(545f) Electrostatic Tomography for Process Measurement and Control
AIChE Annual Meeting
Thursday, November 16, 2006 - 2:10pm to 2:30pm
Among tomography techniques for process control and visualization, electrical based tomography systems are among the most prominent due to their low construction cost, high speed, and safety. Emphasis in electrical tomography has been mainly focused on permittivity, conductivity, or permeability imaging. Successful implementation of tomography systems depends on the sensor configuration, the data acquisition hardware, and the algorithm used for reconstruction. However, electrical tomography results can be challenged by electrostatic charges present in the imaging domain. Electrostatic charges are common in multi-phase flows and their effect affects both process control and measurements.
Electrostatic charges have been used for tomography imaging using electrodynamic sensors. Measurements obtained from electrodynamic sensors are based on detection of varying electric field from moving particles. Application of this technique has been focused on measurements of flow rates in multi-phase flow systems. A modification of the system has been recently introduced for measuring concentration profiles of dry powders. In this case, the measured signal represents the accumulated charges on sensor plates resulting from static charges in the imaging domain. However, electrodynamic tomography has been used mostly for flow rate measurements, and the electrostatic charges effects are yet to be more fully explored in tomography applications.
Similarly to other electrical tomography systems, electrostatic tomography systems (EST) are composed of three main parts: (1) sensor, (2) data acquisition hardware, and (3) reconstruction algorithm. In EST, a set of sensors is mounted around the boundary of the process vessel. The sensor plates are designed to measure voltages due to static charges introduced through process dynamics. The acquisition hardware is designed to measure the voltage difference (resulting from static charges in measurement domain) between each pair of sensors in the passive mode. The passive mode refers to the state in which the sensor is independent of any voltage or current source.
In this work, we study different sensor designs in electrostatic tomography systems for charge mapping. In addition, we provide an overview of reconstruction algorithms for 2D and 3D charge imaging. Moreover, boundary treatment of electrostatic charges is presented based on results for EST system.