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The prediction of grinding particle size is an effective measure to optimize the grinding process. Cassiterite polymetallic sulfide ore and lead-zinc ore, as the research object in this paper, thei...

Nanoporous thermal insulating composites of fumed silica, opacifier, and fiber have been prepared by a dry molding method. SiC is adopted as an opacifier to improve thermal insulating performance at higher temperatures where radiation heat transfer plays an important role in entire heat transfer system. Radiative heat attenuation mechanisms have been illuminated by calculating thermal radiation optical parameters including scattering, absorption, and attenuation factors. The result shows fumed silica has low attenuation factor in infrared wavelength range, only 0.00188 for infrared radiation with a wavelength of 3.14 μm. The introduction of SiC can remarkably restrain radiative heat transfer, and the maximum attenuation factor reaches up to 5.848 for infrared radiation with a wavelength of 8.646 μm. The effect of SiC particle size on thermal radiation optical parameters is also studied. The choice of SiC particle size should match up with serving temperature of this insulation. In addition, thermal conductivity measurement has been employed to verify the accuracy of calculation results. Thermal conductivity can significantly decrease from 0.119 to 0.041 W/(m K) at 773 K when 25 wt% SiC (0.877 μm) is added into the composites.

This work investigated thermal stability of fumed silica based thermal insulating composites prepared by dry molding technology. The results showed that the composites could keep excellent thermal stability at the temperatures below 800 °C. However, when the samples were used at higher temperatures (>800 °C), the volume shrinkage increased sharply, which directly led to a serious deformation and then affected thermal insulating properties in applications. The utilization of fumed alumina could significantly improve thermal stability of the composites. When 5 wt.% fumed alumina was added, the volume shrinkage decreased from 10.49% to 3.47% at 1000 °C. The desirable results would be achieved by adjusting the amount of fumed alumina according to practical using temperature. In addition, field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase transformations of the composites treated at different temperatures.

In this study the removal of sulfur and arsenic from a refractory flotation gold concentrate by microwave heating was investigated. The results showed that cooling pattern of the heated products, heating time, temperature and atmosphere had significant effect on the removal of sulfur and arsenic.