Research On The Law Of Working Face Gas Emission Of Doubule U Type Ventilation Working Face

Double U type ventilation system is a new ventilation system which uses gateway to connect two U ventilation. It has two roadway to intake air and two roadway to return air. And it also increase volume of blast, so it can dilution gas in working face and improve the ability of anti-calamity. It was widely used in high gas mine. Thus the tail roadway of double U type ventilation system is in goaf. The length of tail roadway is changed with the working face-advancing. It makes the distribution of air leakage in goaf and gas concentration changed So the phenomenon of gas exceeding the limit in working face and tail leakage happens some times. In order to solve this problem, I use Yuwu mine N2202as the main object of study in this paper. And build a mathematical and physical model through the gas flow equation. I get the gas concentration in each measure point through in working face and goaf through detection of beam tube, field measurement and data statistics.Using MATLAB to analysis the data of gas concentration measurements in working face and goaf, we can get the three-dimensional distribution of gas concentration. The details are as follows.1、Using Fluent software analysis of concentration of air leakage in goaf when the working face reached310m and330m, we get the distribution of air leakage in goaf, gas concentration and pressure. After analysis the distribution map, we know that the air leakage in goaf is divided into three parts:one part flow back to working face with the high-concentration gas; one part to tail roadway, and through the gate way to gas drainage gateway; the last part to the gateway directly. When the distance between working face and opened across is over23meters, increased resistance of return airway can increase the amount of the air leakage, and reduce the amount of air leakage back to working face,and the airflow in the gateway is increased. It can solve the problem of gas to limit in upper concern and gateway.2、After analysis the field measure dates, the result showed that the gas concentration of the back chute and the side wall is higher, and this change is more dramatic when it is nearer to return airway; in the tail lane the side of goaf is higher reached2%-3%because of the gas of goaf; especially between the back chute and filling body wall prone to accumulation of gas to cause gas exceeding the limit; when the distance between working face and goaf is40-90m, the highest gas concentration is close to the central of goaf. So, we must strengthen the tail lane to avoid gas exceeding the limit. We also need to strength the sealing filling body wall, avoid the gas flow from back chute to the tail lane.3、After statistical analysis, the results showed that he gas concentration of the rear of working face, the upper concern and the rear of ventilation roadway changed little; the gas concentration of tail lane have a great change when working face in different location. The gas concentrations of tail lane is maximum when the first time of opening the across.It reaches minimum when the distance between working face and opened across is23meters. When the distance is40meters the gas concentration reaches the maximum of the first time., and further increase. From the perspective of controlling the gas, the reasonable distance between return airway and gas drainage gateway is40meters;and according the economic,the distance should not exceed50meters.