Method of sorting and utilizing coal and rock for coal and rock combined mining face

Abstract

The present invention relates to a method for sorting and utilizing coal and rock for a coal and rock combined mining face, and is especially applicable to the sorting and utilization of coal and rock mined from a coal and rock combined mining face when an extremely thin coal seam is used as a protective layer in combined mining of multiple coal seams. Underground gangue transport, storage and filling systems are directly established underground to convey a large amount of coal and gangue mined from the coal and rock mining face to an underground sorting and washing chamber for efficient separation of the coal and the gangue, sorted gangue is crushed and then filled in a mined-out area of a protected layer, thus realizing the environment-friendly cut and fill mining of the protective layer while the gangue is not lifted, and effectively preventing the ground subsidence caused by combined mining of multiple coal seams; sorted middlings are conveyed to a gangue power plant on the ground for power generation through a main conveying system, so that the pressure on mine coal quality is alleviated when benefits are created in the power plant, and thus the average ash content of commercial coal is reduced, and the selling price is increased. The method provided by the invention realizes the efficient utilization of coal and rock while realizing the efficient separation of coal and gangue, and has remarkable economic and social benefits and excellent promotional value.

Claims

1. A method for sorting and utilizing coal and rock for a coal and rock mining face: a. when mining a thin protective layer, providing a protected layer as a coal seam to be mined, and conveying gangue mined from a coal and rock mining face on the thin protective layer to a sorting and washing chamber along a gangue conveying lane; b. the gangue in a multi-stage way by a multi-stage tooth roller screen arranged in the sorting and washing chamber, wherein after sorting, large particles with a particle size of more than or equal to 100 mm are used as an oversize product, small particles with a particle size of less than or equal to 13 mm are used as an undersize product, and medium particles with a particle size of more than 13 mm and less than 100 mm are used as a sized product; c. conveying the undersize product comprising coal and small-particle gangue as main components to an underground middlings bin by a belt conveyor and to be stored; d. conveying the oversize product comprising big-lump rock as a main component to an underground crushing system by the belt conveyor and to be centrally crushed; e. conveying the size product comprising mixed coal and rock to an underground washing system by the belt conveyor, wherein rock with high density and coal with low density are sorted out by the underground washing system, the coal with low density is directly conveyed to the underground middlings bin by the belt conveyor, and the rock with high density is conveyed to the underground crushing system to be centrally crushed; f. crushing the sorted oversize rock and the washed sized rock centrally, after entering the crushing system into small-particle rock with a particle size of less than or equal to 25 mm, and the small-particle rock is all conveyed to the underground gangue bin by the belt conveyor to be ready for use; g. conveying the gangue in the underground gangue bin to a mined-out area of the protected layer, when the protected layer is stopped, along a filling and conveying lane and a gangue exhaust lane to carry out gangue backfilling, thus realizing the cut and fill mining of the underground protected layer; and h. allowing the sorted undersize coal and the washed sized coal to enter the underground middlings bin, and then be conveyed to a ground gangue power plant by a mine lifting and conveying system and a conveyor to realize power generation of the gangue power plant, wherein a washing density boundary value of the sized product with mixed coal and rock is set by the coal quality needs of the power plant, and the washing density boundary value is determined to be 1.9 g/cm3, calculated by the ash content of washed coal being not more than 60%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow diagram of a method provided by the present invention.

DETAILED DESCRIPTION

(2) Hereinafter, the present invention will be further described in conjunction with embodiments in the accompanying drawings.

(3) A method for sorting and utilizing coal and rock for a coal and rock mining face provided by the present invention comprises the following steps: a. when a thin protective layer is mined, a protected layer as a coal seam to be mined is to be mined, and gangue mined from a coal and rock mining face on the thin protective layer is conveyed to a sorting and washing chamber along a gangue conveying lane; b. the gangue is sorted in a multi-stage way by a multi-stage tooth roller type roll screen arranged in a sorting and washing chamber, wherein after sorting, a large particle with a particle size of more than or equal to 100 mm is used as an oversize product, a small particle with a particle size of less than or equal to 13 mm is used as an undersized product, and a medium particle with a particle size of more than 13 mm and less than 100 mm is used as a sized product; c. the undersize product comprising coal and small-particle gangue as main components is conveyed to an underground middlings bin by a belt conveyor to be stored; d. the oversize product comprising big-lump rock as a main component is conveyed to an underground crushing system by a belt conveyor to be centrally crushed; e. the sized product comprising mixed coal and rock is conveyed to an underground washing system by a belt conveyor, rock with high density and coal with low density are sorted out by the underground washing system, the coal with low density is directly conveyed to the underground middlings bin by a belt conveyor, and the rock with high density is conveyed to the underground crushing system to be centrally crushed; a washing density boundary value of the size product with the mixed coal and rock is set by the coal quality needs required by the power plant, and the washing density boundary value is determined to be 1.9 g/cm.sup.3, calculated by the ash content of washed coals being not more than 60%. f. the sorted oversize rock and the washed sized rock enter the crushing system to be centrally crushed into small-particle rocks with a particle size of less than or equal to 25 mm,

(4) and the small-particle rock is all conveyed to an underground gangue bin by a belt conveyor to be ready for use; g. when the protected layer is stopped, the gangue in the underground gangue bin is conveyed to a mined-out area of the protected layer along a filling and conveying lane and a gangue exhaust lane to carry out gangue backfilling, thus realizing the cut and fill mining of the underground protected layer; and h. the sorted undersize coal and the washed sized coal enter the underground middlings bin, and then are conveyed to a gangue power plant on the ground by a mine lifting conveying system and a conveyor to realize the efficient power generation of the gangue power plant.

Embodiment 1

(5) A method for sorting and utilizing coal and rock for a coal and rock mining face is as follows: firstly, for a coal seam group, a thin coal seam at the upper part of a main mining layer is used as a protective layer of the main mining layer for mining. The average thickness of the thin coal seam is only 0.5 m, and planned mining height is 1.8 m, therefore, a large amount of gangue is produced by mining of the protective layer. It is estimated that the gangue mined from the mining face accounts for 72.2% of the total amount of coal and gangue. The normal production is carried out by using a method used for mining a stope face of the protective layer, and two heads and one face (two protective layer heading faces and one stope face) are needed. The daily gangue exhaust amount can be up to 1600 m.sup.3 (coal content) by calculation, and the mine coal quality is reduced by the production of a large amount of gangue. Through research and analysis of washability of mined gangue and coal quality, it can be seen from table 1 that particles with sizes of more than 50 mm account for 36.17%; by taking the factor of cutting by using a tunnel boring machine into account, it is predicted that particles with sizes of more than 50 mm on the protective layer face accounts for more than 40%, and have washability. After the protective layer face mining is calculated, the ash content of commercial coal will rise by 14 percentage points and be up to 39%. The selling price difference is calculated by 10 to 15 yuan/ton, plus ultra ash fine. The selling price per ton is reduced by 139 to 250 yuan, and the annual loss will be 18 to 32.5 million yuan if the annual output is 1.3 million tons. Therefore, a scientific coal and rock sorting and utilizing method is needed to carry out the efficient sorting and environment-friendly utilization of coal and rock, wherein the economic benefit of coal mines is improved while realizing the safe and environment-friendly mining of mines.

(6) TABLE-US-00001 TABLE 1 Ash content Water content Sizes Weight kg Yield % % % Numbers mm Group Total Group Total Group Total Group Total Total 1. less 1324. 50.64 50.64 60.47 9.09 9.09 2877 than 13 2 13 to 25 242. 1566 9.25 59.89 76.57 62.96 3.24 8.19 3 25 to 50 301 1867 11.51 71.4 86.91 66.82 2.82 7.32 1934 4 50 to 100 397 2264 15.18 86.58 89.86 70.86 5 more 351 2615 13.42 100 89.51 73.36 The content of 1530 than coal with a 100 particle size of more than 100 mm is 1.7% 6 Total 2615 73.36

(7) Therefore, it is necessary to establish gangue transport, storage and filling systems in the pit to scientifically and efficiently treat and utilize the mined gangue. When the thin protective layer is mined, a large amount of rock also can be produced when coal is produced, and the gangue produced from the coal and rock mining face is conveyed to the sorting and washing chamber along a special conveying lane; the gangue is sorted in a multistage way by the multistage tooth roller type roll screen arranged in the sorting and washing chamber, and the upper and lower scale of sorting are respectively set to be 100 mm and 13 mm according to the coal and gangue particle size distribution from Table 1, so as to realize the efficient sorting and full utilization of coal and gangue. After sorting, the particles with sizes of more than or equal to 100 mm are used as an oversize product, particles with sizes of less than or equal to 13 mm are used as an undersized product, and particles with sizes of more than 13 mm and less than 100 mm are used as a sized product; the undersize product (coal and small-particle gangue as main components) is conveyed by a belt to a middlings bin to be stored; the oversize product (big-lump rock as a main component) is conveyed to a crushing system to be centrally crushed; the sized product (coal and rock mixture) is conveyed to the washing system, and the washing system adopts a heavy-medium shallow-slot washing process; washing boundary density is determined to be 1.9 g/cm.sup.3, calculated by the ash content of washed coal being not more than 60% in order to meet the coal quality requirements of the power plant; high-density rock and low-density coal are sorted; pulverized coal is directly conveyed by a belt to the middlings bin, and the rock enters the crushing system to be centrally crushed; the sorted oversize rock and the washed sized rock enter the crushing system to be centrally crushed into small-particle rock with a size of less than or equal to 25 mm, and are all conveyed by a belt to a gangue bin; based on research, it was known that the smaller the particle size is during actual filling, the quicker a stable value of sedimentation can be reached, and it was determined that the particles with sizes of less than or equal to 25 mm as a target particle size range can be used as a filling material to be stored according to experimental research; the gas pressure of the protected layer is effectively relieved while the thin protective layer is mined, the volume of gas of the protected layer is reduced by pre-extracting the gas of the protected layer, the risk is reduced, and the protected layer is safely mined; when the protected layer has a stopping condition, the gangue in the gangue bin is conveyed to the mined-out area of the protected layer along the filling and conveying lane and the gangue exhaust lane to carry out gangue backfilling, thus realizing the filling mining of the protected layer. Accordingly, the thin protective layer creates a safe condition for the protected layer after mining; meanwhile, the mined coal and gangue are separately conveyed, washed and crushed and then directly fill the mined-out area of the protected layer, thus realizing gangue non-lifting, saving the lifting cost, solving the problems that a gangue hill occupies large land areas with the environmental pollution, reducing the mining damage, and realizing the environment-friendly and safe combined mining of multiple coal seams. The sorted undersize coal and the washed sized coal enter the middlings bin, and then are conveyed to the gangue power plant on the ground by a main mine conveying system, thus realizing the efficient power generation of the gangue power plant. Through an experiment, after run-of-mine coal from the thin protective layer is screened, the product with the particle size of less than 20 mm, having the yield of 58.89%, the ash content of 62.96%, and the calorific value of 2000 to 2500 kcal/kg is added to part of the washed middlings so as to meet the coal service requirements of the calorific value of the gangue power plant (the calorific value of the gangue power plant is 2700 to 3000 kcal/kg, and the particle sizes are less than 20 mm). In the gangue power plant, if the middlings screened by three horizontal protective layers are used as a raw material, a lot of coal purchase cost is saved annually. In the gangue power plant, a lot of middlings are consumed annually, so that the pressure on coal quality is alleviated, and the average ash content of commercial coal is decreased by 3 to 4 percentage points. The selling price will rise by 30 to 40 yuan/ton, and the annual benefit is increased by 45 yuan1.3 million=58.5 million yuan, so that a huge economic value is created after the middlings from the thin protective layer are supplied to the power plant.