18 June 2010

Live and Breathe Underwater Indefinitely In Personal Sub or Habitat

Once you get your hands on your personal submarine, you will probably want to be able to stay submerged for long periods of time -- especially if something unpleasant awaits you at the surface. You will first need to power your sub with a super-safe and efficient small nuclear reactor. Such a reactor could power your craft while submerged for years without re-surfacing.

But you will also require clean air -- free of built-up exhaled CO2. CO2 from expired air will build up in a sub or underwater habitat if not scrubbed regularly. That is where a collaboration between Bath University chemical engineers and Duke University mechanical engineers may be very helpful indeed. Their idea promises to allow subs to stay submerged for as long as the power and food supply hold out. In involves the use of "Dixon Rings" (see below) packed in a column.
Sea water and ship air are circulated in counter-current fashion, allowing the seawater to absorb the CO2 in the ship's air.
Based on technology developed in 1948, Dixon rings consist of a fine wire mesh folded into a ring of approximately 3mm in size. The space in the wire mesh provides an extended surface area for the absorption of the CO2.

Many rings are packed into a column, through which gas and liquid flow in a counter-current direction. The combination of salt water and Dixon rings form a compact gas scrubbing unit, which removes CO2 from a closed-circuit breathing environment before safely discharging it into the sea.

Using this system, chemicals to absorb CO2 will no longer be needed in the submersible environment and time spent on the sea bed could be extended.

Prof Kolaczkowski said: ‘Chemical engineers are excited about using Dixon rings in applications where gaseous or volatile species are transferred between gas and liquid phases, and where the device needs to be compact.

‘With the Computational Fluid Dynamic modelling skills at S and C Thermofluids, we will make rapid progress with developing novel and compact gas scrubbers. The removal of carbon dioxide from exhaled air is a great application. There will be many more possibilities to consider.’

Dr Lew Nuckols of Duke University said: ‘An estimated 90 per cent of human-produced carbon dioxide is absorbed by oceans. The research at Bath, in partnership with us, could revolutionise techniques to remove metabolically produced carbon dioxide from subsea operations.’ _Engineer
When perfected, this technology will make permanent seafloor habitats and colonies possible. Eventually, similar technology may even allow for rebreathers that allow humans to swim free underwater for long periods of time, without coming back inside the habitat for air.

Of course you may also want to learn to grow CO2 utilising plants or algae insider your sub or habitat, which can also perform part of the job of CO2 scrubbing. Saltwater plants may do best. Since you will need a lot of food for an extended underwater stay, learning to grow plants in your undersea living space is not such a bad idea anyway.

Dixon rings are used in other separation processes as well -- such as the separation of heavy water from ordinary water.

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Blogger kurt9 said...

Since you will need a lot of food for an extended underwater stay, learning to grow plants in your undersea living space is not such a bad idea anyway.


You also need your lab on a chip and other process tools to make all of your life extension supplements as well.

Friday, 18 June, 2010  
Blogger Bruce Hall said...

Since removing CO2 also removes oxygen from the "close circuit" environment, what replenishes the O in the equation for extended stays underwater?

Obviously, the system is dependent on the amount of oxygen you can carry or using plants to convert CO2 into plant food + oxygen.

Why not use the "mini nuclear reactor" to convert water into hydrogen and oxygen and then release the hydrogen? That provides the supply of oxygen the crew needs. Not a "closed circuit" but a viable one.

Friday, 18 June, 2010  
Blogger al fin said...

Yes. Nuclear power allows for electrolysis of water for O2 replacement and supplementation.

Still, CO2 is more soluble in water than oxygen by roughly 30 times or more. The losses of O2 are not as high as you might think compared to CO2.

Friday, 18 June, 2010  
Anonymous Anonymous said...

I think the problem is that you breathe the oxygen in the air and convert it into CO2, so even if you get rid of CO2 you still need a source of new oxygen to breathe. Afetr all every CO2 molecule you get rid of contains 2 oxygen atoms. You can't keep getting rid of them.

Saturday, 25 September, 2010  

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