Abstract: Modern day tomographs enable the research community to investigate the internal flow behavior of a fluidized bed by non-invasive methods that partially overcome the opaque nature of a dense bubbling bed. Each tomographic modality has its own limitations and advantages and in the present study two modern day tomographic systems were evaluated with respect to their performance on a cold dense fluidized bed. The two tomographs investigated are an electrical capacitance tomography (ECT) tomograph and a time-resolved X-ray tomography tomograph. The study was performed on spherical glass particles with various particle size distributions that could mainly be classified as Geldart B or D particles. Two experimental towers were employed, one with a diameter of 10.4 cm and the other 23.8 cm while compressed air was used as fluidizing fluid during all of the experiments. Results obtained with both systems are provided in comprehensive figures and tables and some first results are obtained with the time-resolved X-ray tomography system. The bubble size measurements of both tomographs are compared with several theoretical correlations via the root mean square error of the predictions (RMSEP). With the results it was also concluded that a small amount of small particles can noticeably alter the fluidization hydrodynamics of a powder. The bubble frequencies are also presented to aid in understanding the hydrodynamic behavior of the powders investigated. A comprehensive summary of the two tomographic modalities is also provided. (C) 2013 Elsevier Ltd. All rights reserved.@en

The performance of two tomographic reconstruction algorithms, Simultaneous Algebraic Reconstruction Technique (SART) and Adaptive Genetic Algorithm (AGA), is evaluated based on synthetic data mimicking X-ray computed tomography of a bubbling fluidized bed. The simulations are based on a high speed X-ray tomography system, consisting of 3 X-ray sources and 32 detectors for each source. The comparison between SART and AGA is made for image resolutions ranging from 20 × 20 to 50 × 50 pixels, for the cases of 2 phantoms (artificial voids) and 3 phantoms in a 23 cm diameter column. The influence of noise on the reconstructions for both algorithms is also considered. It is found that AGA provides better reconstructions than SART at low resolutions. At high resolutions, the reconstruction quality is comparable, but the calculation times for AGA are much longer. AGA is better at finding the phantom position as it is less sensitive to measurement noise@en

A downward micro-nozzle system is investigated for the fluidization of fine particles. To study the impact of the gas flow from the nozzle on the fluidization, the gas distribution below the nozzle is measured in a bed filled with 76 pm Puralox particles. A high speed X-ray tomography system, consisting of 3 X-ray sources and 2 layers of 32 detectors for each source, is employed to visualize the gas distribution with a temporal resolution of 2500 fps. Both the time-averaged and time resolved results are analyzed by combining the tomographic images from different measurement heights. A bubbling area, diluted area, and compacted area are found from the time averaged results. From time-series analysis, a stable bubbling flow is detected from both the cross-correlation of the raw data and image reconstruction. The penetration depth is also estimated. The results are validated with correlations from literature. (C) 2014 Elsevier B.V. All rights reserved.@en