Control of Temperature Distribution in a Supercritical Gas Extraction Tower

Abstract

The control scheme recently proposed by the authors is applied to the control of axial temperature distribution in a bench-scale supercritical-gas extractor. The extraction unit is constructed from a packed column of 3 m length covered by a coaxial cylindrical casing. Although the actual structure of the extractor is very complicated, it is modeled by a simple double-pipe and therefore its mathematical model becomes a pair of partial differential equations. The models are reduced to lumped parameter systems with a finite dimension by use of the finite Fourier transform technique. The controller is designed on the basis of the reduced model. Extended Kalman filter is used to estimate simultaneously the state variables and unknown parameters. The results demonstrate that both the state estimation and the controller performance are satisfactory. This implies that the control scheme is very robust in spite of the incompleteness of the model used. © 1988, The Society of Chemical Engineers, Japan. All rights reserved.