Exploiting the Synergy between Fluid Catalytic Cracking and Visbreaking to Increase the High-Value Product Yields

摘要

An investigation was carried out to test the feasibility of processing a 360-510℃ visbreaker fraction in the fluid cata-lytic cracking unit, in order to maximize high-value product yields. It was found that in a commercial visbreaker unit with a soaker, the viscosity of visbreaker residue (>200℃) and the conversion of the visbreaker feedstock ― vacuum residue (>482℃) ― correlated directly with vacuum residue viscosity. Depending on the conversion in the visbreaker, the yield of 360-510℃cut var-led in the range 16-24% on feed. Character-ization of this fraction showed no difference in quality with conversion and a high level of gasoline precursors - 68%. Cracking experiments with a heavy vacuum gas oil, distilled from Russian Export Blend crude oil (73% gasoline precursors) and with an 80% Rus-sian Export Blend heavy vacuum gas oil / 20% visbreaker 360-510℃ cut blend using a commercial equilibrium catalyst in a labo- ratory MAT unit exhibited almost the same yield patterns. Therefore, addition of 25% of the visbreaker 360-510℃ cut to the FCC feed does not negatively affect the FCC yield pattern. Deriving the 360-510℃ fraction from the visbreaker and processing it in the FCC unit could increase the crude oil conversion by 2.8%. The yield of high value LPG and gasoline could increase by 0.8% and 2.6% of the crude oil respectively whilst reducing yields of fuel oil and FCC LCO by 3.7% and 0.6% respectively. Characterization of the 200-360℃ visbreaker cut showed that this material is more suitable as a component for transportation diesel than FCC LCO because of the lower aromatics content, 41% versus 72% of FCC LCO and higher cetane index ― 42 versus 21 of FCC LCO.