Re: Coal cooking summary

[AJH <andrew.heggie@dtn.ntl.com>]

On Thu, 28 Feb 2002 10:39:44 -0800, Tami Bond <tami.bond@noaa.gov>
wrote:

>Dear Stovers,
>
>Thanks everyone for your quick responses. 
>
>I summarize what I have heard from you:
>
>1. Low-vol coal needs forced draft to burn (Dan, Andrew)

Not quite, it obviously will burn under natural draft, however if you
achieve a high air velocity (which may be done with a chimney) the
coal will become a glowing mass and produce CO which then burns with a
blue flame. In lesser air flows the carbon is all converted to CO2 in
the coke bed. Any volatiles being released from fresh coal will not
then readily flare.

>3. Try holey configuration (Ron) [I agree with this too-- you have to
>make a cavity to keep radiation heat losses from sucking all the heat
>out-- I find this easier with wood than with coal.]

Radiation is very important in igniting char. I have just made some
high volatiles char in order to demonstrate clean flaring for a
project that I had hoped to scale up. I have been seeing how far from
a glowing char bed it will light, it looks like about 50mm whilst in
the primary airflow.

>4. People light coal, prefer hi-volatile [Me too!], bring it into house
>after volatiles are extinguished and cook over the coke. (John) (Note--
>if I get my own lab setup someday, I would love to test your improved
>coal stove)

I had posted some queries on this when the subject was last aired. I
would like to see if we can look at them again, if I can find the
message. There seems little reason to favour hi-volatile coal for easy
lighting if the volatiles are uncleanly flared to waste. Even taking
the glowing coke into the dwelling seems risky to health. Anyway it
looks like the cooks have little choice in the coal they use. I think
we should concentrate on clean burning from start up and cooking on a
system which vents the flue via a chimney. The heat all stays in the
dwelling, combustion product and contaminants in the coal going
outside at an acceptable level for other households.

As I said at the time there appears more scope for an engineering
solution here than with woodstoves. One day I will have a bit of time
and money to pursue this.
>
>This all makes TOTAL sense, but NONE of it changes the fact that I have
>some coal that is used for cooking in Yunnan province, and it is
>typically lit by putting on top of a wood fire. These people (1) do not
>have fans; (2) I have tried it with fairly small (walnut sized) chunks;

Walnut sized is much bigger than I used, my "house" coal was in ~2kg
lumps, I broke it into flakes no bigger than my finger up to the first
joint, this produced smaller shards also, which I used. Did you see
the fires started in Yunnan? It was the practice in this country to
keep embers going over night, the cry "curfew" was derived from
"couvre feu" which meant protect your embers and turn in. On sacking
village where the inhabitants had fled having the cooking fires
extinguished by urination as a "punishment" suggest staring fires was
not as easy as survival programs may suggest.

AJH
-- 


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