Chapter 6 Wet Grinding in Stirred Media Mills

Kwade, Arno; Schwedes, Jörg

doi:10.1016/s0167-3785(07)12009-1

Cited by 70 publications

(63 citation statements)

References 25 publications

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“…For that purpose, simulations were run, with and without product particles between the beads. The accumulated plastic strain for the simulation of the situation with the product particles between grinding beads reaches 0.057, while this value is 0.01 in the case without the product particles, indicating that the presence of product particles increases the accumulated damage on the surface of the grinding beads, and thus, leads to higher wear of the beads, as observed experimentally by Kwade [5].…”

Section: Micro-impactmentioning

confidence: 52%

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Advanced M5 Modeling of Stirred Media Milling

Rodič

Langus

2010

Chem Eng & Technol

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The numerical tools that are integrated in the M5 model of stirred media milling include the Discrete Element Method (DEM) for macroscale simulations, Finite Element Method (FEM) based Fluid-Structure Interaction (FSI) for mesoscale simulations and combined FEM and DEM for microscale simulation of grinding bead impacts. Statistical analyses of the impacts derived by DEM at a macro-level are used for optimization of the mill design and its operational parameters. The thermo-mechanical and hydrodynamical phenomena that occur at the mesoscopic FSI scale between the approaching grinding beads are analyzed by FEM for various impact scenarios with different combinations of impact velocity, direction and rotation as a function of macroscopic mill design. Therefore, the M5 concept takes into account global-local coupling so that the influences of macroscopic design can be derived at nano levels by downscale coupling of influential phenomena. IntroductionThe basic principle in scales separation that allows explicit modeling of the stirred media milling process is shown in Fig. 1. On the macroscale, DEM was used to simulate the motion of thousands of grinding beads in a grinding chamber. Statistical analysis of the bead trajectories yields several interesting impact statistics, e.g., distribution of impact velocities, etc., that are very difficult to obtain with other observation methods. Statistical results strongly depend both on the design of the mill and the operating conditions. Thus, they can be used to optimize both mill design and operation.Mesoscale simulations of motion and impacts of beads in a fluid medium were undertaken using a dedicated Fluid-Structure Interaction (FSI) code based on FEM [1]. The experimental values of the coefficient of restitution (COR), i.e., the ratio of the normal velocity of a bead after and before the impact, and which was experimentally measured as described by Yang and Hunt [2], were reproduced by semi-analytical modeling of the interaction force between two beads moving in a liquid medium.Macro-and mesoscale simulations were performed primarily to retrieve the boundary conditions for microscale simulations. Typical impact scenarios (velocity and angle) were taken from the impact statistics. These scenarios were then used as boundary conditions in the microscale simulations. On the microscale, irregularly shaped product particles were inserted at different locations between two approaching bead surfaces. All expected events, i.e., particle trapping and breakage as well as particles being washed away, were observed. Product particles were modeled using FEM with plastic material properties in order to allow deformation and damage accumulation.M5 numerical problems are inherently difficult to solve with a single numerical tool as they are often specialized for one particular class of problems, and thus, the need to integrate several different numerical tools in solving M5 problems is unavoidable. In the present work, DEM and FEM simulations were performed with the DEM software system ...

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Section: Micro-impactmentioning

confidence: 52%

“…The process parameter that controls the velocity of grinding spheres is called tip speed [5] and is defined as the highest speed on the surface of the stirrer. The bead impact velocity distributions for the rotational mill with different filling ratios and with a tip velocity of ca.…”

Section: T Rodič J Langusmentioning

confidence: 99%

Advanced M5 Modeling of Stirred Media Milling

Rodič

Langus

2010

Chem Eng & Technol

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“…The optimal bead diameter and the volume fraction of bead loading were obtained from the literature and they were respectively: 0.5 mm and 60% [6]. Additional factors contributing to the milling performance such as the stress number (SN) and the stress intensity (SI) were calculated using the stress model developed by Kwade and Schwedes [18]. This model which is based on stress energies and bead collision frequencies in the field of microorganisms describes the cell disruption process using two numbers: SN, the stress number which is the number of media contact and SI, the stress intensity of these events.…”

Section: Cell Disruption Phasementioning

confidence: 99%

Extraction of astaxanthin from microalgae: process design and economic feasibility study

Zgheib

Saade

Khallouf

et al. 2018

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. In this work, the process design and the economic feasibility of natural astaxanthin extraction from Haematococcus pluvialis species have been reported. Complete process drawing of the process was first performed, and then the process was designed including five main steps being the harvesting process, the cell disruption, the spray drying, the supercritical CO2 extraction and the anaerobic digestion. The major components of the facility would include sedimentation tanks, a disk stack centrifuge, a bed miller, a spray dryer, a multistage compressor, an extractor, a pasteurizer and a digester. All units have been sized assuming a 10 kg/h of dried biomass as a feedstock to produce nearly 2592 kg of astaxanthin per year. The investment payback time and the return on investment were all estimated for different market prices of astaxanthin. Based on the results the production process was found to become economically feasible for a market price higher than 1500$/Kg. Also, a payback period of 1 year and an ROI equal to 113% was estimated for an astaxanthin market price equal to 6000$/Kg.

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“…Neben der erzeugten Produktfeinheit spielt auch die Produktmenge pro Zeiteinheit eine wichtige Rolle. Die laufenden Kosten für eine Zerkleinerung mittels Rühr-werkskugelmühle werden durch die folgenden Punkte beschrieben [1]…”

Section: Wirtschaftlichkeitunclassified

“…Die übrigen Kosten, die bei einem Zerkleinerungsprozess anfallen, bleiben hier unberücksichtigt [1]. Die spezifischen Kosten K m (I/kg Produktpartikel) setzen sich aus der Summe der Einzelkosten für Mahlkörper und Energie zusammen und sind jeweils auf ein kg Produkt bezogen: …”

Section: Wirtschaftlichkeitunclassified

Einsatz unterschiedlicher Rührwerkskugelmühlen für die Erzeugung von Nanopartikeln

Breitung‐Faes¹,

Kwade²

2007

Chemie Ingenieur Technik

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EinleitungNanopartikel erschließen aufgrund ihrer außer-gewöhnlichen Eigenschaften immer mehr Anwendungsfelder in den unterschiedlichsten Industriezweigen. Außer durch chemische Synthese (Bottom-up-Verfahren) besteht die Möglichkeit, Nanopartikel durch Nasszerkleinerung in Rührwerkskugelmühlen (Top-downVerfahren) zu erzeugen. Zum Beispiel konnte Schmelzkorund in einer Rührwerkskugel-mühle in wässriger Phase auf unter 10 nm zerkleinert werden, wenn die Suspension elektrostatisch stabilisiert wird [2 -5, 7]. Schwachpunkte der Nanozerkleinerung sind der relativ hohe Energiebedarf und der Mahlkörperver-schleiß, die eine stärkere Akzeptanz dieser Dabei wird ersichtlich, dass die Zerkleinerung mit abnehmender Mahlkörpergröße energetisch günstiger wird, da die Beanspruchungsenergie größer ist als die optimale Beanspruchungsenergie.Abb

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Chapter 6 Wet Grinding in Stirred Media Mills

Cited by 70 publications

References 25 publications

Advanced M5 Modeling of Stirred Media Milling

Advanced M5 Modeling of Stirred Media Milling

Extraction of astaxanthin from microalgae: process design and economic feasibility study

Einsatz unterschiedlicher Rührwerkskugelmühlen für die Erzeugung von Nanopartikeln

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