Dielectric Properties of Zinc Sulfide Concentrate during the Roasting at Microwave Frequencies

Abstract

Abstract:Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for two different apparent densities-1.54 and 1.63 g/cm 3 -have been measured by using the resonance cavity perturbation technique at 915 and 2450 MHz during the roasting process for the temperature ranging from room temperature to 850 • C. The variations of dielectric constant, the dielectric loss factor, the dielectric loss tangent and the penetration depth with the temperature, frequency and apparent density have been investigated numerically. The results indicate that the dielectric constant increases as the temperature increases and temperature has a pivotal effect on the dielectric constant, while the dielectric loss factor has a complicated change and all of the temperature, frequency and apparent density have a significant impact to dielectric loss factor. Zinc sulfide concentrate is high loss material from 450 to 800 • C on the basis of theoretical analyses of dielectric loss tangent and penetration depth, its ability of absorbing microwave energy would be enhanced by increasing the apparent density as well. The experimental results also have proved that zinc sulfide concentrate is easy to be heated by microwave energy from 450 to 800 • C. In addition, the experimental date of dielectric constant and loss factor can be fitted perfectly by Boltzmann model and Gauss model, respectively.

High Temperature Dielectric Properties of Iron- and Zinc-Bearing Products during Carbothermic Reduction by Microwave Heating

“…In all cases, penetration depth is reduced as temperature increases. This result is in agreement with observations made of similar materials by other researchers [15,25]. As expected, the penetration depth is higher in the case of lower carbon content due to lower loss factor values that allow deeper penetration of microwave energy into the sample.…”

“…As expected, higher dielectric properties are observed for more compacted samples, since the amount of air is reduced in the mixture. Previous studies made on similar materials within narrow density ranges (i.e., from 1.54 to 1.63 g/mL in [25]) concluded that temperature has a greater effect on dielectric properties than apparent density. The presented results show that, if a wide range of densities is considered, the effect on the dielectric properties can be comparable to the effect of temperature rise.…”

Microwave heating oxidative stabilization of KMnO4 modified polyacrylonitrile-based carbon fiber precursor

“…Moreover, the dielectric properties of powder samples were measured using the resonant cavity perturbation method. [20,31] Therefore, the dielectric properties of the ber can be obtained by the resonant cavity perturbation method. The principle is to measure the resonance frequency and quality factor before and after the ber is loaded, so that the dielectric constant is calculated based on the difference between the resonance frequency and the quality factor.…”