Hydrodynamic characteristics of magnetically stabilized fluidized admixture beds of iron and copper particles

Abstract

Hydrodynamic characteristics of fluidized beds of pure iron (1416 pn), copper (934 pn) and their admixture (25,50 and 75 mass %) particles when exposed to a uniform magnetic field collinear with the gas flow are investigated. Bed pressure-drop data taken as a function of increasing and decreasing gas velocities (up to about 8 d s ) for different values of magnetic-field intensity over a wide range (0 to 17 272 N m ) are employed to determine the superficial minimum bubbling and fluidization gas velocities at ambient temperature and pressure. The minimum bubbling velocity is found to increase with an increase in the value of the magnetic-field intensity, as well as with the mass fraction of magnetizable particles in the bed, These data are correlated with an empirical relation, as well as with a semi-theoretical expression. The bed voidage data are also generated and analyzed, as also the bed quality fluidization in terms of interparticle magnetic forces. These hydrodynamic properties of magnetically stabilized fluidized-bed reactors are useful in their design and operation for a variety of chemical and biochemical applications.On a etudie les caracteristiques hydrodynamiques de lits fluidises de particules de fer pur (1416 p) et de c u k e pur (934 pm), puis de leur melange (25,50 et 75% en masse) lorsqu'elles sont exposees a un champ magnetique uniforme colineaire avec le debit de gaz. On a employe des donnees de perte de charge de lit en fonction des vitesses de gaz croissant et decroissante (jusqu'a environ 8 m) pour une large gamme d'intensite de champ magnetique (0 a 17272 N m ) afin de determiner le bullage superficiel minimum et les vitesses de gaz de fluidisation a la temperature et a la pression ambiante. On a trouve que la vitesse de bullage minimum augmentait avec la valeur de I'intensite du champ magnetique ainsi qu'avec la fraction de masse des particules magnetisables dans le lit. Ces donnees sont correlees a une relation empirique et a une expression semi-theorique. Les donnees de vide de lit sont egalement calculees et analysees tout comme la fluidisation de qualite de lit en termes des forces magnetiquement stabilises sont utiles dans leur conception et leur fonctionnement pour diverses applications chimiques et biochimiques.Keywords: magnetically stabilized fluidized beds, minimum bubbling velocity. Figure 1 -Schematic of the UIC magnetofluidized-bed column facility. uppression and delay of bubbling phenomena in a flu-S idized bed of ferromagnetic particles under the influence of an uniform external magnetic field parallel to the gas velocity vector have been well investigated, as is evident from the reviews of Liu et al. (1991), Saxena et al. (1994, and several others. The work on mixtures of magnetic and nonmagnetic particles is relatively scarce. Lucas et al. 'Author to whom correspondence should be addressed. E-mail address: saxena@uic.edu (1984) and Arnaldos et al. (1985) investigated beds of mixed particles of sintered nickel-silica, steel-copper, and steel-silica up to magnetic-field int...

MAGNETIC FIELD ASSISTED FLUIDIZATION – A UNIFIED APPROACH Part 1. Fundamentals and relevant hydrodynamics of gas-fluidized beds (batch solids mode)

“…The values of k vary from 0.5 to 2.5 (Arnaldos ,1986) and depend mainly on the type of the magnetic particles used. The value of k^ depends on the admixture composition and the field intensity as indicated by Saxena and Wu (1999) ( Table 2 in the corresponding paper) The further investigations have validated that equation for data treatment. Saxena and co-workers have adopted a simpler form (57) giving an accuracy of ± 15%.…”

“…The first reports of Lucas et al (1984), Arnaldos et al (1983Arnaldos et al ( , 1985 and Amaldos (1986) employed silica sandnickel, copper-nickel and steel-silica and steel-copper systems fluidized with air in an axial magnetic field. The recent works of Saxena's group (Wu et al 1997a;1997b, Ganzha andSaxena, 1998;Saxena and Wu, 1999) presented further results in an axial magnetic field. The recent works of Saxena's group (Wu et al 1997a;1997b, Ganzha andSaxena, 1998;Saxena and Wu, 1999) presented further results in an axial magnetic field.…”

“…The results of Saxena's group practically repeat those obtained by Amaldos. Rosensweig (Rosensweig, 1980a(Rosensweig, , 1980b and Saxena (Wu et al 1997a(Wu et al , 1997bSaxena and Wu, 1999) and Rosensweig have reported the first results on the velocity corresponding to the onset of MSB -U e in axial fields. Rosensweig (Rosensweig, 1980a(Rosensweig, , 1980b and Saxena (Wu et al 1997a(Wu et al , 1997bSaxena and Wu, 1999) and Rosensweig have reported the first results on the velocity corresponding to the onset of MSB -U e in axial fields.…”

“…Rosensweig made an attempt to use a magnetic system based on permanent magnets. (Penchev and Hristov, 1990a;Hristov, 1996;Hristov, 1998;Leu, 1994, 1996;Saxena et al 1994;Saxena and Wu, 1999) • Solenoids (Ushiki et al 1991;Sajc et al, 1992Sajc et al, , 1996Jovanovic et al, 1996) Figure 17 presents the systems employed by Saxena's group (Saxena and Shrivastava, 1991;Wu et al, 1997aWu et al, , 1997b. This limits the use of such electromagnets for laboratory use only.…”

“…The approach mentioned above was applied here on the data of Saxena and Wu (1999) Saxena and Wu (1999) and Rosensweig (1980aRosensweig ( , 1980b. The basic plots are on Fig.…”