Transferência de oxigênio e parâmetros hidrodinâmicos de um reator de leito fluidizado trifásico

Abstract

In this work a laboratory scale three-phase fluidized bed equipment was built. The hidrodynamic and mass transfer of concurrent gas-liquid upwards flow, has been characterized. The fluid phase were air and tap water, and solids where made of PVC, either cylíndrical, cubic and irregular shaped particles, with density varying between 1.3 e 1.4 g/cm3. The study of hidrodynamic included bed expansion, the individual phase holdup, the pressure drop and minimum fluidization velocity under gas flow rate varying from 0 to 38.5 cm3/s and liquid velocity up to 7 cm/s. Mass transfer studies in fluidized bed was center in volume mass transfer coefficient. The gas holdup was measured according to EFREMOV E VAKRUSHEV (1970) method is and the volume mass transfer coefficient was measured by a method envolving a slow chemical reaction under transient condition. Experimental data has shown that bed exansion was different for the three types of particles used. The gas holdup increases with gas flowrate and diminishes with greater liquid flowrate, while the different shaped particles used had neglible effect. The pressure drop is greater for cylindrical particles, smaller for irregular particles and cubics particles behave intermediately. Minimum fluidization velocity was not significantly affected by bed height, it decreases with higher gas flow rate, was similar for cylindrical and cubic shaped particles and greater for irregular shaped particles. The volume mass transfer coefficient (KLA) is highly depended of gas-liquid distributer design. In spite of this, within the range of conditions used, KLA increases with both gas liquid flowrates. For the same flow condition the three-phase fluidized bed has a higher mass transfer than the equivalent bubble column, showing that the effect of the particles is to break the bubble and increse the volume mass transfer coefficient.