fuel cell rebreather tech!

[kelemvor]

The article only mentions applications in atmospheric environments. 2" by 2" would scrub 2 liters per minute (a fraction of the breathing rate). Take that to 90m depth where the flow increases by a factor 10. What size would be needed and how would that compare to a sofnolime cartridge?

Probably why the article mentions using it in large scale installations such as spacecraft and submarines.

 

[Miyaru]

If you're gonna carry hydrogen you mgiht as well breathe it too, hydrox is the ultimate deep gas (if you can avoid exploding).

It's a candidate for helium replacement, the availability is not really an issue anymore.
Below 30m you can breathe a safe mix containing 4% oxygen. Travel gas....

Anyway, the concept is really interesting. What's the effect of carbondioxide plus hydrogen under higher pressure?
As far as I know, there hasn't been any (technical/)recreational diving with hydrogen, but it has been used in commercial diving. Maybe the commercial divers on the board know about this development?

 

[mlavigne]

While overall mass flow increases with depth due to increased density, the mass of CO2 is not depth related. How sensitive the efficiency of the technology to the concentration and flow rates is not indicated in the blurb.


Emphasis, mine:


Some napkin calculations:

Something on the order of a soda can will process approx 10 l/m of "air" - Exercise respiratory volume is 40-60 l/m - so lets say a factor of 5x
C02 in the exhaled gas stream is approximately 100x normal air concentration.

So ignoring unknown efficiency factors of concentration/pressure/flow rate: something on the order of 21 cases of soda (500 cans) should do it.



It is a shame. I was envisioning a a fully self contained eco-rebreather.

Mr. Fusion power source
Chess-Evans Desalinator
Electrolysis H2 & O2 production
UD CO2 scrubber

The portable carbon capture system would l have to be worked out, though to be "non-polluting".

Pure speculation, but my assumption (from other heat/mass transfer systems) is that if you sacrifice total efficiency, you could massively downsize the unit. So if you only needed 90% CO2 removal (from breath levels to normal atmospheric ~400-500ppm) you could likely increase the throughput. I just ran a heat exchanger (mass transfer is basically the same equations) simulator and its showing that dropping from 98% to 90% approach makes the same size exchanger 6x higher throughput.
So now its just 84 cans of soda (~30L)! Still might need some work.

 

[-JD-]

Pure speculation, but my assumption (from other heat/mass transfer systems) is that if you sacrifice total efficiency, you could massively downsize the unit. So if you only needed 90% CO2 removal (from breath levels to normal atmospheric ~400-500ppm) you could likely increase the throughput. I just ran a heat exchanger (mass transfer is basically the same equations) simulator and its showing that dropping from 98% to 90% approach makes the same size exchanger 6x higher throughput.
So now its just 84 cans of soda (~30L)! Still might need some work.

Since exhaled CO2% is 100x inhaled for nominal air, you need 99% removal or "You're gonna die."

 

[mlavigne]

Since exhaled CO2% is 100x inhaled for nominal air, you need 99% removal or "You're gonna die."

well thats an embarrassing math error on my part... 4% is 40,000 ppm, not 4,000.... yikes