Interesting Dynamics in Azeotropic Distillation Systems

Abstract

In spite of significant nonlinearities even in the simplest model, some types of steadystate and dynamic behavior common for nonlinear systems have never been associated with distillation columns. In recent years, multiplicity of steady states has been a subject of much research and is now widely accepted. Subsequently, stability of steady states has been explored. Another phenomenon that, although widely observed in chemical reactors, has not yet been associated with models of distillation columns is the existence of periodic oscillations.In this article we study the steady-state and dynamic behavior of the azeotropic distillation of the ternary homogeneous system methanol-methyl butyrate-toluene. Our simulations reveal nonlinear behavior not reported in earlier studies. Under certain conditions, the open-loop distillation system shows a “sustained” oscillation associated with branching to periodic solutions. The limit cycles are accompanied by traveling waves inside the column. Significant underdamped oscillations are also observed over a wide range of product rates. To our knowledge, this is the first simulation result reporting the presence of Hopf bifurcation points in open-loop distillation models.