Effect Of Raw Material Composition On The Formation Of Needle Coke

Da Qing FCC slurry with more than 50% weight fraction of aromatics was a high-quality rawmaterial for preparing needle coke. However, FCC slurry can not be directly as raw material for preparingneedle coke, due to relatively high contents of aliphatic hydrocarbons, gelatine, asphaltene and heteroatom.Slurry needs to be pretreated to improve the content of aromatic hydrocarbons and decrease the content ofaliphatic hydrocarbons, heteroatom and heavy metals iron. Effect of raw material on the structure andperformance of needle coke is the focus of this thesis to explore.There were two aspects of the main work of this thesis: One was that FCC slurry was extracted withfurfuraldehyde as the extraction solvent. The aromatic hydrocarbons were enriched and used as the rawmaterial to produce mesophase through carbonization, coking processes. By means of four-compositionanalysis, FTIR and NMR analysis and other methods, the compositions of feedstock were studied. As thecomponent and microtexture of mesophase pitches, thermal conversion behaviors of FCC slurry andenriched aromatic hydrocarbon had been investigated with polar optical microscope, FTIR and NMR. Therheological properties of MP-FCC and MP-FCCRF had been studied with high-temperature rheometer,X-ray diffractometer(XRD) and polar optical microscope. The other aspect was that the carbonization ofFCC slurry blended with coal tar pitch in different ratios was conducted at 440 and atmospheric pressure.℃The microtexture of mesophase had been studied with polar optical microscope and the characters of freshcoke had been studied with XRD.Results indicated that composition has been greatly changed. The aromatic hydrocarbons content rosefrom 52.48% to 87.33%, and the aliphatic hydrocarbons content declined from 33.68% to 9.50%, and thereactivity of pyrolysis and condensation abated as the contents of heteroatom and heavy metals irondecreased. The composition of raw material determinatively affected microtexture, rheological propertiesand crystal structure of mesophase pitch. The rheological properties and crystal structure of MP-FCCRFwas superior to MP-FCC. The main optical texture of MP-FCCRF was flow domain texture and that ofMP-FCC was coarse and fine mosaic texture. Under atmospheric pressure, 430~440℃, 6~15h, and inert atmosphere, mesophase pitch with good performance could be prepared by carbonization from enrichedaromatic hydrocarbon. Results shows that FCC slurry blended coal tar pitch with the ratio of 1 to 4, canprepare mesophase pitch with good properties. The nature of mesophase pitch from aromatic componentwhich essentially define the quality of needle cokes, depends strongly on the carbonization reactivities ofthe blended feedstocks.