Brian do you have any old steel car wheels lying around? You could use your propane tank as the whole unit by fitting the wheel rim inside the tank as an air jacket for nozzles.
You’ll want to find one that either drops right in with a small gap to weld, or one that if you cut a shoulder down will fit.
The inch sizes of car wheels is kind of Nominal, a 12" wheel is slightly larger than 12" at the bead seat edge.
A car rim would be good thick steel to affix your nozzles.
Is this anything like you are suggesting? The wheel rim inside the tank leaving an air gap. I only plan on one nozzle and was hoping to use it as the lighting port.
This reminds me. How can the WK gasifier get away with conduit nozzles right on the burn tube? I assume we don’t do it that way with charcoal because the burn tube is often the tank itself and we want the fire further away from the side.
Might this work? Must be a good reason it won’t work like the burn tube would melt instead of melting a replacable nozzle.
WKs don’t necessarily use conduit as the nozzle, but the burn tubes are in excess of 1/4" thick.
As far as single nozzles go I’ve been twice bitten forever shy of them. Even my 5lb weighing super thick 2" nozzle for my truck looks like a dog chewed on it after a few miles. Bear in mind I’m talking a 4.3L engine so I’m sure your generator would have a much smaller demand.
Granted I didn’t run water drip or EGR, just moistened charcoal. In your stationary setup you could do that very easily. EGR will definitely preserve the nozzle but won’t add power like steam/water drip will.
Perhaps the increased surface area of the burn tube will help preserve your nozzle.
With that setup you could make a Double Flute downdraft without needing a ring of jets or an air jacket. Just have the flutes right at the level of the top of the burn tube.
Probably just trying to over complicate this again but, so far, I’m happy with the single flute nozzle in my simple fire. Seems to be holding up better than just a single open pipe.
I still have the hexaloy nozzle that I haven’t tried yet.
I will have to see what I end up with for this new down draft gasifier but a double flute might work. I can only guess but the heat should be spread out more with the same draw so it isn’t all concentrated on one spot of the nozzle. I did find a big, thick piece of pipe that’s about 12 inch diameter and really heavy. Bigger than I wanted but I might try it anyway. The dream of putting this on the lawn mower isn’t going to happen so this will probably be for the generator.
It’s going to rain all day today so probably not much gasifier work going to happen. I did fire up the simple fire last night and cut the top off my 100 pound tank and then emptied my filter and remade the gasket. I had just been using silicone and grease to seal it but got some stove rope now so hopefully that works without needing grease. Probably going to replace the planer shavings with fresh ones and thinking about putting some rocks or gravel in the bottom to keep the shavings from soaking up as much moisture since any condensed liquids now end up in that filter. The last fill of charcoal (with the small flakes) had been sitting outside and I got a good bit of moisture in that filter and less power from the generator. Couldn’t notice it when only using the grinder but the compressor was struggling to run.
I’m hoping this down draft can handle damper charcoal than the simple fire. I probably should have just thrown that pile of fine charcoal on the compost like I was going to but didn’t want to waste it. The fresher charcoal that I grind I will leave the flakes in and only separate the dust.
Next job for the generator is probably going to be welding and that takes everything my little generator can give which is why I wanted to clean out the filter and probably put fresh, Dry charcoal back in the simple fire.
Oh, by the way, I tried my charcoal grinder with a hand crank instead of the cordless drill. I think when I build the better hopper for it I will put a hand crank on it and stop using the drill or worry about rigging up a gear reduction and motor. Worked good and I could feel if I hit a brand or a nail or screw. Seemed to make less dust since I was spinning it slower but had more power to cut through the bigger pieces of hardwood charcoal.
Suggestion; when you have a fresh batch of charcoal don’t screen out the fines. Just put the mix of fines, some larger and some ground charcoal in the gasifier. A range of sizes will produce the same fuel density, and permeability as all ground charcoal. With experience you will be able to judge a good mix, and add more ground or lump or fines as needed.
Rindert
This post by Kristijan describes the engine grade charcoal I should be using.
My simple fire doesn’t have a good way to shake it (no grate) and with my filter attached shaking the whole thing isn’t easy but I did notice that after I run it and would poke a rod down into the charcoal the level would drop a lot which sounds exactly what he descibed. I burnt the fines and left the bigger stuff.
That whole thread has some good information. Like this sketch from Tone.
Along with that skech, Tone says:
the difference between the upward method and the downward method is that in the former, all the water vapor rises during the generated gas and travels towards the engine, the charcoal dries completely and it is necessary to add water, well, in the downward process, a moist atmosphere is created above, which presses down through the hot zone, the steam is well superheated above and the conversion process is guaranteed.
Brian,
Yup, you get it.
Just one more note: the fines from your tlud are much more valuable as fuel than the fines from your simple fire, because they contain less ash.
Rindert
This was another option but I’m pretty sure it’s too small at about 4 inch inside diameter and 5-1/2 inches high. Too bad though, it’s pretty thick. I might try to use it as the ash clean out port.
This really old tank has already provided the metal for some projects so I’m tempted to cut a piece out and pound it into a tube shape for my burn tube.
I hope everyone isn’t getting tired of my posting all my crazy ideas while I try to build this gasifier. I’m trying to post the process I’m going through (good and bad) instead of just waiting till I have a working gasifier and edit out all the problems and mistakes along the way.
I’m trying to design this so, when it doesn’t work right, I can easily take it back apart to make changes. I’m also trying to do it with what I have available. I have way more time than money so can’t go buy everything I’d like to use.
This is my idea for a fixed grate. It will likely get plugged up but might do as a test. I can always pull it back apart, cut out the bottom, and add a movable grate later if it actually produces usable gas.
A lot of mass here that might cause problems or make it take a while to get hot enough to produce good gas but it all comes back apart so nothing is permanent.
About 8-1/2 to 9-1/2 inches from the top of the stack of brake rotors to the grate depending on how I stack them which is a little higher than Giorgio’s version but smaller diameter.
The nozzle will probably be a little higher and removable so I can get these back out when it doesn’t work. The whole stack will be covered with ashes to insulate it and seal the spaces around them.
This was a sketch I made last night. Not exactly how I will probably build it though. Hopefully there isn’t much condensed liquids so the drain from the condenser could probably just be a plug in the lowest point.
The way my filter from the simple fire is made I used the original threaded opening for the propane valve as the drain. It only catches a tablespoon or so of liquid depending on how damp my charcoal is.
This hasn’t been tested yet. I filled the bottom of the filter with gravel. My thought is this will help condense any moisture that the gas contains and keeps my planer shavings from sitting in that liquid. Obviously, using dry charcoal in the simple fire should eliminate most of the moisture problem and hopefully the down draft won’t have as much problems with less than ideal fuel.
I could change my design and just try the stainless steel tube but it’s really thin metal but bigger diameter.
In the grate plate you need a lot more holes so it does not plug up. All the rotors will take time to heat up but will hold the temp inside and give you a good turn down ratio. But this is need in gasifiers that are not stationary and are not run at a constant velocities like running a vehicle engine. This will will be running a generator right. Some sort of a cone will be need to funnel the Charcoal into the smaller fire tube from the hopper, I like 60%. It should work if it is sealed up air/gas tight.
Thank Bob. There’s still a lot left to do so I’m sure this isn’t the final design. I’ll probably make an actual grate of some kind or at least cut the holes bigger in the fixed one.
Yes, my plan is to use this to run a generator. It’s going to be too big and too heavy to easily move around especially if I stick with the stack of brake rotors.
I was hoping I could just stack/compress ashes to make the cone funnel but I suppose that would be above the main heat so sheet metal should be good enough.
If you can I would put a grate in that will hang by chains, then you can reach in through the clean out hatch and give it a bump or shake to clear the ash off the grate and out of the fire tube or linkers that might form above the grate. Leave 1" to 1 1/2" of space above the grate to the bottomof the fire tube. Make your grate larger than the opening of the fire tube by at least 2" in diameter. If the grate plugs up the gases can still go out the side of the Charcoal pile. This is great for a standing gasifier stationary unit. Some people put grate shakes on their units. I have never put any on my Charcoal gasifiers.
Thanks again Bob. I made some notes for what I’ll look for to make the grate. That grate will need to fit through the opening I just welded in place. Might make it a little tricky to go at least 2" bigger diameter but I could either cut the opening bigger or make the grate in pieces that can be assembled in place. Will depend on what I find or build for the grate.
I still need to make the clean out hatch and the gas outlet.
Even though this is supposed to be charcoal only, I probably should make the lid able to handle a poof. I would like to try Rindert’s idea using square tubing idea to hold the ash door closed.
Might be able to add springs to those brackets to allow the lid to lift if it needs to.
Hi Brian , I’m no expert when it comes to downdraft but i am pretty sure just ash pressed around the outer diameter will work on top of the brake rotors just fine , also the charcoal will naturally form a cone of sorts .
I have read comments from other people that have had much longer run times of there downdraft compared to me i have only run maybe 40 hours , but if what everyone else says about no need for a reduction as such them maybe just use the 1 brake rotor that way at least it will make it a lot lighter to move around .
Dave
PS there is no such thing as crazy idea’s and your posts will help a lot of people new and old that follow you through your journey so keep on doing what you are doing is what i say .
I was wondering about that. Just put the nozzle at a height that gives enough space for the reactions to take place and use it basically like an upside down simple fire. Sounds like a good idea unless someone disagrees.
I don’t think it will hurt to have a reduction as it will for sure help to concentrate a hot area if you were intending of mixing in some raw wood chips , with my attempt i lay a sheet of stainless steel to hold back the charcoal from the bottom of the drum and just drilled some 12mm holes in it at the far end to allow the gasses to flow down and out .
Dave
Forgive me if l sound critical, but unfortunaly this design achives the exact opposite as is the goal with a gasifier. You want to keep as much heat in the hearth as possible and prevent losses to the outside. Those rotors will work as heatsinks pumping heat from the inside out. But you answered all the solutions your self alredy. One brake rotor at the bottom will work just fine. By the time gas comes there there isnt much heat left and also it isnt needed anymore.
The gasifier will then form its own firetube, nicely insulated by charcoal and ash.
On this note, the grate can be a peace of 1/2" mesh. Used that plenty of times. A stiff rabbit fence even. Again, not much heat here to melt/bend it if the nozzle is at right height.
Thanks Kristijan. That’s the answer I was hoping for.
As far as the nozzle height above the grate, I would like it to be as close as possible so I can use more of the fuel before it needs refilled.
17 centimeters = 6.693 inches which is where the 7 inches I drew on the tank came from. The 12 inches on one of my drawings came from looking at my simple fire and thinking about the fuel level when it quit making good gas. Maybe split the difference and put the nozzle 10 inches above the grate. Cutting the nozzle out, patching the hole, and moving it is an option if I get the height wrong but I’d rather get it in the right spot first try. Higher up should mean less heat at the grate and less heat in the gas but less space above the nozzle as the “hopper”.
My simple fire can run the generator at least 2 hours before needing refilled. I would hope to get double that time from this bigger one.
I would like to try mixing in some wood chips or charcoal that didn’t fully convert but the main reason for wanting to switch to down draft is the ability to use damp charcoal. My last few batches are still in the sealed barrel so should be pretty dry but all the rest of my charcoal is in open top buckets or containers that are not air tight.
