[Gasification] wood moisture meters?

[Tom Miles]

Andrew,

Microwave on High
Place 50 gm sample on 3 paper towels (industrial towels work fine. They are
about 3 gm per towel.) 
There are different drying schedules for hog fuel, chips or sawdust. I think
the standard calls for 1600 W microwave. All heating on high. In general for
fine wet fuel:
1 min on high. Stop weigh and fluff,
1 min on high. Stop weigh and fluff
1 min on high. Stop weigh and fluff
30 sec on high. Stop weigh and fluff. 
Repeat until weight is stable. 

I was running about 10-15 min per sample total. The stirring is important
because it releases moisture. As with any material it is easy t overcook the
sample.

Moisture meters measure electrical resistance. They are fine when the probe
is sticking in the same chunk of wood, or in hay bales that are reasonably
packed (10 lb/ft3, 160 kg/m3). They are now accurate up to about 40% MC.
They are no good for loose materials like straw, chips or hog fuel.  

Tom
      

-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] On Behalf Of andrew
Sent: Sunday, December 23, 2007 2:59 AM
To: Discussion of biomass pyrolysis and gasification
Subject: Re: [Gasification] wood moisture meters?

On Sunday 23 December 2007 05:48, Tom Miles wrote:
> There is an ASTM standard for using a microwave for fuel moisture
> that works well. I have used it recently.

Could you precis it to give a working method for those of us that 
just want it as a tool rather than to work to a standard? I have 
been drying using a microwave oven for some years now, I'm sure the 
resistance probes are fine for wood that has dried uniformly but 
suspect not accurate in determining a drying log's state.

AJH

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