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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.
5
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
27
CENTER VORTEX
28
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
29
• 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
3
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
31
DIMENSIONLESS NUMBERS IN AGITATION
32
53
a
PDN
PN
Power
2
aRe
NDN
3
a
QND
QN
NNb
32
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
33
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
35
OWARI DESU
36