Happy birthday Koen, I enjoy seeing your projects.
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Hi guy’s,
Thanks for the wishes, only Carl… progress i make in age ? 
anyway, charcoal/chicken tastes so good on the dark side, lets vote for GG to be dark vader
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Belated Happy Bithday. If Gary is Dark Vader, does that make you “Looken Skywalker?”
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You guys made me laugh 
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Alumina Tube Nozzle Failure
The post near the top of this topic shows the nozzle design I have been running:
Continuing the discussion from Nozzles for Charcoal gasifier's:
This is basically an alumina tube protruding about 2 inches from a steel pipe.
The nozzle has failed. I just removed it from the gasifier.
Here is what it looks like.
As you can see, the alumina tube finally cracked and/or eroded away. Now, there is less than a half inch protruding. The steel tube as also started to melt / oxidize now that the heat lobe is so close to it.
All in all, I would estimate that there is less than 10 hours run time on this nozzle.
This is a pretty disappointing result since the alumina tube is a relatively expensive component.
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Here is the design I plan to try next
This is basically a TIG cup stuck in the end of a metal hoze barb.
I decided to try casting some refractory cement around it.
Here, I have stuck it into a coke can and put refactory cement around it.
However, I am not optimistic that this is going to work because I don’t have the right kind of refactory cement (castable refactory). The kind I have is just more like mortar for fire bricks. But, we will see what happens.
In the longer term, I imagine I will be moving more towards a hearth style design. But, I already had this stuff on hand, so thought I would try it.
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I guess any refractory cement shuld work if there is no ctacking. So what l wuld do in your place is to make a wire or fiberglass cage and cast the cement in it. Much like is done with every cement casting.
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Well, it has been about 3 days, and the cement is still not setting up at ambient temperature. There is a hard crust on top, but I can tell that it is squishy below that.
In the mean time, we took the damage alumina nozzle, pulled the alumina tube out of the steel tube, turned it around, and coated the entire assembly with about 1/8 inch of the refactory cement. This set up promptly.
Since we are sitting around waiting for the other thing to dry, we stuck this reconditioned nozzle back into the gasifier.
Did a test run tonight. Cranked up and ran for an hour without touching anything. Ran great. As usual, we stopped the test when the gasifier outlet reached about 150F.
Don’t know yet how well the nozzle held up.
Note that we are currently running without any exhaust gas return and without any water drip, so it gets pretty hot.
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Hi Kyle , strange that after 3 days your mix has still not gone off , but maybe because its the mortar type after air drying for a while it will need gentle stages of heating to get it to cure completely .
What you have done is simular to how I do my refractory nozzles and to be honest unless I need extra power I don’t even bother with a water drip and my nozzles tend to last around the 100 hour marks , some a longer even .
I am still in the throws of testing the thick wall mild steel tubes , I just got side tracked away when I had an engine that started behaving differently and so just to get things straight I put one of my old nozzles back in so as to find out what my problem was , after sorting the problem out its been running so well the past month I have not bothered to swap it back over as yet .
I also found out that my 1 inch nozzles also work incredibly well on very small engines , I have just converted one of the new 24 volt Dc generators to charcoal this week and found that its running very well indeed on the nozzle set up designed for my larger engines , in fact this 87cc engine has lost only a small amount of its output power and yesterdays run of 4.5 hours only used up 4 inches of charcoal , I have uploaded a short video for a friend to see ,take a look if u want , ignore the poor audio as I had to compress the video small and its affected the sound a bit .
Dave .
https://www.youtube.com/watch?v=39rloT3uGac&feature=youtu.be
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I want to post an absorvation regarding on my type of nozzle (post 21). There was always a biger fuel consumption on the last hole thain the rest. Didnt give it that much atention but with such hot days as we had last week it became more of an isue. The last nozzle exposed glowing char faster thain the rest thus shortening the cars range ( gas got to 55*c whidouth glowing char exposed due to high outside temperatures). l looked at the air intake and the end nozzle was glowing dark red (as always), the first was cold. Thain it occured it to me. I have made a difusor! How culd l not think of that? The air intake is smaller thain the nozzle pipe so at high air consumptions the velocity of the air pulls all the air to the end of the pipe where it hits the wall and goes trugh the nearest nozzle! the first one gets starved of air.
Just a thing to consider if anyone starts building a similar nozzle setup.
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Kristijan,
Thanks for this observation. My MGB nozzle is based on your design but is 1 inch ID straight through AND air enters from both ends (post 77). It will be interesting to see how this arrangement performs. I’m within a few hours of first fire, but I am currently in Oklahoma visiting grandbabies.
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I wanted to say but forgot to that l think you have overcome this problem with haveing air intakes from both sides.
Dont forget to document it! We have waited to see this work of art for a long time!
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Yes, the long wait has been painful for me. The next possible day to work on the MGB char-iot is August 3. On the subject of nozzles, I have some old 2 inch ID cast iron drain pipe with a wall thickness of about 3/16 inch. I hope to try it in a small gasifier someday with a slot instead of holes. The diameter is great enough to allow a crescent shaped blade to be inserted to clear clinkers.
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Hi Bruce, Kristijan,
The path off the least resistance… the air flows where the vacuum pulls,
Keep the path unrestricted unto the nozzles ( input orifice bigger then the sum of nozzle orifice’s)
In your case Kristijan, you’ll have to look further downstream in your design… remember my observation on your nozzles clogged up ?
First recommondation: enlarge your air intake to eliminate restrictive vacuum. ( other then the nozzles )
Rule of thumb Nozzles are 70% of the air intake size
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The clogging can not be an issue becouse l poke the nozzles every day now (thanks Bruce) with a poking wire.
The path of least resistance yes, but thain the closest nozzle to the airtake shuld get more air not the other way around. Allso the nozzle tube is about 10 cm dia. 40cm long so that isnt very restrictive. But the air intake is 3/4" so at high air velocitys it creates a Venturi efect. Imagine a propane burner difusor. The pressure is lower at the air intake thain the the burner tip.
Unfortunaly l can not enlarge the intake. lll try to put a restriction in to swirl the air a bit rather thain have it all rushing to the back.
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Hi Kristijan,
Based on what i have seen on your pictures and from your observations, i would suspect following happening in your system: ( my personal obeservation on your case)
after cleaning and starting, you will have all 4 nozzles working, but the first one will get clogged up, then the second and so on, due to your high temperatures,
The last nozzle will not clog so easy because of the increasing velocity after the clogging from 1, 2 and 3…
( cutting torch effect, vissible in your earliar picture.)
since your engine creates a vacuum above the nozzles and your airinlet is bigger then the 4 nozzles, its more likely to have an even divided force on all your nozzles ( same vacuum on same hole size )
Any turbelance in your nozzle pipe would be minor due to the airspeed increasing on your 4 nozzles at start up.
In my opinion, even neglectible since you have a nearly constant flow and not pulsating from a single cylinder…
anyway, its a nice phenomen to study into…
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l think that is exactly what is happening. But the fact that the last nozzle always stays clean the longest got me thinking. Like you sayd, it shuld be the opposite ( path of least resestance).
The real question now is what to do about it. l was thinking to thread the nozzles and put smaller inserts in them. This wuld increase air velocity and aid slag breaking. Maybe put a smaller nozzle on the last hole zo equalize air flow on all four.
By the way, l was playing a litle with water injection today and l got the speedometer from usual 95km/h (60mph) on plain chargas to 110km/h (70mph) with water. lnjected about 4l/100km (1,5 gal/100miles ) of water. Charcoal catching world speed record on wood. Brigt side beware 
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Copying this from my post on another string to keep this info under nozzles:
My nozzle is 4 vertical holes in thick-walled copper tube passing through the reactor and sucking air from both ends. Copper because it has been used successfully for crude iron smelting.
“A suggestion by Dr. K. Smith on the possible use of copper tuyeres historically led to some experimentation with this material. Several tuyeres were forged from differing thickness of scrap copper plate and tested at a workshop in February 2005. … During this workshop, Sauder, Williams and McCarthy worked with a tuyere forged from 1/4 inch thick (about 7 mm) plate. The forming process created a conical shape that varied in thickness from roughly 3 mm at the air supply end to about 7 mm thick at the smelter end. … The interior diameter was approximately 20 cm in the smelter. This copper tuyere proved extremely durable. the high conductivity of the copper allows it to radiate away the heat its working tip is exposed to.”
I hope to have my MG running on this nozzle by the end of August. Don’t hold your breath, I previously thought I would have it going by the end of May. I fear that there may be a good reason that we have not seen copper nozzles in gasifiers (other than war-time scarcity). Time will tell.
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Hi Bruce,
Really enjoyed reading this and it might opened my eyes for the reason why…
Thinking: Could it be that; the thermal conductivity capacity from the copper, prevents the heating from the glowing because the inside of the nozzle is fed with cooler air ?
This also can explain why some nozzles, be it ceramic or others, crack from the temperature stress between the inner and outside of the nozzle
On other “strange” observation; one of my test sets, stainles 1/2" pipe, does not “touch” the glowing carbon and seems to stay “in-affected”
Could we “assume” that, glowing carbon from the charcoal, strips away the carbon content from metals, in contact with oxygen from the incoming air, even some catalyctic processing / thermo chemical reactions between metals and the glowing carbon ?
The nozzle from my “water pump demo set” is a reducing 1" to1/2" welding piece steam pipe material, after so many hours still not corroded away…
the nozzles i use for my “farmer cooking sets” are cast grey iron nipples, 1/2", drilled and grinded to fit the purpose. waiting for the next results afters hours testing…
So many things to observe… so much still to learn… real life, not lab scale…
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My latest uses a cast iron power steering (vane pump) housing. I have not had much time to play with it yet, Only about 5 hours on two small engines( 21/2 hp Kawasaki flat head and a 3 1/2 hp Subaru /Robin (Fuji) flat head. The nozzle is vertical. I have not used any water or exuaste yet. I have only run it about 5 hours so far and have not dumped the char to inspect yet. It dose seem to pull a great deal of heat out of the bottom of the gasifire. I have plans for some insulation and a water drip. I hope toplay with it some more real soon. I have built a new DC charger from a 8 hp Briggs and Stratton flat head( smokes and drinks) and will need an overhaul eventually. It runs two 150 amp generator starters from a tow truck car starting unit. In a short run I was putting 150 - 180 amps in my battery bank till one of my home made wired together belts failed. I will need a charge controller to protect my batteries before further testing. This and my 3200 att inverter should make a nice little generator. I have a third one of these generators to couple with a 5hp OHV Tecumseh engine and 2200 watt inverter. That will be my first OHV engine. I have run 5 different flat heads on chargas so far.
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