How to Prevent Secondary Pollution During Dust Removal in Mines

Core Concept: Treating Dust as a "Product" and Implementing a Fully Enclosed Management Process

The key to preventing secondary pollution lies in changing the perception that "dust is merely waste that needs to be discarded," and instead treating it as a "product" that needs to be properly collected, transported, and stored. 

Any open points, leaks, or improper operations at any stage will lead to secondary pollution.

Stage One: Source Suppression and Precise Capture – Reducing Dispersion and Alleviating Load

Controlling dust at the point of origin is the most efficient and economical strategy.

1. Enclosure and Micro-Negative Pressure Design:

All dust-generating points (crusher inlet and outlet, screening machines, transfer points) are physically enclosed with reliable sealing covers.

Reasonably sized dust collection ports are installed on the enclosed covers, connected to the dust collector via ducts. This ensures a stable micro-negative pressure state inside the cover (usually -50 to -100 Pa). 

This is crucial: if the negative pressure is too weak, dust will escape; if it's too strong, too much unnecessary air will be drawn in, increasing equipment load and energy consumption.

2. Source Dust Suppression Technology Assistance:

Optimized Chute Design: At the transfer points of belt conveyors, a double-layer sealed chute is used, with damping idlers and dust curtains inside to effectively suppress dust generated by material impact.

Micron-Level Dry Fog Dust Suppression: Dry fog dust suppression devices are installed above the material drop and impact points. 

The resulting water mist particles smaller than 10μm collide, condense, and settle with dust particles, reducing more than 80% of airborne dust at the source, greatly reducing the processing pressure on subsequent dust collectors.

Stage Two: Refined Design of the Dust Collector Itself – Preventing it from Becoming a Source of Pollution

If the dust collector is improperly designed or operated, it can itself become a major source of secondary pollution.

1. Leak Prevention in the Filtration Zone:

High-Quality Filter Material and Bag Mouth Sealing:  Using coated filter materials suitable for mining conditions (wear-resistant, anti-static, moisture-proof). 

Ensure the connection between the filter bags and the tube sheet is absolutely sealed, using elastic tension rings and special sealant to prevent dust from bypassing the filter bags and entering the clean air chamber through the gaps.

Casing structure strength and sealing: The dust collector casing must have sufficient strength to prevent it from being sucked in during negative pressure operation. 

All inspection doors and flange connections use aging-resistant silicone rubber sealing strips to ensure airtightness.

2. Optimization of the dust cleaning system – the biggest risk point for secondary pollution:

Intelligent dust cleaning strategy: Abandon the fixed time interval dust cleaning mode, and adopt a "constant resistance dust cleaning" mode (i.e., automatic dust cleaning when the pressure difference between the inside and outside of the filter bag reaches a set value) as the main method, supplemented by timed dust cleaning. 

This avoids unnecessary and overly frequent dust cleaning, reducing dust "re-mixing" and instantaneous emission peaks during dust cleaning.

Low-pressure pulse technology: Using a low-pressure, high-flow, and long-cycle dust cleaning method can effectively remove the filter cake while avoiding excessive impact on the filter bags from high-pressure cleaning, extending the life of the filter bags and reducing leaks caused by filter bag damage.

3. Targeted design of the hopper:

Hopper angle and fluidization: The inclination angle of the hopper wall must be greater than the angle of repose of the dust (usually ≥65°), and the inner wall should be smooth to ensure that the dust can slide down smoothly by gravity. 

For dust that is prone to moisture absorption and caking, pneumatic or electric heating vibrators, air cannons, or fluidization plates can be installed on the hopper wall to prevent dust from accumulating and bridging in the hopper.

High-level monitoring and anti-caking: Install radio frequency admittance or radar level gauges to monitor the hopper level in real time, promptly reminding for ash discharge to prevent the filter bags from being submerged after the hopper is full.

Stage Three: Enclosed Dust Conveying and Storage – The Last Line of Defense

This is the most easily overlooked stage, yet it is precisely where secondary pollution is most likely to occur.

1. Reliable Ash Discharge and Airlock Devices:

A rotary ash discharge valve (airlock) or double-layer flap valve must be installed at the bottom of the ash hopper. Its function is to continuously discharge ash while consistently isolating the inside of the dust collector from the outside air, maintaining negative pressure in the system. 

The wear of the ash discharge valve blades must be checked regularly, as wear will drastically reduce the airlock effect.

2. Fully Enclosed Conveying System:

Pneumatic conveying is preferred: For centralized processing over longer distances, a low-pressure dilute phase or dense phase pneumatic conveying system should be used to pump the dust directly to the ash storage silo through pipes. The entire process is completely enclosed with no leakage points.

Enclosed modification of mechanical conveying: If using scraper conveyors or screw conveyors, they must be fully enclosed, and dust collection ports should be installed at the head and tail ends, connected to the dust collection system to form a closed loop.

3. End-of-Line Treatment of Ash Storage Silos:

A silo top dust collector (usually a small pulse bag filter) must be installed at the top of the ash storage silo to balance pressure changes inside the silo during feeding and prevent dust-laden air from escaping from the silo top.

When discharging ash from the storage silo to trucks, a combination of a telescopic discharge head + dry mist dust suppression or a side suction hood should be used to control dust during loading.

Stage Four: Intelligent Monitoring and Lean Operation and Maintenance – Sustainable Guarantee

Even the best equipment will fail without scientific management.

1. Establish a Key Parameter Monitoring System:

Online monitoring of the pressure difference at the inlet and outlet of the dust collector, main fan current, dust concentration at the discharge port (optional), ash hopper level, and air tank pressure. Any abnormal fluctuations may be early signals of leaks, filter bag damage, or poor ash discharge.

2. Predictive Maintenance:

Develop a maintenance plan based on monitoring data. For example, a continuous increase in pressure difference indicates the need to check the cleaning system or filter bag condition; abnormal fan current may indicate damper or pipe blockage.

Regularly use fluorescent powder leak detection or a handheld dust detector to scan the dust collector casing, flanges, and access doors to proactively identify leakage points. 3. Standard Operating Procedures (SOPs):

Develop strict start-up and shut-down sequences, inspection routes, and checklists. For example, during start-up, the dust removal system should be started first, followed by the process equipment; the reverse procedure should be followed during shut-down, ensuring the system always operates under negative pressure.

Summary: Systems Engineering Thinking

Preventing secondary pollution during the mining dust removal process is a comprehensive systems engineering project covering the entire chain from "source capture — efficient filtration — reliable dust removal — smooth dust transport — safe storage — intelligent monitoring." 

It is crucial not to focus solely on the dust collector itself.

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