Christophe wrote:I don't think the amounts of ash are that small...I'm even pretty sure not (or very little...)
I don't think I'll teach you much, but let's clarify anyway....
What everyone calls "ashes" is what is recovered from the bottom of the stove or boiler when it is emptied in the case of a solid fuel appliance (wood, coal, pellets, "Paper/cardboard briquettes",...). We speak more of "soot" when it comes to a liquid fuel, even if it is also ash.
But there are ashes and ashes.
The "real" ashes are the materials which are not combustible but which are contained in "the fuel", typically SiO2, CaCO3 (CaO once in ash),... Nothing to do there, there is for example coals with 40% ash in India, bah Indian boiler operators have to deal with it. You find all of it in the solids you collect.
And then there are the "false ashes", which are in fact unburned, which would normally have had the capacity to burn but which did not do so because the combustion was incomplete, disturbed or whatever.
We talked about it a little higher, but the papers/cardboards are generally additives with generally non-combustible mineral "fillers". It is therefore not abnormal to have relatively abundant "true ashes".
On the other hand, the quality of the combustion of the briquettes will have a strong impact on the rate of unburned matter, therefore of "false ashes".
This is where the structure of the briquette comes in, its shape, its moisture content,...
PS: I'm going to repeat myself and fiddle once more, but from this point of view the "Ahmed design" with its two through holes certainly seems to me very well placed to optimize the most complete possible combustion of the briquette.