By Dr. Syd S. Peng
China is rich in coal, but poor in other forms of energy resources such as oil and gas. To ensure a steady, reliable energy supply, China relies largely on domestic energy resources to develop its economy. Under this policy, coal has been the dominant component of China’s primary energy and accounts for more than 70% of the primary energy consumption, boldly carrying the load for sustaining China’s 8%-9% annual growth in Gross Domestic Product for the past three decades. The rate of self-sufficiency has been above 90%.
There is no simple way to describe, nor summarize the Chinese coal mining industry. The entire sector varies greatly as far as its immense scale, geology, production technology and safety performance. Moreover, different types of statistics related to coal mining are collected by various independent agencies not related to the coal industry. Individual mine production ranges from a few thousand tons per year to those producing more than 20 million metric tons per year (mtpy). The mining techniques vary from totally labor-intensive coal loading to automated longwall production with the same type of equipment used in the U.S.
In fact, the Chinese are very innovative. Many mines are using state-of-the-art technology not seen in western coal mines. For example, Figure 1 shows a self-contained cap lamp, weighing less than 4 oz that lasts more than 24 hours. It was developed in-house at Zhang-Cun coal mine, LuAn Group, Shanxi Province, and has been in use for more than two years.
The Chinese are also extremely conscious of coal reserve recovery. They do not waste reserves and mine many seams in poor geological conditions, including seams up to more than 45° in inclination—seam conditions U.S. coal operators would likely never consider.
China has a total proven coal reserve of 997 billion mt. They are located mainly in the west and northeast, while population is concentrated in the southeast coastal areas (Figure 2). Table 1 shows the distribution of type, quality as well as geological conditions of reserves. An overwhelming majority of the reserve are deep and amenable for underground mining only.
China is by far the largest coal producer and consumer in the world.
China reports production as raw coal tonnage and Figure 3 shows the annual raw coal production from 1980 to 2010. Today, nearly 60% of total production is washed before it ships. Since 2003, coal production has been growing at an average annual rate of 250 million mt. At the end of May 2010, production stood at 1.29 billion mt. The 3.2 billion tons in Figure 3 is an estimated production number. With 1.1 billion clean tons in 2009, the U.S. is a distant second.
Until the People’s Republic of China was established in 1949, coal production was insignificant. From 1949 to 1980, the national strategic mines were established to mine coal under a planned economy in which production, sales and pricing were strictly controlled, and production fluctuation was kept to minimum. In the early 1980s, economic reform and a more open policy brought about vibrant economic activity in all walks of Chinese life and demands for energy increased sharply. Consequently from 1980 to 1997, in addition to an accelerated production increase in national strategic mines, township mines were developed to meet demand. As a result, there were a total of 64,000 mines in 1997 of which 61,000, or 95.3%, were small mines. Under that policy, over-decentralization of production caused a supply-demand imbalance and eventually led to a severe recession in the coal industry.
From 2000 to present, the coal industry has been re-organized. Coal production is being properly controlled and production distribution is being optimized. Larger coal production groups have been formed and small and medium coal mines are being consolidated. Township mines in particular were consolidated with larger national strategic mines under government guidance. Meanwhile, a Chinese-styled market economy was applied to the coal industry.
Today China has about 15,000 mines of which 12,000 mines produced less than 300,000 mt annually. The latest policy is to build larger group companies with sufficient resources to manage and operate the state-of-the-art coal mines. In 2008, there were 268 safe and high-efficient mines producing 836 million mt and accounting for one third of the total production (Figure 4). Among them, 25 extra-large companies produced more than 30 million mtpy (Table 2). Another 14 conglomerates or groups of extra-large coal mines have been under construction. Those mines were and continue to be developed using state-of-the-art technology.
Coal mines in China are traditionally grouped into three types: national, provincial national and township mines. National strategic mines are mines developed and operated directly by the central government under the original planned economy. In recent years, consolidated small mines have been included. There are a total of 268 national mines located in 22 provinces. In 2008, their production accounted for 50.7%
Provincial national mines are mines developed and operated directly by the 26 provincial governments in which the mines are located, and in recent years the consolidated small mines have been included. In 2008, their production accounted for 12.7%.
Township mines are those developed after coal markets opened in 1980 and operated by the county and city governments in which the mines are located or by private citizens. They are located in 26 provinces and in 2008, their production accounted for 36.6%.
Strictly, this type of classification of mines was only valid before the Ministry of Coal Industry was abolished in 1997. Thereafter, control and operation of all types of mines was transferred to the provinces. Today only two large groups of mines are controlled directly by the central government, Shenhua and China Coal, while many provincial national mines have been transferred to township and/or private contractors.
In 2008, underground mining accounted for 85.9% of total production, open-pit mining 6%, and other types 8.1%. There are more than 20 different underground coal mining methods in China, almost exclusively longwall. In general, they can be classified into the following six major types:
Thin seams 0.4- to 1.3-m (1.3- to 4.3-ft) thick—For thin seams, based on types of face equipment used, especially the cutting machines, three types of mining methods are practiced:
• A shearer cutting machine, armored face conveyor (AFC) and shields for mining heights less than 1.3 m (4.3 ft) and for seams less than 5° in inclination. Panel widths are normally 120- to 150-m (394-492 ft). The average annual production would be 1–1.2 million mt.
• Plow cutting machine, AFC, and shields for 0.8- to 1.2-m (2.6-4 ft) seam thickness. Panel widths are up to 260 m (853 ft) with annual production 734,000-2.5 million mt.
• Auger mining for seams 0.4- to 0.6-m (1.3-2 ft) thick and soft seams for mining irregular property boundary coal blocks or extraction of coal pillars.
Medium seams 1.4- to 3.5-m (4.6- to 11.5-ft) thick and low inclination (5°-25°)—For this type of seam, the fully-mechanized longwall mining method is employed for most mines, while a small portion uses the semi-mechanized method.
• Fully-mechanized longwalls are similar to that employed in the U.S. with the following features of face equipment: shearer with electric haulage, 700-1,500 kw (966-2,070 hp); and an AFC, with a pan width +1,000 mm, 630-1,400 kw (870-1,932 hp) driving power; and shields (or chock shields), 2- or 4-legged, yield capacity 400 to 800 mt (440 to 880 tons).
• Semi-mechanized longwalls in which single hydraulic props with roof beam rather than shields are used.
Thick seams, >5 m (> 16.4 ft) thick and low inclination (5°-25°)—For thick seams, multi-slicing longwalls are used. The upper 3 to 3.5 m (9.8-11.5 ft) of the seam is extracted first using the fully- or semi-mechanized longwall methods. The remaining lower portion of the seam is then mined one to two years after. In the upper slice mining, a false roof is prepared for the lower slice mining by laying wire mesh either on top of the canopy or below the base plate of the shields. The face equipment used is similar to those for the fully- or semi-mechanized longwalls.
Thick seams, 3.5- to 6.5-m (11.5- to 21.3-ft) thick and low inclination (5°-25°)—In this type of mining the whole seam is mined in one slice. Some features of the face equipment include a shearer with electric haulage, 900-2,200 kw (1,242-3,036 hp); AFC with a 800- to 1,200-mm pan width, 800-2,500 kw (1,104-3,450 hp) driving power; and shields, up to 6 m (20 ft) high and yield capacity 800 to 1,000 mt (880 to 1,100 tons).
Extra-thick seams, 5- to 7-m or more (16.4- to 23-ft or more) thick and low inclination (5°-25°)—For the extra thick seams, top coal caving method is employed. In this method, the lower 3- to 3.5-m (9.8-11.5 ft) is mined by the fully-mechanized longwall method except the 4-leg chock shields are used with an additional AFC installed behind the base plate of the shield in the gob area for drawing and hauling the caved top coal. The ratio of mining coal height to caving coal height is normally within the range of 1.33 to 3 m. This method began in the 1980s and has grown into a mature technology. Some features of the panels, face equipment and production include a shearer with electric haulage, >900 kw (1,242 hp); AFC, with a 1,000- to 1,200-mm pan width and 1,200- to 1,400-kw (1,656- to 1,932-hp) driving power; and chock shields with two AFCs (one in front and one in rear), 3.5- to 6.3-m (11.5- 20.6-ft) high and yield capacity 560 to 1,000 mt (616 to 1,100 tons). Annual production ranges from 6 to 8 million mt raw with a maximum 17 million mt raw.
Seams with special geological conditions—Seams with special geological conditions include the following three types:
• Seams with hard coal (4,350 to 6,380 psi compressive strength) and hard roof (>15,000 psi). Under this geological condition, the hard roof is softened prior to mining with blasting or water and heavy powered supports are used.
• Seams with soft coal (435 to 2,175 psi), soft roof and soft floor (<3,000 psi) e.g., claystone. For this type of geological conditions, large capacity shields are used.
• Seams with great inclination, 25°-45°. For this type of geological condition, top coal caving is used.
The percentage of each mining method used by all of the mines is not available. However, the 2008 data for distribution of mining methods employed by the 268 national strategic mines is available. They operated 1,545 longwall faces and 4,808 development faces. Of these, 88.3% would be considered mechanized. Mechanized mining could be further subdivided into fully-mechanized (82%), semi-mechanized (6%), and hydraulic (0.3%).
Due to the extremely large numbers of township mines, detailed statistics regarding each mine’s mining and geological conditions are not available. In general more than half of the township mines in Shanxi and Inner Mongolia employ mostly mechanized mining methods. However, due to poor geological conditions for coal seams in Hunan, Sichuan and Chongqing, mechanized methods are difficult to apply. Therefore, production methods and techniques described in this article were confined to the national mines, in particular, national strategic mines.
Transportation of Coal
In China, coal is mined in the less populated western and northeastern regions. The population is concentrated in the southeastern coastal areas, where the economy is the most developed. Such a great difference of location between the producers and the consumers has led to the following basic framework for China’s energy flow: large-scale transportation of coal over long distances.
Coal transportation relies on railroads, trucks, inland waterways and offshore shipping. In 2008, railroads handled roughly 60% of the total production, inland waterways and offshore shipping 30%, and trucking 10%. Despite the recent completion of many railroads, coal transportation to the consuming areas, especially to the southeastern coastal areas, remains very tight.
For Chinese coal, there are four major users (Figure 5): electric generation (52%), metallurgical (17%), cement (15%), chemical feedstocks (5%), and others (11%, which includes approximately 6% for residential use). In 2008, Chinese generating capacity stood at 792.53 mw, of which coal accounted for 75.9%, hydro 21.6%, and wind 1%. In 2008, electrical power consumption was 3,433,400 mw-h, of which coal accounted for 81%, hydro 16.4%, nuclear 2% and wind 0.4%.
Steelmakers accounted for roughly 18% of total coal consumption. In terms of total energy used for steelmaking, coal’s share, including met, steam and powder coals for coke oven, was about 70%.
Chemical feedstocks include the making of fertilizers and other coal-derived chemical products. Notable development in this category was the successful production of oil from coal (coal-to-liquid) at the end of 2008 by LuAn and Shenhua groups. The plants are capable of producing 5 million mt of oil annually.
In the process of changing administrative control of national industries in 1997, the central government decided to abolish the ministries of several industries including coal. The more than 800 employees with the Ministry of Coal Industry in Beijing were going to be laid off. So I wrote a letter to then Prime Minister Zhu Rongji and suggested that rather than abolish it outright, it would be much more beneficial to re-organize the Ministry into an organization similar to the U.S. Mine Safety and Health Administration (MSHA) to deal with the severe mine accident issues. He accepted and created, after more than a decade’s evolution, the State Administration of Coal Mine Safety (SACMS). Today, SACMS functions similar to MSHA. It has 26 provincial branch offices in coal-producing provinces with a total of 73 district offices.
Similar to Chinese mining technology, the accident rates vary widely for different mining groups. They have many safe mines but they also have many mines employing unsafe mining practices. Accident rates such as the fatality rate is defined by number of fatalities per 1 million mt raw of coal production. The fatality rate has been decreasing steadily for the past 30 years. Since 2000, the fatality rate has improved considerably (Figure 6). For national strategic mines, the fatality rate in 2008 was 0.33. Aside from the direct causes discussed below, the imbalance between areas of production and demand provides the opportunity for the unsafe small township mines to continue to contribute to the fatality numbers.
Major Types of Accidents
Table 4 is a summary of all fatalities for the three mine types in 2008. Obviously, township mines were the major problem areas. They produced 37% of the total coal but accounted for 73% of the fatalities.
The major categories of accidents consisted of gas, flooding, roof fall, fire and haulage (Figure 7). Gas accidents included primarily coal and gas outbursts, followed by methane explosions. They occurred more at the faces of roadway development and in the township mines. The causes for methane explosions included either no methane monitoring system or if it existed, improperly installed or insufficient sensors, improper local ventilation or mine ventilation system, and illegal blasting and electric equipment. Coal and gas outbursts occurred mostly in geologically disturbed areas or where coal seams were subjected to rapid geological changes.
Flooding accidents occurred the most at the roadway development faces cutting into the abandoned mines that were flooded with water. The major causes were unknown geological conditions, advance water detection procedures were faulty, or ignorance of legal requirements.
Roof fall accidents occurred largely in township mines, and in descending order of frequency, at the coal mining faces, roadway development faces, roadways, shafts and gob. The major causes for roof falls were no support and poor quality of supports.
Mine fire accidents were due to spontaneous combustion of coal in the gob areas that were not sealed properly or timely, mismanagement, no monitoring system for hazardous gases, and poor ventilation systems.
Haulage accidents involved mainly hoisting equipment due to poor maintenance, brake failures, wire rope failure, mine car collisions, etc.
Methods for Fatality Reduction
The governments have been working very hard to reduce the accident/fatality as shown by the sharp reduction in fatality in recent years (Figure 6). In addition to strengthening the enforcement of safety supervision of coal mines, and guiding local governments and enterprises to intensify efforts in technological upgrading for coal mine safety, the construction of safety facilities, and shutting down the illegally operated small township mines, the most effective measure is closure of small township mines.
In 2007, 11,155 township mines were closed. More than 1,000 more township mines were closed in 2008 and 2009 respectively eliminating approximately 250 million tons of production capacity. The target is to close small mines to less than 10,000 in 2010. The on-going approach to deal with those township mines is that small township mines surrounding the national strategic mines are being consolidated and put under the supervision of the corresponding national strategic mines. Under this policy, small township mines began to employ proper mining methods and safe practices. Consequently the fatality rate for township mines has been reduced considerably from 5.5 in 2005 to 2.337 in 2008.
Coal Mining Machinery
In 2007, the latest statistics available, there were a total of 115 Chinese manufacturers making all types of coal mining machines and the number of manufacturers increased on average five per year. As an example, there are more than 160 models of Chinese shields. As many as 14 Chinese manufacturers made 546 shearers (509 double-drum ranging arm, 35 single-drum ranging arm and three plows) in 2007. A total of 32 companies built 725 AFCs.
China also imports equipment. Imported mining machines can be grouped into two types: complete and partial sets. In the complete set category, the whole set of face equipment was imported, mainly because no comparable quality of products existed in the domestic market. The best example is the Shenhua group in Inner Mongolia where the geological conditions are similar to U.S. For the past 15 years they had imported many sets of longwall face equipment from the U.S. and Germany. In the partial set category, one or more types of face machine were imported while the remainders were from domestic manufacturers. The typical example was the Tiefa group’s plow system in which the plow, AFC and shield’s electro-hydraulic control system were imported from Germany while shields were made domestically.
Import and Export of Coal
Chinese coal exports are controlled and a quota is distributed by the central government to a few coal groups. It is adjusted periodically depending on the domestic situation of supply and demand. Major receiving countries and areas for steam coal exports were India, Japan, South Korea and Taiwan, while Brazil, India, Japan and the U.S. imported Chinese coke.
More recently, however, China has become a net importer of coal. And, the import policy for coal is more liberal. The import climate is most ripe for the southeastern coastal areas where it is farthest from the coal producing areas, while the demand is the greatest due to concentrated population. Fujian, Guangdong and Guangxi are the three major provinces importing coals. Preliminary statistics shows for the first five months of 2010 net import of coal totaled 60.11 million tons.
Since the implementation of reform and the more open policy in the early 1980s, coal supply has advanced from shortage to a near equilibrium state. The coal economy has evolved from planned to Chinese-styled market economy.
Production has changed from small-scale numerous coal mines to conglomerates of extra-large mines. For example in 2003, the numbers of mines were reduced from more than 81,000 to about 25,000. That figure was further reduced to 15,000 in 2009. Development of 13 +100 million-mt coal mining conglomerates has begun, the first of which went into production in December 2008. Under this policy:
• Mechanization improved considerably in recent years, more than 90%, in national strategic mines with productivity reaching 5.06 mt/man.
• Coal mining companies have expanded from single product enterprise, i.e., producing coal, to multiple coal-based enterprises to include electric generation, aluminum, chemical, construction, coking and coalbed methane.
• Fatalities for all coal mines have decreased steadily from 9.44 per million raw tons in 1978 to 1.485 in 2007.
• Continue to renovate medium- and small-sized coal mines and shut down small ones not conforming to industrial policies, with poor safety conditions, wasting resources and harming the environment, so as to further optimize the structure of the coal industry.
• Promote the coordinated development of related industries, and encourage coal-electricity joint operation or coal-electricity-transport integrated management, so as to extend the coal industry chain.
Coal is and will be the main energy source for China and it will remain that way for a long time to come. This is not to say coal supply and demand will not experience supply shortage or oversupply in any types of coals or in some districts or within some brief periods. Coal consumption and consequently production in China will grow in response to national economic growth in the long run. To sustain the current rate of GDP growth of 8.9%, coal production in 2020 will have to reach more than 4 billion mt.
About the Author
Dr. Peng is the Charles E. Lawall Chair of Mining Engineering for West Virginia University. He can be reached at: Syd.Peng@mail.wvu.edu. This article was prepared while the author was on assignment during July 2010 with Henan Polytechnic University, which is located in Jiaozuo, Henan, China.