| The early monitoring,identification and warning of coal spontaneous combustion are of great significance to prevent coal spontaneous combustion.At present,monitoring and early warning methods for coal spontaneous combustion mainly adopts the beam tube monitoring system,which makes a speculative judgment on the coal spontaneous combustion degree by analyzing the composition and concentration changes of the index gas.However,the traditional beam tube monitoring system adopts the method of extracting gas by negative pressure,which has the problems that the composition and concentration of the gas are easily distorted and the transmission delay time is long.In order to overcome the problems of the negative pressure beam tube,the positive pressure beam tube came into being,but it is difficult to remotely control the downhole distributed pump of the positive pressure beam tube,and there are still few researches on key issues such as the law of positive pressure gas transmission and the delay time of gas transmission.In view of the current status and existing problems of the current beam tube monitoring system,In this paper,a positive pressure beam tube monitoring system of sharing pipeline for gas transmission and pump control is proposed and applied.In this paper,through the coal spontaneous combustion temperature-programming experiment,the change law of the index gas during the low-temperature coal oxidation process and the corresponding relationship with the coal temperature are studied.According to the principle of index gas selection,the index gas of 6#and 4#coal seam coal spontaneous combustion in Donglin Mine was optimized,and a corresponding monitoring and early warning index system was established.The structure and working principle of the system are introduced in detail,the key components of the system are designed and selected,and the advantages and disadvantages of the positive and negative pressure beam tubes are compared and analyzed from the principle.Aiming at the problem of positive pressure gas transport,a gas positive pressure transport test system was established,the effect of pipe diameter,pressure and negative pressure suction pipe length on gas transmission time and flow rate was experimentally studied,and the diameter of positive pressure gas pipe,the selection of positive pressure pump and the reasonable range of negative pressure suction pipe length were determined.Based on the continuity equation,gas state equation and energy equation,the flow equation of the isothermal and stable flow of compressible gas is derived,and the calculation formula of the gas transmission lag time is given.By judging the flow state of the gas,the theoretical resistance loss along the gas transport is calculated,and the local resistance loss is calculated.A control scheme using the positive pressure gas pipe itself to remotely start and stop the downhole distributed positive pressure pump is proposed,and the feasibility of the control scheme is experimentally verified,and a remote control device is designed according to the principle of remote control.Combined with the actual situation at the site of Donglin Mine,completed the installation and commissioning of the system in response to the key issues such as the arrangement of measuring points and the installation of positive pressure pumps,the gas transmission lag time and gas distortion is tested in the actual application environment,and the system application effect is analyzed based on the monitoring data.The positive pressure beam tube monitoring system for monitoring coal spontaneous combustion not only solves the problem of gas composition and concentration distortion,but also realizes the remote control of starting and stopping the positive pressure pump and the small flow and high positive pressure to transport the gas,shortening the gas transmission lag time and improving the monitoring real-time performance,provides an ideal solution for monitoring coal spontaneous combustion fire. |
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