Hi, Kristijan!
4.3.2017
The whole bottom would be flat plane! The 3 ashboxes would be inside the rectangular lower square-tube frame.
Who are the two that you mention. I would like to see if I can find pictures of what they have done.
âcollecting pyrolyse gas under an overhanging balcony ringâ "When I pointed this benifit out to two of them setting up the condition for constant recycling/refining (???) âthey insisting their overhanging ring was just for fuel particle flow guidingâ. It does not sound like they understood what you were saying in the end if they still felt the overhang was directing the flow of gas. As usual I have tried hard to follow this discussion but have to say at this point I am totally lost.
Let me throw what I think I have heard here. Number one, the only way to get rid of tar is to burn it. You donât filter it out or condense it out. Burning takes place up in the oxidation zone, near the nozzles. Tars can be pulled down towards the restriction between the nozzles and possibly miss getting oxidized. If you put this overhanging ring just above the nozzles, the oxygen will come through the nozzle and meet a certain back force that will push part of the oxygen along the nozzle to the fire tube. When it hits the fire tube, it will tend to go in all directions. The over hang will stop the motion of the oxygen from going up and it will follow down towards the restriction, burning any tar that may have passed between the nozzles.TomC
âAs usual I have tried hard to follow this discussion but have to say at this point I am totally lost.â
l must admit, l was scratching my head the last few days too. l hope SteveU explains his thods a bit.
âTars can be pulled down towards the restriction between the nozzles and possibly miss getting oxidized.â
This is exactrly what l was thinking about a lot lately. l have some ideas, and l have some more education to do before l put mind to metal, but for now let me just say l am drawing my inspiration from @bsoutherland air curtain smoke free charcoal retort, Imbert and WK gasifiers.
Kristijan and Tom,
Seems like we are those three (not so) wise men the prophets are refering to.
Steve and Max,
I made this scetch when I was building my hopper and thatâs what it still looks like.
So if I were to make my lower funnel narrower - smaller diameter than the burntube - I would get an âoverhangâ or a âbalconyâ above the turbulent nozzle area. But what would the benefit be? Thatâs still hidden in smoke to me. Would that prevent oxidation products go up the chimney (into the hopper circulation) or what? Wouldnât that be a good thing - being able to condence even some chemically bound water from the wood?
Straighten us out, please!
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Aha! It seems your superior experiances with the topic and the foregin interpretation shed some light to my mind! Love the direction this talk is goeing to 
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Hi, Observers!
5.3.2017
We usually try to undestand ânewâ fenomena with help of more or less understood earlier observations.
The better and more thorough an observation in one case is, the easier we understand the essence of it in new circumstances.
We all have played with air and steam beams in different settings? That should have learned what a rushing beam does???
We donât get it if we only look at the final part of a beam.
The important part is in the beginning of the beam! IT SUCKS!
This sucking is the useful phenomenon we are utilizing in a hearth.
It collects 3-dimensionally âreturngasesâ from the the center glowball.
The âbalcony ringâ just abowe the nozzle-tips provides a convenient free collection route for the out pouring gases from the center, for renewd in-blasting by the succing beams.
There is absotutely NO OXYGEN in the return gases, they are productgases from the intence glow-pitt.
But they pick up pyrolyse gases on the upper return route. (From abowe the glow-pitt).
On the lower side there is a mix of CO and CO2 etc.
And competing with the general down draftâŚ
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Hi, Kristjan!
5.3. 2017
Yes, ruffly so, but the balcony-edge has to be almost touching the tip-ends, otherwise fuel avalanches in behind the nozzles, and the collecting âvalleyâ will be blocked!
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Hi, Kristijan!
5.3.2017
Well, the collecting from the zone abowe the nozzles can be improved if the balcony is made like PEPEâS funnel in the lower part inside the hearthtube diameter.
But tight enough! 5 â 10 mm maximum between the pins.
Max,
Very good explanation on the nozzleâs ejector effect. We have now learned a balcony will improve the circulatory recycling of the pyrolyse gases. Ok - but my question was rather whatâs the final benefit, - chemically, heat/material- wise or other? My guess at this point is itâs about more effectively burning the tary gases? This would suggest a top plate petruding inside the burntube perimeter.
EDIT: But with an effective monorator hopper most tary gases will rise to be condenced, right !
Hi, Jan-Ola!
6.3.2017
If we donât have a collecting âfree-flowâ (for gases) ringchannel along the hearth perifery on the nozzle height, (nowhere else!)
the nozzlesâ succing area does not reach out backwards all the way to the hearth walls!
Instead, gases returning from the hot center outer parts are easily tempted to join the general flow downward and avoiding a nessesary revisiting of the active center glow.
And there is no significant temperature rise between the nozzle-tips and the heart wall!
With other words: A passive zone for targas to creep down and around the hottest center.
That is, so long tar and char hasnât formed an impenetrable âcokewallâ, but that can take 50 hours to form!
Tar gases rising along the center line up in the silo wood will condense on cool wood and return down until the temperature drives the tar gas into the cooler mantelâŚ
A sloping âPEPE grillâ just abowe the nozzle-tips will âsaveâ a part of it for âchemicalâ purposesâŚ
A protruding horizontal ringplate, on what height and how deep?
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Thanks Max,
Iâve done some digesting now.
However this svirl void above nozzles is probably not for my present setup. Iâve got too short nozzles (1/4") to benefit from it.
Forget about the protruding top plate. I was talking in WK terms and just thinking out loud. Itâs too far above nozzles anyway for the the fuel not to cave in.
Thanks again, for sharing your knowlidge.
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The first time I heard of this concept was when Max brought it up in my 1995 Geo Tracker thread posts 300 to 302. I think I am going to try this on my 1996 S10 project
[quote=âgasman, post:303, topic:1191, full:trueâ]
Protruding or not, there is sucktion from all around the air beam.With no preference from which direction.
But, if you have a horizontal ring channel, relatively free from indropping chunks, there will be a âpreferenceâ route for collecting pyrolysis gases between the nozzles.
This way, a more uniform collection of pyrolysis gases happens on the right height and are redirected with the air-beams back into the âwhite h-llâ.Better to not make any significant protruding, as the sucking is best at the air-beam ârootâ!
I see it happen in my hearth as the silo funnel is slightly âover-roofingâ my nozzle-tips.
Under the âroof-edgeâ the pyrolysing gases are effectively collected and re-blasted into the white glow.
In a hearh with only 4 nozzles this phenomenon plays a remarkable role to get tarless gas at long idles and town traffic jams⌠idling at ~800 RPM.
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Jan,
my brain is slowly turning sour from all the thinking and research lately, but l squeezed a idea out of it, regarding you saying this effect culdnt help you.
Well, perhaps it doesent help you on you current sistem, but it culd help in your stile of gasifier (with the inner gutter and cool hopper)
Agen, a slopy skech of mine 
l think if posotioned right, the air nozzles culd act like venturi ejectors, helping to draw the cooled, dryed gas from the outer hopper in the hot zone, thus helping the natural gas flow you showed above. Just a idea 
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Don and Kristijan,
I agree that the ejector phenomenon is still present even with short nozzles. What I meant was that short nozzles make it less likely to let tary gases pass behind and between them. The heart wall will have to take more beating from the heat but thatâs why I went with the sacrificial plates.
I might try a balcony on my next build. The only downside to it that I can see - in a small gasifier - is narrowing down the fuel flow even more.
EDIT: Just one word of caution: Having the nozzles close to the monorator return loop will create a very hot enviroment for those tary gases and bake the tar. My return void is about an in inch wide and plugs up totaly after about 1000 miles. Already half way into that distance I see less hopper temp and less juice collected. I have to punch out that hard ember-like tar from time to time to free the void. A bit messy working inside the hopper. As soon as the weather allows I will rip my funnel/inner silo out to attach higher spacers.
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Good point.
On all of the above.
This tarry gas passing between the nozzles is what l am currently trying to eliminate. Will see.
Oh, l forgot all about you haveing sacrificial plates. How are they holding on? Any sign of them wearing out?
This picture is from when I installed the sacrificial plates. They hold on only by the nozzles and brackets. The burntube was later cut off the same hight as the plates.
I havenât checked them out since before christmas but I saw no wear on them at that point. I think ss may have lower melting point, but it seems it doesnât flake from high heat. So far so good.
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In KristiansKâs first illustration ~9 posts above . . .
undercut the slope and extend it to nozzle face to create an underslope cavity. Now make the upper orange flow arrows circular.
As Max G said the trapped pyrolis gasses will be held here circulating and drawn back out to the nozzle face active area for long chains breaking down.
Heat and turbulence oxidized then into reduction area input gases of CO2 and H2O HOT vapors. AND MORE oxidization zone created system heat!
I have seen this âsystemâ work well even with flush mounted nozzle faces so long as that overhanging cone space is formed.
Cone slope will get HOT. Vaporizing upper system dripping down tars. Tars dripping down off the cone edge falling right in front of the nozzles blast.
Nope. No names, named. I get myself in enough hot water as is. System illustrations and pictures will show who is doing this intentionally/unintentionally.
As said this will greatly expand the turndown ratio of a system.
J-I-C Steve Unruh
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Hi Kristijan, my plates are looking good. The only thing to remember is make sure you have two opposite flats cuts on any circular choke plate or disk you use, so you can remove them. My plates are bolted at the top and have a little gap behind them at the bottom from the high heat. With 12 of them in place I lost about a 1/2" of diameter at the bottom from heat. Better to have the plates to take all the heat than the fire tube wall. I cut my circumstances on my choke plates smaller also. The ash fills in the voids.
Bob
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High, Kristijan @ All!
7.3.2017
This principal, with injecting nozzles has been used in south-western Finland during the 40-ties, commerciallyâŚ
The only backdraw is, that the return gas from the silo-condenser is cool, and 100% wet; negative factors for airblasts!
The blasting âfreshâ air is dryer, but their mix is heat consuming.
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