Environmental Aspects of Historical Ferromanganese Tailings in the Šibenik Bay, Croatia

The former manganese ferroalloy plant and the remaining tailings are affecting the quality of the environment in Šibenik Bay, Croatia, even though industrial activities ceased more than 25 years ago. This study has revealed that the main manganese mineral phases present in the recently collected tailings, as well as in the dust collected on the roof of the plant during the production period, are bustamite and Mn-oxides. The same type of Mn mineral phases was also found in recently collected sediments from Šibenik Bay. Detailed chemical and phase analyses (XRD, BCR sequential analysis, aqua regia and lithium borate fusion) of the dust sample revealed high manganese values (24.1%), while granulometric analysis showed that 50% of the particles are smaller than PM2.5. The influence of the tailings is visible in the sediment, but the concentrations of the potentially toxic elements determined by the sequential BCR analysis are within the legal limits. Some higher values (20.3 g/kg Mn, 595 mg/kg Pb and 494 mg/kg Zn) are detected in the tailings, which are still exposed to weathering and as such should be additionally monitored. On the other hand, this material contains a considerable number of elements that could be considered lucrative (∑ REE up to 700 mg/kg, Mn up to 23 g/kg, Fe up to 37 g/kg and Al up to 25 g/kg), opening the possibility of reuse and recovery.

Concentrating Solar Thermal Process Heat for Manganese Ferroalloy Production: Plant Modelling and Thermal Energy Storage Dispatch Optimization

This paper investigates the economic benefit of incorporating solar-based preheating of Manganese ore before smelting in electric submerged arc furnaces. Manganese ore is smelted to produce Manganese ferroalloy, a key component in steel production. The smelting process is highly energy intensive, with temperatures up to 1600 °C. The paper discusses the developed methodology for determining the configuration of a concentrating solar thermal (CST) plant to produce high temperature process heat. The CST plant is sized to preheat the ore to 600 °C before it enters the smelter — currently ore enters at ambient temperature. The preheating leads to economic and environmental benefits by offering lower cost heat and reducing carbon emissions for the process.

The Calculation for Saturated Solubility of Oxygen in Mn–Si Melts Equilibrated with MnO–SiO2 Slags

The MnO–SiO2 slag in equilibrium with Mn–Si melts with a Si molar ratio between 0.1 and 0.3 at 1,700 K was a single liquid phase. However, it was liquid phase saturated with solid MnO or solid SiO2 in the case of XSi less than 0.1 or greater than 0.3, respectively. Based on a subregular solution model, the calculated saturated solubility of oxygen in Mn–Si melts was 0.0236 mass % in pure manganese at 1,700 K and increased with the increasing silicon in the range of XSi from 0.1 to 0.3. However, the saturated solubility of oxygen decreases as the silicon exceeded 0.3, and the minimum solubility was 0.0041 mass % in pure silicon at 1,700 K. The results could be used to predict the compositions of endogenous oxide inclusions and evaluate the cleanliness of manganese ferroalloy.