Basic Theory And Technology Of Bath Smelting Process For Treating Molybdenite

Molybdenum is an important strategic metal reserve, mainly sourcing from molybdenite. The existing processing of oxidizing molybdenite has such drawbacks as small production capacity, low concentration of SO2in fume and high energy consumption. Therefore, a novel idea of recovering molybdenum directly from gas phase is proposed. A Bath Smelting Process is put forward based on the new idea, during which molybdenite is dissolved in white copper matte, and extracted from the copper molybdenum matte after its oxidization and volatilization. The obtained achievement is presented as follows.1) Research on phase diagrams of Cu2S-MoS2binary system and Cu-Mo-S ternary system is carried out using the Cooling Curve Method. Cu2S-MoS2binary system is a simple eutectic system in the range of0to4.48wt.%MoS2with eutectic composition of1.70±0.20wt.%MoS2and eutectic temperature of1117±10℃. Ternary compounds such as CuMo2S3or Cu2Mo6Ss forms when the content of molybdenite in system is more than4.48wt.%and its amount increases with the growing content of molybdenite. The freezing point for the compositions close to Cu2S in Cu-Mo-S ternary system is lower than aforementioned eutectic temperature and drops with reducing molybdenum content and approaching to the composition point of Cu.2) The solubility of molybdenite in white copper matte from Jiangxi Copper Corporation as an example is measured as a function of temperature, primary composition, the content of Fe and the grade of white copper matte. If increasing the primary composition of MoS2between0-20wt.%, the content of MoS2dissolved in white copper matte grows. Nevertheless, it drops dramatically over20wt.%. The solubility of molybdenite in white copper matte at1150,1200,1250and1300℃is21.04,18.79,17.58,17.74g MoS2/(100g Cu2S), respectively. What’s more, the solubility drops with the growth of the iron content and the grade of white copper matte.3) The thermodynamics for oxidizing the molybdenum in copper matte is investigated. Two zones in Cu-Mo-S-O thermodynamic equilibrium diagram, Q1and Q2, are found being suitable to oxidize molybdenum in copper matte. For Q1, log PSO2=7.0-10.0, log PO2=0-2.5; Q2, logPSO2=0-5.0, log PO2=0-2.0. In addition, the occurrence of the impurity Fe is adverse to the oxidization and volatilization of molybdenum.4) The kinetics for oxidizing molybdenum in copper matte is studied. A kinetic model is built based on the assumption that the oxidization and volatilization process of molybdenum is controlled by mass transfer of molybdenum between gas-liquid boundaries. The equation for this process is as follows.The influence of series factors, which include oxygen enrichment, air flow, reaction temperature and conditions for chemical reaction engineering, on the oxidization and volatilization kinetic of molybdenum in copper matte are theoretically discussed. The partial pressure of MoO3in bubble increases as oxygen enrichment increases, however, it shows contrary relationship to the air flow and outside diameter of the nozzle. Additionally, the deeper the nozzle immersed in melts, the higher the utilization of oxygen reaches.5) The effects of reaction time, air flow, and oxygen enrichment on oxidization and volatilization of molybdenum is experimentally studied. The volatilization ratio of molybdenum increases with prolonged reaction time, higher air flow and oxygen enrichment. Furthermore, the influence of oxygen enrichment on volatilization of molybdenum is more distinct as oxidization time prolongs.