A three$-$stage flash unit is being operated in a plant. The feed enters flash drum $2($FD$2).$ The vapour

from FD$2$ is cooled to a two$-$phase mixture and flashed in FD$1.$ The vapour from FD$1$ is taken out as a

product, while the liquid from FD$1$ is heated to the operating temperature of FD$2$ and returned to FD$2.$

The liquid from FD$2$ is heated to a two$-$phase mixture and introduced into FD$3.$ The liquid stream from

FD$3$ is taken out as a product, while the vapour from FD$3$ is cooled to the operating temperature of FD$2$

and returned to FD$2.$

The feed is $100k\frac{g}{h}$ liquid containing $40\%$ ethanol and the rest being water. This feed is heated to

$87C$ and enters FD$2.$ The flow rate and the composition of the vapour stream leaving stage $1$ is $50$

$k\frac{g}{h}$ and $0\mathrm{.}75,$ respectively. All the flash units are operating at $1k\frac{g}{c}{m}^2.$ Based on this information

calculate the following: a$)$ Sketch the process. $[6$ points$]$

b$)$ What is the operating temperature of stages $1$ and $3?[15$ points$]$

c$)$ The flow rates and compositions of all streams leaving the three stages. $[15$ points$]($By hand please$)$ A three$-$stage flash unit is being operated in a plant. The feed enters flash drum $2($FD$2).$ The vapour from FD$2$ is cooled to a two$-$phase mixture and flashed in FD$1.$ The vapour from FD$1$ is taken out as a product, while the liquid from FD$1$ is heated to the operating temperature of FD$2$ and returned to FD$2.$ The liquid from FD$2$ is heated to a two$-$phase mixture and introduced into FD$3.$ The liquid stream from FD$3$ is taken out as a product, while the vapour from FD$3$ is cooled to the operating temperature of FD$2$ and returned to FD$2.$ The feed is $100$ kg$/$h liquid containing $40\%$ ethanol and the rest being water. This feed is heated to $87\backslash$deg C and enters FD$2.$ The flow rate and the composition of the vapour stream leaving stage $1$ is $50$ kg$/$h and $0\mathrm{.}75,$ respectively. All the flash units are operating at $1$ kg$/$cm$2$ Calculate the following: a$)$ Sketch the process. b$)$ What is the operating temperature of stages $1$ and $3?$ c$)$ The flow rates and compositions of all streams leaving the three stages$\mathrm{.}600600500$ Dax$-$line, Iko$/$sg$.$ cm$.300$ Auxiliary Line for Interpolating Equilibrium Compositions $400400$ Enthalpy, K COU Kg$.300300\mathrm{.}6693948990962\mathrm{.}187$&s $78//77\mathrm{.}65\backslash$deg C $77899192200-889868285784\backslash$deg $83\backslash$deg $20080\mathrm{.}59$ Isothermal lid vine $80\backslash$deg C$.$ Composition $100100$ GA TOO Boiling Ling $1$K $/$ s$$ cm$.8604020$ Watar $0\backslash$deg C Liquid Freezing Line $-20$ Solid Ica $0\backslash$deg C $-1000$ HO $-100010\mathrm{.}20\mathrm{.}70\mathrm{.}80\mathrm{.}90\mathrm{.}3040\mathrm{.}50\mathrm{.}6$ Concentration of Alcohol, Weight Fraction $$