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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


Sentrifugasi-2017

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)


Sentrifugasi-2017

General principle

3 28/02/2017 Nur Istianah-T.Separasi-

Sentrifugasi-2017

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

8 28/02/2017 Nur Istianah-T.Separasi-

Sentrifugasi-2017

centrifugal filtration

1

centrifugal settling

2


Sentrifugasi-2017

Ultracentrifugation

1000-15000 rpm

Digunakan untuk

pemisahan atau

analisa campuran

makromolekul

(AUC). Ex: protein Rpm tinggi

menimbulkan

panas sehingga

memerlukan

cooling


Sentrifugasi-2017

Ultracentrifugation

separating macromolecules from solvents

fractionating mixtures of macromolecules

studying the properties of macromolecules

Analyzing complex mixtures of macromolecules


Sentrifugasi-2017

Persamaan pada

sentrifugasi


Sentrifugasi-2017


Sentrifugasi-2017

Persamaan pada centrifuge settling

Centrifugation time

• Time taken by the particle to move though

the liquid layer is called residence time (tr).

dt

drVt

Nur Istianah-T.Separasi-

Sentrifugasi-2017

28/02/2017

18

)( 22 rDv ss

t

18

)(22 ss rD

dt

dr


Sentrifugasi-2017

28/02/2017

)(

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

3 Nur Istianah-T.Separasi-

Sentrifugasi-2017

28/02/2017

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


Sentrifugasi-2017

28/02/2017

• 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


Sentrifugasi-2017

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


Sentrifugasi-2017

28/02/2017

srad

N

/20.104

60

9952

60

2

Find ω

2


Sentrifugasi-2017

28/02/2017

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


Sentrifugasi-2017

28/02/2017

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


Sentrifugasi-2017

28/02/2017

• 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


Sentrifugasi-2017

28/02/2017

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


Sentrifugasi-2017

28/02/2017

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


Sentrifugasi-2017

28/02/2017

1

5


Sentrifugasi-2017

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).

2


Sentrifugasi-2017

28/02/2017

• Solution

mr

r

r

n

n

n

098.0

130

783.0025.2

8701000

)03.0(870)045.0(1000 222

2


Sentrifugasi-2017

28/02/2017

Latihan soal


Sentrifugasi-2017

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

1

28/02/2017

Latihan soal


Sentrifugasi-2017

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

28/02/2017

THANKS FOR YOUR ATTENTION

The best person is one give something useful always


Sentrifugasi-2017

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