[Stoves] Damp fuel in TLUDs

[neiltm at uwclub.net]

On 23 Mar 2016 at 12:00, stoves-request at lists.bioenergylists.org wrote:

> 
> ?It cannot occur at the relatively low temperatures of pyrolysis, and
> certainly not occur in the zone where the char is not glowing red-hot.?
> 
>  
> 
> Prof Lloyd (a chemistry professor) disagrees and I have numerous lab
> tests
> to support his position. When wet fuel is in close contact with hot fuel
> (I
> am not sure about the requirement for ?glowing?)


Not sure if this might be relevant, so my apologies if not, but I recall 
threads on a wood gas list mostly devoted to running internal combustion 
engines from wood gas, a consensus based on experience that the vehicles 
ran noticeably better with some moisture content to the wood as opposed 
to little or none.  I can't recall any figures if there were any I'm 
afraid, and this was mostly empirical observation.  I don't think it 
could have been down to an increase in tar as this was fastidiously 
filtered out to avoid valves sticking and wrecking engines on cold 
restart, and the opinion was that it was down to 'cracking' the water to 
produce hydrogen and oxygen.  Not sure if the temperatures involved in 
these 'reactors' might be significantly higher than in stoves for this 
not to be relevant.

Incidentally, with the Chinese ND 'ebay' camping stoves that can be run 
in TLUD mode I have observed that the behaviour of the stove both in 
terms of a steady, more cooking friendly heat output and noticeably less 
smoke is reliably obtained by using air dried found wood, even in the 
winter months in England!  Whereas my top of boiler dried woodchip which 
seemed necessary for a reliable burn in the Reed fan stoves, especially 
at half power, is simply too volatile for these stoves and results in a 
towering inferno and a lot more smoke than with the damper found wood.  
It is as if these particular stoves were designed for burning found wood 
in a northern damp climate, and as such reminded me of what Paal Wendelbo 
was always saying about designing the stove to match the fuel.  Even wood 
that feels damp after being rained on a day or two previously and that I 
would never have considered for the fan stoves, I have cooked on 
successfully, and it just needed a little extra of the candle wax 
gratings sprinkled over the top to start, but once going the stove would 
increase its heat output throughout the burn, being most vigorous as 
pyrolysis reached the bottom.  Perhaps the small scale and depth (micro 
gasification) mitigates against the effect of increasing dampness below 
the pyrolysis front Paul mentions?  The only time I have ever had a stove 
extinguish itself after a good start was at a transition in the fuel bed 
I laid, between damper wood underneath a top layer of dryer.

I have been experimenting with 'poor' fuels.  I even cooked successfully 
on elder which is a terrible insubstantial flaky pithy wood, although it 
wouldn't be a fuel of choice.  I am also having great success with air 
dried rotten pine - it still counts as biomass!  Old wine corks, lollipop 
sticks, broken clothes pegs, sawdust, all jumbled up, it burns anything!  
Going to try some poplar next as that has a reputation for being smokey.  
Might be ideal for a TLUD!

Neil Taylor