otk 1 lecture1#agitationmixing.ppt

PENGADUKAN DAN MIXING FLUIDA AGITATION AND

MIXING OF FLUIDS

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PERAN MIXING FLUIDA DALAM PROSES INDUSTRI

RAW MATERIAL STORAGE

FEED PREPARATION REACTION

PRODUCT SEPARATION

PRODUCT PURIFICATION

PRODUCT STORAGE

RECYCLE OF UNREACTED MATERIAL BY PRODUCTS

WASTES

STAGE 1 STAGE 2 STAGE 3 STAGE 4 STAGE 5

STAGE 6

SALES

• RAW /INTERMEDIATE • KAPASITAS :

HOURS/DAYS/WEEKS • STORAGE TGT SIFAT

R.M., CARA DELIVERY, KONTINYUITAS PASOKAN

• PERLU PURIFIKASI • LIQUID PERLU

DIUAPKAN BILA REAKSI FASA GAS

• SOLID PERLU DIHALUSKAN BILA REAKSI FASA PADAT

• JANTUNG PROSES • DICAMPUR PADA

KONDISI UNTUK MENGHASILKAN PRODUKSI YANG DIINGINKAN

• BY PRODUCTS & IMPURITIES

• PEMISAHAN PRODUCTS, BY PRODUCTS & UNREACTED MATERIAL

• PEMISAHAN PRODUCTS, BY PRODUCTS & UNREACTED MATERIAL 2

POKOK BAHASAN

PERSPEKTIF AGITATING & MIXING (FLUIDS) GEOMETRI STANDAR AGITATED TANK KARAKTERISTIK IMPELLER KARAKTERISTIK ALIRAN SCALE UP/SCALE DOWN

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PERSPEKTIF MIXING

• What is mixing? We define mixing as the reduction of inhomogeneity in order to achieve a desired process result. The inhomogeneity can be one of concentration, phase, or temperature. Secondary effects, such as mass transfer, reaction, and product properties are usually the critical objectives.

• What is agitation ? Generally refers to forcing a fluid by mechanical means to flow in a circulatory or other pattern inside a vessel.

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PERSPEKTIF MIXING

What constitutes a mixing problem? Process objectives are critical to the successful manufacturing of a product. If the mixing scale-up fails to produce the required product yield, quality, or physical attributes, the costs of manufacturing may be increased significantly, and perhaps more important, marketing of the product may be delayed or even canceled in view of the cost and time required to correct the mixing problem.

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PERSPEKTIF MIXING

How much mixing is enough, and when could overmixing be damaging to yield or quality? These critical issues depend on the process and the sensitivity of selectivity, physical attributes, separations, and/or product stability to mixing intensity and time. The nonideality of residence time distribution effects combined with local mixing issues can have a profound effect on continuous processes.

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Mixing plays a key role in a wide range of industries:

• Fine chemicals & pharmaceuticals

• Agrichemicals & petrochemicals

• Biotechnology

• Polymer processing

• Paints and automotive finishes

• Cosmetics and consumer products

• Food

• Drinking water and wastewater treatment

• Pulp and paper

• Mineral processing

SCOPE OF MIXING OPERATIONS

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• Blending of two miscible/immiscible liquids • Dissolving solids in liquids • Dispersing a gas in a liquid as fine bubbles • Suspending of fine solid particles in a liquid • Agitation of the fluid to increase heat

transfer

PURPOSE FOR AGITATING FLUID

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EQUIPMENT for AGITATING FLUIDS

Conventional stirred tank with top-entering agitator 9

EQUIPMENT for AGITATING FLUIDS

Conventional stirred tank with top-entering agitator

Wall

Baffles

Gearbox

Shaft

Motor

Impeller

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EQUIPMENT for AGITATING FLUIDS

Conventional stirred tank with bottom-entering agitator

Motor Gearbox

Shaft

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EQUIPMENT for AGITATING FLUIDS

Side-entering agitator for large tank

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EQUIPMENT for AGITATING FLUIDS

Angular top-entering mixer for small tanks with portable mixers 13

IMPELLER

• Desain impeller sangat berpengaruh thd karakteristik pengadukan & energi yg dibutuhkan

• Tipe impeller tergantung pd sifat fluida : • Fluida viscous or non-viscous • Fluida newtonian/non-newtonian • Single or multiphase

• Tipe impeller berdasarkan aliran fluida yang dihasilkan : • Impeller aliran turbulen • Impeller aliran laminer

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IMPELLER

• Impeller aliran turbulen (N>>): • Diameter impeller < diameter tangki for

transport momentum • Radial impeller : disc turbine, fan turbine, paddle • Axial impeller : propeller, inclined fan turbine,

hydrofoil • Tangki dengan baffle

• Impeller aliran laminer (N<<): • Diameter impeller ≈ diameter tangkinot

transport momentum • Tipe impeller : helical ribbon, anchor, screw • Tangki tanpa baffle

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RADIAL IMPELLER

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RADIAL IMPELLER

Disk turbine or

Rushton turbine

Curved blade open turbine

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AXIAL IMPELLER

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AXIAL IMPELLER

Propeller

Inclined fan turbine

Pitched blade fan turbine

Hydrofoil

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IMPELLER ALIRAN LAMINER

Helical ribbon 20

IMPELLER ALIRAN LAMINER

Anchor

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FLOW PATTERN AXIAL IMPELLER

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FLOW PATTERN AXIAL IMPELLER

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FLOW PATTERN RADIAL IMPELLER

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FLOW PATTERN RADIAL IMPELLER

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Velocity Vectors Colored By Velocity Magnitude (m/s)FLUENT 5.0 (3d, segregated, ke)

Jan 19, 2000

2.50e+00

2.29e+00

2.08e+00

1.87e+00

1.66e+00

1.46e+00

1.25e+00

1.04e+00

8.35e-01

6.27e-01

4.19e-01

2.12e-01

4.17e-03

Z

Y

X

SIMULASI FLOW PATTERN RADIAL IMPELLER

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TRAILING VORTEX

Visualisasi Simulasi

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CENTER VORTEX

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TYPICAL STANDARD DESIGN TURBINE

5020 ,

D

D,

t

a

5

1

aD

W

3

2

a

d

D

D

4

1

aD

L

12

1

tD

J

1tD

H

3

1

tD

C

0170 ,D

D,

t

a

Turbulen

Laminer

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• Design variables : power, torsi dan impeller tip velocity

• Faktor2 yang berpengaruh : geometri & ukuran, sifat2 fluida (viscosity μ, density ρ, surface tension σ, thermal conductivity k, heat capacity Cp), impeller rotational speed N untuk kalkulasi power P , torsi Tq dan impeller tip velocity Utip

• Power adalah biaya terbesar dalam operasi tangki berpengaduk : dalam turbulent mixing P ≈ρN3Da

5 ; dalam laminer mixing P ≈μN2Da

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DESIGN VARIABLES

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• Torsi (Tq= P/2πN) • Torsi menentukan desain shaft impeller dan

gear drive • Impeller tip velocity : Utip=πND

DESIGN VARIABLES

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DIMENSIONLESS NUMBERS IN AGITATION

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53

a

PDN

PN

Power

2

aRe

NDN

3

a

QND

QN

NNb

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aWe

DNN

Reynolds

Pumping

Blending

Weber

Mempunyai korelasi dengan NRe pd baffled system dan konstan bila NRe>104

Rasio inertial force/visous force; aliran laminer bila NRe≤10, aliran turbulen bila NRe≥104

Berhubungan dengan pumping capacities

Berhubungan dengan homogenitas mixing atau blending

Berhubungan dengan karakteristik permukaan liquid untuk sistem dua fasa

DIMENSIONLESS NUMBERS IN AGITATION

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Froude

Nusselt

Prandtl

Schmidt

Mempunyai korelasi dengan NRe dan NP pd unbaffled system dan bila ada partikel padat

Berhubungan dengan heat transfer dalam tangki berpengaduk

Berhubungan dengan fluid properties untuk korelasi heat transfer

Berhubungan dengan luid properties untuk korelasi mass transfer

g

DNN a

Fr

2

k

hTNNu

k

CN

p

Pr

L

ScD

N

Sherwood L

LSh

D

TkN

Berhubungan dengan mass transfer antara solute dan solvent dalam pengadukan

POWER CONSUMPTIONS

• Faktor penting desain agitated tank adl konsumsi daya utk menggerakkan fluida

• Konsumsi daya P tdk dapat diprediksi secara teoritis diprediksi secara empiris

• P adalah fungsi kecepatan impeller (Bilangan Reynolds impeller=NRe)

• Kecep Impeller menentukan jenis aliran dalam tangki : • NRe < 10 laminer seluruh tanki • NRe > 104 turbulen seluruh tanki • 10 < NRe < 104 turbulen sekitar impeller

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POWER CORRELATIONS

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OWARI DESU

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