Water-cooled pelletizing and air-cooled pelletizing are two common granulation methods in the processing of polymers (such as plastics and rubber). Their core difference lies in the cooling medium and process flow, which directly affect pellet characteristics, production efficiency, and applicable scenarios.
Below is a comparison of their core differences:
| Comparison Aspects | Water-cooled pelletizing | Air-cooled pelletizing |
|
Cooling medium |
Water (usually circulating cooling water) | Air (forced cold air) |
| Process flow | Melt is extruded from the die → Immediately cut by the cutter → Hot pellets fall into the water tank for rapid cooling and solidification → Undergo dehydration/centrifugal drying → Finished pellets are obtained | Melt is extruded from the die → Cut by the rotating cutter → Pellets are cooled and solidified in the air stream → Fall directly into the collector (no drying required) |
| Cooling efficiency | Extremely high. Water has rapid heat transfer efficiency, enabling pellets to solidify instantaneously, making it suitable for high-temperature and sticky materials. | Relatively low. Air has slow heat transfer efficiency, resulting in a long cooling time and typically longer production lines. |
| Pellet shape and quality | Shape: Mostly approximately cylindrical, spherical, or teardrop-shaped. Surface: Stress may occur due to rapid cooling, which can affect transparency or glossiness. Drying: Thorough drying is required, as residual moisture may impact subsequent processing. |
Shape: Regular and uniform cylindrical or cuboid pellets. Surface: Smooth and uniform, with no residual moisture issues. Cutter life: Causes minimal wear to the cutter. |
| System complexity and cost | System Complexity: Relatively complex. It requires the installation of water circulation, filtration, and drying systems. Energy Consumption: The drying process increases energy usage. Maintenance: It involves addressing issues such as water quality control, scale prevention, and wastewater treatment. |
System Complexity: Simple. No water treatment or drying equipment is required. Energy Consumption: Mainly comes from the air blower, with generally lower total energy consumption. Maintenance: Simple, with no water quality issues. |
| Applicable Materials and Products | Advantageous Applications: High-temperature melts (e.g., PA, PET, certain engineering plastics). Oxidation-prone and sticky materials. Materials with high requirements for cooling rate. High-output production lines. |
Advantageous Applications: Moisture-sensitive materials (e.g., certain grades of ABS, PC). Materials requiring pellets with high surface quality and regular shapes. Production lines with medium to small output or frequent color changes. |
| Environmental Impact | It consumes water resources and may generate wastewater that requires treatment. | No wastewater is generated, making it more environmentally friendly, although it may produce fan noise. |
Comparison Aspects
Water-Cooled Pelletizing: The core principle is "rapid quenching". It achieves efficient, forced rapid cooling through water, making it suitable for high-temperature, high-viscosity, and sticky materials with high output capacity. However, the system is complex and requires a drying process.
Air-Cooled Pelletizing: The core principle is "slow cooling". It enables gentle, gradual cooling via air, producing pellets with uniform quality, smooth surfaces, and no water-related issues. The system is simple and environmentally friendly, but it has low cooling efficiency and typically lower output capacity.