refinery_highlightThe Asarco Copper RefineryImagine a building bigger than ten football fields — so long, it’s said, that the builders had to account for the curvature of the earth when laying out the foundation!It’s the Asarco Copper Refinery in Amarillo, Texas, a state known for big things where big things happen.  Every year, more than 480,000 tons of copper anodes and copper scrap pass through this facility, leaving as 99.99% pure copper.  

 
Why Refine? Copper is ductile
Compared to other metals, copper is very ductile, meaning that it can be drawn through a tiny hole into very fine wire without breaking. Refining improves the ductility of copper so that extremely fine wires can be drawn. Impurities increase the chance that the wire will break during the drawing process.Copper conducts electricity
Only silver conducts electricity better than copper, traditionally Silver cost 40 times the price of Copper. Refining improves the conductivity of copper by lowering the electrical resistance.Resistance is like friction to electricity, and it causes energy to be lost as heat in poorly conducting wires.  Improved conductivity means more energy is delivered to the desired destination when you flip that switch or turn that dial.  Copper is recyclable
More than one-third of the copper refined in the United States comes from recycled material. That’s a higher recycling rate than aluminum!  Scrap copper comes from manufacturers of all sorts of copper and brass products. The copper is melted and cast into anodes and refined just like ‘new’ copper from the mines and smelters.   That other 1% is valuable stuff!
refinery_by-productsRefining removes the impurities from the copper, but those impurities are valuable elements like…   

  • silver
  • gold
  • platinum
  • palladium
  • antimony
  • nickel sulfide
  • selenium, and
  • tellurium

ASARCO recovers, refines, and sells those by-products.
Since anodes are already 99% pure copper when they come from the smelter, why go through all this effort for that extra one percent?  It all has to do with the physical properties of copper that make it so useful.   

    

The Refining Process
The process of passing an electric current through a liquid from one electrode to another is called electrolysis. When used to refine copper, the process is called electrorefining.tank_houseForty-four anodes are hung by their ‘handles’ in a large, rectangular tank containing a liquid electrolyte made of sulfuric acid and copper sulfate.  The Amarillo refinery houses 2,400 of these tanks in a single building covering more than 11 acres.Forty-five pure copper sheets suspended on solid copper bars are inserted into the same tank, one sheet between each anode.  These thin sheets (1/32 of an inch thick) are called cathodes, and they weigh about 15 pounds apiece. When an electric current is passed from the anodes through the electrolyte to the cathodes, copper from the anodes moves into the solution and is plated onto the starter sheet. Impurities from the anodes settle to the bottom of the tank.   After 14 days, each cathode has accumulated enough copper to become almost 3/4 of an inch thick and weigh about 375 pounds.  At this point, all 45 cathodes are pulled from the tank, rinsed with water, and bundled for shipment.   Forty-five new starter sheets are inserted into the tank, and the process continues for another 14 days. Spent anodes are removed after 28 days, melted, and cast into new, full-sized anodes in the anode casting plant at the refinery..   

Periodically, the tanks are drained and the sludge collected at the bottom is further refined to recover silver, gold, and other metals.   

TOUR NOTE:
Our refinery is located in Amarillo, Texas, so we can’t take you there on a tour.  But the exhibits about refining at the Mineral Discovery Center are the next best thing.