Description of Reactors, their types

1. Nasir Hussain
Production and Operations Engineer
PARCO Oil Refinery
Types of Chemical Reactors

2. Introduction
• Reactor is the heart of Chemical Process.
• A vessel designed to contain chemical
reactions is called a reactor.
• An industrial reactor is a complex
chemical device in which heat transfer,
mass transfer, diffusion and friction may
occur along with chemical with the
provisions of safety and controls

3. Basic Principle
• 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.

4. Basics for Design
• Reaction Type
• Removal/addition of heat
• Need for catalyst
• Phases involve
• The mode of temperature and pressure
control.
• Production capacity or flow
• Residence time
• Contact/mixing between the reactants

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

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

7. 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

8. Endothermic/Exothermic Reactions
• “within- heating” describes a process or
reaction that absorbs energy in the form of
heat.
• Release energy in the form of heat, light, or
sound.
• ∆S > 0
• ∆H < 0

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

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

11. Modeling Principle:
Inputs + Sources = Output + Sink +
Accumulations

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

13. 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 .

14. Mass Balance
Mathematically the mass balance
for a system without a chemical
reaction is as follows
Input = Output + Accumulation

15. 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.

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

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

19. Reactor Types
• They can be classified according to the;
1. Mode of operation
2. End use application
3. No of Phases
4. A catalyst is used

20. Classification by Mode of Operation
• Batch Reactors
• Continuous reactors
• Semi-batch reactors

21. Batch Reactor
• A “batch” of reactants is introduced into
the reactor operated at the desired
conditions until the target conversion is
reached.
• Batch reactors are typically tanks in which
stirring of the reactants is achieved using
internal impellers, gas bubbles, or a pump-
around loop where a fraction of the
reactants is removed and externally
recirculated back to the reactor.

22. Batch Reactors
• Temperature is regulated via internal
cooling surfaces (such as coils or tubes),
jackets, reflux condensers, or pump-
around loop that passes through an
exchanger.
• Batch processes are suited to small
production rates, too long reaction
times, to achieve desired selectivity, and
for flexibility in campaigning different
products

23. BatchReactor

24. Applications of Batch reactor
• Fermentation of beverage products
• Waste water treatment

25. Continuous Reactors
• Reactants are added and products
removed continuously at a constant
mass flow rate. Large daily production
rates are mostly conducted in
continuous equipment.

26. Continuous Reactors
• CSTR
• Plug Flow Reactor
• Tubular flow reactor

27. CSTR
• A continuous 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 or by
internally (or externally) recycling the
contents.
• CSTRs may be employed in series or in
parallel.

28. CSTR
• Residence time – average amount of time a
discrete quantity of reagents spend inside the
tank
• Residence time = volumetric flow rate
volume of the tank
• At steady state, the flow rate in must be equal
the mass flow rate out.

29. CSTR Applications
• Continuous stirred-tank reactors are most
commonly used in industrial processing,
primarily in homogeneous liquid-phase
flow reactions, where constant agitation is
required. They may be used by themselves,
in series, or in a battery.
• Fermentors are CSTRs used in biological
processes in many industries, such as
brewing, antibiotics, and waste treatment.
In fermentors, large molecules are broken
down into smaller molecules, with alcohol
produced as a by-product.

30. Advantages/Disadvantages of CSTR
• Good temperature control is easily
maintained
• Cheap to construct
• Reactor has large heat capacity
• Interior of reactor is easily accessed
Disadvantage:
• Conversion of reactant to product per
volume of reactor is small compared to
other flow reactors

31. Plug Flow Reactor
Plug flow, or tubular, reactors consist of a
hollow pipe or tube through which reactants
flow. Pictured below is a plug flow reactor in
the form of a tube wrapped around an
acrylic mold which is encased in a tank.
Water at a controlled temperature is
circulated through the tank to maintain
constant reactant temperature.

32. Plug Flow Reactor
•Reagents may be introduced into the reactor’s inlet
•All calculations performed with PFR’s assume no
upstream or downstream mixing.
•Has a higher efficiency than a CSTR at the same value

33. Schematic Diagram of Plug Flow Reactor

34. Applications of Plug flow reactor
• Plug flow reactors have a wide variety of
applications in either gas or liquid phase
systems. Common industrial uses of tubular
reactors are in gasoline production, oil cracking,
synthesis of ammonia from its elements, and
the oxidation of sulfur dioxide to sulfur trioxide.

35. Tubular Flow Reactor
• A tubular flow reactor (TFR) is a tube (or pipe)
through which reactants flow and are
converted to product.
• The TFR may have a varying diameter along the
flow path.
• In such a reactor, there is a continuous gradient
(in contrast to the stepped gradient
characteristic of a CSTR-inseries battery) of
concentration in the direction of flow.
• Several tubular reactors in series or in parallel
may also be used. Both horizontal and vertical
orientations are common

36. Tubular Flow Reactor
Chemical reactions take place in a stream of gas
that carries reactants from the inlet to the outlet
The catalysts are in tubes Uniform loading
is ensured by using special equipment that
charges the same amount of catalyst to
each tube at a definite rate.

37. Semi Batch Reactor
• Some of the reactants are loaded into the reactor, and
the rest of the reactants are fed gradually. Alternatively,
one reactant is loaded into the reactor, and the other
reactant is fed continuously.
• Once the reactor is full, it may be operated in a batch
mode to complete the reaction. Semi-batch reactors are
especially favored when there are large heat effects and
heat-transfer capability is limited. Exothermic reactions
may be slowed down and endothermic reactions
controlled by limiting reactant concentration.

38. Semi Batch reactors
• In bioreactors, the reactant concentration may
be limited to minimize toxicity.
• Other situations that may call for semibatch
reactors include control of undesirable by-
products or when one of the reactants is a gas
of limited solubility that is fed continuously at
the dissolution rate.

39. Classification By End Use
• Chemical reactors are typically used for the
synthesis of chemical intermediates for a
variety of specialty (e.g., agricultural,
pharmaceutical) or commodity (e.g., raw
materials for polymers) applications.

40. Classification by End use
• Polymerization Reactors
• Bio-reactors
• Electrochemical Reactors

41. Polymerization Reactors
• Polymerization reactors convert raw materials
to polymers having a specific molecular weight
and functionality. The difference between
polymerization and chemical reactors is
artificially based on the size of the molecule
produced.

42. Bio Reactors
• Bioreactors utilize (often genetically
manipulated) organisms to catalyze
biotransformations either aerobically (in the
presence of air) or an-aerobically (without air
present).

43. Electrochemical reactors
• Electrochemical reactors use electricity to drive
desired reactions.
• Examples include synthesis of Na metal from
NaCl and Al from bauxite ore.
• A variety of reactor types are employed for
specialty materials synthesis applications (e.g.,
electronic, defense, and other).

44. Classification by Phase
• Despite the generic classification by operating
mode, reactors are designed to accommodate the
reactant phases and provide optimal conditions for
reaction.
• Reactants may be fluid(s) or solid(s), and as such,
several reactor types have been developed.
• Single phase reactors are typically gas- (or plasma- )
or liquid-phase reactors.
• Two-phase reactors may be gas-liquid, liquid-liquid,
gas-solid, or liquid-solid reactors.

45. Classification by phase
• Multiphase reactors typically have more than
two phases present. The most common type of
multiphase reactor is a gas-liquid-solid reactor;
however, liquid-liquid-solid reactors are also
used. The classification by phases will be used
to develop the contents of this section.

46. Classification by Phase
• In addition, a reactor may perform a function other
than reaction alone. Multifunctional reactors may
provide both reaction and mass transfer (e.g., reactive
distillation, reactive crystallization, reactive membranes,
etc.), or reaction and heat transfer.
• This coupling of functions within the reactor inevitably
leads to additional operating constraints on one or the
other function. Multifunctional reactors are often
discussed in the context of process intensification.
• The primary driver for multifunctional reactors is
functional synergy and equipment cost savings.

47. CATALYSIS

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

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

50. •Catalysis and
reaction energetic.

51. What is Phase?

52. Two Types of Catalyst:
∙Homogeneous
∙Heterogeneous

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

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

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

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

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

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

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

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

61. 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.

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

63. 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

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

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

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

68. Multi tubular Reactor

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

70. Fluidized Bed Reactor

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

73. Fixed Bed Reactor

74. 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

75. 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.

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

78. 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

79. Diesel Hydrotreator
reactor

80. Hydrotreating
• Hydrotreating is an established refinery process
for reducing sulphur, nitrogen and aromatics
while enhancing cetane number, density and
smoke point. The refining industry’s efforts to
meet the global trend for more-stringent clean
fuels specifications, the growing demand for
transportation fuels and the shift toward diesel
mean that hydrotreating has become an
increasingly important refinery process in
recent years.