Image reconstruction for wet granules by electrical capacitance and microwave tomography

The moisture content of granules in fluidized bed drying, granulation and coating process is typically between 1%~25%, which results in the change of permittivity and conductivity during the process. In such conditions, the application of capacitance tomography has some limitations. Considering that Microwave Tomography has a wide range of frequency (1.0MHz~2.5GHz) and can be used to measure materials with high permittivity and conductivity, the objective of this research is to combine capacitance and microwave tomography to investigate the solid concentration with different moisture content. The reconstructed images show that both capacitance and microwave tomography are functions of moisture content. The measurement results demonstrate that the two process tomography technologies can complement with each other. The analysis results might be used to process control in a fluidized bed drying, granulation and coating to improve operation efficiency.