Breakage parameters for ultrafine grinding in stirred-media mills
- Pennsylvania State Univ., University Park, PA (United States)
Ultrafine grinding into the micron and sub-micron size range is becoming increasingly important for a wide range of industries involving ceramics, chemicals, paints, coating, pharmaceuticals, coal and others. Investigations of long-time grinding of fine quartz (to about 80% passing 0.35 {micro}m) in a 0.6 liter stirred-media mill are described. Breakage rates and primary breakage distributions have been determined based on extensive characterization of the ground products by laser scatterings diffraction and gas adsorption. The results indicate that, while there is qualitative similarity between the breakage parameters for ultrafine and conventional (coarse) grinding, there are important, quantitative differences. In particular, it is found that primary breakage distributions become significantly narrower in the submicron sizes. The trend can be described using double-truncated log-normal distributions in which both a maximum (breaking) size and a grind limit are specified. The breakage distributions become progressively narrower as the size being broken becomes finer. Breakage rates follow a typical, consistent pattern in which the rate decreases with size according to a simple power law. Further decrease in the rates seems to occur after very long grinding times when the entire mill contents become finer than about 1 {micro}m. The effect is explained as a result of changes in the rate/size relationship in the submicron range.
- OSTI ID:
- 271948
- Report Number(s):
- CONF-9510120--; ISBN 0-87335-140-1
- Country of Publication:
- United States
- Language:
- English
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