Pressure Relief and Permeability Enhancement with Carbon Dioxide Phase Transition Blasting: Fracture, Seepage, and Practice

Abstract Coal seams are generally characterized by high pressure, low permeability, and strong adsorption in China. Moreover, carbon dioxide phase transition blasting (CDPTB) is an effective way to achieve pressure relief and permeability enhancement in high-gas pressure coal seams. Multiple fractures can be created in the coal body by CDPTB due to its characteristics of having a great impact stress and high energy efficiency. To determine the dual characteristics of coal fracturing and seepage after CDPTB, this paper developed a fluid solid coupling programme based on CDPTB cracking and permeability enhancement, which unifies the fracture and seepage of CDPTB. FLAC was used to determine the distribution characteristics of the stresses and fractures caused by CDPTB. The results showed fracture propagation from the initial fracture to multiple additional fractures or the main fractures over time. Then, the fractures were introduced into COMSOL software to simulate the characteristics of the gas flow field. The main fracture forms an effective channel for gas flow, which greatly reduces the gas pressure in coal. The successful application of CDPTB in the field induced the increase in the gas drainage effect by 10-20 times.

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Experimental Study on the Gas Flow Characteristics and Pressure Relief Gas Drainage Effect under Different Unloading Stress Paths

Geofluids ◽

10.1155/2020/8837962 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Chaolin Zhang ◽

Jiang Xu ◽

Enyuan Wang ◽

Shoujian Peng

Keyword(s):

Coal Seam ◽

Gas Flow ◽

Flow Characteristics ◽

Gas Production ◽

Gas Pressure ◽

Coal Seam Gas ◽

Pressure Relief ◽

Gas Drainage ◽

Coal Temperature ◽

Drainage Effect

Coal seam gas is a critical substance because it can be a source of a large quantity of clean energy as well as a dangerous source of risk. A pressure relief gas drainage is an effective and widely used method for coal seam gas recovery and gas disaster control in coal mines. A series of pressure relief gas drainage experiments were conducted using large-scale coal samples under different unloading stress paths in this study to explore the unloading stress paths. From the experimental results, the dynamic evolutions of gas pressure, coal temperature, and gas production were analyzed. The trends of gas pressure and coal temperature during pressure relief gas drainage were similar: dropping rapidly first and then slowly with time. Correspondingly, gas production was fast in the early stage of pressure relief gas drainage and became stable thereafter. Meanwhile, gas flow characteristics were significantly affected by the unloading stress paths. Gas pressure and coal temperature had the maximum descent by unloading stress in three directions simultaneously, and the unloading stress of the Z direction had the minimal impact when only unloading in one direction of stress. However, the influence of unloading stress paths on gas production was complex and time dependent. The difference coefficient parameter was proposed to characterize the influence degree of unloading stress paths on the pressure relief gas drainage effect. Eventually, the selection of unloading stress path under different situations was discussed based on time, which is expected to provide the basis for pressure relief gas drainage.

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Understanding Carbon Dioxide Transfer in Direct Methanol Fuel Cells Using a Pore-Scale Model

Journal of Electrochemical Energy Conversion and Storage ◽

10.1115/1.4050369 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Nathaniel Metzger ◽

Archana Sekar ◽

Jun Li ◽

Xianglin Li

Keyword(s):

Carbon Dioxide ◽

Pressure Drop ◽

Gas Flow ◽

Direct Methanol Fuel Cells ◽

Gas Pressure ◽

Mass Transfer Resistance ◽

Transfer Resistance ◽

Cell Components ◽

Direct Methanol ◽

Methanol Fuel Cells

Abstract The gas flow of carbon dioxide from the catalyst layer (CL) through the microporous layer (MPL) and gas diffusion layer (GDL) has great impacts on the water and fuel management in direct methanol fuel cells (DMFCs). This work has developed a liquid–vapor two-phase model considering the counter flow of carbon dioxide gas, methanol, and water liquid solution in porous electrodes of DMFC. The model simulation includes the capillary pressure as well as the pressure drop due to flow resistance through the fuel cell components. The pressure drop of carbon dioxide flow is found to be about two to three orders of magnitude higher than the pressure drop of the liquid flow. The big difference between liquid and gas pressure drops can be explained by two reasons: volume flowrate of gas is three orders of magnitude higher than that of liquid; only a small fraction of pores (<5%) in hydrophilic fuel cell components are available for gas flow. Model results indicate that the gas pressure and the mass transfer resistance of liquid and gas are more sensitive to the pore size distribution than the thickness of porous components. To buildup high gas pressure and high mass transfer resistance of liquid, the MPL and CL should avoid micro-cracks during manufacture. Distributions of pore size and wettability of the GDL and MPL have been designed to reduce the methanol crossover and improve fuel efficiency. The model results provide design guidance to obtain superior DMFC performance using highly concentrated methanol solutions or even pure methanol.

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Study on Dynamic Behavior of a Gas Pressure Relief Valve for a Big Flow Rate

ASME/BATH 2013 Symposium on Fluid Power and Motion Control ◽

10.1115/fpmc2013-4479 ◽

2013 ◽

Author(s):

Victor Sverbilov ◽

Dmitry Stadnick ◽

Georgy Makaryants

Keyword(s):

Flow Rate ◽

Gas Flow ◽

Dynamic Properties ◽

Gas Pressure ◽

Pressure Relief Valve ◽

Relief Valve ◽

Pressure Relief ◽

Wide Range ◽

The Impact ◽

Pilot Valve

The paper investigates instable behavior of a poppet-type gas pressure relief valve operating at a big flow rate (more than 2 kg/s) under super critical pressure drop. Instability is experienced as noise and vibration and leads to severe damage of a seat and other elements. Significant and unsteady flow forces coupled with small inherent damping make it difficult to stabilize the system. In previous works, the analytical and experimental research was carried out to reveal the most essential factors influencing stability and dynamic properties of the valve. The impact of the pilot valve dynamics on the system behavior was studied for the purpose of obtaining required accuracy and stability in a wide range of flow rate. It was shown in some testing that unstable behavior of the main valve occurred when the pilot valve was stable. This paper considers inherent stability of the main valve in the gas flow. CFD software ANSYS FLUENT is employed to study the effect of the poppet geometry on aerodynamic lifting force and valve stability in axial and lateral direction. The results have been verified through comparison with experimental data.

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Research on the Effective Influence Radius of Hydraulic Reaming in Mining Seam

The Open Fuels & Energy Science Journal ◽

10.2174/1876973x01508010161 ◽

2015 ◽

Vol 8 (1) ◽

pp. 161-167

Author(s):

Li Peng ◽

Wang Kai ◽

Li Bo ◽

Jiang Yifeng ◽

Gou Jianqiang

Keyword(s):

Gas Flow ◽

Coupling Model ◽

Field Investigation ◽

Coal Mass ◽

Gas Content ◽

Coal Seams ◽

Gas Drainage ◽

Permeability Increase ◽

Influence Radius ◽

Drainage Effect

In Accordance with the present situations suggesting that the construction of the gas drainage boreholes in mining seam is sufficient and the gas drainage effect in low permeability coal seams does not yield perfectly, the hydraulic reaming technology in mining seam was proposed to increase the gas drainage efficiency. Through the gas flow method, the effective influence radius of hydraulic reaming was determined and the fluid-solid coupling model of gas drainage along boreholes after hydraulic reaming was established theoretically. Following this, the changes in the laws of gas content around the boreholes in the coal seam were simulated and analyzed. The results indicated that hydraulic reaming can effectively promote the stress-relief and permeability-increase of the coal mass around the boreholes, and the coal mass around the reaming boreholes can be divided into gas flow increase zone, gas flow delay attenuation zone and fast decay zone. The effective influence radius of hydraulic reaming was 5.5~6 m. The obtained simulation results were basically in accordance with the field investigation.

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Increasing Permeability of Coal Seam and Improving Gas Drainage Using a Liquid Carbon Dioxide Phase Transition Explosive Technology

Advances in Civil Engineering ◽

10.1155/2018/3976505 ◽

2018 ◽

Vol 2018 ◽

pp. 1-15 ◽

Cited By ~ 2

Author(s):

Wenrui He ◽

Fulian He ◽

Kun Zhang ◽

Yongqiang Zhao ◽

Hengzhong Zhu

Keyword(s):

Phase Transition ◽

Carbon Dioxide ◽

Numerical Simulation ◽

Blast Hole ◽

Liquid Carbon ◽

Gas Drainage ◽

Liquid Carbon Dioxide ◽

Drainage Hole ◽

Drainage Effect ◽

Coal Damage

The low permeability of coal seams makes gas drainage difficult in lots of coal mines. This study presents a low-temperature, safe, and efficient liquid carbon dioxide phase transition explosive technology (LCDPTET) to increase the permeability of coal, thereby improving the efficiency of gas drainage and eliminating the dangers of coal and gas outburst. Meanwhile, an integrated approach for experimental determination, numerical simulation, and field testing was applied to study the damage ranges of coal and to determine a reasonable spacing between the gas drainage hole and blast hole. A numerical simulation model of liquid carbon dioxide phase transition explosion (LCDPTE) was built, and the damage index M was introduced to analyze the degree and range of coal damage after explosion at different spacings between the blast hole and the gas drainage hole. Furthermore, another aim was the assessment of the permeability changes and comparison of the gas drainage effects of different borehole spacings. The results showed that as the borehole spacing became smaller, the degree of coal damage around the gas drainage hole increased, and the gas drainage effect improved. However, to avoid the collapse of the gas drainage hole, the gas drainage holes should not be located in the crushing zone caused by LCDPTE. Based on the numerical analysis conducted to guide the borehole arrangement of the field test, the latter was carried out to study the increasing ranges of permeability of coal and the drainage effect after explosion. The results indicated that LCDPTET could greatly improve the permeability of the coal seam and gas drainage efficiency. In addition, this new technology could not only improve the safety and efficiency of mine production but could also turn carbon dioxide into an effective energy source worthy of popularization and application.

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A fully coupled gas flow, coal deformation and thermal transport model for the injection of carbon dioxide into coal seams

CO2 Storage in Carboniferous Formations and Abandoned Coal Mines ◽

10.1201/b11645-6 ◽

2011 ◽

pp. 69-93

Author(s):

Hongyan Qu ◽

J Liu ◽

Zhongwei Chen ◽

Zhejun Pan ◽

Luke Connell

Keyword(s):

Carbon Dioxide ◽

Thermal Transport ◽

Gas Flow ◽

Transport Model ◽

Coal Seams ◽

Coal Deformation ◽

Fully Coupled

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Numerical Analysis on Apeature of High-Pressure Water Jet Punching Hole to Preventing Outburst

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.421.360 ◽

2011 ◽

Vol 421 ◽

pp. 360-363

Author(s):

Jia Yong Zhang ◽

Xue Min Gong ◽

Li Wen Guo

Keyword(s):

Gas Flow ◽

Gas Pressure ◽

Analysis Software ◽

Coal Seams ◽

Gas Emission ◽

Element Analysis ◽

The Face ◽

Pressure Water ◽

High Pressure Water Jet

As impacting and cutting role of the small jet, coal around slots occured violent displacement and expansion, increasing coal cracks, which greatly improved gas flow in coal seams and made for gas emission. The original coal stress changed and stress concentration belt moved to coal seams depth constantly. With gradual relief expansion and fracture increased, coal seam permeability coefficient increased, gas pressure decreased. Coal potentiality released, coal crushed and moved, a lot of gas with adsorption state changed free, then gas fully released and gas pressure gradient decreased, which reduced outstanding risk. it was determined that aperture size was 4/15 or so of roadway floor length using ANSYS finite element analysis software, thus roadway fissures developed full, and maintained rock integrity, in favor of speeding up the face driving.

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A New Method for Controlling Rockbursts in the Mining Roadway of Ultrathick Coal Seams Based on the Dual Pressure Relief Method

Shock and Vibration ◽

10.1155/2021/7565004 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Guangyuan Yu ◽

Jiong Wang ◽

Zimin Ma ◽

Wei Ming ◽

Xingen Ma

Keyword(s):

Energy Release ◽

Abutment Pressure ◽

Average Energy ◽

Field Testing ◽

High Energy ◽

Low Energy ◽

New Method ◽

Coal Seams ◽

Pressure Relief ◽

Working Face

To control rockbursts in mining roadways in ultrathick coal seams, a new method for preventing rockbursts through dual pressure relief by roof cutting through cumulative blasting in medium-deep boreholes from the conveyor gateway and return airway was proposed. The mechanical characteristics of key overlying strata of the working face under the effect of dual pressure relief were theoretically investigated. Furthermore, a mathematical relationship between the roof-cutting depth and the advanced abutment pressure on the working face was established to reveal the mechanism of dual pressure relief in controlling rockbursts. Moreover, the effect of the dual pressure relief method on controlling rockbursts was validated through numerical simulation and field testing. Results showed that artificially increasing the caving height of gangues in goaf based on the dual pressure relief method can restrict the subsidence of key strata, thus reducing the advanced abutment pressure of the working face; the method influences a range of 20 m in front of the working face along the strike and areas 30 m away from the two roadways along the dip. The average energy density of coal in the side of the conveyor gateway is decreased by 15.4%, while that in the side of return airway is reduced by 13.8% within the range of influence. The field test results indicated that the average pressure on support declines by 21.4% within 30 m from the working face to the conveyor gateway, while it decreases by 20.5% within that region 25 m from the return airway by using the dual pressure relief method. After conducting dual pressure relief, the total number of microseismic (MS) events during mining of the working face is decreased by 25.4%. The number of MS events with energy release exceeding 103 J falls by 36.6%, while the number of events releasing less than 103 J is increased by 28.6%. The characteristics of MS energy release change from coexistence of low-energy events and a small number of high-energy events to the occurrence of numerous low-energy events. Results can verify the effectiveness of the dual pressure relief method in controlling rockbursts in the mining roadway of ultrathick coal seams.

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