Mathematical Simulation Of Kinetics Of Radial Chromatography

Radial chromatography has been widely applied in biological engineering, pharmacy-engineering, chemical engineering, environmental engineering and food engineering in recent years. The research on kinetics of radial chromatography was focused on the analytical purpose, but few work was reported on the preparative. A mathematical model of the radial chromatography is set up in this study, based on the intraparticle surface diffusion of solid phase, the different equilibrium isotherm, the external mass transfer resistance, and the shape and size of the adsorbent.Orthogonal collocation tables for symmetric geometry and unsymmetric geometry are constructed. The mathematic model of dimensionless equations is first made discrete by orthogonal collocation method, and then solved by four-order Runge-Kutta. During the process, a proper unsymmetric orthogonal collocation table that contains an element which is closed to the ratio of the inner to the the middle cylinder radial of the column should be explored. The matrix is chosen from the table whose numbers of the elements are between 18 and 36, and the relative error is less than 5% for this process. The simulated results showed that the accuracy is satisfied.The concentration distribution of fluid phase in the column was obtained by numerical simulation, and the effect of various parameters on breakthrough curve was studied. The breakthrough time increases as Biot number, flowrate or the radial thickness of the adsorbent section increasing, and decreases as feed concentration increasing. Spheric adsorbents had the best column efficiency, while the cylindric ones are inferior and the slablike ones are the worse. If the adsorbent shapeis the same,the larger the adsorbents, the less the breakthrough time, but the slope of the breakthrough curve remains the same. High concentration part of the concentration wave moves faster than the low one, for favourable adsorption isotherm. The shape of concentration wave does not change at all from the beginning of the operation to the end. The case for the unfavourable isotherm is just opposite.