Double Roller Press Granulator

Equipment Introduction

Double roller press granulator is a widely used solid material granulation equipment in industries such as chemical, fertilizer, pharmaceutical, food, and building materials, and is the core of the entire extrusion granulation production line. It is a room-temperature granulation device that forces materials into shape through mechanical pressure. Its design concept is to directly compress powder materials into granules with a certain strength without adding binders (or with very little addition). As an advanced dry granulation process, double roller press granulator has been widely used in the fertilizer, chemical, pharmaceutical, and environmental protection fields due to its significant advantages such as high energy utilization, no need for a drying process, and low investment cost.

Equipment Structure

The double-roller press granulator is the core of the entire extrusion granulation production line. It is a room-temperature granulation device that forces materials into shape through mechanical pressure. Its design philosophy is to directly compress powder materials into granules with a certain strength without adding binders (or with very little binder).

Core Structural Components

Frame: Utilizing thickened channel steel or a cast base, it serves as the support platform for the entire machine, bearing the enormous reaction force during extrusion.

Power Drive System: Driven by an electric motor, transmission is made to the pressure roller shafts via a reducer, V-belt, and chain (or gear). Professional-grade equipment typically features a hardened gear reducer to handle high torque requirements.

Pressure Roller Assembly (Core): Contains a pair of parallel, counter-rotating alloy steel shafts. The shafts are fitted with specially heat-treated roller skins. The roller skin surfaces are engraved with spherical, strip-shaped, or flattened spherical grooves, determining the shape of the finished granules.

Feeding Device: Located above the pressure rollers, it is usually equipped with a forced feeder or gravity hopper to ensure that the material enters the extrusion zone evenly.

Crushing and screening system: The extruded flakes are broken up by the crushing shaft below and then enter the matching screening machine for grading.

Raw Material Requirements for the Equipment

Raw materials suitable for double roller press granulator generally possess a certain degree of flowability and compressibility, and are mostly powders or fine granules. This equipment has a high tolerance for raw materials, primarily including:

Fertilizers: Urea, ammonium chloride, ammonium sulfate, monoammonium phosphate, potassium chloride, potassium sulfate, and other compound fertilizer raw materials.

Inorganic powders: Lime powder, bentonite, zinc oxide, activated carbon, catalysts.

Organic materials: Dried livestock and poultry manure powder, humic acid, wood ash.

Equipment Working Principle

The working principle of a double-roll press granulator is physical extrusion molding, and the entire process can be divided into the following stages:

Stage 1: Uniform Feeding Various dry powder materials are fed into the hopper at the top of the equipment. After degassing and spiral pre-compression, they enter the double rolls. A forced feeder ensures that the material continuously and uniformly enters the extrusion zone between the two rolls.

Stage 2: High-Pressure Extrusion The two rolls rotate in opposite directions at the same speed. The material enters the arc-shaped triangular area between the two rolls and is gradually compressed as the rolls rotate. When the material reaches the geometric center line of the double rolls, it is subjected to maximum pressure—one set of roll shaft seats is fixed, and the other set is pressed together by a hydraulic cylinder. Under the extreme extrusion force of the double rolls, the material undergoes plastic deformation and is compressed into flakes or strips. The shape of the regularly arranged arc grooves (die grooves) on the roll surface determines the final particle shape (such as elliptical, flake, or strip).

Stage 3: Demolding and Crushing After being demolded between the rolls, the formed flake or block material flows by gravity to the crushing chamber at the bottom of the roll body. The dual-shaft hydraulic press in the crushing chamber breaks flaky materials into smaller pieces.

Fourth Stage: Screening and Return Material The crushed material is screened, and finished particles that meet the particle size requirements flow out of the machine through the discharge chute. The oversize material (large, non-compliant particles) is mixed with new raw material and re-enters the granulation process. With the continuous rotation of the motor and the continuous feeding of material, continuous batch production is achieved.

The extrusion pressure can be adjusted by the hydraulic cylinder pressure according to the needs of the granulation operation.

Granulation Process of Equipment

The granulation process of a double-roller press granulator belongs to the dry extrusion granulation process. Its core process parameters and control points are as follows:

1. Process Principle: The principle of dry granulation is physical extrusion combined with material self-adhesion—by extruding, air between powder particles is expelled, causing the particles to rearrange. Under high pressure, van der Waals forces, adsorption forces, crystal bridges, and intercalation forces are generated, causing the material to self-adhere into granules without the addition of any binder.

2. Key Process Parameters

Extrusion Pressure: Adjustable according to material characteristics; 15-18MPa for soft raw materials, 20-25MPa for hard raw materials

Roller Gap: Generally 1-1.5mm (0.5-1mm for organic fertilizer)

Material Moisture Content: 2%-15% for inorganic materials, 18%-28% for organic materials

Feed Particle Size: ≤0.5mm

Finished Particle Size: Φ2.5-Φ30mm adjustable

3. Process Features

Room temperature granulation, no heating or drying required

One-step molding, streamlined process

High particle density, high strength, high granulation rate (up to 95% or more)

Avoids high-temperature damage to heat-sensitive materials

No wetting agents added, ensuring product purity

Application of Equipment in Production Line

Double roller press granulators are typically used as the core granulation equipment in production lines, forming a complete production line in conjunction with upstream and downstream processes.

1. Typical Fertilizer Production Line Flow: Feeding → Crushing → Mixing → Buffering → Feeding → Granulation (Roller Extrusion Granulator) → Crushing → Screening → Shaping → Packaging → Finished Product

2. Advantages of Production Line Integration:

Employs a non-drying, ambient temperature process for one-step molding.

Compact and scientifically designed layout of the complete set of equipment.

No waste discharge, energy saving and consumption reduction, stable and reliable operation.

Low equipment investment, quick returns, and good economic benefits.

When integrated with other related auxiliary equipment, it can form a mechanized continuous production line with a capacity of 1.5-50 tons/hour.

Double-roll press granulators are powerful tools for the industrial-scale processing of fertilizers and powder materials. Their core characteristics of "cold extrusion, no drying, and low investment" make them the first choice for enterprises pursuing green and low-carbon production. In practice, efficient, stable, and long-term operation can be achieved through proper material moisture control and standardized equipment maintenance.

For specific model selection advice or equipment integration solutions, please feel free to contact us or discuss practical case studies.