Simple Filters for Simple Fire Systems

Hi Thierry,

There is indeed “some” influence between the diameter and length vs the amount of power to be generated.
size and position of the nozzle included.

The biggest role however, in making good charcoal gas, besides good fuel, is the filter setup ( the topic )

The less “drag” your “filter” creates, the more easy the system can “breathe” the more gas can be conveyed to your engine.

I will try to extract some data to compare from my research material and post it here.

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i will be running with 3 tiny cyclones (in parallel), like a Dyson vacuum cleaner, and fine-grade perlite as a final media filter. I like perlite because it has a massive surface area, won’t burn, can get wet, is washable, and you can burn off the particulates and reuse the stuff almost indefinitely… it’s also cheap…

Anyone else using perlite? I love it…

If the cyclones are operating at 90%, it should be a pretty good system.

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What do you think about a filter lid for a wide bodied reactor/hopper that has a layer of coarse perlite followed by fine perlite? A coarse screen to support the coarse perlite and a fine screen above and below the fine perlite. No cyclones or filter plumbing, just one tall column with a clean gas outlet at the top.

For a plug style filter wall action can be an issue. For example a five gallon bucket filled with some kind of media. Inlet at one end and outlet at other. Gas is like electric it takes the path of least resistance. So, the gas will tend to fallow the walls of the bucket and somewhat skip the filter media. Not completely but some.

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I can’t help to think that that a charcoal filter would work well. Why wouldn’t it work? I envision a vertical pvc pipe or 2-3 in parallel sharing a condensate tank.One could attach a tee at the bottom so one can use couplers. A flush style screw cap on top so it could be easily emptied.

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Jeff,

Thanks for the wall action reminder. What if we glue wool blanket, window screen or foam rubber or something else to the walls? Are there other simple solutions for this phenomenon?

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Bruce, I think that would do the trick. Anything to break up the path along the wall. I remember reading something about that. The dirty filter media should tell the story.

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I was reading down through this old topic as I’m designing a new gasifier for Africa. This discussion went a little sideways about the difficulty starting up on previously run charcoal. Then I saw this screw in earth anchor at tractor supply.


I thought it might auger down to the nozzle in my MGB to lift old charcoal away and let fresh char fall into place.


After giving it a try, I made this modification:

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Great find on a off the self item. That is going to work great for reconditioning the char bed and fluff it up with new char.
Bob

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Clever use of materials. But the real question is,did it help ease the startup as hoped?

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This is a great example of having a thought and finding the right tool for it… :+100: = :+1: * 100

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Andrew,
Too many household projects to get the MGB out. When I get some time, I’m going to install an O2 sensor and A/F gauge. I’ll report on start up times when I get her back on the road.

Koen,
Thanks for the thumbs up. For my Africa rig, I’m keeping your maintenance advice in mind: full clean out of reactor and filter every day.

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For the Africa gasifier I will need to add something that gets occasional mention in the old literature, but has been largely overlooked by those of us who drive on paved roads. The dirt roads will require a filter on the primary nozzle inlet. It has been reported that the dust entering the gasifier can make its way into the gas stream and cause significant engine wear. Perhaps a safety filter at the engine will do, but an ounce of prevention is worth a pound of cure. What are your thoughts on this filtering issue?

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I agree with your proverb but l think a gasifier produces a lot more dust thain the air holds. Til sugests chargas is as such wery rough on the engine if not cleaned properly (opposite to woodgas-the moisture participates out together with most ash). And l agree. I think a sack filter or a paper filter is a must with chargas. I was wery pleased with the arrangement on my Seat, first a towel filter then a air mixer, then the gas/air mix passed the original paper airfilter.

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Hi Bruce,

What engine you’r going to run in Africa, hence what’s the size of the gasifier ?

I also use ( sometimes) an original sportsfilter in line with the engine to filter out the unwanted particles. But mostly not needed if the foam filter is been maintained daily.

Thinking of: what about the oiled filters they use in motorcrossing ? clean the large hole’s sponge, then soak with sticky oil, squese out the residu ond of you go…

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Koen,
250cc engine. 10 inch diameter gasifier. Height is 30 inches of charcoal above nozzle. How long will this run under load before refill?

I too had oiled foam motocross filter in mind for gasifier air inlet. That is what I use for my mixing air filter on the MGB.

Kristijan,
I intend to use a cyclone followed by two vertical 4 inch X 30 inch PVC cylinders in series for the main gas filter. First one filled with stainless steel scouring pads and a piece of oiled open cell foam at the top exit. The second filled with polyester batting or wool sock. I may add a final safety filter just in case someone isn’t careful with these main filters.

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Hi Bruce,
I’m in accordance with Kristijan. I suggest a fabric filter for the gas (felt, fine woven filter cloth or similar) which is the best for dry charcoal gas but I think no filter is needed for the generator air inlet. The gas should be filteres anyway, so some road dust passing the generator is caught here.
Maybe extend the air inlet to a higher level where there is less dust (similar to a snorkel on some 4WDs).
Regards, Til

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Thanks, Til. Makes sense.

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So, it quickly became evident that my filter was too open and let char dust pass. I cut a couple discs of old towel to go between furnace filter material. I think that should catch the fine stuff.

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Looks good. How’s it so far?

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