Oxygen options

[MikeS]

Great report. With a 24 cu. ft. "E" bottle and a pulse dose regulator I normally can go to the East Coast and back and still have some left in the bottle, using it constantly. But not the last trip. My regulator is not working right for some reason, or I've got a leak somewhere along the line. Still investigating this but meanwhile am again looking at these little concentrators that have been showing up the last couple years.

Thanks for the feedback on your system!

[1001001]

Originally Posted by airguy

That's not the source of nitrogen in question - it's the nitrogen from the concentrator. The concentrator pulls the oxygen out of the air and sends it to the pilot, and rejects the remainder which is almost entirely nitrogen. Since oxygen is 21% of the atmosphere, the concentrator is putting 4 times as much nitrogen into the cockpit as oxygen into the pilot.

I still don't think it's enough to worry about with our leaky cockpits.

Is this true? Industrial non-cryogenic oxygen separation processes with which I am familiar have a reject stream which is slightly nitrogen (and water vapor) rich, but not by much. These processes don't split the air efficiently, they take in large amounts of air and strip off a small volume of oxygen at high purity while rejecting the rest, which doesn't come out as oxygen-poor as you might expect.

[bigginsking]

Originally Posted by MikeS

Great report. With a 24 cu. ft. "E" bottle and a pulse dose regulator I normally can go to the East Coast and back and still have some left in the bottle, using it constantly. But not the last trip. My regulator is not working right for some reason, or I've got a leak somewhere along the line. Still investigating this but meanwhile am again looking at these little concentrators that have been showing up the last couple years.

Thanks for the feedback on your system!

my only experience is with a mountain high system, two of us flew from San Diego to eastern Colorado at 17.5k and after that flight the bottle was at something like 900 lbs, which is still enough to get you somewhere but not a full 5 hr leg if the first flight was any indication of what the consumption rate should be.

[BobTurner]

Originally Posted by bigginsking

my only experience is with a mountain high system, two of us flew from San Diego to eastern Colorado at 17.5k and after that flight the bottle was at something like 900 lbs, which is still enough to get you somewhere but not a full 5 hr leg if the first flight was any indication of what the consumption rate should be.

O2 use varies tremendously depending on the person and the system. Old systems flowed huge amounts 'to be sure'. Get a pulseoxymeter and conserving canulas (or a pulsed system) and see what flow rates you need. It may be less, or more.

[airguy]

Originally Posted by 1001001

Is this true? Industrial non-cryogenic oxygen separation processes with which I am familiar have a reject stream which is slightly nitrogen (and water vapor) rich, but not by much. These processes don't split the air efficiently, they take in large amounts of air and strip off a small volume of oxygen at high purity while rejecting the rest, which doesn't come out as oxygen-poor as you might expect.

Total quantity of effluent may vary, but there is no getting around the math. If you want to supply 1 liter of oxygen to the pilot, you MUST dispose of 4 liters of nitrogen via some method, if you are using atmospheric air as your feedstock. That doesn't mean the concentrator is disposing of 4 liters of pure nitrogen, it could be 40 liters (or 400) of nitrogen-enriched air, but the net result is the same. For every liter of oxygen you strip from the air, your going to have 4 liters of nitrogen to dispose of, one way or another.

[1001001]

Originally Posted by airguy

Total quantity of effluent may vary, but there is no getting around the math. If you want to supply 1 liter of oxygen to the pilot, you MUST dispose of 4 liters of nitrogen via some method, if you are using atmospheric air as your feedstock. That doesn't mean the concentrator is disposing of 4 liters of pure nitrogen, it could be 40 liters (or 400) of nitrogen-enriched air, but the net result is the same. For every liter of oxygen you strip from the air, your going to have 4 liters of nitrogen to dispose of, one way or another.

From an overall material balance standpoint, what you say about the ratio of nitrogen discharged to oxygen is correct. However, in a pressure swing adsorption based gas separation, the regenerating bed is purged with feed air to discharge the separated nitrogen, argon, etc. This results in a low concentration of the separated gases in the concentrator's waste stream.

Add in the fact that the cabin of a nonpressurized aircraft is not remotely a closed system, and the continual venting of the cabin makes nitrogen buildup a non-issue.

[skylor]

Originally Posted by airguy

Total quantity of effluent may vary, but there is no getting around the math. If you want to supply 1 liter of oxygen to the pilot, you MUST dispose of 4 liters of nitrogen via some method, if you are using atmospheric air as your feedstock. That doesn't mean the concentrator is disposing of 4 liters of pure nitrogen, it could be 40 liters (or 400) of nitrogen-enriched air, but the net result is the same. For every liter of oxygen you strip from the air, your going to have 4 liters of nitrogen to dispose of, one way or another.

The mistake with this logic is failure to consider the cabin-pilot-O2 Seperator as a single closed system. You have to remember that the O2 Seperator is not producing Nitrogen, it's only removing it from the "air" that the pilot is breathing. This means that while the pilot is breathing less nitrogen with each inhale, he's also exhaling less nitrogen with each exhale (and the O2 content of the exhale will be higher). Therefore, the net aircraft cabin N2 concentration should be unchanged when an O2 Seperator is being used.

Skylor