Page 103 - Separation process engineering

A2. Can weight units be used in the flash calculations instead of molar units?
A3. Explain why a sequential solution procedure cannot be used when T is specified for a flash
feed
drum.
A4. In the flash distillation of salt water, the salt is totally nonvolatile (this is the equilibrium

statement). Show a McCabe-Thiele diagram for a feed water containing 3.5 wt % salt. Be sure to
plot weight fraction of more volatile component.
A5. Develop your own key relations chart for this chapter. That is, on one page summarize everything
you would want to know to solve problems in flash distillation. Include sketches, equations, and
key words.

A6. In a flash drum separating a multicomponent mixture, raising the pressure will:
a. increase the drum diameter and increase the relative volatilities.

b. increase the drum diameter and cause no change to the relative volatilities.
c. increase the drum diameter and decrease the relative volatilities.

d. not change the drum diameter but increase the relative volatilities.
e. not change the drum diameter and not change the relative volatilities.

f. not change the drum diameter but decrease the relative volatilities.
g. decrease the drum diameter and increase the relative volatilities.

h. decrease the drum diameter and not change to the relative volatilities.
i. decrease the drum diameter and decrease the relative volatilities.

A7.
a. What would Figure 2-2 look like if we plotted y vs. x (i.e., plot less volatile component mole
2
2
fractions)?
b. What would Figure 2-3 look like if we plotted T vs. x or y (less volatile component)?
2
2
c. What would Figure 2-4 look like if we plotted H or h vs. y or x (less volatile component)?
2
2
A8. For a typical straight-chain hydrocarbon, does:

a. K increase, decrease, or stay the same when temperature is increased?
b. K increase, decrease, or stay the same when pressure is increased?

c. K increase, decrease, or stay the same when mole fraction in the liquid phase is increased?
d. K increase, decrease, or stay the same when the molecular weight of the hydrocarbon is
increased within a homologous series?

Note: It will help to visualize the DePreister chart in answering this question.
A9. In the vapor-liquid equilibrium data for methanol-water, if the methanol vapor mole fraction is
0.60, what is the methanol liquid mole fraction?

A10. Is there an azeotrope in the methanol-water system at a pressure of 1.0 atmospheres?
A11. The equilibrium K value is usually defined as

a. K = y/x, where y and x are weight fractions of the component in the vapor and liquid phases,
respectively.
b. K = x/y, where x and y are weight fractions of the component in the liquid and vapor phases,

respectively.
c. K = y/x, where y and x are mole fractions of the component in the vapor and liquid phases,