$14\mathrm{.}5.$ A paper mill producing $300$ tons of pulp per $24$ hr by the magnesium sulfite

process concentrates a $12$ per cent waste liquor to $55$ per cent in a quintuple$-$effect

long$-$tube evaporator. The solution entering the last two effects in parallel at $135$

is evaporated by $45$ psig saturated steam. Assume the following: $($a$)$ Feed contains

$2800$ lb total solids per ton pulp produced; $($b$)$ first effect is divided into two parallel

bodies of $4500$ and $7000f{t}^2,$ respectively; $($c$)$ water is available at $75F$; $($d$)$ vacuum

in the last$-$effect vapor body is $26in.$Hg ; $($e$)7F$ water approach to condenser satura$-$

tion temperature; $(f)$ BPR is $18,16,13,10,5,7F,$ respectively, for all bodies; $(g)$

product from first effect is flashed to fourth$-$effect steam chest; $(h)$ vapor condensate

flashes between effects.

Find $($a$)$ material and heat balance for the evaporator, $($b$)$ total water required $($gal$-$

lons per minute$),($c$)$ the total surface required, $($d$)$ steam economy of the evaporator.