Balance for a Direct-Heat Dryer. A continuous, cocurrent-flow direct-heat dryer is to be used to dry

Balance for a Direct-Heat Dryer. A continuous, cocurrent-flow direct-heat dryer is to be used to dry crystals of Epsom salt (magnesium sulfate heptahydrate). The feed to the dryer, a filter cake from a rotary, vacuum filter, is 2,854 lb/h of crystals (dry basis) with a moisture content of 25.8 wt% (dry basis) at 85°F and 14.7 psia. Air enters at 14.7 psia, with dry-bulb and wet-bulb temperatures of 250°F and 117°F. The final moisture content of the dried crystals is to be 1.5 wt% (dry basis), at no more than 118°F to prevent decomposition of the heptahydrate (see Figure 17.2). Determine: (a)

Balance for a Direct-Heat Dryer. A continuous, cocurrent-flow direct-heat dryer is to be used to dry crystals of Epsom salt (magnesium sulfate heptahydrate). The feed to the dryer, a filter cake from a rotary, vacuum filter, is 2,854 lb/h of crystals (dry basis) with a moisture content of 25.8 wt% (dry basis) at 85°F and 14.7 psia. Air enters at 14.7 psia, with dry-bulb and wet-bulb temperatures of 250°F and 117°F. The final moisture content of the dried crystals is to be 1.5 wt% (dry basis), at no more than 118°F to prevent decomposition of the heptahydrate (see Figure 17.2). Determine: (a) rate of moisture evaporation, (b) outlet temperature of the air, (c) rate of heat transfer, and (d) entering air flow rate. The average specific heat of Epsom salt is 0.361 Btu/lb-°F.