Steam
Heavy kero
LGO pumparound
Hold down grid
LGO / HGO fractionation MellapakPlus
Steam
Hold down bar
Light gasoil
Steam
Tie rod
Flash zone
Heavy gasoil
Stripping section
Support grid
Steam
Atmospheric residue
Figure 2 HGO section modification
Support bar
x Improve the VGO tail-end distillation curve for a superior quality of feed to the downstream units. y Reduce flash zone pressure by lowering the pressure drop in the vacuum column. z Integrity issues in the vacuum column: • The HVGO PA packing and the wash bed were found dis - lodged during every turnaround. • Rapid vapour-traffic shifts during block-mode crude changes (low-sulphur ↔ high-sulphur) caused mechanical disturbances. • Loss of bed integrity degraded mass-transfer efficiency, worsening VGO-VR overlap.
Implemented solutions (2024 turnaround) IOCL has provided test run data to build the process sim - ulation model of the existing running units. A deep pro - cess and hydraulic study was performed jointly by Sulzer and IOCL to identify the bottlenecks in both columns and develop remedies to achieve the goals. A focused column Figure 3 Post-revamp HVGO wash section sandwiched bed design with tie rods
Atmospheric distillation unit
Vacuum distillation unit
O -gas
Overhead
LVGO to diesel pool
LVGO PA Mellapak
LN /HN fractionation
Light naphtha
HN /ATF fractionation
Steam
LVGO / MVGO fractionation MellapakPlus
Heavy naphtha
MVGO
ATF pumparound
MVGO / HVGO fractionation bed removed
Steam
ATF / HK fractionation
Aviation turbine fuel
VGO pool
HK pumparound
HVGO PA packing reused
HVGO
Steam
Heavy kero
LGO pump a round
Wash section MellapakPlus Mellagrid AF
Diesel pool
SLOP wax
LGO / HGO fractionation MellapakPlus
Steam
Light gasoil
Heavy gasoil routed directly to VGO pool
Flash zone
Steam
Crude
Stripping section
Stripping section
Steam
Steam
Atmospheric residue
Vacuum residue
Figure 4 AVU flow diagram – post-revamp
11
Revamps 2026
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