An equation-based batch distillation simulation to evaluate the effect of multiplicities in thermodynamic activity coefficients

TL;DR

This paper develops a rigorous simulation of batch distillation based on MESH equations to analyze how multiplicities in activity coefficients affect process dynamics, revealing that different parameters can lead to distinguishable profiles.

Contribution

The paper introduces a novel index reduction method transforming an index-2 system into an index-1 system for more accurate batch distillation simulation.

Findings

Alternative NRTL parameters can produce distinguishable distillation profiles.

The new simulation approach clarifies the impact of activity coefficient multiplicities.

Dynamic differences arise even when activity coefficients and VLE diagrams are similar.

Abstract

In this paper, we investigate the influence of multiplicities in activity coefficients on batch distillation processes. In order to do so, we develop a rigorous simulation of batch distillation processes based on the MESH equations. In particular, we propose a novel index reduction method to transform the original index-$2$ system into a well-posed differential-algebraic system of index $1$. With the help of this simulation, we then explore whether the alternative NRTL parameters, which yield indistinguishable activity coefficients and VLE diagrams when compared to the reference data, can produce distinguishable profiles in dynamic simulations. As it turns out, this can happen in general and we explain the reasons behind the dynamic distinguishability.