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Fluidized-bed drying of wet granules is a common process in many industrial sectors, and monitoring of the moisture and the hydrodynamics of the granules during drying is important in order to ensure the quality of the final product. Electrical capacitance tomography (ECT) is an electrical imaging modality in which the permittivity distribution inside an object is computed using capacitive measurements from the boundary of the object and mathematical algorithms. Here, three-dimensional moisture distributions were computed through an experimentally determined relationship between granule moisture and relative permittivity. Estimates for the average moisture content were calculated and evaluated. The hydrodynamics of the wet granules were characterized with respect to air velocity and granule moisture.

The objective of this study was to determine whether electrical impedance tomography (EIT) can be used to image the mixing of two miscible liquids in a turbulent flow, using the Trumpjet mixing system of papermaking chemicals and additives. Trumpjet is a jet injection mixer developed and produced by Wetend Technologies Ltd. An EIT system and a linear impedance sensor, developed at the Department of Physics, University of Kuopio, were used as a monitoring system. In EIT, a difference reconstruction approach was used to produce two- and three-dimensional images of the conductivity distribution with a frame rate about of 40 frames/s. In the linear impedance sensor, 8 impedance values can be measured with a speed of 4 s −1 . In order to make changes in the conductivity distribution a saline solution was used as chemical. In order to evaluate the quality of the mixing, a mixing index was calculated based on the reconstructed images. Laboratory tests were carried out in a pilot plant. The efficiency of the mixing of the chemical into the main flow using Trumpjet technology and using the conventional chemical injection system was compared. It was found that the Trumpjet technology is more efficient, and that EIT and a linear sensor can be used in mixing studies.

In this paper, we examine how the estimation method of the electrode contact impedances proposed earlier works in two different laboratory experiments. In the first experiment, the performance of the method was studied for a tank filled with a homogeneous liquid. In this case a single parameter for the contact impedances was used. In the second experiment the method was tested with a single target within a tank. In this case the contact impedances on all the electrodes were estimated. It was found that in the two-electrode measurement protocol the estimation of the electrode contact impedances improves reconstructions substantially. If only a single electrode contact impedance value for all the electrodes was estimated it was found that in certain cases it was not adequate.

A case study is presented where electrical impedance tomography is used to image paste during extrusion. This indicates regions of high moisture at the wall of the barrel permitting slip and so making extrusion more efficient. Multi-step Gauss–Newton image reconstruction methods are used. Techniques include (i) axi-symmetric smoothing that is coupled with ultrasound measurement to provide discretization information, (ii) full impedance imaging and (iii) full three-dimensional field modelling. These provide clear images of the paste that can be used to gauge extrudability of a paste formulation.

In this paper we propose a method for detecting faults in resistive thin films and coatings with an electrical-impedance-tomography-related approach. The motivation of our study is the need to develop methods for the evaluation of coating properties and quality of implants. The method is based on the complete electrode model. We model the coating as one electrode with spatially varying contact impedance. Using a set of current and voltage measurements in a specially developed measurement cell including the coating and additional electrodes, we estimate the spatially varying contact impedance on the coating. The estimated contact impedance distribution can be regarded as a measure of the condition of the coating; that is, low contact impedance indicates a fault in the coating. The necessary modifications of the complete electrode model are given. The suggested method is tested with simulations and real measurements and it is shown that, with feasible regularization, faults in the coating can be detected with good precision.

Classical electrical impedance tomography is an imaging modality in which the internal impedivity distribution is reconstructed from the known injected currents and voltages measured on the surface of the object. However, in many industrial cases there are a priori known internal structures inside the vessels which could be used as internal electrodes in tomographical imaging. In this paper we consider modelling of certain types of internal structures and using them as internal electrodes in two-dimensional electrical process tomography. We also propose an inversion approach in which directional smoothness of the resistivity distribution can be taken into account. Simulations and laboratory experiments show that, by utilizing internal structural information and using these internal structures as additional electrodes, we can achieve significant improvements in image reconstruction. Improvements are shown for the cases in which the electrodes are placed at the centre of the object and are surrounded by a resistive layer.

Electrical impedance tomography (EIT) was adapted to monitor drug release three-dimensionally as a function of time. EIT is an electrical imaging modality in which the three-dimensional conductivity distribution inside an object is computed based on electrical measurements from the boundaries. Here, the three-dimensional concentration distribution was monitored with the help of the experimentally determined relationship between drug concentration and conductivity. The EIT monitoring was carried out with propranolol hydrochloride tablets in an apparatus similar to USP dissolution apparatus 2. The release profiles estimated using EIT matched well with the UV/VIS spectrophotometric analyses that were performed as a reference. There are several benefits conferred by three-dimensional monitoring, i.e., comprehensive information about the release process; no need to take samples during experiments; and not essential to assume homogenous concentration distribution in the drug release analysis. EIT is an in-line technique, and moreover, it is non-intrusive and non-invasive. The possibilities and the characteristics of the EIT monitoring are described in detail, and some potential drug release applications are proposed. EIT is especially encouraged to be exploited for research and development purposes.

An approach to monitor in vitro dissolution process from pharmaceutical tablets utilizing electrical impedance tomography (EIT) is introduced. In the demonstration, a tablet containing sodium chloride (NaCl) was dissolution tested using tap water as a dissolution medium within an apparatus similar to the United States Pharmacopoeia dissolution apparatus II. During the process, the three-dimensional sodium chloride concentration distribution was monitored with EIT measurements as a function of time. For EIT measurements, an array of electrodes was attached on the boundary of the dissolution vessel, a set of alternating electric currents was injected through the electrodes, and the resulting voltages were measured. With these data and by applying mathematical algorithms, an approximation for the spatial/temporal concentration distribution inside the vessel was computed. It was found that the computed distributions were relatively homogeneous. A NaCl release curve was computed by integrating the concentration distribution over the vessel volume, and the final value of the curve matched well with the reference point based on the weight loss of the tablet. Finally, EIT monitoring is suggested to be used for research and product development purposes.

In process tomography the aim is to obtain information typically from the interior of the process vessels based on the measurements made on the surface of the vessel. Electrical impedance tomography (EIT) is an imaging modality in which the internal resistivity distribution is reconstructed based on the known injected currents and measured voltages on the surface. Since the reconstructed image represents the resistivity distribution of the interior, certain internal structures such as highly conductive mixing paddles in a stirred vessel may entail difficulties in the image reconstruction. This is because EIT is a diffuse, nonlinear imaging modality which makes it difficult to reconstruct high contrasts in the internal resistivity distribution. In this paper the effects of internal conductive structures on the reconstructed images in two-dimensional cases are considered and possible improvements in the reconstructions by taking into account the locations and resistivities of these structures are studied. I...