A direct-heat, countercurrent-flow, rotary dryer with a 6-ft diameter and 60-ft length is available to dry titanium dioxide particles at 70°F and 1 atm with a moisture content of 30% (dry basis) to a moisture content of 2% (dry basis). Hot air is available at 400°F with a humidity of 0.015 lb/lb dry air. Experiments show that an air-mass velocity of 500 lb/h-ft2 will not cause serious dusting. The specific heat of solid titanium dioxide is 0.165 Btu/lb-oF, and its true density is 240 lb/ft3. Determine:

(a) A reasonable production rate in lb/h of dry titanium dioxide (dry basis).

(b) The heat-transfer rate in Btu/h.

(c) A reasonable air rate in lb/h (dry basis).

(d) Reasonable values for the exit air and exit solids temperatures.