Industrial Mixers

8/3/2019 Industrial Mixers

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PREPARED BY

KIRAN.S.SALIAN

B.E. CHEMICAL

ROLL NO. 73

DATTA MEGHE COLLEGE OF ENGINEERING.


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CONTENTS

SR.NO. CHAPTER

1 INTRODUCTION

2 TYPES OF HIGH SHEAR MIXERS

3 SOME INDUSTRIAL APPLICATIONOF HIGH SHEAR MIXERS

4 CASE STUDY

5 CONCLUSION

6 REFERENCES


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y Mixing of solids is the distribution of at least onecomponent through another. The mixing ofgranular solids is a widely employed process inChemistry, Pharmacy, Food manufacturing,

Ceramics industry, and ore beneficiationyWilliamssays, Although the mixing of particulate

solids is one of the oldest and most importantoperations in the process industries, it is one of theleast well understood (Williams, 1990).

y The mixing process with solids is influenced bydisperse properties such as grain shape, grain size,particle-size distribution (gradation), and frictionin the bulk material.


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y

MIXER POWDER

Tumbling mixers Free-flowing component of similar particle size

Tumbling mixers withshear

Slightly cohesive powders, free-flowing powders.

Shear mixers Cohesive powders, free-flowing, segregating mixtures

1.2) Mixture Quality

To determine mixture quality Danckwerts defines ascale of segregation and an intensity of segregation

(Danckwerts, 1953), which describe the size andamount of dilution of patches or volumes of unmixed

material within the mixture, respectively.


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y Throughputy Batch integrity

y Product containment

y Product sensitivity

y Cleaning1.4)What are High-Shear Mixers

y High-shear mixers are industrial developments ofthe alchemists mortar and pestle and the millers

millstone for the grinding of grain (Harnby, 2000).y High shear mixers (also know as high intensity

mixers) are equipped with mechanical agitatorrotating at moderately high speed.


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Powder is pinched between a moving and a staticsurface as in a comil or between two moving surfaces

as in a pair of pressurized rollsSome high shear mixers are equipped with coolingjacket, because the temperature may rise markedlydue to the high energy input supplied by the mixing

tools


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A major use of these mixers is in theagglomeration of powders by addition of

liquid binders, for example in the

manufacture of granular products in thefine chemical, pharmaceutical,foodstuff, household product,

metallurgical and microbiologicalproduct industries.


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y 2.1) Pan Muller Mixersy 2.2) Roller Compactorsy 2.3) Helical Blade Mixersy 2.4) Banbury Mixersy 2.5) HighSpeed Mixers/Granulatorsy 2.6) Double-Arm Kneading Mixersy 2.7) Roll Millsy 2.7.1) Two-Roll Mills

y 2.7.2) Three-Roll Millsy 2.8) Gate Mixersy 2.9) Shear-Bar Mixers


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2.1)Pan Muller Mixers

These mixers can be used if the paste is not toofluid or too sticky.


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2.2)Roller Compactors

Roller Compactor: (a) Alexanderwerk and (b) Hutt types.

Roller compaction is an alternative gentlermethod, the powder mix being squeezedbetween two rollers to form a compressed sheet .


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2.3) Banbury Mixers

Preeminent in the field of high-intensity mixers,with power input up to 6000 kW/m3 (30 hp/gal), isthe Banbury mixer (Figure 5).

It is used mainly in the plastics and rubber


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2.4)HighSpeed Mixers/Granulators

This type of granulator (e.g. Diosna, Fielder) isused extensively in pharmaceutics.


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2.5)Double-Arm Kneading Mixers


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2.6)Roll Mills:

2.6.1)Two-Roll Mills 2.6.2)Three RollMills


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y 3.1) High shear dispersion of Bentonitey 3.2) High shear dispersion of Titanium dioxidey 3.3) High shear dissolving of viscosity index improves

in Luboilsy 3.4) Preparation of paper coatingsy 3.5) Redispersion of filter cakey 3.6) Production of polymer modified asphalt for road

surfacingy

3.7) Agrochemical industry manufacture of pesticidesy 3.8) Preparation of drilling fluidsy 3.9) High shear Preparation of rubber solution


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4)Case Study:-

Following case studies (taken from mixes.com)show how a particular high shear mixer is selected for

a given system:-

4.1) Mixing ofPlastisols

4.2) Mixing ofSilicone Sealant


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4.1) Mixing of Plastisols:-

Application Pigmented plastisols. Similar mixing

applications might include: Dental whitening gels, polyestercompounds, epoxies, transdermal drugs.

Ingredients - Plasticizers, pigments, fillers (Cabosil, calciumcarbonate), powdered PVC resins.

Viscosity - Final: 50,000 centipoise (cps); max during theprocess: 2 million cps or 2.5 million cps, depending on mixerused.Application Batch Size - 500 gallons.

Other Key Parameters - Pigments require high shear for fastand thorough dispersion. Vinyl resins are temperaturesensitive and therefore indirectly shear sensitive, too, sincelocalized heat is always produced by a high shear agitator.


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Process - The manufacturer in this case had been mixing aPlastisol with a High Speed Disperser. The Disperser provided

enough shear to disperse the pigment, but as viscosity went upit failed to maintain adequate circulation and product turnoverin the vessel. Zones of unmixed material remained, even aftervery long batch cycles.

4.2) Mixing of Silicone Sealant:-

Application - Viscous silicone gel used to manufacture anindustrial sealant. Similar mixing applications might include:dental composites, butyl sealants, propellants, automotivesound absorbing compounds, color pigment compoundingpastes, and chewing gum formulations.Ingredients - Silicone resin and fumed silica.


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Viscosity - Final: 6-7 million cps.Application Batch Size - 200 gallons.Other Key Parameters - None.Process - Materials over 2.5 million cps generally require aswitch from a conventional Double Planetary Mixer to aDouble Arm Kneader. However, because of the high cost of aKneader, it would be preferable to stick with the DoublePlanetary, if it is equipped to handle viscosities as high as 7-8 million cps, far beyond the normal range of classic

rectangular planetary blades.


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5) Conclusion:-

The use of High Shear Mixers for agglomeration ofpowders is common throughout the pharmaceuticaland detergent process industries (especially in thecase of compact laundry detergents) due to their fast

operation and ability to produce granules with highdensity and strength.

Moreover power consumption by high shear mixers

is high so it can be used only for specialty chemicalfor which product value is immaterial infront of themarket appeal of the final product form.


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6) References:-

1.)Danckwerts, P.V., Theory of Mixtures andMixing, Chem. Eng. Res., 6, pp 355 (1953)

2.)Fischer, J.J., Solid-Solid Blending, Chem. Eng.,

67(16), pp

107 (

1960).

3.)Miller, S.A., et al, Liquid-Solid System, inPerrys Chemical Engineers Handbook, 6th ed, Green,D.W., et al (Eds.) , McGraw-Hill Book Company, pp

19-14 to 19-24 (1984).4.)Roseman, B., Mixing of Solids, Ind. Chemist,

39, pp 84 (1963).

5.)www. mixes.com


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Industrial Mixers