Research On Reasonable Negative Pressure In Gas Drainage System For No.2-1Coal Seam Of Jiu Lishan Mine

In recent years, in somepcoal fields,gas relatedldisasters occur fromltime totime,which restricts production scale and operation efficiency as well as the corporateprofit.Gasodrainage is an approach to0reduce gasoemission andoeliminate gashazards.So,the effectiveness of gas drainage determines the safety production of coalmine and its economic benefit. Negative pressure is one of the important factors aboutthe effectiveness of gas drainage.There are some controversy about the effect of thechanges of negative pressure and the other parameters to the effectiveness of gasdrainage.This thesis tries basedoon the characteristics of coal and the0storage rule and flowlaw of the gas in the0coal seam.The effective extraction radius under the condition ofdifferent negative pressure of drainage borehole is numerical simulated using Comsolsoftware,result shows that:in the same drainage conditions,the effective extraction radiusincreases with increasing the negative pressure;under the same drainage conditions,theeffective extraction radius of soft coal is smaller than the hard coal.Under45kPa negativepressure and180d drainaged,the effective extraction radius of soft coal-1.113m is smallerthan the hard coal-1.758m.Through the drainage effect numerical simulation of drainage boreholes along coalseam,we can know:the drainage effect increases with increasing the negativepressure;under the condition of the same negative pressure,residual gas content of softcoal is bigger then hard coal;the drainage effect of hard coal is better than soft coal.Underthe same condition,when the drilling space is smaller,the drainage time is shorter.Through the spot inspection,when the negative pressure roses form26kPa to42kPa,gas flow increases with increasing the negative pressure,when the negativepressure is45kPa,gas flow does not increase.When the negative pressure is38-42kPa,gasflow and gas flow of15d are biggest.The result combines numerical simulation and spotinspection,when the appropriate negative pressure is38-42kPa.