Drum Cooler

Equipment Introduction

The fertilizer cooler, also known as a rotary cooler or drum cooler, is a core cooling device used in conjunction with the dryer in organic fertilizer, compound fertilizer, and blended fertilizer production lines. Its main function is to rapidly cool the high-temperature fertilizer granules after drying to a safe packaging temperature, while further removing some moisture.

The temperature of the hot granules from the dryer is typically 45-60℃. Direct packaging at this temperature can easily lead to condensation inside the packaging bag, fertilizer clumping, nutrient loss, and even affect the activity of microbial agents. The cooler uses forced cold air to exchange heat with the material, lowering the fertilizer granule temperature to slightly above room temperature (typically ≤40℃), meeting the requirements of rapid packaging.

This equipment features a compact structure, high cooling efficiency, reliable performance, and strong adaptability. It can also be used for cooling other powdery and granular materials.

Equipment Structure

The fertilizer cooler can be divided into five core systems:

1. Cylinder System: The cylinder is the main body of the equipment, a slightly inclined rotating cylinder (inclination angle typically 2°–5°) welded from high-quality medium carbon steel plates. Lifting flights are installed on the inner wall, their distribution angle optimized to repeatedly lift the material to the top of the cylinder and evenly distribute it, forming a "material curtain," maximizing the gas-solid contact area, eliminating cooling dead zones, reducing particle breakage, and maintaining the roundness of the finished product.

2. Support Frame System: The support frame is welded from medium carbon steel plates and channel steel. The support rollers are made of high-quality corrosion-resistant and wear-resistant materials, some using integrated casting technology. Heavy-duty riding rings are fixed to both sides of the cylinder, supporting the weight of the rotating parts of the machine and allowing the cylinder to expand and contract freely due to thermal expansion and contraction. Lifting hooks are usually provided at the four corners of the support frame for easy loading, unloading, and transportation. 3. Transmission System: Composed of a main motor, reducer, pulleys/V-belts, split pinion gears, and a large gear ring fixed to the cylinder. The motor, after reduction, drives the pinion gear, which in turn drives the large gear ring to rotate the cylinder at a set speed (typically 3–8 r/min) at a uniform speed. A nylon coupling is used between the reducer and the main shaft for drive transmission, ensuring smooth operation and vibration damping.

4. Thrust Roller System: The Thrust Roller device controls the axial movement of the cylinder, preventing horizontal drift during operation and ensuring the cylinder remains in the correct working position.

5. Feeding, Discharging, and Sealing System: Feeding End: Equipped with a feed chute, high-temperature materials enter from the higher end.

Discharging End: Equipped with a discharge device, cooled materials exit from the lower end.

Sealing System: Both ends of the cylinder are equipped with heat-resistant rubber seals. Operating under the negative pressure created by the induced draft fan, it effectively prevents air leakage and dust escape, meeting environmental emission requirements.

Applicable Raw Materials 

Working Principle (Countercurrent Heat Exchange Process)

The entire machine is installed at a slight tilt, with the motor driving the cylinder to rotate continuously at low speed. It employs a countercurrent air-cooled heat exchange process:

1. Feeding and Conveying: High-temperature fertilizer granules (60~90℃) discharged from the dryer are fed into the cylinder from the high-end feed inlet;

2. Cold Air Convection: A matching induced draft fan draws in ambient temperature cold air at the cylinder discharge end. The cold air flows counter-currently from the low end to the high end, contacting the sliding high-temperature material in the opposite direction;

3. Material Lifting and Heat Dissipation: Lifting plates inside the cylinder continuously lift and drop the bottom granules, forming a material curtain. Cold air penetrates the material curtain, carrying away heat and surface moisture from the granules;

4. Discharge and Transfer: Relying on the tilt and rotational thrust of the cylinder, the material slowly moves towards the low end, and after sufficient cooling, it is discharged from the discharge outlet and sent to the screening and packaging processes;

5. Exhaust Gas Treatment: Hot air carrying dust and moisture is discharged from the feed end, purified by a dust collector, and then released into the atmosphere. Fine powder is recovered for secondary granulation.

Applications and Processed Materials

Fertilizer coolers have a wide range of applications, not limited to the fertilizer industry:

The cooler can process materials in granular, powdery, and small lump forms, with optimal cooling effect for fertilizer granules with a diameter of 1–5 mm. For heat-sensitive materials (such as microbial organic fertilizers), controlling the cooling airflow and residence time is particularly important to avoid sudden temperature drops that could cause granule breakage or damage to beneficial bacteria.

Equipment Application in Production Lines

In modern fertilizer production lines, the cooler is located after the dryer and before the screening/coating machine, forming a standard process chain of "granulation → drying → cooling → screening → coating → packaging":

Fermentation/Ingredient Mixing → Crushing → Mixing → Granulation → Dryer → Cooler → Screening → Coating → Packaging

Process Functions:

1. Terminating Residual Heat Reaction: Rapidly reduces granule temperature, preventing crystal bridging, granule adhesion, and nutrient degradation caused by high temperatures.

2. Fixing Granule Properties: Cooling hardens the granule surface, improving compressive strength and wear resistance, and reducing pulverization during subsequent conveying and packaging.

3. Removing Residual Moisture: A small amount of moisture evaporates during cooling, further reducing the moisture content of the finished product and extending shelf life.

4. Creating Packaging Conditions: Lowering the granule temperature to near room temperature avoids "sweating," clumping, and packaging bag deformation caused by hot bagging.

5. Dust recovery: The negative pressure system of the cooler can collect fine powder generated by particle collision, reducing raw material waste.

Target Customers for this Equipment:

1. Organic Fertilizer and Bio-organic Fertilizer Production Enterprises: Fertilizer coolers are standard equipment in organic fertilizer production lines with an annual output of 10,000-500,000 tons. Suitable for large-scale production enterprises processing organic waste such as livestock and poultry manure and straw.

2. Compound Fertilizer and Blended Fertilizer Production Enterprises: Core equipment in the cooling process of granular materials during the production of compound and blended fertilizers. Especially suitable for the production of fertilizers such as NPK, DAP, MAP, and TSP.

3. Enterprises Building or Expanding Fertilizer Production Lines: For fertilizer production projects requiring a drying and cooling system, a cooler is an indispensable component.

Summary of Comprehensive Technical Features of the Equipment:

High Adaptability: Adjustable speed, cylinder inclination angle, and cooling airflow in multiple dimensions, accommodating organic fertilizer, compound fertilizer, and heat-sensitive bio-fertilizer;

Uniform Cooling and Low Breakage: Optimized lifting plate structure, counter-current heat exchange eliminates localized high-temperature zones, resulting in a particle breakage rate of less than 1%;

Low Operation and Maintenance Costs: Wear-resistant standard parts, clear lubrication and maintenance cycles, and simple replacement of vulnerable parts;

Environmentally Compliant: Equipped with a dust removal system, eliminating disorderly dust emissions and the generation of no wastewater or waste residue;

Continuous and Stable Production: All-steel heavy-duty structure supports 24/7 uninterrupted feeding operation;

High Compatibility: Matches the size and capacity of similar model rotary drum dryers, ensuring coordinated production line layout and reducing investment in civil engineering and conveying equipment.