Batch Drying a Filter Cake in the First Falling Rate Region $(30$ pts$)$

Using the same filter cake and conditions from problem $33\mathrm{.}6-4$ from HW$11,$ you are to calculate

the time for drying the sample from the critical free moisture content of $0\mathrm{.}09l{b}_m{H}_2\frac{O}{l}{b}_m$ dry

solid to a final free moisture value of $0\mathrm{.}04l{b}_m{H}_2\frac{O}{l}{b}_m$ dry solid. Recall that the wet filter cake is

in a pan $1ft.x1ft.$ square and $1in.$ thick. The dry density of the cake is $120l{b}_m$ solids$/f{t}^3$ solids.

You may use results from problem $33\mathrm{.}6-4$ in your calculations here; for example

$R_C=0\mathrm{.}08284l{b}_m$ water $\frac{?}{(hr*f{t}^2)}.$

$33\mathrm{.}6-4$ Drying a Filter Cake in a Constant Rate Region $(40$ pts$)$

A wet filter cake in a pan $1ft.ft.$ square and $1in.$ thick is dried on the top surface with air at

a wet bulb temperature of $80F$ and a dry bulb temperature of $120F$ flowing parallel to the

surface at a velocity of $2\mathrm{.}5f\frac{t}{s}.$ The dry density of the cake is $120lb\frac{m}{f}{t}^3$ and the critical free

moisture content is $0\mathrm{.}09lb{H}_2\frac{O}{l}b$ dry solid. How long will it take to dry the material from a

free moisture content of $0\mathrm{.}20lb{H}_2\frac{O}{l}b$ dry material to the critical moisture content?

Ans. $t=13\mathrm{.}3hr.$