High-Temperature Permittivity and Microwave Pretreatment Characteristics of Nickel-Containing Sludge from Battery Production

Abstract

Permittivity is a vitally important parameter for the description of the absorption and heating characteristics of materials under microwave irradiation. In this paper, the permittivity of nickel-containing sludge (NCS), which is created during battery production as a cheap secondary resource, was measured at temperatures from 20 • C to 600 • C at 2.45 GHz using the cavity perturbation method. In addition, the loss tangent (tanδ) and penetration depth (Dp) of microwaves into the material were calculated. The results of the permittivity study show that the dielectric constant (ε ) and dielectric loss factor (ε") of the NCS increase with increasing temperature. The variations of the loss tangent (tanδ) and penetration depth (Dp) with the temperature can be divided into two parts at 200 • C. The effect of the initial moisture content on the dielectric properties of the material is notably greater than that of the temperature, which was confirmed by the heating curve. After microwave pretreatment, the nickel-containing phase is transformed into NiO, while the weight of NCS is reduced by more than 20%, the particle size is significantly reduced and the leaching time reduce 20 min than that of conventional heating.

Microwave drying of nickel-containing residue: dielectric properties, kinetics, and energy aspects

“…The system accuracy has been demonstrated in our preliminary work which was estimated to be 3% in the dielectric constant and 10% in the loss factor during the tests [27].…”

“…A permittivity measurement system based on microwave cavity perturbation method was used to measure the dielectric parameters of the NCR. The testing equipment has been widely used for the measurement of dielectric properties of materials [25][26][27]. A schematic of the system is shown in Figure 2.…”