Mineral Processing and Recycling – 14 and 15 November 2018 in Freiberg, Part 2

Processing secondary raw materials/recycling

In the paper “Recycling CF-containing lightweight composites – recycling at any price?“ by Dorothea Hamann M.Sc. and Dr Hans-Georg Jäckel (Freiberg University of Mining and Technology – IMB/RM), the speakers discussed mechanical processing (recycling) of fine and ultrafine structured material composites and the ever-increasing problems associated with this. Starting from the principle limits of recycling, in the paper especially the current problems in recycling resulting from the use of modern functional material composites, e.g. CFK, CF concrete, were addressed. While CF recovery from the largely unmixed CF/CFK production waste and its recycling in favourable conditions can be described as expedient where appropriate, CF removal from only low-CF-containing materials (end-of-life waste) is only acceptable with regard to pollutant removal and therefore constitutes the actual “recycling problem” in future. For this, a novel material recycling approach was presented, which is to be tested in cooperation with the company SiC-Processing Deutschland GmbH Bautzen in the scope of an DBU (German Federal Environmental Foundation) project.

Dr Sören Lottner (BiFa Bindemittel Filterasche GmbH Schkopau) reported on “Processed lignite filter ash for construction material applications – using mineral waste in practice”. The recycling of industrial waste and its use as alternative construction materials is a very promising approach to conserve natural resources, lower primary energy consumption and CO₂ emissions, and ultimately reduce the CO₂ footprint of construction products and systems produced with it. A construction material produced from specially processed high-lime lignite filter ashes was presented that is – up to now unique in Germany – produced on industrial scale and used in the construction industry.

In his paper, Prof. Dr. Samuel Schabel (TU Darmstadt – Department of Paper Technology and Mechanical Process Engineering) posed the question “Is economic recycling of mineral filler materials from wastepaper possible?“. Paper has the reputation of being very easy to recycle and of being recycled to a large extent. An important trend in recent years is the increased use in packaging paper. In this connection, a considerable increase in the use of filler material to 17 – 20 % in packaging paper can be observed. With around 17 mill. t wastepaper produced in Germany per year, there is currently no reasonable use for around 3 mill. t recycled filler material. Intention of the paper was to outline the problem and the so far only moderately successful approaches, and to encourage the experts in mineral processing and mechanical process engineering to come up with new ideas and concepts to enable an economic utilization of this material.

“Processing track ballast – technical-economic comparison of wet and dry methods” was the title of the paper by Dr Metodi Zlatev and Dr Hagen Müller (HAVER Engineering Freiberg). As a result of, for example, wear and overstrain as a result of the train traffic load, subsidence and softening of the subsoil, the fine content in the track ballast bed increases, which is only tolerable in certain circumstances. For this reason, it is necessary to inspect the track bed regularly and to process the track ballast when required to reduce the fines content. In the paper, dry and wet mechanical processes are presented and evaluated. The application of the respective method depends primarily on the contamination, especially with oil or pesticides.

Processing primary resources

“Characteristic process data of tailings separation with sensor-assisted sorting” were discussed by Dr Christopher Robben (TOMRA Sorting Solutions I mining). Sensor-assisted sorting of ores is attracting increasing attention in various applications and is developing into a standard process. In the paper, the typical behaviour of sensor-assisted sorting plants based on the processing of tungsten, tin and gold ores was described, in order to encourage discussion of what consequences result for the operation and planning of processing plants.

“On the processing and mineralogy of REE ores with parisite” reported R. Gerhard Merker¹, Dr Robert Möckel², Thomas Heinig², Prof. Phan Quang V.³, Dr Henning Morgenroth⁴ (¹Merker Mineral Processing, Elpenrod; ²HIF, Freiberg; ³HUMG, Hanoi; ⁴UVR-FIA GmbH, Freiberg). The relatively small (in terms of volumes), but in some cases very dynamically growing REE market (above all for Nd and Pr) is encouraging the development of new deposits. The relationship between mineralogy and processing was described with reference to tests conducted at the Helmholtz-Institute Freiberg for a new REE project in Vietnam. This concerns a carbonatitic gangue ore structure with the main REE mineral parisite. As gangue types, Ba-Sr-sulphates as well as carbonates, silicates and sulphides are present. It was possible in a relatively short time in orienting processing tests with the focus on flotation and magnetic separation to produce REE mineral concentrates with over 40 % REE oxide from the unusual ore with a high yield on laboratory scale. Tests based on optical pre-sorting open up the possibility of a considerable preconcentration of the REE with rejection of the tailing fractions that are almost free of recoverable material upstream of flotation. On the basis of the available interim results, a first concept for a processing method was suggested.

The paper “A study on the impact of flotation hydrodynamics for the optimization of fine-grained carbonaceous sedimentary apatite ore beneficiation” by Duong Huu Hoang^1,2,3, Prof. Urs Peuker³, Dr Martin Rudolph¹ (¹Department of Processing, HIF Freiberg; ²Department of Mineral Processing, Faculty of Mining, Hanoi University of Mining and Geology, Vietnam; ³Institute MVT/AT, Freiberg University of Mining and Technology) addressed the flotation of apatite from finely distributed sedimentary ores that are rich in carbonates. The effects of various turbulent hydrodynamic variables such as air flow velocity, impeller speed and slurry density were tested to optimize the operating parameters on laboratory scale and to understand the role of turbulence in the separation of carbonate from phosphate ore in ultrafine particle flotation. With the application of optimum conditions from the coarse particle flotation, flotation tests with recirculation were conducted to achieve an experimental simulation of a continuous circuit.

Dr Uwe Lehmann (Saxony‘s State Office for the Environment, Agriculture and Geology) reported on “The application of intermittently operated launders in the recovery of heavy minerals” especially of placer gold from sand and gravel. With suggestions to improve the retaining capacity for recoverables with changes to the launder design and the launder lining, the yield can be improved. In addition, current work in a German gravel plant in the Upper Rhine region has led to the conclusion that the frequency of launder cleaning is also a key factor for increasing the overall yield. Tests in the above-mentioned gravel plant led to modelling of the saturation of heavy minerals in an intermittently operated launder with a mathematical saturation function. From the application of the specified saturation function in practice, important conclusions resulted both for basic processing-relevant questions and for the use of launders in the gold- and other heavy-mineral-extraction industry.

The paper “Processing of cell nuclei from thymus tissue” by Maria Schäfer¹, A. Kupka¹, J. Heinrich², J.I. Schoenherr¹, T. Wiegert², K. Adam³ (¹Institute of Process Development, Research into Peat and Natural Materials, Zittau/Görlitz University of Applied Sciences; ²Faculty of Environmental and Natural Sciences, Biotechnology Department, Zittau/Görlitz University of Applied Sciences; ³EUROIMMUN Medizinische Labordiagnostika AG) concerned the preparation of medical products with methods of mechanical process engineering. In immunodiagnostics, purified proteins are used to prove antibodies in autoimmune disorders and infectious diseases as well as in allergies. Goal of the project funded by the European Fund for Regional Development EFRE) at Zittau/Görlitz University of Applied Sciences, which is conducted in an alliance with EUROIMMUN Medizinische Labordiagnostika AG, is the integration of processes and technologies for continuous, gentle and efficient separation of vital cell nuclei from animal tissue on a large scale.

Plants and equipment

Dr Stefan Jäckel, B.Sc. Raphael Sperberg (Gebrüder Jehmlich GmbH, Nossen) presented “Concepts for explosion-proof design of equipment for ultrafine grinding of organic substances”. In the production and processing of organic, dry and powder substances, explosive dust atmospheres may be formed. For this reason, manufacturers have to take precautions to ensure explosion protection in compliance with the ATEX directive 2014/34/EU. Cause of explosions is the coming together of three factors: flammable substance, oxygen and source of ignition. The solutions applied by the company Jehmlich to be able to guarantee a safe explosion-proof plant for the customer were described and shown based on examples of realized grinding plants.

In the paper of Dr Mathias Trojosky and Marcel Wettring (ALLGAIER Process Technology GmbH, Uhingen) “Drying industrial wastewater with the CD Dryer”, a very efficient process was presented with which solids-loaded liquids, e.g. saline solutions, seepage water, fermentation residue from liquid manure and biogas plants, pigment suspensions, metal-containing liquids can be processed. In a test dryer at the Allgaier Test Centre, various tests were conducted with a wide range of products, which were presented in the paper and illustrated with photos and videos. The results enable safe design of large-scale plants.

Dipl.-Ing. Robert Claussnitzer (AKW Apparate + Verfahren GmbH) reported on “Control options for AKA-VORTEX hydrocyclones”. Starting from information on the company‘s product range, which includes solutions for the wet-mechanical processing as well as the treatment of wastewater, especially the (AKA-VORTEX) hydrocyclone, which is suitable for classifying as well as thickening or sorting, was presented. AKW Apparate + Verfahren GmbH has developed patent-protected processes that can be controlled with today‘s computer and sensor systems and electronics and are available for customers.

In his paper, Dipl.-Ing. Andre Schmidt (Freiberg University of Mining and Technology, Institute of Thermal, Environmental and Resources‘ Process Engineering – ITUN) provided information about the EXIST research transfer project “Energy-efficient and low-wear hydraulic press for the agglomeration of renewable and fossil resources (EVA)“. Depending on the type of feed materials and the required formats (briquets, pellets, granulates), for briquetting, primarily extruder presses and roller presses are used while for pelletization, die presses are used. The aim of the presented new press technology is the briquetting of an as wide as possible range of feed materials. Besides the wide spectrum of use, in the scope of the new development, importance was attached to minimizing the power requirement. To this end, a multistage press principle with hydraulic drive was developed, which in comparison with established technologies, substantially reduces the power requirement and wear thanks to optimized travel of the hydraulic cylinders. Goal of the project is to develop an optimized process for industrial application and to distribute it internationally with the establishment of a company and a corresponding market launch.

In the paper “Pressure distribution in the ideal material bed” by Dipl.-Ing. Lisa Kühnel, Dr Jens Friedrich, Prof. Holger Lieberwirth (Freiberg University of Mining and Technology, Faculty of Mechanical, Process and Energy Engineering), a report was given on a possibility for measurement of pressure in a closed particle bed. The pressure comminution of particle collectives is especially important for processes in high-compression roller mills. The simulation of such comminution processes is time- and computation-intensive. In addition, there is often an absence of pressure values to adequately calibrate the models. The tests were conducted in an ideal material bed in a stamp press. The results show that the pressure distribution in the model bed is inhomogeneous, With the help of pressure distribution, conclusions can be drawn with regard to the comminution behaviour. An application of the pressure measurement films in other machines that work with material beds is realistic, too. Prospectively, the data can be used for the calibration of 3D simulations.

Under the heading “Empirical determination of an effective ball mill make-up” Dr Dietmar Espig (UVR-FIA e.V. Freiberg) reported on his methodical experiences resulting from a large number of successful projects on comminution systems. His resumé that was proven also with examples is in the following statements: A general calculation model for comminution in ball mills with which the influence of the grinding media size or its make-up can be predicted cannot be set up, Far more, for a concrete comminution application, special grinding tests are necessary that generally have to be performed on a small scale, batch-operating mill to determine quantitatively the effectiveness of different grinding media sizes. As before, the d₈₀ particle size of the feed material, as already suggested by BOND, should be used to define the maximum size of the grinding balls. Another important finding is to strive to achieve the mill feed material filling level 1, that is to fill all spaces between the grinding media with mill feed material. This requires in the transition to continuous grinding a usable estimation of the transport behaviour (dwell time) of the feed material and is also applicable for wet grinding. The BOND grindability test can be simply extended not only to obtain the work index as point information, but also to determine a characteristic curve that can be applied for evaluation and calculation of the comminution behaviour with more information and details.

Under the title “A survey on troubleshooting of closed-circuit grinding system”, reported Ahmad Hassanzadeh (Department of Processing, HIF Freiberg) on tests in a ball mill operated in a closed circuit with hydrocyclones. The objective of the study was the optimization of the operating parameters (grinding media load, size of the filling balls, mean dwell time of the mill feed dispersion, number of hydrocyclones and the solid content of the hydrocyclone feed) to achieve a throughput increase from 225 to 300 t/h. This can be successful in practice when all relevant parameters lie within the optimized ranges.

Poster exhibition and company presentations

The Institute of Mechanical Process Engineering and Mineral Processing at Freiberg University of Mining and Technology was represented with the following five posters:

In the poster “Processing of solvent-contaminated solids by means of steam-pressure filtration”, Simon Esser M.Sc. and Prof. Urs A. Peuker showed that excellent washing and dewatering of the filter cake are possible with this process.

“Production of high-grade permeable dolomite grades for the firing process” was presented by Tony Fraszczak M.Sc. and others.

On “Modelling of the through-flow of cement clinker piles” informed Gregor Schmandra, Lieven Schützenmeister M.Sc., Dr Thomas Mütze and Guido Kache¹ (¹ thyssenkrupp Industrial Solutions AG).

The topic “Flow behaviour of mechanically loaded metal powders for additive manufacturing” was presented by Robert Kratzsch M.Sc., Dr Thomas Mütze, Prof. Urs A. Peuker.

“Process stages in the recycling of lithium-ion batteries from electric vehicles” were presented in the poster of Denis Werner M.Sc., Dr Thomas Mütze, Dr Hans-Georg Jäckel¹, Prof. Urs A. Peuker (¹Freiberg University of Mining and Technology, Institute of Mechanical Engineering and Recycling Machines).

Other poster presentations addressed the following subject areas:

“Ultrafine flotation processes for a tin-containing skarn ore from the Hämmerlein deposit in the Ore Mountains” was addressed in the presentation by Edgar Schach M.Sc. ¹, Dipl.-Ing. Markus Buchmann², Paul Wesley Chang¹, Marius Kern¹, Prof. Urs. A. Peuker², Dr Martin Rudolph¹ (¹Helmholtz-Institut Freiberg of Resource Technology, ²Freiberg of Mining and Technology, Institute of Mechanical Process Engineering and Mineral Processing).

The poster “Bioflotation – combination of biotechnology with the classical process of flotation” by Sylvi Schrader M.Sc., Dr Sabine Kutschke, Dr Katrin Pollmann and Dr Martin Rudolph (Helmholtz-Institute Freiberg for Resource Technology) gave information on this new work area in mineral processing.

The “Processing of iron-hydroxide-containing mixed sludge” was presented by Dipl.-Ing. A. Kupka¹, L. Bresler¹, J. Schoenherr¹, M. Leiker², J. Helbig² (¹Institute of Process Development, Peat and Natural Materials Research, Zittau/Görlitz University of Applied Sciences, ²P.U.S. Produktions- und Umweltservice GmbH, Lauta).

An “Analysis of fine fractions from metal-containing waste streams” was addressed in the poster by M.Sc. Kay Johnen (RWTH University of Aachen – Department of Processing and Recycling).

In the poster “Sample preparation in the routine chemical analysis laboratory – a challenge for materials, instruments and quality assurance”, Axel Ulbricht and Dr Thomas Hoppe (Eurofins Umwelt Ost GmbH, NL Freiberg) presented the work of the routine laboratory.

The industry representative of the company Eirich (Ingenieurbüro Dill, Misch- und Verfahrenstechnik Jena) held a company presentation. The companies in the Eirich Group are suppliers of machines, equipment and services for the processing of flowing materials, slurries and sludges.

Closing remarks and announcement of the Annual Conference 2019

In the final remarks by the Chairperson of the “Gesellschaft für Verfahrenstechnik UVR-FIA e.V. Freiberg” Dipl. Ing. Silke Thümmler, she observed that together with the “Helmholtz-Institute Freiberg for Resource Technology” and “Freiberg University of Mining and Technology” as well as the employees of “UVR-FIA GmbH Freiberg”, they had been successful in organizing a very good conference. They were particularly successful in commemorating Prof. Heinrich Schubert, who died in spring 2018, and acknowledge his services for the development of his specialist field. Gratitude was expressed to the conference organizers for the individual sections of the programme of papers Prof. Peuker and Dr Mütze (TU Bergakademie, IMV-AT), Dr Rudolph (Helmholtz Institute Freiberg), Dr Kamptner (UVR-FIA Freiberg), Prof. Lieberwirth (TU Bergakademie, Institute of Mineral Processing Machinery) und Dr Jäckel (TU Bergakademie, IMB Recycling Machinery).

The next “Mineral Processing and Recycling” Conference will take place on 7 and 8 November 2019 at the same venue in Freiberg, in the auditorium at the facility of the HIF/HZDR (former FIA building). Focuses of the conference are mineral resources – recoverables from waste with the focus on machinery, equipment and sensors as well as the processing of primary resources and processing of secondary resources/recycling. Organizers are again the “Gesellschaft für Verfahrenstechnik UVR-FIA e.V. Freiberg“ in cooperation with the “Helmholtz-Institute Freiberg for Resource Technology” and “Freiberg University of Mining and Technology”. Abstracts of papers, posters and company presentations should be submitted by the end of July 2019 to the Conference Organization UVR-FIA GmbH at the internet address www.uvr-fia.de, E-Mail tagung@uvr-fia.de:tagung@uvr-fia.de%3C/a%3E">. Abstracts of the conference papers can also be accessed at the above-mentioned internet address.