Study On Combined Power-frequency And High-voltage Heating Method For In-situ Oil Shale

With the rapid growth of human society and economy, the demand and consumptionof energy are increase at the same rapid, leading the traditional fossil energy resources,such as oil and coal, to exhaustion. The oil shale, as a kind of alternative energy sources, isdrawing more and more attention of researchers around the world because of its hugereserves and centralized distribution.Nowadays, the oil shale is processed with the traditional overground dry distillationmethod, which needs to extract the oil shale from a mine, causing a considerable damageto the geological structure and the process itself will produce a large amount of exhaust gas,leaving a significant impact on environment. Therefore, many research institutes have paida lot of attention on the development of the more effective underground in-stitu miningtechnology, among which, the Shell, Exxon Mobil and other tycoons have developed theirown in-situ technologies, most of which are facing the problem of complexity and high costand still staying in the laboratory stage. Furthermore, the oil content of oil shale in China isrelatively low, which causes the current technologies even harder for application in China.Based on the existing research results and the comprehensive analysis on properties of oilshale, this paper developed a combined work frequency and high-voltage heating methodthrough cooperation with Tomsk Polytechnic University in Russia. In this paper, thefollowing research contents are included:(1) Measurement of relationship of relative dielectric constant, dielectric loss tangentand conductivity within20-6000C,25Hz-1MHz, thermal conductivity and heat capacitywithin50-3000C wih temperature and frequency;(2) Establishment of mathematical model of oil shale in-situ heating, using themeasured parameters to calculate heating rate, the temperature distribution in the oilshale to assess the feasibility of heating method;(3) According to the test and simulation results, the best parameters and set theheating equipment to carry out heating tests. During the test, firstly use the high pressure to achieve the breakdown of oil shale to form the conductive channel, the conventional220V voltage can then be used to heat it, after about an hour, the oil shale was heated tothe pyrolysis temperature (400oC). The analysis found that pyrolysis products mainlyinclude: H2, CH4, C2H6, C3H8and other combustible gases and aliphatic hydrocarbons,aromatic hydrocarbons and other organic matters.