Page 112 - Separation process engineering

F3.* (Long Problem!) We wish to flash distill a mixture that is 0.517 mole fraction propane, 0.091
mole fraction n-pentane, and 0.392 mole fraction n-octane. The feed rate is 100 kmol/h. The feed
to the flash drum is at 95°C. The flash drum will operate at 250 kPa. Find the drum temperature,
the value of V/F, and the mole fractions of each component in the liquid and vapor products.
Converge |ΔT drum | to < 0.20°C.

F4. We wish to do a flash distillation of 10 kmol/h of a feed that is 25 mol% water and and 75 mol%
n-propanol. The flash chamber is at 1.0 atm and is adiabatic. We vaporize 40% of the feed in the
flash chamber. Find the flow rates of the liquid and the vapor and the mole fraction of water in the
liquid and vapor products.

G. Computer Problems

G1. We are operating a flash drum at a pressure of 1000 kPa. The flash drum is adiabatic. The feed to
the flash drum is 100 kmol/h of a multicomponent mixture. This feed is 5.3 mol% ethylene, 22.6
mol% ethane, 3.7 mol% propylene, 36.2 mol% propane, and 32.2% n-butane. The feed is at
10,000 kPa and 100°C (this is at the point after the pump and heater—immediately before the
valve to the drum where the feed is flashed).

Find the values of L, V, x, and y.
i
i
Use a process simulator and report the VLE package you use and briefly (one sentence) explain
why you made this choice.
G2. We are operating a flash drum at a pressure of 1000 kPa. The flash drum is adiabatic. The feed to
the flash drum is 100 kmol/h of a multicomponent mixture. This feed is 8.3 mol% ethylene, 23.6
mol% ethane, 4.7 mol% propylene, 34.2 mol% propane, and 29.2% n-butane. The feed is at
10,000 kPa and 100°C (this is at the point after the pump and heater—immediately before the

valve to the drum where the feed is flashed). Use a process simulator and report the VLE package
you use and briefly (one sentence) explain why you made this choice.
Find the values of L, V, x, and y.
i
i
G3. Use a process simulator to solve Problem 2.D3. Compare answers and comment on differences.
Report the VLE package you use and briefly (one sentence) explain why you made this choice.

G4. Use a process simulator to solve Problem 2.D16. Do “what if?” simulations to see what happens
to V/F and product compositions as temperature and/or pressure vary.
G5. One kmol/s of a feed containing 0.20 mole fraction furfural, 0.75 mole fraction water, and 0.05
mole fraction ethanol at 105°C and 3.0 bar is fed to a three-phase flash drum. The drum is at 1 bar
and operates with V/F = 0.4. The key component in the second liquid (bottom of drum) is water.
Find the outlet temperature, heat duty in kW, the ratio of the first liquid/total liquid, and the
compositions of the three phases.

G6. Use a process simulator to solve the following flash distillation problem. Feed is 2 mol%