100
Design / early post-revamp Degraded operation (~3 years)
200
80
180
60
160
40
140
120
20
0
20
40
60
80
100
Heat ow (MW)
0
Pinch target
Degraded operation After digital twin
Model boundaries typically include crude and vacuum preheat trains, major pumparound circuits, and other heat recovery-intensive sections. During crude transitions or rapid throughput changes, comparisons are suspended until a new steady envelope is established, avoiding false diagnostics. Validation is performed through correlation with exchanger cleaning events, furnace performance trends, and historical plant tests. The model is deliberately conservative: Figure 2 Comparison of pinch design intent and actual operation, highlighting pinch-point drift and loss of heat recovery over time “ By translating thermodynamic deviations into economic and emissions metrics, the system aligns engineering insight with operational and managerial decision-making ” ambiguous signals are flagged for review rather than acted upon automatically, preserving operator confidence. While digital monitoring enables partial recovery and stabilisation of heat integration performance, full restoration to theoretical pinch targets is often constrained by physical equipment limits, fouling behaviour, and operational priorities. Ultimately, value is realised only when these insights influence daily operational trade-offs between efficiency, reliability, and throughput. Making trade-offs visible: the human element A key operational benefit of digital heat integration monitoring is its ability to make everyday trade-offs explicit. Many energy- impacting decisions are taken instinctively to
operates continuously as a decision-support system for operations, energy-management teams, and unit leadership. Its primary role is not closed-loop optimisation, but the governance of heat integration performance. Key outputs include real-time deviation from pinch targets, exchanger-level approach temperature trends, fired heater duty normalised to throughput and crude severity, and ranked heat recovery losses expressed in energy, cost, and CO₂ terms. By translating thermodynamic deviations into economic and emissions metrics, the system aligns engineering insight with operational and managerial decision-making. A conceptual example of this information delivery is shown in Figure 1 , illustrating a digital heat integration performance dashboard. Figure 2 illustrates the thermodynamic impact of heat integration degradation by comparing pinch design intent with actual operation using a grand composite curve (GCC). The GCC shows net process heat surplus or deficit versus shifted temperature, highlighting pinch location and loss of recoverable heat. In pinch analysis, shifted temperature refers to stream temperatures adjusted by half the minimum allowable temperature approach (ΔT min ) to represent maximum feasible heat recovery. Model scope, validation, and practical limits The digital twin is implemented as a steady- state diagnostic model, updated once operating conditions stabilise. It does not replace dynamic simulations or process control systems; instead, it provides a consistent thermodynamic reference against which day-to-day operation can be evaluated. Figure 1 Digital heat integration performance dashboard (illustrative)
Refining India
37
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