Closed-Trough Conveyor Belts Ensure Energy-Efficient and Low-Dust Coal Transport in China

The operator of the coal mine, YanKan Coal, in the northern Chinese province of Shanxi, is therefore relying on Continental closed-trough conveyor belts, also known as pipe conveyor belt. Especially with the demand of the Chinese government for climate protection in coal mining, these are increasingly becoming the means of choice. In general, conveyor belts have emerged as the financially and environmentally more advantageous transport solution within a certain distance compared with alternatives such as truck fleets, since their operation emits less CO2 and there is no need for empty trips. Closed systems such as tube conveyors also offer other decisive benefits. They minimize dust emissions. In addition, the transported material itself is well protected against environmental influences such as wind, snow, sun and rain. “This is done by rolling up the belt,” explains Weisgerber. The outside edges of the belt overlap throughout the entire duration of transportation like a protective casing for the transported material. Only when taking up and delivering material do the closed-trough belts open up and assume the shape of a conventional conveyor belt.

It is estimated that coal dust emissions caused by gusts of wind, snow and rain amount to 0.12 percent of transported materials when open conveyor systems are used. In Yangquan, the Continental tube conveyor, with a width of 1,600 mm and an outer pipe diameter of 458 mm, transports 1,000 metric tons of coal per hour and 2.4 million metric tons of coal per year. “This results in an enormous saving of 2,880 metric tons of coal dust emissions per year – and thus significantly improves air quality. Thus, our system also protects the health of mine workers and improves the quality of life of the people living in the area,” Weisgerber emphasizes.

“We decided to use Continental’s closed-trough conveyor belts because they fully meet the relevant requirements with regard to climate protection, safety and efficiency,” says BiGui Chen from YanKan Coal. Continental’s technology helps meet stringent safety regulations for coal mines that dictate the maximum concentration of dust in the air. This is required not only when it comes to health and air quality, because among the most dreaded accidents in mining are coal dust explosions – a destructive reaction of coal dust with oxygen. These can occur very quickly when whirled particles of coal dust react with the oxygen in the air due to sparks, heated parts of equipment or similar. “The closed system from Continental is ideal, because no dust can escape. The closed-trough conveyor belts in Yangquan are also flame-retardant, adding another layer of safety,” BiGui Chen adds.

In Yangquan, the closed-trough conveyor belt system transports pit coal at a high speed of 4 m/s or 14.4 kilometers per hour. This is about three times the speed of a pedestrian walking briskly or a cyclist riding at a moderate pace. In terms of efficiency, the system scores points not only with its speed, but also with its energy efficiency. Miles of conveyor belts can consume as much electricity as a small town. Continental has developed a solution for this, too. Using a special rubber compound has enabled it to minimize the rolling resistance of conveyor belts and thus significantly reduce their energy consumption. This arises when the belt runs over the idlers, and accounts for two thirds and therefore the largest share of the total resistive forces of a conveyor system. “With the right compound, we reduced the energy consumption involved in transporting raw materials by 25 percent. This special compound is also used in the facility in Yangquan. This will improve the facility's carbon footprint and save on energy costs for the operator,” says Weisgerber.

Measurements by the Institute for Transport and Automation Technology of the University of Hanover have confirmed results according to which a conveyor system five kilometers in length can save over 3,000 kW of energy. The energy saved in 1.5 hours is therefore as large as the average annual consumption of a household in Germany or that of five households in China.

One particular challenge is the precise transverse rigidity, which ensures a good tube shape so that the belt does not collapse. If the rigidity is too high, the belt moving resistance will be too high and energy consumption will rise. Here, the expert knowledge of the appropriate engineers is required. In addition, Continental’s customer service engineers in Shandong visit the coal mine on a regular basis to ensure smooth belting, measure wear and check the condition of the closed-trough belt. They remain in constant contact with the operator in the process.

Continental closed-trough belt conveyors have already proven themselves in many places in China – in coal mines as well as in power plants and steel mills. Yangquan’s Shangshe coal mine has a 4.9-kilometer closed-trough conveyor belt system in operation. At the Anyang coal mine in Chenghe (Shaanxi province) and the Hongyuan coal mine in Puxian (Shanxi province), there are also four-pipe conveyors with a total conveying length of 8.7 km. Further projects are already being planned.