In most instances, both phases are molten (such as the matte and slag in a conventional copper smelting operation). The gas phase may also be used to advantage, either as a means of separating valuable volatile constituents or for removing unwanted volatile impurities. These separation techniques form the basis of thermal smelting and refining operations.

There are no universally applicable pyrometallurgical technologies. Most industrial processes are commodity-specific, because they were developed to deal with the unique physical and chemical properties associated with a particular metal and its naturally occurring impurities. Thus, pyrometallurgical process development demands a keen understanding of thermochemistry, kinetics, reactor design, and materials and refractory selection. Hazen has these capabilities and can utilize them to our clients’ advantage.

Our laboratory and pilot plant programs employ a full range of pyrometallurgical methods. We have completed projects on reduction and matte smelting, drossing, and selective volatilization (fuming). Our experience includes evaluating exotic slag chemistries and using molten salts. Additionally, we have considerable expertise in developing methods of treating slag, flue dust, scrubber sludge, and other metallurgical streams.

Thermodynamic analysis and process modeling can aid concept development and parameter selection. Our recent pyrometallurgical experience includes:

• Indium recovery from lead smelter dusts
• Chloride drossing of lead–tin–bismuth bullion
• Copper matte smelting and injection smelting
• Recovery of platinum group metals
• Ferronickel refining
• Refractory metal recovery and refining
• Magnesium reduction