1、Application of HEMS cooling technology indeep mine heat hazard controlHE Man-chao1,21School of Mechanics 2) the Sanhejian model with a shortage of source of cold energy and a geothermal anomaly and 3) the Zhangshuanglou model with plenty of source of cold energy. The cooling process of HEMS applied
2、in deep coal mine are as follows: 1) extract cold energy from mine water inrush to cool working faces; 2) use the heat extracted by HEMS to supply heat to buildings and bath water to replace the use of a boiler, a useful energy saving and environmental protection measure. HEMS has been applied in th
3、e Jiahe and Sanhejian coal mines in Xuzhou, which enabled the temperature and humidity at the working faces to be well controlled. Keywords: deep mine heat hazard; mine classification; mine water inrush; heat hazard control model 1 IntroductionCoal has been the major energy source in China for a lon
4、g time, occupying an irreplaceable position in the one-off energy structure. Shallow resources have become increasingly exhausted as a result of exploitation over long periods. Therefore, most coal mines have had to resort to deep exploitation. In addition, the complex geo-mechanical environment inc
5、reases the risk of frequent engineering accidents. This complex geo-mechanical environment is caused by “the three highs and one disturbance”, i.e., high ground stress, high ground temperature, high osmotic pressure and intensive disturbance through exploitation1.There are many local disasters, such
6、 as gas explosions, pressure bumps, laneway bottom water inrushes, serious mine pressure, severe deformation and pheological behavior of surrounding rock. However, the high temperature heat hazard in deep mines is the risk of disaster we have to cope with at present. High temperature heat hazard in
7、deep mines affect not only the mechanical properties of surrounding rocks, but also safety in mine production2. According to incomplete statistics, there are a total of 33 mines in China with a mining depth exceeding 1000 m, with the temperature of the working face reaching 3040 C. The problem of de
8、ep mine heat hazard has already seriously affected the energy resource development in China, which needs to be urgently solved. With the increase in mining depth, the temperature of the surrounding rock keeps rising, seriously increasing heat hazard in exploitation and tunneling working faces. Durin
9、g the 1950s and 1960s, serious heat hazard occurred in some deep mines both at home and abroad. In the 1970s, the problem became more widespread with a tendency of developing from a few individual mines to all coal mines. According to some preliminary statistics of mines in foreign countries3, the a
10、ir temperature in mines of western South Africa has risen to 50 C at a depth of 3300 m. Because of the near presence of geothermal water, the air temperature in the Fengyu lead-zinc ore mine in Japan is up to 80 C at a depth of 500 m. By the year 2000, the average mining depth of state-owned coal mi
11、nes in China was about 650 m and the average temperature of the original rock ranged between 35.9 and 36.8 C at the production level. For those mines with a depth exceeding 1000 m, the original rock temperature ranged between 40 and 45 C while the temperature at the working faces was between 34 and
12、36 C, causing most mines to become heat hazard areas of the first or second level. Such hot environments do serious harm to the workers health and are the cause of low physical ability, such as low work efficiency, heat-strokes and thermal blooming. All that above results in neurological disturbance
13、s for workers, reducing the ability to protect themselves and may seriously affect the safety production.In order to further our understanding and control of the conditions of high temperature mines in China, the China University of Mining in Jiangsu, the Jiahe and Sanhejian coal mines of the Xuzhou
14、 Mining Company, the Yaoqiao coal mine of the Datun Coal and Electricity Company, the Baiji coal mine of the Lianyungang Mining Company and the Liuzhuang coal mine of the Guotou Xinji Company. Included in the investigation in Anhui province was the Panyi coal mine of the Huainan Mining Company and i
15、n Henan province, the #4, #6 and #11 mines of the Pingmei Company and the Liangbei coal mine of the Shenhuo Company. At present in China, the coal mines can be divided into three groups, based on investigations of high temperature coal mines at home and abroad and on in-situ studies of typical mines
16、 on their cooling measures applied to any kind of coal mine.2 Distribution law of ground temperaturesAccording to information provided from these investigations, there are 13 coal mines in Shandong province with temperatures exceeding 26 C at the working faces, six of them with temperatures ranging
17、between 26 and 30 C at the working face and seven with temperatures exceeding 30 C. There are five coal mines in Jiangsu with working face temperatures exceeding 26 C, three of them with working face temperatures between 26 to 30C and two with working face temperatures exceeding 30C. In Anhui, there
18、 are 10 coal mines with working face temperatures exceeding 26C, seven of them with temperatures between 26 to 30C and three with working face temperatures exceeding 30C. There are 12 coal mines in Henan with working face temperatures exceeding 26C, two with temperatures between 26 to 30C and 10 wit
19、h temperatures exceeding 30 C. Distribution law of ground temperatures in some areas of China were obtained from analyses of ground temperature parameters in several typical mines.Fig. 1 shows relationships among ground temperatures, working face temperatures and depths in the Xintai Suncun coal min
20、e. As shown in the two figures, ground and working face temperatures increase sharply with increase of exploitation depth. High temperature heat hazard at working faces are problems we must face.Fig. 1 Relationship between strata and ventilation temperature at working face and depth in the Suncun co
21、al mineFig. 2 shows the distribution of ground temperatures of the Jiahe coal mine in Xuzhou. We can see from this figure that the temperature becomes higher and higher with an increase in depth. The increase becomes nonlinear when the mining depth is from 700 to 1200 m, especially when the mining d
22、epth is 1000 m, this nonlinear distribution of ground temperature shows how serious the increase in heat hazard in the mine is.3 Classification and characteristics of minesClause 102 of the Safety Regulations in Coal Mines4 in China prescribes that the air temperature at the tunneling working face o
23、f a mine shall not exceed 26C. If the temperature were to exceed 26C, the work time should be shortened and protective measures supplied to workers. The workers should stop work when the air temperature at the working face exceeds 30 C. Based on investigations of typical mines, the definition of a h
24、igh temperature mine is a mine where the air temperature exceeds 26C at the working face during production.According to national investigations and typical studies in mines, high temperature mines are mainly found in the eastern mining areas of China, such as the Huaibei and Huainan mining areas in
25、Anhui province, the Xuzhou mining area in Jiangsu province, the Xinwen mining area in Shandong and the Pingdingshan mining area in Henan province. Mines in these areas have a common characteristic when high temperatures appear for the first time: there is no high temperature heat hazard above a spec
26、ific production level, but once the mining depth exceeds this level, heat hazard will appear to different degrees. According to temperatures at the working face, mines can be divided into three groups.3.1 Normal temperature minesIf the air temperature at the tunneling working face in a mine does not
27、 exceed 26 C, this kind of mine is called a normal temperature mine. The mining depth is usually less than 800 m and the temperature of the surrounding rock of the laneway is about 30C. The geothermal gradient is from 1.5C/100 m to 1.8C/100 m, the relative air humidity at the working face is less th
28、an 80% and usually there is no illness caused by heat hazard. 3.2 Middle-high temperature mines If the air temperature at the tunneling working face is between 26 and 30 C, the mine is referred to as a middle-high temperature mine. The mining depth of this kind of coal mine is between 800 and 1000 m
29、 according to our investigation. Included in this group are mines such as the Xincun and Yaoqiao coal mines. This kind of coal mine has been expanded to deep exploitation. High temperatures at the working face have gradually become an important factor that limits normal production. Surrounding rock
30、temperatures of laneways are about 35 C. The geothermal gradient is about 2 C/100 m and the relative air humidity at the working face is less than 90%. In these middle-high temperature mines, thermal blooming and heat strokes are frequent occurrences in workers at the working face. 3.3 High temperat
31、ure minesIf the air temperature at the tunneling working face exceeds 30 C, this kind of mine is called a high temperature mine. Mining depths of this kind of coal mine usually exceed 900 m. At present, these depths are largely between 1000 and 1300 m, such as in the Jiahe, Sanhejian, Suncun and Tan
32、gkou coal mines. In these mines, the surrounding rock temperatures of the laneways range from 37 to 42 C, the geothermal gradient is more than 2 C/100 m, with a maximum geothermal gradient of 3.42 C/100 m. Maximum temperatures on the corner of return airways in the summer range from 34 to 37 C and t
33、he relative air humidity at the working face is between 95% and 100%. Heat hazard are therefore a very serious possibility. Workers often suffer heat-strokes and feel faint when working in high temperature mines. There are frequent casualties in deep mines. This hot environment not only harms the he
34、alth of workers, but also leads to neurological disorders, which cause people to go into a trance, feel fatigue, a general weakness or become dazed. These states of mind are the main reasons inducing accidents.4 Suggestions for the three kinds of minesFor normal temperature mines, we suggest that so
35、me effective measures, such as a perfect management system or improvement in management should be implemented For middle-high temperature mines, we should enhance non-mechanical technology, such as increasing ventilation and improving the ventilation layout. With such improvements, we can meet the c
36、ooling needs. For high temperature mines, we must take mechanical cooling measures. The suggested measures to be taken in all three groups of mines are shown in Table 1. 5 Operating principle of HEMSBased on the research cited above and given the existing problems in cooling technology at present as
37、 well as the deep mine heat hazard situation in the Jiahe coal mine of the Xuzhou Mining Company, it had been suggested that the China University of Mining it saves energy and reduces pollution and conforms with sustainable development of energy use in China.6 Cooling models and technologyThree cont
38、rol models of deep mine heat hazard are proposed and the HEMS technology is formed according to the characteristics of the strata temperature field in the Xuzhou mining area and on differences of mine water inrush1115.6.1 Jiahe model: moderate cold energyThe mining depth of the Jiahe coal mine is do
39、wn to 1000 m and the heat hazard is very serious, with a working face temperature of about 36 C. The mine water inrush is from 95 to 135 m3/h. The building heating and bath water are supplied by boilers, which wastes plenty of resources and seriously pollutes the environment. According to the specif
40、ic conditions in the Jiahe coal mine, the HEMS is adopted to reduce the temperature in the mine. The source of cold energy is moderate and meets the need of the objective for refrigeration. Cold energy in water is utilized and heat is generated during the process of cooling, which can be used for he
41、ating buildings and bath water instead of using the boiler.There are two phases of engineering construction, given the specific conditions in the Jiahe coal mine. Phase one uses mine water inrush as cold energy; its operating principle is shown in Fig. 4a. Phase two uses high-low water level circula
42、tion for cold energy. Its operating principle is shown in Fig. 4b. This system has been successfully applied at two working faces and four tunneling faces in the cooling project in this mine. The design and construction of the heat utilization project on the ground has been completed.Fig. 4 Diagram
43、of cooling function of Jiahe model with mine water inrush and circulation of water levels as sources of cold energy 6.2 Sanhejian model: cold energy shortage and geothermal anomalyThe mining depth of the Sanhejian coal mine is now 1000 m and heat hazard are very serious. The temperature at the worki
44、ng face is about 38C. Mine water inrush is 60m3/h and its temperature ranges from 25 to 30C. Complementary dynamic water of the Ordovician system amounts to 1020 m3/h, where the water temperature is 50 C because of a geothermal anomaly. Heat for the buildings and bath water is supplied by a boiler,
45、which wastes plenty of resources and seriously pollutes the environment. According to the specific conditions in the Sanhejian coal mine, the HEMS is adopted to reduce the temperature in the mine. There is insufficient mine water inrush and sources of cold energy are in short supply. Therefore, we s
46、hould make use of a geothermal anomaly in the Sanhejian coal mine. First, heat energy is extractedfrom the hot mine water inrush for building heating on the ground in the winter. The HEMS replaces the boiler and cold energy is obtained during the process. Cold energy is stored underground and will b
47、e used for cooling at the working faces in the summer.There are two phases of engineering construction, given the present conditions in the Sanhejian coal mine. Phase one uses horizon circulation of water as cold energy, whose function diagram is shown in Fig.5a; phase two is the geothermal utilizat
48、ion project. Its function diagram is shown in Fig. 5b. This system has been successfully applied at two working faces and four tunneling faces in the cooling project of the Sanhejian coal mine. The design and construction of the ground heat energy utilization project is now completed. Fig. 5 Diagram
49、 of horizontal circulation and geothermal anomalous cooling function of Sanhejian model 6.3 Zhangshuanglou model: rich in cold energy The mining depth of the Zhangshuanglou coal mine is down to 1000 m and the heat hazard is very serious. The working face temperature is about 37 C and mine water inrush ranges from 1000 to 1200 m3/h.Heat for buildings and bath water is supplied by boilers, which wastes plenty of resources and pollutes the environment seriously. According to the specific conditions in the Zhangshuanglou coal mine, the HEMS
