Hydrodynamics of gas fluidized beds with mixture of group D and B particles

Ajbar, Abdelhamid; Alhumaizi, Khalid; Ibrahim, Ahmed A.; Asif, Mohammad

doi:10.1002/cjce.5450800213

Cited by 7 publications

(3 citation statements)

References 19 publications

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“…According to Ajbar et al [8], the mixing of particles belonging to different Geldart's classification groups could introduce some interesting behaviour that is not found for single-group fluidization. For example, by adding a small proportion of Group B-particles to a Group D-particle bed, the famous character of coarse particle fluidization (slugging) can be significantly suppressed [27].…”

Section: Introductionmentioning

confidence: 99%

The Effect of the Presence of Very Cohesive Geldart C Ultra-Fine Particles on the Fluidization of Geldart A Fine Particle Beds

et al. 2019

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The effect of the presence of ultra-fines (d < 10 μm) on the fluidization of a bed containing fine particles (d < 100 μm), is the subject of this paper. Practically, it can happen due to breakage or surface abrasion of the fine particles in some processes which totally changes the size distribution and also fluidization behaviour. The materials used in this study are both ground calcium carbonate (GCC); fine is CALCIT MVT 100 (Geldart’s group A) and ultra-fine is CALCIT MX 10 (group C). The experimental results for different binary mixtures of these materials (ultra-fines have 30%, 50%, or 68% of the total mixture weight) show that the physical properties of the mixtures are close to those of pure ultra-fine powders. Using mean values of the bed pressure drop calculated from several independent repetitions, the fluidization behaviour of different mixtures are compared and discussed. The fluidization behaviour of the mixtures is non-reproducible and includes cracking, channelling and agglomeration (like for pure ultra-fine powders). Increasing the portion of ultra-fine materials in the mixture causes a delay in starting partial fluidization, an increase in the bed pressure drop as well as a delay in reaching the peak point.

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Section: Introductionmentioning

confidence: 99%

The Effect of the Presence of Very Cohesive Geldart C Ultra-Fine Particles on the Fluidization of Geldart A Fine Particle Beds

et al. 2019

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“…The mixing can alter in a substantial way the dynamics of the gas-solid system. For instance, in a previous study (Ajbar et al, 2002) on gas fluidization behaviour of coarse particles, it was shown that the addition of a small proportion of group B to existing group D particles can significantly reduce the slugging that is a characteristic of fluidization of coarse particles.…”

mentioning

confidence: 99%

Improvement of the Fluidizability of Cohesive Powders through Mixing with Small Proportions of Group A Particles

2005

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The gas fluidization behaviour of fine cohesive powders, classified as Geldart group C, is known to be characterized by cracks and channels leading to severe non‐homogeneities in the bed. Geldart group A particles, on the other hand, are known to show more homogeneous and regular fluidization behaviour. This paper studies the effects of the addition of small proportions of group A on the fluidization behaviour of a group C powder. Differential pressure fluctuations data at a sampling frequency of 200 Hz were recorded for two cases. In the first case, the bed contained only group C powder while in the second case small amounts of group A particles were added to the existing group C powder. Visual/image observations coupled with time series analysis showed that the addition of small proportions of group A particles substantially improved the fluidization behaviour of the bed even at low superficial gas velocities, leading to a more uniform fluidization. Evaluation of mean and standard deviations has shown the advantage of mixing the two powders as it allowed larger pressure fluctuations and smaller standard deviations. Power spectra, on the other hand, showed that unlike group C, for which fluctuations were small in magnitude and broadband in structure, the mixture showed stronger periodic behaviour as result of the attenuation of the small and rapid fluctuations caused by the flow of gas in the cracks and channels. Advanced methods such as the principal component analysis of the embedded trajectories allowed a quantitative comparison between the fluidization behaviour of the two systems.

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“…Dilute-phase flow and dense-phase slugging flow regime models were verified for this system by Sivasanmugam and Lakshmi. 3 Ajbar et al 4 studied the hydrodynamic behavior of Geldart group D particles mixed with a small proportion of Geldart group B particles using pressure fluctuations data. Recent research on the hydrodynamics and mixing of biomass particles in fluidized beds has been reviewed by Cui and Grace.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Hydrodynamic Properties of Mixed-Particle Systems and Theoretical Analysis of Loop Pressure Profile in a CFB Unit

Das

Meikap

Saha

2008

Ind. Eng. Chem. Res.

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The hydrodynamic behaviors of mixed system of particles were investigated in a circulating fluidized bed (CFB) unit consisting of fast column (riser) with an inner diameter of 0.1016 m and a height of 5.62 m. Particle mixtures containing a Geldart group-A-like fluid catalytic cracking (FCC) catalyst with group-B-like sand and iron ore with coal were used to study the hydrodynamic features including static pressure, voidage, and loop pressure profile. The mixed system consisting of FCC catalyst and sand contained 20, 50, and 80 mass % sand, and the coal-iron ore mixture contained 80 mass % coal. The superficial air velocity ranged between 2.01 and 4.681 m/s, and the corresponding mass fluxes were 12.5-50 kg/(m 2 s). A comparison of the available experimental values for static pressure profiles at different operating conditions for mixedparticle systems shows good agreement with those predicted from the single-particle systems. Using experimental data on the loop pressure balance, a simplified theoretical analysis was performed to predict the pressure profile in the CFB loop. The deviations between the two sets of values are within reasonable limits of accuracy.

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Hydrodynamics of gas fluidized beds with mixture of group D and B particles

Cited by 7 publications

References 19 publications

The Effect of the Presence of Very Cohesive Geldart C Ultra-Fine Particles on the Fluidization of Geldart A Fine Particle Beds

The Effect of the Presence of Very Cohesive Geldart C Ultra-Fine Particles on the Fluidization of Geldart A Fine Particle Beds

Improvement of the Fluidizability of Cohesive Powders through Mixing with Small Proportions of Group A Particles

Prediction of Hydrodynamic Properties of Mixed-Particle Systems and Theoretical Analysis of Loop Pressure Profile in a CFB Unit

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