Analysis of the Space–Time Synergy of Coal and Gas Co-mining

Abstract

The co-mining of coal and gas is the inevitable future direction of the mining of coal resources. Taking coal mining and gas extraction as the two subsystems of the coal and gas co-mining system, to reveal the mechanism of action between coal mining and gas extraction is the premise of orderly co-mining. On the basis of a similar simulation experiment of coal and gas co-mining, by obtaining the gas migration law during the mining process and collecting a large amount of data on the coal production and gas extraction, it is found that the two subsystems of coal extraction and gas extraction in the coal and gas co-mining system promote and restrict each other. The control parameters for coal mining and gas extraction that affect co-mining are identified. To coordinate the process connection between coal mining and gas extraction, the optimal synergistic relationship of co-mining should be found. The recovery rate and economic benefit of coal and gas resources are taken as the optimization objective function of coal and gas co-mining. Taking the safety production laws, regulations, and production technology-level restrictions of coal mining and gas drainage as constraints, by constituting a nonlinear model for the collaborative optimization of coal and gas co-mining, the method of determining the optimal advancing speed and optimal gas drainage volume of the working face is proposed. By optimizing variables, such as coal mining advancement, coal mining time, gas extraction time, and gas extraction volume, the co-mining of coal and gas is ensured to be safe and efficient, and the output of coal and gas resources is optimized. The time connection and the process succession of the two subsystems are attained. An overall orderly structure is formed between the coal mining system and the gas extraction system, and the mechanism of the cooperative co-mining of coal and gas is revealed. This research has important significance with regard to improving the basic theoretical system of coal and gas co-mining. The control variables of the co-mining working face in the Shaqu mine are optimized. After optimization, the profit is increased by 16.3%, and the gas extraction rate is increased by 2.6%. The drilling spacing is optimized according to the optimization results. The simulation shows that 7 m is the optimal drilling spacing of the working face.

Substantiation of Drilling Parameters for Undermined Drainage Boreholes for Increasing Methane Production from Unconventional Coal-Gas Collectors

“…Proceeding from the experience of practical working in mine conditions allows for concluding that the quality of the normative forecast turned out to remain low. In most scientific works, two-dimensional curves or their aggregates in the form of projections on a two-dimensional plane are mainly considered [70][71][72][73]. For example, a two-dimensional curve characterized by the relationship between the methane concentration and distance S at different times, as well as the methane concentration change over time at different positions, is insufficiently representative (see Figure 2 in [26]) owing to the deformation of a three-dimensional surface when it is projected onto a two-dimensional plane.…”

Study on the Pseudo-Slope Length Effect of Buried Pipe Extraction in Fully Mechanized Caving Area on Gas Migration Law in Goaf

“…where c s is the volume fraction of component s; D s is the diffusion coefficient, m 2 /s; and S s is the mass of the component produced by the chemical reaction per unit time, kg/(m 3 •s). 4 Considered the extraction area as a porous medium and add momentum sources, which included viscous loss term and inertial loss term.…”

“…This led to frequent gas overrun problems in the return airway and upper corner. It hindered the safety production of the mine [3][4][5]. The concentration of gas extracted during coal mine production is less than 30%.…”

Study and Application of High-Level Directional Extraction Borehole Based on Mining Fracture Evolution Law of Overburden Strata

“…In addition, with the increase in coal mining depth and mining intensity, in the process of coal mining, the gas in adjacent layers or surrounding rock enters the work plane through mining fissures. The gas in the upper corner of the work plane easily causes the gas concentration in the return air flow to exceed the limit, which affects the safe mining of the work plane [8,9]. Former research has shown that a rock drainage roadway and high-level directional extraction borehole can effectively extract gas in the fissure zone and have great operational stability in the upper corner of the goaf and return air flow [10][11][12][13].…”