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Tomography
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
The transport of dry and damp minerals via hoppers and in conveying lines is of importance, as plant operability is often poor due to the pluggage of conveying lines due to subtle changes in the feedstock (e.g. moisture content, size distribution, particle shape). Electrical capacitance tomography (ECT) can be used to image the dielectric constant inside conveying lines for dilute- and dense-phase processes, and has been in routine laboratory use since about 1999.9, 10 Analyses of the changes in the image with time can be used to identify the prevailing flow regime. For instance, Figure 6.7.2 shows a real-time visualization of powder flow for two conditions in dense phase conveying, from which characteristics such as slug length and velocity can be computed and statistical analysis of void age fluctuation data (Figure 6.7.3).
Process Imaging
Published in David M. Scott, Industrial Process Sensors, 2018
Tomographic techniques are not limited to the use of X-rays; in fact, much of the research effort in the area of process tomography has focused on measurements of electrical characteristics, such as capacitance and impedance. Electrical tomography techniques are interesting because they are fast and relatively inexpensive. Electrical capacitance tomography (ECT) is used to measure the capacitance between pairs of electrodes mounted on the perimeter of the pipe or vessel (Figure 9.4a). The capacitance between two electrodes is proportional to the average dielectric constant of the material between them, so capacitance values can be used as projection data. By measuring the capacitance between every electrode pair and back projecting the measurements along the field lines shown in Figure 9.4a, one can reconstruct a map of the dielectric constant within the process. Since the dielectric constant (i.e., relative permittivity) is a material property, this image provides information about solids distribution, mixing, or even the stage of chemical reactions taking place within the process.
Online techniques for performance and condition monitoring of hydrocyclone: present status and the future
Published in Mineral Processing and Extractive Metallurgy Review, 2023
S. Mishra, Arun Kumar Majumder
Electrical Capacitance Tomography (ECT) method measures the differences in capacitance between electrode pairs that are applied to construct the permittivity distribution which provides the material distribution over a cross section by an appropriate algorithm (Yang et al., 2003). Amongst other industrial tomography modalities, ECT has a great potential in multi-phase flow measurement owing to its high speed, low cost of construction, safety, and adaptability for all vessel sizes (Meng et al. 2008). In view of these advantages, ECT has been considered to be the most powerful tool among all other tomography techniques and thus has been widely investigated by many researchers for industrial processes monitoring (Chaplin and Pugsley 2005; Niu, Jia and Wang 2004; Ostrowski et al. 2000; Warsito and Fan 2001).
Flotation Froth Phase Bubble Size Measurement
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Electrical tomography images distribution of electrical properties in an object (Tapp et al. 2003) to produces cross-sectional images ‘Tomos’ that depicts this distribution from sets of boundary measurements (Wei, Qiu and Primrose 2016). This low costs, noninvasive tomography utilizes low-frequency electromagnetic waves to detect the electrical properties (permittivity, conductivity, and permeability) of an object. Since its inception, the technique has been used in several fields. Xie et al. (1995), York (2001) and Wei, Qiu and Primrose (2016) provide reviews on industrial applications of electrical tomography in the process industry. Yang and Ren (2018) reviews use in medicine, Dong et al. (2003) describe uses in two-phase flow systems, while (Cilliers, Wang and Neethling 1999; Hu, Ofori and Firth 2009; Nissinen et al. 2014; Wang, Bergholm and Yang 2003; Xie, Neethling and Cilliers 2004) explores uses in mineral froth flotation. The choice of the sensing principle (capacitance, resistance, inductance) depends on the technical needs of tomographic information. Factors such as the spatial resolution of sensing method, cost, hazard, ease of implementation, etc. may determine the sensing method. Generally, electrical capacitance tomography (ECT) is appropriate for non-conducting material of different permittivities. Electrical resistance tomography (ERT) is suitable for a measuring space with a continuous phase that has good conductivity properties (i.e. good conductor) while electrical inductance tomography is suitable for mixtures containing ferromagnetic and/or conducting materials (Xie et al. 1995). The set-up for electrical tomography typically consists of a sensor, data acquisition system, and image reconstruction system (Dickin et al. 1992; Dickin and Wang 1996). A generalized acquisition set-up is shown in Figure 6. The sensing techniques and set-up for estimating bubbles in froths/foams are discussed further in sections that follow.