Ten thousand lb/h of wet sand at 70oF with a moisture content of 20% (dry basis) is to be dried to a moisture content of 5% (dry basis) in a continuous, fluidized-bed dryer operating at a pressure of 1 atm in the free-board region above the bed. The sand has a narrow size range, with an average particle size of 500 μm; a sphericity, ϕs, of 0.67; and a particle density of 2.6 g/cm3 . When the sand bed is dry, its void fraction, ϵb, is 0.55. Fluidizing air will enter the bed at a temperature of 1,000oF with a humidity of 0.01 lb H2O/lb dry air. The adiabatic-saturation temperature is estimated to be 145oF. Batch pilot-plant tests with a fluidization velocity of twice the minimum show that drying takes place in the constant-rate period and that all moisture can be removed in 8 minutes using air at the same conditions and with a bed temperature of 145oF. Determine the bed height and diameter for the large, continuous unit
Ten thousand lb/h of wet sand at 70oF with a moisture content of 20% (dry basis) is to be dried to a moisture content of 5% (dry basis) in a continuous, fluidized-bed dryer operating at a pressure of 1 atm in the free-board region above the bed. The sand has a narrow size range, with an average particle size of 500 μm; a sphericity, ϕs, of 0.67; and a particle density of 2.6 g/cm3 . When the sand bed is dry, its void fraction, ϵb, is 0.55. Fluidizing air will enter the bed at a temperature of 1,000oF with a humidity of 0.01 lb H2O/lb dry air. The adiabatic-saturation temperature is estimated to be 145oF. Batch pilot-plant tests with a fluidization velocity of twice the minimum show that drying takes place in the constant-rate period and that all moisture can be removed in 8 minutes using air at the same conditions and with a bed temperature of 145oF. Determine the bed height and diameter for the large, continuous unit
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