Montanuniversitaet Leoben Research Articles

A Technology-Enhanced ‘Assessment System for Teaching and Assessment using a Computer Algebra Kernel’ (STACK)

After two years of online meetings we had the great pleasure to host the meeting of the STACK Community 2022 at the Montanuniversitaet Leoben in Austria in a hybrid setting. STACK (System for Teaching and Assessment using a Computer algebra Kernel) allows for a wide variety of technology-enhanced teaching, learning and assessment approaches. The accelerated significance of this approach over the last couple of years has been impressively demonstrated at the 2022 community meeting. The best contributions to the meeting have been carefully selected by an international program committee and are collected in this special issue.

Optimization of a Pyrometallurgical Process to Efficiently Recover Valuable Metals from Commercially Used Lithium-Ion Battery Cathode Materials LCO, NCA, NMC622, and LFP

With an ever-growing demand for critical raw materials for the production of lithium-ion batteries and a price increase of respective commodities, an ever louder call from the industry for efficient recycling technologies can be noticed. So far, state-of-the-art industry-scaled pyrometallurgical recycling technologies all suffer from the same bottleneck of lithium slagging. At the Chair of Thermal Processing Technology at Montanuniversitaet Leoben, a novel reactor was developed to recover lithium and phosphorus via the gas phase in a pyrometallurgical process. Critical elements such as Li, Ni, Co, and Mn of the commercially used cathode materials LCO (LiCoO2), LFP (LiFePO4), NCA (LiNi0.8Co0.15Al0.05O2), and NMC622 (LiNi0.6Mn0.2Co0.2) were analyzed in a batch version of the so-called InduRed reactor concept. The analyses underline that the reactor concept is highly suitable for an efficient recovery for the metals Ni and Co and that slagging of Li can not only be largely prohibited, but the elements lithium and phosphorous can even be recovered from the gas phase. Plant engineering issues were also considered for further development toward a continuous process. The MgO crucible used shows significant diffusion of various elements from the battery material, which is why the choice of crucible material still requires in-depth research.

Influence of Impurities on the High-Temperature Behavior of the Lithium-Ion Battery Cathode Material NMC under Reducing Conditions for Use in the InduRed Reactor Concept

In terms of an efficient circular economy in the field of the steadily increasing use of lithium-ion batteries, sustainable recycling methods are of fundamental importance. Therefore, the Chair of Thermal Processing Technology at Montanuniversitaet Leoben has developed the so-called InduRed reactor, a carbo-thermal concept to recover valuable metals from this waste stream. For optimization and further development of this technology, it is essential to have a sound knowledge of the cathode materials' behavior in combination with various impurities in the high-temperature range under reducing conditions. Detailed experiments were carried out in a heating microscope at temperatures up to 1620°C and argon purge. Aluminum from the electrode conductor foils and an excessive proportion of graphite from the anode were identified as the impurities with the most significant negative influence on the process. An optimum melting behavior was found during the tests at an admixture of 10 wt. % C and 1.95 wt. % Al to the cathode material NMC622 (LiNi0.6Mn0.2Co0.2O2).

Applicability of Electrostatic Separation on Talc-Containing Mineral Samples for Production of a High-Grade Talc Concentrate in Comparison to Flotation

In the course of this study, the applicability of electrostatic separation and flotation for processing a mineral sample rich in talc was examined. The aim was a comparison of those two separation processes and the concentrates obtained. Furthermore the separation behaviour of the silicates and carbonates was a goal of the examination. The electrostatic separation test work was conducted with a triboelectric belt separator. The feed, an artificially prepared mineral sample, was composed of four components: talc, quartz, dolomite, and magnesite. The lab scale test work was done exclusively at the Chair of Mineral Processing, Montanuniversitaet Leoben, Austria.

A New Methodological Approach on the Characterization of Optimal Charging Rates at the Hydrogen Plasma Smelting Reduction Process Part 2: Results.

To meet the target for anthropogenic greenhouse gas (GHG) reduction, the European steel industry is obliged to reduce its emissions. A possible pathway to reach this requirement is through developments of new technologies for a GHG-free steel production. One of these processes is the hydrogen plasma smelting reduction (HPSR) developed since 1992 at the Chair of Ferrous Metallurgy at the Montanuniversitaet Leoben in Austria. Based on the already available publication of the methodology in this work, potential process parameters were investigated that influence the reduction kinetics during continuous charging to improve the process further. Preliminary tests with different charging rates and plasma gas compositions were carried out to investigate the impacts on the individual steps of the reduction process. In the main experiments, the obtained parameters were used to determine the effect of the pre-reduction degree on the kinetics and the hydrogen conversion. Finally, the preliminary and main trials were statistically evaluated using the program MODDE® 13 Pro to identify the significant influences on reduction time, oxygen removal rate, and hydrogen conversion. High hydrogen utilization degrees could be achieved with high iron ore feeding rates and low hydrogen concentrations in the plasma gas composition. The subsequent low reduction degree and thus a high proportion of oxide melt leads to a high oxygen removal rate in the post-reduction phase and, consequently, short process times. Calculations of the reduction constant showed an average value of 1.13 × 10−5 kg oxygen/m2 s Pa, which is seven times higher than the value given in literature.

Qualitative analysis of post-consumer and post-industrial waste via near-infrared, visual and induction identification with experimental sensor-based sorting setup

Sensor-based sorting in waste management is a method to separate valuable material or contaminants from a waste stream. Depending on the separation property different types of sensors are used. Separation properties and their corresponding sensors are e.g. molecular composition with near-infrared sensors, colour with visual spectroscopy or colour line scan cameras, or electric conductivity with electromagnetic sensors.The methods described in this paper deal with the development of sorting models for a specific near-infrared, a visual spectroscopy and an induction sensor. For near-infrared and visual spectroscopy software is required to create sorting models, while for induction only machine settings have to be adjusted and optimized for a specific sorting task. These sensors are installed in the experimental sensor-based sorting setup at the Chair of Waste Processing Technology and Waste Management located at the Montanuniversitaet Leoben. This sorting stand is a special designed machine for the university to make experiments on sensor-based sorting in lab scale. It can be used for a variety of waste streams depending on the grain size and the pre-conditioning for the sensor-based sorting machine. In detail the methods to create these sorting models are described and validated with plastic, glass and metal waste.•Near-infrared spectroscopy measures the molecular composition of near-infrared-active particles.•Visual spectroscopy measures the absorption of visible light by chemical compounds.•Induction sensors use induced currents to detect nearby metal objects.

Transformation of a rolling mill aggregate to a cyber physical production system: from sensor retrofitting to machine learning

This paper describes the transformation of a rolling mill aggregate from a stand-alone solution to a fully integrated cyber physical production system. Within this process, already existing load cells were substituted and additional inductive and magnetic displacement sensors were applied. After calibration, those were fully integrated into a six-layer digitalization architecture at the Smart Forming Lab at the Chair of Metal Forming (Montanuniversitaet Leoben). Within this framework, two front end human machine interfaces were designed, where the first one serves as a condition monitoring system during the rolling process. The second user interface visualizes the result of a resilient machine learning algorithm, which was designed using Python and is not just able to predict and adapt the resulting rolling schedule of a defined metal sheet, but also to learn from additional rolling mill schedules carried out. This algorithm was created on the basis of a black box approach, using data from more than 1900 milling steps with varying roll gap height, sheet width and friction conditions. As a result, the developed program is able to interpolate and extrapolate between these parameters as well as different initial sheet thicknesses, serving as a digital twin for data-based recommendations on schedule changes between different rolling process steps. Furthermore, via the second user interface, it is possible to visualize the influence of this parameters on the result of the milling process. As the whole layer system runs on an internal server at the university, students and other interested parties are able to access the visualization and can therefore use the environment to deepen their knowledge within the characteristics and influence of the sheet metal rolling process as well as data science and especially fundamentals of machine learning. This algorithm also serves as a basis for further integration of materials science based data for the prediction of the influence of different materials on the rolling result. To do so, the rolled specimens were also analyzed regarding the influence of the plastic strain path on their mechanical properties, including anisotropy and materials’ strength.

Advancing Plastic Recycling by Wet-Mechanical Processing of Mixed Waste Fractions

In this paper, an arc was drawn over ten years of research activities from three chairs of the Montanuniversitaet Leoben, as well as industrial partners. The superior objective of this research effort was to develop a wet-mechanical process for the recovery of polyolefin concentrates (90 wt% polyolefins) from mixed waste fraction for use in chemical recycling and to advance this new technology to commercial maturity. As a bridge technology, it would close the gap between state-of-the-art dry processing of mixed plastic waste materials and chemical plastic recycling via thermo-chemical conversion. The methods used were mainly tested in a lab-scale plant with a throughput capacity of 50 to 200 kg/h depending on the bulk density of the used feedstock. Further studies for the treatment and usage of the main products and by-products, as well as chemical analyses of them, were completed during the investigation. Within these series of tests, polyolefin concentrates, which satisfied the requirements for chemical recycling, could be recovered. With these data, a concept for an industrial pilot plant was developed and evaluated from an economic point of view. According to this evaluation, the realization of such an industrial pilot plant can be recommended.

Thermal analysis of lithium ion battery cathode materials for the development of a novel pyrometallurgical recycling approach

Since pyrometallurgical approaches on lithium ion battery recycling are not yet capable of recovering lithium but only nickel, cobalt and manganese, the Chair of Thermal Processing Technology at the Montanuniversitaet Leoben started to investigate experimental reactor concepts on their suitability to overcome this major drawback. Therefor, the general behaviour of currently used cathode materials under reducing conditions and high temperatures is of great interest. This work expands previous performed heating microscope experiments by thermogravimetric analysis (TGA) to characterize the reactions that are responsible for certain changes in the cathode materials. By comparing the superficial changes of the samples in the heating microscope with the corresponding data from the TGA, it was possible to identify the temperature zones in which reduction reactions occured. For all investigated cathode materials, the reduction reactions started at technically feasible temperatures of approx. 1000 °C, which is favorable for the desired recycling process. On the other hand, this is some hundred degrees higher than the temperature at which first changes in the heating microscope could be observed and indicates that there are changes in the material before the reduction starts. Therefore, the results also emphasize the need for further analysis to clarify this offset and to complete the thermal characterisation of the cathode materials.

A Study on the Stability Fields of Arc Plasma in the HPSR Process

One of the major challenges for Europe’s future steel production will be minimizing the inherent process emissions in the production of crude steel based on iron ores. In this case, mainly the reduction of CO2 emissions is a focus. One promising process to overcome these problems is the hydrogen plasma smelting reduction (HPSR) process. This process has been studied for several years already at the Chair of Ferrous Metallurgy at Montanuniversitaet Leoben. The work presented focused on the stability of plasma arcs in the DC transferred arc system of the HPSR process. The stable operating plasma arc is of utmost importance for the future development of the process. The major objective is the definition of the most favorable conditions for this kind of arc. Therefore, tests were conducted to define fields of a stable operating plasma arc for multiple gas compositions and process variables. For several gas compositions of argon, nitrogen, argon/nitrogen, argon/hydrogen and nitrogen/hydrogen, fields of stability were measured and defined. Besides, the major influencing parameters and trends for the fields of stability were evaluated and are shown in this work.

The RecoDust Process—Upscale of a Pilot Plant

The RecoDust process is a pyrometallurgical approach for the treatment of heavy metal–containing basic oxygen furnace dusts (BOFD) and delivers two products without any residues: the iron rich RecoDust slag and a zinc rich filter dust, called crude zinc oxide (CZO). The state of the art Waelz process has some disadvantages and is only suitable for dusts with zinc contents >15%. Within the frame of a project of the Austrian competence center program K1‐MET and with financial support of voestalpine Stahl, a RecoDust pilot plant is operated at the Chair of Thermal Processing technology at the Montanuniversitaet Leoben and has shown good dezincification rates of BOFD in eleven smelting campaigns with a throughput up to 300 kg h−1. The target is the design of an industrial plant with a throughput capacity of 1000 kg h−1 in the next years. For the upscale, a new pneumatic conveying system was installed at the pilot plant, which uses natural gas as conveying medium. The commissioning of the developed pilot plant was successful and revealed a good product quality of the CZO. An enhanced dezincification of the RecoDust slag is one open challenge, therefore the dust feed conveying must be more precise.

Improved Slippage Model for Sucker Rod Pumps Developed in a Pump Test Facility and Verified by Field Measurements

Summary Sucker rod pumps provide a cost-efficient way to produce hydrocarbons from low-pressure reservoir formations. Their design is dependent on predictive models used to optimize the system before implementation in the field. The greater the accuracy of these models, the better the performance of the pumping system in the field. The scope of this paper is to present an improved plunger slippage model, developed in connection to the pump test facility (PTF) and validated by field data. This paper provides an analysis of plunger slippage. Existing plunger-slippage models are compared with field data. Based on the result of this comparison, an improved plunger-slippage model is derived based on the Navier-Stokes equation and dimensional analysis. Adjustments are applied to increase the model's validity. The mathematical and laboratory work have shown that a proper fit to reality requires four coefficients that make the equation an empirical one. An extensive laboratory test campaign, using real field equipment, was performed at the PTF at Montanuniversitaet Leoben (MUL). Numerous influencing parameters, such as plunger velocity, clearance magnitude, and fluid viscosity, were studied. Historical plunger-slippage models overestimate the slippage rate, whereas field data showed that newer models underestimate the slippage rate. In general, dynamic models are more accurate than static slippage models. The fit of the four model coefficients, based on laboratory tests, indicate that the chosen strategy of using laboratory tests and allocating the results to field conditions has worked out. The comparison of the results obtained by the presented improved slippage model and the field tests indicate a good match. The presented slippage model predicts the plunger slippage rate precisely and results in greater accuracy. The plunger wear rate approach is presented, which can be used to plan well interventions, decrease intervention costs, and increase the mean time between failures.

Slag Formation during Reduction of Iron Oxide Using Hydrogen Plasma Smelting Reduction.

Replacing carbon by hydrogen is a huge step towards reducing CO2 emissions in the iron- and steel-making industry. The reduction of iron oxides using hydrogen plasma smelting reduction as an alternative to conventional steel-making routes has been studied at Montanuniversitaet Leoben, Austria. The aim of this work was to study the slag formation during the reduction process and the reduction behaviour of iron oxides. Furthermore the reduction behaviour of iron ore during continuous feeding was assessed. Mixtures of iron ore and calcined lime with a basicity of 0, 0.8, 1.6, 2.3, and 2.9 were melted and reduced by hydrogen. The off-gas composition was measured during the operations to calculate the process parameters. The reduction parameters, namely the degree of reduction, degree of hydrogen utilisation, produced iron, and slag, are presented. The results of the batch-charged experiments showed that at the beginning of the reduction process, the degree of hydrogen utilisation was high, and then, it decreased over the operation time. In contrast, during the continuous-feeding experiment, the degree of hydrogen utilisation could be kept approximately constant. The highest degrees of reduction and hydrogen utilisation were obtained upon the application of a slag with a basicity of 2.3. The experiment showed that upon the continuous feeding of iron ore, the best conditions for the reduction process using hydrogen could be applied.

Development and Efficiency Testing of Sucker Rod Pump Downhole Desanders

Summary Tense economic situations push the demand for low-cost oil production, which is especially challenging for production in mature oil fields. Therefore, an increase in the meantime between failure and the limitation of equipment damage is essential. A significant number of wells in mature fields are suffering under sand by-production. The objective of this paper is to show the development process and the testing procedure of an in-house-built, effective downhole desander for sucker rod pumps on the basis of a sophisticated analytical design model. In weak reservoir zones, often the strategy to prevent equipment damage due to sand by-production is the sand exclusion method using a gravel pack. Nevertheless, a certain amount of small sand grains still enter the wellbore and may damage the sucker rod pumping system over time. In early 2018, various types and sizes of downhole desander configurations were tested at the pump testing facility (PTF) at the University of Leoben (Montanuniversitaet Leoben). In a period of about 4 months, testing took place under near field conditions to find the optimum and most efficient design. The design optimization was focused on the geometry of the swirl vanes and the sand separation distance at the sucker rod pump intake. An analytical model provided the basis for geometric optimization. Concurrently, field tests of the in-house downhole desander were performed in the Vienna Basin that confirmed the findings of the tests at the PTF. The test results have shown that the downhole desander design and the pumping speed are the most influencing parameters on sand separation efficiency. Poor design in combination with a wrongly selected pumping speed can reduce the sand separation efficiency to lower than 50%, while if all parameters are chosen correctly, the sand separation efficiency can be 95% or higher. The grain size distribution is the additional parameter that enables a decision and ranks the performance. The sensitivity analysis, performed for several downhole desander types, has shown the high dependency of the sand separation efficiency on the major desander design parameters. Proper selection of the components and operating parameters will contribute to an increase in the meantime between failures. This paper will present the testing configurations, the development of the high-efficiency in-house downhole desander, and the sensitivity analysis performed on the design.

A Holistic Didactical Approach for Industrial Logistics Engineering Education in the LOGILAB at the Montanuniversitaet Leoben

The successful implementation of Industry 4.0 initiatives can only be established by focusing on a multitude of complex and partially interdepending requirements and enabling factors. Thereby, the education and further training of employees can be seen as one of the major prerequisites to understand, handle, and further develop existing Industry 4.0 concepts and technologies. This paper reviews the current state of the art regarding the usage of learning labs, as modern teaching and learning methods, for industrial logistics engineering education from a holistic perspective. Moreover, the authors discuss learning within the framework of action-based learning approaches as a reflected form of meaningful social interaction and introduce an exemplary system-theoretical and constructivist approach based on the LOGILAB at the Montanuniversitaet Leoben.

Extended performance comparison of different pressure drop, hold-up and flooding point correlations for packed columns

Eight correlations for the prediction of pressure drop, liquid hold-up and flooding for packed columns were evaluated in an initial analysis in Wolf-Zoellner et al. 2019. The best predictions were achieved with the Wolf 2014 model and a modified model of Maćkowiak 2003 by Wolf-Zoellner.The objective of this work is to extend the performance investigation to other well-known correlations available in literature: Spiegel and Maier 1992, Brunazzi 2002, Bozzano 2007, NNA-Model of Piché 2001, GPDC of Kister 2007, Robbins 1991, Jammula 2014.Therefore, the significant combined databases of the Separation Research Program (SRP) at The University of Texas and the Montanuniversitaet Leoben (MUL) provide the perfect basis to evaluate the correlations. The databases include pressure drop, hold-up and flooding point data for 50 different random (2nd, 3rd and 4th generation) and structured packings (sheet and grid structured packings) for different test systems under absorption and distillation conditions. At present 32 packings are included in the study.Based on this evaluation, the Kister GPDC-charts show the best agreement for pressure drop and flooding point estimation. Generally, all examined models perform well for pressure drop calculation but none of the considered models are able to predict reliable liquid-hold ups. In addition, the overall poor modelling performance involving viscous liquids is obvious and needs further investigations.

KIC RawMaterials: Iron Balance\u2014Austria

An evaluation of the iron flow in Austria was executed at the RIC ESEE at the Montanuniversitaet Leoben within the context of the European network EIT RawMaterials. The main idea was to develop a system that visualizes the mass flow of iron and steel of Austria. To build up the system, it was essential to provide all necessary information regarding the production, consumption and inventory as well as information about the trading (including import and export) of semi-finished products, goods and scrap. The boundary conditions for the system were the national economics of Austria in the year 2010. The mass flow software STAN2 was used for visualization of the system. A main objective of the project was the calculation and visualization of the required iron scrap for the steel production in Austria. The influencing factors on the iron balance were identified and the question of the steady state of scrap return was answered.

Performance comparison of different pressure drop, hold-up and flooding point correlations for packed columns

The hydraulic properties of pressure drop, hold-up and flooding point are of immense importance to describe the performance of random and structured packings. Therefore, accurate modelling of these performance parameters over the whole operating range has to be ensured. For this reason, many correlations have been developed by different institutions in the past (Billet and Schultes, 1991, 1999; Wolf, 2014; Engel, 1999; RBF (Rocha, Bravo, Fair), 1993, Delft-model (Olujić) 1997; Verschoof, 1999; Maćkowiak, 2003, Stichlmair, 1989). As these correlations are usually only reliable for validated packings, the purpose of this work is to evaluate these models based on the significant database of the Separation Research Program (SRP) at The University of Texas and the database of Montanuniversitaet Leoben (MUL). Combined, these databases include pressure drop, liquid hold-up and flooding point data for 50 different random and structured packings at different operating conditions. Furthermore, some pressure drop and flooding data obtained from the SRP 43cm diameter distillation column are also used.In this work, the predictions of the various correlations are compared and the application fields of the various models are revealed. In particular, the paper shows the operating ranges as well as packing types for which the models provide reliable predictions but also the weaknesses of the various correlations. Particularly, a modification of the Maćkowiak model is introduced which leads to a significantly improved modelling performance.

Overview of current research work at the Chair of Subsurface Engineering at Montanuniversitaet Leoben

AbstractThe Chair of Subsurface Engineering at the Montanuniversitaet Leoben is part of the Department of Mineral Resources Engineering. Regarding research and development, the chair cooperates with several departments of the university, such as the Departments of Petroleum Engineering, Environmental and Energy Technology, Product Engineering and Polymer Engineering. In addition to the construction of the ZAB, a research and development but also training and education centre at the Styrian Erzberg, some other research projects at the chair have recently been reported in this journal. These include, for example, research on segmental lining design in collaboration with with the ÖBB‐Infrastruktur AG, and also topics such as disc force and face monitoring systems for TBMs. This research is deliberately not discussed here; rather research is reported that has received less attention lately. This includes further developments mainly relating to laboratory tests, the research field of rockfall simulations, international research cooperations, and also work on BIM implementation at the ZAB‐Zentrum am Berg.

Experimental Investigations on Spray Characteristics of Water-Air Nozzles

In the secondary cooling zone of the continuous casting process, the steel is cooled down by water and water-air nozzles. The cooling has to be sufficiently intensive to ensure a certain shell thickness and the controlled solidification of the strand. Furthermore, a controlled and uniform cooling strategy is important to minimize the amount of defects in the solidified steel. To determine the cooling characteristics of different nozzles at different operation parameters, the Nozzle Measuring Stand (NMS) at Montanuniversitaet Leoben is used. In the first part of this work, the measuring principle of the NMS is explained. Secondly, the influence of different cooling parameters is discussed. The water distribution (WD) and the heat transfer coefficient (HTC) for a single nozzle type have been measured using the NMS. To show the change in cooling intensity over the width of the spray, the HTC has been determined in several positions. Of particular interest is the area of overlapping of the spray cones. The modified process parameters for this investigation are the water flow, air pressure, and casting velocity.