Hi everyone. I am a postgraduate student, working on a research to generate low oxygen gas from diesel engine exhaust gas for ship's ballast water treatment. However, the oxygen content of typical exhaust composition is around 11-17% and ballast treatment requires
Hi
You may be going about it the wrong way. Most commercial Membranes permeate Nitrogen and carbon dioxide, while retaining Oxygen. Your should be looking at the permeate to be depleted in Oxygen rather than hoping to have oxygen permeating the membrane. Now if you could get a membrane to permeate Oxygen rather than Nitrogen you would have a novel discovery.
best wishes
Hi, You may be think of membranes prepared by using PDMS polymer. PDMS has good Oxygen selectivity and it is also hydrophobic which will also avoid water to be pass through the membrane.
good luck!
The permeances of gases through polymers generally follows the sequence: :H2O > CO2> O2> N2. O2/N2 selectivity varies from a low ~ 2 for PDMS to highs of 7-10 for glassy polymers. You can easily make a pressurized residue stream with ~ 1-2% O2 from air using membranes (for example google MEDAL Air Liquide membrane & look at N2 applications). You will be able to do this from the diesel exhaust gas with some pre-treatment. There are definitely commercial membranes that would work with some residual HC in the exhaust gas but there is an economic trade-off. Permanent gases are not usually a problem but you want to consider NOx and SOx.
I checked datasheets of some commercially available N2 separators - PSA as well as membrane technology.
Though seemingly great to use exhaust fumes with already reduced oxygen percentage, a lot of problems are introduced due to the combustion process: the N2 percentage is unaltered at best (if no NOx is created during combustion and no H2O vapor is present) as compared to 'fresh' air. And you have a lot of combustion byproducts plus HC.
PSA clearly requires dry, clean air to work. Membrane technology was less precise, but the mention of easily exchangeable filter blocks indicates that the preconditions will be about the same.
Thus either you will have to implement a very good filter - getting rid of at least HC, H2O and NOx - or you will run into massive problems. My feeling is that even developing a membrane technology coping with "normal" levels of air contaminations is challenging.
Wish you success
On-going discussions are getting interesting. I have a question for suggestions from the esteemed members about a type of membrane which has following features:
ü Long durability under water and air contact and have strength to be kept in hanging condition (curtain kind membrane)
ü Allow to permeate oxygen to water side from air-water interface.
ü Allow to permeate nutrients from water to other side from air-water interface
ü Membrane surface should have favorable conditions for attachment of biomass
I would like to research on membranes which has above features. I would be very much appreciated for the suggestions from the members. If such kind of product is available in the market, please let me know product(s) name. I am ignorant about membrane characteristics.
I fully agree with you. I am sorry to distract the attention of the members.
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