Application Of Electrical Capacitance Tomography Research Articles

Analysis and Interpretation of Hopper Flow Behaviour Using Electrical Capacitance Tomography

AbstractThis paper presents a critical analysis of the application of electrical capacitance tomography (ECT) to exploring the behaviour of solids flow during hopper discharge. Particulate media are employed in many areas such as the food industry, civil and chemical engineering etc. This is a report of work on the measurement of parameters that determine hopper flow for several different types of particulate systems, using a hopper of adjustable geometry equipped with ECT sensors. There is a comparison of different data analysis methods including: Bayesian/MCMC spatial modelling; reconstructed measurements analysis; raw data processing and theoretical descriptions. Measurement and interpretation protocols suited to detection of particular flow phenomena are assessed and recommended.

Application of electrical capacitance tomography for imaging industrial processes

Application of electrical capacitance tomography for imaging industrial processes

Application of electrical capacitance tomography to the fluidized bed drying of pharmaceutical granule

A novel calibration technique that accounts for the presence of moisture has allowed for the application of electrical capacitance tomography (ECT) to a fluidized bed dryer containing wet pharmaceutical granule. A statistical attractor comparison test denoted as the S-statistic has been used to analyze both the reconstructed and non-reconstructed ECT images to determine radial variations in hydrodynamic behavior at an axial location 10.5 cm above the distributor. This analysis has shown that variations in the bed dynamics associated with the loss of moisture during the drying process are most intense near the walls of the dryer, while the central region is characterized by a more consistent dynamic behavior. Investigation of the voidage distribution in the individual tomograms over this period in the drying process shows that the changes in the S-statistic correspond to a reduction in area of the region involved in bubbling behavior. Tomograms from early in the drying process indicate a central core of gas channeling through the very wet granule. This is due to the high cohesive forces present at high moisture. At moisture contents below 5-wt%, near the end of drying, significant divergence in dynamic behavior is identified in the S-statistic. This divergence is associated with the appearance of asymmetric bubbling behavior in the individual tomograms.

Applications of electrical capacitance tomography in two phase flow visualization

The successful application of Electrical Capacitance Tomography (ECT) depends heavily on the image reconstruction speed and quality. The two requirements usually cannot be satisfied simultaneously. Also, for a large number of acquired 2D ECT images, a 3D presentation of them is much desired to track the variations of the material distribution in a third dimension. To facilitate ECT for practical flow analyses in process engineering, the authors have recently developed algorithms for 3D image presentation and for online iterative image reconstruction that only takes the same time as a linear back projection method but yields good image qualities as the Landweber iterative method does. The new methods have been successfully applied to visualize several classes of two phase flows, namely fluidization, cyclone separation, circulating rate determination in circulating fluidized beds, pneumatic conveying, rotating drum mixing. Special characteristics in each case have been discussed and valuable results are obtained, which are reported in this paper.

Analysis of the effect of stray capacitance on an AC-based capacitance tomography transducer

An ac-based capacitance transducer has been designed for use in electrical capacitance tomography (ECT) systems. The stray capacitance between the measurement electrodes and earth can be relatively large and may affect the performance of the transducer. This paper analyzes this effect, taking into account the ON-resistance of the CMOS switches in the circuit, the finite gain of op-amps and gain errors in the detection measuring unit, so that the overall measurement error can be estimated. It is shown that if the stray capacitance varies between 90 and 210 pF, the measurement error would be between +0.03% to -0.1%. This is negligibly small for ECT applications, confirming that this ac-based capacitance transducer is effectively stray-immune.

Application of electrical capacitance tomography to the void fraction measurement of two-phase flow

Based on the electrical capacitance tomography technique, a new method for the void fraction measurement of two-phase flow is proposed. A 12-electrode void fraction measurement system is established. A mathematical model of image reconstruction of electrical capacitance tomography is developed. To obtain the quantitative information of two-phase flow, combining the Tikhonov regularization principle and the algebraic reconstruction technique algorithm, a new image reconstruction algorithm is presented. The experimental results show that the accuracy of void fraction measurement is satisfactory. The proposed method is suitable for the void fraction measurement of many kinds of two-phase flow.

Application of electrical capacitance tomography for measurement ofgas-solids flow characteristics in a pneumatic conveying system

Transient three-dimensional multiphase flows are a characteristic feature ofmany industrial processes. The experimental observations and measurements ofsuch flows are extremely difficult, and industrial process tomography has beendeveloped over the last decade into a reliable method for investigating thesecomplex phenomena. Gas-solids flows, such as those in pneumatic conveyingsystems, exhibit many interesting features and these can be successfullyinvestigated by using electrical capacitance tomography. This paperdiscusses the current state of the art in this field, advantages andlimitations of the technique and required future developments.Various levels of visualization and processing of tomographic data obtainedin a pilot-plant-scale pneumatic conveying system are presented. A case studyoutlining the principles of measuring the mass flow rate of solids in a verticalchannel is shown.

Application of capacitance electrical tomography for on-line and off-line analysis of flow pattern in horizontal pipeline of pneumatic conveyer

Investigation and control of flow phenomena in the pneumatic conveying of solids requires a detailed knowledge on the flow regimes and a number of phase flow properties. Electrical capacitance tomography (ECT) is shown here to be a robust tool for this purpose, particularly when dense phase plug flow is to be monitored. The application of ECT to dense phase powder conveying in an experimental vacuum system is demonstrated and described, including the visualisation of slug size, shape and velocity. Measured gas and solid flow rates were also analysed in an attempt to ultimately provide a basis for comprehensive on-line analysis. A number of statistical estimators were selected and used in data processing, in order to distinguish between particular types of dense flow. The results show the potential for use of the method for the on-line control of dense phase pneumatic conveyors.

A method for measuring low capacitance for tomography

The applications of electrical capacitance tomography (ECT) to image multiphase flows in pipelines, fluidization process, interfaces in separation vessels, and combustion phenomena in internal combustion engines have been studied for some years. In these applications, none of the equipment imaged has an inner diameter exceeding 1 m. When ECT techniques for large industrial equipment like blast furnaces are explored, the existing methods for measuring low capacitance have some limitations. This article proposes a method for measuring low capacitance which is suitable to construct ECT systems for imaging large industrial equipment. The method is based on single high-voltage excitation and magnetic C/V converting principle which can resist interference by stray capacitance. Experiment results indicated that the method has good performance in regard to resolution, linearity, and stability. Though the method was designed for imaging large equipment, it can also be applicable to other fields where low capacitance measurements are required.

Real time visualisation and analysis of dense phase powder conveying

Investigation and control of flow phenomena in the pneumatic conveying of solids requires a detailed knowledge on the flow regimes and a number of phase flow properties. Electrical capacitance tomography (ECT) is shown here to be a robust tool for this purpose, particularly when dense phase plug flow is to be monitored. The application of ECT to dense phase powder conveying in an experimental vacuum system is demonstrated and described, including the visualisation of slug size, shape and velocity. Measured gas and solid flow rates were also analysed in an attempt to ultimately provide a basis for comprehensive on-line analysis. A number of statistical estimators were selected and used in data processing, in order to distinguish between particular types of dense flow. The results show the potential for use of the method for the on-line control of dense phase pneumatic conveyors.

Application of Electrical Capacitance Tomography to Flow Modelling within a Circulating Fluidized Bed

The results of the measurements of the solids concentration region in a circulating fluidized bed are described. An electrical capacitance tomography system has been used to measure both instantaneous and average solid distributions as a function of a superficial air velocity and a solid mass flux. The fractional wall coverage by clusters and the solids concentration within the annulus layer was measured. The data is compared with the results available from the literature.

Principles and Industrial Applications of Electrical Capacitance Tomography

Principles and Industrial Applications of Electrical Capacitance Tomography