Disc Granulator

Disc Granulator

Equipment Introduction

The Disc Pelletizer/Pan Granulator is a wet physical granulation device that uses a rotating disc as its working chamber. It leverages the synergistic effects of centrifugal force, gravity, and liquid surface tension to form spherical particles from powdered or fine-grained materials under moist conditions through a rolling agglomeration mechanism.

The powdered material forms a dynamic tumbling bed under the combined force field (centrifugal force and gravity) generated by the rotating disc. Atomized liquid binder wets the particle surface, forming liquid bridges under surface tension. The process involves four stages: nucleation, layering, compaction, and rounding, ultimately forming dense spherical particles. The equipment utilizes the centrifugal force gradient caused by particle size differences to achieve self-classification. Qualified particles automatically overflow and are discharged, while unqualified particles remain in the disc to continue growing. This equipment features simple structure, flexible operation, low investment, high pelletizing rate, and low return ratio, and is widely used in the powder spheroidization processing of industries such as fertilizers, organic fertilizers, chemicals, and building materials.

Equipment Structure Components

1. Granulation Disc

Structure: Overall arc structure, reinforced with multiple radial steel plates at the bottom, sturdy, durable, and non-deformable.

Material: Lined with high-strength fiberglass (FRP) or stainless steel plate, thickness 3–8 mm.

Diameter Range: 1.0 m – 6.0 m (2.0 m – 4.5 m commonly used in industry)

Disc Edge Height: 200 – 450 mm, determines bed depth.

Surface Treatment: Disc surface can be coated with PTFE or polyurethane to prevent material adhesion.

2. Transmission Mechanism

Drive Method: Electric motor → Flexible belt drive → Reducer → Main shaft → Disc

Advantages of Flexible Belt Drive:

Smooth starting, reduces impact force

Overload protection, prevents equipment damage

Increased equipment lifespan

Reducer: Hardened cylindrical gear reducer, high transmission efficiency (>95%)

Main Gear: High-frequency quenched, hardness HRC 45–55, service life doubled

3. Scraper Device

Installation Location: Bottom and sidewall of the disc

Material: High wear-resistant alloy steel or tungsten carbide coating

Gap Setting: 2–3 mm (distance from disc surface)

Function:

Prevents material from sticking and accumulating on the disc surface

Keeps the disc surface clean and ensures uniform material tumbling

Assists in moving material towards the center or edge of the disc

4. Angle Adjustment Screw

Adjustment Range: Inclination angle 40° – 55°

Adjustment Method: Manual screw or electric push rod

Adjustment Accuracy: ±0.5°

Impact on Granulation:

Increased inclination angle → Shortened material residence time → Smaller particles

Decreased inclination angle → Increased material residence time → Bigger particles
5. Spray System

Nozzle Type: Atomizing nozzles (fan-shaped or cone-shaped)

Arrangement: Multi-point arrangement (usually 2–4 nozzles)

Spray Medium: Water, diluted molasses solution, liquid fertilizer, special binder

Control Method: Manual valve or automatic flow control

Spray Pressure: 0.2 – 0.5 MPa

6. Base

Structure: Thickened and heavy-duty welded steel plate structure

Features: Low center of gravity, good stability

Installation: Stable operation without anchor bolts (small equipment)

Working Principle of the Equipment

The working principle of the disc granulator can be summarized as "snowball-like agglomeration and granulation," and the entire process is divided into the following stages:

Stage 1: Wetting and Nucleation

After the powder enters the disc, it is wetted by spraying water or a binder. A thin water film forms on the surface of the powder particles. Due to the surface tension of water, the water and powder combine to form very small nuclei.

Stage 2: Rolling Growth

As the disc rotates, the nuclei are subjected to the combined effects of centrifugal force, friction, and gravity, moving along a parabolic trajectory. The nuclei continuously attract surrounding powder during rolling, gradually growing larger. This process is similar to a "snowball"—small particles adhere to material and grow larger as they roll.

Stage 3: Grading and Discharge

When the tilt angle of the granulating disc, the height of the disc edge, the rotation speed, and the moisture content are constant, particles of different sizes leave the disc edge and roll downwards at different release angles due to different gravitational forces. Particles that reach the target particle size are discharged from the disc edge under the action of centrifugal force; particles that do not meet the target size continue to roll and grow within the disc. The entire process repeats itself continuously, with new materials constantly being added and existing particles being continuously discharged, thus achieving continuous production.

Equipment Manufacturing Process

Applicable Industries and Typical Materials

1. Fertilizer Industry

Nitrogen Fertilizer: Urea, Ammonium Bicarbonate, Ammonium Chloride

Phosphorus Fertilizer: Monoammonium Phosphate (MAP), Diammonium Phosphate (DAP), Superphosphate

Potassium Fertilizer: Potassium Chloride, Potassium Sulfate

Compound Fertilizer: NPK Compound Fertilizer, BB Fertilizer, Blended Fertilizer

New Fertilizers: Slow-Release Fertilizer, Controlled-Release Fertilizer, Water-Soluble Fertilizer

2. Organic Fertilizer Industry

Livestock and Poultry Manure: Chicken Manure, Pig Manure, Cow Manure, Sheep Manure

Agricultural Waste: Straw Powder, Rice Husk Powder, Biogas Sludge, Biogas Liquid

Industrial Organic Waste: Distillers' Grains, Vinegar Residue, Sugar Residue, Medicinal Residue

Humic Acids: Weathered Coal, Lignite, Peat

3. Other Industries

Building Materials: Cement Clinker, Ceramic Powder, Refractory Materials

Chemicals: Dye Intermediates, Catalyst Carriers, Molecular Sieves

Metallurgy: Iron Powder, Mineral Powder Pelletizing

Environmental Protection: Sludge Solidification, Fly Ash Stabilization

Common Equipment Problems and Solutions

Low pelletizing rate is the most common problem with disc granulators. The main causes and solutions are as follows:

If you still have any questions about fertilizer production equipment and processes, or would like to learn more about customized solutions, please feel free to contact us. Whether it's equipment selection and pricing, installation, commissioning and operation training, or after-sales maintenance and process upgrades, we can provide you with professional and timely answers and support to help your project be implemented efficiently.