A New Method for the Determination of Cluster Velocity and Size in a Circulating Fluidized Bed

Abstract

The investigation on the cluster velocity and size was conducted in a 2-D circulating fluidized bed by using FCC, glassbeads, and sand particles under various operating conditions. Digital image system, 2-channel and 4-channel optical fiber probes were used to identify particle aggregates in the riser. A new method was developed to calculate the cluster size and cluster velocity by analyzing the video images and the optical fiber probe signals. The cluster sizes and velocities were also obtained for particles with different density, size, and sphericity.

Particle‐level dynamics of clusters: Experiments in a gas‐fluidized bed

“…Nevertheless, local or point signals are not sufficient to characterize the entire evolution of a cluster, as the cluster varies with time and its shape is hardly spherical, showing streamline, arch, horseshoeshape, and so on. 2,3 Visualization methods, such as the videography with optical-fiber micrograph probe, 23 high-speed videography, [24][25][26][27] and laser sheet technique, [28][29][30] have been widely employed for cluster analysis since the 1990s. In those methods, clusters are normally distinguished from the other phases by a grayscale threshold, such as the grayscale intensity of the practical boundary of the cluster, 25 the mean grayscale intensity of the whole image, 26 and the local mean grayscale intensity corrected by n-times its standard deviation.…”

Physicochemical Processes Occurring inside Clusters Consisting of FCC Catalyst Particles

“…They are larger and more stable near the wall region of the riser reactor, whereas they are smaller and less stable in the core of the riser reactor [12]. The size of the cluster was observed to decrease up the riser [25]. For cluster motion in the riser, the cluster tended to fall down at the wall with a velocity in the range of 0.3-2.0 m s -1 [26].…”

“…changed dynamically due to complex interactions (gas-solid, solid-solid, solid-wall, etc.) in gas-solid systems [16,25,[27][28][29][30][31][32][33].…”

An alternative method for mapping solids holdup in a narrow rectangular CFB riser through image calibration

“…It is often operated in combination with narrow rectangular transparent risers due to the quite small depth to width ratio of the riser cross section so that the flow structure along the depth direction is relatively uniform. [1,[21][22][23][24][25] Based on the correlating of the image information (grayscale) and the solids holdup, an image calibration method can be applied to obtain the lateral distribution of solids holdup, which is considered to be an alternative method to provide accurate and quantitative information about the flow structure. [17][18][19][20] With the development and improvement of modern video cameras and application of imaging process and analysis methods, more and more quantitative details are provided by the visualization methods, such as solids holdup, cluster size and velocity, and the cluster formation mechanism.…”

“…[17][18][19][20] With the development and improvement of modern video cameras and application of imaging process and analysis methods, more and more quantitative details are provided by the visualization methods, such as solids holdup, cluster size and velocity, and the cluster formation mechanism. [1,[21][22][23][24][25] Based on the correlating of the image information (grayscale) and the solids holdup, an image calibration method can be applied to obtain the lateral distribution of solids holdup, which is considered to be an alternative method to provide accurate and quantitative information about the flow structure. [26] Therefore, the aims of the present study are to exhibit the lateral distribution of the solids holdup obtained by the image calibration method at two axial levels along the riser, and then to verify the feasibility and accuracy of this method by comparing the results with that of the commonly use optical fibre probe.…”