Give step-by-step solution with explanation and final answer:Problem 2 (25 points)
The figure below illustrates some of the major streams in a two-component distillation column with
N trays and a reboiler. For parts a-e below, indicate how the composition of the two streams given
are related -by the operating line (either enriching line or stripping line), the equilibrium line, the g-
line, or equal to each other. For example, in part (a), are the compositions of Vi and L are related to
each other by the operating line, equilibrium line, g-line, or alternatively, the compositions are equal?
a. Viand L (5 points)
b. Land D (5 points)
c. Vzand L; (5 points)
d. Vn:+rand W (5 points)
e. Vn+iand Li (5 points)
“—()
yi f— YT
ve | -
F
_—
Vn Ln.1
Tray N
uy =
N w
Question:
Give step-by-step solution with explanation and final answer:Problem 2 (25 points)
The figure below illustrates some of the major streams in a two-component distillation column with
N trays and a reboiler. For parts a-e below, indicate how the composition of the two streams given
are related -by the operating line (either enriching line or stripping line), the equilibrium line, the g-
line, or equal to each other. For example, in part (a), are the compositions of Vi and L are related to
each other by the operating line, equilibrium line, g-line, or alternatively, the compositions are equal?
a. Viand L (5 points)
b. Land D (5 points)
c. Vzand L; (5 points)
d. Vn:+rand W (5 points)
e. Vn+iand Li (5 points)
“—()
yi f— YT
ve | -
F
_—
Vn Ln.1
Tray N
uy =
N w
This is AI generated Response.
Asked by: francis
Created at: 2025-12-14 21:37:07
Final Answer:
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# Step-by-Step Solution
Let's consider the relationships in a standard two-component distillation column. The main concepts are:
- **Operating Lines:**
- **Enriching (Rectifying) Line:** Above feed, relates vapor and liquid compositions.
- **Stripping Line:** Below feed, relates vapor and liquid compositions.
- **Equilibrium Line:** Relates vapor and liquid in equilibrium on a tray.
- **q-line:** Feed condition (not directly related to the streams in these parts).
- **Equality:** Streams might be equal in composition in some cases.
Let’s answer each part:
---
## (a) \( V_1 \) and \( L \)
- **\( V_1 \):** Vapor leaving the top tray and going to the condenser.
- **\( L \):** Liquid returning from the condenser (reflux).
### Relationship:
- **\( V_1 \)** and **\( L \)** are not in equilibrium; rather, \( L \) is formed from condensation of \( V_1 \).
- The composition of **\( L \)** is **equal** to the composition of the condensed vapor \( V_1 \) (full condensation is assumed).
**Final Answer:**
**The compositions are equal.**
---
## (b) \( L \) and \( D \)
- **\( L \):** Reflux returned to the column.
- **\( D \):** Distillate withdrawn from condenser.
### Relationship:
- Both are drawn from the same condensed stream (the overhead vapor is condensed and then split).
- Thus, the composition is the **same**.
**Final Answer:**
**The compositions are equal.**
---
## (c) \( V_2 \) and \( L_1 \)
- **\( V_2 \):** Vapor rising from tray 2 to tray 1.
- **\( L_1 \):** Liquid descending from tray 1 to tray 2.
### Relationship:
- On a tray, the vapor leaving (upwards) and the liquid leaving (downwards) are in **equilibrium** with each other.
**Final Answer:**
**Their compositions are related by the equilibrium line.**
---
## (d) \( V_{N+1} \) and \( W \)
- **\( V_{N+1} \):** Vapor entering the reboiler.
- **\( W \):** Bottom product, liquid withdrawn from reboiler.
### Relationship:
- The reboiler acts as an equilibrium stage: the vapor leaving and the liquid remaining are in equilibrium.
**Final Answer:**
**Their compositions are related by the equilibrium line.**
---
## (e) \( V_{N+1} \) and \( L_N \)
- **\( V_{N+1} \):** Vapor rising from the reboiler to the bottom tray (tray N).
- **\( L_N \):** Liquid descending from tray N to the reboiler.
### Relationship:
- On a tray, the vapor going up and the liquid going down are in **equilibrium** with each other.
**Final Answer:**
**Their compositions are related by the equilibrium line.**
---
# **Summary Table**
| Part | Streams | Relationship |
|------|-------------------|--------------------------------------------|
| (a) | \( V_1 \) and \( L \) | Compositions are equal |
| (b) | \( L \) and \( D \) | Compositions are equal |
| (c) | \( V_2 \) and \( L_1 \) | Related by the equilibrium line |
| (d) | \( V_{N+1} \) and \( W \) | Related by the equilibrium line |
| (e) | \( V_{N+1} \) and \( L_N \)| Related by the equilibrium line |
---
These relationships are fundamental in McCabe-Thiele analysis and distillation column design.
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