A Comparison of Direct Concentrating Solar Thermal Treatment of Manganese Ores to Fossil Fuel Based Thermal Treatments

In South Africa, the world’s largest land-based manganese reserves occur in an area coincident with high annual solar irradiance. The use of direct concentrating solar thermal treatment, as opposed to fossil fuel based thermal treatment, reduces the CO2 emissions associated with thermal treatment of manganese ores greatly and could open new processing opportunities when scaled up. The application of direct concentrating solar thermal treatment of manganese ores is compared to other thermal treatment methods. The evaluation is based on the results of exploratory on-sun experiments conducted in 2019. Pellets prepared from manganese ores, bentonite binder and charcoal were treated with concentrating solar radiation. The solar treated samples were analyzed to determine changes to their mineralogy with X-ray diffraction and scanning electron microscopy. In addition, the solar treated pellets were tested to determine their compressive strength. The pellets did not pass the strength requirement of 500 N/pellet to qualify as feed for submerged arc furnaces. Results from these experiments were then further compared with other thermal treatments of manganese ores such as calcination, nodulizing, pelletizing, sintering and reductive roasting to evaluate the feasibility of applying concentrating solar thermal treatment in these treatment options. The direct concentrating solar thermal treatment was found to strengthen manganese pellets sufficiently to be considered dried and preheated for pelletizing but not cured. Temperatures were achieved suitable for calcination or reductive roasting of manganese ores, where agglomeration is not required.