ANALYSIS OF THE EFFECT OF SIO2/MGO RATIO IN SAPROLITE NICKEL ORE ON THE INTERACTION BETWEEN SLAG AND REFRACTORIES

• Main Author: Hananto Putra, Yudhistira
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/66260
• Institution: Institut Teknologi Bandung

Indonesia has the largest nickel reserves in the world, which is around 21 million tons of nickel in the form of laterite nickel ore. One of the nickel extraction routes from laterite nickel ore is through pyrometallurgy using rotary kiln - electric furnace (RKEF) technology. One of the concerns in using RKEF technology is the availability of ore with appropriate quality. SiO2/MgO (S/M) ratio in the ore is one of important parameters in the ore quality. Incompatible S/M ratio in the ore ca cause issues, one of which is agresive chemical interaction between slag and MgO refractory during smelting process in electric furnace. The experiment in this study began with the preparation and characterization of laterite nickel ore samples and coal reducing agents as well as the refractory preparation process. Several methods were carried out to find the best method to study the interaction of slag and refractories. The techniques used are the cup test technique and the finger test technique with different crucibles made of Pt, Al2O3, and MgO refractory. The experiments were carried out at process temperatures between 1450 and 1550 oC. The smelting was carried out in two furnaces i.e., vertical tube furnace and horizontal tube furnace. The smelted samples in the form of slag and refractories were then mounted and analyzed using an optical microscope and scanning electron microscope - electron dispersive spectroscopy (SEM-EDS). Experiments with the finger test technique using MgO refractory rod and Pt crucible are expensive and were not employed further. Experiment with finger test technique in horizontal tube furnace using MgO refractory rod and Al2O3 crucible showed significant Al2O3 dissolution into slag and spinel solid formation between slag and crucible. Experiments with the cup test technique in a vertical tube furnace using a crucible made of burnt MgO refractory showed the higher the S/M ratio in saprolite nickel ore, the higher the tendency for slag to react with the refractory. This can be seen based on the increasing amount of MgO refractory that was converted into the olivine phase with the higher S/M ratio in the initial ore. The cup test technique using the burnt MgO refractory has been found as the best technique because the interaction between the slag-refractory can be well observed and the quenching carried out on the sample causes the phases formed at high temperatures can be identified accurately. Based on the results of the analysis that has been carried out the mechanism of corrosion in refractories begins with wetting of the refractories by slag, followed by penetration of slag through the pores in the refractories, and then the chemical bonds between refractory particles are disrupted due to the presence of slag which cause MgO dissolution into the slag and formation of new phase.