Munusamy, Sri Raj Rajeswari
(2011)
Numerical And Experimental Studies On Production Of Fine Silica In An Opposed Fluidized Bed Air Jet Mill.
PhD thesis, Universiti Sains Malaysia.
Abstract
This study is mainly focused on the production of fine silica in an opposed
fluidized bed air jet mill through numerical and experimental techniques. In this mill,
fine grinding occurs through collisions between solid particles in the continuous air
stream. The stages in numerical techniques include the three-dimensional (3-D)
modeling and simulations of the air jet mill using GAMBIT 2.3.16 and FLUENT 6.3
softwares. The major domain of the air jet mill and the nozzle parts consist of
144,237 elements of T-Grid mesh and 422 elements of Pave mesh respectively. The
Eulerian Granular Model (EGM) approach with k-epsilon turbulence model and
Syamlal-O’Brien drag function was adopted for modeling the air-solid flows in air
jet mill. Validations of the CFD model with experimental and numerical results were
made based on the mass output of silica from the jet mill. The mass difference within
11.50% to 19.97% indicates that the model is fairly suitable and satisfactory for
simulations of fine grinding process. Variations in the operating variables of air jet
mill influence the air-solid flow fields and the product characteristics. The air and
solid velocities, �� and �� vary from 357.88 m/s to 509.86 m/s and 41.45 m/s to
57.82 m/s respectively, while the solid volume fractions, � � at the air jet mill’s
pressure outlet are within 0.01 to 0.03.
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