Mitigator
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How to burn hydrogen without burning nitrogen?
I've heard on wikipedia and everywhere that whenever hydrogen burns in air (even when some other more common/used gases) it also causes nitrogen to be
oxidized. And this is toxic or dangerous. Is there any way to mitigate this?
I am not interested in burning hydrogen in oxygen or anywhere, but in air! Is catalyst solution for this, or something else (opposite than catalyst,
because catalyst helps something react, but we need to kind of "make it more difficult" or "unhelp it react").
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Vomaturge
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This is a real problem, and can also happen with fuels besides pure hydrogen. Car designers are always trying to reduce the nitrogen oxides in the
exhaust.
There are several techniques to stop the nitrogen oxides (NOx). Oxidizing nitrogen takes energy (is endothermic), so breaking the oxides back into
oxygen and nitrogen releases energy. There are catalysts to decompose nitrogen oxides back into oxygen and nitrogen. This is one of the things
catalytic converters are supposed to help with. Or, you could use a slight excess of hydrogen, to make sure that it burns up all the oxygen, and
there's none to react with the nitrogen. But that's a waste of fuel.
Also, the NOx-producing reactions happen mostly at very high burn temperatures. For example, on page 3 of this document (https://www.tandfonline.com/doi/pdf/10.1080/00022470.1964.10...) table 1 shows that you will get about 1/1000th as much NOx at 1350F (730C) as at
4950F (2730C) If you only used a little hydrogen, then you'd still have lots of excess nitrogen and oxygen, but they (hopefully) wouldn't get hot
enough to react. Or, you could use exhaust gas re-circulation (EGR), and mix the right fuel and air mix with some exhaust (steam, in this case) to
dilute it and limit the temperature the reaction could reach.
Finally, you could use a mixture and combustion temperature that works well in an engine, but produces a lot of nitrogen oxides. Then, add some other
chemicals into the exhaust to neutralize the NOx. Search "diesel exhaust fluid" for a real world example of this.
[Edited on 23-5-2018 by Vomaturge]
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aga
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/What Exactly do you want to make ? Water ?
[Edited on 23-5-2018 by aga]
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Mitigator
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Aircraft, torch, lighter, weapon, car, fuel cell, lamp... Or simply said EVERYTHING, but nothing in this exact moment. Stuff I plan to keep close to
me my whole life, and inhale air around such devices.
Yeah, synthetic water too.
[Edited on 23-5-2018 by Mitigator]
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Sulaiman
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You should check but I believe that NOx formation is a function of temperature, over 1600oC is required.
'normal' flames such as hydrocarbons, in air, do not produce the same temperatures as found in compressed fuel-air, or fuel-oxygen, flames.
So, provided that there are no nitrogen containing compounds in your fuel and the flame temperature is below 1600oC I would not worry about
NOx production.
P.S. published adiabatic flame temperatures are much higher than 1600oC,
but 'normal' flames in air are not adiabatic.
[Edited on 24-5-2018 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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MrHomeScientist
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Please stop making new accounts. You aren't fooling anyone.
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Bert
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Mood: " I think we are all going to die. I think that love is an illusion. We are flawed, my darling".
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Since you have prevously said that you will never build anything or find the time to do any experiments, you probably don't have to worry about NOx.
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Mitigator
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"To some people, surrender may have negative connotations, implying defeat, giving up, failing to rise to the challenges of life, becoming lethargic,
and so on. True surrender, however, is something entirely different. It does not mean to passively put up with whatever situation you find yourself in
and to do nothing about it. Nor does it mean to cease making plans or initiating positive action. Surrender is the simple but profound wisdom of
yielding to rather than opposing the flow of life." - Eckhart Tolle
[Edited on 24-5-2018 by Mitigator]
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