The ‘short-cut’ calculation methods are often used to obtain a preliminary designestimate for distillation columns separating multicomponent mixtures. Discuss their usefulness and their limitations and state clearly the assumptions and specifications needed before using them.
Solution:
A. Use of short-cut calculations methods for distillation columns
1. Design of distillation column- Using short-cut method distillation column design is done. Designing consist of all parameters required for separation using distillation column. More volatile component and less volatile components are analyzed.
2. Obtain minimum reflux ratio- Rmin is calculated using short-cut methods. It is the limiting condition in distillation column.
3. Calculation of minimum number of stages - Nmin is calculated using short-cut methods. It clearly explain the required plates for separation of components.
4. Simple for application- Short-cut methods are easy to to use and simple in application.
B. Limitations of short-cut methods:
1. Difficult for calculations when relative volatility is 1.
2. Limitations for minimum reflux ratio value while considering relative volatility.
3. Difficult to select reference component.
C. Assumptions and specifications for short-cut methods
1. Constant molar flow rate along the column.
2. Constant relative volatility throughout the process.
3. Negligible vapor and fluid accumulation within the column.
4. Enthalpy of vaporization is same for all components.
The ‘short-cut’ calculation methods are often used to obtain a preliminary designestimate for distillation columns separating...