[Default] On Wed, 12 Jun 2013 19:22:04 +0000 (UTC),[email protected] 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 _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://stoves.bioenergylists.org/
