Circulating fluidized bed (CFB) is used for a wide range of gas−solid reactions. However, most of the data reported on CFBs are for Geldart's group A particles, although the applications of Geldart's group B CFBs are numerous. In the current work, the solid flow field is deciphered in a pilot-plant-scale Geldart's group B CFB riser. Solid motion is tracked by using a radioactive particle tracking technique. The data are reported in a fully developed flow region of 0.1 m diameter and 6.5 m height CFB riser at different inlet gas velocities (7.6−9.2 m/s) and solid fluxes (100−200 kg/m 2 s). The different flow quantities such as mean axial and radial velocities, rootmean-square velocities, granular temperature, and turbulent intensities are calculated for all the cases. It is observed that solid motion predominantly lies in the axial direction. The probability distribution function of instantaneous solid velocity shows wider distribution near the wall as compared to the center of the riser. This shows that the probability of mesoscale metastable structure formation increases while moving from the center to the wall. Furthermore, the results show that the mean solid velocity largely depends on gas−solid interactions. However, for the fluctuating velocity, both gas−solid and solid−solid interactions are critical. The results indicate that the solid turbulent intensity in Geldart's group B riser is significantly higher than that in the group A riser. Hence, solid velocity fluctuations are higher in the group B riser.
Pulsed sieved plate columns (PSPCs) are used for liquid–liquid extraction processes in several industries such as mineral processing, pharmaceuticals, and nuclear fuel cycle. Despite their widespread use in the industry, there is a dearth of experimental insights into the local hydrodynamics in PSPC. This work for the first time reports the local hydrodynamics inside a PSPC using the radioactive particle tracking technique. Local instantaneous velocity, mean velocity, turbulent quantities such as root-mean square (rms) velocity, turbulent kinetic energy, and turbulent intensity are measured through the radioactive particle tracking technique. The effects of pulsing velocity and liquid flow rate on local hydrodynamics and turbulence parameters are studied for no net flow and single-phase flow conditions. Results indicate that the mean flow velocity is low; however, significant fluctuating velocity components are generated due to the pulsing action. Though the fluctuations in the axial direction dominate, significant radial velocity is observed in all of the cases. Further, results show that the fluctuations in the axial direction attenuate in the case of single-phase flow when compared with the no flow condition. This leads to lower axial rms velocity, turbulent kinetic energy, and turbulent intensity in the case of single-phase flow as compared with the no flow condition. In all of the cases, significant fluctuations are observed, which signify a higher degree of mixing and hence enhanced mass transfer in PSPCs.
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