Chul-Woo Nam

A new approach to the recycling of gold mine tailings using red mud and waste limestone as melting fluxes

Gold mine tailing, red mud and waste limestone cause very serious problems to the environment. Due to their abundant amount of waste as well as difficulties with disposal, an appropriate recycling technology of this waste is necessary to mine and smelting industries. As a prospective process for treating a large volume of the waste, slag atomizing technology is developed. Slag composition is the most important factor in manufacturing slag granules. The waste was mixed with the ratio of 26 wt% of tailing, 38 wt% of red mud and 36 wt% of waste limestone for a better melting operation regarding product property, viscosity and melting temperature. After pelletizing the above mixture, the pellets were dried in an oven for 2 days and were melted in an electric arc furnace at 1500(C for 2 hours. Separated slag was atomized under air gas surrounding with the velocity of 75 m/second. The final obtained precious slag balls might have good physical properties, such as highly spherical shape and narrow size distribution for application in abrasives, roofing granules, polymer concrete and road paving materials.

A noble Process to Recover Metal Values from Spent Hydrodesulphurization Catalyst

ABSTRACT A combination of pyro-and hydro-metallurgical process has been proposed to selectively recover molybdenum, cobalt and aluminium from the spent hydrodesulphurization catalyst containing 12.3% Mo; 31.8% Al; 2.38% Co; 9.5% S and 2.9% C. Before a two stage alkali-acid leaching process to selectively target Mo, Co and Al from the uncrushed sample, the spent catalyst was roasted at different temperature. Characterizations of different roasted samples were carried out in order to understand the structural changes and dissolution behavior of spent catalyst. Mo was selectively separated and recovered from the leach liquor by carbon adsorption method; whereas, Al and Co were separated by an organo-phosphinic based extractant, Cyanex 272. In the whole process, 95.9% Mo, 89.6% Co and 39.8% Al was recovered from the spent catalyst.

Thermodynamics of Simultaneous Desulfurization and Dephosphorization of Silicomanganese Alloy

Because sulfur and phosphorus are very harmful in steel products, there are increasing requirements for refining these elements from ferroalloys industries. Hence, in the present study, simultaneous desulfurization (de-S) and reducing dephosphorization (Rde-P) from silicomanganese (SiMn) alloy were investigated using metal-slag equilibration method under highly reducing condition at 1773 K. Experiments were carried out by equilibration between SiMn alloy and MnO-based slag in graphite crucible under p(O2) = 10−18 atm. Slag composition was designed by changing basicity (CaO/SiO2) and MnO content at fixed Al2O3 (=20%) and MgO (=5%) contents. De-S ratio increased with increasing basicity until C/S = 1.5 whereas Rde-P ratio was not significantly affected by slag basicity. This was because thermodynamic driving force of de-S reaction was greater than that of Rde-P reaction under present experimental conditions. The de-S and Rde-P ratios commonly increased with decreasing oxygen partial pressure.