A foam bath for ores - part 3

Simulation for greater accuracy

One approach is known as computational fluid dynamics. Team member Gregory Lecrivain is working on the development of a computer model to simulate particle attachment on gas bubble surfaces. Together with colleagues at Kyoto University in Japan he has already developed a three-phase model within the frame of the research project “CAPTURE”. He has managed to simulate the attachment of hydrophobic particles to a rising gas bubble. “My aim is to continue developing the code so that we can recreate froth processing,” the fluid mechanics specialist explains. “Due to the three phases and the high level of complexity it is very difficult, especially as numerical modeling is still in its infancy.”

Flotation - Nahaufnahme ©Copyright: HZDR/ Detlev Müller

Flotation is the most common industrial method for processing raw materials. Photo: HZDR/ Detlev Müller Download

Attachment can only occur when air bubbles and hydrophobic mineral grains make contact. The bubbles often miss the very fine particles. Experiments in a bubble column are designed to elicit new insights into how collision frequency can be increased. By equipping model particles with fluorescent labels and using several high-speed cameras, the researchers can reconstruct particle positions and paths and measure collision and attachment with optical methods.

The results they achieve on microprocesses are entered into complex process models which simulate various parameters and should facilitate better predictions. In the future, they could replace the much more expensive pilot plants. “Unfortunately, you can’t describe flotation in a single formula,” says Martin Rudolph. “And in many areas, there are still a lot of question marks.” His department consequently works in other fields, as well. A new project titled “MultiDimFlot” aims to develop a technology for separating ultrafine particles based on a number of characteristics like size, shape, roughness and surface wettability.

In the meantime, Kerstin Eckert’s research group is working on further froth flotation applications. She is examining whether the method is suitable for separating microplastics and textile particles. Because microplastic particles are usually coarse and have external air pockets, the question is how this will affect the flotation process.

In her role of coordinator for the NetFlot Network, Eckert also seeks to connect flotation expertise at European level and to expand their international presence. Both project leaders are agreed: “So far, countries like Australia and Canada are heading the field in this area, but at conferences we have observed that much more attention is now being paid to our research.”

Author: Inge Gerdes


M. Rudolph, U.A. Peuker: Mapping hydrophobicity combining Afm and Raman spectroscopy, Minerals Engineering, 2014 (DOI: 10.1016/j.mineng.2014.05.010)

T. Leistner, M. Embrechts, T. Leißner, S. Chehreh Chelgani, I. Osbahr, R. Möckel, U.A. Peuker, M. Rudolph: A study of the reprocessing of fine and ultrafine cassiterite from gravity tailing residues by using various flotation techniques, Minerals Engineering, 2016 (DOI: 10.1016/j.mineng.2016.06.020)

Z. Lei, B. Fritzsche, K. Eckert: Evaporation-assisted magnetic separation of rare earth ions in aqueous solutions, The Journal of Physical Chemistry C, 2017 (DOI: 10.1021/acs.jpcc.7b07344)

G. Lecrivain, R. Yamamoto, U. Hampel, T. Taniguchi: Direct numerical simulation of an arbitrarily shaped particle at a fluidic interface, Physical Review E, 2017 (DOI: 10.1103/PhysRevE.95.063107)


Dr. Martin Rudolph

Prof. Kerstin Eckert

Dr. Gregory Lecrivain