Electrical capacitance tomography

W. Warsito, L.S. Fan, Measurement of real-time flow structures in gas—liquid and gas—liquid-solid flow systems using electrical capacitance tomography (ECT), Chem. Eng. Sci. 56 (2001) 6455-6462. 

The fluidized bed systems have been utilized extensively in many physical, chemical, petrochemical, electrochemical, and biochemical processes. Successful applications of the fluidization systems lie in a comprehensive understanding of hydrodynamics, heat and mass transfer properties, and mixing. Various non-intrusive measurement techniques, such as electric capacitance tomography and radioactive particle tracking technique, are available to advance the fundamental understanding of the microscopic and macroscopic phenomena of fluidization. Till date, the... 

Kuhn, F.T., J. C.Schouten, C. M. Van den Bleek, and B. Scarlett, Electrical Capacitance Tomography Applied to Fluidization Dynamics for Chaos Analysis, Second Internl. Particle Tech. Forum, 5th World Congress of Chemical Engineering, VI, AIChE, San Diego, CA., July 14-18, 1996, pp. 216-219. 

Wang, S. J., T. Dyakowski, and M. S. Beck, An Application of Electrical Capacitance Tomography to Measure Gas-Solid Motion in a Fluidized Bed, AIChE Symposium Series, National Heat Transfer Conf., Houston, Ed, M. S. El-Genk, 92, 310, Aug. 3-6, 1996, pp. 155-160. 

Du, B., Warsito, W., and Fan, L.S. (2006), Imaging the choking transition in gas-solid risers using electrical capacitance tomography, Industrial Engineering Chemistry Research, 45(15) 5384-5395. 

Gamio, J.C., Castro, J., Rivera, L., Alamilla, J., Garcia-Nocetti, R, and Aguilar, L. (2005), Visualization of gas-oil two-phase flows in pressurized pipes using electrical capacitance tomography, Flow Measurement and Instrumentation, 16(2-3) 129-134. 

Makkawi, Y.T., and Wright, P.C. (2002), Fluidization regimes in a conventional fluidized bed characterized by means of electrical capacitance tomography, Chemical Engineering Science, 57 2411-2437. 

Pugsley, T., Tanfara, H., Malcus, S., Cui, H., Chaouki, 1., and Winters, C. (2003), Verification of fluidized bed electrical capacitance tomography measurements with a fiber optic probe, Chemical Engineering Science, 58 3923-3934. 

Advanced measuring techniques With the advent of sophisticated imaging and velocimetry techniques, better understanding of the flow behavior and consequently a better prediction of regime transition is possible. The techniques used in the literature are listed below with the corresponding references. Readers interested in a specific technique may refer to these references Electrical capacitance tomography (ECT) (Bennett et al. 1999 Tapp et al. 2003) Electrical impedance tomography (EIT) (Tapp et al. 2003)... 

Ismail I, Shafquet A, Karsiti MN. (2011) Application of electrical capacitance tomography and differential pressure measurement in an air-water bubble column for online analysis of... 

Tomographic techniques allow to reconstruct the instantaneous particle holdup (porosity) of a 3D fluidized bed, thus allows to extract information especially on the bubble phase. Well-known techniques include electrical capacitance tomography. X-ray tomography, and magnetic resonance imaging (MRI). 

Malcus S, Pugsley TS. Investigation of the axial variation of the CFB riser hydrodynamics by means of electrical capacitance tomography (ETC). In Kwauk M, Li J, Yang WC, eds. Fluidization X. New York Engineering Foundation, 2001, pp 763-770. 

Rhodes M, Wang X. Stud5nng fast fluidization using electrical capacitance tomography. Werther J, ed. Proc 6 Conf CFB. Wurzburg, Germany, 1999, pp 891 896. 

Arko A., Waterfall R.C., Beck M.S., Dyakowski T., Sutcliffe P. and Byars M., Development of Electrical Capacitance Tomography for Solids Mass Flow Measurement and Control of Pneumatic Conveying Systems, Proceedings of the C World Congress on Industrial Process Tomography, 140 - 146, 1999. 

The industrial process tomography systems can be based on a number of measurement principles, including nucleonic, optical, acoustic, microwave, NMR and electrical methods [21] - each of them usually having a number of distinctive variants. From the practical point of view only a few are routinely used for investigating fluidised beds. This chapter will concentrate therefore on nucleonic transmission tomography (x-ray and y-ray tomography) and electrical capacitance tomography (ECT). 

Electrical capacitance tomography (ECT) belongs to a larger family of electrical impedance methods. Here, unlike in nucleonic tomography where, the photon beam attenuation is measured, the measured quantity is electneal impedance (i.e. conductance and/or capacitance) between all possible pairs of electrodes placed around the vessel or pipe periphery. 

The electrical techniques described in the paper are Electrical Capacitance Tomography (ECT) and Electrical Resistance Tomography (ERT). Both techniques used non-invasive passive metal electrodes, with low amplitude electrical excitation. The techniques are rugged, low-cost, low-impact and fast. Absolute accuracy, on the other hand, is currently not better than 5%. 

Two particular cases are discussed in this paper, firstly, monitoring non-conductive solid particles conveyed in a conductive fluid and secondly, pneumatic conveying of dry solid particles. The first case uses Electrical Resistance Tomography (ERT) and the second. Electrical Capacitance Tomography (ECT). 

Bruun HH (1996) Hot-film anemometry in liquid flows. Meas Sci Technol 7 1301-1312 Burgess JM, Calderbank PH (1975) The measurement of bubble parameters in two-phase dispersions-1 the development of an improved probe technique. Chem Eng Sci 30 743-750 Cao Z, Xu L, Fan W, Wang H (2010) Electrical capacitance tomography with a non-circular sensor using the dbar method. Meas Sci Techn 21(1-6) 015502... 

Liu S, Chen Q, Wang HG, Jiang F, Ismail I, Yang WQ (2005) Electrical capacitance tomography for gassolids flow measurement for circulating fluidized beds. Flow Meas Instrum 16 135-144... 

Yang W (2010) Design of electrical capacitance tomography sensors. Meas Sci Technol 21(1-13) 042001... 

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