Study On Preparation Of Needle Coke From Co-carbonization Of FCCDO And Heavy Coker Gas Oil

The co-carbonization of fluid catalytic cracking decant oil (FCCDO) and heavy coker gas oil (HCGO) to form needle coke was studied in this thesis. The feedstock properties had important influence on needle coke. In order to improve the feedstock, FCCDO was removed most of solid particle through filtration, it was distilled into light fraction and heavy fraction; the heavy coker gas oil was thermally pretreated, the thermal pretreatment oil was distilled for three fractions: light oil, gas oil, and residuum, the gas oil was the proper fraction to form needle coke. The carbonization of single fraction to form needle coke, the co-carbonization of single fraction and gas oil to form needle coke was studied respectively. The affection of reaction temperature and press on needle coke formation and mechanism was investigated. In addition, the formation kinetics of toluene insolubles (TI) and pyridine insolubles (PI) of reaction residuum was studied.A polarized-light microscopy was used to analyze the optical texture of the coke and determine the quality of the coke in this experiment. The effect of reaction temperature and press on coke formation was investigated by the formation gas production and product distribution.The texture of needle coke showed that 7:3 was the proper proportion for the co-carbonization of the light fraction or heavy fraction and HCGO. Simultaneity it was also found that the optimum condition for the co-carbonization of the light component and HCGO was 480℃, 1.2MPa, the optimum condition for the co-carbonization of the heavy fraction and HCGO was or 480℃, 0.1MPa. On this condition, the optical texture of the coke took an elongate flow domain structure, high anisotropy and good ordered regions.The reaction residuum was separated into four subfractions by the method of sequential solvent extraction , they were heptane solubles (HS), toluene solubles (TS), pyridine solubles (PS) and pyridine insolubles (PI). The solvents used were heptane (H), toluene (T) and pyridine (P). The transition of the four subfractions suggested that the early stages of the condensation reactions of the carbonization involved a fast dealkylation process of the long aliphatic side-chains, the transition from HS to TS was the main dealkylation process; changes in solubility resulted from increase in molecular weight and the degree of condensation increased from HS to PI; the conversion of HS to PI occurred according to the following scheme: HS→TS→PS→PI. The formation kinetics of TI and PI showed that, when the feedstock was FCCDOQ, their first order apparent activation energies were 61.9kJ/mol and 73.2kJ/mol respectively, their second order apparent activation energies were 74.2kJ/mol and 88.1kJ/mol respectively; when FCCDOQ and HCGO co-carbonized, the first order apparent activation energies of TI and PI were 86kJ/mol and 100kJ/mol, the second order apparent activation energies were 103kJ/mol and 115kJ/mol.The above experiments showed that the thermal pretreatment heavy coke gas oil can also be used as the needle coke feedstock ,and this feedstock can make up the FCCDO deficiency to form needle coke, as well as improved the experimental and theoretical basis of carbonization.