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Instability is a severe barrier to the successful development and evolution of industrial symbiosis systems. In this paper, a novel approach for stability analysis of industrial symbiosis systems is proposed. Two parameters (symbiosis profit and symbiosis cost) are defined on the basis of profit consideration. With the introduction of asymmetric distribution coefficient as a quantitative index, the distribution of symbiosis cost and symbiosis profit can be analyzed. An illustrative example demonstrates that the approach can be used to assess the stability of a hypothetical coal-based symbiosis system under different states. Specifically, the impact of changes in the system structure and external environment on the stability of the coal-based symbiosis system is investigated. The results confirm the practical applicability and effectiveness of the proposed approach.

In the oil refining and petrochemical industry, hydrogen flows in so-called hydrogen networks are a common feature. A practical problem in hydrogen network analysis is to identify the minimum fresh hydrogen input flowrate to ensure that the hydrogen streams produced by combining the flows of internal sources satisfy certain concentration specifications of sinks for hydrogen and impurities such as H2S. To tackle this problem, this paper presents a novel graphical procedure, much inspired by the pioneering work of Shelley and El-Halwagi (2000) that makes use of the unique features of ternary composition diagram for three-component systems. In addition, accounting for constraints on flowrates inside a ternary visualization diagram is another novel aspect of this graphical method. Two literature case studies based on hydrogen systems with multiple impurities are solved to illustrate the effectiveness and elegance of the proposed method.

Hydrogenation units are often operated at high pressure, requiring the use of compressors which are one of the most expensive chemical processing equipment. Optimizing a hydrogen network should therefore take into consideration not only purity and flowrate constraints but also pressure requirements. In this paper, based on the hydrogen surplus diagram approach, the average pressure profiles of hydrogen sources and sinks are proposed through the introduction of a system’s minimum pressure drop Δp. Combined with the traditional purity profiles, whether a source can meet a sink either for hydrogen concentration or for pressure requirements can be determined intuitively. In cases where the pressure of a source is not sufficient for a sink, installing a hydrogen compressor or using another source with higher purity and pressure could be potential solutions. A cost equation is established to determine which of the two solutions is economically more viable. For different matching situations between sources and sinks, strategies for optimum placement of compression equipment within a given hydrogen network are proposed. A case study is used to illustrate the application and effectiveness of the proposed method.