Experimental and numerical investigation of the behaviour of complex shaped particles in a model scale fluidized bed

In this study a laboratory scale fluidized bed is examined experimentally and numerically through a coupled discrete element method (DEM) and computational fluid dynamics (CFD) approach. Five differently shaped Geldart D particle groups including spheres, cylinders and cuboids are considered. Numerically obtained results for the pressure drop are in good agreement with experiments for most particles. A study on particle orientations is performed which gives valuable insight into deviations between experiments and simulations. The DEM-CFD correctly describes preferred orientations taken up by elongated particles in the fluid flow

Predictive tracking with improved motion models for optical belt sorting

Optical belt sorters are a versatile means to sort bulk materials. In previous work, we presented a novel design of an optical belt sorter, which includes an area scan camera instead of a line scan camera. Line scan cameras, which are well-established in optical belt sorting, only allow for a single observation of each particle. Using multitarget tracking, the data of the area scan camera can be used to derive a part of the trajectory of each particle. The knowledge of the trajectories can be used to generate accurate predictions as to when and where each particle passes the separation mechanism. Accurate predictions are key to achieve high quality sorting results. The accuracy of the trajectories and the predictions heavily depends on the motion model used. In an evaluation based on a simulation that provides us with ground truth trajectories, we previously identified a bias in the temporal component of the prediction. In this paper, we analyze the simulation-based ground truth data of the motion of different bulk materials and derive models specifically tailored to the generation of accurate predictions for particles traveling on a conveyor belt. The derived models are evaluated using simulation data involving three different bulk materials. The evaluation shows that the constant velocity model and constant acceleration model can be outperformed by utilizing the similarities in the motion behavior of particles of the same type

Optimal numerical design of bucket elevators using discontinuous deformation analysis

Bucket elevators are efficient machines to transport granular materials in industrial and civil engineering applications. These materials are composed of hundreds, thousands or even more particles, the global behavior of which is defined by contact interactions. The first attempts to analyze the transportation of granular materials were treated by very simple continuum methods that do not take into account these interactions, producing simulations that do not fit the experimental results accurately. Given the internal discontinuity nature of granular media, it is reasonable to use numerical methods to model their behavior, such as discontinuous deformation analysis (DDA)-a member of the discrete element method family that started to be used in the 90s to analyze similar problems. The version of DDA used in the current work treats grains as rigid circular particles with friction, damping and eventually cohesion with the objective of simulating and analyzing in detail the discharge of granular materials with bucket elevators. A deterministic computer code has been implemented and validated against simplified analytical formulae and experimental results taken from the literature. This computer code is then used to obtain optimum two-dimensional bucket geometries under specific working conditions. The optimization aims to maximize transport distance and to minimize remaining material, taking into account bucket velocity and the properties of the grains. The resulting geometries are discussed and compared against standard designs.J.L. Perez-Aparicio, R. Bravo were partially supported by the MFOM I+D (2004/38), both by MICIIN #BIA 2008-00522 and the first also by Polytechnic University of Valencia under grant PAID 05-10-2674. J.J. Gomez-Hernandez was partially supported by MICIIN #CGL 2011-23295.Pérez Aparicio, JL.; Bravo, R.; Gómez-Hernández, JJ. (2014). Optimal numerical design of bucket elevators using discontinuous deformation analysis. Granular Matter. 16(4):485-498. https://doi.org/10.1007/s10035-014-0485-5S485498164Rademacher, F.: Non-spill discharge characteristics of bucket elevators. Powder Technol. 22(2), 215–241 (1979)Koster, K.: Bulk material discharge of bucket elevators, especially high-capacity bucket elevators. [zum schuettgutabwurf bei becherwerken, insbesondere bei hochleistungsbecherwerken]. Aufbereitungs-Technik 25(8), 450–463 (1984)Koster, K.: Use of high-capacity bucket elevators in the cement industry. [zum einsatz von hochleistungsbecherwerken in der zementindustrie]. Zement-Kalk-Gips 33(3), 116–119 (1980)Koster, K.: Development and state of the art in heavy-duty bucket elevators with central chains—part 2 [entwicklung und stand der technik von hochleistungs-becherwerken mit zentralkette—teil 2]. ZKG Int. 49(4), 173–187 (1996)Koster, K.: Centrifugal discharge of bucket elevators. Bulk Solids Handl. 5(2), 449–460 (1985)Koster, K.: Problem of complete emptying of high-speed elevator buckets. Aufbereitungs-Technik 27(9), 471–481 (1986)Korzen, Z.: Mechanics of gravitational discharge of cell-less bucket wheels in reclaiming machines. Bulk Solids Handl. 7(6), 801–812 (1987)Korzen, Z., Dudek, K.: Mathematical model of the operational efficiency of a multibucket centrifugal discharge wheel [model matematyczny wydajnosci roboczego procesu kola wieloczerpakowego z odsrodkowym wysypem]. Politechnika Warszawska Prace Naukowe Mechanika 1(121), 187–199 (1989)Shi, G., Goodman, R.: Two dimensional discontinuous deformation analysis. Int. J. Numer. Anal. Methods Geomech. 9(6), 541–556 (1985)Pérez-Aparicio, J., Bravo, R.: Discrete Elements, vol. 2, pp. 41–77. Consorcio TCN (2006)Shi, G.: Discontinuous Deformation Analysis: A New Model for the Statics and Dynamics of Block Systems. Ph.D. thesis, University of California, Berkeley (1988)Moosavi, M., Grayeli, R.: A model for cable bolt-rock mass interaction: integration with discontinuous deformation analysis (DDA) algorithm. Int. J. Rock Mech. Min. Sci. 43(4), 661–670 (2006)Pérez-Aparicio, J., Bravo, R., Ortiz, P.: Refined element discontinuous numerical analysis of dry-contact masonry arches. Eng. Struct. 48, 578–587 (2013)McBride, W., Sinnott, M., Cleary, P.: Discrete element modelling of a bucket elevator head pulley transition zone. Granul. Matter 13(2), 169–174 (2011)Kruggel-Emden, H., Sudbrock, F., Wirtz, S., Scherer, V.: Experimental and numerical investigation of the bulk behavior of wood pellets on a model type grate. Granul. Matter 14(6), 681–693 (2012)Walton, O., Moor, C., Gill, K.: Effects of gravity on cohesive behavior of fine powders: implications for processing lunar regolith. Granul. Matter 9(5), 353–363 (2007)Gao, Y., Muzzio, F., Ierapetritou, M.: Optimizing continuous powder mixing processes using periodic section modeling. Chem. Eng. Sci. 80, 70–80 (2012)Shmulevich, I.: State of the art modeling of soil-tillage interaction using discrete element method. Soil Tillage Res. 111(1), 41–53 (2010)Moon, T., Oh, J.: A study of optimal rock-cutting conditions for hard rock tbm using the discrete element method. Rock Mech. Rock Eng. 45(5), 837–849 (2012)Makokha, A., Moys, M., Bwalya, M., Kimera, K.: A new approach to optimising the life and performance of worn liners in ball mills: experimental study and DEM simulation. Int. J. Miner. Process. 84(1–4), 221–227 (2007)Balevičius, R., Kačianauskas, R., Mroz, Z., Sielamowicz, I.: Discrete element method applied to multiobjective optimization of discharge flow parameters in hoppers. Struct. Multidiscip. Optim. 31(3), 163–175 (2006)Hu, L.: Gradual deformation and iterative calibration of Gaussian-related stochastic models. Math. Geol. 32(1), 87–108 (2000)Bravo, R., Pérez-Aparicio, J., Laursen, T.: An energy consistent frictional dissipating algorithm for particle contact problems. Int. J. Numer. Methods Eng. 92(9), 753–781 (2012)Belytschko, T., Liu, W., Moran, B.: Nonlinear Finite Elements for Continua and Structures. Wiley, New York (2000)Beckert, R., Föll, R.: Untersuchung der abwurfverhältnisse an kettenbecherwerken. Förden Heben 1(15), 833–836 (1966)Jaskulski, A.: Engineer-to-order approach to high speed bucket elevator design in a small-enterprise. Appl. Eng. Agric. 24(5), 545–557 (2008)Beverley, G.: Mechanics of High Speed Bucket Elevator Discharge. Ph.D. thesis. University of Newcastle (1986)Beverley, G., Roberts, A., Hayes, J.: Mechanics of high speed elevator discharge. Bulk Solids Handl. 3(4), 853–859 (1983)Korzen, Z., Dudek, K.: Reclaiming with a high-speed bucket wheel with centrifugal discharge. Bulk Solids Handl. 11(3), 615–626 (1991)Bravo, R., Pérez-Aparicio, J., Laursen, T.: An enhanced energy conserving time stepping algorithm for frictionless particle contacts. Int. J. Numer. Methods Eng. 85(11), 1415–1435 (2011)Jaskulski, A.: Methodology of Multi-Criteria Optimization of Appliances for Vertical Grain Transportation. Ph.D. thesis. Warsaw University of Technology (1992

A laboratory-numerical approach for modelling scale effects in dry granular slides

Granular slides are omnipresent in both natural and industrial contexts. Scale effects are changes in physical behaviour of a phenomenon at different geometric scales, such as between a laboratory experiment and a corresponding larger event observed in nature. These scale effects can be significant and can render models of small size inaccurate by underpredicting key characteristics such as ow velocity or runout distance. Although scale effects are highly relevant to granular slides due to the multiplicity of length and time scales in the flow, they are currently not well understood. A laboratory setup under Froude similarity has been developed, allowing dry granular slides to be investigated at a variety of scales, with a channel width configurable between 0.25-1.00 m. Maximum estimated grain Reynolds numbers, which quantify whether the drag force between a particle and the surrounding air act in a turbulent or viscous manner, are found in the range 102-103. A discrete element method (DEM) simulation has also been developed, validated against an axisymmetric column collapse and a granular slide experiment of Hutter and Koch (1995), before being used to model the present laboratory experiments and to examine a granular slide of significantly larger scale. This article discusses the details of this laboratory-numerical approach, with the main aim of examining scale effects related to the grain Reynolds number. Increasing dust formation with increasing scale may also exert influence on laboratory experiments. Overall, significant scale effects have been identified for characteristics such as ow velocity and runout distance in the physical experiments. While the numerical modelling shows good general agreement at the medium scale, it does not capture differences in behaviour seen at the smaller scale, highlighting the importance of physical models in capturing these scale effects

Experimental and numerical investigation of the behaviour of complex shaped particles in a model scale fluidized bed

In this study a laboratory scale fluidized bed is examined experimentally and numerically through a coupled discrete element method (DEM) and computational fluid dynamics (CFD) approach. Five differently shaped Geldart D particle groups including spheres, cylinders and cuboids are considered. Numerically obtained results for the pressure drop are in good agreement with experiments for most particles. A study on particle orientations is performed which gives valuable insight into deviations between experiments and simulations. The DEM-CFD correctly describes preferred orientations taken up by elongated particles in the fluid flow

A Study on the Role of Reaction Modeling in Multi-phase CFD-based Simulations of Chemical Looping Combustion

Chemical Looping Combustion is an energy efficient combustion technology for the inherent separation of carbon dioxide for both gaseous and solid fuels. For scale up and further development of this process multi-phase CFD-based simulations have a strong potential which rely on kinetic models for the solid/gaseous reactions. Reaction models are usually simple in structure in order to keep the computational cost low. They are commonly derived from thermogravimetric experiments. With only few CFD-based simulations performed on chemical looping combustion, there is a lack in understanding of the role and of the sensitivity of the applied chemical reaction model on the outcome of a simulation. The aim of this investigation is therefore the study of three different carrier materials CaSO4, Mn3O4 and NiO with the gaseous fuels H2 and CH4 in a batch type reaction vessel. Four reaction models namely the linear shrinking core, the spherical shrinking core, the Avrami-Erofeev and a recently proposed multi parameter model are applied and compared on a case by case basis

A Study on the Role of Reaction Modeling in Multi-phase CFD-based Simulations of Chemical Looping Combustion Impact du modèle de réaction sur les simulations CFD de la combustion en boucle chimique

Chemical Looping Combustion is an energy efficient combustion technology for the inherent separation of carbon dioxide for both gaseous and solid fuels. For scale up and further development of this process multi-phase CFD-based simulations have a strong potential which rely on kinetic models for the solid/gaseous reactions. Reaction models are usually simple in structure in order to keep the computational cost low. They are commonly derived from thermogravimetric experiments. With only few CFD-based simulations performed on chemical looping combustion, there is a lack in understanding of the role and of the sensitivity of the applied chemical reaction model on the outcome of a simulation. The aim of this investigation is therefore the study of three different carrier materials CaSO4, Mn3O4 and NiO with the gaseous fuels H2 and CH4 in a batch type reaction vessel. Four reaction models namely the linear shrinking core, the spherical shrinking core, the Avrami-Erofeev and a recently proposed multi parameter model are applied and compared on a case by case basis. La combustion en boucle chimique (Chemical Looping Combustion) est une technologie de combustion efficace permettant le captage in situ du CO2 pour des charges gazeuses ou solides. Dans l’optique du développement et de l’extrapolation du procédé, la CFD est un outil de simulation à fort potentiel qui s’appuie notamment sur des modèles cinétiques pour décrire les réactions gaz-solide. Ces modèles décrivant les réactions sont généralement assez simples pour limiter les temps de simulation et sont obtenus à partir d’expérimentations en thermobalance. Il y a encore peu de travaux de modélisation CFD du procédé CLC et il est difficile d’estimer l’importance du modèle décrivant les réactions chimiques sur les résultats des simulations. Le but de ce travail est donc d’étudier la combustion de charges gazeuses H2 et CH4 dans des réacteurs en batch en considérant 3 matériaux transporteurs d’oxygène (CaSO4, Mn3O4 et NiO). Quatre modèles cinétiques (le modèle à coeur rétrécissant linéaire, le modèle à coeur rétrécissant sphérique, le modèle d’Avrami-Erofeev et un modèle plus récent multi-paramètres) ont été utilisés et comparés au cas par cas