Effect of Time-Scale Assumptions on Process Models and Their Reconciliation

Traditionally, models are generated building on macroscopic field theory substituting as much of the transformations as possible with the aim to generate models of sets of ordinary differential equations when ever possible. Today, computer programs are available solving Differential Algebraic Equations (DAEs) efficiently rendering most of the algebraic substitutions unnecessary. Our Modeller tool builds models on the fundamental principles, namely the conservation of extensive quantities, and adds the flows, reactions, state variable transformations and properties as algebraic equations. Unknown flows and unknown kinetics are substituted with additional information such as equilibria information. We show that the thereby introduced index problem can be resolved through local model reduction. The resulting model is always a DAE of index 1 and guaranteed structurally solvable.