Is.5553.5.1989 Reactors- Specification Part 5 Tuning Reactors
Membrance Reactors
description
Transcript of Membrance Reactors
Chemical Reaction Engineering (CRE) is thefield that studies the rates and mechanisms of
chemical reactions and the design of the reactors inwhich they take place.
Lecture 5c
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Lecture 5c
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Balances in terms of molar flow rates Block 1: Mole Balances
Balance Equation on Every Species Block 2: Rate Laws
Relative RatesTransport Laws
Block 3: Stoichiometry Block 4: Combine
Reactor Differential Algebraic Integral
The GMBE applied to the four major reactor types(and the general reaction AB)
CSTR
0
∫=A
A
N
N A
A
Vr
dNtBatch
NA
t
€
dFAdV
= rAPFR
FA
V
∫ ′=
A
A
F
F A
A
r
dFW
0
PBRFA
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Reactor Mole Balances SummaryReview Lecture 1
Reactor Differential Algebraic Integral
€
V =FA0X−rA
CSTR
∫ −=
X
AA r
dXFV
0
0PFR
Vrdt
dXN AA −=0
Batch
X
t
€
FA 0dXdW
= − ′ rAPBR
X
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Building Block 1: Mole Balancesin terms of conversion, X
Review Lecture 2
Using CA (liquid) and FA (gas) in theMole Balances and Rate Laws
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There are a number of instances when it is much more convenientto work in terms of the number of moles (NA, NB) or molar flowrates (FA, FB, etc.) rather than conversion.
The main difference is that when conversion is used as our variableto relate one species concentration to that of another speciesconcentration, we needed to write a mole balance on only onespecies, our basis of calculation. When molar flow rates andconcentrations are used as our variables, we must write a molebalance on each species and then relate the mole balances to oneanother through the relative rates of reaction
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Membrane reactors can be used to achieveconversions greater than the original equilibriumvalue. These higher conversions are the result ofLe Chatelier’s principle; you can remove thereaction products and drive the reaction to the right.
To accomplish this,
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Membrane Reactors
Dehydrogenation Reaction:
Thermodynamically Limited:
Xe
T
exothermic
Xe
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Membrane Reactors
X
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Membrane Reactors
Cross section of IMRCF Membrane Reactors
Cross section of CRM Schematic of IMRCF for mole balance
Inert membrane reactor with catalyst pellets on the feed side
Catalytic Membrane Reactor
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Membrane Reactors
A,B,C
sweep
FA0
B
B
A,C stay behind since they aretoo big
CBS
CB
= ∗
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Mole Balance on Species A:
AA r
dV
dF =
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Mole Balance on Species B:
Species B: In – out – out membrane + generation = 0
0=∆+∆−−∆+
VrVRFF BBVVBVB
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2
molar flow rate through membrane' ( )surface area of membraneB C B BS
molW k C C
m s = − = ⋅
[ ]BSBCBB CCakaWR −== '
[ ]
⋅−=
sm
molCCkR BSBCB 3
Neglected most of the time
akk CC'=
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Mole Balances:
Rate Law:
( )2 BBB Rr
dV
dF −=
( )1 AA r
dV
dF =
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Relative Rates:
Net Rates:Transport Law:
Stoichiometry:
Parameters:
( ) ,5 CABA rrrr −=−=
( )6 BCB CkR =
( )7 0T
ATA F
FCC = (isothermal, isobaric)
( )8 0T
BTB F
FCC =
( )10 CBAT FFFF ++=
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Example: The following reaction is to be carried outisothermally in a membrane reactor with nopressure drop. The membrane is permeable toproduct C, but impermeable to all other species.
For membrane reactors, we cannot use conversion. Wehave to work in terms of the molar flow rates FA, FB, FC.
C6H6 (B)
C6H12 (A)H2 (C)
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Inert Sweep GasC6H6 (B)
Inert Sweep Gas
′= AA r
dW
dF
′= BB r
dW
dF
CCCC Ckr
dW
dF −′=
Mole Balances
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Relative Rates:
Net Rates:
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′=
′=
−
′CBA rrr
Membrane Reactors
Stoichiometry:Isothermal, no Pressure Drop
0
00 RT
PCT =
T
ATA F
FCC 0=
T
BTB F
FCC 0=
CBAT FFFF ++=19
Membrane Reactors
Combine: - Use Polymath
Parameters:s
molFA 100 =
scatkg
dmkA 10
3
=
6
2
200dm
molKC =
20
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Ci
W
C6H12 (A)
H2 (C)C6H6 (B)
Membrane Reactors
End of Lecture 5c
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