石炭の圧縮強度

石炭の微粉砕機構に関する一考察

抄録

The compressive strength have been measured on irregular shaped coals ranging from 0.1mm to 2.0mm particle size for low ash coals in Hokkaido. The results obtained from these experiments and those obtained from the silica ball-mill grinding test for the same coals are summerized as follows:
1) There are linear relationships between mean compressive strength and mean particle size of coals, and the extent of the effect of particle size on the compressive strength increases with increase of H. I.(Hardgrove index) (Fig. 2 and Table 1)
2) The size distribution of broken coals by static compression correlates to M. I. of coals tested.(Fig. 3)
3) For coals showing high H. I. as Naie coal, the weakest link theory could be appricable to the compressive breakage of irregular shaped coals in the range of these particle size. However this theory should not be applicable to coals showing low H. I., because the amount of cracks and flaws in these coals are not so much.
4) Rate of grinding, except for two coals, is approximately proportional to H. I.(Fig. 9)
5) In case of ball-mill grinding, the mode of breakage of low coals under compressive stresses is taking place through breaking process among each coal particles. Under the same grinding condition, the size distribution pattern of ground coals varies with increasing H. I. from the surface grinding pattern to the bulk crushing pattern.
6) Wear of silica balls in the ball-mill grinding decreases rapidly with increasing H. I. up to about 60, and then decreases slightly.(Fig. 10)