ANALYSIS OF A ONE-DIMENSIONAL FLUID DYNAMIC-MODEL FOR DILUTE GAS-SOLID FLOW IN A PNEUMATIC DRYER WITH A SPOUTED BED TYPE SOLID FEEDING SYSTEM

The pneumatic bed with a spouted bed type solid feeding system reporte d by Ferreira and Freire (1992) allows stable solids conveying in a wi de range of solids flowrates. This is being developed with the aim to dry products with high initial moisture contents. A one-dimensional mo del based on continuity and momentum balances is used to describe non- accelerating gas-solids flow and to predict pressure gradient data. Ex perimental data were obtained for the transport of glass spheres (d(p) =1.00 to 2.85 mm) in galvanized iron pipes of four different diameters (D-t=53.4 to 148.0 mm). Good predictions for the pressure gradients w ere obtained from the model. Estimated values of the solid-fluid inter action forces and slip velocities, however, were often not physically consistent. This result leads to the conclusion that the one-dimension al model does not provide a good description of the physical phenomena and flow pattern involved in dilute pneumatic vertical transport.