First Down Draft Charcoal Gasifier

BrianAltEnergy · October 22, 2023, 11:52am

Been raining for days and looks like it’s going to do it again today so not getting much done with my gasifier build.

D = 1 Inches
L = 2 Inches
W = 1 Inches
C = 0.26 Inches
J = 5 Inches
F = 1 Inches
L0 = 5.1 Inches
L1 = 5.06 Inches
L2 = 5.04 Inches
L3 = 5.05 Inches

I know a cyclone filter is controversial if it is good or bad for a gasifier. I’m not sure how this down draft gasifier will work and a cyclone probably isn’t needed but I’d still like to try building one even if it doesn’t get added to this build.

I do use a bigger plastic Cyclone on a bucket for some of my wood working tools and almost nothing escapes. Obviously, charcoal dust and fine ash is way different than wood chips and shavings. The Cyclone was originally meant for a sandblast cabinet but is mostly used on a jointer or router.

BrianAltEnergy · October 22, 2023, 4:09pm

Building the paper patterns for the cyclone.

This one should be easy enough to just mark out on the metal but I wanted a paper pattern to make a model.

This was the input pipe that starts out round but transitions to rectangular.

This was enough to get me a life size model.

Not what I wanted.

This could work but kind of defeats the plan to keep the dust out of the cooling pipes.

Oh well, it’s the thought that counts. And, it was only built out of paper and tape.

KristijanL · October 22, 2023, 4:58pm

Brian, you put much effort in to that cooler and will probably want to keep it, but a cyclone like this, specialy if you weld fins on it, will probably cool the gas more thain the cooler, plus filter the gas. Just a thod.

BrianAltEnergy · October 22, 2023, 5:35pm

Kristijan, I did wonder about that. Plus, that cooler might be a nice size for use on a lawn mower with a smaller simple fire along with a smaller filter so the cooler will find a use even if it doesn’t go on this one.

Grass mowing season is over here. Supposed to be close to freezing by morning but I considered trying to put an alternator on an old lawn mower engine for battery charging.

I don’t know how much heat this down draft will make compared to the simple fire so I don’t know how much I need to cool it but I assume it will be hotter considering it won’t have as much charcoal to pass through before exiting.

KristijanL · October 22, 2023, 6:09pm

The engine on my BCS is a slow turning flathead 470cc engine and its probably similar in gas consumption to yours. Gas first contacts a water cooled surface, about 20x20cm, to “take the edge off” the heat, then straight to a oiled towel filter. If the gasifier runs good and efficiant, its gas looses heat extremely fast. Its the steam that carryes a lot of energy downstream. But a good gasifier must not make any in the first place.

This sayd, if you add fins to the cyclone l think this plus a filter shuld be plenty of cooling area.

BrianAltEnergy · October 22, 2023, 7:06pm

Somehow I missed this short thread:

Bobmac · October 22, 2023, 8:12pm

Putting fins on the cyclone filter, that is a great idea Kristijan, I think I will try that on mine. And may be the piping coming out of the gasifier to the cyclone and the piping leaving the cyclone going to the cooling rails. But keeping the heat in the lower part of the gasifier with well insulation, but is not needed once it leaves the lower part of the gasifier. Holding the heat in the gasifier and then releasing the heat, by cooling the gases down as quickly as you can to get the moisture/soot to drop out of the gases. Part of a good built gasifier and components to go with it. DOW

trikebuilder57 · October 23, 2023, 2:27am

I have a cyclone with fins on the Ranger. It works but does collect some water.

BrianAltEnergy · October 23, 2023, 3:42pm

I put a cover on the clean out port.

It’s made from the saw blade but I cut all the teeth off.

The hold down clamps are just bent pieces of 3/8 inch threaded rod and wing nuts.

I used high temp silicone and stove rope as the gasket and welded/siliconed the holes in the blade from the back side. The flat bar was just spot welded to the blade.

BrianAltEnergy · October 23, 2023, 7:02pm

Probably shouldn’t admit this but I tested the gasifier out again.

First I didn’t put enough charcoal back in and, combined with the lid just held down with gravity, I blew the lid open.

Wasn’t a bang, just a puff.

Then I added more charcoal, hooked up my filter without any extra cooler and got the generator to run.

Again, too much air leaking in the lid and blew the lid clean off that time.

Still not smart enough to stop, I put the lid back on and started the generator back up.

I was able to run the chop saw and the planer (not at the same time of course). It run the air compressor but wasn’t running it at full power and really loading down the generator.

I’m assuming the problem is everything is too wet and my nozzle holes might be too small but at least I know the thing works.

I ordered an assortment of springs to hopefully get the lid held down better but still allow it to poof if it needs to. They should be here today but don’t know if they are going to be what I need. I want it strong enough to seal on the stove rope gasket but weak enough to open slightly if it has another poof.

Once I had enough charcoal in it (still not full), the gasifier stayed cool. The gas outlet was pretty warm so it will need a cooler of some kind when I run it longer. I only run it for 10 minutes or so just to see if it worked. I assume it should run better once the ashes I used to seal it up are dried back out and I’m going to drill the nozzle holes a little bit bigger but it looks promising.

Another probably shouldn’t admit…

Put a few little broken up sticks in just a bit above the nozzle before adding more charcoal. They were bigger (longer) than they probably should be but I wanted to make sure I could find them again.

They started to char. The outlet pipe right out of the gasifier had some moisture and charcoal dust but didn’t look like tar. I didn’t screen the dust out of the charcoal from the last test. Just dumped it back in. The outlet pipe closest to the engine wasn’t even damp so the filter must be catching the dust and the moisture although, with such a short run, it wasn’t a real good test and there was only a few sticks added.

No water came out of the filter either but again, not surprising with the short run.

I’m still using the expanded metal grate. I was able to push a piece of rebar through the holes but I’d like to put a movable grate on it. Didn’t start working on cutting out pieces for the Cyclone yet. I need to redesign the inlet. I made it 1 inch and my outlet pipe is around 1-3/8 inches outside diameter.

This means my top pattern for the 4" round section has the cut outs drawn wrong but that is easy enough to fix without printing another pattern. The inlet will now be 1.5" x 2" so it is big enough to fit the 1-3/8" pipe.

The part I’m not sure about is what I will use as the catch jar or container.

BrianAltEnergy · October 23, 2023, 8:59pm

Well, this wasn’t exactly right.

It will hold the lid down but very little room to poof.

A little bit crooked but this is more like what I wanted.

I’m not sure the springs are strong enough but should keep the lid from flying clean off the tank.

Bobmac · October 23, 2023, 9:01pm

So Brian, why did you put raw wood on top of the Charcoal and more wood on top of the big sticks. Wood chips would probably pyrolysis down better then the larger wood. If it did make some tar though, I would change out my filter medium and start with fresh stuff.

Matt · October 23, 2023, 10:13pm

LOL that just described everyone on this forum. We all still here building!!!

BrianAltEnergy · October 23, 2023, 10:57pm

i only put a little bit of raw wood and then put more CHARCOAL on top of that. I just had some small sticks that I broke up by hand. The ones in the picture were easy to locate again digging through the charcoal. I plan to mostly stick with charcoal but hope I don’t need to worry so much about keeping it real dry.

I couldn’t see any tar but there was very little raw wood. I was just curious if it would char and it looks like it was starting to convert. I wasn’t sure how much heat would be above the nozzle but didn’t want to risk putting too much raw wood in since I was running the generator on the gas.

I fired it up again (twice) after putting the clamps on the lid but only to flare it. I was blowing air into the nozzle instead of pulling the gas through because I didn’t want to suck hot gasses through the pump. There was some liquid leaking out in a couple places from the lid. I am pretty sure it was water though and not tar. It might not have leaked with a vacuum instead of being pressurized though. My charcoal got rained on so it wasn’t dry. Probably a good reason to get black paint instead of yellow or red though.

The flare started out yellow but turned more blue and almost invisible after it run a while. There was some “sparks” if I gave it full air blowing into the nozzle. Getting rid of the fine dust in the charcoal should help with that though. What I put in it wasn’t screened at all.

Next thing I plan to try is take the flute nozzle back out and drill the holes bigger and maybe add one more. The one in it has smaller holes than the simple fire and one less hole so I don’t think it is getting enough air through it to run the generator at full power.

BrianAltEnergy · October 24, 2023, 3:56pm

You were right. I still think it is just damp charcoal dust but really plugged up my filter.

This is gravel and not charcoal. I wondered why I couldn’t even get the simple fire to run my generator today.

Now I get to test out my idea of cleaning these rocks using the drain plug and a garden hose.

This is the first layer of felt above the gravel. That caterpillar obviously doesn’t mind the dust.

The worst part was getting the planer shavings off the gravel.

I’m going to try only the rocks and several layers of felt. The top layer above the planer shavings was still mostly clean.

I’m going to burn up most of the charcoal that’s in my simple fire but then I’ll go back to stopping at 1/8 inch instead of using the window screen to catch the smaller charcoal. Most of the dust was from the test of the down draft gasifier which wasn’t screened at all but I was loosing power even with the simple fire. I expect the filter was putting too much restriction on it and not allowing enough gas to get to the engine.

Much better. The simple fire runs the air compressor at full power again.

The down draft will need emptied back out again and screen the charcoal instead of just shoveling it in.

Bobmac · October 24, 2023, 4:39pm

When I tried using felt it did not matter how many layers of it I used. The first layer would plugged up and then the gases just tried to by pass around the edges if it could. If not you will get a very high vaccum in the filter and the gas flow will stop making it hard to get a flare or start up your gasifier. Wool and open foam are better but did the same thing but not as quickly.
I have found just using hay that is moist and nothing else works the best. If you are concerned about it you could put wood shavings on top of the hay. I would put it all in a laundry netted bag. You can make up a few of them and have them ready to change out. That course rock gravel is a mess to clean out once it gets full of soot. Pressure washing it helps get it clean out but it takes time to do it and you can not get it clean like it started in the first place. The hay and wood shavings in a bag will clean out much faster with just a garden hose with lots of water. Open the filter drain plug and wash it out from the top. Let it drip down close your drain and it is ready to go agin. Of course this is with my WK Gasifer on the 5.2 liter V-8 engine, not a smaller unit.

BrianAltEnergy · October 24, 2023, 5:31pm

I’ll have to experiment and see what filter material I can get that will work better. The felt did/does stop the dust from getting through it.

This is the front and back of the first layer.

Most of this was from the testing though. The simple fire wasn’t getting it that bad.

The rocks weren’t bad to wash out but it did take some time. Mostly trying to get the planer shavings off them.

I’ll see if I can get a couple laundry bags and some hay or straw. The planer shavings are nice but they really hold the water once they get wet.

I thought welding the ring on the lid would be better than on the tank like I did on my filter but condensation and tar leaks out.

I was playing around and put a bunch of wood chips in just with a flare. Tried to get a picture of the flame but it doesn’t show up good enough. It had a yellow color but I could get around a 2-1/2 foot long flame roaring out of it.

The tar was dripping out around the lid but the gas outlet pipe didn’t show any signs of tar.

This is inside after burning it.

I tried to dig down to the nozzle but I’d have to empty some out to reach it. It did look like it was all charcoal by the time I got to the nozzle. The tank did get pretty hot too but I was feeding it a lot of air. Way more than the generator would need.

Bobmac · October 24, 2023, 5:44pm

If you have a good charbed and hot heat above it to crack the tars, you will not get tar down stream of the charbed, it is all converted to good gases. This goes for any well built gasifier of what ever draft design you have. Keeping a active charbed and the hot heat and not over pulling the gasifier system with to much flow or velocities which shortens the time for converting the gases and tars to good gases Carbon Monoxide, Methane, and Hydrogen.

BrianAltEnergy · October 25, 2023, 4:44pm

Tried adding a ring around the lid to help direct the condensation and tar back down instead of dripping out around the lid. Probably should have done this to start with and make it so the stove rope had a pocket to hold it in place. This was just tacked in place in case it didn’t work but it looks like it should help.

Then I hooked it back up to the generator after adding more charcoal.

I run it until the charcoal was bridging and the generator wasn’t running as good.

This is a view inside just after shutting it off.

Switching back to the more uniform and smaller charcoal should help.

I opened up the filter and it caught a lot of condensation. Probably just everything including the charcoal is still not dry enough.

Once I get the Cyclone filter made and/or put the cooler on it to catch the water before the filter it should help.

The outlet pipe did get hot but not as hot as the simple fire has been before so I think the cooler I made should be enough. The amount of moisture leaving with the gas wasn’t good but I hope using a bit dryer fuel stops that problem.

I probably will try more “rocket fuel” but want to get it running good with just charcoal before trying that with the engine. I wasn’t too worried when just flaring it and it did look promising but not going to risk it yet.

All in all, it still looks like this will be worth the time I’ve spent and the time still needed to finish it.

My simple fire needs more charcoal ground up and screened since I used up a lot of it yesterday. Like I said, I still plan to use that one but I’m hoping to get this new one set up specifically for the generator so I can use the smaller simple fire as my portable gasifier. I’ve already proven that one can run the log splitter but I’ve been keeping it hooked to the generator because I use that almost daily. Sometimes it’s just for a quick grinding job or refilling the air compressor tank but other times it can be an hour or more running the welder, cutting and planing boards, or recharging batteries although I try to do that one with the solar panels unless I’m using the generator for other stuff and remember to plug the batteries in.

d100f · October 26, 2023, 1:04am

Thanks for the updates Brian keep them coming as your adventures will help a lot of people joining the group in time to come .and those here today .
Dave.