Hand Calculations for Distillation Towers

Vapor-Liquid Equilibrium, Absorption, and Strippii Calculations 

The top of a distillation tower works like an absorber whereas the bottom of a distillation tower works like a stripper. The upper and lower parts of a tower are the rectification section, which is the upper portion above the feed inlet, and the stripping section, which is the lower portion between the feed inlet and reboiler vapor return nozzle. 

In this chapter we will discuss single theoretical stage Bubble-Point and Dew Point calculations and give examples as to how these can be used in our work. Then weTl discuss the use of the Absorption Factor and Stripping Factor chart, which can be used to design distillation towers. In order to use this chart in that way it is necessary to consider a distillation tower as two separate towers. The top of the tower is considered an absorber. The chart is then used in a different way to design the lower part of the distillation tower as a stripper. 

Distillation towers were designed using this same chart for nearly half a century before the first computer simulations were ever written. Indeed, the use of computer simulations in design did not really begin until the early 1960s. 

As long as we pay attention to the assumptions needed when using this chart, it is still a valuable tool that provides an understanding of how the process works and what to expect when conditions change. 

---