HYDRODYNAMICS OF SAWDUST AND MIXTURES OF WOOD RESIDUES IN CONICAL SPOUTED BEDS

It has been proven that conical spouted beds allow for stable operation with sawdust and with wood residues, even with mixtures of these materials of wide particle size range and without being diluted with an inert solid. Peculiar hydrodynamic characteristics for sawdust have been observed; a great hysteresis in the pressure drop vs velocity curve, a pronounced peak of maximum pressure drop, and a difference between the velocity for which spout and fountain are formed and the velocity of the fully spouted bed. From the hydrodynamic study of sawdust, the ranges of the contact or geometric factors (cone angle, inlet diameter/base diameter ratio, inlet diameter/particle diameter ratio) for which operation is stable have been determined. Original correlations for calculation of minimum spouting velocity, of stable operation pressure drop, of maximum pressure drop, and of minimum voidage of complete spouting have been proposed.