An ultra-wideband system for measuring the dielectric properties of mineral compounds in a heat-reaction chamber at high temperatures

• Published in: IEEE transactions on instrumentation and measurement 2023, Vol.72, p.1-1
• Main Authors: Ottosson, Patrik, Andersson, Daniel, Choudhary, Vipin, Ronnow, Daniel
• Format: Article
• Language: English
• Subjects: calcination; dielectric permittivity; heat-chamber; High-temperature techniques; radio measurement; thermogravimetry; ultra-wideband; UWB
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2023.3265760

A measurement system for the measurement of microwave dielectric properties of mineral compounds at temperatures up to +1000°C is presented. It includes the simultaneous measurement of mass and temperature. Samples volumes in the range 0.01 to 0.1 m 3 can be studied. The system comprises a heat reaction chamber on a mass scale with mounted ultra-wideband (UWB) radio sensors and temperature probes. The complex refractive index is determined from the UWB signals using a technique with windowing to suppress interference and fitting of a modelled signal to the experimental ones. The developed method is validated by measuring the complex refractive index of water from +82°C down to +23°C and comparing with literature values. The systems is used to study calcination of limestone, i.e. the chemical decomposition of CaCO 3 to CaO and CO 2 when heated up to +1000°C. The chemical decomposition is clearly seen as a decrease in mass and as significant changes in the complex refractive index. The system could be used also for other mineral compounds and other types of materials.