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Experiment DC: Distillation Column
Overall Column Efficiency
OBJECTIVE To determine the overall column efficiency. METHOD To operate the column over a selected boil-up rate, taking samples in order to measure the refractive index (and hence to determine the concentration of the components).
DESCRIPTION The UOP3CC Continuous Distillation Column is a self-contained distillation facility (see Figure 1) consisting of a 50mm diameter sieve plate column made up of two glass sections, each containing four sieve plates. The plates are arranged vertically for counter-current vapour/liquid flow. The column is insulated to minimise heat loss. A reboiler is situated at the base of the column and incorporates a flameproof immersion type heating element. Because the experiment is in batch operation, valve (V1) remains closed. A level sensor inside the reboiler protects the heating element from overheating due to low operating level and a plastic tube allows the level in the reboiler to be observed. Vapour from the top of the column passes to a water-cooled, coil-in-shell condenser. The shell of the condenser incorporates a pressure relief valve (PRV1) to protect the system in the event of a blocked vent and cooling water failure. Cooling water enters the condenser at a regulated rate through a variable area flowmeter (FI1) and the flowrate is controlled by diaphragm valve (V5). A cooling water supply is connected to the inlet nozzle and serves also to operate the vacuum pump if operation at reduced pressure was required. Water supply to the vacuum pump is controlled by valve (V14), which must only be operated when valve (V5) is open.
Condensate is collected in a glass decanter (phase separator) which is by-passed for normal distillation experiments by opening valve (V10). With valve (V10) open, condensate from the condenser outlet passes directly through the decanter to the inlet of the reflux ratio control valve which is a 3-way solenoid operated valve. Depending on the setting of the reflux timers, condensate is directed by the reflux valve either back to the top of the column or to the top product collecting vessel. When directed to the column, the reflux passes through a U-seal where a valve (V3) can be used for measuring boil-up rate or for draining the U-seal. The contents of the top product tank
1
can be drained into the reboiler for re-use via valve (V12).
Temperatures within the system are monitored by fourteen thermocouple sensors (T1 to T14) located at strategic positions in the system. T1 to T8 are located in the column and measure the temperature of the liquid on each sieve plate.
All of the vessels in the system are connected to a common vent on the top product receiver. This vent is normally connected through a 4.0m length of tubing to a fume cupboard or safe atmospheric vent outlet. Console and computer control/display
The console is attached to the process unit for display and control of the various operating parameters of the distillation column (see Figs. 2-4). Optionally the process can be fully controlled from the connected computer (see Fig. 5). Tabular Display
To view the Table screen click the View Table icon from the View dropdown menu as shown:
from the main tool bar or click Table
The data is displayed in a tabular format, similar to the screen as shown:
2
As the data is sampled, it is stored in spreadsheet format, updated each time the data is sampled. The table also contains columns for the calculated values. THEORY
To calculate the number of theoretical plates for a given separation at total reflux, Fenske developed the following formula:
where
n = number of theoretical plates xA = mole fraction of more volatile component xB = mole fraction of least volatile component av = average relative volatility
Subscripts d, b indicate distillate and bottom respectively
The efficiency is given by:
Knowing the composition of distillate and bottom and the corresponding volatilities, the column efficiency can be determined.
3
PROCEDURE The reboiler is already filled with the liquid to be distilled (15 mole% ethanol, 85 mole% water).
1. Switch on the computer.
2. At the big control panel on the wall, set the “UOP AREA EXTRACT FAN”
(selector on the left), at “Hand position”.
3. Switch on the Armfield console by the computer. Load the software in the
computer. Go to “View” and select “Diagram”.
4. Identify all components in Figure 1. All valves must be closed except for V5
(cooling water) and V10 (below the decanter).
5. Set the equipment to operate at total reflux: on the reflux controller of the
console, put the selector on Manual position and make sure the ON/OFF button
is not on (no green light).
6. In the small room where the rig is, open the red valve on the wall to get cooling
water to the condenser. Set the water rotameter (above valve V5) to 3000
ml/min.
7. Choose options A or B and leave the apparatus for at least 30 minutes so that
the system can reach equilibrium conditions.
A. Automatic control using the software (PID1).
On the console, press the red button to activate the heater. Then put the selector
on I/O Port position to have it controlled from the computer. Press PID1 on the
screen’s diagram and set the following parameters:
Mode of operation: Set point (T7): Proportional band: Integral time: Derivative time:
Automatic 77 oC 50% 15 s 0 s
B. Manual control using the console.
On the console, press the red button to activate the heater. Then put the selector on Manual position. For about 5 minutes set the heat controller at high rate, 1.75 kW. Reduce to 0.85 kW once liquid starts flowing from the decanter back to the
4
column.
8. Start recording the data by clicking on .
9. Check that temperatures increase so that T1 reaches approximately 77 oC.
10. While the system is heating up, mark in Figure 1 the flow of products (cooling
water in blue and ethanol/water in red). The experiment takes place at total
reflux, so there will be no feed to the top product receiver or bottom product
receiver. It is a batch operation and takes place at normal pressure.
11. Take a sample of the distillate through valve V3 and a sample of the bottom
through valve V2. Use googles and gloves for this. CAUTION! SAMPLES ARE
HOT! Keep the vials in an upright position.
Repeat this procedure every 10 min until at least 3 samples of both distillate
and bottom are obtained. Label them carefully as D1, D2, D3,…, B1, B2, B3,….
Take the samples to the lab with your supervisor, to learn how to use the
refractometer. Measure and register the refractive index for the different
samples.
12. Record the temperatures T1 to T8 to calculate the average top and bottom
column temperature. 13. Click on
to stop recording the data and save the file as Excel 5.xls.
14. Cool down by pressing the red button in the console to turn off the heater.
Check that temperature is dropping down.
15. Switch off the cooling water (red valve on the wall).
16. Shut down everything when temperatures have dropped down:
16.1. Turn off the console and the computer.
16.2. On the wall panel (UOP Area extract fan), set it “Automatic”.
16.3. Dispose the samples in a safe manner, using googles and gloves: pour
them in the plastic jerry can available in the rig’s room, labelled as “WATER
AND ETHANOL”.
5
Fig. 1. Schematic diagram of apparatus
6
Fig.2. Display and control of reflux ratio
Fig. 3. Display and control of power to rebolier heating element
7
Fig. 4. Display of distillation column temperature
Fig. 5. Display of distillation column temperature
8
Experiment DC: Distillation Column
Data Sheet
Group Number:
Group Members:
Date: NB Wait 10 minutes before taking a fresh set of samples.
Distillate composition- ethanol
Reading
1
2
3
Average
Composition
Volatility
Refractive index
Bottom Composition- ethanol
Reading
1
2
3
Average
Composition
Volatility
Refractive index
Average top column temperature Average bottom column temperature Average column temperature
= = =
°C °C °C
9
T [°C] y 100
 – 10.575
x 0 0.019 95.5 0.0721 89 0.0966 86.7 0.1238 85.3 0.1661 84.1 0.2337 82.7 0.2608 82.3 0.3273 81.5 0.3965 80.7 0.5079 79.8 0.5198 79.7 0.5732 79.3 0.6763 78.7 0.7472 78.4 0.8943 78.1 x = mole fraction of ethanol in liquid y = mole fraction of ethanol in vapour
0 0.17 0.3891 8.197 0.4375 7.274 0.4704 6.286 0.5089 5.202 0.5445 3.92 0.558 3.578 0.5826 2.869 0.6122 2.403 0.6564 1.851 0.6599 1.792 0.6841 1.612
0.7385 1.352 0.7815 1.21 0.8943 1
= relative volatility
10

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1

Experiment DC: Distillation Column

Overall Column Efficiency

OBJECTIVE

To determine the overall column efficiency.

METHOD

To operate the column over a selected boil-up rate, taking samples in order to measure

the refractive index (and hence to determine the concentration of the components).

DESCRIPTION

The UOP3CC Continuous Distillation Column is a self-contained distillation facility

(see Figure 1) consisting of a 50mm diameter sieve plate column made up of two glass

sections, each containing four sieve plates. The plates are arranged vertically for

counter-current vapour/liquid flow. The column is insulated to minimise heat loss.

A reboiler is situated at the base of the column and incorporates a flameproof

immersion type heating element. Because the experiment is in batch operation, valve

(V1) remains closed. A level sensor inside the reboiler protects the heating element

from overheating due to low operating level and a plastic tube allows the level in the

reboiler to be observed.

Vapour from the top of the column passes to a water-cooled, coil-in-shell condenser.

The shell of the condenser incorporates a pressure relief valve (PRV1) to protect the

system in the event of a blocked vent and cooling water failure. Cooling water enters

the condenser at a regulated rate through a variable area flowmeter (FI1) and the

flowrate is controlled by diaphragm valve (V5). A cooling water supply is connected to

the inlet nozzle and serves also to operate the vacuum pump if operation at reduced

pressure was required. Water supply to the vacuum pump is controlled by valve (V14),

which must only be operated when valve (V5) is open.

Condensate is collected in a glass decanter (phase separator) which is by-passed for

normal distillation experiments by opening valve (V10). With valve (V10) open,

condensate from the condenser outlet passes directly through the decanter to the inlet

of the reflux ratio control valve which is a 3-way solenoid operated valve. Depending

on the setting of the reflux timers, condensate is directed by the reflux valve either

back to the top of the column or to the top product collecting vessel. When directed to

the column, the reflux passes through a U-seal where a valve (V3) can be used for

measuring boil-up rate or for draining the U-seal. The contents of the top product tank

2

can be drained into the reboiler for re-use via valve (V12).

Temperatures within the system are monitored by fourteen thermocouple sensors (T1

to T14) located at strategic positions in the system. T1 to T8 are located in the column

and measure the temperature of the liquid on each sieve plate.

All of the vessels in the system are connected to a common vent on the top product

receiver. This vent is normally connected through a 4.0m length of tubing to a fume

cupboard or safe atmospheric vent outlet.

Console and computer control/display

The console is attached to the process unit for display and control of the various

operating parameters of the distillation column (see Figs. 2-4). Optionally the process

can be fully controlled from the connected computer (see Fig. 5).

Tabular Display

To view the Table screen click the View Table icon from the main tool bar or click Table

from the View dropdown menu as shown:

The data is displayed in a tabular format, similar to the screen as shown:

3

As the data is sampled, it is stored in spreadsheet format, updated each time the data is

sampled. The table also contains columns for the calculated values.

THEORY

To calculate the number of theoretical plates for a given separation at total reflux,

Fenske developed the following formula:

where n = number of theoretical plates

xA = mole fraction of more volatile component

xB = mole fraction of least volatile component

av = average relative volatility

Subscripts d, b indicate distillate and bottom respectively

The efficiency is given by:

Knowing the composition of distillate and bottom and the corresponding volatilities, the

column efficiency can be determined.

4

PROCEDURE

The reboiler is already filled with the liquid to be distilled (15 mole% ethanol, 85

mole% water).

1. Switch on the computer.

2. At the big control panel on the wall, set the “UOP AREA EXTRACT FAN”

(selector on the left), at “Hand position”.

3. Switch on the Armfield console by the computer. Load the software in the

computer. Go to “View” and select “Diagram”.

4. Identify all components in Figure 1. All valves must be closed except for V5

(cooling water) and V10 (below the decanter).

5. Set the equipment to operate at total reflux: on the reflux controller of the

console, put the selector on Manual position and make sure the ON/OFF button

is not on (no green light).

6. In the small room where the rig is, open the red valve on the wall to get cooling

water to the condenser. Set the water rotameter (above valve V5) to 3000

ml/min.

7. Choose options A or B and leave the apparatus for at least 30 minutes so that

the system can reach equilibrium conditions.

A. Automatic control using the software (PID1).

On the console, press the red button to activate the heater. Then put the selector

on I/O Port position to have it controlled from the computer. Press PID1 on the

screen’s diagram and set the following parameters:

Mode of operation: Automatic

Set point (T7): 77 oC

Proportional band: 50%

Integral time: 15 s

Derivative time: 0 s

B. Manual control using the console.

On the console, press the red button to activate the heater. Then put the selector

on Manual position. For about 5 minutes set the heat controller at high rate, 1.75

kW. Reduce to 0.85 kW once liquid starts flowing from the decanter back to the

5

column.

8. Start recording the data by clicking on .

9. Check that temperatures increase so that T1 reaches approximately 77 oC.

10. While the system is heating up, mark in Figure 1 the flow of products (cooling

water in blue and ethanol/water in red). The experiment takes place at total

reflux, so there will be no feed to the top product receiver or bottom product

receiver. It is a batch operation and takes place at normal pressure.

11. Take a sample of the distillate through valve V3 and a sample of the bottom

through valve V2. Use googles and gloves for this. CAUTION! SAMPLES ARE

HOT! Keep the vials in an upright position.

Repeat this procedure every 10 min until at least 3 samples of both distillate

and bottom are obtained. Label them carefully as D1, D2, D3,…, B1, B2, B3,….

Take the samples to the lab with your supervisor, to learn how to use the

refractometer. Measure and register the refractive index for the different

samples.

12. Record the temperatures T1 to T8 to calculate the average top and bottom

column temperature.

13. Click on to stop recording the data and save the file as Excel 5.xls.

14. Cool down by pressing the red button in the console to turn off the heater.

Check that temperature is dropping down.

15. Switch off the cooling water (red valve on the wall).

16. Shut down everything when temperatures have dropped down:

16.1. Turn off the console and the computer.

16.2. On the wall panel (UOP Area extract fan), set it “Automatic”.

16.3. Dispose the samples in a safe manner, using googles and gloves: pour

them in the plastic jerry can available in the rig’s room, labelled as “WATER

AND ETHANOL”.

6

Fig. 1. Schematic diagram of apparatus

7

Fig.2. Display and control of reflux ratio

Fig. 3. Display and control of power to rebolier heating element

8

Fig. 4. Display of distillation column temperature

Fig. 5. Display of distillation column temperature

9

Experiment DC: Distillation Column

Data Sheet

Group Number:

Group Members:

Date:

NB Wait 10 minutes before taking a fresh set of samples.

Distillate composition- ethanol

Reading Refractive index Composition Volatility

1

2

3

Average

Bottom Composition- ethanol

Reading Refractive index Composition Volatility

1

2

3

Average

Average top column temperature = °C
Average bottom column temperature = °C
Average column temperature = °C

10

x T [°C] y 
0 100 0 –
0.019 95.5 0.17 10.575
0.0721 89 0.3891 8.197
0.0966 86.7 0.4375 7.274
0.1238 85.3 0.4704 6.286
0.1661 84.1 0.5089 5.202
0.2337 82.7 0.5445 3.92
0.2608 82.3 0.558 3.578
0.3273 81.5 0.5826 2.869
0.3965 80.7 0.6122 2.403
0.5079 79.8 0.6564 1.851
0.5198 79.7 0.6599 1.792
0.5732 79.3 0.6841 1.612
0.6763 78.7 0.7385 1.352
0.7472 78.4 0.7815 1.21
0.8943 78.1 0.8943 1
x = mole fraction of ethanol in liquid
y = mole fraction of ethanol in vapour

= relative volatility

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Chemical Engineering & Applied Chemistry

CE2103: Separation Processes Chemical Engineering Process Laboratory

1

Distillation Column
Independent group work activity – assessment requirements

The Distillation Column laboratory experiment is assessed with a Group Report.
You need to follow the CONTENT and FORMAT described below.

CONTENT:

x Cover page – The front page of the report should contain the: title of the experiment, group
number and names of group members, module code, institution, laboratory supervisor, date of
the report submission.

x Introduction and theory behind your experiment – Here you present the aim of your
experiment and some basic context of the area your experiment relates to, as well as equations
and assumptions. Do not directly copy/paste what is written in the laboratory manual; use your
own words instead.

x Experimental data – This section contains some information regarding the experimental set-
up, as well as your experimental data and working conditions. Do not copy/paste the laboratory
manual.

x Experimental results and discussion – This part contains the calculations and results you
obtained. You can present your final results using tables, because they are more visually
attractive and easier for the audience to read. When you show your results, you must explain
and justify the quality of what you calculated/obtained, as well as discuss whether they are in
agreement with the theoretical trends and predictions. Simply mentioning “we observed this, we
observed that, we obtained this…” is not enough. In this section, you should also highlight any
hazards associated with your experiment and appropriate safety measures.

x Conclusions – This is a summary of your findings and shows how you answered the
experimental aims (for example ‘Aim: to determine the number of theoretical plates’ –
‘Conclusion: The number of theoretical plates was 25’). You also need to mention how this work
helped you develop your professional skills.

x Reference list – Create a reference list at the end of the report. This should contain the sources
you used to get your information (other than the laboratory manual). Use a consistent and
detailed format when you present your references. Choose a reference style (e.g. Harvard,
Vancouver, etc.) and follow it throughout the report and the reference list.

FORMAT:
Your report should be no longer than 6 pages (including Cover page and Reference list).

x Use Arial 11, 2 cm page margins and single spacing for the main text.

x Number all pages.

x Split the document in sections with subheadings. Add the names of those who contributed to
each section (in brackets) at the end of each subheading.

x Use the equation editor in Word to present equations and calculations. Number the equations
and use this number to refer to them within the text. Explain the meaning of the symbols you
use immediately below each equation.

x All figures and tables should be numbered and have captions and legends respectively. Refer
to them in the text by their number. Figure caption must appear below the figure and table
caption must appear on top of it.

Chemical Engineering & Applied Chemistry
CE2103: Separation Processes Chemical Engineering Process Laboratory

2

x If you present a figure, table and/or equation, you must refer to them in the text.

x Use technical language.

IMPORTANT INFORMATION RELATED TO THE ASSESSMENT:
What do you have to do?

x The submission will take place two teaching weeks after the week the experimental data was
given to you (for example: if you get the data on the Wednesday of week 16, you must submit
on the Wednesday of week 18.

x Group reports must be submitted via Blackboard page of the module CE2103. A submission link
is available on the main module page, as well as on the group homepage. Submissions
through email will NOT be accepted.

How are you going to be assessed?
Contribution to the group report is mandatory. All group members will receive a common mark.
Assessment criteria:

x Content of the report: 50/100

x Editorial efforts: 50/100

A marking rubric, to help you understand the feedback for your written report, can be found on
Blackboard under Assessment and Feedback Information (CE2103) and CEAC General Æ
CEAC Year 2 Chemical Engineering Laboratories.

RUBRIC FOR MARKING DISTILLATION COLUMN LABORATORY – Written report
CONTENT OF THE REPORT 50%

The report contains all sections as described in the Contents section. The majority of the
‘Introduction and Theory’ section is copied from the Laboratory manual. The calculations are not
easy to follow. Some of the parameters and/or their corresponding units are missing or are
incorrect. There is no attempt to explain/discuss the results. There is no mention of Hazards and
Safety procedures or they are mentioned in a very superficial way.

Pass

40-49

The report contains all sections as described in the Contents section. Some of the ‘Introduction
and Theory’ section is copied from the Laboratory manual. The calculations are easy to follow.
Most parameters and their corresponding units are included and correct. There is some attempt
to explain/discuss the results, but it is very superficial. There is mention of Hazards and Safety
procedures.

2.2

50-59

The report contains all sections as described in the Contents section. The ‘Introduction and
Theory’ section is not copied from the Laboratory manual. The calculations are easy to follow. All
parameters and their corresponding units are included and are correct. There is some discussion
but misses some of the results. Hazards and Safety procedures are presented and discussed
appropriately.

2.1

60-69

The report contains all sections as described in the Contents section. The ‘Introduction and
Theory’ section contains information from trustworthy published scientific literature. The
calculations are presented in a clear, consistent and logical manner and are easy to follow. All
parameters and their corresponding units are included and are correct. All results are explained,
and cross referenced within the discussion. Assumptions are clearly stated and referenced
appropriately. Hazards and Safety procedures are presented and discussed appropriately.

1st

70-

Chemical Engineering & Applied Chemistry
CE2103: Separation Processes Chemical Engineering Process Laboratory

3

EDITORIAL EFFORTS 50%

The report follows most of the format specifications requested. The cover page is missing some
of the requested information. There are many spelling/grammatical mistakes and the language is
not technical. Most figures/tables/equations are not numbered, and/or are inconsistently drawn
and difficult to read.

Pass
40-49

The report follows the format specifications requested. The cover page contains all the requested
information. There are some spelling/grammatical mistakes and some of the language is not
technical. Few figures/tables/equations are not numbered and/or some are inconsistently drawn.
There are some references for the information provided, but most/all are not from trustworthy
sources.

2.2
50-59

The report follows the format specifications requested. The cover page contains all the requested
information. There are very few spelling/grammatical mistakes and the majority of the language
is technical. All figures have captions and all tables have legends. All figures/tables/equations
are numbered and consistently drawn. Most of the information provided is referenced
appropriately using trustworthy sources.

2.1
60-69

The report follows the format specifications requested. The cover page contains all the requested
information. The report contains no typographical or grammatical errors and the language used
is technical. There is good signposting and the report is very easy to read. Any figures and/or
tables have captions that explain the contents of the figure/table and help the reader to follow the
data they present. All information provided is referenced appropriately using trustworthy sources
and the references are presented in a consistent format.

1st
70-