Biochar / Drum Retort combustion problem

Hello,

I come to you for a story of combustion.

60l drum upside down in a 200l drum

The 200l is pierced for primary air at the base with 6 turns of 28mm. (37cm²)
The neck for the secondary air is in 12 holes of 13 mm (16cm²)
The extraction is 75 cm² in 1.3m long

Combustion, this is where I do not understand everything:
Ignition from th etop
When the barrel is open, beautiful combustion, dynamic, without smoke
When I close the barrel (plate and extraction), I have a beautiful smoker for 4 hours (apart from 1 minute at most after 5min of closing)

My questions are the following:
Why do I have a smoker and not a clean combustion, without smoke? (all the demonstrations that I see I do not make smoke)
Should the air arrivals / extractions be modified?
Do you have any recommendations?

Attached are some photos:

I have exactly what your experienced.  I solved it using two different methods.  The first is to just leave the chimney off altogether and just use the bottom barrel with an open top.  That worked pretty well for me, but there were still times that I would get a lot of smoke.  I haven't used my retort for awhile, but if I remember correctly, I would start having issues when the barrel was burned down to about 3/4 full.  Another thing I tried was using another complete barrel the same size as the bottom one for a chimney.  That works much better.  

I use a new method now that I find much, much better than a retort, and you don't waste the wood that burns up heating the retort.  I just call it the "tilted barrel" method.  I made a thread about it here if you are interested:  Tilted barrel biochar  

This is the only way I make charcoal now and I'm very happy with it.  You get much bigger yields than from the retort and no smoking or chimneys to deal with.  I quench it to stop the burn now, but if you are in an area with no water, you can use a stick to stand the barrel up at the end of the burn and put a lid on to extinguish it.  If you feel like experimenting, I think you will be very happy with the results.

Thanks for your reply ! I was lloking for alternative and this one was well plebicited !
I also read your other post. Will give a try ! But need to find a new barrel before !

Florian Fff wrote:Thanks for your reply ! I was lloking for alternative and this one was well plebicited !
I also read your other post. Will give a try ! But need to find a new barrel before !

I would give it a try with your current barrel.  It may be that the additional holes don't bother anything at all.  If you find they do cause a problem, maybe some clay mud could be used to cover the holes around the bottom of the barrel?  It may or may not last, but it would be a free way to try it.

I experimented with TLUD retorts like this design as I started my biochar production journey and found them temperamental in the same way you did: Inconsistent burning, too much smoke, incomplete charring of the material in the inner drum (or going all the way to ash if I wasn't careful). I shifted my focus to flame cap and haven't really looked back...

...until now, when I was asked by a research supervisor if I could make biochar out of coconut coir chips. It turns out that these will burn readily once they're dry, but they don't achieve a flame, and in a kontiki or trough they smolder and smoke like mad. So I'm making a barrel retort again, only this time things are different.

No TLUD in this design. It's the Black Ripple approach and we discussed it in this thread a few weeks ago. The primary heat comes from a rocket J-tube and the outer wall of the reactor is insulated to keep in more heat. My hope is that I can run it with a smaller amount of sacrificial wood but get it up to temperature quickly. I have all the parts and if this weekend isn't too wet I hope to put it together and do a trial.

Hi Florian,
I also had some of these problems when my system was like yours, so I made some adjustments.  There are echoes of all of us responding in each others' recommendations.  First, I used this system, which was the first one I saw that I could use and would work:

https://www.youtube.com/watch?v=YIbGkmt1VdE&t=105s

I didn't use a retort because I wouldn't have made enough biochar in it. I use a TLUD burn system, like the video.  I also put my barrel on four bricks, sideways, with holes in the bottom. Some air can come up from the bottom so the flame is burning the gas off of the wood.  I made a much wider chimney than yours.  I think it would be hard to limit smoke with such a narrow diameter chimney.  I think that mine is about 10" wide. You can get another chimney at a restore if there's one near where you live.  Mine burns well with the chimney off, but better with the chimney on.  When I add more wood, I just lift it quickly and slide the piece of wood in.  This system makes great biochar with little smoke.  Your system will have to fit your particular situation, like ours do for us.  

You could go back through all of the posts, but I'm sure we'll be glad to answer your questions, too.

John S
PDX OR

Great to have lot of feedback !
I try a new batch today, without chimney, it works great
Not the first time, but was great at last.

I think my error comes from Open 60l barrel (no holes, just open)
It didn't seal weel with 200l bottom.
Will give a try with 60l barrel with lid and holes on bottom

And looking for an other 200l lid barrel for tilted experiment

Will also investigate the 2 new method given here
Thanks guys !

Tiltled drum works way better. Needs more attention to refill but way easyier to handle !
I feel like consuming more wood.
With retort, all you put inside was converted (plus outside chamber combustible!)
With tilted, feels like 30-40% of good wood is heated by the process

Florian Fff wrote:Tiltled drum works way better. Needs more attention to refill but way easyier to handle !
I feel like consuming more wood.
With retort, all you put inside was converted (plus outside chamber combustible!)
With tilted, feels like 30-40% of good wood is heated by the process

I'm glad you thought it worked better.