Page 137 - Separation process engineering

A8. What are the purposes of reflux? How does it differ from recycle?
A9. Without looking at the text, name the streams or column parts labeled A to H in the following
figure.

A10. Explain in what ways reflux and boilup have similar functions.
A11. For a binary separation, is K MVC V/L usually less than, equal to, or greater than 1.0?

For a binary separation, is K LVC V/L usually less than, equal to, or greater than 1.0?

A12. Explain how to do mass balances if the percentage recovery of the more volatile component is
specified in the distillate and the percentage recovery of the less volatile component is specified
in the bottoms.

B. Generation of Alternatives

B1. There are ways in which columns can be specified other than those listed in Tables 3-1 to 3-3.

a. Develop alternative specifications for design problems.
b. Develop alternative specifications for simulation problems.

C. Derivations

C1. For the column shown in Problem 3.D2, derive equations for D, B, Q , and L/D.
c
C2. For the column shown in Problem 3.D3, derive equations for D, B, , and Q .
R
C3. Show that Eqs. (3-3) and (3-4) are valid for a column with two feeds (e.g., shown in Figure 4-18)
as long as we define F = F + F and z = (F z + F z )/F.
1
1 1
2
2 2
C4. 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
portion of mole fraction x is returned to the column as reflux. The liquid and vapor leaving the
0
partial condenser can be assumed to be in equilibrium. Derive the mass and energy balances for a
partial condenser.

D. Problems

*Answers to problems with an asterisk are at the back of the book.
D1. A distillation column with two feeds is separating ethanol from water. The first feed is 60 wt %
ethanol, has a total flow rate of 1000 kg/h, and is a mix of liquid and vapor at 81°C. The second