Properties of a good wood gasifier

Also Tone I want to give some food for thought: I’ve been thinking of improved preheating for a similar system with a bottom air intake.

It’s essentially a bucket that the gasifier sits inside. A thin open top sheet metal shell to guide intake air from the top down the sides and along the bottom of the hot output jacket portion of the system into where intake air is drawn in. The paths of air in the shell and gas in the output jacket go opposite directions for optimal countercurrent heat exchange. The shell would also insulate the gasifier somewhat from touch (safer for bush fires) and wind cooling.

The shell sits only a bit away from the gasifier, fixed into place around it using welded tabs. Gasifier mounting struts can simply go through it as the shell doesn’t have to be particularly airtight or structurally strong and can have cutouts or panels for performing operations like lightup and ash cleanout. The ash cleaning cutout would also work as a drain for any rainwater.

This shell could also later be filled with an insulator like rockwool or fiberglass if needed.

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I’ve occasionally seen you Like a comment here and there, I was wondering when you’d start posting! A belated welcome to the forum Antero.

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Yes , what Cody said.

Welcome Antero :blush:

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Hello Antero.

If l read you right, l had versions of this on a couple of gasifiers. Having been building in trunks mainly, l had to use every possible way to get rid of some heat. My latest Mercedes gasifier (or was it swcond last?) Had l think at least 3 or for lairs like this, welding was a pain and l even missed a full section, about 8" of weld right next to the exit of the heart :smile: miraculously, the thing ran quite some time with a 8" long slit pouring air right in the superhot gas.

Anyway, sorry, got carried away here. Carry on…

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Antero, I’m trying to keep the construction simple, … considering the fact that only about 30% of the thermal energy of the gas leaving the hot zone can be introduced into the preheating of the fresh air, I think that this part of the thermal energy is already transferred on the internal exchanger - grate , and the desire is for part of the energy to be returned to the heating of the walls of the storage tank, along which the cooled gases from the condensation zone descend, so the output gas should first rise against the inner wall and thus release part of the heat. the storage tank next to the wall is definitely cooler than the gas that leaves the grate. I also want the outer casing of the gasifier to act as a cooler, so that the gas cools down a lot before it comes into contact with the condensate collection chute… I agree that it would be good to insulate the lower part, but if we assume that the bottom collected ash and covered the bottom and thus the bottom will be insulated, only the lower part of the outer jacket remains, but here too there is no excessive loss, because most of the hot gases rise up, and the cooler gas is retained here, which creates insulation inside.

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Welcome Antero, the outer shell design is what I am trying to do for my 1995 Jeep Grand Cherokee WK Gasifier build. Thanks for more info on that design.
Bob

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Again thanks everyone for the greetings! Glad to see many of the big names here :slight_smile:

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Thanks for the explanation, paints a clearer picture of your goals for the system. All valid points and as I said, your design already has plenty of intake preheating, not to mention the central nozzle to provide oxygen for the otherwise dead zone. No tar will ever pass through your system, this I know.

As for preheating fuel in the hopper, heat exchange fins on the inner hopper wall should be the clear winner solution. Simple, easy and cheap to fabricate and effective to increase the surface area of the inner hopper wall. They should be installed at an angle like turbine blades to impart rotation to the outgoing gas for the cyclone effect, corresponding to the rotating direction of an angled output pipe. If the outgoing gas is rotating around the hopper wall as it rises it takes a longer path, which means more dwell time for heat exchange and cooling to take place and particulates to fall out.

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…like the turbine blades, … that’s a great idea , I know of some used turbines and I’ll just cut those blades and weld them to the exchanger , they are perfectly curved … when it comes time to build them. I should mention one more thing, I have to install one pipe or the rib of the grate demountable, so I can remove the lumps of minerals that may be formed in the hot area. Thanks Antero, it’s nice to chat with you.

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Welcome to the DOW AnteroS.
You are somewhat of a name yourself. I have read you previously on some of the northern European woodgasing exchanges.

Each base country region affects and influences all of our works.
This is sometime good. This is sometimes bad.
Interesting to a student of human nature good or bad in native/historic designs has little to do with the actual mechanical designs of a region themselves.
But the nature of the man himself emulating, building, and “improving”-using them going forwards.

Examples: to build quickest, easiest, and get a system up and working use common carbon steels. Good. Good. Not so good the carbon steel unit will now in mere hundreds of hours of usage erosions spawl burn-through, pinhole-corrode to become a fix and repair often nightmare.
So jump into the mid-20th century forward and use all acid proof stainless steels. Your Nordic areas decades proven best practices. Well then to prevent welds thermal cracking, flat areas warping and buckling; then the whole design must obey the SS in woodgas heats dog’s rules.
My friend Ben Peterson (American) learned this the hard way when he transitioned over to all SS building. Get the sectional flange joints at least 4 inches (100mm) away from the nozzles plane! Then later. Why make protruding heat bleeding out, many bolts, flanges at all? Not like these systems have to seal extreme pressures. Grooved channel joints with woven rope seal over centering clamped; weld tab ears bolted drawn tight; or V clamped together work just fine. Not just for hopper lid sealing.
Ha! Ha! And on the DOW Premium side where the internal feature of the W.K. systems are pictured, proof improved is it’s counter current flowing heat exchanger hot gas slow down soot dropper. As you said many, many welded in gas slowing heat dropping internal fins.
And the W.K. began as the American F.E.M.A. embarrassment that was step but step, features added. Improved; to be the fastest driving vehicle system on the planet. With ability to use the wettest input fuel woods. Using the widest variety of wood portions and species as proven with cross continental trips.
An Ideal system? A Perfect system? No. And No. Its best performance is as fully integrated into the whole vehicle. Made as a slide-in removable - performance drops off. Due to shortened post gasifier flows pathways; non-best placement of lower hearth ash storage and lower condensates and tars tanks storages. Made as a trailer towed system performance would really drop off with then zero engine exhaust heat contribution and short pathways and cooling.
Downsized under larger four-cylinder engines and imho it just will not have the thermal pulled loading to work at all well. Some still try though. Small engine generator guy me says; Good luck with that.

And some of the current builders-users here on the DOW basing off of 1940’s though 1990’s Soviet works and designs are getting good results too. Lot of unique work was done by the Soviets apparently now not so hidden. Not just older German systems copying.

You seem to have the flexibility of nature to absorb and appreciate woodgas diversity.
Welcome here.
Steve unruh

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It is hard to follow that flattering and insightful welcome from Steve U. But I’ll try—Welcome, Antero. You are among comrads.

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Welcome Neighbour!
On this forum we like pictures and videos. Maybe you have something interesting to show us already :smile:

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Thank you for the welcome, both Steves and Jan.

SteveU I’ll have to disappoint you by clarifying that I have never posted on other wood gas sites. Finnish surnames have these similar structures so I don’t blame you for the mixup. Happens to the best of us.

I appreciate your writing. I also love seeing the almost organic way in which different people design and build their gasifiers around so many different vehicle and drivetrain configurations. Variety naturally breeds innovation as technologies have to be adapted to different regions.

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The assertion that all processes take place in gaseous form and the desire for the gasifier to produce clean, quality gas led me to the idea of ​​installing a dense mesh in the lower hot part in front of the exchanger, which would retain fine coal dust. This small coal would be gasified here on the hot surface by adding oxygen through the central nozzle, and the ash would slide down through the openings at the bottom into the lower separate part. Maybe the vibrations of the single cylinder engine would provide for shaking the ash out of the grid, but I’m just thinking out loud.


the first picture is a used part of a natural gas burner, where the mixture of gas and air burns on the surface of the grid, which is made of a special material to withstand high temperatures

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I have learned not to be critical of new ideas, especially yours, Tone. You will have to try the idea and see how it works, holds up, clogs / clears! :cowboy_hat_face: Yee-Haaaa!

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Interesting idea Tone, Stig-Erik Werner, (swedish long-time woodgasser) uses a dense mesh directly after the gasifier (glowing hot), he claims it makes a great difference in power, and cleaner gas, i believe he has used that setup on almost all of his builds.
Should be interesting to see how yours work out, i have no doubt you make it work great :+1: :smiley:

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I belive S-E Werner calls it a “hot screen”, right? I’m not sure if he introduces additional air or not?

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Friends, I enjoy this discussion, well, I am attaching pictures of this piece that I cut and another simplified sketch of a gasifier with only a center nozzle




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Does S.E. Werner have an email that he can be reached at? I’d like to ask him about the mesh size.

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No, he does not introduce any air, i believe. Just seems the principle are like?

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