Evaluating the Nakajima et al. model for rectangular-aperture screens

Kruggel‐Emden

2019

Powder Technology

Screening is a technical simple but still not fully understood process step, which can be used in a wide field of applications to separate bulk materials according to their particle sizes. A severe issue in screening technologies is that particles frequently prevail in moist conditions, due to effects related to the environment, the material or the process. This is often not preventable, although it is not preferred due to attractive forces altering the screening efficiency. For the design of dry screening processes, phenomenological models and detailed particle-based simulation approaches like the discrete element method (DEM) are available. The latter method has recently been extended and validated against experiments to calculate forces caused by liquid bridges formed out between particles or walls close to each other to meet the requirements to tackle real particle systems under moist conditions. In the investigation here, batch screening under the influence of moisture involving different sized glass spheres is investigated numerically with DEM simulations and by using process models. Therein, the related subprocesses stratification and passage as well as the influence of the operating parameters and the liquid amount on the fraction retained per size class are examined. Existing phenomenological process models, which can be applied efficiently for industrial applications due to their short calculation time, are extended to represent batch screening processes under moist conditions for the first time. Therefore, a benchmark is realized in which the fraction retained per size class over time for discontinuous screening under the influence of various amounts of liquid and different mechanical agitations obtained by DEM simulations and process models is compared. In this context, the process models are first adjusted to fit related simulation results and later used in a novel method to predict the outcome of screening with different operating parameters and liquid amounts. Thereby, process models, which consider the subprocesses stratification and passage, predict screening results for process parameters requiring interpolation or extrapolation in the 2 investigated range very well. As a consequence, newly derived process models can function as prototypes to be applied in dynamic process simulation frameworks.

Section: Extended Phenomenological Screening Process Modelsmentioning

confidence: 99%

Section: Extended Phenomenological Screening Process Modelsmentioning

confidence: 99%

Extension of process models to predict batch screening results under the influence of moisture based on DEM simulations

Kruggel‐Emden

2019

Powder Technology

“…(14), so müsste h eff mit abnehmender Drehzahl zunehmen, um die experimentellen Resultate richtig wiederzugeben. 17b zeigt den Vergleich von Modellkurven mit den experimentellen Kurven, wobei die effektive Viskosität bei n = 15 000 min -1 angepasst wurde und dann für die anderen Drehzahlen übernommen wurde.…”

Section: Vergleich Der Trennkurvenunclassified

“…(14)) angreifendem Kräftegleichgewicht erörtert werden. Während bei der Siebung speziell der Einfluss der Partikelform auf das Trennverhalten untersucht wird, steht beim Abweiseradsichter die Erfassung der Partikelbewegung mittels Hochgeschwindigkeitskamera bei geringen Gutbeladungen, bei denen die Partikel/Partikel-Stöße mittels DEM erfasst werden, im Vordergrund.…”

Section: Introductionunclassified

“…Neben den probabilistischen Modellen , wie dem Modell von Dong existieren für den stationären Siebprozess auch kinetische Ansätze . In der Literatur finden sich ebenfalls Arbeiten von Dehghani sowie Nakajima und Whiten , , bei denen zusätzlich zum zeitlichen oder örtlichen Durchtritt die Partikelform berücksichtigt wird und die Ergebnisse leicht in Trennkurven umgesetzt werden können. Für die Siebung wurde die Diskrete‐Elemente‐Methode (DEM) seit den ersten kleineren diskontinuierlichen Untersuchungen zu Beginn dieses Jahrhunderts durch Shimosaka schon in verschiedenen Fällen genutzt, um einen besseren Einblick in den Prozess zu erhalten.…”

Section: Introductionunclassified

See 1 more Smart Citation

Separation Curves of Screening and Air Classifying Processes at Low Material Loadings

Spötter

Chemie Ingenieur Technik

Hennig

et al. 2017

Zur Abtrennung unterschiedlich großer Partikeln sind in der Feststoffverfahrenstechnik trockene Klassierprozesse zur Herstellung enger Fraktionen von großer Bedeutung. Um das Trennverhalten von Strömungs-und Siebklassierprozessen genauer vorhersagen zu können, wurden experimentelle Resultate mit DEM-Simulationen verglichen. Bei der Siebklassierung wurde der Einfluss der Partikelform auf den Trennprozess betrachtet, während das Partikelverhalten zwischen den Schaufeln eines Abweiseradsichters mit DEM simuliert wurde. Die Kombination aus DEM und Experiment ermöglicht es, Modellvorhersagen durch Ermittlung prozessspezifischer Parameter zu verbessern und Klassiermodelle abzuleiten, die in dynamischen Feststofffließschemasimulationen verwendet werden.For the separation of particles with different sizes, dry classification processes are of great importance for the production of narrow fractions in the solid processing technology. To be able to more accurately predict the separation behavior of flow and sieve classifying processes, experimental results were compared with DEM simulations. In screening the influence of the particle shape on the separation process was considered while the particle behavior between the paddles of a deflector wheel classifier was simulated with DEM. The combination of DEM simulation and experiment makes it possible to improve model predictions by identifying process-specific parameters and to develop classification models, which are applicable in dynamic flowsheet simulations of solids processes.

Modeling of Screening Processes with the Discrete Element Method Involving Non‐Spherical Particles

Kruggel‐Emden

2014

Chem Eng & Technol

Phenomena related to sieving of non‐spherical particles are investigated numerically in two batch apparatuses and on a horizontally aligned continuous sieve by particle‐based simulation approaches in the framework of the discrete element method. The feed material is approximated by complex‐shaped particles composed of clustered spheres. Comparisons are made with regard to the passage through the screen as well as the segregation and transportation on the screen. Results for passage are compared to data from literature, where simulations with spherical particles were performed of a laboratory‐scale sieve operated with non‐spherical quarry rock particles. Additionally, variations in screen inclination are investigated. Experimental results are matched by the simulations. A distinctive influence of particle shape on flow rates and residence times is identified.