Research On Characteristics And Mechanism Of Oil Shale Catalytic Retorting

Oil shale is an alternative energy source of oil and has abundant reserves in China.High-quality shale oil and gas can be obtained by retorting oil shale.At present,many problems such as low oil yield,low shale oil quality and pollution occur during the process of retorting oil shale.Catalytic retorting of oil shale helps to improve the quality characteristics of products deriverd from retorting oil shale.So this paper has carried out catalytic retorting of Gonghe oil shale produced from Huadian oil shale mining area to explore the effects of different reaction conditions on the characteristics of oil shale retorting and catalytic retorting.Based on the experimental results,the inherent mechanism of oil shale pyrolysis was explored by means of simulation.The main conclusions are shown below.Firstly,the thermogravimetric analysis-Fourier transform infrared spectrometer（TG-FTIR）was used to explore the weight loss characteristics during non-isothermal and isothermal retorting process of Gonghe oil shale as well as distribution characteristics of retorting products.The distribution of non-condensable gases（CO₂,CO,CH₄,SO₂）and functional groups（C-H,C=O,C=C and S=O）were mainly analyzed.The research results show the main retorting temperature range of Gonghe oil shale is between 206^oC and608^oC.Large amounts of volatiles are released at this stage and the peak temperature of the thermogravimetric weight loss rate is 457^oC.Product characteristic analysis results show that the optimal reaction temperature is 520^oC,because 520^oC is more conducive to full pyrolysis of Gonghe oil shale and reducing the content of heteroatoms such as S and O in the oil and gases to improve quality of oil and gases.Secondly,based on the research results of retorting Gonghe oil shale using TG-FTIR,the pyrolysis gas chromatography-mass spectrometry（Py-GC/MS）was used to study the effects of temperatures,catalyst types,and catalyst dosages on the distribution properties of products generated from retorting Gonghe oil shale.The saturated hydrocarbons,unsaturated hydrocarbons and heterocyclic compounds in the pyrolysis products were specifically studied.The results show that the carbon number of saturated hydrocarbons in the pyrolysis products is C5-C44,the carbon number of unsaturated hydrocarbons is C5-C24,and the heterocyclic compounds are mainly heterocyclic compounds containing oxygen.According to the yields and compositions of oil and gases produced from retorting oil shale as well as the effect of heteroatom removal,it is further concluded that the optimal temperature of retorting Gonghe oil shale is 520^oC,the best catalyst is Ni O,and the optimal Ni O/oil shale mass ratio is 10%.Thirdly,the PSR reactor in Ansys Chemkin Pro 17.0 was used to study the distribution characteristics of products derived from retorting Gonghe oil shale at different temperatures.The GRI-Mech3 is selected as the mechanism file.The results show that the pyrolysis products of retorting Gonghe oil shale mainly include non-hydrocarbon gases（such as H₂、H₂O、CO、CO₂ and N₂、HCN,etc.）,hydrocarbon gases（such as CH₄、C₂H₂、C₂H₄、C₂H₆、C₃H₈,etc.）and heteroatomic hydrocarbons（such as CH₃CHO、CH₂O and CH₃OH,etc.）.Increasing the retorting temperature helps to reduce the oxygen-containing heteroatom hydrocarbons in oil and gas products,and also increases the production of harmful gas HCN.The lower temperature is not conducive to full retorting of Gonghe oil shale and produces less saturated hydrocarbon products as well as harmful gases such as formaldehyde and acetaldehyde.Overall,520^oC is the optimal temperature for retorting Gonghe oil shale,which is consistent with the experimental results of TG-FTIR and Py-GC/MS.To sum up,this study explored the characteristics and mechanism of Gongsha oil shale retorting by combining experiments and kinetics simulations,and compared the simulation results with the experimental research results.The research results can provide a reference for studying the retorting mechanism and high-value utilization of Gonghe oil shale,and also provide theoretical guidance for improving the yield and quality of the oil and gas products of Gonghe oil shale retorting.In addition,the catalytic effects of oxide catalysts and carbonate catalysts containing the same active metals can be further compared in the future.The simulation conditions can also be optimized to further discuss and analyze the reaction path of the oil shale retorting process,so as to deeply study the internal mechanism of oil shale retorting and optimize the oil shale retorting process.