A FEMA style gasifier is the first one l have run. And tarred up my first engine with it. Plus it was a 2 stroke
But some time has past since then and l think you can make a decent gasifier out of it in a couple of hours.
You didnt give us any dimensions but lets take a wag at this.
drill 5 1/2" holes 4" from the top flange.
-weld or scemrew in drillded ss bots. Hole in the bolts about 1/4". Protrudeing anout 1/4" in the firetube.
make a mantel around the firetube, airtight, for air manifold/preheat/firetube cooling.
add in a restriction about the same depth as the firetube diameter. Restriction about 2" wide.
Set the grate about one firetube radius lower.
Yep. Yep.
90% Ben Peterson’s 2007/08 era EPS system. Ran open topped with the commercial fuel woodpellets providing the upper air-in restriction. Calculate running time just right to leave NO unheated seared/blacken/sealed pellets on shutting down.
Or have to dig out decomposed pellet sawdust on the next firing up.
S.U.
Can you kindly explain this: “make a mantel around the firetube, airtight, for air manifold/preheat/firetube cooling.” do you have a picture or drawing of this possibly?
When designing for low HP (say <20hp) is the only fuel possible wood chips/pellets/etc?
Based on the imbert empirical design rules the restriction would be what, 40-60mm, I assume
large chunks (~2") would clog a small system like this? Forgive me if my terminology is less than
proper - I am still very new to this
Fuel sizing is where you have an opportunity to learn and try different things. You can try pellets, chips, 1" chunks and then try going bigger and see what happens. Try mixing two together. Chips and chunks, pellets and chunks, pellets and chips. Find out what works best. Softwood will be different than hardwoods. Just make sure it’s burning hot enough before you hook up to an engine.
I know that this idea is old, but----
Why not bubble your gas through water to get any tars out on its way to the engine? You could use this process to evaluate design changes until you get the data that you need.
Make a run.
Empty the water chamber
Evaporate the water
Weigh and evaluate what’s left.
(you may have to cool the water chamber if it is small or if you are making long runs)
This way you don’t clog up your engine on your way to the “perfect” design. Then, once you have it right, eliminate the water filter.
Following construction principals in some of the library books and using one or two sheets of paper makes more interesting results than random guessworking…
Everything starts with the motor’s displacement and RPM, “rounded” by the degree of load.
All critical flow areas are in direct proportion to the calculated gas demand.
That applies to the process volumes too.
The practical formulas are plain multiplications and divisions, and a few calculations made by internet formulas only needing an input of diameters and height.
Then the fuel size will also appear as how many bits needs to fill the upper hearth = oxidation zone.
The only formula on the internet needed is a “conical frustum” calculator, which will sort out the measures for a needed hearth volume.
If chips and pellets pack to tight and normal chunks are to big, there is a Youtube of a gentleman who takes wood pallet slats and cuts them into about 5/4 or the thickness of the slat by 3/4 by 3’ pieces with an automatic machine he made with a Skill type saw. Then another Youtube the gentleman feeds these pieces into a tube that feeds them automatically into a table saw that produces squares about 3/4 in. TomC
I have cut 3/4" x 1" x 1" (approx) blocks and several other size cube like fuel and always had problems with bridging. I now use round branches 1" to 2 1/2" diam, cut them as long as the diam (ie. 2" diam piece 2" long, etc) and had much better luck with the feed. I still run my vibrator at regular intervals. Just as important for gas production is a regular shaking of the grate to keep the gas flowing through the char bed.
Pepe; I think round chunks are best. I have always run limbs chunked to length, but this summer a friend brought his band saw over and cut a couple of logs into 2x2 that I will chunk. I guess I will learn if square blocks are worse than rounds.---- if I ever get my truck back together. TomC
Hello Max, Thank you for the follow up, it is very appreciated! I have indeed been studying.
I have bought and been reading “handbook of biomass downdraft gasifier engine systems”, can you suggest any other reading material on the matter?
For my specific case, I have a small generator - 1200W - engine is very small, 98CC OHV
We live ‘off grid’ and we use this generator to supplement our battery bank and run fans when it
gets too warm in the house. I would love to have a gasifier capable of powering this small engine
but also be possible to (use larger restriction plate?) power a larger generator if needed.
I know this engine is very small, and I am worried that the size of a restriction needed would enable potential bridging issues.
As for fuel, we have large amounts of poplar saplings, from 1-3" in diameter. My plan is to ‘farm’ these wild grown poplar saplings and chunk them into gasser fuel… This will be a renewable resources for me as they grow fast and there is a large amount of them.
Good want/need-to-use feed back ChadR.
Does this 98cc engine generate at 3000 or 3600 RPM?
Is it a four-stroke, or a two-stroke engine?
It would be much, much easier to woodgas with your stated poplar sapling bits to fuel a larger displacement four-stoke engine power down rated.
Easier will begin at ~212cc and top out for a single cylinder at ~390cc.
Past that then the smaller V-twin generators will be even another step-up woodgasing easier.
For verification of my claims read/study:
www.woodgas.nl MicroGasifiers
It seems that you are at the moment under the treshhold for selfgeneration of the energy needed to prepare the fuel by own “sources”.
The motor will only put out about 60% of the gasoline power.
If you intend to prepare for the comming wood handling for power and home-heating, you seem to need a “multipurpose” tractor.
It needs to have a mechanical power outlet to drive a chunker or rebak and circleblade for cutting.
Additionally a good hydraulic pump for driving a woodsplitter. The tractor brings home the wood and so on… Drying roofs and sun drying… off ground!
Preplanning for an enlargable gasifier goes the other way around: A bigger one needs inserts to satisfy a smaller process volume. The exchangeing process needs to be taken into account from the very beginning to avoid bad surprises.
Yes, Dutch John learned a lot during a few years back! And he has an excellent network of helpers, all you can dream of…
The guy in the wideo does not tell any specifics about the motor:
Displacement, RPM, LOAD!
His firetube seems to end into an OPEN basket of charcoal!
His restriction “throat” gives free radiation to the surrounding.
All these items makes it a floating guesswork where no calculations have a reference in reality!
A motor under full load makes it possible to estimate the gasflow.
Everything else is then possible to come to turns with…
In a working gasifier the process stages have to be interconnected in an uninterrupted row, without “pauses” and cooling zones, loosing the process heat by radiation and metal connection outward.
So, going backward:
The 5 KW generator is driven by a motor at what RPM, having what displacement?
Does this 98cc engine generate at 3000 or 3600 RPM?
Is it a four-stroke, or a two-stroke engine?
I am not sure the RPM of the engine, I can check the specs. It is indeed a four stroke.
It would be much, much easier to woodgas with your stated poplar sapling bits to fuel a larger
displacement four-stoke engine power down rated.
Easier will begin at ~212cc and top out for a single cylinder at ~390cc.
Past that then the smaller V-twin generators will be even another step-up woodgasing easier.
I do have another generator which is in the low 200CC range (it might even be 212CC), and I also
have a larger older briggs and Stratton 17HP from a riding lawn tractor (craftsman ls1000 if memory serves me).
I planned on using this engine (the 17hp briggs) to build a multifunction device - drive an alternator to charge my battery bank, run an air compressor when needed, drive a generator
head (somewhere around 3-4KW). If I were to build a gasifier to run this engine it would be
quite convenient and further my self sufficiency lifestyle.
I will gather real specs (CC/CI of engine, RPM, load, etc). In the meantime does this seem like
a decent candidate?
It seems that you are at the moment under the treshhold for selfgeneration of the energy needed
to prepare the fuel by own “sources”.
The motor will only put out about 60% of the gasoline power.
Ah yes this makes sense, and with such a low powered generator already, a 60% drop in power
would make it significantly less useful.
If you intend to prepare for the comming wood handling for power and home-heating, you
seem to need a “multipurpose” tractor.
It needs to have a mechanical power outlet to drive a chunker or rebak and circleblade for
cutting.
I have a John Deere 1010 RU with loader (has PTO), and also an old Farmall M with PTO.
I have seen a couple chunkers and it looks much easier than my current means. I will be
definitely building one of these as soon as I have some free time.
I do heat exclusively with wood already, do people normally use only branches/saplings/etc or is it common practice to also split to kindling sizes and then chunk?
Additionally a good hydraulic pump for driving a woodsplitter. The tractor brings home the
wood and so on… Drying roofs and sun drying… off ground!
Hmm I am embarrassed to admit I haven’t thought of using the tractor hydraulics to run a wood splitter. Another project on my list now!
Preplanning for an enlargable gasifier goes the other way around: A bigger one needs inserts
to satisfy a smaller process volume. The exchangeing process needs to be taken into account
from the very beginning to avoid bad surprises.
I would really love to have a gasifier which can handle different volume requirements… But is it
realistic? Could I build a gasifier to power a 17hp lawn tractor engine, and also power - say - my 1010? By the way, not really relevant however the FEMA gasifier paper used the same model tractor for its testbed - funny I thought. To clarify I do not intend to build a FEMA, I just thought it was interesting they used this tractor since it was rather rare.
