Unit Operations

The primary organization of the V-Tour website is by process, but there are other ways to arrange the information contained here. The following tables list all the unit operations by process type and cross-references them to the appropriate online tours. Each listing is alphabetical by unit operation.

• Mineral Processing Unit Operations
• Pyrometallurgical Unit Operations
• Hydrometallurgical and Electrometallurgical Unit Operations
• Other Unit Operations

A note on terminology: under the heading of "Unit Operations" fall a number of plants, circuits, and processes that contain multiple unit operations. The term "Unit Operations" here is used to refer to all of these instances.

Mineral Processing unit operations are employed to concentrate materials and modify their physical attributes (e.g., particle size). Since mineral processing is such a general classification, its unit operations are included in many applications. Crushing and grinding circuits, flotation cells, thickeners, granulators, etc. are used in conjunction with many other unit processes.

Pyrometallurgy covers metallurgical operations that involve processing at temperatures substaintially above ambient conditions, generally involving chemical reactions as distinct from metal casting which involves only a physical transformation (i.e., solidification). Pyromet unit operations include calcining, roasting, reduction, smelting, refining and recycling.

Hydrometallurgy pertains to metallurgical operations that involve processing in which the principal phase is water, can be at temperatures and pressure substaintially above ambient conditions when autoclaves are used, and generally involves chemical reactions.

Electrometallurgy involves processing with the passage of electrical current; it can be in an aqueous system or can be at temperatures substaintially above ambient conditions in fused salt systems, it generally involves chemical reactions to either precipiate a metal from the liquid phase or to refine a metal by transferring the metal from an anode to a cathode leaving the impurities in the anode behind.

The theory underlying these two fields is very similar and they are often considered together. Processes include atmospheric and pressure leaching, ion exchange, solvent extraction, hydrogen reduction, electrowinning and electrorefining. Water pollution problems in metallurgical industries are also often solved by hydromet techniques.

Of course, not all processes fall into the three categories outlined above. The following table lists all the unit operations not included in the previous categories, including casting and solidification operations as well as several chemical engineering processes.