OXIDE PHASES EQUILIBRIUM IN LATERITE NICKEL ORE SMELTING AS A FUNCTION OF SIO2/MGO RATIO WITH ADDITION OF LIMESTONE AND BAUXITE AT 1450-1550°C TEMPERATURE

• Main Author: Alam Erguna Sembiring, Dipo
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/65997
• Institution: Institut Teknologi Bandung

The use of nickel is spread across various sectors, such as raw material for making stainless steel, manufacturing batteries, nickel-based alloys, and as a metal alloying element. Indonesia is a country with the largest nickel reserves and production in the world, with the main reserves in the form of laterite nickel ore. In ferronickel smelting, the operating temperature determines the effectiveness and efficiency of the process. The operating temperature is the melting temperature of the slag, and the melting temperature of the slag is based on its composition. The main ingredients of ferronickel smelting slag are SiO2 and MgO, so the ratio of SiO2 and MgO determines the operating temperature in the ferronickel smelting process. In this research, an experiment was conducted to study the effect of adding limestone and bauxite at various ratios of SiO2 and MgO to nickel ore in ferronickel smelting on the composition and phases present in the slag and its effect on the liquidus temperature of the slag. The research was conducted at melting temperatures of 1450, 1500, and 1550 °C. The experiment was started by conducting a simulation using FactSage 8.0 software with reference to the results of the characterization of the composition of saprolite nickel ore, coal and additives. After that, the saprolite nickel ore, coal, and additives were mixed and put into a platinum envelope with the addition of 2% bauxite and variations of limestone 2 and 4% by weight of the saprolite nickel ore. Next, the reduction process was carried out in a vertical tube furnace for two hours in an inert state by exhaling 1 L/min of argon gas at various temperatures, such as 1450, 1500, ans 1550 °C. The smelted powder was than analyzed for its microstructure using an optical microscope and its composition was measured using scanning electron microscopy - electron dispersive spectroscopy (SEM-EDS). The average levels of slag produced in this experiment were 10% FeO, 63% MgO, and 27% SiO2. The liquidus temperature of the slag in the smelting of saprolite nickel ore decreases with the addition of additives in the form of bauxite and limestone. The addition of limestone and bauxite which reduces the temperature the most significantly is in laterite nickel ore with SiO2/MgO content of more than 2, this is due to the widening of the slag melting zone which is getting bigger. The solid phase that appears in the smelting product that has not reached the liquidus temperature is olivine in the form of Mg2SiO4, FeMgSiO4, NiMgSiO4, and silica.