Tar Cracking device

Since i got the tools, claim that i can read and understand, i am building this (tuff nut) tar cracker and share the outcome.

It all started with reading old books , first picture. ( producergassketc00sextrich, page 6 )

Tar breaks up into carbon, CH4 and hydrogen when passed over glowing red hot carbon…

So, lets do just that.

Building a small reduction zone, electrical heated, to fit under a charcoal gasifier tube…
temperature aimed for: red glowing, anything between 1000ºC and 1300ºC

Diameter internal: 4" , height 6"
Heating coil: kanthal A1 wire, 3000 watts 220 volts

The goal is to find out how the effect on the gasquality will be when tar is dripped in, just above the glowing zone…

Probably this setup will feed the 5 Kwh test set…

The inner core is high aluminia ceramic

putting in a plastic container to poor the casting refractory

Letting it dry overnight, tomorrow i put it in my oven to dry and then the high temp bake off

New tools arrived, oven it is… build now by my specs
more experiments in the pipeline
all about gasification.


Pretty lab equipment, in the end, but as in any design, it should not, the energy of bass is more important than the developed energy, for me the radiation of alumina (with wood with the help of a fan is obtained 1600 degrees) is sufficient to make the tests in a diabolo of gasogene.

Chopower in France with the plasma torch has the same problem.


Hi Francois,

I agree about the “devil’s mouth” in a gasifier…
The device being build here is just that part… ( Bocca del diablo)

Its just as a fun little project, easy to build and a lot of useful information to get from…

Strange , but i was involved in the design stage of Chopower, the fuel prep for the gasifier and i also predicted difficulty’s
My company in France is not so far from them…


You make me drull Koen :smile: be carefull for diabetes having such sweet life :wink:

Joke aside, in case you are interasted, l did some electric heated carbon catalyst things too early in my “mad sciencetist” days. I made a contraption like this


This was basicly a clay pot filled with charcoal with two steel pipes sticking out. I hooked the pipes on my stick welder (40v 100A AC) and it caused the “hearth” to glow white hot from the arc jumping the carbon particles. I injected steam in the pipes to obtain pure water gas for Fischer-Tropsch Synthesis.

Anyway, the contraption worked but the electrodes only lasted minutes. Enough for my needs but on a larger scale l bet this culd be duplicated, graphite electrodes perhaps…

Looking forward for reports!


Hi Kristijan

do you manage to condense a liquid hydrocarbon with this process?

this “devil’s mouth” is looking great so far…
Now its in the oven for drying and “baking”


Hi Kristijan,

Yep, i think we follow the same path… playing around is fun…

Because i want to “duplicate” the process in the gasifier, in a most controlled way, i build this, so i can optimize, observe the temperature changes and measure the different outcomes…

I think we could call it an “electric gasifier” ?

Bottom center vertical there should come a thermocouple in closest contact with the glowing carbon and maybe a second one in the refractory.

At my age i started drooling about 5 years ago, with the first readings on DOW and looking all those clips and pictures from other builds…

Must be a “pavlovian reaction” , be aware when arriving in Argos, very addictive…
You will , most certain, start drooling there, when you sit next to Wayne, driving shotgun in a real DOW car :grin:
At least, i did…


Thierry, you mean with the Fischer-Tropsch synthesis? Yes, l obtained a sample. My setup was realy small and crude. It was my graduation project. I am still gathering information and courage to do it again on a larger scale thugh…

Koen, looking fantastic! I like the term electric gasifier. I bet even raw wood culd be gasifyed this way.

Haha, l saw that on your 360° video :smile: your smile sayd it all :smile:


Any updates or new developments with this project Koen? I had a similar idea for cracking tar, just using an induction heater instead of a resistance heater. Like this one http://inductionheatertutorial.com/. A resistance heater like yours probably makes more sense though, simpler power supply. Plus resistance heaters are more efficient for a long run time.

You should look up the Riche’ retort gasifier. It’s a french gasifier from the late 1800’s, early 1900’s. As I understand it, it’s the same general concept that you’re going for with a zone of glowing hot char heated by an external energy source to crack tar. I’m hoping to build one in the near future. I might do a thread just on the original, just as an informative thing, and do a separate thread of my actual build, if and when I get to it.

Kristijan, I’ve done the same thing with my welder using gouging electrodes. Honestly a welder isn’t quite up to the task. While most will provide the 35 volts needed for a stable arc (not the little 125 VAC ones though), no welder I’m aware of will be able to create an arc at 100 volts or more. That would produce a nice long arc giving more energy to the electrons, and effectively increasing the surface area being heated by radiant energy. I’ll have to see if I can dig up an old patent I saw, I think it explains it better. Something from the 50’s or 60’s dealing with coal gasification.

As far as the life of the electrodes, if you know how to do any kind of electronics, an auto feed system wouldn’t be to hard to make. A comparator would read the voltage between the electrode and ground. As the rod burns back the arc gets longer and the voltage climbs (we’re using a constant current power supply), when the voltage hits a specified point a feed motor turns on pushing the electrode forward. Once the arc is shortened and the voltage drops the motor shuts off. if the voltage is too low, the motor kicks in reverse. Add an electrode magazine and every time an electrode runs out, another is ready to go. Or you can try to do what the big boys do and have an electrode extruder. Makes the electrode as it’s using it. If you make charcoal, you have the ingredients, raw powdered carbon (charcoal) and heavy tar. You’ll need to pyrolyse your wood and collect the off gasses, then distill that until you have the really thick, gummy tar. The kind Norwegian’s like to eat (no joke). Mix it up, put it in a hopper, heat it to make it soft, feed it through an ectruding device, heat it even more to cook off the tar and that’s it, as I understand it. The heat to cook off the tar can even be the heat from the arc as you’re using the electrode.

Not to get off topic, but an idea for either one of you since you like to experiment, large industrial facilities use “cold” plasma to crack pollutants, including creosote, in their smoke stacks. Cold is a relative term, it’s still screaming hot. Basically all it’s just an array of Jacob’s Ladders (the arc machine in mad scientists labs) that the gasses pass through. All you need is a transformer for a neon light, and a healthy respect for very high voltages. Then figure a way to put it in the outlet of your gasifier. Should be more efficient than trying to crack the tars by brute force like the two methods above, where you’re supplying enough external energy for gasification plus cracking. The “cold” plasma just supplies enough external energy to finish cracking what the gasifier missed.


I can not find anything on the internet about this system. Do you have information to share?



Some books.
A treatise On Producer-Gas and Gas-Producers by Samuel S. Wyer. Page 215

Gas Engines and Producer Gas Plants by Rodolphe Edgar Mathot. Page 190

A Text Book on Gas, Oil, and Air Engines by Bryan Donkin. Page 235

Found them on Google play books. Some have multiple editions, try to find the ones with the latest publishing date.


"The only exit of the retort is at the bottom, and in travelling down through the retort the gases pass through the lower bed of fuel, which is at a very high temperature, being practically in a state of incandescence.

Any condensable gases or vapors in this part of the retort are broken up and fixed so that the gases which pass through the U– shaped pipe L to the holder K are in the condition of permanent gases. When wood is used as fuel the composition of these gases is about 18 per cent, carbonic acid, 22 per cent, carbon monoxide, 15 per cent, methane, and 45 per cent, hydrogen."

I did not know that the place where the gas was taken from the autoclave affected the quality of the gas.
should the quality of the coal produced also be influenced by the location of extraction?
I presume that the gas extracted at the top of the horn (vs. gas extracted at the bottom of the horn) reduces "the work
dissociation "tars and vapors from wood distiation
Less work means less energy and faster carbonization
can also be coal with less tar residue ?



The bottom of the retort is heated to cherry red, the charcoal inside that part should be hot enough to glow. The glowing hot char cracks the tars as they pass through. Same idea as Koen’s electric heater, the “devil’s mouth.” Red hot char cracks the tar.

The books I listed describe it slightly better than the website Gary linked. Just slightly. I had to read the short descriptions a few times to catch what was actually going on. I’m on vacation and only have my phone, otherwise I would have started a thread with screen shots from the books and such. I’ll try to put together a detailed description, as best as I understand it, by Wednesday or Thursday. It’ll probably be under the charcoal section, even though technically charcoal is a byproduct. But I know a lot of people who make charcoal wish they could put the off gasses to use some how.

I don’t know if less tar would require less energy input or not. The books suggest the temperature might climb, and actually recommend using wet wood, 40% moisture. The water gas reaction is endothermic and might even be necessary to control the heat. Like I said, the descriptions were brief. But this thing is a tar splitting machine. The first Riche’ plant made actually ran off of petroleum. So if you have low tar material, why not just gasify it in a more conventional method? Use the Riche’ for problematic feedstock. That’s what he designed it for.


But if you consider the composition and energy content of the resulting gas, it would be a high grade engine fuel and feedstock for Fischer Tropsch processing.


Yes it is high grade. The books I listed all day it has about 2.5 times the energy per cubic foot as other producer gas. As far as Fischer Tropsch, that’s out of my league. My plan is to have a Riche’ type unit for a stationary cogeneration set up, then use the charcoal for mobile applications and biochar. I have access to a LOT of hemlock, which is in the pine family, so I’m hoping to possibly make pine tar or bio oil as well. Which I suppose, now that I think of it, could be run through again later to produce gas on demand. Hmmmm grey cells are starting to run amok.

Sorry if I’ve hijacked your thread Koen. I’ll try to start another one tonight, even though I don’t have the files and stuff with me that I wanted to put in it.


to crack the tars of the distillation of the wood it is necessary to expose the tars with very high temperature and a certain time
can we reach these temperatures with a wood fire? and how should the bottom of the autoclave be built to withstand these thermal constraints?

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Apparently. It’s an actual documented gasifier. Hundreds of them were built less than 120 years ago.

I started a thread under charcoal. I’ll post all the info I have about it there in a couple of days.

I’m sorry you have to wait. I know you are eager to know more. It’ll probably just drive you crazy if I told you that there’s a second design he made. :grin:

Though you may have seen a smaller more “modern” version of it. Besides the retort gasifier, there was the Riche’ Combustion gasifier.

Check out post 20 and 21. Not specifically a Riche’ Combustion gasifier, but it embodies the main idea behind it. The charcoal reduction filter. Heat from the burning wood gets the charcoal hot enough to crack the tars.

And if you pause and think about it, any gasifier that puts out low tar/tar free gas pretty much has to have glowing char in it, unless you have pure carbon fuel, or an extensive filtration system.

In a standard combustion based gasifier the products in the pyrolysis zone really aren’t any different than the distillation gasses. It only takes them a moment to pass through the hot coals. Granted there is oxygen present to support partial combustion to supply the heat needed. With the retort, the same heat is being supplied by an external source instead of an internal one.


That is the essence of any good gasifier… having sufficient glowing charcoal in a layer to pass all tar and gasses, to be reduced into good quality woodgas…

and; cherry red isn’t hot enough to do the job :wink:

My research / development is actual focussed on the glowing carbon as “catalyst” for tar and much more…
How to do it and what materials are available to do the job, is quite the challenge…

the hype “biochar” ought to be abolished as a usefull way to sequester GHG… Biochar should be used as energy source instead of any fossil fuel…

Biochar+Water+Co2= a great replacement for any known fuel ( based on fossil ) there is now.
And with a lot less pollutants since the synthetic fuel is much more pure…

as in the original start of this topic, V1, i might be now at V9 or 10… past the original testing and now working on the follow up’s…

Lots of fun with hot glowing materials… :grin: