Design of a Countercurrent Adiabatic Rotary Dryer.

Fluorspar $)$ is to be dried from $10\%$ to $0\mathrm{.}2\%$

moisture $($dry basis$)$ in a countercurrent adiabatic

rotary dryer at a rate of $12,000k\frac{g}{h}r$ of wet

solids. The heating air enters at $500C,$ a humidity

of $0\mathrm{.}03kg$ water per $kg$ of dry air, and a wet$-$bulb

temperature of $60C.$ The solids have a specific

heat of $0\mathrm{.}48$kca$\frac{l}{k}g-C($dry basis$),$ enter the

dryer at $40C$ and leave at $85C.$ The maximum

allowable mass velocity of the air is $11,500kg/$hr$-$m$2$

$m^2$ on a dry basis. Draw a schematic of the dryer showing

all the problem data and design the dryer using a

reasonable approach temperature. Report the required air

rate and the length and diameter of the dryer. Check if the

length$-$to$-$diameter ratio is reasonable. State all assumptions.