Development of a continuous process chain for mechanical separation of EnAM from solidified metal slags

• Applicant: Dr.-Ing. Marco Gleiß
• Subject Area: Mechanical Process Engineering
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 470336895

Within the priority program "Engineered Artificial Minerals (EnAM) - a Geo-metallurgical Tool to Recycle Critical Elements from Waste Streams" (SPP 2315), the applicant investigates a modular plant design for the mechanical processing of EnAM from solidified metal slags. For the mechanical processing of the EnAM crystals present in the solidified metal slag, a process chain consisting of various basic operations such as wet comminution, pre-classification, selective separation by means of flotation and filtration, washing, mechanical and thermal drying will be developed in order to obtain a powdery product for further processing. The mechanical processing focuses on gallium and indium oxide, which are increasingly used in very thin copper indium gallium selenide-based (CIGS) solar cells and LCD screens. The development of the process chain requires an extensive process understanding of the individual basic process operations and is essentially dominated by the dispersity properties (particle size, particle shape, wettability, composition), which influence the process behavior to a significant extent. As a result, a comprehensive characterization of the material properties on a laboratory scale is first necessary in order to derive property functions for the purification of gallium and indium oxide. Subsequently, the property functions serve as criteria for the apparatus design. By experimentally investigating kinetics and residence time behavior of the individual process steps, tuning of the individual apparatuses in the process chain is achieved. Monitoring the efficiency of the individual process units requires off-line and on-line measurement equipment (UV-Vis spectroscopy, ultrasonic measurement system, FT-IR spectroscopy, etc.) to characterize the composition and particle size distribution during processing. Another important aspect is the establishment of two-phase flotation for the mentioned material systems by selecting suitable carrier fluids and collector molecules, as well as the transfer from batch to continuous flotation of EnAM in the two-phase system. The optimization of the process control (co-current/counter-current or cross-current) of the novel flotation vessel including the necessary gassing unit is carried out depending on the flow conditions. The manufacturing of the flotation cell is based on a 3D printing process in order to be able to specifically investigate geometric variations. In addition, the project is focusing on a modular plant design that allows the rapid integration of new basic process engineering operations for the preparation of further EnAM material systems.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2315: Engineered Artificial Minerals (EnAM) – a geo-metallurgical tool to recycle critical elements from waste streams
• Co-Investigator: Professor Dr.-Ing. Hermann Nirschl