Environmental concerns and depleting resources motivate economies to become more circular and encourage engineers to re-consider plant design by enhancing internal integration. This can be achieved by designing an eco-industrial park (EIP), in which a cluster of plants are synergistically integrated for mass and energy resources. Deciding which plants to include in the cluster determines its overall performance. In terms of economic performance, this is especially challenging as raw materials, products, and utility prices continuously fluctuate on the market, which results in the overall profit of a cluster becoming variable and imposes an investment risk to consider in decision making. In this study, Modern Portfolio Theory (MPT) is adopted to guide the selection of plants to be included in a process investment portfolio, considering both integrated (clusters) and non-integrated process plants or clusters. While integrated clusters typically enable improved returns through savings of energy and mass inputs over individual, stand-alone plants, their coupling may affect variability, and therefore, the risk dimension of portfolio construction. An MPT approach is proposed, which extends a recently presented MPT approach for stand-alone plant portfolio selection to consider optimally integrated clusters of plants, which are synthesized using an optimal design method that simultaneously considers all energy and material resources of a cluster. The MPT approach determines the process plant portfolios that are most attractive for investment from a risk-return perspective and the optimum capital distribution among portfolio constituents. A case study of six plants is presented to illustrate the MPT approach. The findings show that optimal risk-return portfolios do not consist of only integrated clusters of plants (EIPs) but are often complemented by stand-alone plants contributing to portfolio stability.

环境问题和资源消耗促使经济变得更加循环，并鼓励工程师通过加强内部整合来重新考虑工厂设计。这可以通过设计一个生态工业园区 (EIP) 来实现，在该园区中，一组植物被协同整合以获取质量和能源资源。决定将哪些工厂包括在集群中决定了其整体性能。就经济表现而言，这尤其具有挑战性，因为原材料、产品和公用事业价格在市场上不断波动，导致集群的整体利润变得可变，并在决策中带来投资风险。在这项研究中，采用现代投资组合理论 (MPT) 来指导选择要包含在过程投资组合中的工厂，考虑集成（集群）和非集成过程工厂或集群。虽然集成集群通常通过在单个独立工厂上节省能源和大量投入来提高回报，但它们的耦合可能会影响可变性，从而影响投资组合构建的风险维度。提出了一种 MPT 方法，该方法扩展了最近提出的独立工厂组合选择的 MPT 方法，以考虑最佳集成的工厂集群，这些集群使用同时考虑集群的所有能源和材料资源的最优设计方法进行综合。MPT 方法从风险回报的角度和投资组合组成部分之间的最佳资本分配来确定对投资最具吸引力的加工厂投资组合。提出了六个工厂的案例研究来说明 MPT 方法。研究结果表明，最佳风险回报投资组合不仅由综合工厂集群 (EIP) 组成，而且通常由有助于投资组合稳定性的独立工厂补充。