CRE L19 Catalyst Deactivation
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Transcript of CRE L19 Catalyst Deactivation
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L -18 Catalyst Deactivation
Prof. K. K.Pant
Department of Chemical EngineeringIIT Delhi.
mailto:[email protected]:[email protected] -
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Slow decay : Temperature time trajectory
Moderate decay: Moving bed reactorsRapid Decay: Straight through transport reactors
For and nthorder activity decay
and mthorder gas phase
Coupled differential eqns to be solved are
(MBR)
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Moving bed reactors
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Thermofer Catalytic crackin unit (Used for reactions with moderate decay)
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Combining activity equation with the mole balance equation:
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For a first order Decay
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Straight through Transport
Reactor (Circulating fludized bedreactor)
Used when deactivation is rapid.Used for production of gasoline
Catalyst pellet and feed enter
together and transported rapidly.Bulk density of the catalyst is low
compared to Moving bed.
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STTR : Used when coking is rapid.
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Mole balance
rA= brA
Or
Z= Height ,and U is velocity of catalyst
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Reading Assignment: Examples : 10.5 ,10.7, 10.8 Fogler
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a
1 R 1= ln +
T E Ta o
Temperature/Time Trajectories A control strategy involves maintaining a
constant conversion with catalyst decay byincreasing operating temperature.
develop a temperature/time trajectory to find Tt
relationship:
-rA (t=0,T0) = -rA (t= t,T) = a(t ,T)[-rA (t=0,T) ]
(For First order reaction ) k T a T,t = ko
E 1 1a -R T To
k e a = ko o
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Temperature/Time Trajectories
a
E1 1d -
R T Tda o n
r = - = k ed ddt
decay law is:
a
Ed- lnaE
da a n- = k e
ddt o
a
E
dn-Ea
= kdo
a
1 R 1= ln +
T E Ta o
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Temperature/Time Trajectories
1- n+ E Ead1-a
t =
k 1-n+ E Ead do
a
1 R 1= ln +T E T
a o
E 1 1a -R T T
oa = e
E -n E +Ea a 1 1d -
R T To1-e
=E
dk 1-n+d Eo a
a
a
Ed-n+E
a tda = -k dt1 0d
o
Ed-n 1
Ea
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THANK YOU