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MICROCOMPUTER-CONTROLLED DISTILLATION UNIT
MANUAL
The microcomputer-controlled distillation column is an interchangeable 50mm diameter
sieve tray column and a packed Raschig ring column that separates 7.5 wt% methanol
and water. A tray column is currently in use with eight sieve trays with downcomers.
Figure 1: Photograph of Distillation Column
A schematic is shown in Figure 2 below.
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Figure 2: Schematic of Distillation Column
A simplified version of this schematic is available by selecting the “Flowsheet”
option on the computer.
The system features are described below:
Temperature readings are available at seven locations:
T1 feed tank
T2 vapor from feed tank entering column
T3 vapor leaving top of column
T4 condensate liquid temperature
T5 reflux returning to column
T6 cooling water into reflux condenser
T7 cooling water out of reflux condenser
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The temperatures are monitored by thermistor sensors in protective pockets and
can be observed on the main control unit by setting the multi-position knob to the
thermocouple number you want to track. If the setting is maintained at “12”, then all
temperatures will be sent to and displayed on the computer. The temperature readings
are displayed in Celsius units.
The feed tank is made of corrosion resistant stainless steel and has two
electrically heated cartridge-type heating elements. The power to these elements can be
continuously varied by adjusting the control knob and monitored from the digital watt
meter above it. The watt meter will supply power from 0 to 2kW.
The reflux ratio is set using the computer control. The manual control on the
main unit does not work when the “12” setting for the temperature readings is selected.
If any other temperature setting is chosen, then reflux can be changed manually on the
unit if desired. After starting the program on the computer, a menu will allow you to
choose between total reflux, varied reflux, programmed reflux “reflux program”, or
controlled reflux. The reflux ratio can be varied from 0.01 to total reflux.
The pressure drop across the column is recorded from the U-tube manometer.
The distillate receiver has height markings for approximate measurement of
flowrate, when used in conjunction with a stopwatch.
The cooling water is available for the distillation column through a cooling water
supply. Yellow valve 5 (against the wall) allows for cooling water supply for the
condenser. The flow rate for cooling water is set by the rotometer, which is equipped
with a black control knob to control the flow. The cooling water flow rate can be varied
from zero to 3 L/min, though it should be maintained at as close to 1 L/min as possible.
There is a pressure relief valve on top of the condenser to protect the system in the event
of a blocked vent or cooling water failure.
The “distill” computer program allows for tracking of temperatures and reflux
ratio. Additionally, it can also be used to graph data (this is under “Reload Old Data
From Disk”), to control the top of the column temperature, or to control the reflux ratio.
Data can be saved on a 3 ½ “ PC formatted disk.
A refractometer with manual is provided for methanol concentration
measurement.
Sample vials with caps are used to inhibit methanol distillate samples from
evaporating before they are measured for concentration using the refractometer.
The level control unit on top of the main control unit is presently not working, so
it is unplugged.
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The “distill” program has a virus associated with it. When you are saving data
onto a disk, the virus will be saved on that disk as well. Use caution before using the disk
again. Open the disk on a university computer or a computer will reliable anti-virus
software. The management is currently working on eliminating the virus.
The “distill” program will not save data that is saved in a file name longer than 8
charcters. This causes the program to crash. The management is also looking into fixing
this issue.
Safety considerations:
1. NEVER start/run the column without cooling water.
2. The reboiler is hot. Avoid touching it unless necessary. Use a heat-safe glove
when touching the reboiler.
3. The column has an insulating jacket that can be held open to make observations,
but should be left on to avoid excessive heat loss and potential burns.
4. NOTHING must go down the drain when using this column. Contents in sample
containers and the distillate receiver must be placed back into the reboiler.
Methanol is a serious groundwater contaminant and any spills result in severe
fines for the university. Alert the lab manager immediately when you encounter
any possible methanol leaks or spills.
5. Gloves, safety glasses, and long pants should always be worn when using the
column or working in the lab.
6. It is the column user’s responsibility to be aware of the health and safety risks of
the chemicals involved with this unit. Every user must look up the MSDS for
every chemical they are in contact or potentially in contact with.
Start –up procedure:
1. If distillate is in the distillate receiver tank (clear tank with cm markings), empty
into the reboiler using the valve under the distillate receiver tank.
2. Be sure the reboiler is at least 2/3 full of liquid before starting. Liquid level can
be observed from the sight tube on the side of the reboiler.
3. Slowly open yellow valve #5, the cooling water supply main valve.
4. Open the rotometer valve to 1 L/min to allow cooling water into the condenser.
After a few moments, cooling water should be draining out of the other side of the
condenser and into a drain on the floor.
5. Turn on power to the unit using the on/off switch. Be sure the temperature select
knob is at “12” so that temperature signals are sent to the computer.
6. Start the computer. At the C:\> prompt, type “distill”.
7. Choose #2, “Use another mixture”.
8. At the function choice menu, select 1. Scan New Data to run the column.
9. On the main control unit, select the reboiler power (kW).
10. Follow the instructions on the screen to select total reflux, continuous reflux,
controlled reflux, etc. Once these choices are entered, the column will begin
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operation and a screen with the temperatures and reflux ratio will be displayed
while the experiment is in progress.
11. Data will be saved to the inserted disk after the run is complete and the user has
exited from the temperature display screen.
12. Be alert and check for methanol leaks and smells for the duration of the
experiment.
Shutdown Procedure:
1. Save data from previous run. Never use a file name that is more than 8 charaters
long otherwise the program will crash.
2. Turn down the reboiler power to zero.
3. Shut off main control unit power.
4. Exit from computer. At C:\> prompt, shut off computer and monitor.
5. Let cooling water flow for 10 minutes until all distillate has been drained from the
condenser. Close rotometer valve. Slowly close main cooling water valve to
avoid causing a water hammer.
6. Drain all collected distillate from the distillate receiver into the reboiler tank by
opening the valve below the distillate receiver. Important - close valve when
finished. Likewise, dump all methanol/water samples used for concentration
analysis into the reboiler. Important – use a glove when touching the reboiler!
7. Be sure to leave the rotometer clean for next time use.
8. Be sure all glassware is clean and/or properly disposed.
Marina Miletic
August 8, 2003