Investigation of wetting and drying process in a gas-solid fluidized bed by electrical capacitance tomography and pressure measurement

Zhang, J. L.; Mao, Minglei; Ye, J. M.; Wang, H. G.; Yang, Wuqiang

doi:10.1016/j.powtec.2016.07.069

Cited by 27 publications

(15 citation statements)

References 32 publications

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“…The dominant frequency in the bubbling regime obtained from ECT results here, 0.09 Hz, is much lower than the typical frequency reported in previous researches, 47 say about 2 Hz. However, it must be pointed out that to date, little work has been carried out on the FFT analysis at the velocity close to umb like what has been done in this research, and the studied ug in previous studies 33,38,40,47,48 are much larger than that used here. As can be seen in Video S2b, indeed, the bubbles appear on the bed surface at a low frequency.…”

Section: Ect Measurement Resultsmentioning

confidence: 87%

“…In addition, it has been confirmed that the raw capacitance and overall solid concentration signals obtained by ECT are much more sensitive to a small change of flow patterns than images. 32,33 Therefore, these two quantities, but not the reconstructed images, are used following previous works. [33][34][35] Here, the raw capacitance is the average over all possible electrode pairs and the overall solid concentration β is obtained via pixel averaging:…”

Section: Measurement Of the Overall Solid Concentration Using Ectmentioning

confidence: 99%

See 1 more Smart Citation

Experimental Verification of Solid-like and Fluid-like States in the Homogeneous Fluidization Regime of Geldart A Particles

Guo

Meng

Zhao

et al. 2018

Ind. Eng. Chem. Res.

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The mechanisms underlying homogeneous fluidization of Geldart A particles have been debated for decades. Some ascribed the stability to inter-particle forces, while others insisted a purely hydrodynamic explanation. Valverde et al. (2001) fluidized 8.53-μm (i.e., Geldart C) particles by the addition of fumed silica nanoparticles and found that even during homogeneous fluidization both solid-like and fluid-like behavior can be distinguished. However, it is still unclear whether both states exist for true Geldart A particles. In this paper, particulate fluidization characteristics of three typical Geldart A powders were studied by camera recording, electrical capacitance tomography, and pressure fluctuation. For the first time, the existence of both solid-like state dominated by inter-particle forces and fluid-like state by fluid dynamics during homogeneous expansion of Geldart A particles was experimentally verified. Furthermore, the ability and performance of the used measurement techniques to identify different flow regimes were compared.

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Section: Ect Measurement Resultsmentioning

confidence: 87%

Section: Measurement Of the Overall Solid Concentration Using Ectmentioning

confidence: 99%

Experimental Verification of Solid-like and Fluid-like States in the Homogeneous Fluidization Regime of Geldart A Particles

Guo

Meng

Zhao

et al. 2018

Ind. Eng. Chem. Res.

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“…Compared with the single point based measurement, process tomography is one of the best options to monitor the gassolids flow process in a Wurster type fluidized bed due to the nature of its non-intrusive and non-invasive. Until now, several type of process tomography have been applied in the investigation of gas-solids fluidized bed, including electrical capacitance tomography (ECT) [11][12][13], microwave tomography (MWT) [14] and magnetic resonance imaging (MRI) [15].…”

Section: Introductionmentioning

confidence: 99%

Monitoring a lab-scale wurster type fluidized bed process by electrical capacitance tomography

Che

et al. 2018

Flow Measurement and Instrumentation

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In this research, two types of electrical capacitance tomography (ECT) sensors, i.e. 12-4-8 combined electrodes and 8-8 dual planes sensors, were designed and used to monitor the gas-solids flow inside a Wurster type fluidized bed. For the 12-4-8 combined electrodes sensor, the measurement was conducted synchronously both inside and outside of the tube, i.e. coating zone and annulus zone, to achieve a fully understand the gas-solids flow characteristics in the bed. For the dual planes ECT sensor, the flow through the two cross-section areas inside the Wurster tube was measured and solids velocity was calculated based on cross-correlation method. A series of test were carried out by varying the operational parameters including the gap between the Wurster tube and air distributor, fluidization air velocity and materials loading. Different flow regimes as well as the flow stability were evaluated based on the ECT measurement results. To evaluate the flow characteristics inside the bed, power spectra density (PSD) and standard deviation (SD) were applied to investigate the fluctuation characteristics in the coating and annulus zones. Experiment results indicate that ECT technology is a powerful tool to monitor the Wurster type fluidized bed process and analysis the gas-solids flow characteristics inside the bed.

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“…To quantify the bubble size determined by different image reconstruction algorithms in experiments, Figure shows the equivalent bubble diameter calculated at each superficial gas velocity using the threshold solid concentration of 0.2 following previous works . Because the studied fluidized bed had a small bed diameter of 6 cm and was operated with a large initial aspect ratio of 5.5, in most cases, it was observed that only a single bubble could pass through the ECT measurement region at a time.…”

Section: Resultsmentioning

confidence: 99%

“…Typically, N is of the order of magnitude of 1000. In particular, for a 12‐electrode ECT sensor, a discretization with 64 × 64 pixels, which generates 3228 effective pixels in an ECT image, is normally used …”

Section: Ect Model and Image Reconstruction Algorithmsmentioning

confidence: 99%

Investigation of gas–solid bubbling fluidized beds using ECT with a modified Tikhonov regularization technique

et al. 2017

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Electrical capacitance tomography (ECT) provides a non-intrusive means to visualize cross-sectional material distribution of gas-solid bubbling fluidized beds. Successful application of ECT strongly depends on the image reconstruction algorithm used. For on-line measurements of bubbling fluidized beds, employing an algorithm that can produce highquality images without extensive computation is necessary. Using the conventional Tikhonov regularization algorithm, image quality in the central area is basically satisfied but suffers from artifacts in the near-wall region. To solve this problem, a similar division operation learned from linear back projection was introduced to modify the conventional Tikhonov algorithm. Both numerical simulations and experiments were performed to evaluate the modified technique.The results indicate that the artifacts can be effectively removed and the reconstructed image quality is similar to Landweber method with dozens of iterations. Furthermore, the modified Tikhonov technique shows high accuracy when obtaining important hydrodynamic parameters in gas-solid bubbling fluidized beds. V C 2017 American Institute of Chemical Engineers AIChE J, 64: 29-41, 2018

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Investigation of wetting and drying process in a gas-solid fluidized bed by electrical capacitance tomography and pressure measurement

Cited by 27 publications

References 32 publications

Experimental Verification of Solid-like and Fluid-like States in the Homogeneous Fluidization Regime of Geldart A Particles

Experimental Verification of Solid-like and Fluid-like States in the Homogeneous Fluidization Regime of Geldart A Particles

Monitoring a lab-scale wurster type fluidized bed process by electrical capacitance tomography

Investigation of gas–solid bubbling fluidized beds using ECT with a modified Tikhonov regularization technique

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