Once the pellets have passed quality control, they are packaged in bags or bulk containers. Packaging must protect the pellets from moisture and other environmental factors that could degrade their quality.

Storing the Pellets

Proper storage is essential to maintain the efficacy of the fertilizer pellets. They should be stored in a cool, dry place, away from direct sunlight and extreme temperatures.


The double roller granulator is a highly efficient and cost-effective dry method for producing fertilizer pellets. By following a precise formulation, preparation, and granulation process, manufacturers can produce high-quality, uniform pellets that are easy to apply and provide essential nutrients to crops. The success of the granulation process depends on the careful control of the machine settings and the quality of the raw materials, ensuring that the final product meets the stringent demands of modern agriculture.  If you want to setup a double roller granulation plant, we can also provide you with extrusion granulation line cost.