Gareth Morris

7/30/2019 Gareth Morris

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Simulating stable orientations oforthorhombic particles in thin films

and their effect on stability

Gareth D.M. Morris, Stephen J. Neethling, Jan J. CilliersFroth and Foam Research GroupRio Tinto Centre for Advanced Mineral RecoveryImperial College London


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Particle stabilised thin films

Flotation is subject to variables over a large range of scales

1000 T/Hr

100 ltr/min

10 mm10 m

Pelculas delgadas estabilizadas por partculas


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Simulation of particles in filmsSimulacin de partculas en pelculas


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Non-spherical particles in films

Non spherical particles can have more than one stableorientation in a film.

Jagged surfaces and sharpedges cause distortion of thefilm surface.

Sharp edges on particles can

draw the opposite sides ofthe film together, causingrupture.

Partculas no-esfricas en pelculas


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Stable orientations

Vertical Rotated

Horizontal Diagonal

There are 4 stable orientations for orthorhombicparticles.They fall into two categories; Flat and Twisted.

Flat Twisted

Orientaciones estables

Plano Retorcido


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Flat orientations

Vertical

Horizontal

Orientaciones planas


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Twisted orientations

Rotated

Diagonal

Orientaciones retorcidas


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Aspect ratio and contact angle

Aspect Ratio1.8

1

0.72

Stable orientationsdepend upon theContact angle andthe aspect ratio

(AR).

s1

Aspect ratio = s1/s2

s1

s2

Long thinparticles

Cubicparticles

Flat wideparticles

Contact angle

90

45

More hydrophobic

Less hydrophobic

s2

Relacin de aspecto y ngulo de contacto


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Simplified table

Particle AR 45 60 65 70 75 80 90

0.65 F F F F F F/T T

0.85 F F F F F/T T T

1 F F F F/T F/T T T

1.18 F F F F/T F/T T T

1.82 F F F/T F/T F/T T T


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Rotating hydrophobic cube (=88)Cubo hidrofbico rotado


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Film distortion by cubic particles

Hydrophobic cubic particle (=88) rotating fromflatto rotated orientation

Distorsin de pelculas por partculas cbicas


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Particle AR 45 60 65 70 75 80 90



1 F F F F/T F/T T T



Long thin particlesPartculas delgadas largas


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Film stability for long thin particlesEstabilidad de pelcula para partculas delgadas largas


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Particle AR 45 60 65 70 75 80 90



1 F F F F/T F/T T T



Flat wide particlesPartculas planas anchas


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Film stability for flat wide particlesEstabilidad de pelcula para partculas planas anchas


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Stable orientations change fromflatto twisted between

65 and 75. The specific contact angle depends on shape.

Summary

Wider flatter particles are more stable inflat

orientations.

Resumen

Partculas ms anchas y planas son ms estables en orientacionesplanas.

Las orientaciones estables cambian de planas a retorcidas entre 65 y75 . El ngulo de contacto especfico depende de la forma.

Flatorientations provide much higher film stability than

twisted ones.Las orientaciones planas proveen una mayor estabilidad depelcula que las retorcidas.


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Conclusions for flotation

Greater froth stability can be achieved if particles haveflatorientations.

High hydrophobicity is desirable in the pulp forcollection. Low hydrophobicity is desirable in the froth

for stability. An equilibrium is required.

A lower hydrophobicity makesflatorientations more

stable for all shapes.

Una mejor estabilidad de espuma se obtiene si las partculastienen orientaciones planas.

Hidrofobicidades menores hacen que las orientaciones planas seanms estables para todas las formas.

Alta hidrofobicidad es deseable en la pulpa para la coleccin. Bajahidrofobicidad es deseable en la espuma para la estabilidad. Elequilibrio es necesario.

Conclusiones para flotacin


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Acknowledgements

With Thanks to Rio Tinto and ImperialCollege London for their support in

this research


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Simulating stable orientations oforthorhombic particles in thin films

and their effect on stability

Gareth D.M. Morris, Stephen J. Neethling, Jan J. CilliersFroth and Foam Research GroupRio Tinto Centre for Advanced Mineral RecoveryImperial College London

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