Reduced heat transfer increased the temperature shortfall at the crude heater inlet. To maintain the target outlet temperature, the fired heater compensated automatically, resulting in a sustained increase in fired heater duty of approximately 1.2 MW. Since heater duty was normalised to throughput and crude severity, the incremental firing could be directly attributed to the bypass rather than operating variability. As a result, the refinery shifted from a fixed six-month exchanger cleaning cycle to a dynamic, value-based intervention strategy, prioritising cleaning based on real-time economic and energy impact rather than elapsed time alone. This avoided unnecessary downtime and delivered approximately INR1.0-1.3 crore per year in operational savings. The resulting degradation, partial recovery, and subsequent stabilisation of heat integration performance following digital monitoring are illustrated in Figure 3 . More importantly, heat integration performance became a shared operational responsibility, embedded in daily decision-making rather than revisited only during periodic audits. Quantified recovery and policy impact By recovering approximately 30-50% of degraded heat integration performance, the refinery achieved sustained improvements
100
95
90
85
80
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Years since revamp
Figure 3 Progressive heat integration degradation and recovery over time
protect throughput or reliability, often without visibility of their full cost. A common example is exchanger bypassing. As fouling increases the pressure drop or limits heat transfer, bypassing part of an exchanger is a practical short-term response. Prior to digitalisation, however, the energy penalty of such actions was rarely quantified in real time. By continuously reconciling live operating data from the crude preheat train against a thermodynamic reference based on pinch design intent, the digital twin detected a sustained reduction in recovered process heat following the introduction of a bypass around a crude preheat exchanger. This loss could not be explained by throughput or crude variability.
Heat integration performance gap – 7 MMTPA Indian refinery case study
Parameter
Design/early post-revamp
Degraded operation (~3 years)
After digital twin intervention
Heat recovery
~100
~78
~89
vs pinch target, % Exchange r approach temperature deviation Fired hea ter duty Specific e nergy consumption (SEC) CO₂ int ensit y Estimated annual energy cost impact Utility head room for
At design ΔT min
+5 to +20°C
30-50% reduction
Baseline
+5-6% +3-4%
−3-6% −2-3%
Target
Target
+~4 kg/bbl
−~2.1 kg/bbl
Baseline
INR30-45 crore increase
INR15-25 crore savings
Available
Increasingly constrained
Restored
throughput increase Note: Values are indicative and reflect reconciled operating trends observed in Indian refineries of comparable scale, benchmarked against pinch design intent and normalised for throughput and crude severity.
Table 2
Refining India
38
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