[Gasification] heat required for drying

[Rodenhuis, E.J. (Erik Jan, Student TBK)]

Lewis, Toby and list,

True, but as you say it doesn't make a difference for our purposes. I
conducted similar tests on samples, simply dry the samples in an oven at
110 degrees Celsius until they stop losing weight. There is no free
water anymore in the cellular space, but there is still bound water in
the cell walls. 
Given the ambient temperature and air humidity we can calculate the EMC
(equilibrium moisture content). There is a calculator available at
http://www.woodbin.com/ref/wood/emc.htm  

Toby, thanks. I knew this, when formulating it this way you have the
theoretical energy need for drying. As you mention correctly the next
step is attributing an efficiency to the drying system used. Same
question formulated another way.

Erik


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Verzonden: woensdag 13 december 2006 14:54
Aan: seilertechco at yahoo.com; gasification at listserv.repp.org
Onderwerp: Re: [Gasification] heat required for drying

               to   Gasification List      from    Lewis L Smith

Ref the terms "free" versus "molecular bound" water.

I recall from my biomass days that we measured the water content of
grasses 
by heating a sample of the grass until dry in a small oven. This gave us
an 
"oven dry" sample which was then weighed. This weight was subtracted
from that of 
the original material, and the difference was divided by the latter to
give 
an estimate of the percent H20 in the harvested [or sun-dried] grass.
Such 
information was of course essential for making boiler efficiency
calculations and 
for other purposes.

I was told by one of the persons performing these tests that the oven
only 
extracted the intercellular water, not the intracellular water, so the
dried 
sample was really only 94% "dry". I eventually came to ignore this
distinction in 
my calculations as everyone else did, and it made no difference of
importance 
for our purposes.

Was our intercellular H2O what you call "free" water, and our
intracellular 
what you call "molecular bound" ?

Cordially. End of message.

 

 
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