Studies on thermal characterisation and its implications in processing of a carbonate hosted uranium ore

Thermal processing of ores is regaining focus in extraction of minerals owing to some positive attributes of the technique. Thermal pre-treatment of ore results in various benefits. Advantages in case of carbonate ores having finely disseminated mineral values include: increased porosity, lowering of energy requirements during comminution and driving-off volatiles linked to sulphide minerals. Realising these benefits, a two-stage thermal pre-treatment study is made on a low-grade carbonate (dolostone) hosted uranium ore which encompasses driving away sulfidic volatiles at primary stage followed by calcination of carbonates at higher temperature. The energy inputs during the thermal treatment shall be offset by the overall energy gains accrued due to presence of high energy density element - uranium, in the ore. The results to be discussed in this paper include thermal characterization (TG-DTG-DTA) on pure minerals which constitute the mineral assemblage of the dolostone ore followed by studies conducted on actual ore. TG-DTG-DTA results were recorded in conjunction with EGA (Evolved Gas Analysis). The ore undergoes active oxidation of pyrite at about 427°C and active decomposition of calcite at about 727°C. It was observed that the size of the ore has no significant effect on oxidation and decomposition of pyrite and carbonate minerals respectively. First estimate of beat requirement for differential thermal pretreatment of the ore has been obtained through heat balance calculations. (author)