The P-graph Framework: A Tool for Solving Process Network Synthesis and Similar Styled Problems through Rigorous Superstructure Development and Combinatorial Algorithms
A process network can be characterized as an arrangement of unit operations; whose sole purpose is the conversion of a set of raw materials to a desired product. Process network synthesis (PNS), on the other hand, involves identifying the optimum network that is most favorable in achieving the desired outcome. This outcome is given by an objective function which could range from minimizing the cost of the process to maximizing the throughput. The two main strategies utilized in tackling PNS problems, are heuristic and algorithmic methodologies, both of which offer their own unique advantages and disadvantages. With a heuristic approach, decisions are made based on human experiences and observations, thus limiting its effective application to that at a local level. Algorithmic approaches are able to handle more complex problems; however, they require excessive time and specialized skills in developing the computational model. Both the heuristic and algorithmic methods share one disadvantage in common, being that when the optimal solution is determined, it is unclear if all alternatives have been considered. The P-graph framework was specifically developed to address PNS problems through the use of combinatorial optimization. In this way, the framework is able to guarantee that all possible solution structures within a superstructure are considered. The P-graph is able to handle complex problems with a reduction in human error and computational time. Albeit initially developed for PNS problems, the applications of this framework have been diverse, ranging from process optimization, the identification of reaction pathway mechanisms, separation network synthesis, resource planning and the development of efficient supply chains, among other applications. In order to facilitate the use of the P-graph, various software platforms have been developed, some of which provide a graphical user interface (GUI) to allow for ease of operation, and to extend the use of this framework beyond the process field. This article provides a review of the P-graph framework, in terms of its development and its applications. Furthermore, derivatives of the P-graph will be highlighted and discussed. Attention will be drawn to the shortcomings of the P-graph, and possible future opportunities to address these shortcomings will be ventured into.
Keywords - P-graph, Review, Framework, Process Network Synthesis, Optimization.