Collection of SiO 2, Al 2O 3 and Fe 2O 3 particles using a gas-solid fluidized bed filter

Abstract

The filtration of SiO 2, Al 2O 3 and Fe 2O 3 particles with average sizes of 4 and 40 μm using a fluidized bed filter at 40 and 300 °C was studied. The collection mechanisms, interparticle forces and bounce-off effect between filtered particles and collectors were analyzed to determine their effect on particle filtration. Experimental results showed that the collection efficiency of 4 μm SiO 2 and Al 2O 3 particles exceeded that of 40 μm particles. Contrarily, the 40 μm Fe 2O 3 particles were collected more efficiently than the 4 μm particles, because of the differences between the microstructures of SiO 2, Al 2O 3, and Fe 2O 3 particles. The interaction between the particles affected the removal of mixed SiO 2, Al 2O 3 and Fe 2O 3. The particle size distribution (PSD) of the particles in the exit was governed by the operating temperature, the original size of the filtered particles, the interparticle force and the hardness of the particles and the collectors. The smallest particles were not those most easily elutriated from the fluidized bed filter because they agglomerated with each other or with large particles. The van der Waal's force dominated the forces between 4 and 40 μm particles. The main collection mechanism for 4 and 40 μm particles was direct interception. The effect of impaction increased with particle size above 40 μm. The strong impaction and bounce-off effect reduced the collection efficiency of 40 μm SiO 2 and Al 2O 3 particles. However, the strong interparticle force between Fe 2O 3 particles and collectors contributed to the high collection efficiency of the Fe 2O 3 particles.