Experimenting with biochar chimneys

I use a TLUD with a 55 gallon drum.  I could get my set up to burn well, but it took awhile and would sometimes smoke and choke out the fire.  Here is what my old set up looked like:

I decided to experiment with a different type of chimney.  I just bought that original one because it was what they had at the restore.  I tried a new one.  This one was 10" across instead of 6" across.  I figured it might have an easier updraft, because the opening is so much wider.  It is shorter, which could be worse, but I figured I would try this out as an experiment to see how it worked.    

I was amazed! It flowed through so much better!  The output was clear almost the whole time.  There was no choking or hesitation.  It seemed to burn faster too, so much so that I let it burn a little too much.  I can check earlier next time.  

I started to feel bad that I hadn't started off with this wider chimney.  Maybe I created more smoke and less char than I needed to. But really, we are making this stuff up.  The best thing we can do is share our experiments with each other and help each other learn.  

Now I can't imagine going back to a narrow chimney.  I am excited to see what can happen with the new one.

Here is what the new one looks like:

John S
PDX OR

I used the new chimney again today.  Things were going along fine when I got the burn really going,  so I put the chimney on.  It burnt really well.  I decided that I probably want more wood in there, so I opened it up to add more wood.  It started smoking and went out. I could hardly keep it burning. It was quite a few frustrating minutes.  

I decided to put the chimney back on and it started burning really efficiently again.  With the narrow chimney, it was the opposite. I would sometimes have to take the chimney off to let it burn well.   It continued to burn well with the wide chimney on for the rest of the time.  I may decide to keep the wider chimney on almost all of the time now.  Less smoke, more char.

John S
PDX OR

Hey John, I see you used angle iron spacers under the lid with the wider chimney.
Did you use themwith the narrow chimney as well?

I use the same spacers for both.  It's a device by which I can lift the chimney off the barrel by myself.  It's really just four pieces of metal bolted to each other. It folds up like an accordion when I'm not using it.  It's also useful if I want to add more wood, or for some reason, the fire isn't burning properly.  
There was one used like that to create space in the original Warm Heart video I used as my template.
John S
PDX OR

Cool.
I was asking because the secondary air has such an impact, so I thought it might be a factor, but clearly that's not the case.

On my next burn I had the same experience. It burned really well, until I had to add more wood.  I took the chimney off to do that.  The fire went out, smoked and suffered. I got it barely burning again and put the chimney back on. It recovered and burned like a champ again.  Still trying to figure that out.

John S
PDX OR

So again, it was burning really well. I took off the chimney to add more wood, and it smoked and went out. I had a hard time getting it going, and then it finally burned well AGAIN.

So I have a new strategy.  After I took the chimney off, it kept burning well for a while. I took a long time to add all of the extra wood and it smoked, went  out, etc.  I noticed that it was no longer burning at the top, ie TLUD.  It was burning low at the bottom.

The next time, I will have some wood ready to add.  I will very briefly add one piece of wood before it dies down, then shut the chimney down quickly to see if it keeps burning well.  Then I'll wait a bit and add one more piece quickly before it dies down again, and shut it again.  

Hopefully, this way, it will never shut down and start smoking.

John S
PDX OR

Today I did the experiment I've been wanting to.  When I needed to add new wood, I didn't take off the lid and the chimney.  I didn't add a lot of wood all at one time.   I just leaned one side up enough to slide one piece of wood in and then shut it.  It didn't shut down the fire. It smoked only a little bit and kept burning, then caught back up to its roaring pace.  When it caught up to its roaring pace again, I quickly slid in another piece and let it recover.  It worked so much better! This was what I was hoping for.  

Until one of you really smart science people tells me otherwise, here is my interpretation: when I take the whole lid off and add a bunch of wood, it is no longer TLUD.  The fire either totally or almost completely goes out.  The fire is only in the lower part of the barrel.  TLUD is efficient because the updraft limits the air and it goes straight up.  The TLUD fire flows very efficiently, but when I do the major wood add, it shuts it down. It would burn efficiently for the whole burn if I just loaded it up the first time, got the fire going, and kept the lid on until the end.  Unfortunately, I need more char for my systems than that, so I need to add more than the first loading.   I am now convinced that I will need to follow this procedure in the future.  

While I was doing the experiment today, it occurred to me that the careful measuring of the amount of wood on the fire is important in other biochar systems.  If I recall correctly from you all, in both the kon-tiki style burns and the trench method, one is careful about how much wood to place on the burn at a time.  There may be some kind of a physics thing going on there.

John Suavecito wrote:Today I did the experiment I've been wanting to.  When I needed to add new wood, I didn't take off the lid and the chimney.  I didn't add a lot of wood all at one time.   I just leaned one side up enough to slide one piece of wood in and then shut it.  It didn't shut down the fire. It smoked only a little bit and kept burning, then caught back up to its roaring pace.  When it caught up to its roaring pace again, I quickly slid in another piece and let it recover.  It worked so much better! This was what I was hoping for.  

Until one of you really smart science people tells me otherwise, here is my interpretation: when I take the whole lid off and add a bunch of wood, it is no longer TLUD.  The fire either totally or almost completely goes out.  The fire is only in the lower part of the barrel.  TLUD is efficient because the updraft limits the air and it goes straight up.  The TLUD fire flows very efficiently, but when I do the major wood add, it shuts it down. It would burn efficiently for the whole burn if I just loaded it up the first time, got the fire going, and kept the lid on until the end.  Unfortunately, I need more char for my systems than that, so I need to add more than the first loading.   I am now convinced that I will need to follow this procedure in the future.  

While I was doing the experiment today, it occurred to me that the careful measuring of the amount of wood on the fire is important in other biochar systems.  If I recall correctly from you all, in both the kon-tiki style burns and the trench method, one is careful about how much wood to place on the burn at a time.  There may be some kind of a physics thing going on there.

John, I had the same type of issues when I used TLUD with a chimney.  I got to the point I just never added new wood, but, like you, I need bigger batches.  When I tested the method I talked about in another thread with a tilted barrel and no chimney, all my issues were solved.  You still need to load wood somewhat slowly.  If you load a bunch at once, it will start smoking.  It isn't really an issue though, because you aren't moving the chimney on and off, so can add wood easily.  Once the barrel gets full to the point you can't add anymore while it is tilted, you can just stand the barrel up and keep adding wood until it is entirely full.  By time you stand it up, the barrel is full enough that the fire keeps burning well while completely upright.  I'm getting very clean burns this way.  Just another possible thing to try while you are experimenting.

The similarity is really intriguing, Trace.  Also the similar feeding of wood on the other systems. It makes me want to envision a type of optimal system for this.  

I love your thread about tilting the barrel. I hope a lot of people try it and comment on what they have found.  The main problem with me trying it is that I have already drilled many holes in the bottom of my barrel, which works for my TLUD system.  I don't know how to "undrill" those holes in the bottom, so it wouldn't really be the same system.  I also don't have a lot of space, so convincing the wife that we need two 55 gallon barrels seems a little difficult at this point.  

Maybe someone will come up with some kind of hybrid that I could try.

John S
PDX OR

I think I would build a second tlud, modeled after this one with the good chimney.
This would free you up from babysitting the burn and adding more wood .

William,
Do you mean without the holes in the bottom and then tilt it, a la Trace?

Nah, I was just thinking duplicate your working model.
It seems to work without being tended to.
Edit:
I missed entirely the wife happiness issue.
Two of your tluds and chimneys should stack on and in each other  pretty well.
A slightly smaller diameter barrel that can store inside the first would be ideal.
Around here ,water heater tanks are cheaper and more readily available than 30 gallon drums.

As far as undrilling the holes in tour existing barrel, I think concrete and/or dirt might be sufficient.

Sounds like a retort. Is that what you're talking about?

John S
PDX OR

Not really- I'm communicating very poorly on this!

Using multiple separate barrel tluds in parallel would save on labor.

Using barrels that can nest inside each other would take up less space when they not in use, thereby helping to keep the marital peace.

I think I get it now.  Just nest them for storage.  Burn two TLUDs at the same time to burn more.  That would certainly make way more biochar with not much more labor during the burn.   Good idea.  I had never considered that one before.  That idea has a lot of potential in many applications.  

Right now, I don't think I have enough dry wood to do that.  Also, it takes more time to chop up the wood to make it dry enough that it burns well.  At some point, I could probably evolve to get more wood and adjust my timelines.  

You guys are coming up with great ideas. This is how the craft of how to do this evolves. Thanks,
John S
PDX OR

Another bonus if I ever get this going. Since I already have one barrel with holes in the bottom, and I would get one without, I would be able to look for the advantages of a TLUD vs. Trace's tilted barrel concept.  There may be certain circumstances in which each is preferable, or does something better in some ways.

John S
PDX OR

So I burned biochar again today.  Again I only added wood by slightly lifting the chimney and shoving wood in for a 5 or less second addition.  Again, it barely smoked and didn't shut down.  It stayed burning strong.  The TLUD stayed top lit.   I realized today that it works so well that I'm adding too much wood, possibly making too much for my system.  I think the timing is rather key-only add the wood when the new stuff has really started burning.  This is my new regular and I'm never going back to taking the whole thing off, adding a whole bunch of wood, almost shutting down the fire and creating a lot of smoke for a long time.  I'm just confirming that it really does work. It wasn't just a one-time fluke anecdote.

John S
PDX OR