Development of cold bonded chromite pellets for ferrochrome production in submerged arc furnace

Abstract

Pelletizing of Indian chromite ores is more challenging due to their high refractory nature. High Cr/Fe ratio and high MgO content in these ores demand high firing temperatures and longer firing cycles but often result in low strength fired pellets. Aim of this study was to develop cold bonded chromite pellets for smelting in submerged arc furnace (SAF) from chromite fines using suitable binder that induce less gangue into the pellets but cures quickly. Different binders were studied through laboratory pelletizing experiments for their suitability for cold bonding the pellets. As result, a composite binder comprising dextrin and bentonite, was found to be suitable and pellets made from the same were tested for their low and high temperature behavior. Electron and optical micro structural studies with image analysis were carried out to find out the type and amount of phases formed in the chromite pellets during high temperature reduction. High temperature reduction studies revealed that pellets were resistant to disintegration up to 1 200°C. Pilot scale arc furnace trials were also carried out to compare the performance of cold bonded pellets (CBPs) with sintered chromite pellets and found that for a constant power input, smelting rate was faster for CBPs than sintered pellets. Loss of Cr to slag was reduced in case of cold bonded pellets usage. © 2013 ISIJ.