[Stoves] [Stove NOX // ACRYLAMIDE

[Nikhil Desai]

Crispin:

Of course biomass has N, but for other fuels combusted at high enough
temperatures, the N comes from air.

That's what I remember from my utility regulatory and climate beancounting
work.

Biomass burnt at over 820 C probably oxidizes nitrogen in the air,
depending on air supplies.

Am I wrong?

Copying Andrew and Harold in case my foolishness needs to be checked again.

Nikhil

------------------------------------------------------------------------
Nikhil Desai
(US +1) 202 568 5831
*Skype: nikhildesai888*



On Tue, Mar 5, 2019 at 9:36 PM Crispin Pemberton-Pigott <
crispinpigott at outlook.com> wrote:

> Having recently been invited to explain NOx formation and getting rid of
> it after it formed, I had a chance to discuss this with Prof Annegarn when
> in China.
>
> The N comes from the fuel and most N in fuel becomes NO even if there is
> not enough O in the fuel to create it. In the case of biomass there is
> plenty.
>
> After NO is created, it can be converted to N2 and O2 which frees the O to
> move on to join H or C.
>
> If it is kept above about 820 C for 250 milliseconds it will go that way,
> or can. Low NOx burners are of two types: those that convert NO to N2 and
> those that prevent the formation of NO2 at a much higher temperature. It is
> actually not very helpful to discuss all NOx as if it was similar and
> certainly not helpful if you are trying to minimize production of it.
>
> You can use a low-N fuel.
> You can use a chamber hot enough to convert NO to N2.
> You can keep the uppermost temperature below 1250 C.
>
> NO forms easily in a gasifier or fire because the N and O are already
> joined together in the cellulose with several combinations easily formed. N
> is often joined to three oxygen atoms with a valence of 4. One of them is
> joined by a double bond so taking off the two with single bonds, you have
> NO with a double bond.   N2O a has a valence of 1 for the N and it can be
> dealt with. NO2 has a valence of 4 for the N and it is "unhappy" because it
> likes 3 or 5 but the oxygen is satisfied by its complete shell (octet).
>
> It is 2 with NO so keeping it hot and providing a second NO gives N2 and
> O2 which happens if given time and temperature.
>
> N2 has a triple bond and is very stable.
>
> As for fuels, the amount of chlorophyll can be used as a vague indicator
> of the N content so leaves have far more and wood far less than average for
> a whole plant.
>
> Therefore we expect pellets made with leafy material (corn stover) to have
> much more NO in the exhaust compared with wood pellets. If the combustor is
> properly constructed, it can be greatly reduced.
>
> I only have detailed tests for coal fires in which the conditions are good
> for NO reduction. The effect is pronounced: exhaust that would otherwise
> have an emission factor of 600 ppm (undiluted sample) can be reduced to the
> low 200's with combustion chamber design alone. Let's call it a 60%
> reduction.
>
> It is quite important to remember that a stove fuel combination has
> inherent emissions, and accidental emissions, and some like NO which are
> from an inherent elemental component but which like Sulphur, can be emitted
> in less or more polluting forms. Poor combustion of S gives H2S when it
> should be SO2. N should be N2 not some other molecule.
>
> Just because NO (and CO) forms easily doesn't mean we have to "accept
> it".we can play a few tricks.
>
> Regards
> Crispin
>
> *From:* winter.julien at gmail.com
> *Sent:* March 5, 2019 6:54 PM
> *To:* peetersfrans at telenet.be; stoves at lists.bioenergylists.org
> *Cc:* franke at cruzio.com; Crispinpigott at outlook.com; boll.bn at t-online.de
> *Subject:* Re: FW: [Stove NOX // ACRYLAMIDE
>
> Hi All;
>
> I have not looked into it in detail, and certainly not in the last three
> years.  However, in the back of my mind, NOx can form in freeboard flame
> area of moving grate gasifiers when there are higher amounts of excess
> (above stoichiometric requirements) air.   I expect that this would be a
> larger problem with fuels that are high in nitrogen.  This could arise for
> biomass stoves that burn compressed fuels that have higher amounts of leafy
> material or dung.
>
> Cheers,
> Julien.
>
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