DEM investigation of the influence of particulate properties and operating conditions on the mixing process in rotary drums: Part 1-Determination of the DEM parameters and calibration process

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.Web of Science82art. no. 22

Analysis and optimization of material flow inside the system of rotary coolers and intake pipeline via discrete element method modelling

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'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.Web of Science117art. no. 184

DEM investigation of the influence of particulate properties and operating conditions on the mixing process in rotary drums: Part 2-Process validation and experimental study

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.Web of Science82art. no. 18

Calibrating polypropylene particle model parameters with upscaling and repose surface method

The discrete element method (DEM) is a computational technique extensively utilized for simulating particles on a large scale, specifically focusing on granular materials. Nonetheless, its implementation requires a substantial amount of computational power and accurate material properties. Consequently, this study delves into an alternative approach referred to as volume-based scaled-up modeling, aiming to simulate polypropylene particles using DEM while mitigating the computational burden and regenerating new material properties. This novel method aims to reduce the CPU time required for the simulation process and represent both the macro mechanical behavior and micro material properties of polypropylene particles. To accomplish this, the dimensions of the polypropylene particles in the DEM simulation were magnified by a factor of two compared to the original size of the prolate spheroid particles. In order to determine the virtual micro material properties of the polypropylene particles, a calibration method incorporating the design of experiments (DOE) and repose surface methodology was employed. The predicted bulk angle of repose (AOR) derived from the upscaled DEM parameters exhibited a remarkably close agreement with the empirical AOR test, demonstrating a small relative error of merely 1.69 %. Moreover, the CPU time required for the upscaled particle model proved to be less than 71 % of that necessary for the actual-scale model of polypropylene particles. These compelling results confirm the effectiveness of enlarging the particle volume used to calibrate micro-material properties in the Discrete Element Method (DEM) through the DOE technique. This approach proves to be a reliable and efficient metho

Modelling of Bulk Material Flow Properties

Flow property testing is important in the design of handling equipment for bulk solids and the Jenike shear tester is a common and reliable method for ensuring flow from hoppers under the force of gravity alone. The Jenike shear test procedure has various stages and is known to have issues with operator dependency, questions have also been raised regarding the stress state within the shear cell. Currently the data for high pressure flow functions, which are applicable to large capacity storage facilities, are extrapolated from low pressure test data using a 3-parameter equation. Very little literature is provided to support the use of the 3-parameter equation and most shear testing devices are limited to major consolidation stresses of 100 kPa