Page 138 - Separation process engineering

feed is 10 wt % ethanol, has a total flow rate of 500 kg/h, and is liquid at 20°C. We desire a
bottoms product that is 0.01 wt % ethanol and a distillate product that is 85 wt % ethanol. The
2
column operates at 1 kg/cm and is adiabatic. The column has a partial reboiler, which acts as an
equilibrium contact, and a total condenser. The distillate and reflux are saturated liquids. Find B
and D in kg/h, and find Q and Q in kcal/h. Use data in Figure 2-4. Do both parts a and b.
R
c
a. External reflux ratio, L /D = 3.0
o
b. Boilup ratio, /B = 2.5.
2
D2.* A distillation column separating ethanol from water is shown. Pressure is 1 kg/cm . Instead of
having a reboiler, steam (pure water vapor) is injected directly into the bottom of the column to
provide heat. The injected steam is a saturated vapor. The feed is 30 wt % ethanol and is at 20 °C.
Feed flow rate is 100 kg/min. Reflux is a saturated liquid. We desire a distillate concentration of
60 wt % ethanol and a bottoms product that is 5 wt % ethanol. The steam is input at 100 kg/min.
What is the external reflux ratio, L/D?

2
D3.* A distillation column separating ethanol from water is shown. Pressure is 1 kg/cm . Instead of
having a condenser, a stream of pure liquid ethanol is added directly to the column to serve as the
reflux. This stream is a saturated liquid. The feed is 40 wt % ethanol and is at −20 °C. Feed flow
rate is 2000 kg/h. We desire a distillate concentration of 80 wt % ethanol and a bottoms
composition of 5 wt % ethanol. A total reboiler is used, and the boilup is a saturated vapor. The
cooling stream is input at C = 1000 kg/h. Find the external boilup rate, . Note: Set up the
equations, solve in equation form for including explicit equations for all required terms, read
off all required enthalpies from the enthalpy composition diagram (Figure 2-4), and then calculate
a numerical answer.

D4. A partial condenser takes vapor leaving the top of a distillation column and condenses a portion
of it. The vapor portion of mole fraction y is removed as the distillate product. The liquid
D