Original scientific paper
Preparation of graded coal dust fractions
Velimir Vouk
Abstract
The preparation of graded coal dust fractions by a modified sedimentation technique is described. A successful fractioning method has to fulfil the following conditions: 1. the sedimenting suspension must contain no aggregates, 2. temperature variations in the suspension and in the environment must be reduced to a minimum, 3. the formation of eddy currents during separation of the supernatant liquid from the sediment must be avoided, and 4. the particle size distribution of the original dust must be favourable, otherwise the number of repeated sedimentations ·be-comes very Iarge. Equations have been deduced enabling the estimation of the number of repeated sedimentations necessary for obtaining a desired degree of homogeneity of fractions. The equations are based on the assumption that moot industrial dusts obey the log-normal particle size distribution. Using the described method a series of six fractions in the size range from 1 to 20 microns was prepared. The results are satisfactory within the limits set by the tendency of coal dust to form aggregates during sedimentation, and by the unequal density of coal dust particles. Enclosed are the data on size distribution of graded fractions and of the original dust. The work described in the paper was caused out in the Research Laboratory on the Medical Research Council. London School of Hygiene and Tropical Medicine. Author's thanks are due to Dr. T. Bedford and C. N. Davies, M. Sc. for their help and friendly criticism.
Keywords
Hrčak ID:
189443
URI
Publication date:
20.3.1950.
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