A rotary dryer fired with bunker oil having HHV = 10, 000 kcal/kg is to produce 20 MT/hr of dried sand with 0.5% moisture from wet feed containing 7% moisture. Specific heat of sand is 0.21 BTU/lb-F. Temperature of wet sand is 30 C and temperature of dried product is 115 C. Assume inlet air relative humidity, RH1 = 50 % and outlet air relative humidity, RH3 = 100 %, calculate the mass flow rate of dry air required in the dryer in kg/hr,