Hydrodynamics of gas-solid fluidization

Circulating fluidized bed hydrodynamics experiments for the multiphase fluid dynamics research consortium (MFDRC).

“…Many gas-solid applications involve fluidized beds (e.g., Lim et al, 1995;Yang, 2003). The behavior of the particles in fluidized beds depends not only on the flow parameters but strongly upon the particle characteristics as well.…”

“…Particle capture and return to the base of the fluidization bed, as in a circulating fluidized bed, then becomes necessary for continued operation. Still higher gas velocities lead to dilute pneumatic transport (Lim et al, 1995).…”

Development, Verification, and Validation of Multiphase Models for Polydisperse Flows

“…As further evidence of the different physics at play in the two groups, Section 4.5.1 ) presented a surprising reversal of the widely acknowledged core-annulus (dense core and dilute annulus) profiles for Group B materials which was traced to the higher Stokes number of Group B particles. Hence, a need exists to determine the hydrodynamic behavior of Group B particles rather than to extrapolate the behavior of their Group A counterparts.As indicated in a review (Lim, Zhu et al 1995), contradictory mass flux trends are present in the literature are due to non-exhaustive datasets, which provide only a limited view of the riser (i.e., comparisons are made at only two riser axial positions and/or under only a couple of operating conditions). Radial mass flux profiles have been previously reported as an inverted Ushape or inverted V-shape (van Breugel, Stein et al 1969;Bader, Findlay et al 1988;Azzi, Turlier et al 1990;Herb, Dou et al 1992;Rhodes and Laussmann 1992; Aguillon, Shakourzadeh et al 1995;Marzocchella and Arena 1996;Coronella and Deng 1998; van der Meer, Thorpe et al.…”

“…Because species segregation varies along the riser, the gas-solid contact times of each species may vary and hence impact the overall efficiency of the unit. Although investigation into species segregation behavior in low-velocity bubbling fluidized beds has been fairly extensive Nienow and Chiba 1985;Kunii and Levenspiel 1991;Lim, Zhu et al 1995;), a similar effort for CFBs is lacking.The current work is divided into two categories: binary mixtures (two species with particle size (d ave ) or material density (ρ s ) differences) and continuous particle size distributions (PSDs). The objectives of this experimental work are to (i) isolate the effect of d ave and ρ s on species segregation in binary mixtures, (ii) investigate a continuous PSD alongside the binary mixtures to better compare their species segregation trends, especially since qualitative differences between the two distributions have recently been observed for bubbling fluidized beds , and (iii) evaluate the impact of a wide range of operating conditions on the observed trends at all riser positions.…”

“…Because polydisperse systems exhibit different behavior from monodisperse systems (e.g. species segregation van Deemter 1980;Nienow and Chiba 1985;Fan, Chen et al 1990;Kunii and Levenspiel 1991;Lim, Zhu et al 1995;Werther and Hirschberg 1997;Rhodes 1998;Ottino and Khakhar 2000;Hrenya 2011), clusters ) and since different behaviors have been reported among various categories of polydispersity (i.e., binary mixtures and continuous PSDs) (Hoffmann and Romp 1991;Lin, Wey et al 2002;, investigation into the impact of the two categories of polydispersity (i.e., binary mixture and continuous PSD) on mass flux profiles is needed.Hence, to bridge the gap in the current knowledge base, this experimental effort is aimed at collecting local mass flux measurements spanning the entire riser for various materials and various operating conditions. Specifically, the focus is on illustrating the impact of local position (radial and axial), operating conditions, and material type (i.e., various monodisperse and polydisperse materials) on mass flux behavior.…”