TLUD Tests

[Eagle66]

I decided to give a TLUD a try for my charcoal to compare it to the retort method I have been using. I went out and got the ductwork to build one like Dagabu’s design in his video.

I drilled 7 - ½” holes in the bottom of one of my gallon paint cans.

 

In retrospect, I can’t remember why so many holes, but I think it was a factor in the results I got. I’ve been splitting my black willow into sticks 7” long and about ½”‘-¾” square. While doing this, I get a lot of smaller sticks, chips, etc.

 

I loaded one can with a bunch of the small chips, etc. It really looked impressive while it was running. When the fire died down somewhat, I removed the chimney, covered the can & set it aside to cool. When I opened it up, I found that it was way overcooked. The volume was about half of what I expected and most of it was covered with ash and it was all punky soft. I decided to try again with a load of thin full length splits and medium size chunks. The result was pretty much the same.

 

While the batches were finishing up, they looked like the coals burning in a campfire, so I concluded that it was getting too much air flow from the bottom holes. To remedy this, I fixed up a baffle to cover the holes most of the way.

 

I loaded up again with the same stuff as in the second batch. The result was better, less ash, but the coal was still a bit over cooked.

 

For a 4^th batch I closed the baffle almost all the way and loaded up the can with the 7” x ¾” square sticks, the same as the cans I cook with the retort method, and ran it like the others. Like the third batch, I pulled it when it seemed to have stopped outgassing and looked like a campfire burning. This batch was the worst of all. More than half was either undercooked or not cooked at all. The coal on top was mostly punky and ashy.

 

The method looks great running, no smoke to speak of, and no outside other fire for heat, but the end results were disappointing to say the least. The coal I got will probably be OK for some applications, but not for anything where power is required, like BP shooting or in hot compositions.

 

Since quite a few people are enthusiastic about this method, I can only conclude that I am doing something wrong, but I have no idea what.

[Nessalco]

I'll make a few suggestions that might improve your yield (while, oddly enough, I'm thinking of setting up a retort)

 

First, make your chimney no more than 50% your burner size, preferably less. For a 12" diameter burner, no more than a 6" pipe. You need a significant constriction to set up the pyrolyzation layer properly.

 

Second, change your airflow setup. Provide a secondary air inlet directly above the material, at least 1/8" the whole circumference of the burner. Then make tertiary air holes in your chimney that are no more than 5% of your primary + secondary air inlet area. Somewhere I have my figures for primary air inlet area to fuel bed diameter - as I recall it was around 3%. At a glance I'd offer that you're admitting too much primary air through too few inlets. For a pot that size you'd want maybe 20 holes 1/8" in diameter, well distributed across the mass.

 

When properly functioning, a TLUD has a pyrolyzation layer that moves through the material top-to-bottom, a combustion layer just above the fuel bed, and a reburn in the chimney thanks to the tertiary air. The temperature in the pyrolyzation layer stays pretty low. For a bucket that size, a load of splits as you describe should take at least an hour to cook - maybe more, depending on moisture content.

 

There is a lot of technical info about these cookers out there. Google either 'TLUD' or 'biochar'.

 

Kevin O

Edited November 13, 2014 by Nessalco

[mikeee]

You also need to seal the TLUD container once it is done cooking. Combustion air will enter through the bottom holes

and continue to burn the cooked wood. If you have a pile of loose soil or sand you can place the TLUD cooker on a flat

surface and pile the loose soil or sand around the bottom of the TLUD cooker, this will restrict air flow from entering the

bottom holes in the can. A snug fitting paint can lid is also needed on top of the TLUD cooker to restrict air flow into the

cooker when it is done cooking the wood. Stopping the flow of combustion air to the charcoal is key in producing a quality

batch of cooked wood. You can also place the entire TLUD cooker inside a 5-gallon bucket and place a solid lid on top

and place a brick or block on top to seal the lid from allowing air to enter, I also place a piece of burning newspaper inside

the bucket to consume the air quickly to stop the wood from cooking.

[dagabu]

Use a vertical strip of masking tape along the height of the can and one all the way around the base. This is a great tattletale for when the bottom of the burn is completed or nearly so.

 

I have only had issues with cedar chips, everything else works VERY well in the TLUD.

[Bobosan]

Try the TLUD with shavings instead of sticks.

[pyrojig]

This is great !! Im glad to see some testing in progress. I wish I had time to provide input and testing . I like seeing trial and error , as it helps others avoid similar probs . and it improves the design. \

Thank you guys for your input.

[Eagle66]

Try the TLUD with shavings instead of sticks.

Good idea, except... This is my stock of black willow.

 

I can't even guess how long it would take to whittle these logs into shavings. If I am lucky, I'll might just get them split into 7" long sticks by spring. About then, I'll be harvesting almost that much more from my source. Well. at least it keeps me off the street and out of bars.

[Blackthumb]

This works well every time for me...

 

[dagabu]

Good idea, except... This is my stock of black willow. Willow Logs.jpg

 

I can't even guess how long it would take to whittle these logs into shavings. If I am lucky, I'll might just get them split into 7" long sticks by spring. About then, I'll be harvesting almost that much more from my source. Well. at least it keeps me off the street and out of bars.

 

Get a 5 gallon can and cut the wood to length, split and cook. 6" starter, 6" reducer to 4" reducer, 5% holes in bottom and stack.