(165e) Predicting the Particle Mass Flowrate in the Draft Tube of a Draft Tube Spout-Fluid Bed

The draft tube spout-fluid bed (DTSFB) is an extremely versatile fluid-particle system which allows designs that can be widely applied industrially. With the availability of today's data acquisition and control hardware elements (plug in boards) combined with extremely flexible, versatile and powerful software packages, practical engineering processes using the DTSFB can be fully automated using powerful and inexpensive personal computers (PC's). Selection of the important variables and parameters needed for prediction and control of the particle mass flowrate in the draft tube is based in this paper on a mathematical model, the inlet section mass balance and on an understanding of the basic principles of operation of the DTSFB. Unlike ordinary spouted or fluidized beds, the particle mass flowrate in the DTSFB is not fixed by the total fluid mass flowrate entering the bed. In the DTSFB, the particle and fluid mass flowrates can be independently varied. The magnitude of the particle mass flowrate is sensitive to changes in the draft tube spacing and the auxiliary fluid flowrate . A 3 x 3 Jacobian matrix maps changes in the inlet section variables with corresponding ones in the draft tube section . The elements of that matrix are evaluated using the Grbavèiæ et al (1992a,b) model and data for hydraulic transport, and show the sensitivity of the draft tube variables to changes in those for the inlet section. It will be shown that the particle mass flowrate in the draft tube can be controlled by manipulating the inlet section variables Faxo and Fjo when is fixed as it normally is in applications. The powerful effect of will also be shown. References Grbavèiæ, ?. B., D. V. Vukoviæ, S. Dj. Jovanoviæ, R. V. Gariæ, Dz. E. Had?ismajloviæ, H. Littman and M. H. Morgan III, Can. J. Chem. Eng. 70 895-904 (1992a). Grbavèiæ, ?. B., R. V. Gariæ, D. V. Vukoviæ, Dz. E. Had?ismajloviæ, H. Littman, M. H. Morgan III and S. Dj. Jovanoviæ, Powder Technology 72, 183-91 (1992b). Nomenclature Faxo - inlet auxiliary fluid mass flowrate Fd - fluid mass flowrate in draft tube Fjo - inlet jet fluid mass flowrate elsubt - length of inlet section -dPd/dz - pressure gradient in draft tube 1 - epsilon - solids fraction in draft tube