SLURRY DRYING IN GAS-PARTICLE CONTACTORS - FLUID-DYNAMICS AND CAPACITY ANALYSIS

The fluid-dynamic characteristics and evaporation capacities of severa l substrates (pure water, a mixture of water and carbohydrates, and ap ple pulps with maltodextrines) for conical spouted bed, fluidized bed and pneumatic dryers was compared. For fluidized and spouted beds, the presence of fluids increased the fluid-dynamics parameters over the v alues when only inert particles were present in the beds. In both case s it was proposed correlations to predict those effects. In the spoute d bed drier, increasing the load of inert particles resulted in a slig ht increase of the water evaporation capacity, while in the fluidized bed drier the effect was more marked. For fluidized and spouted beds, under similar operation conditions, the maximums of the suspension dry ing capacities are lower than the values of water evaporation, but for pneumatic drying this effect was the opposite. In general terms, the maximal capacities of fluidized bed dryers are higher than those obser ved in the spouted bed dryers.