oxygen concentrators

Hi,

I was listening to the BBC world service the other day and there was a programme on about providing oxygen in Africa for Covid 19 patients. As it said 'what happens when the electricity fails'? It went on to describe a technique for producing oxygen from the air without using electricity. Here's a link to the idea;-

https://pneumonia.biomedcentral.com/articles/10.15172/pneu.2015.6/529

I think you might have to copy that into your search bar. Anyway the idea seems very simple and I wonder why we buy oxygen cylinders from BOC at huge cost when you can extract 95% pure oxygen from the air around us with just a compressor and a canister of zirconia which is apparently abundant and low cost. Take a look at it and see if you can see any reasons why it couldn't be used for a welding or brazing torch.

That's a very clever adaptation of the systems used for domestic oxygen concentrators, like the one my Nan had for her emphysema.

Neil

My oxycon will produce up to 5 litres of oxygen per minute at around 88% purity (better at lower volume rates). It is not quite big enough for a decent sized surface mix burner capable of easily melting borosilicate glass - works well on soda glass. I have considered buying another, if at the right price, to double the flow rate. 10 litre versions are (readily) available.

I’ve used it for small brazing jobs only, but I think one needs to collect more gas at higher pressure for bigger jobs - and I’m not too keen on collecting compressed pure oxygen.🙂

Adding ethanol/acetone to the fuel supply (as per my recent post about the ban good HHO machine) might provide a good fuel for brazing, along with my little oxycon?

Thread Here

I bought a used oxycon from a glass bead maker a little while ago. (and called into Arc Eurotrade on the way home)
The chap was using two of them together to run a bigger burner, but has upgraded to a larger setup.

I've been using it with propane as a fuel and both a small lead welding torch, and a normal sized oxy acetylene setup.
It seems to work well enough for the smaller silver soldering jobs I've wanted to do.

Certainly the £80 outlay, plus diesel in the Disco, costs in well for me compared to even rent free oxygen bottles.

Bill

It sounds like the OBOGS (On Board Oxygen Generating System) used on at least some military aircraft. The System takes air from the gas turbines and passes it over zirconia powder to remove most of the nitrogen. There are several packs of zirconia and when one is 'full' of nitrogen it is flushed out with air whilst another pack does the work. By this means the aircraft's range is not limited by how many heavy oxygen cylinders it can carry, though a short-term reserve of gaseous oxygen is carried, in case of emergencies.

Roy

**LINK**

The economics need looking at carefully; if this was the cheapest way of making oxygen everybody would be doing it!

• I see 2kg of Zirconium Dioxide costs £256.
• The paper discusses providing Medical Oxygen in Papua New Guinea. I think it can be assumed there isn't a local BOC just round the corner and cylinders have to be carried long distances over poor roads or flown in. High prices in the third world are likely due to transport and availability issues rather than the manufacturing cost of Oxygen.

My regional British hospital doesn't use BOC either! Makes its own Oxygen in a whopping big Air Liquification Plant that takes up as much space as my house and garden and is slightly taller. Presumably a big Teaching Hospital consumes enough high-grade oxygen to make it worth eliminating transport and third party costs. Economies of scale look to have failed my dinky little Cottage Hospital - it has Oxygen cylinders delivered by lorry.

I can see an Oxygen Concentrator would win if very low volumes of not very pure oxygen are needed, because it eliminates the cylinder hire, recharging and transport costs.

Cryro methods are more expensive the either the Zircona, Membrane, or Hydroylsis methods. But there are loads of gotchas. High purity Oxygen is most cheaply made by cryogenic processes, which also produces pure Nitrogen and pure Argon as valuable by-products. If there's a market for them, the Oxygen can be sold more cheaply than it cost to make. And when Hydrogen is made by hydrolysis, Oxygen comes off as the "free" by-product.

As is often the case in engineering, the right answer depends on money and circumstances.

Dave

Yes , it's called pressure swing absorption. You have two canisters of zirconia and they are used sequentially. The BBC programme though emphasised that it doesn't have to be high tech and could be repaired by mechanics because its intrinsically safe. There are no high pressures or tanks of oxygen. I couldn't find any references to anyone trying to make one however.

Old folk across the UK have them in their homes.

Much less faff than changing oxygen cylinders, especially if you are old, weak and arthritic and no worry about cylinders running out.

My nan only used cylinders when she went out on her mobility scooter (courtesy of the RAFA).

Neil

I think the economics of all supplied atmospheric gas is dominated by the steel industry. Vast amounts of oxygen are used in the conversion of iron to steel which can only be provided by liquefying air. All the other gases, mostly nitrogen and argon, are by-products.

JA

Edited By JA on 23/05/2020 14:23:01

Edited By JA on 23/05/2020 14:24:29

The other advantges of concentrators for home use is the removal of the safety hazards of high pressure cylinders and stored quantiities of oxygen in the home and and the logistics of supply and transport t multiple users.

Robert G8RPI.

The process on the Fre02 website which refers to the Africa project is described as low cost compared with cylinders. To quote;-

These devices contain ‘molecular sieves’ of zeolites, which are made from an abundantly available, low-cost mineral. When air is compressed and brought into contact with zeolite, nitrogen in the air is preferentially adsorbed over oxygen.

A look for zeolite on eBay shows it costs about £10 a kg. I don't think they would have considered it if it was costly. They were talking on the World Service programme about very low costs. I think the programme is still available on Iplayer.

Mine is a reconditioned one like the ones down the RHS of THIS page. One might understand why I was considering buying a second 5l example (not a new 10l example). I’ve had mine several years and even these recon units, from Martin, are much more expensive than back then...

I expect I will try an internal mix nozzle, if I ever need one - but the connections are different than the simple ones on my surface-mix Nortel Minor

Zeolite also used by fish keepers for removing ammonia from the water, the ammonia being waste product excreted by the fish, too much dissolved ammonia will burn the fishes gills and also build up to toxic levels.
Dave W