Abstract
Microwaves can be applied to treat iron ores in comminution, sintering, and reduction unit operations. Previous studies (mainly pyrometallurgy) have used pellets/briquettes to control for sample uniformity. Depending on where microwaves are applied in a flowsheet, the material may be bulk rocks or pellets/briquettes. However, a study demonstrating the effect of the sample geometry on the microwave heating behaviour is lacking, given that rocks of different sizes and variable mineralogy will have profound effects on the heating behaviour. Therefore, the objectives of the current study are to: 1) determine the relationship between the iron content and the temperature distribution within a treated sample, and 2) to compare the temperature distribution between bulk rocks and briquettes. Bulk rocks were individually microwave treated at 3.2 kW (2450 MHz) for 10 s, and the infrared pattern was captured with a FLIR camera. Next, these rocks were crushed, pulverized, riffle split and assayed via XRF to determine the iron content. Subsequently, these samples were prepared into briquettes to study the effect of the geometry, while keeping the mineralogy constant. It was found that the temperature distribution of most bulk rocks was in the range of 60-70oC. Briquettes with higher iron content tended to have higher average maximum temperatures, and lower standard deviations within their temperature distribution. Briquettes with a lower iron content demonstrated more uniform heating but reached lower temperatures.