Dielectric properties and temperature increase characteristics of zinc oxide dust from fuming furnace

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

“…It can be seen from Figure 4 that the zinc sulfide concentrate is medium loss material when the temperature less than about 450 • C, and zinc sulfide concentrate is high loss material because of tan δ > 3 × 10 −2 when the temperature change approximately from 450 to 800 • C. The loss tangent at 915 MHz is larger than that at 2450 MHz for temperature above 400 • C, the maximum values of loss tangent are 0.232 at 2450 MHz and 0.100 at 2450 MHz, respectively. The zinc sulfide concentrate of bigger apparent density for a given temperature mostly has a higher value of dielectric loss factor, it can be concluded that the loss tangent increases and reaction process accelerates as the apparent Minerals 2017, 7, 31 7 of 10 density increases suitably, similar results for room temperature can be found in literature [24,25], so we can enhance the ability of absorbing microwave by increasing the apparent density. Figure 5 presents the temperature dependence of penetration depth at 915 and 2450 MHz for two different apparent densities-1.54 and 1.63 g/cm 3 .…”

“…The loss tangent at 915 MHz is larger than that at 2450 MHz for temperature above 400 °C, the maximum values of loss tangent are 0.232 at 2450 MHz and 0.100 at 2450 MHz, respectively. The zinc sulfide concentrate of bigger apparent density for a given temperature mostly has a higher value of dielectric loss factor, it can be concluded that the loss tangent increases and reaction process accelerates as the apparent density increases suitably, similar results for room temperature can be found in literature [24,25], so we can enhance the ability of absorbing microwave by increasing the apparent density. The dielectric loss factor at 915 MHz from Figure 3b is smaller than that at 2450 MHz from Figure 3d when the temperature under 400 • C, but reverse results when the temperature above 400 • C. It can be concluded that dipolar rotation is the main contribution to the loss factor when temperature under 400 • C, while ionic conduction contributes mainly to the loss factor when temperature above 400 • C because thermal agitation disturbs the alignment of the molecule dipole with the electric field and conduction increases as the temperature increases, similar results have also been reported by some literature [22,23].…”

Dielectric properties of zinc sulfide concentrate during the roasting at microwave frequencies

“…The loss tangent at 915 MHz is larger than that at 2450 MHz for temperature above 400 °C, the maximum values of loss tangent are 0.232 at 2450 MHz and 0.100 at 2450 MHz, respectively. The zinc sulfide concentrate of bigger apparent density for a given temperature mostly has a higher value of dielectric loss factor, it can be concluded that the loss tangent increases and reaction process accelerates as the apparent density increases suitably, similar results for room temperature can be found in literature [24,25], so we can enhance the ability of absorbing microwave by increasing the apparent density. Figure 5 presents the temperature dependence of penetration depth at 915 and 2450 MHz for two different apparent densities-1.54 and 1.63 g/cm 3 .…”

Microwave absorption properties of steelmaking dusts: effects of temperature on the dielectric constant (ε′) and loss factor (ε′′) at 1064 MHz and 2423 MHz

“…The penetration depth (D P , cm) is dened as the distance from the material surface where the absorbed electric eld falls to 1/e of the electric eld at the surface. 16,25 D P is given by the following eqn…”

“…It was found that both the dielectric constant and the loss factor of the EAF dust increase as the temperature rises; a sharper increase of both values was noticed when the temperature exceeded 300 C. The authors did not provide an interpretation of the changes in the dielectric properties of the EAF dust with temperature. Zhang et al 16 measured the dielectric properties of zinc oxide dust in different apparent densities. They concluded that the dielectric properties of zinc oxide dust increase when the apparent density increases.…”