Рубрика: The History of Grinding

Cryogenic Crushers

Impact breakage processes are used to reduce the size of hard, brittle materials but are not useful for reducing soft or elastic materials unless the materials can be cooled to the point at which they become brittle. This is where cryogenic breakage is becoming very important. Its main use is in recycling processes for plastic […]

THE CYANIDE PROCESS

The discovery of fine-grained gold ores on the Witwatersrand in South Africa in 1886 highlighted the importance of finding a new method to extract the gold, because the losses with the amalgamation process used at the time were excessive. Chemists had known for 100 years that gold could be dissolved in potassium cyanide. A patent […]

PRIMARY MILLS

Wet Mills In the early 1930s, the economic depression was in full force, and the only interest in new grinding machines was for milling gold ores, because gold was the only metal that was not falling in price. In 1933, gold rose from $21 to $35/oz. Alvah Hadsel, a mechan­ical engineer in California with considerable […]

RAKE CLASSIFIERS

Figure 9.2a shows the Dorr classifier as it was in 1940, and it has changed little since then. Mineral companies quickly accepted the rake classifier and thickener, and closed — circuit wet grinding became part of mineral processing technology. With its reciprocating rakes, the Dorr classifier soon had competition from the Akins classifier (Figure 9.2b), […]