On the minimum fluidization velocity in 2D fluidized beds

• Published in: Powder technology 2011-02, Vol.207 (1-3), p.145-153
• Main Authors: Sánchez-Delgado, S., Almendros-Ibáñez, J.A., García-Hernando, N., Santana, D.
• Format: Article
• Language: English
• Subjects: 2D fluidized bed; Applied sciences; Chemical engineering; cohesion; Correlation; Correlation analysis; Electrostatic charge; electrostatic interactions; Exact sciences and technology; Fluidization; Fluidized beds; Fluidizing; Mathematical models; Minimum fluidization velocity; Miscellaneous; Particle size; Solid-solid systems; Two dimensional; Wall effects
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2010.10.020

In the present study, a new correlation for the determination of the minimum fluidization velocity in 2D fluidized beds was developed. The proposed correlation was based on the experimental results obtained in 2D fluidized beds with different particle sizes, bed thicknesses and bed heights. Thus, the proposed correlation depends only on the nondimensional variable t/dp, where t is the bed thickness and dp is the particle size. The proposed correlation was compared with other experimental results that can be found in the literature, and two different trends were observed. Namely, one set of experimental results was in accordance with the proposed correlation, while the other set deviated from the theoretical results. In particular, the minimum fluidization velocities of the experimental results were greater than the predicted values of the proposed correlation. In view of the differences in the experimental conditions, the observed discrepancies may be attributed to the effects of electrostatic charge and particle shape. In addition, the experimental fluidization–defluidization curves were compared to the theoretical results of Jackson's model, and the parameters were fitted to the experimental data. However, Jackson's model is based on a 1D bed; thus, general parameters could not be obtained for a bed with a fixed particle size and thickness due to the two dimensional voidage distribution in the bed and bed cohesion effects, which are a result of electrostatic forces and are not considered in Jackson's model. A new correlation quantifies the influence of the 2D geometry on the measurement of the minimum fluidization velocity (Umf). Umf in a 2D geometry increases as the ratio between the particle size and the bed thickness (dp/t) increases, although negligible differences were observed with the fixed bed height variation. [Display omitted] ►A new correlation for the determination of the Umf in a 2D fluidized bed is presented.►The correlation is a function of the bed thickness and the particle diameter, t/dp.►A set of experiments found in literature is not in accordance with the correlations.►The discrepancies are attributed to the electrostatic charge and particle shape.►The correlation does not fit with Jackson´s model due to the 1D of the model.