Thermodynamics and chemical systems stability: The CSTR case study revisited

This paper is dedicated to the stability analysis of the Continuous Stirred Tank Reactor (CSTR) model by considering thermodynamics based arguments. Different Lyapunov function candidates related to the thermodynamics, more specifically based on the entropy, the entropy production and the internal energy, are considered. These provide new insight and physical interpretation in the stability/instability of the equilibrium points of the CSTR. This includes in particular extension of the results of Georgakis [C. Georgakis, On the use of extensive variables in process dynamics and control, Chemical Engineering Science 41(6) (1986) 1471–1484] for less restrictive conditions on the system dynamics and thermodynamics, and invariants sets for the stable equilibrium points of the CSTR by considering an internal energy based Lyapunov function.