Through-Circulation Drying in the Constant-Rate Period. Spherical wet catalyst pellets having a diameter of 12.7 mm are being dried in a through-circulation dryer. The pellets are in a bed 63.5 mm thick on a screen. The solids are being dried by air entering with a superficial velocity of 0.914 m/s at 82.2°C and with a humidity H = 0.01 kg H2O/kg dry air. The dry-solid density is determined as 1522 kg/m3, and the void fraction in the bed is 0.35. The initial free moisture content is 0.90 kg H2O/kg solid and the solids are to be dried to a free moisture content of 0.45, which is above the critical free moisture content. Calculate the time for drying in this constant-rate period.