"Cooking" oxygen is possible!

This post is to update the process done so far.

At a time when inhaling with a high proportion of oxygen is becoming increasingly relevant for treating patients with covid, we have started exploring options that can be decentralized and enhance community capacity and know-how.

There are several DIY approaches, some of them listed in a previous thread here:

https://metastudio.org/t/let-us-explore-how-we-can-produce-oxygen/11597

Chemical method

We are following a chemical process, while other teams are working on oxygen concentrators.

schematic-oxygen-generation-photo_2021-05-05_21-34-56

We managed to successfully generate oxygen as this video shows below.

https://badal.hbcse.tifr.res.in/index.php/f/191697

We used a 20litre mineral water bottle, filled it with tap water, and displaced water for the released gas, which is definitely oxygen (with some expected gases and humidity). The following reaction is used;

2Na_2CO_3⋅3H_2O_2→2Na_2CO_3+3H_2O_2

which is Sodium Percarbonate releasing hydrogen peroxide, and

2H_2O_2→2H_2O+O_2

hydrogen peroxide in turn releasing oxygen. We roughly calculated that more than 20 liters of oxygen can be generated from 200gms of the reagent. We used KMnO_4 to increase the rate of reaction.

Next Challenge

The released oxygen to be compressed in either oxygen cylinders when available, or a large size pressure cookers (we still need to design how to do this).

This post is also to keep tinkering on this part of the puzzle, viz., how to compress and deliver oxygen to the patients.

Parallel Challenges

DIY methods of making nasal canula. For example, see the following post:

If any of you are interested in supporting this, please reply below. We need people to document, write safety procedures to be followed, alert us about possible precautions to be taken, etc.

Testing the quality of oxygen generated: we need help in this. Go and look out for sensors, beg, borrow or bring as soon as possible.

At this moment we are focussing on compressing the gas into cylinders or pressure cookers, based on availability.

We will post updates as soon as possible.

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If a sick person is able to inhale as much as 5lpm, an empirical figure based on widespread reports from homes with oxygen concentrators in use in the emergency, while waiting for transfer to a full fledged hospital, the actual O² needed, at concentrations of 95% and above, in humidified condition, will be 10lpm. For safety, the device that delivers this needs to have a capability to supply about 15lpm, which is why the machines under development (eg the Houston Oxi-kit being completed by the various teams pulled together by the Maker’s Asylum initiative) are working out quite expensive (final figures awaited, but seems like tens of thousands of rupees). Reliable oil free pumps/compressors of that capacity are not cheap.

However, any system that can fill readymade pressure vessels, such as modified pressure cookers for storage, means that the production system and delivery system can be divorced, and operate at different scales. This could be an effective way of lowering the capital cost.

For the delivery system, if a valve can be devised that senses when the user is breathing out, and stops the oxygen flow for that period of time, the oxygen requirement will be roughly halved. This can also be a major area of cost efficiency.

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120 ATM agriculture spray pumps are available online at Rs.900/- . These are diaphragm pumps and use two 12 v 4 A motors. I have been using one for a month without problems. A standard car battery works well as a supply source. If the grid is available a regular pc smps will provide power. O2 can be pumped into tyres, which can hold substantial volumes and at pressure. But will require pressure regulators before being released to a patient. Before use tyre can be cleaned by pumping soapy water in and out.

Two ball cocks in series can act as inlet for chemical charge. Open the top valve add chemical and close. Open the bottom to let it flow into chamber, then close. Ball valves are commonly used in agriculture. They are rated to work upto 80^oC.

One can automate the valve with a 10 rpm geared motor.

Rural areas have a fantastic variety of pipes, tubes, valves and accessories to hook them up in any imaginable configuration. Cities have a very limited choice in such items.

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Googling long forgotten high school physics tells us that 20 Li of gas at STP (standard temperature and pressure ) compressed to 120 atm will occupy .16667 Li. Therefore a 20 Li can capable of withstanding 120atm will hold 2200 li when expanded to STP.

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which is your diaphragm pump please? For solar water pumps, my analysis indicated that a 100 watt 3 litre/minute can fill a 500 litre overhead water tank in 3 hours. 12 v 100 watt solar panel available for Rs 3500. I did find a suitable Shakti diaphragm pump but could not get it from Kochi or Coimbatore.

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How much pressure can a standard mineral water bottle withstand? how do we test?

Can we use pumps made for liquid for gases? If the pump is made liquid leak proof, can the same pump be gas leak proof as well?

Is this the kind of pump you have in mind?

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Dental compressors I was told are better. for example this one:

This is the same as the one I am using.

It is rated at 10bar.
A thumb test shows it to be gas leak proof too. Liquid pumps like this one dont use lubricant oil as the liquid acts as lubricant. With gas the diaphragm is guaranteed to wear out without lubrication. Spares are easily available in rural areas.