Lanny,
I think you said that you were using oak blocks of wood. What type? The
heart wood of most of the white oaks have pores filled with tylose which
prevents the ingress of water and decay agents, while the red oaks
don't. I expect you would see quite a difference in their rate of
re-hydration even when submerged.
Alex
On 11/08/2013 7:31 AM, [email protected] wrote:
[Default] On Sat, 10 Aug 2013 16:10:56 -0400,"Lanny Henson"
<[email protected]> wrote:
It does take a long time for dry wood to totally absorb water but 50 min is
not insignificant, and concrete block soaks up water a lot faster. I am
thinking that even the water on the surface of wood or even dry wood is a
problem for most top lit batch burners.
Yes anything that robs the pyrolysis front of heat will compromise a
TLUD burn. As has been shown in the past primary air has to increase
to provide oxygen to burn nascent char to provide the heat to drive
off moisture, such that at 25%mc there is no residual char.
Green wood is a problem, it stinks up the place and smuts the pot but it
will still burn fresh green wood after the fire heats up. Green wood
probably takes away more energy than it provides but it will burn fist size
chunks.
Yes but this is the acid test, it takes a lot of time and energy to
get heat into the middle of a bit of green wood to drive off the
moisture which is why solar/air drying is very useful even if slow.
I will weigh the wood before and after soaking next time.
Good
How much moisture content is the break even point?
Theoretically we can postulate that you need about 0.75kWh(t) to drive
off 1kg of water and raise it to flue exhaust temperature, this is
energy lost. Each kg of dry wood burned completely will yield about
5kWh(t) so the break even point is when the energy content of the wood
equals the energy loss of the vapour. This point is 86% moisture
content. Of course in practice this is unattainable and even on the
industrial scale sustaining combustion at more than 66% (green poplar
or spruce) is difficult and will not be clean. The reason is that the
combustion chamber cannot ever get hot enough for a clean burn with
high moisture content fuel, the char will burn out but the offgas
never gets hot enough to sustain a flame.
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/
_______________________________________________
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/
