[Stoves] benefits from reduced indoor air pollution.

[Crispin Pemberton-Pigott]

Dear Tom

This is very helpful.

When I was at the CAU conference in Beijing last week, there was a presentation from a researcher from the Chinese Academy of Sciences – the guy who is working on the decoupled combustion device. Looking at his production model, and the KG4.0 (etc) from the Central Asian pilots, they have enough combustion chamber length to get 0.25 seconds of travel and a great deal of it is in that temperature range.

At the bottom of the hopper, in both cases, there is pyrolysis taking place, but on the very bottom it is burning coke – right on the grate, because there is quite a lot of air there. So at least some of the route to the gas burning chamber is above 750 C.

Do you agree that to really work on this problem we should be measuring NO and NO2 directly to be able to pick up precise changes in the combustion process with edits of the design?

Thanks
Crispin


From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of tmiles at trmiles.com
Sent: 16-Oct-17 12:05
To: 'Discussion of biomass cooking stoves' <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] benefits from reduced indoor air pollution.

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
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