Abstract
Coal spontaneous combustion (CSC) in gob causes notorious safety issues to workers, especially during withdrawal period. Withdrawal period was normally divided into three stages (initial stage, expanding back channel stage and equipment returning stage) when evaluating and preventing the risk of CSC. This study first analyzed the characteristics of ventilation system at each stage, such as oxidized zone movement, local fire wind pressure and air leakage. Then, principles and specialized measurements were applied to minimize the ranges and effects of CSC in gob. In detail, this includes reducing the total air volume flow of mining face in initial stage, adding windscreen in outlet way and local fan in inlet way to increase the pressure of working face, and lowering external air leakage. Considering the working face ventilation area shrinks at equipment returning stage, keeping it bigger than windscreen’s areas can help to reduce air leakage. Further, foamed gel was grouted into gob to narrow and stop the moving forward of oxidized zone. Field application was applied in Zhang Shuang-lou coal mine. Findings of these studies could be used in other coal mine with similar conditions during withdrawal period.
Highlights
Coal is currently the most commonly used energy source in the world (Jennifer et al 2018; Li et al 2018; Pen~a et al 2018; Reisen et al 2017; Shi et al 2018)
The main objective of our study is to identify the ventilation change and choose a feasible way to control Coal spontaneous combustion (CSC) during withdrawal period
Expanding back channel stage As described above, external air leakage will increase in this stage, which aggravates the risk of CSC in gobs of mining face
Summary
Coal is currently the most commonly used energy source in the world (Jennifer et al 2018; Li et al 2018; Pen~a et al 2018; Reisen et al 2017; Shi et al 2018). Withdrawal of working face is one of the key and must processes for coal mines (Hao et al 2012; Wen et al 2014). Qinyuan coal mine in Shanxi province had sealed four working faces because of the CSC occurring withdrawal period and hydraulic supports not able to get back, which resulted in millions loss in 2015–2016. Liu and Qin (2017a, 2017b) indicated that CSC in gob was the result of interaction of multi-physical fields, including air seepage and heat transfer. Among those factors, ventilation system plays the most significant role, because the stability of ventilation system is the premise for safety mining. Field application was implemented in Zhang Shuang-lou Coal Mine in Xuzhou Jiangsu province
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