Microwave Power Absorption in Materials for Ferrous Metallurgy

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© 2016, The Minerals, Metals & Materials Society. The characteristics of microwave power absorption in materials for ferrous metallurgy, including iron oxides (Fe2O3, Fe3O4 and Fe0.925O) and bitumite, were explored by evaluating their dielectric loss (QE) and/or magnetic loss (QH) distributions in the 0.05-m-thick slabs of the corresponding materials exposed to 1.2-kW and 2.45-GHz microwave radiation at temperatures below 1100°C. It is revealed that the dielectric loss contributes primarily to the power absorption in Fe2O3, Fe0.925O and the bitumite at all of the examined temperatures. Their QE values at room temperature and slab surface are 9.1311 × 103 W m−3, 23.7025 × 103 W m−3, and 49.5999 × 103 W m−3, respectively, showing that the materials have the following heating rate initially under microwave irradiation: bitumite > Fe0.925O > Fe2O3. Compared with the other materials, Fe3O4 has much stronger power absorption, primarily originated from its magnetic loss (e.g., QH = 1.0615 × 106 W m−3, QH/QE = 2.4185 at 24°C and slab surface), below its Curie point, above which the magnetic susceptibility approaches to zero, thereby causing a very small QH value at even the surface (QH = 1.0416 × 105 W m−3 at 880°C). It is also demonstrated that inhomogeneous power distributions occur in all the slabs and become more pronounced with increasing temperature mainly due to rapid increase in permittivity. Characterizing power absorption in the oxides and the coal is expected to offer a strategic guide for improving use of microwave energy in ferrous metallurgy.

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