Date: Sun, 1 Nov 2009 11:31:05 -0500
Reply-To: mcneely4@COX.NET
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dave Mcneely <mcneely4@COX.NET>
Subject: Re: Vanagon Winter Survival Kit Question
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What you say is generally correct, I believe. However, the reason that
cooler temperatures produce more creosote has to do with completeness of
combustion, and creosote output is a function of species of wood as
well. As I understand it, the chemistry of combustion is that creosote
is produced by burning with less oxygen supply. Oxidation is only
partial, and the wood alcohols are converted to creosotes, which are
carbonaceous, tarry substances related to sterols. Supply more oxygen
and the combustion is more complete, leading the creosote to break down
into constituents (carbon and hydrogen), which combine with oxygen to
produce carbon dioxide and water. The reason cool fires produce more
creosote is that they draw less air. The reason the SEEM to produce
more creosote is that the creosotes they produce condense more readily.
At least that is my understanding.
The creosote from partial combustion condenses on a cool flue to coat it
and create a fire hazard. Then a hot fire, often produced by light
weight (high oxygen content) wood like pine ignites the creosote,
resulting in a flue fire. The risk is exacerbated when light woods are
burned, because people have a tendency to try to cool the fire by
reducing the air supply (partially closing the damper to make the fire
draw less or closing off air doors). What they create is a creosote
distillation device of the stove.
If one burns only heavy woods like oak (an important commercial source
of creosote btw) that are well cured, and provides a hot burn once
daily, the stove produces little creosote and burns what it does produce
before it can become a fire hazard.
That's how I understand it.
David McNeely
On Sun, Nov 1, 2009 at 9:21 AM, Max Wellhouse wrote:
> When I'm burning pine, I only burn scrap kiln-dried 2x4" pine in my
> wood burning stove while working on my Vanagon in the winter time in
> my detached shop. I have a pretty much unlimited supply of it from a
> pallet manufacturer in Waterloo. They occasionally give away scrap
> oak as well. 3 winters now and NO CREOSOTE!! Enough of it will get
> the flue thermometer up to 800 degrees right quickly. I was always
> under the impression that the cooler smoldering fires were the ones
> that developed the creosote. problems. I was also told that exposed
> metal flues with creosote(not chimneys) in them could be cleaned by
> getting the firebox full of the dry 2x4's and get the flue temp in the
> 800 range(not to where it gets glowing red on the outside) After
> letting it cool, you simply tap the exposed flue pipe with a thick
> screwdriver shank and listen for the sound of falling creosote in the
> firebox. If you've got 90's in your flue, you could have problems
> retrieving that however, but even 1 90 would increase creosote
> production due to the exhaust not being able to escape as quickly as
> it wants to.
>
> YMMV
>
> DM&FS
>
> At 08:01 AM 11/1/2009, Dave Mcneely wrote:
>> When you say, "ranks pine at the top," that ignores that there are
>> multiple species of pine listed, and that the "top" ranking that you
>> mention is for pitch pine by weight, not by volume. Pitch pine is a
>> very poor wood for home heating, as it produces a lot of creosote (or
>> pitch), and is thus dangerous. Pitch pine was one of the most
>> abundant
>> trees in the area where I lived in eastern Kentucky, but no one
>> burned
>> it for home heating. David
>>
>>
>> On Sun, Nov 1, 2009 at 5:23 AM, Mike S wrote:
>>
>>> At 01:01 AM 11/1/2009, Rob wrote...
>>>> Extra heat? That is the wood burning in addition to the wax.
>>>
>>> Hey, just like an artificial log! But, wax holds much more heat
>>> energy
>>> than wood, so your claim doesn't make sense, since the one could
>>> just
>>> use more wax in place of the wood. (paraffin ~= 20,000 BTU/lb, wood
>>> ~=
>>> 6,000)
>>>
>>>> All wood has the same energy?
>>>
>>> Pretty close, by weight.
>>>
>>>> Oh wow, think of all the time I spent messing with the oak rather
>>>> than
>>>> the aspen... See that was my problem, I thought I was getting more
>>>> heat from the oak than I did from the softwoods all those years.
>>>
>>> I know what you mean. If you don't study or research things, and
>>> just
>>> believe "old wive's tales," then you don't always make good choices.
>>> Don't you wish you had found out sooner that aspen holds 14.7M
>>> BTU/cord, weighs 2290 lbs/cord, and produces 6419 BTU/lb, while
>>> white
>>> oak holds 25.7M BTU/cord, and weighs 4012 lbs/cord, which is 6405
>>> BTU/lb? So, the difference is a full 0.2% in energy per pound. The
>>> US
>>> Forest Service ranks pine at the top.
>>>
>>> Sources:
>>>
>>>
>>> http://www.daviddarling.info/encyclopedia/W/AE_wood_heat_value_BTU.html
>>>
>>> http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr29.pdf
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