Effect of high-voltage thermal breakdown on pore characteristics of coal

Zhu, Chuanjie; Lu, Ximiao; Gao, Zi-shan; Yan, Fazhi; Guo, Chunhui; Zhang, Xiangliang

doi:10.1016/j.ijmst.2017.06.027

Cited by 25 publications

(10 citation statements)

References 7 publications

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“…Moreover, it can be concluded that the initial speed of carbon dioxide diffusion is larger than the initial speed of methane diffusion (k CO 2 >k CH 4 ). According to the outburst threshold of 10 mmHg (Zhu et al., 2017), and the linear equations as shown in equations (10) and (11), coal seams should be identified as outburst-prone seams when carbon dioxide pressure is higher than 0.069 MPa and methane pressure is higher than 0.074 MPa, which confirms that the coal and carbon dioxide outburst is more dangerous than the coal and methane outburst. In addition, the IVDCG (Δ P ) and the adsorption constants (a and b value) of coal have a certain relationship (Tang, 2014).…”

Section: Resultsmentioning

confidence: 96%

“…The adsorbed and free gas take up the most of coal bed gas, which dominates the occurrence of coal and gas outburst. In order to prevent the occurrence of coal and gas outburst in the process of uncovering coal in deep mines, numerous sensitivity indexes attached to the gas desorption properties were established, including the variation of gas emission (K V ) (De Vegeron and Belin, 1966a, 1966b; Somnier, 1960; Yan et al., 2017), prediction method attached to the gas adsorption index K 1 and Δh 2 of drilling cuttings (Zhu et al., 2017), and the index initial velocity diffusion of coal gas (IVDCG) (Δ P ) (Lama and Bodziony, 1998; Skoczylas, 2012).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Desorption characterization of methane and carbon dioxide in coal and its influence on outburst prediction

Wang

Luo

2018

Adsorption Science & Technology

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Coal and gas outburst is a dynamic phenomenon with violent eruptions of coal and gas from the working coal seam. It has been proved that the rapid desorption within a short period is necessary for the occurrence of an outburst. Due to limitation of the present test condition, gas desorption characterization for the first 60 s has not been researched sufficiently. In the present study, an experimental apparatus with the ability of high-frequency data collection was developed. Initial desorption characterization of methane and carbon dioxide in coal was experimentally studied. Both the initial desorption characterization of methane and carbon dioxide were experimentally studied with different equilibrium pressures. The desorbed gas pressure was measured at desorption time phase of 0-10 and 45-60 s, besides the initial amount of desorbed gas and initial diffusion velocity of coal gas were calculated to assess their risk of outburst. The results show that the gas pressure for both methane and carbon dioxide increases sharply in the initial time and then levels off, and the total amount of desorbed gas increases with the increasing desorption time. Although the amount of desorption methane is slightly larger than that of carbon dioxide at the beginning, the total amount of desorbed carbon dioxide is significantly larger than that of methane at the desorption process. Therefore, it can be concluded that the coal and carbon dioxide outburst is more dangerous than the coal and methane outburst based on the obtained experimental results.

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Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Desorption characterization of methane and carbon dioxide in coal and its influence on outburst prediction

Wang

Luo

2018

Adsorption Science & Technology

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“…To study the variations in the fracture and pore structure of coal samples crushed by HVEP, environmental scanning electron microscopy (SEM, Quanta 250, FEI Company, Hillsboro, OR, U.S.A.) and nuclear magnetic resonance (NMR) were used in our experiment. , In addition, an energy-dispersive spectroscopy (EDS) point scanning test was performed to investigate the effects of NaCl solution on electrical breakdown, and Fourier transform infrared spectroscopy (FTIR, Bruker) was used to study variations of various functional groups on the coal surface. , …”

Section: Methodsmentioning

confidence: 99%

Improving the Conductivity and Porosity of Coal with NaCl Solution for High-Voltage Electrical Fragmentation

Lin¹,

Zhang²,

Yan

et al. 2018

Energy Fuels

Self Cite

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High-voltage electrical pulse (HVEP) technology is a useful method to improve the pore structure of coal. However, the breakdown voltage of coal is very high; therefore, it is necessary to improve the conductivity of coal first to decrease its breakdown voltage before subjecting it to HVEP. In this work, a solution of NaCl was used for ameliorating the conductivity of Linhua anthracite coal and Hongliu bituminous coal. Both breakdown voltage and energy consumed by the coal sample saturated with the solution of NaCl decreased. The breakdown voltage of Linhua and Hongliu raw coal sample (RCS) was 3.44 and 2.88 times that of coal saturated with NaCl, respectively. The energy consumed by Linhua and Hongliu RCS was 11.82 and 8.21 times that of coal saturated with NaCl solution, respectively. Scanning electron microscopy images showed that the surface cracks on crushed coal samples after saturating with NaCl solution were more than those on RCS. Nuclear magnetic resonance results indicate that meso-and macropores were chiefly enhanced by the electrical breakdown. Chlorine and sodium elements were found on the surface of both Linhua and Hongliu coal through energy-dispersive spectroscopy point scanning, which indicates that these elements play a positive role in electrical breakdown. A Fourier transform infrared spectroscopy test showed that the discharge channel left a trail of burning on the surface of the coal sample and the changes in the functional groups after crushing.

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“…When the tail drum of the permanent magnet semidirect drive cutting transmission system in the coal cutters cuts coals and rocks, due to the uneven intensity of the coal seam, the brittle caving of the coal rock mass, and hard parcels existing, the loads on the drum exhibit the characteristics of randomness, major fluctuations, great impact, etc. [1][2][3]. Besides, since coal cutters operates in a relatively tough environment, the electrical parameters of its driving motor change with the different temperatures.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Torsional Vibration Analysis and Nonlinear Feedback Control of Complex Permanent Magnet Semidirect Drive Cutting System in Coal Cutters

Sheng

Xin

et al. 2019

Complexity

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The semidirect drive cutting transmission system of coal cutters is prone to unstable torsional vibration when the resistance values of its driving permanent magnet synchronous motor (PMSM) are affected by changes in temperatures and tough conditions. Besides, the system has the properties of complex electromechanically coupling such as the coupling between electrical parameters and mechanical parameters. Therefore, in this study, the nonlinear torsional vibration equation was established on the basis of the Lagrange-Maxwell theory. Moreover, in light of the nonlinear dynamic bifurcation theory, the system stability was analyzed by taking the resistance value of power motor as the bifurcation parameter. In addition, the influence of subcritical bifurcation on the torsional vibration was studied by investigating the necessary and sufficient conditions for dynamic Hopf bifurcation and classifying the bifurcation types. At last, in order to suppress destabilizing oscillation induced by Hopf bifurcation, the nonlinear feedback controller was constructed, with the introduction of feedback from the motor velocity as well as the selection of voltage value on the q shaft as the controlled variable. Meanwhile, the three-order normal form and controlling parameters of the system were obtained with the aid of the multiple scales method and the harmonic balance method. In this way, the Hopf bifurcation point was transferred to control the stability of Hopf bifurcation and the amplitude of limit cycle, thus guaranteeing reliable and safe operation of the system. The numerical simulation results indicate that the designed controller boosts an ideal controlling effect.

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Effect of high-voltage thermal breakdown on pore characteristics of coal

Cited by 25 publications

References 7 publications

Desorption characterization of methane and carbon dioxide in coal and its influence on outburst prediction

Desorption characterization of methane and carbon dioxide in coal and its influence on outburst prediction

Improving the Conductivity and Porosity of Coal with NaCl Solution for High-Voltage Electrical Fragmentation

Nonlinear Torsional Vibration Analysis and Nonlinear Feedback Control of Complex Permanent Magnet Semidirect Drive Cutting System in Coal Cutters

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