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Analysis for Gas Control Technology of Coal Mine in Guizhou
来源:  作者:李青松  编辑:龙涛  日期:2015-05-05  点击率:297  [我要打印]  [关闭]
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Analysis for Gas Control Technology of Coal Mine in Southwest Guizhou

Li Qingsong1,2,a, Li Guohong1,2,b,Heng Xianwei1,2,cZhang Shujin1,2,d

1Guizhou Coal Mine Design and Research Institute, Guiyang, Guizhou 550025;

2Guizhou Province Engineering Technology Research Center for Coal Gas Prevention & Control, Guizhou Guiyang 550025

aliqingsong@126.com, b85653214@qq.com, c272160330@qq.com, d328833372@qq.com

 

Keywords: Gas Occurrence; Gas Control; Coal Mining Area of Southwest Guizhou

Abstract: Through on-site inspection for the typical coal mines of each coal tectonic units in Southwest Guizhou as well as analysis of gas parameter, highlight information and gas control technology, the thesis makes the following conclusions. Namely, the overall state of coal seam gas occurrence in Southwest Guizhou mining area presents characteristics with high degree in north and west together with low degree in east. With regard to the existing problems in gas control of this region, it has put forward some suggestions. For example, people shall add test parameters for coal seam gas in most mines, find out status of the mine gas occurrence, make specialized design in terms of gas emission characteristics and perform strict management to ensure proper implementation. Moreover, people can carry out targeted research for outburst prevention indicator, establish suitable predictor system, optimize instrument and equipment, match with current advanced production technology, introduce professional talents and strengthen training for related technology and management personnel.

1 Coal mining status and laws of coal seam gas occurrence in Southwest Guizhou

(1) Current distribution status of mines

Located in the Southwest of Guizhou province, Southwest Guizhou belongs to the mining area of outburst hazardous zone set by the state. Up to June 30, 2013, Southwest Guizhou has established 141 pairs mining rights with a total scale of 29.19 million t/a. Within this region, there are 32 pair outburst mines, accounting for about 23% of all coal mines. As for outburst mines, they mainly distribute in four counties and cities including Puan County, Qinglong County, Xingren County and Xingyi City. In addition, the coal seam gas of Zhenfeng and Anlong County is relatively small. Thus, there are no outburst mines at present.

(2) Research on laws of coal seam gas occurrence

From figure 1, most outburst mines distribute in the north and southwest of Southwest Guizhou, a region near the Liupanshui coal mine[1]. As a matter of fact, coal tectonic units in this area are Zhongying syncline, Bihenying syncline, Laoguishan anticline, Nibao syncline, Nasheng anticline and Huangnihe anticline. Historically, these regions are the significant gas control areas in Southwest Guizhou with several outburst accidents[2]. As a matter of fact, Occurrence status of gas in each coal tectonic unit is quite different. For instance, Zhongying syncline shows higher gas content of the overall coal seam and its gas pressure is bigger. As for Laoguishan anticline, Nibao syncline and Huangnihe anticline, they show higher gas content in No.17 coal seam and the gas pressure is big. While the rest of coal seam gas is relatively small. In terms of outburst areas, coal seam gas presents a tendency with high degree in north and low degree in south. As for Zhongying syncline – Binghenying anticline area, due to the thicker and well-preserved covering bedrock, the fault are mainly closed with better gas storage condition. Besides, the largest with gas pressure of No.15 coal seam in Faxiang coal mines is reaching 2.11 MPa. What’s more, Pannan anticline – Laoguishan anticline area come to the second with gas pressure of No. 17 coal seam in Jialong coal mine reaching 0.85 MPa. Moreover, gas pressure of No. 19 coal seam comes to 0.8 MPa. With regard to Nasheng anticline – Huangnihe anticline areas, the gas is relatively small with gas pressure of No. 17 coal seam in Aozichong coal mine reaching 0.26 MPa[3,4].

Figure 1  Distribution of southwest Guizhou coal mine

According to statistics and analyses, it can conclude the outburst dangerous level of each coal seam: Zhongying syncline, Qinglong syncline and Bihenying syncline areas conform to the law. Namely, gas size increases with the depth of coal seam and the outburst dangerous degree of coal seam rises from top to bottom in turn. As for Pannan anticline and Laoguishan anticline areas, several outburst accidents have happened in No. 17 coal seam. Beside, its outburst danger level is the biggest, No.19 comes to the second and No.17 is the smallest. With regard to Panjiazhuang region, from big to small, the outburst dangerous degree of coal seam can be shown in this way: No.5 > No.7 > No.3. In terms of Nasheng anticline and Huangnihe anticline, coal seam outburst of No.17 is the severest[5,6].

2 Problems in gas prevention

In recent years, Southwest Guizhou has obtained excellent achievements in the gas control. However, some problems are revealed.

(1) Selection of protective coal seam is unreasonable

With regard to outburst mines of Southwest Guizhou, they are mainly multi-seam mining. As a matter of fact, regional outburst prevention measures put protective seam mining as the priority. From the analysis results of the typical mine, regardless of outburst dangerous degree of each minable coal seam, people mostly exploit upper mine firstly as a protective coal seam. Thus, it can not select protective coal seam in a real sense. As for the reason, it attributes that each coal seam owns outburst danger degree, while insufficient original data lead people unable to evaluate the danger degree.

(2) Selection attitude of mine towards special gas drainage lane

According to relevant requirements of codes and specifications, regional outburst prevention measures take protective seam mining as the priority. However, as mining protective coal seam, one shall demonstrate outburst danger. If protective coal seam exist outburst danger, people must adopt other regional outburst prevention measures, such as arrange special gas drainage lane. From research situation, the implementation of special gas drainage lane is not optimistic. Since the cost of special gas drainage lane is higher and current coal market is slump, some mines that supposed to take special gas drainage lane as regional outburst prevention measures still avoid using special gas drainage lane. For instance, Laoguishan anticline – Nibao anticline with severe outburst condition, its No.17 coal seam have soft coal and the gas pressure is bigger. Thus, special gas drainage lane shall be taken as regional outburst prevention measures. Nonetheless, most regions have not implemented special gas drainage lane.

(3) Pre-drainage effect is not ideal

Most mines in Southwest Guizhou are minable coal seam with soft coal and poor permeability. Thus, broach construction is difficult to realize and it is unable to reach the designated position. All in all, the pre-drainage effect is not ideal. In general, drainage concentration of high negative pressure is less than 10%, while drainage concentration of low negative pressure is only about 5%. Taking Hengtai coal mine as an example, the drainage concentration of high negative pressure is less than 7.5%, while drainage concentration of low negative pressure is 3.5%. In addition, the gas concentration in groove of working face for No. 17 comes close to 0.8%. Moreover, the low gas drainage concentration and high gas concentration of the groove show that the gas drainage has not obtained expected effect.

(4) Borehole construction is difficult

Geological structure of Southwest Guizhou coal mine area is complex with uneven coal seam occurrence. This lead to more short distance borehole and the borehole length can not be guaranteed. In addition, constrained by coal itself conditions of soft coal and larger gas, it tends to appear phenomena like stuck freeing, crown drill, ejector drill and hold drill. According to the survey, the drainage borehole depth of most mines is around 50 ~ 60 m. Thus, it can not completely cover the whole working face and is prone to appear blank zone of gas drainage.

(5) Lack of fundamental mine gas data   

By the research, most mines and even some outburst mines lack fundamental gas data. With regard to on-site reference materials involving mine gas, there are no original gas content and pressure data. In the Special Design of Gas Drainage, there are no measured data including permeability coefficient of coal seam and flow decay of borehole. However, even in the Outburst Dangers Appraisal Report of some mines, the gas parameters are not measured data. They are just cited from adjacent mines as reference. Thus, without the support of fundamental data, the calculated gas content and pressure data are quite distinct from the actual mine situation. Besides, the selection of equipment’s like fan and drainage pump will have deviation, affecting the mine gas control effect.

(6) Quality of special design for gas drainage and outburst prevention is low

In fact, as programming mine gas drainage and outburst prevention design in the research, people failed to combine with actual situation like mine coal seam occurrence, gas distribution laws and gas emission sources and formulate specific design. Beside, operating procedures organized by ore party ignore the relevant information like coal seam occurrence and geological structure that affect gas occurrence. Actually, they just copy design parameters of other measures. As a result, in the production process, the gas drainage effect is bad and working face will have transfinite gas accidents.

(7) Technical personnel are insufficient and technical force is weak

Through understandings of some mines, technical personnel are able to meet the basic requirements of mine production. However, the technical force is relatively weak. In some part of the mine, only one or two people can really do literal data. Moreover, the cultural and technical level of down-hole inspectors and outburst prevention members are relatively low. When some unexpected situations happen, it’s difficult for them to make the most effective response.

(8) The equipment configuration is good but utilization rate is low

From statistics data and communications with mine technical personnel, most instruments and equipments of coal mining enterprises are good. However, their effective utilization for them is not enough. As a matter of fact, coal mining enterprises equip instruments and equipments in accordance with relevant requirements. While after purchase, some instruments do not play the corresponding function. Moreover, some instruments have not been put into application. Besides, due to improper operation, some instruments are unable to measure accurate gas parameters in the coal seam, leaving practical problems in the mine production unsolved. Finally they will be given up.

3 Some suggestions for comprehensive outburst prevention system of gas control in Southwest Guizhou coal mining area

(1) The selection of regional outburst prevention measures

As for the Zhongying syncline, Qinglong syncline and Binhenying syncline area, in terms of outburst dangerous degree of each coal seam, the thesis suggests exploiting the No. 4 coal seam as protective coal seam. Due to the outburst danger of No. 4 coal seam, it recommends to arrange special gas drainage lane in the No.8 coal floor. People can make borehole drainage through strata towards No.4, 5, 7 and 8 coal seam gases by up construction. Then, they can mine No.4, 5, 7, 8, 10 and 14 coal seams in turn. In terms of Panan anticline - Laoguishan anticline area, regional outburst prevention measures conclude “special gas drainage lane protective coal seam mining”. In fact, protective coal seam is the No.19 and special gas drainage lane is arranged in its coal floor. As exploiting No.5 and No.7 coal seam in Panjiazhuang areas, people can mine No.7 firstly so as to be taken as protective coal seam of No.5. With regard to Nasheng anticline and Huangnihe anticline, regional outburst prevention measures can select lower-protective layer to exploit and No.19 coal seam is the protective coal seam.

Apart from the above areas in Southwest Guizhou coal mine area, the outburst is not serious. As for outburst mine area with small outburst danger but must in accordance with outburst management, the thesis suggests not constructing special gas drainage lane. As for coal mining enterprises or mine managers, they can not arrange special gas drainage lane for feasibility analysis. However, the premise is to publish relevant policies and standards and define arrangement situation for special gas drainage lane accurately.

(2) Adopt regional outburst prevention measures

With regard to regional outburst prevention measures in Southwest Guizhou mine, it recommends adopting drainage method of conventional drainage outburst prevention. Nonetheless, it must select appropriate measures according to the actual situation of the mine.

(3) Optimize borehole construction technology and improve gas drainage effect

In terms of mine with unsatisfied drainage effect, people can explore and find out the real reason as well as formulate reasonable and effective measures according to the reason. Moreover, they may cooperate with scientific research departments and make related research, or organize expert consultation, establish targeted research and solve gas drainage difficult problems in a real sense.

(4) Test of fundamental mine gas data and programming of drainage outburst prevention design

For some mines lack of fundamental data, the thesis recommends testing fundamental parameters for coal mine gas as well as understanding actual situation including mine gas occurrence, distribution law and permeability parameters of coal seam. Besides, according to the actual test circumstance, people can program special design and implement effective gas control.

(5) Technical personnel

First of all, department setup and personnel equipment must meet the requirements of related regulations. Meanwhile, the thesis suggests improving safety consciousness and comprehensive quality of mine management and technical personnel, attaching importance to gas control from the heart, strictly checking drainage outburst prevention measures construction and ensuring the implementation of the measures. Besides, it is suggested to strengthen talents introduction work, form a stable gas control team, enhance professional and technical exchanges and learning between team members and improve the gas control level of the team.

(6) Requirements of outburst prevention equipment

According to the actual situation of the mine and survey data analysis, people shall highlight that the equipped main test instruments of gas parameter are the parameters corresponding equipment for the effect inspection of outburst prevention measures. Moreover, these equipment’s include test instrument, equipment testing for gas drainage concentration and drilling rig for gas drainage construction. As for Panan anticline - Laoguishan anticline areas, the coal is soft and geological conditions are complex. Thus, for the mines with difficulty of borehole construction for bedding drainage, people must strengthen requirements for the drilling rig. For instance, they can buy drilling rig with high power and torque. In addition, they can cooperate with related scientific research departments for targeted research, make specific improvements for he drilling rig so as to maintain precision of drilling construction, satisfy the outburst prevention requirement and obtain better drainage effect. As a matter of fact, accidents of Southwest Guizhou area mainly happen in the region with geological conditions changes. With regard to the outburst mines, people shall strengthen the detection work for the geological structure. Moreover, combination of geophysical exploration and drilling probing measures are the better choice. Besides, in Yizhong coal mine, Rayleigh wave detecting instrument has been put into practice. After field investigation, the application effect is ideal. Thus, Rayleigh wave detecting instrument is a better geophysical instrument. As for drilling probing equipment, the general one is fine. While the drilling depth of coal – roadway shall at least reach 60 m.

4 Conclusions

(1) All in all, the overall state of coal seam gas occurrence in Southwest Guizhou mining area presents characteristics with high degree in north and west together with low degree in east. In terms of outburst coal mine, Qinglong syncline – Binhengying anticline area is the highest, Pannan anticline – Laoguishan anticline area comes to the second, Nasheng anticline- Huangnihe anticline is the lowest.

With regard to Zhongying syncline – Bihenying anticline area, the outburst dangerous degree increase from top to the bottom. As for Pannan anticline – Laoguishan anticline, the outburst dangerous degree from top to bottom are No.17, No.19 and No.18 coal seam.

(2) In terms of Southwest Guizhou outburst mines, people shall combine with the situation of its geological structure, coal seam occurrence and gas occurrence law of coal seam, formulate reasonable and targeted outburst prevention and drainage design, strictly implement outburst prevention measures and optimize mining plan so as to make full use of mine resources and realize safe and sustainable mining.

(3) Each outburst area of Southwest Guizhou belongs to multi-seam mining and possesses protective coal seam conditions. Thus they can select protective coal seam mining as regional outburst prevention measures. However, as mining protective coal seam, people shall demonstrate outburst danger, reasonably select protective coal seam and guarantee the reasonable mining deployment and coal seam mining sequence.

In addition, according to regulations of relevant documents, apart from Nasheng anticline and Huangnihe anticline area in Southwest Guizhou with outburst mines, special gas drainage lane shall be arranged in other areas. Beside, people need to determine reasonable layout layer for special gas drainage lane.

As for part of outburst mines, though its outburst danger is not high, it must conform to outburst management. The thesis suggests adopting economic and practical prevention measures in accordance with actual circumstances.

(4) According to outburst prediction and efficiency inspection indicator of most outburst mines in Southwest Guizhou, people can analyze indicator K1 valuesΔh2and drilling cutting quantity Smax for gas content, gas pressure and drilling gas. In addition, in terms of other tested and effective indicator adopted for mine reality, people can combine the sensitivity of these indicators to determine critic value and necessary instruments and equipment’s.

(5) One can analyze locations and characteristics of Southwest Guizhou with outburst accidents. With regard to mines in the area, the detection work for geological structure needs to be improved. Moreover, combination of geophysical exploration and drilling probing measures are suggested.

(6) It is suggested to bring in some management and operational talents with higher business level as well as professional and technical personnel mastering advanced technology. Besides, enhancing related training for outburst prevention and management personnel is also necessary.

(7) Reasonably set up outburst prevention and drainage equipment. As ensuring the outburst prevention effect, improving quality of outburst prevention measures and reducing unnecessary outburst prevention quantities, one can increase the intensity of gas drainage and increase gas utilization channels.

Acknowledgements

This work was financially supported by the national key technology support program "The 12th Five Year Plan"(2012BAK04B07).

References

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[2]   Zhang Zimin & Zhang Yugui, Three Grade of Gas Geological Maps and Their Application to Gas Controlling [J]. Journal of China Coal Society. 2005 (04)

[3]   Wang Zhaofeng et al, Research and Application of Gas Geology [M]. Coal Industry Press. 2003

[4]   Long Zugen &Huang Zhengxiang, Gas Geological Map of Guizhou Coal Mine [R]. 2011

[5]   Huang Zhengxiang & Long Zugen, Analysis for Gas Geological Law of Guizhou Coal Mine [C]. Gas Geology Professions Council of Chinese Coal Society, “Proceedings” of 2012 National Gas Geology Academic Annual Conference. 2013(37~43)

[6]   Ma Shu, Analysis on Guizhou Coal Mine and Controlling Factors and Laws for Gas Outburst [D]. Guiyang: Guizhou University. 2009

作者:李青松
编辑:龙涛
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