1. M. Awais Yaqoob
2011-ch-32
(University of Engineering and Technology, Lahore)

2. Chemical Reactors
• An industrial chemical reactor is
complex device in which heat transfer,
mass transfer, diffusion and friction may
occur along with chemical reaction with
provisions of safety and controls.
• Are vessels designed to contain
chemical reactions.

3. These are the two main basic
vessel types:
•tank
•pipe

4. Basic Principles:
• All chemical processes are centered
in a chemical reactor. The design of a
chemical reactor Is the most
important factor in determining the
overall process economics.

5. At the start the design work , the following
information is presumably available:
. Reaction Type
. Need for catalyst
. Phases involve
. The mode of temperature and
pressure control, and
. Production capacity

6. Reaction Types
• Direct Combination or Synthesis
Reaction
A + B = AB
• Chemical Decomposition or
Analysis Reaction
AB = A + B

7. • Single Displacement or
Substitution Reaction
A + BC = AC + B
• Metathesis or Double
Displacement Reaction
AB + CD = CB

8. In addition to the basic data, include:
• A heat and mass transfer characteristics
• Physical, chemical and thermodynamic
properties of components taking part in the
reaction.
• CORROSION- erosion characteristics of any
potential hazard associated with reaction
system.
• Reaction Rate

9. Endothermic Reactions
• “within- heating” describes
a process or reaction that
absorbs energy in the form
of heat.

10. Exothermic Reactions
• Release energy in the form of
heat, light, or sound.
• ∆S > 0
• ∆H < 0

11. Reaction Rate
• Speed at which a chemical
reaction proceeds, in terms of
amount of product formed or
amount of reactant consumed
per unit time

12. Factors Influencing
Reaction Rate
• Concentration
• The nature of reaction
• Temperature
• Pressure
• Catalyst

13. Modeling Principle:
•Inputs + Sources = Output
+ Sink + Accumulations

14. Basic Reactor Element
•Material Balances
•Heat Transfer and
Mass Transfer

15. Material Balances
• Also called mass balance.
• Is an application of conservation of
mass to the analysis of physical
systems.
• The mass that enters a system must,
by conservation of mass, either leave
the system or accumulate within the
system .

16. Mathematically the mass balance
for a system without a chemical
reaction is as follows:
•Input = Output +
Accumulation

18. Applications of Differential
Mass Balance
• Ideal (stirred) Batch reactor
• Ideal tank reactor, also named
Continuous Stirred Tank Reactor
(CSTR)
• Ideal Plug Flow Reactor(PFR)

19. Mass Transfer
• Is the phrase commonly used in
engineering for physical processes
that involve molecular and
convective transport of atoms and
molecules within physical system.
• Transfer of mass from high
concentration to low concentration.

20. Heat Transfer
• Is the transition of thermal energy
from a heated item to a cooler
item.
• Transfer of Thermal Energy

21. Modes Of Heat Transfer
• jacket,
• internal coils,
• external heat exchanger,
• cooling by vapor phase
condensation
• fired heater.

22. Jacket

23. Internal Coil

24. External Heat Exchanger

25. Cooling by Vapor Phase Condensation

26. Heat Exchange in Packed Reactors

27. Chemical Reactor can be
operated in:
1. Batch Modes
2. Semi Continuous Modes
3. Continuous Modes

28. BATCH REACTOR
•One in which feed material
is treated as a whole for a
fixed period of time.

29. Types of Cooling
Jacket:
Single External Jacket
• Consists of an outer jacket which
surrounds the vessel.
• Heat transfer fluid flows around the jacket
and is injected at high velocity via nozzles.
• The temperature in the jacket is regulated
to control heating or cooling.

30. Single External Jacket

31. • The half coil jacket is made by welding a half
pipe around the outside of the vessel to create a
semi circular flow channel.
•A large reactor may use several coils to deliver
the heat transfer fluid.
Half Coil Jacket

32. Half Coil Jacket

33. •Has a series of 20 or more small jacket
elements.
•The temperature control valve operates by
opening and closing these channels as
required.
Constant Flux Cooling Jacket

34. Constant Flux Cooling Jacket

35. SCHEMATIC DIAGRAM OF CRUDE SEWAGE

37. Semi Batch Reactor
• One or more reactant is in a batch
modes, while co reactant is fed
and withdrawn continuously.

38. Schematic Diagram of Semi Batch

39. Stirred Tank
Reactor

40. Consist of a tank fitted with
a mechanical agitator and a
cooling jacket or coils.

42. Continuous Stirred-Tank
Reactor
(CSTR)
• One or more fluid reagents are
introduced into a tank reactor.

43. • Residence time – average amount
of time a discrete quantity of
reagents spend inside the tank
• Residence time = volumetric flow rate
volume of the tank

44. Some Important
Aspects of the CSTR:

45. • At steady state, the flow
rate in must be equal the
mass flow rate out.

46. • All calculations performed
with CSTR’s assume perfect
mixing.

47. • The reaction proceeds at the reaction
rate associated with the final (output)
concentration.
• Economically beneficial to operate in
series or in parallel

48. • Small CSTR operating in
series would be equivalent to a
PFR.

51. Plug Flow
Reactor
(PFR)
One or more fluid reagents are
pumped through a pipe or tube

52. Some Important
Aspects of the PFR:

53. • All calculations performed with
PFR’s assume no upstream or
downstream mixing.
• Reagents may be introduced into the
reactor’s inlet

54. • Has a higher
efficiency than a CSTR
at the same value.

55. Schematic Diagram of Plug Flow Reactor

56. Tubular Flow
Reactor
(TFR)
are generally used for gaseous
reactions but are also suitable for
some liquid-phase reactions.

57. Some Important
Aspects of the TFR:

58. • Chemical reactions take place in a
stream of gas that carries reactants
from the inlet to the outlet
• The catalysts are in tubes

59. • Uniform loading is ensured
by using special equipment
that charges the same amount
of catalyst to each tube at a
definite rate.

62. CATALYSIS

63. CATALYSIS
•It is the acceleration of
chemical reaction by
means of substance
called catalyst.

64. Principles of Catalysis:
∙Typical mechanism:
A + C → AC (1)
B + AC → ABC (2)
ABC → CD (3)
CD → C + D (4)

65. •Catalysis and reaction
energetic.

66. What is Phase?

67. Two Types of
Catalyst:
∙Homogeneous
∙Heterogeneous

68. Homogeneous
• the catalyst in the
same phase as the
reactants.

69. Heterogeneous
•Involves the use of a
catalyst in a different phase
from the reactants.

70. How the heterogeneous
catalyst works?
•Adsorption
•Active Sites
•Desorption

71. Adsorption
•Is where something
sticks to a surface.

72. Active Sites
•Is a part of the surface
which is particularly good
at adsorbing things and
helping them to react.

73. Desorption
• means that the
product molecules
break away.

74. Kinds of Catalyst
• Strong Acids
• Base Catalysis
• Metal oxides, Sulfides, and Hydrides
• Metal and Alloys
• Transition-metal Organometallic
Catalysts

75. Strong Acids
•Is an acid that ionizes
completely in an
aqueous solution

76. Base Catalysis
• Is most commonly thought of as an
aqueous substance that can accept
protons.
• Base the chemical opposite of acids.
• Often referred to as an alkali if OH−
ions are involved.

77. Metal Oxides
•Form a transition between
acid/base and metal
catalysts.

78. Metal and Alloy
• Metal is a chemical elements whose
atoms readily lose electrons to form
positive ions (cations), and form metallic
bonds between other metal atoms and
ionic bonds between nonmetal atoms.
• The principal industrial metallic catalyst,
are found in periodic group VII

79. Transition-metal
Organometallic Catalysts
•More effective
hydrogenation than are
metals such as platinum.

81. Fluid and Solid
Catalysis
• Multitubular reactors
• Fluidized beds
• Fixed Bed
• Spray Tower
• Two-Phase Flow

82. Multitubular reactors
•These reactors are shell-
and-tube configuration and
have catalyst in the tubes.

83. Multi tubular Reactor

84. Fluidized Bed
• Device that can be used to carry
out a variety of multiphase
chemical reactions.
• A catalyst possibly shaped as tiny
spheres.

85. Fluidized Bed Reactor

86. Fixed Bed
• Fixed bed reactor is a
cylindrical tube, randomly
filled with catalyst particles,
which may be spheres or
cylindrical pellets.

88. Fixed Bed Reactor

89. SPRAY TOWER
• Are a form of pollution control
technology.
• Consist of empty cylindrical vessels
made of steel or plastic and nozzles
that spray liquid into the vessels

90. Two types of Spray Towers:
1.Cocurrent Flow
-are smaller than countercurrent-flow
spray towers
2.Crosscurrent Flow
- the gas and liquid flow in directions
perpendicular to each other.

92. Two-Phase Flow
• occurs in a system containing
gas and liquid with a meniscus
separating the two phases.

93. Two-phase flow may be
classified according to the
phases involved as:
• gas-solid mixture
• gas-liquid mixture
• liquid-solid mixture
• two-immiscible-liquids mixture

94. Goodbye!!!!!
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