Validation of the CFD model for prediction of flow behaviour in fluidized bed reactors

Thapa, Rajan Kumar; Halvorsen, Britt

doi:10.2495/afm120211

Cited by 1 publication

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“…A good agreement between the experimental measurements and the model predictions were established. The details of the validation work performed by the authors can be found in WIT Transactions on Engineering Series 2012 [13].…”

Section: Viscous Limit Set Of Scaling Rulesmentioning

confidence: 99%

Scaling of bubbling fluidized bed reactors with glicksman’s viscous limit set and CFD simulation

Thapa¹,

Halvorsen²

2014

Int. J. CMEM

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Glicksman's viscous limit set of dimensionless parameters have been investigated using experimentally verifi ed computational fl uid dynamics model. Simulations have been performed for the two bubbling fl uidized beds with different particle sizes and densities. Dimensionless average pressure drops across the bed height, dimensionless pressure standard deviations and dimensionless relative pressures have been investigated as a function of dimensionless superfi cial gas velocities for the two beds. Fluctuation of solid volume fraction and contours of solid volume fraction have also been investigated at different dimensionless gas velocities. Time series data of the pressure fl uctuation and solid volume fraction are compared. The results indicate that the fl uid dynamic similarity between two beds holds up to particle Reynolds number of 15. After this, the bubble activities in the two beds start to deviate signifi cantly. The results of the work show that the analysis of solid volume fraction fl uctuation gives higher accuracy than time-series pressure fl uctuation when scaling the bubbling fl uidized bed within the viscous limit. Keywords: Fluidized bed, scaling, viscous limit, Glicksman, CFD. INTRODUCTIONScaling of fl uidized bed reactors in a proper way remains a major challenge in process industries. Scaling of fl uidized beds is still an inexact science rather than a mix of mathematics, witchcraft, history and common sense as indicated by Matsen [1]. The scaling law for fl uidized bed reactors has been developed by Glicksman. The law is derived by non-dimensionalizing the governing fl uid dynamic equations for gas-solid fl ow [2]. This gives a set of dimensionless parameters. For two fl uidized bed reactors to be fl uid dynamically similar, the set of dimensionless parameters should be matched. The set of the dimensionless parameters is used to developed lab-scale cold models that simulate the fl ow behavior of an operating plant. This enables to improve the fl ow behavior of an existing plant when it is required. In addition, scaling is useful for the modifi cation of the existing plants.Glicksman has derived two sets of dimensionless parameter for scaling of fl uidized beds: full set and simplifi ed set. In the full set, dimensionless parameters such as Froude number, Reynolds number, density ratio, bed to particle size ratio, bed geometry ratio, particle sphericity and particle size distribution should be matched. van Ommen et al. studied the simplifi ed set, full set and extended full set with additional dimensionless pressure group and found reasonable agreements [3]. In the particular application such as biomass gasifi cation reactors, it is diffi cult to match all the parameters of the set. Sometimes exotic particles (very high density and very low particle size) are required when it comes to scaling down a very large operating plant to a lab-scale cold model [4]. To overcome this problem, Glicksman has simplifi ed the full set. In the simplifi ed set, Reynolds number has been replaced by the ...

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Section: Viscous Limit Set Of Scaling Rulesmentioning

confidence: 99%