NASA Technical Reports Server (NTRS) 20120003152: Joule-Heated Molten Regolith Electrolysis Reactor Concepts for Oxygen and Metals Production on the Moon and Mars

6 MB·English

by  NASA Technical Reports Server (NTRS)

BACKGROUND
• The maturation of Molten Regolith Electrolysis (MRE) as a viable technology for
oxygen and metals production on explored planets relies on the realization of the
self-heating mode for the reactor.
• Joule heat generated during regolith electrolysis creates thermal energy that
should be able to maintain the molten phase (similar to electrolytic Hall-Heroult
process for aluminum production).
• Self-heating via Joule heating offers many advantages:
• The regolith itself is the crucible material -7 protects the vessel walls
• Simplifies the engineering of the reactor
• Reduces power consumption (no external heating)
• Extends the longevity of the reactor
• Predictive modeling is a tool chosen to perform dimensional analysis of a self
heating reactor:
• Multiphysics modeling (COMSOL) was selected for Joule heat generation
and heat transfer
• Objective is to identify critical dimensions for first reactor prototype
January 12, 2012 50th Aerospace Sciences Meeting
Pg.2
Lab Scale Cell for Molten Regolith Electrolysis
Self-heating Hall-Heroult reactor {Aluminum}
Crust L .J carbon
2 0 2 +C ~ CO + 4 e
-
2
Anode
molten fluoride
+
AI 0
2
January 12, 2012 50thAerospace Sciences Meeting
Pg.4
Self-heating Molten Regolith Electrolysis
PMtr'Ie(IngToE~theFutUfe
current
feed
point feeders break
crust and introduce\-::.----1
metal oxide here
frozen
electrolyte
~xygengas
anode
t-----l bubbles
molten oxide electrolyte
liquid
cathode
cell
sidewall
---1__ metal pool
cell floor I
8
collector bar
I
I
I
ct
January 12, 2012 50th Aerospace Sciences Meeting
Pg. 5
In-Re olith Conce t for Lunar Electrowinnin
Electrowinning
e
Anode
January 12, 2012 50th Aerospace Sciences Meeting
Pg.6
Self-heating Molten Regolith Electrolysis
PMtrt«1ngToE~tMFUll,Jrr
REACTOR MODEL
Anode
lead
Vessel
Cathode
collector
January 12, 2012 50th Aerospace Sciences Meeting
Pg.7
Heat Transfer Modeling
General Energy Equation for
solids Radiative Intensity forgray & isotropic
medium
pC aT -V.(kVr)=Q
at VI{r,s)=kalb(r)-(k +aJI{r,s)+ as r4 I{r,s')P(s',s~'
P T+a~ Jo1< ~--
Heat 4n
Sources change in emission absorption scattering
radiative
~h:~a~~d~a:o:i:P~~c:~in~ --:
2' intensity
Q Q1J+
=
This equation needs to be integrated over the spatial as well as
media . I the angular domain. Spatial discretization is done by dividing
I spatial domain into discrete control volumes orcells. The angular
I discretization is done usingcontrolangles.
Joule
I
heating
I
~ I The radiation direction vector s is
I
defined in terms of two angles a
I
andf3
I
~--.-----.-~.y
: G= :2I(r,s) x
L__ (, )
Boundary Conditions Qr =ka\G-4oT4
• Radiative heat transferbetween outer
surfaces and ambient. p =density s =position vector
• Radiative heat transferbetween outer Cp =heatcapacity r =direction vector
surfaces ko =thermalconductivity 0' =variable forcontrolangledirection
=electrical et> =scatteringphasefunction
• Free convective heat transferwith ambient conductivity k. =adsorptioncoefficient
• Constant voltage at the top ofanode lead T =temperature as =scatteringcoefficient
• Electrical groundatthe top Ofcathode J =currentdensity I(r, s) =radiativeintensityatrpositionandsdirection
I =blackbodyintensity
collector b
G =incidentradiation withintheparticipating
• Thermal insulation at the outerbottom ofthe media
cell
• All surfaces electricallyinsulated
January 12, 2012 50th Aerospace Sciences Meeting
Pg.8
Thermophysical Properties of regolith
'¥tI't«ingToEng~theFuture
10.0 10.0000
~ ,,"
""
E E
~ ~ 1.0000 ...r.nO
~ 3 0 600 ,,,900
~ '$ ....
''n$ 1.0 I ~ 't; 0.1000
'c:0t::ll r 4 0 8 0 1..2.0..0. ... ...f1' 1110o 'lu:0t:::ll 0.0100 ...
U ... iii
iE.i,i 0.1 II -. -- ..... , ...... 'Q.uI,: 0.0010
.tc::. I~ .........'" !.C.B.l. 0.0001
..C0..l 0
I
0.0 0.0000
TemperatLl'e(el Temperature(e)
• FJS·1 • SyntheticApollo11 Fitting • Tholeiiticbasalt • lunarsample12002.85 Fitting
Thermal Conductivity Electrical conductivity
-
-
1,150 - ...... ---
_ 1,100 ...... 3000 .----.--~--.,----,---.---,
t~b 1,050 ..... '" 2800 +----+---+---+---+---t~£-.
~ M
:i'1,OOO --' .<[ 2600 +---+---f----+---+~~+_-___j
'~u 950 -' -~' 2400 +---+--__jf----60,,£,.-+--+_-___j
! 900 ,?
«l ~ 2200 +---+--~~~-+---+--+_-___j
u 850 , '0
16
Cl 800 ~ 2000 +--~~-+---+--+_--+----I
:I:
750 C 1800 ~--+--_+--+---+--__+-__j
700
1600 +---1---+---+----+----+---1
o 300 600 900 1200 1500 1800
300 550 800 1050 1300 1550 1800
TemperatLl'tl(C)
Temperature(C)
• FJS·1 - - Fitting
Heat Capacity Density
January 12, 2012 50th Aerospace Sciences Meeting
Pg,9
Optical Absorption
Absorption coefficient
1Dl-r---------------,
_ 35000
..€
30000 r---..
M
:; 25000 "
c
.u~ 20000 .....-....-.
~ 15000 ............
8
10000
g 5000 II' I
~ """"li"'-- I
0
(;)
~ 400 450 500 550 600 650 700 750 800
«
Wavelenght(nm)
_0:~omlaometer-s _0:l~Omlaometer-s
Lunar glassy spherules obtained from
lunar dust brought to earth by Apollo 14
Commercial glass (clear and
. .
mission
gray) and bronze
January 12, 2012 50th Aerospace Sciences Meeting
Pg.10