Study On The Experiment And Molecular Simulation Of Oil Shale Pyrolysis

With the rapid growth of global energy consumption, the oil shale is known asan important alternative energy source in many countries. Because of the hugereserves and diverse ways of comprehensive utilization, the oil shale has become thefocus of national energy strategy. Oil shale is a kind of fine-grained sedimentary rockthat contains the dispersed organic constituents. It is a kind of energy and mineralresource, which belongs to the solid fossil fuel with low calorific value. Oil shale canbe used in many aspects, for example, the dispersed organic matter can be convertedinto shale oil and pyrolysis gas after the thermal decomposition process. During thethermal decomposition process, the macromolecule and its pyrolysis products caninteract with the associated minerals. So the simplex experimental technology isdifficult to identify and describe the composition, properties and processingparameters of the products accurately.The characteristics of oil shale retorting pyrolysis have great significance on thedevelopment and utilization of oil shale resources. In recent years, with thedevelopment of computer technology and theoretical chemistry, molecularsimulation plays an important role in the field of energy research. This papercombines the molecular simulation technology and experimental technique to studythe details of oil-generated matter, the relationship between minerals and kerogen(contain its pyrolysis products). And then the forming process of pyrolysis productsand the mineral characteristics to improve oil yield was studied. The main contentsare as follows:(1) A variety of experimental characterization methods was used to study thekerogen molecular structure and physicochemical properties. The structuralparameters of kerogen were obtained from pyrolysis gas chromatography massspectrum (Py-GC-MS) and13C solid state nuclear magnetic spectra (13C NMR). Thedegree of crystallization and morphology were determined by the powder X-ray diffraction spectroscopy (P-XRD) and scanning electron microscopy (SEM). Thedensity was determined with a pycnometer using i-PrOH and the kinetic parameterswere obtaind using thermal analysis technology. This provides a new method tostudy the properties of oil shale.(2) The kerogen average molecular structural model was obtained byrecombination of the selected fragments using computer simulation technology. Thecorrection and evaluation were carried out to make the established model be logical.This structural model can be viewed as a foundation for the theoretical study of thekerogen. The microstructural parameters of the model (charge distribution, relatedbond length and bond order) were calculated by semi-empirical quantitativechemistry method. The forming process of pyrolysis products was speculated andthis has a guiding significance on the research of oil and gas generation.(3) The influence of the four minerals on organic matter has been studied in thedesigned pyrolysis device. The results show that the four minerals can change the oilproduction rate, organic carbon conversion rate and coking rate. The kerogenpyrolysis behavior with the presence of mineral was discussed. The resultsdemonstrate that montmorillonite can improve the oil production rate obviously.Gypsum and coke can react easily and generate calcium sulfide and carbon dioxide.It can reduce the yield of coke. Montmorillonite and gypsum can improve the qualityof the oil and gas. This study has a practical significance in improving the efficiencyof the dry distillation and reducing the cost of oil shale pyrolysis.(4) The molecular simulation technology was used to study the relationshipbetween pyrolysis products (oil and gas) and minerals surface. The adsorptionlocation, adsorption heat, sorption isotherm and diffusion coefficient of methane inthe four mineral models has been studied. The adsorption and diffusion properties ofpyrolysis gas and the influence of minerals on the pyrolysis product composition were explained from microscopic view. This can give a guide for comprehension ofoil shale pyrolysis and improving the yield of oil and gas.