MICROWAVE TREATMENT OF ROCKS: EFFECT ON SPECIFIC GRAVITY, WHITENESS, AND GRINDABILITY

摘要

Heating of ores usually improves the liberation of minerals and reduces grinding energy consumption. One of the heating methods is using microwave electromagnetic radiation, which may change the rock's physical properties. This paper investigates the effect of microwave heating of rocks on their physical properties. The physical properties monitored were specific gravity, whiteness, and grindability due to their importance for the downstream processes. Two rock types were investigated: coral as the soft rock and quartzite as the hard rock. The rock samples tested were treated for different time intervals in a microwave oven (frequency - 2.45 GHz, P = 1.7 kW). The results snowed that specific gravity of the soft rock decreased by 1.82 % after the microwave treatment (150 s), while that of the hard rock was not affected. It was also found that the maximum change in rock whiteness for the soft rock is 8.65 % after the microwave treatment (150 s), while that of the hard rock was 6.02 % after a 120 s microwave radiation exposure period. Following a 60 s microwave radiation exposure, the soft rock demonstrated the work index of 20.99 % against the value of 45.03 % of the hard rock. The results of FTIR and XRD analyses suggest that changes in the physical property and a phase shift of minerals may be responsible for the improvement in the work index and whiteness of the rocks studied.