Granular size segregation in silos with and without inserts

Abstract

The storage of granular materials is a critical process in industry, which has driven research into flow in silos. Varying material properties, such as particle size, can cause segregation of mixtures. This work seeks to elucidate the effects of size differences and determine how using a flow-correcting insert mitigates segregation during silo discharge. A rotating table was used to collect mustard seeds discharged from a three-dimensional (3D)-printed silo. This was loaded with bidisperse mixtures of varying proportions. A 3D-printed biconical insert was suspended near the hopper exit to assess its effect on the flow. Samples were analysed to determine the mass fractions of small particle species. The experiments without the insert resulted in patterns consistent with segregation. Introducing the insert into the silo eliminated the observed segregation during discharge. Discrete element method simulations of silo discharge were performed with and without the insert. These results mirrored the physical experiment and, when complimented with coarse graining analysis, explained the effect of the insert. Most of the segregation occurs at the grain–air free surface and is driven by large velocity gradients. In the silo with an insert, the velocity gradient at the free surface is greatly reduced, hence, so is the degree of segregation.

DEM Modelling of Segregation in Granular Materials: A Review

“…Parameters from literature. Many DEM studies on segregation have taken either all or merely a selection of the parameters from the literature (Asachi et al, 2021;Chibwe et al, 2020;Cliff et al, 2021;Hong et al, 2021;Ketterhagen et al, 2007Ketterhagen et al, , 2009Ketterhagen and Hancock, 2010;Kou et al, 2013Kou et al, , 2015Kou et al, , 2018Kou et al, , 2019Liao et al, 2023;Mandal and Khakhar, 2019;Tian et al, 2022;Wu et al, 2013;Xu et al, 2018bXu et al, , 2021You et al, 2016;Yu et al, 2018;Yu and Saxén, 2010, 2012Zhang et al, 2021;Zhao and Chew, 2020a). This approach has the same shortcoming as the previous group, since the parameters are obtained from resources that have not conducted calibration.…”

“…Sampling spaces composed of 24 cuboid-shaped cells inside the hopper (Combarros Garcia et al, 2016) The discontinuous start-stop sampling method (Standish and Kilic, 1985) has been mostly adopted (Ketterhagen et al, 2007;Yu and Saxén, 2010; Including a number of sampling boxes at the bottom to capture the trajectory segregation of materials (Bhattacharya and McCarthy, 2014;Mio et al, 2008bMio et al, , 2009Mio et al, , 2010Mio et al, , 2012Yu and Saxén, 2012) Heaps are divided into a number of sub-regions in the horizontal and/ or vertical direction (Li et al, 2017;Mio et al, 2020;Qiu and Pabst, 2022;Terui et al, 2017;You et al, 2016) Using rotating sampling table with pie slicing configuration (Cliff et al, 2021) Measuring mass flow rate of fine particles using Copley flowability tester BEP2 model (Barik et al, 2023) Sampling in the horizontal and vertical direction of the sinter cooler (Izard et al, 2021) Sampling box in QPM segregation tester (Combarros et al, 2014) Non-invasive Taking pictures and counting the number of different components (Yu et al, 2018) Colouring equal-sized components and using image analysis to analyse segregation (Combarros et al, 2014) Taking pictures and using image processing to measure the fraction of components (Alizadeh et al, 2017;Wang et al, 2018) for "flow behaviour" on the bulk level, it cannot necessarily prove the validity of the model for segregation. In other words, to validate the models for segregation, component fractions are required to obtain local information and assess segregation.…”

The Influence of Moisture on the Frequency Spectrum of Time Varying Mass Engineering Structure

“…The obtained frequency spectrum of each mode is shifted to the 'baseband' by mixing with an exponential tune to the respective estimated centre frequency. Finally, the bandwidth is estimated through the H 1 Gaussian smoothness of the demodulated signal (the squared L 2 -norm of the gradient), resulting in a constrained variational problem shown in Equation 6.…”

“…In silo operations, it is in the best interest of the operator to empty and refill the silo as quickly as possible to maximize production throughput. In all cases, the granular particles inside the silo are unrestrained, differ in size and shape [1], and the moisture content ratio [2] can vary between seasons, especially if the stockpile is subjected to the weather. To our knowledge, how particle size, shape, and moisture content ratio dynamically interact with the overall silo structure has not been studied in detail because the silo structure has always been assumed to be infinitely rigid as suggested by the fundamental silo load theory, Janssen's silo theory, formulated in 1895.…”

Dynamical behaviour of non-spherical grains in granular rapid flows

“…Most of the research on silos and hoppers have used spherical particles, especially the numerical studies. Many of these studies investigated the influence of particle size on the discharge process [52][53][54][55][56][57][58][59]. Spheres have a perfectly round shape, the most ideal shape a particle can have and it is also easy to generate and simulate then in numerical codes.…”