Question about the physics of wood drying
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How about you stop commenting on this ok? I would like to hear from others perhaps from dry climates who have experienced this not just a northern wet under the eaves guy.
stoveliker
Minister of Fire
Entirely correct as you can see from my location.
You clearly want to hear what you want to hear. I.e. you don't want to hear that your creosote is due to system issues or operation parameters. That's your prerogative.
I'll stop. Go, confirm yourself by whatever you can find on the web. That's how the world rolls these days.
Just one last remark: the physics of wood burning does not change with location. And ultimately dry wood is available here too. It's called 2*4s.
You clearly want to hear what you want to hear. I.e. you don't want to hear that your creosote is due to system issues or operation parameters. That's your prerogative.
I'll stop. Go, confirm yourself by whatever you can find on the web. That's how the world rolls these days.
Just one last remark: the physics of wood burning does not change with location. And ultimately dry wood is available here too. It's called 2*4s.
Obviously you are the smartest person to ever burn wood and are REALLLLY hung up on creosote aspect of my post. I am hung up on too dry wood so go smoke that if you need to. I found one of the articles that I saw the other day and could not find it previously till now. And you show a hint of ignorance in saying dry wood is a 2x4! Well we all know that not all 2x4s are the same. Sooo that said until you understand a dry climate that is 10-20% humidity just play in the forest.
A non-commercial service in support of responsible home heating with wood - Can Firewood be too Dry?
The Wood Heat Organization was formed to support the public in the responsible use of wood energy in the home. We fulfill our mandate by providing reliable information, by conducting research into wood heating-related issues and by representing the public interest in discussions of policies that...
"
Can Firewood Be Too Dry?
Yes, although it is not a common problem
Properly seasoned firewood still has a fair amount of water in it, say 15 to 20 percent of its weight. That water regulates the combustion process along with a few other factors like piece size, load configuration and combustion air supply.The higher the fuel moisture, the slower the wood breaks down when heated because of all the heat energy soaked up in boiling the water out of the wood and raising the temperature of the steam.
Conversely, the dryer the wood, the more quickly it breaks down when heated. By breaking down, I mean the vaporization of the volatile components of the wood; that is to say, it smokes. The dryer the wood, the more dense is the smoke at a given heat input rate.
Since wood smoke is fuel, we want to burn it as completely as possible and that means mixing with adequate oxygen in the combustion air. The problem is that a firebox load of very dry wood produces far more smoke than the air supplies of stoves are designed to provide. Besides, even if you could supply enough air, you would produce an inferno that would howl in the stove and make everyone in the house nervous. Fires that intense can seriously damage the stove's innards. Wood that is very dry produces a fire that is hard to control without making a lot of smoke.
Kiln-dried wood is down around 10 percent moisture. Depending on climate and conditions of storage, normal firewood won't dry down to kiln-dried moisture because of normal outdoor humidity. For example, I've never measured wood below about 14 percent in my firewood supply. But I suppose that firewood could get very dry by natural seasoning in desert conditions. Or firewood stored in old barns, which are like kilns in hot summer weather.
The right band of firewood moisture is between 15 and 20%. When you get much over 20% you start to see symptoms of sluggish ignition and the inability to turn down the air without extinguishing the flames. Towards 30% the wood sizzles and fires are very sluggish and it is hard to get a clean burn until the wood is almost to the charcoal stage. Above 30% water bubbles from the end grain when the wood is heated and it is very hard to burn at all. Species like poplar/aspen, which have very high native moisture content are virtually non-combustible when not adequately seasoned.
The main difference between EPA low-emission certified stoves and conventional stoves is that you can turn down EPA stoves for a long burn without extinguishing the flames. That is, they are better at producing a clean, controlled fire. The EPA test method requires wood with a moisture content between 16 and 20 per cent (19 - 25% dry basis) and when the wood is outside this moisture band, the stove's emission rate goes up. So even the best wood stove's performance will suffer if the wood is not in the right moisture range.
If you have some very dry firewood, like kiln-dried cut offs or old wood stored in a hot place, mix it with regular firewood to raise the moisture content of a full load.
JG"
stoveliker
Minister of Fire
As you address me again, I'll respond.
Creosote is a danger, so yes, that stands out to me. In fact, if you can avoid that, you'll be in perfect shape. By
And you are selectively reading my posts. I noted that combustion should be complete to avoid creosote. That is precisely what that article says. If you keep your chimney hot enough. (In fact, even wet wood can be burned safely IF the chimney is kept (quite) hot.)
Yes, you can mix wood. Often it is the other way around: mix dry wood in with too wet wood to keep the total moisture you have to push thru the chimney below a certain amount for the BTUs loaded in the firebox. Given that every pound of wood burned completely produces a half pound of water (and if you are so smart yourself, I invite you to do that calculation as I have done), you can do the calculation of how much 15 pct wood you want to mix in the supposedly zero percent you have. These are weight percentages, not molar percentages, for your intellectual information.
Finally, I DID measure the moisture content of my full load of 2*4s, in fact.
Creosote is a danger, so yes, that stands out to me. In fact, if you can avoid that, you'll be in perfect shape. By
And you are selectively reading my posts. I noted that combustion should be complete to avoid creosote. That is precisely what that article says. If you keep your chimney hot enough. (In fact, even wet wood can be burned safely IF the chimney is kept (quite) hot.)
Yes, you can mix wood. Often it is the other way around: mix dry wood in with too wet wood to keep the total moisture you have to push thru the chimney below a certain amount for the BTUs loaded in the firebox. Given that every pound of wood burned completely produces a half pound of water (and if you are so smart yourself, I invite you to do that calculation as I have done), you can do the calculation of how much 15 pct wood you want to mix in the supposedly zero percent you have. These are weight percentages, not molar percentages, for your intellectual information.
Finally, I DID measure the moisture content of my full load of 2*4s, in fact.
stoveliker
Minister of Fire
A useful table of data.
www.woodworkerssource.com
Quite close to zero is indeed possible.
Woodworkers Source: Equilibrium Moisture Content [custom wws]
Quite close to zero is indeed possible.
Did I EVER say I was smart? Nope but you my Nobel Sage are all knowing so I bow down to your intellect. The point of my post was to talk to people who have experienced TOO DRY WOOD and to discuss it in plain language not physics. Is that clear?
That said since people here seem to be too high and mighty to mix with common wood burners I turn to other blogs and forums and here is one of interest!
Can Firewood Be Too Dry? | Brockley Tree
Firewood left to season for longer than needed might lose more moisture than is necessary.
brockleytree.com
stoveliker
Minister of Fire
Have some patience. And a less abrasive attitude. Others will chime in.
Sawset
Minister of Fire
Drying rate for wood is dependent on the relative humidity at the surface. Once the free water evaporates (>30%), there is a gradiant of moisture content that develops based on depth from surface.
Drying slows the closer equalibrium at the surface is reached. If there is free flowing air, there would be a constant RH based on the surrounding environment. Soo, my bs answer would be, the 10% wood would stay at that. The 40% would dry quickly to 30%, then dry at a decreasing rate until EMC is reached. Stacking wet stuff next to dry would change almost nothing that wouldn't happen anyway.
Drying slows the closer equalibrium at the surface is reached. If there is free flowing air, there would be a constant RH based on the surrounding environment. Soo, my bs answer would be, the 10% wood would stay at that. The 40% would dry quickly to 30%, then dry at a decreasing rate until EMC is reached. Stacking wet stuff next to dry would change almost nothing that wouldn't happen anyway.
My standard stress dream is graduation is approaching. I haven't been to a class all semester. Always English if identified in dream. I don't have the credits to graduate. Will they know?
We were talking about stress dreams before a meeting when I was a consultant. Just about all had a variation of the same dream. We are frauds. Will we be found out?
EbS-P
Minister of Fire
Wood that contains little or no water does not need to convert as much or any water to steam. The latent heat ( energy required for the phase change is considerable).
That extra energy inside the firebox can cause increased temperatures, faster combustion and higher exhaust gas temperatures. This results is a quick burn and reduced efficiency.
Dry wood does not cause creosote. Exhaust gas temperatures below the creosote condensation point of 265 degrees causes creosote.
That extra energy inside the firebox can cause increased temperatures, faster combustion and higher exhaust gas temperatures. This results is a quick burn and reduced efficiency.
Dry wood does not cause creosote. Exhaust gas temperatures below the creosote condensation point of 265 degrees causes creosote.
stoveliker
Minister of Fire
EbS-P
Minister of Fire
I’m the dream killer sadly this isn’t a dream as there will be one student that didn’t bother to attend class made 50% or below on exams didn’t complete the homework and will ask is there any extra credit I can offer so they can pass the class and graduate.
Had a very successful career. Grad school for chemistry and senior executive in my field. Amazing the number of people that have occasional stress dreams and how similar they are.
Have lots of friends way smarter than I am. 😀
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Sawset
Minister of Fire
My reoccurring dream is that of losing my variables. And the problem remains unsolved, what a nightmare.
Ashful
Minister of Fire
I have no experience with "too dry" wood, probably can't in my climate, but just a thought with regard to it's effect on the cursed "EPA hole": If the EPA has mandated a certain minimum air inlet, would that have been determined at some assumed MC% closer to 15% - 20%? If not, we'd have most users able to shut down their stoves beyond the secondary stall point.
So, now we have these holes in our air inlet dampers, designed to keep a minimum reburn temperature with 20% wood, and some poor guy comes along with 4% wood. While I can't imagine how creosote would result, I would think it could make for one heck of a challenging control scenario. No?
So, now we have these holes in our air inlet dampers, designed to keep a minimum reburn temperature with 20% wood, and some poor guy comes along with 4% wood. While I can't imagine how creosote would result, I would think it could make for one heck of a challenging control scenario. No?
Wood cannot be to dry to burn properly. It just doesn't happen. Now the drier it gets the harder it will be to control because it will offgas allot faster. So if your wood is down close to 10% you better be sure you don't have excessive draft or the stove will over fireObviously you are the smartest person to ever burn wood and are REALLLLY hung up on creosote aspect of my post. I am hung up on too dry wood so go smoke that if you need to. I found one of the articles that I saw the other day and could not find it previously till now. And you show a hint of ignorance in saying dry wood is a 2x4! Well we all know that not all 2x4s are the same. Sooo that said until you understand a dry climate that is 10-20% humidity just play in the forest.
It saysA non-commercial service in support of responsible home heating with wood - Can Firewood be too Dry?
The Wood Heat Organization was formed to support the public in the responsible use of wood energy in the home. We fulfill our mandate by providing reliable information, by conducting research into wood heating-related issues and by representing the public interest in discussions of policies that...www.woodheat.org
"
Can Firewood Be Too Dry?
Yes, although it is not a common problem
Properly seasoned firewood still has a fair amount of water in it, say 15 to 20 percent of its weight. That water regulates the combustion process along with a few other factors like piece size, load configuration and combustion air supply.
The higher the fuel moisture, the slower the wood breaks down when heated because of all the heat energy soaked up in boiling the water out of the wood and raising the temperature of the steam.
Conversely, the dryer the wood, the more quickly it breaks down when heated. By breaking down, I mean the vaporization of the volatile components of the wood; that is to say, it smokes. The dryer the wood, the more dense is the smoke at a given heat input rate.
Since wood smoke is fuel, we want to burn it as completely as possible and that means mixing with adequate oxygen in the combustion air. The problem is that a firebox load of very dry wood produces far more smoke than the air supplies of stoves are designed to provide. Besides, even if you could supply enough air, you would produce an inferno that would howl in the stove and make everyone in the house nervous. Fires that intense can seriously damage the stove's innards. Wood that is very dry produces a fire that is hard to control without making a lot of smoke.
Kiln-dried wood is down around 10 percent moisture. Depending on climate and conditions of storage, normal firewood won't dry down to kiln-dried moisture because of normal outdoor humidity. For example, I've never measured wood below about 14 percent in my firewood supply. But I suppose that firewood could get very dry by natural seasoning in desert conditions. Or firewood stored in old barns, which are like kilns in hot summer weather.
The right band of firewood moisture is between 15 and 20%. When you get much over 20% you start to see symptoms of sluggish ignition and the inability to turn down the air without extinguishing the flames. Towards 30% the wood sizzles and fires are very sluggish and it is hard to get a clean burn until the wood is almost to the charcoal stage. Above 30% water bubbles from the end grain when the wood is heated and it is very hard to burn at all. Species like poplar/aspen, which have very high native moisture content are virtually non-combustible when not adequately seasoned.
The main difference between EPA low-emission certified stoves and conventional stoves is that you can turn down EPA stoves for a long burn without extinguishing the flames. That is, they are better at producing a clean, controlled fire. The EPA test method requires wood with a moisture content between 16 and 20 per cent (19 - 25% dry basis) and when the wood is outside this moisture band, the stove's emission rate goes up. So even the best wood stove's performance will suffer if the wood is not in the right moisture range.
If you have some very dry firewood, like kiln-dried cut offs or old wood stored in a hot place, mix it with regular firewood to raise the moisture content of a full load.
JG"
stoveliker
Minister of Fire
No, this is a thermostat regulated stove shoved with its back into a fireplace. Aspen v3. That explains the creosote as the thermostat thinks it's hot so it closes,. leading to (and I quote) consistent smoke belching. (With this dry wood.) Turns out this was conveyed before to the poster in another thread.
Wow that got…heated. Pun intended. First and foremost, yes I just had flashbacks to gen chem. Next, I don’t know where this member is from whose on the “desert,” and lastly I don’t currently have the bandwidth as the rest of you to get into the knotty gritty chemistry and physics.
With that said, I’m in NE Nevada. I’ll tell you I wholeheartedly agree with @stoveliker. The creo problem isn’t related to 0%. Next, I’m not sure I’ve gotten anything down to 0%, or at least not that I’m aware of (could have I suppose). I’ve gotten wood down to single digit percentages, however come fall and then winter it’ll pick up some moisture again. This I have tested before (ie for example it’s 8% in august, come December when I throw it in its back up to 12%). As far as it being a problem? Again I agree with stoveliker and some of the others. The “problem” is it will burn/off gas very quickly, and create an “inferno,” or lose energy (in the rapidly forming smoke that you can’t burn fast enough). Now is that a problem? Maybe if your running an old stove, or a newer one that wants to be a free range pony, but if you can control your stove/air well, then no this isn’t really a problem minus losing some burn times. Is it a problem to lose energy? Sure, but I wouldn’t describe that as a problem compared to saying it’s more of an inefficiency. Again, as already noted the article/post posted reports that. Furthermore, even the greatest things in science are still sometimes debated, with plenty of evidence for both conclusions. Who is right? No need to get belligerent on here.
Lastly, if your that worried about it then experiment yourself. Try your suggestion that you took from the post and mix some higher mc wood, or put it back out in the environment for fall/winter to grab some moisture. Happy hunting.
With that said, I’m in NE Nevada. I’ll tell you I wholeheartedly agree with @stoveliker. The creo problem isn’t related to 0%. Next, I’m not sure I’ve gotten anything down to 0%, or at least not that I’m aware of (could have I suppose). I’ve gotten wood down to single digit percentages, however come fall and then winter it’ll pick up some moisture again. This I have tested before (ie for example it’s 8% in august, come December when I throw it in its back up to 12%). As far as it being a problem? Again I agree with stoveliker and some of the others. The “problem” is it will burn/off gas very quickly, and create an “inferno,” or lose energy (in the rapidly forming smoke that you can’t burn fast enough). Now is that a problem? Maybe if your running an old stove, or a newer one that wants to be a free range pony, but if you can control your stove/air well, then no this isn’t really a problem minus losing some burn times. Is it a problem to lose energy? Sure, but I wouldn’t describe that as a problem compared to saying it’s more of an inefficiency. Again, as already noted the article/post posted reports that. Furthermore, even the greatest things in science are still sometimes debated, with plenty of evidence for both conclusions. Who is right? No need to get belligerent on here.
Lastly, if your that worried about it then experiment yourself. Try your suggestion that you took from the post and mix some higher mc wood, or put it back out in the environment for fall/winter to grab some moisture. Happy hunting.
nola mike
Minister of Fire
What the hell, I'll join in. 1. You don't have 0% wood. Not possible under any normal conditions. 2. You reference other blogs as evidence of your point. These blogs are just other opinions, not science. As someone that has to parse scientific papers/evidence, this chafes me. (Btw, go look up "confirmation bias" for a better explanation of point 2)Did I EVER say I was smart? Nope but you my Nobel Sage are all knowing so I bow down to your intellect. The point of my post was to talk to people who have experienced TOO DRY WOOD and to discuss it in plain language not physics. Is that clear?
That said since people here seem to be too high and mighty to mix with common wood burners I turn to other blogs and forums and here is one of interest!
Can Firewood Be Too Dry? | Brockley Tree
Firewood left to season for longer than needed might lose more moisture than is necessary.
Thank you I didn’t have the cognitive load for this last night. I’d also throw in “cherry picking” for the poster to look into when it comes to confirmation bias.
I have very similar ones. My buddy also says it's quite common.
