Estimation of transport rate coefficients in packed beds of porous particles

Abstract

When an adsorbable gas was passed through a packed bed of porous particles, estimation methods of extracting the system parameters from its chromatographic adsorption data were investigated. Using the chromatographic pulse technique with ethane as a tracer, elution curves were obtained by varying the radius of packed silica gel particles and carrier stream velocities. From these elution curves, five system parameters contained in the model equations, that is, effective diffusivity, axial dispersion coefficient, mass transfer coefficient, adsorption rate constant and adsorption equilibrium constant were determined by means of the moment method. Though Fourier analysis was applied to a single experimental curve selected from several elution curves, the system parameters could not be obtained because of the countless local minimums and interaction between parameters. Parameter estimation using the Fourier analysis was carried out for the hypothetical experimental curve which was generated by inserting the known parameter values into the model equations. A large number of local minimums and interaction between parameters were also observed as before, so the parameters could not be obtained. Optimum system parameters could not be extracted with the Fourier analysis method, since the response surface was not unimodal and the parameters to be evaluated did not have a significant influence on determining the nature of the elution curve.