There are simple experiments that anyone can do to to split water into hydrogen and oxygen. All that’s needed is a couple of simple electrodes and a power source. The electricity will split apart the water molecules and the hydrogen will cling to one electrode and the oxygen to the other. Could something like that be cobbled together to provide supplemental oxygen for breathing at a similar rate as being hooked up to an oxygen tank? So rather than the mask being hooked up to the tank, the mask is hooked up to the electrolysis setup.
Napkin math:
Per Wikipedia, a 100% efficient electrolysis generator would consume 39.4 kilowatt-hours per kilogram of Hydrogen. There’s a 1:8 ratio of hydrogen to oxygen in water, so oxygen generation is limited to 4.9 kW-hr / kg.
Given a 2L / min supplemental oxygen flow rate, at 1.429g/ Liter of oxygen at STP, this is a consumption of 0.171 kg/ hr. Which should mean that it should take a constant power draw of 0.84 kW to generate this. Given typical industrial electrolysis efficiencies, let’s just round up to a nice even 1 kW.
Of course, you still have to deal with the hydrogen production in a way that doesn’t burn your house down, but it doesn’t seem completely unfeasible.
I am not a doctor and there are other considerations critical to health before electrolyzing water for this application. For example, pressure of produced oxygen and safe disposal of produced hydrogen comes to mind. I am doing these calcs just to hypothetically show the amount of water and electrical power needed.
That Said :
High Flow Nasal Cannula (HFNC) - requires about 50 l/min of air with Oxygen concentration at 45%. High Flow Nasal Cannula (HFNC) - Part 1: How It Works - REBEL EM - Emergency Medicine Blog
Since Air already has 21% oxygen, and 79% nitrogen, the math gives :
35 l/min of air will need to be combined with 15 l/min of pure oxygen to give 50 l/min of 45% Oxygen air.
22.4 l = 1 mole, so 15 l = 0.67 moles of Oxygen / min
Since one mole of water gives 1/2 mole of oxygen, you will need 1.34 moles of water to disintegrate every mins. 1.34 moles of water = 1.34 x 18 = 24.12 grams of water per min
237.13 kJ is required to split 1 mole of water.
318 kJ is required to split 1.34 moles of water (24.12 grams) in 1 min
318 kJ/min = 19,080 kJ/Hr
19,080 kJ/hr = 5300 Volt Ampere
Roughly the size of a home AC unit.
So accounting for inefficiencies, if you used a electrolysis voltage of 5 V (it has to be over 1.23 V), you will need about 1060 Amps.
You can do many smaller cells, but the overall power will be the same. You will also need Platinum or Gold or Stainless Steel electrodes with the largest possible surface area to not have bubbles stick to it.
Good luck
I think we have comparable numbers, except the 2 L /min is more like 15 L / min, so your nice even 1 kW becomes 7.5 kW - comparable to what I got.
Good to see that our calcs match.
Other than as a thought experiment, how is this any better than current technology oxygen concentrators?
The OP was thinking of something that can be cobbled together from things found around the house (or hardware store). I don’t think it would be easy to MacGyver an oxygen concentrator.
Although now that you mention it, would an oxygen-enriched gas stream be a by-product of a liquid nitrogen plant?
It is not better in any aspect. I think the OP maybe asking because of wide shortages of concentrators in India and the dire need of oxygen.
I was wondering if it would be feasible in an emergency when oxygen tanks or a concentrator isn’t available (like the oxygen emergency in India). Since most everyone has water and electricity, most everyone can easily produce oxygen. But it looks like the energy requirements needed to produce enough for supplemental oxygen would be impractical for an improvised electrolysis device. If someone can setup a sufficient at-home oxygen electrolysis system, then likely they would be able to get something more efficient.
Yes
Argon, Oxygen and Nitrogen (liquid and gaseous) are usual products of cryogenic Air Separation Plants. Concentrations vary per needs, It’s is not uncommon to have oxygen 99% +.
In metal processing, Oxygen is desirable but nitrogen is not. In a fertilizer plant making ammonia, Nitrogen is desirable and oxygen is not, etc etc.
But whenever you make oxygen, you will make nitrogen and vice versa. (Cryogenic separations)
I ask because a previous employer had a LN2 separator on site, provided and maintained by a vendor (Air Products?). I remember a large storage tank for the LN2 (the separator produced more LN2 than we used, the vendor would periodically swing by with a tanker to siphon off the excess) but no other tanks. Would the other gases just be vented away? I assume our setup was not uncommon, which means that there may be a lot of concentrated O2 being generated but thrown away.
I have no expertise here, but …
ISTM that given the significant hazards of concentrated oxygen, whether liquid or gaseous, the best thing you can do with any you generate and cannot use in your industrial processes is to immediately vent it to the atmosphere to achieve dilution to safe concentrations ASAP.
Yes, one could store it and have the separation plant vendor come and take it away periodically. That would be more efficient in terms of energy consumption & effort expended. But that may not be a paying (= economically efficient) proposition given the safety requirements for storage and handling.
Depending on the exact application, you could increase your efficiency via CO2 capture. A human needs <1 kg/day of actual O2; the rest is wasted. If you’re breathing pure O2, then the output will be mostly O2 with some CO2 mixed in.
You can scrub CO2 from air with sodium hydroxide (lye, drain cleaner). If you’re trying to MacGyver something, I think you could probably bubble the waste air through a solution of water and NaOH and get pure O2 as a result. You’d probably have to change it fairly frequently and it produces a lot of waste heat, but it would definitely reduce the electrolysis needs.
This won’t work if the person is just getting extra O2 via cannula, etc. They need to be breathing pure O2 and you have to capture the output.
The specifications for this electronic closed-circuit rebreather
https://www.jfdglobal.com/products/defence-divers-equipment/underwater-life-support-systems/stealth-cdlse-mk2-ed/ (24 kg)
says the extended-duration scrubber allows dives of up to 6–8 hours (3–5 hours with the non-extended variant)
There is some market for compressed or liquified oxygen, and it’s produced by the same companies that produce nitrogen and argon. That said, it’s probably a fairly inflexible market, and much smaller than the market for nitrogen, so I expect that they do end up venting a lot of oxygen.
I’m not so sure about that. Ideally, you would use the waste O2 to pre-chill the incoming air. If you had a reasonable cross-flow heat exchanger setup, you’d pay almost no extra cost for the O2. You wouldn’t have to worry about storage at all.
I was just wondering if, assuming that there are likely metric craptons of LN2 separation units in India (due the the heavy usage of LN2 in the tech industry) if there would be some easy MacGyver-ish modification to the units to capture the O2 for medical use. As opposed to setting up jury-rigged electrolysis contraptions.
Of course that is assuming that the shortages are the actual oxygen and not an issue of logistics…
There are a lot of Oxygen plants in India. They are mostly used in the production of Steel, Copper and Other Metals. These plants are mostly concentrated near the metal production hubs : East and South of India.
Cryogenic Oxygen vaporizes during transport and has limited life. You also need special tankers + plumbing for transporting it - things that are long lead items.
1 Vol of Liquid Oxygen will give you 800 volumes of ambient conditions oxygen
1 Vol of Compressed Oxygen will give you about 200 of the same
So transporting liquid oxygen maybe a better ideas
It’s a very very bad idea to compress oxygen unless you have a special compressor. Recovering oxygen from exhaled breath will need you to somehow compress the recovered Oxygen - again very dangerous.
No compression needed. If you breathe in pure O2, then you breathe out O2+CO2. The CO2 can be scrubbed out by various means. Make sure the output is at the right temperature, etc., mix in a tiny bit of extra from a tank or electrolyzer, and you have an almost closed loop. Same principle as the rebreathers linked to above.
Oxygen has its own market. Coal gasification in China is driven by reacting coal with very pure oxygen , and most of Chinese plastic comes from gasification products like methanol …
Oxygen is needed for many of the rockets going to space. It is needed For metals processing : Steel, copper, …
Though phasing out slowly, the US also has a few gasification plants.