9.10. EQUATIONS FOR VARIOUS TYPES OF DRYERS

9.10A. Through-Circulation Drying in Packed Beds

For through-circulation drying, where the drying gas passes upward or downward through a bed of wet granular solids, both a constant-rate period and a falling-rate period of drying may result. Often the granular solids are arranged on a screen so that the gas passes through the screen and through the open spaces or voids between the solid particles.

1. Derivation of equations

To derive the equations for this case, no heat losses will be assumed, so the system is adiabatic. The drying will be for unbound moisture in the wet granular solids. We shall consider a bed of uniform cross-sectional area A m2, where a gas flow of G kg dry gas/h · m2 cross section ...

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