技術論文とプレゼンテーション

This work presents a numerical proof of concept for the model-based optimal control of a gas chromatography separation process using COMSOL Multiphysics. The objective is to enhance the temporal separation of two gaseous species, denoted A and B, initially injected as a mixed sample at the inlet of a capillary chromatographic column.

Owing to the large aspect ratio of the capillary column, the process is described by a one-dimensional model along the axial direction. The transport of each species in the carrier gas is governed by an advection-dominated transport equation, with axial diffusion included when relevant. These equations are coupled with adsorption–desorption kinetic equations describing the exchange of mass between the mobile gas phase and the stationary phase located at the column wall.

The separation mechanism relies on the different retention behaviours of the two species. The control variables are the carrier gas velocity and the temperature programme applied to the column. Their role is to favour the preferential retention of species B in the stationary phase, while species A remains mainly in the mobile phase and is transported first towards the detector. The subsequent modification of the operating conditions promotes the release of species B, which is then transported towards the detector with a controlled delay.

An optimisation procedure was developed to determine the time-dependent control laws. The cost function is formulated to increase the separation between the outlet concentration peaks of species A and B, reduce peak overlap, and penalise excessive variations of the control variables or deviations from prescribed operating constraints. The resulting optimal control problem couples the chromatographic transport model, adsorption–desorption dynamics, and detector response.

The proposed approach illustrates how COMSOL Multiphysics can be used to combine transport phenomena, surface interactions, and optimisation tools for the analysis and improvement of controlled chromatographic systems. The optimised strategy is intended to be assessed by comparing the outlet chromatograms obtained with and without control, with the aim of demonstrating delayed elution of species B and reduced overlap between the two species.