Options Analysis Of Vacuum Columns and Ejector systems

Desired increases in gas oil feed to FCCU’s often drive reviews of atmospheric and vacuum column revamp options. Upgrading vacuum resid to VGO has financial attractions depending on operations downstream of the column. Gains are typically about $10/bbl with no downstream vacuum resid processing and $4/bbl where there are such operations. This paper analyses vacuum column revamp options targeted for cut point improvement from 1050° F to 1100° F to reduce vacuum resid.

For the purposes of the approach adopted herein the author has made the following process assumptions:
• that the vacuum column diameter and mass transfer capabilities do not restrict performance
• that column overhead discharge diameter is not limiting column effluent capacity
• that modern tower internals for low pressure drop are the basis for establishing flash zone and tower top pressure

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