Abstract

VERDUZCO-MORA, L.A.; MARTINEZ-VERA, C.  and  VIZCARRA-MENDOZA, M.G.. Hydrodynamic study of a continuous multistage fluidized bed dryer with downcomers. Rev. Mex. Ing. Quím [online]. 2015, vol.14, n.2, pp.467-479. ISSN 1665-2738.

In this work a multistage continuous fluidized bed drier provided with downcomers with a conical reduction at their bottom was characterized hydrodynamically. The solids to be dried were silica gel particles. The stable operation zone (SOZ) and the solid's residence time distribution (RTD) were determined. The SOZ is a function of the solids and air flows and the free area in the conical reduction. The range of values of these variables for which the column operation lies in the SOZ was determined. It was found from the analysis of the RTD of the solids in the column that the solid's flow pattern in it can be represented adequately by the series of perfectly stirred tanks model and that this pattern tends to piston flow as the number of stages increases. A statistical model for the total pressure drop (ΔP_total) in the multistage dryer was obtained employing the surface response technique and taking as variables the number of stages (N), the ratio of the downcomer length to column diameter (L/D) and the temperature of the air fed to the dryer (T). This model represents adequately the observed variability of the total pressure drop and can be employed as a predictive tool.

Keywords : hydrodynamics; downcomers; fluidization; multistage drier; residence time distribution.

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