Base case details: CDU product
Stream name
Heavy naphtha 66,910 787.84
Unstab. naphtha 162,061 705.35
Light kero
Heavy kero
LGO
Total mass rate, kg/hr Liquid std. density, kg/m³
55,202 806.93
105,343 828.43
250,260 848.37
ASTM D86 at 760 MM HG (LV), C 5%
118.7 136.1 143.0 150.1
16.2 55.7 84.0 95.0
162.1 174.7 180.2 186.8 198.0 202.8
185.8 210.3 220.8 232.9 254.8 266.6
184.9 257.1 283.5 308.0 343.2 357.5
30% 50% 70% 90% 95%
Table 4 Savings of utilities 161.4
111.0 119.1
168.4
Table 1
Base case details: VDU product
Stream name
RCO
VAC_DIESEL
LVGO
HVGO
VR
Total mass rate, kg/br Liquid std. density, kg/m³
335,782 901.22
30,805 861.59
135,725 877.89
108,050 894.74
50,416
1,013.22
ASTM D1160 at 760 MM HG (LV), C 5%
312.5 406.3 447.2 505.2 609.9 670.9
261.3 303.3 319.2 335.2 354.3 361.8
356.6 389.2 406.9 430.6 466.1 486.4
420.0 470.6 493.7 521.1 557.8 573.1
571.1 611.9 641.0 689.1 812.8 907.7
30% 50% 70% 90% 95%
Table 2
Results and discussion The proposed configuration significantly reduces vapour dilution in the rectification section by 30-40%, as steam is confined to stripping while clean vapours feed the rectification zone. This transforms the conventional column into a dual-zone system with independent control of stripping and rectification. In conventional designs, flash zone, stripper, and rectification pressures are intrinsically linked through cumulative pressure drops. In contrast, the proposed configuration decouples these interactions, enabling independent optimisation of stripper pressure, which enhances stripping efficiency while maintaining stable rectification conditions. The integrated wash oil system, utilising condensed stripper overhead hydrocarbons (raw diesel/HVGO), enhances overflash and ensures uniform bed wetting. This suppresses coking tendencies and improves fractionation sharpness, with diesel and HVGO end points
rectification with selective steam utilisation in stripping sections, along with an integrated wash oil system to optimise separation performance. This results in a reduction in overall steam consumption, primarily through elimination of dedicated VDU stripping steam and reuse of recovered steam within the CDU- VDU system. In addition to tangible energy savings, the configuration delivers key operational benefits. Improved wash oil circulation enhances the removal of entrained heavy components, leading to better product quality, particularly in diesel and HVGO streams. Reduced steam ingress into rectification sections minimises overhead condensation, thereby lowering corrosion tendencies and improving equipment reliability. Furthermore, reduced vapour load and improved column hydraulics create additional operating margin, enabling a potential increase in feed throughput within existing hardware constraints.
Refining India
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