[Stoves] The upside of Down feed

Tue Jan 24 01:58:54 CST 2012

Dear Alex

>>This is interesting news. The grate looks great, and if there is a pile of
char that is maintained in front, we must conspire to burn it.

>Not so fast. I rather like the idea of a naturally formed  biochar
venturi:)

I agree and want to see it in action - it might have a good mixing
contribution to make.

>>I presume at the moment the ash is blown into the larger chamber of the
stove. 

>I see the odd spark or glowing particle fly into the stove. 

I noticed that on the video. The flames looked like they needed more tube
length, actually. You can see them chilling as they enter they open space.

>This is what you see in most pellet stoves which do tend to have relatively
low PM emissions. In part that has to do with the way the size of the
particles in the pellet ('sawdust' is really tiny wood chips) and how they
tend to hold together. When the hopper  does runs out of fuel the added air
flow literally blows whole charred pellets into the stove. A chimney draft
is nothing to sneeze at, so to speak. 

 That is good news. How about turning the tube supplying air through the
grate upwards?

>>Is there any reason you can think of that the hopper, feed tube and
burning chamber should be round?

>No.

 OK. Might assist in suppressing CO sneakage in the corners.

>>How deep is the fuel in the hopper?

>40 cm. I have materials to go up to 100cm, and I could take it up to near
the ceiling with some stove pipe, though I might have to counter balance the
stove:)

Interested to know if it will feed that whole tube. If so, it could have a
large hopper with a low slope. If you want, bring material and I will cut
and weld it for you.

>These pellets are highly resistant to bridging. On the other hand I have
seen chips defy gravity:) 

Are they noticeably slippery to the touch?

>It is difficult to measure but the pellet flow is in fact air (wind)
assisted. However they are more bullet than sail. Small dry wood chips are
sails and if they make it down through the hopper, they blow right out of
the tube.

There are just so many advantages to using pellets.

>>Using wood, I can report that I have seen flames reaching more than 24
inches along the tube so you may get better combustion efficiency by
lengthening the one you have.

>Yes, a view of the flame is useful for understanding the process but is not
ideal for combustion.

It seems from the look and the layout, that adding more flame tube
would/could bring CO down to zero, or at least undetectable.

>>Thanks for an interesting (tiny) burner idea. If you bring it here I have
some 5mm switchgrass pellets I have had difficulty burning it anything yet.
Maybe.

>I suspect the ash would bung it up, but maybe...not.

Ask is not the problem that I see, it is that it is so dense it will not
breathe properly. TLUD's it chokes immediately. It would need a fan to get
much air through it. But if dropped from above it would certainly flow, if
it is dry. I would like to try it. Ask Roger Samson to drop off some
different sized pellets when he next passes by your place, which is quite
often.

Thanks

Crispin

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