On The Research And Production Of The Gas Sensor For Methane Detecting

In recent years, the frequently happened coal mine accidents have invoked the disaster for miner's lives. Gas ( consists mainly of methane) is fatal to harm the safety in production of coal mines. It should be strengthen the control of gas to prevent the danger of high-density gas and gas explosion. At present, most of the safety control systems in our country's coal mines use the thermocatalytic principle to detect methane, but there are many disadventages of this device, such as complicated, high power consumption, short-lived and instability. The another comparatively mature method ----oxide semiconductor gas sensor also lacks consistence and stability. In this paper, we made a critical review of the advantages of the carrier catalysis component and the semiconductoring gas sensor for methane detection like consistency, sensitivity, low power consumption, integration, basing on three main headings of the gas-sensing research ( i.e.material,process,apparatus). The gas sensitive has been tested by XRD, TG-DTA, FT-IR, SEM, TEM and so on, in order to detect the effect of preparation method, calcination temperature and dopant . A new inorganic salt sol-gel which combined the hydrogen peroxide with semi-permeable membrane was first to make the nanometer SnO2 gas sensitive . This method can control the process of jelling and obtain the SnO2 powder gas sensitive with uniform distribution and pretty dispersibility. These materials are featured by excellent repeatability and consistency, low-cost. I t ensure that heating one hour at 600℃is the most suitable heat treatment for the SnO₂ gas sensitive. Through dopping 1.5%(wt%)PdCl₂ and 5%(wt%)α-Fe₂O₃ separately. The testing of the performance shows that the two dopants' sensibility to the 5000 ppm methane will reach to 5 when heated at 2.5 voltage. It consider on analysis that the oxide defect of the PdO which derive from the fired PdCl₂ dopant by absorb more oxygen and develop an overflow effect to improve the component's sensitibility. α-Fe₂O₃ dopant by restrain the growth of the SnO₂ crystalline and improve the effect by its bulk conductor characteristic. In the terms of WO₃ gas sensitive, the crystal octagonal γ-WO₃ gas sensitive which made by the thermal decomposition has hardly sensibility to the methane. However, the sensibility of the lozenge – shapedly octagonal β-WO3 and amorphous mixture to the 5000 ppm methane can reach to 2.6 when heated at 2.5 voltage. It has guiding significance in the field of WO3 semiconducting oxide gas sensitive methane detecting. A new structure carrier catalysis component has been designed via an edification based on the Seebeck effect that taken use of the impacts of the thermoelectromotive force regulation and catalyzer to the capability to simplify and improve the carrier catalysis component. The device takes the varying quantity of the thermoelectromotive force regulation between that two components as the standard for the change of methane's density. The device can test the density directly, differs from the traditional test pattern which use the resistance change to cause the variation of the Wheatstone bridge output electromotive force. The new component is featured by high-sensibility, compact sized, simple and low-cost consumption and so on.