| 其他摘要 | As the dwindling of the oil and natural gas resources on land, countries in the world will focus on development of the marine resources. Marine oil and gas resources, especially the natural gas hydrate will be the key point for exploration and development of the world’s oil and gas resources in the future. Natural gas hydrate contains huge reserves of CH4, which is twice the sum of the proven coal, oil and gas reserves. It is mainly in the stage of exploration for the research of the natural gas hydrate in the current world. At present, many countries are using seismic exploration, submarine heat flow measurements, seafloor soil sampling and geothermal method for the exploration of the natural gas hydrate, but rarely using them for the detection of the thermogenic CH4 gas, which forms the natural gas hydrate in submarine volcano and hydrothermal vents. As for the chemical sensor for in situ measurement of CH4 fugacity/activity in submarine volcano and hydrothermal vents has not been reported. Therefore, it is a very important guiding significance for ascertaining the distribution of gas hydrate by developing a kind of chemical sensor for in situ measurement of CH4 in submarine volcano and hydrothermal vents, which supplies the existing detection methods internationally. The theory of the solid electrolyte based electrochemical sensors for the detection of CH4 or other hydrocarbon gases in high temperature and normal pressure non-hydrothermal system is introduced in high temperature hydrothermal system. Then solid electrolyte based potentiometric sensor is developed for in situ measurement of CH4 fugacity/activity in high pressure hydrothermal system in this experiment. The sensor is made up of various components, including an autoclave (modeling temperature and pressure environment in submarine volcano and hydrothermal vents), an autoclave plug (sensor’s elements bearing device), YSZ frustum of a cone (YSZ, solid electrolyte yttria stabilized zirconia), Al2O3 frustum of a cone (two Pt wires axially interpenetrating the Al2O3 aiming at leading potential signal from high temperature and high pressure hydrothermal system to normal temperature and normal pressure environment), Pt electrode (active electrode), Au electrode (inert electrode), and Pt wire. YSZ and Al2O3 ceramic cylinders are prepared by slip casting method，and then are processed from cylinders into YSZ and Al2O3 frustum of cones of the major parts of sensor by grinding machine and diamond cutting machine in our research group. Paste sintering techniques are used to fire the semicircle Pt active electrode and semicircle Au inert electrode respectively on the top surface of the YSZ frustum of a cone ensuring so that the two electrodes are not contacted with each other. As for the Al2O3 frustum of a cone, two semicircle Pt electrodes are fired on it separately. After completing the above components of the senor, the elements are assembled in a certain order into the data testing system. Under the condition of different temperature, the potential response signals of sensor to different concentrations are tested. An autoclave manufactured by our group is used for modeling high temperature and high pressure hydrothermal environment. Before piping the CH4 gas into the system, the strength, gas-tight, and conducting of the signal of the sensor system are tested. The experiment temperature and pressure is set at 500 oC and 500 bar, results show that the sensor has certain strength, stable signal transmission and good sealing property, which satisfies the requirement of experiment. The experiment temperature is sustained at 300 and 400 oC, and then 1, 3, 5, 7 bar CH4 are piped into the hydrothermal system respectively to research on the influence of the system temperature and the CH4 concentrations on sensor response signal values. The experiment results indicate that the response signal values of CH4 sensor increase with the growth of CH4 concentrations, and within the invest |
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