The real wood story of Btu continues

Edwin Pawlowski wrote:
> Just in case you haven't had enough in the recent threads about this, here
> is more information.
>
> http://apt.allenpress.com/aptonline/?request=get-abstract&issn=0735-6161&volume=017&issue=02&page=0214
>
> ABSTRACT
>
> Compression drying is basically a process of forcing the free water in
> wood to move under high hydrostatic pressure through a solid structure.
> Fundamental information regarding the time-dependent characteristic of
> compression drying is necessary to develop efficient commercial processes.
> The purpose of this study is to provide an initial evaluation of the effect
> of some factors-pressure, wood density, and particle (chip) size-on free
> water extraction.
>
> Five species-aspen, balsam fir, jack pine, red maple, and red oak-were
> tested in this study. For each species both typical pulp size chips and
> particles from hammermilled chips were used. Drying rates were determined
> under constant ram face pressures at 500 psi, 1,000 psi, 1,500 psi, and
> 2,000 psi, respectively. The concept of drying rate is one of the important
> factors in dealing with compression drying, especially in designing
> dewatering pressure cycles.
>
> The most efficient compression drying is achieved during the first two
> minutes. Drying rates are negligible after 3 to 4 minutes of constant
> pressure in the 500 to 2,000 psi range. The analysis of variance for species
> shows highly significant differences in final moisture contents. Size of
> chips had a significant effect on final moisture contents. Compressed
> density of hammermilled chips is slightly higher than that of unrefined
> chips. High density chips require higher pressure to initiate effective
> drying rates.
Well Duh! on the last sentence.
> http://www.kppc.org/KWWRS/ValueAdded/
>
> Moisture content affects the energy content of wood when burned and the
> amount of wood fuel required to achieve desired heat or steam outputs.
> Harvested wood or wood from landscaping has a moisture content between 35
> and 50 percent and an energy content of approximately 5,500 BTUs (British
> thermal units) per pound. Kiln-dried wood residue has a moisture content of
> 5 to 10 percent and an energy content of approximately 7,500 BTUs per pound.
> Wood separated from a process waste stream and used for cogeneration is
> typically air dried to a moisture content of 15 to 20 percent and has an
> energy content of approximately 6,000 to 6,500 BTUs per pound.

Something a little screwy here. 35-50 percent moisture is
a rather large range. Even so, the numbers don't add up.
How do they get they get 5,500 BTU from 35-50 percent
moisture if 5-10 percent moisture produces 7,500 BTU.
Assume that the 5-10 percent is really 5 percent then 0
percent would be 7894 BTU, 50 percent would be 3947 BTU, and
35 percent would be 5131 BTU. You can work it with 10
percent giving 7,500 BTU and it still doesn't come out.
And that's is just considering that the water has no heat
content.

In burning, a lot of the heat is going to be used up in
driving the water off. I would suspect that a wood that
produces 7900 BTU when 100 percent dry would net not 1/2 of
that (3950 BTU) when the weight was 50 percent water but
something like only 40 percent of dry wood or 3160 BTU as a
maximum per pound. Driving off the water takes a lot of the
heat.


>
>
> http://www.pelletheat.org/3/benefits/
>
> Efficiency
> a.. More efficient fuel than cordwood. Pellets have five to 10 percent
> moisture content in comparison to 30 to 60 percent for cordwood and
> woodchips. This means pellets are a more efficient fuel.
> b.. Higher Btu content than cordwood. Wood pellets have a Btu output
> content of 350,000 per cub. Ft. of fuel, versus 70,000 to 90,000 for
> cordwood or wood chips. This means pellets produce more heat.

a. Who in hell burns cordwood that is 60 percent water?
Rather a specious argument for pellets.

b. Well yes if you compare it on a volume basis. What is
the efficiency basis? storage space?

I love it, Ed, when those promoting a product or an idea get
so carried away that they makes statements that are just
plain silly.

"Edwin Pawlowski" <[email protected]> wrote in message
news:%[email protected]...
> Just in case you haven't had enough in the recent threads about this, here
> is more information.
>
>
http://apt.allenpress.com/aptonline/?request=get-abstract&issn=0735-6161&volume=017&issue=02&page=0214
>
SNIP
> http://www.pelletheat.org/3/benefits/
>
> Efficiency
> a.. More efficient fuel than cordwood. Pellets have five to 10 percent
> moisture content in comparison to 30 to 60 percent for cordwood and
> woodchips. This means pellets are a more efficient fuel.
> b.. Higher Btu content than cordwood. Wood pellets have a Btu output
> content of 350,000 per cub. Ft. of fuel, versus 70,000 to 90,000 for
> cordwood or wood chips. This means pellets produce more heat.
>
>
Increases in moisture will take back some of the heat, because the pellets
_do_ readsorb moisture, making covered storage necessary.

They do not, of course produce more heat in an absolute sense - can't be -
but the density is favorable, the product is largely made of what normally
becomes waste, or at least is here, and most important - can be augered into
the box as needed to maintain proper burn. It's not Methane or fuel oil,
but it's more convenient than wood, and a hell of a lot more convenient than
gofer wood.

Robatoy wrote:

> In article <%[email protected]>,
> "Edwin Pawlowski" <[email protected]> wrote:
>
>> Just in case you haven't had enough in the recent threads about this,
>> here is more information.
>>
>
> The more wood fibre (carbon) squeezed into a given volume the more BTUs
> per given volume.
> The fewer contaminants (non carbon components) ie water per given
> volume, the more BTUs per given volume.
> I'm okay with this so far?
> If you put enough 'squeeze' on wood fibres you could even end up with
> something that rivals coal.
>
> ...but you'd have to deduct the energy used during the
> compression/drying stage, no?
>
> I guess it all comes down to getting as much carbon in as small a space
> as possible... which is why we like oil.
>
> Biomass energy is pretty much finite, which is why I'm a big fan of
> nuclear energy. Windmills are cool too, but some assholes are bitching
> that in some places the windmills are knocking birds out of the sky....

Also unsightly and some of them are noisy, although the proponents tell me
that the newest ones are inaudible, which I'll believe when I don't hear
it. The Appalachian Trail Conference recently took some flak by opposing a
windfarm in a scenic and previously undeveloped location that would be
visible from the trail.

> they count them and make little notes on rice paper and stick those in
> their little fanny packs and suck on some tofu whilst hugging a tree on
> their way to their Volvos...

Geez, somebody needs to make note of the resources they're wasting driving
those Volvos--they should be riding wooden bicycles instead of burning up
all that gas and supporting all those miners digging those big ugly
ecologically unsound holes in the pristine countryside of Scandinavia,
Germany, and other picturesque places of a like or similar nature, not to
mention the poor barnacles that get killed when they try to stick to the
toxic antifouling paint on the bottoms of the freighters that bring them
from Sweden.

Surprised the birds don't wreck the windmills. Hit an effing _owl_ (not
spotted fortunately or I'd be filling out forms for the rest of my life)
the other day (he came swooping down from the side of the road late at
night at about Warp 16--it appeared to be suicide) and did about 1500 bucks
worth of damage.

However ecosteria seems to be Balkanizing itself--with any luck soon the
factions will all be at each others throats and they'll mostly leave the
rest of us alone.

> but I digress.
>
> They have this really cool reactor on board Cassini..we all should have
> one of those.
>
> Look at the time....
>
> +¿+
>
> Rob

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)

In article <%[email protected]>,
"Edwin Pawlowski" <[email protected]> wrote:

> Just in case you haven't had enough in the recent threads about this, here
> is more information.
>

The more wood fibre (carbon) squeezed into a given volume the more BTUs
per given volume.
The fewer contaminants (non carbon components) ie water per given
volume, the more BTUs per given volume.
I'm okay with this so far?
If you put enough 'squeeze' on wood fibres you could even end up with
something that rivals coal.

...but you'd have to deduct the energy used during the
compression/drying stage, no?

I guess it all comes down to getting as much carbon in as small a space
as possible... which is why we like oil.

Biomass energy is pretty much finite, which is why I'm a big fan of
nuclear energy. Windmills are cool too, but some assholes are bitching
that in some places the windmills are knocking birds out of the sky....
they count them and make little notes on rice paper and stick those in
their little fanny packs and suck on some tofu whilst hugging a tree on
their way to their Volvos...

but I digress.

They have this really cool reactor on board Cassini..we all should have
one of those.

Look at the time....

+¿+

Rob