Dielectric Sensing of Mass Concentration and Moisture in Coal Powders

In powder processing industries, information about the mass concentration, and the moisture content of the material is often required for process monitoring and control. Capacitive sensors are widely applied for measurements of powder materials, as they are sensitive to variations in mass concentration and changes in moisture content. However, for processes where the mass concentration and the moisture content of the material can vary, it is not possible to distinguish between the two effects based on capacitive measurements alone. This letter shows how permittivity and conductivity measurements can be used to independently determine the mass concentration and the moisture content of a powder. The proposed method is demonstrated for an exemplary coal powder. A dielectric characterization based on impedance measurements of a coaxial probe is carried out. Based on these measurement experiments, a modeling approach is presented that allows the independent determination of the mass concentration and the moisture content of powders, which is of great interest for the development of measurement systems for powder processing industries.