I too am seeing quite a bit of black coal
in the ash pan of an Axeman Anderson.
It is the smaller boiler, an AA130, and the coal
is supposedly from Stockton.
My fire is lower in the tube and the anthrastat
has been calibrated and set to 136*. I believe I am getting good heat from this coal
in spite of what I am seeing in the ash bucket. Keep in mind, the draft fan (negative pressure) creates a very robust fire in these fire-pots.
I am not *Boo-Hooing" here, just trying to gain some insight and share my experiences here with others.
The black pieces in the ash are very noticeably burnt and reduced in size. Started out as pea size, but now looks like buckwheat size more or less.
These unburnt pieces are still black and have a finely layered
look about them.
Now the rest of the ash is a mix of fine power and crunchy clinkers that will break up easily, sometimes a bigger one but an AA chews most clinkers up before they drop to ash bucket.
As I understand, clinkers happen when a coal
burns above it fusion temperature...so I have some of that going on, but with some of the coal
that is not the case.
I have read of coal
breakers blending different coals for achieving a better burning and more consistent product, and believe this is the case for this coal
I have looked closely at the raw coal
in the bin and after studying a bunch of different pieces can notice 3 different types of coals in the mix.
is like what I saw when I burned Harmony coal
...shiny black and fractured randomly with lots of sharp edges.
is dull black no shine and most pieces have 2 flat sides opposite. (shale like)
is glittery shiny with a flaky look, not sharp or flat.
I'll try to get some pictures up to allow a better understanding of what I'm trying to describe.