REACTORS - A. James Clark School of Engineering

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REACTORS
By: 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). Wellmixed 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:
 0 - +

 
0 
=
 At steady state,




=0
 Rate Law:
 − =

1+ 
 Conversion:
=
0− 
0
=
0 
−
;
 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:
 0 - +

 
0 
=
 At steady state,
 V=0
 
0 −
 Rate law:
 − = 
 Conversion:
=
0 −
0
 Stoichiometry:
  =






=0
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:
 0 - +

 
0 
=


 No inflow or outflow, 0 =  = 0



=
− 
0
 Rate Law:
 − = [ −
 
]

 Conversion:
 =
 
0 − 
 Stoichiometry:
  =


= 0 (1 − )
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
www.techrem.ruhr-uni-Bochum.de
 Surface Reactions
 Langmuir-Hinshelwood mechanism
 Rideal-Eley mechanism
 Precursor mechanism
http://cdn.comsol.com/wordpress/2015/02/Eley-Rideal-mechanism.png
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