Chemical reaction engineering is that engineering activity which is concerned with the exploitation of chemical reactions on commercial scale.
The areas of different fields of science like:
Oil Refining
Pharmaceuticals
Biotechnology
Chemical Industries
Sustainable Development
DC MACHINE-Motoring and generation, Armature circuit equation
Group 2
1. Contents:
Batch Reactor and Plug Flow Reactor by
Aamir Shahzad
Mixed Flow Reactor by
Hafiz Shoaib Munir
Reactions by
M. Waqas Nawaz
Stoichiometry by
Ateeq U Rehman
3. Definition
•The continuous flow stirred-
tank reactor (CSTR), also known as back-mix
reactor.
•In a perfectly mixed reactor, the output
composition is identical to composition of the
material inside the reactor, which is a function
of residence time and rate of reaction.
4. MFR/CSTR
• A continues stirred tank reactor(CSTR) is a vessel to
which reactants are added and products removed while
the contents within the vessel are vigorously stirred
using internal agitation.
• At steady state, the flow rate in is must be equal to
flow rate out.
5. Basic Terms
• Back Mixing:
The tendency of reacted chemicals to
intermingle with unreacted feed in reactors, such as stirred
tanks, packed towers, and baffled tanks.
• Residence Time Distribution:
The residence time
distribution (RTD) of a chemical reactor is a probability
distribution function that describes the amount of time
a fluid element could spend inside the reactor
8. APPLICATIONS
• CSTRs are most commonly used in industrial
processing , primarily in homogeneous liquid-phase
flow reactions, where constant agitation is required.
• Fermentors are CSTRs used in biological processes in
many industries, such as brewing, antibiotics and
waste treatment.
• In fermenters, large molecules are broken down into
smaller molecules, with alcohol produced as a by-
product.
10. ADVANTAGES
Cheap to construct.
Good temperature control is easily maintained.
Reactor has large heat capacity.
Interior of reactor is easily accessed.
13. REACTORS
Definition:
A reactor is a system (volume) with boundaries. Mass may enter
and leave across boundary.
Characteristics:
System:
1. Closed or intermittent: no mass enters or leaves during reaction(s) are
batch or semi-batch reactors
2. Open (control volume): mass enters/leaves during reaction(s) are
continuous flow reactors
14. Batch Reactor
Introduction:
The batch reactor is the generic term for a type
of vessel widely used in the process industries.
Vessels of this type are used for a variety of process
operations such as solids dissolution, product
mixing, chemical reactions, batch
distillation, crystallization, liquid/liquid extraction
and polymerization.
In some cases, they are not referred to as reactors but have a
name which reflects the role they perform (such
as crystallizer, or bioreactor).
15. Construction:
A typical batch reactor consists of a tank with
an agitator and integral heating/cooling system.
These vessels may vary in size from less than 1 litre to
more than 15,000 litres.
They are usually fabricated in steel, stainless steel, glass-
lined steel, glass or exotic alloy.
Liquids and solids are usually charged via connections in
the top cover of the reactor.
Vapours and gases also discharge through connections in
the top. Liquids are usually discharged out of the bottom.
16. Heating and Cooling Systems
• Products within batch reactors usually liberate or absorb heat during
processing.
• Even the action of stirring stored liquids generates heat.
• In order to hold the reactor contents at the desired temperature, heat
has to be added or removed by a cooling jacket or cooling pipe.
• Heating/cooling coils or external jackets are used for heating and
cooling batch reactors. Heat transfer fluid passes through the jacket or
coils to add or remove heat.
• Within the chemical and pharmaceutical industries, external cooling
jackets are generally preferred as they make the vessel easier to clean.
17. Working Principle:
A batch reactor has neither inflow nor outflow of
reactants or products while the reaction is being
carried out.
This is an unsteady state operation where
composition changes with time.
However, it is assumed that at any instant the
composition throughout the reactor is uniform (in
composition and temperature etc), because of
efficient stirring.
18. Advantages
The advantages of the batch reactor lie with its versatility.
A single vessel can carry out a sequence of different operations without
the need to break containment.
This is particularly useful when processing toxic or
highly potent compounds.
19. Applications:
Batch reactors are often used:
In the process industry.
In many laboratory applications, such as small scale production and inducing
fermentation for beverage products.
In medical production.
for experiments of reaction kinetics, volatiles and thermodynamics.
Highly used in waste water treatment.
Effective in reducing BOD (biological oxygen demand)of influent untreated
water.
20. Plug Flow Reactor
20
Fluid passes through the reactor with no mixing of earlier and later
entering fluid, and with no overtaking.
It is as if the fluid moved in single file through the reactor.
21. In an ideal plug flow reactor, it is assumed that there is no mixing of the medium
along the long axis (X-axis) of the reactor although there may be lateral mixing in
the medium at any point along the long axis (ie the Y-axis).
22. Assumptions:
Plug flow
Steady state
Constant density (reasonable for some liquids but a 20% error for
polymerizations; valid for gases only if there is no pressure drop, no
net change in the number of moles, nor any large temperature change)
Single reaction occurring in the bulk of the fluid (homogeneously).
23. Applications:
Plug flow reactors are used for some of the following applications:
Large-scale production
fast reactions
Homogeneous or heterogeneous reactions
Continuous production
High-temperature reactions
24. Advantages and Disadvantages of Plug flow Reactor
Advantages:
Easily maintained as there are no moving parts.
High conversion per unit volume.
Unvarying product quality.
Good for studying rapid reactions.
Disadvantages:
Poor temp control.
Hot spots may occur when used for exothermic reactions.
26. Order Of Reaction
For a general reaction between A and B where
‘a’ moles of A and ‘b’ moles of B react to form ‘c’ moles
of C and ‘d’ moles of D .
aA + bB cC + dD
We can write rate equation
27. R = [A]a[B]b
The exponent ‘a’ and ‘b’ gives the order of reaction with
respect to the individual reactant.
Thus
Overall order of reaction = (a+b)
28. Define :
The sum of all the exponent to which the
concentration in the rate equation are raised.
29. Facts
The order of react is an experimentally determined quantity and can
not be determined by simply looking at the reaction equation.
The sum of exponents in the rate equation may and may not be same
as in chemical equation .
30. The Chemical reaction are classified as
Zero
First
Second
Third
The order of reaction provides valuable information about
mechanism of a reaction.
31. Order of Reaction
Decomposition of nitrogen pentaoxide involves the following equation
2N2O5 2N2O4 + O2
Rate = K [N2O5]
First Order reaction
32. Hydrolysis of tertiary butyl bromide
(CH3)3CBr + H20 (CH3)3COH + HBr
Rate = k [ (CH3)3CBr ]
pseudo First order reaction
33. Finding order of reaction
• Method of Hit and Trail
• Graphical method
• Differential method
• Half life method
• Method of Large Excess
