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SENTRIFUGASI
28/02/2017 Nur Istianah-T.Separasi-
Sentrifugasi-2017
Sentrifugas
i Proses pemisahan solid dari liquid dengan prinsip
grafitasi. Densitas solid harus lebih besar dari
densitas liquid
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Peran gaya sentrifugal:
1. Mendorong partikel kecil agar mengendap
2. Menahan brownian motion
3. Mencegah arah free convection fluida
4. Mengurangi penumpukan “cake” pada screen (untuk
centrifugal filtration)
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General principle
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Klasifikasi centrifuge
Kapasitas
Labratory centrifuge
Preparative centrifuge
Kegunaan
Sedimenting
centrifuge
Filtering
centrifuge
Ultracentrifugation
Tubular bowl
Basket
Disk stack
Scroll decanter
Basket
Pusher
Baffle
Inverting bag
Cone screen
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centrifugal filtration
1
centrifugal settling
2
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Ultracentrifugation
1000-15000 rpm
Digunakan untuk
pemisahan atau
analisa campuran
makromolekul
(AUC). Ex: protein Rpm tinggi
menimbulkan
panas sehingga
memerlukan
cooling
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Ultracentrifugation
separating macromolecules from solvents
fractionating mixtures of macromolecules
studying the properties of macromolecules
Analyzing complex mixtures of macromolecules
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Persamaan pada
sentrifugasi
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Persamaan pada centrifuge settling
Centrifugation time
• Time taken by the particle to move though
the liquid layer is called residence time (tr).
dt
drVt
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18
)( 22 rDv ss
t
18
)(22 ss rD
dt
dr
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)(
ln18
18
)(ln
18
)(1
22
1
2
22
1
2
0
222
1
ss
r
r
ss
t
ss
r
r
D
r
r
t
tD
r
r
dtD
drr
2
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Calculation of flow rate for continuous
centrifuge
• flow rate (Q)
1
2
222
1
2
2
1
2
22
22
1
2
ln18
)()(
ln18
)(
)(
ln18
r
r
Dbrr
r
r
DVQ
D
r
r
V
t
VQ
ssss
ss
r
2
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• r1 = inside radius (m)
• r2 = outside radius (m)
• b = height of
centrifuge(m)
• µ = viscosity (Pa.s)
• ω = an angular velocity
(rad s-1)
• ρs = density of solid
(kg/m3)
• ρ = density of liquid
(kg/m3)
• Ds= diameter of
particle(m)
• V(m3)=operating
volume of the
centrifuge
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Example 1 Find centrifugation time tr of a
particle d=1mm. In a
centrifuge
Given
.25.0
.20.0
/1000
/1100
.101.8
995
3
3
4
mR
mR
mkg
mkg
sPa
RPMN
o
i
f
P
Ri
Ro
2
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srad
N
/20.104
60
9952
60
2
Find ω
2
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sec1025.3
1000110020.104001.0
)20.0/25.0ln(101.818
)/ln(18
3
22
4
22
r
r
fp
ior
t
t
d
rrt
Find time
tr of particle d=1mm. in centrifuge≥3.25x10-3sec
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Example 2
Beer with a specific gravity of 1.042 and a
viscosity of 1.0 x10-3 N s/m2 contains solids which
have a density of 1160kg/m3. It is clarified at a
rate of 240 l/h in a bowl centrifuge which has and
operating volume of 0.09 m3 and a speed of
10000 rev/min. The bowl has a diameter of 5.5
cm and is fitted with a 4 cm outlet. Calculate the
effect on feed rate of an increase in bowl speed
to 15000 rev/min and solid particle diameter at
the higher speed.
2
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• Solution
Initial flow rate
new flow rate
)/ln(18
)60/2( 22
1
1
io
fp
rr
DNVQ
)/ln(18
)60/2( 22
2
2
io
fp
rr
DNVQ
2
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As all conditions except the bowl speed
remain the same,
Therefore,
Q2 = 0.15 l/s
2
2
2
2
1
2
2
1
2
)60/10000142.32(
)60/15000142.32(
)3600/240(
)60/2(
)60/2(
Q
N
N
Q
Q
2
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To find the minimum particle size
mmxD
VN
rrQD
fp
io
18.0108.1
09.0)10421160()60/1500014.32(
)]02.0/0275.0ln(100.118[00015.0
)()60/2(
)]/ln(18[
7
2
3
2
2
22
2
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1
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1
# A and B are dense and
light liquid,
rA, rB =outlet radius
rn= radius of neutral zone.
Fig 6.1. Separation of immiscible liquids
# t (s)=residence time
ω = angular velocity,
Q = volumetric flowrate,
V = operating volume of the centrifuge,
D = diameter of the particle,
r2 = radius of light phase outlet,
r1 = radius of dense phase outlet,
N =speed of rotation
2
3
Separation of liquids
Example3
• A bowl centrifuge is used to break an oil-
in-water emulsion. Determine the radius of
the neutral zone in order to position the
feed pipe correctly. (Assume that the
density of the continuous phase is 1000
kg/m3 and the density of the oil is 870
kg/m3. the outlet radius from the centrifuge
are 3 cm and 4.5 cm).
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• Solution
mr
r
r
n
n
n
098.0
130
783.0025.2
8701000
)03.0(870)045.0(1000 222
2
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Latihan soal
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Dua buah sentrifuge digunakan pada kecepatan putar
sama yaitu 53.34 m/s. Tentukan kecepatan putar dalam
rpm dan gaya sentrifugal pada masing-masing
sentrifuge untuk 1 kg feed jika:
Diameter sentrifuge pertama (D1) 15.24 cm
Diameter sentrifuge pertama (D2) 61 cm
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Latihan soal
Nur Istianah-T.Separasi-
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Sebuah centrifuge digunakan untuk memisahkan krim
dengan jari-jari discharge 50.8 mm dan jari jari luar
sentrifuge 76.2 mm. Densitas susu skim adalah 1032
kg/m3, densitas krim 865 kg/m3.
Hitunglah jari-jari zona netral pada sentrifuge!
2
ri
ro
50.8 mm
76.2 mm
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THANKS FOR YOUR ATTENTION
The best person is one give something useful always
28/02/2017 Nur Istianah-T.Separasi-
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