Developing dry separation methods to replace the commonly used water-based separation has become crucial due to increasing water shortages. One of the candidates for dry processing is gas–solid fluidized beds. The bed behavior and solid motion in fluidized beds have been investigated using various visual and numerical methods for decades. However, there are not enough studies focused on the separation behavior of the fine particles. This work details the investigation of particle motion through a fluidized bed using the positron emission particle tracking (PEPT) technique. Single-particle tracking is a powerful mechanism providing knowledge about separation mechanisms through direct visualization of the particle trajectory determined from recording the particle position over time. In this study, the movements of different-sized beds were characterized by tracking an activated single quartz particle and then by tracking an activated single hematite particle. The separation behavior of a heavy particle was determined for different-sized fractions.

The metallurgical performance of a flotation machine is largely defined by phenomena occurring in the froth zone. The water content in the froth affects recovery by influencing froth stability and mobility and, at the same time, reduces grade by mechanical entrainment of gangue particles in the overflow water. Efficient operation requires a compromise between the water carried by bubbles from the collection zone and that which overflows. It is believed that the most suitable operating strategy could be based on the measurement of froth water content, as a strong correlation with water overflow is anticipated. This work reports the testing results of an in situ electrical conductivity sensor continuously measuring the froth zone water content in a laboratory-scale flotation column. The test program included simultaneous measurement of froth conductivity and water overflow rates for changes in gas flow rate and frother concentration. The results show a stronger dependence of the measured top-of-froth water content on frother concentration than on the gas flow rate. A relatively linear trend was shown between top-of-froth water content and water overflow rate for a given air rate and frother.

Saline water froth flotation has received increasing attention in recent years due to sustainability-related concerns. Although the presence of electrolytes in these flotation systems is known to produce the desired bubble swarms, i.e., a macroscopic observation, the fundamental mechanism through which the solutes produce such an effect at the microscopic level remains obscure. For example, there is no agreed mechanism (i.e., break-up or coalescence—two major bubble formation mechanisms) of how the effect is achieved. Not only is understanding the impact of electrolytes on the bubble formation mechanisms a fundamental question, but it can also provide insight into the design of more efficient air dispersing mechanisms for saline flotation systems. Previous studies have demonstrated that electrolytes can inhibit coalescence, but their potential impact on break-up remains vague, which is the focus of this study. It is hypothesized that electrolytes have an impact on break-up, and by isolating break-up from coalescence, the effects of electrolytes on break-up can be revealed. A break-up-only bubble formation system was built. Under this condition, any impact from the electrolytes on the produced bubble can be attributed to an impact on break-up. High-speed cinematography and a passive acoustic technique were employed to capture the bubble size, acoustic frequency, and damping ratio during the break-up process. Under the quasi-static condition, an increase in the electrolyte concentration increased the bubble size produced via break-up, contradicting the common observations made for bubble swarms. The break-up imparted an initial capillary wave to the bubble surface, which is correlated with the bending modulus of the air/water interface affected by the electrolytes. No direct correlation was observed between the acoustic damping ratio and that of the capillary wave, suggesting that the electrolytes affect the break-up via a different mechanism from that by surfactants.