Towards process tomography for monitoring pressure filtration

This paper reports on progress towards the first continuous application of electrical impedance tomography to a production scale industrial process. It includes the design and implementation of the worlds first certified intrinsically safe electrical tomography system. Zener barrier (ZB) modules and intrinsically safe relays provide electrical isolation and the instrument is certified for operation in a Zone 0 environment. Two systems have been operating successfully on production pressure filters for two years. A sensor architecture has been implemented that is compliant with the process such that it is not detrimental to efficiency or the integrity of the associated vessel structure. The MATLAB-based EIDORS three-dimensional software toolkit has been employed to yield images from simulated data. To overcome problems that arise due to dramatic changes in the conductivity of materials in the vessel during the process, a new approach is introduced that proposes the use of dynamic sensitivity maps that evolve during the batch based on the predicted mean conductivity at each stage. Real data present challenges due to a number of factors, notably the ZB modules that are integral to the intrinsically safe instrumentation. However, a simple approach to data processing has yielded process relevant information using real tomographic data.