Distillation Column
Labview Program Overview
August 30, 2002
Laura Trimboli
TABLE OF CONTENTS
I.
II.
INTRODUCTION
PROGRAM WITHOUT CONTROL PARAMETERS
i. Page 0
a) Column and Surrounding Temperatures
b) Valves
ii. Page 1
a) Individual Tray Selectors
b) Plots
iii. Page 2:
a) Levels
b) Steam Pressure
c) Flows
d) Tray Labels
iv. Page 3 File Headings
v. Page 4 Data Logging
vi. Page 5 Start Up
vii. Page 6 Pumps
viii. Page 7
a) Valve Instructions
b) Shut Down
ix. Page 8
a) Reboiler Warning
b) Feed Warning
c) Valve Attributes (visuals)
x. Page 9
a) McCabe Thiele Plot Equations
b) T- x - y Plot Equations
III.
PROGRAM WITH CONTROL PARAMETERS
i. Page 0
a) Column Temperatures
b) Surrounding Column Temperatures
c) Valves
ii. Page 1
a) Individual Tray Selectors
b) Plots
iii. Page 2
a) Levels
b) Steam Pressure
c) Flows
d) Tray File Labels
iv.
v.
vi.
vii.
viii.
ix.
IV.
V.
Page 3 File Headings
Page 4 Control System
Page 5 Data Logging
Page 6 Start Up
Page 7 Pumps
Page 8
a) Valve Instructions
b) Shut Down
x. Page 9
a) Reboiler Warning
b) Valve Attributes (visuals)
xi. Page 10
a) McCabe-Thiele Plot
b) T- x- y Plot
APPENDIX A
i. Conversions
a) Valves
b) Tank Levels
c) Steam Pressure
d) Flows
APPENDIX B
i. McCabe-Thiele Equations
ii. T -x -y Equations
INTRODUCTION
This program is designed in a sequence of pages within a while
loop, which continuously runs the program. A picture of the setup
showing the first page is shown below. In some pages, there are subpages, formula boxes, and ‘True/False’ cases. These are all very easy to
understand in terms of their functions.
This report gives only an overview of the program’s contents. It
does not go into much detail. But again, the set-up is not difficult to
follow.
Sequence, Page 0 of 9
Sub-Sequence, Page 0 of 1
While Loop, runs until 'SHUT DOWN' button is hit
PROGRAM WITHOUT CONTROL PARAMETERS

PAGE 0
COLUMN AND SURROUNDING TEMPERATURES
All tray and surrounding column temperatures are taken from a VI1 named
‘Temp Grab.’ This VI contains the calculations from thermocouple voltage
readings to temperatures.
Each temperature indicated on the front panel2, is an average of 9 consecutive
values coming from the thermocouples.
VALVES
The valve values input by the user are put into a VI called ’Valves.’ This VI
controls the valves. Conversions (See Appendix A) are included to adjust each
valve to operate at a value of 0(closed) to 100(fully opened.)
The labels for data logging are also included on this page.

PAGE 1
INDIVIDUAL TRAY SELECTORS
Each tray and reboiler has a button and a color associated with it. When
selected, the temperature values are plotted on a plot on the front panel.
PLOTS
Tray and reboiler temperatures are taken from the “Temp Grab’ VI and plotted
on the front panel if button is selected. Temperatures are displayed in a oneminute time frame.

PAGE 2
Level, Steam Pressure, and flow values are all taken from a VI named ‘Lev-FlowS.Pres.’
LEVELS
Tank levels are indicated visually and numerically on the front panel. An
appropriate value is added/subtracted (See Appendix A) from the reading to
scale to zero. The levels are displayed in percentage full as a function of voltage
reading.
STEAM PRESSURE
Steam pressure is displayed on the front panel in units of psig using a formula.
(See Appendix A.)
1
VI is an abbreviation for Virtual Instrument. These are programs within Labview. The extensions of these
programs are ‘VI’, as ‘doc’ is to a word document.
2
The front panel is the viewable interface of the program.
FLOWS
Flow rates are displayed on the front panel in voltage readings. An appropriate
value is added/subtracted (See Appendix A) to the original reading to scale to
zero when flows are zero. Next, a conversion is displayed on the front panel to
convert to units of ml/s, which is also displayed on the front panel.
TRAY LABELS
Column trays and reboiler are labeled and sent to file heading for data logging.

PAGE 3
FILE HEADINGS
A combination of all temperature readings, tank levels, flow rates, valve
settings, data logging time in seconds, and date and time are all sent to a blank
file heading to be read by an Excel spreadsheet file when logging data.

PAGE 4
DATA LOGGING
All data mentioned in the previous page is sent to an Excel spreadsheet as soon
as the ‘Start Logging’ button is selected. The data is automatically saved in the
C directory as: ‘C:\Temp\’current date’ + optional user name.’ Date is in the
form ‘Friday, August 23, 2003.’ The user can add an additional name to be
appended to the date. The file must be opened with a ‘tab’ AND ‘commas’
format.

PAGE 5
START UP
The start up program is designed for the lab staff to set the column to steady
state at total reflux. The button is disabled when reflux is turned on and
enabled when the program is restarted.

PAGE 6
PUMPS
This page reads the values of the valve settings and turns on the appropriate
pumps for that operation. The distillate and reflux valves turn on the same
pump. Also, the pumps are originally set to the ‘ON’ state. Therefore, the pumps
turn on with a value of ‘False.’ The maintenance pump is also set to the ‘OFF’
position on this page.

PAGE 7
VALVE INSTRUCTIONS
By selecting the valve headings on the front panel, an appropriate VI had been
designed to open with instructions.
SHUT DOWN
All valves are set to zero when the shut down button is selected.

PAGE 8
REBOILER WARNING
A warning is set to appear on the screen when the reboiler level is close to the
green/red lower line on the glass level indicator next to the reboiler. When the
fluid reaches that level, the steam valve will automatically shut off. When the
level reaches the black line on the level indicator, the bottoms pump will shut
off.
FEED WARNING
A warning appears for 5 seconds when the feed valve is open. This warning
reminds the user to check the direction of the feed flow to the system.
VALVE ATTRIBUTES
When the valves are open, a picture of a valve, set to the selected valve opening
appears on the screen in the appropriate place on the column diagram.

PAGE 9
MCCABE-THIELE
An equilibrium curve, x = y curve, and tray compositions are plotted on a
waveform chart. This chart is displayed on the front panel when the appropriate
button is selected. Tray compositions are connected to form what appears as
trays on the diagram. See Appendix B for formulas used.
PROGRAM WITH CONTROL PARAMETERS
PAGE 0
Same as Page 0 in program without controls


PAGE 1
Same as Page 1 in program without controls
PAGE 2
Same as Page 2 in program without controls


PAGE 3
Same as Page 3 in program without controls
PAGE 4
The control system uses the VI named ‘Basic PID’ to control the feed, steam,
reflux, and bottoms valves. All trays and reboiler temperatures are set as the
controlled variables.

PAGE 5
Same as Page 4 in program without controls


PAGE 6
Same as Page 5 in program without controls
PAGE 7
Same as Page 6 in program without controls

PAGE 8
Same as Page 7 in program without controls
Included is a plot of the controlled output variable and the set-point value.

PAGE 9
Same as Page 8 in program without controls


PAGE 10
Same as Page 9 in program without controls
APPENDIX A
CONVERSIONS
VALVES (Page 0, sub-Page 1, w/o controls & w/ controls)
Valve
Reflux
Product(Distillate)
Feed
Bottoms
Steam
Original Settings
0–9
0–7
0–7
0–5
0–9
Conversion
0.09
0.07
0.07
0.05
0.09
New Settings
0 – 100
0 – 100
0 – 100
0 – 100
0 – 100
TANK LEVELS (Page 3, sub-Page 0, w/o controls & w/controls)
NOTE: Reflux, distillate product, and bottoms tank levels were all calibrated starting 2
inches below the cylindrical bottom tank edge. Feed and reboiler levels were calibrated
starting at the bottom of the glass level indicators on the side of the tanks.
See attached Excel sheets for voltage reading calibrations.
Voltage readings from the board did not read zero when tanks were empty. Therefore,
the following values were either added or subtracted from the displayed values to get an
accurate value
CONVERSIONS TO ZERO
Product (Distillate)
Reflux
Feed
Reboiler
Bottoms
Subtract
Add
Subtract
Subtract
Add
0.418
0.118
0.336
0.320
0.268
CONVERSIONS TO PERCENTAGE
Product (Distillate)
Reflux
Feed
Reboiler
Bottoms
y = percentage full
y=42.212*x
y=45.949*x
y=68.993*x
y=28.726*x+21.51*
y=75.299*x
x = voltage reading form board
*REBOILER LEVEL: Only data taken from 6 inches from the bottom was used for the
following calculations. (See Excel sheet.) This tank level may be off.
STEAM PRESSURE (Page 3, sub-Page 1 w/o controls & w/controls)
Steam pressure valve was calibrated using six values (See Excel sheet.)
Steam Pressure
y=0.945*x^3-7.6675*x^2+27.965*x-22.909
y = pressure in psig
x = reading from board
FLOWS (PAGE 3, SUB-PAGE 2 W/O CONTROLS & W/CONTROLS)
The following values were subtracted from the board readings to display
accurate flow readings.
CONVERSION TO ZERO (AT ZERO FLOW)
Reflux
Product (Distillate)
Cooling Water
Bottoms
Feed
1.02
0.57
0.62
0.62
1.00
APPENDIX B
MCCABE-THIELE AND T-X-Y DIAGRAM FORMULAS
The following data was taken from a T-x-y diagram on Distil-student for a
methanol/water mixture.
Bubble point curve
x
0.99999
0.96000
0.90000
0.86000
0.80000
0.76000
0.70000
0.66000
0.60000
0.56000
0.50000
0.46000
0.40000
0.36000
0.30000
0.26000
0.20000
0.16000
0.10000
0.04000
0.00001
Temp
64.4833
65.0488
65.9154
66.5065
67.4159
68.0398
69.0076
69.6783
70.7320
71.4737
72.6619
73.5177
74.9280
75.9777
77.7780
79.1806
81.7228
83.8321
87.9650
94.0411
99.9964
Dew point curve
Y
0.99999
0.95594
0.89804
0.85746
0.79780
0.75949
0.70222
0.65894
0.60388
0.55678
0.49661
0.45952
0.40000
0.36433
0.30171
0.26000
0.20000
0.16000
0.10000
0.04000
0.00010
Temp
64.4833
65.9154
68.0398
69.6783
72.2543
73.9690
76.5440
78.4553
80.8050
82.7268
85.0572
86.4252
88.5172
89.7135
91.7182
92.9908
94.7414
95.8600
97.4715
99.0099
99.9964
This data was plotted to get composition as a function of temperature (See Excel
sheet.) These equations were then used in the distillation program to plot the
column compositions on both the McCabe-Thiele and T-x-y plots using the tray
and reboiler temperatures.
The equilibrium curve for the McCabe-Thiele diagram was drawn using
constants and an empirical expression taken from the book Conceptual
Design… by Doherty and Malone3.
Table 2.6
Constants in the Empirical VLE model for selected binary mixtures
Mixtures without inflections or azeotropes
Light Component Heavy Component
(bp, C)
a
Methanol
Water
64.6 - 100
7.15
3
Doherty.and Malone. Conceptual Design of Distillation Systems McGraw Hill, 2001.
b
-0.33
Equilibrium Curve for McCabe-Thiele
Equation 2.35
y=
ax
1 + (a-1)x
+ bx(1-x)