Agitation and Mixing of Fluid

8/12/2019 Agitation and Mixing of Fluid

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A GITATION A ND MIXING OFFLUIDS

Purpose o f ag i t at ion : intensification of transport processes in agitated batch (heat and mass transfer) preparation of materials of required properties (suspension, emulsion)

Examples of indu s t r ia l appl ica t ions : blending of two miscible liquids as ethyl alcohol and water

dissolving solids in liquids, such as salt in water

dispersing a gas in a liquid as fine bubbles, such as oxygen fromair in a suspension of microorganisms for fermentation or for theactivated sludge process in waste treatment

liquid-liquid dispersion, such as dispersion of pigment in solvents

suspending of fine solid particles in a liquid, as in catalytichydrogenation of a liquid

agitation of the fluid to increase heat tranfer between the fluid anda coil or jacket in the vessel wall


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mechanical mixing (rotating, vibrating) hydraulic mixing pneumatic mixing pipeline mixing (turbulent flow, static mixer)

Method o f m ix ing f lu ids

A mechanical mixing usingturbines

B mechanical mixing usingblade impellers

C hydraulic mixingD pneumatic mixing with

stationary inputsE pneumatic mixing with

automatic regulationF hydraulic mixing with

antifoaming shower


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Pipe l ine m ixing Reyn olds exper iments

Paul, E. L., Atiemo-Obeng, V. A., Kresta, S. M.:H an d b oo k o f i nd u s tr ia l m i xi ng : s c ie nc e a nd practice. Canada: Wiley-Interscience, 2003,1377 p. ISBN 0-471-26919-0


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a axial-flow pattern, baffled vessel, b radial-flow pattern, baffled vessel,c tangential-flow pattern, unbaffled vessel

Flow in agi ta ted b atch


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Equipm ent for mechanica l m ix ing

Des ign l ayou t o f mix ing equ ipments

A B C

A Centrally placed impeller in bafled vessel, B Side-entring propeller, C Agitatorwith draught tube

A B

A Equipment with a drive at the top, B Equipment with a drive at the bottom

Mechanical seal


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Clos e c learanc e ag i tato r High -s p eed im p eller

Design layou t o f ag i tators


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Maine type of c lo se c learanc e agi tators

No. Layout of agi ta tor Name T/dGeometr ica lparameters

1Anchor (paddle)

agitatorCVS 69 1014

1,118,0/ d hv

12,0/ d h 055,0/2 d H

2Helical-screw agitator

with draught tubeCVS 69 1028

2

5,1/ d hv 1/ d s 1,1/ d D 15,1/ D H

3 Eccentrically placedhelical-screw agitator 2

5,1/ d hv 25,0/2 d H

1/ d s 02,0/ T c


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No. Layout of agi tator Name T/dGeometr ica lparameters

4

Helical-ribbon

agitatorCVS 69 1029 1,05

1/ d hv

1/ d s 1,0/ d h

5 Leaf agitator

CVS 69 10162 1/ d h

6 Multi-stage agitator 2

2,0/ d h

65,1/

d hv 45 45

02,0/ T c 175,0/2 d H


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Main type o f h igh-speed impe l ler s

No. Layou t of imp el ler Name T/dGeometr ica lparameters

1

Six-blade turbinewith disk (Ruschton

turbine)CVS 69 1021

3 4

2,0/ d h 25,0/1 d 75,0/1 d d

6 blades

2 Six-blade openturbine 3 42,0/ d h

6 blades

3

Pitched six-bladeturbine with pitch

angle 45CVS 69 1020

3 420,0/ d h

45


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No. Layout of imp el ler Name T/dGeometr ica lparameters

4

Pitched three-bladeturbine with pitch

angle 45 CVS 69 1025.3

3 42,0/ d h

45

5 PropellerCVS 69 1019 3 4

1/ d s 22,0/ d h 4,0/ d R 16,0/1 R R

6High shear stress

impellerCVS 69 1038.1, .2

2 4

1st variant1,0/ d h 8,0/2 d d

2nd variant075,0/ d h

85,0/2 d d


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Power consum pt ion o f ag i t ato r

Charac te ri s t ics of m ix ing sy s tem

Re f Po 53d n P Po

2nd Re

Re

A Po

creepingf low

turbulentf low

t rans i t ionzone of f low

baffledvessel

unbaffledvessel

.const B Po


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Pow er character is t ics of clo se clearance agi tators

1 anchor agitator (CVS 69 1014), 2 helical-screw agitator with draught tube (CVS69 1028), 3 eccentrically placed helical-screw agitator, 4 helical-ribbon agitator

(CVS 69 1029), 5 leaf agitator (CVS 60 1016), 6 multi-stage agitator


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Pow er character is t ics o f high -speed imp ellers operated in baff led vessel

1 six-blade turbine with disk (Ruschton turbine) (CVS 69 1021), 2 six-blade openturbine, 3 pitched six-blade turbine with pitch angle 45 (CVS 69 1020),

4 Pitched three-bl ade turbine with pitch angle 45 (CVS 69 1025.3), 5 propeller(CVS 60 1019), 6a,b high shear stress impeller (CVS 69 1038.1.2)


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Blend ing effect o f agi tator

Homo geniza tion o f m isc ib le liqu ids : due to recirculation flow (convective diffusion) due to turbulent flow (turbulent diffusion) due to molecular diffusion

Re f t nt m

.konst t nt m

.konst t nt m

During homogenization (or blending) of miscible liquids are compensated temperature andconcentration differences in agitated batch.


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Hom ogenizat ion ch arac ter i s t ics of ag i ta tors

1 helical-screw agitator with draught tub (CVS 69 1028), 2 eccentrically placedhelical-screw agitator, 3 helical-ribbon agitator (CVS 69 1029), 4 eccentrically

placed multi-stage agitator, 5 anchor agitator (CVS 69 1014), 6 six-blade turbine

with disk (Ruschton turbine) (CVS 69 1021)

Re f t nt

m


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1 roubov mchadlo (CVS 69 1028), 2 roubov mchadlo umstn excentricky,3 psov mchadlo (CVS 69 1029), 4 tynsobn lopatkov mchadlo umstnexcentricky, 5 kotvov mchadlo (CVS 69 1014), 6 turbnov mchadlo (CVS 691021), 7 estilopatkov mchadlo (CVS 69 1020), 8 tlopatkov mchadlo (CVS

69 1025.3)

mt P E


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Im pel lers for d i spers ing o f gas in l iqu id

Im pe l le r pow er cons um pt ion fo r gas l iqu id d i spers ing

3nd

V f P

P g g


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Mixing o f susp ens ion

Imp e ller power con sum pt ion fo r mix ing o f suspens ion

Re f Po 53 d n P

Po su

sund Re2

l v sv su cc 1


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Jus t -sus pend ed im pel ler speed

0,1

1

10

0,0001 0,001 0,01 0,1

D/T

F r '

0,0250,05

0,1

0,15

0,2

c v

c

T

DC r F

g

d nr F

2

vc B AC exp

vcc


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EXAMPLE: B l en d in g eff ic ien c y o f im p eller s

Select type of high-speed impeller with minimum energetic requirementsfor continual blending (homogenization) of two miscible liquids A + B ( = 5mPas, = 1100 kgm -3) with flow rate of mixture 10 ls -1. For suitable degreeof homogenization must be residence time of liquids in equipment 5 x longer than blending time. Mixing equipment has standard geometrical configuration(baffled cylindrical vessel with diameter T = 1200 mm, T/d = 3.3; H 2 /d = 1, H/T = 1 ) .

Dimensio nless b lending t im e of h igh-speed imp el lers in turbu lent f low regim e

Type of im peller T/d H 2 /d nt m Six-blade turbine with disk (Ruschton

turbine), CVS 69 1021 3.3 1 51.8

Pitched six-blade turbine with pitchangle 45, CVS 69 1020 3.3 1 53.1

Pitched three-blade turbine with pitch

angle 45 , CVS 69 1025.33.3 1 60.5

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Agitation and Mixing of Fluid