Determination of optimal conditions for pressure oxidative leaching of Sarcheshmeh Molybdenite concentrate using Taguchi method

The present research work is based on finding the optimum conditions for pressure oxidative leaching of the molybdenite concentrate to produce technical-grade molybdic oxide (MoO3) with high recovery through further treatment of the filtrate solution. The Taguchi method was used to design and minimize the number of experiments. By using Taguchi orthogonal (L25) array, five parameters (time, temperature, oxygen pressure, pulp density and acid concentration) at five levels were selected for 25 experiments. The experiments were designed and carried out in a high-pressure reactor in the presence of nitric acid as solvent and oxidizing agent for the molybdenite concentrate and its ReS2 content. The optimum conditions for pressure leaching of molybdenite were obtained through using Signal to Noise analysis and modified by using Minitab software prediction tool. Furthermore, the optimum condition for an economical pressure leaching of rhenium sulfide (ReS2) was achieved with the same process. Analysis of variance (ANOVA) showed that the pulp density is of paramount importance in this process.

Treatment of Molybdenite Ore Using a 2 kw Solar Furnace

Hydrometallurgical methods of extracting molybdenite (MoS2) from the raw ore consume 145 × 106 Btu ton of fossil fuel equivalent energy per ton of concentrate produced. Processing the ore using a solar heat source could save 56 percent of this energy. Thermodynamic considerations indicate that MoS2 is the easiest of the economically valuable ores to extract. If the technique can be developed with this ore, it may be possible to extend it to other ores. Oxidation of the sulfide to molybdic oxide (MoO3) is an exothermic process, and it should proceed autogenically if the concentration of MoS2 is high enough. Experiments to measure the specific heat of the raw ore were conducted to determine the crossover point for this autogenic reaction. Using a calorimeter, we found three distinct reaction temperature ranges corresponding to water and organic vapors, oxidation of pyrite (FeS2), and oxidation of molybdenite. The production rate of SO2 was measured for 0.5-g samples of three different concentrations of molybdenite: (a) 95 percent MoS2 concentrate, (b) 10 percent concentrate in the raw ore, and (c) the unadulterated raw ore. A crude mass balance was obtained between the reaction products and the unreacted ore in the hearth. The curves of reacted product wersus time look very similar to the curves of SO2 gas produced versus time. Both sets of curves show the reaction is more than 90 percent complete in one minute. This work is sponsored by the US Department of Energy and the French Center Nationale de Recherche Scientifique. It is a cooperative effort of the Los Alamos Scientific Laboratory in the US and the Laboratoire des Ultra-Refractaires and the Laboratoire d’Energetique Solaire in Odeillo, France.