Environmentally friendly coal mining with the 2200 SM
The rapid industrialization of China and the related increase in the standard of living have resulted in a sharp rise of the energy demand of the People’s Republic in recent years. Coal is China’s most important resource for securing the country’s energy requirements. Some 70 percent of the entire energy production is covered by domestic coal mining, with environmental compatibility being an important aspect of the country’s energy policy. The Chinese government is investing huge sums of money in renewable energy, and coal mining is to become more environmentally friendly as well. That is why Shenhua Beidian Energy Co. Ltd. (short: Shenhua) relies on the use of Wirtgen surface miners. As it dispenses with drilling and blasting operations, surface mining proves to be the ideal alternative when it comes to making coal mining more environmentally friendly and more economically efficient at the same time.
Efficient process yielding high-quality results
The city of Xilinhot in Inner Mongolia, which is approximately 610 km from Beijing, is one of the largest energy centres in China. In addition to huge wind farms with more than 200 wind turbines, the coal deposit of Shenhua Beidian Shengli Energy Co. Ltd. (short: Shengli) is also situated in the immediate vicinity of Xilinhot. The entire deposit encompasses an area of 340 km² and some 22.442 billion tons of coal. Mining takes place both above ground and underground. The site has been split into five separate mines.
Shenhua Beidian Energy Co. Ltd. was incorporated in 2003. The new company’s main activities focus on the development of Surface Mine No. 1. This opencast mine, which covers an area of some 37 km² and resources of some 1.89 billion tons of coal, is the first of five opencast mining operations planned in the Shengli coal field. Some 20 million tons of coal per year will be mined in the Shenhua coal mine. The coal is supplied to a coal-fired power plant located in the immediate vicinity of the mine, which is one of the largest coal-fired plants in the world directly connected to a coal mine. The plant has a capacity of 8 x 660 MW.
The mine has meanwhile become a reference project in China for the environmentally friendly mining of coal using surface miners. “We have been very interested in the innovative surface mining technology right from the start. What convinced us in the end was a visit to coal mines in India that were operated solely by means of surface miners. We were very impressed by the efficiency of the machines,” says Mr. Liu, President of Shenhua Beidian Shengli Energy Branch Co. Ltd.
A surface miner of type 2200 SM equipped with a 3.80 m wide cutting drum unit gives impressive proof in the Shenhua mine, too, of how high-quality material can be mined without the tremendous strain usually put on the environment by drilling and blasting operations.
The principle of surface mining
- Surface miners cut, crush and load rock in a single operation – a single machine completes the job of various different pieces of equipment. Drilling and blasting is not required.
- Additional primary crushing is eliminated. The material can be either directly loaded onto trucks via a conveyor system or, alternatively, deposited as a windrow right behind the machine.
- The cutting depth of the surface miners can be adjusted to allow even thin seams of material to be mined selectively and with a high degree of purity, thus maximizing exploitation of the mineral deposit.
Mining coal with the 2200 SM
Embedding the Shenhua mine into the Shengli large-scale opencast project places the innovative Wirtgen surface mining technology in a direct comparison with conventional mining methods. Shenhua also used to employ conventional mining methods in the past: “We have employed two different mining methods: either dragline excavators which directly loaded the material onto trucks, or dragline excavators and mobile primary crushers. The first method involves very high current costs, however, while the second method requires a huge initial investment to be made. With the surface miners, we intend to strike a new and more efficient path in coal mining,” explains Mr. Liu.
The 2200 SM has been in operation in two fields of the Shenhua mine since the spring of 2009. In the first field, which encompasses roughly 50% of the entire work space, the machine with 3.8 m wide cutting drum removes an up to 25-cm thick coal seam. The cut material is deposited as a windrow behind the machine. While the surface miner cuts coal from the seams in the second field, the material cut in the first field is loaded onto trucks by means of wheel loaders.
The 3.80 m wide cutting drum unit: Maximum productivity for all types of soft rock
More than 150 Wirtgen surface miners of type 2200 SM are in operation around the globe. The standard 2200 SM model is equipped with a 2.20 m wide cutting drum. An optionally available 3.80 m wide cutting drum unit enables productivity rates in soft rock to be increased significantly.
Some 40 of the 2200 SM miners currently in operation are fitted with the 3.80 m wide cutting drum unit. The wider cutting drum unit enables tremendous production rates to be achieved, as is shown by the Shenhua example: equipped with the wider drum, the machine cuts up to 5,000 tons of coal in an 8-hour shift. A 1,500-litre fuel tank enables operating times to be maximized while keeping breaks in operation as brief as possible. In addition, the miner has been designed so as to minimize the time required for maintenance procedures. Vital machine components, such as the cutting drum, are readily accessible, allowing the quick replacement of wear parts, such as the cutting tools. These features make the 2200 SM with 3.80 m wide cutting drum unit a compact machine that offers maximum productivity levels.
Wirtgen GmbH has developed the 4200 SM for even higher performance levels: with its loading system, this miner is capable of loading heavy-duty trucks of up to 200 tons in a mere matter of minutes. The 4200 SM is the biggest surface miner produced by Wirtgen GmbH and is capable of mining up to 12 million tons per year in soft rock.
Surface mining – The environmentally gentle mining method
Blasting is the standard method used to remove material in opencast mining and rock operations. It creates heavy vibrations, and the environment is polluted by noise and dust. In China, surface mining has been specifically chosen because the innovative mining method entirely dispenses with drilling and blasting operations. It is gentle on the environment in more than one respect:
- It does not create any vibrations.
- The excessive noise pollution levels caused by blasting are eliminated.
- Low levels of dust are generated during the mining operation. To reduce the formation of dust even further, the surface miner is equipped with large tanks from which water is directly sprayed onto the cutting tools and cutting drum.
Surface miners create a safe work environment in the opencast mine
Surface miners are not only gentle on the environment but also increase safety during the mining operation:
- Wirtgen surface miners give surfaces and embankment walls a highly stable and accurate cross-section, thus enabling steeper embankment walls to be produced.
- Surface water can be specifically conducted away to the sump. Water cannot ingress into the surface. Loading the material by means of wheel loaders and trucks is safer and easier as the surface miner produces an even and stable subgrade.
- Positioning the cutting drum unit in an enclosed housing underneath the machine not only reduces the generation of dust but also eliminates the risk of flying chunks of rock.
Economical advantages of surface mining: Improve quality, reduce costs
Dispensing with blasting operations has a positive effect also on economic efficiency: maintaining a safe distance to residential areas at the periphery of the coal deposit is not required, and maximum exploitation of the mine is guaranteed. In addition, the costs of material processing are reduced: Wirtgen surface miners produce particle sizes of less than 100 mm, which dispenses with the need to crush the material in an additional operational step. The use of surface miners reduces both the overall investment cost, as it dispenses with the need to purchase crushing equipment, and the current production costs.
These advantages have positive effects also on the coal mining operation in China: 97 percent of the mined material has a particle size smaller than 100 mm. The small particle size enables the trucks to accept 10% more coal per truck load. In actual figures, the use of conventional mining methods in the Shenhua mine required 526,000 truck transports per 10 million tons of coal. The use of surface miners, on the other hand, enabled the number of truck transports to be reduced to 500,000. Fewer trucks, less fuel and less maintenance are required for the same production volumes.
Selective mining guarantees high degrees of material purity
Selective mining produces material of high quality, which is an important economical aspect that carries weight in particular in coal mining. Wirtgen surface miners enable the coal to be extracted in a precise operation, thus influencing the product quality at an early stage. The higher quality results in a higher calorific value: less coal is needed to generate the same amount of energy.
The coal mining project in China gives impressive proof that Wirtgen surface miners are ideal candidates for the environmentally compatible, safe and economically efficient mining of useful minerals.