This post is devoted to serve as a complement to the Instructions Manual for the Armfield - Continuous distillation column UOP3CC. This post is intended to give a more hands on explanation of that document so students using this equipment can get up and run as fast as possible with such an equipment.
1 Safety first
- Always keep at hand the Instructions Manual so that trouble shooting and operation difficulties can be solved easily and quickly. You are advised to have a printed copy rather than an electronic version in your cellphone. In a printed version you can access faster to the information.
- Always read the background theory and instructions to follow before each experiment.
- Were safety clothing as necessary. Remember that you will be handling solvents and high temperature liquids.
- Always be aware of what other team members are doing so that accidents can be avoided.
2 The flowsheet
Before using the distillation column use sometime to know the equipment and its operation procedure through the flowsheet so that you can get a whole picture of it and have a feeling of what to expect during the experiments and while operation of the column.
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| Fig. 01 Distillation column UOP3CC flowsheet. Notice that in labels and tags T, V, P and F indicate: temperature, valve, pressure and flow rate; respectively. |
This flowsheet may challenging at first look but you must use your experience to identify,
- equipments (column, condenser, pumps, etc.),
- temperature probe locations,
- valve locations and type of it,
- streams and its nature,
- process understanding based on your interpreation of how streams, equipment, instrumentation and valves are integrated in the flowsheet.
Recall that the idea of this flowsheet is the most information in such an schematic way.
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| Fig. 02 A photo of the distillation column by Armfield model UOP3CC. |
A quick understanding and interpretation of the flowsheet depends on your experience on how the distillation process takes place and how peripherial equipment works. If you do not have this previous knowledge and experience you can cause an accident, harm yourself and others and damage the equipment or in the best of cases just poor value product recovery.
This distillation columns was built for demonstration purposes in a lab so that some safety is assured but this is not infalible.
3 Components of the distillation column
Well, in fact, these components correspond no only to the column as such but to those required to make it work. These are listed here,
- a distillation column, including a rectifying and a stripping section,
- a condenser for the rectifying section,
- a reboiler to boil the column feed,
- a decanter for phase separation and flow rate estimations,
- a heat exchanger for heating of feed to the column and heat recovery,
- two receiver tanks for bottom and top, of the column, products,
- a set of thermocouple probes located in different parts of the equipment,
- a U-tube manometer for distillation column pressure drop measurements,
- a rotameter for condenser flow rate feed measurements,
- a peristaltic pump to feed the column and
- a control console for either manual or through a computer software control of the whole equipment (not shown in the flowsheet).
Try to identify these components first in the flowsheet in above Fig. 01 and then physically in the equipment. All this has makes sense to you. Some parts in the equipment are labelled so that identification is not too difficult.
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| Fig. 03 A close up to the control panel of the distillation column. |
4 How the distillation occurs in the column
As you read the different experiments described in the Instructions Manual a number of paths about how the distillation column works shall be discovered. However, the present basic explanation could be a good point of start.
It all start with a binary mixture. You can use a number of fluids but some are recommended based on the fluids compatibility with the materials of construction of the column and operation limits of it. The mixture to be separated is to be placed in two locations:
- the feed tank (5 and 6). There are two feed tanks but only the one connected to the peristaltic pump (7) is in use, and
- the reboiler (13) boiling chamber, where the mixture is heated by means of a electric resistance to its boiling point.
Once the mixture is loaded it is feeded to the column by the peristaltic pump (7) from the feed tank (5) to one of the following plates:
- the main plate if you want rectifying and stripping operation,
- to the top (first) plate and
- to the bottom (last) plate.
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| Fig. 04 Pipe routing of feeding and from the reboiler. |
Since the distillation column is fed at the mid main plate, rectifying and stripping take place. Therefore, as the vapor phase with high concentration of the most volatile component reaches the top exit of the distillation column it is passed to a condenser (8) working with water as the cooling media. After this, the condensate flows downwards to a small vessel called: decanter or phase separator.
Since no further separation in the decanter will take place, it can be left unused by letting fully open the valve (V10), right below.
The stream coming out from the phase separator is split in two:
- a reflux stream feeding the top of the distillation column at the first plate and
- a stream, carrying the separated component, to the top tank product (10).
How do we control the flow rate in each of the above streams? For this task, the equipment has a solenoid 3-way valve also called reflux valve (12) whose time to be actuated can be estimated and programmed so that its operation is automated. Estimation of the operation rate of the reflux valve (12) is of interest since this may change efficiency of the separation.
At top tank product (10) you have a dead end but the reflux stream enters the process again so that it could reach the reboiler again. One may think that already separated component would end in the bottom tank product (9) but this is unlikely: the vapor rising from the bottom actually heats the liquid coming in countercurrent and since this liquid has high concentration of the most volatile component it evaporates easily so that only the solvent, having the highest boiling temperature, will reach the boiler (13). and eventually end in the bottom tank product (9).
This is a brief explanation of how the distillation column at hand works. Several othe subjects need to be explained:
- reflux valve (12) estimation and operation,
- peristaltic pump (7) flow rate estimation and operation,
- column distillation operation using the software or manually,
- sampling,
- pressure loss measurement, etc.
One final comment shall be given here. How do we operate the distillation column in batch mode? In this case, no feed at the main plate is done. The whole mixture is loaded into the reboiler (13) chamber and it is left to boil it. Eventually, the most volatile component ends in the top tank product (10) and the component of highest boiling temperature remains in the boiler (13) chamber.
This is the end of the post. I hope you find it useful.
Other stuff of interest
- LE01 - AC and DC voltage measurement and continuity test
- LE 02 - Start and stop push button installation 24V DC
- LE 03 - Turn on/off an 24V DC pilot light with a push button
- LE 04 - Latch contact with encapsulated relay for turning on/off an AC bulb light
- LE 05 - Emergency stop button installation
- About PID controllers
- Ways to control a process
- About pilot lights
- Solving the Colebrook equation
- Example #01: single stage chemical evaporator
- Example #02: single stage process plant evaporator
- Example #03: single stage chemical evaporator
- Example #04: triple effect chemical evaporator
- Gas absorption - General comments
- Equilibrium diagrams from gas component solubility data
- Distillation - General comments
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Ildebrando.
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