Study On Preparation Of Needle Coke From FCC Slurry

Needle coke is an excellent carbon raw material developed in carbon materials from the 1960s to the 1970s.It is mainly made of graphite electrodes and then used for electric arc furnace steelmaking.The production raw materials mainly include FCC oil slurry and coal tar,etc.The use of FCC oil slurry to prepare high-quality needle-shaped coke is of great significance to improve the high value utilization rate of China's rich petroleum resources,reduce dependence on foreign products,and produce high value-added products.In this thesis,the FCC oil slurry is pretreated with FITS hydrodeolefination process,supercritical fluid extraction and co-carbonization process,and the aromatics fraction is enriched.The treated oil slurry is used as a coking raw material,which is carbonized,coked and calcined.Needle coke is prepared with performance indicators that meet or exceed similar products at home and abroad.The work of this thesis mainly includes the following aspects:?1?The raw materials were pretreated.The FCC oil slurry was treated by supercritical propane extraction technology and co-carbonization experiment of hydrogenation oil slurry and FCC oil slurry.By means of elemental analysis,four-component analysis,and nuclear magnetic resonance analysis,the composition before and after the pretreatment changed greatly.The raw materials after hydrogenation increased from 68.21%to 76.60%,and the saturation content changed from the original 7.28%to 14.04%,the sulfur content was reduced from 1.17%to0.31%.After the supercritical propane extraction of#3 raw materials,the aromatics increased from 68.21%to 88.59%,the saturated content decreased from the original7.28%to 2.31%,and the sulfur content decreased from 1.17%to 0.96%.The co-carbonized 3#raw material aromatics changed from 68.21%to 74.10%,the saturation content changed from 7.28%to 17.51%,and the sulfur content decreased from 1.17%to 0.57%.After the oil slurry was pretreated,the ash content and heteroatom content were significantly reduced,and the thermal cracking polycondensation reaction tended to be mild.?2?By means of polarizing microscope and product distribution analysis,the composition of mesophase and the changes of polarizing microstructure during carbonization were analyzed,and the thermal conversion behavior of FCC slurry and its aromatic-rich fraction was studied.Experiments have shown that temperature,pressure,and the composition of the raw materials have a decisive influence on the carbonization process of the raw materials.At an appropriate temperature,an appropriate increase in pressure will be beneficial to the formation and development of the mesophase;the carbonization process is a thermal cracking and thermal polycondensation process,and an appropriate raw material composition is a prerequisite for the preparation of acicular coke.Using a hydrogenated oil slurry as a carbonized raw material,by observing under a polarizing microscope,carbonization under the protection of an inert gas N₂at 470°C,0.6MPa,and 180 min can obtain a wide-range streamlined mesophase with good anisotropy.Carbonized raw materials,carbonized at 450°C,0.6MPa,180min,protected by inert gas N₂can obtain wide-area streamlined mesophases with good anisotropy;co-carbonized distillates into carbonized raw materials,at 450°C,0.6MPa,180min,inert gas Carbonization under N2 protection can obtain a wide-area streamlined mesophase with good anisotropy.?3?The crystal structure characteristics of petroleum coke before and after calcination were studied by means of XRD,polarizing microscope and scanning electron microscope.Studies have shown that crystal structure and crystallization can be analyzed using thermodynamic knowledge combined with lattice parameters.The calcination process of petroleum coke is both a crystal rearrangement process and a thermal decond ensation process.During the crystal rearrangement process,the orderliness of the crystals increases,which is mainly manifested by a decrease in the entropy value and an increae in the size of the particles.The result of the thermal cracking polycondensation is Increased inactivity.The calcination of green coke at1400?can not only significantly reduce the S,N and other heteroatoms in the mesophase,but also remove the light components in the sample.Calcining can improve the crystal structure of the condensation product,while increasing the height of the layer stacking of aromatic molecules,and also can make the arrangement of molecular layers tend to be dense.A cooked coke having a true density of not less than 2.13g/cm³and a volatile content of substantially zero was obtained.