Microwave permittivity of limestone and quicklime at high temperatures

The complex relative permittivity vs temperature at microwave frequencies (1.45–2.45 GHz) of limestone (CaCO 3 ) and quicklime (CaO) is reported in the range from room temperature to 1000°C. Limestone gravel was heated to calcinate from limestone to quicklime in a heat reaction chamber. The permittivity was determined continuously during calcination from measured propagated microwave signals. The calcination degree and volume fractions of CaO 3 and CaO were determined from the measured mass during calcination. Using the experimental volume fractions, an inverse electromagnetic mixing formula (EMF) was used to separate the permittivity of CaCO 3 and CaO that coexist during calcination. The permittivity for bulk CaCO 3 and CaO was estimated and both the real imaginary parts were found to increase monotonically with temperature for both materials. The estimated values for bulk materials were validated by comparing calculated and measured permittivity of a limestone block during calcination. Calculated and experimental data were in agreement within experimental errors. • Effective permittivity of limestone gravel is measured during calculation. • Inverse dielectric mixing formula used to separate permittivity of constituents. • Permittivity of bulk CaCO3 and CaO for temperatures up to + 1000 C are given.