page_title: Electrical capacitance volume tomography
section_title: Gas-Solid
hierarchical_section_title: Electrical capacitance volume tomography / Applications / Multi-Phase Flow / Gas-Solid
caption_attribution_description: English: ECVT Imaging in the Bend of a Fluidized Bed Riser
context_page_description: Electrical capacitance volume tomography is a non-invasive 3D imaging technology applied primarily to multiphase flows. It was first introduced by W. Warsito, Q. Marashdeh, and L.-S. Fan as an extension of the conventional electrical capacitance tomography. In conventional ECT, sensor plates are distributed around a surface of interest. Measured capacitance between plate combinations is used to reconstruct 2D images of material distribution. In ECT, the fringing field from the edges of the plates is viewed as a source of distortion to the final reconstructed image and is thus mitigated by guard electrodes. ECVT exploits this fringing field and expands it through 3D sensor designs that deliberately establish an electric field variation in all three dimensions. The image reconstruction algorithms are similar in nature to ECT; nevertheless, the reconstruction problem in ECVT is more complicated. The sensitivity matrix of an ECVT sensor is more ill-conditioned and the overall reconstruction problem is more ill-posed compared to ECT. The ECVT approach to sensor design allows direct 3D imaging of the outrounded geometry.
context_section_description: Gas-solid fluidized bed is a typical gas-solid flow system, and has been widely employed in chemical industries due to its superior heat and mass transfer and solid transport and handling. ECVT has been successfully applied to gas-solid fluidized bed systems for system properties measurements and dynamic behaviors visualization. An example is the study of choking phenomenon in a 0.1 m ID gas-solid circulating fluidized bed with a 12-channel cylindrical ECVT sensor, where the formation of slug during transition to choking is clearly recorded by ECVT. Another experiment studies the bubbling gas-solid fluidization in a 0.05 ID column, where the solid holdup, bubble shape and frequency obtained from ECVT are validated with MRI measurements. The flexibility of the ECVT sensor geometry also enables it for imaging of bend, tapering and other non-uniform sections of gas-solid flow reactors. For example, a horizontal gas jet penetrating into a cylindrical gas-solid fluidized bed can be imaged with a modified ECVT sensor, and information such as penetration length and width of the jet as well as jet coalescence behavior with the bubbles in the fluidized bed can be obtained from ECVT.
  Another example is ECVT imaging of the riser and bend of a gas-solid circulating fluidized bed (CFB). A core-annulus flow structure in both the riser and the bend and a solid accumulation in the horizontal section of the bend are identified from quantitative ECVT images.
caption: Illustration of the CFB reactor (left), ECVT sensor configuration at the bend (middle), and reconstructed images of the solids holdup distribution in the bend (right).[21]
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