Electrical capacitance tomography
ECT is a measurement technique for obtaining information about the contents of process vessels and pipelines.
Multiple electrodes are arranged around the boundary of the vessel at fixed locations in such a way that they do not affect the flow or movement of materials. For electrically insulating pipes the electrodes can be mounted externally and for electrically conducting pipes the electrodes must be mounted internally.
What of the applications of the technique?
A typical application is real time monitoring of multicomponent flows within pipelines. Specific applications where ECT has been successfully exploited include solid/gas and liquid (organic)/gas systems such as fluidised beds, pneumatic conveying and multi-phase flow. In principle, ECT can be used to investigate and monitor any process where the main continuous phase is non- conducting and the other phases and components have differing values of permittivity.
An ECT system produces a cross-sectional image showing the distribution of electrical permittivity of the contents of a process vessel or pipeline from measurements taking at the boundary of the vessel.
Our m3c system injects a voltage on to an electrode and measures the resultant voltage difference between this and other electrodes according to a pre-defined measurement protocol.
This interrogates an entire ‘slice' through the measurement zone - analogous to a ‘body-scan' in medical imaging. A single measurement set for a 12-electrodes sensors consists of 66 voltage measurements. The voltage measurements are processed by an image reconstruction algorithm to determine the electrical permittivity distribution.
What is ECT?
ECT stands for Electrical Capacitance Tomography ECT is used where the bulk medium does not conduct electricity. In ECT the tomogram has red for high dielectric (eg oil) blue for low dielectric (eg air).
Should I use ERT/ECT in my process?
ERT should be used where the continuous material is electrically conducting (eg water acids bases and ionic solutions).
ECT should be used where the continuous material does not conduct electricity eg air/oil. If the process moves to from conducting to no-conducting or visa versa then a combined ECT/ERT system is recommended.
