A Complete Guide to Wet Granulation Fertilizer Machines: Principles, Advantages and Selection Tips
What Is Wet Granulation?
Wet granulation is a process that agglomerates powdered or fine-grained raw materials into regular pellets by adding liquid binders (e.g., water, urine, humic acid solution). The core mechanism relies on surface tension and adhesion from the liquid, forming "liquid bridges" between particles. Through mechanical pressing, rolling, or stirring, these bridges solidify into granules, which are then dried to remove excess moisture, yielding fertilizer pellets that meet quality standards.Compared to dry granulation which directly compresses materials into pellets via mechanical pressure, wet granulation is better suited for hygroscopic, low-viscosity, or complex raw material blends . It is particularly effective for producing high-nitrogen, high-phosphorus, or micronutrient-enriched compound fertilizers, as the liquid medium ensures even nutrient distribution and prevents stratification.
Current applications of wet granulation equipment include
Compound fertilizer plants (e.g., high-concentration formulas like 15-15-15 or 17-17-17);Organic/organic-inorganic fertilizer plants (requiring liquid additives like microbial agents or humic acid);
Blended fertilizer plants (post-blending granulation to enhance market appeal);
Specialty fertilizer production (e.g., slow-release fertilizers, water-soluble fertilizers in pre-granulation stages).
Main Types of Wet Granulation Equipment and Their Features
Based on structure and process differences, wet granulation equipment can be categorized into several types, each with distinct pros and cons. Selection depends on production capacity, raw material characteristics, and budget.Drum Granulator – The Classic One-Step Forming Choice
Principle: In a tilted rotating steel drum, materials roll under gravity, friction, and sprayed liquid, gradually forming pellets.Simple operation and low maintenance costs;
Adjustable pellet size (typically 2–4mm) via speed and tilt angle control.
High return rate (20%–30%), necessitating screening systems;
Relatively high energy consumption (due to continuous heating for drying).
Best For: Large compound fertilizer plants, conventional NPK fertilizer production.
Pan Granulator – Flexible Solution for Small Batches + High Uniformity
Principle: In a tilted circular pan, materials spiral under centrifugal force and sprayed liquid, building layers to form pellets.Advantages:
High granulation rate (up to 90%+), with well-rounded pellets;
Precise pellet size control (via adjusting pan tilt and rotation speed);
Ideal for multi-variety, small-batch production (e.g., specialty fertilizers, lab-scale trials).
Limitations:
Low single-machine capacity (0.5–8 tons/hour), limiting scalability;
Manual liquid monitoring required, challenging for automation.
Best For: Small-to-medium organic fertilizer plants, lab formula validation, custom high-end specialty fertilizers.
Extrusion Granulator – Innovative Low-Moisture + High-Efficiency Option
Principle: Mixed materials are extruded into strips via screws or rollers, then crushed and screened into pellets. Some models integrate "wet extrusion + low-temperature drying" to reduce moisture evaporation energy.Advantages:
No high-temperature drying , preserving heat-sensitive nutrients;
Dense pellets with strong anti-powdering properties;
Handles high-moisture raw materials (e.g., biogas residue, distiller’s grains for wet-based organic fertilizers).
Limitations:
Strict raw material preprocessing (thorough mixing and homogenization required);
Complex structure, higher initial investment.
Best For: Organic-inorganic blended fertilizers, bio-organic fertilizers, sludge-based resource fertilizers.
Some types of the wet granulation fertilizer machine
The powdered material to be granulated is added into the drum granulator from the feed end.
In the drum granulator, a certain amount of water or steam is introduced to make the fertilizer fully react chemically after being humidified in the drum.
With the help of the rotating motion of the drum, the materials are squeezed and agglomerated into spherical particles. The special structure in the drum helps to enhance this squeezing and agglomeration effect.
With the continuous rotation of the drum and the continuous entry of materials, the formed particles gradually increase.
Finally, these particles flow out from the discharge port, completing the granulation process.
The working principle of a disc granulator is mainly based on the mechanical squeezing, rolling, and collision formed by the material in a rotating inclined disc, which causes the material to aggregate into particles of specific shapes.
Its core component is a rotating disc with a tilted angle, which is driven by an electric motor to rotate. The material is first crushed, screened, and mixed before being evenly added to the disc. Inside the disk, the material is subjected to a combination of centrifugal force, frictional force, and gravity, moving along a parabolic trajectory.
Prepare the raw materials required for the roller granulator (such as powdered organic fertilizer, compound fertilizer, graphite, etc.) and feed them into the roller granulator through the feed hopper. Through the rotation of the screw rod, the material is forced to be extruded between the two rollers at the bottom.
After the material reaches the bottom, the two rollers rotate relative to each other and use the mold shell to extrude the material, and the material becomes a cake or strip under strong pressure.
Then, the extruded material enters the granulator and is broken into loose particles by the rotating knife row. Then enter the granulator and further organize it by the rolling knife row to make the shape of the particles more regular.
The processed particles enter the rotary vibrating screen for screening, and the qualified particles are screened out, and the screened powdered materials are sent back to the raw material bin for secondary rolling.
The extrusion force of the roller granulator can be controlled by the hydraulic system to meet the granulation needs of different materials. At the same time, by changing the groove form of the roller surface, different shapes of materials such as flakes, strips, and oblate balls can be obtained.
Stirring pin Granulator
First, the organic materials to be processed are mixed and fermented.
Add an appropriate amount of water or steam to the raw materials to make the materials reach a humidity suitable for granulation. This step is crucial for the formation of particles. Appropriate humidity can promote the bonding and molding of particles.
Use mechanical devices such as spiral rotation to stir and extrude the materials. During high-speed operation, pressure is generated between the materials, and the particles gradually form and detach from the mold. At the same time, the air volume is adjusted to control oxygen supply and normal heat dissipation, so as to ensure that the equipment can operate continuously.
After stirring and extrusion, the materials form spherical particles. The shape and size of these particles can be appropriately adjusted by adjusting the equipment. Generally, the lower the mixing amount and the higher the speed, the smaller the particles formed; conversely, the larger the particles.
The newly formed particles need to be cooled before being collected and packaged.
The rotary drying and cooling machine is a kind of high-efficiency equipment integrating drying and cooling, which is widely used in chemical industry, fertilizer, mining industry, building materials and other industries.
The rotary drying and cooling machine realizes the continuous drying and cooling process of materials in the same body, which saves space and equipment investment and simplifies the process.
The rotary drying and cooling machine has the advantages of large processing capacity, strong adaptability, easy operation and maintenance, energy saving and environmental protection, etc. It is an indispensable and important equipment in the production of fertilizers.
Key Advantages of Wet Granulation: Why It’s Industry-Preferred
Compared to dry granulation or direct blending, wet granulation offers:Quality Enhancement: Strong pellet strength (compressive strength ≥20N), minimal powdering, and easy storage/transport; uniform nutrient distribution (CV ≤5%), preventing localized seedling burn;
Broad Adaptability: Compatible with inorganic fertilizers, organic matter, microbial agents, and micronutrients (e.g., zinc, boron);
Eco-Friendliness: Heat recovery in drying processes; some equipment (e.g., spray granulators) meets strict dust emission limits (≤50mg/m³);
Economic Efficiency: Despite higher initial costs than dry granulators, reduced return rates (less raw material waste) and premium pricing (pelleted fertilizers sell 10%–20% higher than powders) make it cost-effective long-term.
Critical Factors for Selecting Wet Granulation Equipment
To avoid pitfalls, consider these factors when choosing equipment:
Match Production Capacity
Select equipment based on target output (e.g., 50k-ton/year requires a drum granulator; 10k-ton/year suits a pan granulator), with 10%–20% surplus capacity for peak seasons.
Raw Material Compatibility
Low-viscosity materials (urea, KCl): Prioritize drum or spray granulators (with binders);
High-organic content (manure, straw): Opt for extrusion granulators (anti-clogging, energy-saving);
Water-soluble fertilizers: Spray granulators excel in "instant dissolution."
Automation & Control Precision
High-end models should feature PLC systems for real-time adjustment of liquid volume, temperature, and speed, ensuring pellet uniformity (e.g., pan granulators with "auto-liquid feeding + variable frequency control").
Energy Consumption & Maintenance Costs
Compare power ratings (e.g., drum granulators typically 55–132kW), drying energy use (coal/electricity/gas per ton), and wear-part replacement frequency (e.g., drum liners, nozzles).
Manufacturer Support
Choose suppliers offering full-cycle services ("design-installation-commissioning-training-aftersales"), with local teams for faster issue resolution.
Future Trends: Smart & Green Upgrades
Driven by carbon neutrality goals, wet granulation equipment is evolving in two key directions:
Intelligence: AI vision inspection (real-time monitoring of pellet size/damage) and digital twins (simulating process optimization) reduce manual intervention;
Greenization: Waste heat recovery (e.g., preheating combustion air with drum exhaust) and low-energy drying (microwave vs. hot-air furnaces) cut carbon emissions.
Conclusion
Wet granulation fertilizer machines are the critical bridge between raw materials and end products, directly impacting quality and competitiveness. Whether large compound fertilizer groups or small organic plants, aligning equipment choice with production needs, raw material traits, and tech trends ensures efficient, stable, and cost-effective operations in the fertilizer industry's upgrade wave.
For more details, please feel free to contact us.
Email: sales@lanesvc.com
Contact number: +8613526470520
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