Monday, September 8, 2008

New charcoal retort, insulated

I wrapped the mineral wool insulation onto the new charcoal retort and did a test burn.  Inside fuel was about a 50/50 mix by volume of flax straw and wood chunks, packed in alternating layers.  Wood comprised both lumber scraps and snagwood.  Outboard fuel was lumber scraps all the way up the sides with flax straw kindling on top.

The burn went better than the uninsulated ones preceding, in that I didn't have to refuel it.  But it still took an hour to get going and burned only on one side for awhile, as before.

Here's a pretty good shot of the smoke escaping from around the bottom of the inner vessel and being burned.

With insulation the outer barrel got orange-hot all the way around and the inner barrel got red hot.

It burned quite hot and clean for about fifteen minutes, here you can see almost the whole outer barrel is orange-hot.  The burn finished clean (odorless.)

Again however, low yield of ashy charcoal (overcooked or overoxygenated) and there were still a couple of embers inside the next morning.


Anonymous said...


Corrie said...

I'd love to know more about this work that you are doing and how to construct a retort like the one illustrated.
My interest is in producing charcoal for horticultural purposes.

Regards John Dudley