I am a newly retired experimental physicist. Is it feasible for an “amateur” to construct a liquid air plant? Do you have detailed descriptions of older (presumably simpler) liquid air plants, or references that might be of assistance?
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I am a newly retired experimental physicist. Is it feasible for an “amateur” to construct a liquid air plant? Do you have detailed descriptions of older (presumably simpler) liquid air plants, or references that might be of assistance?
2 Comments
Dr. Randall Barron
August 1, 2008It is definitely “feasible” to construct a small (4 to 8 liter/hour capacity) system to produce liquid air. The addition of the distillation column to separate LN2 and LOX involves a little more intricate design, however. Some older references that might be of interest to you include the following. The books are out of print, but they should be available at any university library.
[1] Mansel Davies, THE PHYSICAL PRINCIPLES OF GAS LIQUEFACTION AND LOW TEMPERATURE RECTIFICATION,” Longmans, Green and Co., London, (1949). This is a British publication—”rectification” in Britain is the same as “distillation” in the U.S.
[2] M. Ruhemann, THE SEPARATION OF GASES, 2nd ed., Oxford University Press, New York/London, (1949).
[3] Guy K. White, EXPERIMENTAL TECHNIQUES IN LOW-TEMPERATURE PHYSICS, 3rd ed., Oxford University Press, New York/London, (1979).
[4] A. J. Croft, CRYOGENIC LABORATORY EQUIPMENT, Plenum Press, New York, (1970).
Another text of interest is: J.G. Weisend, HANDBOOK OF CRYOGENIC ENGINEERING, Taylor & Francis, Philadelphia, PA, (1998).
Dr. Ray Radebaugh
August 1, 2008I’m responding to your question regarding the possibility of an amateur constructing a liquid air plant. I am fascinated by this question because as a senior in high school in 1958 I did just that, well almost. I set out to demonstrate the liquefaction of air as a science fair project. I learned about the process from encyclopedia articles.
I designed and made a two-stage compressor to achieve a pressure of about 2000 psi. Fortunately, I had a metal lathe in my basement that I could use to machine the compressor parts. The first stage was larger because of the lower pressure and I had some castings made for it. The second stage was smaller and I machined those parts from solid material. The crankshafts for both compressor stages were connected together and driven at about 60 rpm with a 1/2 hp motor and surplus gearbox. The compressor was successful in achieving the 2000 psi, but the heat exchanger I made was not effective enough to liquefy air, although I did reach about 120K. I used the Linde double expansion process, so I had an intermediate pressure line in the heat exchanger, which was made as a tube inside a tube inside a tube from copper refrigeration tubing and insulated with glass wool. Unfortunately, as a senior in high school, I did not design the heat exchanger well. It was too large and the heat transfer was poor. Thus, I could not get below 120K.
The most difficult part besides the heat exchanger design was the fabrication of the compressor. After finishing the system, I was able to buy a surplus military compressor that had three stages and an outlet pressure of 1500 psi. It performed about the same as the one I built. It turns out that it was this science fair project that got me interested in cryogenics and I have been in the field ever since.
After many years experience in the field, I might do things a little differently, such as design a better heat exchanger. Your question regarding what an amateur might be able to do is not so easy to determine. That all depends on what resources the amateur has available and what the budget limitations are. The budget limitations would determine how much is purchased and how much is home made. I would assume that such an amateur would at least have some sort of home shop with a metal lathe and drill press.
Putting together a small liquid air plant using new or used components, such as a compressor, along with some specially machine parts could easily be done by an amateur. However, most amateurs would need help in designing the system. I am not aware of any published plans for such a system where someone could simply follow the plans and put together a system without having a lot of engineering know-how.
Perhaps when I retire I may try to re-do what I did in high school and publish something on making a simple air liquefier. If you do run across something published about this, I would be interested in hearing about it.