Rise velocity verification of bubble-floc agglomerates using population balance in the DAF process

Abstract

The dimension of the separation zone in the dissolved air flotation (DAF) process is practically determined by the rise velocity of the bubble-floc agglomerates: flocs attached to several bubbles. To improve the flotation velocity and particle removal efficiency in the DAF process, many researchers have tried to attach as many bubbles as possible to flocs. In this study, the rise velocity of bubble-floc agglomerates, considered to be the most important factor in designing the separation zone of the flotation tank in the DAF process, was investigated on the basis of comparison between theoretical and observed results. The observed rise velocity measured by a particle image analyser (PIA) and the predicted value, however, did not show similarity, in contrast to what we had expected. Furthermore, the simulated results using population balance to predict the maximum number of attached bubbles on a floc were too impractical to accept under the practical condition of the surface of the floc if there was no change of bubble size. These findings led us to suggest that there were three possible causes which could conceivably explain the observations. It was suggested that the differences between predicted and observed values could be attributed to one or more of the possible causes.

Influência do tamanho de flocos e da concentração de ar dissolvido na eficiência da flotação

“…Com relação às técnicas atualmente empregadas na captura e análise de imagens de flocos e microbolhas de ar formados durante o processo de flotação, tem se verificado que ao longo dos últimos anos ocorreu um aumento significativo no número de pesquisas desenvolvidas, dada a importância que essas partículas exercem sobre a cinética do processo de flotação (BACHE & RASOOL, 2001;RODRIGUES & RUBIO, 2003;MORUZZI, 2005;LEE et al, 2007;HAN et al, 2007;KWAK et al, 2009;SOHN et al, 2009;OLIVEIRA et al, 2010).…”

Comparative evaluation of particle separation efficiency based on carbon dioxide and air bubble sizes in flotation separation processes

“…To obtain its value, it is tested according to the collision-attachment tendency of the particle on the bubble. A typical value for an inorganic particle such a sa kaolin in the DAF process is 0.3-0.4 [19].…”

Feasibility of carbon dioxide bubbles as a collector in flotation process for water treatment

“…Many previous studies (Edzwald 1995;Fultushi et al 1995;Han 2002;Kwak et al 2009) have reported that the most important parameters in the DAF system are the surface characteristics (zeta potential) and the size distribution of both bubble and particle. Particle size as an important parameter in flotation has been the focus of flotation research for decades (Shahbazi et al 2010).…”