Previous studies in Magnetically Stabilized Fluidized Bed (MSFB) are well known for conventional two-phase, gas-solid or liquid-solid fluidization. Many researchers have investigated the fluid dynamic behavior of the MSFB, however, all of these studies are based on a uniform magnetic field that is constant throughout the bed column. Currently, there are no references in the open literature indicating either fundamental or applied research with a magnetically fluidized bed where a non-uniform magnetic field is used in a two-phase liquid-solid fluidization. In this study, the fluid dynamic behavior of a Magnetically Assisted Fluidized Bed (MAFB) in a non-uniform magnetic field is experimentally observed. In the MAFB, a magnetic force, F[sub m] , is created which acts on the ferromagnetic particles (20% ferrite) by varying the magnetic field intensity from the top to the bottom of the fluidization column. However, the field gradient is kept constant throughout the bed. Because of the differences in the magnetic field intensity at any location in the bed, the particle holdup, or inversely the bed voidage, has to change to accommodate the equilibrium of forces acting on the particles (drag force, gravitational force, buoyancy force, and magnetic force). In the laboratory experiments, performed magnetic field gradient, [see PDf for equation] Alm/m, -18,289 Alm/m, -20,543 Alm/m and -33,798 A/m/m) and fluid flow rate (U[sub 0] =0.0153 m/s, 0.0176 m/s, 0.0199 m/s and 0.0222 m/s) are varied. These experiments show that the increase in the magnetic field gradient and the magnetic field intensity results in the decrease in the height of the bed, and therefore, in the decrease of the bed voidage. The dynamic pressure drop, [delta]P[sub f][sub(d)], is also experimentally measured, then converted to a corresponding voidage. The relationship between the dynamic pressure drop and the bed voidage is given by the following equation:[see PDF for equation] The fluid dynamic behavior of the MAFB is described by the equation of motion and the equation of continuity for both liquid and solid phases. A mathematical model is developed and used to evaluate the voidage distribution in the MAFB. The resulting expression for the voidage distribution in the MAFB is given as [see PDF for equation]. Experimentally obtained bed voidage data in both, laboratory experiments (1g) and on board of the NASA KC-135 plane (0g) fit very well the above equation which does not have any adjustable parameter. / Graduation date: 2001

2 ��m average sized silicon powder was nitrided with 90% N���/10% H��� in a fluidized-bed reactor, operated at 1200��C, 1250��C and 1300��C. To fluidize silicon powder, alumina particles with an average size of 300 ��m were used as an inert fluidizing conditioner. The feasibility and operating conditions of the fluidization were studied at room temperature. The effects of silicon content and operating temperature on the nitridation of silicon as well as on the formation of ��- and ��-silicon nitride were investigated in batch and semi-continuous operations. The effects of the average residence time of silicon/alumina mixtures in the fluidized-bed reactor on the nitridation process were studied in semi-continuous operations. In batch operations, a maximum mass fraction of 15 wt% silicon powder could be added to alumina particles at temperatures in the range of 1200 to 1300��C without changing the fluidization quality. When the silicon fraction was increased to 20 wt%, fluidization failed immediately. With a mass fraction of 5% silicon powder, almost 100% ��-silicon nitride, which was preferred in applications, was found in the product. ��-silicon nitride was facilitated with an increase in silicon fractions in silicon/alumina mixtures. The nitridation process was strongly affected by the reaction temperature. The overall conversion of silicon increased with an increase in reaction temperature. Higher temperature also promoted the formation of ��-silicon nitride. The overall conversion of silicon into silicon nitride was also enhanced by hydrogen concentrations. An increase in hydrogen concentration facilitated the formation of ��-form silicon nitride. In the semi-continuous operation, the nitridation of 30 wt% silicon/70 wt% alumina mixtures could be achieved without changing the fluidizing quality. Almost 100% ��-silicon nitride was found in the product when a 20 wt% silicon/80 wt% alumina mixture was nitrided at 1250��C for an average residence time of up to 4 hours. However, ��-silicon nitride was formed when the mixture was nitrided at 1300��C for an average residence time of 3 hours. A mathematical model incorporating kinetic data and carryover of silicon powder was developed to described the total conversion of silicon in batch operation. A semi-continuous model was also proposed, which successfully predicted the overall conversion of silicon powder. / Graduation date: 1997

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xiii, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 70-72).

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.

Graduation date: 1992

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xvi, 119 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 103-106).

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xi, 137 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 136-137).

Thesis--M. Phil., University of Hong Kong, 1974.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy