How to deal with the pollution caused by coal gangue accumulation?

Feasibility study on solving the problem of coal gangue piling pollution in Dong Qing coal industry by using advanced reclamation of subsided land

There will be two environmental problems in the process of coal mining: coal gangue accumulation pollution and ground collapse in goaf, which are urgent problems to be solved in the sustainable development of coal enterprises. Because it is difficult to form the scale of goaf collapse in the early stage of new mine, the problem of coal gangue treatment is more prominent. Through advanced reclamation technology in subsidence area, the treatment of coal gangue is organically combined with reclamation in subsidence area, and good economic and ecological benefits are obtained.

Keywords: coal gangue treatment; Collapse of goaf; Reclamation in advance; Benefit; feasibility study

In the process of coal mining, there will be two major environmental problems: the accumulation and collapse of coal gangue and the pollution of occupied land, which are urgent problems to be solved in the sustainable development of coal enterprises. Because it is difficult to form a scale in the newly-built mine Tashande goaf in a short time, the treatment problem caused by coal gangue is more prominent. In this paper, through advanced water resource technology, the treatment of coal gangue and the resource utilization of Taxende are organically combined, and good economic and ecological benefits are obtained.

Keywords: coal gangue processing; Irregular shape, etc.; Advanced reclamation project; Benefit; feasibility study

General situation of Dong Qing coal mine field, gangue pile and collapse influence range

Brief introduction of Dong Qing coal mine

Dongqing Mine is located at the junction of Suixi County and Guoyang County in Anhui Province, and its administrative division belongs to Suixi County (see figure 1- 1). The mine has good resource conditions, abundant reserves and superior construction conditions. It is a pair of large-scale mines encouraged by the state in the overall planning of Huaibei mining area 10.

Large modern mine. Dong Qing Mine adopts three levels of mining, one is-620m, the other is-920m, and the third is-1200m. Mine design service life is 68.7 years.

Figure 1- 1 Geographical Location of Dong Qing Coal Mine

Dong Qing Coal Mine and Coal Preparation Plant are invested and constructed by Huaibei Mining Group Co., Ltd. Dong Qing Coal Mine is a newly-built coal resource development project, and the designed raw coal production capacity is 1. 8 tons/year; The supporting Kengkou Coal Preparation Plant is a newly-built raw coal washing and processing project, and the designed raw coal dressing capacity is1.8mt/a/a.

1.2 general situation of coal gangue reserves and annual output of coal gangue

Since the establishment of Youdong Coal Mine in 2004, the coal gangue produced by mining has not been effectively treated. At present, the total amount of coal gangue in Dong Qing is large, the height of coal gangue hill is high, and the area of coal gangue hill is increasing year by year (see table 1- 1 and figure 1). These unfavorable factors may cause secondary disasters such as spontaneous combustion and collapse of waste hills. In addition, according to the statistical data of driving footage and pre-production of gangue in recent years from 20 12 to 20 16 released by the group company (see table 2), the average annual output of coal roadway and rock roadway in our mine is about 458,000 tons. In addition, the coal gangue is calculated as 20% of the annual output, and the fully mechanized production of Dongqing Mine is180,000 tons/year. This further aggravates the seriousness and urgency of waste rock treatment in our mine.

1.3 Overview of the influence range of collapse

After the mining of the whole mine field in Dong Qing Mine, the subsidence area is 54.20km2, of which the accumulated water area (sinking more than 2m) is 20.32 km2, and the maximum subsidence depth is10.8m. According to the maximum expected surface deformation, the horizontal tensile deformation caused by coal mining in Dong Qing Mine is small, and discontinuous deformation such as cracks generally does not occur. See table 1-3 for the maximum subsidence value, maximum dip angle value, maximum curvature value, maximum horizontal movement value and maximum horizontal deformation value of the surface after mining in the first mining area and the whole mine field.

2. Analysis of advanced regeneration methods

1 Advance reclamation, also known as pre-discharge gangue filling reclamation technology, is to take out the topsoil and pile it around the area where the surface subsidence is expected above the goaf during the well construction and the initial stage of production. According to the expected subsidence contour map, the gangue is discharged in advance and filled to a predetermined level. When the settlement is consistent with the surface elevation, the topsoil around the pile is pushed to the gangue layer to form arable farmland, thus realizing the goal of harmless treatment and disposal of gangue.

Concrete construction technology and effect analysis of advanced reclamation in 82 mining area

2. 1. 182 Introduction of the first mining area

No.82 mining area in Dongqing Coal Mine reaches the contour line of -585 meters in the north, faults f 1 1 in the east, faults f6 and fs96 in the west and faults fs11and fs98 in the south, with an area of about1./kloc. The ground is flat, and there is no big river crossing it, but artificial ditches are vertical and horizontal. The villages on the ground include Luo Zhuang, Chenyoufang, Liucaiyuan, Xinzhuang and Lixiao Temple. During mining, the ground may form a subsidence area (see Table 2- 1). According to the underground comparison chart, the total recoverable thickness of fully mechanized mining faces in No.726, No.728, No.828, No.2 and No.3 in No.82 mining area is about 7.5-8.5m Through mining subsidence technology, the average subsidence depth of No.82 goaf is 5. 17m, and the estimated reclamation elevation is about 5-6m.

2. 1.2 specific construction process

Specific implementation stage: 1. According to the information provided by the survey and design unit of the production technology department, choose the advanced reclamation area (first choose the old village site area in the subsidence area); 2. First, the topsoil should be stripped about 1m, and the topsoil, subsoil and other stratum materials suitable for plant growth should be stored and utilized in a protective way, which can be used as the soil for soil reconstruction in the reclamation of subsided land in priority; 3. Take measures to prevent leakage, and collect and discharge the water in the backfilling area of the gangue hill (2. Use geotextiles (multifunctional products with six functions of drainage, filtration, isolation, reinforcement, seepage prevention and protection) to prevent surface water and groundwater from leaching; 4. Transport the gangue to the backfill area, fill it evenly and compact it in layers until the stacking height reaches the set height. 3. Introduce microorganisms into coal gangue waste to promote the generation of plants and rhizobia, thus promoting the rapid growth of plants and accelerating the weathering of solid waste into soil. After full exploitation and stabilization, the advanced backfill area will be covered with soil (considering the factors of soil tillage layer, crop species and soil erosion, the thickness of the overlying soil layer of reclaimed soil is greater than 600 mm), and it will be converted into cultivated land to supplement the land. Strive to form a "balance of occupation and compensation" situation of cultivated land-coal mining subsidence-comprehensive management-formation of new cultivated land-comprehensive utilization.

2.2 Solutions to problems left over from advanced reclamation projects.

Because the subsidence speed of the mined-out subsidence area is relatively slow, it will inevitably lead to the situation that the pre-discharged gangue is higher than the ground by a certain height within two or three years. In case of rainy weather, a large amount of gangue dripping water may pollute the surrounding farmland; If the accumulated gangue is not effectively reinforced, it may also lead to secondary geological disasters. In order to solve these problems, the drainage ditch can be repaired in time around to solve the problem of wastewater discharge and reduce the impact on agricultural production activities. In the process of backfilling, in addition to strengthening the accumulated gangue, measures such as planting plants and covering the dam surface and slope should be taken to prevent dust, landslide and soil erosion. After the land subsidence is stabilized, the area will be leveled and repaired on a large scale, and become permanently available arable land.

3. Benefit analysis of land reclamation in advance

3. 1 Economic benefit

The coal mine produced by this mine was transported to the pre-subsidence area in time, which not only solved the problem of coal gangue stacking and land occupation, but also completed most projects for subsequent land reclamation. On the other hand, the cost of land acquisition is generally several times more than the cost of reclamation, so reclaiming land in this way is not only beneficial to the sustainable development of local agriculture, but also gives priority to solving the major problem of global treatment of coal gangue, and at the same time saves a considerable amount of land acquisition cost for enterprises and greatly reduces the production cost of raw coal; And after the land reclamation is completed, the relevant state functional departments give subsidies and rewards to enterprises according to the scale and quality of reclamation, which shows that advanced reclamation not only solves the problem of coal gangue disposal, but also brings good economic benefits to enterprises.

3.2 Environmental and ecological benefits

The environmental benefits of reclamation in advance are obvious. Without advanced reclamation, on the one hand, abandoned hills occupy and pollute the land, on the other hand, the ground in the subsidence area is fragmented due to cracks and landslides, and soil erosion is more serious, which will seriously damage the ecological environment of the mining area. Therefore, the reclamation of coal mine subsidence areas and abandoned hills under unified planning is essentially the most important part of the comprehensive environmental management project in mining areas. The application of coal gangue in the treatment of subsidence area not only makes the land resources destroyed by mining be reused, but also disposes of coal gangue, which not only beautifies the environment, but also restores the natural ecology of the mining area, and receives the dual benefits of resource development and environmental protection.

3.3 Analysis of social benefits

(1) has obviously improved the ecological environment of the mining area, reduced soil erosion and atmospheric dust caused by coal gangue accumulation, and provided a good ecological environment and living space for people engaged in production, management and life in the mining area.

(2) After land reclamation and improvement, the coal mining subsidence area has been transformed into nursery planting land, economic forest land and breeding pond, the land utilization level has been improved, and the economic benefits are higher than the original cultivated land and grassland.

4. Conclusion

Whether on the theoretical basis or in the specific implementation process, the feasibility of the advanced reclamation scheme is worthy of recognition, which is of positive significance to solve the problem of coal gangue treatment in new mines. At the same time, the economic benefits, social benefits and ecological benefits after reclamation are unified.

refer to

[1] Development and application of Guo Yongjuan's coal mining subsidence area (I). Mining safety and environmental protection. 2003（4）

[2] Wang Pinghu. Application of geotextile technology in land reclamation in coal mining area (II). 2008（ 12）

Fan, Lu,,, WU GANG; Main ecological environment problems and ecological reconstruction technology in China coal mining area [J]; Journal of Ecology; /10 2003 released in 2003

[4] Popularization and application of summer land reclamation technology in Huainan mining area (b) Shandong Coal Science and Technology No.3 in 2009.

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