Mineral Processing Handbook, Volume 2, Issue 2

Author: Chief Editor: Chen Bingchen et al.
Publisher:
Publish Date: 1999-06-01
Features:
Fragment: The degree of complete overflow of mineral particles is measured. The representation method of separation particle size, commonly used, has two types: (1) specified separation particle size, which is directly specified according to the needs and purposes of classification operations; the design selection of equipment, operation, and calculation of classification efficiency are all based on this as the benchmark. For example, the separation particle size of some desliming classifiers is set to 74 micrometers, and some mechanical classifiers working in closed-circuit with grinding machines specify that the content of particles smaller than 200 mesh in the overflow is 85%, which also belongs to the variation of specified separation particle size. (2) The particle size of mineral particles entering the underflow and overflow at 50% each is taken as the separation particle size, usually expressed as d50; this representation method is applicable to all classification processes, but it is necessary to perform particle size analysis on the classification products and draw particle size characteristic distribution curves to determine it. The separation particle sizes obtained by these two methods are different, and thus the classification efficiency calculated based on them varies. The particle size distribution characteristic curve is drawn based on the weight percentage (i.e., distribution rate) of various particle sizes of mineral particles in the feed that are distributed to the overflow and underflow after classification. Particle size analysis of the classification products, after conversion, can determine the particle size distribution rate. Then, with the average particle size as the horizontal coordinate and the distribution rate as the vertical coordinate, the particle size distribution characteristic curve can be drawn. Since if the weight percentage of a certain particle size of mineral particles distributed to the overflow is a, then the weight percentage distributed to the underflow must be 100-a, it is sufficient to draw only one curve of either the overflow or the underflow.