Study And Preparation Of Needle Coke From Extracted FCC Slurry

There were two purposes to study and prepare the needle coke, one of which was that the feed crude oil to be refined became heavier. The heavy oil of the imported and domestic crude oil reached over 40%, which increased the petroleum coke yield and lowered the quality of the product. In this view, crude oil's deep processing was the urgent problem for petroleum refinery enterprise. On the other hand, the metallurgical industry has been developed quickly in recent years. The electric furnace steelmaking technique was widely used for the sake of energy saving and environmental protection, which resulted the increasing demand for the needle coke. The needle coke used for preparing ultra high power (UHP) graphite electrode was supplied mainly by importation, because the quality or quantity of domestic needle coke products could not satisfy need. When catalytic cracking slurry or ethylene tar were used as raw material for carbonization, the latent value of residue oil could be raised, and the nation demand on the needle coke could also be satisfied. In this research, FCC slurry was extracted with furfuraldehyde and the aromatic hydrocarbons of FCC were enriched and used as the raw material to produce the high-grade needle coke through carbonization, coking and calcinations processes. The characteristics of the result needle coke reached or exceeded the imported products. The main work of this thesis was shown as follows:①Feedstock extraction.An orthogonal test for extraction temperature and solvent–oil ratio had been done with a continuous extraction device. The results showed that the selectivity was increased with the increase of solvent–oil ratio and decreased with the temperature rising. At same time, with the temperature rising, the density of the extracted oil was declined but relative molecular weight and H/C value were raised with the temperature. The extraction was efficient due to higher aromaticity of the raw material after extraction. The optimum extraction condition was at 50℃and with the solvent–oil ratio of 2:1. The compositions of feedstock before and after extraction were examined respectively by four-composition analyses, FT-IR and H-NMR analyses etc. The result showed that the aromatic hydrocarbon content and the sulfur content were raised from 52% to 90% and 0.36% to 0.20% respectively. The average number of aromatic carbon atom and naphthenic carbon atom were raised from 9.36 to 16.5 and 6.4 to 8.52 per molecular. The reactivity became mild with the decreasing concentration of heavy metals iron②Thermal conversion behaviors of FCC slurry and enriched aromatic hydrocarbon.The texture of mesophase pitches had been investigated with polarized microscope, FT-IR and 1H-NMR. Results indicated that the modified FLORY formula revealed the law of growth of Brooks-Taylor spherules, whose development and distribution was inherent necessity, and factors such as the fractions of quinoline insolubles, high viscosity and multi reactive center would all prohibit the growth of the spherules. It was considered that the pressure, temperature as well as the component all influenced the carbonization processes. The factors above showed interacting relations although they had different functions. For given raw material at suitable temperature, the increase of pressure favored the coalescence of mesophase and formation of needle coke. It could be understood that the appropriate composition of raw materials was attained by precondition for the preparation of carbon materials Ethylene tar mixed with FCCRF gives a performance of synergetic effect during carbonization. With conditions of 3.5MPa, 400～430℃, 6～20h and 500℃, 1.0MPa, 3～4h, inert atmosphere, the needle coke could be prepared by carbonization from enriched aromatic hydrocarbon of FCC slurry or its mixture with ethylene tar.③The rheological properties of mesophase pitches derived from FCC and FCCRF.FCC-MP and FCCRF-MP had been studied with high-temperature rheometer, X-ray diffractometer (XRD) and polarized microscope. Results indicated that the microtexture of mesophase was affected the shearing stress and it also affected the rheological behaviors at the same time. The flow domain masophase pitch showed strong non-Newton rheological properties, larger temperature sensitivities and lower apparent viscosity. FCCRF-MP showed better rheological behavior than that of FCC-MP.④The characteristics of fresh and calcined coke.The characteristics of fresh and calcined coke had been monitored by differential thermal analysis (DTA), XRD and FT-IR methods. The results showed that combination the entropy function with lattice parameters was a rational way to investigate crystal structure and crystallization. Calcination process was a crystal rearrangement stage as well as a dehydrogenation, polymerizing, aromation process. In the stage of crystal rearrangement, the molecular assembling order degree was increased. The process was appeared the decrease of entropy and increase of the crystal cell size. The temperature band between 200～700℃was the key stage for crystallization. The temperature at 1400℃was not high enough to change the stacking state of graphite layer structure because the value of d002 didn't change much and P1 was very small.