# Is reducing nitrogen oxides with ammonia practical in a gasifier? [closed]

Sorry if this is an outright stupid question. I am no chemist.

For nitric oxide:

$$\ce{2NH3 + 2NO -> 2 N2 + H2 + 2H2O}$$

For nitrogen dioxide:

$$\ce{2NH3 + 2NO2 -> 2N2 + H2 + 2H2O + O2}$$

or

$$\ce{4NH3 + 2NO2 -> 3N2 + 2H2 + 4H2O}$$

As you can see, I'm trying to find if it is practical to take two toxins and convert them into non-volatile substances. Also, of course, harvesting this hydrogen gas would also be preferred; you could just add it back into the resulting Syngas. And I suppose ammonia doesn't have to be used. It just seemed convenient and the above reactions (producing useful Hydrogen and other non-volatiles) somehow came into my mind.

And it seems for every $\ce{O}$ (or $\ce{N}$) in the $\ce{NO_{x}}$ it can make another $\ce{O2}$ (or $\ce{N2}$, respectively). Or double the ammonia, to effectively double up on the first reaction.

If its the case that one reaction is more practical than another (as it usually is). I have noticed that conversion is simple:

$$\ce{2NO + O2 -> 2NO2}$$

readily happens in air and at 150C it reverses:

$$\ce{2NO2 -> 2NO + O2}$$

Most of this leads to gasification. Gasifiers stratify the combustion process to extract producer gas (Called Syngas. It is $\ce{H2 + CO}$, and it burns clean.). If a gasifier is built a certain way, the only pollutants could be $\ce{NO_{x}}$, and since some gasifiers can use biowaste, then ammonia is not hard to reconstitute on-site in some applications. Plus, I think it might be possible to extract ammonia directly from the pyrolysis stage when using garbage in certain gasifiers. As well, I think Ammonia is in the resulting trace gases sometimes depending on the gasifier/fuel setup.

There are some resources to be had. Gasifiers also have to typically filter out sulfur and mercury from the resulting Syngas. If those can help at all here and/or could also be included in this detoxification. As well, there are usually sources of heat (up to 1100C), tar, char (hot carbon), and hot or cold ash (burnt charcoal), $\ce{H2 + CO}$, $\ce{CO2}$, and other trace gases like $\ce{CH4}$ or whatever, depending on the gasifier and fuel. These resources could be utilized if needed, but most already have a role to play. Carbon dioxide, methane and tar are used to make more Syngas. The wasted byproducts are: sulfur, mercury, cold ash, and the "whatever" trace gases. I believe sulfur is in the form hydrogen sulfide. There is also probably substantial unsued hot Char (hot reactive carbon), but it burns quick, and only exists in the heart of the machine, then once all the heat is extracted it turns to ash.

Actually, I wonder if I could pump the $\ce{NO_{x}}$ (or other pollutants) back into the pyrolysis stage, if they would might reform into something else. Less toxic, eventually.

Of course, I feel like I'm barking up the wrong tree. As $\ce{NO_{x}}$ gases are closely scrutinized by municipalities, any practical reduction would probably be used already and emission of $\ce{NO_{x}}$ gases into the environment wouldn't be a problem, but that is assuming way too much for humans. So, I have to ask:

Do any chemists see a way, using these resources (or other practical external ones), to detoxify the nitrogen oxide from the resulting burnt Syngas fumes?

## closed as unclear what you're asking by hBy2Py, airhuff, getafix, M.A.R. ಠ_ಠ, ronApr 6 '17 at 16:28

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• use of ammonia to for NOx reduction is in widespread practice en.wikipedia.org/wiki/Selective_catalytic_reduction – DavePhD Jan 7 '15 at 17:52
• Oh wow! Darn I googled left and right, off and on, for a few days and never came up with that link. lol! At least I see that it's not barking up the wrong tree, specifically. Now hows about the practical way to use it here? I guess I got a lot more reading up ahead... – Pimp Trizkit Jan 7 '15 at 17:56
• Also, SCR uses a different reaction, and doesn't produce Hydrogen gas. With temperatures up to 1100C and some other wasted byproducts at our disposal, I wonder if Hydrogen could be made at this point instead. – Pimp Trizkit Jan 7 '15 at 17:58
• Please tell me how this question is unclear? I find it quite clear and the graceful edits help to attune this question. Also, I would think an unclear question would have a negative vote score... not positive. Even DavePhD seemed to understand my question. I even give very specific formulas that I would like to achieve. But I do not know if they are possible. – Pimp Trizkit Apr 9 '17 at 22:29