[Stoves] Burning wet wood

[ajheggie at gmail.com]

[Default] On Wed, 12 Jun 2013 19:22:04 +0000
(UTC),rongretlarson at comcast.net wrote:

Crispin said >Burning very dry wood is difficult and it makes a lot of
smoke. 
>This below may be true for "burning", but it has not been my experience for pyrolysis. Colorado is pretty dry and I never experienced a smoke problem due to dryness. I hope someone with a TLUD will "bake" some wood or pellets for awhile and report their results. If a fuel dryness problem exists for TLUDs, it is not clear why that should be so. During pyrolysis a lot of water is created through numerous chemical reactions . 


Ron and [stoves]

I've had similar experience to Crispin with very dry wood in an
ordinary burn, this is because the wood pyrolyses in a chain reaction,
evolving lots of high CV offgas which then if burned in a diffuse
flame produces sooty flames because you cannot get enough oxygen to
the offgas through the flame surface.

When there is a small amount of moisture present I think the latent
heat of the water evaporating modifies the rate at which pyrolysis can
travel through the wood.

TLUD is a special case because the rate of decent of the pyrolysis
front is controlled by the primary air burning at the interface of the
fresh fuel and the pyrolysis front, if the primary air is controlled
the bulk of the fuel below the front cannot reach pyrolysis
temperatures and stays cool so only the fuel at the interface and any
partly formed char above it is subject to the temperature of the
pyrolysis front, hence less chance of a chain reaction. I also believe
the cooling effect of the primary air rising through the fuel
contributes to preventing a runaway.

AJH