Air Recirculation in a Continuous Dryer. The wet feed material to a continuous dryer contains 50 wt % water on a wet basis and is dried to 27 wt % by countercurrent air flow. The dried product leaves at the rate of 907.2 kg/h. Fresh air to the system is at 25.6°C and has a humidity of H = 0.007 kg H2O/kg dry air. The moist air leaves the dryer at 37.8°C and H = 0.020, and part of it is recirculated and mixed with the fresh air before entering a heater.
The heated mixed air enters the dryer at 65.6°C and H = 0.010. The solid enters at 26.7°C and leaves at 26.7°C. Calculate the fresh-air flow, the percent air leaving the dryer that is recycled, the heat added in the heater, and the heat loss from the dryer.
