Improving Mixing Uniformity and Energy Efficiency in Plastic Recycling with Vertical Mixers
2025-04-23 Page view：
In the plastic recycling industry, the performance of vertical mixers plays a crucial role in determining the quality of recycled pellets and the overall production costs. A report from the 2023 Global Plastic Recycling Equipment Whitepaper revealed that optimizing vertical mixers can enhance mixing uniformity by 40% and lower energy consumption by 22%. This article explores the key technologies behind these improvements and presents a real-world case study from a recycled polyethylene (PE) plant upgrade.
1. Innovative Mixer Design: Addressing Traditional Mixing Challenges
The traditional design of vertical mixers often results in dead zones where materials don't mix efficiently. However, the dual-layer spiral blade system found in newer vertical mixers allows for three-dimensional movement of materials, improving the mixing process. This innovative design significantly enhances dispersion efficiency, especially for PET flakes (3-5mm particle size), with a 27% improvement in mixing.
Key Features:
Upper blades lift and pre-disperse materials.
Lower reverse blades promote effective axial mixing.
After upgrading their equipment, a factory in Jiangsu reported a dramatic reduction in the mixing uniformity (CV value) from 18% to just 6.5%.
2. Optimizing Energy Use: Dynamic Temperature Control
Traditional plastic recycling equipment often wastes over 30% of thermal energy due to uneven heating. To combat this issue, the integration of PID algorithms and zoned temperature modules can significantly improve energy efficiency. This combination ensures that temperature fluctuations are reduced from ±15°C to just ±3°C, leading to energy savings.
Case Study: A PP recycling plant in Shandong saw a reduction in energy consumption from 85 kW·h to 62 kW·h per ton of recycled material, resulting in annual savings of ¥280,000 after installing a German-made thermal system.
3. Smart Feeding Systems: Ensuring Stable Mixing Quality
Contaminants, such as metals and fibers, are a common cause of torque instability in mixers. To address this, several technologies can be employed:
Magnetic separators (≥12,000 Gauss) to remove metal contaminants.
Dynamic weighing feeders with ±0.5% accuracy to ensure consistent material feeding.
By implementing this combination, a manufacturer in Zhejiang reported a 65% reduction in equipment failures and reduced black spot impurities to less than 0.2%.
4. Key Parameters for Optimal Efficiency
Through 300 experimental trials, the following settings have been identified as ideal for maximizing mixer performance:
| Material Type | Speed (rpm) | Filling Rate | Mixing Time (min) |
| LDPE Films | 45-50 | 55% | 8-10 |
| PET Bottle Flakes | 35-40 | 60% | 12-15 |
Exceeding these recommended ranges can lead to an 18-25% increase in energy waste. It's also essential to adjust settings dynamically based on material moisture content.
5. Case Study: Upgrading a Recycled PE Plant
Before the upgrade, the PE recycling plant faced issues such as:
Color inconsistencies due to uneven mixing
High energy costs, averaging 90 kW·h per ton of material
Post-upgrade improvements included:
Installing a vertical mixer with a 55kW permanent magnet motor
Adding an online Near-Infrared (NIR) monitoring system to ensure consistent quality
Results:
Hourly output increased from 2.8 tons to 3.5 tons
Energy savings amounted to ¥146,000 annually
