委内瑞拉常压渣油悬浮床加氢裂化尾油循环反应实验研究

Experimental Study on Slurry-Bed Hydrocracking Bottom Oil Recycling Reactions of Venezuela Atmospheric Residue

以委内瑞拉常压渣油为原料,分别采用3种加氢裂化反应产物(>500℃馏分、>400℃馏分、>350℃馏分)作为循环尾油,在高压釜中进行了425℃、14 MPa下的悬浮床加氢裂化尾油循环反应研究,考察了循环尾油馏程以及尾油外甩比对循环反应体系生焦量、沥青质含量和液体产物分布的影响,并采用SEM、1 H-NMR测定了焦炭形貌和沥青质结构参数,以探索重油悬浮床加氢裂化尾油循环工艺的可行性。结果表明,相对于一次通过反应,尾油循环反应能有效提高原料转化率;采用>500℃馏分作为循环尾油时,体系生焦量随循环反应次数的增加而持续增加,而采用>400℃馏分或>350℃馏分作为循环尾油时,循环反应4次后,体系生焦量、焦炭形貌、液体产物分布、沥青质含量和结构均基本保持不变。说明当选择合适馏分作为悬浮床加氢裂化循环尾油时,重油悬浮床加氢裂化尾油循环工艺可行。此外,当反应温度和压力一定时,降低循环尾油的初馏点或减小外甩尾油比可提高原料的转化率,同时会使新鲜原料空速降低。因此,为保证较高的新鲜原料空速和转化率,必须采用合适的循环尾油馏程和尾油外甩比。

The reactions of slurry-bed hydrocracking bottom oil recycling of Venezuela atmospheric residue at 425℃ under a hydrogen pressure of 14 MPa were processed in autoclave with three kinds of products(>500℃fractions,>400℃fractions and>350℃fractions)as recycling bottom oil,and the effects of distillation range of recycling bottom oil and ratio of swing bottom oil to fresh oil on coke yield,asphaltene content and distribution of liquid products were investigated.And then the microstructure of coke and structural parameters of asphaltene during recycling reactions were characterized by SEM and 1 H-NMR.The results showed that compared with once-through reaction,the bottom oil recycling reaction could increase the conversion rate of raw oil effectively.With >500℃ fractions as recycling bottom oil,the coke yield increased as the times of recycling reactions increased,but with >400℃ fractions or>350℃ fractions as recycling bottom oil,after four times of recycling reactions,the yield and microstructure of coke,the distribution of liquid products and the content and structure of asphaltene were almost unchanged,indicating that with suitable cut fractions as recycling bottom oil the bottom oil recycling technology of slurry-bed hydrocracking of heavy oil was feasible.In addition,under certain reaction temperature and hydrogen pressure,decreasing the initial boiling point of recycling bottom oil or increasing the ratio of swing bottom oil to fresh oil could increase the conversion rate of raw oil,but decrease the space velocity of fresh oil.Therefore,in order to get higher space velocity and conversion rate of fresh oil during bottom oil recycling reactions,appropriate distillation range of recycling bottom oil and ratio of swing bottom oil to fresh oil are necessary.