This document discusses chemical reactions, their rates, and the design and operation of Continuous Stirred Tank Reactors (CSTRs). It outlines key concepts including rate equations, reaction rates, and the importance of steady-state conditions in CSTRs. The document emphasizes the need for experimental determination of rate laws and describes the ideal behavior of CSTRs as being well-mixed with consistent properties throughout.

1. Kinetics and Reactor Design
Design and operation of CSTR
C h a p t e r 3

2. 2
Introduction

3. 3
Chemical Reactions and Rate of Reactions:
 The rate equation (i.e. rate law) is an algebraic equation that is solely a function of the
properties of the reacting materials and reaction conditions including species,
temperature, pressure or type of catalyst, if any at a point in the system.
aA bB cC dD
  
Reaction rate definition is independent of reactor type.
Rate of reaction is change of concentration with respect to time!
Mathematically, it can be represented as:
   
, ,.....
A B
r k T f C C

Dimension: Units:
3
Mole
Time Length
 3
Mole
s m

where k (T ) is a function of temperature. The rate law must be determined experimentally.
The common form of the rate law is: − rA = kCA
a
CB
b
Rate constant dimension (K)
𝐴 =
−𝑟 𝐴
C A a C B b
=
(𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛)
(𝑇𝑖𝑚𝑒) .(𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛
𝑛
)
 
1
,
n
Concentration
k n
Time
 

  
n= a+b
𝐶𝑖=
𝑛𝑖
V
Units:
1
s

4. 4
Relative Rates of Reaction
It is defined for each species in the chemical reaction, i.e.
aA bB cC dD
  
C
A B D
r
r r r
a b c d
  
- -

5. 5
Extent of Reaction (Mass balance calculations)
This can also be written in terms of a molar flow as, ni = ni,0 + νiξ
.
.
The ratio of the change in the number of moles present, d Ni, to the stoichiometric coefficient,
for the reactant is the same in each case, and this ratio is called the extent of reaction, ξ,
Ni = Ni,0 + νiξ

6. 6
Conversion

7. 7
General Mole Balance for Reactors

8. 8
Continuous Stirred Tank Reactor (CSTR):
Definition:
Continuous Stirred Tank Reactors (CSTR) are defined to be flow reactors characterized by
intense mixing so that the properties anywhere inside the reactor are exactly the same as
that of the exist stream.
Input Rate
Liquid Surface
V
Stirrer
Schematic Representation of CSTR:
Output Rate
Assumptions :
1. Steady state
2. Well-mixed

9. 9
Continuous Stirred Tank Reactor (CSTR):
1- Steady state: No accumlation dNi/dt=0

10. 10
Continuous Stirred Tank Reactor (CSTR):

11. 11
Continuous Stirred Tank Reactor (CSTR):

12. 12
Continuous Stirred Tank Reactor (CSTR):

13. 13
Continuous Stirred Tank Reactor (CSTR):

14. 14
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