[Stoves] benefits from reduced indoor air pollution.

[Nikhil Desai]

Tom:

Were the emission standards for co-firing (industrial or power plant boiler
fuel, I imagine) and gas engines the same? And if so, did they apply
equally to urban and rural areas in the US?

It may be counter-productive to apply the same NOx emission standards to
cookstoves as for big sources unless the ambient NOx levels and ozone
levels were much higher in that air basin than the national standards.
Cookstoves being intermittently used and not moved across large distances
during the course of their operation, I fail to see the rationale for NOx
standards for biomass cookstoves.

Nikhil

-------------------------------------


On Mon, Oct 16, 2017 at 12:04 PM, <tmiles at trmiles.com> wrote:

> Crispin,
>
>
>
> Thaksf or the comments.
>
>
>
> In 1990 and later we designed some burners for producer gas that held the
> gas to between 760C--980 C for at least ¼ second. We reduced NOX when
> burning high N fuels by about 40%. This was on fixed and fluidized bed
> gasifiers, and staged combustors,  from 10 GJ/hr to 90 GJ/hr. We use
> partial oxidation to reach the temperature and chamber design and gas flow
> to get the residence time. It still didn’t meet regulatory requirements but
> it did reduce the amount of urea/ammonia used for deNOx in the boilers. We
> also piloted the use of producer gas as a “reburn” fuel in a coal boiler.
> Producer gas was overfired in a coal boiler to “reburn” the combustion
> gases and reduce NOx. We again were able to reduce NOx by about 40%. The
> idea was to use a gasifier to convert agricultural residues and other
> biomass to gas for co-firing with coal. Energy prices fell so full scale
> industrial cofiring was not implemented. NOx control alone didn’t justify
> the investment in a biomass gasifier since there are cheaper alternatives.
>
>
>
> The challenge of using this strategy at any scale is the geometry to hold
> the gas at temperature in the sub-stoichiometric conditions.
>
>
>
> I agree that you are not likely to reduce or reform CO at these
> temperatures. If you don’t cool producer gas quickly you can get reversion
> to soot which would theoretically reduce CO.
>
>
>
> In my experience NOX generation is pretty consistent as long as you have a
> consistent fuel composition so it’s realistic to think about a baseline NOx
> range.
>
>
>
> When they add odorants to natural gas and LPG are they making “clean
> fuels” dirty? : - )
>
>
>
> Tom
>
>
>
>
>
> *From:* Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On
> Behalf Of *Crispin Pemberton-Pigott
> *Sent:* Monday, October 16, 2017 3:59 AM
>
> *To:* Discussion of biomass cooking stoves <stoves at lists.bioenergylists.
> org>
> *Subject:* Re: [Stoves] benefits from reduced indoor air pollution.
>
>
>
> Dear Tom
>
> That is a very valuable contribution at this time. I attended a short
> conference on Wednesday and a presentation by a Professor from the Chinese
> Academy of Sciences who is researching 'Decoupled combustion". He has
> created a stove that is all but identical to the KG4 crossdraft gasifier
> being made in Bishkek. Quite astonishing. After years of investigation he
> came to the same architecture: a hopper without air moving through it, a
> pyrolysis zone under it, a coke bed blocking the gases from getting to the
> combustion chamber, and a gas burning area above the coke.
>
> He said something I have never heard before which is that passing the fuel
> N through the semi-coking and coke burning zones reduced the NOx. He said
> it reduced the CO as well but I believe that less than the story about the
> NOx.
>
> As I understand what you wrote below, the NOx precursors, held in the
> semi-coking and coke burning zones long enough would reduce to N2O if the
> conditions are right. Possible? The stoves are small, so it might be
> difficult, but relative to many other stoves, the combusting fuel mass is
> relatively large and the gas velocity slow. The temperature is adequate.
>
> I doubt the temperature in the coke bed is high enough to split N2 but we
> can remain open minded on that. So is there a glimmer of truth to the idea
> that a horizontal coke bed could achieve a NOx reduction? That is really
> work checking out. Perhaps what we need is a target 'regular burn' NOx
> benchmark then compare that with the crossdraft gasifier burning the same
> fuel.
>
> The modeling work being done at the CAS include NOx formation so I need to
> following this more closely, if they got that correct, at least under
> certain circumstances.
>
> Incidentally, Prof Jinghai Li, Academician and Vice-Director of the
> Chinese Academy of Sciences (Institute of Process Engineering),
> Vice-President of the China Association for Science and Technology and the
> Vice-President of the International Council for Science, agrees
> enthusiastically with the proposition that *there is no such thing as a
> “dirty fuel**”*.  He laughed heartily at the “dirty fuel” idea. At first
> he said that a *stove* can be dirty, but we agreed in the end that a
> stove+fuel+context is what determines actual performance. On top of being
> sensible, he is a very nice guy.
>
> Regards
>
> Crispin
>
>
>
> Fuel bound nitrogen is usually the cause of NOx with biomass fuelas rather
> than thermal NOx. Grains, manures, and biosolids can all be high NOx
> fuels.  Grains and manures can generate abundant NOx. As others have
> commented it is difficult to get to high enough temperatures for thermal
> NOx except by burning charcoal. Pyrolysis and gasification  generate NOx
> precursors that can be "inerted" to N2O if held long enough at high enough
> temperatures (760C--980 C) in the absence of air. Unfortunately this is not
> practical in a stove. Catalysts are typically used to reduce NOx from wood
> gas in engine applications.
>
>
>
> Tom
>
>
>
> ________
>
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