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REACTORSBy: Shaimaa Soarkati,
CHBE446
Section: 0301
A. James Clark School of Engineering
Constant Stirred Tank Reactor (CSTR)
Steady-state continuous flow of reactants (A) and Products (B). Well-mixed reactor, so exit stream has the same composition as reactants in the tank
Phases present:
Liquid, Gas-liquid, Solid-liquid
Advantages:
Continuous process
Maintainable temperature
Simple design
Easy to clean
Low operating cost
Disadvantages:
Low conversion per unit volume
CSTR Equations
Mole Balance:
-
At steady state,
Rate Law:
Conversion:
;
Note: The volume is also calculated by measuring the area under the CSTR curve
Plug Flow Reactor (PFR)
A long reactor tube with consisting of many “plugs”
Concentration changes down the reactor (length-wise)
No radial variation in reaction rate/ concentration
For large scale
Heterogeneous and homogeneous reactions (fast)
Advantages:
High conversion per unit volume
Efficient heat transfer
Continuous process
Easy maintenance
Typically contain catalyst
Disadvantages:
Poor temperature control
Undesired thermal gradients possible
Poor mixing (static mixers)
PFR Equations
Mole Balance:
-
At steady state,
V=
Rate law:
Conversion:
Stoichiometry:
BATCH REACTOR
Reactants are supplied via the top two holes on the reactor and nothing can be added or extracted while the reaction process occurs.
Can be heated or cooled via jacket
Small scale
Used mostly for pharmaceutical or fermentation processes
Advantages:
High conversion per unit volume
Can be used for multiple operations
Easy to clean
Disadvantages:
Varied product quality
High operation cost
Batch Reactor Equations
Mole Balance: -
No inflow or outflow,
Rate Law:
Conversion:
Stoichiometry: =
Heterogeneous Catalysis
Form of catalysis where the catalyst phase is different from the reactants
Adsorption is an essential first step in heterogeneous catalysis Molecule in gas phase binds to a liquid or
solid surface
Surface Reactions Langmuir-Hinshelwood mechanism
Rideal-Eley mechanism
Precursor mechanism
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http://cdn.comsol.com/wordpress/2015/02/Eley-Rideal-mechanism.png
