Study on Parameters of Gas Extraction in Spontaneous Combustion in Goaf and Comprehensive Prevention Process of Gas in Hongmiao Mine

2014 ◽  
Vol 962-965 ◽  
pp. 973-979
Author(s):  
Xiang Li
Keyword(s):  
Spontaneous Combustion ◽  
Break Line ◽  
Gas Extraction ◽  
Gas Explosion ◽  
Gas Drainage ◽  
Comprehensive Management ◽  
Working Face ◽  
The Face ◽  
Extraction Parameters ◽  
Selection Of

Aimed at the comprehensive management of gas and spontaneous combustion in goaf of 5-2S fully mechanized caving face in five district of Hongmiao coal mine. The impacts on the air flow field and concentration distribution of the goaf are analyzed, that the changes of gas drainage value, and the location of drainage outlet as well as injection capacity of nitrogen. The results show that, the larger of the volume of gas drainage, the greater risk of gas explosion and spontaneous combustion. Appropriate increasing gas drainage volume is used to ensure the safety of the working face, with injecting nitrogen or accelerating the speed of face promote. The drainage outlet location should also be in an appropriate range (5~25 m) after the break line of the face. The result has important guiding significance in goaf of inflammable thick seam of gas mine, on the selection of gas extraction parameters, which is reasonable to prevent both gas explosion accident and spontaneous combustion caused by drainage excessive.

scholarly journals Study on Optimization of Gas Drainage Methods in High-burst Mines

2019 ◽  
Vol 118 ◽  
pp. 03034
Author(s):  
Fengfeng Yang ◽  
Dongfang Gao ◽  
Jufeng Zhang ◽  
Kezhen Zhao ◽  
Tai Xu ◽  
...  
Keyword(s):  
Coal Mine ◽  
Extraction Method ◽  
Gas Extraction ◽  
Gas Emission ◽  
Gas Drainage ◽  
Composition Ratio ◽  
Gas Outburst ◽  
Actual Production ◽  
Extraction Parameters ◽  
Production Conditions

After the mechanization upgrade of Yongjing Coal Mine, the original extraction method cannot solve the problem of gas. According to the actual production conditions of the mine, the source and composition ratio of gas emission are analyzed.By combining with the gas extraction method before upgrading and transformation, it is of great importance to determine the appropriate comprehensive gas extraction method and optimize the gas extraction parameters for improving the gas extraction effect and eliminating the risk of gas outburst.

scholarly journals Disastrous Mechanism and Concentration Distribution of Gas Migration in Fully Mechanized Caving Stope in Wuyang Coal Mine

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Li Chong ◽  
He Sifeng ◽  
Xu Zhijun
Keyword(s):  
Coal Mine ◽  
Concentration Distribution ◽  
Spontaneous Combustion ◽  
Concentration Field ◽  
Gas Migration ◽  
Coal Spontaneous Combustion ◽  
Gas Drainage ◽  
Gas Concentration ◽  
Research Results ◽  
Working Face

The overrunning disaster of harmful gas tends to occur in the working face in thick coal seam with high gas concentration, as the fully mechanized caving stope has the characteristics of high mining intensity, high remnant coal, and high gas content. Therefore, the disastrous mechanism and concentration distribution of gas migration in fully mechanized caving stope are the theoretical basis for gas control scheme. Based on the 7607 working face in Wuyang coal mine, the gas emission quantity in working face is comprehensively analyzed by field measurement in this paper. The gas leakage field, oxygen concentration field, and gas concentration field in 7607 working face are simulated by establishing the equal proportional numerical model. Due to the increase of air leakage in working face caused by the high alley pumping drainage, the risk of coal spontaneous combustion is also analyzed, when gas extraction in goaf is carried out. The research results show that the gas drainage technology in high drainage roadway has a remarkable effect on the gas overrunning phenomenon. The gas concentration near the upper corner of the working surface has been reduced from 0.7%-1% to 0.5%. At the same time, it is necessary to pay attention to the risk of coal spontaneous combustion in the goaf for gas drainage in the high drainage roadway. The width of the oxidation zone in the goaf is about 25 m deeper than that before the drainage. Research results provide the references for gas control technology and coal spontaneous combustion prevention in similar working faces.

scholarly journals Numerical simulation study on gas drainage by interval hydraulic flushing in coal seam working face

2021 ◽  
pp. 014459872110102
Author(s):  
Shengrong Xie ◽  
Junqi Cui ◽  
Dongdong Chen ◽  
Ping Chen
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Coal Mine ◽  
Simulation Software ◽  
Gas Pressure ◽  
Gas Extraction ◽  
Gas Drainage ◽  
Drainage Radius ◽  
Working Face ◽  
Effective Drainage

In order to solve the problem of difficult gas extraction in coal mine, a method of gas extraction from coal seam by interval hydraulic flushing is put forward. Based on the coal seam gas occurrence conditions of 7609 working face in Wuyang Coal Mine, the numerical simulation research on gas drainage by ordinary drilling and hydraulic flushing drilling was carried out by using COMSOL numerical simulation software. The results show that with the increase of hydraulic flushing coal quantity, the effective gas drainage radius also increases. The effective extraction radius of ordinary drilling is 0.5 m, and the effective extraction radius is 1.0 m, 1.2 m and 1.3 m respectively when the coal flushing quantity is 0.5t/m, 1.0t/m and 1.5t/m. As multiple boreholes are drained at the same time, the boreholes will affect each other, which will reduce the gas pressure and increase the effective drainage radius, the spacing between boreholes can be greater than twice the effective drainage radius of a single borehole when arranging boreholes. And the smaller the flushing interval, the more uniform the gas pressure reduction area. According to the numerical simulation results, the ordinary drilling and 1.0t/m interval hydraulic flushing test were carried out in the field. Through observation and analysis, the gas concentration of the interval hydraulic flushing drilling module was increased by 31.2% and the drainage purity was increased by 5.77 times compared with the ordinary drilling module. It shows that the interval hydraulic flushing drilling can effectively improve the gas drainage effect.

scholarly journals Numerical Simulation of Coal Spontaneous Combustion around a Borehole Induced by Negative Pressure Gas Drainage

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Youxin Zhao ◽  
Qingjie Qi ◽  
Xinlei Jia ◽  
Yingjie Liu ◽  
Jingwen Zhang
Keyword(s):  
Oxygen Concentration ◽  
Negative Pressure ◽  
Spontaneous Combustion ◽  
Combustion Process ◽  
Extraction Process ◽  
Gas Extraction ◽  
Growth Trend ◽  
Gas Drainage ◽  
Gas Seepage ◽  
Spontaneous Combustion Of Coal

The suction negative pressure is an important factor affecting the spontaneous combustion of coal around a borehole. Because the mechanism of suction negative pressure in the gas extraction process remains unclear, a constant suction negative pressure is often used in coal mines, leading to a low efficiency of gas extraction in deep coal seams. Moreover, the coal body easily undergoes spontaneous combustion during the extraction process, which is not conducive to safe mining. To study the effect of the suction negative pressure near the end sealing section, a numerical model of the combustion process around a borehole under the influence of suction negative pressure was established using COMSOL. The variation laws of the gas seepage velocity, oxygen concentration, and coal temperature in the borehole cycle were analyzed, and the gas suction negative pressure under different sealing parameters was optimized to ensure efficient gas extraction and prevent the spontaneous combustion of coal. The results showed that the negative pressure of extraction provides the power required for gas seepage into the borehole, and the gas flow rate increases with increasing negative pressure of extraction, exhibiting a linear growth trend. The range of the coal suffocation zone around the sealing section decreases with the increase in the negative pressure. With the extension of the gas extraction time, the oxygen concentration decreases rapidly, and the inflection point advances with the increase in the negative pressure. When the negative pressure of gas extraction is <40 kPa, the range of the high-temperature area around the block increases with the negative pressure of gas extraction. Based on the present situation of the spontaneous combustion induced by gas drainage in the Pingdingshan No. 10 Coal Mine, different sealing parameters should be set with different negative pressures of extraction, and the negative pressure of extraction should not exceed −18 kPa when the sealing depth is 20 m and the sealing length is 8 m in the 24130 working face. These parameter settings can help effectively prevent spontaneous combustion during the extraction process.

Research on the Comprehensive Control Technology about Gas in the Large Mining Height and Extended Mining Face for the High Gas Mine

2011 ◽  
Vol 347-353 ◽  
pp. 1580-1583
Author(s):  
Hua Min Li ◽  
Zheng Kai Yang ◽  
Zu Qiang Xiong ◽  
Dong Ying Li ◽  
Wang Wen
Keyword(s):  
Gas Extraction ◽  
Shielding Gas ◽  
Gas Drainage ◽  
Simultaneous Extraction ◽  
Comprehensive Management ◽  
Methane Drainage ◽  
High Efficient ◽  
Large Mining Height ◽  
Mining Face ◽  
Mining Height

The paper describes the three-tier stereo comprehensive management gas model for the mining height and extended mining face in the high gas mine. The model consists of gas drainage with surface drilling, progressive and shielding gas drainage with 1000m drilling machine from underground and so on. The measures make it easy to realize the combination of surface fracturing and gas extraction, establish the model of cooperation methane drainage from the surface and underground. Meanwhile, the ventilation type, three incoming-air gateways and two returning-air gateways, is used in the mining face. It can effectively avoid exceeding gas in the upper corner of mining face. It can guarantee safe and high-efficient mining. The green mining technology for coal and gas for simultaneous extraction is easily realized. It has important guiding value for mine gas management at similar conditions.

Evaluation of the Modified Naranjo Criteria for Assessing Causal Attribution of Clinical Outcome to Homeopathic Intervention as Presented in Case Reports

Homeopathy ◽  
2020 ◽  
Vol 109 (04) ◽  
pp. 191-197
Author(s):  
Chetna Deep Lamba ◽  
Vishwa Kumar Gupta ◽  
Robbert van Haselen ◽  
Lex Rutten ◽  
Nidhi Mahajan ◽  
...  
Keyword(s):  
Clinical Outcome ◽  
Causal Relationship ◽  
Clinical Case ◽  
Assessment Tool ◽  
Causal Attribution ◽  
Case Reports ◽  
Face Validity ◽  
Rater Agreement ◽  
The Face ◽  
Selection Of

Abstract Objectives The objective of this study was to establish the reliability and content validity of the “Modified Naranjo Criteria for Homeopathy—Causal Attribution Inventory” as a tool for attributing a causal relationship between the homeopathic intervention and outcome in clinical case reports. Methods Purposive sampling was adopted for the selection of information-rich case reports using pre-defined criteria. Eligible case reports had to fulfil a minimum of nine items of the CARE Clinical Case Reporting Guideline checklist and a minimum of three of the homeopathic HOM-CASE CARE extension items. The Modified Naranjo Criteria for Homeopathy Inventory consists of 10 domains. Inter-rater agreement in the scoring of these domains was determined by calculating the percentage agreement and kappa (κ) values. A κ greater than 0.4, indicating fair agreement between raters, in conjunction with the absence of concerns regarding the face validity, was taken to indicate the validity of a given domain. Each domain was assessed by four raters for the selected case reports. Results Sixty case reports met the inclusion criteria. Inter-rater agreement/concordance per domain was “perfect” for domains 1 (100%, κ = 1.00) and 2 (100%, κ = 1.00); “almost perfect” for domain 8 (97.5%, κ = 0.86); “substantial” for domains 3 (96.7%, κ = 0.80) and 5 (91.1%, κ = 0.70); “moderate” for domains 4 (83.3%, κ = 0.60), 7 (67.8%, κ = 0.46) and 9 (99.2%, κ = 0.50); and “fair” for domain 10 (56.1%, κ = 0.38). For domains 6A (46.7%, κ = 0.03) and 6B (50.3%, κ = 0.18), there was “slight agreement” only. Thus, the validity of the Modified Naranjo Criteria for Homeopathy tool was established for each of its domains, except for the two that pertain to direction of cure (domains 6A and 6B). Conclusion The Modified Naranjo Criteria for Homeopathy—Causal Attribution Inventory was identified as a valid tool for assessing the likelihood of a causal relationship between a homeopathic intervention and clinical outcome. Improved wordings for several criteria have been proposed for the assessment tool, under the new acronym “MONARCH”. Further assessment of two MONARCH domains is required.

scholarly journals The construction of leadership practice: Making sense of leader competencies

Leadership ◽  
2021 ◽  
pp. 174271502199649
Author(s):  
Dag Jansson ◽  
Erik Døving ◽  
Beate Elstad
Keyword(s):  
Professional Practice ◽  
Leadership Competencies ◽  
The Self ◽  
Leadership Practice ◽  
Choral Conductors ◽  
Making Sense ◽  
Sensemaking Process ◽  
The Face ◽  
Depth Interviews ◽  
Selection Of

The notion of leadership competencies is a much-debated issue. In this article, we propose that how the leader makes sense of his or her competencies is key to leadership practice. Specifically, we look at how leaders reconcile discrepancies between the self-perceived proficiency of various competencies and their corresponding importance. Empirically, we study leaders within the music domain – how choral conductors make sense of their competencies in the shaping of their professional practice. We investigated how choral leaders in Scandinavia ( N = 638) made sense of their competencies in the face of demands in their working situations. A mixed methodology was used, comprising a quantitative survey with qualitative comments and in-depth interviews with a selection of the respondents. The results show that when choral leaders shape their practice, they frequently face competency gaps that compel them to act or adjust their identity. The key to this sensemaking process is how they move competency elements they master to the foreground and wanting elements to the background. The concept of ‘sensemaking affordance’ is introduced to account for how various leader competency categories are negotiated to safeguard overall efficacy.

scholarly journals Facial Expression Recognition Based on Multi-Features Cooperative Deep Convolutional Network

2021 ◽  
Vol 11 (4) ◽  
pp. 1428
Author(s):  
Haopeng Wu ◽  
Zhiying Lu ◽  
Jianfeng Zhang ◽  
Xin Li ◽  
Mingyue Zhao ◽  
...  
Keyword(s):  
Facial Expression ◽  
Facial Expressions ◽  
Facial Expression Recognition ◽  
Video Data ◽  
Expression Recognition ◽  
Convolutional Network ◽  
Facial Movements ◽  
The Face ◽  
Deep Convolutional Network ◽  
Selection Of

This paper addresses the problem of Facial Expression Recognition (FER), focusing on unobvious facial movements. Traditional methods often cause overfitting problems or incomplete information due to insufficient data and manual selection of features. Instead, our proposed network, which is called the Multi-features Cooperative Deep Convolutional Network (MC-DCN), maintains focus on the overall feature of the face and the trend of key parts. The processing of video data is the first stage. The method of ensemble of regression trees (ERT) is used to obtain the overall contour of the face. Then, the attention model is used to pick up the parts of face that are more susceptible to expressions. Under the combined effect of these two methods, the image which can be called a local feature map is obtained. After that, the video data are sent to MC-DCN, containing parallel sub-networks. While the overall spatiotemporal characteristics of facial expressions are obtained through the sequence of images, the selection of keys parts can better learn the changes in facial expressions brought about by subtle facial movements. By combining local features and global features, the proposed method can acquire more information, leading to better performance. The experimental results show that MC-DCN can achieve recognition rates of 95%, 78.6% and 78.3% on the three datasets SAVEE, MMI, and edited GEMEP, respectively.

scholarly journals A Clinical Study to Correlate the Facial Form and Maxillary Central Incisor Tooth Form in Males and Females of Davangere Population

2016 ◽  
Vol 04 (03) ◽  
pp. 156-164
Author(s):  
Deepak Bansal ◽  
Shruti Sharma ◽  
Manjit Kumar ◽  
Amrit Khosla
Keyword(s):  
Facial Appearance ◽  
Central Incisor ◽  
Incisor Tooth ◽  
Maxillary Central Incisor ◽  
Anterior Teeth ◽  
The Face ◽  
Tooth Form ◽  
Males And Females ◽  
Selection Of ◽  
Made In

AbstractAn altered facial appearance is more difficult to face, than problems related to ill-fitting denture or eating. The selection of maxillary anterior teeth for complete denture has long posed problem in clinical practice and a controversy about the best method to employ still exists. An attempt is made in the present study to clinically correlate the face form with maxillary central incisor tooth form in males and females of Davangere population. In 1914, Leon William's projected the “the form method” where he classified facial forms as square, tapering, and ovoid. Maxillary central incisors were selected according to the facial forms.Of total 100 subjects four different tooth forms and face forms were evaluated. They are: square, ovoid, square-tapered, tapered. No significant correlation existed between face form in male and females. Females exhibited greater correlation between face forms and inverted tooth form but that correlation is not sufficient to serve as a guide for selection of anterior teeth.

Sign in / Sign up

Export Citation Format

Share Document