Permittivity Study of a CuCl Residue at 13–450 °C and Elucidation of the Microwave Intensification Mechanism for Its Dechlorination

Permittivity is a vitally important parameter for describing the absorbing and heating characteristics of a material under microwave irradiation, and it is also strongly dependent on temperature. However, the literature contains little information on this topic and even less particular permittivity data at elevated temperatures. In this paper, the permittivity of a CuCl residue at temperatures from 13 to 450 °C at 2.45 GHz was measured using the cavity perturbation method. The relationship of its real part (ε′) and imaginary part (ε″) with temperature (T) was deduced. In addition, the temperature-dependent tangent (tan δ) and the penetration depth (d) of microwaves into the material were calculated. The results of the permittivity study show that the dielectric constant (ε′) of the CuCl residue increased linearly with increasing temperature. In contrast, the dielectric loss factor (ε″) and loss tangent first maintained on a steady value between 13 and 300 °C and then substantially increased from 300 to 450 °C. The positive interaction of the dielectric property and temperature showed the reasonableness of our earlier metallurgy process, where the CuCl residue for dechlorination was roasted at 350–450 °C under microwave irradiation