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

This study aims to observe the transformations, both mineralogy and morphology oflimonite nickel ore with coal as reducing agent and Na2SO4 as an additive in the selectivereduction processes. A series of selective reduction processes were carried out at varioustemperatures in Carbolite muffle furnace for 1 hour. The range of reduction temperature wasdetermined from Thermogravimetric-Derivative Thermal Analysis (TG-DTA). The mineralogyof raw and reduced ores was characterized by using XRD analysis. The morphology, particlesize, and mapping were characterized by using SEM-EDS analysis. The results showed thatgoethite was the main component in the raw limonite nickel ore and it was decomposed bylosing the crystalline water at 300 ºC. The decompositions were continued to lizardite andtrevorite at 600 ºC and 800 ºC respectively, then Fe and Fe-Ni were formed at 900 ºC.Metallization continuously occurred by increasing reduction temperature up to 1100 ºC.Moreover, the particle size and porosity of reduced ore were greater up to 2.5-times. Theaddition of Na2SO4 on the selective reduction processes decreased silica content; it also causedthe formation of fayalite and FeS at 600 ºC and 800 ºC respectively. The intensity of fayaliteand FeS decreased when the reduction temperature was more than 900 ºC. IOP Conf. Series: Materials Science and Engineering 202 (2017) 012016