Energy expenditures associated with the production and recycle of metals

Since the presently used resources of our structural metals are being depleted, the equivalent coal energy requirements associated with the production of Mg, Al, Fe, Cu, and Ti metals for varying grades of ore deposits have been evaluated. Future energy requirements for Mg and Fe production will remain essentially constant at 91,000 kWh/ton and 3600 kWh/ton, respectively. Use of poorer-grade bauxite ores will not significantly change the energy requirements for Al (approximately 55,000 kWh/ton); however, eventual use of clays and anorthosite will increase the consumption of energy by more than 35 percent. The energy requirements for Cu and Ti are 13,530 and 126,300 kWh/ton, respectively. Since both Cu and Ti have limited resources, energy expenditures will increase considerably as poorer grade ores must be used. Recycle of Cu and Ti from scrap metal requires 1560 and 39,000 kWh/ton, respectively, which is significantly lower than that required to process the metals from their virgin ores. Sulfuric acid, gold, silver, selenium, and tellurium are the principal by-products from copper ores, while zirconium and pig iron can be recovered from titanium deposits. The energy requirements associated with the recovery of these by-products have also been evaluated. (auth)