First Down Draft Charcoal Gasifier

BrianAltEnergy · October 26, 2023, 5:41pm

More progress but more problems

I cut the first piece for the cyclone. This is the bottom cone.

Clamped up ready to weld.

Next up, the top round section.

Not pretty but welded together. There was at least one hole I had to reweld.

This one I wasn’t looking forward to. Turned out to not be as bad as I imagined. I cut it out with the grinder and cut off wheel then cut grooves for the bends.

I actually meant to put the weld joint on the bottom to hide it but I guess this will do.

This it the first problem I found. I’m going to need to cut a little off the corner of the inlet pipe so the outlet pipe doesn’t hit it. Shouldn’t be a big deal but I wish I would have noticed that before I welded it on.

This is the next problem. I know what needs to happen but don’t want to do it. I’m going to need to cut off the outlet pipe and raise it up to give it room for a collection jar. This jar is from the simple fire that I haven’t been using. I’d like to think I could just put a plug in the bottom of the cone but then I wouldn’t be able to SEE what it was catching. I had some problems with this catch jar not closing tight enough.

This is one possible idea for cooling fins. I’m not sure if it would be too ugly or too dangerous. I could grind off the teeth or at least knock off the sharp points.

ForbiddenTuna · October 26, 2023, 7:15pm

You can have the cyclone at an angle, it will still function. Since you made a great cone shape it will still find it’s way downwards.

BrianAltEnergy · October 26, 2023, 8:52pm

Too late.

I figured if I had to raise it up I’d add some cooling fins to the extension. Got some of them warped but should still help a little.

Looking at the cyclone, I found more holes. I think I’ll end up coating the joints with silicone. I’m not going to do that until I get the rest of the pieces finished for it. It is not real thin sheet metal but still easy to burn holes in it.

The simple fire gasifier got a work out today. Over 450 degrees F. near the nozzle and over boiling at the top. The little cooler on it kept the temperature down some and it was cool by the time it left the filter. Burning the paint off the main tank but the generator was running good. No hour meter on it but I think I’ll get some oil this weekend and change it. I’ve used it more on charcoal gas than it had been run on gasoline since it was new. Doesn’t seem as bad when I know I can make my own fuel compared to buying gasoline for it.

I hope this new gasifier works as good as the simple fire and isn’t as picky about the fuel.

ForbiddenTuna · October 26, 2023, 9:46pm

I wouldn’t be afraid of brands being mixed in, but I wouldn’t try blending any raw wood in. Lacking a true restriction your gasifier doesn’t have a zone to crack tars.

It will definitely run better on engine grade charcoal like your updraft, but it won’t be as picky on size because of it being downdraft. My Double Flute ran alright on my poor size selection of charcoal. My issue with that gasifier was having rubber connectors too soon and melting them.

Bobmac · October 26, 2023, 10:13pm

Just put a few extra coats of paint on it and it will be fine. Any color will do, as long as it is black paint.

BrianAltEnergy · October 26, 2023, 10:33pm

Thanks Cody and Bob. I should probably pick up a can or two of black paint this weekend too. I knew I had tar stains from my testing but that last picture looks bad.

I was only running a flare with the raw wood mixed with charcoal and hopefully the ring I put in the lid helps keep the drips inside instead of dripping out of the lid. The main problem was blowing air into the nozzle which pressurized the tank. It didn’t leak like that (even water) when it had the engine vacuum sucking the gas out.

I’m almost out of dry charcoal again so I’ll need to make another batch soon. The last batch I ground up filled the simple fire for today’s run and I dumped the remains into the new gasifier. Actually, I have more nice charcoal from some of my first charcoal batches but I’ve kind of been saving those bigger chunks in case I wanted it for cooking, melting metal, or for the forge. The rest is in a barrel that got wet. I did set some wood aside to keep it dry for my next batch but haven’t made any for a few days or so. I did take a little out of the furnace but it hasn’t been cold enough to have much of a fire yet. I’ll have to get another good barrel or even a metal bucket with a good lid for saving the charcoal from the furnace. I don’t expect to use the gaasifier as much once it does get cold but I hope to save up a good bit of charcoal over the winter.

I didn’t keep track of where I got this picture but I’d like to have something like this with ready to use charcoal. Thanks to whoever came up with this.

EDIT: That picture was from Giorgio.

giorgio · October 27, 2023, 2:15pm

brian, also the white 1000 liter containers in plastic are good for storing charcoal and keep it dry
originally this containers are for chemical stuff or motor oil, and normally after one use they were sold…only the well in the bottom is a bit small for bringing the coal out, but this can be modyfied…

BrianAltEnergy · October 27, 2023, 3:33pm

Not much going to happen with the gasifier today but I did empty it back out to cut the bottom opening bigger to fit a grate through that’s bigger than the brake rotor opening.

This was not much fun reaching inside with the torch. Would have been much easier to cut this opening bigger to start with when the barrel was in two pieces. My oxygen tank isn’t even moving the needle on the gage anymore so I’ll need to get it exchanged soon. Cutting the brake rotors really used it up.

Made another batch of charcoal for the Simple Fire.

Figuring this should give me 3 or 4 hours worth of fuel for the generator (enough to refill it twice).

I got a bucket of nicer sized charcoal out of the down draft after screening out the dust.

This would be perfect for the Simple Fire but there’s a little bit of tiny pieces of raw wood mixed in so this will have to be saved for the down draft.

This is the bigger stuff I emptied out of the down draft. Again, it has at least some brands that didn’t completely convert to charcoal.

I think I’ll put some kind of restriction in the down draft when I get the grate figured out and put it back together. There didn’t seem to be tar making it into the gas or filter from my experiments but I did have a lot of fine dust in the charcoal that I separated out when I emptied it so combined with it being too wet probably explains why my filter clogged up when I tried it on the generator but it did run it so I’m sure it will do good once it is put back together and fed better fuel. I’m hoping the cyclone helps keep the dust out of the filter but just starting with better graded charcoal should stop most of that problem. I was just testing the down draft so didn’t want to waste my good charcoal and I wanted to find out what I could get away with since most of the testing was just flaring it to see if a little raw wood would convert. That’s what caused all the tar drips on the outside of the tank.

This does look like it was working.

This was some of my normal made charcoal that almost has a graphite shine to it.

Pretty conductive too. This piece is reading under 5 ohms resistance according to my cheap meter.

BrianAltEnergy · October 27, 2023, 10:32pm

Well, I didn’t think I would do much more today but I know tomorrow I can’t work on it at all so I found a piece to build a new grate.

The torch left a lot of slag.

Cleaned up pretty good.

I tried welding pieces of chain on it to hold it on the brake rotor. Kind of held it but it wouldn’t fit through the hole at the bottom of the gasifier and welding to thick cast iron wasn’t holding good enough.

I used up the remains of my oxygen and then resorted to the angle grinder trying to cut that opening bigger.

I ended up cutting 2 of the ears off and only holding it with 2 short chains. It rocks more than shakes but could work. This is likely going to be stationary and shaking it will have to be done through the clean out port.

I’m not sure if I made enough holes and slots but it hangs down into the ash pan so the gas should be able to get around it if it can’t go through.

Then I went back to my original plan with the stack of brake rotors. I used up a lot of oxygen cutting them so have to at least try that idea.

I packed around each brake rotor with ashes before putting the next one on and repeating the packed ashes. Towards the top I started using the fine charcoal and really packed it down to try to form a funnel to help direct the good charcoal into the burn pit.

I must not have taken a picture of the initial charcoal but I used some of the bigger pieces directly on the grate. Then I filled it up to the nozzle with the charcoal I had sifted the fine dust out of that was originally in it.

I had to dip into my freshly made charcoal to fill it fuller. It probably would have held another bucket but I need the new charcoal for the Simple Fire. The fresh charcoal wasn’t ground up so it is kind of big but I did sift out any real fine charcoal.

I put it all back together but it was getting dark and trying to rain so I didn’t try to light it. I still need to finish the cyclone filter and other stuff but at least it is closed up so it won’t fill up with water. I even remembered to put the lid back on my new charcoal this time.

I might try lighting it in a couple days or I might just leave it alone until I get some more done to it.

BrianAltEnergy · October 29, 2023, 6:18pm

Another nice, rainy, foggy, fall day in Pennsylvania.

More of a cooking type apple.

The deer really like them. Everything seemed to do good this year. Lots of fruit and nuts. Don’t know if that’s a sign of a bad winter this year or not.

I know, the cooler isn’t hooked up right but I only had 2 of the rubber couplers.

This setup run the generator for about 45 minutes but it wasn’t running at full power.

The jar caught about 2 ounces of dirty water with fine charcoal dust.

Then I checked the bigger filter with the rocks in it. It caught about 5 more ounces of the same dirty water. Very slight oil (rainbow) look on the surface but couldn’t notice any tar.

It did use a good bit of the charcoal and it seemed to be bridging a little after the 45 minute run. Again, better graded charcoal should help and the moisture was likely from the ashes and fine charcoal that I packed in around the brake rotors to seal them. At least that’s what I’m hoping and it will run better as everything dries out and gets settled in place.

This was what the underside of the felt out of the filter looked like. Probably another reason the generator was lacking power. The felt was damp and coated with the damp charcoal dust. Guess I should try to find some straw before trying this again.

Hopefully the cyclone will catch most of that dust once I get it done and the cooler should work a lot better when it gets hooked up right.

Still though, this new down draft gasifier looks like it could work. The fins on the outlet pipe dropped the temperature at least 30 or 40 degrees F. and the cooler helped a tiny bit but it was mostly all just going straight through the bottom pipe. The filter with the rocks dropped the temperature to around 100 degrees F. but I think the gas still had a lot of moisture in it.

I then ran the generator for a while on gasoline just in case.

This was the experiment while it was running on gasoline. Along with continuing to charge some cordless tool baterries, I hooked a small arc welder up to an old car battery. A couple of the cells were not bubbling as aggressively as the rest. I kept turning the power up and down but kept blowing the 13 Amp breaker on the generator if I turned it too high for too long.

I tested that battery after charging it from the welder and it read about 200 CCA. It should have been over twice that when new. I hooked it back up to my solar panels but not much power from them today. It probably won’t help enough but it wasn’t working before so the other choice is trade it in on a new battery or sell it as scrap. Either way, this experiment won’t lower its value and might make it usable for a little longer. That trick has worked before.

KristijanL · October 29, 2023, 6:42pm

Those apples look exactly like the ones we had, those were hard cider apples. Horible to eat raw but gave best, long lasting cider.

Bobmac · October 29, 2023, 6:59pm

I just use long dry couse grass will work. I have used long dry year old wild wheat that the grains have fallen off. It is mixed with some long wild grasses that grow along next to it. Works great and it is free all around where I live in the fields.
Make sure you wet it down and I like putting it in the cheap net laundry bags. Drop it into the filter wet it down drain the water out the bottom of the filter barrel, you are ready to go. You can make up more than one bag, and change it when it is time to replace the old filter net laundry bag.

BrianAltEnergy · October 29, 2023, 7:54pm

I forgot about looking for the mesh laundry bags yesterday. I should have written everything I wanted down so I didn’t forget anything. I was in a few stores that probably had them but never even thought about it.

I did get some black spray paint and a quart of oil that cost way more than I remember it being. One quart was $7.50 and it wasn’t even the most expensive quart they had. I probably could have shopped around and found it a little cheaper but I only needed one quart to change the oil in the generator. Some of the stores that used to sell cheap motor oil didn’t even have any.

The rubber couplers were bigger than I probably needed (1-1/4 inches) but the smallest ones they had. I should have bought at least a couple more but wasn’t sure they would clamp down on the pipes. I think they were around $2.50 each which didn’t sound too bad and was around half the cost I saw them for on Amazon. Better than welding them on solid or using duct tape or silicone. I don’t know if I can get away with the one closest to the gasifier but that’s where I hope to put the cyclone which should help cool it down to the point that the rubber will survive from the outlet of that filter on.

This is the cyclone I use with my shop vacuum for wood working tools. This one is all plastic and is bolted onto the lid of a plastic bucket. It was meant to catch the dust from a sand blasting cabinet but I used it mainly with a jointer and router powered by a small shop vac on a speed controller which I used mostly just to keep the noise down but it still had enough power to stop most of those chips and shavings from going all over the place. Then the bucket was just dumped outside around the building as mulch. It decomposes back to dirt pretty fast though. Sometimes I’d save it up for starting the fire in the furnace but there usually isn’t as much as the planer makes.

I wonder if something like this would work to attach a canning jar to the cyclone? I had to wrap electrical tape around the jar I used for today’s test run to get it to seal. That was why I stopped using that on the simple fire. It just wasn’t sealing tight enough.

I went ahead and refilled the new down draft gasifier almost to the top with the rest of the charcoal I made a couple days ago. I’ll have to make more now for the Simple Fire.

bsoutherland · October 29, 2023, 8:22pm

I love this topic and the great progress on Brian’s project. I’m back from my trip and here is a sketch of my “First Downdraft” proposal for my 14 horse power garden tractor: 100 pound propane tank, 1-1/2" schedule 80 pipe tuyere with 2-3/8" nozzle holes pointed 20 degrees down from horizontal, tuyere pipe passes through tank and is open on both ends,1/8" thick stainless steel perforated plate with 1/8" perforations for the grate (held in place on 4" nipple by 4" pipe cap. All comments, and suggestions welcome.

BrianAltEnergy · October 29, 2023, 9:26pm

I don’t really have enough experience yet to be fully trusted but my simple fire and this new down draft have 4 holes (I think they ended up about 3/8" holes) in a flute nozzle and my engine is only a 212cc. I think my filter was plugging up so 2 of the holes might have been enough.

My nozzles are just made out of normal 1/2" black iron pipe and are holding up pretty good so far. I do get lumps of slag in both the simple fire and this new one. Sometimes they are stuck on the nozzle but usually they have already broken off and are just mixed with the charcoal. Your bigger diameter pipe would be easier to poke a wire/rod through the nozzle holes to make sure they were open. My nozzles are easily removable to clean or replace them. The simple fire I get to from my clean out port and this new down draft I can reach from the top once enough of the charcoal is used up or scooped out.

Is your 4 inch pipe cap where you can clean out the charcoal? Will the gas out pipe be removable so you can get that cap off? I don’t think a rubber coupler will survive that close to the outlet.

Another thought is that both my gasifiers blow flames and sometimes bits of glowing charcoal out the nozzle pipe especially when shutting it down. You might want to have something to stop that or at least make sure the openings aren’t facing you. If I remember right, I think Cody used some stainless steel scrub pads or something to keep the hot coals from getting out of the nozzle opening.

Keep posting your ideas and hopefully the build itself. I’m curious how the refractory insulation protects the tank and holds/ reflects the heat into the burn zone. I’m also curious to see how you mount it to your garden tractor or if it has to go on a small trailer.

bsoutherland · October 30, 2023, 2:50am

Thanks Brian for your reply. Yes, the 4" cap allows charcoal, dust and slag cleanout. The gas outlet is attached to the cooler with steel pipe and a pipe union for high temperature operation and easy removal. Thanks also for the reminder about catching flames and glowing charcoal at the tuyere pipe openings. My nozzle holes will be drilled at 45 degrees to allow easy cleaning with a bent rod like in my MGB. My plan is to drill them at about 7 inches apart with the 45s both pointing inward toward each other to create a concentrated central burn zone.

BrianAltEnergy · October 30, 2023, 2:01pm

Raining again so I thought I’d edit Bruce’s drawing.

I think I got the angles drawn right. I couldn’t remember the name of the “pipe union” but that could be a good way to make the parts removable but more heat resistant than rubber couplers. I might be misunderstanding the 20 degree angle part. Both holes might be along the same side.

I’m not sure how the tuyere pipe is sealed where it passes through the tank on both sides.

Does this mean the grass (or straw/hay) needs to be wet to work as the filter or is that just to make sure any dust is washed out?

bsoutherland · October 30, 2023, 4:00pm

Brian, thanks for the great edit of my proposed design. The 20 degree part looks right, but I think both nozzle holes should be on the same side of the tuyere pipe. They both point away from the gas outlet, but toward each other in order to make the burn zone more centered horizontally and vertically. I was thinking tuyere pipe extending out both sides of the tank by 2 inches and welded in place.

Pipe union:

Bobmac · October 30, 2023, 4:23pm

When first putting a new filter material like long dry grasses or hay it carries lots of very fine material even fine dirt with it that will pass through and migrate to the intake and into the engine not good. So wet it down first will stop most of this from happening. I do not just wet it a little I flood it down with lots of water and let it drip dry while the filter drain plug is out so the filter material starts out wet. When the gases make there way through the filter material it changed the filtering material so it will not mold or rot, kinds a smoking prosses it goes though. I changed my filter medium one time and just let it sit a few days with out running it and letting the wood gases go through it not a good idea it started to mold and I had to redo the filter medium with new stuff and then run my gasifier to smoke or cure the hay and grasses. It was fine after that. Part of the other 75% of gasification. Right.

BrianAltEnergy · October 30, 2023, 6:49pm

Still raining (misting) but I wanted to run the gasifier some more to try to dry it out some more.

Almost all of this is good charcoal but I finished filling it with a layer of small chunks of wood. Good or bad idea? Doesn’t matter, I had to try it.

I run for half an hour and then shut it down.

Emptied a full jar of dirty water out of the filter.

Two pulls and it was running again.

15 minutes later I shut back down and got another 3 ounces of water.

I opened the top of the gasifier and poked it down.

I expected it to be bridging but poking at it only changed it a little but this was around the 45 minute mark and the level was noticeable lower but still had lots left.

Two pulls and it started back up but took a little while before it was running right again.

My cordless batteries still weren’t charged after another half hour (1 hour 15 minutes total run time) so shut down and drained 6 more ounces of water. Most of the charcoal should have been dry so I figure this must be from all the damp ashes and fine charcoal around the brake rotors.

Again, two pulls and it was running again. First pull I get a puff at the nozzle and the second pull the generator is running again.

This is a view into the nozzle as it’s running.

I’m not getting as much power as I normally can from the simple fire but it could be the moisture content too high.

The next 15 minute mark it was still running as good as it had been and my batteries aren’t charged yet.

There’s two of these and they were both almost fully discharged but I didn’t really expect them to take this long although I did have a smaller battery on the charger first until it was charged.

The temperature at the outlet of the gasifier is around 230 degrees F. and it is down to around 130 at the outlet of the filter.

Oh oh!!! About 10 minutes later the engine shut itself off.

I drained 5 more ounces of water out of the filter. I opened the gasifier lid and poked it around and clean down to the grate to make sure it wasn’t plugged up.

I also opened the filter and the grass looked OK. Steaming but OK.

Tried to restart and it wouldn’t stay running. Forced air through the nozzle and tried to start it again. Just wouldn’t run.

Unhooked the hose and a lot of water run out.

Switched to gasoline and finally got it running with a lot of white exhaust coming out. Once it was running smoothly again I shut off the gasoline and hooked up the gasifier hose. This took a little time waiting for the float bowl to run out of gasoline and get the air/fuel mixture adjusted but it’s back running on the fuel out of the down draft gasifier.

One of my cordless batteries was charged so I swapped it for another smaller one. Also hooked up a 30 Amp battery charger to the car battery I tried fixing with the welder but it just isn’t holding a charge.

Over 2 hours run time now which is about the most I could get from the simple fire although that one didn’t make as much water to keep draining out.

I’m still not getting the power out of the generator that I hoped for but it’s doing pretty good.

At about 2 hours and 15 minutes it started running worse so I shut it off and there was more water in the line. I restarted it on gasoline and refilled my air tank and finished charging the second small battery. There’s still one of the big cordless batteries not fully charged but that was enough for one day.

There was another 7 ounces of water in the filter and that isn’t counting the little bit that was in the gas line.

I’m hoping that was mostly from the damp ashes and fine charcoal and the problem fixes itself with more running.

This is the best picture I could get of the remaining charcoal after the 2+ hour run. Most of the raw wood looks like it has been converted to charcoal but there wasn’t really as much as the first picture made it look. Still though, it seems to have converted it long before it reaches the nozzle.

It looks like the level dropped about 9 inches so probably about a bucket full of fuel or about the same as the simple fire would have used in that same time.