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Doug,<br>
<br>
The AVUD method is ignited at the level of the "grate" (actually a
pipe with holes on side and bottom, so the char can pass around the
pipe, drop below the hot zone, and be extracted at regular
intervals). The heat rises and pyrolyzes the biomass above, and
additional fuel is added regularly on top of the fuel pile. That
makes it a continuous process. No need to stop.<br>
<br>
The tarry gases exit and are combusted with turbulent air, coming
from an air compressor. The combustion is quite complete and
clean. This has similarities to the Dasifier made by Agua Das
almost 20 years ago. You should read these materials at my
website:
<br>
<br>
<a class="moz-txt-link-freetext"
href="http://www.drtlud.com/?s=dasifier">http://www.drtlud.com/?s=dasifier</a>
that link leads to
<br>
<br>
<a class="moz-txt-link-freetext"
href="http://www.drtlud.com/wp-content/uploads/2015/01/Dasifier-Foundry-Gasifier.pdf">http://www.drtlud.com/wp-content/uploads/2015/01/Dasifier-Foundry-Gasifier.pdf
</a><br>
<br>
and see a 2012 video with Das himself melting metal with woodgas at:
<br>
<br>
<a class="moz-txt-link-freetext"
href="https://www.youtube.com/watch?v=t08tj4NWUQY">https://www.youtube.com/watch?v=t08tj4NWUQY</a>
<br>
<br>
Many years ago Das was one of my teachers and mentors, and a good
friend of Tom Reed.<br>
<br>
Paul<br>
<pre class="moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
<div class="moz-cite-prefix">On 1/5/2017 8:19 PM, Doug wrote:<br>
</div>
<blockquote
cite="mid:e110a6af-10d9-07f5-fcb1-c2b3a8cec404@gmail.com"
type="cite">Hi Paul,
<br>
<br>
There is a difference in how pyrolysis (smoke gas ) can evolve,
and from what I see of the AVUD design, it appears that it still
follows the top lit philosophy. Maybe I scan read too fast, but
neither write ups stated how the bed is ignited. My understanding
from the drawing, is that the bed is ignited at the top, and they
burn down towards the grate which has air aspirated or blows at
low pressure in from the bottom. This changes both how the gas
evolves and it's hydrocarbon content, depending on they type of
fuel available. While it can be considered pyrolysis gas, it
certainly has to be a higher quality than the chocking yellow
smoke gas that most charcoal makers see full of hydrocarbons. The
give away is that pyrolysis gas burns red/yellow with air, and
better quality gas burns blue. What is considered a good color for
your stoves?
<br>
<br>
When the fire is located at the grate of an updraft and
interfacing the incoming air, high temperature oxidation forms at
the bottom of the bed, and depending on the air pressure, can
build an oxidation bed up to 4" deep, driving incandescent CO2 up
through the incoming raw fuel. It is one might say, almost instant
charring. Fine chars and carbon blacks are carried out of these
types of air flows. Our charmaker has a controllable blower type
fan capable of 15" W.G. max. and this is able to push the gas
through a 48" vertical bed loaded from the top.
<br>
<br>
Hope that clarifies how the carbon escapes.
<br>
<br>
Doug W.
<br>
<br>
<br>
On 06/01/17 11:26, Paul Anderson wrote:
<br>
<blockquote type="cite">
<br>
I agree that what Rolf is seeking is not a TLUD.
<br>
<br>
You wrote:
<br>
<blockquote type="cite">May be the ash from the carbon dust will
settle in the tunnel depending on combustion gas velocity.
Usually, a correctly sized flue stack is required to assist
with removing the exhaust gas, and this is where ash dust can
become an emission.
<br>
</blockquote>
I have not experienced carbon dust or ash from carbon dust or
ash dust with the AVUD design.
<br>
<br>
Again, thank you for your strong support for gasification of
biomass.
<br>
<br>
Paul
<br>
</blockquote>
<br>
<br>
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