Phase Transformation of Limonite Nickel Ores with Na2SO4 Addition in Selective Reduction Process

This study aims to observe the transformations, both mineralogy and morphology of limonite nickel ore with coal as reducing agent and Na2SO4 as additive in the selective reduction process. Limonite nickle ore from Halmahera, North Maluku was used in this study. Limonite nickel ore, coal and Na2SO4 was uniformly mixed by physical blending before reduction process. A series of selective reduction process was carried out at various temperatures in the Carbolite muffle furnace for 1 hour. The range of reduction temperatures was determined from Thermogravimetry - Derivative Thermal Analysis (TG-DTA) that indicates the decomposition temperature so that causing the transformation. The mineralogy of raw limonite nickle ore and reduced ores were characterised using XRD analysis, while morphology, particle size and mapping using SEM-EDS analysis. The results showed that goethite is the main component in the limonite nickel ore. Selective reduction process affected phase and microstucture transformation as result of decomposition. The decomposition was started by losing the crystalline water of goethite at 300ºC. It was continued with decomposition of lizardite at 600ºC. For further reduction temperature, trevorite was decomposed at 800ºC, Fe and Fe-Ni were formed at 900ºC and metallization continuously occurred up to 1000ºC. Intensity of metal formed increases by increasing reduction temperature up to 1100ºC. The addition of Na2SO4 on the selective reduction process decreased silica content, also it caused the formation of fayalite at 600ºC and FeS at 800ºC. When reduction temperature more than 900ºC, intensity of fayalite and FeS decreased. According to the morphology, the particle size and porosity of limonite ores is greater up to 2.5-fold by increasing the reduction temperature up to 1100ºC. Mapping of SEM-EDS analysis showed the distribution of each substances has agreeable with XRD analysis result. International Conference on Advanced Materials Science and Technology