Bioreactor Design

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Bioreactor Design

MATA KULIAH: PENGANTAR TEKNOLOGI BIOPROSES

Nur Istianah-THP-FTP-UB-2014

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Bioreactor: device, usually a vessel, used to direct the activity of a biological catalyst to achieve a desired chemical transformation.

Product Bioreactor

Recycle

Product

separation & purification Nutrients tank

Waste Input

Pre-filtration

Fermenter: type of bioreactor in which the biocatalyst is a living cell.

What is a bioreactor?

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1

Biomass concentration

Nutrient supply

Sterile conditions Effective

agitations

Heat removal

Shear conditions

Product removal Product

inhibition

Aeration

Microbial activities

Bioreactor Performance

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2

1. Aerobic bioreactor: Need adequate mixing and aeration 2. Anaerobic bioreactor: no need agitation

3. Semiaerobic bioreactor: No mixing, but need aeration

20%

70%

10%

aerobic anaerobic semiaerobic

Groups of Bioreactor

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3

-1. Stirred tank

•Baffles are usually used to reduce vortex. D=3m, 4 baffles. D>3m, 6-8 baffles

• Applications: free and immobilized enzyme reactions. High shear forces may damage cells

•Require high energy

input. Cooling can be used to cover excess heat

(+) Low cost

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4

- 2. Bubble column

Application: production of baker’s

yeast, beer, vinegar, and waste water treatment

Mixing method: Gas sparging

•Simple design

•Good heat and mass transfer

•Low energy input

Gas-liquid mass transfer coefficients depend largely on bubble diameter and gas hold-up.

1< H/D < 6

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- 3. Airlift reactor

There are two liquid steams: up-flowing and down-flowing steams.

Liquid circulates in an airlift reactor as a result of density difference between riser and downcomer. Aplication: alcoholic fermentation

Steril

Large capacity

Low shear

High cost

Poor nutrient distribution

Foaming

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6

Packed-bed reactors are used with

immobilized or particulate

biocatalysts.

Medium can be fed either at the top or bottom and forms a continuous liquid phase.

- 4. Packed-bed reactor

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•The trickle-bed reactor is another

variation of the packed bed reactors.

•Liquid is sprayed onto the top of the packing and trickles down

through the bed in small rivulets.

• Application: aerobic wastewater treatment

- 5. Trickle-bed reactor

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8

•When the packed beds are operated in upflow

mode, the bed expands at high liquid flow rates due to upward motion of the particles.

•Channelling and clogging of the bed are avoided.

•Application: wastewater treatment and the

production of vinegar.

- 6. Fluidized bed reactor

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Nur Istianah-THP-FTP-UB-2014 9

FED

BATCH

PLUG

FLOW CSTR

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http://www.aspentech.com

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Bioreactor Operation Modes

BATCH

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10

A batch bioreactor is normally equipped

with an agitator to mix the reactant, and the pH of the reactant is maintained by

employing either

buffer solution or a pH controller

S m

S s

C K

C r

dt r dC

 



^max

 ^C ^C  ^r ^t

C

K C

_s _s

s s

m 0 max

ln

0

  

Change of Cs with time, t

Batch operation with stirring

•A foam breaker may be installed to disperse foam

-1.a. Batch Operation

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-1.b. Fed Batch Operation

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In a plug-flow

reactor, the substrate enters one end of a cylindrical tube with is packed with

immobilized enzyme and the product steam leaves at the other

end.



₀



_max

^

ln

0

C C r

C

K C

_s _s

s s

m

  

F, Cs0 F, Cs

t = 0

F

 V



An ideal plug-flow reactor can approximate the long tube, packed-bed and hollow

fiber or multistaged reactor

Residence time Continuous operation

without stirring

V

-2. Plug-flow mode

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12

A continuous stirred- tank reactor (CSTR) is an ideal reactor which is based on the

assumption that the reactants are well mixed.

Continuous operation with

stirring

F, Cs0

F, Cs V

-3. Continuous stirred-tank

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dt V dX V

r X

X

F( ₀  )  _x 

F, Cs0

F, Cs V

Mass balance of cell:

on Accumulati G

Output -

Input  eneration 

the ratio of biomass rate of generation to biomass concentration, r_x/X, that is the specific growth rate; μ





 ) (

)

( ₀

X X D

r X

V X F

x

 X 

r_x

 D 

 0 dt dX _s Steady state:

V D

F  



1

0

 0

No cell in inlet:

X

-3. Continuous stirred-tank – cont.

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Monod rate:

S K

S

s 





^max



S K

D S

s 



  ^max

D S DK^s

 

max

At steady state, substrate utilisation is balanced with a rate equation:

S V K

S S S

F

s



 





 

 ^max

0 )

( 



 





 

 K S

S S S

D

s max

0 )

( 

S S

X Y X



 

0



 





 



 D

S DK Y

X

X ^s

max 0

0 

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Bioreactor Design Properties

1

• Mass Transfer

2

• Heat Transfer

3

• Dimension

4

• Power consumption

5

• Hold Up

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1

• Mass Transfer

Determine K_La

α is proportionality factor, 2x10^-3

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2

• Heat Transfer

The reaction in bioreactor, especially fermentation:

generate HEAT

 Need cooling (coils or jacket in vessel)

Conduction

single layer

multi layer

Convection

Natural Forced

x kA T

q

_x ^ ^_

T

q

_x ^ hA^

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• Dimension

1. Reactor volume 2. Reactor diameter

3. Ratio of reactor diameter to impeller diameter D_t/D_i

4. Ratio of the height of the liquid level to impeller diameter, H_L/D_i

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4

• Power consumption

Power consumption per unit volume of liquid

Power consumption:

5 3

i c

p N D

N Pg

 

c i p

g

D N P N

5

 3



N_P is a function of Re and type of impeller Use graph

N = rpm/60

= ... rps

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Correction factors are used to define actual power

P_act = P. F_c. number of impeller

There is a further discussion for aeration power

(next subject)

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5

• Hold Up

 Assume air in water

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Ykcal

C V

q 1



 



Heat production rate:

q : heat production rate, kcal/ls

V: reactor liquid volume, l

: specific growth rate, s^-1 C: biomass concentration (g/l) Y_kcal: a yield coefficient given as

grams of cells formed per kcal energy released, g cells/kcal

Heat load: Heat load is determined by energy balances Practical Issues for Bioreactors

- Temperature Control (Heat Load)

Popular method

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-Temperature control (heat transfer)

Heat transfer surface area:

1. Low in (a) external jacket and (b) external coil for small reactors

2. High in (c) internal helical coil and (d) internal baffle coil for large reactors 3. Easily adjustable in (e) a separate external heat exchange unit

Difficult to clean Easily fouled by cell

growth on the surface

No cleaning problem

• Sterility requirement

• Shear forces imposed on cells

• Depletion of oxygen

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1. Biological reactions almost invariably are three-phase reactions (gas-liquid-solid). Effective mass transfer between phases is often crucial. For example, for aerobic fermentation, the supply of

oxygen is critical.

H P

CA^*  Ag



A A_g



l

A

K C C

J 

^*



The equation governing the oxygen transfer rate is:

Agitation:

•Mechanical stirring (for small reactors, and/or viscous liquids, low reaction heat)

•Air-driven agitation (for large reactors and/or high reaction heat)

-Agitation (gas transfer)

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1. Mechanical foam breaker (a supplementary

impeller)

2. Chemical antifoam agents (may reduce the rate of oxygen transfer)

- Foaming removal

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1. Aseptic operation (3-5% of fermentations in an

industrial plant are lost due to failure of sterilization.

2. Construction materials (glass for small

bioreactors, e.g., < 30 liters and corrosion-resistant stainless steel for large reactors)

3. Sparage design (three designs: porous, orifice and nozzle)

4. Evaporation control due to dry air input - Other issues

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THANKS FOR YOUR ATTENTION

The best person is one give something useful always

Bioreactor Design

Bioreactor Design

MATA KULIAH: PENGANTAR TEKNOLOGI BIOPROSES

What is a bioreactor?

Groups of Bioreactor

-1. Stirred tank

- 2. Bubble column

- 3. Airlift reactor

- 4. Packed-bed reactor

- 5. Trickle-bed reactor

- 6. Fluidized bed reactor

PLUG

FLOW CSTR

Bioreactor Operation Modes

C K

C r

dt r dC

 



 C C  r t

C

K C

ln

  

-1.a. Batch Operation

-1.b. Fed Batch Operation







ln

C C r

C

K C

  



-2. Plug-flow mode

-3. Continuous stirred-tank

 D 



 0

X

-3. Continuous stirred-tank – cont.





Bioreactor Design Properties

• Mass Transfer

• Heat Transfer

• Dimension

• Power consumption

• Hold Up

• Mass Transfer

• Heat Transfer

q

q

• Dimension

• Power consumption

• Hold Up

Heat load: Heat load is determined by energy balances Practical Issues for Bioreactors

Heat transfer surface area:





K C C

J 



Agitation:

THANKS FOR YOUR ATTENTION

 ^C ^C  ^r ^t

^