Monitoring of coal fracturing in underground coal gasification by acoustic emission techniques

Su, Faqiang; Itakura, Keiichi; Deguchi, Gota; Ohga, Kotaro

doi:10.1016/j.apenergy.2016.11.082

Cited by 72 publications

(36 citation statements)

References 30 publications

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“…During the outer section excavation process of the F 15 With the increasing depth of the mining, the ground stress is also increasing, and the dynamic phenomena being dominated by the ground stress are increasingly apparent.…”

Section: Coal and Gas Outburst Disasters Overviewmentioning

confidence: 99%

“…[5][6][7] These methods can only reflect the indicators and changes of a certain factor of coal-rock gas dynamic disaster, and not realize dynamic continuous prediction and early warning. [12][13][14][15] A thorough and detailed research on AE-related indicators and their changing laws is an important direction for predicting and understanding coal-rock gas dynamic disasters. The occurrence of coal-rock gas dynamic disasters has a preparation process from quantitative change to qualitative change, that is, the process from small fracture to failure of coal rock.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic emission monitoring technology for coal and gas outburst

et al. 2019

Energy Science & Engineering

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In recent years, with the increase in mining depth and strength, coal‐rock gas dynamic disasters, such as coal and gas outburst, have shown an increasing trend. Acoustic emission (AE) technology has been viewed as a promising method that can effectively forecast coal and gas dynamic disasters. This paper first tests the AE characteristics of coal and rock samples during loading. Then, self‐developed AE continuous monitoring and early warning equipment is used to monitor and predict the coal and gas outburst dynamic disasters on the working face. And it is found that the coal samples primarily show ductile failure, and the AE exhibits the evolutionary characteristics of “rise‐peak‐fall”. The rock samples primarily exhibit brittle failure, and the AE evolution mode is almost no falling stage. Coal and gas outbursts occur after the stress peak. Before coal and gas outbursts occur, there is a clear increasing trend in the AE ahead of the gas concentration variation. When the gas‐bearing coal is damaged by the load, the coal body first breaks due to the stress, and the AE value increases. Then, due to the fracture of the coal body, the crack penetrates, gas rushes out, and the gas concentration increases. The research results can provide an advanced technical method for the monitoring and early warning of coal–rock gas dynamic disasters, and improve the prediction accuracy for dynamic disasters.

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Section: Coal and Gas Outburst Disasters Overviewmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Acoustic emission monitoring technology for coal and gas outburst

et al. 2019

Energy Science & Engineering

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“…Xin et al obtained a syngas with 121.9 kJ/mol by applying using shaft method in UCG technology. Su et al performed modeling studies on UCG and studied the effect of operational parameters on cavity growth and formation. Duan et al developed a model for CO 2 ‐O 2 dual‐stage–based gasification.…”

Section: Introductionmentioning

confidence: 99%

Movable injection point–based syngas production in the context of underground coal gasification

Kashyap

Vairakannu

2020

Int J Energy Res

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Summary Underground coal gasification (UCG) has been proven as a viable technology for the generation of high calorific value syngas using deep mine coal seams. The use of multiple injection points/movable injection point method could be an alternate technique for efficient gasification of high ash Indian coals. In this context, the present study is focused on evaluating the heating value of syngas using a variety of gasifying agents such as pure O2, air, humidified O2, and CO2‐O2 dual‐stage gasification under movable injection method for high ash coals. It is found that the use of movable injection point method had significantly increased the heating value of the product gas, compared with the fixed point injection method. For high and low ash coal under pure O2 gasification, the calorific value of syngas obtained using movable injection point is 123.2 and 153.9 kJ/mol, which are 33.5% and 24.3% higher than the syngas calorific value obtained using fixed injection point, respectively. Further, the air as a gasification agent for high ash coals had increased the gross calorific value of the syngas by 24%, using this technology. The results of high ash coal gasification using humidified oxygen at optimum conditions (0.027‐kg moisture/kg dry O2) and CO2‐O2 gas had enhanced the syngas calorific value by 12.6% and 5%, respectively. Humidified O2 and CO2‐O2 gasifying agents produced a high‐quality syngas with the calorific value of 190 kJ/mol, among the gasifying agents used. The experimental results had shown that the movable injection point method is found to be a better alternative for the generation of calorific value‐enriched syngas using high ash‐based Indian coals.

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“…According to rock damage theory, high stresses on the entry wall tend to produce more mining-induced fractures [23][24][25]. The degree of damage differs as the pillar width changes.…”

Section: Model Description At the Laboratorymentioning

confidence: 99%

Analysis and Optimization of Entry Stability in Underground Longwall Mining

et al. 2017

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For sustainable utilization of limited coal resources, it is important to increase the coal recovery rate and reduce mine accidents, especially those occurring in the entry (gateroad). Entry stabilities are vital for ventilation, transportation and other essential services in underground coal mining. In the present study, a finite difference model was built to investigate stress evolutions around the entry, and true triaxial tests were carried out at the laboratory to explore entry wall stabilities under different mining conditions. The modeling and experimental results indicated that a wide coal pillar was favorable for entry stabilities, but oversize pillars caused a serious waste of coal resources. As the width of the entry wall decreased, the integrated vertical stress, induced by two adjacent mining panels, coupled with each other and experienced an increase on the entry wall, which inevitably weakened the stability of the entry. Therefore, mining with coal pillars always involves a tradeoff between economy and safety. To address this problem, an innovative non-pillar mining technique by optimizing the entry surrounding structures was proposed. Numerical simulation showed that the deformation of the entry roof decreased by approximately 66% after adopting the new approach, compared with that using the conventional mining method. Field monitoring indicated that the stress condition of the entry was significantly improved and the average roof pressure decreased by appropriately 60.33% after adopting the new technique. This work provides an economical and effective approach to achieve sustainable exploitation of underground coal resources.

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Monitoring of coal fracturing in underground coal gasification by acoustic emission techniques

Cited by 72 publications

References 30 publications

Acoustic emission monitoring technology for coal and gas outburst

Acoustic emission monitoring technology for coal and gas outburst

Movable injection point–based syngas production in the context of underground coal gasification

Analysis and Optimization of Entry Stability in Underground Longwall Mining

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