bbnx wrote:My question is this.... Should the ash I collect be 100% dust or is it typical when burning coal to have a combination of ash and hard debris as well?
Yes, it is typical to have hard debris. When you burn wood, all you put in is wood and all you get out is ash. Coal however comes out of the ground and has had millions of years for inorganic materials to work into the organic materials that we mine as coal. The part of the coal that burns leaves you with ash, the part that doesn't can be melted, fused or just warmed up like a rock. Nevertheless, it will leave you with something other than ash. It's the nature of the beast.