Three-component solids velocity measurements in the middle section of a riser

Abstract

Coincident three-component experiments are conducted in a 8.7-m-high cylindrical riser (internal diameter 0.10 m) of a Pilot-Scale Cold-Flow Circulating Fluidized Bed set-up using two LDA probes. At heights close to the solids inlet, the flow is highly disturbed due to the asymmetrical position of both the air and solids inlets. A fully developed parabolic axial solids velocity field is observed at a height of 2.5 m. The radial and azimuthal solids velocity components are significantly smaller than the axial one and are close to zero. The velocity fluctuations in the flow direction are larger than in the other directions, showing that the flow is anisotropic. However, the radial and azimuthal velocity fluctuations are higher than the corresponding mean velocities. All fluctuating velocities are decreasing significantly with increasing riser height, i.e. as the flow becomes more developed. No average down-flow of solids is recorded, not even close to the wall, probably due to the very high dilution (ε s <0.2%) used in the presented work. The measured turbulent kinetic energy indicates that the flow is dominated by wall-particle rather than intra-particle collisions. The acquired data can be useful for validation of riser simulations.

Three-component particle velocity measurements in the bottom section of a riser

“…A detailed description has been given in previous publications (e.g. Pantzali et al, 2013;Van engelandt et al, 2007;Van Engelandt et al, 2011). The solids used are FCC-E catalyst particles with a density of 1550 kg/m 3 and a mean diameter of 67 lm, classified as Geldart A particles (Geldart, 1973).…”

“…Details are provided elsewhere (Pantzali et al, 2013). As the particle size is relatively large, the particles cannot be used as 'tracers' for the gas flow.…”

“…Analyzing the Kolmogorov entropy in a riser, de Castilho and Cremasco (2012) reported that at the inlet of a riser, for very diluted conditions, turbulence and particle-wall interactions prevail, resulting in more chaotic behavior. The present work extents our previous study (Pantzali et al, 2013) to the inlet section of the riser and aims to investigate the solid phase acceleration and the http://dx.doi.org/10.1016/j.ijmultiphaseflow.2015.02.010 0301-9322/Ó 2015 Elsevier Ltd. All rights reserved. physics of the flow development following the abrupt solids injection in the gas flow.…”

“…Chew et al (2011) studied experimentally the effect of the solids polydispersity on the riser dilute gas-solid flow and concluded that particle clustering was observed, even in extremely dilute flow. Complete and accurate experimental data on three velocity components in dilute flow riser have been reported in our previous work for the middle section of a riser with fully developed gas-solid flow (Pantzali et al, 2013). To the best of the authors' knowledge, accurate experimental data on dilute gas-solid flow in riser inlet sections, where the solids input is usually abrupt, are hardly available in literature.…”

High-fidelity simulation of the 3-D full-loop gas–solid flow characteristics in the circulating fluidized bed

“…For a long time, lots of the experiments related to the CFB have been conducted. Plenty of valuable information have been obtained to understand the gas-solid flow characteristics in the CFB, such as the core-annulus structure (Chew et al, 2012;You et al, 2008;, the cluster characteristics (McMillan et al, 2013;Yang and Leu, 2009), the solid velocity distribution (Pantzali et al, 2013;Yan and Zhu, 2005), the hydrodynamic similarity (Qi et al, 2008), the effect of internal device on solid distribution (Guío-Pérez et al, 2013;Jiang et al, 1991;Samruamphianskun et al, 2012), the particle resident behavior (Harris et al, 2003), and so on.…”