Page 107 - Separation process engineering

drum operates at 400 kPa, what is the highest temperature at which the flash drum can operate and
still have vapor and liquid present? Use the DePriester chart for equilibrium.
D5. We have a feed that is a binary mixture of methanol and water (55.0 mol% methanol) that is sent

to a system of two flash drums hooked together. The vapor from the first drum is cooled, which
partially condenses the vapor, and then is fed to the second flash drum. Both drums operate at a
pressure of 1.0 atm and are adiabatic. The feed rate to the first drum is 1000 kmol/h. We desire a
liquid product from the first drum that is 30.0 mol% methanol (x = 0.30). The second drum
1
operates at a fraction vaporized of (V/F) = 0.25. The equilibrium data are in Table 2-7.
2
a. Sketch the process labeling the different streams.

b. Find the following for the first drum: vapor mole fraction y , fraction vaporized (V/F) , and
1
1
vapor flow rate V .
1
c. Find the following for the second drum: vapor mole fraction y , liquid mole fraction x , and
2
2
vapor flow rate V .
2
D6. A feed that is 45.0 mol% n-butane, 35.0 mol% n-pentane, and 20.0 mol% n-hexane is fed at a rate
of 1.0 kmol/min to a flash drum operating at 50°C and 200 kPa. Find V/F, liquid mole fractions
and vapor mole fractions. Use the DePriester charts.

D7. A flash drum is separating methane from propane at 0°C and 2500 kPa. The feed is 30.0 mol%
methane and 70.0 mol% propane. Find V/F, y and x. Use the results of Problem 2.C2. Use the
DePriester chart for K values.
D8.* You want to flash a mixture with a drum pressure of 2 atm and a drum temperature of 25°C. The

feed is 2000 kmol/h. The feed is 5 mol% methane, 10 mol% propane, and the rest n-hexane. Find
the fraction vaporized, vapor mole fractions, liquid mole fractions, and vapor and liquid flow
rates. Use DePriester charts.
D9.* We wish to flash distill an ethanol-water mixture that is 30 wt % ethanol and has a feed flow of
2
1000 kg/h. Feed is at 200°C. The flash drum operates at a pressure of 1 kg/cm . Find: T drum , wt
frac of liquid and vapor products, and liquid and vapor flow rates.

D10. We have a mixture that is 35 mol% n-butane with unknown amounts of propane and n-hexane. We
are able to operate a flash drum at 400 kPa and 70°C with x = 0.7. Find the mole fraction of n-
C6
hexane in the feed, z , and the value of V/F.
C6
D11. A vapor stream which is 40.0 mol% ethanol and 60.0 mol% water is partially condensed and
sent to a flash drum operating at 1.0 atm.

a. What is the highest vapor mole fraction which can be produced?
b. If 60.0 % of the feed is liquefied, what are the outlet mole fractions of liquid and vapor?

D12. Find the dimensions (h and D) for a horizontal flash drum for Problem 2.D1c. Use h /D = 4.
total total
D13. The phenol-cresol system has an approximately constant relative volatility at α = 1.76. Phenol
p–c