Method for recycling precious metal from used printed circuit boards

Abstract

A method is disclosed for recycling precious metal from used printed circuit boards. The used printed circuit boards are roasted with plasma at 800 degrees Celsius for less than 10 minutes, thus producing exhaust and residue that contains the precious metal. The exhaust is treated with an exhaust-treatment system before it is released to the atmosphere. The residue is ground and turned into scraps of a diameter smaller than 2 mm. The scraps are subjected to magnetic separation, thus separating ferromagnetic scraps from non-ferromagnetic scraps. The ferromagnetic scraps are refined. The non-ferromagnetic scraps are screened, thus separating tiny non-ferromagnetic scraps from big non-ferromagnetic scraps. The tiny non-ferromagnetic scraps contain silver and gold. The big non-ferromagnetic scraps contain copper.

1 . A method for recycling precious metal from used printed circuit boards, the method comprising the steps of:
 roasting the used printed circuit boards with plasma at 800 degrees Celsius for less than 10 minutes, thus producing exhaust and residue that contains the precious metal;   treating the exhaust with an exhaust-treatment system before releasing it to the atmosphere;   grinding the residue and turning it into scraps of a diameter smaller than mm;   subjecting the scraps to magnetic separation, thus separating ferromagnetic scraps from non-ferromagnetic scraps;   refining the ferromagnetic scraps;   screening the non-ferromagnetic scraps, thus separating tiny non-ferromagnetic scraps from big non-ferromagnetic scraps, wherein the tiny non-ferromagnetic scraps contain silver and gold, while the big non-ferromagnetic scraps contain copper.   
     
     
         2 . The method according to  claim 1 , wherein the tiny non-ferromagnetic scraps are smaller than 0.149 mm in diameter. 
     
     
         3 . The method according to  claim 1 , wherein the big non-ferromagnetic scraps  72  are larger than 0.149 mm in diameter.