First Down Draft Charcoal Gasifier

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.

Bobmac · October 31, 2023, 12:08am

Looking at the three pictures of your hopper it looks like in the fist picture the wood is crowned up in the middle and in the second and third pictures it is the lowest in the middle of the pile of wood. In my hoppers it seems to center feed the wood in the middle first and the sides of the hopper would feed last. So it is possible the raw wood went through first on top. This would explain the extra moisture you were getting. Could you tell if any of the raw wood was still right on top of the hopper pile?
Yes it can take a few runs to get all the wet ash moisture out, but it should work it way out. Good job.
A extra moisture trap would be handy just before going into the carburetor.

KristijanL · October 31, 2023, 4:40am

You got vacuum and warmth in a woodgas sistem. Means the gas can hold A LOT of water vapour. The water you got out is just a fraction, most water went to the engine in gaseous form. No harm, but think about how much this dilutes your gas…

BrianAltEnergy · October 31, 2023, 5:53am

Thinking about this some more I still think the problem is the wet ashes and fine charcoal that I used around the brake rotors. It was raining so the air in had a lot of moisture too.

What I wasn’t realizing was all (or most of) that moisture getting boiled out of the wet materials would probably go up through my charcoal making everything wet and then condense on the lid and run back down through the cooler raw wood and charcoal making it even wetter.

All that unconverted water vapor either had to be condensed and caught in the filter or lines or end up being sucked into the engine. That would explain both the quantity of water I drained out and the lack of power in the generator.

What I have to decide is if I should continue using it like I just did and hope the moisture problem fixes itself or if I should take the lid off so the water vapor can get out and just burn off the charcoal without feeding it to the engine. Probably no sense adding more dry charcoal until the water in the ashes is mostly gone. There’s probably enough charcoal left in the gasifier to run another hour or two before it gets to the nozzle.

Another possibility is to empty as much of the charcoal out as I can and refill it with raw wood. Light it from the top and use it to make charcoal just like I do with the water heater tank which should help dry it out and get me more charcoal as long as I catch it after the raw wood has turned into glowing coals. That charcoal could probably be smothered out by putting the lid back on and sealing the output pipe and nozzle. It would contain some ashes and fine charcoal so probably should be taken out once cooled down to be ground or at least screen out the ash and fine dust. Could possibly shovel a lot of the charcoal out while hot and put it in my metal barrel with the good lid and add more wood if one batch isn’t enough to dry it out or if it worked real good just to get more charcoal. It should be easy to blow air back through the grate to get a roaring fire quickly. My clean out cover could also be removed to let more air in the bottom and then closed when it was done just like the draft door on a furnace.

KristijanL · October 31, 2023, 6:48am

You can also push air in the gasifier with its lid open. Will dry the remaining content

BrianAltEnergy · October 31, 2023, 5:12pm

I decided to try just burning some wood in the gasifier like I do for making charcoal. Partially to get some more charcoal but mostly to dry out the ashes I used to seal the brake rotors.

This is what I took out of the gasifier as well as the nozzle. Some was obviously bigger than it probably should be and some looks too fine. I don’t remember if I added some that wasn’t screened or if it just got smaller from burning and poking at it. I’ll screen this before reusing it and might even grind some of the bigger stuff. The nozzle might be a little bent. I might have hit it when pushing a piece of rebar down into the charcoal when it was hot. It might just look that way from the flaking metal or slag stuck on it. Still usable either way.

I didn’t burn a lot of wood but it got the top of the tank hot enough to burn off the paint. Testing it there were spots that were over the limit of my temperature gage. Over 600 degrees F. and the lower section where my ashes and brake rotors are was a little over boiling.

I closed it up by closing the clean out door, shoving a rag in the gas outlet pipe, and setting the lid in place. The moisture and tar from the lid was smoking and steaming around the lid.

So much for a nice, tar-free surface to paint.

I’m leaving it cool down now. Hopefully this helps the moisture problem and I’m guessing there should be a half a bucket of charcoal left. Might be more but I didn’t really pack it with wood. Playing around with it a little as it was burning showed that the clean out door did work as a draft door. I did use a blower to get it started and I left the charcoal in the burn chamber to get it started. I set the rusted out garbage can on top with an air gap in between the propane tank and the garbage can. That worked good and was mostly smoke free without needing the blower once it was burning good. I did use the blower after I added some more wood to get it burning smoke free faster.

BrianAltEnergy · October 31, 2023, 8:12pm

Just a quick update.

I refilled this gasifier and gave it a quick half hour test charging my drill battery and a different car/truck battery. That worked good.

Then I unhooked the 30 Amp charger but left the drill battery charging and tried using the wire feed welder to touch up some holes in the cyclone filter. It loaded the generator down but did it.

The compressor run up till the pressure got to about 125 psi and then it was loading the generator down and the motor wasn’t spinning full speed so I stopped it.

Kristijan mentioned on another thread that he had to drill his flute nozzle bigger than he thought it should be because of the slag build up. Right now I think I have 2 holes at 3/8 inch and 2 at 1/4 or maybe 5/16 inches. That might not be why I still don’t have full power on my 212cc generator but I might try drilling the other 2 holes to 3/8 inch.

This short run I only got maybe a couple ounces but probably less than that of dirty water. Making the charcoal and heating it up open to dry the ashes must have helped.

Bobmac · October 31, 2023, 8:27pm

Yup just clean it up the best you can and spray paint it with black paint. It will look fine.

BrianAltEnergy · October 31, 2023, 10:25pm

Here’s a question for anyone using a flute nozzle.

Mine is 11 inches long. Is there any chance I’m not getting all of the holes ignited causing one or more holes to just be sucking air through the charcoal or would any unlit holes light theirself from the ones that did light?

Bobmac · October 31, 2023, 10:29pm

Brian, How far are the holes apart from each other?