Research On Gas Distribution Law In Longwall Repeated Mining Of Residual Coal

When longwall working face mines lignite in old mining goaf,it is very easy to produce some gas accumulation in old mining empty roadway which is produced in front of the working face after the production in small coal mine,so it can cause great impact in gas prevention,ventilation management and safety production,therefore it is an important topic in the study of residual coal remining.This paper is on the background of mining the residual coal resources about Shanxi Shenghua 3#old mining again,and to research the coal resource left and the distributional pattern of the mining empty roadway after the first mining,and to research maximum concentration and pressure in these confined spaces after a long period in the evolution of gas,and the empty roadway excavation,return air trough during the process of old twice-mining residue coal resources,and the speed when the gas emission in the empty lane and area,the distribution rule and airflow situation of gas in the process of excavation roadway and so on in some empty roadways,which are formed after a mining research,which can Provide theoretical basis for the spot-gas control and the mine ventilation management in the field.The main contents are as followings:(1)Through theoretical analysis and calculation to get maximum amount of gas emission from coal wall to mining roadway in the first mining roadway excavation,and calculate the gas concentration in tunnel,then according to the ideal gas equation of state to get gas pressure and gas mixture density at a certain concentration.(2)Through theoretical analysis and calculation,to get the remaining amount of gas after mining the coal wall,and calculate the amount of gas released from coal wall to the gob(district)in different conditions,then deduce functional expression of gas released from coal wall to the gob(district)under different conditions.(3)Using Fluent to do numerical simulation,and then to simulate the distribution of gas concentration in working face when drifting exposing abandoned workings under two situations,which are with auxiliary fan and without auxiliary fan when driving in mine empty roadway,the distributional situation of gas during the process of drifting and empty roadway,and then comparing and analyzing it's simulation of those two situations particularly.(4)By using Fluent to simulate the distributional situation of gas concentration in exposing,working face and distributional pattern of gas when working face re-mined the exposing abandoned workings in different situations,and then comparing the upper corner gas concentration changes,and the influential scope for working face when the empty roadway is located in different situations.