It has been said that the flotation rate of coal is favourable within the size range of 48-150 mesh. In the case of both sizes of over 20mesh and under -325 mesh, however, the flotation operation is very difficult on account of the decrease of flotation rate.
In the present paper, a series of flotation tests was done by useing fraction of different sizes. The experimental samples was prepared by the clean coal and refuse from the baum jig in Yubari-Shinko washing plant.
As can be seen in Fig. 2, the flotation yield was the best within the size range of 35-100 mesh. On the other hand, it decreased with the decrease of particle size. Especially, the flotation yield of -325 mesh fraction was very poor. In the case of over 20 mesh fraction, it was 51.1-63.7%. these results was rather better than fine particle fractions. If the addition of flotation oil and the flotation time are increased, the flotation yield will increase even if paricle size is larger than over 20 mesh.
The flotation yield of refuse increased with the decrease of particle size. The yield of under 325 mesh was 16.9%.