A stark difference in gold ore vs. printed circuit boards (PCBs) is that a rich gold ore might have 0.5 – 1.0 oz of gold per ton of ore, but computer PCBs contain 3 – 8+ oz gold, 15 – 20+ oz silver, 500+ lbs copper per ton of boards, plus multiple other base and precious metals. Given the commodity nature of electronics such as computers and cell phones, this makes PCB recycling a great way to minimize waste while turning a profit. By following the principles of separating gold from hard rock ore, we developed a system to mechanically separate the waste plastics and glass fibers from the valuable metallic content: no burning, leaching or electrolysis.
The primary components of a PCB processor are:
• Hammer mill – Using the screen with holes, this machine breaks up the components to <1/8” pieces, and discharges them onto the shaker table to separate the larger metal from the board material. Using the screen with slots, the board material is pulverized to liberate the metals from the plastics and fiber
• Shaker table – This separates materials based on density (specific gravity). The metals in PCBs are all higher density than the waste material, so behave differently on the table, allowing density separation of metals and plastic/fiber waste.
There are other valuable separations this system is used for:
- Auto-shred suitable for separation is a combination of what’s leftover after cars are shredded and the various sorts have been completed. Remaining is a mixture of fine metals, some PCB boards, and fine copper wire all mixed in with worthless fluff, plastics, broken glass, sand/gravel, and other contaminants. Pulverizing it all in the hammer mill and running over the shaker table will separate the valuable metals from the worthless fraction, via density separation.
- Separating copper wire from insulation is accomplished by chopping the wire into short pieces to liberate the copper from the insulation, usually with a granulator, and then the mixture is separated on a dry air-separation table using shaking and airflow. We’ve recovered up to 5% additional fine copper particles from the waste insulation by running on our wet shaker table.
- The hammer mill-shaker table combination performs well in pulverizing boiler bottom ash and separating the dense (metallic) fraction, or in separating metallic values from refinery slag.
