Have you looked up the war-time Kalle (Källe) gasifier, it worked well with small fines (2-6mm)
advanced construction, but i think it deserves further attention and improvements.
We have to have in mind we got some better materials available today, for nozzle and sliding grate.
Ofcourse this gasifier has it’s drawbacks, but as i mentioned it are alot of improvements to be done.
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My personal issue with the Kalle is how difficult it can be to reproduce at home. I think Gary Gilmore got the closest and had a good running copy. But if I remember correctly it had a demanding maintenance schedule. Checking the stainless mesh grate etc. Also finding the sweet spot to mix in exhaust gas to prevent the nozzle burning away. Don’t know if he experimented with silicon carbide, I think he used a TIG nozzle cup.
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I had the same experience with the Kalle type. Fussy to build, fussy to maintain, and nozzle meltdown balanced on a knifes edge. I didn’t go so far as use engine vacuum to vary the reduction zone but I could move the nozzle in and out manually. Didn’t work very well with my small engine because any time the nozzle moved down into more fuel it caused significant restriction. I also became suspicious of the Kalle literature that described the screen as playing an important role in reduction… it looked to me like the screen did little more than reduce fuel blow by. I ended up thinking the ‘magic’ of the Kalle was in the premium graded small sized fuel:)
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The experiments I’ve done with really small dense charcoal have gone pretty much as you would expect.
Trying to use 1/4 minus in updraft works really well for a few minutes and then it gradually chokes itself.
Leaving the 1/4 minus in with the 3/4 minus does pretty much the same thing but over a longer time.
Here is the aftermath of a run in a 16 inch diameter updraft where I left all the fines in with 1 inch minus (3/8 inch nozzle, 200 cc engine). As you would expect, it had very fast startup (like crushing fuel ahead of a Kalle nozzle), and good quality gas to start. Over an hour and a half run at 1kwe the mixture had to be adjusted to less air several times and the power began to drop off… when the engine would only sustain a 200 watt load I shut it down and opened it up. The glowing char bed was 16 inches tall! All the fine charcoal had been consumed from between the 1 inch pieces above nozzle.
This is a pic after emptying down to the nozzle where you can see the original fuel around the edges and the course pieces left over in the middle.
This has prompted me to think that injecting more fine charcoal through the nozzle into over sized fuel might work.
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That is also what the Kalle did, all dust sucked back through the nozzle. And yes, it is a cumbersome build.
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The fine dust and ash plugging issue is really obvious when you run gasifiers with identical fuel, nozzles, and engines but with different physical dimensions.
Because there is so much space for the ash and dust to go, this updraft 55 gallon drum gasifier will run a generator at 1kw for 10 hours, unattended (with one air/fuel adjustment after warm up).
This 16 gallon updraft unit, with the same fuel, nozzle, and engine, will start to plug up after three hours. Simply less space for junk to fill.
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I had totally forgotten about the Kalle recycling of the cyclone dust… wonder what percentage of overall gasification it represented. If it is significant then just building a Kalle looking gasifier without that feature would be misguided. I know I didn’t try to do that with my build. hmmm
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I grind my char to 1/2 inch and screen out anything that is smaller than 1/4 for bio-char. Originally I was not real careful about rescreening it after I ground it and even some ash got into it. Now I run it through a separate screening process. I have thought about washing it with water like some here do but so far have not seen the necessity for the extra effort and drying. I have never tried a long run like you describe and only one of my units, all updraft, has a 30 gallon capacity. The others are only about 10 gallons. I hope someone tries to build the unit Tone suggests. I’ll certain copy it. There is a lot of potential in this topic IMO.
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I do not think l will ever build an updraft ever again, other thain as a proof of concept or in an emergancy.
In my Mercedes l built an updraft for to keep the gasifier height low. After less thain 50 miles the ash and dust wuld slowly start plugging the charbed, pushing the glowzone up. At that point the updraft gasifier made no sence any more, height wise.
I think runing pure dust trugh any classical downdraft hearth is utopia. If we want to run on dust, sadly l think we need to think outside the box, make something completely new. The fine mesh “afterburner” design comes to mind…
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Another reason to target dust as fuel is the percentage lost in processing and handling.
I don’t know what portion it is, and it’s useful for the garden, but it would be nice to not have any waste.
Video of my charcoal grinder and the dust it wastes:
https://youtu.be/xsl8hTQHK6g
Grinder details:
1725 rpm, 1/4hp
pulleys are 1 and 18 inch
grinder rpm is 96
tooth height is just under 1/2 inch on a three inch tube
teeth and anvil are 4140 (not hardened)
fan winnowing instead of screening seems to work
Recently reduced tooth height from 3/4 to 1/2. Throughput dropped significantly.
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That’s pretty similar to the smaller hand cranked grinder I made Chuck. I was going to build a better model but I can process a five gallon bucket of char in about 5 minutes so didn’t bother. I’m wondering if a catalytic converter for a wood stove could not be made to gasify char dust with some kind of eternal shaker to agitate the packed dust?
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Tone, is that a mesh over the glowzone?
The problem l see with the mesh gasifiers is how to prevent ash buildup.
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I think the only way that makes the most sense to add charcoal particles to a nozzle would be to replicate a sandblaster venturi.
Issue lies in now you have two hoppers to manage. Hard to tell how big to make the dust hopper, or how to tune it to nozzle size. The venturi would aid in atomizing water, but may backfire metaphorically because it’ll mix with the dust and turn to a carbon mud in the air pipe. Maybe it could be mitigated if you used a water cooled nozzle and had a small delivery tube near the end. Or in a downdraft style use slightly moistened charcoal.
I’ve heard from some that moistened charcoal bridges very easily.
I’m honestly convinced for charcoal either keep it a simple updraft and do your due diligence in fuel prep, or build something like a Mako downdraft with a ring of replaceable nozzles.
It’s good to sequester that carbon dust back into the soil. Apparently cats like it for kitty litter too.
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Isnt that the thing from the Kalle ‘manual’ Chuck refers to?
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I did a little experiment with dust.
I fueled up with 1/2 inch charcoal that was cleaned of 1/4 minus. Then I added some 1/4 minus into the fuel bed something like this;
I wasn’t precise in measurement or placement but I’d estimate the dust was 10% of the fuel load.
It didn’t plug up, which might mean a lot of the dust was consumed.
Don’t know how useful it is, but it might let me use some of my dust in my updraft gasifiers.
I think I’ll try a few different configurations of ‘dust loading’ and see what happens.
I should probably point out that this is a modified ‘updraft’, sort of a side draft, but the gas exit is 360 degrees. Gasses travel up between the two vessels which makes a pretty good cooler.
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So the air is coming in from the bottom big nozzle and gases go up the barrel side. Is it loaded from the top? Yes I see a side up draft gasifier. A barrel in a barrel design gasifier. I like it KISS Keep It Super Simple.
If the nozzle would be placed higher it would be a down side draft gasifier. With charcoal dust placed in the top it would go strait down to the nozzle with the center charcoal flow. Some might migrate to the side.
Bob
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IS there a cheap enough type of glue that would make char dust pellets, or spray char dust on demand maybe?
Yeah, there is a hatch at the top of the inner vessel for loading.
Based on the glowing char pattern when you open it up hot, I suspect the flow is something like this;
One interesting consequence of the very large volume the gases flow through, between the barrels, is that very little dust ends up in the course filter. The gas flow is very slow and doesn’t seem to carry much junk with it. I ran the same gasifier as a straight updraft before adding the liner and it produced significantly more dust without it, all other things being the same.
There is soo little dust in the filter I’d say it would be fine for 20 hours or more.
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Hey Kevin, yeah, pelletizing is a sure fire way of using the dust, eh?
There are quite a few conversations about that topic around here…
Totally doable (and would make a premium fuel) but it would take more tools and equipment which would end up more complicated. I’m trying to stay with ultra-simple.
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