Help me build a pyrolysis/incineration chamber

[autumnwillow]

I'm working on a project that would combine a pyro/incinerator in a single chamber.
The idea is simple, close the lid for pyro, then open it for incineration.
This is a very small one, that will be used for high grade jewelry wastes.
The ideal material is Inconel, but since its not readily available and fabricators are nowhere to be found I would be using SS 304.

The sides will be compression sealed with nut and bolt, if a copper lining would be required to further seal the chamber I would add it.
I would use a high pressure stove for this one to achieve the temperatures required.
The top part will have a compression fitting for a copper tube, this copper tube will then go thru a water container for filtration, then the gasses will go out back to either the stove or just in the air (ignited) to reduce pollution.
The thickness will be 2.0mm, any suggestions for this one? Maybe thicker? Or thinner?
This is only 40x40x10cm (for the container). I'll build a bigger one for low grade wastes if this succeeds and will probably be made of Inconel.

Any suggestions would be awesome!
Feel free to use the drawing.
I'll post updates in this thread.

 

[olawlor]

2mm sounds a bit thin for the bottom side if the flames hit it directly, I've found stainless tends to scale and flake away when kept red hot for prolonged periods if there's any oxygen in the service atmosphere.

I don't do any pyrolysis, but could you replace the fabricated bottom with a stainless cooking container? They sell fairly heavy-wall stainless kitchen cooking / mixing containers for almost nothing, which would simplify replacement if the container only lasts a few heats. If you need a different lid profile for sealing, you could weld on a separate ring.

Sealed boxes with a single vent can get very dangerous if the vent plugs up (with soot, creosote, glass fiber, etc), so I'd make sure to have some pressure relief plugs built in, and/or stay behind a blast shield when using it!

 

[Yggdrasil]

The reason to pyrolize is to get rid of polishing wax and such?
Will it be too much smoke if you went directly to incineration?
Less demand for gaskets and less need for an airtight compartment.
If you keep it closed but with a small opening and an exhaust in the gas flame you could get a venturi effect,
creating a slight vacuum in the incineration chamber dragging in a small amount of air helping the ashing.
Doubling the effect and halving the steps needed to do.

Just an idea.

Sincerely Per-Ove

 

[autumnwillow]

They sell fairly heavy-wall stainless kitchen cooking / mixing containers for almost nothing, which would simplify replacement if the container only lasts a few heats.

Sealed boxes with a single vent can get very dangerous if the vent plugs up (with soot, creosote, glass fiber, etc), so I'd make sure to have some pressure relief plugs built in, and/or stay behind a blast shield when using it!

Are there any other materials better than stainless that is not as expensive as inconel and is readily available? I find that most stainless cooking containers are clad types, they have an aluminum core that melts when I use them.

Coating, I've thought of using some sort of ceramic coating, but these coatings deflect heat. Maybe there are other types of coating that can work well to prolong the life of the metal?

The reason to pyrolize is to get rid of polishing wax and such?
Will it be too much smoke if you went directly to incineration?

Yes too much smoke for incineration (shellac, waxes, etc.), and the gold dusts are fine, I want to capture the flue gasses to a water tank for a later recovery of PMs.

 

[Jado]

At the required temps, 14ga mild steel would hold up better. Chemical resistance sucks either way though, and 316 doesn’t grow on trees.

Square corners are typically avoided in high heat applications both for thermal efficiency and for minimizing hot spots.

Neither the copper tube nor the compression fitting will be much fun with 700•+ offgas, but I can’t think of a good solution right now.

 

[Yggdrasil]

At the required temps, 14ga mild steel would hold up better. Chemical resistance sucks either way though, and 316 doesn’t grow on trees.

Square corners are typically avoided in high heat applications both for thermal efficiency and for minimizing hot spots.

Neither the copper tube nor the compression fitting will be much fun with 700•+ offgas, but I can’t think of a good solution right now.

As I see it, it don't need to tolerate pressure. Add an empty chamber with bigger volume then the wet collection chamber, in case back suction happens.

It just need to be "smoke proof". Just add "copaslip"(copper paste for threads) or similar to stop the direct outsmoking.

If you make a bubble chamber where the smoke is released into bubbling liquid it would reduce the back pressure significantly comparing to straight into liquid.

And as Orvi say, round is better in all ways. Less stress, better utilitation of the heat and so on (less volume to area factor).

And 4-5mm mild steel will be easy to fabricate and easy to replace.

Of course, the lower part is the most exposed.

Coat it in linseed, olive oil or other oil if its not going to be used for a while.
It will hold longer.
Even used motor oil can be used

 

[autumnwillow]

I found this coating HiE-Coat 840-M High Emissivity Coating for Carbon and Metals
I'll probably use this coating after making a second one, since its cheap to make anyway. I'll observe the flaws on the first project before applying this expensive coating on the second version.

I'll use 3mm for the bottom, change the square to a round one.

304SS is still preferred over MS/GI according to the numerous google pages I've read, regardless of surface attacks but rather its temperature tolerance.

Thank you!

 

[Jado]

I found this coating HiE-Coat 840-M High Emissivity Coating for Carbon and Metals
I'll probably use this coating after making a second one, since its cheap to make anyway. I'll observe the flaws on the first project before applying this expensive coating on the second version.

I'll use 3mm for the bottom, change the square to a round one.

304SS is still preferred over MS/GI according to the numerous google pages I've read, regardless of surface attacks but rather its temperature tolerance.

Thank you!

304’s temperature tolerance is great at a steady temp, but not good at cycling. MS is a lot more forgiving for intermittent use at high temps, especially if it’s thicker. 304 tends to crack. Limit your research to thermal cycling and it’s drawbacks should reveal themselves.