[Stoves] RE Central channel combustion stoves. Was RE: Henson CenterFiure Burner System

[AJH]

On Thu, 8 Jun 2006 13:59:30 +0200, Crispin Pemberton-Pigott wrote:

>Dear Andrew
>
>I remember them but only that they had masses of long filaments coiled 
>inside and they burst the glass when the evaporated.

Yes, it was magnesium in a wire of some sort which burned in oxygen
and produced a bright light but there was no flame, a flame by
definition is an area of combining gases.

>Well...OK.  I was being a bit extreme.  I think it was you who mentioned the 
>combustion that takes place on the surface of charcoal with the carbon going 
>directly from solid C to gaseous CO2.  Someone else perhaps.

No it was me, I'm not laying down the law on this but it is what I
think happens, the double oxygen bond is broken by energy from the hot
char surface the two oxygen atoms are then free to be adsorbed onto
the carbon atom and combine with it.
>
>My point is that there is little in a fire that does not involve burning a 
>gas.

Yes in general
>
>Back to more substantial things...

I actually think it is significant but I am rushed.

Whilst I don't particularly advocate charcoal cooking it has struck me
that IF it can be burned with low CO then it fills a different niche
from a wood fired stove. Running on from that we know that wood fires
have heath hazards associated with particulates, these seem to be
spawned from sooty particles that are Products of Incomplete
Combustion. What I would like to know is how CO exposure compares with
high pm10 and 2.5 from wood fires as a hazard. We know that CO is a
poison but heavy smokers apparently live with 9% of their blood
haemoglobin occupied by CO and the half life is ~4hours, what I wonder
is the long term problem compared with carcinogens.

I've been considering this a long time, since when Ronal first told me
the reason he championed what we now call the top lit updraught
principle that it had very low levels of PICs as particulates IF it
was supplied with minimum primary air. This resulted in production of
char.

So it seemed to provide a route for cooking with a high cv offgas and
low particulates and low PICs plus provide a char which could also
burn very cleanly if done right. The figures Dr. Karve provided seemed
to show that burning char right, i.e. at low temperature and excess
air could do this. Using both these techniques seemed to provide a
means to reduce the health hazard.

I'd like to expand on this as it raises a quandary, burning char at
low temperatures will result in poor heat exchange but need it? The
other was that at the time we had a contributor that sold a "glossy"
charcoal barbecue device which he loaded with special "array" of
briquettes. At the time I thought this just a marketing ploy but since
I have wondered if the array caused just sufficient mutual radiation
to maintain combustion without having sufficient mutual contact to
raise local temperature and favour conditions for CO production.

As I said at the beginning of the discussion the aim must be to
minimise CO production as burning it out is a problem.

AJH