When I generated a lot of sweeps as an operating refinery I was able to ship out multiple drums of low grade powder to a smelter in Europe. Boliden in Sweden is one I remember well. The ash would yield in the neighborhood of 1/2 ounce of gold per drum which was typically 400 pounds. So something around 0.075 grams per pound. This was just from the fines after incineration and sifting. At that concentration, and at the time $300 gold, it was not worth recovery in house.
The process used was to ash the circuits to burn off all of the plastics and, if the feed rate was slow enough, burn off the toxins in an afterburner. The resulting ash was very much like the ash in the video’s after the torch ashed them. That material was sifted through a screen to separate the metallic fraction from the powder. The metallic fraction was melted into bars and assayed and the customer was paid on the recovery value of that bar. The powder was also assayed but was never concentrated enough to process in house.
If I had a rotary furnace at the time, I think the rotation of the load would have allowed the molten copper to recover the small percentage remaining in the powder as well. Ironically I had customers that came back to me after using refiners with a rotary saying my returns were better. So I never had issues with not paying on the powder.
To address your issue with the cost of crucibles why don’t you start a thread discussing how the crucibles used in the video’s are made. Seeing the simple shape they use, I think the proper mix of ingredients is all you need to confirm to make your own.
The process used was to ash the circuits to burn off all of the plastics and, if the feed rate was slow enough, burn off the toxins in an afterburner. The resulting ash was very much like the ash in the video’s after the torch ashed them. That material was sifted through a screen to separate the metallic fraction from the powder. The metallic fraction was melted into bars and assayed and the customer was paid on the recovery value of that bar. The powder was also assayed but was never concentrated enough to process in house.
If I had a rotary furnace at the time, I think the rotation of the load would have allowed the molten copper to recover the small percentage remaining in the powder as well. Ironically I had customers that came back to me after using refiners with a rotary saying my returns were better. So I never had issues with not paying on the powder.
To address your issue with the cost of crucibles why don’t you start a thread discussing how the crucibles used in the video’s are made. Seeing the simple shape they use, I think the proper mix of ingredients is all you need to confirm to make your own.