First-Principles Process Engineering Modeling: A Review from a Practitioner’s Perspective

Process models are mathematical representations of selected behaviors and properties of a system. Their formulation defines the model’s mathematical structure and enables the mapping of input variables to output variables. Over recent decades, various approaches have been developed and applied in process modeling. These are broadly categorized into First-Principles Models (FPMs) and Data-Driven Models (DDMs). This paper focuses on FPMs while acknowledging the complementary role of DDMs. It emphasizes that first-principles form the foundational basis of process modeling, while recognizing that other techniques can enhance accuracy and, in some cases, be essential to model development. Flowsheet modeling and the application of conservation laws and constitutive equations are reviewed. As both approaches require a solid understanding of first-principles and constitutive relationships, these topics are discussed with annotations informed by practical experience. The paper also outlines core competencies considered essential for process modeling practitioners, encompassing both numerical and domain-specific expertise.