| Guangxi is one of the most important provinces of China in exploration and production of the nonferrous mineral resources, including sulfur concentrate. Industry, the refined processing of pyrite and its associated minerals was extremely imperfect, which was also a difficult topic to be overcome in iron ore smelting. In order to improve the utilization of these resources, this paper attempted to introduce the microwave radiation roasting method. As a new form of heating energy, microwave has advantages in energy saving, control easily and clean in the field of microwave metallurgical. However, this metallurgical technology was also disadvantages in microwave attenuation, thinner material thickness requiring, small processing capabilities of the equipment, and so on. In the past, low-power microwave devices were selected to research small quantities of ore samples, which was limited to reveal the influencing factors. Therefore, this paper tried to use high-power microwave metallurgical equipment to study the processes, including viability exploring of sulfur concentrate microwave directly roasting, and predicting of transformation behavior of pyrite and sulfur arsenic iron minerals in the microwave metallurgical. It could provide a theoretical basis to the metallurgical technology. The experimental results demonstrated some effective equipment and environmental conditions. Microwave should be tried to avoid radiateing the other magnetrons by directly, or the normal working capacity and service life of the magnetron might be affect. A baffle of microwave breach should be subjoined to effectively block the hazards of dust and harmful gases on the magnetron. The baffle material could be quartz with owning high performance of microwave penetrating and temperature resistance. Exhaust pipe was preparated with the iron material. A large buffer space in the pipeline was set to help the recovery of sulfur, arsenic, and other dust in solid particles deposition, reducing the turbidity of the exhaust gas in the other hand. Series of devices filled with the concentrated alkaline solution after the buffer device were used to absorb toxic substances, such as SO2or As2O3, greatly reducing the poisons and suspended dust in the exhaust. On the tail of the pipe, an exhaust fan with500W power was connected to remove the product in gas phase from the solid phase sublimation. Ore samples can be placed in crucible container from quartz material or Mx materials when microwave treatment. Both materials had similar effects on the weight loss rate of the ore. The airflow must avoid obstruction to lower partial pressure of the gas products which would help improve the equilibrium constant of the mineral decomposition reaction. Unimpeded airflow can improve the separation effect. The ore samples also avoided mechanical rotating or stirring, because the movement might lower the energy efficiency of microwave. Certainly, the mechanical rotation may be good for the uniformity level of the roasted mineral.Removal laws of sulfur, arsenic included:(1) Activated carbon powder didn’t take effect completely, as a result, remaining carbon leaded to lower the variation of the mineral weight relatively. Consequently, additional activated carbon could not enhance the weight loss rate.20g activated carbon played a best performance on the mass loss rate when its added weight was between5-25g.(2) The increasing of the decomposition rate of sulfur arsenic ore samples were slower than the weight of ore sample when the time and the thickness of ore samples were fixed, so the relative weight loss rate lowered.(3) A smaller quality of mineral, a greater microwave power, and a longer microwave radiation time, could help adequate decomposition of sulfur arsenic and higher the rate of weight loss.(4) The weight loss of certain mass of the ore, showed a visible linear trend with the changing microwave power. Specifically, this linear trend was particularly apparent between1000-4000W, the largest fitting constants was0.9972. The decomposition process needed enough time and energy.(5) Large microwave power and suitable mineral quality with an appropriate thickness by spreading out might advance the microwave treatment in the industry.The phase’s changes were analysised by XRD diffraction analysis and semi-quantitative of chemical elements. The calcined product surface layer was red; the surrounded surface was black; the lower layer changed little. The surface product layer showed a smallest proportion of sulfur content (S5.62%), while the relative largest content of iron was appearing. It indicated that the superficial part of the mineral can obtain more full decomposition. The mineral from the surrounding of the surface appeared black and great iron content, but the sulfur content is quite high (S27.72%). These cases suggested the ore in these part mainly occured alienation reaction, which caused partial decomposition for sulfur. However, the arsenic content of these calcine was very low. In the inner layer, the iron content changed little after burning product, and little sulfur was released (S30.20%). The unobvious processing effect was possible related to the processing time, the ore sample thickness of the accumulation and microwave penetration ability. As a result, the removal effect of microwave radiation on arsenic was more significant than the desulfurization by microwave roasting. |
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