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Pinch analysis is vital in optimizing heat exchanger networks (HENs). Targeting methods are used when determining cost effectiveness with pinch analysis. However, the existing targeting methods for the capital cost of HEN are not suitable for wide application scenarios. Therefore, we developed a high-accuracy general capital-cost-targeting method. It is built on a final structure that was evolved from the spaghetti structure of HEN through four loop elimination stages. This structure helps to reduce the prediction deviation of the method. To achieve high adaptability while establishing this method, we considered the different heat exchanger cost categories, different cost laws for one stream pair, and area limitations of heat exchangers that may be encountered in practice. In addition, allowing streams to use individual temperature difference contributions enhances the method’s predictive capacity. The potential defects of the method found in numerical experiments and case studies were corrected with improvement measures. As a result, the accuracy and stability of the targeting method were further enhanced, with absolute target deviations generally within 10% and often within 5%. This study provides a benchmark for the optimal capital cost of HEN, allowing for a better economic effect when applying pinch analysis.

Ahead of heat exchanger network (HEN) design, setting an optimal pinch temperature difference for pinch analysis depends vitally on the capital cost target. Conventional methods based on the spaghetti (SPA) structure ignoring matching optimization might result in calculated cost targets of large deviations. This work evolved the SPA structure via four stages by shifting energy towards low-cost matching. The fourth structure evolved from the SPA structure (ESPA-IV structure) with the lowest-cost matching after loops elimination forms the base to establish the ESPA method. It is validated by numerical experiment and applied to a case reported in literature, meanwhile comparisons are always made to the SPA method. The numerical experiment proves that the ESPA method can obtain capital cost targets with higher accuracy than the SPA method. The target deviations (often within ±5%) given by the ESPA method are much lower than those (well above 10%) derived by the SPA method. In the case study, the given HEN is further optimized as hinted by ESPA method results. Of two target methods, the cost target indicated by ESPA method is closer to the optimum capital cost newly derived after optimization. The high accuracy of the ESPA method is further verified.

Data for two systems of isobaric vapor–liquid equilibrium (VLE), n-heptane + sec-butyl acetate (SBAC) and methylcyclohexane + SBAC, were determined under atmosphere with an Ellis vapor–liquid equilibrium still. The Herington method and Wisniak test were employed to determine the thermodynamic consistency of the two systems. The experimental results of n-heptane + SBAC and methylcyclohexane + SBAC were correlated by three activity coefficient models, which are the nonrandom two-liquid, universal quasichemical, and Wilson, and the correlation results fit well with experimental data. The binary interaction parameters of these models were obtained, and the results showed that these models can give good predictions. The VLE data provide theoretical basis and data support for the further study on separation of n-heptane + SBAC and methylcyclohexane + SBAC.

The retrofit of heat exchanger network often needs topology changes to overcome the network pinch to increase heat recovery. It is difficult to maximize energy recovery and minimize topology changes. Owing to good interactive and visualized effects, graphical tools are widely applied in the retrofit. However, for a heat exchanger network with different minimum temperature differences, it becomes difficult to screen retrofit options to avoid crossing the pinch. An efficient graphical tool is needed during retrofit. The shifted temperature driving force plot is proposed to solve this problem by shifting the stream temperature. With the aid of Pinch Analysis, the ideal regions are divided to indicate where heat exchange matches should be located. The emerged stagger of ideal regions before shifting the stream temperature can be avoided. This makes the screening of retrofit strategies easy and convenient. The retrofit of an industrial case is conducted with this graphical tool. The key changes are for the heat exchange matches that cross the pinch. Obtained results show that more energy is recovered with fewer topology changes, thereby yielding improved economic benefits. Application of the shifted temperature driving force plot illustrates its effectiveness in finding better retrofit solutions.