Transmission characteristics of gas in a circulating fluidised bed

White, Christopher C.; Dry, R.J.

doi:10.1016/0032-5910(89)80012-9

Cited by 9 publications

(1 citation statement)

References 2 publications

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“…Radial gas transport in the riser is mainly due to convective mass transfer between the core and annulus of both the gas and solids. This mass transfer is characterized by exchange coefficients, for both the gas and solids. ,,,, These coefficients appear to be the most important parameters of the model.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic Model for the Gas Flow in Circulating Fluidized Bed Reactors

Vandewalle

Baeyens

Claerbout

2002

Ind. Eng. Chem. Res.

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The circulating fluidized bed (CFB) riser may be regarded as composed of two hydrodynamically distinct regions: in the central part, the “core”, particles, and gas are transported upward in a cocurrent dilute flow with a fairly high voidage. In the wall zone or “annulus”, particles are, on average, transported downward, countercurrently to the gas flow: the voidage in this region is significantly lower than that in the central region. The hydrodynamics of the gas phase in CFBs are of dominant importance for predicting the conversion of CFB chemical reactions. Both the core plug-flow gas and the annulus backmixing determine the average residence time, the residence time distribution, and hence the reaction yield. The scope of this paper is to develop a model to predict the residence time and the residence time distribution of the gas phase. Values of underlying parameters are selected from fitting experimental data and model predictions. The model contains two dominant parameters: the exchange coefficient for the gas phase, k g, and the exchange coefficient for the solids between the annulus and core, K A → C. The model is evaluated for different values of these coefficients so that the predicted response curve for the concentration in the gas phase is in best possible agreement with the measured one. The values of both parameters are given and compared with literature data. To complete the assessment, a sensitivity analysis was performed.

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Section: Introductionmentioning

confidence: 99%

Hydrodynamic Model for the Gas Flow in Circulating Fluidized Bed Reactors

Vandewalle

Baeyens

Claerbout

2002

Ind. Eng. Chem. Res.

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Hydrodynamics of circulating fluidized bed risers: A review

et al. 1995

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Any vessel in which solids are transported upward by a gas stream and then recycled to the bottom may be classified as a Circulating Fluidized Bed (CFB). We describe possible CFB operating regimes in the context of this broad classification and highlight commercial processes that employ CFB technology and potential applications. Process design and development require a fundamental understanding of gas and solids hydrodynamicssolids hold-up, mixing and velocity distribution. We discuss techniques used to measure solids mass flux, which is a critical parameter for both design and control. In the last decade, significant research efforts have been devoted to new experimental techniques to measure both gas and solids spatial and temporal distribution. We list these techniques and detail the different modelling approaches that have emerged based on the new data. Characterization of the data is still incomplete and the available models require further refinement to reliably predict the effect of scale, operating conditions and particle characteristics on hydrodynamics. N'importe quel contenant dans lequel des particules sont emportks dans la direction ascendante par un courant gazeux puis recyclkes par le bas peut Stre class6 c o m e un Lit Fluidisk Circulant (LFC). Nous dkrivons les rkgimes possibles des op6rations dans ces LFC en tenant compte de cette dkfinition ktendue et les prockddcs industriels existants et potentiels qui utilisent cette technologie des LFC. La conception et le dkveloppement des proctklks exigent une comprkhension fondamentale des hydrodynamics du gaz et des particulesrktention de solides, degrk de mklange et distribution des vitesses. Nous discutons les diffkrentes techniques utiliskes pour mesurer le taux de circulation de solide qui est un paramttre critique pour aussi bien le design que le contr6le. Durant le dernitres mks, un effort significatif'de recherche a kt6 consenti au dkveloppement de nouvelles techniques exp6rimentales pour mesurer les distributions temporelle et spatiale des diffkrentes caractkristiques du gaz et du solide. Nous reportons ces techniques et nous dktaillons le diffkrentes approches de modklisation qui ont kt6 introduites en se basant sur ces nouvelles donnks.La caradrisation de ces donnks est encore incompltte et les modkles existants doivent Stre encore raflids afin de pddire ad6quatement les effets d'khelle, des conditions @ratoires et des mactkristiques des particules sur I'hydrodynamique.

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Experimental techniques

Louge¹

1997

Circulating Fluidized Beds

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Transmission characteristics of gas in a circulating fluidised bed

Cited by 9 publications

References 2 publications

Hydrodynamic Model for the Gas Flow in Circulating Fluidized Bed Reactors

Hydrodynamic Model for the Gas Flow in Circulating Fluidized Bed Reactors

Hydrodynamics of circulating fluidized bed risers: A review

Experimental techniques

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