Research On Pyrolysis And Product Formation Characteristics Of Oil Sands

With the improvement of people's living standards,the demand for energy is becoming larger and larger,but the reserves of non-renewable resources such as coal and oil are decreasing.Conventional energy supply shortage,need to increase the comprehensive study of unconventional resources.Oil sand as unconventional energy caused the attention of the world.Canada has the highest oil sand reserves in the world.The reserves of China's oil sand resources are also very abundant,and there are not many studies on oil sand pyrolysis.Therefore,it is very valuable to explore the changes of oil sands pyrolysis process,hydrocarbon generation mechanism and molecular structure information,and it is also of great significance to the comprehensive utilization of oil sand resources.Oil sand samples from two areas of Quanzhou and Rizhao were pyrolyzed with different retorting temperatures by self-built retort furnace.Pyrolysis experiments of Quanzhou and Rizhao oil sand were conducted on Thermogravimetric analyzer,Fourier Transform Infrared Spectrometer and Mass Spectrometer.Pyrolysis process and products of oil sands were analyzed.The results show that,based on the pyrolysis TG-DTG curves with different heating rates,the pyrolysis process was divided into three stages:Dehydration degassing stage,release of low-carbon compounds and decomposition of inorganic substance at high temperature section.At same heating rate,the devolatilization temperature of Quanzhou oil sand is lower than that of Rizhao.The pyrolysis characteristic is getting better with the heating rate increases.The pyrolysisproductsmainlyinclude:aliphatichydrocarbons,aromatichydrocarbons,oxygen-containing functional groups and hydroxyl groups.In this paper,the gas products produced at different heating rates were analyzed and explored,such as H₂O,CO₂,CO,CH₄ and C_n H_m.Gaseous hydrocarbons,oxygen-containing organic compounds and other organic gases are generated from the decomposition of carbonyl and carboxyl groups,as well as methoxy groups,methylene and methyl groups at low temperature during the pyrolysis process of oil sand.The gas types and yields change with pyrolysis time altering according to the mass spectrum.According to Kissinger and Friedman methods,the pyrolysis kinetic parameters of oil sand were calculated by utilizing AKTS-Thermokinetics software.The activation energy is distributed linearly at different heating rates for the data with same conversion rate.The activation energy of Rizhao is higher than that of Quanzhou.The oil sand that the pore structure,electron microscope and fractal dimension of the oil sand semi-coke were also analyzed.The research shows that when the final temperature of dry distillation is 450?,the oil and water yield and nitrogen adsorption amount reach the maximum value.The adsorption loop of oil sand char is close to the loop of B type,and the pore is mainly the slit hole,and the pore structure is very developed.The BET specific surface area and pore volume also have a peak at 450?and the fractal dimension obtained by FHH equation peaked at 450?,and then the pore structure of semi-coke particles began to reform.The pore surface was affected by thermal stress and surface tension occurring plastic deformation,resulting in semi-coke surface smooth and uneven pore size distribution and other reasons causing the reduction of fractal dimension.The surface structure and its irregularities were observed by semi-coke SEM images of the oil sand,the pore structure was loose and there was no obvious connection between the particles.The Matlab software was used to study the fractal dimension of the SEM grayscale image,and the overall fractal value slightly lower than the nitrogen adsorption fractal value.