Tonnage, mineral processing

The methods used to create larger entities from fine particles so that the bulk properties of particulates can be improved is the subject of this book. These so-called size enlargement methods evidently concern a broad spectrum of technical disciplines and industries ranging from the relatively small scale requirements of pharmaceutical manufacturers through the tonnage requirements of the fertilizer and minerals processing industries. 

Facilitate pre-vulcanisation processing, increase softness, extensibility and flexibility of the vulcanised end-product. The rubber processing industry consumes large quantities of materials which have a plasticising function complex mixtures (paraffinic, naphthenic, aromatic) of mineral hydrocarbon additives, used with the large tonnage natural and synthetic hydrocarbon rubbers, are termed process oils. Because of the complexity of these products, precise chemical definition is usually not attempted. If the inclusion of an oil results in cost reduction it is functioning as an extender. The term plasticiser is commonly reserved for synthetic liquids used with the polar synthetic rubber. 

The majority of the ore tonnage treated by hydrometallurgical means is processed at atmospheric pressure because of the obvious economic advantage. In the case of the secondary recovery of additional copper values from mine waste dumps, mined-out ore bodies, and marginal deposits of ores with complex mineralization, the only economic process has to be at ambient pressure. 

Fig. 10.2. The bimodal curve represents the probable distribution of a geochemically scarce metal in the earth s crust. The large peak is the distribution in common rocks, where scarce metals occur not as separate minerals but as atomic substitutes for abundant metals the small peak represents deposits produced by ore-forming processes such as those resulting from the circulation of brines in the crust. Current mining has already reached the point where the distribution curve for easily accessible scarce minerals turns downward. Further reductions in the grade of ore mined will produce declining tonnages of ore and will eventually bring us to a mineralogical barrier — which lies somewhere in the area between the two humps.

The most common minerals of high metric tonnage (iron, aluminum, copper, titanium, nickel, chromium, magnesium, zinc, etc.) are found in nature as oxides and sulfides and as a combination of both. Ores are sometimes a mixture of rich metal composition and poorer compositions called gangue. The gangue can be acidic or alkaline, and determines the type of flux used for pyrometallurgy. Since ores come in all levels of complexity, various methods of processing have been developed over the years. 

---