[Stoves] Biomass testing questions
frank at compostlab.com
Wed Jan 21 13:13:53 CST 2009
Andrew and stovers,
>I doubt any free oxygen would leave the char.
>Its true that once the char was held constant at 400C it would stop evolving
>offgas, so no further compounds containing O would leave but there would
>still be about 20% of the mass of char that would be less volatile substances
>containing C, H and O.
>>C+H+N is left to make the Char. So its the amount of oxygen in biomass
>>that determines the amount of fixed carbon and amount of pyrolyzed gases
>>that will be produced after low temperature lipids and resins have left.
>>- I think?
>Actually I think it's the ratio of lignin:cellulose:hemicellulose that
>determines the char yield at any given temperature.
So complex! I agree we need to group constituents but I am not sure
lignin, cellulose and hemicellulose are the ones we should go for
because the tests take a long time and are expensive. We would need to
add fats, waxes and oils, resins, water soluble polysaccharides, and
protein to the hemicellulose, cellulose and lignin that you mention. I
have done lots of these and suggest we do something else if we can. I am
thinking after the easily volatile compounds (trouble makers) go off
(they consist of the fats to resins?) the rest is based on the oxygen
in the wood structure. To get CO, CO2 and H2O we need oxygen so they
will not be made when the wood oxygen is used up in an oxygen free
I am thinking of a hybrid stove that runs off electricity and biomass to
use for testing biomass. Fill a pipe with biomass, cap both ends and
drill a small hole in one end. Place the pipe in a gasifier stove. Block
all primary air and purge the stove body with nitrogen. Heat the outside
of the pipe with hot wire. The pyrolysis gases form and expand out the
small hole in the pipe. This replaces the nitrogen to fill stove body
with highly concentrated combustible gases. The small amount of trouble
makers will go off first and bypass the secondary as smoke as always.
Then we will have a concentration of CO (not enough O2 to make CO2) and
H (not enough O2 to make water) heading to the secondary. This will
work as long as there is O2 provided from the fuel structure. We test
these gases. So like running a hybrid car on gasoline and electricity we
get more for the buck from biomass using electricity to produce high
quality combustible gases without air. Perhaps the secondary could be a
fuel cell. Have no idea how the $ add up.
Leaving tonight to drive to Washington.to ETHOS. Perhaps you will be there?
>>Just still looking for easily obtained measurements that we can use to
>>charatorize the combustion of biomass.
>I'm still interested in what you come up with.
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