Coal cooking summary

[Tami Bond <tami.bond@noaa.gov>]

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)
2. Smaller size could help, use smaller chunks (Andrew) [I agree with
what you said about heat conduction impeding ignition-- you can see the
heat traveling away-- this is problem with starting coal briquettes
too.]
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.]
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)

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;
(3) have done radiation cavities as best I can. I am burning this in a
simulated firepit which is how they do. I have lined it with ashes, but
no insulation other than that; I did a trial with firebrick around the
outside of the pile to avoid heat loss, but it didn't seem to help much.

So far I haven't used more than 0.6 kg of coal per test, figuring that
you can finish the water boiling test with ~0.6 kg of wood, and coal has
a higher heating value. Nor have I used more than 0.3 kg of wood to try
and start the coal, again thinking that if you were going to use 0.5 kg
of wood as kindling, you might as well cook over it and forget the coal.

Now if I used a bigger pile of coal, the surface-to-volume ratio of the
pile would be smaller, so there would be less heat loss. But this means
that people are probably using more coal than we think they are (or
cooking fewer times per day). 

John, how much coal do people typically burn for a meal? And what do
they do if they cannot get the high-volatile stuff?

    Still puzzled

    Tami

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