Theoretical And Experimental Research Of Oil Shale In-situ Pyrolysis By High Voltage-power Frequency Electrical Heating Method

Energy is the serious problem to be solved for the world. The crude oil is non-renewable, that makes the resource shortage even more, and the crude oil externaldependenceof our countryincreases every year. The development and utilization ofoil shale has come back to people’s vision, and has become an important bargainingchip at the High Oil Price Times. Jilin province seriously lacks of energy, but it isvery rich of oil shale resources, its reserves in the first place of China. Thedevelopment and utilization of oil shale are still in the stage of undergroundexcavation and ground retorting. And the oil shale available for excavating andretorting is dwindling. The serious environmental pollution restricts thedevelopment of retorting. While the in-situ conversion technology could overcomethe most shortcomings of retorting, it is not mature enough, still in the experimentalstage. The oil shale of Jilin province has low oil content, thin reservoir and bigburied depth, so that there is no in-situ conversion technique applicable for theexploration of the oil shale of Jilin province. Therefore, high voltage-powerfrequency electrical heating method has been innovated for Jilin oil shale resources,and which also provide a new thinking for in-situ oil shale pyrolysis process.The high voltage-power frequency electrical heating method of oil shalepyrolysis is put forward on the basis of theory and experiment. High voltage-powerfrequency generator and reactor have been designed and manufactured, and theexperiments are done at different factors such as distance, voltage and current in thispaper. The average temperature in the experiment is judged by the inversion of theexperiment results from the law summarized by basic experiment, just because thetemperature is too difficult to test.The7oil shale samples are tested by thermogravimetric analysis (TGA),industrial analysis and gas chromatographyanalysis，after keeping the samples atdifferent temperature each for two hours. The weight lost peak from theexperiment has a lag relative to the TGA peak, it is because the temperature of theoil shale block increases with the environment temperature, and the heat need timeto transfer from the surface to the inside so that the peak temperature migratesbackward. The heat transfer process should be considered in both experiment andin-situ mining, and the pyrolysis temperature should be controlled at about500℃. The variation ofingredients on product and residues is concluded through testing.When the average temperature is at500℃-600℃,gas production reaches itsmaximum, and the peak moves forward gradually as the temperature rises. That isbecause the high temperature makes the macromolecular hydrocarbon fracture intosmall molecule, which is more conducive for gaseous product purification.The feasibility of high voltage-power frequency electrical heating in-situpyrolysis method is demonstrated on solid breakdown theory, plasma theory andheattransfer theory. Compared with the In-situ Conversion Process, the heatingchannel of high voltage-power frequency electrical heating in-situ pyrolysis methodis perpendicular to oil shale bedding, and has larger effective heating area at samethickness, and more suitable for the in-situ mining of Jilin oil shale resources. Thephysical model is established to analogue simulate the heat transfer law in the in-situ pyrolysis process.Most physical property of oil shale will change as thetemperature increases, and these variation as thermal conductivity, dielectricconstant, specific heat and other parameters are considered in the simulation to builda non-steadystate model. The simulation of experiment is done to adjust the areaand time of the oil shale reaching pyrolysis temperature, and verified by the lateexperiment, providing data base for in-situ mining.The test platform is built for high voltage-power frequency electrical heatingin-situ pyrolysis method, the high voltage-power frequency generator is used tobreak down the oil shale by controlling the current or voltage; the experiment reactorhas met the temperature and pressure check that is used to provide a safe and reliabletest space. The pyrolysis process could be more intuitive and convenient observedand the experiments can be repeated over the test platform, which providing anexperimental basis and reference for in-situ mining of oil shale. The experimentsare done to produce the shale oil and fuel gas through the breaking down and heating,which proves that the method is available for in-situ mining of oil shale. And thistechnique make the energy accumulated in the oil shale, the energy loss is small.The function of the breaking down current/voltage, time and distance is matched atthe same experiment condition, same oil shale property according to the experimentdata, providing the reference for in-situ experiment. Through the thermalgravimetric analysis, X diffraction analysis, elemental analysis of the product, whatcan be concluded is the electrodes are the heating part, the oil shale near the electrodes pyrolysis violently. The average temperature reaches more than600℃,the internal temperature reaches860℃which are estimated according to the law ofoil shale pyrolysis.The high voltage-power frequency electrical heating method of oil shalepyrolysis can successfully produce the shale oil and fuel gas, whose feasibility isverified by the theory and experiment. This method is a promising in-situ pyrolysistechnique for oil shale, for its fast production of shale oil and gas, small energy lossand no environmental pollution.