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Abstract

The main goal of this study is to further understand the fluidized bed hydrodynamics by determining the effects of superficial gas velocity and bed density on the hydrodynamics of gas-solid fluidized beds by using a 14-cm-diameter Plexiglas cylindrical fluidized bed column, air at room temperature was used as the fluidizing gas, two different Geld art type-B particles were used glass bead and copper particle with material densities of 2500, 5300 Kg/m 3 respectively with the same size particle 210 µm. Three different superficial gas velocities were investigated U g =25, 30, and 35 cm/s. Non-invasive flow measurement technique gamma ray computed tomography (CT) has been used to measure the timeaveraged cross-sectional and radial profiles of solids and gas holdups distribution. The results show that local time-averaged gas holdup is a function of bed material density, that as material density decreases, gas holdup increases, gas holdup increases with increasing superficial gas velocities.Keywords: fluidized beds hydrodynamics, computed tomography, gas hold-up In this study the effects of gas velocity and material density on local time-averaged gas holdup in fluidized bed are investigated by using gamma ray computed tomography technique (CT). Therefore, our detailed local measurements of the cross-sectional distribution and radial pro-files of solids and gas holdups will be valuable benchmarking data to evaluate and validate these CFD. Experimental setupThe experimental works were carried out in 14 cm cold flow fluidized bed. A schematic diagram of the setup used in this study is illustrated in Figure 1. The 14 cm column was 1.68 m high connected from the top with an upper section that had a diameter of 42 cm and was 84 cm high; this upper section of the fluidized bed (the disengagement zone) had a larger diameter to reduce the superficial gas velocity of the gas phase to enhance the solids separation. The plenum was located at the bottom, which consisted of a sparger tube. The gas phase at ambient temperature was introduced through a distributor at the bottom after passing through the sparger. The gas distributor was made of a porous polyethylene sheet and had a pore size of 40 µm. The sparger was plugged at one end, and had 14 holes, all facing downward with respect to the column. The properties of solids, static bed height used in the experiments are listed in Table 1. Measurement technique a. Dual Source gamma ray computed tomography (DSCT)DSCT consists of two sealed sources (Cs-137 and Co-60) and two sets of 15 NaI detectors located in front on each sealed source as shown in Figure 2. In this work CT experiments were performed under two-phase conditions gas and solids, and hence a single sealed source (Cs-137) and its related 15 NaI scintillation detectors located opposite to the (Cs-137) sealed source has been used. As shown in Figure 2 the sources and detectors are built on a rotary plate to move together in 360˚ around the studied bed providing 197 views in each scan and 21 projections in each view...