A comprehensive gas extraction system coupling high-level suction roadway and boreholes for gas disaster prevention in closely-spaced multiple coal seams

2020 ◽  
pp. 1-14
Author(s):  
Feng Yang ◽  
Zhaolong Ge ◽  
Jiufu Chen ◽  
Liang Cheng ◽  
Hongbo Lei ◽  
...  
Keyword(s):  
Extraction System ◽  
Gas Extraction ◽  
Disaster Prevention ◽  
Coal Seams ◽  
Gas Disaster ◽  
High Level ◽  
System Coupling

scholarly journals Fully Coupled Multi-Scale Model for Gas Extraction from Coal Seam Stimulated by Directional Hydraulic Fracturing

2019 ◽  
Vol 9 (21) ◽  
pp. 4720 ◽  
Author(s):  
Ge ◽  
Zhang ◽  
Sun ◽  
Hu
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Scale Model ◽  
Gas Extraction ◽  
Coal Seams ◽  
Directional Hydraulic Fracturing ◽  
Coal Mine Methane ◽  
Multi Scale ◽  
Fully Coupled

Although numerous studies have tried to explain the mechanism of directional hydraulic fracturing in a coal seam, few of them have been conducted on gas migration stimulated by directional hydraulic fracturing during coal mine methane extraction. In this study, a fully coupled multi-scale model to stimulate gas extraction from a coal seam stimulated by directional hydraulic fracturing was developed and calculated by a finite element approach. The model considers gas flow and heat transfer within the hydraulic fractures, the coal matrix, and cleat system, and it accounts for coal deformation. The model was verified using gas amount data from the NO.8 coal seam at Fengchun mine, Chongqing, Southwest China. Model simulation results show that slots and hydraulic fracture can expand the area of gas pressure drop and decrease the time needed to complete the extraction. The evolution of hydraulic fracture apertures and permeability in coal seams is greatly influenced by the effective stress and coal matrix deformation. A series of sensitivity analyses were performed to investigate the impacts of key factors on gas extraction time of completion. The study shows that hydraulic fracture aperture and the cleat permeability of coal seams play crucial roles in gas extraction from a coal seam stimulated by directional hydraulic fracturing. In addition, the reasonable arrangement of directional boreholes could improve the gas extraction efficiency. A large coal seam dip angle and high temperature help to enhance coal mine methane extraction from the coal seam.

Design and Implementation of a Device for Nanostructuring of Metallic Materials by Multiaxial Forging Method

2014 ◽  
Vol 657 ◽  
pp. 193-197 ◽  
Author(s):  
Alin Marian Cazac ◽  
Costică Bejinariu ◽  
Iulian Ionita ◽  
Stefan Lucian Toma ◽  
Cosmin Rodu
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Deformation Process ◽  
Extraction System ◽  
Metallic Materials ◽  
Severe Plastic Deformation Process ◽  
Design And Implementation ◽  
Discontinuous Process ◽  
Plastic Deformation Process ◽  
High Level

This paper presents materialization through a device of severe plastic deformation process by multiaxial forging. In essence, by design, the device includes a board reinforced with fretting rings where the severe plastic deformation takes place and an assembly, punch-counterpunch that transmits the force from the source and performs multiaxial forging as a discontinuous process. The device has a high level of universality and has the following advantages: contains an extraction system of deformed blank from the active fretted broad; ensures workpiece centering into place of active plate, contains a system for measuring the strength of forging; can be used on any type of press.

Forced Caving Technique for Gas Disaster Prevention in Coal Mine

2011 ◽  
Author(s):  
Hui Wang ◽  
Bai-sheng Nie ◽  
Xiang-chun Li ◽  
Zhen Liu ◽  
Qin-qin Zhang
Keyword(s):  
Coal Mine ◽  
Disaster Prevention ◽  
Gas Disaster

scholarly journals A Sequential Approach for Integrated Coal and Gas Mining of Closely-Spaced Outburst Coal Seams: Results from a Case Study Including Mine Safety Improvements and Greenhouse Gas Reductions

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3023 ◽  
Author(s):  
Liang Cheng ◽  
Zhaolong Ge ◽  
Jiufu Chen ◽  
Hao Ding ◽  
Lishuang Zou ◽  
...  
Keyword(s):  
Coal Mining ◽  
Mine Safety ◽  
Coal Bed ◽  
Gas Extraction ◽  
Coal Seams ◽  
Sequential Approach ◽  
Coal Mine Safety ◽  
Working Face ◽  
Protective Seam

Closely-spaced outburst coal seams (COCS) is the main condition of coal seams in southwest China, and gas disasters are one of the major problems affecting coal mine safety. Mining a protective seam and pre gas extraction are the most safety way to improve the efficiency of mining under these conditions. However, low pre-mining gas extraction efficiency coupled with the close proximity of adjacent working faces is a problem. When mining at an old working face has been completed but the new working face is not yet ready to be mined, coal-bed gasses can flow into the new working face from adjacent seams and this commonly causes methane monitoring instruments to sound an alarm. These gas extraction difficulties lead to a conflict between mine safety and profit. To solve these problems, a sequential approach for integrated coal and gas mining of closely-spaced outburst coal seams is introduced in this paper. Two fundamental principles are proposed: (1) Fully coordinating the spatiotemporal relationships between gas extraction, roadway development, and coal mining to maximize both mine safety and coal and gas production; (2) Defining a mining sequence for outburst coal seams and choosing the coal seam with the weakest outburst risk as the protective seam. A system for comprehensive gas extraction in underground coal mines is divided into four stages for gas extraction: gas extraction before coal roadway tunneling, gas extraction before coal mining, gas extraction during coal mining, and gas extraction from the goaf after coal mining. The Songzao mining area, China, is used as a case study to demonstrate the effectiveness of this model, and it brings three major benefits: it improves underground coal mine safety with physical gas accidents decreased by 66.8%, it makes underground coal-bed methane (CBM) extraction more efficient with the average gas extraction rate were respectively 45.13 m3/t and 62.4%, the highest in China, and it reduces greenhouse gas emissions equivalent to 3.5 million tonnes of carbon dioxide. This study could be used as a valuable example for other coal deposits being mined under similar geological conditions.

scholarly journals Pressure Relief by Blasting Roof Cutting in Close Seam Group Mining under Thick Sandstone to Enhance Gas Extraction for Mining Safety

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 603
Author(s):  
Kui Gao ◽  
Ping Huang ◽  
Ze-Gong Liu ◽  
Jian Liu ◽  
Fei Wang ◽  
...  
Keyword(s):  
Blast Hole ◽  
Thick Layer ◽  
Mine Pressure ◽  
Gas Extraction ◽  
Coal Face ◽  
Pressure Relief ◽  
Excessive Pressure ◽  
Gas Concentration ◽  
Mining Safety ◽  
High Level

Close seam group mining under thin immediate roofs and thick sandstone walls is typically performed with a strong mine pressure and gas concentration, which pose considerable risks to miners. In this study, the mechanism of pressure relief and permeability enhancement to enhance gas extraction for mining safety through blasting roof cutting were investigated through theoretical analyses, numerical simulations, and laboratory tests. The results revealed that, near the blast-hole, which produced numerous cracks, blasting disturbed the integrity of the thick-layer roofs and redistributed the stress near the blast-hole, which prevented violent mine pressure caused by excessive fracture distances on the thick and hard roofs, reduced the additional load on the support, increased vertical gas migration, and ameliorated the effect of gas drainage caused by high-level boreholes. The field applications of forced roof cutting through deep-hole blasting in the II 7224N face of the Renlou coal mine (Huaibei, Anhui, PR China) demonstrated that the occurrence of excessive pressure on the fully mechanized mining hydraulic support was prevented. The gas extraction volume of high-level boreholes was maintained at 6–8 m3/min; the extraction concentration was stable at approximately 35%; and the gas concentration in the upper corner of the coal face was lessened from 7% to <1%, which ensured normal mining in the coal face. The current results can provide data reference and a theoretical basis for roof management and gas control of the same type of coal face.

scholarly journals Fracture evolution and gas transport laws of coal and rock in one kilometer deep coal mine with complicated conditions

2019 ◽  
Vol 23 (Suppl. 3) ◽  
pp. 907-915
Author(s):  
Jianguo Zhang ◽  
Man Wang ◽  
Yingwei Wang
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Coal Mine ◽  
Fracture Zone ◽  
Gas Flow ◽  
Gas Transport ◽  
Enhancement Effect ◽  
Gas Extraction ◽  
Coal Seams ◽  
Long Distance

As coal mining gradually extends deeper, coal seams in China generally show high stress, high gas pressure and low permeability, bringing more difficulty to coal mining. Therefore, in order to strengthen gas extraction, it is necessary to carry out reservoir reconstruction after deep coal seams reached. In this paper, the distribution and evolution laws of fracture zone overlaying strata of J15 seam in Pingdingshan No. 10 coal mine after excavation were studied by combining similar simulation and numerical simulation, meanwhile, the gas transport law within fracture zone was numerically simulated. The results show that the fracture zone reaches a maximum of 350 mm in the vertical direction and is 75 mm away from W9,10 coal seams in vertical distance. Since W9,10 coal seams are in an area greatly affected by the bending zone of J15 coal seam under the influence of mining, the mining of J15 coal seam will exert a strong permeability enhancement effect on W9,10 coal seams. The J15 coal seam can act as a long-distance protective layer of W9,10 coal seams to eliminate the outburst danger of the long-distance coal seams in bending zone with coal and gas outburst danger, thereby achiev?ing safe, productive and efficient integrated mining of coal and gas resources. The gas flux of mining-induced fractures in the trapezoidal stage of mining-induced fracture field is far greater than that in the overlaying stratum matrix. The horizontal separation fractures and vertical broken fractures within the mining-induced fracture field act as passages for gas-flow. Compared with gas transport in the overlaying stratum matrix, the horizontal separation fractures and vertical broken fractures within the mining-induced fracture field play a role in guiding gas-flow. The research results can provide theoretical support for the arrangement of high-level gas extraction boreholes in roof fracture zones.

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