Horizontal TLUD

I of course can't find the link now, but I came across a biochar kiln design that consisted of a long horizontal tunnel that had a chimney at one end and allowed air in at the other.  You basically fill the box with feedstock (theirs was crop residue of some sort), and then ignite it at the chimney end.  The flame front moves from the chimney end to the open end, sort of like a horizontal TLUD.  What was interesting to me was that it seems like you could adapt this design to make a low-cost continuous feed system, if you inserted a collection bin that the biochar could fall into between the tunnel and the chimney.  When the flame front has moved far enough through the tunnel, you could shove more feedstock into the tunnel, and push the finished biochar over the edge into the collection bin.  You could even have a sliding door that isolates the collection chamber and allows you to quench and cool the biochar before its removal.

Anyway, I'm just starting to think about this, and thought I'd share in case others are interested.

I found the link:
https://www.biochar-international.org/wp-content/uploads/2018/04/Liberty_Biofuel_Products_LLC_biochar_processor.pdf

Awesome! I'd been thinking about something along those lines, but hadn't worked out the details yet.

You could even have a sliding door that isolates the collection chamber and allows you to quench and cool the biochar before its removal.

Make the collection bin with a metal plate that goes from the top to about halfway down, and fill it with enough water to cover the bottom edge of that plate. That way the water itself acts as an airlock.

Not sure I'm describing that very well. I tried to draw a diagram, hopefully that will help.

I feel like this is one of those ideas that holds promise.  I can just barely understand it.  I use a TLUD myself, but it is in a 55 gallon drum with a chimney.  I have felt that if people could make a continuously feeding TLUD, it could make a lot more biochar more quickly.  We get a lot of rain here, so we have a lot of trees and a lot of wood.  I think it's great to have an adapted method for grasslands, which grow a lot more grass like stuff and less wood.  The horizontal feeding reminds me of the rocket mass heaters and their evolution over time into super efficient heaters that are better for the environment as well.  Good work!
John S
PDX OR

Very interesting.
I wonder, could a file cabinet become a  HTLUD?
Also should it be a called a SLUD(Side lite updraft ?)

I don't have switch grass, but I do grow sunchokes ,harvest pallets  and pollard mulberries.
I think a stack of long strait-ish fuel might allow enough air flow.
The horizontal surface above the trough could allow heat to be harvested.
Drying the next load of feedstock is the obvious use.
Instead of top loading, a front loader might be useful.
If there was grate and water douse system like mentioned above , unloading could be as easy as draining the tank.
A slide in fuel  basket could work as well.
A front loader also would make water heater tanks and 55gallon barrels viable as the body of the SLUD.
A gas water heater might even contribute a chimney to the set up.
This would resemble certain Japanese charcoal making set ups, but instead of a fire heating up the feed stock from the outside, it would be a self fueling operation.

The loading door could be on the same end as the chimney.
Primary air could be "remotely controlled" with piping and valves.
It could even pass through the firebox for preheating.
In a cylindrical design, a flat plate could form the bottom of the pyrolosis chamber and a chase for delivering primary air to where it was needed.

Crap, I just realized, I'm describing an un-insulated  batch box rocket with the door on the "wrong end", optimized  for incomplete combustion by limiting oxygen  with a progressive flame front...

Is that a good thing or a bad thing?

I think, if it actually works, it would be a useful alternative.
It would give char.
Since it would operate at lower temperatures, metal could be used throughout.
Would it burn "clean" ?
I'm not sure.

William Bronson wrote:
Crap, I just realized, I'm describing an un-insulated  batch box rocket with the door on the "wrong end", optimized  for incomplete combustion by limiting oxygen  with a progressive flame front...

It's funny, in my initial draft, I had written that it was "sort of like a horizontal TLUD or an L-tube rocket with a long lower leg".

For truly continuous, I think you would want the loading end opposite the collection end.  You might, for example, have a sliding gate that closes off the front end (airlock) as you open things up (maybe a small lid on top).  And maybe put a long handle on the primary air distribution plate, so that you could use it to shove feedstock into the tunnel.  So, basically:

1.  Close gate/airlock
2.  Pull back air distribution plate
3.  Open lid of fill-chamber, add new feedstock, close lid
4.  Open airlock
5.  Use air distribution plate to push feedstock into the burn tunnel (and nudge downstream char into the collection box/trap)

SLUD -- it's growing on me :-)

SLUD does have nice horror movie ring to it...
Horizontal Up Draft or HUD is more neutral.
Continuous fill is less appealing to me than taming the TLUD for space heating, but I certainly see the usefulness.
I'm struggling to picture it-more drawings!

Depending on what the feedstock is, an auger might come in handy for continuous-feed. It wouldn't have to go the full length of the burn chamber, just far enough to reach the middle is probably enough. But again, that would depend on the feedstock being used.

If anyone ever figures out a way to automate this, let me know. I have a ton of crop debris every year that I would love to convert into biochar. But burning one batch at a time takes ages, and I can't always spare the time between other chores.

I, too, am interested in using this to process large-ish quantities of crop residue (probably 10-20 cubic yards of chopped sweet sorghum stalks).

It should be possible to incorporate an auger to automate loading. The tricky parts will include 1) synchronizing the feed rate to the rate of pyrolysis (it will depend on the type of material, moisture content, packing density, etc), and 2) figuring out how to automate removal of the finished biochar.

Given the large volume of material that I want to pyrolyze, I'm trying to figure out what sort of cross-sectional area makes sense

Curtis McCue wrote:

It should be possible to incorporate an auger to automate loading. The tricky parts will include 1) synchronizing the feed rate to the rate of pyrolysis (it will depend on the type of material, moisture content, packing density, etc),

Infrared sensors to track the pyrolysis front as it moves through the fuel? If a heat-sensing camera can show a person through a brick wall, it should be able to show a flame through a metal wall. The image may be fuzzy because the metal itself will heat up, but it should still be close enough to allow the machine to monitor the burn rate in real time.

and 2) figuring out how to automate removal of the finished biochar.

Another auger? Or an Archimedes screw leading to a settling tank, with a way for the water to return to the dousing chamber afterward? Or simply a metal mesh conveyor belt?

Ellendra Nauriel wrote:Infrared sensors to track the pyrolysis front as it moves through the fuel? If a heat-sensing camera can show a person through a brick wall, it should be able to show a flame through a metal wall.

Good thinking.  An even easier setup would be to have a thermistor located at a certain point, and if it reaches a certain temperature, then it triggers a step motor controlling the auger.  Basically, "OK, the flame front has reached this point, so it's okay to add another increment of feedstock."

Edit:  That should be "thermocouple", not "thermistor"

Here is a quick sketch of what I have in mind for a manual continuous system (not to scale).  PNG for viewing, SVG for editing

You people got skillz!
John  S
PDX OR

I had a thought on the automated charcoal machine. It would have more in common with one of those automatic pellet stoves than with the horizontal TLUD, but I'm not sure it's enough for it's own thread.

Anyway, picture one of those self-feeding pellet stoves, but with a funnel-shaped burn chamber along the lines of a kon-tiki. At the bottom of the funnel is another auger, treating the burn chamber as if it were a hopper, and feeding the hot char through to a dousing chamber.

There would still have to be some kind of sensors monitoring the burn, and also something to tell it when the burn chamber is full enough that it needs to remove some char.

Thoughts?

Curtis McCue wrote:Here is a quick sketch of what I have in mind for a manual continuous system (not to scale).  PNG for viewing, SVG for editing

The way the air-distribution plate is used to push fuel, looks a lot like some of the designs I've seen for mini-haybalers.

Ellendra Nauriel wrote:Anyway, picture one of those self-feeding pellet stoves, but with a funnel-shaped burn chamber along the lines of a kon-tiki. At the bottom of the funnel is another auger, treating the burn chamber as if it were a hopper, and feeding the hot char through to a dousing chamber.

Tbh, I don't know much about pellet stoves, but it sounds like they have a constant feed rate (e.g., pounds per hour) that is turned on or off by a room thermostat.  Inside, there are low/high temp sensors (up to 300F?) to control things like fans and shut off the feed if things get too hot.  I'm not sure how to apply that to a pyrolytic setup, unless maybe you are able to monitor the combustion of pyrolysis gases (as opposed to combustion of the char).