Molybdenum Concentrate Research Articles

Process and Kinetics of Preparing Ammonium Molybdate from Molybdenum Concentrate by Microwave Roasting-Ammonia Leaching

Process and Kinetics of Preparing Ammonium Molybdate from Molybdenum Concentrate by Microwave Roasting-Ammonia Leaching

Preparations of Mo2C or Mixture of Mo2C and Mo by Silicon/Carbon Synergistic Reduction of Molybdenum Concentrate

Preparations of Mo2C or Mixture of Mo2C and Mo by Silicon/Carbon Synergistic Reduction of Molybdenum Concentrate

Removal Mechanism of Mineral Impurities in Molybdenum Concentrate Treatment Process

The removal of impurities in molybdenum concentrate has become a new challenge for enterprises due to the cancellation of pickling. Whether impurity minerals can be converted into soluble ions during roasting is important for the impurity removal by current water washing. In this work, the interaction between various impurity elements in the treatment process of molybdenum concentrate was studied by process simulation experiments combined with X-ray fluorescence (XRF) and X-ray diffraction (XRD), inductively coupled plasma-optical emission spectrometer (ICP-OES), ion chromatography (IC), scanning electron microscope-energy dispersive spectrometry (SEM-EDS), the use of FactSage7.0 modeling and the mineral liberation analyzer (MLA). The results show that most of the impurity elements such as K, Si and Al exist in the form of alkaline minerals with large molecular weight. In the roasting process of molybdenum concentrate, K-containing minerals, such as muscovite and orthoclase, can be transformed into K+, Al3+ and other soluble ions, and then can be removed by water washing. Humidification increased the conversion degree of orthoclase to soluble ions, which was conducive to the removal of impurities by the washing process. The results of MLA microscopic analysis confirmed that impurities such as FeS2, CaSO4, SiO2, and especially FeS2, would form a high density mixture with MoO3 during the high temperature roasting process, and thus reduced the leaching rate of Mo. Therefore, the humidification and control of the molybdenum concentrate is an effective measure to remove impurities.

A Novel Self-Heated Roasting Technology for Molybdenum Concentrate

Abstract Thermodynamic analysis of roasting process of molybdenum concentrate was conducted in the present work. The results show that the roasting reaction is an exothermic reaction. Once the reaction begins, it may occur spontaneously without any external heat source under industrial production conditions. It is revealed by thermal analysis experiment that higher oxygen concentration is more beneficial for the increase of the conversion rate of molybdenum concentrate, and the molybdenum concentrate with smaller granularity is easier to achieve the complete reaction degree. The thermal test results of conventional rotary kiln present that coal, as an external heat source, provides heat of 4.42 GJ/t by flue gas after combustion, in which the oxygen concentration is 10%. The temperature of main reaction zone is high, which results in the material agglomeration and inhibits roasting of the molybdenum concentrate. A novel self-heated roasting technology has been proposed in the present study. The technology can reduce the temperature of main reaction zone and increase the oxygen concentration in roasting gas via setting up a heat exchanger to recycle the heat released from the roasting process. And the preheated air is fed into the rotary kiln instead of original coal-fired flue gas. The coal combustion in conventional rotary kiln is no longer required in the novel technology. The whole roasting process works only by 6.45 GJ/t from chemical reaction heat. There is no carbon containing fuel input and no CO 2 emission. Therefore, it is an energy and environmentally responsible process.

Combined Determination of Phosphorus and Arsenic in Molybdenum Concentrate by Molybdenum Blue Spectrophotometric Method

This paper determined the total absorbance of phosphorus molybdenum blue and arsenic molybdenum blue by using the additive property of their absorbance values. By eliminating the interference of arsenic by reduction masking with composite reducing agent Na2SO3-Na2S2O3-KBr, the absorbance of phosphorus could be obtained. Thus, the content of phosphorus and arsenic could be calculated, respectively. The results show that the work curves of this method for phosphorus and arsenic are consistent with Beer’s law when the content of phosphorus and arsenic is 0-0.60ug/mL and 0-2.00ug/mL, respectively. The standard addition recovery rate of phosphorus and arsenic is 98.80%-101.04% and 99.00%-101.50%, respectively. The relative standard deviation of phosphorus and arsenic is less than 4.0% with good accuracy and precision. This method is simple and fast to determine phosphorus and arsenic in molybdenum concentrate, and the results are accurate and reliable.

The Development and Applications of the Dust and Rhenium Recovery Integrated Device of Calcination Exhaust of Molybdenum Concentrate which Contain Rhenium

A device, was used to recover dust and rhenium from molybdenum concentrate roasting exhaust gas, was developed. The device combine the self-swash dust catcher and spherical tray tower technology: the self-swash dust catcher was used to recover dust and rhenium; spherical tray tower was used to further dust and rhenium recovery and its application to engineering in practice. This was the first successful such devices used to recover dust and rhenium integration from calcination exhaust of molybdenum concentrate which contain rhenium in production practice. Through production practice, proved that the device is feasible, with high efficiency. And it has the advantages of simple structure, convenient operation, low cost and low energy consumption etc.. In addition, the dust removing system can also be used to the wet dust collector in the filed of metallurgical , mining, chemical and building.

NSC Hydrometallurgical Pressure Oxidation of Combined Copper and Molybdenum Concentrates

The need for copper and molybdenum continues to grow as does the need for clean efficient metallurgical technologies capable of treating mixed metal concentrates. Currently, the use of hydrometallurgical pressure oxidation for copper concentrate treatment is growing. Furthermore, with limited molybdenum roasting capacity, stringent industrial molyb-denum concentrate roaster feed specifications, poor rhenium recoveries, and the inherent environmental issues asso-ciated with pyrometallurgical treatments, hydrometallurgical options are also now being pursued for molybdenum concentrates. Moreover, given the inherent grade, recovery and cost inefficiencies in the differential flotation process normally employed for molybdenum concentrates produced as a by-product of copper mining, there is a growing need to directly treat combined bulk copper and molybdenum concentrates. This minimizes molybdenum concentrate roasting limitations, specifications and requirements, while allowing simplification of increased efficiency of and cost reductions in upstream mineral processing circuits now producing separate copper and molybdenum concentrates by differential flotation. It would also allow more direct and efficient recovery of rhenium. Finally, hydro metallurgical technology will also reduce the need for costly final molybdenum concentrate impurity treatment circuits, thereby allowing for lower grade mixed metal molybdenum concentrates to be treated directly for a greater metal value realization. In summary, industrial nitrogen species catalyzed (i.e. NSC) hydro metallurgical pressure oxidation has many advantages over conventional pressure oxidation systems and offers a tangible process route to treat mixed bulk concentrates.This paper illustrates the fundamental concepts, confirmatory testing, application, proposed design and associated cost estimates for the development and industrial implementation of this proven mode of hydro metallurgical processing as applied combined to copper molybdenum rhenium concentrates.

Friction and Wear Studies on Polyphenylene Sulfide Filled with a Complex Mixture

The tribological behavior of PPS filled with molybdenum-concentrate (MC) deposit from Armenia was studied. The deposit MC was a complex mixture of compounds such as MoS2, SO2, CuS, Al2O3, and others. Whereas MC as the filler in particulate form reduced the steady state wear rate of PPS, the optimum reduction in wear was found to occur with the addition of PTFE along with PPS. The behavior of PPS composites made with MC and PTFE sliding against a steel counterface was investigated as a function of the MC and PTFE proportions, sliding speed, and counterface roughness. Of all the above factors, the change in MC proportion, while PTFE was also present, had the greatest effect on the reduction in wear rate. The variation of the coefficient of friction was found to be in the narrow range of 0.27-0.33. The lowest wear rate was found in the case of PPS+ 17vol.%MC+10vol.%PTFE composite sliding at 1.5 m/s against a counterface roughness of 0.1 μm Ra.

Study on Mechanism of Molybdenum Concentrate Roasting

Study on Mechanism of Molybdenum Concentrate Roasting

Study on Mechanism of Molybdenum Concentrate Roasting

Thermo gravimetric analyzer was used to investigate the thermo-gravimetric behavior and the exothermicity of molybdenum concentrate roasting. Roasting reaction mechanism of molybdenum concentrate was concluded with the double extrapolated method. Data processing and fitting was constructed with the integral methods of Costs-Redfern and Flynn-Wall-Ozawa, and roasting reaction kinetic parameters were proposed. The results showed that roasting reaction process of weight loss was divided into four stages, namely preheated drying stage, diffusion stage, rapid reaction stage and deep oxidation stage respectively. The heat released from the oxidation reaction mostly concentrated in the rapid reaction stage, the main product of this stage was MoO2, and the activation energy was 227.7kJ/mol. The main product of deep oxidation stage was MoO3. When the temperature was about 600°C, the formation rate of MoO3 was maximum, less heat released at this stage and the activation energy was 163.2kJ/mol.

Friction and wear studies using Taguchi method on polyphenylene sulfide filled with a complex mixture of MoS 2, Al 2O 3, and other compounds

The tribological behavior of polyphenylene sulfide (PPS) filled with molybdenum-concentrate (MC) deposit from Armenia was studied. The deposit MC was a complex mixture of compounds such as MoS 2, SiO 2, CuS, Al 2O 3, and others. Whereas MC as the filler in particulate form reduced the steady state wear rate of PPS, the optimum reduction in wear was found to occur with the addition of polytetrafluoroethylene (PTFE) along with PPS. The behavior of PPS composites made with MC and PTFE sliding against a steel counterface was investigated as a function of the MC and PTFE proportions, sliding speed, and counterface roughness. For this purpose, pin-on-disk configuration and the design of experiments approach utilizing Taguchi's orthogonal arrays were used. Of all the above factors, the change in MC proportion, while PTFE was also present, had the greatest effect on the reduction in wear rate. The variation of the coefficient of friction was found to be in the narrow range of 0.27–0.33. The lowest wear rate was found in the case of PPS + 17 vol.% MC + 10 vol.% PTFE composite sliding at 1.5 m/s against a counterface roughness of 0.1 μm Ra. Optical and scanning electron microscopy of the transfer films were performed for observation of the features such as coverage, thickness, topography, and bonding. Friction and wear results are discussed in terms of these observations.

Recovery of Molybdenum from Sulfide Concentrate by Electro-Oxidation and Precipitation.

Leaching of molybdenum concentrate in NaCl aqueous solutions by electro-oxidation has been investigated, and the major process parameters, such as current density, temperature, and pulp density (nominal content of the concentrate in slurry) have been experimentally examined. The leaching rate of the concentrate was found to be proportional to current density, while the molybdenum concentration in the leach solution increased linearly with time. These results show that the concentrate was effectively oxidized by oxidizers produced by electrolysis of the NaCl solution, then dissolved rapidly into the solution. Increase in pulp density results in preferential oxidation of iron and copper in the concentrate, and it reduces the efficiency of molybdenum extraction. With the purpose of examining the feasibility of molybdenum recovery through solubility change, the pH dependence of molybdenum solubility in 10 mass% NaCl solution was investigated at various temperatures between 298 and 353 K. The solubility of molybdenum was found to be lower than 0.05 mol/l in the range of pH from 2 to 3, and increased with increasing temperature and pH of the solution. Precipitation experiments from leach solution were then examined by changing pH of the solution, and solid MoO3·(H2O)x crystals, free of sulfur, were obtained from the leach solution containing large amount of SO42-. Trace rhenium in the concentrate was found dissolve into the leach solution and co-precipitate with molybdenum during this process.

Electro-Oxidation of Molybdenum Concentrate Using Bipolar Cell, and Recovery of Rhenium.

With the purpose of extracting rhenium from molybdenum concentrate, electrolysis of slurry, prepared by mixing molybdenum sulfide concentrate and 10 mass% NaCl aqueous solution, was carried out at 1 A, 313 K. The slurry was continuously circulated into a vertical type 10 stack bipolar electrolytic cell consisted of carbon electrode disks, and the concentrate was dissolved by electrochemically generated oxidizers. The current efficiency for molybdenum dissolution was 73 % after 10 hours electrolysis, and the leach solution was found to contain 0.2 mol / l of molybdenum and 4×10-5 mol / l rhenium. This result shows the dissolution speed is more than 8 times faster than that obtained using a single cell at applied current of 1 A. Prior to rhenium separation from the leach solution, preliminary experiments for rhenium extraction by MEK (Methyl-ethyl-keton) were carried out using synthesized test solutions having similar composition. The behavior of molybdenum, rhenium, and sulfur was investigated for examining the extraction conditions and efficiency. The leach solution obtained by electro-oxidation was then subjected to a solvent extraction experiment, and rhenium present at several tens of mass ppm in the concentrate was enriched to more than 1,000 times, and recovered as sulfides. After rhenium separation, molybdenum was recovered by precipitation after changing pH of the solution.

Electro-oxidation of Molybdenum Concentrate in Sodium Chloride Solution.

Dissolution behavior of molybdenum concentrate by electro-oxidation has been investigated in acidic and alkaline condition at constant current density of 625 A/m2 (1A) and temperature (313K). The experiments on electro-oxidation of molybdenum concentrate obtained from Erdenet mine from Mongolia were carried out in an laboratory scale electrolysis cell with 10 mass % NaCl electrolyte. The overall current efficiency for MoS2 dissolution was 97 % in alkaline and 92 % in acidic solution after 6 hours electrolysis, respectively. The current effeciency decreased to 82 % when the electodes were not separated from the slurry. It has been shown that the dissolution of MoS2 proceeds mainly by electrochemically produced oxychlorites in the solution. The residue obtained in acidic solution consisted of Si and Al, and that in alkaline solution consisted of Si, Al, Cu and Fe. In alkaline solution, Cu and Fe, which are main impurities of the concentrate, are separated by precipitation from leaching solution.