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This study presents a new approach in the quantification of the deposited amount of impurity inside a filter cake made up of filter aid material. For this purpose, three-dimensional imaging by X-ray tomography is applied. Based on the X-ray attenuation properties, a model system consisting of kieselguhr as filter aid and barium sulphate as impurity is chosen. Due to the impurity particle size being smaller than the spatial resolution of the measuring setup, a calibration approach is necessary to gain insight into subvoxel information. A so-called phantom of similar material composition is prepared. The grey values are linearly correlated with the impurity volume fraction resulting in a calibration function, which facilitates the calculation of impurity volume fraction based on grey values measured inside the filter cake. First results are presented, showing that the approach delivers valid results for the chosen material system and reveals unexpected characteristics of the filter cake structure. Challenges in the context of the phantom approach and their influence on the obtained results are discussed.

The characterization of multidimensional particle property distributions through computed tomography requires an adapted sample preparation strategy. This strategy should both generate as many spatially separated particles as possible in the smallest achievable volumes and also enable mechanically and vacuum-stable samples that are suitable for correlative measurement, for example with high-energy ion beam methods. In the present study an epoxy-based method is presented that minimizes the negative influence of particle sedimentation by adding very low X-ray absorbing graphite nanoparticles as spacer. A machine learning-based method is presented to discretize the particle system. Results are compared with data from 2D SEM validation measurements and data of a previous study.

The use and development of lithium-ion batteries (LIBs) are promoting the technological transformation of individual mobility, consumer electronics and electric energy storage. At their end of life, the complex compounds are disposed by different recycling technologies with defined secondary raw material production. The applied depollution temperatures of the process routes influence not only the recycling efficiency but also the process expenditure, design, medium and costs. Different pretreatment strategies in terms of dismantling depth and depollution temperature are existing. Furthermore, manual and mechanical methods for cell opening are distinguished, which together with the depollution leads to a respective organic solvent evaporation. In this contribution to LIB recycling, the influence of different dismantling depths, achieved by manual cell opening, on the thermal depollution of the LIB cells regarding the mass difference originating by organic solvent evaporation are quantified, in order to determine cell and equipment properties for a safe cell opening. As a result, combinations of thermal depollution and manual cell opening are discussed regarding technical and economic feasibility. The process medium and equipment properties for a safe cell opening are determined. Furthermore, recommendations for future industrial LIB waste management are presented.

The rising production of lithium-ion batteries (LIBs) due to the introduction of electric mobility as well as stationary energy storage devices demands an efficient and sustainable waste man-agement scheme for legislative, economic and ecologic reasons. One crucial part of the recycling of end-of-life (EOL) LIBs is mechanical processes, which generate material fractions for the pro-duction of new batteries or further metallurgical refining. In the context of safe and efficient processing of electric vehicles’ LIBs, crushing is usually applied as a first process step to open at least the battery cell and liberate the cell components. However, the cell opening method used requires a specific pretreatment to overcome the LIB’s hazard potentials. Therefore, the depend-ence on pretreatment and crushing is investigated in this contribution. For this, the energy input for liberation is determined and compared for different recycling strategies with respect to dis-mantling depth and depollution temperatures. Furthermore, the respective crushing product is analyzed regarding granulometric properties, material composition and liberation and decoat-ing behaviour depending on the pretreatment and grid size of the crushing equipment. Finer particles and components are generated with dried cells. Pyrolysis of cells, as well as high dis-mantling depths, do not allow to draw exact conclusions. The calculated and measured mass-specific mechanical energy input of different dismantling depths shows good accuracy. Consequently, trends for a successful separation strategy of the subsequent classifying and sort-ing processes are revealed, and recommendations for the liberation of LIBs are derived.

A more thorough understanding of the properties of bulk material structures in solid–liquid separation processes is essential to understand better and optimize industrially established processes, such as cake filtration, whose process outcome is mainly dependent on the properties of the bulk material structure. Here, changes of bulk properties like porosity and permeability can originate from local variations in particle size, especially for non-spherical particles. In this study, we mix self-similar fractions of crushed, irregularly shaped Al2O3 particles (20 to 90 µm and 55 to 300 µm) to bimodal distributions. These mixtures vary in volume fraction of fines (0, 20, 30, 40, 50, 60 and 100 vol.%). The self-similarity of both systems serves the improved parameter correlation in the case of multimodal distributed particle systems. We use nondestructive 3D X-ray microscopy to capture the filter cake microstructure directly after mechanical dewatering, whereby we give particular attention to packing structure and particle–particle relationships (porosity, coordination number, particle size and corresponding hydraulic isolated liquid areas). Our results reveal widely varying distributions of local porosity and particle contact points. An average coordination number (here 5.84 to 6.04) is no longer a sufficient measure to describe the significant bulk porosity variation (in our case, 40 and 49%). Therefore, the explanation of the correlation is provided on a discrete particle level. While individual particles 100 µm took up to 25. Due to this higher local coordination number, the liquid load of corresponding particles (liquid volume/particle volume) after mechanical dewatering increases from 0.48 to 1.47.

Variable interfacial tension could be desirable for many applications. Beyond classical stimuli like temperature, we introduce an electrochemical approach employing polymers. Hence, aqueous solutions of the nonionic-cationic block copolymer poly(ethylene oxide)114-b-poly{[2-(methacryloyloxy)ethyl]diisopropylmethylammonium chloride}171 (i.e., PEO114-b-PDPAEMA171 with a quaternized poly(diisopropylaminoethyl methacrylate) block) were investigated by emerging drop measurements and dynamic light scattering, analyzing the PEO114-b-qPDPAEMA171 impact on the interfacial tension between water and n-decane and its micellar formation in the aqueous bulk phase. Potassium hexacyanoferrates (HCFs) were used as electroactive complexants for the charged block, which convert the bishydrophilic copolymer into amphiphilic species. Interestingly, ferricyanides ([Fe(CN)6]3-) act as stronger complexants than ferrocyanides ([Fe(CN)6]4-), leading to an insoluble qPDPAEMA block in the presence of ferricyanides. Hence, bulk micellization was demonstrated by light scattering. Due to their addressability, in situ redox experiments were performed to trace the interfacial tension under electrochemical control, directly utilizing a drop shape analyzer. Here, the open-circuit potential (OCP) was changed by electrolysis to vary the ratio between ferricyanides and ferrocyanides in the aqueous solution. While a chemical oxidation/reduction is feasible, also an electrochemical oxidation leads to a significant change in the interfacial tension properties. In contrast, a corresponding electrochemical reduction showed only a slight response after converting ferricyanides to ferrocyanides. Atomic force microscopy (AFM) images of the liquid/liquid interface transferred to a solid substrate showed particles that are in accordance with the diameter from light scattering experiments of the bulk phase. In conclusion, the present results could be an important step toward economic switching of interfaces suitable, e.g., for emulsion breakage.

The three-dimensional characterization of distributed particle properties in the micro- and nanometer range is essential to describe and understand highly specific separation processes in terms of selectivity and yield. Both performance measures play a decisive role in the development and improvement of modern functional materials. In this study, we mixed spherical glass particles (0.4–5.8 μm diameter) with glass fibers (diameter 10 μm, length 18–660 μm) to investigate a borderline case of maximum difference in the aspect ratio and a significant difference in the characteristic length to characterize the system over several size scales. We immobilized the particles within a wax matrix and created sample volumes suitable for computed tomographic (CT) measurements at two different magnification scales (X-ray micro- and nano-CT). Fiber diameter and length could be described well on the basis of the low-resolution micro-CT measurements on the entire sample volume. In contrast, the spherical particle system could only be described with sufficient accuracy by combining micro-CT with high-resolution nano-CT measurements on subvolumes of reduced sample size. We modeled the joint (bivariate) distribution of fiber length and diameter with a parametric copula as a basic example, which is equally suitable for more complex distributions of irregularly shaped particles. This enables us to capture the multidimensional correlation structure of particle systems with statistically representative quantities.

This paper highlights on the comminution and to the lesser extent liberation properties of two greisen-type lithium bearing-mica ores (L1, L2) subjected to different breakage devices; cone crusher (CC), roller crusher (RC), rotor beater mill (RBM) and a screen mill (SM). The particle size distributions (PSD) of the products from each device were evaluated to search for an appropriate PSD model using Gates-Gaudin-Schuhmann (GGS) and Rosin-Rammler (RR) functions. To determine an appropriate function, coefficients of determination (R2 ) were used as a criterion. Due to budget constraint, only products from rotor beater mill (RBM) were examined for mineral liberation by an automated scanning electron microscope (SEM) technique. It was found that RBM, RC and SM products were better described by the RR model than the GGS model with higher R2 values of 0.97 to 1.0. However, cone crusher products for L1 were better described by GSS model, while that for L2 were better described by RR model. In terms of the spread of size distribution as indicated by RR model parameters, RC products were more uniformly distributed compared to those from other devices, for both ores. Also the RBM products were more scattered than those from other devices. The results indicate that the composition of individual ores affected the comminution products PSDs as different PSD model parameters were obtained for samples comminuted by same devices. The modal mineralogy indicated that both ores are rich in quartz, topaz, zinnwaldite and muscovite. Furthermore, the result indicates that, for both ores, the zinnwaldite phase is more enriched in the fraction < 250 µm. Moreover, better liberation of zinnwaldite is observed for L1 compared to L2. This could be explained by differences of the two ores in three aspects; the nature of mineral association, reduction ratio of the fractions analysed and the spread of the size distribution.

The Ergun equation is commonly used to predict velocity-pressure drop behaviour in packed beds. For many particular systems, the measurements deviate significantly from this relationship. Because of this, the equation is often treated as a purely empirical relationship, and its factors as fit parameters. This paper shows that the physics-based model underlying the Ergun equation should be treated by careful investigation of the included parameters. It is shown that discrepancies between experiment and theory for particle collectives in the millimetre range and above are caused by insufficient methods to determine the specific surface area. This effect is especially large for coarse particles with very rough surfaces. As a 2D measurement method, dynamic image analysis can not provide a good measure of specific surface area. It does not account for both macroscale particle shape and microscale surface roughness, which is confirmed by an analysis of 3D particle measurements from X-ray microscopy.

In the present paper, as part of an interdisciplinary research project (Priority Programme SPP2045), we propose a possible way to design an open access archive for particle-discrete tomographic datasets: the PARROT database (https://parrot.tu-freiberg.de). This archive is the result of a pilot study in the field of particle technology and three use cases are presented for illustrative purposes. Instead of providing a detailed instruction manual, we focus on the methodologies of such an archive. The presented use cases stem from our working group and are intended to demonstrate the advantage of using such an archive with concise and consistent data for potential and ongoing studies. Data and metadata merely serve as examples and need to be adapted for disciplines not concerned here. Since all datasets within the PARROT database and its source code are freely accessible, this study represents a starting point for similar projects.

Prediction of micro processes, filter cake build-up and porous media flow is a key challenge to describe macroscopic parameters like filter cake resistance. This is based on a precise description, not only of the disperse solid fraction, but the distributed properties of the voids between the particles. Lab-experiments are carried out with alumina and limestone, which differ in particle size distribution (PSD) and resulting filter cake structure. Filter cakes of both materials are characterized by standardized lab tests and additionally, alumina cakes are measured with X-ray microscopy (XRM). Focusing on distributed process key parameters, the data gives a deeper understanding of the laboratory experiments. The solid volume fraction inside the feed strongly influences the particle sedimentation and leads typically to a top layer formation of fine particles in the final filter cake, which has a negative influence on subsequent process steps. The top layers seal the filter cake for washing liquid and increase the capillary entry pressure for gas differential pressure de-watering. The influence on cake structure can be seen in a change of porosity, particle size and shape distribution over the height of the filter cake. In all measurements, homogenous filter cake structures could only be achieved by increasing the solid volume fraction inside the suspension above a certain percentage, at which particle size related sedimentation effects could be neglected and only zone sedimentation occurred. XRM offers the chance to quantify these effects, which previously could only be described qualitatively.

X-ray computed tomography (XCT) has seen significant development in scan time and spatial resolution over the last decades. It is now increasingly used in the field of particle technology including ex-situ and in-situ applications to study time-lapse processes. This is due to its non-destructive principle giving 3D information on the inner structure and composition of specimens. This article shortly summarizes the field of XCT focusing on terms relevant for particle technology. It also gives a brief outlook on promising directions of development, which may significantly improve XCT. Using different examples from bulk solids handling, flow in porous structures and filtration, the monitoring of concentration differences and the fracture of particles, the application of XCT in particle technology is shown and its perspective is discussed.

With decreasing wettability and rough surfaces the adhesion forces between the interacting surfaces shift to higher values. This is due to capillary bridging by nanobubbles which are sitting on one or both rough surfaces and cause capillary interactions. For particles, the coverage with such bubbles for different wettability and gas oversaturation is shown. Also, it is possible to identify three general types of force distance curves: curves with no capillary interactions, curves with capillary interactions but no repulsion during approach and curves with capillary interactions and a small repulsion just before snap-in. Possible reasons for repulsion are analysed and a calculation of Hamaker constants is presented. Furthermore, well-known models for adhesion on rough surfaces are compared with the experimental data.

Interfaces between two fluid phases are a potential barrier for particles. Certain particles may not be able to pass such an interface, because they have to overcome a certain resistance. The latter depends on the strength of the interface, which is the surface tension. The second relevant property is the three phase wetting angle, which shows the fluid with the preferred wetting to the particle surface. It depends on the particle properties, like chemical composition, surface structure and surface modification. The third relevant parameter is the particle size. From these three main influence parameters it emerges that fluid-fluid interfaces can show a selectivity to special particle properties, which enables a separation of a particle mixture. Since there are possibilities to address the governing effects, the separation cut, size or composition cut respectively, can be engineered in a certain range. Separation at boundaries is feasible when the driving force is in the same order of magnitude as the retaining resistance force of the interface. The driving force is either the Brownian movement for very small particles or any field force like gravity or the centrifugal force. To describe the separation at interfaces it is necessary to understand the process of the phase transfer of particles through the interface, either the gas-liquid or the liquid-liquid interface between two immiscible liquids. In addition to the effects mentioned above, also dynamic phenomena such as surfactant depletion of the interface may have to be taken into account.

Since more than 100 years blast furnace slags are used as additive material or substitute material in cementitious systems like mortar and concrete. Due to their different syntheses the slag systems have binding properties which differ from conventional clinker. With the help of mechanical activation due to fine grinding the properties of blast furnace slags are shifted towards clinker systems. The application of stirred media mills allow for a production of a very fine reactive system.

Impurities and resulting inclusions are an issue when processing higher amounts of scrap during steel making. To increase the recycling rate, the removal of impurities from the scrap in form of inclusions is of great interest. In previous studies was found that inclusions attach primarily on carbon containing refractories, especially if on their surface an interfacial layer (1–3 µm thickness) was formed in-situ. This study investigates the formation mechanism of this in-situ layer in detail by application of computer tomography (CT) measurements on two scales. The large scale CT scans visualized the general appearance whereas the small scale measurement regarded the in-situ formed layer and the attached inclusions in detail. Based on these measurements, previous results and a literature review it was concluded that the layer formed mainly due to carbothermally reduced impurities which moved to the decarburized surface of the refractory in gaseous form and enhanced sintering of the surface region to develop the layer.

In the photovoltaic industry a total of 100,000 tons of silicon is lost as waste per year. This waste is originating from several cropping and sawing steps of the high purity silicon blocks and ingots during the solar cell wafer production, resulting in a silicon containing suspension. Among different approaches to recycle the silicon from this waste is the utilization of hydrocyclones, which can be used to separate or classify particles by weight and size. In this work the use of a hydrocyclone was evaluated to upgrade the silicon fraction from a typical sawing waste. A potential field of use for the recycled silicon particles might be as anode material for next generation lithium ion batteries.

Shrinkage cracking is an undesired phenomenon that is encountered frequently during the filtration process, especially of fine particulate filter cakes. The consequence is the significant disadvantage of the economy (orders of magnitude increase the gas/washing water consumption) and process results (higher moisture content/lower purity). In some literature, this issue is considered as a random phenomenon. Some recent research shows that cracking is formed by considering capillary force between particles arising during dewatering within filter cake. In the current research, one of the parameters is the slurry volume fraction, which affects the formation of cracks, are studied. The permeability ratio - i.e., gas permeability divided by liquid permeability is suggested to quantify cracking. Results show differences between materials, i.e., fewer cracks for coarse materials and more than cracks for fine ones. Along with that, the permeability ratio also differs markedly. Regarding the volume fraction of solids in the coarse particle suspension, the probability and degree of cracking reduce gradually when the concentration increases from 0.05 to 0.4. Saturation is also showed the decreasing trend when filter cakes are dewatered without shrinkage cracking. Meanwhile, this effect for fine particles is very complicated and depends strongly on the capillary pressure entry. By visual observation, macro- and micro-cracking is described for shrinkage behaviors on filter cake. The relationship between saturation and tensile stress is mentioned and used as one of the ways to explain the crack formation. Base on the analysis and interpretation of the experimental result, the mechanism of crack formation should be discussed. Together, other methods are also proposed to reduce the degree as well as to avoid the formation of cracks.

The flotation beneficiation of phosphate ore is increasingly facing challenges, especially for finely disseminated sedimentary ores rich in carbonates. This study aims to optimize and assess the impact of key hydrodynamic parameters including pulp density, air flowrate and impeller speed on flotation and metallurgical responses (i.e. grade, recovery, flotation rate constant and selectivity index (SI)). We carried out locked cycle flotation tests using the best conditions from the rougher flotation test to generate an experimental simulation of a continuous circuit. The mineralogical and chemical properties were characterized by mineral liberation analysis (MLA) and inductively coupled plasma optical emission spectroscopy (ICP-OES) techniques, respectively. A modified-McGill bubble size viewer was used for measuring bubble sizes and evaluating the interaction between hydrodynamic factors and bubble diameters. Finally, the design of experiment (DOE) method was applied to determine the relative intensity of the studied factors. It was found that under optimal conditions with the targets of high recovery and maximum SI, the final apatite concentrate achieved a recovery of 86.3% at a grade of 35.5%, while the MgO content was 1.2% and 84.3% of dolomite was removed from a feed ore containing about 25% P2O5, 4.6% MgO, and 41% CaO. Furthermore, another locked cycle flotation test showed that a 0.82% MgO content in the final apatite concentrate can be achieved with an apatite recovery of 75.6% at a P2O5 grade of 36.76% , and a ratio CaO/P2O5 = 1.33. The obtained concentrate in this investigation under the optimum conditions is the highest in both apatite recovery and grade with low MgO content reported in the literature.

Solid-liquid separation is carried out in many industries and plays a crucial role in overall process efficiency and product specification. The dewatering characteristics of solid-liquid mixtures, or particulate suspensions, have to be determined to compare filtration equipment performance or to design new equipment. Two theoretical frameworks used to describe solid-liquid separation, and therefore analyse experimental results, are the conventional filtration theory developed by Ruth, Tiller and Shirato and the compressional rheology framework developed by Buscall, White and Landman. In this paper, we compare the characterisation techniques that have developed over time based on these two approaches. This includes a comparison between an air-driven Nutsche Filter, a Compression-Permeability cell and a piston-driven Filtration Rig. The test material is calcium carbonate coagulated by attractive Van der Waals forces at its isoelectric point. We use three different particle sizes, leading to varying degrees of compressibility. The results show good agreement between the two theoretical frameworks for these compressible materials. Overall, this work highlights the differences and similarities between the theories and characterisation techniques alike and gives recommendations for good practice.

In flotation, the froth characteristics strongly influence the separation process as they are linked to water recovery, bubble size, entrainment of gangue particles, flotation rate constants and finally grade and recovery. In the case of a high-grade apatite ore with a high mass pull in lab-scale flotation, significant changes in pulp and froth properties occur, such that the froth stability decreases with increasing flotation time. These changes can be related to different particle and reagent concentrations. We describe the change of entrainment in a rich apatite ore batch flotation with time more precisely by measuring froth properties using a Dynamic Froth Analyzer (DFA). It is concluded that the degree of entrainment is not only dependent on particle size but also the pulp density due to its effect on particle settling and also froth properties in varying resistance to drainage. Through a combination of time-resolved dynamic froth analysis and automated mineralogy, we identify the dynamic effects governing in the froth and compare the entrainment results with existing models. Furthermore, our analyses offer novel support for the extension of the common understanding of the entrainment phenomena.

The determination of the grain size distribution of blasted rock exceeds the capability of an analytical sieving machine which only gives reliable results within a range of 63 μm to 125 mm. Other sophisticated methods are often not available for particle size measurement in coarse-grained applications in medium scale mining. Therefore, an alternative low cost method to investigate the grain sizes of blasted rock is introduced which can cover a range from 63 μm at the lower end without an upper limit. Three different options to examine blasted dolomite grains are investigated and combined with sieve analysis to determine a complete sieving equivalent grain size distribution. Comparison with results of a technical sieving shows that this method gives a good approximation of the size distribution, improving the possibilities for design of mineral processing equipment.

Lithium-ion batteries (LIBs) are an important pillar for the sustainable transition of the mobility and energy storage sector. LIBs are complex devices for which waste management must incorporate different recycling technologies to produce high-quality secondary (raw) materials at high recycling efficiencies (RE). This contribution to LIB recycling investigated the influence of different pretreatment strategies on the subsequent processing. The experimental study combined different dismantling depths and depollution temperatures with subsequent crushing and thermal drying. Therein, the removal of organic solvent is quantified during liberation and separation. This allows to evaluate the safety of cell opening according to the initial depollution status. These process steps play a key role in the recycling of LIBs when using the low-temperature route. Therefore, combinations of pretreatment and processing steps regarding technical and economic feasibility are discussed. Moreover, the process medium and equipment properties for a safe cell opening, the technical recycling efficiencies and their consequences on future industrial LIB waste management are pointed out.

This study addresses the question of whether mercury intrusion porosimetry is an appropriate measurement devise for the porosity characterization of reticulated ceramic foams which features three kinds of pores: functional pores, material pores and strut cavities remaining after decomposition of the polymeric foam. Reticulated ceramic foam samples made of Al2O3 and Al2O3-C and with functional pore sizes between 10 and 60 ppi (pores per inch) were investigated. The results show that it is feasible to measure the strut cavities and the entryways of the material pores with the help of the mercury intrusion porosimeter. The results for the strut cavity diameter depends strongly on the ppi number of the polyurethane foam used for the preparation of the ceramic foam. For the reticulated Al2O3-C foam samples no extrusion of the mercury is observed. Reasons for the missing extrusion of mercury are discussed. Furthermore, atomic force microscopy (AFM) measurements on Al2O3 and Al2O3-C samples are carried out using a recent AFM method to examine interactions between a mercury droplet and rough surfaces. Factors like approach/retrace speed, reproducibility and applied force are investigated. It is seen that for Al2O3 larger attractive forces are measured than for Al2O3-C.

Despite the application of aluminum melt filtration with ceramic foam filters since the 1960s the process is not fully understood. Outstanding issues are for example the influence of the wetting behavior and filter chemistry on the filtration efficiencies.Contact angle measurements by the sessile drop method coupled with non-contact heating and capillary purification technique were conducted at 730 °C with AlSi7Mg alloy on the substrates of four different oxides (Al2O3, MgAl2O4, 3Al2O3·2SiO2 and TiO2). The highest contact angle was measured on 3Al2O3·2SiO2, followed by MgAl2O4, Al2O3 and TiO2.Experimental values of contact angles were correlated with the evaluated filtration efficiencies of filtration trials performed at Constellium. They show a good correlation for inclusions smaller than 110 μm - the larger the contact angle the higher is the filtration efficiency.The adhesion forces of alumina inclusions on the four filter materials were experimentally estimated with an AFM in water based model system. The highest adhesion forces were measured on the Al2O3 substrate, followed by the 3Al2O3·2SiO2, the MgAl2O4 and the TiO2 substrate. For inclusions >70 μm, both the measured filtration efficiencies for >70 μm and the adhesion forces increase by the following order of coatings: TiO2, 3Al2O3·2SiO2, MgAl2O4, Al2O3. Keywords: Aluminum, Ceramic, Contact angle, Adhesion force, Filtration

The flotation beneficiation of apatite for phosphate production is challenging for finely disseminated sedimentary ores rich in carbonates. Similarities in surface properties of the semi-soluble salt-type carbonate and phosphate calcium minerals combined with fine intergrowth are the main reasons for poor grade and low recoveries. Imperfect depression of the calcium/magnesium carbonate minerals, e.g. calcite and dolomite, will lead to weak hydrophobic surface properties and thus true flotation of this gangue. Furthermore, fine particles, even though sufficiently liberated, strongly affect the bubble-particle collection due to negative rheological effects within the pulp leading to a drop in flotation kinetics of the fine valuables and an increase in entrainment of fine gangue particles. This study presents the results and discussions based on automated mineralogy (conducted with a Mineral Liberation Analyzer – MLA) of size-by-size-by-liberation analyses for various mineral groups. In addition, results on different turbulent hydrodynamic parameters are presented based on various tests in a lab cell.

The comminution of composites for liberation of valuable components is a costly and energy-intensive process within the recycling of spent products. It therefore is continuously studied and optimized. In addition to conventional mechanical comminution innovative new principles for size reduction have been developed. One is the use of high voltage (HV) pulses, which is known to be a technology selectively liberating along phase boundaries. This technology offers the advantage of targeted liberation, preventing overgrinding of the material and thus improving the overall processing as well as product quality. In this study, the high voltage fragmentation of three different non-brittle composites (galvanized plastics, carbon fibre composites, electrode foils from Li-ion batteries) was investigated. The influence of pulse rate, number of pulses and filling level on the liberation and efficiency of comminution is discussed. Using the guideline VDI 2225 HV, fragmentation is compared to conventional mechanical comminution with respect to numerous criteria such as cost, throughput, energy consumption, availability and scalability. It was found that at current state of development, HV fragmentation cannot compete with mechanical comminution beyond laboratory scale.

This research paper introduces a numerical model describing the stripping and drying phase during steam pressure filtration treating water insoluble volatile pore liquids. The model is based on mechanical and thermodynamic equations derived from the theory of steam pressure filtration for aqueous pore liquids and from the steam distillation theory. One main input parameter is the pressure profile determining the state variables of the vapour mixture. This work is first to resolve the pressure profile across a filter cake during stripping and drying based on temperature measurements within the filter cake. The developed model describes the stripping kinetics and the temperature profile across the filter cake and furthermore reveals a complete removal of the volatile organic compounds from the filter cake. The findings are evaluated by the experimentally determined stripping and drying kinetics. Additionally, exemplary calculations of the temporally and spatially resolved model are shown in order to promote the process understanding.

The formation of surface microbubbles induced by air nucleation on graphite surfaces and the air diffusion process in oversaturated water play important roles in increasing the recovery of graphite and other valuable minerals in flotation. A microscope equipped with a cuvette, a laser diffraction particle size analyzer, and single bubble pick-up experiments were combined with micro-flotation experiments to clarify these effects. The diffusion-controlled growth process of surface microbubbles was observed with a microscope. It can be shown that higher degrees of dissolved air can improve the probability of surface microbubbles forming on graphite surfaces. Micro-flotation and microscopic experiments confirmed that surface microbubbles occurred selectively on graphite surface but not quartz. Besides, bubble-particle aggregates formed during the conditioning process were observed under the microscope while bubble pick-up experiments indicated that the bubble load increased with the increasing degree of dissolved air. Size distribution analysis also showed that the nucleation microbubbles on graphite surfaces improved the recovery of fine graphite particles due to the formation of microbubble-particle aggregates. Coarser microbubble-particle aggregates induced by surface nucleation bubbles can improve the collision and attachment probability to external carrying bubbles compared to single graphite particles, which is especially relevant for fine particles. This study indicates that nucleation microbubbles on graphite surfaces can significantly promote flotation efficiency, and shows the importance of air nucleation on mineral surfaces in flotation process.

Within the scope of the evaluation and optimization of a grinding circuit, the breakage and mineral liberation characteristics of three low grade sulphide gold ore blends have been investigated by Bond tests, batch grinding tests, and mineral liberation characterization. The tests were conducted in a size range from 0.063 to 2 mm. It was found that the breakage of all blends follows a first-order behaviour for all feed sizes. The work index was correlated with the quartz content and the breakage rate deceleration parameter, which both showed a linear relationship. The correlation between breakage function fineness parameter and first-order rate constant also satisfied a linear relationship .The breakage parameters established from batch grinding and grindability studies indicate differences in the breakage behaviour of the three ore blends. However, the mineral liberation properties of the valuable phase in three blends show minor differences.