Smelting furnace

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twangin4u

Member
Joined
Apr 7, 2021
Messages
18
I'm new to smelting. I've come across some black sand that I want to assay and decided to build a smelting furnace. My problem is that it's not quite getting hot enough to melt the sulphides. The flux melts but the material just gets gooey and orange. I'm using a lead collector metal and Chapman flux. Here are some photos of my home made furnace. Maybe someone can suggest any improvements to get a few hundred more degrees out of it...
 

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Yea that will be the lid when I get more wool.. but for now I was using the bricks that u see in that same picture sitting in the ground. I just stacked them on top in a way that left a3x3 hole in the middle
 
I have those same bricks lined on the bottom and I'm wondering if those bricks are absorbing too much heat
 
I try never to use untreated quarts' wool.
Even the hardeners are only partially effective in preventing degradation.
A good layer of castable refractory cement is best.
Or you will find a very fine dust is formed that will cause silicosis in very little time.
https://en.wikipedia.org/wiki/Silicosis
It also makes a bombproof furnace that will last for years.
 
twangin4u said:
I have those same bricks lined on the bottom and I'm wondering if those bricks are absorbing too much heat

Are the bricks soft and light, or hard and heavy? The hard heavy ones are often used to build the insides of fireplaces. They will indeed absorb a lot of heat. The soft light ones don't absorb nearly as much heat.

Dave
 
justinhcase said:
A good layer of castable refractory cement is best.

Yes I agree - other wise you will find you soon need to replace the wool - the wool alone is not really fire proof it is really only fire resistant - without a layer of refractory cement over the wool you will be replacing the the wool sooner rather then later

Kurt
 
It looks to me like your burner (flame) is entering straight into the furnace :?:

the flame needs to enter the furnace at an angle (as shown in the pic) so that the flame swirls around (like a cyclone) inside the furnace (walls) & the crucible providing even heat all the way around the furnace & the crucible (once the furnace is FULLY heated)

When the flame blows straight into the furnace it is heating the flame side of the crucible more then the far (non flame) side of the crucible - which may (or not) cause problems with the smelt chemistry as well as may (or not) cause the crucible to break (uneven expansion of the crucible)

Also - (& I may be wrong) but it doesn't look like you have a way of adding air to your burner - without being able to add air to your burner flame you may (or NOT) be able to get the furnace up to temp

Kurt
 

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Just noticed one more thing based on your bottom/last pic

there is NO refractory (wool/cement/brick) in the bottom of your furnace - that means heat is sinking (transferring) out of the furnace to the ground the furnace is sitting on

Edit to add; - in other words - you may (or not) be getting enough heat out of you burner (unless you are able to mix air with your gas) your not getting even heat in the furnace &/or around the crucible due to "straight on" flame entry into the furnace - & you are loosing heat due to not having furnace fully &/or properly insulated with refractory

Kurt
 
Yes insulation and a vortex flame inside do help a lot.
But to start with: Enough capacity in the burner and fuel that can get hot enough. What are you using as fuel?
 
kurtak said:
justinhcase said:
A good layer of castable refractory cement is best.

Yes I agree - other wise you will find you soon need to replace the wool - the wool alone is not really fire proof it is really only fire resistant - without a layer of refractory cement over the wool you will be replacing the the wool sooner rather then later

Kurt

Ok. Ordered dry cement. How thick should I apply it?
Thank u
 
Martijn said:
Yes insulation and a vortex flame inside do help a lot.
But to start with: Enough capacity in the burner and fuel that can get hot enough. What are you using as fuel?

Propane
 
kurtak said:
Just noticed one more thing based on your bottom/last pic

there is NO refractory (wool/cement/brick) in the bottom of your furnace - that means heat is sinking (transferring) out of the furnace to the ground the furnace is sitting on

Edit to add; - in other words - you may (or not) be getting enough heat out of you burner (unless you are able to mix air with your gas) your not getting even heat in the furnace &/or around the crucible due to "straight on" flame entry into the furnace - & you are loosing heat due to not having furnace fully &/or properly insulated with refractory

Kurt

So I could leave the brick as a platform and just put a layer of wool with cement over it, right?
I'm also getting a fluttering sound from the burner.. I'm guessing because inadequate air intake?
 
Updated furnace

Find out tomorrow if it performs better...
 

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What did you use to cut off the top of the tank with? I have a Helium Tanks I would like to used.
 
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