Harvesting Luna (was: Harvesting Mars)

{{Date: 21 Aug 2003 00:36:13 GMT
From: (Ron Baalke)
Newsgroups: sci.space.news
When CO2 is compressed to a pressure of 73 atm and heated to 31.1
degrees Celsius, it becomes a supercritical fluid--and a marvelous
solvent, ... A supercritical fluid has some advantages over other
solvents: Its solubility changes dramatically when you alter the
temperature or the pressure. You can control it, so that sometimes
it's a solvent for a particular substance, and sometimes it's not.
That makes it easy to recover the material that has been dissolved.}}

That gives me an idea. When mining Lunar material, we can easily
extract water from the polar deposits, use electrolysis to separate the
hydrogen, then extract oxygen from the ordinary regolith by heating it
with lots of hydrogen. But then it becomes difficult to separate the
various metals left behind. Maybe supercritical CO2 could be used to do
that? Does anybody know of specific research along that idea?

In article , wrote:
That gives me an idea. When mining Lunar material, we can easily
extract water from the polar deposits...

For small values of "easily". :-) That may be quite a job, depending on
the exact physical details of the material.

use electrolysis to separate the
hydrogen, then extract oxygen from the ordinary regolith by heating it
with lots of hydrogen.

Almost certainly, if we've got electrolyzed water available, it will be
easier to just use the oxygen from the electrolysis rather than trying to
get more out of regolith. Pulling oxygen out of metal oxides is hard;
there are all kinds of nasty problems once you start getting into the
details. (E.g., hydrogen extraction will also turn traces of sulfur into
H2S and thence into sulfuric acid, which will not be good for the
machinery.)

But then it becomes difficult to separate the
various metals left behind. Maybe supercritical CO2 could be used to do
that?

I'm skeptical, although supercritical CO2 is strange stuff and I wouldn't
want to definitely say it's impossible.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

wrote:
{{Date: 21 Aug 2003 00:36:13 GMT
From: (Ron Baalke)
Newsgroups: sci.space.news
When CO2 is compressed to a pressure of 73 atm and heated to 31.1
degrees Celsius, it becomes a supercritical fluid--and a marvelous
solvent, ... A supercritical fluid has some advantages over other
solvents: Its solubility changes dramatically when you alter the
temperature or the pressure. You can control it, so that sometimes
it's a solvent for a particular substance, and sometimes it's not.
That makes it easy to recover the material that has been dissolved.}}

That gives me an idea. When mining Lunar material, we can easily
extract water from the polar deposits, use electrolysis to separate the
hydrogen, then extract oxygen from the ordinary regolith by heating it
with lots of hydrogen.

Nice idea, but why attempt to create a chemical reaction to heat
regolith to extract oxygen? Or are you heating the hydrogen so that it
will react with the oxygen in the regolith making a big, muddy mess? Of
course, the hydrogen would be able to go anywhere within the regolith
fairly easily.

But then it becomes difficult to separate the
various metals left behind. Maybe supercritical CO2 could be used to do
that?

After a little research, I found a .gov site that tells a little bit
about the subject (http://www.pnl.gov/supercriticalfluid/). In the RTDS
section it tells about creating small powder products from metal
compounds, and the RESS section tells of bringing the dissolved
compounds out of solution by rapidly decreasing the pressure, creating a
gas of the CO2 and leaving the compounds out to dry. Seemingly the CO2
use has been limited, because the compounds had to have low polarity and
molecular weight before they would dissolve, but they have an emulsion
process down that will allow a greater range of products to be
dissolved, including the metals.


Does anybody know of specific research along that idea?


My interest in this subject lies in a sci-fi book I am writing. This
tech looks like a good candidate for it. My question is, what are some
other supercritical fluids that could be used (tried a quick Google,
didn't get a whole lot), since carbon would be very valuable in space
until we got a belt processing plant going? Maybe N2 would work under
some coaxing? Of course, you would get some _very_ interesting chemical
reactions from that...
Still, considering the number of materials on the Moon (iron, silicon,
titanium, cesium, oxygen, He3, aluminum, magnesium, etc.), you will have
many different extraction processes, but many have fairly simple
chemical means of doing so.

--
Schwert

A rose by any other name is still a rose, even if the name is esor. The
same goes for spam...and you have to get rid of it before you can email me.



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{{Date: Sat, 23 Aug 2003 17:28:21 GMT
From: (Henry Spencer)
if we've got electrolyzed water available, it will be easier to just
use the oxygen from the electrolysis rather than trying to get more
out of regolith.}}

The reason for removing oxygen from regolith is not necessarily to get
the oxygen itself, but merely as the first step in reducing the oxides
of the regolith so that the remaining slag can be used to produce
metals for construction. (We may simply use the abundant excess oxygen
as reaction mass in return vehicles, or as thermal carrier to pump heat
from one place to another, and not worry about it leaking out and being
"wasted" because it's so abundant.)

{{Pulling oxygen out of metal oxides is hard; there are all kinds of
nasty problems once you start getting into the details. (E.g.,
hydrogen extraction will also turn traces of sulfur into H2S and
thence into sulfuric acid, which will not be good for the machinery.)}}

My idea, which I posted here a few months ago, was to operate the
oxygen-from-regolith extraction process in a hydrogen-rich environment,
so that H2S would not be converted to SO3 or even to SO2, not even
precipate out as elemental sulfur to clog up plumbing. At some point,
the H2S could be mixed with just the right amount of oxygen, perhaps
aided by prokaryotes, to generate elemental sulfur, which is then safe
to store indefinitely until we have a use for that element.

Because excess hydrogen tends to convert CO2 to methane plus water, of
course we can't do both processes (oxygen extraction, and supercritical
CO2 separation of metals) at the same time. First we'd use hydrogen to
extract as much of the oxygen and sulfur as possible, and anything else
that came out in the same process (probably carbon and nitrogen). Then
we'd switch to supercritical CO2 mode on the remaining slag to separate
the scCO2-soluble metals from the other metals. Presumably there
wouldn't be enough sulfur remaining at that point to present a sulfuric
acid problem. Regolith has a lot of silicon, the one remaining element
in the slag which isn't a metal. Does anybody know what happens to it
in scCO2?

{{Date: Sat, 23 Aug 2003 13:56:20 -0500
From: Schwert
then extract oxygen from the ordinary regolith by heating it
with lots of hydrogen.
Nice idea, but why attempt to create a chemical reaction to heat
regolith to extract oxygen?}}

You misunderstood my use of "with": I meant in the same sense as
heating a room with forced-air, the hydrogen is heated first, then
pumped through the regolith, and that hot hydrogen provides most of the
heat for warming the regolith so it'll react with the hydrogen. (Some
additional heat is generated when oxygen in the regolith combines with
the hydrogen, but I'm not relying on that little bit of extra heat,
although it must be figured into the overall calculation.)

{{Or are you heating the hydrogen so that it will react with the oxygen
in the regolith making a big, muddy mess?}}

Yes, except it won't be muddy because the temperature will be higher
than the boiling point of water so most of the water produced will
simply blow away as vapor, a small amount perhaps staying behind as
hydrated minerals.

{{Of course, the hydrogen would be able to go anywhere within the
regolith fairly easily.}}

Yes. Regolith is essentially vacuum-welded and shock-welded dust/sand,
which is very porous, and as hydrogen removes some of the oxygen it'll
become even more porous until welding is broken and free particles of
dust/sand then settle down toward the bottom of the reaction chamber
thereby maintaining an equilibrium of nearly constant porosity. I'm
taking full advantage of that initial and continued porosity when I
concentrate on processing regolith instead of full-size rocks. In any
batch of regolith, there should be a few pebbles and an occasional
small rock mixed in, which for the most part won't participate in this
oxygen-extraction process, and can be discarded easily afterward by
passing the dust/sand pebble/rock mixture through a sieve that lets the
dust/sand fall through to the next process while holding the
pebbles/rocks to be discarded from this process (but possibly examined
by science instruments).

{{what are some other supercritical fluids that could be used ... since
carbon would be very valuable in space until we got a belt processing
plant going?}}

Before we do the supercritical CO2 work, we'd have an earlier mission
that just extracts hydrogen (water or whatever) from the Lunar polar
abyss material and studies its composition. Somebody has suggested that
cometary debris frozen in the polar craters would have significant
amounts of methane and ammonia. If so, we have a ready source of CO2
per my idea and N2 and NH3 per your suggestion here. NH3 might in fact
be the very best chemical to use, if it's available from the polar
abyss, because it's hydrogen rich instead of oxygen rich, hence can be
used for both the initial extraction of oxygen and the later
supercritical extraction of metals, and we never have to worry about
sulfur coming out as SO3.

{{Maybe N2 would work under some coaxing? Of course, you would get
some _very_ interesting chemical reactions from that...}}

Well, N2 tends not to react with much of anything most of the time. It
takes considerable evolutionary expertise, and **energy**, for
nitrogen-fixing prokaryotes to convert it to anything else.

{{Still, considering the number of materials on the Moon (iron,
silicon, titanium, cesium, oxygen, He3, aluminum, magnesium, etc.),
you will have many different extraction processes, but many have
fairly simple chemical means of doing so.}}

Electricity from sunlight is readily available on Luna. Processes
(using electric power) that do purely mechanical tasks, such as
pressurizing gasses, pumping fluids, carrying buckets of material, are
simple and if erosion of various kinds can be kept to a minimum they
can operate for months or years without re-supply. By comparison,
traditional chemical processes where a reactant chemical is added,
require constant resupply of that reactant chemical, requiring on Luna
a system for recycling it. Supercritical gas methods have that big
advantage compared to traditional chemical-reactant methods. We'll
surely have systems for distilling water, and for electrolyzing water
into hydrogen and oxygen, so using either hydrogen or oxygen or water
as a chemical reactant will be no problem. If, and only if, we have a
large supply of ammonia from the Lunar polar abyss, distilling ammonia
and using it as a chemical reactant will be practical. Likewise methane
is a "maybe" if present in the abyss. Perhaps there'll be enough carbon
or sulfur present that we can manufacture useful quantities of carbonic
acid (CO2 + water, i.e. carbonated water) or sulfuric acid (SO3 +
water) to dissolve metals that resist supercritical-gas leaching. Any
other chemical is likely to be in too short supply on Luna to be
practical as a chemical reactant during early years of infrastructure
development. (As for worry of SO3 corroding equipment: As I noted
before, my proposals involve working in a hydrogen-rich environment
most of the time, where SO3 would never form. In those few places where
we need to use SO3 i.e. H2SO4, we make it from elemental sulfur or from
H2S, then use it in special equipment that is resistant to sulfuric
acid corrosion, then dilute it with water and feed it with hydrogen to
sulfate-reducing bacteria to render it harmless again.)

Can't sulfur and it's compounds be removed before any chemical processing is
done by just heating the crushed rock?

1) Crush rock and place in sealed heater.

2) Raise temperture to 100C. Store outgassed hydrogen/water/whatever.

3) Raise temperture to 400+C (600?). Store outgassed sulfer products.

4) Flush with high temperture/pressure hydrogen, use heat exchange to extract
out water and re-heat hydrogen.

5) Flush with high temperture/pressure CO2, use heat exchange to extract out
metals and re-heat CO2.

6) Process what remains - note should be enriched in the denser metals.

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

Earl Colby Pottinger wrote:
Can't sulfur and it's compounds be removed before any chemical processing is
done by just heating the crushed rock?

1) Crush rock and place in sealed heater.

2) Raise temperture to 100C. Store outgassed hydrogen/water/whatever.

3) Raise temperture to 400+C (600?). Store outgassed sulfer products.

4) Flush with high temperture/pressure hydrogen, use heat exchange to extract
out water and re-heat hydrogen.

5) Flush with high temperture/pressure CO2, use heat exchange to extract out
metals and re-heat CO2.

well, if you managed to convince chemistry to work this way then yes,
it would work. In realy it depends on a lot of other things, staring with
what exact compunds you have in rocks, the moment any water separates
you will have inteersting results, but the water will not just nicely boil
out. did you consider melting it all, electrolyzsing and then trying to get
the interesting gasses separated?


6) Process what remains - note should be enriched in the denser metals.

Earl Colby Pottinger


--
Sander

+++ Out of cheese error +++

{{Date: Mon, 25 Aug 2003 03:33:53 -0000
From: Earl Colby Pottinger
Can't sulfur and it's compounds be removed before any chemical
processing is done by just heating the crushed rock?}}

I'm not proposing crushing any rock, during the first few years of
Lunar resource mining/processing, because there's an abundant amount of
pre-crushed stuff in the form of regoligh. Why bother with the extra
equipment to try crushing rocks? Just scoop up regolith and use it
as-is, and discard any pebbles/rocks found within it.

Given that the only "chemical processing" I propose initially consists
of temperature changes, pressure changes and pumping fluids,
electrolysis, feeding hydrogen or oxygen from the electrolysis back
into the mix at various times, and perhaps pumping supercritical gasses
such as CO2 or N2 or NH3 through regolith, what you propose of heating
the stuff before anything such as heating is self-contradictory.

Given that regolith is bits of rock vacuum/shock-welded together, with
absolute vacuum filling all the spaces between the pieces, how exactly
would you "heat" the rock except by forcing a hot gas (I propose
hydrogen) through it? You can't put it in a microwave oven to excite
the liquid water molecules, because the dry regolith doesn't have any
water content and the ultra-code stuff from the polar abyss is too cold
to have any liquid water, and any water you accidently melt will
immediately sublime to a gas unless you put it under pressure from some
gas in the first place.

Even if you could just heat it, there's so much oxygen present in
regolith that any sulfur content would probably come out as SO3 which
forms concentrated sulfuric acid if there's any hydrogen, hence water,
present. That's why I prefer to force hot hydrogen through the
regolith, so the sulfur comes out as H2S instead of SO3.

{{2) Raise temperture to 100C. Store outgassed hydrogen/water/whatever.}}

How do you propose heating it?

{{3) Raise temperture to 400+C (600?). Store outgassed sulfer products.}}

SO3 immediately corrodes all the metallic piping/vessels/instrumentation.

{{4) Flush with high temperture/pressure hydrogen, use heat exchange to
extract out water and re-heat hydrogen.}}

My proposed method starts with this step (from regolith input), using
distillation to separate the water from the H2S, then using
electrolysis of the water to recycle the bulk of the hydrogen. (Sulfur
content is a couple orders of magnitude less than oxygen content, so
only a tiny bit of the hydrogen gets sequestered with the H2S, so
almost all is recycled by H2O electrolysis, so only a little new
hydrogen from the polar abyss is needed to maintain constant supply of
hydrogen.)

{{5) Flush with high temperture/pressure CO2, use heat exchange to
extract out metals and re-heat CO2.}}

Or N2 or NH3, whichever supercritical gas turns out to be most useful,
or use several in turn. (CH4 is supercritical at too low a temperature
to be useful in this way, right? What about carbon monoxide, CO?) Yes,
we're thinking exactly the same idea at this point. But I wonder if
anyone with access to both regolith samples and chemical processing
equipment is actually doing experiments to see which metals come out of
regolith when which supercritical gasses are applied, so that we can
start making better plans based on real data instead of just wishful
thinking?

Schwert wrote in message ...

My interest in this subject lies in a sci-fi book I am writing. This
tech looks like a good candidate for it. My question is, what are some
other supercritical fluids that could be used (tried a quick Google,
didn't get a whole lot), since carbon would be very valuable in space
until we got a belt processing plant going? Maybe N2 would work under
some coaxing? Of course, you would get some _very_ interesting chemical
reactions from that...
Still, considering the number of materials on the Moon (iron, silicon,
titanium, cesium, oxygen, He3, aluminum, magnesium, etc.), you will have
many different extraction processes, but many have fairly simple
chemical means of doing so.

The Artemis Society (now the Moon Society) and the Lunar Reclamation
Society have both done quite a bit of research in this direction. You
best bet is to look through archived copies of the Moon Miner's
Manifesto (I think you have to join the moon society first though).

www.moonsociety.org
most good free stuff is in the Artemis Data Book (ADB)

Tom Merkle