[Stoves] Some Basic Properties of ND-TLUD Gasification

[Julien Winter]

Hello Frank;

Thanks for your comments.  You have given me some interesting things to
think about.

I have sub-samples of my fuels to send of for analysis after I have
measured them for thickness.  After that I will have values for ash.  Then
I will redo my analysis on a dry ash-free basis.  Since all the fuels were
wood, I don't expect they contained much ash, and I don't expect my
conclusions to change.  I may be able to get a lab to do a slow heating to
450 °C to get a measure of the maximum amount of char possible.  I can't do
that myself, because I don't have that kind of oven.

As well as particle size (fuel bed pore size), minerals could substantively
affect the Tmax vs. %Char relationship.

Thermogravemetric analysis shows that most pyrolysis is over by 450 °C,
which may match with what you read from Tom Reed.  The high temperatures I
measured are indicative of fast heating rates.  Faster heating rates mean
more energy available for endothermic reactions creating volatiles.  Higher
heating rates lead to less char.

I don't know what the real heating rate of the fuel solids were, because it
is dependent not only on the temperature in the fuel bed voids, but also
the conduction of heat from particle surfaces inwards.

>From the thermocouple traces of void temperature, I calculated the heating
rate of thermocouples (°C/min).  However, I didn't use the data, because
the heating rate of the thermocouples was often slower than the heating
rate in the fuel bed, so my observations would be biased.  I understand
that it is possible to calculate a rate of temperature rise if you use two
thermocouple probes of different thicknesses.  ... next time.

Cheers,
Julien.

-- 
Julien Winter
Cobourg, ON, CANADA
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