Contribuição ao estudo experimental e em CFD da fluidodinâmica de colunas de bolhas com aplicações na separação de misturas oleosas e processamento mineral por ar dissolvido

Abstract

Bubble columns are equipments used in many unit operations on food, textile and chemical industries. Flotation columns and phase invertors are examples of bubble columns used on separation processes. Due to the great interaction between continuum and disperse phases, they are equipments of simple operation, but present a very complex fluid dynamics. This thesis is about the fluid dynamics interaction between phases of a non regular cylindrical bubble column which may be operated by dissolved air or dispersed air. The work was conducted in two distinct fronts that are interrelated: a) experimental and CFD studies of the bubble column fluid dynamics b) study on the application of the column operated with micro bubbles in separation processes. The first front aimed to study the influence of its geometrical characteristics and the operational variables feed and recirculation flow on the fluid dynamics properties on the three regions of the bubble column. On this stage, equations that allow relating the operational variables with the properties analyzed were established. The other front aimed to study the column application operating with dissolved air on the separation process of oily mixtures ranging from 50000 ppm v/v to 600 ppm v/v, as well as on the fines apatite beneficiation. On oily separations the flocculant polymer polyvinyl alcohol 20 ppm was used as the chemical agent. The higher values of efficiency and oil recovery rate by phase inversion, obtained on concentration range of 50000 to 10000 ppm and emulsion volumes of 0.76 to 0.24 L were 95% and 0.02L of oil/min respectively, obtained on the higher concentration values and the higher emulsion volumes. On the emulsion separation with concentration of 600 ppm, the higher efficiencies were obtained for the equipment operating with the number and diffuser disposition 0/4, 0/5, 1/5, 4/2 e 5/1, obtaining on these cases, effluents which meet the Brazilian norms of disposition of oily effluents with hydraulic retention time (HRT) between 21 and 32 seconds. On the bubble column application on mineral processing, the higher contents may be obtained to the column operating with a recirculation flow of 0.75 L/min, solids concentration of 12%, pH of 11.5, inlet recirculation 1.05 m above the base, and with saturated air feed by the intermediate flange, when it is expected a content of about 36% and recovery of about 90%.