Investigation and analysis of a fluidized bed dryer by process tomography sensor

Hai-Gang Wang,Wu-Qiang Yang,Yong-Lei Lin

doi:10.1007/s12182-019-00406-z

Abstract

In the pharmaceutical industry, fluidized beds are typically used for pellets drying, coating and granulation. The gas–solids flow characteristic in the process plays an important role to control the heat and mass transfer as well as the end-point product quality. Therefore, it is necessary to investigate the flow characteristics based on advanced measurement technologies. In this research, electrical capacitance tomography (ECT) sensor with eight electrodes was used to investigate the pharmaceutical fluidized bed drying process with different operation conditions. Key process parameters including solids concentration, particle moisture and capacitance signals in the process are given and analysed based on the ECT sensor. In addition, the fluidized bed process with Wurster tube is also investigated based on this ECT sensor. The effect of Wurster tube on the hydrodynamic behaviour and the dominant frequency spectrum distribution in the chamber were analysed based on fast Fourier transform. Test results reveal that process moisture change can be addressed from the raw capacitance of adjacent electrode pair combined with calibration model. Experimental result also indicates that ECT technology can provide useful information for process monitor in a fluidized bed dryer.

Highlights

Introduction and backgroundFluidized bed drying, granulation and coating are important processes in pharmaceutical industries for solid dose formulation
During a granulation, coating or drying process, particle properties including particle density, particle diameter, viscosity and restriction coefficient can change dramatically due to the change in moisture and agglomeration. All these parameters would affect the hydrodynamic behaviour in a fluidized bed process (Geldart 1973; Gidaspow et al 1992)
The objective of this research is to investigate the behaviour of drying process in a fluidized bed by electrical capacitance tomography (ECT) with and without Wurster tube, which can provide online monitoring and fault diagnosis and possibly provide a new approach to process control

Summary

Introduction

Granulation and coating are important processes in pharmaceutical industries for solid dose formulation. The main advantage of using fluidized beds is that they provide efficient heat and mass transfer and can mix and agglomerate excipients and active material ingredients to produce uniform blends of particles (Walker et al 2009). Water or water-based binder solution is sprayed on the particle surface to increase adhesion. Handled by Associate Editor Jun Yao. University of Chinese Academy of Sciences, Beijing 100049, China All these parameters would affect the hydrodynamic behaviour in a fluidized bed process (Geldart 1973; Gidaspow et al 1992)

Objectives

Results

Conclusion