Shifting to pyrometallurgy process

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Ayham Hafez

Well-known member
Joined
Sep 7, 2023
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Lybia
After long read and thinking about the differences between hydrometallurgy and pyrometallurgy processes for gold and PM's recovery from E-waste I noticed the following:

A- regard cost, chemicals used in hydrometallurgy process make it much expensive than pyrometallurgy.
B- Time consumption in hydrometallurgy much higher because in most of cases we have to leach e-waste for several hours and days to get the desired results.
C- Gold and PM's recovery rate is much lower in hydrometallurgy process, specially when we thinking about ic chips value lost during washing process and gold lost or postponed to recover when use AP method (considering the possibility of dissolving some gold in AP in most cases), before couple weeks I published a post depended on an internet article talking that hydrometallurgy process has higher recovery rate which I was totally wrong.

Because of mentioned points, I decided to start use pyrometallurgy processes, which I don't have field experience within it at all, but after long reading about it I came to the following scenario as a begining to shift to pyrometallurgy, considering cost and time to shift.


My idea is:

Use the dismantling machine as an incineration furnace to incinerate the naked circuit boards and its components(after already dismantling them using same machine), after modifying the dismantling machine screen holes to avoid small components falling, I will just run it to incinerate the e-waste.

Next step is to grind the incinerated circuit boards and components to less than 200 mesh size, after that mix the grinded powder with 3 times fluxes consist of 50:50 borax and soda ash then smelt them to get complex metal ingot without adding any metal collector since I believe that gold will be always less than 1% and copper will be high as required to collect the gold.

As last step, will go with nitric acid to dissolve base metals from the melted ingots or beads then start to recover PM's and gold.

Considering my low experience in pyrometallurgy process, can I successfully use this scenario or I missed something?

Attached the dismantling machine photo.
 

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Look into a copper refinery. This should make your copper waste a marketable product and still return any higher values to you as well. Since your expecting around 98 to 99 percent of your ground materials to be copper it makes a viable and logical choice.
 
Shark nailed it. Save on nitric which will digest the copper and use the copper as a friend. Smelt with proper fluxes will help you generate copper based bullion holding all of the precious metals and copper. A copper electrolytic cell will produce 999 copper which you can sell and concentrate all of your PM's in the slimes.
No need to reinvent the wheel, all of this is discussed here.
 
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If you decide to process your copper alloy with PM, you have to size your electrolysis equipment taking into account that if you melt PCBs, the copper content in them is approximately 20%, that is, you will have to electrolyze 200 kg of copper anodes for each ton. of PCBs.
 
Shark said:
Look into a copper refinery. This should make your copper waste a marketable product and still return any higher values to you as well. Since your expecting around 98 to 99 percent of your ground materials to be copper it makes a viable and logical choice.
Click to expand...
I didn't mean that, less than 1% gold not mean 99% copper, there will be ash and other metals, I meant copper exist in the incinerated materials will be enough to collect gold so no need to add more, anyway that's not my main question
 
4metals said:
Shark nailed it. Save on nitric which will digest the copper and use the copper as a friend. Smelt with proper fluxes will help you generate copper based bullion holding all of the precious metals and copper. A copper electrolytic cell will produce 999 copper which you can sell and concentrate all of your PM's in the slimes.
No need to reinvent the wheel, all of this is discussed here.
Click to expand...
I don't reinvent anything, just try to use what I already have to start smelt PCBs, just want an advice about my scenario
 
rusti2 said:
If you decide to process your copper alloy with PM, you have to size your electrolysis equipment taking into account that if you melt PCBs, the copper content in them is approximately 20%, that is, you will have to electrolyze 200 kg of copper anodes for each ton. of PCBs.
Click to expand...
Copper in most of circuit boards are less than 5% of weight, only reach 20% in electrical circuit boards like power supply boards, this counted from my small experience
 
Generally I have seen depopulated circuit boards yield on average 300 pounds of copper per ton of pre incineration boards. My experience comes from shops that take in computers and strip them down to components and refine the boards. These shops run in the 3-10 tons per day of incoming material.
 
Ayham Hafez said:
I didn't mean that, less than 1% gold not mean 99% copper, there will be ash and other metals, I meant copper exist in the incinerated materials will be enough to collect gold so no need to add more, anyway that's not my main question
Click to expand...
After proper smelting, and with the use of the right fluxing agents and sparging (the use of air to oxidize melted metals). You are already very close to the proper ratio of copper for a copper cell. Maybe not 98 or 99 percent, but very close. While it may take a little longer to process you can be producing two valuable products instead of one. After running the copper a time or maybe two, having extra copper to use is no longer an issue. The waste acid from a copper cell can be treated and often reused, reducing excess waste acids to deal with as well.
 
Shark said:
After proper smelting, and with the use of the right fluxing agents and sparging (the use of air to oxidize melted metals). You are already very close to the proper ratio of copper for a copper cell. Maybe not 98 or 99 percent, but very close. While it may take a little longer to process you can be producing two valuable products instead of one. After running the copper a time or maybe two, having extra copper to use is no longer an issue. The waste acid from a copper cell can be treated and often reused, reducing excess waste acids to deal with as well.
Click to expand...
Right fluxes, I read about using 3 times fluxes 50:50 borax and soda ash, is it right in most of cases?
 
Sample of the product will determine the fluxes. 4metals knows way more about that than I do, and kurtak is very knowledgeable as well. There are others here as well and maybe if this goes well they will add some input also.
 
Ayham Hafez said:
Thanks, hope will success cause I don't have experience with pyrometallurgy or fluxes at all
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The smelting thread goes into great detail about what various components of a flux blend accomplish. Analysis of the copper based bullion you produce for base metals will allow you to modify your flux blend to optimize your results. This is a process where you learn and your methods evolve and the mixture you start with will very likely change as well. A close guarded secret of refiners processing copper based bullion for PM's is their flux blend.

The thread will give you the tools, you need to do the testing for a production setup.
 
The limiting aspect is always the percentage of PM recovery that the procedure manages to obtain, for this it is necessary to have an oven with an adequate working temperature of no less than 1300°C, management of the viscosity of the slag by adding flux mixtures that achieve a final chemical composition with a low melting point, the cost of these fluxes will have an important impact on the final production cost, so you must choose the appropriate and cheapest ones, for example sodium borate is suitable but It is expensive and not used industrially for that reason, some of them are sodium oxide (Na2O), potassium oxide (K2O), calcium oxide (CaO), calcium carbonate (CaCO3), silicon dioxide (SiO2), aluminum oxide (Al2O3) and magnesium oxide (MgO) or combinations of two or more of them, if you melt PCBs, SiO2 will be the main component of the slag and you should use CaO or a mixture containing it, fluorides such as Calcium fluoride or Cryolite are used in small quantities, calcium oxide and fluorides lower the melting point and reduce the viscosity of the slag, forming silicates with silicon oxide, calcium oxide increases the basicity (%CaO/% SiO2) and also the solubility of O2 favoring the oxidation refining process with air/oxygen bubbling. The result of a good oven temperature plus the appropriate mixture of fluxes concludes in an optimal recovery of the PM contained in the PCBs and this is monitored with the analysis of the content of Au, Pd and Ag in the final slag. Try to do smaller scale tests before making large expenditures on equipment, I have a book "Slag Atlas Alivert and Gaye" where there are all types of phase diaphragms, viscosity, surface tension of slags that allow you to know how to dose the fluxes, the file It weighs 33 MB and I ask the appropriate person for permission to download it.
 

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