Development of chromite sinter from ultra-fine chromite ore by direct sintering

Abstract

A significant quantity of chromite ore is available in form of fines and is friable in nature. Agglomeration is necessary for utilizing these fines. Briquetting gives green agglomerates with inferior high temperature properties. Pelletization requires further grinding of the naturally available ore fines and the subsequent firing of the green pellets for strength development which make it energy-intensive and complex process. In contrast, sintering can be done directly on the as-received friable chromite ore in the presence of coke breeze (as in case of iron ore sintering), which is likely to be free from the above limitations. In the current work, an optimum combination of temperature, flux (added to increase the relative quantity of molten phase required for sintering) and coke (added as fuel to attain the sintering temperature in a sinter pot) was computed using the thermochemical software, FactSage 6.1 and enthalpy balance calculation. Sintering of a mixture of chromite ore fines and flux with the optimum composition at 1 600°C was carried out in; (i) resistance furnace (100-g scale), without using carbon and (ii) a pot sintering set-up (10-kg scale), using the computed quantity of carbon. A good correlation between experimental result and predicted equilibrium phases has been observed. The characterization of the sinters prepared in pot sintering set-up was done by conducting shatter, tumbler, and abrasion tests, and their phase identifications by XRD and EPMA/EDS. The developed sinter was found to possess adequate handling strength that would be well acceptable to produce ferrochrome in the SAF. © 2014 ISIJ.