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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. Keywords: Coal; Sample; Sampling device.

Traditionally, chain conveyors with classic structural carriers are used to transport bulk materials. The research topic of the study was how various geometric carrier shapes could affect, for example, transportation efficiency, wear or the action of forces. For this purpose, 53 alternative geometric shapes were designed and simulated in DEM. The efficiency of the geometric shapes was calculated in terms of the material transport speed, the acting compressive forces, the particulate velocities around the carriers, the wear of the carrier surface, and the resistances in carrier movement. The input parameters of the DEM model of the bulk material and conveyor were experimentally verified by the angle of repose and the validation device of the chain conveyor. Deviations of the DEM validation of material and processes in the conveyor fell in the range 0.29–3.17%. The effect of compressive forces acting on carrier I, II and V was also investigated to determine the efficiency of the processes. Because of the large number of simulations, we designed an optimal simplified model, which was validated with a 2% difference from the original and more computationally demanding model. Based on all the (measured and simulated) values, we determined the optimal design of the carriers by examining the overall efficiency. We found four alternative carrier shapes for the effective area. The article provides a comprehensive overview of the modern methods of analysis and subsequent optimization of contact geometrical surfaces for the purpose of creating prototypes with low economic requirements.

The trend of modern times is to use the increasingly more advanced technology of design, research and validation of transport, handling, storage and treatment processes using simulation methods. Programs used take advantage of computational algorithms that determine a large variety of different parameters. To extend the applicability of these programs, collaborative plug-ins (systems) are created that allow two or more simulations, analytical programs and methods to work together. In this study the cooperative plug-ins are utilised in an application dealing with the issues caused by Janssen forces/pressures of bulk material and deformation effects acting on the bottom of a bin. An examination of such issues includes observing a change in the position of a measuring plate due to the deformation of a force sensor placed at an outlet of an innovative prototype for measuring deformation effects. The experiment was evaluated and validation of discrete element method (DEM) simulation created; the force effects acting on the bottom of the bin were then transferred to a finite element method (FEM) analysis. This was followed by strength analysis of the force sensor deformation located under the outlet of the bin. A comparison was made between a real experiment and simulations that consisted of filling the bin with bulk material. Force reactions occurring at the bottom of the bin and the change of the position of the measuring plate due to the deformation of the force sensor were observed. The results show a low percentage deviation of the simulation from the real experiment. The maximum percentage deviation of the simulation from the real measurement expressed by the change of the measuring plate position due to the deformation of the force sensor is 3.70% and 0.23% when the forces acting on the measuring plate are compared using DEM. The results confirmed the assumption that the coupled DEM and FEM simulation is suitable for this type of engineering tasks. Application of the above mentioned DEM simulation and FEM analysis appears to be a universal tool for designing, modifying or upgrading of equipment for transporting, treatment and storing bulk material and includes equipment where the active member comes into contact with bulk material.

Currently, pressure from industry to streamline processes by creating their simulation models, and thus to gradual digitization is increasing. The essence of representative simulation models of bulk materials is to understand the principles and laws of the real behavior of particles. The aim of this study is therefore to find and quantify the possibilities and principles of how particles can change their position relative to other particles. The possibilities of particle displacements were expressed using their specific trajectories and work ratios, or internal friction angle values. This created a new comprehensive model of the internal friction angle of particles independent of particle size. It enables the interpretation of the determined values of the angles of internal friction of particles and its application in the field of simulations of mass and process models. The model can be used to determine the basic composition of particles in volume and the dominant ways of their mutual displacements.

Results obtained from measuring the required amount of steel abrasive material with various fragmentations, which is transported by a special kind of scraper conveyor, offers information that is useful for operators of the abrasive blast cabinets. The presented article describes an innovative methodology developed for determination of the most relevant operational parameters relating to the above-mentioned situation. The most important parameters in this case are: the optimal amount of the abrasive material, the conveying speed of the scraper conveyor and the feeding of the conveyor with regard to partial or full elimination of instable operational area. Elimination of the instable operational area is possible by means of a simple constructional modification of the given conveying system according to the results obtained from experimental investigation, which was performed using special, originally developed laboratory testing equipment. Web of Science 11 4 art. no. 1852

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 carried 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.

This paper&rsquo, 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 &ldquo, packing test&rdquo, 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 &ldquo, pilling&rdquo, method and by the rotating drum&mdash, 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&rsquo, 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 coefficient of restitution e is determined as the ratio of the final to the initial relative velocity between two moving objects after their collision. It is also one of the basic features and parameters for contact models of the discrete element method (DEM). The virtual simulation of industrial processes using DEM modelling is currently undergoing a great development both in the ways of application and in the complexity of the individual models. Therefore, input values need to be constantly refined to ensure the quality outputs of these numerical models. This article describes an experimental method of measuring the coefficient of restitution of two particles by means of a double pendulum, which presents a number of problems especially for non-spherical particles. At the same time, this article presents three options for evaluating the proposed experiment, including their comparison and description of their pros and cons. A series of experiments with particles of different sizes, shapes and materials was performed and their coefficients of restitution were determined. The presented method allows to be used on a broad scale especially for spherical particles of >5 mm, the coefficient of restitution can be determined very accurately. To some degree, this applies to non-spherical particles of mass in tens of grams and of different materials as well. Their initial coefficient of restitution can be determined with a high degree of precision, which is important for using in contact models definition. The accuracy of the contact model is dependent on accurate specification of restitution coefficient. In this study, values of the coefficients of restitution of various shapes such as wood particles, particles of maize, spruce cylindrical pellets and coal were experimentally determined.

The prerequisite for a modem approach to innovative procedures of the development of current or even newly created equipment for the transport of particulate materials is the utilization of simulation methods, such as the Discrete Element Method (DEM). This article focuses on the basic, or initial, validation of movement of material through the sample divider. The mechanical-physical properties of brown coal were measured. Based on these parameters the preliminary input values for EDEM Academic were selected, and a simulation of the dividing process was run. The key monitored parameters included density and friction coefficient. Experiments on a realistic model of the equipment were performed and assessed. The total weights of brown coal at the exit from the divider were determined for a specific speed of the divider. The aim of this task was to simulate the realistically determined weight division of the brown coal sample. The result from the DEM was compared with the results of measurement on a realistic model. Web of Science 12 1 199 194

This paper describes optimisation of a conveyor from an underground hopper intended for a coal transfer station. The original solution was designed with a chain conveyor encountered operational problems that have limited its continuous operation. The Discrete Element Modeling (DEM) was chosen to optimise the transport. DEM simulations allow device design modifications directly in the 3D CAD model, and then the simulation makes it possible to evaluate whether the adjustment was successful. By simulating the initial state of coal extraction using a chain conveyor, trouble spots were identified that caused operational failures. The main problem has been the increased resistance during removal of material from the underground hopper. Revealed resistances against material movement were not considered in the original design at all. In the next step, structural modifications of problematic nodes were made. For example, the following changes have been made: reduction of storage space or installation of passive elements into the interior of the underground hopper. These modifications made were not effective enough, so the type of the conveyor was changed from a drag chain conveyor to a belt conveyor. The simulation of the material extraction using a belt conveyor showed a significant reduction in resistance parameters while maintaining the required transport performance. Web of Science 11 3 252 246

The coefficient of thermal conductivity of particulates and powders is of great importance in the process of engineering. The prediction of thermal properties of powders using empirical equations is still difficult due to the wide range of specific attributes. This article describes a new measurement methodology for a laboratory device, which can be used to determine the thermal conductivity of bulk solids. The presented results show that the created device is very well applicable for industrial practice. It is possible to examine the coefficient of thermal conductivity depending on the sample temperature, granulometry and morphological composition, moisture content, degree of consolidation and other variables that may enter into the entire process and affect it significantly.

There is hardly any industry that does not use transport, storage, and processing of particulate solids in its production process. In the past, all device designs were based on empirical relationships or the designer&rsquo, s experience. In the field of particulate solids, however, the discrete element method (DEM) has been increasingly used in recent years. This study shows how this simulation tool can be used in practice. More specifically, in dealing with operating problems with a rotary cooler which ensures the transport and cooling of the hot fly ash generated by combustion in fluidized bed boilers. For the given operating conditions, an analysis of the current cooling design was carried out, consisting of a non-standard intake pipeline, which divides and supplies the material to two rotary coolers. The study revealed shortcomings in both the pipeline design and the cooler design. The material was unevenly dispensed between the two coolers, which combined with the limited transport capacity of the coolers, led to overflowing and congestion of the whole system. Therefore, after visualization of the material flow and export of the necessary data using DEM design measures to mitigate these unwanted phenomena were carried out.

Metal powders are components with multidisciplinary usage as their application is very broad. Their consistent characterization across all disciplines is important for ensuring repeatable and trouble-free processes. Ten metal powders were tested in the study. In all cases, the particle size distribution and morphology (scanning electron microscope-SEM photos) were determined. The aim of this work was to inspect the flow behavior of metal powders through another measured characteristic, namely the angle of internal friction. The measured values of the effective internal friction angle in the range 28.6-32.9 degrees, together with the spherical particle shape and the particle size distribution, revealed the likely dominant mode of the metal particle transfer mechanism for stainless steel 316L, zinc and aluminum powder. This third piston flow mechanism is described and illustrated in detail. The angle of internal friction is mentioned as another suitable parameter for the characterization of metal powders, not only for the relative simplicity of the determination but also for gaining insight into the method of the movement of individual particles during the flow. Web of Science 8 4 art. no. 255

This article addresses the optimization of a dosing tank using a spiral harmonic motion. The dosing tank is used for ashort-term storage of cohesive sand, which is then released into a tubular mold. Originally, a solution based on the principle of wiping the material using rotary blades and brushes was used to fill the molds. However. this method was not effective enough. This solution suffered from uneven dosing as well as a loss of material. The mold filling time ranged around 20 seconds. During the course of optimization of the dosing tank, a new design of the tank was created and external energy in aform of harmonic spiral vibrations was introduced into the system. The chosen shape of the harmonic spiral motion proved to be the most suitable for continuous emptying of the cohesive sand from the dosing tank into the tubular mold in a very short time. There was also a significant elimination of material losses. It was determined that the frequency of harmonic motion affects uniform dispensing of material fromtanks. Web of Science 12 3 149 143

This paper presents the use of new modern methods for the research of movement of material on a belt conveyor. One of the innovative methods is Particle Image Velocimetry (PIV), which was used to scan and assess the two-dimensional vector field of speed of particles on the belt conveyor. Outputs from PIV were compared to simulations of the same transport process. These simulations were performed using the Discrete Element Method (DEM). Four transport speeds of material were assessed for a real and simulative belt conveyor model. Software tracking of particle movement was used to determine and compare the trajectories of paths of particles leaving the belt conveyor drum. Validation of the DEM simulation of material movement over a belt conveyor drum using PIV provided acceptable results in the area of particle speed fields. Comparison of the particle path trajectory corresponds to the preliminary hypothesis which leads to calibration of the DEM simulation. The results and assessment of this paper were created based on validation. Web of Science 11 2 124 118

This experimental study focusses on the viability of three low-grade biofuels in small-scale biomass units of 7&ndash, 12 kW The tested materials were homemade grass pellets (gp1 and gp2) and a mixture of leaves and woody pellets (lp50) that were made without binders and completely characterized in terms of their chemical and physical properties (proximate analysis, elementary composition, ash content, flowability, etc.). The results obtained with the non-commercial fuels were compared with commercial wood pellets (wp). The viability study comprised the operational parameter influences, such as primary and secondary airflow, fuel consumption, etc., together with the impact of those parameters on the main problems in combustion (concentration and particle distribution, fouling and slagging). The results revealed that the biomass whose behavior during combustion induced fewer particulate emissions and deposits was the mixed fuel, made of 50% leaf + 50% wood pellet (lp50). Contrary to the grass-based pellets, lp50 has the possibility of being used in commercial devices with the incorporation of processes during the manufacturing that improve their properties.

The basis is a device that contains tension sensor. The output of tension sensor is associated with the input control unit. The tension sensor is connected between the two loads. The sensing signal is processed using a PC measuring card with special software. The resulting device will be part of trains. Data sensing by this device will be transmitted from the PC to the control unit.

This experimental work aims to study the viability of making use of agricultural and forest residues as an alternative to produce biofuels for commercial devices. It focuses on the feasibility of three non-commercial biomass fuels in an underfed biomass pilot combustor with a power range of 7-12 kW(th) (500-800 kW/m(2)). To carry out the investigation, the repeatability of the facility was studied using fuel with a high ash content. The relative deviations in the main parameters considered (combustion rate, gaseous emissions and particulate matter emissions) were below 10%. A feasibility analysis was performed by comparing the result obtained with a barley and leaf pellet with that obtained with a commercial wood pellet as a reference. The parameters used in this study were the operational parameters of the plant as well as the particle concentration and distribution, fouling and slagging. Comparing the results of the different fuels, it was determined that 25% leaf + 75% wood pellet (lp25) could be used as a commercial pellet with the incorporation of an additive. However, the two other fuels presented undesirable behavior characterized by high particle concentrations and notable amounts of slag. Web of Science 9 10 art. no. 1823

Given that most sensorless methods use the “flux linkage” algorithm for their control, this paper deals with possibilities to improve this sensorless method. When using the sensorless “flux linkage” method it is necessary to know not only the values of phase voltages and currents, but also the correct value of the phase resistance. During the operation of the switched reluctance motor, the value of the phase resistance is significantly changing due to the temperature dependence. Such resistance error causes an inaccurate estimation of the flux linkage. For this reason, it was desirable to implement a sensorless control algorithm for estimating phase resistance. In this paper, the experimental results of the implemented algorithm for estimating the phase resistance under the sensorless operation of a switched reluctance motor are presented. The practical implementation of control of the switched reluctance motor is carried out using a control system with a 16-bit digital signal processor. DOI: http://dx.doi.org/10.5755/j01.eee.20.5.7093