Batch Distillation
Introduction
After completing the intial exploration of the LEGO Dacta kit, the
capabilities and limitations of future projects were found. Being a Chemical
Engineer, it was difficult to find any engineering aspects of the LEGOs that
could be applied to this discipline. The LEGOs seemed to fit in better with
the mechanical and electrical engineering backgrounds of my lab partners.
However, given the limitations of the LEGOs in the field of Chemisty, it is
still possible to design some interesting projects. One such project is a
mini-scale batch distillation drum. This project would fit well within the
limits of the LEGO kits, while giving a freshman engineer an introduction to
basic chemical engineering.
Project Description
Using the LEGO kit, a very simple batch distillation drum can be built.
The actual construction of the model will involve mechanical engineering. Motors
and pulleys will have to be arranged in order to open and close valves on the
drum in order to release the vapor and liquid contents after distillation has
been completed. The theory behind the project will involve chemical
engineering. As it is only a model, water will be used as the feed. A
container within an insulated, LEGO shell will act as the distillation
chamber. This chamber should be completely sealed during operation. It
should have to closable outstreams, one for the vapor component and one for
the liquid component. Also, there should be a means of refilling the chamber
after a distillation is completed. A temperature sensor is placed within the
chamber, along with a heat source that can heat the drum.
The actual operation of the apparatus should be fully automated through use
of a computer program. After an initial charge of fluid is injected into the
chamber, the heat source is turned on. The temperature is monitored until an
equilibrium value is reached. Ideally, if two components were being
separated, such a value would be reached, but in this case, a temperature
should be set. Once this temperature is reached, the two valves are opened,
with both streams being collected in separate containers. The chamber is
flushed of its contents, a new batch is installed, and the process repeated.
This project emphasizes the theory behind the design of the project. Basic
mass balances will have to be solved in order to size the containers used.
Energy considerations will have to be addressed in order that the LEGOs are
not melted by the heat source. Also, a freshman would learn the basic concept
of distillation while designing the project.
Besides just distillation, if the appropriate equipment could be obtained,
this project could be expanded to a batch reactor. Using the much alluded to
pH meter, a simple acid-base reaction could take place within the reactor and
the pH monitored instead of the temperature. A heat source may again be used
to start the reaction, but the vapor exit would be eliminated.
Conclusion
Given the limitations of the LEGO Dacta kits, only simple chemical
engineering designs are possible. It is very unlikely a freshman engineer
would be able to design an entire distillation column or manufacturing
process. A batch distillation or reactor is simple enough that it can be
modeled on a small scale. While teaching the basics of engineering design, it
would also introduce the concepts of chemical engineering. There would not be
much of a possibility for a competition in this project, unless the projects
were evaluated on efficiency and economic considerations.
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