I Have been thinking about ways to produce cleaner gas while being able to use different types of wood fuel like pellets, chips,chunks, wetter stock ect. Making enough chunks seems impractical when you have alot of different sizes of fallen trees to utilize and no sawmill waste as in my situation. So i have built a charcoal unit that runs well but would like to be able to use raw wood in the future.
One idea i came up with was to have a larger main gasifer that could run on wood chips. This bigger unit would feed gas into a charcoal only gasifier that would get rid of the tar by heating it a second time with higher tempatures
Im sure someone else has tried this. One concern i have is making the incoming gas mixing with oxygen in 2nd reactor. It may take a little trial and error getting the air mixture right. Also explosion could be possible but im not sure how big the explosion wouls be or high the risk. I think minimal but its worth considering.
Im currently working on running generators in the 3k watt range to 8000k. Eventually i would like to convert a truck.
Also i will mention that alot of the tree trimmers around here will give away piles of free wood chips so that is another motivation to try and use other fuel types.
Hi Taylor Krull,
Welcome to getting active on the DOW. Lots of charcoal making small engine-generator guys here. Exchanging experiences.
If you look up at the top of page, in the dark blue band there is a gray tone Magnifying glass. The previous discussions search tool.
Open it up and search out:
Gasifing wood chips
Using multiple gasifers together
Why not to use arborist free mixed chips
Ha! The Gasifing Wood Chips will list a current new topic : “Swedish Chip Gasifier”
Good reading.
If you can evolve to doing this without tars goobering up your generator engines, please do post up details. (Internally tared developing, getting to there. Clean them up with acetone, lacquer thinner, or heating kerosene.)
Regards
Steve Unruh
Snow is mostly gone for now. Just waiting for the mud to harden so I can get back to work. First thing is reassembling a Slightly modified WK I built in 2014 and then let sit for a long time. It only has an 8 inch fire tube. I’m going to run it as a downdraft charcoal unit and see if it holds up. To me the whole reactor is fueled by charcoal anyway so what does it matter if there is charcoal in the hopper. If that works then it is a duel fuel gasifier and will run on either straight charcoal or wood. If it melts down then more scrap for me to do something else with.
You may want to go straight in raising your oxidation zone giving gas post oxidation more dwell time and more carbon to react with. The key is velocity and penetration.
Right now my gas exit is downward pointing in the center of the base of the tank, if I were to go with two nozzles I would either have them pointing directly opposite each other or maybe 90 degrees from each other, the nozzles would be facing towards the center of the tank 90 degrees from the wall it’s coming in from like a regular nozzle. I could probably lower the nozzle to distance grate as well, right now it’s about 16 inches from the tip of the 2" nozzle to the mouth of the gas exit. Right now my grate will essentially be a cage around the exit pipe with a solid top to force the gasses around to filter through more charcoal.
I know my units are simple and I yeah I beat my head against the wall over this all the time. As its my nature to over complicate the crap out of everything. So now I beat my head against the wall any time I get the great idea to change stuff. I have to keep reminding myself “Stop fixing it stupid!” lol.
My main concern is the issues that Gragas reactors had, and because of the straight down direction it can blast right through the grate. I haven’t ran the gasifier yet, mostly because I don’t have a blower setup strong enough to really see it’s potential.
I also don’t have much reserve volume above the nozzle as it sits and I can’t help but feel if I went for standard sideways nozzles I could set them to maybe a 13 inch or 10 inch to grate level and see no issues. Example, a Svedlund had as much as 18 inches between nozzle tip and grate, but a Mako with a pipe ring had about a 12 inch distance if I recall correctly. I’ll edit after checking if I’m wrong.
Edit: looks like the Mako S1 had a 10"x10" cylindrical portion between the grate and the nozzles. That was the 2.5-4 liter sized units.
You only need one nozzle. I think adding more may result in just adding more complexity with actually less performance.
Yeah I think you can lower your nozzle though 8 to 10 inches above the grate is where mine sit at. Keep in mind the air even with the nozzle pointing straight in the air does not follow that path for more than inch after leaving the nozzle. It will draw down immediately. The larger the nozzle does not necessarily limit how much air you pull in but the velocity. To big of a nozzle then yeah the air incoming will drop hard and not penetrate the fuel. Too small then you will run into limitations of air flow but high velocity. You want to find where that limiting air is penetrating but making more gas that is expanding from your fuel making up for those restrictions of the smaller nozzle size. If that makes sense. Even though your pulling in less air you are making more going out with more energy density.
1 inch pipe is way to big for a down draft small engine gasifier. 1/2 inch pipe has worked excellent so far on mine for both charcoal and now wood.
Ah ok, I have not gone there yet But I will soon as the first M-4 is just waiting on filter system. On those units I have revisions to add two size nozzles. The 1/2 inch NPT pipe and a 3/4 Im really only guessing and judging from the size or length of the unit. I think 3/4 pipe will be plenty larger enough. But we will see what happens here soon.
Just a little bit of area crunching comparing the Mako S1 with my two different nozzle ideas.
Mako S1 used 4 14mm nozzles, and the combined area is 615.75
A single 25mm(1") nozzle would be 490.87, two would be 981.74
My 2" 50mm nozzle has an area of 1963.49. WOW.
I did all of these in mm size
I was using Koens spreadsheet earlier and found I was barely getting double digit air velocity with the Sierra at cruising speed RPM. Not great if you want 25m/s.
One single 25mm nozzle iirc gets me about 30m/s (based on memory) at cruising speed, so maybe just one of these is enough.
I quit crunching numbers a long time ago. It dont work might get you close but the real world is real world. I can just look at it and use good intuition what will work and Im usually right. Wood gas is not linear, fuels are not linear nor are the they the same. Just build and use what you think will work and have a back up plan in case it dont or make it so you can adjust and or adapt.
I just use the numbers as a general guide. Like the 25m/s idea at cruise. It’ll help me figure out as I go along and eventually I’ll be able to size a gasifier by memory.
But I will soon as the first M-4 is just waiting on filter system. On those units I have revisions to add two size nozzles. The 1/2 inch NPT pipe and a 3/4 Im really only guessing and judging from the size or length of the unit. I think 3/4 pipe will be plenty larger enough. But we will see what happens here soon.