THE EFFECT OF MIXING METHODS BEFORE THE DECOMPOSITION PROCESS OF FERRONICKEL SLAG

Ferronickel slag is the by-product that was obtained from ferronickel production and contains Si and Mg as the main elements. The decomposition process using alkali could decrease energy consumption to process ferronickel slag by decreasing its melting point. The mixing methods before the decomposition process could significantly affect the interaction between reactants over the process, therefore it is essential to study. This study aims to determine the effect of mixing methods of ferronickel slag and NaOH prior decomposition process on the chemical composition, phase, and microstructure of decomposed ferronickel slag. Two different mixing methods, physical mixing and impregnation, followed by roasting process at 350 ℃ for 60 minutes were performed, characterized, and analysed. Thermodynamic analysis was calculated and shows a good agreement with the characterization results which the formation of sodium silicate, magnesium hydroxide and iron oxide were identified. The formation of spotty decomposition and distribution of the product layer can be observed as the decomposed ferronickel slags that were priorly mixed by physical mixing and im-pregnation, respectively. Therefore, the effectiveness of impregnation over physical mixing was investigated.