1. General

Over the last quarter century, pyrometallurgy, as a thermal operation for extracting metals, has been subjected to constraints which, in the course of its history, had not been so strikingly asserted. The high cost of energy during the oil crises of the 1970s and 1980s, and the need to reduce emissions harmful to the environment, were powerful motivations for modifying strategies and techniques. Although the same period saw major developments in hydrometallurgy, which covers wet processes, the igneous route and associated refining processes are still the royal road to extracting metals. This is because reaction rates are high enough that they do not constitute a major limiting parameter, residence times in the equipment are generally short enough, and reactions are completed as a result of the high activation energy inherent in the thermal process.

In addition,...