Entropy Production Minimization as Design Principle for Membrane Systems: Comparing Equipartition Results to Numerical Optima

Entropy production minimization procedures presented in literature show that under different assumptions the optimal solution might be characterized by different thermodynamic quantities being constant. These constant quantities might be the local entropy production, the thermodynamic driving forces, the thermodynamic speed, or the thermodynamic length. After presenting the assumptions made in the different derivations, we use the results as design principles to reduce entropy production in a membrane unit for CO2 separation from natural gas, and we compare them to the numerically determined optimum. For a continuous process, we consider the equipartition of forces (EoF), the equipartition of entropy production (EoEP), and the equal thermodynamic speed (ETS) results. When we can independently control all driving forces, the numerical optimum and EoEP coincide. Even though EoF and ETS differ from the optimum, they approximate it well. When the transport coefficients are constant, EoF follows from EoEP. If ...