Refractory linings in ladle metallurgy are heat-resistant materials that protect ladles from high temperatures and aggressive chemicals during metal processing. They must withstand mechanical wear, chemical corrosion, and thermal shocks. The most common lining materials are MgO and CaO bricks, known for their high temperature resistance and good durability against both acidic and basic slags. This process generates significant amounts of waste due to wear and spalling during operation. While some by-products are already being reused, a large portion is still landfilled. This study focuses on the development of a new type of refractory material produced using direct ink writing. For this purpose, MgO refractory waste (MGW) was mixed with either B1M or IBV kaolins. A total of 12 mixtures with the addition of 50, 60, 70, 80, and 90 wt% MGW were prepared. All materials were characterized using chemical, phase, granulometric, and scanning electron microscopy analyses. Rheological properties of the mixtures were studied. For each sample, two firing temperatures (1000 degrees C and 1200 degrees C) were tested. Compressive strength, bulk density, apparent porosity, and water absorption of the fired samples were evaluated.

This study introduces a comprehensive calibration technique for discrete element method (DEM) simulations. Its focus is on particles smaller than 2 mm and this showcase shows comparison between spherical and polyhedral particle shape calibration. Very fine powders or particulate materials with small particles are usually calibrated with upscaling. Unfortunately, some applications are dependent heavily on a quite precise particle size range, such as abrasion, crushing, pneumatic conveying, feeding, and dosing. Traditional DEM simulations often rely on spherical or multi-spherical particle models, which lack the precision needed, particularly due to the surface waviness introduced in the latter case. This limitation impacts dynamic industrial applications like mixing, hopper discharge, and abrasion. To address this gap, we present a comparative calibration approach for spherical and polyhedral particles, using silica sand as the test material. The calibration combines static and dynamic parameters such as rolling resistance, particle-to-particle restitution, and wall friction, validated through experiments on a powder flow calibration stand. Results revealed significant differences in flow dynamics, highlighting the enhanced realism of polyhedral models despite increased computational demands. This work provides a comprehensive framework for DEM calibration of fine particulate materials, specifically validated for particle sizes between 400 and 1500 µm, improving simulation accuracy and extending applicability across various industrial processes.

In the context of the circular economy and raw material sustainability, it is essential to explore alternative raw materials for the development of formulations with optimized physical and mechanical properties. This study focused on the rheological characterization of refractory ceramic waste blended with clay, aiming to optimize compositions for 3D printing. A mixture exhibiting the highest strength and resistance to shear stress was identified, making it a promising candidate for use in complex structural components. Mixtures with lower strength proved suitable for less demanding applications with simpler geometries. The presence of finer particles and lower bulk density of the filler led to increased viscosity and critical shear stress, contributing to higher mechanical stability. In contrast, mixtures with higher bulk density exhibited lower viscosity and reduced resistance to mechanical loading, despite demonstrating higher elasticity within the linear viscoelastic region. These findings represent a significant contribution to the effective selection and design of refractory ceramic formulations for additive manufacturing, tailored to the specific functional requirements of targeted applications. The research also demonstrated the feasibility of using waste-derived materials as feedstock for Direct Ink Writing (DIW) 3D printing of refractory ceramics, supporting both material circularity and sustainable manufacturing practices.

The sensitivity analysis investigates the effect of particles shape (made by sphere, multi-spheres or polyhedral) for various contact force models on the calibration procedure via ring shear test. Experimental shear tests were performed using a Schulze Ring Shear Tester RST-01 with spherical and cubic particles. Pre-shear stress and vertical lid position behaviour were observed using Hertz-Mindlin and Linear Spring contact models. The findings confirm the necessity to include not only the shear force but also the compress behaviour of the particles in the shear test calibration. The results clearly indicate that the position of the shear lid provides discrete element method users with an important overview of the fundamental deformation behaviour and particle displacement during the pre-shear process. The results reveal differences between particle and contact force models considering the changes due to increased shear velocity useable for different representation of real-life particulate materials. The research is intended to provide DEM modellers with general information on which parameters are affected by changing the input data for each contact force model and particle shape. These insights enhance calibration procedures in both industrial and academic settings serving as a foundation for not only time optimizing DEM models and improving their accuracy.

Solid recovered fuel (SRF) is highly suited for thermal treatment, but its low bulk density and other physical properties limit the number of compatible energy systems that can effectively process it. This study presents the findings on SRF energy utilisation, focusing on mechanical treatment and a novel approach to its small-scale co-combustion with certified softwood (SW) pellets and catalytic flue gas control. In this study, the processes of certified SRF feedstock characterisation and mechanical treatment were thoroughly examined. Unique SRF pellets of proper mechanical properties were experimentally prepared for real-scale experiments. Mechanical and chemical properties, such as mechanical resilience, toughness, moisture and heating value, were examined and compared with standard SW A1 class pellets. The prepared SRF pellets possessed an energy density of 30.5 MJ∙kg–1, meeting the strict requirements from multiple perspectives. The influence of pelletisation temperature on pellet quality was investigated. It was found that increased resilience and a water content of 1.59% were achieved at a process temperature equal to 75 °C. Moreover, the moisture resilience was found to be significantly better (0.5 vs. 14.23%) compared with commercial SW pellets, while the hardness and durability values were reasonably similar: 40.7 vs. 45.2 kg and 98.74 vs. 98.99%, respectively. This study demonstrates that SRF pellets, with their improved mechanical and energy properties, are a viable alternative fuel, from a technical standpoint, which can be fully utilised in existing combustion units.

This work focuses on whether the used mixing technology can affect the flow properties of the created mixture. For these purposes, 3 test mixtures were created from the same materials only with a different mixing technology. Their flow properties were subsequently measured on these mixtures in the laboratory. These properties were compared with each other. The influence of the mixing technology on the flow properties was demonstrated. Differences were mainly shown by the flow function and the values of the angle of external friction. For internal friction, the influence of mixing technology was not significant.

Abstract The paper deals with the economic optimisation of ferrite powder preparation during producing hard ferrite magnets. The magnetic properties of ferrites are investigated by replacing feedstock and reducing calcination temperature and particles in the order of tens of microns. The granulates about 8–10 mm in size were calcined for 2 h in the temperature range from 1100 °C to 1300 °C and additionally crushed and milled to an average particle size of about 80–90 µm. The scanning electron microscopy images confirmed the agglomerates of particles with different shapes and sizes in tens of µm. The X-ray diffraction measurements revealed that, besides the SrFe12O19 and BaFe12O19 phases, there was also the presence of 2–39% hematite. The highest values of maximum energy product (BH)max = 930 J/m3 and remanent magnetic induction Br = 72.8 mT were obtained at a calcination temperature of 1300 °C. The Henkel plots confirmed the presence of exchange-coupling and dipolar magnetic interactions at lower and higher magnetic fields, respectively. The strength of interactions was also dependent on the calcination temperature. Replacing strontium with barium led to a deterioration of the magnetic parameters, which were optimal at a lower calcination temperature (1100 °C). This phenomenon was partly overcome by reducing the mean particle size of Ba-based hexaferrites to 45–50 µm.

The study investigates the effect of particle shape representation with various contact models on the calibration procedure via shear test. Experimental shear tests were performed using a Schulze Ring Shear Tester RST-01 using spherical and cubic particles. Pre-shear stress and vertical lid position were used for calibration. Hertz-Mindlin and Linear Spring contact models behaviour trends for preshear, vertical lid position, coordination number, porosity and particle shift angle were observed. The changes of the shear zone for different input parameters are show. The findings confirmed the necessity to observe not only the shear force but also the compression behaviour of the particles in the shear test calibration. The results clearly indicate that the position of the shear lid provides DEM users with an overview of the fundamental deformation behaviour during the shear process. The results highlighted fundamental differences between particle models, considering the changes in kinematics due to increased shear rate. The research is intended to provide DEM modellers with general information on which parameters are affected by changing the input data for each contact model and particle shape. These insights can enhance calibration procedures in both industrial and academic settings, serving as a foundation for optimizing DEM models and improving their accuracy.

This paper describes the formation of the natural repose angle of non-cohesive bulk materials. The repose angle of particulates α is the angle between the tangent plane to the surface of the slope and the solid base. The paper presents a thermodynamic theory for the formation of the most energy-efficient natural slope α≈ 30 ^∘ that can be found very often both in nature and industry. The theoretical foundation is based on Janssen theory of the statistical distribution of vertical and horizontal stress and adds its own consideration about dissipative work during the movement of material as a slope is being formed. The presented model is expanded to include an experimental part describing four methods of creation of a natural repose angle on three sand samples. The experiments performed demonstrated the validity of the submitted theory and the thermodynamic model with certain deviations derived from the essence of the experiments performed. These experiments explain a frequent occurrence of natural slopes with a repose angle of around 30 ^∘ .

Shear cell tests are now commonly applied in particulate calibration procedures for the discrete element method. Usually, only the shear stresses at the shear plane in the particle bed are examined in short-time instances. This work aimed to find the regularities between the internal friction angle, the vertical position of the shear lid, and the rearrangements of particles in the layers during the shear test with the time instance duration of tens to hundreds of seconds. The Schulze RST Ring Shear Tester was used to compare real experiments to numerical DEM models of non-cohesive materials. The shear tests were investigated for different contact models and DEM input parameters. We also simultaneously monitored the overall specimen stiffness, material dilatancy during calibration, and shear stress. Particle bed stiffness increases with increasing shear modulus and coefficient of static friction for two contact models. The internal friction angle, which is a bulk property of the material determined by a set of particle properties, determines the ability (or resistance) to make displacements of rigid non-deformable particles in the shear testing process. The angle of the resultant of the vector of particle motion in space from the horizontal plane correlates with the angle of internal friction (at each location of the shear cell).

Due to relatively new solutions in the field of 3D printing, there are few studies on the possibility of using printed elements in measuring devices. The aim of this study was to investigate the possibility of using instruments made by material extrusion 3D printing method for measurement of selected mechanical-physical properties of bulk materials. Study explores the feasibility of measuring bulk material mechanical-physical properties when there are obstacles for printing original or modified measuring instruments in common practice. To achieve the goals a series of experiments such as Schulze's ring shear tests, Freeman's FT4 shear tests, compressibility tests, and Flow Rate and Stability tests were performed with use of original aluminium or steel made instruments and 3D printed instruments from polylactic acid and acrylic styrene acrylonitrile materials, using lunar regolith simulants LHS-1 and LMS-1 produced by CLASS Exolith Lab as a sample material. The results obtained from tests with original and printed instruments were then compared. The compared values of tests showed applicability of the 3D printed measuring instruments in a 5% range of measurement deviation. The biggest advantages of the 3D printed measuring instruments were the lower weight, the ability to print on the spot, to replace a damaged part with a new 3D printed part on-demand if extremely fast results are needed or due to the logistical unavailability, customization of the standardized tests for better understanding the behaviour of the particulate materials, and cheaper manufacturing costs.

Computer simulation of bulk materials behavior, including comminution and fragmentation, using DEM has been growing fast, recently.One of the important tasks to get the reliable simulation results is to provide proper materials and contact parameters, which need to be determined in a series of laboratory experiments.For comminution simulation the additional parameters describing the breakage probability and breakage functions are necessary.While some simulation parameters are available in the literature for brittle materials, valid data are lacking for biomaterials such as cereal, rice or corn grains, especially for comminution parameters.The aim of this study was to present the calibration approach and determination of materials, contact, interaction and breakage parameters for grainy biomaterials.The calibration process was done for rice and corn grains.The calibration approach consists of grains size distribution and shape characterization, friction and restitution coefficient determination, and breakage probability description.Based on the results of the experiments, the models were created in the DEM software.The result was the set of calibrated parameters for rice and corn grains.

Currently, emphasis is placed on the efficiency of process technology in the production of energy. Large energy corporations are forced to develop new and optimize existing technologies to reduce emission limits. In coal and biomass combustion technologies, it is important to continually monitor and evaluate the quality of input material. A sampling device is used to obtain a representative sample of the fuel from the continuous conveying process. In this research work, the effect of setting the operating conditions of the rotating sampling device for coal, which is intended for combustion, is investigated. From the operating tests, we found that the different settings of the sampling device (velocity, dimensional parameters) influence the quality and quantity of a representative sample of coal taken from the belt conveyor of the technological line.

Cooling is an important process during the production of pellets (as post-treatment). The pellet cooling process significantly impacts the quality of the pellets produced and the systematic use of energy. However, the cooling systems currently in use sometimes encounter technical problems, such as clogging of the perforated grids (sieves), the discharge hopper, or pellet degradation may occur. Therefore, a prototype of a new pellet cooling system using a vibrating feeder was tested. The aim of the study is to present a new variation of pellet cooling system using spiral vibration cooler as a possible solution next to a counterflow cooler. The presented system was tested (critically evaluated and discussed) in two design variants. The first variant consists in cooling by chaotic movement of the pellets. The second is then in combination with the chaotic movement of the pellets together with the action of intense air flow using specially placed air hoses. All tests involved pelletization of rapeseed straw. It was found that both cooling system variants could, realistically, be used. However, the variant with an intense air flow was more energy-intensive, a factor which is, however, offset by the higher quality of the pellets. No negative impact of vibrations to pellets quality was occur. Studies provide insight into new usable technologies that do not reduce the efficiency of the process as a result of grate clogging.

Dalton hoard is an experimental device invented by Francis Dalton in 1873. A particle thrown into the Dalton board moves down due to gravity and bounces off pegs along its path down. Galton claimed it to be a random system, in which each particle has equal probability of moving to the left or right side of each peg it bounces off. It means that the final distribution of particles in the bottom part of the device shall approximate the shape of the binomial curve or Gaussian distribution. In this work, the behaviour of particles when moving through the Galton hoard using the discrete element numerical method was studied. The objective was to verify if the result of the simulation with calibrated input parameters of the contact model shows binomial distribution of particles in the bins in the bottom part of the Gallon board as in the case of real experiments with various constructions and versions of Galton hoards.

This paper’s goal was to select methods and a calibration procedure which would lead to the determination of relevant parameters of a discrete element method (DEM) and virtual material creation. Seven particulates were selected with respect to their shape (spherical and non-spherical), size and density. The first calibration experiment involved “packing test” to determine the shape accuracy and bulk density of virtual packed particulates. The series of simulations were compared with real experiments, and the size, shape and density of virtual particles were optimized. Using three apparatuses, the input parameter values were experimentally determined for a contact model that defines the behavior of particulates in DEM simulations. The research part of the paper examines the influence of factors such as particle number; pile formation method; and the method of evaluation of the angle of repose on the process of the calibration of virtual material. The most reproducible results were achieved by the “pilling” method and by the rotating drum—both evaluated by the geometric method. However, it is always advisable to make an overall visual comparison of the slope shape between the calibration simulation and the experimental curves. The bowl’s diameter to particle size ratio should be greater than 25, and the calibration experiment should contain approximately 4000 particles to ensure representative results during angle of repose calibration experiment.

The paper aims to summarize a modern approach to design of new or optimization of the existing vibration technologies, respectively. The optimization method consists of several necessary phases, which need to take place with utmost precision. In the first phase, a study of the current state of the solved problem is caned out along with analysis of the used bulk material performed as a measurement of mechanical -physical properties. Furthermore, a model of a new structural solution is designed and subjected to a number of simulation experiments using the DEM method. The parameters obtained from the performed simulations are used for manufacturing the vibration separator prototype including the design of a suitable vibration source. Operational tests of the vibration separator are carried out followed by putting the technology into operation.

The process of homogenization of particulates is an indispensable part of many industrial processes, and, therefore, it is necessary to pay a special attention to this area and develop it. This paper deals with a complex study of homogenization of particulate matters in a rotary drum in terms of shape, size, and density of particles. In addition, the influence of operating parameters, such as drum filling capacity, rotational speed, and drum filling pattern are also investigated. Studies of reproducibility of discrete element method simulations, effects of rotary drum sizes or effects of drum volumetric filling to the mixture homogeneity index were also carried out. In general, the least satisfactory values of the homogeneity index resulted from the mixing of particles with different densities. The dominating factor of homogenization was the drum filling-up degree. The course of the homogeneity index in 140, 280, and 420 mm drums was very similar and after five revolutions of the drum, identical values of the homogeneity index were achieved for all the drum diameters. The optimal drum filling-up degree is at 40–50% for the spherical particles and 30–40% for the sharp-edged particles. The repeatability of simulations showed the maximum relative standard deviation of the homogeneity index at 0.6% from ten simulation repetitions with the same parametric conditions.