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<div class="moz-cite-prefix">Tom, Crispin and tangled thread
followers,<br>
<br>
It's a challenge to keep up with the chat while traveling....<br>
<br>
I guess Tom's numbers below would be illuminated by numbers for
pressure drop across the bed or the fixed reaction zone/throat.<br>
<br>
Quite a different beast the batch TLUD. <br>
<br>
With restricted primary air, the throatless throat of a TLUD's
descending pyrolysis front can travel downward at as little as 3
inches per hour through a 40 pound per cubic foot pellet fuel with
a energy yield of say 5000 Btus per pound (this number could be
challenged). <br>
<br>
The peak temperature in the pyro front would be just under 500C or
~900F.<br>
<br>
So this example represents something close to a low or slow end
scenario of 50000 btus/ft2/hr or 158kW/m2. The pressure drop
across the bed or front would be so small as to be difficult to
measure. The primary air introduction could be through a drinking
straw or two/ft2. (Possible slight exaggeration alert!)<br>
<br>
Not hard to drive up those numbers with more primary air. With
natural draft from modest chimneys can certainly double the rate.
High pressure blowers can turn it into something that sounds like
a rocket but at this point I am uncertain what the upper limit
might be. <br>
<br>
Beastly different again is the Pasifier.<br>
<br>
Using the same fuel (non charcoal making mode-so 8000btus/lb), and
the grate area in the up draft portion, I get 150000btus/ft2/hr
under 0.1"wc pressure drop, and up to triple that, so far, with
higher suction in electrically powered draft mode. <br>
<br>
Then again the pellet world is a bit ivory towerish.<br>
<br>
Later, I should be able to offer wrougher numbers for wrougher
fuels with my wood chip "linear" Dasifier.<br>
<br>
<br>
Alex<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
On 29/09/2012 4:08 PM, Tom Miles wrote:<br>
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<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Crispin,
Alex,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">If
my calculations are correct the burn rate for downdraft
gasifiers is in the order of 70-100 lb/ft2/hr (340-490
kg/m2/hr; 1688-2400 kW/m2) with a high performer being about
140 lb/ft2/hr (65 kg/m2/hr; 3377 kW/m2). So in 24 in
diameter you can fire from 220-315 lb/hr (100-143 kg/hr), or
up to 440 lb/hr (200 kg) dry (15% MC) fuel. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">What
is the burn rate for a TLUD?<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><br>
Tom <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<br>
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