Emerging technologies for metals production

Abstract

The present annual world production of iron and steel, aluminum, copper, zinc, lead, nickel, magnesium and titanium is close to 1 billion tonnes. Based on current trends, metals are likely to remain one of the primary materials of choice for several decades to come. Most metals and their alloys are synthesized from oxide, sulfide, and halide sources. The energy required for metals production is obtained in one way or another from carbon, hydrocarbons, and oxygen. The reactants and energy sources often contain many additional elements, such as sulfur, phosphorous, nitrogen, halogens, and other metals. During processing, these elements sometimes combine with each other and other elements to form many toxic compounds. The major processing routes for metals production are electosynthesis, pyrosynthesis, and aqueous synthesis, all of which are very energy intensive and generate an order of magnitude more wastes and byproducts than the desired metal product. Metals are generally considered to be commodity materials. However, the metals industries, with their matured technologies, are among the top industrial polluters (1999 Toxic Release Inventory available at www.epa. gov/tri/tri99/press/press.htm) and energy consumers (Figure 1)1 in the United States; it is true globally as well. The impact of the metals industry on pollution and energy consumption is likely to worsen—as the grade of the raw materials declines in the future, energy required for processing will increase greatly.2 In addition, an increasing global population will demand a higher standard of living, driving industrialization and, in turn, depleting energy sources and compounding the effects of the associated pollution. It is, therefore, important to reevaluate processing alternatives and to develop new energy and environmentally efficient technologies in light of the changing external constraints and an expanding dependence on metals for industrial growth. The choice of the processing technology is always based on economic viability, which is subject to many constantly Figure 1. Total energy consumption of the U.S. Manufacturing Industries.2 Emerging Technologies for Metals Production