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Solids Velocity (solid + velocity)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Effect of various parameters on the solid circulation rate in a liquid,solid circulating fluidized bed

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2008
P. Natarajan
Abstract A liquid,solid circulating fluidized bed (LSCFB) is operated at high liquid velocity, where particle entrainment is highly significant, and between the conventional liquid fluidized bed and the dilute-phase liquid transport regimes. In the present work, systematic experiments were carried out in a 0.094 m i.d. and 2.4 m height laboratory-scale LSCFB apparatus by using various solid particles and tap water as fluidizing medium to study the hydrodynamics. The effects of operating parameters, i.e. primary liquid flow rate in the riser (jf), auxiliary liquid flow rate (ja), total liquid flow rate (jl), particle density (,s), particle diameter (dp) and solid feed pipe diameter (do) on the solid circulation rate were analyzed from the experimental data. Finally, a correlation was developed from the experimental data to estimate solid velocity (solid circulation rate), and was compared with the present experimental and available data in the literature. They agree well with a maximum root mean-square (RMS) deviation of 12%. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Experimental investigation of the hydrodynamics in a liquid,solid riser

AICHE JOURNAL, Issue 3 2005
Shantanu Roy
Abstract Liquid,solid fluid dynamics has been investigated in a 6-in. (0.15 m) "cold-flow" circulating fluidized bed riser using non-invasive flow monitoring methods. Gamma-ray computed tomography (CT) was used to measure the time-averaged cross-sectional solids volume fraction distributions at several elevations. The time-averaged mean and "fluctuating" solids velocity fields were quantified using the computer-automated radioactive particle tracking (CARPT) technique. The experimental equipment, protocol of implementation, and data analysis have been discussed briefly, with particular emphasis on the specific features in the use of these techniques for studying high-density turbulent flows as in a liquid,solid riser. The experimental study examines nine operating conditions, that is, three liquid superficial velocities and three solids flow rates. The solids holdup profile is found to be relatively uniform across the cross section of the riser, with marginal segregation near the walls. The time-averaged solids velocity profiles are found to have a negative component at the walls, indicating significant solids backmixing. Detailed characterization of the solids velocity fields in terms of RMS velocities, kinetic energies, Hurst exponents, residence time distributions, trajectory length distributions, dispersion coefficients, and so forth are presented. Comparative and symbiotic analyses of the results were used to develop a coherent picture of the solids flow field. In addition, the work also serves to demonstrate the power and versatility of these flow-imaging techniques in studying highly turbulent and opaque multiphase systems. © 2005 American Institute of Chemical Engineers AIChE J, 51: 802,835, 2005 [source]

Gas-solid Two-phase Mixtures Flowing Upward through a Confined Packed Bed,

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3-4 2006
Yurong He
Abstract This paper deals with flows of a gas-solid two-phase mixture through a confined packed bed. Both experimental work and numerical modelling are performed on the behaviour of suspended particles within the packed bed. The experimental work is carried out with a non-intrusive Positron Emission Particle Tracking (PEPT) technique, which tracks particle motion at the single particle level for a prolonged period thus allows both the microscopic and macroscopic solids behaviour to be analysed under the steady-state conditions. A continuous based model is used to simulate the flow behaviour. The model uses a newly proposed porosity model and treats the suspended and packed particles as a binary mixture with the packed particles being at zero velocity. The results show that the model captures the main features of solids behaviour in terms of the radial distributions of the suspended particle concentration and the axial solids velocity. Both the experiments and modelling suggest that the wall effect on the motion of suspended particles be limited to a small region close to the wall (,0.5,1 packed particle diameter). However, deviations exist between the model predictions and experiments; more work is therefore proposed to improve the interaction terms in the model between the suspended and packed particles. [source]

Lateral flux and velocity of FCC particles in a CFB riser

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2001
Stefan Malcus
Abstract The radial profiles of the lateral solids mass flux and the lateral solids velocity were determined for FCC particles in a 7 m tall circulating fluidtzed bed riser 0.14 m in diameter by applying a lateral flux probe and electrical capacitance tomography. The external solids mass flux was varied between 148 and 302 kg/(m2.s), while the superficial gas velocity was varied between 3.7 and 4.7 m/s. Under these conditions, a dense bottom region and an upper dilute region coexisted in the riser. Lateral fluxes in the dense bottom region reached 100 kg/(m2.s) at the wall, but fell to 14 kg/(m2.s) at the wall in the upper dilute region. At both axial locations, a net deposition of solids from the core to the annulus occurred, indicating that fully developed flow was never established under these conditions. The lateral fluxes in the bottom region were significantly larger than those found in previous studies. It was further concluded that considering the lateral solids flux to be only a function of solids concentration is an over-simplification. Les profils radiaux du flux massique de solides latéral et de la vitesse de solides iatérale ont été déterminés pour des particules de FCC dans une colonne à lit fluidisé circulant de 7 m de hauteur et de 0,14 m de diamètre, en appliquant une sonde de flux latérale et la tomographic par capacitance électrique. On a fait varier d'une part le flux massique de solides externe entre 148 et 302 kg/(m2.s) et d'autre part la vitesse de gaz superficielle entre 3,7 et 4,7 m/s. Dans ces conditions, une région inférieure dense et une région supérieure diluée coexistent dans la colonne. Les flux latéraux dans la région inférieure dense atteignent 100 kg/(m2.s) à la paroi, mais tombent à 14 kg/(m2.s) à la paroi dans la région supérieure diluée. Aux deux régions axiales, une déposition nette de solides se produit du coeur vers l'espace annulaire, indiquant que un écoulement pleinement développé n'a jamais été établi dans ces conditions. Les flux latéraux sont nettement plus important que ceux trouvés dans les études antérieures. II a en outre été conclu que le fait de considéer le flux de solides latéral uniquement comme étant fonction de la concentration de solides constituait une sur-simplification. [source]