Dehumidification with Nafion Membrane for Oxygen Concentrator

Sounds a little pricey for 3rd world application....maybe powdered rice could be used....then eaten...In any case I think a desiccant might be cheaper for removal of moisture, and a combination of compression and desiccant would be even better....

https://en.wikipedia.org/wiki/List_of_desiccants

Why Nafion? Because these have been published on so much in conjunction with PEM fuel cells?

You should consider the effect humidity has on the relative permeability of your material if using PSA or if using a separation membrane for oxygen and nitrogen. Since you may not be interested (I have no assumptions about that) in pure oxygen, you might want a method that is highly permeable to nitrogen and water vapor, such that a relatively dry oxygen stream is left in process. Then it is simple to rehumidify.

Common Zeolites as molecular sieves are not the most efficient materials. Zeolite analogues are used as molecular sieves, and I have seen these materials used in drying process air to upgrade to instrument air.

I think you should keep searching for better ways. I seem to recall a new "re-breather" technology, that actually emits oxygen and allows very light weight dive gear, and does not rely on carbon dioxide absorption (but my old mind is a bit cloudy with a chance of rain).

Nafion, although it is not its main use, has been reported to be very effective in dehumidification processes (particularly in microfluidics). We are using a PSA technique for the project, and this is why we are focusing on removing humidity before passing it through the zeolite (as the water will bind tightly to the zeolite and not desorb when the pressure drops).

Although we looked into membrane concentration techniques, we decided that a traditional PSA process is more robust for this application. I will be looking into the tech used in rebreather systems though! Thanks!

This article doesn't mention any problem with water vapor in oxygen concentrators.

The oxygen concentrator uses zeolite to absorb nitrogen from air under pressure. When the remaining air is removed (mostly oxygen), under reduced pressure, the zeolite gives back the nitrogen, which is then vented to the atmosphere.

https://en.wikipedia.org/wiki/Pressure_swing_adsorption

Is this the same process you are using?

I think I might look at incorporating a regeneration cycle into the concentrator, have it regenerate automatically, perhaps include rotating zeolite capsules, one cooks while one works....

http://www.sciencedirect.com/science/article/pii/S1387181109003357

You understand that you will not be the first with concerns about using oxygen concentrators in the developing world, and that others have already addressed some of the issues. I do note that they did not mention your problem of a shortened lifespan of the zeolite. However, CR4 has already run a thread on refilling zeolite cartridges so maybe the users out there are truly having problems the manufacturers are not willing to admit to.

The idea of humidifying the outgoing oxygen with the water from the dehumidification of the incoming air is superficially attractive and new technology (Nafion) may be the ultimate answer. However, as a former medical professional, I may point out that humidifying the oxygen is not always essential. When it is necessary the required kit is cheap. Old technology (a series of silica gel cartridges on the oxygen concentrator inlet, dried out in turns) may still be a simple and cost-effective solution.

I certainly agree that a cheap bottle method for re-humidification would be cheaper and easier (although less novel) but this is probably best for the project.

I have been looking for information on the silica gel beds used, with absolutely no luck. Would you be able to provide a list of references for this so I can investigate it further?

The "dried out in turns" aspect is critically important for this project and it would be incredibly helpful to have more background on this. It seems that there are VERY few sources online that provide information about silica gel or other desiccants being used in standard concentrators (even in searching through service manuals).

I was thinking of using the canisters used for soda lime in the rebreathing circuit of an anaesthetic machine (see fig). They are designed to be easily removed and replaced with a freshly filled one. Silica gel is available in bulk on Amazon, so I would not foresee a difficulty in finding an industrial source. Equally, drying out a wet canister-full should not be too awkward.

I was hoping there could be an application for the new cobalt based material.

See this article:

oxygen storing substance - based on cobalt. This material certainly has a higher capacity than anything we have dealt with before. The molecule does not appear to difficult to make.

It would be ideal for situations where one does not require nitrogen in the flow, or can add air to the flow if pure oxygen is undesirable.

Nafion is hardly new technology.

I looked at developing this concept some 20 years ago. The use of the nafion was normally to produce nitrogen.

I met with complete obstruction by the distributors/manufacturers and I eventually threw in the towel. I would have used a primary dessicant to treat the inflow. Perhaps I should have kept the towel