In Yangquan, northern China’s Shanxi province, Continental says it is using a closed-trough conveyor belt system to ensure the smooth and environmentally friendly extraction of pit coal. The closed system minimises dust emissions at operator YanKan Coal’s mining site, and is also fireproof and has low rolling resistance, making it particularly energy-efficient. The system, which is one of the longest closed-trough conveyor belt systems in China, covers a distance of 8.1 km.
Making coal mining environmentally friendly while at the same time investing in the expansion of renewable energies are important aspects of China’s energy policy. This is where the products from Continental help, says the manufacturer. In China, as is the case around the globe, it is all about balancing the energy needs of the population and industry on the one hand, with climate change mitigation on the other. “For the operators of mining facilities, the fundamental question is which technical solution is the safest, most reliable and cost-effective method of transporting coal and other raw materials from the perspective of climate protection and energy efficiency,” says Stephan Weisgerber from Continental 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 conveyors. 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 minimise 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% 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 tonnes of coal per hour and 2.4 million metric tonnes of coal per year. “This results in an enormous saving of 2,880 metric tonnes 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 emphasises.
“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.
Shanxi’s coalfields account for 37% of the province’s total area. There are approximately 200 billion metric tonnes here, which roughly equates to one third of China’s coal deposits. Much of the province is more than 1,000 m above sea level. And the 13.37-square-kilometere mining area of YanKan Coal Ltd in Yangquan is also hilly and almost impassable.
In mining, whether above or below ground as well as in industrial applications, large inclines and tight bends with low space requirements and high mass flows must often be overcome. While the angle of incline of troughed belt conveyors is usually 20° or less and curve radii remain very large, a pipe conveyor allows curve radii and tilt angles of up to 30°. The Yangquan closed-trough conveyor belt overcomes elevation differences of up to 172 m over its 8.1 km stretch from the coal deposit to the transfer station, going through a complex route with over 39 convex, concave and 20 horizontal bends. “Our closed-trough conveyor belt easily masters tight bends and steep conveyor angles and thus adapts perfectly to the landscape to save space. Our system is characterized by the fact that it manages without transfer points,” says Ming-Ya Tang from Continental. This also has a positive effect on the installation costs of the assembly, which are generally cheaper than for assemblies with transfer points.
In Yangquan, the closed-trough conveyor belt system transports pit coal at a high speed of 4 m/s or 14.4 km per hour. 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 minimise 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%. 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 5 km 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.
In cooperation with conveyor manufacturer Sichuan Zigong Conveying Machine Group (ZGCMC) and the Continental experts in China, it has been possible to develop a closed-trough conveyor belt system in Yangquan that meets the highest conveyor system engineering requirements and optimally overcomes geographical hurdles – to the customer’s great satisfaction and ensuring the best possible protection for the climate and employees. Closed-trough conveyor belt systems such as the one in Yangquan are also unique. That is because every belt is custom-made to suit the local circumstances. Depending on the requirements, the closed-trough belt is designed with high-quality fabric or steel cable tension members.
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 km 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.
