Monitoring Fluidization Dynamics for Detection of Changes in Fluidized Bed Composition and Operating Conditions

In many industrial applications of gas-solids fluidized beds, it is worthwhile to have an on-line monitoring method for detecting changes in the hydrodynamics of the bed (due for example to agglomeration) quickly. In this paper, such a method, based on the short-term predictability of fluidized bed pressure fluctuations, is examined. Its sensitivity is shown by experiments with small step changes in the superficial gas velocity and by experiments with a gradual change in the particle size distribution of the solids in the bed. Furthermore, it is demonstrated that the method is well able to indicate if a stationary hydrodynamic state has been reached after a change in the particle size distribution (a ‘grade change’).

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Hydrodynamics of Multiple Size Particles in a Liquid Fluidized Bed Classifier

Volume 1: Fora, Parts A, B, C, and D ◽

10.1115/fedsm2003-45494 ◽

2003 ◽

Author(s):

Dinesh Gera ◽

Madhava Syamlal ◽

Thomas J. O’Brien

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Fluidized Bed ◽

Volume Fraction ◽

Fluid Model ◽

Operating Conditions ◽

Particle Sizes ◽

Two Fluid Model ◽

Predicted Values

A two fluid model is extended to an N-phase, multi-fluid model, in which each particulate phase represents a collection of particles with identical diameter and density. The current N-phase model is applied to a fluidized bed classifier with six different particle sizes to investigate the effects of different operating conditions—fluidizing liquid flow rate, feed voidage, and particle size distribution in the feed stream—on the particle size distribution inside the classifier and the discharge streams. The predicted volume fraction of different particle sizes is compared with the experimental data reported by Chen et al. (2002) for two columns, 191 mm and 292 mm in diameter, each having different geometries and containing glass beads of different sizes fluidized with water. A fairly good agreement is observed between the measured and predicted values for mono- and poly-dispersed systems.

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Development of the Bed Particle Size Distribution in a Circulating Fluidized Bed Combustor

18th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2005-78115 ◽

2005 ◽

Author(s):

Cornelis Klett ◽

Ernst-Ulrich Hartge ◽

Joachim Werther

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Fluidized Bed ◽

Circulating Fluidized Bed ◽

Calculated Data ◽

Operating Conditions ◽

Attrition Rate ◽

Balance Model ◽

Fluidized Bed Combustor

In the present work a particle population balance model for a circulating fluidized bed combustor (CFBC) is developed that allows a description of the fate of individual particles in terms of attrition and transport effects. Besides the operating conditions and the particle size distribution the residence time of particles in the system is considered in the modeling of abrasion and shrinking of particles. The model takes account of the fact that fresh particles have a higher attrition rate than particles which have stayed for some time already in the system. The model aims at the description of the dynamic adjustment of the particle size distributions in a given system. The model has been validated with experimental data from a pilot-plant combustor, i.e. a CFBC with an inner diameter of 0.1 m and a height of 15 m. A comparison between experimental and calculated data shows the applicability of the model.

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