Study on high-efficiency application scheme of U+L type ventilation system in coal mining face

In order to make the U+L type ventilation system of the working face be applied efficiently, theoretical analysis methods were adopted to analyze the U+L type ventilation system of the working face from four aspects: the gas concentration of the return airway, the coal spontaneous combustion in the goaf, the ventilation system management and the economic rationality. The U+L type ventilation system simulation model was constructed, and the numerical simulation method was used to supply air volume of 1 000,2 000,3 000,4 000 m3 to the working face, respectively. The relationship between the distance between the connecting lane and the working face and the gas concentration in the upper corner of the working surface was analyzed, and the relationship between the air supply of the working face and the width of the oxidation zone when the connecting lane was in different positions was studied. The results show thatthe distance between the connecting lane and the working surface and the gas concentration in the upper corner of the working surface approximately satisfy the exponential function relationship, and the lower the air volume, the more obvious the relationship. Taking 1% as the upper corner gas concentration overrun standard, when the air supply volume of the working face is 1 000,2 000 and 3 000 m3/min, the spacing between the connecting roadways shall not be greater than 11, 34，50 m respectively;when the air supply volume of working face is 4 000 m3/min, the gas concentration at the upper corner does not exceed the limit.The relationship between the air supply and the gas concentration in the upper corner of the working face approximately satisfies the negative exponential function, and the greater the distance between the connecting roadway and the working face, the more obvious the relationship is.With 1% as the upper corner gas concentration overrun standard, when the distance between connecting roadways is 10,20,30,40,50 m, the air supply volume of the working face shall not be less than 1 000,1 500,1 800,2 400,3 000 m3/min respectively.The air supply of the working face and the width of the oxidation zone in the goaf approximately satisfy an exponential function relationship, and the larger the distance between the connecting roadway and the working face, the more obvious the relationship is.Taking 50 m as the maximum allowable width of the oxidation zone in the goaf, when the spacing between the connecting roadways is set as 40,30,20,10 m, the air supply volume of the working face shall not be greater than 1 200,1 900,2 200,2 000 m3/min.Finally, based on the standard that the maximum width of the oxidation zone in the goaf is 50 m and the maximum allowable gas volume fraction of the upper corner of the working surface is 1%, two sets of technical solutions for efficient gas emission in the connecting lane are proposed:①When the air supply volume of the working face is 1 000,2 000 m3/min, the spacing between the connecting roadways should not be greater than 11 m and 34 m; When the air supply rate of working face is 3 000 m3/min or 4 000 m3/min, the connecting lanes are likely to cause spontaneous combustion of residual coal in the goaf.②When the distance between connecting roadways is set as 10,20,30 m, the air supply of working face should be 1 000～2 000，1 500～2 200，1 800～1 900 m3/min.