Water cooler
Gas
Heat recovery
Air cooler
Separator
Wash water
Wild naphtha-re ux pump
Crude column
Crude charge pump
Re ux
(In case of Pre-frac.)
Crude
3 stage ejectors + LRVP
SS1
Sour water pump
Steam
PA1
Heavy naphtha
Vacuum column
SS2
Pre- ash drum/ Pre-fractionator
PA2
Preheat-1
Vac. diesel
PA4
Kerosene
Gas
PA3
(In case of Pre-frac.)
SS3
Hot well
LVGO
PA5
Diesel
Separator
CDU Over ash
Desalter
HVGO
(Absence of Pre- ash/Pre-frac.)
PA6
Sour water pump
Slop oil pump
Heat recovery
CDU wash oil pump
Sour water
Partition Plate with downpipe/ downcomer
VDU Over ash
CDU ash drum
VDU ash drum
Steam Ejectors
(Self draining)
Fired heater
Fired heater
VR
Coil steam
Preheat-2
VDU wash oil pump
(Self draining)
RCO pump
(In case of Pre- ash/Pre-frac.)
Can be used as heater purging steam/top ejector
Figure 3 Novel CDU-VDU configuration suits revamp scenario of existing refinery
the load on overhead ejectors, compounded by unintentionally stripped vacuum diesel components from the VDU top section. In the Indian context, where nearly 70% of refining capacity was commissioned prior to 2000, the proposed CDU-VDU configuration offers immediate operational benefits through low-Capex, revamp-friendly modifications. As refineries increasingly process a wider spectrum of crudes – from imported heavy feedstocks to domestic light variants – this configuration addresses existing energy inefficiencies while enhancing flexibility to handle fluctuating crude slates and tightening emission norms. The need for such upgrades is further amplified by evolving fuel quality requirements, including BS-VI compliance, and increasing integration of biofuels and emerging hydrogen- based processing schemes, all of which demand low-emission and operationally adaptable configurations. These challenges are particularly pronounced in ageing assets, where legacy designs must accommodate heavier, higher- sulphur crudes without compromising margins. With domestic crude production plateauing and import dependency rising significantly, refinery economics are increasingly exposed to
global market volatility, including crude price swings, currency fluctuations, and geopolitical uncertainties. In this scenario, energy-efficient and adaptable CDU-VDU configurations become essential to sustain profitability, making the processing of opportunity crudes not just advantageous but a strategic necessity. Seamless integration: process flow in a revamp lens For a revamp case, as shown in Figure 3 , the rectification section is effectively decoupled from the stripping section within the existing column using a partition. This is achieved through chimney tray blanking, vapour draw- offs, and liquid-in nozzles, enabling seamless integration during scheduled shutdowns with minimal disruption. Figures 3 and 4 build upon the conventional CDU-VDU configuration (Figure 1), with additional details marked in red to emphasise the novel configuration revamp requirements. Crude oil is desalted and preheated through an integrated heat exchanger network, utilising heat recovered from CDU and VDU product streams along with pumparound circuits, prior to final heating in the furnace. It is then heated
Refining India
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