Grinding Ball Design
Grinding balls are essential mechanical components in ball and semiautogenous (SAG) mills. Their function is crushing and grinding ore rocks weighing up to 45 kg (100 lb) preparatory to recovery of valuable minerals, from lead through rare earth elements, which are essential to the approaching 21st century technological society. Their design, manufacture, and selection deserve […]
Effect Grinding Mill RPM Speed, Loading & Ball Size on Mineral Liberation
Grinding is generally considered to be a size reduction operation. However, in most cases the primary objective of grinding is the liberation of valuable minerals from gangue material, irrespective of the amount of size reduction required. If fracturing of an ore occurs in a random manner, it may be possible to use the grain size […]
L / D Ratio in Overflow Ball Mill Design & Operation
Ball mill shape factors in the period prior to 1927 averaged 1.1/1 for 29 center discharge mills and 1.0/1 for 30 peripheral discharge mills. With the resumption of new plant construction after the 1930’s depression, the Morenci concentrator continued the 1/1 ratio with its 3.1 x 3.1 m (10 x 10 ft) mills. The ratio […]
Recommended Ball Mill Speed & Liner Configuration
With particular reference to mill size, it is apparent that a change in diameter in a large mill is relatively far less significant than the same change in diameter for a small one. For example, using well established relationships between power draw and mill diameter and speed, 50 mm (2 inches) of liner wear results […]
How to Improve Ball Mill Performance
Application of value engineering techniques to grinding process modelling led to the identification of two basic functions of the ball mill-classifier circuit. In terms of a specified circuit product size which is used to differentiate between “coarse” or oversize material and “fines” or undersize material, these basic functions are (a) breakage of the coarse material […]
How Temperature Affect Grinding Efficiency
The effects of temperature on autogenous grinding can be immediately divided into rheological effects and mechanical effects. The rheological effects are a result of the substantial increase in the viscosity of water as the freezing point is approached. The change in apparent slurry viscosity which results from changing temperature is shown in Figure 1. As […]
Typical Average Grinding Ball Consumption
Grinding Ball Wear & Breakage by Impact & Abrasion Tests
Impact and abrasion properties of various commercial US grinding balls were evaluated and compared by the Bureau of Mines, US Department of the Interior. Laboratory tests were conducted on balls obtained from eight major US manufacturers. The balls included forged steel, cast steel, and alloyed white cast iron and were subjected to repeated impacts until […]
SAG Mill Expert System Grinding Circuit
The original process control interface consisted of a series of stand alone 4-20 ma controllers requiring the operators to dial in set points for the numerous processing parameters. In many cases these controls were set to their manual mode of operation with the operators making all the dynamic process changes. This procedure was very time […]
Effect of P80 Grind Size on Flotation Collector
Flotation Performance in Function of Collector Type & Dosage at Fixed Grind Size: The drop-off in measured plant recovery due to excessive collector dosage has been described. In the above publications, a rate model was used for describing experimental cumulative recovery versus time data of the form: r = R { 1 – [1/(Kt)][1- exp(-Kt)]} where […]