Just want to post this, since I drew it for Max last night. His thinking is, the bell shape would create a cavity, shielding the nozzle tip from direct contact with the glowing coals, and preventing nozzle erosion. If the bell is wide enough, it will also be outside the hot zone.
Max had previously drawn this one, same concept.
Seems simple to make, maybe somebody should try one.
Interesting! I’ve been meaning to build a simple fire, perhaps I’ll try this. Seems like you are now drawing the gas directly from the reaction zone though instead of filtering it through the cool char. Is that desirable?
That is true, the gas exit temps will be a bit higher this way. It should burn just as good once cooled. You do get some preheat of the air, and the char in the hopper.
The nozzle should be high-speed enough to create turbulent flow in the char, and get reasonably deep penetration. This means the active lobe will be more teardrop shaped, and hopefully not too wide. That will force the gas to filter through more char, and should cool it a bit too.
So the “gas out” comes from inside the bell? Wouldn’t that only expose the top surface of charcoal to the gas flow and keep the bulk of the charcoal to reducing the gases? I very well might be wrong, but that seems like all you’d get is very high quality CO2.
So why not maintain it as an up draft and use the cone for the stated purpose but have the gas escape out the sides and travel up through the charcoal… hmm I would have to redesign a bit. Someday maybe. Hope someone tries it…
That;s kinda what I was thinking. Also, if the bell is too wide, will there be a problem with the char flowing down?
I have been reading up on this and would like to ask why no one seems to have tried to make a water cooled or air cooled tuyere.
See Fig 40 in this PDF document for an example.
Well, just go back about 5 years and check out Gary Gilmore’s unit. He wrapped the nozzle in ceramic. The output gas must flow through a layer of glowing charcoal above 900 degrees, so in Gary’s unit, there is a screen wrapped around the inner nozzle and the concentric outer nozzle. Martin Payne and I built one of these as our first charcoal unit and flared it for hours. Somehow we missed the part where Gary said the charcoal must be between 1/8" and 3/4", with the fines screened out. (We know that now!) He recommended hardwood charcoal, and we got that part correct. I also built the special filter he shows, with an outer part that acts and a cyclone and a cooler, and then gas at the bottom is sucked up through charcoal and then a foam filter. The inner portion is filled with the same sized charcoal as used in the reactor, and being very porous, would grab and tar and water vapor in the wood gas. A recycled Freon can at the very top holds open cell foam rubber at the final filter.
The second video describes the fuel hopper with auger. ( Our copy did not bother with the hopper or auger, but later on when I built the Simple-Fire, I did build sort of a hopper that could be filled quickly.) Gary lights the charcoal with a “quick match” cotton string that has been dipped in black powder. This is the same technique Martin used last weekend at the Mother Earth News Fair in Belton, Tx to light the charcoal gasifier on his Honda motorcycle. In the second video, Gary is dropping small wood chunks down the inner nozzle tube, explaining that wood contains hydrogen, whereas pure charcoal does not. This gasifier can run engines up to 40 hp, and is the same one he had on the VW Beatle. In this video, Gary is running a twin cylinder military electric generator which he starts with a rope wound around a pulley, with help of a bit of gasoline priming. (Electric start is really nice!)
In the third video, Gary shows how he runs the engine exhaust through a coil in a bucket of water and feeds it back into the charcoal air intake leading to the nozzle, where water vapor and carbon dioxide help cool the nozzle. When a portion of the exhaust hits the glowing charcoal it will be reduced to CO, H, and methane, which means more fuel, less charcoal consumption, and helps keep the temperature down. He has dropped various fuels down the input nozzle, including small chunks of wood, pellets, corn, oats, and plastic. He had a mixture of these fuels soaked in used motor oil that he threw into the hopper. It just has to go through the auger. It doesn’t smell…no smell of plastic or corn. The last part of the third video show the auger feeding this fuel down the inlet nozzle into the glowing inferno.
These three videos were filmed by Gary Parrot and posted in 2011. Martin and I found out that a person can get carried away with dropping stuff down the inlet nozzle…
I get a 404 “Not Found” error on that link.
Hi guys. This is a drawing I have in my pad. I can’t tell you when it was done, long enough ago that I don’t even remember doing it… As you can see, at the time I credited it to Max. It may address the things you are looking at from a stand point of not cooling the gas. Other wise very similar. TomC
Yes, Gary’s design is very similar, but it doesn’t have the bell to shield the nozzle, which is Max’s main point.
I suspect as long as the nozzle is flowing fast enough into the char pocket, all the oxygen will find hot char to react with and the gas will be produced just CO. Probably a much smaller nozzle than what Gary shows.
Brian,
Me too. Had to strip the end and google search. Try this: http://www.drtlud.com/nml-resources/BEF-BK-DrivingOnWood2006.pdf
This is a great read.
I understand what is proposed, and it is putting a crimp in my brain. Here are some things to consider: High velocity air would cut deep into the charcoal. Remember what our sand blasting nozzles do when they hit sand? Imagine blasting ash and small particles everywhere. In this case, the heat would be intense which would form slag. A cyclone could remove the particles. Perhaps multiple cyclones feeding a settling box? When we clean out the Simple-fire charcoal gasifier by removing all the charcoal and screening it again, there are large amounts of fines as well as hunks of slag. I imagine these fines are trapped by the charcoal bed above the nozzles in the Simple-fire. Without passing through charcoal, these fines would just be sucked out? I suppose the biggest question would be whether or not the output gas in the bell nozzle system would be diluted with the incoming air. So, who is going to build a bell nozzle test set-up? Has it been done before?
I wish Gary would chime in on this. Where is Gary?
It must work like Beetlejuice; Gary,Gary,Gary…
Clinkers form when you melt the ash.
This is a temperature range above what is actually needed for proper gasification.
please correct me if I am wrong ( armchair gasification expert here ).
If you cool your tuyere it will not melt right?
If you use the steam generated in the process of cooling your tuyere then lower the temperature in the oxidation zone and have less clinker formation.
This is what I have been reading.
In practice I have not seen anyone do it.
Also air velocity through the tuyere is less important in charcoal ?
On the drawing Chris did it shows the nozzle inside of the bell and on the second drawing the nozzle is shown as protruding from the below the bell , what do you think would be the way to go ? if as Max has said the bell would be for shielding the nozzle .
I will make something up once I have some spare time and a spare tank to make it air fed from the top .
Dave
I am not quite understanding what will make the bell work. won’t the gas and char always burn all the way back to the oxygen source?
Are we all agreeing that glowing coals in contact with the nozzle is what is causing nozzle erosion?
Both drawings are credited to Max Gasman— I hope he will chime in. Either way you definitely will have to control the heat by exhaust gas or water, other wise I see it making one big clinker in the middle. Holding the proper temperature will allow the carbon to be “eaten” away. The funnel may stop the char from refilling the cavity as it is eaten away. With the second dwg. that is just a plate and I think in reality you would have to pick just the right distance for the nozzle to protrude from the plate. The dwg. is out of proportions.TomC
