QUESTION TWO $-$ DRYING: $20$ MARKS

$2\mathrm{.}1.CaC{O}_3$ filter cake in a tray is to be dried by cross$-$circulation from the top surface. Each tray is $0\mathrm{.}082$ foot high with an area of $16\mathrm{.}15f{t}^2$ and is filled with $160\mathrm{.}9lb$ of wet filter having a water content of $30\%$ on the dry basis. The heating medium is air at $1$atm and $170F$ with a relative humidity of $10\%.$ The velocity of air passing across or parallel the wet solid is $13\mathrm{.}12f\frac{t}{s}.$ Estimate time in hours needed to reach the experimentally determined, critical moisture content of $10\%$ on dry basis. Neglect preheat period.

$(20)$