[Stoves] benefits from reduced indoor air pollution.

[Jaakko Saastamoinen]

I studied nitrogen release from single wood particles [1], NO formation in fireplaces [2] and in grate combustion [3] with colleagues ([1] Release of nitrogen compounds from wood particles during pyrolysis. Environmental Combustion Technologies 1 (2000), 289-316. [2] Emission formation during wood log combustion in fireplaces - Part II: Char combustion stage. Progress in Computational Fluid Dynamics 6 (2006), 209-216.  [3] NOx formation in grate combustion of wood. Clean Air: International Journal on Energy for a Clean Environment 4 (2003), 30 p.).

About 50% of fuel N is released in volatiles. Part of NO produced is reduced to harmless N2 by reaction with char 2NO+2C=N2+2CO. NO emissions from TLUD can become small after a thick char layer is formed, since NO formed below can be reduced in the reaction with char when the flue gas is flowing through the layer.  This applies to the NO formed in the flame in the ignition front, but not to NO formed in the flame above the bed from the precursors NH3 and HCN. Lowering air rate reduces NO emissions. 

Jaakko

-----Original Message-----
From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of tmiles at trmiles.com
Sent: sunnuntaina 15. lokakuuta 2017 19.25
To: 'Discussion of biomass cooking stoves' <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] benefits from reduced indoor air pollution.

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  

-----Original Message-----
From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Andrew Heggie
Sent: Sunday, October 15, 2017 3:26 AM
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] benefits from reduced indoor air pollution.

On 15 October 2017 at 00:43, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:

> ‎Prof Stuart Piketh said last night that the conversion of N2 to NOx is copious above 1850 C which is easily reached in a power station with only 5-6% excess air.

...but wood is already partially oxidised so the adiabatic flame temperature is only around 1600C and I seldom see more than 1100C .

This of course is why charcoal was needed before iron could be smelted, even then it depended on the fact iron carbide formed a eutectic mixture that lowered the iron melting point.

P
>
> The only way to get really high temperatures, which I define as melting the ash (in the absence of significant quantities of fluxes), ‎is to blow on the fire.

Yes this is char burning



I
>
> There is a very practical side to this. Is it worth separately measuring NO and NO2 when testing a stove? Many emission standards mention pollutants and metrics that are copied straight from power stations where the combustion process and goals are very different.

I wouldn't have thought so but stand to be corrected. I worked most of my adult life  by the exhaust of two stroke engines and they are particularly bad for both particulates and NOx, especially when running lean which gave some extra revs. You soon notices the acridity  from NO2 if working in a poorly ventilated hollow.



>
> ‎So the question is, what are the appropriate measurements to make and what should be the reporting framework?


That's for someone better qualified than me to answer but black sooty particulates come high on my list and then CO if unvented.

Andrew

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