[Stoves] benefits from reduced indoor air pollution.

[Crispin Pemberton-Pigott]

Dear Andrew

Thanks for trying.

‎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. We asked around the table what the disassociation temperature was at ambient pressure and there were no guesses offered.

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. I have seen consistent formation of clinkers at the bottom of TLUD coal stoves left on high power through the burn. That is an indication that the NO2 formation would be above the random few per cent one gets above 700 C when NO starts.

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.

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

Regards
Crispin



On 14 October 2017 at 16:02, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:

> We had a very interesting discussion about NO and its formation, the source
> of the N in that NO, and the appropriate metric. There are two sources of NO
> in a stove: fuel N and ambient N2. If the temperature is high enough, NO and
> NO2 will form from ambient N2, with fuel N have a good chance of making NO.


Yes Formation of NOx becomes higher as temperature and pressure is
increased in the presence of spare oxygen. Most wood fires are
temperature limited and at atmospheric pressure so probably don't
account for much formed from atmospheric nitrogen, whereas a diesel
engine has high pressure, excess oxygen and a high temperature when
operating at a high loading, at low part load the temperature is too
low and at high power oxygen is limited so it peaks below maximum
power at any given rpm.

So I also would expect most nitrogen compounds from biomass to be
formed from nitrogen in the fuel and this will be higher as proteins
increase, wood will have much less than agricultural residues. Burning
leguminous wood (black wattle?, robinia pseudoacacia in UK) gives of a
distinctive aroma which may be PICs from protein oxidation.

NOx is important in densely populated areas as it is a precursor of
very fine particulates (possibly ammonium bi-sulfate?) if high sulphur
fuels are also burnt to give sulphur dioxide, the two react in the
atmosphere. I doubt these particulates are as bad as polycyclic
aromatic hydrocarbons found on soot but they are probably smaller and
more likely to reach deep into the lung.
>
> What is the current EPA target for NO, and how it is calculated?

I'll have to pass on that, I couldn't see it from a cursory look.

Andrew

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