[Stoves] ***SPAM*** RE: Risk of CO poisoning with TLUDs

[Crispin Pemberton-Pigott]

Dear Julien

That was a helpful qualification.

Yes the risk is high.  Of course it depends on where it is – inside or out, basically.

When you dump char out (any burning charcoal, and let it smoulder) the CO production is about 12% to 14% (ppm) of the CO2 emissions.

This is not as high as can be obtained from a badly designed stove, but it is substantial.  It is not correct to assume that all the burn releases CO.  A great deal of the carbon burns directly to CO2 on the surface.  In other words even though you don’t see flames, most of the carbon comes off as CO2.

If you make the calculation as CO/(CO+CO2) that 12-14 per cent becomes 10.7 to 12.3 per cent of the emitted carbon mass.

So…this means you can calculate the emission rate if you can put your char onto a scale and watch it for a while.  Whatever the mass loss is, about 11% of it is CO.  From that you get a mass emission rate. Maybe that is useful.

For a decent TLUD, the CO emission will be very low, and the dumped smouldering char represents a large increase in the emission rate.  For a charcoal stove, unless is it of the latest designs, there is often a drop in CO emissions.  Most charcoal stove have dreadful CO emission rates, worse than a smouldering pile of char (which is amazing, really).   What matters in such a case is how much eventually burns away.  It is probably less than you imagine.

To date charcoal stoves in Africa have failed to meet the Tier 3 requirement for entry into the RFB projects.  Recently there has been some training courses for producers in charcoal stove design held in Kigali, Rwanda.  Some 20 companies participated and there are several stoves now coming to market with Tier 4 and Tier 5 CO rates. In some cases only a single change was required, meaning a new combustion chamber replaced the original creating, in one case, a 99% drop in CO.  In that case it went from a CO/CO2 ratio of 12% to 0.13% which is deep into Tier 5. That is comparable to a good LPG stove which are typically 0.2%.

In this new case there is a rise in emissions if you were to tip out the fuel and let it sit smouldering on the ground. In most cases, unfortunately, charcoal stoves are no better than a smouldering pile.

So watch this space for some spectacular changes in the charcoal stove product offerings.  I am hoping one of them will qualify as a Tier 4 on all metrics.

For the TLUD’s producing char fuel, it will be interesting to see if the latest designs can use the fuel directly without making pellets and pass ISO Tier 3.

If someone want to try, let’s talk.

Regards
Crispin


Crispin Pemberton-Pigott

New Dawn Engineering Inc.
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From: Stoves <stoves-bounces at lists.bioenergylists.org> On Behalf Of Julien Winter
Sent: Tuesday, September 19, 2023 8:04 AM
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] Risk of CO poisoning with TLUDs

Hi All;

I should mention that I am most concerned with the potential risk when char is not handled efficiently, such as char leaving the TLUD unattended after running the TLUD with the primary air turned down, or dumping the char into a pile without quenching it.

Cheers,
Julien

On Mon, Sep 18, 2023 at 9:36 PM Julien Winter <winter.julien at gmail.com<mailto:winter.julien at gmail.com>> wrote:
Hi All;

Something just occurred to me.  If a large amount of char is allowed to accumulate at the bottom of a TLUD, and the primary air flow is low, is there a risk of carbon monoxide poisoning?

Cheers,
Julien

--
Julien Winter
Cobourg, ON, CANADA


--
Julien Winter
Cobourg, ON, CANADA
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