Development of Flow Diagrams for Increasing Vacuum Gas Oil Extraction

Analysis of the performance of vacuum columns of ELOU-AVT plants showed that in many cases long residue contains as much as 30 % vacuum gas oil with final boiling point up to 560°C. A comparative analysis was made of three options for increasing extraction of heavy gas oil in the residual fuel oil fractionation process. A conventional scheme involving pressure reduction at the vacuum column top, fractionation of the long residue without its heating after the primary vacuum column in an additional vacuum column, and fractionation of the residual fuel oil by a two-column scheme without heating of the residual fuel oil in the first column with extraction of only the light gas oil and with heating of the long residue of the first column, followed by its fractionation in the second column with extraction of the heavy vacuum gas oil was investigated. The performance of the vacuum column of the ELOU AVT-6 vacuum fractionation plant was analyzed. The process was simulated in Apen HYSYS environment. It is shown theoretically that extraction of heavy vacuum gas oil can be increased by deep-vacuum fractionation of vacuum residue. The merits and demerits of two-column vacuum fractionation of residual fuel oil were examined. A design of the fractionating column and feedstock feeding device is proposed.