When clients consult us on how to select a waste sorting line, their primary focus is often the equipment’s throughput per ton. However, in many real-world projects, this single-dimensional selection approach leads to low sorting efficiency and high operating costs after the production line is built.
We’ve seen many sorting lines perform poorly, not because of inherent equipment quality issues, but because of a flawed understanding of key parameters such as trommel screening, air separation, and magnetic separation during the selection phase, or neglecting their system compatibility with throughput per ton. These parameters, seemingly independent technical indicators, collectively determine whether the entire sorting line operates smoothly and stably, or suffers from frequent jams, incomplete sorting, and constant maintenance.
This article will analyze the selection logic behind these key parameters from the perspective of real-world waste resource recovery projects.
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1. Rotary Trommel Screening: More Than Just Screen Size, It’s a Key Starting Point for Pre-treatment
Drum trommel screens are often simply viewed as equipment for particle size classification, but their design parameters directly affect the efficiency of all subsequent sorting units.
In mixed municipal solid waste and construction waste sorting projects, a common mistake is selecting the drum screen size solely based on theoretical throughput, neglecting the matching of screen diameter, rotation speed, inclination angle, and material characteristics.
– Mismatch between screen aperture combination and material characteristics: If the screen aperture design (e.g., first stage for bag breaking, second stage for screening, third stage for fine screening) is mismatched with the material’s moisture content and entanglement properties, it can easily lead to screen clogging and a sharp drop in screening efficiency. For example, if high-moisture municipal solid waste uses screens with too small apertures, the screen will become clogged within minutes.
– Hidden thresholds of rotation speed and inclination angle: Too high a rotation speed or too large an inclination angle results in a short material residence time and incomplete screening; conversely, insufficient throughput becomes a bottleneck for the entire production line. For lightweight, easily dispersed materials, sealing and dust suppression designs must also be considered.
Tips from Experience:
When selecting a drum screen, the first step is to analyze the particle size distribution, moisture content, and viscosity of the material to be processed. A well-designed drum screen should provide a stable material flow for subsequent processes such as air separation and magnetic separation, rather than simply performing the screening action.
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2. Air Separation: The precise balance between wind speed and air pressure determines the separation purity.
Air separators separate light materials (such as plastics and paper) from heavy materials using airflow. The biggest misconception when selecting a model is focusing solely on whether it has air separation capabilities, while neglecting the precise correspondence between wind speed, air pressure, airflow uniformity, and the specific gravity and shape of the material.
In actual operation:
– Insufficient wind speed: Fails to effectively lift the target light materials, causing recyclable materials such as plastics and paper to enter the heavy material end, resulting in resource loss.
– Excessive wind speed: Blows some heavy materials (such as broken wood blocks and small bricks) into the light material end, severely contaminating the recycled material and reducing its economic value.
– Turbulent Airflow: Uneven feeding or improper fan selection leads to significant differences in sorting efficiency across different areas of the screen, resulting in overall low sorting efficiency.
We’ve seen a typical case: a construction waste sorting line experienced a purity fluctuation exceeding 30% during seasonal changes because the air separator’s wind speed settings didn’t account for differences in air density between winter and summer. Refined adjustments to the air separator are crucial in determining the overall value of the recycled products.
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3. Magnetic Separation: Synergy between Magnetic Field Strength and Material Flow Mode
Magnetic separation is used to separate ferromagnetic metals. A common drawback is that the magnetic separator becomes ineffective—it can attract iron, but not completely.
Problems often arise from:
– Mismatch between magnetic field strength and material layer thickness: Insufficient magnetic force to penetrate thick material layers prevents effective capture of iron at the bottom.
– Mismatch between magnetic system layout and material flow rate: Excessive material flow rate results in insufficient residence time for iron in the magnetic field zone, causing it to detach before being adsorbed.
– Neglecting the subsequent sorting of non-magnetic metals: Configuring only magnetic separation results in the loss of valuable non-ferrous metals such as aluminum and copper. In high-value recycling scenarios, eddy current separators are often required.
The key is that the selection of a magnetic separator must be comprehensively determined based on the particle size, content, and burial depth of the metal parts in the material, as well as the belt speed and material layer thickness of the conveyor belt, ensuring that the magnetic field has sufficient “capturing force” and “acting time.”
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4. Processing Capacity per Ton: The Most Misunderstood Parameter, Without a Doubt
The “rated processing capacity per ton” on the equipment nameplate is measured under standard materials (such as MSW with a defined composition) and ideal operating conditions. However, on-site conditions vary greatly.
Actual processing capacity is profoundly affected by the following factors:
– Material Composition Complexity: Construction waste mixed with a large amount of tangled materials (textiles, ropes) will have a much lower processing efficiency than relatively simple, aged landfill waste.
– Pre-treatment Level: Whether effective bag-breaking and coarse crushing equipment is installed directly determines the feeding status of subsequent sorting units.
– Equipment Coordination: The individual capabilities of units such as drum trommel screens, air separators, and magnetic separators must be matched. If any link becomes a bottleneck, the entire line’s “tonnage throughput” will be limited.
– Operation and Maintenance: Whether the screens are cleaned regularly, the dampers adjusted, and the magnetic force checked directly affects the continuity and stability of production.
For example, a municipal solid waste sorting line rated at 200 tons/hour may only achieve a stable throughput of 140-160 tons/hour when processing high-moisture, high-mixture incoming raw waste. Using the rated value as the design capacity is one of the main sources of project risk.
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5. Why These Parameters Must Work as a System
An efficient sorting line is not simply the accumulation of individual pieces of equipment, but a systematic integration of units, such as drum screens, air separators, and magnetic separators, all centered around the “tonnage throughput” target.
Typical failures often stem from:
– Insufficient drum screen screening efficiency, leading to excessive amounts of heavy materials entering the air separator, severely interfering with the air separator’s accuracy.
– The magnetic separator’s capacity was insufficient, failing to effectively remove iron parts, leading to a surge in the risk of damage to the subsequent crusher.
– Excessively increasing the conveyor belt speed in pursuit of high throughput resulted in insufficient effective working time for air separation and magnetic separation units, deteriorating the sorting effect.
In successful projects, all key parameters are derived from material characteristic analysis, with the ultimate goal of achieving high purity and recovery rate of the sorted product, through reverse engineering and collaborative design.
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6. What questions do we typically ask before recommending a configuration?
To avoid configuration errors, we typically need to understand the following core information before providing you with a solution:
- Material type and composition? (Mixed municipal solid waste, renovation/construction waste, bulky waste, landfill aged waste, etc., approximate proportions of each component)
- Material physical properties? (Moisture content, average particle size, entanglement content, proportion of light materials)
- Target capacity? (Average and peak throughput in tons, daily operating time)
- Sorting objectives? (Which components are primarily desired for recovery? What are the purity requirements for the product?)
- Site and operating conditions? (Site dimensions, power supply, environmental requirements such as noise and dust control levels)
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Conclusion: Configuration precedes model; system is more important than individual unit.
Most performance problems in sorting production lines stem not from equipment manufacturing, but from systemic deviations in initial configuration and selection. The screening efficiency of the drum screen, the wind speed and pressure of the air separator, the magnetic field strength of the magnetic separator, and their combined actual throughput per ton determine whether the line is a profitable asset or a continuous burden.
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Ready to configure an efficient sorting line for your waste recycling project?
Choosing sorting equipment involves much more than comparing parameters in brochures. The key is whether the system can stably process your specific materials, achieve the expected sorting purity and recovery rate, and operate reliably over the long term at a controllable cost.
If you are planning a waste sorting line with a processing capacity of 50-500 tons/hour, you can start by providing the following information:
– Project location and materials (What type of waste will be processed? What are its characteristics?)
– Capacity requirements (Expected daily processing volume and operating procedures)
– Sorting objectives (What renewable resources are desired? What are the requirements for impurity content?)
– Site constraints (Available site dimensions, are there any special environmental requirements?)
Based on this information, Guoxin Machinery can provide you with a practical sorting production line configuration plan, including a process flow diagram, equipment list, investment estimate, and delivery cycle. We avoid one-size-fits-all solutions and are committed to tailoring a feasible solution for your project.