Document text
Advanced Water Purification System for
In Situ Resource Utilization
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Steve Anthony
NASA Kennedy Space Center
September 12, 2013
In Situ Resource Utilization
One of NASA's goals is to enable long-
term human presence in space,
without the need for continuous
replenishment of consumables from
Earth.
In situ resource utilization (ISRU) is
the use of extraterrestrial resources
to support activities such as human
life-support, material fabrication and
repair, and radiation shielding.
Potential sources of ISRU
resources include lunar and Martian
regolith, and Martian atmosphere.
CROPS Mars ISRU Demonstration Unit
Water and Oxygen Production from Lunar Regolith
Water and byproducts (including
hydrochloric and hydrofluoric acids) can
be produced from lunar regolith via a
high-temperature hydrogen reduction
reaction and passing the produced gas
through a condenser.
900°C
FeO + H 2 -> Fe + H 2 0
Due to the high solubility of HCI and HF
in water, these byproducts are expected
to be present in the product stream (up
to 20,000 ppm) and must be removed
(less than 10 ppm) prior to water
consumption or electrolysis.
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Contaminant Removal Techniques
'V''
• Due to their consumable nature, typical water purification methods may not be
suitable for HCI and HF removal in extraterrestrial applications.
• Membranes and adsorbents are often regenerated with large amounts of water
and/or basic solutions, which aren't available in the lunar environment.
• Naturally-occurring adsorbents may be replaced rather than regenerated.
Method
Examples
Membrane
(solute retention)
Reverse osmosis
Nanofiltration
Proton Exchange
Membrane
(solute transport)
Dialysis
Electrodialysis
Anion Exchange
Alumina-based adsorbents
Adsorption
Natural adsorbents (mud, ore,
clay, soil, chitosan)
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Nafion® Membranes for Contaminant Removal
Nafion®, a common fuel cell proton
exchange membrane, was investigated for
its chloride and fluoride rejection capability
in a previous study
The ability to reject 98-99.9% of chloride
and 50-80% of fluoride was demonstrated
This rate of rejection was not sufficient to
produce electrolysis-grade water
Since water had to diffuse across the
membrane and be recovered in the vapor
phase, relatively small amounts of water
were recovered using large amounts of
carrier gas
Other technologies were researched with
an emphasis on maximizing water recovery
and contaminant removal:
- Higher contaminant removal/rejection rate
- Contaminant removal/water retention instead of
contaminant rejection/water transport
- Liquid phase only process
b) Solution Temperature, °C
Anthony, S.M., et al. "Contaminant Removal from Oxygen
Production Systems for In Situ Resource Utilization." AIAA
SPACE 2012 Conference & Exposition, AIAA 2012-5167.
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Cathode
Electrodialysis for Contaminant Removal
Anode
Experimental Apparatus
Electrolyte Pump
|Feed and Waste]
Peristaltic Pumps
Waste Solution
Electrolyte
Membrane Stack
Feed Solution
High Efficiency Electrodialysis (HEED®) membrane stack purchased from EET Corp.
Stack contains 20 alternating Ralex® anion and cation exchange membranes
0.5% NaS0 4 solution circulated through outer cells to protect electrodes
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Baseline Contaminant Removal:
20,000 ppm HCI/HF Solution
• Starting volume
- 500 mL diluent
- 500 mL concentrate
• Final volume
- 295 mL diluent
- 685 mL concentrate
• Power supply
- 30 V maximum
- 3 A maximum
• Pump speed
- 100% diluent
- 100% concentrate
• Reached steady state
within 30 min
Diluent Stream
Fluoride
Chloride
Initial (ppm)
18,800
26,400
Final (ppm)
71.1
11.4
Removal (%)
99.44
99.94
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Power [W]
Baseline Contaminant Removal:
200 ppm HCI/HF Solution
• Starting volume
- 500 mL diluent
- 500 mL concentrate
• Final volume
- 500 mL diluent
- 500 mL concentrate
• Power supply
- 30 V maximum
- 3 A maximum
• Pump speed
- 100% diluent
- 100% concentrate
• Reached steady state
in less than 10 min
Diluent Stream
Fluoride
Chloride
Initial (ppm)
166
179
Final (ppm)
0.26
0.07
Removal (%)
99.85
99.96
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Power [W]
Variable Matrix Testing:
Concentrate Volume
Initial Concentrate
Volume (mL)
Final Diluent
Volume (mL)
Final Concentrate
Volume (mL)
Final Fluoride
Concentration
(ppm)
Final Chloride
Concentration
(ppm)
0
170
290
550
23
130
305
310
290
25
250
335
400
167
22
500
295
685
71
11
• Parameters:
- Initial diluent volume: 500 mL
- Initial diluent concentration: 20,000 ppm HCI/HF
- Pump speed: 100% of maximum
- Voltage: 30 V maximum
- Current: 3 A maximum
• 130 mL is minimum volume required to fill the concentrate membrane cells and tubing
• Final fluoride concentration decreases substantially with decreasing initial concentrate
volume
• Final chloride concentration does not decrease with increasing initial concentrate
volume below 250 mL
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Variable Matrix Testing:
Pump Speed
Pump Speed (% of
maximum)
Final Diluent
Volume (mL)
Final Concentrate
Volume (mL)
Final Fluoride
Concentration
(ppm)
Final Chloride
Concentration
(ppm)
< 10
500
510
14,500
13,700
20
280
650
71
8.6
50
300
700
158
20
100
295
685
71
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• Parameters:
- Initial diluent volume: 500 mL
- Initial diluent concentration: 20,000 ppm HCI/HF
- Initial concentrate volume: 500 ml
- Voltage: 30 V maximum
- Current: 3 A maximum
• Pump speed does not affect final fluoride and chloride concentrations, or final diluent
and concentrate volumes at or above 20% of maximum setting (at least 200 mL/min)
• Minimum pump speed does not appear to allow for any ion exchange
li
Variable Matrix Testing:
Power Supply
Maximum
Voltage (V)
Maximum
Current (A)
Final Diluent
Volume (mL)
Final
Concentrate
Volume (mL)
Final Fluoride
Concentration
(ppm)
Final Chloride
Concentration
(ppm)
30
3.0
296
685
71
11
15
3.0
325
675
1,170
47
60
350
640
26
2.8
30
1.5
355
610
132
26
6.0
365
685
79
9.8
• Parameters:
- Initial diluent volume: 500 mL
- Initial diluent concentration: 20,000 ppm HCI/HF
- Initial concentrate volume: 500 mL
- Pump speed: 100% of maximum
• Decreasing voltage or current increases final diluent fluoride and chloride
concentrations
• Increasing voltage decreases final diluent chloride and fluoride concentrations
• Increasing current does not affect final diluent chloride and fluoride concentrations
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ISRU Scenario Testing:
Concentrate Replenishment
Initial volumes:
- 500 mL diluent
- 100 mL concentrate
(replaced every hour,
300 mL total)
Power supply:
- 30 V maximum
- 3.0 A maximum
Pump speed: 100%
Final volumes:
- 250 mL diluent
- 600 mL concentrate
Contaminant removal
improved versus
baseline, but at the
expense of longer
processing time
45,000
40,000
• - Feed Chloride
--O — Waste Chloride
■ Feed Fluoride
— □ — Waste Fluoride
- a - Power
\d — a — o
-Q —
^ A- -A -A- -a-
80
70
60
50
40
30
20
10
0
20 40 60
80 100 120
Time [min]
140 160 180
Diluent Stream
Fluoride
Chloride
Initial (ppm)
17,000
17,400
Final (ppm)
27
3.9
Removal (%)
99.92
99.99
13
Power [W]
ISRU Scenario Testing:
Diluent Replenishment
Initial volumes:
- 250 mL diluent
(replaced every hour,
1250 mL total)
- 250 mL concentrate
Power supply:
- 30 V maximum
- 3.0 A maximum
Pump speed: 100%
Final volumes:
- 360 mL diluent
- 830 mL concentrate
Contaminant removal
was not significantly
improved versus
simply processing at a
higher diluent to
concentrate volume
ratio
14
Power [W]
ISRU Scenario Testing:
Obtaining Electrolysis-Grade Water
1000 mL
HCI/HF
Solution
390 mL
Clean Water
500mL
130 mL
*
Diluent
Concentrate
"A"
"A"
500 mL
300 mL
Diluent
"B"
300 mL
130 mL
330 mL
Concentrate
Ur\U
'B
130 mL
330 mL
Diluent
"C"
Concentrate
" C"
435 mL 565 mL 130 mL
330 mL
Diluent
Concentrate
"D"
"D"
415 mL
130 mL
Diluent "A"
Fluoride
Chloride
Initial (ppm)
14,200
15,100
Final (ppm)
736
124
Removal (%)
94.8
99.2
Diluent "B"
Fluoride
Chloride
Initial (ppm)
16,200
19,000
Final (ppm)
214
126
Removal (%)
98.7
99.3
Diluent "C"
Fluoride
Chloride
Initial (ppm)
1,140
222
Final (ppm)
12.6
10.9
Removal (%)
98.9
95.1
Diluent "D"
Fluoride
Chloride
Initial (ppm)
80.4
41.4
Final (ppm)
0.41
0.16
Removal (%)
99.5
99.6
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Future Work:
System Optimization
• Added new and additional components to increase system robustness and
minimize processing time:
- Larger membrane stack that contains two 20 membrane cells which can run in series or parallel
- Higher voltage/current power supply to achieve rapid equilibrium
- In-line conductivity meters for real-time measurement of water purity
- Hastelloy® electrodes which offer superior protection against hydrofluoric acid versus stainless steel
DUAL CELL
1 1
m
is*
cel) cell
’ 1 * 2 *
• • ♦
% ceH „cell„
1 2 t
. . .
1 1
HU
PARALLEL
SERIES
Other considerations for future work:
- Different types of anion/cation exchange membranes
- Alternate membrane stack configurations
- Integration with additional water processing unit (e.g., Nafion®)
- Increase system automation
http://www.eetcorp.com/lts/flowconfig.htm
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Future Work:
Mars ISRU Water Purification
Ion
C (wt%)
C th (wt%)
Na +
0.27
0.10
Mg 2+
0.44
0.60
K +
0.28
0.03
Ca 2+
0.05
0.04
ci-
0.79
0.04
cio 4 -
0.72
0.60
HC0 3 -
0.73
?
so 4 2 -
0.78
?
Kounaves, S.P., et al. "Aqueous Carbonate
Chemistry of the Martian Soil at the Phoenix
Landing Site," 40 th Lunar and Planetary Sciences
Conference, 2009.
Time [min]
• Attemped to simulate ionic contaminants in water recovered by Phoenix lander
• In absence of specific ion standards, measured contaminant removal indirectly via
conductivity meters in diluent and concentrate streams
• Achieved minimum diluent conductivity after about 10 min
17
Power [W]
Acknowledgements
Collaborators
• Dr. Scott Jolley, QinetiQ North America
• Jim Captain, QinetiQ North America
Funding Sources
• KSC Center Innovation Fund
• KSC Core Technical Capabilities Program
• KSC Independent Research & Technology Development Program
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vanced Water Purification System for
In Situ Resource Utilization
Steve Anthony
NASA Kennedy Space Center
September 12, 2013