Over the past few decades, the need to process more minerals while lowering capital costs has led to an increase in the size of flotation cells, e.g., 0.03 m3 to 1000 m3. However, this increase has created new challenges in the operation and design of industrial flotation cells, particularly in terms of froth removal, because the distance the froth must travel increases with an increase in the flotation cell diameter. This has a negative impact on recovery. Physical froth flow modifiers can be used to improve froth removal. Their major functions are to modify and optimise the flow of the froth, improve froth drainage, reduce dead zones, and improve froth flow and removal dynamics. Therefore, physical froth flow modifiers are discussed, evaluated, and compared in this paper. The literature indicates that physical froth flow modifiers such as crowders and launders are used extensively as industrial solutions to enhance froth transport and recovery in large flotation cells. Other modifiers (including froth baffles and froth scrapers) have been found to have a profound effect on local froth phase sub-processes, including drainage and bubble coalescence. However, industrial uptake is either dwindling or limited to small-volume rectangular/U-shaped cells in the case of scrapers, or, there is no uptake at all in the case of froth baffles. Further research on how some of the physical modifiers (e.g., baffles and launders) impact the selectivity of particles is required.

In the attempt to process lower-grade ores, mineral flotation has taken centre stage as the preferred recovery route. However, in many instances, the froth product does not have a high grade due to the entrainment of gangue minerals. Industry has solved this challenge by introducing froth washing mechanisms. Clean wash water is introduced into or on top of the froth to reduce the amount of entrained gangue in the final concentrate. This article reviews froth-washing systems in detail and highlights the advantages and disadvantages of each wash-water delivery mechanism. Comments on industrial uptake are provided. The indications are that froth washing improves the grade of the concentrate and influences froth stability and mobility. Other researchers have reported an improvement in recovery—especially of coarse particles—with wash water being added, while others have reported a reduction in recovery, especially with composite particles. Froth washing is generally applied in mechanical flotation cells by washing at the lip. In column flotation cells and Jameson cells, wash water is added to the entire froth surface. The literature also indicates that the wash-water rate, wash-water quality, type of wash-water delivery/ distribution mechanism and the area covered by wash water are critical parameters that dictate the efficacy of the washing system. Further research is necessary on the impact of wash-water quality on the froth phase sub-processes including froth rheology.