Hydraulic Roller Granulator
The hydraulic double-roller granulator employs a dry roller-pressing process. It utilizes a pressurized feeding method to force material through the gap between two counter-rotating rollers, compressing it into sheets or blocks. These are subsequently crushed, shaped, and screened to produce granules that meet specific application requirements. The equipment enables direct granulation of dry powder without the need for additives or subsequent drying stages. When integrated into a fertilizer processing line with auxiliary equipment, it facilitates continuous, automated production with significant output capacity. Capable of granulating materials at ambient temperature, the machine is suitable for processing single-nutrient fertilizers as well as multi-nutrient compound fertilizers based on materials such as ammonium bicarbonate, urea, ammonium chloride, ammonium phosphate, and potassium chloride.

Component Composition and Functional Zoning

From a process perspective, the hydraulic double-roll granulator comprises the following functional units:

(I) Feeding unit: Includes a hopper and a volumetric feeder. It utilizes variable-frequency stepless speed control to precisely regulate the material feed rate.

(II) Pre-compression and degassing unit: Includes a screw pre-compression device; material undergoes degassing and screw pre-compression before entering the roll gap.

(III) Extrusion and forming unit: Consists of a fixed roll and a movable roll. One set of roll bearing housings is fixed within the frame, while the other moves along guide rails, held tightly against the first set by hydraulic cylinder pressure. The roll surfaces feature regularly arranged pockets of uniform shape and size.

(IV) Hydraulic drive unit: Includes a hydraulic pump station, cylinders, and a control valve assembly; it provides an adjustable pressure range of 10–30 MPa.

(V) Crushing and granulation unit: Breaks the extruded material sheets or flakes into smaller fragments.

(VI) Screening and material return unit: Includes a vibrating screen and a return screw conveyor. Qualified granules are discharged directly, while undersized fines are returned for re-granulation.
Production Line Roles and Process Flow

The hydraulic double-roller granulator serves as the core granulation unit in fertilizer and chemical production lines. The complete dry granulation process flow consists of: raw material crushing → batching and mixing → hydraulic double-roller granulation → crushing and sizing → screening → packaging.
This equipment fundamentally revolutionizes the production model associated with traditional wet granulation. Conventional methods—such as disc granulation and rotary drum granulation—rely on wet processing, requiring subsequent drying and cooling stages that entail high energy consumption and complex workflows. In contrast, the hydraulic double-roller granulator utilizes a dry, single-step forming process; the resulting granules are hard and structurally stable, allowing for immediate screening and packaging, thereby eliminating the need for drying equipment and associated fuel costs. The time from raw material input to finished product output is merely 1–2 hours. The unit integrates seamlessly with upstream and downstream equipment—such as crushers, batching systems, screening machines, and packaging scales—to form a complete automated production line. The feeding system features variable-frequency stepless speed control, enabling a single operator to manage multiple machines; the system is characterized by low labor intensity and the capability for long-term, continuous operation.

Description of the Granulation Process and Stages

The granulation process of the hydraulic twin-roll granulator can be divided into the following stages:

Feeding and distribution stage: Raw materials are evenly delivered to the feed hopper via a volumetric feeder. Dry powder enters from the top of the equipment, undergoes degassing and screw pre-compression, and then enters the twin-roll assembly. The feeding process must be steady and continuous to prevent clogging.

Nip and compression stage: The two rolls rotate in opposite directions at the same speed. Dry powder material enters the gap between the rolls continuously and evenly—driven by gravity and forced feeding—initially flowing freely before being gradually drawn into the roll pockets within the nip zone. As the rolls continue to rotate, the space occupied by the material decreases, leading to progressive compression and the attainment of the required forming pressure. Under extrusion, air between the powder particles is expelled, causing the particles to rearrange and eliminating inter-particle voids.

Shape retention and release stage: The pressure gradually decreases, and the formed briquettes are released from the roll pockets due to elastic recovery and gravity.

Crushing and screening stage: The briquettes enter the crushing, sizing, and screening unit, yielding qualified granular product. Fine powder and substandard granules are conveyed by a return screw back to the elevator inlet, where they mix with fresh material in the pre-feed hopper to re-enter the process cycle.

Operational Guidelines and Key Control Points

Standardized operation of the hydraulic twin-roll granulator is crucial for ensuring granulation quality and equipment longevity:

Pre-start preparation: Conduct a comprehensive inspection before each startup to ensure the hydraulic oil level is normal, there are no leaks, and all components are securely fastened. Check the gap between the rolls and adjust it appropriately based on material characteristics. The granulator must be started under no-load conditions; starting with material inside is strictly prohibited. Prevent any iron-containing foreign objects from entering the machine to avoid fracturing the roll shafts.

Feed regulation: The feeding process should be steady and continuous to prevent clogging. Avoid overfeeding or underfeeding, as this can compromise processing results. Adjust pressure, roll gap, and feed rate via the PLC control cabinet.

Operational monitoring: During operation, regularly monitor parameters such as hydraulic oil temperature, pressure, and current to ensure they remain within normal ranges. Closely observe the equipment for smooth operation and check for any abnormal vibration or noise. If any abnormality is detected, shut down the machine immediately to inspect and identify the cause of the fault.

Shutdown procedure: Stop the feed before shutting down; allow the machine to run idle briefly to clear out internal material before cutting off the power.