Abstract
Microwave heating is one of the emerging techniques studied by mineral processing researchers aiming to reduce ore competency while extending the benefit into better liberation of valuable minerals. Through generation of microcracks induced by microwave, ore particles is softened and broken into a more preferential tendency along mineral boundaries. However, the knowledge on how heating performance of different particles properties (e.g., size and shape) on the comminution performance are still very limited. That is because microwave heating performance assessment in the past was limited only to observing surface temperature. Surface temperature of samples can be measured using different type of thermometer (infra-red or digital). Recently, another parameter has been developed which represent the actual heat energy absorbed by microwave opposed to the actual energy supplied by the microwave (energy input). This parameter was termed as heat over microwave efficiency (HOME), which is calculated based on a calorimetry measurement on the treated sample by microwave heating.
In this study, two different sizes of a kimberlite ore (coarse: -31.5 +16mm; fine: -16 +6.7mm) were irradiated in a single-mode 15 kW microwave with different microwave energy input. After thermal image was captured and calorimetry was performed, each sample was crushed in a single-roll crusher to see the impact on specific crushing energy (ECS). Each test condition was replicated, and results were then compared against the untreated samples reference. The results have shown that coarse feed samples absorb more heat as compared to fine feed samples across different microwave energy input, more significantly at low microwave energy input. The HOME are ranging from 26 – 35% for coarse feed versus 37 – 40% for fine feed. However, the differences on HOME % do not translated to linear correlation on ECS where higher ECS reductions are observed on coarse feed (6 – 15% reduction). On the other hand, there are no significant ECS reduction ( -2 – 4%) on fine feed size. The maximum ECS reduction is observed on coarse feed at low microwave energy input. These results suggest that reduction in crushing energy is not positively correlated with heat absorbed by microwave, while feed particle size is a more significant parameter.