Optimizing The Role of Limestone in Cassiterite Smelting to Improve Slag Formation

This study addresses the intricate relationship between cassiterite smelting and the role of limestone as a fluxing material in the charge, while focusing on the optimization of the role of limestone in cassiterite smelting to improve slag formation and environmental sustainability. Cassiterite smelting, which have become a key technique for extracting tin, employs limestone as a flux to produce slag that removes impurities; however, it faces challenges such as elevated CO₂ emissions and high energy costs due to its overuse or under-utilization. The study aims to determine the optimal ratios of limestone to cassiterite, improve the smelting process (temperature, reduction time, and atmosphere) with the help of Minitab 22, to analyze slag characteristics, and examine carbon emissions. The method utilized included Response Surface Methodology (RSM), ANOVA, and regression modelling to optimize results from experiments that varied limestone to cassiterite ratios (5–15), smelting temperatures (1100–1300°C), and reducing agents (charcoal, coke). Morphological analysis was conducted using Scanning Electron Microscope (SEM), while mechanical tests were performed to assess the compressive strength of the slag particularly as concerns its use as a supplementary cementitious material (SCM), hardness in Mohs scale with regard to its use in abrasive environments, porosity in percentage as regards to concreate applications, and crushing resistance for usability as SCM. Under optimal conditions (a limestone-to-cassiterite ratio of 14.9, 1300°C, and coke), the slag demonstrated low porosity (2.4%) and high compressive strength (93.0 MPa), thereby minimizing environmental waste through recyclable slag. This study revealed the importance of the optimization of limestone to cassiterite ratio in cassiterite smelting to improve slag formation and usability.