Lecture 7: Batch Reactors - Notes, Chemical and Biological Reaction Engineering, Notes | EduRev

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: Lecture 7: Batch Reactors - Notes, Chemical and Biological Reaction Engineering, Notes | EduRev

 Page 1


10.37 Chemical and Biological Reaction Engineering, Spring 2007 
Prof. K. Dane Wittrup 
Lecture 7: Batch Reactors  
 
This lecture covers batch reactor equations, reactor sizing for constant volume and 
variable volume processes. 
 
Batch Reactors
 
Run at non-steady state conditions 
 
Which to choose? Batch vs. CSTR? 
   
  
  
CSTR 
Batch 
 
 
 
 
 
 
Figure 1. Schematics of a batch reactor and a 
 
CSTR. 
 
Small Amount of Material (small quantities) (does not tie up 
  equipmentcontinuously) 
 
Flexibility + -
 
Expensive Reactants + - 
 
If product does not flow, + - 
 Materials Handling (e.g. Polymers)  
 
Do not have to shut down and - + 
 clean, less down time 
 
Captial costs? For size of reactor, + - 
 for given conversion               (concentration stays 
               higher longer) 
 
Operability & Control (T, P, p4) - + 
 e.g. Exothermic reaction  (Manipulate only one  
   setpoint, steady state. 
  You can control additional  
  variables. Such as flow rates.) 
 
 
Material Balance 
 
   
 In – Out + Product = Accumulation 
   0       0 
 
Cite as: K. Dane Wittrup, course materials for 10.37 Chemical and Biological Reaction Engineering, Spring 
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on 
[DD Month YYYY]. 
 
 
Page 2


10.37 Chemical and Biological Reaction Engineering, Spring 2007 
Prof. K. Dane Wittrup 
Lecture 7: Batch Reactors  
 
This lecture covers batch reactor equations, reactor sizing for constant volume and 
variable volume processes. 
 
Batch Reactors
 
Run at non-steady state conditions 
 
Which to choose? Batch vs. CSTR? 
   
  
  
CSTR 
Batch 
 
 
 
 
 
 
Figure 1. Schematics of a batch reactor and a 
 
CSTR. 
 
Small Amount of Material (small quantities) (does not tie up 
  equipmentcontinuously) 
 
Flexibility + -
 
Expensive Reactants + - 
 
If product does not flow, + - 
 Materials Handling (e.g. Polymers)  
 
Do not have to shut down and - + 
 clean, less down time 
 
Captial costs? For size of reactor, + - 
 for given conversion               (concentration stays 
               higher longer) 
 
Operability & Control (T, P, p4) - + 
 e.g. Exothermic reaction  (Manipulate only one  
   setpoint, steady state. 
  You can control additional  
  variables. Such as flow rates.) 
 
 
Material Balance 
 
   
 In – Out + Product = Accumulation 
   0       0 
 
Cite as: K. Dane Wittrup, course materials for 10.37 Chemical and Biological Reaction Engineering, Spring 
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on 
[DD Month YYYY]. 
 
 
dN
r
A
V =
A
 
dt
Constant V, 
dC
r
A
A
= 
dt
In terms of conversion, 
dX
Cr
A
Ao
= 
dt
A
Integrating, t
C
A dC
=
?
A
 or 
C
Ao
r
A
tC
X
A dX
=
A
Ao
?
 
0
r
A
 
 
1
st
 Order Reaction A ?
k
? ?B 
 
-= rk
AAA
C =kC
o
(1-x
A
) 
dx
?
x
A
A
11 ??
tC=?
Ao
??= t ln 
0
??
-- kC
Ao
(1 x
A
) k
??
1-x
A
x
A
=- 1 e
-kt
 
 
90% conversion 
11 ??2.3
t
90.0%
== ln
??
 
kk
??
10 - .9
 (order of 
1
) 
k
 
 
2
nd
 Order Reaction A+? AB
k
? ? 
 
-= rk
22
AA
C =kC
Ao
(1-X
A
)
2
 
tC
XX
AA dX
AA
1 dX
==
Ao
??
 
22
00
-- kC
Ao
(1 X
A
) -kC
Ao
(1-X
A
)
2
 
1 X
t =
A
 
kC
Ao
1 -X
A
kC
X
Ao
t
A
= 
1 +kC
Ao
t
 
 
If kk
firstorder
=
second order
C
A
, which is faster? 
o
 
 1 2 3 
1
st
 order 0.63 0.86 0.95 
2
nd x
 order 0.50 0.67 0.75 
}
A
 
For a given Damkohler number, 1
st
 order is faster. The second order reaction has 
greater concentration dependence. Exponential approach (1
st
 order) is faster. 
10.37 Chemical and Biological Reaction Engineering, Spring 2007 Lecture # 
Prof. K. Dane Wittrup  Page 2 of 5 
 
Cite as: K. Dane Wittrup, course materials for 10.37 Chemical and Biological Reaction Engineering, Spring 
2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on 
[DD Month YYYY]. 
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