70 years of non-university processing and recycling in Freiberg/Saxony
Finally, Dr. Morgenroth announced that he would be stepping down as managing director on December 31, 2024, and that Dipl.-Ing. Steffen Schmidt would be taking over this position on January 1, 2025 (see article AT 01/02, 2025, pp 4).
Under the theme of “Mineral raw materials and recyclable materials from waste,” the conference focused on
Processing of secondary raw materials/recycling
Machines, equipment, and sensors
Nineteen technical presentations showcased the latest research and operational results on the above-mentioned key topics, although it was not always possible to assign them to a specific category.
Starting with a presentation of the Freiberg-based recycling company Feinhütte Halsbrücke AG and its own engineering office POWPRO GmbH, Dresden, Dr.-Ing. Stefan Jäckel reported on the “Processing of secondary finely dispersed metallurgical intermediate products” and presented the approach used, from the feasibility study to the plant concept and commissioning. The Halsbrücke site produces high-quality metals and metal alloys in a wide range of compositions, variants, formats, and degrees of purity. The task was to achieve more energy-efficient process control and CO2 savings compared to the previous technology. To optimize the furnace process, the various input materials are now mixed and agglomerated directly with the reducing agent coke or hard coal in a new mixing and agglomeration process with the addition of slag formers. The presentation provided an insight into the applied process engineering and the project schedule for one of the largest environmental protection and modernization projects at the Halsbrücke fine rolling mill, right up to the commissioning of the processing plant in 2024.
Another process engineering topic was addressed by Dr. mont.Karl Friedrich, Montan University Leoben/Austria, with his presentation on “Evaluation of comminution processes for refractory breakout material based on the degree of disintegration of particles < 4 mm.” Jaw crushers, impact mills, cone crushers, and electrodynamic fragmentation (EDF) were investigated. This is a sub-task in the EU Horizon project “Refractory Sorting Using Revolutionizing Classification Equipment", which aims to ensure the green and digital transformation of the refractory recycling value chain. The aim is to validate the most suitable crushing technology for refractory bricks in terms of degree of comminution. MgO-C (origin: steel ladle) and fired magnesia-hercynite bricks (origin: rotary kiln waste) were used as refractory materials.
The best results in terms of element enrichment (Mg and C for MgO-C, Fe and Al for magnesia hercynite) were achieved with the baking and cone crushers. The EDF did not show any significant enrichment results for MgO-C, and with this technology, almost no crushing was possible for magnesia hercynite.
Dr. Özüm Yasar, UVR-FIA GmbH, Freiberg, gave a presentation on “Sorting strategic elements from Indonesian Fe-Pb-Zn-(Cu-Ag) skarns in the ‘StratOre’ project”. After preliminary laboratory-scale tests to optimize the test parameters, pilot tests were carried out on samples from the aforementioned skarn ores (galena, arsenopyrite, magnetite, hematite, sphalerite, chalcopyrite, and calcite). Herd sorting and flotation resulted in significant enrichment of Pb, Cu, and Zn.
Construction waste recycling
The recycling of old building materials and demolition waste continues to be of great importance due to the large quantities involved, because despite high recycling rates, there is still enormous room for improvement in terms of recovery. This topic was represented by four presentations at the conference. Dr. Pierre Landgraf, TU BAF, presented the results of a group of authors on “Concrete recycling: Mechanical and electrodynamic crushing (EDF) of old concrete”. The aim of the project is to move away from so-called downcycling (use of old concrete in road substructures, for example) and toward upcycling. This requires the efficient separation of the individual concrete components (gravel, sand, cement stone) so that they can be reused as secondary raw materials in the production process. As part of this so-called Up-Zement project, the waste material was treated using EDF, which weakens it along the grain and phase boundaries and breaks it down into its various components. Mechanical comminution in roller mills is then planned, with 20 tons of concrete bridge demolition waste from Aachen available as test material.
Another upcycling project was presented by Dr. Anett Lipowsky, IAB – Institut für Angewandte Bauforschung gGmbH, Weimar. In her presentation “Sorting and activation of fine-grained construction waste”, the focus was on the extraction of fine-grained brick powder from a mixture of brick, mortar, and concrete as a substitute for cement. However, previously unused rock fillers such as rhyolite, greywacke, and basalt from quarry spoil heaps were also investigated as possible cement substitutes in their original state or after further processing or treatment. The brick particles were separated from the masonry rubble using RER magnetic separators (Rare Earth Roll Separators with Nd-Fe-B magnets). By using various comminution units (ball and planetary ball mills, also with the addition of grinding aids and shock wave comminution), corresponding activation effects were achieved, so that brick flour in particular could be used as a cement substitute.
Two presentations on the application of the Substitute Building Materials Ordinance rounded off the lecture series, explicitly addressing the hurdles of this ordinance that have already been discussed at length in other events, particularly with regard to its implementation (quality control, proof of suitability, analytical effort).
Resource efficiency
The sustainable use of raw materials while minimizing their impact on the environment, in other words resource efficiency, is not just a buzzword that is widely used today, but an absolute necessity in terms of the sustainable use of our planet’s limited resources, which was also emphasized in four presentations at this conference.
With a view to the energy transition, Vadim Greshnow, ERCOSPLAN Ingenieurbüro Anlagentechnik GmbH, Erfurt, reported on the “Potential and significance of NaCl recycling from residues of the potash industry”.
From the large portfolio of HAVER & BOECKER GmbH, Freiberg, for the recycling of slag, dust, and sludge, Dr.-Ing. Jan Lampke presented several practical examples that address the framework conditions that must be taken into account in process development and project planning as well as in the construction, commissioning, and operation of crushing and classification plants for slag from non-ferrous metallurgy (Examples: Europe’s largest screening machine in a recycling plant, crushing and classification plants for the selective comminution and separation of brittle slag with ductile copper components). The speaker emphasized that the concepts of recycling, the circular economy, the waste-to-value approach, and the Green Deal are not new, complex processes, but have always been an integral part of the work of processors and thus serve the goal of resource efficiency.
News from mechanical and plant engineering
Not only machine improvements and new developments in machinery and plant engineering, but also the use of artificial intelligence (AI) enriched the presentation program in this block.
For example, Johannes Müller, Köppern Aufbereitungs GmbH & Co. KG, Freiberg, gave a presentation on “AI for investigating crushing plants in the cement industry”. This topic was also covered in a presentation from the next section, in which M.Sc. Adrian Valenas, TU BAF, Freiberg, presented “Investigations into sensor-based sorting of brass-contaminated aluminum concentrates using AI-supported image recognition”, which is of great interest to the automotive industry in particular. The Yolo model for image recognition was used to validate the sorted products. It was “trained” with approximately 1000 images and optimized in this way. High recognition and sorting accuracy was achieved under controlled conditions.
“New developments in a spiked roller profile for the Jehmlich roller crusher” were the subject of a presentation by Raphael Sperberg, Gebrüder Jehmlich GmbH, Nossen. This machine is particularly suitable for clumping materials such as kaolin. The presentation focused on its use in the comminution of brittle plates.
Luca Nivelstein, NEUMANN ESSER Process Technologie GmbH, Übach-Palenberg, dealt with cryogenic grinding and presented the corresponding NEA Cryo X machine, which can achieve a high increase in efficiency in the comminution of soft, flexible, and moist materials. The speaker provided technical details from the development process and operational experience with this plant component, which can also be used in conventional cryogenic grinding plants to increase efficiency.
Innovations in the recycling sector
The projects that were the focus of the presentations in this section of the conference demonstrated the wide range of possibilities for processing waste materials in a sustainable manner. It is not always bulk waste that can be recycled to achieve high economic results. In the interests of a comprehensive circular economy, however, niche recycling products should not be underestimated.
First, M.Eng. Markus Kammer, Hanover University of Applied Sciences and Arts, IfBB Institute for Bioplastics and Biocomposites, presented the institute’s areas of expertise and then turned to the actual topic of his presentation, “Multifunctional additive from eggshells for the plastics industry” (ADD Egg project). After all, around 720 kt/a are produced in Europe, which have been insufficiently utilized to date and must be disposed of at a cost. With a CaCO3 content of 93 %, eggshells are ideal for use as a filler, nucleating agent or to increase aging resistance in the plastics industry. Based on these considerations, small-scale tests were carried out with 25 – 40 % eggshells in PP and PA, with positive results. The work is to be continued on a larger scale in a new project (Tec4Egg) with additional partners.
Robert Clausnitzer, AKW Apparate + Verfahren GmbH, Hirschau, reported on another very special topic, “Recycling of plastic turf”, in his presentation “Sustainable sports field recycling: Innovative solutions for a green future”. Until now, this waste has also been thermally recycled or temporarily stored in landfills at best. After all, there are 6000 artificial turf pitches and 45 000 corresponding sports fields in Germany (Europe: 30 000 and 70 000, respectively), of which only 10 – 20 % are currently recycled. With sustainability in mind, a unique concept has been developed and tested on a pilot scale, which allows sports field residues such as sand, rubber granulate, and fibers to be shredded and crushed before being processed in an environmentally friendly and economically viable manner. The semi-mobile plant based on these results, designed with a feed capacity of > 10 t/h and in operation for two years with a throughput of 13.5 t/h, was presented.
In the last presentation, Ms. Dip.-Ing. Alexandra Kaas, TU BAF Freiberg, presented an overview of the work on the mechanical processing of Li-ion batteries at the Institute for Mechanical Process Engineering/Processing Technology. For several years, this institute has been successfully addressing the difficult problem of economically recovering valuable metals and products, primarily Al, Cu, black mass, anode material, and cathode foil. In addition to the proper discharge of the batteries, their mechanical comminution and subsequent sorting into individual components play a key role. The focus of the work is on achieving high black mass quality depending on the pretreatment, such as the state of charge or thermal pretreatment, as well as on different battery types in the process.
Summary
The “Processing and Recycling” conference once again demonstrated the versatility and importance of processing and process engineering for the recovery of recycled products and thus for sustainability and resource conservation. Innovative solutions that lead to positive results are constantly emerging. This Freiberg conference stands out in particular because it presents application-oriented research work, some of which has already been tested in industry.
It was great that the authors, mostly young scientists, of the ten posters on display got to give short talks about their work. The evening event on the first day of the conference and the breaks between talks gave everyone plenty of chances to chat and get to know each other. The organization was awesome, and Dr. Morgenroth made sure to thank the organizers for that in his closing remarks. At the same time, he announced the date for the next conference, which is planned for November 6 and 7, 2025.
