Design and Application of a Comprehensive Coal Spillage Handling System for Downwards Transportation Belt Conveyor

A belt conveyor with an annual production capacity of 3 million tons is installed in a main inclined roadway with a steep angle of 22°. During operation, issues such as coal overflow, spillage, and falling coal occur, particularly when transporting raw coal with high moisture content. The daily spillage can reach tens to hundreds of tons, necessitating frequent cleanup, which affects operational efficiency and safety. To address the spillage, a water storage tank was installed at the conveyor's head to flush away the spilled coal. During operation, workers manually open the tank's gate valve to wash the loose coal to the conveyor's tail, where it is then cleared by a loader. However, due to the large volume of flushing water, excessive loose coal, untimely cleanup, and the proximity of the loose coal to the sump, the coal is often washed directly into the sump. As a result, the sump requires monthly dredging, leading to high labor intensity, difficulties in sump cleaning, and significant safety hazards. To resolve these issues, the mine introduced a comprehensive coal spillage handling system for steeply inclined main belt conveyors to effectively manage spillage and related problems. 

 

1 Analysis of Coal Spillage Causes  

1.1 Main Causes of Coal Spillage  

First, the steep inclination angle (22°) and high speed contribute to spillage. Second, uneven surfaces at multiple points along the conveyor body cause belt fluttering, leading to coal spillage.  

 

1.2 Difficulties in Sump Dredging  

1. The manual adjustment of the water storage tank’s gate valve is inconsistent, resulting in excessive flushing water—averaging 800 m³ per cycle—washing coal slurry into the sump.  

2. The uneven floor of the main conveyor roadway causes loose coal to accumulate in low-lying areas, preventing proper sedimentation. As a result, water carries the coal into the sump, necessitating frequent cleaning.  

3. Loose coal at the conveyor tail is not cleared promptly or thoroughly, leading to its entry into the sump during flushing.  

4. The 150-meter proximity between the conveyor tail and the sump allows insufficiently settled coal slurry to flow into the sump.  

5. The presence of large coal chunks in the loose coal complicates dredging. When using a walking dredger (equipped with a slurry pump), the front-end spiral collector struggles with efficiency, and the slurry pump suffers severe wear. Consequently, the first 100 meters of the sump must be dredged manually or with a loader, resulting in high labor intensity and low efficiency.

 

2 Design of belt conveyor coal spillage comprehensive treatment system

2.1 Scheme research and measures

1.The 22° steep inclination of the belt conveyor cannot be altered, but its operating speed can be adjusted according to coal volume. The solution involves installing a belt weigher at the feeding source to monitor coal volume in real time and provide feedback to the control system. This allows dynamic speed adjustment of the main conveyor to reduce spillage.

2. To address belt fluttering caused by uneven surfaces along the conveyor, corrective measures include adjusting the conveyor frame and roadway to ensure the belt runs in a straight line. Additionally, pressure rollers are installed to stabilize the belt and minimize spillage. 

 

2.2 Automatic cleaning system of tail loader

1. A roller screen and a high-frequency vibrating screen are installed at the tail of the belt conveyor. The roller screen automatically collects and grades the scattered coal. The under-screened materials are washed by water to the scraper type cleaning machine, and the over-screened materials are transported to the high-frequency vibrating screen and then to the main conveying belt conveyor through the transfer belt conveyor. The under-screened materials of the high-frequency vibrating screen flow by gravity to the scraper type cleaning machine.

2. The coal slurry water flows by gravity to the scraper type cleaning machine, and the coarse particles of 0.5 mm are directly discharged to the transfer belt conveyor. The overflow water of the scraper type cleaning machine flows by gravity to the sedimentation tank.

3. A guide rail and an electric hoist are installed above the sedimentation tank. A heavy-duty forced discharge slurry pump with stirring is installed in the sedimentation tank. It moves back and forth in the sedimentation tank and transports the slurry settled at the bottom of the sedimentation tank to the high-pressure filter press. After being filtered by the high-pressure filter press, the coal slurry cake falls on the transfer belt conveyor, and the filtrate water flows by gravity to the water tank. The process flow of the scattered coal comprehensive treatment system.

 

2.3  Features of the Comprehensive Coal Spillage Handling System  

 

1. Automatic Speed Control & Water Reduction

- The system automatically adjusts the main conveyor’s speed to minimize spillage and eliminates belt fluttering.  

- Intelligent control of the water tank’s gate valve optimizes flushing volume.  

- Ultra-high-molecular-weight polyethylene (UHMWPE) panels installed on the roadway floor reduce required flushing water.  

- Flushing water consumption decreased by 75% (from 800 m³ to 200 m³ per cycle), easing sump dredging and reducing mine drainage load.  

 

2. Roller Screen for Comprehensive Collection & Grading

- Installed at the tail end, the roller screen collects, classifies, and conveys spilled coal.  

- Coarse coal (>10 mm) is separated, while undersized material flows by gravity into the scraper-type cleaning machine.  

 

3. High-Frequency Vibrating Screen for Dewatering

- Reduces moisture content in lump coal, improving transport efficiency on the steeply inclined conveyor and minimizing spillage.  

 

4. Scraper-Type Cleaning Machine with Inclined Plate Settling

- Coal slurry flows into the machine, where a honeycomb inclined plate settler separates coarse particles (≥0.5 mm). 

- A scraper discharge mechanism removes settled coarse slurry, transferring it to the transfer conveyor.  

- Overflow water enters the rear sedimentation tank.  

- Eliminates issues such as filter cloth wear and "layered filter cakes" in high-pressure filter presses.  

 

5.High-Pressure Filter Press for Efficient Sludge Treatment  

- **Feed pressure: 1.5 MPa | Rubber diaphragm squeeze pressure: 2.0 MPa**  

- **Advantages:  

  - Fast cycle time, high efficiency  

  - Low-moisture filter cakes (non-sticky to cloth)  

  - Fully automated operation  

 

6.Centralized Control 

- Integrated with the mine’s wireless network for remote monitoring & centralized control.  

- Enables one-key start/stop, unmanned operation, and real-time video surveillance.  

 

7.Pre-Treatment Eliminates Frequent Sump Cleaning 

- By processing sludge before it enters the sump, dredging frequency is drastically reduced.  

- Achieves >5-year intervals between sump cleanings, resolving long-standing dredging challenges.  

 

3 Conclusion

The comprehensive coal spillage handling system for the main belt conveyor is simple, practical, reliable, and easy to operate, demonstrating excellent application results. It effectively resolves the long-standing challenges of coal spillage cleanup on steeply inclined conveyors and sump dredging at the discharge end.  

The successful implementation of this system has not only enhanced operational efficiency and delivered significant economic benefits but also eliminated underground safety hazards. Given its proven effectiveness, this system holds considerable potential for broader industry adoption.