NAME:

$(30$p$)1.$ A filtration test was carried out, with a particular product slurry, on a laboratory filter press under

a constant pressure drop of $55$kPa. The area of the laboratory filter was $0\mathrm{.}24m^2$ and the filtrate viscosity is

$3\mathrm{.}6cp.$ The suspension concentration is $21\mathrm{.}4kg$ solid$/m^3$ filtrate. Filtration equation given below was

obtained for this process.

$\frac{t}{V}=105\mathrm{.}5{10}^{4}V+2273$

where $t$ is in $s,$ and $V$ is volume of filtrate in $m^3.$

a$)$ Calculate the specific cake resistance and the resistance of the filter medium.

b$)$ The same suspension given above is to be filtered in a filter press with area $12\mathrm{.}56m^2.$ The same

pressure will be used in constant pressure filtration. Assuming the same filter cake properties and

filter cloth, calculate the time to recover $2\mathrm{.}6m^3$ of filtrate.

c$)$ After filtration process $($obtaining $2\mathrm{.}6m^3$ filtrate$),$ the cake is to be washed with $0\mathrm{.}35m^3$ of water.

Calculate the time required for washing.

d$)$ Considering the conditions given in part $($b$)$ calculate the time to recover $2\mathrm{.}6m^3$ of filtrate for

continuous filtration $($the resistance of the filter medium is negligible$).$

e$)$ Assume that filtration process given in part $($b$)$ is carried out at constant rate filtration $($dV$/$dt is

constant$).$ The specific cake resistance is independent of pressure. If the filtration is run at a

constant rate of $4\mathrm{.}8$ liters $\frac{?}{s},$ how long will it take to reach $290$kPa.

$(20$p$)2.$ An agitated vessel with a centrally located flat blade disk turbine agitator having a diameter of $1$

$m$ is required to disperse gas in a fruit juice $(=1\mathrm{.}35{10}^{-3}(Pa).s,=985\frac{kg}{m^3})$ of properties similar to those

of water. The tank will be $3m$ diameter and depth of the liquid $($height of the tank$)$ is equal to tank

diameter. A power level of $0\mathrm{.}78k\frac{W}{m^3}$ is chosen. Assuming fully turbulent conditions $(NRe>{10}^4)$ and the

presence of the gas does not significantly affect the relation between the Power and Reynolds numbers.

For this agitation system answer the following questions:

For calculations use curve $1$ in the figure given below

a$)$ What power will be required by the impeller?

b$)$ At what speed should the impeller will be driven?