Hi Paul,
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?
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.
Hope that clarifies how the carbon escapes.
Doug W.
On 06/01/17 11:26, Paul Anderson wrote:
I agree that what Rolf is seeking is not a TLUD.
You wrote:
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.
I have not experienced carbon dust or ash from carbon dust or ash dust
with the AVUD design.
Again, thank you for your strong support for gasification of biomass.
Paul
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