NeqSim Heat Integration Skill

Linnhoff-method pinch analysis to determine minimum hot/cold utility duties, the pinch temperature, composite & grand-composite curves, and to evaluate heat-exchanger network (HEN) opportunities.

When to Use

• Determining MER (Minimum Energy Requirement) for a flowsheet
• Setting utility duties before equipment sizing
• Retrofit analysis — quantify potential savings vs. existing HEN
• Comparing process alternatives on energy footprint
• Sizing utility headers (steam, cooling water) consistently across a plant

Standard reference: B. Linnhoff & E. Hindmarsh (1983), Chem. Eng. Sci.; operational guidance from Smith — Chemical Process Design and Integration (2nd ed.).

Core Concept

Hot streams (need cooling)  ──┐
                              ├── shifted by ΔTmin/2 → temperature intervals → cascade → MER
Cold streams (need heating) ──┘

The pinch divides the system in two:

• Above pinch — heat sink (only hot utility allowed)
• Below pinch — heat source (only cold utility allowed)
• Across pinch — every kW transferred costs 1 kW hot + 1 kW cold

Three golden rules — never violate any of them:

1. No external heating below the pinch
2. No external cooling above the pinch
3. No heat transfer across the pinch

Pattern 1 — Streams Defined Manually

import neqsim.process.equipment.heatexchanger.heatintegration.PinchAnalysis;

PinchAnalysis pinch = new PinchAnalysis(10.0);   // ΔTmin in °C
// addHotStream(name, supplyT_C, targetT_C, mCp_kW_per_K)
pinch.addHotStream("H1 — reactor effluent",  180.0,  80.0, 30.0);
pinch.addHotStream("H2 — flash gas",         150.0,  50.0, 15.0);
pinch.addColdStream("C1 — feed preheat",      30.0, 140.0, 20.0);
pinch.addColdStream("C2 — reboiler feed",     60.0, 120.0, 25.0);
pinch.run();

double Qh   = pinch.getMinimumHeatingUtility();    // kW
double Qc   = pinch.getMinimumCoolingUtility();    // kW
double Tpinch = pinch.getPinchTemperatureC();

Pattern 2 — Auto-Extract from a ProcessSystem

PinchAnalysis pinch = PinchAnalysis.fromProcessSystem(process, 10.0);
pinch.run();

This walks every Heater, Cooler, and HeatExchanger and registers their duties as streams.

Pattern 3 — Choosing ΔTmin

Trade-off: lower ΔTmin → less utility (good OPEX) but bigger HX area (worse CAPEX). Optimum is found from supertargeting — sweep ΔTmin and plot total-annual-cost.

Pattern 4 — Composite Curves for Visualization

// (after pinch.run())
double[] Th  = pinch.getHotCompositeT();
double[] Qh_ = pinch.getHotCompositeQ();
double[] Tc  = pinch.getColdCompositeT();
double[] Qc_ = pinch.getColdCompositeQ();
// Plot T vs Q → composite curves; the overlap = recoverable, the tails = utility

Plot the grand composite curve (getGrandCompositeQ/T()) to choose utility levels (HP/MP/LP steam, CW, refrigeration).

Pattern 5 — Retrofit Diagnostics

double existingUtility = sumExistingHotUtilities(process);   // user supplies
double saving = existingUtility - pinch.getMinimumHeatingUtility();
double saving_pct = 100.0 * saving / existingUtility;

Identify cross-pinch transfer with stream-level diagnostics (each violation costs double).

Common Mistakes

Validation Checklist

• ΔTmin chosen and justified (table above + sensitivity sweep)
• Three golden rules satisfied in any proposed HEN
• Composite curves plotted; pinch temperature reported
• Hot + Cold utility duties cross-checked: ΣQ_hot − ΣQ_cold = enthalpy balance
• Retrofit savings quantified vs. base case
• Utility level selection justified by grand composite curve
• Result saved to results.json under heat_integration with min_hot_utility_kW, min_cold_utility_kW, pinch_T_C, delta_T_min_C

Related Skills

• neqsim-power-generation — utility-side: HRSG, steam levels; also the "added exhaust heat recovery for a heating-medium circuit" retrofit pattern (hot-end versus stack-end coil: the temperature driving force, not the heat quantity, sets area and cost)
• neqsim-equipment-cost-estimation — HX area→cost for supertargeting
• neqsim-platform-modeling — apply pinch across multiple process areas