THE FLOTATION PROCESS The History of Grinding

The background to the flotation process was similar to that for the cyanide process. The reserves of ores containing coarse-grained minerals were dwindling, and ores containing fine-grained minerals—which were difficult to extract by the processes of the time— needed to be mined. The cyanide process was unsuitable for ores containing lead, zinc, and copper, all Read more

The Early Years: 1890-1950 The History of Grinding

The history of cyclones goes back to 1891 when E. Bretney obtained the first patent (Bretney 1891). The Bretney cyclone was designed with a closed apex for intermittent discharge and was the forerunner to present-day desanders that are used for separating sand from water in pressurized water systems. The Bretney cyclone had a roof entry Read more

The Science and the Scientists The History of Grinding

THE ROLE OF SCIENCE Scientists and inventors have long worked to develop and improve size-reduction pro­cesses and machines to solve the engineering challenges associated with grinding. Size reduction-used in every mineral-processing operation—has been a continuing field for scientific inquiry and this has contributed to more efficient size-reduction processes in a number of areas: ■ The Read more

Impact Crushers The History of Grinding

In these types of crushers, high-velocity impacts are used to break rocks. They work either by hitting rocks with a high-speed hammer (hammer mills) or throwing rocks against each other or against a steel plate (Barmac crusher). Breakage by impact was the FIGURE 5.17 Material flows through the crushing chamber of a cone crusher (SME-AIME Read more

Ball Loadings The History of Grinding

Balls used in the first compartment are larger than those in the second because much larger particles must be broken. Sizing distributions vary according to clinker character­istics and whether the mill is in open or closed circuit. Some clinkers contain small, hard nodules about 10-15 mm in size that grind slowly and may enter the Read more

Initiation of Explosions The History of Grinding

Reliable initiation of the explosive decomposition of nitroglycerin was a problem from the start. Black powder safety fuses were tested but gave erratic results, so Nobel returned to a detonator that he had patented in 1867 before dynamite was invented. This was a tin capsule containing mercury fulminate that exploded when struck, and when used Read more

Hand Stones The History of Grinding

His berries, nuts, acorns and corn were pounded into meal; and his invention of the first pounding appliance constituted, without doubt, one of the earliest attempts to devise an instrument useful in the peaceful arts. (Bennett and Elton 1898-1904) In this chapter we discuss how stones driven by muscle power—which were first used for grains Read more

INNOVATIONS IN ROLLER MILLS The History of Grinding

Many roller mills were sold from 1930 to 1950, but there was little enthusiasm for new designs because of the economic depression and World War II. The revival of industry after the war increased the demand for materials, and new mills were required with grinding chambers that had higher processing capacities. Fixed Rollers and a Read more

SLOW-SPEED MILLS The History of Grinding

The first mills to produce fine particles at a rate of a few tons per hour were slow-speed ball mills and roller mills that were developed about 1880. By 1920, there was a strong demand for fine grinding as industry revived after World War I. By then the ball mill was so successful that for Read more

STAMP MILLS FOR ORE BREAKAGE The History of Grinding

As the world’s population and its demand for minerals continued to grow, it became nec­essary to devise a machine that could crush abrasive ores to small sizes at higher rates and that could be driven using a renewable power source. Enter the stamp mill. Although water-driven trip hammers had been used in China for crushing Read more