Question

A homogeneous azeotropic distillation process separates an azeotropic AB binary feed using a heavy entrainer, \( E \), as shown in the figure. The loss of \( E \) in the two product streams is negligible, so \( E \) circulates around the process in a closed circuit. For a distillation column with fully specified feed(s), given operating pressure, a single distillate stream, and a single bottoms stream, the steady-state degrees of freedom equals 2. For the process in the figure with a fully specified AB feed stream and given column operating pressures, the steady-state degrees of freedom equals: \includegraphics[width=0.5\linewidth]{q14 CE.PNG}

• A. 3
• B. 4
• C. 5
• D. 6

Hint:

In distillation problems involving azeotropes or entrainers, include additional constraints from recycle streams, azeotropic behaviors, and column operating conditions to determine the total degrees of freedom.

Answer 1

The Correct Option is C

Step 1: Understand the degrees of freedom in distillation processes. The degrees of freedom (DoF) in a distillation column represent the number of independent variables that can be adjusted to achieve steady-state operation. For a typical distillation column with: - Fully specified feed streams, - Given operating pressure, - A single distillate and a single bottoms stream, The steady-state degrees of freedom is \( 2 \). Step 2: Include the effects of azeotropic distillation. In the given process, an additional constraint is imposed by the closed-circuit circulation of the heavy entrainer \( E \). Since \( E \) is recycled with negligible loss, this introduces an additional degree of freedom. Furthermore, the separation process requires careful specification of conditions such as flow rates, reflux ratios, and temperature for both the azeotropic and heavy entrainer behaviors. Step 3: Determine the total degrees of freedom. Considering the additional complexities of azeotropic separation and entrainer circulation, the total degrees of freedom for the process increases to: \[ \text{DoF} = 2 + 3 = 5. \] Step 4: Conclusion. The steady-state degrees of freedom for the process equals \( 5 \).