Study On The Integrated Process Of FCC Slurry Oil Cracking And Solid Removal

Catalytic cracking slurry oil derived from fluid catalytic cracking?FCC?of heavy oils,such as atmospheric and vacuum residues,was a heavy product at the bottom of the tower.With the increasing of proportion of heavy and inferior crude oil,the quality of slurry oil was uneven and gradually becoming worse.Besides,its output was also greatly increased.As a byproduct of FCC process,most refineries chose to throw most of the slurry oil out.The slurry oil was mainly sold as low-priced heavy quality fuel oil,which was low value in utilization and caused huge waste of resources.Slurry oil was usually high in aromatics,and the composition characteristics of slurry oil could potentially make it to be a kind of value-added material in the preparation of rich-aromatic products.In order to improve the utilization value of slurry oil,this paper studied the determination and composition of solid content,solid removal during cracking,oriented conversion for oil and gas,gasification of deposited coke to realize the comprehensive utilization of slurry oil.The main conclusions of this paper were as follows:?1?Determination and composition analysis of solid contents in slurry oil.The methods of ash analysis,filtration and centrifugation analyses were adopted to measure the solid particles content of Dagang slurry oil and the experiment results were contrasted and analyzed in terms of solid content,finding that the solid content of slurry oil was about 3100?g/g.The centrifugation method results indicated the strong adsorption between fine particles,centrifugal method coupled with subsequent calcination could isolate and obtain a certain amount of solid particles from the slurry oil.The solid particles and the original FCC catalyst were characterized by means of laser particle size analyzer,Elemental analyzer,X-ray diffraction?XRD?,Brunauer-Emmett-Teller?BET?,scanning electron microscopy&energy spectrum analysis?SEM-EDS?,etc.The results indicated that the fresh FCC catalyst possessed the normal spherical distribution in the range of 32-120?m,while the solid particles in the oil slurry were scattered and irregular with the particle size of 0.4-40?m,in which the fine catalyst was mostly between 1-30?m.The solid particles in FCC slurry oil mainly consisted of catalyst powder,coke powder,inorganic metal salts,such as alkali metal?K,Ca?,antimony?Sb?,iron?Fe?,etc.?2?Study on the characteristics of slurry oil cracking and solid removal.A small fixed-fluidized bed experimental device was used to study the characteristics of slurry oil cracking and solid removal with inert quartz sand.The results showed that inert quartz sand was not suitable for slurry oil pyrolysis since it had no pore structure and smaller specific surface area.The properties of oil after being cracking were similar to the raw slurry oil.After thermal treatment,almost of solid in slurry was precipitated on the surface of quartz sand,and the removal rate of slurry oil was about 92%.?3?Optimization of the operation parameters for oil slurry cracking.It could obtain a certain yield oil with low solid content and containing considerable aromatic compounds when using FCC catalyst with moderate activity.Among the variables investigated,temperature was the most important factor which affected the distribution of cracking products from slurry oil,while the ratio of catalyst to oil weight ratio was in the middle,and the steam to oil weight ratio was the least.The results demonstrated that the optimum reaction conditions for temperature was 470?,catalyst to oil ratio was5.7 and steam to oil ratio was 0.5.Under these conditions,we could obtain about 70%cracked oil,while the H/C ratio of the oil was the smallest.The light oil was about 14%,with about 96%solid contents to be removed,and the content of 1-4 cyclic aromatic reached 85%.The SEM-EDS results expressed that FCC catalyst was more likely to precipitate solid in slurry oil for its larger pore and catalytic activity,which could promote the coke formation and other reactions.?4?Analysis and regenration of coked-catalyst via gasification.It had been discussed about carbon amount,carbon species and gasification characteristics of coked-catalyst after cracking pyrolysis.The results demonstrated that the thermogravimetric method had the highest accuracy and repeatability among the carbon amount measurement methods.The muffle roasting and elemental analysis method were suitable for daily batch and repeated measurement.The thermogravimetric method and sulphur-carbon analyzer were mainly used for small batch precision measurement.Carbon deposition was mainly composed of polycyclic aromatic hydrocarbons?PAHs?from binary to pentacyclic rings.The PAHs were mainly formed by a series of hydrogen transfer,cyclization,dehydrogenation and condensation reactions of small molecular hydrocarbons derived from raw slurry oil and pyrolysis products.The experimental results of carbon deposit gasification showed that the carbon deposit on the catalyst surface could be fully transformation by steam only or steam with adding part of oxygen.At the same time,it could gain 80%of syngas?H₂and CO?in the gasification.