OXIDE PHASE EQUILIBRIUM IN NICKEL SAPROLITE ORE SMELTING AS A FUNCTION OF SIO2/MGO RATIO BY ADDING BAUXITE AT TEMPERATURE OF 1550°C

• Main Author: Puri Syahieka, Manira
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/66321
• Institution: Institut Teknologi Bandung

Nickel is one of the strategic metals that plays an important role in the development of modern infrastructure and technology. Indonesia has nickel resources and reserves of 33 million tons and 21 million tons, respectively. 72% nickel is produced as stainless steel. Ferronickel as the raw material for making stainless steel comes from saprolite nickel ore. The nickel production process in Indonesia is generally carried out through a pyrometallurgical process with a Rotary Kiln- Electric Furnace (RKEF) because the ore used is saprolite nickel ore. The challenge of production using RKEF is the variation in the ratio between SiO2 and MgO contained in saprolite nickel ore in nature. A high SiO2/MgO ratio can cause the liquidus temperature of the slag to increase and result in an increase in electricity demand. Therefore, it is necessary to add additives to overcome the increase in liquidus temperature due to the increasing ratio of SiO2/MgO in saprolite nickel ore. One of the materials that can be used as an additive in the reduction of saprolite nickel ore is bauxite. From this research, it is expected to know the effect of adding bauxite for the reduction of saprolite nickel ore in various SiO2/MgO ratios on the liquidus temperature of the slag and the phase composition in the formed slag. This research was conducted with 12 samples of a mixture of nickel saprolite with a ratio of SiO2/MgO 1,46., 1,77., 2,36., 2,62., 2,85., 3,02., and coal, with variations in the addition of additives in the form of bauxite, as much as 2% and 4% of the weight of nickel saprolite used. The mixture of the three raw materials is then put into a vertical kiln and melted at a temperature of 1550°C. The sample then undergoes quenching process. The smelting results were then observed and analyzed using an optical microscope, Scanning Electron Microscope– Energy Dispersive Spectroscopy (SEM-EDS), and ImageJ software to determine the phase composition formed. The results showed that solids were formed in the form of pyroxene in the saprolite nickel slag in the SiO2/MgO ratio at 2.62 and a solid in the form of cristobalite in the saprolite nickel slag with the SiO2/MgO ratio at 2.85 with the addition of 2% bauxite. Solids also formed in the saprolite nickel slag in the SiO2/MgO 1.77 ratio in the form of olivine and in the saprolite nickel slag in the SiO2/MgO 2.36 ratio in the form of pyroxene with the addition of 4% bauxite. The addition of 2% bauxite increases the liquidus temperature of the saprolite nickel slag with a SiO2/MgO ratio of 2.62 and 2.85, while the addition of 4% bauxite increases the liquidus temperature of the saprolite nickel slag with a SiO2/MgO ratio of 1.77 and 2.36, and lowering the liquidus temperature of the saprolite nickel slag with the SiO2/MgO ratio above 2.36.