Clean burning: Is it possible to avoid white smoke entirely?

YEAH, YOU AIN'T BURNIN' IT HOT ENOUGH

 

That OWB that I started that other thread about was belching real thick grey/green smoke that just hung in the air. It took a long time and a long distance for it to dissipate. There was a light wind that day, not a good breeze.

I get white smoke that dissipates quickly when I reload the stove. 5-10 minutes tops, depending how warm the stove is when reloading.

 

I've been adding paper to the reload also. That and keep the door open to get her a burning quickly.

 

Same here, in fact most of the time even on a reload I leave the air wide open to get a good char going and there's no smoke. Very well seasoned wood ignites nice.

 

That's exactly what I get. I'm new to burning a stove so this is good to hear. Stove is rolling right now and even when shining a work light on it, I can't see a thing..

 

Seems to me, smoke is NOT "steam" (condensing water vapor), and should not be confused with it. (Steam is totally transparent, BTW.)

Looking at the top of the flue, a plume of smoke will remain visible as a plume of smoke for quite a distance, depending on wind, etc.

Moisture showing up as a plume of "steam" will disappear in short order on leaving the flue, as the moisture re-evaporates. Big difference, no?

Besides free & bound water in the wood, moisture in the exhaust results from burning hydrogen in the volatiles distilled from the wood.

 

First of all, you contradict yourself. How can a plume of steam show up if steam is totally transparent?
Technically speaking you are correct in saying steam is invisible, however, in common language it is often used to refer to the visible mist or aerosol of water droplets formed as this water vapor condenses in the presence of (cooler) air. Also, just how long the "steam" or mist stays visible depends on a lot of things like air temperature and relative humidity. Sometimes it can remain visible for quite a long time, after all, clouds and fog are just made of the same stuff and they often remain visible for a very long time.
Secondly, although there may be some hydrogen that combines with oxygen to form H2O in the combustion of the wood, the vast majority of "steam" comes from H2O trapped in the cells of the wood that will be evaporated off during the combustion process. Somewhere between 12% and 20% in seasoned wood to be exact, and more in unseasoned wood.

 

Steam is visible in the cold. Think of when you can see your breathe-- that's not smoke.

 

"My electric clothes dryer has a white output in the winter" ... so Grizzly Adam... does the loud clunking sound of the splits drying bother you at all? ... Does drying on high cause the splits to catch on fire? When the load is on fire... and rotating... have you ever noticed a change in smoke color? How about a change on your wife's face? ... ...

 

This describes my setup to a T...I had a good one going last night, draft inlet knobs almost fully closed, damper fully damped, and a pile of soft maple coals with 2 giant splits on top of it that would have busted into coals at the slightest poke. No smoke. Stove held steady at 650* for 3 hours untouched.

 

You guys must spend a heck of a lot of time outside watching your chimneys???

 

That's because our fires are so hot we have to go outside to cool down.

 

I have a good view of it from both home offices... From the window by the computer, and outside at the splitting stump!

 

Okay CTYank and Lumber-Jack , you've forced me to go back to high school chemistry to figure out the truth. From this reference on page 2, you can see that there are several molecular formulas for "wood" which include cellulose and lignin (anywhere from 57-77% of wood composition, remainder is sugars or hemi-cellulose). From the molecular formulas, C6H10O5, C9H10O2, C10H12O3 and C11H14O4 one can derive molecular weights based on the basic atoms of Carbon, Hydrogen and Oxygen having atomic weights of 12, 1 and 16 respectively. The weights derived for the four molecules are 162, 150, 162 and 162. When figuring out moisture content of firewood, we use a dry wood basis. So 120 lbs of wood at 20% moisture is 100 lbs of wood and 20 lbs of water. Applying that to our molecular weights, at 20% moisture content, the molecular weight of water would be about 32 or just under two molecules of H2O per molecule of lignin/cellulose. Conversely, in perfect combustion, every 2 atoms of Hydrogen would need 1 atom of Oxygen to complete the combustion process. For our molecules mentioned above, the requirement for Oxygen atoms would be 5, 5, 6 and 7 respectively. The total molecular weight of the H2O given off by combustion would be 90, 90, 108 and 126 respectively (over half the weight of the original wood molecule). So while the moisture content of the firewood was about 2 molecules of H2O for each molecule of lignin or cellulose, the products of combustion include 5-7 molecules of H2O for every molecule of lignin/cellulose. Thus, a greater amount of the water vapor that travels through the flue comes from the combustion of wood molecules and not from water trapped in the wood. As the moisture content of the wood goes down, the difference becomes more dramatic. While I didn't do the calculation for the Hemi-Cellulose (sugars contained in the wood including xylose, mannose, galactose, rhamnose, and arabinose) I'm sure the calculations are about the same.

Smoke is incomplete combustion. If the fire is smoldering (not generating enough heat or getting enough oxygen) you will get smoke. If it's burning hot and your wood is dry, you will get water vapor. Whether or not you see that water vapor will be determined by how much heat is carrying it up the chimney as well as the outside temperature and humidity. Just look at the tailpipe of your car next time you start it up on a cold wet day. No water in my gas but plenty of water vapor (even liquid water) exits the tailpipe..

The fact that we are all discussing this means that we give a chit about clean wood burning and about our neighbors... We are not part of the problem. Some incidental visible moisture or smoke exiting your chimney is just a sign that you're self sufficient and not shoveling your dollars overseas to people who hate us..

Another good link http://www.marioloureiro.net/ciencia/ignicao_vegt/ragla91a.pdf

Bill Lion my answer to your original question is an unequivocal YES. But to avoid any appearance of burning, you would not be able to burn on high humidity days thus allowing your neighbors to see water vapor exit your chimney. If you want to burn throughout the winter, you will inevitably at some point be able to see the product of combustion.

 

Awesome post -thank you!!

 

For some of us, it doesn't take an act of God to (get off the couch,) open the door, go out, take two steps away , look up, take two more steps to the door and go back inside. Some of us even have windows that are clean enough to look out of and see if our chimneys are smoke dragons or not.

 

It takes an act of God for my wife to clean my windows.........Cheers!

 

As someone who spends a lot of time looking at my chimney, and others, and trying daily to make it cleaner, I will say that in my opinion even the cleanest burner with the best stove will always have moments of visible smoke. They may be short and not happen often, but they will happen...on start up, maybe on coaling, on reload....for every stove there is a certain set of circumstances where it will smoke. The trick is learning your stove and minimizing those events.

And yep, if you are doing it right you will certainly have visible steam at times.