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Subtopics:Ideal Batch Reactor

Steady state mixed fow reactor(MFR)

Steady state plug fow reactor

Space time and space elocity

!olding time and space time "orfow reactor

Si#e comparison o" single reactors

Re"erence: Fogler and $eenspiel

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Reactors coered in %opic & are:

'Batch Reactor Steady State MFR * Mixed FlowReactor+ Steady State ,FR * ,lug Flow

Reactor

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 ApplicationSmall scale production/one-off production

Pharmaceutical and fermentation

 Advantages

Easy to cleanHigh conversion per volume

Flexiility of operation-same reactor can

produce one product one time and a different

product the next

!isadvantages"

 High operating cost

 Product #uality more variale than with

continuous operation

$deal %atch &eactor 

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$deal %atch &eactor 

 Material Balance: In - .ut / ,roduct 01ccumulation

' '

Batch Reactor Design Equation

2 the reactants are initially charged into a container3 are wellmixedand are le"t to react "or certain period

4 Recall the batch reactor design e5uation

Vr dt

dNA

A =   ( )X1 N NAoA  −=

Vr dt

dX N

AAo  −=

  ( )

∫    −=

  tX

0A

Ao

Vr 

dX Nt

diferentialorm

integralorm

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$deal %atch &eactor 

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6raphical representation o" the per"ormancee5uations "or batch reactors3 isothermal and non*isothermal7  6eneral case

8onstant*density systems

only

$deal %atch &eactor 

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Steady State (ixed Flow &eactor )(F&*

1pplication

1 production o" where agitation isre5uired

8ontinuous production

1dantages

9asy to clean

6ood temperature control

$ow operating cost (labour)

isadantages:

$owest conersion per unit

olume

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Steady State (ixed Flow &eactor )(F&*

4  %he contents are well stirred and uni"orm throughout

+ The exit stream from this reactor has the same

composition as the fluid within the reactor  

4Recall the 8S%R esign 95uation:

( )X1FFAoA  −=

A

AAo

r 

FFV

−

−=

( )exit

A

Ao

r 

XFV

−

=

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4 esign e5uation A

 A Ao

r 

 F  F V 

−

−

=

In terms o"conersion   A

 Ao

r 

 X  F V 

−

=

Reactor si#ing3 theolume o" MFR canbe calculated "rom

s A

 Ao

r 

 F 

−

 X 

 A

 Ao

r 

 F 

−

 X 

SS-(F&

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4 Reactors in series can also be designed proided there are noside streams by de;ning the oerall conersion at any point

reactor firsttofedAof moles

i pointtoupreactedAof moles=i X 

Mole balance at reactor '

Mole balance at reactor

0111

  =+−   V r  F  F  A A Ao

1

1

1

 A

 Ao

r 

 X  F V 

−

=

02221

  =+−   V r  F  F  A A A

( )

2

12

2

 A

 Ao

r 

 X  X  F V 

−

−=

SS-(F&

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Steady State Plug Flow Reactor

1pplication

For large scale production

,roduction with "ast reactions<high temperature Both homogenous and heterogeneous reaction

8ontinuous production

1dantages

!igh conersion per olume

$ow operating cost

6ood heat trans"er

isadantages:

  =ndesired thermal gradients may exist

  ,oor temperature control

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4esign e5uation  A

 A

r dV 

dF =

In terms o"conersion

 A Ao  r 

dV 

dX  F    −=

∫ −=

 X 

 A

 Ao

r 

dX  F V 

0

 %he olume o" ,FR can be represented as

shaded area under the cure

* 1rea under the curecan be calculated usingnumerical method such

as Simpson>s Rule

Steady State Plug Flow Reactor

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Space Time and Space elocity

o

V 

υ 

τ    =

Space time3 isobtained by diidingreactor olume by

the olumetric fowrate entering thereactor

τ 

 %ime ta?en "or fuid

to enter reactorbased on entrancecondition - olumeand olumetric rate

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+ Space velocity, S is defined as

τ  

υ  1==

V 

SV    o

V  LHSV 

  liquid o |υ 

=

V GHSV    o STP|υ 

=

Space Time and Space elocity

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For %atch reactor 

∫ =

 A

 Ao

C 

C    A

 A

r 

dC d τ  

∫   −

=

 Ao

 A

C 

C    A

 A

r 

dC τ  

 A A r 

dt 

dC =

!olding time and Space Time or Reactor

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 A

 A Ao

r 

 F  F V 

−

−

=

For .ST&/(F&,

 A

o

 A

o

 Ao

o   r 

 F  F V 

−

−

=

υ υ 

υ 

 A

 A Ao

r 

C C 

−

−

=τ  

!olding time and Space Time or Reactor

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For PF&

 A

 A

r 

dC d    =τ  

 A

 A

r dF dV   =

∫ −

=

 X 

 A

 Aor 

dX  F V 

0

∫ −=

 X 

 A

 Ao

r 

dX C 

0

τ  

!olding time and Space Time or Reactor

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Si"e #omparison o Single Reactors

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Si"e #omparison o Single Reactors

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9xam @ A 1pril ''

 %he li5uid phase o" reaction  A -» B is an elementary

reaction in a fow reactor with 85% conersion o" 1 %he inlet concentration o" 1 is + mol<liter and theolumetric fowrate isC liter<hr1dditional in"ormation: ?1 0 D hr*'

a) etermine the space time and olume i" this

reaction is carried out in a 8S%R(& mar?s)

b) etermine the space time and olume i" thisreaction is carried out in a ,FR

(& mar?s)c) Repeat part (a) and (b) i" the reaction now obeys

nd order ?inetics(E mar?s)

d) 8hoose the best reactor "or both order o" reactionand usti"y your answer

(C mar?s)

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9G .F %.,I8 &