Binary Distillation
University of Illinois at Chicago
(Image from "Fractional Distillation.")
Binary Batch Distillation
Lab Prep Report
Unit Operations Lab 2
14 February, 2011
Group 4
Tien Diep
Kevin Estacio
Sebastian Iskra
Zack Labaschin
Kevin Thompson
Felix Velazquez
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
1. Introduction
Distillation is a separation process that takes place in a column which is able to separate a feed
into two components which exit in either the top or the bottom of the column. It works by
heating the fluid, which causes the more volatile component to evaporate. As the vapor phase
flows up, the liquid phase flows down as it gathers on the many trays. The liquid that gathers on
the trays is then able to be reheated to allow for more of the more volatile component to become
a vapor. This allows for a high purity in both the top and bottom of the distillation column. It is
important to chemical engineers because it “is the most widely used separation process in
chemical engineering” (Lab Manual, 1).
The advantage to using a distillation column over other methods of separation is that the
products produced are usually of very high purity. The disadvantage to using distillation is that it
can only separate a mixture into two different components; this can be offset by using a sequence
of distillation columns. In industry, distillation columns are used for a large amount of processes,
including the production and refinement of petroleum, pharmaceutical drugs, and alcoholic
beverages. Although there are several types of distillation methods, such as batch (used mostly in
the pharmaceutical industry), this lab will focus on continuous distillation, which allows for a
process to be run at steady state for an unspecified amount of time.
In this lab, a methanol/water system will be analyzed. First, a calibration curve will be
calculated for the index of refraction of the system using a refractometer. This will allow for later
analysis of the composition of binary mixtures present at each stage of the distillation column.
The distillation column will then be operated and a material balance will be carried out in order
to find the amount of methanol recovered in the distillate and the amount of water recovered in
the bottoms.
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
2. Literature Review/Theory
The purpose of this module is to perform a binary distillation on a feed of methanol and water.
Distillation is defined as a process by which components are separated at equilibrium into gas
and liquids phases. This occurs on each tray present in the system, and the result is the vapor
components move up as the liquid products move down. This process is controlled by adjusting
the temperature and pressure of the system. Components with lower boiling points will become
vapor and components with high boiling points will remain liquid (or become liquid). In this way
a mixture can be separated, and when distillation columns are put in seris, the vapor/liquid
products can be further purified with the same process. Because of this simplicity, distillation
columns are iconic structures in chemical engineering . This particular unit operates at total
reflux – the vapor product does not exit the system. In this way the Methanol, the lighter of the
two components, will be separated from the water. In this way water will be purified. The
overall picture of a distillation column includes a mass and energy balance on the column
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
(overall and for each compoenent) and a mass and energy balance on each tray.
Figure 1 (Binary Distillation w/ overall Mass Balanace, Wankat 2009)
Figure 2 (Tray Mass Balance, Wankat 2009)
The basic equation for a Mass Balance in a Binary Column:
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
F=B+L
University of Illinois at Chicago
EQ 1
F = Feed (mol / hr)
B = Bottoms (mol / hr)
D = Distilate (mol / hr)
In this way, we see that the mass entering the system is equal to the mass coming out of the top
and bottom of the column. In order to analyze the system, the McCabe – Thiele method is used.
The McCabe – Thiele method allows for the equilibrium relationship to be solved from the
vapor-liquid fraction curve and the mass balances from the operating line. An example of an
operating line (top):
y=L/V * x + (1-L/V) * x_d
EQ 2
This top operating line is graphed for the rectifying or top section of the column (also known as
the absorbing section). The same equation is used for calculating the bottom half of the column,
the stripping section, except the L and V are calculated for the bottom section and the y-intercept
utilizes the liquid mole fraction of the bottoms product. Plotting such a graph results in the
following:
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
Figure 3 (McCabe – Thiele diagram, Wankat 2009)
The McCabe – Thiele diagram thus shows the number of trays needed in a system and the
optimal placement for the feed stream to be place between. While the McCabe – Thiele method
is very useful, assumptions include vapor-liquid equilibrium at each stage, which is not practical
in reality. An efficiency is associated with the system.
n = (y_n – y_n+1) / (y*_n – y_n+ 1)
EQ 3
n = efficiency
y_n = vapor fraction at tray n
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
y_n+1 = vapor fraction of tray n +1
y*_n = composition at equilibrium with X_n
With the McCabe – Thiele method and a method for accounting for the efficiency of the system,
this module can successfully be anaylized for a separation of Methanol and Water.
3. Experimental
3.1 Apparatus
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
1
2
9
3
7
7
10
11
4
5
12
5
13
5
14
6
5
15
7
16
5
8
5
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
Figure 3.1 Distillation Column (Shown above)
No. Manufacture Component
1
N/A
Condenser
2
N/A
Water supply
3
F&P Co.
4
N/A
Liquid
Rotameter
Stages 1-6
5
N/A
Filling tank
6
N/A
Ladder
7
N/A
8
N/A
Ball valve for
draining
distillation
column
Fill/Drain valve
9
10
N/A
N/A
11
N/A
12
Powerstat
13
N/A
14
Newport
15
N/A
16
N/A
Pressure gauge
Flow rate control
valve
Valve for
pressure gauge
Heater box
Thermometer
gauge
Digital
Thermometer
Large round
bottom flask
Reboiler
Description/Safety
Condenses the water in the system.
A bulb valve used to fill the tank with water. Be cautious of
splashing water when opening the valve.
Measures the flow rate of the water going into the condenser.
There are 6 stages of the distillation column. At each stage,
both liquid and vapor can be extracted. Use caution when
extracting samples. Use a ladder or the staircase. Do not climb
on the metal bars to extract samples.
The filling tank retains the methanol and water until it can be
drained into the round bottom flask of the distillation column.
Used to fill the holding tank and to extract of the distillation
column.
Used to drain the distillation column. System must be cooled
to room temperature before draining, or else the glass might
break.
Used to fill the distillation column with the methanol and water
solution from the filling tank. When the knob is pointing
towards “fill” the filling tank can be filled with solution. When
the knob is pointing towards drain, the filling tank will be
drained of the solution and transported into round bottom flask
of the distillation column.
Reads the pressure of the water flowing into the condenser.
ControlS the flow rate of the water flowing into the condenser.
Needle valve used to control the pressure of the condenser.
Controls the boiler of the distillation column. Instructor must
unlock and turn on the reboiler.
Reads temperature at the top of the distillation column.
Reads the temperature at each thermocouple location from
each stage of the distillation column.
Retains the methanol and water solution while the boiler heats
it up.
Heats up the round bottom flask containing the methanol and
water solution.
3.2 Materials and Supplies
No. Materials/Supplies Description/Use
1
Goggles
Used to protect the eyes
2
Napkins
Used to clean excess water to prevent spillage
3
Mop
Used to mop any excess water around lab area to prevent spillage
2
Gloves
Used to protect your hands from Methanol because it can dry out
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
3
4
Water
Methanol
5
6
7
Graduated
Cylinders
Ladder
Small test tubes
8
Refractometer
8
9
10
Distilled water
Kimwipes
Ice
11
Digital
Thermometer
University of Illinois at Chicago
your hands.
Used to make the 10 wt % methanol and supplied to the condenser
99.8% anhydrous methanol used to make the 10wt% methanol
solution.
Measure the amount of Methanol needed to make methanol
solutions.
Used to add methanol to the filling tank.
Used to collect samples of the liquid and vapor at each stage of the
distillation column.
Samples of different wt% methanol solutions are placed in the
refractometer to later obtain the refraction index scale
Used to clean the refractometer in between readings.
Used to clean and dry off the refractometer.
Used in the ice bath for the refractometer to maintain the
temperature at approximately 33°F
Used to read the temperature of the ice bath.
3.3 Procedure
Starting the batch distillation column:
1. Make sure the filling tank is closed and the knob of the Fill/Drain valve is pointing in the
direction of “Fill”.
2. Using a graduated cylinder, measure 1.6 liters of 99.8% anhydrous methanol. Using the
ladder, carefully climb up to the top of the tank and pour the methanol into the funnel.
3. Turn on the water valve and fill the filling tank to the 32 liter mark, indicated by the
black line.
4. Once the filling tank is full, turn off the water supply and carefully climb back down to
ground level. Turn the Fill/Drain valve so that the knob is pointing in the direction of
“Drain”. Make sure the yellow ball valve of the distillation column is closed which is
indicated by the knob facing perpendicular to the pipe.
5. Open the filling tank valve by turning the green knob all the way to the right. The
solution should start to fill the round bottom flask of the distillation column.
6. Once filling tank is completely drained, close the filling tank valve by turning the green
knob all the way to the left.
7. Call the instructor or the TA to turn on the reboiler.
8. Record the temperature of thermocouples at each stage every 20 minutes until the
temperature has reached steadystate.
9. Obtain samples of liquid and vapor at each stage.
10. Use the refractometer to determine the refraction index for each of the sample.
Instructions are listed below.
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
Using the refractometer:
1. Make solutions of 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 wt% methanol solutions
and cover each solution with parafilm.
2. Obtain ice from the CHE office on the 2nd floor.
3. Turn on the ice bath and add ice to cool the water to approximately 32 or 33°F. Try to
maintain this temperature throughout the experiment.
4. Turn on the light switch for the refractometer.
5. Open the illuminating prism and add a droplet of solution or sample. Close the
illuminating prism. And adjust the light source upwards.
6. While looking into the eyepiece, use the refocusing knob to obtain a clearly defined
horizontal line in which the bottom is green and the top is white.
7. Use the adjusting knob to raise or lower the line until it is exactly centered at the middle
of the X.
8. Press the scale illumination button to make the refraction index scale appear. Record the
value.
9. Repeat these steps for all the solutions of the calibration curve and the liquid and vapor
solutions from the distillation column after it has reached steady-state.
4. Anticipated Results
The purpose of this lab is to study the process of continuous binary distillation, a
common physical separation process which works by exploiting the difference in volatilities of
the two components of the mixture (McCabe, 576-578). By heating the mixture to near its
boiling point, the more volatile component (Methanol) will vaporize first and travel up the
distillation column (Wankat, 280). In cases where the boiling points of the two pure components
are less than 25C apart, a simple distillation column will not be sufficiently effective,
necessitating the use of a fractional distillation column.
For this experiment a two-component system consisting of water and methanol will be
studied at differing mass fractions. This mass fraction difference will be directly proportional to
the mass flux rate which is also directly proportional to the rate of separation (Bird, 515).
Thermocouples are in place to measure the temperature at each stage. Using the refractometer, a
calibration curve will be generated for differing methanol concentrations and used as a reference
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
for the experimental data. The higher the stage in the distillation column the higher the
concentration should be as well as the stage temperature decreasing up the column. The stage
temperatures also should have ranged between 65-100C, as pure methanol boils at 65C and
pure water boils at 100C. Methanol will be collected in the distillate as it is the more volatile
component and will evaporate out of the mixture at a rate faster than that of water.
5. References
"Binary Batch Distillation." University of Illinois at Chicago - UIC. Web. 14 Feb. 2011.
<http://www.uic.edu/depts/chme/UnitOps/che382-2005f-frame.html>.
Bird, R. Byron, Warren E. Stewart, and Edwin N. Lightfoot. Transport Phenomena. New York:
J. Wiley, 2007. Print.
"Fractional Distillation." Engineering. Web. 14 Feb. 2011.
<http://engineering.wikia.com/wiki/Fractional_distillation>
.
McCabe, Warren L., Julian C. Smith, and Peter Harriott. Unit Operations of Chemical
Engineering. Boston: McGraw-Hill, 2005. 576-78. Print.
Wankat, Phillip C. Separation Process Engineering. Upper Saddle River, NJ: Prentice Hall,
2007. Print.
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011
Binary Distillation
University of Illinois at Chicago
6. Appendix I: Job Safety Analysis
What is the purpose of this experiment?
The main purpose of this experiment is to understand the process of distillation by separating a
binary mixture of 5 vol% methanol and water at total reflux. The compositions of vapor and
liquid samples will be collected at various stages of the column and will be determined by using
the calibration curve. The calibration curve can be plotted by measuring the refractive indices of
methanol and water solutions of known compositions. (0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and
100 wt% methanol)
What are the hazards associated with the experiment?
This experiment involves heating a mixture in a pressurized system. Potential hazards from the
heating component involve boiling liquid and the hot pipes coming into contact with the
operator. Potential hazards from the steam also involve hot pipes coming into contact with the
operator as well as pressurized steam. Another hazard includes handling the methanol solution
since methanol is a highly flammable concentration. Methanol is moderately irritating to the
skin. Methanol can be absorbed through the skin and harmful effects have been reported.
Inhalation of methanol concentrations can also irritate mucous membranes, cause headaches,
sleepiness, nausea, confusion, loss of consciousness, digestive and visual disturbances. Methanol
is a mild to moderate eye irritant. High vapour concentration or liquid contact with eyes causes
irritation, tearing and burning.
How will the experiment be conducted in a safe manner?
To work in safe manner, eye protection should be worn at all time to avoid exposure to methanol
solution. It is highly recommended to wear gloves and face mask when attempting to handle the
methanol solution during the transferring and mixing the binary mixture in the column to avoid
inhalation or skin contact. Conduct an inspection of the electrical outlet and make sure the heater
is working properly before conducting experiment.
What safety controls are in place?
If methanol or water spills on floor, clean up immediately to prevent slippery surface. Quickly
breathe in fresh air if methanol is inhaled. Use eye wash station in the event of eye contact with
methanol. When the heater is not in use, make sure to turn off the switches to prevent
overheating and burning.
Describe safe and unsafe ranges of operations.
Safe ranges of operations include working with methanol wearing protective gear, gloves and
face mask. When heating up the mixture solution, do not exceed the desired temperature and
pressure. Unsafe ranges of operations include working with methanol when transporting samples
to the refractometer station for further examination.
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
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Binary Distillation
University of Illinois at Chicago
I have read relevant background material for the Unit Operations Laboratory entitled: “Binary
Batch Distillation” and understand the hazards associated with conducting this experiment. I
have planned out my experimental work in accordance to standards and acceptable safety
practices and will conduct all of my experimental work in a careful and safe manner. I will also
be aware of my surroundings, my group members, and other lab students, and will look out for
their safety as well.
Signatures:
Unit Operations ChE-382 Group No. 4
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Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/14/2011