INTERACTION OF TIN SMELTING SLAG AND MAGNESIA REFRACTORY AT 1250 AND 1400°C

• Main Author: Khoirunnisa
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/82096
• Institution: Institut Teknologi Bandung

The production of tin in Indonesia has declined due to a decrease in both the quantity and quality of tin ore resources. Therefore, optimizing the tin production process chain in Indonesia is essential. One optimization effort that can be undertaken is the adoption of the latest technology. This direction of optimization has been implemented by PT Timah Tbk, which replaced its smelting technology from the Reverberatory furnace to the Top Submerged Lance (TSL) Ausmelt furnace. A critical variable in the Ausmelt TSL furnace tin smelting process is the prevention of refractory components, including magnesia (MgO), from dissolving into the slag to extend the refractory's lifespan. This study investigates the effects of smelting temperature, Sn content in the slag, the CaO/SiO2 ratio in the slag, and the Fe/SiO2 ratio in the slag on the solubility of MgO in the slag and the phases formed due to the interaction between the slag and refractory. The experiments in this study began with the preparation and initial characterization of tin smelting materials, coal reductant, and additive materials such as limestone, hematite, and dolomite. The smelting materials, coal reductant, and additives were mixed and placed into pure MgO crucibles, then melted in a Vertical Tube Furnace at varying temperatures of 1250 and 1400°C for 2 hours under inert conditions. The resulting slag and MgO crucibles were analyzed using Scanning Electron Microscopy – Energy Dispersive Spectroscopy (SEM-EDS). Thermodynamic simulations were also performed to calculate the solubility of MgO in tin smelting slag as a function of temperature, Sn content in the slag, the CaO/SiO2 ratio in the slag, and the Fe/SiO2 ratio in the slag. The experimental results indicate that at a temperature of 1250°C, the solubility of MgO in the slag is below 12 %, whereas at 1400°C, it reaches 18 %. The increase in smelting temperature impacts the rise in MgO solubility in the slag. Increasing the CaO/SiO2 and Fe/SiO2 ratios affects the reduction of MgO refractory solubility in tin smelting slag with constant Sn, TiO2, and Al2O3 content in the slag. Increasing the Sn content in the slag impacts the reduction of MgO refractory solubility in tin smelting slag with constant CaO/SiO2, Fe/SiO2, TiO2, and Al2O3 ratios. The solid phases that might form during smelting at 1250°C, based on thermodynamic simulations and experimental results, are olivine and spinel. In contrast, the solid phases that might form during smelting at 1400°C are olivine and monoxide.