Estudo da geração de bolhas de diversos tamanhos em coluna de flotação

• Autor(a) principal: Reis, Angelica da Silva
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFU
• Texto Completo: https://repositorio.ufu.br/handle/123456789/15258; https://doi.org/10.14393/ufu.di.2015.39
• topic: Flotação em coluna; Diâmetro de bolhas; Técnicas de filmagem; Flotação; Column flotation; Bubble diameters; Filming techniques; CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA

Flotation is a complex process in which is present physicochemical and hydrodynamic phenomena. There are several industrial applications of flotation, and their use in separation and mineral concentration has emerged as the most important and successful unit operation. The flotation performance is related to the probability of bubble-particle collisions and stability of aggregate formed. The collision efficiency is a function of particle diameter and air bubbles. Therefore, a better understanding of the bubble-particle interaction is critical to improving the performance of the flotation process. Currently one of the biggest challenges of the mining industry is the flotation of fine and ultrafine particles because of their low probability of collision due to their intrinsic characteristics, such as their small mass. The scientific literature has shown that a possible solution to increase the recovery of these fine particles is the use of bubbles with intermediate size (200-600m). Therefore, determining and controlling the bubble size become important actions to produce bubbles in the range of desired diameters. Several techniques have been developed to determine the bubbles size, and among these techniques the image analysis has emerged as the most used and closer to the real results. Thereby, this task aimed to study the characterization and the control of bubble sizes in a flotation column, and check the system\'s ability to produce bubbles with intermediate size. The bubbles were generated in a flotation column by passing the recycle stream by a Venturi aerated. Thus, by statistical analysis, the influence of the flotation process variables in bubble diameter and the air holdup was evaluated for operation with air-water system with and without addition of surfactants, and also during the ore flotation process (three-phase system). To determine the size of the bubbles was used sampling and direct shoot bubbles techniques in the air-water system. The PVM and FBRM techniques were also used to determine the bubble size distribution (BSD) on air-water system and ore flotation, and the data obtained in real time. The results showed that the Venturi system produced satisfactorily intermediate bubbles. In the air-water system, without added surfactant, the air flow rate was the variable that most influenced the process, and the conditions tested resulted in the generation, preferred, large bubbles with low holdup values of air. Thus, the addition of surfactants showed up with a good alternative for the production of smaller bubbles, reaching in some conditions one BSD with 80-90% of intermediate bubbles and holdup in the 10-12% range. In ore flotation, the same effect was observed by the addition of surfactants in reducing the size of bubbles, and it was observed that the bubble size decreased when ore is added to the system. In the kinetic study of the flotation process it was observed that decreasing the apatite content is related to the depletion (reduced mineral particles) foaming phase and bubble size reduction, according to the data obtained in the online method using the PVM and FBRM techniques.