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Location of Bulianta colliery.

Location of Bulianta colliery.

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Spontaneous combustion of residual coal in longwall goaf is a long standing hazard. Airflow leakage into goaf is a major driver to the hazard and this issue deteriorates where longwalls are operating in multiple seams and shallow covers because mining-induced cracks are very likely to draw fresh airflow into goaf due to presence of pressure differe...

Contexts in source publication

Context 1
... colliery is situated 13 km south to Ordos city of Inner Mongolia Autonomous Region of Northern China (see Fig. 1). The colliery is operated in Shendong coalfield which is featured with flat and thick coal seam under shallow cover. Mining area of the colliery is approximately 34 km 2 and the total proven reserve exceeds 506 million tons of coal. Due to recent upgrade of mining technology and equipment, extraction height of LW working face has ...
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... three, section four, and section five, respectively) and the pressure loss is validated through the three paths. The detail of the validation is only presented at section three as LWs in section three are the most risky area in terms of coal spontaneous combustion and ingress of goaf gas. The follow-up studies will focus on LW22307 path as well. Fig. 10 is a simplified airflow path through LW22307. Most fresh air is taken from main intake incline and then directs to 2 À2 coal seam intake main. Part of the fresh airflow in 2 À2 seam intake main is taken to section three longwalls via section three intake main. Then fresh air in LW22307 is supplied through both LW22307 maingate and ...
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... three longwalls via section three intake main. Then fresh air in LW22307 is supplied through both LW22307 maingate and LW22308 tailgate. Contaminated air is drawn to section three exhaust main via LW22307 tailgate and it is then delivered to 1055 level exhaust main before the contaminated air is discharged through fan at south exhaust incline. Fig. 11 shows the validation of pressure loss along LW22307 path. It can be seen the overall trend of it resembles that of measured LW22305 path. It underwent a slight increase of pressure loss comparing to that of LW22305 path due to its longer flow path and the major of pressure loss occurs at exhausting airways. It can be also observed at ...
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... pressure differential across LW face and therefore affect air leakage into goaf [18,20]. To reduce pressure differential along LW22307 face, the first possible measure is to modify ventilation network within panel. In this study, total seven scenarios are proposed and analyzed (see Table 1). The results of the simulation are presented in Figs. 12 and 13. Fig. 12 depicts the pressure loss paths of various ventilation modes within panel. It can be seen the pressure differential is not able to be eliminated. The pressure differential at face shows little difference except for two Bleederless ventilation modes. To meet comfortable working conditions at LW face, no less than 30 m 3 /s ...
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... differential across LW face and therefore affect air leakage into goaf [18,20]. To reduce pressure differential along LW22307 face, the first possible measure is to modify ventilation network within panel. In this study, total seven scenarios are proposed and analyzed (see Table 1). The results of the simulation are presented in Figs. 12 and 13. Fig. 12 depicts the pressure loss paths of various ventilation modes within panel. It can be seen the pressure differential is not able to be eliminated. The pressure differential at face shows little difference except for two Bleederless ventilation modes. To meet comfortable working conditions at LW face, no less than 30 m 3 /s fresh air is ...
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... various ventilation modes within panel. It can be seen the pressure differential is not able to be eliminated. The pressure differential at face shows little difference except for two Bleederless ventilation modes. To meet comfortable working conditions at LW face, no less than 30 m 3 /s fresh air is required in this colliery. As can be seen from Fig. 13, ''Homotropal U" and ''Bleederless homotropal U" are clearly not suitable due to low quantity of airflow across LW22307 even though ''Bleederless homotropal U" can slightly reduce the pressure differential. ''Bleeder return" and ''Double return" ventilation modes are able to supply sufficient air to working face but the pressure ...
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... sufficient fresh air to LW working face, a solution called pressurizing LW panel is proposed. The essence of the solution is to provide a positive pressure at the start of panel intake to offset the pressure lost in the past airways. To achieve the positive pressure, an auxiliary fan and several ventilation control devices are required (see Fig. 14). Fig. 14 shows a possible deployment plan to pressurize LW22307. At the start of the panel intake, an auxiliary fan is installed at one LW22308 recovery roadway and a ventilation regulator is installed at one cut-through between LW22306 maingate and LW22307 tailgate to adjust the pressure and airflow. The ventilation regulator is ...
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... fresh air to LW working face, a solution called pressurizing LW panel is proposed. The essence of the solution is to provide a positive pressure at the start of panel intake to offset the pressure lost in the past airways. To achieve the positive pressure, an auxiliary fan and several ventilation control devices are required (see Fig. 14). Fig. 14 shows a possible deployment plan to pressurize LW22307. At the start of the panel intake, an auxiliary fan is installed at one LW22308 recovery roadway and a ventilation regulator is installed at one cut-through between LW22306 maingate and LW22307 tailgate to adjust the pressure and airflow. The ventilation regulator is essentially a ...
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... to pressurize LW22307. At the start of the panel intake, an auxiliary fan is installed at one LW22308 recovery roadway and a ventilation regulator is installed at one cut-through between LW22306 maingate and LW22307 tailgate to adjust the pressure and airflow. The ventilation regulator is essentially a ventilation door with adjustable opening. Fig. 15 shows the pressure loss trend along ventilation path with varying resistance factor and fan duty. It is noticeable pressurizing LW22307 working face would considerably reduce pressure differential and in addition, ideally true balance could be acquired by adjusting the resistance factor or fan duty. Fig. 16 shows pressure differential ...
Context 10
... door with adjustable opening. Fig. 15 shows the pressure loss trend along ventilation path with varying resistance factor and fan duty. It is noticeable pressurizing LW22307 working face would considerably reduce pressure differential and in addition, ideally true balance could be acquired by adjusting the resistance factor or fan duty. Fig. 16 shows pressure differential and airflow quantity across LW222307 with varying resistance factor (R) and auxiliary fan duty (F). It is obvious airflow quantity across LW22307 would increase with more powerful fan and/or less resistance from ventilation regulator. The pressure differential evolves from negative to positive with more ...
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... of locally isolating and pressurizing LW22307 panel, utilization of a booster ventilation system (Blower-Exhaust) can initially provide airflow with a positive pressure to overcome the pressure loss along ventilation path before airflow arrives at LW22307 working face. The mechanism can be explained in Fig. 17. For an exhaust ventilation system, neutral point locates at start of the intake opening and the negative pressure grows along path and reaches peaks at fan. While for a force system, at intake fan provides airflow with a positive pressure to overcome the pressure loss along path and neutral point lies at the end of the ventilation ...
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... of the two previous systems and the neutral point can be adjusted to any point in the middle of the ventilation path. By this way the pressure differential between LW face and surface can be significantly reduced. Therefore, the performance of a booster ventilation system is simulated with varying fan duties and the results are shown in Figs. 18 and ...
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... and 19. From Fig. 18, it can be observed airflow is given a positive pressure initially by the forcing fan to offset the pressure loss along path. The pressure differential significantly decreases if fan dust is adjusted properly. ...
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... is illustrated in Figs. 18 and 19. From Fig. 18, it can be observed airflow is given a positive pressure initially by the forcing fan to offset the pressure loss along path. The pressure differential significantly decreases if fan dust is adjusted properly. The neutral point can move to any point by manipulating fan duties. As can be seen in Fig. 19, it is obvious the airflow quantity reduces slightly with fan duty dropping but the pressure differential is very sensitive to fan duty. Ten percent alteration of fan duty may have dramatically changed the pressure differential across LW ...
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... determined to pressurize the LW panel (solution two) to reduce the air leakage at the end of 2014. After reviewing the failure modes and conducting risk assessments, an auxiliary fan was employed to provide the positive pressure and associated ventilation regulators were also constructed to adjust the pressure and airflow across working face (see Fig. 14). Quantity of air leakage and gas composition at LW face were continually monitored after excising this control measure. As can be seen from Fig. 20, quantity of airflow across working face underwent a slight growth and the airflow leakage from goaf was substantially reduced after balancing the pressure differential. Fig. 21 shows gas ...
Context 16
... working face (see Fig. 14). Quantity of air leakage and gas composition at LW face were continually monitored after excising this control measure. As can be seen from Fig. 20, quantity of airflow across working face underwent a slight growth and the airflow leakage from goaf was substantially reduced after balancing the pressure differential. Fig. 21 shows gas monitoring data of a sampling point at conjunction of working face and LW22307 tailgate. The oxygen concentration increased considerably and an inverse trend was found for the nitrogen concentration. Goaf gas ingress was constrained and the working conditions were greatly improved after the control was exercised. Therefore, ...

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... Ventilation system failure can cause localized gas accumulation, generating gas pressure. Consequently, the presence of hot air pressure in high-temperature slopes in deep wells often results in gas pressure, which obstructs heat dissipation by disrupting the ventilation system, further increasing the hot air pressure [11][12][13]. The formation and coupling of hot air pressure and gas pressure can severely disrupt the normal operation of mine ventilation systems, increasing airflow instability. ...
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... This also shows that simply increasing the air volume has the risk of increasing the spontaneous combustion of residual coal. [32][33][34] C. Influence of air distribution ratio on gas concentration distribution in combined goaf during normal mining period ...
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