The document discusses the conversion process of raw materials to products through chemical reactions. It covers key concepts in chemical reaction engineering including: 1) The conversion process typically involves physical preparation of raw materials, a chemical reaction step, separation of unconverted materials, and separation of unwanted and wanted products. 2) Chemical reaction engineering is concerned with designing chemical reactors and analyzing their performance. This involves determining factors like reactor size, flow configuration, and product distribution. 3) Key concepts in designing chemical reactors include steady-state vs. unsteady-state conditions, ideal vs. non-ideal mixing, conversion, selectivity, yield, and throughput. Material and energy balances are also important. 4) Common reactor types

1. 1 2 3 4
Raw
Materials
Wanted
and
unwanted
Products
Figure 1.1 Steps of the conversion process
The conversion process of any raw materials to
products could pass through a number of steps. For
illustration see the following schematic approach:
Step 1. Physical preparation of raw materials( Purification,
Grinding etc.).
Step 2. Chemical process with partial conversion
Step 3. Separation of non-converted raw
Step 4. Separation of unwanted and wanted products.

2. In the above processes, the steps 1, 3 and 4 are physical
treatments and are mainly carried out in unit operations. Step 2
is the chemical treatment / process / which is carried out
in the reactors.
The steps of a chemical process can be simple or complex,
depending upon the purity of the raw material, the desired quality
of the products etc.
The main objective of the chemical engineer is to design
appropriate reactor and or analysis of performance of
chemical reactors to secure quality of the wanted products
with a minimum cost of production using the tools of
chemical reaction engineering.
Chemical reaction engineering (CRE)
•is concerned with the rational design and/or analysis of
performance of chemical reactors
•is a means to determine something about the reactor: size,
flow and thermal configuration, product distribution, etc.

3. A Chemical reactor is a vessel or a container into which a chemical
reaction takes place. The size of such reactor can be a laboratory
beaker or an industrial reactor, for example ammonia reactor,
which has diameter up to 3 meter and length up to 30 meter.
A chemical reactor
•is a device in which change in composition of matter occurs
by chemical reaction
•is a device also involved in energy production, as in engines
(internal-combustion, jet, rocket, etc.) and in certain
electrochemical cells (lead-acid, fuel), in animate objects
(e.g., the human body),etc.. The rational design of this last is
rather beyond our capabilities
•is usually the “heart” of an overall chemical or biochemical
process
•is used to carry out the reaction and that is used as a tool for
determining something about the reacting system: rate of
reaction, and dependence of rate on various factors, such as
concentration of species j(cj) and temperature (T)

4. •design includes determining the type, size, configuration,
cost, and operating conditions of the device
The cost of production depends on step 2, i.e., appropriate
design of a reactor. To ensure good designing of a reactor in
the chemical treatment under step 2, it needs:
•Information, knowledge and experience from the different
sciences such as fluid mechanics, heat transfer, mass transfer,
economics etc.
•To answer the following two questions:
•What changes can we expect to occur? :-Thermodynamics
•How quickly will they take place? :-Kinetics
The second question deals with the various rates of processes
such as chemical kinetics, heat transfer and mass transfer.

5. Thermodynamics Fluid Flow Mathematics
Mass
transfer
Chemical
Reactor
Heat transfer
Materials
Economics
Kinetics
Chemical
Process $P

6. Generally there are four basic forms of homogeneous
chemical reactors which differ from each other in their
mixing pattern
1.1. Classification of Reactors
Reactors can be classified in a variety of ways:
 based on the size,
 method of operation and
the phase involved in the process
•The batch reactor (BR)
•The semi-batch reactor (SBR)
•The continuous-stirred tank reactor(CSTR)
The plug-flow reactor (PFR
Generally the basic reactors are classified

7. In the above, all reactors are also named based on the thermal
operations such as isothermal, adiabatic and non-
isothermal reactors. Most of the industries now a days are
working with heterogeneous catalytic reactors, some of them
are:
•Fixed Bed Gas Reactors
•Non-isothermal, Non-adiabatic Fixed Bed (NIHAF) Reactors.
•Fixed Bed Gas-Liquid Reactors.
oTrickle Bed Reactors
oFixed Bed Bubble Reactors(FBBR)
•Fixed Bed Reactors
•Suspended Bed Reactors.
oContinuous Stirred-Tank Reactors(CSTR)
oSlurry Reactors
• Bulleted Bed Reactors
• Three Phase Transport Reactors

8. The design procedure for homogeneous and heterogeneous
reactors is essentially the same and consists of establishing
 material balance and energy balance for specific type of
reactors involved
 finding the appropriate rate of equation and
 solving the required size of the reactor or other
parameters
1.2 Design Concept
The design of a reactor involves the following concepts:
1.2.1 Steady-State Condition Concept
This is a condition, where at the operation the variables at each
point within the system do not vary with the time. Therefore, in
the reactor the following variables remain unchanged with the
time.
•The concentration of the reactants and products.
•The reaction temperature
•The reaction rate

9. In steady-state condition, where the above compositions
remain unchanged with time. Hence, there is no
accumulation. On the other side, this type of operation is simple
to model (simple equipment) and accomplish in the case of
continuous reactors
1.2.2 Unsteady-State Condition Concept
This is opposite to the steady-state condition i.e., the
compositions change with time and therefore,
accumulations exist. This type of reactor is complicated to
model and only used in batch reactor.
1.2.3. Ideal concept in the reactor
The contents of the reactor are instantaneously and
perfectly mixed i.e., ideally mixed, so that the condition
through out the reactor remains the same.

10. 1.2.4. Calculation concept
Consider the general equation,
dD
cC
bB
aA 
 
From the equation we select an element to be the basis of
calculation, such as A. The base of calculation is most always
the limiting reactant. One of the criteria to select the limiting
reactant in a single reaction is the cost of the reactant.
1.2.5. Conversion
The conversion of species A in a reaction is equal to the number
of moles of A reacted per mole of A fed.
fed
A
of
moles
reacted
A
of
moles

A
X
To understand the concept of conversion, reaction,
dD
cC
bB
aA 
 
is carried out in a batch reactor under isothermal condition. This
is illustrated in Figure 1.1. The conversion obtained through time
is calculated in table 1.1.

11. nA,0
nA
Figure 1.1 Variable in batch reactor
t (min)
0 0
10 0.5
20 0.75
30 0.88
40 0.99
0
,
A
n
2
0
,
A
n
4
0
,
A
n
8
0
,
A
n
16
0
,
A
n
A
n A
X

12. •For Irreversible reactions
The maximum value of conversion, XA, is that for complete
conversion, i.e., XA = 1.0
•For Reversible reactions
The maximum value of conversion, XA, is the equilibrium
conversion, i.e., XA = XA,equ.
Progress Test 1.1 For the reaction
dD
cC
bB
aA 
 
Write equilibrium constant in terms of conversion

13. 1.2.6 Selectivity
Is the formation of the desired product (species j) divided
by the formation of all products
formed
products
all
of
amount
formed
j
product
desired
of
amount
j 
S
This is a number that goes from zero to unity as the selectivity
improves. We can use the number of moles nj, chosen on some
basis for each species such that we divide each nj by its
stoichiometric coefficient to normalize them. For a steady-
state flow system the molar flow rates Fj are appropriate.
If we can identify a reactant A on which to base the selectivity,
then we can define the selectivity as
F
-
F
F
n
-
n
n
A
A,0
B
A
A,0
B
B 

S
as long as loss of one mole of A can form one mole of B.

14. If the system is also at constant density, this can also be written
C
-
C
C
A
A,0
B
B 
S
and, for the A B C or A B, A C
systems, the selectivity to form B becomes
C
C
C
C
B
B
B


S
1.2.7Yield
in multiple reactions is the amount of the desired product formed
divided by the amount of the reactant fed
fed
reactant
formed
j
product
desired
j 
Y
For reactant A and product B with one mole of B formed per mole
of A reacted, the yield is given by the expression
C
C
F
F
n
n
A,0
B
A,0
B
A,0
B
B 


Y

15. Note finally that the yield is always the selectivity times the
conversion
X
S A
B
B 
Y
Since the conversion is based on a reactant species, the yield is
based on a specific product and a specific reactant.
For our A B C and A B, A C reaction
systems, species A is the reactant, species B is the desired
product, and C the undesired product, and there is no change in
number of moles ( ) so these
expressions become particularly simple,
1
,
2
,
2
,
1
,
1 




 C
B
B
A 



A,0
A
A,0
A
C
C
-
C

X C
C
C
C
C
C
A
A,0
B
C
B
B
B




S
C
C
X
S
A,0
B
A
B
B 

Y

16. Using Differential/ instantaneous/ selectivity, for a single
reactant A, the product ratio is,
B
s
A
dC
B
dC
C
dC
B
dC
B
dC




Which is the rate of forming B divided by the rate of loss of A or which
determines to what extent reactant A being is converted into B at
some place or at some moment. This is a useful tool for choosing local
reaction conditions in any reactor.
Using the above equation, we can formulate:
B
dC A
dC
B
s


And integrating, we obtain
0
,
B
C A
dC
A
C
A
C
B
s




17. 1
-
C
S
0
,
0
,
0
,
B
B A
A
C
A
C
B
A
A
A
A
dC
s
C
C
C
C





For two parallel irreversible reaction with orders α1, α2
becomes
k
k
k
r
C
0
,
2
2
1
1
1
1
0
, 2
1
1
B A
A
C
A
C A
A
A
A
A
C
A
C
dC
C
C
C
dC
r
r







 


The total selectivity can be found by writing as

18. If α1 = α2 , then the integral becomes
)
-
(
k
k
k
k
C 0
,
2
1
1
0
, 2
1
1
B A
A
A
A
C
A
C
C
C
dC
k
k 





If α1 = 0 and α2 =1, then this expression becomes
A
A
A
C
A
C
A
A C
k
k
C
k
k
k
k
dC
C
k
k
k
2
1
0
,
2
1
2
1
0
, 2
1
1
B ln
C







and the total selectivity is
A
A
A
A
A
A
B
C
k
k
C
k
k
C
C
k
k
C
C
C
2
1
0
,
2
1
0
,
2
1
0
,
B ln
)
(
S







19. t
C
m
C



j
m
1.2.8 Throughput (capacity) Feed Rate
This is the volumetric or mass flow rate through the reactor system
is the mass flow rate of species j
Where
1.2.9 Load (Intensity)
This is the volumetric or mass flow rate per unit reactor
volume or catalyst mass.
W
t
C
m
V
t
C
m
V
C
I
1
1





1.3 Material Balance see Rxn Eng’g I - Kinetics

20. 1.4 Energy Balance
A similar word statement as of material balance can be used for energy
balance, i.e the application of the principle of conservation of energy leads to
an energy balance which is in general states that:
Rate of Rate of Rate of Rate of
Accumulation = Energy - Energy + Energy
of Energy In Out Production
In principle, all forms of energy, like heat, kinetic energy, potential
energy, electrical and magnetic field must be taken into
consideration. In most reactor calculations, the terms with
thermal energy and work done on the surroundings are of the
main importance.
Hence, leaving out the other effect, the energy balance for an
open system in which reaction takes place, illustration is given in
the Figure 1.2

21. HF HE
Q
dt
dH
Figure 1.2 Energy balance on an open system: HF – inflow of
enthalpy; HE – outflow of enthalpy; Q – rate of heat supply from
the surrounding or withdrawn from the system Using equation
(1.10) the energy balance for the above open system is
dt
dH
Q
E
H
F
H 

 ( 1.10.1)
or
dt
dH
T
S
T
KA
E
H
F
H 


 )
( (1.10.2)

22. dt
RV
R
H )
(

dT
P
C
T
m
The enthalpy change should be expressed into two elements:
i)The enthalpy change with time due to the change in
composition. In another word, the energy change due to
the heat of the reaction.
ii) The enthalpy change due to the change of temperature
If we now substitute the enthalpy change to equation (1.10.2),
we obtain
dt
dT
P
C
T
m
dt
rV
R
H
T
S
T
KA
E
H
F
H






)
(
)
(
or
dT
P
C
T
m
dt
rV
R
H
dt
T
S
T
KA
dt
E
H
F
H 




 )
(
)
(
)
(
Rearranging the equation, we can now write the general energy
balance for the system
)
(
)
(
)
( T
S
T
KA
E
H
F
H
rV
R
H
dt
dT
P
C
T
m 






23. where
K-Overall heat transfer coefficient
TS-Surrounding (cooling, heating) temperature
A- Effective area for heat transfer
T- The temperature of the reaction mixture
∆HR - Heat of reaction
To put this general energy balance equation in a more applicable
form, there are two conditions for modification:
In a batch process where there is no in- and out-flow, then the
energy balance equation yields to
)
(
)
( T
S
T
KA
rV
R
H
dt
dT
P
C
T
m 



To put this general energy balance equation in a more applicable
form, there are two conditions for modification:
In a continuous process where accumulation is not existing,
the energy balance equation then becomes
)
( T
S
T
KA
dH
E
H
F
H 




24. )
(rV
R
H
dT
P
C
R
F
dH 


)
(
)
( T
S
T
KA
rV
R
H
dT
P
C
R
F 



where
Then, the enthalpy balance for continuous process is
(1.12)
(1.13)
1.5 Designing of a Reactor
In a reactor design, the main parameters are to choose the
type of reactor, to select the method of operation and to find the
size of the reactor.
In this selection, common types of reactors and operation
methods are known. Therefore, the choice of reactor would be
made on the basis of profit, safety and environmental factors
which will influence the reactor performance.
Sizing of a reactor means to determine the reactor volume
necessary to achieve a specified conversion. The condition in the
reactor varies with position as well as with the time and therefore,
it is necessary to find the rate equation.

25. Normally the rate of reaction is expressed in terms of the
concentration, but not in terms of conversion. However, we need
to express the concentration of the reacting species in terms of
conversion, for which we use stoichiometry relationship for batch
and flow processes.
1.5.1 Batch Process - see Rxn Eng’g I- Kinetics
1.5.2 Flow Process - see Rxn Eng’g I- Kinetics
1.6 Conversion in multiple reactions
- see Rxn Eng’g I- Kinetics