Simulation Of Unique Pressure Changing Steps And ... · Simulation Of Unique Pressure Changing...
Transcript of Simulation Of Unique Pressure Changing Steps And ... · Simulation Of Unique Pressure Changing...
Simulation Of Unique Pressure Changing Steps And Situations In Psa Processes
Armin D. Ebner, Amal Mehrotra, James C. Knox, M. Douglas LeVan, and James A.
Ritter
Department of Chemical Engineering, University of South Carolina, Columbia, SC
Marshall Space Flight Center, National Aeronautics and Space Administration,
Huntsville, AL, USA
Department of Chemical Engineering, Vanderbilt University, Nashville, TN, USA
A more rigorous cyclic adsorption process simulator is being developed for use in the
development and understanding of new and existing PSA processes. Unique features of
this new version of the simulator that Ritter and co-workers have been developing for
the past decade or so include: multiple absorbent layers in each bed, pressure drop in the
column, valves for entering and exiting flows and predicting real-time pressurization
and depressurization rates, ability to account for choked flow conditions, ability to
pressurize and depressurize simultaneously from both ends of the columns, ability to
equalize between multiple pairs of columns, ability to equalize simultaneously from
both ends of pairs of columns, and ability to handle very large pressure ratios and hence
velocities associated with deep vacuum systems. These changes to the simulator now
provide for unique opportunities to study the effects of novel pressure changing steps
and extreme process conditions on the performance of virtually any commercial or
developmental PSA process.
This presentation will provide an overview of the cyclic adsorption process simulator
equations and algorithms used in the new adaptation. It will focus primarily on the
novel pressure changing steps and their effects on the performance of a PSA system that
epitomizes the extremes of PSA process design and operation. This PSA process is a
sorbent-based atmosphere revitalization (SBAR) system that NASA is developing for
new manned exploration vehicles.
This SBAR system consists of a 2-bed 3-step 3-layer system that operates between
atmospheric pressure and the vacuum of space, evacuates from both ends of the column
simultaneously, experiences choked flow conditions during pressure changing steps,
and experiences a continuously changing feed composition, as it removes metabolic
CO2 and H20 from a closed and fixed volume, i.e., the spacecraft cabin. Important
process performance indicators of this SBAR system are size, and the corresponding
CO2 and H20 removal efficiencies, and N2 and O2 loss rates. Results of the fundamental
behavior of this PSA process during extreme operating conditions will be presented and
discussed.
!
https://ntrs.nasa.gov/search.jsp?R=20080013427 2020-04-03T16:16:22+00:00Z
iiili(
;i
iilil_
Simulation of Unique Pressure ChangingSteps and Situations in PSA Processes
Armin D. Ebner, _ Amal Mehrotra, _ James C. Knox, 3 M.
Douglas LeVan, 2 and James A. Ritter 1
1Department of Chemical Engineering, University of South CarolinaColumbia, SC
2Department of Chemical Engineering, Vanderbilt UniversityNashville, TN
3Marshall Space Flight Center, NASA
Huntsville, AL
AIChE 2007 Annual Meeting
Salt Lake City, UtahNovember 6, 2007
Introduction1. Rigorous cyclic adsorption process simulator (Ddaspk-Fortran) being
developed to assist in the design, development and understanding of new
and existing PSA processes.
2. Unique features of this simulator include:
• Multiple absorbent layers and columns
• Pressure drop in the column
• Entering and exiting flows defined by constant flow, valve equations,
or choke flow approaches (Isentropic, Fanno, etc.)
• Interaction with other processes: cabin, distillation units, etc.
• Simultaneous feed, exit, pressure varying steps through multiple ports
• Ability to handle large P ratios and v's associated with deep vacuum
systems.• Equalization between pairs of columns (single and dual ended) in
progress.
These features provide for unique opportunities to study the
performance of virtually any commercial or developmental PSA
process under extreme process conditions.
1
!
ObjectivesFocus primarily on a particular PSA system that NASA is
developing: referred to as the sorbent-based atmosphere
revitalization (SBAR) system
o:. this PSA system is unique because it uses deep space
vacuum for regeneration in lieu of processed air as purge
Describe NASA's PSA System, with emphasis on the alternative
regenerative steps that NASA has developed to further improve
performance: single, dual, and triple ended blowdown
Show validation of the PSA process simulator against NASA's
experimental data of an 8.8 L dual blowdown system
Use the simulator to discuss the role of these regenerative steps
on PSA performance in terms of H20 and CO 2 removalefficiencies
This SBAR system might be used in a new Crew Exploration
Vehicle (CEV) to remove metabolic H20 and CO 2 from cabin air.
Schematic of Base Case Column Simulated for Water andCarbon Dioxide Removal from Cabin Air
MSFC SBAR
Experimental System
V b = 8.88 L
L b = 0.2654 m
rb = 0.1032 m
HCT = 450 s
D Zeolite 13X
_-] Zeolite 5A
F (10-14.5 SCFM)
2.357 kg
4.062 kg
LP
_- 34%
66%
Schematic Diagram and Cycle Sequencing of VSACycle Used for Air Revitalization
F
FP SEB F SEB
/
e L
11r
J[ U
/
t
I I
Pt
_V
tL
m i
lV
To
Space
F
ToCabin
2
I I
P.[
,--li
I I
Pt
'V[L
I I
Ir
To
Space
FP
SEB
!
' FI
IIi SEB
I
!
' SEBSEB,
I
FP , F
I
TimeY
SBAR Cycle Step Times
tF =420 s
tsEB = 30 s
tsE B = 420 s
tFp-- 30 s
SEB: single ended blowdown
Schematic Diagram and Cyc_e Sequencing of VSACycle Used for Air Revitalization
F
FP SEB F DEB
ToCabin
2
/ I I
PL P t
T
I I I
PP[
1
tL
F
To
Space
I
t
I
FP ' F!
!
ISEB , DEB
!
' DEBSEB,
I
IFP , F
I
Time
t'
L tF - 420 SI
tsEB - 30 s
, tDEB 420 S
SBAR Cycle Step Times
To
Space
tFp-30 s
SEB: single ended blowdownDEB: dual ended blowdown
Schematic Diagram and Cycle Sequencing of VSACycle Used for _ir Revitalization
F
FP SEB
/
e L
11r
J¢ U
/
tTo
Space
F
To
Space
!
III
,!
Time
!
'TEB!
I
!
!
I
SBAR Cycle Step Times
tv = 420 s
tSEB = 30 S
tTEB = 420 S
tFp-- 30 s
SEB: single ended blowdown
TEB: triple ended blowdown
Simulator InputBed Characteristics and Transport Properties
MSFC SBAR Experimental System
bed layer fraction (%)
porosity
pellet density (kg m -3)
heat capacity (kJ kg -1 K -1)
heat transfer coefficient (kW m -2 K-l) a
mass transfer coefficients (s -1)
H20
CO 2
02
N 2
r b (mm)p,eff
13X 5A
66% 34%
0.26 0.35
1100 1201
1.10 0.84
0.0017 0.0017
0.00550 0.00310
0.00150 0.00067
0.001 0.001
0.001 0.001
3.3 2.1
Motivation: Single vs Dual Ended BlowdownPressure profiles @ End of Blowdown Step
Single Dual
_LJ
ii
15 S (_1'M
6.0800 _ .....
I7O0
€_
0
n
600
iO0
LO0
_00
>>
Final State of Step
Cycle 40
5.0
4-- Press urlzation
........Feed t,=, Blowdown_single
I4,0
3.0
O2.0 _"
n
1.0
I
!oo
IOO
o
o o.1 o.2 0.3 0.4 0.5 o.6 0.7 o.8 0.9 1
Z/L
iv
O.
800
TO
6.0
700
600
;00
,00
;00
_00 !_ __' _--0O S'_
___=_[................
--r °"
Final State of Step
Cycle 40
5.0
4.0
3.0
2.0
F .-..-> ..... 1
Press ui:iZation
Feed
Blowdown_single ._ 1.0Blowdown dual
0 0.1 0.2 0.3 0A 0.5 0.6 0.7 0.8 0.9 t
Z/L
,.£,It,.
o
O..
Motivation: Single vs Dual Ended BlowdownCycle Performance Parameters Zeolite System
15 ,_,Z[ M
Single Dual
100
90
o_" 8O
¢n 70
L9"o 6O03
IJ.
_'6 50e,,,o 40
_ 30
20
10
_._=_ H20, Blowdown Heavy End/
/
CO2, Biowdown, Heavy End
CO2, Light Product
H20, Bed Accumulation
in E_2,=B_dRI_cI_!FRuI_R=Io_II_ 1 1 ,i=
0 10 20 30 40 50
Time (hr)
1 1 i 1
60 70 80
H20, Blowdown Heavy End
H20, Blowdown, Light End
H20, Light Product
CO2, Blowdown, Light End i
CO2, Blowdown, Heavy End
BIIIlll IB1 l l l
CO2, Light Product
H20, Bed Accumulation
Bed Accumulation
0 10 20 30 40 50 60 70 80
Time (hr)
Modeling the SBAR DEB Experimental SystemTemperature History Profiles at Three Bed Locations
120 h
F = 13.5 SCFM
V b : 8.88 L
HCT = 450 s
t F = 420 s
tsE B = 30 s
tDEB = 420 S
tFp = 30 S
90
85
80
75
%.. 70k--
65
6O
55
50
--z = 0.00 o exp,z = 0.00
--z = 0.50 exp,z = 0.50
--z = 1.00 o exp,z = 1.00
! I
0 5
I
10
i I
15
time (min)
Cycles 481-482i I i I
20 25 30
Modeling the SBAR DEB Experimental SystemPressure History Profiles at Three Bed Locations
120 h
F = 13.5 SCFM
V b -- 8.88 L
HCT= 450 s
t F = 420 s
tSEB = 30 S
tDEB = 420 S
tFp = 30 SA
L_O
t_.
4
3
2
1
0
t t
--z = 0.00 o exp, z = 0.00
--z = 0.50 exp, z - 0.50
--z = 1.00 exp, z = 1.00
i
0 5
ICycles 481-482
I
10 15 20
time (min)
<
o
I I I
25 30
Modeling the SBAR DEB Experimental SystemPco2 History Profiles at Two Bed Locations
120 h
F = 13.5 SCFM
V b = 8.88 L
HCT = 450 s
tF = 420 s
tSEB = 30 S
tar B = 420 S
tFp = 30 S
t_L_
OV
O4Oto
(1.
8
7
6
5
4
3
2
--z = 0.00 _ exp, z = 0.00
--z = 1.00 exp, z = 1.00
0
0 5
Cycles 481-482
10 15
time (min)
20 25 30
Modeling the SBAR DEB Experimental SystemBed Profiles at End of Steps for P, T, PH2O and Pco2
120 h
F = 13.5 SCFM
V b -- 8,88 L
HCT= 450 s
tv = 420 s
tsE _ = 30 s
tDwB = 420 s
tFp = 30 S
120
11o t End State of Step
Cycle 480
10
9
8
7
i -,_- Pressurization
.........Feed
_ Blowdown_duai
10
8
6
5
4
3
End State of Step
Z/L
\\
\
End State of Step
cycle 480
_- Pressurization
.......Feed
Blowdown_dual
Blowdown_duai
•_ Pressurization
Feed
End State of StepC_cle 480
0.1 02. 03 0.4 0.5 0,8 0.7 0.8
Z/L
0.9 1
80O
790
780
770
760
750
740
730
720
710
700
!ii.
Modeling the SBAR DEB Experimental SystemSummary of Modeling vs Experimental Results of
Eight Different Test Runs
'ii
Modeling the SBAR DEB Experimental SystemSummary of Modeling vs Experimental Results of
Eight Different 7rc._stRuns: H20 Removal
_!i'i
Modeling the SBAR DEB Experimental SystemSummary of Modeling vs Experimental Results of
Eight Different Test Runs
.Qm
5.X
:>oE
n_04
o(3
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.0 0.1
I CO2 Rem°val I I Cycle Bed Temperatures I
0.2 0.3 0.4 0.5 0.6 0.7 0.8
CO2 Removal, model, Ib/h
100
90
LI.o 805.x(9
_ 70
_ 6OEI--
50
40
• Maximum
e Minimum52 42 @t 43
12 20
• 18 23
54
12
_3 Z/L=0.5
4O 50 60 70 80 90
Temperature, model, °F
100
Triple Ended BlowdownEffect of Location of Third Exhaust Port
F
FP SEB
/
eL
JL U
m
t
I I
PI
'r[L
_r
To
Space
F
F DEB
To
Cabin
I
P
II
[
I
L
m ii
P_
,p,
IL"_
I I
_r
To
Space
Test Run 18F = 13.5 SCFM
V b = 8.88 LHCT = 450 s
tv = 420s
tSE D ---- 30S
tDE D = 420 S
tFp = 30 S
Third Port Location
z/L = 0.2, 0.3, 0.4, or 0.5
Triple vs Dual Ended BlowdownBed Pressure Profiles at the End of the Blowdown step
Significant Increase of Driving Force
=A
L_L_
n
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.0
_ 0.3 0.4 0.5
Double
\
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
z/L
_J=
.=o j=(
Triple vs Dual nded BlowdownHistory of H20 and CO 2 Removal Per Cycle
I DUAL I I Trip.e,z,,=0. 0I110
100
90
80
"O 70
14. 60
Oe- 50O
40¢J
=" 30LI.
20
10
0
_..___ C HO220' ;BiBol°wWddo °wWn,nHHeeaavVyYEEnndd
i
0
C02, Light Product
C02, Blowdown, Light End
! I I I i I ! I ! I I ! I I I I I | i I • I .
10 20 30 40 50 60 70 80 90 100 110 1200
Time (hr)
H20, Blowdown, Heavy Product End
__ CO2, Blowdown, Heavy End
--[---_-xtZiZ..................... _±_g_-_-_d_,_t ...... -....=--
_____C_, B_wdown, Light End
r • I i I . I , I l I I I ! I I I I | • I . I i
10 20 30 40 50 60 70 80 90 100 110 120
Time (hr)
Triple vs Dual Ended BlowdownHistory of H20 and CO 2 Removal Per Cycle
I DUAL I I Triple, z/L=0.40 I110
100
90
A
0_ 80
"o 7O
_ 60
O
so40
_- 30IJ.
20
H20, Blowdown Heavy End
_"_.---_ CO2,,Blowdown, Heavy Endii ,,,,mill
C02, Light Product .
C02, Blowdown, Light End
10
0
0 10 20 30 40 50 60 70 80 90 100 110
Time (hr)
H20, Blowdown Heavy End
CO2, Blowdown, Light End
1200 10 20 30 40 so 60 70 80 90 100 110 120Time (hr)
Triple vs Dual Ended BlowdownHistory of H20 and CO 2 Removal Per Cycle
I DUAL I I Triple, z/L=0.30 I
110
100
9O
A
80
"o 7O(DOu. 60N_
o50
Co
4OO
_- 30IJ.
2O
10
0
H20, Blowdown Heavy End
Blowdown, Heavy End
CO2, Light Product
CO2, Blowdown, Light End
0 10 20 30 40 50 60 70 80 90
Time (hr)
100 110
H20, Blowdown Heavy End
CO2, Blowdown, Heavy End
120 0 10 20 30 40
CO2 Blowdown ht End
50 60 70 80 90 100
Time (hr)
110 120
Triple vs Dual Ended BlowdownHistory of H20 and CO 2 Removal per Cycle
i_i!i
I ou,, I I Trip.e,z,,=0.20I110
100
90
80v
"o 7O
(9u. 60s4-.
O50
cO
40
"_ 30
20
10
0
Blowdown Heavy End
Blowdown, Heavy End
CO2, Light Product
CO2, Blowdown, Light End
H20, Blowdown, Heavy End
CO2, Blowdown, Heavy EndCO2, Light Product
CO2, Blowdown, Light EndI I . I . I . I n I I I ! I I I • i . I . I ,t
0 10 20 30 40 50 60 70 80 90 100 110 120 0 10 20 30 40 50 60 70 80 90 100 110 120Time (hr) Time (hr)
Triple vs Dual Ended BlowdownH20 and CO 2 Removal after 120 hr
I Optimal Third Port Location I
U)
Om=
--!Balm
"0O
m
OO
O
Nr-
m
Q.
m.
N
r-
Conditions Modeling Results
z o -_ 5" 5" -,1 5- o o z= m m -- -- _ _ O O _-_ _o
o --I --I "o _ ;0 --i :;0 _ ::0 ::0
o 3 3 o z _. 3 3 3 3 3• " m co 0 _ m- "- - "_ O O O O
3 Et p .O _ - < < < <3 = = O o _ m _'- "- _ --
..,, mJl 9
=
co
---I
"0m
8.88
0.5 8.88
0.4 8.88
0.3 8.88
0.2 8.88
7.5
7.5
7.5
7.5
7.5
7.0 ==
7,0
7.0
7.0
7.0
5.0 9.1 13.5 69.9 0.47 0.74 0.49 1.00
5.0 9.1 13.5 69.9 0.50 0.79 0.49 1.00
5.0 9.1 13.5 69.9 0.55 0.86 0.49 1.00
5.0 9.1 13.5 69.9 0.54 0.85 0.49 1.00
Conclusions
A description of the new NASA SBAR PSA system for H20
and CO 2 removal, with particular emphasis on its purgeless
deep vacuum regenerative steps has been given
Regeneration consisted of blowdown steps subject to deep
vacuum through an increasing number of evacuation ports, i.e.
single, dual and triple ended blowdown was studied,
The USC PSA process simulator, for which adsorbent and
adsorbate properties were independently obtained, successfully
predicted NASA's experimental results of a dual ended system.
The USC PSA process simulator was also used to discern the
role of the regenerative steps on the performance of NASA's
SBAR PSA system.
The USC PSA process simulator is currently being
used in other projects of equal complexity.
;ii
Acknowledgements
Funding being provided by theNASA MSFC
is greatly appreciated!
Thank You!