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Prediction of single particle settling velocities through liquid fluidized beds

✍ Scribed by Željko B. Grbavčić; Zorana Lj. Arsenijević; Radmila V. Garić-Grulović


Publisher
Elsevier Science
Year
2009
Tongue
English
Weight
419 KB
Volume
190
Category
Article
ISSN
0032-5910

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✦ Synopsis


Single particle settling velocities through water fluidized beds of mono-sized glass spheres (d p = 0.645, 1.20, 1.94, 2.98 and 5 mm in diameter) were studied experimentally using a column, 40 mm in diameter. The settling spherical particles (D p = 10 and 19.5 mm) had different densities (1237 to 8320 kg/m 3 ), while the settling particles (D p = 5 and 2.98 mm) were glass spheres. The pseudo-fluid model, which considers a liquid fluidized bed as a homogenous pseudo-fluid, predicts single particle settling velocities quite well if the ratio D p /d p is larger than about 10. With decreasing ratio D p /d p , the overall friction between the settling particle and the fluidized media increases. A method for predicting single particle settling velocities through a liquid fluidized bed is proposed and discussed. Following the approach of Van der Wielen et al. [L.A.M. Van der Wielen, M.H.H Van Dam, K.C.A.M. Van Luyben, On the relative motion of a particle in a swarm of different particles, Chem. Eng. Sci. 51 (2006) 995-1008], the overall friction is decomposed into a particle-fluid and a particle-particle component. The effective buoyancy force is calculated using the transition function proposed by Ruzicka [M.C. Ruzicka, On buoyancy in dispersion, Chem. Eng. Sci. 61 (2006Sci. 61 ( ) 2437Sci. 61 ( -2446]]. A simple model for predicting the collision force is proposed, as well as a correlation for the collision coefficient. The mean absolute deviation between the experimental and calculated slip velocities was 5.08%.


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