No description available.

No description available.

No description available.

No description available.

A bench-scale, two-dimensional multi-compartmentalized fluidized reactor was designed and studies of hydrodynamic behavior of fluidization of struvite pellets were performed. Also size growth distribution tests were analyzed qualitatively. The study validated a previously-proposed theory, concerning the relationship between dynamic pressure drop and upflow velocity as well the experimental protocol to determine the minimum fluidization velocity. Findings indicated that the mixture of two-sized particles would behave rather independently of each other, before the bed expansion. It was suggested that bed height measurement could be another promising method to pinpoint minimum fluidization velocity as there is a sharp bed surface "waking episode" during the process of a packed bed being gradually fluidized. Bed expansion equations for the prediction of void fraction as a function of superficial upflow velocity or vice versa, have been established for 4 groups of monosize particles, as well as two mixtures of two-sized particles. The equation constants did not agree well with previously established ones. The two layers of segregated mixture bed had congruent linear relationships between the logarithmic void fraction and logarithmic upflow velocity. It was found that a mixture does not always go through segregation, but only when the size difference is large enough. Size growth distribution tests were performed under different hydrodynamic configurations as well as seeding conditions. Conclusions can be made that a bed with uniformly- distributed particle void fractions and higher mixing energy input (upflow velocity), normally has better performance of struvite growth in size.

No description available.

No description available.

No description available.

A study of heat transfer to tubes in the freeboard region of a fluidized bed was conducted in a column of cross section 0.254 m x 0.432 m and height 3.00 m. The operating variables covered included superficial gas velocity (up to 1.7 m/s), average particle diameter (102, 470, and 890 (mu)m), height of the instrumented tube above the expanded bed surface (up to 0.6 m), horizontal tube spacing, position of tube within the tube bundle, and number of tubes. Silica sand particles were fluidized by air in all experimental runs. An instrumented oil-cooled tube of outer diameter 25.4 mm was used to collect heat transfer data. / Heat transfer coefficients to tubes in the freeboard were found to be significantly influenced by the superficial gas velocity, average particle diameter, and height of the tube above the expanded bed surface. The heat transfer coefficient increased with increasing superficial gas velocity and decreasing distance between the tube and the bed surface due to increased impingement of particles on the tube. The heat transfer coefficient for a tube in the freeboard was found to increase with decreasing particle size as for immersed tubes. The effects of horizontal tube spacing and single tube versus bundle were found to be small, less than 20%, over the range of experimental conditions investigated. / Values of heat transfer coefficients for a tube in the splash zone, in the immediate vicinity of the expanded bed, are nearly as favourable as for immersed tubes. The high rates of heat transfer are associated with impingement of particles on the heat transfer tube. / The experimental results are in qualitative agreement with the few data available in the literature. The present experimental data were correlated in a form suitable for design purposes. The correlation approaches limits at low and high heights above the expanded bed surface. At the bed surface, heat transfer coefficients correspond to in-bed values. Heat transfer coefficients for tubes far removed from the bed surface correspond to dilute phase suspension or to air alone in cross flow, depending on particle size. The correlation fits the data obtained in this work to within (+OR-) 12%. / Entrainment rates for the finest silica sand particles were measured with and without tubes in the freeboard. Under conditions of the present experimental work, entrainment rates were affected very little by the presence of tubes in the freeboard. The entrainment rates were compared with entrainment correlations available in the literature. There were substantial differences between data and almost all of the correlations. Fair agreement was obtained with the Zenz and Weil correlation for saturation carrying capacity. / Hydrodynamics of bed and particles motion around tubes were also investigated visually, photographically and by means of pressure profiles. The information obtained was helpful in explaining the heat transfer results.

No description available.