Numerical And Experimental Studies On Production Of Fine Silica In An Opposed Fluidized Bed Air Jet Mill
| dc.contributor.author | Munusamy, Sri Raj Rajeswari | |
| dc.date.accessioned | 2020-02-24T04:01:08Z | |
| dc.date.available | 2020-02-24T04:01:08Z | |
| dc.date.issued | 2011-11 | |
| dc.description.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. Observations showed high solid volume fractions at the center and regions away from the nozzles. At low solid feed rate and grinding pressure, the products undergo size reduction with volume moment diameter, (4.3) up to 8.66 μm due toThis 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. Observations showed high solid volume fractions at the center and regions away from the nozzles. At low solid feed rate and grinding pressure, the products undergo size reduction with volume moment diameter, (4.3) up to 8.66 μm due to effective particle collisions at lower solid volume fractions, and phase velocities, and . The products of high solid feed rate have lowest specific surface area of 3.066 m2/g due to ineffective penetration of air jets and collisional activities between the particles in the air stream at higher particulate loading. Increase in the amount of mesopores (2-50 nm) and micropores (< 2 nm) showed that the products have wider surface pore size distributions compared to feed silica. At high grinding pressure, coarser size crystallites are produced due to higher turbulence, phase velocities and drag force pulling the particles sooner from the grinding chamber. Overall, the crystallite size and lattice strains of products ranged between 190 nm to 453.5 nm and 0.116 to 0.187 while the degree of crystallinity varies from 99.37% to 76.57% compared to 100% in feed silica. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/9553 | |
| dc.language.iso | en | en_US |
| dc.subject | Air jets | en_US |
| dc.title | Numerical And Experimental Studies On Production Of Fine Silica In An Opposed Fluidized Bed Air Jet Mill | en_US |
| dc.type | Thesis | en_US |
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