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https://ntrs.nasa.gov/search.jsp?R=20170008931 2020-07-12T17:28:23+00:00Z

Investigation of

Desiccants and CO2 Sorbents

for Advanced

Exploration Systems

2016-2017James C. Knox

and

Gregory E. Cmarik

Background – 4BMS• 4BMS = 4-Bed Molecular Sieve

system• CDRA is the variant in use on the ISS

• Concerns over performance and reliability

• The present CO2 sorbent material

can no longer be manufactured

• Final selection criteria:

• Remove 4 kg CO2/day at 2 torr

• No shutdowns due to dust

• Integrated “closed-loop” operation

CO2

Sorbent

CO2

Sorbent

Desiccant

CO2 outHC2

HC1

HC2

Schematic Overview of 4-BMS operation

HC1 = Half-Cycle no.1

Power and CoolingWater Inputs

CO2 Product to Regenor Overboard

Humid Air + CO2

Humid Air + CO2

Humid Air

Humid Air

Cabin Air In

Cabin Air Out

Cabin Air Out

Cabin Air In

HC2 = Half-Cycle no.2

CO2 outHC1

Desiccant

Sorbent Selection and Characterization• Collaborative effort among the CO2 removal teams at MSFC/ARC/JSC

• Multiple aspects to study on these materials:

• Pellet integrity

• Adsorption performance

• Fault tolerance and recovery

• This is a summary of recent results as well as previously presented work:• Single Pellet Crush, Bulk Crush, Attrition, and Hydrothermal Stability tests

• Pure Component CO2 Isotherms and Water Vapor Isotherms at 0 to 200°C

• CO2 Isotherms on Water Preloaded Samples at 25 to 100°C

• CO2 Breakthrough Measurements

• Thermal Profiles for Adsorption Performance Recovery

• Cyclic CO2 Adsorption Performance

• Layered Desiccant Breakthrough Comparison

Sorbent Structural Reliability

Sorbent Structural Tests

• Criteria: Match or exceed ASRT in structural performance metrics• No material was as robust in Single Pellet Crush as ASRT

• Several exceeded ASRT in Bulk Crush and Attrition testing

• Two prime candidates are Grade 544 13X and BASF 13X• Other sorbent options that passed the 2016 downselect: VSA-10 LiLSX, APGIII 13X, Grade 522 5A

Taller is better Taller is better Shorter is better

Hydrothermal Stability Testing

• The testing with the HST system has correlated very strongly with flight data on sorbent degradation.

• ASRT is presently operating for over 2 years without incident while RK-38 failed within 6 months.

• Numerous options to outperform ASRT and RK-38

Gra

de 5

44 (1

3X)

Gra

de 5

44 C

(13X

)

VSA

-10

(LiLSX)

BAS

F 13X

(13X

)

Gra

de 5

14 (4

A)

BAS

F 5A (5

A)

APG

-III (

13X)

Gra

de 5

22 (5

A)

Gra

de 5

64 (3

A)

Polym

er-IE

X (L

iLSX)

UI-9

4 (4

A)

NSA-7

00 (L

iLSX)

ASR

T (5A)

RK-3

8 (5

A)

0

20

40

60

80

100

120

Incre

ase in P

ressure

Dro

p (

Pa/1

000 h

r)

Water Vapor

-90oC (Dry)

-21oC

Increase in Pressure Drop across HST Bed Assembly

per 1000 Hours of Cyclic Operations

Adsorption Performance

Pure Isotherm Measurement• Collaboration with Ames

Research Center• Pure Component CO2 and Water Vapor

Isotherms

• Measured data encompasses all conditions

found in 4BMS operation

• Data fit to a 3-site Langmuir

model• High precision for interpolation in computer

simulations

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

0.000 0.001 0.010 0.100 1.000 10.000 100.000

Up

take

(m

ol H

2O

/kg)

Water Vapor Pressure (kPa)

Water Vapor Isotherms - Grade 544 13X

25 C data 35 C data 50 C data 70 C data 100 C data

25 C fit 35 C fit 50 C fit 70 C fit 100 C fit

Lines are generated from an isotherm model.Test data is shown with markers.

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

0.001 0.010 0.100 1.000 10.000 100.000

Up

take

(m

ol H

2O

/kg)

Water Vapor Pressure (kPa)

Water Vapor Isotherms - Grade 514 4A

25 C data 25 C fit 35 C data 35 C fit

50 C data 50 C fit 70 C data 70 C fit

Lines are generated from an isotherm model.Test data is shown with markers.

0.01

0.10

1.00

10.00

0.001 0.01 0.1 1 10 100

Up

take

(m

ol C

O2

/kg)

Carbon Dioxide Pressure (kPa)

Carbon Dioxide Isotherms - Grade 544 13X

0 C data 0 C fit 10 C data 10 C fit 25 C data 25 C fit 50 C data

50 C fit 75 C data 75 C fit 100 C data 100 C fit 125 C data 125 C fit

150 C data 150 C fit 175 C data 175 C fit 200 C data 200 C fit Henry's Law

Lines are generated from isotherm model.Test data is shown with markers.Henry's Law behavior is shown as an aid.

Huang, R., Belancik, G., Jan, D., Cmarik, G., Ebner, A. D., Ritter, J., and Knox, J. C. "CO2 Capacity Sorbent Analysis using Volumetric Measurement Approach," 47th International Conference on Environmental Systems. Charleston, 2017.

0.01

0.10

1.00

10.00

0.001 0.01 0.1 1 10 100

Up

dat

e (m

ol

CO

2/k

g)

Carbon Dioxide Pressure (kPa)

Carbon Dioxide Isotherms - APGIII 13X

0 C data 0 C fit 10 C data 10 C fit 25 C data 25 C fit50 C data 50 C fit 75 C data 75 C fit 100 C data 100 C fit125 C data 125 C fit 150 C data 150 C fit 175 C data 175 C fit200 C data 200 C fit Henry's Law

Mixture Isotherm Measurement• A custom instrument built by Rubotherm was used to obtain

CO2/H2O mixture isotherms• Samples are loaded with water vapor during a timed, continuous operation

• Preloading is not intended to reach equilibrium

• Preloading is determined by the change in mass observed with a microbalance

• CO2/He mixtures are prepared in a mixing loop and measured with a GC

• The prepared mixture is circulated across the sample

• The composition of the gas phase is sampled again after circulation

• No water is observed to desorb at temperatures of 25, 50, 75, and 100°C

• Measurements at 175°C show small, measurable quantities of desorbed water

• Comparisons made to reference data show:• Good agreement to dry isotherms

• Disagreement to the preloaded isotherms. This is attributed to the activation temperature achievable in that work

0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.5

1.0

1.5

2.0

2.5

3.0

9.0

3.4

1.0

2.19

1.581.08

1.01

0.65

Upta

ke (

mol C

O2

/kg)

CO2 partial Pressure (kPa)

Water Preloaded CO2 Adsorption:

Grade 544 13X at 25oC

Dry

Rubotherm:

Reference:

Water Preload

(mol H2O/kg)

0.01 0.1 10.1

1

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00.0

0.5

1.0

1.5

2.0

9.0

3.4

1.0

2.00

0.96

Upta

ke (

mol C

O2

/kg)

CO2 partial Pressure (kPa)

Water Preloaded CO2 Adsorption:

Grade 544 13X at 50oC

DryRubotherm:

Reference:

Water Preload

(mol H2O/kg)0.1 1

0.1

1

Huang, R., Belancik, G., Jan, D., Cmarik, G., Ebner, A. D., Ritter, J., and Knox, J. C. "CO2 Capacity Sorbent Analysis using Volumetric Measurement Approach," 47th International Conference on Environmental Systems. Charleston, 2017.

Wang, Y., and LeVan, M. D. "Adsorption Equilibrium of Binary Mixtures of Carbon Dioxide and Water Vapor on Zeolites 5A and 13X," Journal of Chemical & Engineering Data Vol. 55, No. 9, 2010, pp. 3189-3195.

Breakthrough Measurement

• Centerline sampling capabilities were added to the

existing CBT• Centerline concentration measurements provide experimental data for fitting

of kinetic parameters such as an LDF constant

• Measurements made with both a GC and an optical sensor (when available)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.00.0

0.2

0.4

0.6

0.8

1.0

1.2

Bed Temperatures and Water Vapor Concentrations

Breakthrough - Grade 544 13X

Wate

r V

apor

Part

ial P

ressure

(kP

a)

Time (hrs)

Gas Inlet

Gas Outlet Centerline

Gas Outlet Bulk

Center TC

End TC

20

25

30

35

40

45

50

55

60

65

Tem

pera

ture

(oC

)

0.0 0.5 1.0 1.5 2.0

0.00

0.05

0.10

0.15

0.20

0.25

0.30

CO

2 C

oncentr

atio

n (

vol%

)

Time (hrs)

Gas Inlet

Gas Outlet (Bulk)

Gas Outlet (Centerline)

Center TC

End TC

25

26

27

28

29

30

31

Bed Temperatures and Carbon Dioxide Concentrations

Breakthrough - Grade 544 13X

Tem

pe

ratu

re (

oC

)

0.0 0.5 1.0 1.5 2.0 2.50.00

0.05

0.10

0.15

0.20

0.25

Cylindrical Breakthrough Test of Candidate Sorbents

2 torr CO2 Equivalent, 16 SLPM N

2

CO

2 C

oncentr

ation (

%)

Time (hr)

Inlet

VSA-10

APGIII

Grade 544 13X

BASF 13X

Grade 522 5A

• CO2 and Water Vapor tests with the Cylindrical Breakthrough Test stand

• The CBT is a lab-scale system (roughly 14 pellet diameters across)

• This means ‘wall channeling’ is a significant contributor to early breakthrough and model-data mismatch

Performance reliability

Thermal Recovery Profiles• Purpose: Determine the required temperature to recover

performance after an off-nominal event (i.e. water saturation during a maintenance operation)

• Tests performed:• Recovery with a 4 hour ‘bakeout’ with a N2 purge at sequentially higher

temperatures. This is not identical to conditions in a 4BMS but is a fair approximation.

• Recovery after a series of simulated CDRA operating cycles.

• Results indicate that 204°C will recover a 13X material to ~95% of peak performance and that a 13X will always outperform a 5A as long as 204°C is achieved.

150 200 250 300 3500

1

2

3

4

5

6

7

8

9

10

Adsorption at 0.5%v/v CO2 and 25oC

CO

2 u

pta

ke (

wt%

)

Activation Temperature (oC)

5A zeolite

RK-38

13X zeolites

APG III

BASF 13X

Grade 544

LiLSX zeolite

VSA-10

Plot of Effect of Activation Time & Temperature on CO2 uptake

after Humidity Conditioning for Five Representative Zeolites

150 200 250 300 3502

3

4

5

6

7

8

3.2

4.2

6.2

6.97.1 7.2

7.2

6.8

7.3

4.8

5.2 5.3 5.3 5.3 5.4 5.5

5.4

Samples begin

water saturated

CO

2 u

pta

ke (

wt%

)

Activation Temperature (oC)

Grade 544 13X

4-hour Activations

CDRA-like Activations

Reference Capacity

ASRT 2005 5A

4-hour Activations

Reference Capacity

Plot of Effect of Activation Time & Temperature on CO2 uptake

after Humidity Conditioning for Grade 544 13X

Adsorption at 2 torr CO2 and 10oC

Simulated 4BMS Cyclic Performance• Upgrades to the TGA system enabled

testing of the equilibrium conditions found

a 4BMS cycle• Imperfections may have allowed trace water vapor onto

the samples between cycles

• Results support the previous data and

indicate that all three 13X materials can

reliably outperform the benchmark 5A• Regardless of initial state or off-nominal events,

operations with the current temperature of 204°C will

enable better performance than with ASRT

0 1 2 3 4 5 6 7 8 9 10 11 12 130

1

2

3

4

5

6

7

8

9

Adsorption at 2 torr CO2 and 10oC

350oC regen

before first cycle

204oC regen only

CO

2 C

apa

city (

wt%

)

Cycle No.

ASRT 2005

BASF 13X

Grade 544

Grade 544

APG III

Results of simulated 4BMS cycles

Working Capacity for CO2 Removal for Four Zeolites

CO2 capacity

from isotherms

Sorbent Selection

Sorbent Selection• After the 2016 report, the field of CO2 sorbents was downselected to five:

• Grade 522 5A, Grade 544 13X, BASF 13X, APGIII 13X, and VSA-10 LiLSX

• New, Overarching Requirement is “No System Downtime Due to Dust”• Two materials are standout performers: Grade 544 13X and BASF 13X

• Grade 544 13X is selected due to familiarity (successful usage history in desiccant beds)

• Performance Reliability/Recovery Concerns for 13X are Eliminated• No major system changes are needed as the present system will be fault tolerant

• Residual Desiccant Selection is Final Outstanding Selection Point

Desiccant Comparison (preliminary)

Desiccant Comparison (preliminary)• System simulation team uncovered large CO2 removal efficiency hits when the residual

layer of 13X is oversized• Predictions confirmed via full-scale 4BMS-X test data

• Candidate desiccants must maintain an extremely low dew point for substantial time• Cyclic operation is the ultimate test required to compare these materials, but requires dedicated lab capability

• 4 materials for comparison• Simple Breakthrough testing on: Zeolites 13X, 4A, and 3A and an Alumina

• The 3A adsorbs no CO2 but adsorbs water too slowly which allows rapid breakthrough

• The Alumina does not have enough capacity

• 13X and 4A are possible candidates

• 13X is presently used, but it has been shown to cause CO2 hold-up which reduces system efficiency

• Further study is needed to make this decision

• Simulate a 4BMS desiccant bed adsorption

and desorption cycles• Augment a commercial instrument

• Adsorb at conditions similar to 4BMS tests for various

lengths of time

• Achieve desorption cycle by pre-heating a copper coil with

the system’s heating mantle

• Run sequence of cycles of this via software

Desiccant Comparison (preliminary)

Heating Mantle

and CoilSample Column

Acknowledgements• Co-Authors: David Watson, Timothy Giesy, and Lee Miller

• Collaborators at Ames Research Center and in the Materials Test Lab at MSFC

who measured many of the properties reported here.

• Incredible dedication and attention to detail in the work done by NASA and

affiliates.

Backup Slides

Backup Slides

Backup Slides

20

40

60

80

100

120

140

160

0

0.5

1

1.5

2

2.5

3

CO2

H2O

Temperature Probes

90 minutes

Desorption Peak

Backup Slides

0 200 400 600 8000

100

200

300

400

500

600

32755.2

Wa

ter

va

po

r (P

a)

Time (min)

SG+13X Outlet

SG Outlet

Inlet

1% BT time

Moisture breakthrough curves:

Silica Gel vs. SG+13X layered bed

Ambient T (oC)

Ambient P (kPa)

0

20

40

60

80

100

120

140

0 200 400 600 8000

100

200

300

400

500

600

24940.8

Wa

ter

va

po

r (P

a)

Time (min)

SG+4A Outlet

SG Outlet

Inlet

1% BT time

0

20

40

60

80

100

120

140

Moisture breakthrough curves:

Silica Gel vs. SG+4A layered bed

Ambient T (oC)

Ambient P (kPa)

0 200 400 600 8000

100

200

300

400

500

600

18566.4

Ambient P (kPa)

Wate

r vapor

(Pa)

Time (min)

SG+3A Outlet

SG Outlet

Inlet

1% BT time

0

20

40

60

80

100

120

140

Ambient T (oC)

Moisture breakthrough curves:

Silica Gel vs. SG+3A layered bed

0 200 400 600 8000

100

200

300

400

500

600

14253.5

Wate

r vapor

(Pa)

Time (min)

SG+Alumina Outlet

SG Outlet

Inlet

1% BT time

Moisture breakthrough curves:

Silica Gel vs. SG+Alumina layered bed

Ambient T (oC)

Ambient P (kPa)

0

20

40

60

80

100

120

140

Backup Slides

ASRTRK-38

Grade 522

BASF 5A BF

BASF 5A

Zeochem Z5-01

VSA-10

Polymer-IEX

APG-III

BASF 13X BF

BASF 13X

Zeochem Z10-02

Grade 544

0

3

6

9

12

15

Mean Pellet Strength

Dusting Fraction

Dusting Initiation Force

Mean C

rush S

trength

(lb

f)

CO2 Sorbents

CO2 Sorbent Properties: Single Pellet Crush Test

LiLSX

Zeolites

Type-13X Zeolites Type-5A Zeolites

0

15

30

45

Dustin

g F

ractio

n (%

)

ASRTRK-38

Grade 522

BASF 5A

Zeochem Z5-01

VSA-10

Polymer-IEX

APG-III

BASF 13X

Zeochem Z10-02

Grade 544

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1.2

1.01.1

0.88

0.72

2.5

1.5

1.9

1.41.3

1.5

0.87

0.65 0.69

0.530.43

2.2

1.2

1.5

1.11.0

1.1

LiLSX

Zeolites Type-13X Zeolites

CO2 Capacity at 4 torr, 25

oC

CO2 Capacity at 2 torr, 25

oC

CO

2 C

ap

acity (

mo

l/kg

)

CO2 Sorbents

CO2 Sorbent Properties - CO

2 Capacity

Type-5A Zeolites

Backup Slides

Backup SlidesMaterial Type Sorbent Name Use/Potential Use Form Factor Pore size Notes

Silica Gel Grace Grade 40 Bulk Desiccant Granular Microporous used in CDRA

Silica Gel Grace SG B125 Bulk Desiccant Beads Microporous used in CDRA

Silica Gel BASF Sorbead H Bulk Desiccant Beads Microporous

Silica Gel BASF Sorbead R Bulk Desiccant Beads Microporous

Alumino-Silica Gel BASF Sorbead WS Guard Layer Beads Microporous Misting Stable,

used in CDRA

Activated Alumina BASF F200 Bulk Desiccant Beads Mesoporous Misting Stable

Molecular Sieve UOP ASRT 1995

and ASRT 2005 CO2 sorbent Pellets 5Å

CaA Zeolite,

used in CDRA

Molecular Sieve UOP RK-38 CO2 sorbent Beads 5Å CaA Zeolite,

used in CDRA

Molecular Sieve Grace MS 564 Residual Desiccant Beads 3Å KA Zeolite

Molecular Sieve Grace MS 514 Residual Desiccant Beads 4Å NaA Zeolite

Molecular Sieve UOP UI-94 Residual Desiccant Pellets 4Å NaA Zeolite

Molecular Sieve Grace MS 522 CO2 sorbent Beads 5Å CaA Zeolite

Molecular Sieve Grace MS 544 CO2 sorbent,

Residual Desiccant Beads 10Å

NaX Zeolite,

used in CDRA

Molecular Sieve BASF 5A CO2 sorbent Beads 5Å CaA Zeolite

Molecular Sieve BASF 5A BF CO2 sorbent Binder-free

Beads 5Å CaA Zeolite

Molecular Sieve BASF 13X CO2 sorbent,

Residual Desiccant Beads 10Å NaX Zeolite

Molecular Sieve BASF 13X BF CO2 sorbent Binder-free

Beads 10Å NaX Zeolite

Molecular Sieve UOP APGIII CO2 sorbent Beads 10Å NaX Zeolite

Molecular Sieve UOP VSA-10 CO2 sorbent Beads 10Å LiLSX Zeolite

Molecular Sieve Tosoh NSA-700 CO2 sorbent Pellets 10Å LiLSX Zeolite

Backup Slides