Enhancement in energy recovery is always an essential element that requires academic spotlights to ensure its capability to contribute towards carbon neutrality. Recent works have extended to cover multi-solution heat exchanger networks (HEN) synthesis instead of generating a single best solution, which is not guaranteed to be practical. Nevertheless, owing to the technical challenges of synthesising all feasible networks, none of the existing works attempts to comprehensively elucidate how network topologies affect the network cost. To address this gap, P-HENS, a graph theoretic-based HEN synthesis tool, was utilised to generate the set of all heat exchanger networks with minimum utility consumption. Its effectiveness is demonstrated through an illustrative case study, which eventually generates more than 45,000 HENs. The impacts of structural variables on the cost, including the number of exchangers and the stream pairings, were analysed. The cost range of the networks was identified, revealing cost differences of 30 % despite minimum utility consumption or 15 % despite the minimum number of exchangers. Key stream pairs required to meet maximum energy recovery and influence cost were identified, leading to recommendations for improving solution searches. The solution set and the insight from this work are available to the research community for further analysis, offering valuable insights to enhance energy integration in the industry.

The rise in biodiesel production results in an excess of crude glycerol, which further leads to environmental concerns. Consequently, transforming crude glycerol into valuable products is deemed an effective way to address this issue. Process Integration techniques are introduced to enhance the overall economic viability by maximizing the energy recovery in the biodiesel plant. However, most of the existing studies merely focused on a single optimal heat exchanger network (HEN) generated. In this study, P-HENS software is utilized to generate viable HENs for a glycerol-derived 1,3-propanediol plant. Subsequently, piping costs of each HEN are estimated to determine the optimal HEN by assuming the respective heat exchanger is placed at the centroid. Finally, the optimal HEN is identified based on the total annualized costs (TAC) (which include the capital cost of the heat exchanger, utility cost, and piping costs) and energy-related carbon emissions of the network. The results show that, among the 4,188 feasible networks generated, network #623 possesses the best overall performance when both cost and environmental aspects are considered. The carbon emissions of network #623 is 16.7% lower than that of the case without heat recovery. This work demonstrates the usefulness of the generated near-best HENs in enabling a more comprehensive HEN optimization. By application of the proposed methodology, the most economical and environmentally friendly HEN can be determined. This contributes to both cost savings and sustainability in HEN design.