Effect of temperature on dielectric property and microwave heating behavior of low grade Panzhihua ilmenite ore
(1. Yunnan Provincial Key Laboratory of Intensification Metallurgy, Kunming 650093, China;
2. National Local Joint Laboratory of Engineering Application of Microwave Energy and Equipment Technology,
Kunming 650093, China;
3. Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology,
Kunming 650093, China;
4. Yunnan Copper Industry Co., Ltd., Kunming 650093, China)
2. National Local Joint Laboratory of Engineering Application of Microwave Energy and Equipment Technology,
Kunming 650093, China;
3. Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology,
Kunming 650093, China;
4. Yunnan Copper Industry Co., Ltd., Kunming 650093, China)
Abstract: The permittivity of low grade Panzhuhua ilmenite ore at 2.45 GHz in the temperatures from 20 °C up to 100 °C was measured using the technology of open-ended coaxial sensor combined with theoretical computation. The results show that both the real (ε′) and imaginary (ε′′) part of complex permittivity (ε′-jε′′) of the ilmenite significantly increase with temperature. The loss tangent (tan δ) is a quadratic function of temperature, and the penetration depth of ilmenite decreases with temperature increase from 20 °C to 100 °C. The increase of the sample temperature under microwave radiation displays a nonlinear relationship between the temperature (T) and microwave heating time (t). The positive feedback interaction between complex permittivity and sample temperature amplifies the interaction between ilmenite and the microwave radiation. The optimum dimensions for uniform heat deposition vary from 10 cm to 5 cm (about two power penetration depths) in a sample being irradiated from both sides in a 2.45 GHz microwave field when temperature increases from room temperature to 100 °C.
Key words: dielectric properties; Panzhihua ilmenite low grade; microwave heating; temperature increase