密闭采空区不同惰化置换方案效果仿真

Simulation of the effects of different inert gas replacement schemes in sealed goaf

针对密闭采空区瓦斯抽采过程中在负压作用下外界O_(2)通过裂隙进入采空区易引发煤自燃的问题,常采用抽采的同时注惰性气体以置换抽出的瓦斯的方案,此法可平衡气压、防止外界空气进入采空区,达到防治煤自燃的目的。采用数值模拟的方法研究置换过程中相关物理参数流场变化规律,并提出了自由混合置换法、正压置换法、负压置换法、正压-负压置换法4种方案;以O_(2)最大体积分数低于2%为置换达标标准,对比了4种方案下耗费总时长、消耗氮量、通风机运转时间、累计注氮时长等置换成本评价指标,找出可用于置换方案决策的方法,并给出不同地质条件下密闭采空区适用方案。

In response to the coal spontaneous combustion caused by external O_(2) entering the goaf through cracks under negative pressure during the gas extraction process in sealed goaf,a common solution is to inject inert gas to replace the extracted gas,it can balance the air pressure and prevent external air from entering the goaf,achieving the goal of preventing coal spontaneous combustion.The numerical simulation method was used to study the changes in the flow field of relevant physical parameters during the gas displacement process,and four schemes were proposed:free mixing displacement method,positive pressure displacement method,negative pressure displacement method,and positive-negative pressure displacement method.Using the maximum volume fraction of O_(2) less than 2%as the replacement standard,the replacement cost evaluation indicators of the four schemes were compared,including total consumption time,nitrogen consumption,ventilation fan operation time,and cumulative nitrogen injection time.Decision-making methods that can be used for gas replacement plan were identified,and suitable plans for sealed goaf under different geological conditions were provided.