Copper sulfide ore: purification and smelting

      Copper sulfide ores are typically processed using pyrometallurgy, the extraction and purification of the metal through a process that involves heating. The process uses a series of physical steps and high temperatures to extract and purify copper from copper sulfide ore, divided into four basic steps: 1. froth flotation, 2. concentration, 3. smelting and 4. electrolysis.

      After being mined, transported and crushed into a consistent gravel, the crushed gravel is further processed in the mill using a secondary crusher and finally turned into fine sand. After the copper ore is crushed, liquid is added to make it a slurry. Mud is a mixture of valuable copper ore and "worthless" rock called gangue. The slurry is placed in a tank and then subjected to froth flotation to separate copper minerals from gangue. Chemical agents called "collecting agents" are added to the slurry and bind to the copper particles, making them hydrophobic or water-repellent. The pipes are used to blow air into the bottom of the tank to create air bubbles that rise to the surface, carrying away the water-repellent copper sulfide particles. The copper-rich air bubbles at the top of the tank are then skimmed off for further processing. Gangue minerals sink to the bottom of the tank and are removed or disposed of as tailings.

      The next stage after froth flotation is the concentration stage. Pour foam into thickener. The bubbles collapse and the solids in the foam solution settle to the bottom of the tank, which is then filtered to remove excess water that can be reused to process more batches of sulfide ore. The final product of the enrichment stage is a combination of 30% copper and other metals, and this copper concentrate is sent to a smelter.

      At the smelter, the ore is further purified using high temperatures in a series of smelting processes. The copper concentrate is first heated to 2,300°F through a smelting furnace and converted into a molten liquid. Pour the heated liquid into the slag furnace. This step produces a mixture of copper, sulfur and iron and slag. The copper matte produced by the smelting furnace contains 58-60% copper. The molten matte is then taken to another furnace called a converter to burn off the remaining iron and sulfur; the product, called blister copper, is 98 percent copper and sent to an anode smelter. Blistered copper is yellow; it turns blue-green as the oxygen in the copper burns off in the anode furnace. The resulting product, molten anode copper, is poured into a mold called an anode casting wheel. The cooled anode plate is 99% pure copper.

      Electrolysis is the last step in the purification of sulfide ore into cathode copper. The copper anode plates are then refined in a final step called electrolysis. The anode plate is suspended in a large tank filled with an electrolyte solution made of copper sulfate and sulfuric acid. Thin sheets of pure copper called cathodes, each weighing about 15 pounds, hang between the anodes. When an electric current is applied, positively charged copper ions leave the anode and move through the solution through the electrolyte solution to plate on the cathode. Other metals and impurities also leave the anode and fall to the bottom of the tank or remain in the electrolyte. These impurities are collected and can be refined to recover other metals such as silver and gold. After 14 days of electrolysis, the anodes faded away and each cathode now weighs 375 pounds of copper and is 99.99 percent pure copper. The cathode was removed from the tank and rinsed with water to prevent further reaction. The finished copper cathode can then be made into wire, plate, tube and other copper products.