The minimum approach temperature (?Tmin) has been used in the design of heat exchanger networks (HEN) and in energy targeting based on Pinch Analysis. It refers to the minimum allowable temperature difference between a heat source and a heat sink for designing an energy-efficient HEN. Smaller ?Tmin can improve process heat recovery but require large heat transfer area and may result in a higher capital cost. Capital-energy trade-off is typically performed to determine the cost-optimum ?Tmin during HEN synthesis (HENs). Conventionally, an entire process is analysed to obtain the optimum value of ?Tmin. In this work, the capital-energy trade-off is performed using the individual stream temperature versus enthalpy plot (STEP) to obtain an optimum ?Tmin for each identified STEP. First, simultaneous area and utility targeting of HEN is performed using the established STEP HEN targeting procedure. The capital-energy trade-off is then analysed separately for every identified STEP. The different values of ?Tmin obtained are then applied for the grassroots synthesis of HEN. Application of the proposed procedure on a literature case study shows that the total annualised cost is reduced by 7.03 % when the capital-energy trade-off is performed separately for every STEP as compared to trading-off ?Tmin for an entire process.
