| Coal mine safety accidents is the first enemy of coal mine safety production atpresent. The characteristics of energy structure in our country is rich in coal but poor in oil.The fact that geological structure of coal mine is complex and gas mine accounts for morethan major is the main reason of coal gas accident in our country being in a long-term,inevitabe, and serious situation. Coal mine gas prevention and control work is the toppriority of safety in China. Methane concentration detection and fault forecasting are theimportant and effective safeguards of the production safety of coal mines in our country,and has always been an important subject of the experts and scholars in the field of energyresearch. In this article, we studied the photoacoustic spectroscopy technology principle ofgas detection system, deeply analysied and finally established a gas detection systembased on photoacoustic spectroscopy technology, and proposed a new method in gasexplosion pre-alarm. Through the experiments, the gas detection and gas explosionpre-alarm system were demonstrated respectively. The main research content is as follows.Through depth study of the photoacoustic spectroscopy gas detection principle,analyzes the feasibility of coal mine gas concentration of photoacoustic spectra. Accordingto the characteristics of the mine gas composition, based on HITRAN and HITEMPdatabase, analysis the methane absorption spectrum characteristic. Gases which are inmine air and methane gas such as water vapor, carbon dioxide, carbon monoxide,hydrogen sulfide, sulfur dioxide, nitrogen dioxide, nitric oxide and some other absorptionlines are analyzed and compared, finally selected1653.79nm methane absorption lines forphotoacoustic signal detection.Based on the depth study of the photoacoustic signal generation mechanism and theacoustic field distribution inside the photoacoustic cell, demonstrated the internal relationsabout photoacoustic signal, photoacoustic cell structure and its working mode. Futherpresents the relationship between photoacoustic signals and first-order vertical cylindricalresonant photoacoustic cell structure and size. All above provides a theoretical basis forthe design of novel photoacoustic cell. Based on fully consideration the internal loss of thephotoacoustic cell in actual working process, combined with the measure of noisereduction, designed the new length-tunable first-order longitudinal feedback resonantphotoacoustic cell. Combined with self-designed photoacoustic cell, designed and implemented the minegas concentration measurement system which based on photoacoustic spectroscopy, andthe characteristics of photoacoustic cell parameters were measured. Following results wereobtained: resonant frequency was1003Hz, quality factor was35.05, cell constant was4194.59Pa cm W-1, and the detection sensitivity was2.78×10-6, SNR was39.5. Formany kinds of buffer gas and measuring gas experiments, analyzes the factors such astypes of buffer gas, measuring temperature, laser output power effect the photoacousticcell performance parameters, the value of photoacoustic signal, and then the detectionsensitivity of the system.Based on the analysis of conditions in the gas explosion, presented a new idea whichis satisfied two of the three basic gas explosion conditions, and based on neural networkpattern recognition algorithms established mine gas explosion pre-alarm network model.the datas by Jizhong Energy Fengfeng mine monitored was used in network training.Using the confusion matrix, ROC curve, MSE curves, the error histogram and some otheranalysis methods analyze the network performance, and achieved the accuracy rate was93.8%. Through simulated the actual changes of the coal mine environmental data beforeand after the alarm, monitored gas concentration real-time using photoacousticspectroscopy gas monitoring system, judged pre-alarm condition by gas explosionpre-alarm network. Point out that alarm time was shorter than the actual alarm time inmine, pre-alarm effect further improved. |
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