Phenomena-Based Graph Representations and Applications to Chemical Process Simulation

Rapid and robust simulation of chemical production processes is critical to address core scientific questions related to process design, optimization, and sustainability. Efficiently solving a chemical process, however, remains a challenge due to their highly coupled and nonlinear nature. Graph abstractions of the underlying physical phenomena within unit operations may help identify potential avenues to systematically reformulate the network of equations and enable more robust convergence of flowsheets. To this end, we further refined a flowsheet graph-theoretic abstraction that consists of a mesh of interconnected variable nodes and equation nodes. The new network of equations is formulated at the phenomenological level�agnostic to the thermodynamic property package�by extending equation formulations widely used to solve multistage equilibrium columns. Decomposition of the graph by phenomena linearizes material and energy balances across the flowsheet by decoupling phenomenological nonlinearities (e.g., phase equilibrium, chemical reactions). Additionally, we further improved a preliminary simulation algorithm which employs this phenomena-based decomposition and demonstrated that it can perform more rapid and robust simulation of large, highly-coupled systems than sequential modular simulation.