Tlud Gasifier Stove Question

[Knothead]

Recently, I have been experimenting with using forced air in my stoves rather than just relying on natural convection. I wanted to make more compact and stable stoves that didn't have to have such big chimneys. I have been basing them on the Everything Nice stove.

I'm really pleased with the results so far though I doubt that I'll ever be satisfied that I've made the perfect stove.

One thing that I've noticed with the forced air is that after the material is consumed and I'm left with only char, if I leave the fan blowing, the stove starts producing what appears to be white smoke. When I shut the fan off. The smoke stops. I've never noticed this happening with my regular TLUDs. It's not really a problem, but it would be nice sometimes to be able to get a few more minutes of cooking by using the heat from the char. What happens when I do that now is that the pot and grate get coated by a pure white soot like material from the "smoke". Am I mistaken in thinking that what I'm seeing might only be really fine ash?

[CraigD]

One thing that I've noticed with the forced air is that after the material is consumed and I'm left with only char, if I leave the fan blowing, the stove starts producing what appears to be white smoke. When I shut the fan off. The smoke stops. I've never noticed this happening with my regular TLUDs. It's not really a problem, but it would be nice sometimes to be able to get a few more minutes of cooking by using the heat from the char. What happens when I do that now is that the pot and grate get coated by a pure white soot like material from the "smoke". Am I mistaken in thinking that what I'm seeing might only be really fine ash?

I think you're correct.

 

Since it's ash that flies up the flue (or at least flies as far as the pot and grate), you could term it fly ash, though I've only heard the term applied to coal burning.

 

I'd be curious to know it's chemical composition. My guess is that, like coal fly ash, it's mostly SiO₂, and CaO, but unlike coal ash, not much Al₂O₃ and Fe₂O₃. It might have some odd stuff, but given your report of its white color, I'm thinking Si, Ca, or Al, maybe some K.

 

It's likely good for something - cement, paint, etc - but could be nastily toxic, too, so if you experiment with it, use caution.

[Knothead]

I think you're correct.

 

Since it's ash that flies up the flue (or at least flies as far as the pot and grate), you could term it fly ash, though I've only heard the term applied to coal burning.

 

I'd be curious to know it's chemical composition. My guess is that, like coal fly ash, it's mostly SiO₂, and CaO, but unlike coal ash, not much Al₂O₃ and Fe₂O₃. It might have some odd stuff, but given your report of its white color, I'm thinking Si, Ca, or Al, maybe some K.

 

It's likely good for something - cement, paint, etc - but could be nastily toxic, too, so if you experiment with it, use caution.

 

Thank you for the reply and education. I was not familiar with the term Fly Ash. It makes sense that that is what it is. It actually flies up in the air and well past the grate and pot. By all appearances, it looks just like white smoke. I don't know how I would experiment with it other than to scrap it off the pot and collect it. However, your warning about the possible toxicity make me think I should just stop the burn when it first appears rather than to take a chance of breathing too much of it.

[CraigD]

Thank you for introducing me to the Everything Nice stove, and the whole technology of woodgas, AKA micro-gasification, which until the last week or so, I didn’t know existed.

 

In the odd way that new ideas seem to come at me from several sources at once, I saw something about this a few days ago on the “Trailer Power” episode of National Geographic channel’s Rocket City Rednecks series, which showed some brief clips of ca 1940s gasifiers used not as cook of heating stoves, but to supply gas to normally gasoline fueled cars and tractors, then went on to build one out of large drums and cans to run an ordinary portable generator. As they didn’t appear to include much or any of a filter in their system, I imagine they wreaked havoc on the generator’s poor engine, but as can be seen from the various old photos and text on pages such as this one, its possible with the right engineering to pretty much run any gasoline or methane powered engine on woodgas from a portable gas generator.

[Essay]

What happens when I do that now is that the pot and grate get coated by a pure white soot like material from the "smoke". Am I mistaken in thinking that what I'm seeing might only be really fine ash?

I agree with these previous replies, and....

 

Yes, I think the "fly ash" is mostly oxidized soot. As the fully charred biomass (charcoal or "coke" or maximally-reduced carbon) continues to be blown by the air, bits of soot (graphenic carbon--along the lines of buckyballs, carbon nanotubes, and shards of these species--mixed with trace salts, metals & heavy-metal impurities) are blown free; and are mostly oxidized as they are carried away from the hot, solid char and up into the cooler, oxygen-enriched updraft.

....

Right! ...Mostly Si & Ca oxides (plus partially oxidized soot), but with all the other metals and elements (toxins or nutrients) concentrated from the source material too. "Toxic" or not, you don't want to be breathing that stuff.

 

You get some extra heat from oxidizing more of the char, but that releases carbon from the solid and converts it into CO & CO2 (and soot). White smoke (on start-up) is high in carbon monoxide too, so.... When the char stop producing gas and starts producing smoke, seems like a good signpost for quenching the char, if you want to maximize carbon enrichment (or minimze carbon release). :)

===

 

Craig, In researching pyrolysis (to make biochar) I recall finding these sites, which seem relevant here.

 

http://taylor.ifas.ufl.edu/documents/Handbook_of_Biomass_Downdraft_Gasifier_Engine_Systems.pdf

"Handbook of Biomass Downdraft Gasifier Engine Systems"

 

I liked fig. 2.2; the picture of the limo, w/ the wood gasifier pulled behind on a little trailor.

 

see also:

http://taylor.ifas.ufl.edu/documents/energywood.pdf

"How to Power a Gasoline Engine with Wood"

 

http://taylor.ifas.ufl.edu/renewable-energy.shtml

"The literature cited... is a compilation of literature addressing the use of downdraft gasification technology for heat power and transportation needs that was developed during WW II. Currently the Extension Office is working with local and regional cooperators to get a local gasifier in operation."

 

~ ;)

[Knothead]

I agree with these previous replies, and....

 

Yes, I think the "fly ash" is mostly oxidized soot. As the fully charred biomass (charcoal or "coke" or maximally-reduced carbon) continues to be blown by the air, bits of soot (graphenic carbon--along the lines of buckyballs, carbon nanotubes, and shards of these species--mixed with trace salts, metals & heavy-metal impurities) are blown free; and are mostly oxidized as they are carried away from the hot, solid char and up into the cooler, oxygen-enriched updraft.

....

Right! ...Mostly Si & Ca oxides (plus partially oxidized soot), but with all the other metals and elements (toxins or nutrients) concentrated from the source material too. "Toxic" or not, you don't want to be breathing that stuff.

 

You get some extra heat from oxidizing more of the char, but that releases carbon from the solid and converts it into CO & CO2 (and soot). White smoke (on start-up) is high in carbon monoxide too, so.... When the char stop producing gas and starts producing smoke, seems like a good signpost for quenching the char, if you want to maximize carbon enrichment (or minimze carbon release). :)

===

 

 

Craig, In researching pyrolysis (to make biochar) I recall finding these sites, which seem relevant here.

 

http://taylor.ifas.ufl.edu/documents/Handbook_of_Biomass_Downdraft_Gasifier_Engine_Systems.pdf

"Handbook of Biomass Downdraft Gasifier Engine Systems"

 

I liked fig. 2.2; the picture of the limo, w/ the wood gasifier pulled behind on a little trailor.

 

see also:

http://taylor.ifas.ufl.edu/documents/energywood.pdf

"How to Power a Gasoline Engine with Wood"

 

http://taylor.ifas.ufl.edu/renewable-energy.shtml

"The literature cited... is a compilation of literature addressing the use of downdraft gasification technology for heat power and transportation needs that was developed during WW II. Currently the Extension Office is working with local and regional cooperators to get a local gasifier in operation."

 

~ ;)

 

Thanks, I agree. I usually always snuff the fire when the flames indicate that the gasses are exhausted. The only time I thought it might be good to use up some of the char for additional cooking is when something is just about ready to boil or something. But I certainly don't want to defeat the purpose or be breathing anything harmful.

 

Craig, I'm glad you discovered this. I get a lot of enjoyment building and using different stoves and I find I use all the bio char that I can produce.

I have always liked to have a little bon fire in a pit or the chiminea but I find using the stoves much more satisfying and a lot cleaner. The only down side is that the stoves only burn for a specific length of time unlike a regular fire that you can keep feeding.

 

Question: How much bio char would one have to produce and sequester in order to erase his carbon footprint? :unsure:

[Knothead]

Here's a video of one of my latest stoves.

 

http://youtu.be/Ay9wUWTjpyM

 

This burn was done in my garage using cardboard. It works well with twigs and small chunks of wood but the burn is much faster. Only about ten minutes.

I would like to try it with wood pellets but they aren't available in Florida. Crushed walnut or coconut shells would probably be great.

[Turtle]

Here's a video of one of my latest stoves.

 

http://youtu.be/Ay9wUWTjpyM

 

This burn was done in my garage using cardboard. It works well with twigs and small chunks of wood but the burn is much faster. Only about ten minutes.

I would like to try it with wood pellets but they aren't available in Florida. Crushed walnut or coconut shells would probably be great.

 

i don't think cardboard char is a good idea. i wouldn't do your experiments indoors or breathe around the fire either. :naughty:

 

oregon state university extension service

Wood ash can be useful in yard if used with caution

...

Do not use ash from burning trash, cardboard, coal or pressure-treated, painted or stained wood. These substances contain trace elements, harmful to many plants when applied in excessive amounts. For example, the glue in cardboard boxes and paper bags contains boron, an element toxic to many plant species at levels slightly higher than that required for normal growth. ...

 

besides the boron in the glue, there are sulfates in the paper & whether they oxidize or not, that can't be good i should think.

 

How is corrugated cardboard made?

...

Manufacturing a corrugated cardboard box begins with the pulping of wood chips in the kraft (sulfate) process. First, tree trunks are stripped of bark and torn into small chips. Next, these chips are placed in a large, high-pressure tank called a batch digester, where they are cooked in a solution, or liquor, made of sodium hydroxide (NaOH) and several other ionic compounds such as sulfates, sulfides, and sulfites. These strongly alkaline chemicals dissolve the lignin, the glue-like substance that holds the individual wood fibers together in a tree trunk....

[Knothead]

i don't think cardboard char is a good idea. i wouldn't do your experiments indoors or breathe around the fire either. :naughty:

 

oregon state university extension service

 

 

besides the boron in the glue, there are sulfates in the paper & whether they oxidize or not, that can't be good i should think.

 

How is corrugated cardboard made?

 

Thanks for the information. I agree that cardboard isn't at all the best material to use for producing biochar. As I said, I would really like to use some really dense, natural material like nut shell or pellets in this little stove. Most of the biochar I produce is from biomass that grows on my property and I use bigger stoves most often. Still, I doubt that the tiny amount of cardboard char and ash that I add to my soil will be a problem.

What I was trying to do here was demonstrate the efficiency and versatility of the stove. The reason I did the burn indoors was two fold. It was kinda windy outside and I wanted to be able to determine how well the stove was working. The only way I know to do that is to use my nose and see if it smelled much. I am happy to report that there was very little odor from the cardboard other than upon lighting. Once it started burning well, it hardly smelled at all. I figure that since there are still millions of people in the world that still use open flame wood fires indoors to do their cooking, it's only fair that I test the stove indoors. But I do burn most of my fires outside.

 

But anyway, my methods aside, what did you think of the stove itself?

[Turtle]

...

But anyway, my methods aside, what did you think of the stove itself?

 

i like the stove. :thumbs_up well crafted and you're reusing materials.

 

a couple other thoughts on methods though if i may. i think that even "primitive" wood cooking indoors uses some fashion of chimney if only a hole in the roof. moreover i would imagine that while your stove emits little smoke, that a "primitive" application would be wanting for electricity to drive the fan. then there is also the matter of carbon monoxide which is colorless, odorless and deadly.

 

if your aim is to produce biochar then you want to restrict airflow, not enhance it. i experimented with a parabolic trough oven for making biochar but my reflector size was inadequate to produce the necessary high temp. my reflector was only 4 feet across and i guessed it would need to be 12 to 16 feet in order to get the job done. here's a link to the thread with all the details. >>Solar Parabolic Trough Charcoal Oven

 

for crying out loud, be careful!!

[Knothead]

i like the stove. :thumbs_up well crafted and you're reusing materials.

 

a couple other thoughts on methods though if i may. i think that even "primitive" wood cooking indoors uses some fashion of chimney if only a hole in the roof. moreover i would imagine that while your stove emits little smoke, that a "primitive" application would be wanting for electricity to drive the fan. then there is also the matter of carbon monoxide which is colorless, odorless and deadly.

 

if your aim is to produce biochar then you want to restrict airflow, not enhance it. i experimented with a parabolic trough oven for making biochar but my reflector size was inadequate to produce the necessary high temp. my reflector was only 4 feet across and i guessed it would need to be 12 to 16 feet in order to get the job done. here's a link to the thread with all the details. >>Solar Parabolic Trough Charcoal Oven

 

for crying out loud, be careful!!

 

Thanks, I'm pretty careful.

I have found that the best biochar, or at least the cleanest, is that which I make in a retort. But the tluds do a pretty good job too. I use a lot of char around the house so I need a pretty constant supply.

The little stove is simply an experiment in how small I could get a stove and still have it functional.

I understand what you mean by restricting air flow, but you need to have some air flow. With the little stove I don't use a chimney. So the fan is necessary to create the airflow that the chimney would have. This way I can keep the stove very low profile.

I could easily run the little 12 volt fan from a battery charged by a solar panel, but I agree that most of the third world would not have stuff like that available unless it were supplied to them as an aid program or something.

Thanks for your thought and the link.

[Turtle]

Thanks, I'm pretty careful.

I have found that the best biochar, or at least the cleanest, is that which I make in a retort. But the tluds do a pretty good job too. I use a lot of char around the house so I need a pretty constant supply.

 

ok. we don't want to loose you. what all do you do with your char?

 

The little stove is simply an experiment in how small I could get a stove and still have it functional.

I understand what you mean by restricting air flow, but you need to have some air flow. With the little stove I don't use a chimney. So the fan is necessary to create the airflow that the chimney would have. This way I can keep the stove very low profile.

I could easily run the little 12 volt fan from a battery charged by a solar panel, but I agree that most of the third world would not have stuff like that available unless it were supplied to them as an aid program or something.

Thanks for your thought and the link.

 

here's a vid of my little experiment with a TLDD stove. youtube has associated dozens of other experimenter vids to it & you may find some ideas to try. have fun & keep your tender dry.

 

http://www.youtube.com/watch?v=UzshYfzxc2Y

[Knothead]

ok. we don't want to loose you. what all do you do with your char?

 

 

 

here's a vid of my little experiment with a TLDD stove. youtube has associated dozens of other experimenter vids to it & you may find some ideas to try. have fun & keep your tender dry.

 

http://www.youtube.com/watch?v=UzshYfzxc2Y

 

Most of the char is powered and mixed with sawdust to be used as a cover material for my composting toilet. The rest is just added to the compost pile directly or mixed with finished compost and worm castings for potting soil. I am still working on the proportions. The last batch of soil I mixed up was so potent that it turned the leaves of the plant yellow until I flushed it with enough fresh water.

 

I've also used some to make a sand filter for filtering rainwater.

I have tried to make briquets in a little press that I made but with limited success.

 

Thanks for the video link.

 

Check out some of my other stoves if you have the time.

 

http://www.youtube.com/user/norseaknothead

[Knothead]

For any interested, here's a link to a video of my latest tlud.

This little stove is extremely simple and yet consistently performs better than any others I've made. It's made pretty much entirely of scrap and I've been able to successfully burn a variety of materials. With hardwoods, I get about a 45 minute burn and lots of bio char. The resultant bio char contains much less ash than my other stoves.

 

http://www.youtube.com/watch?v=Rjluv6GPfbc

[Essay]

For any interested, here's a link to a video of my latest tlud.

This little stove is extremely simple and yet consistently performs better than any others I've made. It's made pretty much entirely of scrap and I've been able to successfully burn a variety of materials. With hardwoods, I get about a 45 minute burn and lots of bio char. The resultant bio char contains much less ash than my other stoves.

 

http://www.youtube.com/watch?v=Rjluv6GPfbc

I'm very impressed with your long burn times. I wonder if the char is lighter than chars produced more quickly--indicating some additional carbon loss--but that is a detail for the future. Right now it is an amazingly efficient cookstove or potential power source, and still relatively carbon negative, it seems to me.

 

Neat, clever, designs too! Thanks for sharing. Ben Franklin would be proud, and happy to finally see a new improvement in these fundamental capabilities.

===

 

I've been playing with a "forced air" design, which creates a vortex/oxygen curtain, sometimes quickly getting good results and sometimes getting a quick pile of ash. The height of the bottom of the vortex (above the fuel) determines the success or failure, but most all the results go into the compost pile. [Turtle, fyi] Char, crushed and rubbed in, solves my sweaty foot problem too; in addition to improving compost.

 

http://www.flickr.com/photos/mitchessay/sets/72157632252564902/with/8274792690/

My goal is to char a tree stump, or whole logs, without all the cutting/processing usually required. If I get back to this over the summer, I'll post an update.

 

~

[Knothead]

I'm very impressed with your long burn times. I wonder if the char is lighter than chars produced more quickly--indicating some additional carbon loss--but that is a detail for the future. Right now it is an amazingly efficient cookstove or potential power source, and still relatively carbon negative, it seems to me.

 

Neat, clever, designs too! Thanks for sharing. Ben Franklin would be proud, and happy to finally see a new improvement in these fundamental capabilities.

===

 

I've been playing with a "forced air" design, which creates a vortex/oxygen curtain, sometimes quickly getting good results and sometimes getting a quick pile of ash. The height of the bottom of the vortex (above the fuel) determines the success or failure, but most all the results go into the compost pile. [Turtle, fyi] Char, crushed and rubbed in, solves my sweaty foot problem too; in addition to improving compost.

 

http://www.flickr.com/photos/mitchessay/sets/72157632252564902/with/8274792690/

My goal is to char a tree stump, or whole logs, without all the cutting/processing usually required. If I get back to this over the summer, I'll post an update.

 

~

 

 

I appreciate your encouraging words. Thanks.

I really think the reason for the long burn times is that once the fire gets burning well, I'm able to limit the amount of air so that it burns slowly for cooking. If I open up the intakes, which I do when I'm just enjoying the fire, it burns much more quickly. The 40 to 45 minute burns would probably be more like 30 minutes.

I could be wrong, but it seems to me that the char is the same whether it's a quick fire or a fast one. With light fuels, like small sticks and twigs or especially like the softwood chips, a lot of the ash is apparently lost as fly ash. That's evidently why the char that I'm left with does not usually contain a lot of ash. Whereas with harder stuff like the oak bark, because the flow of air is so much more restricted, the draft is slower and if I let it burn too long and the char starts to burn, the ash doesn't fly off.

 

I wish I had enough stuff to burn to experiment with stoves as big as yours, which seems to work wonderfully. Never-the-less, your post inspired me to try to burn a firewood log in the tlud last night. I picked a log that was a little higher than the can so that it stuck up into the combustion area. I had to whittle down the corners to fit it into the can. I packed smaller oak sticks and branches around it as best as I could. It was a bear to get lit, but once it got going, I was able to maintain a smallish, but adequate fire by completely, or as least as completely as I could, shutting down the secondary air. With this stove, restricting the secondary air causes more primary air to be sucked in. Burning a single big log seemed to need this.

I didn't time the burn, but I started the fire before the first pitch of a spring training game and it burned into the sixth inning. I would estimate about an hour or so.

The flame rarely shot out of the top much more than a few inches, but it would have been perfect for cooking. The char that remained was mostly all fom the log. All but the largest sticks were gone. After shaking the can to remove the ash, I was left with almost 1/2 a can of char.

I don't seem to have as much success controlling or limiting a softwood fire. But the more I experiment with this set up using different fuels and different ways to pack the can, the more I learn.