| Delayed coking process plays a more and more important role in upgrading of heavy oil, as the crude oil exploited in the world becomes worse. However, the process still has some practical problems, such as relatively low yield of liquid and the unsatisfied distribution of products. In order to promote the yield of distillates, improve the distribution of products reduce the yield of coke and extend the working period of units, the visbreaking-coking combined process was studied, using Karamay extra-heavy oil(CCY)as the feedstock.First of all, the coking reaction of CCY was researched under several reaction temperatures and in different time. It was indicated that the suitable reaction temperature was 490℃and the reaction time was 2.0h. After that, the liquid, which was obtained under the suitable condition, was distillated into several parts through true boiling point distillation. The coking diesel(180℃~350℃), LCGO(350℃~420℃) and HCGO(>420℃) were chosen as the HDA, HDB,HDC, respectively. The hydrogen transfer capabilities of the three distillates were studied subsequently. The result showed that the capability of HDB was greater than that of HDA which was greater than HDC. Then, HDB was blended into CCY with different proportion and the mixtures were used as the feedstock for coking reaction under the chosen condition. The result demonstrated that the feed with 20% HDB provided the highest yield of liquid. Under the same blending proportion, HDA, HDC were also blended into CCY and the reactions were carried out. The research indicated that HDB affected the distribution of product most, comparing with the result of reaction using pure CCY as feed. The amount of coke was reduced by 0.87% and the liquid yield was increased by 0.44%, especially the light distillates (gasoline plus diesel) were promoted by 1.79%.Secondly, the visbeaking-coking combined process with and without hydrogen donor (HDA, HDB, HDC) were studied and the results from the two kinds of combined reactions were compared. The result in common was that the pyrolysis products (gas and gasoline) and condensation products (coke) increased with the increasing of reaction temperature. Meantime, the stability of visbroken residuum fell. Besides, the difference between the two kinds of combined process was that the blending of hydrogen donor would affected the coke-induction period of coking feed and HDB was the most effective donor. That could be beneficial for the crack and the yield of pyrolysis products. In the combined process, the result indicated that the stability of visbroken residuum became worse and the yield of coke increased too when the visbreaking degree exceeded a certain limit. That would increase the total amount of coke in the combined process. However, if the feed had a relatively low level of visbreaking, the viscosity would not change too much and the yield of light distillates was low. So there was a best match between the visbreaking reaction condition and delayed coking reaction condition. In the combined process, HDB affected the result mostly. The proper visbreaking temperature was 420oC. Reaction time was 30min. The pressure was 0.4MPa and the blending proportion (HDB) was 10%. Comparing with the result of reaction using CCY as feed, the coke yield dropped by 1.77%. Liquid, light distillates and diesel increased by 1.86%, 5.71% and 3.57%, respectively.The properties of products were analyzed at last. Compared with direct coking process, it demonstrated that, the combined process did not affect the amount of S and N in liquid product too much. But the amount of S increased in coke and N did on the opposite way. The combined process with HDB did not affect the distribution of S and N in products very much. Furthermore, the combined process significantly changed the morphology of coke and improved the tropism of coke. The combined process with HDB had a better result comparing the aforementioned combined process.
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