ChE$334$

CW $8$

$95\%$ of the acetone vapor in an $85$vol$\%$ air stream is to be absorbed by countercurrent contact with a stream of pure water in a valve$-$tray column with an expected overall tray efficiency $30\%.$ The column will operate essentially at $20C$ and $101$kPa pressure. Equilibrium data for acetone$-$water at these conditions are:

$\backslash$table$[[$Mole percent acetone in water,$1\mathrm{.}51,3\mathrm{.}15,4\mathrm{.}96,7\mathrm{.}02,9\mathrm{.}45,12\mathrm{.}60,18\mathrm{.}77],[$Acetone partial pressure in air, torr,$15,30,45,60,75,90,105]]$

Calculate:

a$)$ Minimum value of $\frac{L^{\text{'}}}{G^{\text{'}}},$ the ratio of moles of water per mole of air.

b$)$ The number of equilibrium stages required, using a value of $\frac{L^{\text{'}}}{G^{\text{'}}}$ of $1\mathrm{.}25$ times the minimum.