Using 3D Electrical Resistance Tomography for Packed Bed Column Monitoring

Electrical Resistance Tomography (ERT) is a scanning technique that has been widely used in various industrial processes. By injecting low frequency signal into measuring samples, ERT technique is able to obtain the conductivity distribution information of the sample. The conductivity information can be an important indicator for process conditions, for example, mixing conditions, material composition and contamination detection. In the past, ITS Plc has successfully implemented 2D ERT technology into the packed bed applications such as chromatography column monitoring. Column chromatography is a widely used technology in chemistry for purifying/separating chemical compounds. It is often an expensive process and the packing cannot be used after certain amount of cycles, due to degradation of the packing. In the life sciences sector which are regulated a conservative approach must be taken to ensure quality and purity of production. The lack of information in columns and their expense makes ERT an attractive technique for monitoring the packed beds and column conditions. By monitoring the column conditions effectively, the user can determine assess its performance and quality, to prevent unnecessary loss and maintain quality and yield. Conventional 2D multi-plane ERT can provide cross sectional distribution information about the conditions. However the result might not be very representative due to the lack of inter-plane information. In this paper, multi-plane 3D ERT modelling is proposed as it is believed that 3D ERT can provide further axial information about the process, which is very critical because of the geometrical features of the pack bed. A 4x16 ERT sensor is used in this paper to demonstrate the difference between 2D and 3D ERT. Both the theoretical and experimental results will be presented in this paper.