Dielectric properties and microwave heating characteristics of Huimin siderite ore

Dielectric properties of Huimin siderite ore were investigated by using the self-made high-temperature cavity perturbation method from room temperature to approximately 1000 °C at 2.45 GHz. The dielectric properties of the siderite ore remain constant from room temperature to 400 °C, then there is a rapid increase in both the dielectric loss factor and loss tangent from 400 °C to 600 °C, due to the decomposition during microwave roasting of siderite. Dielectric loss factor of siderite plays a leading role in the microwave heating process. Siderite has a maximum penetration depth at 400 °C and then gradually decreases with increasing temperature. According to dielectric properties of siderite, the maximum microwave absorption is achievable at the appropriate penetration depth. The temperature of siderite can be increased to 1000 °C in 10 min, showing that microwave heating is fast and saving time compared to conventional heating methods. The heating rate reaches a maximum at about 7 min, and decreases with microwave heating time, in accordance with the dielectric properties of the siderite.