1. Correlation between Reflux Ratio and
Mass Fraction of Distilled Ethanol
Group 9 - A01: Melissa Nguyen
Alan Tam, Reiko Liu, Joseph Guarnes
January 28th, 2016
2. Continuous Rectification: Separation of
Ethanol from ethanol and water mixture
Separate two or more liquids that are
miscible in each other.
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Distillation Process
Batch Distillation
Continuous Distillation
3. Methods and Measurements
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1. Initial composition
2. Heat up
3. Reach steady
state
4. Change Reflux
Ratio
5. Collect
Distillate
Reflux Ratio = L/D
Recorded Data:
➢Temperatures
at top and
bottom of
column
➢Column
Pressure
Drop
Recorded Data:
For Distillate
sample
➢Time stamp
➢Volume
➢Mass
➢Temperatur
e
5. Column has 6 Stages using Flash Calculation and
McCabe Thiele Graphical Method
xB = 0.0411
xD = 0.7881
6. Future Experiment:
Recommendation
★ Find the initial composition of ethanol in
the mixture.
★ Make sure your system is at steady state.
★ Small reflux ratios show more obvious
trends in a short amount of time.
QUESTIONS OR COMMENTS ?
Editor's Notes
Hello everyone. My name is Melissa Nguyen and I’m presenting for group 9. Our group experiment is continuous rectification. Through this experiment, we wish to see the correlation between the reflux ratio and the mass fraction of the distilled ethanol.
There are 2 types of distillation process: Batch Distillation and Continuous Distillation. This technique is used to separate two or more liquids that are miscible in each other.
This is a diagram of the batch distillation column. Before starting, we took out a sample of the mixture from the tank to find the initial ethanol composition. The mixture of ethanol and water is heated up and reach steady stead at reflux ratio at 100%. The system is at steady state when there is no significant change in temperatures, and pressure of the system. We recorded the temperatures of the top and bottom of the column and the column pressure drop for the flash calculation. To start collect our distillate, the reflux ratio was changed. This determines how much liquid is going back to the column and how much is going to the distillate. We picked our reflux ratios to be 25%, 45% and 65%
The data from distillate sample was used to find the average mass fraction of ethanol in the distillate
Looking at the data for reflux ratio at 25%, there seems to be a decrease in ethanol average mass fraction over time. We predicted that there should be a similar trend going on with other reflux ratios. At R = 25%, comparing to others ratio, the rate of distillate accumulate was higher than that of reflux ratios at 45% and 65%. This led to a significant change in the average mass fraction of ethanol in a shorter amount of time. In other to see better trend, it is recommended that the system should be run over a longer period of time.
With the measured pressure drop and temperatures, we calculated the ethanol compositions at the top and bottom of the column through flash calculation using Modified Raoult’s Law. Iteration method was used with the initial guess for x to be 0.5. When the change of the x values is less than .001%, we got the composition at the top equals .7881 and at the bottom, 0.0411.
From there, using McCabe Thiele graphical method, the number of stages was found to be 6 stages, as shown on this graph
![Continuous Rectification: Separation of
Ethanol from ethanol and water mixture
Separate two or more liquids that are
miscible in each other.
[usdidactic.com]
Distillation Process
Batch Distillation
Continuous Distillation](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)