[Stoves] [Stove NOX // ACRYLAMIDE

[Daniel]

Crispin, call me stupid but why do people insist on burning " green " fuels"?  Even in our humid climate, the greenest fuels dry out and loose the nitrogen in a couple months. I can always smell a distinct trace of HCN when I pass farmers throwing green branches on burn off piles. Who wants to breathe that stuff?  Dan Dimiduk

Sent from my Verizon 4G LTE Droid
On Mar 5, 2019 10:40 PM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
>
> Dear Nikhil
>
> NOx comes at three temperatures. Domestic stoves don't make NO2 except occasionally by accident. It is nearly impossible to make NO3 without adding pressure (car engine).
>
> N2 with its triple bond is not separated without a high temperature and that doesn't happen in a stove. That is why it is used as an shielding gas for welding.
>
> Formation depends of residence time. Typically NO2 forms after one second at or above 1540 degrees C with an excess air level between 25-45%.
>
> Stoves don't have such low EA levels.
> Stoves don't reach that temperature.
> Stoves don't provide that residence time.
>
> NO2 can form above 1200 but it needs five seconds to generate some. That is simply not going to happen.
>
> If we restrict the conversation to what is possible, we have NO formed from fuel N, and we have to keep it hot enough, long enough to convert to N2. Then we have a low-NOx combustor.
>
> Regards
> Crispin
> From: pienergy2008 at gmail.com
> Sent: March 5, 2019 10:02 PM
> To: crispinpigott at outlook.com
> Reply to: ndesai at alum.mit.edu
> Cc: winter.julien at gmail.com; peetersfrans at telenet.be; Boll.bn at t-online.de; Franke at cruzio.com; stoves at lists.bioenergylists.org; hannegarn at gmail.com; aj.heggie at gmail.com
> Subject: Re: [Stoves] [Stove NOX // ACRYLAMIDE
>
> 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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