Equipment Introduction
Fertilizer coolers are crucial post-processing equipment in fertilizer production lines, bridging upstream and downstream processes. Their core function is to rapidly cool fertilizer granules (typically 65–85°C) after high-temperature drying in a dryer to near ambient temperature (generally ≤40°C), facilitating timely packaging, storage, and transportation. This also prevents granule softening, sticking, clumping, and nutrient degradation caused by residual heat.
In the fertilizer industry, the rotary drum cooler is the most prevalent type of equipment. Similar in structure to a drum dryer, it does not heat the drum itself. Instead, it relies on forced convection heat exchange between ambient air or regulated cold air and the tumbling material inside the drum to achieve efficient cooling. This equipment features a compact structure, uniform cooling, stable operation, low energy consumption, low breakage rate, and strong adaptability. It is a standard component in production lines for organic fertilizers, compound fertilizers (NPK), ammonium phosphate, ammonium sulfate, and various soil conditioners.
Equipment Structure
| Module |
Component List |
Function Description |
| Cylinder Section (Main Body) |
Cylinder, Lifting Plate (Scoop Plate) |
Core main body of the unit, fabricated by high‑quality medium steel plate welding. The cylinder is installed at 2‑5° inclination to horizontal plane. Wear‑resistant lifting plates are fitted inside with reasonable layout angles. During operation, materials are lifted and cascaded to form material curtains, expanding contact area between material and cold air to realize heat exchange and cooling. |
| Riding‑ring & Support Section |
Support frame, supporting roller, riding‑ring, stop roller, front riding‑ring, rear riding‑ring |
Bears rotating parts and main load of the whole machine. Support frame adopts integrated welded steel plate & channel steel structure with lifting lugs at four corners for convenient hoisting and installation. Supporting rollers are made of wear‑resistant material to support riding‑rings, limit axial displacement of cylinder and ensure stable rotation. |
| Transmission Section |
Transmission frame, main motor, reducer, pulley, V‑belt, pinion, big gear ring |
Provides rotary power for cylinder. Motor transmits power to reducer via V‑belt, then pinion meshes with big gear ring mounted on cylinder to drive continuous cylinder rotation. |
| Inlet‑Outlet & Sealing Assembly |
Feeding hopper, feeding pipeline, discharge outlet, floating sealing components |
Materials enter cylinder through elevated feeding hopper and feeding pipeline. Low‑temperature finished products are discharged from discharge end. Floating sealing assemblies are equipped at both cylinder ends to reduce ambient air infiltration and prevent internal dust overflow. |
| Auxiliary Equipment |
Induced draft fan, dust removal equipment, belt conveyor, quantitative feeder |
Induced draft fan accelerates air flow inside cylinder for higher cooling efficiency. Dust‑removal unit handles dust to meet environmental‑protection requirements. Conveyor and quantitative feeder complete front‑end feeding & batching to realize whole production‑line linkage. |
Applicable Raw Materials (Scope of Materials to be Processed)
1. Organic Fertilizer Granules: Fermented organic fertilizer from livestock and poultry manure, bio-organic fertilizer, microbial fertilizer, straw/microbial residue/distillers' grains granulated fertilizer;
2. Compound Inorganic Fertilizers: Drum granulation compound fertilizer, extrusion granulation compound fertilizer, BB fertilizer, urea-based/sulfur-based compound fertilizer, slow-release coated fertilizer;
3. Extended Materials: Various dried high-temperature powdered and granular biomass and chemical granular materials.
Working Principle of the Equipment
The fertilizer cooler operates on the principle of counter-current heat exchange and mechanical tumbling.
1. Counter-current Cold Air (Core Principle)
The cooling method employs counter-current cold air flow—that is, forced cooling through reverse contact between cold air and the material. Cold air is drawn in from the rear of the equipment (discharge end), flowing counter-currently to the material entering from the feed end. This allows the cold air to cool the material about to be discharged first, achieving the most efficient heat exchange.
2. Material Tumbling and Heat Dissipation
As the cylinder rotates, lifting plates installed on the inner wall of the cylinder continuously scoop up and evenly distribute the material. The material is constantly tumbled, lifted, and scattered within the drum, forming a material curtain, greatly increasing the contact area between the material and the cold air. Simultaneously, under the suction of the induced draft fan, the airflow inside the cylinder accelerates, promoting the cooling process.
3. Material Propulsion and Discharge
Due to the inclined installation of the cylinder (angle 2-5 degrees), the material gradually moves towards the drum outlet end under the influence of gravity and during the scattering process. The cooled material flows out from the discharge port. With the continuous rotation of the electric motor and the continuous feeding of materials, large-scale continuous production is achieved.
4. Dual Effect of Cooling and Dehumidification: During the cooling process, the cold air not only removes heat from the materials, lowering their temperature, but also further removes some moisture, ensuring the fertilizer granules reach the ideal packaging state.
5. Classification of Cooling Methods: Based on material characteristics and process requirements, coolers can be classified into various types, including air-cooled, water-cooled, and air-water hybrid cooling.
Applications and Processed Materials
Fertilizer coolers have a wide range of applications, not limited to the fertilizer industry:
| Application Fields |
Typical Materials |
| Organic Fertilizer |
Livestock & poultry manure granules, biogas residue granules, straw powder, sludge granules, kitchen waste granules |
| Compound / Inorganic Fertilizer |
NPK compound fertilizer, Mono‑Ammonium Phosphate (MAP), Di‑Ammonium Phosphate (DAP), ammonium sulfate, ammonium nitrate, potassium hydroxide, urea granules |
| Soil Conditioner |
Gypsum powder, limestone powder, humic acid, biochar |
| Feed Industry |
Granular feed, fish feed, pet feed |
| Chemical & Building Materials |
Chemical granules, dyestuffs, plastic granules, cement clinker, ceramic granules |
| Food Processing |
Food granules, condiments, starch |
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 operation and maintenance methods
| Item |
Sub‑item |
Description |
| Installation & Commissioning |
Foundation Installation |
The equipment shall be installed on horizontal concrete foundation. The cylinder is mounted with inclination of 2‑5°, adjustable on demand. |
| Base Leveling |
Install adjusting shims (30‑35 mm thickness) between each base and foundation. Adjust base height via shims to achieve designed cylinder inclination. |
| Body Position Calibration |
Check horizontal level with steel wire alignment; measure elevation of riding‑ring highest point to inspect vertical position; adjust supporting rollers to calibrate equipment position. |
| No‑load Test Run |
Continuous no‑load running for 8 h. Bearing temperature rises steadily, final bearing temperature ≤50℃. Gear rotation sound shall be uniform. Inspect bearings for no severe wear or scratches after test. |
| Start‑up Operation |
Pre‑start Inspection |
① Clear foreign matters inside machine; ② Check overall status; ③ Inspect feeding device and auxiliary transmission; ④ Clean residual materials in hopper and chute; ⑤ Confirm sufficient lubrication for all bearings & friction surfaces; ⑥ Complete inspection for cooler and auxiliary units. Do NOT start before full check. |
| Start‑up Sequence |
Start main motor and verify cylinder rotation direction; stop immediately if reverse. Feed materials evenly after stable rotation status. |
| In‑running Operation |
Production Operation |
Continuous and even material feeding. Real‑time monitor motor running status and listen for abnormal noise. |
| Safety Notes |
① No personnel shall pass under running machine; ② No internal inspection or maintenance during operation; ③ Do not remove safety guards; ④ Do not touch motor and cables with wet hands; ⑤ Ensure reliable cable connection; forbid starting equipment with faults. |
| Shutdown Operation |
Shutdown Procedure |
Stop feeding first; shut down after all materials inside cylinder are fully discharged. |
| Maintenance |
Lubrication Maintenance |
① Grease gears before start‑up; ② Apply grease to riding‑ring surface every 7 days; ③ Add or replace grease for bearing housings every 3 months; ④ Fill gear oil for reducer for first use, replace gear oil every 4 months afterwards. |
| Regular Cleaning |
Regularly clean external filter of equipment to avoid component damage caused by filter blockage. |
| Regular Inspection |
Check wear of vulnerable parts: V‑belts, bearings, pinion, gear ring, riding‑ring, lifting plates, shafts and coupling sleeves. Replace timely when wear exceeds limit. |
Equipment Application in the Production Line
1. Core Position in the Fertilizer Production Line
The cooler connects drying and screening/packaging in the fertilizer production line, serving as a crucial link between these processes. The hot granules after drying are too high for direct storage and must be cooled before proceeding to the next step.
Complete Processing Flow:
Raw Material Pretreatment → Fermentation and Composting → Crushing → Batching and Mixing → Granulation → Drum Drying → Drum Cooling → Screening → Coating (if required) → Packaging
2. Relationship with the Dryer
The cooler is typically used in conjunction with the dryer. The dryer removes a large amount of moisture from the material, while the cooler cools the material and further removes some moisture. Together, they complete the drying and cooling process of the fertilizer granules.
3. Impact on Product Quality
The cooling process directly affects the final product quality:
Preventing Agglomeration: Fully cooled granules are less likely to clump after packaging.
Protecting Microbial Agents: Low-temperature environments help protect the activity of microbial agents in the bio-organic fertilizer.
Maintaining Granule Strength: Prevents granule softening and breakage caused by high temperatures.
Facilitating Packaging: Cooled materials can directly enter the automated packaging system.
4. Continuous Production
The cooler supports 24-hour continuous and stable operation, seamlessly connecting to the entire production line from drying, screening, to packaging. The equipment design considers production margins; small increases in output do not require equipment replacement.
5. Environmental Protection and Energy Saving
The cooler operates under overall negative pressure, resulting in less dust. Exhaust gas after heat exchange can be introduced into other systems to improve thermal efficiency. Some advanced systems heat the cooling water discharged from the cooler and supply it to the granulator, achieving energy recycling.
Common Faults, Causes, and Standardized Solutions
| Fault Phenomenon |
Main Causes |
Solutions |
| Low Cooling Capacity (Poor Cooling Effect) |
Insufficient air‑volume supply, inadequate cooling capacity |
Increase air‑volume supply; when air‑volume reaches standard, adjust feeding rate or raise rotating speed to improve processing capacity |
| Riding‑ring Slippage |
Poor fitting between riding‑ring and concave joint; uneven tension causing machine jerk and vibration |
Clamp riding‑ring and concave joint side faces; control clamping force to avoid jerk and vibration caused by uneven tension |
| Machine Displacement |
Wear of supporting rollers and riding‑rings leading to position offset |
For worn supporting rollers: repair or replace according to wear degree; For worn riding‑rings: repair, adjust or replace with new ones |
| Gear Offset |
Double‑side wear of pinion; damaged connection structure between big gear ring and cylinder |
For worn pinion: flip for reuse; replace if both sides are worn. Correct connection structure between big gear ring and cylinder, carry out fitting treatment if necessary |
| Cylinder Vibration |
Failed connection between supporting roller assembly and base; side wear of riding‑ring |
Correct connection of supporting roller assembly, lock bolts to reset position; machine‑tool repair worn side of riding‑ring or replace riding‑ring |
| Over‑heated Bearing |
Insufficient lubricant, bearing damage, improper installation position |
Add or replace lubricant; inspect bearing condition, replace damaged bearing timely |
| Excessive Equipment Vibration |
Unstable installation foundation; cylinder unbalance; wear on supporting rollers and gears |
Reinforce installation and fasten anchor bolts; correct cylinder dynamic balance; replace worn supporting rollers and gear parts |
| Poor Sealing Performance |
Aging & damaged sealing parts, cold‑air leakage, reduced cooling efficiency |
Replace aged and damaged sealing components; check connecting joints to ensure tight fitting |
Target Customers for Fertilizer Coolers
The main target customer groups for fertilizer coolers include:
1. Organic Fertilizer Manufacturers: Manufacturers using livestock manure and agricultural waste as raw materials to produce commercial organic fertilizers, requiring the cooling of dried granules to a safe temperature.
2. Compound (Mixed) Fertilizer Plants: Enterprises producing inorganic or organic-inorganic compound fertilizers such as NPK, ammonium phosphate, and potassium sulfate; coolers are standard equipment for these plants.
3. Large-Scale Livestock Farms: Enterprises with their own manure resource utilization centers, requiring cooling equipment to complete the processing of finished organic fertilizer products.
4. Sludge Treatment and Environmental Protection Companies: Cooling of municipal sludge and industrial organic sludge after drying and granulation.
5. Biomass Energy and Feed Enterprises: Cooling of distiller's grains, medicinal residues, straw pellets, and feed pellets.
6. Soil Remediation and Conditioner Manufacturers: Cooling of soil conditioner granules such as gypsum, limestone, and humic acid.
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.
