Dear Ron
Addressing only one sentence of your very interesting list: “For those not having experience with TLUDs, Dean's reference to "no primary air can make it up", means that the oxygen is "entirely" used to produce carbon monoxide.” The Hydrogen in biomass (about 5.6%) requires almost exactly the amount of Oxygen available in it (46%) to create water. While CO can form at a low temperature, the tendency of Oxygen to react with Hydrogen is so strong that given a chance, biomass heated in a TLUD environment creates H2O. Lots of it. The thick fog of ‘smoke’ coming of a totally choked TLUD does have lots of CO in it but it has a heck of a lot more water (which we usually don’t measure). It is really rare to find a normalised CO emissions factor (not concentration in the emerging gases) above 100,000 ppm. I have only see it once and I work with some of the wildest devices the imagination has produced. So we need to talk about the produced numbers: If you multiply the measured CO number (the concentration) by the Excess Air (EA) present at the time adding 100% to the EA figure you get the CO emission factor CO(ppm) * (EA+100%) = CO(EF) at O2=0% (the O2 is factored out). An emission factor calculated in this manner makes it possible to compare any stove emission to any other without worrying that ‘the conditions’ were different. This normalises the conditions. So, back to the CO. If the O2 available in the biomass (about 46% by mass) were turned into CO, it would create far more than 10% of the total non-O2 component of the total emissions. That 5.6% H2 mass is a heck of a lot of H atoms. Normally it is unusual to see a CO(EF) above 50,000. In a single case I have seen +130,000 briefly during the test of an ‘improved stove’ which put it unfortunately into the category where many ‘improved stoves’ belong. That high a value does not seem to be able to be created without first heating the fuel quite a bit so I am expressing doubts that level could be created in a TLUD that was not first run as a regular fire. I mention this to support my conclusion that the O2 tends to create ‘fuel moisture’ very easily. Biomass needs just a little more air (Oxygen) to completely use up the H2 and then breathe in whatever additional air would burn all the Carbon. In any real file, some of the C becomes CO and CO2 (surface reactions mentioned by Dr Tom Reed in a previous discussion). Regards Crispin
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