Granular temperature in a gas fluidized bed

Biggs, Mark J.; Glass, Donald; Xie, Liansong; Živković, Vladimir; Buts, A.; Kounders, M. A. Curt

doi:10.1007/s10035-007-0077-8

Cited by 30 publications

(24 citation statements)

References 64 publications

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“…Compared to their binary-mixture counterparts, segregation studies on continuous PSDs are rare (Hirschberg and Werther 1998;Karri and Knowlton 1998). The trends observed to date are largely consistent with the segregation of the larger (i.e., more massive) species toward the bottom of the riser and toward the wall.For the mixture types investigated here, the more massive species preferentially segregates toward the wall at all axial locations, as is consistent with previous experimental work( Hirschberg and Werther 1998;Karri and Knowlton 1998;) and known granular temperature profiles (Lu, Liu et al 2000;Lu, Gidaspow et al 2001;Zhou, Flamant et al 2002;Lu and Gidaspow 2003; Tartan and Gidaspow 2004;Biggs, Glass et al 2008;Songprawat and Gidaspow 2010). Comparison among the three systems indicate that the greater the mass ratio between the species, the greater the extent of this radial segregation observed, which corroborates previous work (Trujillo, Alam et al 2003; Trujillo and Herrmann 2003;Yoon and Jenkins 2006;Liu, Metzger et al 2008).…”

supporting

confidence: 78%

“…First, for all three systems and consistent with previous experimental work ( Hirschberg and Werther 1998;Karri and Knowlton 1998;, the more massive species preferentially segregates to the wall at all axial locations. This radial segregation behavior can be explained in terms of thermal diffusion, which drives the more massive species toward the lower granular temperature at the wall, as has been indicated from both experimental (Tartan and Gidaspow 2004;Biggs, Glass et al 2008) and modeling (Lu, Liu et al 2000;Lu, Gidaspow et al 2001;Lu and Gidaspow 2003;Songprawat and Gidaspow 2010) results. Comparison among the three mixture types indicate that the greater the mass ratio between the species, the greater the extent of radial segregation observed.…”

mentioning

confidence: 84%

“…189 2004; Biggs, Glass et al 2008) and kinetic-theory-based models (Lu, Liu et al 2000;Lu, Gidaspow et al 2001;Lu and Gidaspow 2003;Songprawat and Gidaspow 2010) that lower granular temperature regions are found at the wall due to augmented dissipation of kinetic energy through (i) particle-wall collisions and (ii) increased particle-particle collisions due to the higher solid volume fraction expected in the annular region (i.e., core-annulus flow). The more massive species have a tendency to segregate preferentially toward the lower temperature region due to thermal diffusion (Lu and Gidaspow 2003), as is also found in granular (Hsiau and Hunt 1996;Luding, Strauss et al 2000;Xu, Louge et al 2003;Liu, Metzger et al 2007; Garzo and Reyes 2010) systems.…”

Section: De-fc26-07nt43098mentioning

confidence: 99%

“…As noted previously from Figure 158, mass flux profiles are more dominated by solids velocity than concentration, since similar mass flux profiles of monodisperse materials are exhibited despite reverse core-annulus (i.e., dense core and dilute annulus) for the larger materials. Correspondingly, species segregation is linked to granular temperature gradient, and granular temperature is also linked to solids concentration (Lu, Liu et al 2000;Lu, Gidaspow et al 2001;Zhou, Flamant et al 2002;Lu and Gidaspow 2003; Tartan and Gidaspow 2004;Biggs, Glass et al 2008;Songprawat and Gidaspow 2010); therefore, since solids concentration has less effect on mass flux profiles, along the same vein as granular temperature, species segregation also is not apparent in mass flux profiles.Finally, G r,net,norm profiles for the small glass with continuous PSD (Table 11) are portrayed in Figure 162. Because the four operating conditions implemented for this continuous PSD are different from the other materials (Table 12), a direct comparison on the effect of material is not possible.…”

mentioning

confidence: 99%

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

Hrenya¹,

Cocco²,

Fox³

et al. 2011

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This report describes in detail the technical findings of the DOE Award entitled "Development, Verification, and Validation of Multiphase Models for Polydisperse Flows." The focus was on high-velocity, gas-solid flows with a range of particle sizes. A complete mathematical model was developed based on first principles and incorporated into MFIX. The solid-phase description took two forms: the Kinetic Theory of Granular Flows (KTGF) and Discrete Quadrature Method of Moments (DQMOM). The gas-solid drag law for polydisperse flows was developed over a range of flow conditions using Discrete Numerical Simulations (DNS). These models were verified via examination of a range of limiting cases and comparison with Discrete Element Method (DEM) data. Validation took the form of comparison with both DEM and experimental data. Experiments were conducted in three separate circulating fluidized beds (CFB's), with emphasis on the riser section. Measurements included bulk quantities like pressure drop and elutriation, as well as axial and radial measurements of bubble characteristics, cluster characteristics, solids flux, and differential pressure drops (axial only). Monodisperse systems were compared to their binary and continuous particle size distribution (PSD) counterparts. The continuous distributions examined included Gaussian, lognormal, and NETLprovided data for a coal gasifier.FINAL TECHNICAL 4 DE-FC26-07NT43098 5 EXECUTIVE SUMMARYThis report is the final technical report for the award DE-FC26-07NT43098 entitled "Development, Verification, and Validation of Multiphase Models for Polydisperse Flows." Below is a summary of work completed under the grant for each of the major goals. Goal I: Continuum Theory for Solid PhaseTwo separate and complementary continuum theories were derived to model polydisperse solids: the kinetic theory of granular flow (KTGF) and the discrete quadrature method of moments (DQMOM). Both theories are based on first principles with no adjustable parameters. The polydisperse KTGF and DQMOM were then encoded in MFIX, and underwent a wide range of verification testing to ensure, to the best possible extent, that no coding errors were present. These verification tests included both granular and gas-solid flows, including cases where an analytical solution and/or DEM (discrete element method) data and/or simple test cases. For the case of KTGF, another set of constitutive equations were derived which rigorously incorporated the gas phase for a simplified case of monodisperse systems at low Reynolds numbers. This derivation used the acceleration model developed in Task 2 from direct numerical simulations (DNS) in the starting kinetic equation, and indicated the effect of the fluid phase on the resulting constitutive relations. Goal II: Improved Gas-Particle Drag Laws -effect of particle size distributionIn this portion of the effort, two types of direct numerical simulations (DNS) were used to extract the drag force experienced by particles in a polydisperse suspension. These two methods, na...

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supporting

confidence: 78%

mentioning

confidence: 84%

Section: De-fc26-07nt43098mentioning

confidence: 99%

mentioning

confidence: 99%

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

Hrenya¹,

Cocco²,

Fox³

et al. 2011

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“…We have used this non-invasive technique to study extensively particle dynamics and the granular temperature in a variety of dense fluidized beds: gas- [14], liquid- [15] fluidized beds (FBs), and dry- [16,17] and submerged- [18] vibrated beds. Using the liquid-FB work as an example, we demonstrate here that kinetic theory of granular flow formulas can be used with DWS-derived granular temperature to obtain the granular pressure and viscosity.…”

Section: Introductionmentioning

confidence: 99%

Determining key variables of the kinetic theory of granular flow using DWS

Živković

Berry

Glass

et al. 2013

AIP Conference Proceedings

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Elutriation and Species Segregation Characteristics of Polydisperse Mixtures of Group B Particles in a dilute CFB Riser

2012

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Experiments in a dilute, gas-solids circulating fluidized bed have been conducted, with an emphasis on the impact of polydispersity on elutriation and species segregation. Two categories of polydispersity were studied: binary mixtures with various compositions and continuous particle size distributions (PSDs) with various widths. Qualitative differences between the two include (i) total elutriation flux of binary mixtures increases with the composition of fines (U t < U s ) but not so for continuous PSDs and (ii) elutriation flux of coarse particles (U t > U s ) depends non-monotonically on fines composition for binary mixtures but monotonically for continuous PSDs. These differences are explained by the increasing size disparity of continuous PSDs as distribution width increases, while the size disparity remains constant in binary mixtures of varying compositions. A third qualitative difference is the monotonic decrease in mass % of coarse particles with riser height observed for continuous PSDs, and a nonmonotonic behavior for binary mixtures. V V C 2012 American Institute of Chemical Engineers AIChE J, 59: 84-95, 2013

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Granular temperature in a gas fluidized bed

Cited by 30 publications

References 64 publications

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

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

Determining key variables of the kinetic theory of granular flow using DWS

Elutriation and Species Segregation Characteristics of Polydisperse Mixtures of Group B Particles in a dilute CFB Riser

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