[Stoves] Fwd: RE: Changing rate of pyrolysis front in TLUDs

[psanders at ilstu.edu]

Andrew and other Stovers,

This reply from Dale came only to me, so I am forwarding it to all.

Paul

----- Forwarded message from dandreatta at sealimited.com -----
    Date: Wed, 11 Apr 2007 15:11:06 -0400
    From: "Andreatta, Dale A." <dandreatta at sealimited.com>
Reply-To: "Andreatta, Dale A." <dandreatta at sealimited.com>
 Subject: RE: Changing rate of pyrolysis front in TLUDs
      To: "Paul S. Anderson" <psanders at ilstu.edu>

For all the fuels I tested at constant primary air the mass loss rate
was close to constant as the burn progressed, except of course at the
beginning and end.  My scale was accurate to 1/4 ounce (not the best
scale but it was the best I could come up with) and I couldn't detect
any significant change to the mass loss rate.  There was some scatter,
but no pattern that I can recall.  I can share my raw data if you'd
like, with minute by minute mass measurements.

As for how the primary air varies as other variables change, I would
think the height of the air column above the fire doesn't have much
influence since it doesn't change by that much of a percentage.  As for
the fuel stack resistance, it could increase or decrease depending on
how the fuel pellets contracted as they pyrolyzed, or turned to ash and
just disappeared.  Of of the things about the Anderson TLUD that
pleasantly surprised me was the the flame seemed nearly constant, at
least with pellets, for a long time.  This suggests the pyrolysis rate
and the primary air were nearly constant.  A lucky accident?

Dale

-----Original Message-----
From: Paul S. Anderson [mailto:psanders at ilstu.edu]
Sent: Tuesday, April 10, 2007 9:50 AM
To: Andreatta, Dale A.; STOVES - Listserve
Subject: Changing rate of pyrolysis front in TLUDs

Dear Andrew, Dale and all.

> [Andrew]  One of the things I never resolved about a long stack TLUD
> fire was how the air supply varied as the column of hot gases above
> the fire lengthened and the column of fuel (and its resistance to air
> and
> offgas) shrank. I think there is a need for an experiment with a
> constant mass air supply.

I think the closest to this experiment with constant mass air supply was
reported this past January by Dr. Dale Andreatta, but I am not sure if
the length of his TLUD unit was sufficient to detect any changes in rate
as the pyrolysis progresses.  See his report at:
http://bioenergylists.org/stovesdoc/Andreatta/TLUD_Report.pdf

I think the more important question is how the rate could change when
the air supply is NOT constant, but is left to natural draft or to
issues of resistance to the flow of the air.

--
Paul S. Anderson, Ph.D., Geography professor - Emeritus
Telephone:  USA-309-452-7072 (residence and office) Internet site:
www.ilstu.edu/~psanders For my gasifier stoves info, go to:
http://bioenergylists.org/contributors#Paul_Anderson





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