Mixing of granular materials in slowly rotated containers

McCarthy, Joseph J.; Shinbrot, Troy; Metcalfe, Guy; Wolf, Johanna; Ottino, Julio M.

doi:10.1002/aic.690421207

Cited by 105 publications

(67 citation statements)

References 44 publications

(32 reference statements)

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“…As the drum rotated the initially straight interface between the coloured regions was deformed making the mixing visible. In the experiments performed by Metcalfe et al (1995) and McCarthy et al (1996) the drum was rotated so slowly that they were in the intermittent flow regime, in which discrete avalanches were observed that stopped completely before the next one began. Here experiments have been performed to investigate the mixing in the steady continuous flow regime, which develops for constant rotation periods in the range 100-10 s per revolution.…”

Section: Steady Mixing Of Granular Materialsmentioning

confidence: 99%

“…Intermittent and continuous flow In many food manufacturing and industrial processes granular materials are often placed into a drum, pivoted so that its axis of rotational symmetry lies horizontally, and slowly rotated to try to mix the grains into a consistent blend (e.g. Ullrich 1969;Metcalfe et al 1995;McCarthy et al 1996;Ristow 1996;de Gennes 1999). In all these flows the motion is characterized by a thin rapidly moving fluid-like avalanche of grains close to the free surface and a large solid-like region, beneath it, which slowly rotates about the axis of revolution.…”

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confidence: 99%

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Granular flow in partially filled slowly rotating drums

2001

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In many industrial processes granular materials are mixed together in partially filled slowly rotating drums. In this paper a general theoretical framework is developed for the quasi-two-dimensional motion of granular material in a rotating drum. The key assumption is that the body can be divided into a fluid-like and a solid-like region, that are separated by a non-material singular surface at which discontinuities occur. Experiments show that close to the free surface there is a thin rapidly moving fluidlike avalanche that flows downslope, and beneath it there is a large region of slowly rotating solid-like material. The solid region provides a net transport of material upslope and there is strong mass transfer between the two regions. In the theory the avalanche is treated as a shallow incompressible Mohr-Coulomb or inviscid material sliding on a moving bed at which there is erosion and deposition. The solid is treated as a rigid rotating body, and the two regions are coupled together using a mass jump condition. The theory has the potential to model time-dependent intermittent flow with shock waves, as well as steady-state continuous flow. An exact solution for the case of steady continuous flow is presented. This demonstrates that when the base of the avalanche lies above the axis of revolution a solid core develops in the centre of the drum. Experiments are presented to show how a mono-disperse granular material mixes in the drum, and the results are compared with the predictions using the exact solution.

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Section: Steady Mixing Of Granular Materialsmentioning

confidence: 99%

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confidence: 99%

Granular flow in partially filled slowly rotating drums

2001

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“…In industry they often occur as part of complicated granular phase-transition flows, in which the granular material behaves as a fluid-like avalanche close to the free surface and as a solid in a large region beneath. This is typical of flows in partially filled rotating drums, which are used to mix or segregate dissimilar grains (Metcalfe et al 1995;McCarthy et al 1996;Gray & Hutter 1997;Hill et al 1999;Shinbrot, Alexander & Muzzio 1999;Shinbrot & Muzzio 2000;Gray 2001), or whenever particles are poured out of containers or deposited to form heaps (Makse et al 1997;Gray & Hutter 1998;Baxter et al 1998). The magnitude of industrial applications is huge: Shinbrot & Muzzio (2000) estimate that US production alone of granular pharmaceuticals, foods and bulk chemicals amounts to a trillion kilograms per year, and most of these materials will be mixed, segregated, poured or deposited in piles at some stage of the manufacturing process.…”

Section: Introductionmentioning

confidence: 99%

Shock waves, dead zones and particle-free regions in rapid granular free-surface flows

2003

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Shock waves, dead zones and particle-free regions form when a thin surface avalanche of granular material flows around an obstacle or over a change in the bed topography. Understanding and modelling these flows is of considerable practical interest for industrial processes, as well as for the design of defences to protect buildings, structures and people from snow avalanches, debris flows and rockfalls. These flow phenomena also yield useful constitutive information that can be used to improve existing avalanche models. In this paper a simple hydraulic theory, first suggested in the Russian literature, is generalized to model quasi-two-dimensional flows around obstacles. Exact and numerical solutions are then compared with laboratory experiments. These indicate that the theory is adequate to quantitatively describe the formation of normal shocks, oblique shocks, dead zones and granular vacua. Such features are generated by the flow around a pyramidal obstacle, which is typical of some of the defensive structures in use today.

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“…Mixing and blending of granular materials, can greatly influence material preparation in the pharmaceutical, metallurgy, ceramics or many other industries [1]. Mixing can be defined as a process of combining particles of solids, liquids or solutions, to obtain a homogeneous product.…”

Section: Introductionmentioning

confidence: 99%

Micro Pulse Mixing- An Efficient Mixing Method of Small Quantities of Powders

Aksenczuk¹,

Calka²,

Wexler³

2017

Jour. Mater. Sci. Eng. Adv. Tech.

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This paper describes a novel mixing method together with mixing device. The Micro Pulse Mixer ( ) PM µ has been designed, constructed and tested using a new mixing concept based on damped harmonic oscillator motion. Advantages of the technique include simplicity of the device, high rates of mixing and high uniformity of product. Furthermore, the device design, with discrete powder containers, allows rapid loading and unloading of samples ( ) 60s -30 enabling powder sampling and/or complex blending operations. The mixer does not require frequent cleaning. It is designed to mix relatively small volumes of powders (up to several grams) for use in either laboratory work or for small commercial samples of high value.In this study we compared the PM µ method with rotating tumbling mixing.Mixing products were evaluated by analysis of scanning electron microscope (SEM) images while X-ray diffraction (XRD) was used to monitor phase evolution A. M. AKSENCZUK et al. 78 during mixing. Powder particle distributions were obtained based on image analysis techniques with mixing efficiency parameters determined based on the calculation of the percentage compounds content within sampled powder is proposed.We believe that the more efficient approach of impulse mixing could be beneficial for laboratory purposes and as a simple and cost-effective powder mixing and blending method.

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Mixing of granular materials in slowly rotated containers

Cited by 105 publications

References 44 publications

Granular flow in partially filled slowly rotating drums

Granular flow in partially filled slowly rotating drums

Shock waves, dead zones and particle-free regions in rapid granular free-surface flows

Micro Pulse Mixing- An Efficient Mixing Method of Small Quantities of Powders

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