Non-Chemical Incinerating questions

[JH123]

We just bought a oxy/acetolene Victor setup, most of you guys might have already been familiar with torches and already used them regulary, but this is our first use of one. We took some e scrap material that we roasted in a covered kettle and then attempted to incinerate the carbon from the material in a cast iron pot. I used the cutting tip and the material burnt to a white color bust still appears to be charred ash. The carbon coating on the lid burnt away in no time. Did I read on here that until the material stops glowing red that it is still burning away carbon?

Our torch came with 3 cutting tips, a rosebud heating tip and a single hole brazing tip. Which tip would be best for burning away the carbon? What is the white that shows up after burning away the carbon? Is there something I have to do to it? Is there any way that during incinerating that values can be lost. Any info is greatly appreciated! Joe

 

[maynman1751]

Did I read on here that until the material stops glowing red that it is still burning away carbon?

Our torch came with 3 cutting tips, a rosebud heating tip and a single hole brazing tip. Which tip would be best for burning away the carbon? What is the white that shows up after burning away the carbon? Is there something I have to do to it? Is there any way that during incinerating that values can be lost. Any info is greatly appreciated! Joe

1. Once your material is glowing red cut the fuel and blow just the oxygen on the 'coals'. This will burn carbon.
2. You could try the rosebud. It seems like it would cover more material with flame.
3. The white is simply ash! That's what you want.
4. Is there something that you have to do to WHAT?
5. I've wondered myself if values can be 'vaporized' during incineration!!!!!! I incinerated a batch of ram chips and ended up with nothing of value after processing!!!!?????

 

[JH123]

Hello Maynman, the "what" was the white ash that is left, I was wondering if it is washed off and with what? So you're saying to kill the gas after the material is glowing red and the oxygen will continue to burn with the glow from the embers and rid itself of the carbon?

My need to know question is after I incinerated some connector heads from their rubber holders I am left with pins and black embers and dust from the process, before these are went over with the torch to rid itself of the carbons, are the dust and embers separated from the pins, do I only work with the pins or could the dust hold values? Crow King said he had seen the gold flake off and mix into the powdered dust, is this a normal expectancy of gold plated items? My goal is to rid the incinerated material from any black substances and end up with all white ash, is this correct? Thanks, Joe

 

[maynman1751]

Hello Maynman, So you're saying to kill the gas after the material is glowing red and the oxygen will continue to burn with the glow from the embers and rid itself of the carbon?

That's correct. It may take several times of heating to red and oxygenating to rid carbon. I burn mine until everything is white, then break the materials up to expose the still black remnants and fire them again until all is ash. Unless you have a really hot, long burning fire, that's the only way I know to do it. That's why I was wondering if the values could be 'vaporized' by exposure to excessive heat (like from a torch).

 

[butcher]

When I am talking about incineration of metal powders, I am not talking about burning circuit boards or integrated circuits; in my mind these would be two different things.

This is the way I see some of these things.

I can take a bar of iron and a torch, heat the iron red hot and add just oxygen and burn off iron into smoke and slag (cutting torch), cutting this iron bar, this is not what I am doing when I incinerate a metal for recovery of precious metals.

You can vaporize most any metal if you get it hot enough, metals have melting points and boiling points, alloys a mixture of two or more metals will also have melting and boiling points, which can be lower than one or both of the metals involved in the alloy, also if acids or even caustic gases are involved these can actually attack the heated metal which can make a metal that normally would not be volatile at a certain temperature actually go up in smoke, plastics or circuit boards when burnt can make acids in the smoke, which could attack metals that normally would not be volatile, lead can dissolve a little gold into it when temperatures as low as a soldering temperature is reached, I would guess that at very high temperatures and blowing oxygen into it could vaporize some of the gold, add polyvinyl chloride which can produce HCL and chlorine and other substances like toxic dioxins to this mix from burning plastic or printed circuits, or some other material with the metal which could attack the metals or gold involved, I can see these metals fuming off in vapors.

If I took something as simple as some gold foils and sprinkled some table salt on them, touched my torch flame to them, my gold could easily be found in the smoke and condensed yellow gases where this smoke cooled down.

I can take a salt that would not normally attack a metal and heat it and it can dissolve a metal, take Rhodium for example, which I can not get to dissolve in aqua regia, if I put a salt of sodium bisulfate on it and heat the salt until it forms a syrup it will dissolve into the Rhodium, which if I dissolved this new formed salt would now be water soluble rhodium sulfate, so it is the temperature that can make this fairly uncreative salt and metals to react where it would not normally.

So when reacting metals or salts of metals at high temperatures I will try to consider some of the chemistry that could be involved in the heated mix under the heat of my torch or other tool, whether I am soldering, welding, incinerating, vaporizing, or just burning.

If I have a powder of a valuable metal, if acid was previously involved I will normally try to neutralize the acid (depending on what acid was used), and rinse the salts off, dry and raise the heat slowly, after dry sometimes these will fuse into a syrup with added heat depending on base metal and any Cation involved, which will dry again after slowly maintaining heat (as volatile gases and vapors escape), then the temperature is raised further after dry to oxidize the metals bringing these metal powders up to a red heat and holding them there for a period of time usually 30 minutes to an hour or more, while providing an ample supply of air or oxygen for these metal powder to absorb to turn to metal oxides in the chemistry produced in part by the heat source, the temperature is not so high to melt the metals, and can volatize some base metals but hopefully not much of my valuable precious metals in my powders, if I perform the incineration step the best I can as I understand it, this is much different in my mind than just torching my powders with a cutting torch from my welding setup.

 

[Harold_V]

It is a huge mistake to incinerate in a cast iron vessel. It has a mass that is too great to be heated adequately, even with a torch. You should be using a thin fry pan, one made of stainless, which will tolerate being heated to high temperatures without degrading rapidly. Steel pans will burn out in only a couple sessions, whereas a stainless pan can be used for months on end.

Use the largest tip you have at your disposal. A rose bud is best, assuming you can use it without a huge amount of pressure. You need the heat volume to raise the temperature of the pan and its contents. A small tip develops as much heat as does a large tip, the difference being fewer btu's. An oxy acet flame is reputed to be in the vicinity of 6,000° F, so it's capable of evaporating values, but it's highly unlikely that you'd ever heat anything to that temperature, considering 3,000° F is a dazzling white, and by now has melted steel.

The idea in using the torch properly is in heating the pan and components (the pan should be on a gas fired hotplate, to raise temperature) to redness. At that point, turn off the gas, leaving only oxygen flowing. It should be set at a low flow, so it doesn't blow the values from the pan. Play this stream of oxygen over the heated material in the pan. Anywhere there's unburned carbon, assuming it is heated to redness, it will quickly glow a bright orange/yellow color, indicating it is being consumed by the free oxygen. When you are finished, the ash should be white, or a light color, but not black.

It pays to process the ash, too, as some value may flake off. Screen the ash from the solids, then digest the fines with heated HCl. Rinse well, then digest with a small amount of solvent of your choosing, to recover any traces of gold that may have been lost in incineration. Test the resulting solution with stannous chloride to determine if there's any values present. If the resulting solution has a yellow coloration, pretty good chance it does have.

You can use the resulting solution to digest other gold, so that's an easy way to deal with excess nitric, should you end up with a strong acid solution after digesting the fines.

Harold

 

[maynman1751]

Thank You Butcher and Harold! I have been wanting to ask if I could be burning off my values in some instances. Some memory chips I incinerated from above (direct flame on the chips). It works quite well, but I think possibly that it vaporized the values. I pan off the residual ash, like Patnor explained in his flatpack process, and process the remains. I'm wondering if my values may also be in the ash that I'm washing out!!!???
Is heating from above the wrong thing to do?

 

[butcher]

When incinerating I heat from below and from above, the values should be in the ash, if you got the small wire too hot they could have melted (or alloy with other metals) and could have formed something like small balls or tiny beads mixed in the ash.

With this type of material it would be best to pyrolyze these in a closed container with a vent hole, to keep everything contained and to lower the toxic waste from gases, this would also help to keep and values that may vaporize to condense onto other metals in this container, and your not exposing your health to the dangerous dioxins and oxidized metals formed in the smoke.