Properties of a good wood gasifier

Hello Giorgio, after the “service” of the gasifier and filter change, the tractor has done more than 10 working hours, the filter container contains hay, sawdust, sheep’s wool and the final paper filter, I have not changed it since the first start. It looks like sheep’s wool works well as a filter medium, I recommend using it. I’ve been thinking about a small tractor for your needs, Kristjan’s tractor (Tomo Vinkovič) has a Lombardini engine, one cylinder, 18 hp, actually these tractors were created from a motor cultivator, the engine is easily attached to the gearbox and is very easy to dismantle, I think he even replaced it with an engine from a lawnmower.


Hi Tone
I don’t see anywhere where you explain where the small central nozzle comes from. It seems to be made of brass or copper .I know that this nozzle is extremely exposed to high destructive temperatures. a massive copper nozzle is hard to find and additionally with a thread to bolt it on
can you explain a bit about this?


I got no dubt wool wuld work good. Look at its microscope picture

Lots of surface area

Since lm alredy typing, Thierry, Tone uses a pneumatic stone drilbit. Its a masive chunk of high carbon steel, he got me a peace too. Excelent nozzle matrrial, about 25mm hexagon with a 6mm hole inside


Some changes in the construction of the gasifier, the sketch will say more than words.


Hi Tone , so I see there is no insulation around the bottom of the gasifier? Are you are using the outer surface to cool your gases down before the gases get radiator cooler for extra cooling? If so I would think it would be hard to keep any paint from burning off the metal on the lower part. Coragated roofing around on the lower part of the barrel wall with ash in between would help in this area.

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The steel roofing material would form a secondry wall inside the barrel and ash will fill in behind and help insulate the out barrel from the very high heat on the outside so the paint will not burn off and then rust would not form on the outside barrel.


Hello Bob, at first I also imagined that the lower part would be hot, but in reality the temperature reaches a little over 100°C, so the paint is intact after a year of use. Apparently the heat exchanger inside does a good job.


That is really good to know Tone, that the heat is being transfered to the income air efficently from the vertical grate tubing. And cooling the out going gases like that. Great design you have created and simple to build too.


I am thinking about a simple construction of a gasifier, in the sense of the Fema shape, well, this method has the main disadvantage that the hot zone with coal can move higher, away from the desired place. Here I have drawn a sketch with “my” middle nozzle, which would maintain a hot zone with charcoal at the bottom, and a part of the air would be supplied above, which would descend into the lower part and “help” to expand the hot zone with greater gas consumption. I assume that in the upper area oxidation is not possible due to the humid atmosphere and too low temperature, oxidation would take place below at a high temperature.


Your idea is bald to say the least. But lm the first in line chearing for this to work. Wuld simplify a lot of things


This is my friend who can tell me I’m stupid and I’m grateful to him for dissuading me from the wrong idea.:grin::woozy_face:


I dont think the translator did his job this time. Im trying to achive the opposite.

Ideja je drzna, sem pa prvi v vrsti ki si želim, da ti uspe! To bi zelo poenostavilo izgradnjo uplinjevalnika.


I’ll bite.
Be the friend to say, "But, but, but . . . "
You will inherit many of the problems that FEMA’s always proved to have Tone.
Plus add in many of the problems all raw wood central nozzle gasifier systems have.

You do not really want me to detail these out, do you?
All anti-opposite the of properties in a good wood (fueled) gasifer.


My translator said this to what you wrote…It is a bold , but I’m the first one in a row, I wish you success! That would greatly simplify things alot to build the carburetor. I agree Kristijan.
Talk about thinking out of the box and making it K.I.S.S. Tone.


I think this is a charcoal gasifier and not a raw wood to charcoal gasifier Steve. Anyways if it is raw wood then yes I see it to be a FEMA and with all the related problems they have making tar.

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If Tone doesnt, I would :grinning:


And where is there any benefit to me detailing out? Risk losing a friendship for what gain?
If this is truly a pre-made charcoal fed gasifier then for over 12 months now I try never to comment on these. You charcoal guys win for the truly small engines.
If this is a charcoal gasifier pretending to be a raw wood fueled gasifier then again, I step out.
And if this is a raw wood gasifier pretending to be a charcoal gasifier I am out.
These are Kristijans area of study and experiences. Francois Pal’s too.

I’m just not smart enough to juggle peoples widely varying desires and goals for their systems anymore. Maybe I never was.
I DO read, ask questions, trial-try; trial-proof extensively for my own desires and goals however.
I have cleanly efficiently combusted up one true metric cube ( 3.62 cords) of seasoned walnut wood for heating this early winter. Cleanly, efficiently combusted up 1/2 cubic meter (near 2 cords) of cotton wood this mid-winter for space heat. Yeah. Great coal makers. Terrible, terrible amounts of ash. How can you fellows stand this?
With my “poor heating value” Douglas Fir wood I can keep the three houses warmer with it’s much more active quicker energy releasing soft char in the very same differently ages designed wood stoves. Only having to deal with ash build-up clean out once-a-week; not daily.
Sure. In a power gasifier like all conifer woods it can tar; WILL soot . . . so design for these. Certainly; Operate bias, for these. You hardwoods using fellows; raw wood or hardwood made charcoal, get to fight your 10X problem clogging mineral ash.

Tone line your lower with thermal insulating vertical bricks. Australians Kurt Johannesons trick that made his single down from the center nozzle vehicle gasifer work for him. Peripheral air jets put the oxidation made heat spread out at the wants to be cold, perimeter. Single center nozzles leave the outer perimeter always cooler. Not good for a raw wood fueled gasifier.
W.K. , Flash0001, and IISC and CPC did convert from FEMA no jets, to peripheral jets. Others too, to gain success.
Many did find they had to have some type of throat for performance reasons.
Some FEMA “Stratified (air) Downdraft” found they had to have tall fuel stacks; have small fuel re-filles; with very tightly controlled fuel bits sizing to keep the air-in predictable and controlled.
And still . . . creeping upward zones. So then onto added tiered rows of variable cut-in, cut-out peripheral jets to follow this upwards “creep”.
To make a FEMA based into a true batch re-fuelable; others found the benefit to go closed sealed tops. Also then true shut down control. Visible emissions control.
You propose a closed top with finite air control.
O.K. That will work too. Operator present batch cycle dependent then for the declining fuel stack air needs perception, adjusting the air-in control.

Your simplification will be very fuel moisture dependent. Or like a few others doing closed hopper venting so another needed Operator job to control? Unsticking tared auto-valves.

Time to face the realities. Complexity is added to systems to make them more widely wood fuels species and bits sizing useable. Or less Operator present dependent. Or for stronger engine power capable.

Your own unique designs, previously could do all of these things.

Please do not go down the dumb-dumb-downed FEMA influenced road.
Your friend
Steve Unruh


Guilty as charged. I am a strong beliver in building the gasifier basedd on your fuel supply. Myne happens to be charcoal, so l build around that. But, l like the features of a wood gasifier. Marriyig the two can be interesting at times…


I agree to what others said, most important it should work for YOU, and your needs, and fuel supply, to build gasifiers for others to operate-very hard…
Some interesting predecessors to the famous FEMA.

Svedlund charcoal tractor gasifier, with recomended mix-in of 15% VERY dry wood.
Basically a FEMA-tube with a air-jacket, to avoid air pass through hopper fuel. 1923, was updated to central nozzle, and recomended to only use charcoal around 1933.

Simplified sketch of George Cristian Imbert’s first working, patented raw wood gasifier, without the throat it resembles a FEMA with nozzles, he probably adapted the nozzle ideas from his first attempts with horizontal draft charcoal, later raw wood gasifiers.


It is known that raw air-dried wood still contains quite a bit of moisture, which must be evaporated and then condensed in the condensation zone, for which it is necessary to sacrifice some thermal energy. This energy is obtained by burning wood in a gasifier, for which we supply a certain amount of air, which affects the energy density of the gas, so I will conduct an experiment and dry the wood well at a high temperature beforehand. In the barrel, where I made a hole in the bottom, I set wood chips on fire, and then fill it to the top. I put a lid with a chimney on top and connect a larger barrel over it, so that the temperature is maintained. The process is very simple, but I will see what the result will be.