[Stoves] FW: Need designs

[Crispin Pemberton-Pigott]

Dear Alex

 

That is akin to tilting a TLUD and allowing the air to blast the top face of
the fuel pile, with a small (tiny) amount of primary air coming from below.
That is exactly how John Davies arranged his (chimney drawn secondary air
supply).

 

I think one reason why the TLUD's that make char have such a low CO/CO2
ratio is that a) they don't burn much of the C in the fuel and b) what C
does evolve into the gases is burned amidst a plentiful supply of hydrogen. 

 

It is worth remembering that the 'low' CO level is comparative, meaning that
it is low compared with a stove that does not burn carbon very well. If you
build a stove well then the TLUD is not 'cleaner' because it is just burning
the fuel like any other good stove.

 

What is probably the main attraction to the TLUD is how easy it is to build
a clean burning one even if you have no idea what is happening in the fire
or what the emissions are. This is a valuable point and might be mentioned
from time to time. If you have no instruments and proven design at hand,
then at least if you build a TLUD it is probably going to be pretty clean
burning. It is going cost you in terms of fuel consumption if it is making
char (which is fuel) but that might not be an issue in that community, or
with that fuel.

 

In short, a TLUD is not clean burning 'because it makes char'. It mostly
burns hydrogen (wood gas) cleanly which leaves behind the char. As Dean
Still has pointed out a couple of times here, being able to choose whether
or not to burn the char at the end is an advantage in certain cases. 

 

Regards

Crispin

 

++++

 

When I was testing a  Rocket Stove back in the 90s I pulled out the fuel
support and tossed chips into a pile in the back of the stove. It made a
nice starved pile with a good gas cloud and flame on top. Almost all the air
became secondary air. Had there been a down leg or sealed container below
the stove with a small hole in the floor of the Rocket stove that you could
nudge the char into it could have been continuous. Most striking was the
fact that the CO/CO2 ratio was much better than I could achieve under normal
operation.

Try it.
Alex



 

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