Student practical training / Bachelor theses / Master theses / Diploma theses / Compulsory internship

The global energy transition requires increasing quantities of raw materials. Critical metals, including copper, lithium, cobalt, nickel, zirconium and platinum, are used, for example, in photovoltaic and wind power plants to exploit renewable energies, in batteries for electromobility, in electrolysers and fuel cells as hydrogen technologies. Rare earth elements, such as neodymium and samarium, are irreplaceable for permanent magnets in electrical generators and motors. The extraction of raw materials from metal ores poses a great challenge to the mineral industry. An important process step in the effective processing of ore minerals, and equally in material recycling in terms of the circular economy, is froth flotation.
In this process, finely ground solid particles are suspended in an aqueous liquid, and gas bubbles are added. Particles with hydrophobic surfaces adhere to the rising bubbles, which then form a particle-laden froth layer on top of the liquid. The particles can be recovered by skimming off the froth. Surfactants and other flotation reagents enable the desired particles to adhere, favour the sinking of the unwanted particles, or serve to stabilise the froth. The deformation and flow behaviour of the froth influences the transport and selective separation of desired and undesired particles due to their surface wettability. However, foam and froth flows are not well understood because typically only the free surface is accessible for optical measurements. Suitable techniques for flow measurement within the foam or froth volume, i.e. below the non-transparent surface, are still lacking and only under development.
This student work aims to experimentally investigate of the overflowing foam in a laboratory-scale froth flotation cell, focussing on the foam height in combination with the foam bubble size and the flow velocity at the free surface. For this purpose, optical measurement techniques will be used, as they are already partly in use for monitoring the froth phase in industrial flotation cells. On the one hand, the results will serve for a better understanding of the overflowing foam, and on the other hand, they represent an important preliminary work for the further development and adaptation of optical measurement techniques for flotation cells.
The following subtasks are mainly to be worked on:

• setup and test of a measurement system consisting of a Raspberry Pi, a Lidar sensor for the point measurement of the foam height, and a camera for the optical detection of the foam bubble size and flow velocity at the free surface
• measurement of the overflowing foam in a laboratory-scale flotation cell, depending of the surfactant concentration and the gas volume flow generating the foam
• analysis of the measurement data, including machine learning if applicable

• Field of study: Chemical Engineering, Process Engineering, Fluid Mechanics, or similar focus in Chemistry or Physics
• Experience with laboratory work, optical measurement techniques or measurement data analysis is beneficial
• High motivation and interest in the subject
• Careful, structured and independent way of working
• Good oral and written communication skills in English or German
• Enjoyment of scientific work

• Working in a multi-disciplinary and international team
• Place of work: HZDR or TU Dresden
• Start: from June/July 2023
• Duration: min. 3 months
• Remuneration according to HZDR internal regulations