Question

In a distillation operation, what is the effect of the temperature of the reflux stream (given below) on the condenser and reboiler loads? Reflux conditions - Reflux stream is completely liquid and is at its bubble point - Reflux stream is below its bubble point

• A. Condenser and reboiler loads are the same in both the cases
• B. Reboiler load is same in both the cases but condenser load is higher in case 2
• C. Condenser load is same in both the cases but reboiler load is higher in case 2
• D. Both condenser and reboiler loads are higher in case 2 compared to case 1

Hint:

In distillation, the reflux stream temperature plays a crucial role in determining the energy required for both the condenser and reboiler. A subcooled reflux increases reboiler load.

Answer 1

The Correct Option is C

Step 1: Understanding reflux conditions.
When the reflux stream is below its bubble point (i.e., in the subcooled liquid state), it requires more heat to vaporize and increase the amount of vapor in the system. This increases the reboiler load, as more heat is required to generate vapor from the liquid in the reboiler. However, the condenser load remains relatively constant because the condenser’s primary function is to condense the vapor into liquid, which is not significantly affected by the subcooled reflux stream in this case.
Step 2: Conclusion.
The correct answer is (3), where the reboiler load is higher in case 2 compared to case 1, but the condenser load remains the same in both cases.