“Bulk Gas Generation and
Storage Systems of the Mars
Homestead Project”
Damon Ellender
MHP Programming Team
DamonE@marshome.org
Design Goals
• Design a Bulk Gas Plant and associated
processes, located on Mars, to meet
settlement and manufacturing needs for O2,
H2, CH4, N2/Ar2 production and storage.
Design Assumptions
• Gas Composition as specified by NASA
• Ready source of water available
• Where possible, known and proven
techologies are used
• CH4 stored and used for fuel
• Initial Storage vessels imported from Earth
Process Assumptions
• Electrolysis:
– 2H20=> 2H2 + O2
• Sabatier Reactor:
– 4H2 + CO2 => 2H2O + CH4
• Compression and Cooling:
– Atmosphere => CO2 (l or s) + N2 (g) +Ar2 (g)
• O2 Liquefaction and Storage:
• CH4 Liquefaction and Storage:
• N2/Ar Liquefaction and Storage:
Process Details
• Electrolysis:
– 2H20=> 2H2 + O2
– Gibbs Free Energy: DG=-237.13 kJ/mol
– 1 Bar , 298K
• Sabatier Reactor:
– 4H2 + CO2 => 2H2O + CH4
– Exothermic after startup
– 1 Bar, 873K
Electrolysis-Sabatier Process
• Basic Electrolysis
assumed
• Hydrogen the
limiting factor
• All water from
Sabatier Process
recycled
Electrical
Power Supply
1 Bar CO2 Supply
0.7 kW
CO2 (5.5 kg)
Redundant Electrolysis Cells
1 bar and 298K
DG=-237.13 kJ/mol
H2O (9 kg)
Sabatier Reactor
1 Bar and 873K
H2 (1kg)
O2 (8 kg)
CH4 (2 kg)
Water Storage Tank
1 bar and 298K
H2O (4.5 kg)
O2 Compression and Storage
50 Bar and 183K
CH4 Compression and Storage
50 Bar and 183K
Gas Liquefaction and Storage
CO2(lr)
CO2(l )
CO2(ll)
Atmosphere
Air
Primary
Compression
20 Bar
Air
Cooling
N2/Ar2
Secondary
Compression
50 Bar
N2/Ar2
1st Stage
Cooling
N2
2nd Stage
Cooling
(Optional0
N2(l)
1
2
3
4
LIN Storage
N2
5
Ar2(l)
CO2(l or s)
Ar Storage
CO2 Storage
Ar
S
c
N2
r N2
Usage
u
b
S
c
Ar2
r Ar
Usage
u
b
CO2
Storage
Sabatier
Processes
Process Flow Diagram-Mars Air Separation and Compression
Wednesday, January 19, 2005
CO2 Basic Separation
• Compression chosen to 20 Bar to keep CO2 in
liquid phase for piping and storage
Specific
Work (kJ/kg)
Compression and Cooling
450
400
350
300
250
200
150
100
50
0
InterCooling
Isentropic
Isothermal
Intercooled
0
•
•
•
•
•
10
Bar (Differential)
20
Compress Mars Atmosphere from .07 to 20 Bar. Provides CO2 Liquid phase
Worst Case Specific Work(Isentropic): -421 kJ/kg
Best Case Specific Work(Isothermal): -199 kJ/kg
Isentropic Dt=~500K requires Inter-cooling: -747 kJ/kg
Additional Compression Cooling to liquefy Ar/N2 gas: -120 kJ/kg
Storage Vessel Design
2500
Volume (m3)
2000
1500
10 Bar
40 Bar
1000
500
0
O2
CH4
Ar2/N2
• Storage for 4 Months full usage
• Higher Pressures Selected to minimize imported
pressure vessel mass
Storage Vessel Design
35
Mass (tonne)
30
25
Steel
Aluminum
Titanium
20
15
10
5
0
O2
CH4
Ar2/N2
• Spherical Vessels
• Maximum Allowable Working Pressure (MAWP)= ~42 Bar
• Composite Vessels are expected to reduce Titanium Mass by 1/2
Summary Power Matrix
Phase One-(2 Years) Gas Production to Storage
Assume full production to storage. Fill 1 Month Emergency Storage in 1 Year.
Gas
Instantaneous Demand
Long Term Storage
Daily Use (kg)
Capacity* (kg/day)
Power (kw)
Emergency Storage
Requirement(kg)
Power (kw)
O2
0
0
157.775
57587
14
H2*
0
0
20.1
-
-
N2/Ar
0
0
4
1461
-
CO2
0
0
156
**16377
-
CH4
0
0
39.56
14439
***
CO2/Ar/N
C&L
3
O2 C&L
2
CH4 C&L
1
Totals:
0
*100% Required for CH4 production
**110kg/day used in CH4 production, excess can be used for cooling.
***Requires some power at start-up, then process self sustaining.
20
Phase Two-(2 Years)All Gas Production to Manufacturing
Gas
Instantaneous
Demand
Refining Needs
Daily Use (kg)
Metals Usage (kg/day)
Plastics Usage(kg)
Power (kw)
O2
70
414
0
110
H2**
2.6
0
60.75
-
N2/Ar
48
0
0
-
CO2
21.8
1515
583.75
-
CH4
5.3
187
0
-
CO2/Ar/N
C&L
30
O2 C&L
8
CH4 C&L
3
Totals:
**Includes H2 used for making CH4, not shown
151
Import Staging
Phase 1 Import Listing Weight and Size
Item
Floor space
m2
Volume
m3
Mass
kg
Assume 50%
reduction using
Composites
CH4 Storage Sphere(r=2.5)*
25
125
4500
(2250**)
O2 Storage Sphere(r=3)*
36
216
8000
(4000**)
Ar/N2 Storage Sphere(r=1.1)*
5
11
500
(250**)
CH4 HX
.25
.125
100
CH4 Sabatier Column
1
2
200
Electrolysis Cells
1
2
200
CO2
N+1 redundancy (est 2 small scroll
units)
4
4
250
O2/CH4/N2/Ar2 Compressors
N+1 redundancy
3
5
600
O2/CH4/N2/Ar2 Heat Exchangers
N+1 redundancy
3
5
400
Total Mass(kg)
14750
(8250**)
Import Staging
Phase 2 Import Listing Weight and Size
Item
Floor space
m2
Volume
m3
Mass
kg
C2H4 Column 1
1
2
200
C2H4 Column 2
1
2
200
m{C2H4} Reactor and catalyst 5
10
200
Electrolysis Cells
4
6
400
Inspection Equipment
1
2
200
Total Mass(kg)
1200