I think somebody tried a purchased ceramic nozzle. Seems like it broke from the thermal expansion. Now making a thick one out of ceramic might actually work. I would be inclined to add some kind of fiber reinforcing to the mix.
3 Likes
Thats my thoughts, make it thick like you guys are doing here.
1 Like
The only real difficulty is the curing in oven before you can use it as nozzle…
If not proper taken care of, then it becomes brittle or cracks easy , thermal shock sensitive.
However, its fun to think of and test it for…
Some info on fine ceramics:
3 Likes
Yes this is still that very same thick walled Hexoloy carbide tube i bought on ebay , i had a 1 inch galv reducer down to 3/4 i turned the thread out of the 1 inch side so it was a plug fit into the nozzel and then just pushed it in firmly .
Bruce if you remember i did say i would try those sand blast nozzles as soon as i take the old one out , but the way this nozzle is holding out i may have to wait a while longer still , still not got round to building a down draft gasifier yet and was going to use those 3 nozzles on that one .
I had tried many types of materials on my nozzles over the past years and the refractory cement i cast around a tig nozzel worked the best, a working life of around 100 /200 hours , it was a large heavy lump and in the end would always turn to molten glass or crack and break apart ,
Matt i was going to ask what you have used for a nozzle on your latest cool charcoal build ,but if you want reliability for cheap then you be hard pressed to find something as long lasting as these tubes .
https://www.ebay.com/c/1832907530
Dave
7 Likes
You need a soft-metal or wood- end poker!! Thanks for the nozzle update, looks like “A Winner”. 
3 Likes
I think it would handle the temperature. But alumina, aka porcelain, aka aluminum oxide is brittle, and very sensitive to thermal shock, as Koen says. In foundry It is used for assay crucibles, because it does not contaminate the molten metal.
Clay-Graphite crucibles are most often used for steel and ferrous alloys. They are brittle and subject to thermal shock, but they do not react with molten iron.
For every day melt and pour foundry work involving nonferrous metals silicone carbide crucibles are most often used. The material is also sometimes called Starrbide, or carborundum. Many grinding wheels are also made of it.
Rindert
4 Likes
I tried a lot of ceramic nozzles. They always broke from thermal expansion. I like stainless steel.
5 Likes
For me its mass and heat disipation, but never heat waste! Sounds familiar? (WK)
5 Likes
Yeah so far I have not had any degradation of the SS Nozzle Im using. However, Im in Michigan and we grow gills in order for us to breath in the humid air. So it maybe why I dont know.
3 Likes
I just ordered some to try. I really like my water cooled nozzle, but some applications cannot handle the water storage, such as my Gravely tractor. In that unit, I use exhaust gas to cool the SS nozzle but your ceramic ones should not need that. thanks for experimenting and sharing the results with us. Looks like this nozzle can really “take the heat”!
Gary in PA
7 Likes
yup, same here, if there is a good heat transfer away from the nozzle tip, then no vitrified ashes glued on the nozzle.
ceramics don’t like rapid heating
All these shared experiences, makes it worth to read…
Me too, i like your way of building things and tinkering around…
the eternal quest, seeking for perfection…
For your purposes Matt, build extremely cheap and sell on mass…
You won’t believe how many want to try, but won’t spent the bucks… so build for the dimes…
5" pipe, low cost…
6 Likes
Thanks Koen. And nozzle horizontal or vertical? Water or exhaust?
2 Likes
Jeop,
I couldn’t decide, so I use it all and it all works. Kristijan’s flute nozzle allows air to enter horizontally, exit vertically and allows water and exhaust gas to flow in with the air—so far the most durable for me.
3 Likes
Thanks, the more I read about charcoal, the clearer things get. In short it doesn’t matter much how you build your gasifier, it will work. Nozzle is a wear-part. Making charcoal the right way is a challenge.
6 Likes
I dont know if this how you guys build your nozzles or not. But what I do is I get a reducing bushing and punch a tap into the reverse side of it. On my unit I have 1 inch coupling weld to the gasifier and then have 1" X 1/2" bushing with the reverse side tapped for 1/2" NPT and I can then change out the jets easily.
A 5/8" 12 point socket will fit the square end of the tap. You can then put that socket on an impact and drive her right in.
3 Likes
On my lawn tractor gasifier I welded the center ring of a inch pipe union to the side of the hopper. The outer 1/3rd of the union turns in to hold the inner 1/3 of the union in place which in turn holds the nozzle assembly which is removable by turning out the outer part. Not sure my description makes sense but it works.
9 Likes
I get it very nice Don!!
2 Likes
Thats some interesting stuff for sure! Im nor sure how it would react in agasifier, but fun to try.
3 Likes
Steve Bowman messaged me about our Kristijan (flute-style) nozzles and I wanted to capture my reply/thought somewhere so I could find it on DOW:
Steve,
Yes, cleaning from the top of the barrel is no problem. I have not opened the stove pipe flange at all. If I were to do it again, I would use a piece of 1-1/2" schedule 80 pipe that fit snuggly inside the barrel and fasten to the barrel with 1-1/4" to 1" reducing bushings threaded into both ends through a 1-1/2" I.D. flat washers. I like having 2 inlets for air cooling, clean out with vacuum cleaner and separate water inlet.
4 Likes