| At present, the United States, as well as the rest of the western world, is dependent on potentially unstable sources for supplies of chromite ores. Additionally, the growing problem of acid rain has prompted research into abatement of sulfur dioxide emissions.; This study focuses on selective sulfation of Montana Benbow chromite to both upgrade the ore and provide a sorbent for sulfur dioxide emissions. Application of this method would alleviate U.S. dependence on South Africa, Zimbabwe, and the U.S.S.R. for chromite imports, as well as contribute to the solution of sulfur dioxide emissions.; To provide a high-grade chromite concentrate, a novel column flotation technique (developed by the USBM) has been utilized. A thermodynamic study of the reaction scheme has shown that sulfation of impurities is feasible under normal operating conditions (500-1,000{dollar}spcirc{dollar}K, 1 atm). Using thermogravimetric analysis, a comprehensive study of gas-solid reaction kinetics was completed. This includes factors of flow rate, temperature, particle size, porosity, partial pressure, and promoter addition. The promoters (alkali sulfates) were found necessary to provide reasonable reaction rates.; To provide an indication of reaction products and of reaction extent, leaching of reacted samples was undertaken. This included factors of pH, temperature, and oxidizing agents. Also, mass balances were calculated to give an indication of overall upgrade in chromite grade.; Finally, to provide a deeper understanding of the reaction system, a mathematical model was used to correlate the kinetic data. This was based on the incorporation of a parallel reaction scheme into the grain model. |
