[Gasification] Wood chunks

[Greg Manning]

Greetings Adam, and list members.


Adam, I would hope 50% is a "high side" guess, as this is basically "green
fresh cut wood", given that, if this is green wood, the process of moisture
moving out of the wood, is mostly a linear rate with temperature rise, until
the temperature hits the low end of torrification (memory says about 285f,
but I may stand to be corrected on that).

The 285f mark, is the actual wood temp, NOT the surrounding air temp,
therefore, the air (in the presence of wet wood) can be as high as 450f
(again if memory is correct).
at this rate, you are basically cooking steak (literally) as in, the
evaporation rate from the wood is the same level as meat, only the meat will
be under 50% MC.

How long does it take to dry out a 2 1/4" thick roast to the point of
"honey, it's dead" ! (cardboard steak) ?

I would guess at 350f about 80 minutes or so. (450f with meat would burn to
quick I think, BUT I'm not the cook in our home.....).

Try this..... get some samples of your chunks.. weigh them to say one Kg
(2.204 lbs.) set them on a old cookie sheet (or a chunk of tin or something
that will not burn),

Place the entire affair in your stove's oven that you preheated to say,
300f, note the time... every 10min, take the sheet and contents out and
weigh them again (scale tare'd to 0 kg. with the sheet in place), keep
repeating until the weight does not reduce, "ta-da", you have found two
things... (remember to use oven mitts...)

 1) The absolute Moisture Content (MC) of the test sample (1 kg, minus the
final sample's weight, (eg: 0.8kg) this would mean that the water content
was 0.2kg or 20% by weight).

 2) and the time to get there.... (your answer to your initial question...)
how long to dry the wood at a given temperature.

Item one is what is called Bone dry, of course, you can reverse engineer the
time after initial testing, and figure out your required level of 10-20 %mc
and the time required to get there.

See my website on gasification:
http://www.inetlink.ca/a31ford/cgcmb/

Regards,
Greg Manning,

Brandon Manitoba, Canada



-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org]On Behalf Of Adam Carr,
Renergy
Sent: Friday, October 27, 2006 10:49 AM
To: gasification at listserv.repp.org
Subject: [Gasification] Wood chunks


Does anyone out there have any information re. the amount of time/energy and
techniques/equipment required to dry wood 'chunks' of ~ 60X60mm @ ~50%
Moisture Content down to <20% MC?  Between 1 - 2 tonnes/hr.

We have a market for the higher grade heat that the gasifier will produce,
so would prefer to utilise lower grade (~90C) heat from the engine water
cooling jacket.

I envisage some sort of perforated/walking floor/fan arrangement, but have
absolutely no idea how much energy/time would be required, or for that
matter how much time would be needed to air dry the chunks at ambient.
(under cover! - it has been raining a lot in Cornwall recently), or whether
it might be an idea to air dry first and then use heat to finally get the
chunks down to slightly below 20% MC?

Adam Carr
Renergy Ltd
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