Let's talk about the chemistry and physics of the coaling stage

[7acres]

I've been trying to understand what's going on in the coaling phase for a few weeks now. Apparently at the coaling stage all the highly flammable VOCs have been driven off and all that's left is a carbonized hunk of ...carbon. The heat must be chemically making the Oxygen combust with the carbon somehow. That's about where my knowledge ends.

What's going on between the pure carbon, heat and oxygen? Is there anything other than pure carbon and oxygen reacting in the coaling phase?

 

[grader]

check out this site (broken link removed to http://www.epa.gov/burnwise/workshop2011/WoodCombustion-Curkeet.pdf)

 

[7acres]

check out this site (broken link removed to http://www.epa.gov/burnwise/workshop2011/WoodCombustion-Curkeet.pdf)

Lots of great info there! Read the whole PDF. So the chemistry bit in there seemed to say that when the carbon burns oxygen is consumed in the chemical reaction producing CO2. The reaction itself is self sustaining once ignition is achieved and as long as there is fuel (wood and oxygen).

Basically burning wood is the exact opposite of photosynthesis. It's simply reverse photosynthesis! Is this correct?

 

[Jags]

It's simply reverse photosynthesis! Is this correct?

In simplistic terms - yes. Wood = stored sunshine.

 

[bobdog2o02]

check out this site (broken link removed to http://www.epa.gov/burnwise/workshop2011/WoodCombustion-Curkeet.pdf)

This is a great resource. This should be a stickey.

 

[Andy S.]

check out this site (broken link removed to http://www.epa.gov/burnwise/workshop2011/WoodCombustion-Curkeet.pdf)

That was a great read - thanks!

 

[Seanm]

Yes great read! I think I will have to hold on to that one. I noticed on the subject of moisture meters they say that many modern moisture meters have a built in calibration for the different kinds of wood. Ive been under the impression from chats Ive been involved with on this site that I need to make my own calibration so on my lodgepole pine if metered at 20% could actually be 25%!! I wonder what the right answer is? Two emails to the company asking about calibration and no response back. I might try them again and cc myself this time.

 

[DBoon]

I'd say that it is probably safe to say that a higher quality moisture meter used by someone in the lumber industry probably has correction for wood type, but the garden variety $25 Harbor Freight type is uncorrected.

 

[Lyndenbrook Farm]

Regarding too-dry wood (page 2):

pulsating combustion

That does not sound good.

I note that it also says MC 18-28% is appropriate. That seems to be a pretty big range compared to the collective wisdom here.

Very interesting link and a discussion I shall follow. Cuz I'm a geek

 

[Seanm]

I'd say that it is probably safe to say that a higher quality moisture meter used by someone in the lumber industry probably has correction for wood type, but the garden variety $25 Harbor Freight type is uncorrected.

Yeah that wood be my assumption to although I got hopeful while reading.

 

[Poindexter]

Good stuff I think.

The "stack by April, burn in October" idea can be done with birch and spruce given good airflow and good sun exposure. Sounds like none of you experienced burners down south are getting oak to season that fast. Birch has to be split pretty small to be ready in one year up here.

Thanks for the link.