Mechanisms of choking and entrainment

Matsen, John M.

doi:10.1016/0032-5910(82)85003-1

Cited by 168 publications

(55 citation statements)

References 7 publications

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“…Solids concentrations needed to exceed 0.05 % which is unlikely in a freeboard of a bubbling fluidized bed. Matsen (1982) also concurred that cluster formation and the size of the cluster formation are strongly dependent on the solids concentration.…”

Section: Introductionsupporting

confidence: 60%

Small-Scale Particle Interactions Are Having Significant Effects on Global Fluidized Bed Behavior

Cocco

Issangya

Karri

et al. 2017

KONA

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Fluidized bed design and scale-up depends strongly on particle characteristics such as size, shape, and for Geldart Group A particles, the level of fines (particles smaller than 44 microns). However, recent research has shown that particle clustering has a significant effect on fluidized bed hydrodynamics which impacts how these units should be designed and scaled up. This is especially true with the estimation of the solids entrainment rate and the cyclone collection efficiency. The amount of fines, particle shape and surface morphology play a role on the level of particle clustering in a fluidized bed. The fine particles are an excellent conduit for moving charge as electrons or ions which appear to be the dominant mechanism of electrostatics for Geldart Group A material in a bubbling fluidized bed. This electrostatic force trades off with particle momentum relaxation and rotational to translation momentum transfer with regard to forming a particle cluster. The issue is the quantification of this effect so more precise calculations can be made with particle entrainment rates and cyclone collection efficiency. Preliminary work on particle shear in a packed and fluidized beds, suggest that particle clustering can be measured and may provide a quantifiable metric for the level of particle clustering.

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Section: Introductionsupporting

confidence: 60%

Small-Scale Particle Interactions Are Having Significant Effects on Global Fluidized Bed Behavior

Cocco

Issangya

Karri

et al. 2017

KONA

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“…(4) is illustrated in Figure 3 for the 84 m rounded sand. For all powders, Leung et al [7] and Matsen [8] underestimate Ch . The Yousfi and Gau [9] prediction is fair at lower and/or values.…”

Section: Resultsmentioning

confidence: 85%

Choking Affects the Operation Diagram of a CFB Riser

Zhang

Degrève

Baeyens

et al. 2014

Journal of Powder Technology

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Experiments in 3 different CFB risers have confirmed that common riser operations can be hampered in a well-defined (U, G) range where choking occurs. Geldart A-type powders were investigated. Experimental results of the choking velocity were empirically correlated, being about 30% lower than predicted by the correlation of Bi and Fan, but largely exceeding other predictions. Introducing the findings into the operation diagram presented by Mahmoudi et al. adds a region where stable riser operation is impossible. The adapted diagram enables CFB designers to better delineate the operating characteristics.

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“…As a first approximation it is assumed that the ratio of the local slip velocity and the terminal velocity of a single particle only depends on the solids concentration, following the approach of Matsen (1982) for dilute systems (e, < 0.01). Figure 7 shows the reduced slip velocity, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…To solve eqs (1) and (2) the solid phase concentration es is required as a function of the radius. According to Matsen (1982) the solids distribution can be considered homogeneous for very dilute flows (c&5%), where its value can be related to the overall mass flux. For more dense systems empirical correlations, reported in the literature (Zhang et al, 1991;Rhodes et al, 1992), can be used to describe the inhomogeneous solids distribution.…”

Section: Constitutive Relations Lmentioning

confidence: 99%

Hydrodynamic modelling of circulating fluidised beds

Nieuwland

Huizenga

Kuipers

et al. 1994

Chemical Engineering Science

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Abstract-A one-dimensional model for the riser section of a circulating fluidised bed has been developed which describes the steady-state hydrodynamic key variables in the radial direction for fully developed axisymmetric flow. Both the gas and the solid phase are considered as two continuous media, fully penetrating each other. As a first approximation gas phase turbulence has been incorporated in our hydrodynamic model by applying a slightly modified version of the well-known Prandtl mixing length model. To solve the resulting set of transport equations, the solids distribution along the tube radius is required. Several strategies are given to obtain this information. In addition the effect of clusters on the momentum transfer between both phases has been modelled using an empirical correlation. Theoretically calculated results agree welt with reported experimental data of different authors.

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Mechanisms of choking and entrainment

Cited by 168 publications

References 7 publications

Small-Scale Particle Interactions Are Having Significant Effects on Global Fluidized Bed Behavior

Small-Scale Particle Interactions Are Having Significant Effects on Global Fluidized Bed Behavior

Choking Affects the Operation Diagram of a CFB Riser

Hydrodynamic modelling of circulating fluidised beds

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