| Having studied other pages of Lunar Resources, it becomes clear that I have concentrated on getting aluminum from regolith. The Damascus Project is all about steel production and steel will probably be the most used metal on the Moon and in outer space, but aluminum is very important for wires and cables since copper is lacking on the Moon. The Typically Favored Al subchloride process Anorthositic highland regolith is 90+% plagioclase (CaAl2Si2O8 and a little Na2Al2Si2O8) with some pyroxene, olivine and basalt. Magnetic separation will clean the iron bearing minerals including titanium bearing ilmenite out of this. Intense solar heat could boil the silica and magnesia out leaving pure anorthite. This could be leached in sulfuric acid. CaO will form CaSO4, calcium sulphate, plaster of Paris and water. Silica for glass will also form. Al2(SO4)3 will be filter out and roasted to AlsO3. Al2O3 is not attacked by readily by acid. This mixture of CaSO4 (anhydrite) and silica can be dried, the water recycled and used to reconstitute H2SO4. The silica and CaSO4 can be separated electrostatically. The Al2O3 is then carbochlorinated to yeild AlCl3 which is electrolyzed. Electrolysis of AlCl3 does not consume the precious lunar carbon electrodes as does conventional Hall-Heroult electrolysis of Al2O3. The carbochlorination step yeilds CO2 that must be shifted to methane that can be decomposed to carbon and hydrogen on red hot refractories like solar heated black cast basalt perhaps. Solar carbothermal? If solar carbothermal reduction of alumina is tried, we must mix the alumina with silica and carbon (1). A very high temperature ceramic retort and window will be necessary. An aluminum-silicon alloy will form. This could be separated by boiling off the aluminum in the vacuum with solar or microwave heating. This would not require chlorine which is so rare on the Moon to be virtually nonexistent. Carbon would be required so CO and CO2 formed by the carbothermal reduction must be shifted to methane and pyrolized to recover carbon. Electricity would not be needed for the carbothermal reduction. It is said that this will use less energy than electrolysis and since the energy comes directly from solar radiation without the inefficiencies of conversion to electricity and power conditioning I suspect that this may be better than the AlCl3-electrolysis process on the Moon. Destructive Distillation? Combined with Fluxed Electrolysis? Preparing Al2O3 for solar carbothermal redux still requires H2SO4 leaching and this will involve complexities preferrably avoided. Harvesting sulfur oxides will corrode mining equipment, esp. if it reacts with H2O to form H2SO4 in the volatiles miner. Though leaching tanks, piping and pumps can be made of high silicon alloy iron and/or lined with cast basalt (resists up to 96% sulfuric acid) the danger of leaks and loss of precious water exists. It may be possible to subject anorthite to intense solar heat to decompose the mineral particles and boil off iron oxide, silica and magnesium oxide leaving calcium aluminate (2). This CaAl2O4 could be subjected to electrolysis in a flux of LiF and CaF2 (EMEC process), but then lithium and fluorine are required and these must be upported to the Moon at great cost and recycled. However, large amount of aluminum are not required on the Moon. Building materals will consist of iron, steel, titanium, cast basalt, ceramics, glass, glass-glass composites and concrete. Aluminum will be used mainly for wiring. 10 gauge Al wire can carry 25 amps. At 14.2 gr/m we need 14.2 kg/1000m and only14.2 metric tons per 1000 km! We could do plenty of wiring with that. 0000 cable 165 amps 290 gr/m 290 kg/km 290 tons/1000 km AWG 1000 cable 380 amps 672 gr/m 672 kg/km 672 tons/1000 km Enormous quantities of aluminum are not needed since it will be used mainly for wiring and cables rather than structural purposes. Thus, the masses of flux upported to the Moon will be limited and not represent an excessive cost. A system that can produce 150 tons of Al per year, 360 tons of calcium and 1000 tons of oxygen from 2500 tons of anorthite using tens of tons of LiF/CaF2 flux has been designed by EMEC consultants. (3) A smaller scale system could be used in early years of lunar industrialization until lunar sources of fluorine were tapped. Possible sources of flourine would be trapped sub-selene volcanic gas, polar ice if of cometary origin, thermal decomposistion of phosphate minerals, acid leaching of phosphate minerals (KREEP bearing regolith). Calcium could be produced on the Moon for fllux and sodium or potassium might substitute for some of the lithium. Whether or not lithium exists on the Moon in deposits of any kind is unknown; however, one Apollo 12 sample consisting of 70% anorthite was enriched in potassium, rubidium, barium, zirconium, yttrium, lithium and ytterbium. Did it come from the "mother load" somewhere, ejected by a meteroite impact??? (4) Fluxed electrolysis will require the use of inert electrodes. Patents for Ni-Fe-Al oxide ceramic anodes exist (5). These elements can be obtained on the Moon. 1) Jean P. Murray Engineering Division, Colorado School of Mines SOLAR PRODUCTION OF ALUMINUM BY DIRECT REDUCTION OF ORE TO AL-SI ALLOY <http://www.kenes.com/Ises.Abstracts/Htm/0450.htm> 2) Rudolf Keller and David B. Stofesky of EMEC Consultants " Selective Evaporation of Lunar Oxide Components" reported in SPACE MANUFACTURING 10 PATHWAYS TO THE HIGH FRONTIER Proceedings of the Twelfth SSI-Princeton Conference May 4-7, 1995; pg. 130. 3) Processing Lunar Soils for Oxygen and Other Materials Christian W. Knudsen and Michael A. Gibson <http://www.belmont.k12.ca.us/ralston/programs/itech/SpaceSettlement/spaceresvol3/plsoom1.htm> 4) David M. Harland. Exploring the Moon. page 49. Praxis Publishing: 1999. 5) Ni-Fe-Al oxide ceramic inert anode http://www.freepatentsonline.com/7033469.html |
| Lunar Aluminum Note |
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| D.A.Dietzler, 2007 |
| A Simpler Way to Get Al? by Dave Dietzler 2008 What if it is possile to subject anorthite to solar heat, boil off and condense the SiO2 for pure silica glass, and get calcium aluminate that is then subjected to even higher temps to break it down into Al2O3 and CaO? Presumably the the Al2O3 will boil off in the vacuum at a lower temp than the CaO because it melts at 2000 C. while CaO melts at 2560 C. and liquids boil in the vacuum. Could the Al2O3 then be condensed and placed in a sealed furnace and melted at 2000 C. with solar heat and electrolyzed with super high temp. oxidation resistant electrodes.? Conductors become resistive at high temp. but semiconductors like many ceramics become conductors at high temp. This would be the simplest most direct way of getting Al and it would not involve any sulfuric acid, chlorine, flourine, lithium or carbon all of which are in short supply on the Moon. http://www.inspi.ufl.edu/data/htmp1_updated.jpg http://www.inspi.ufl.edu/data/htmp2.jpg At these URLs, just copy and paste into yer browser, are the melting points of a large number of ceramics. Some of them are sure to fit the bill of high temperature oxidation resistance (oxides are already oxidized and won't react with oxygen) and conductivity at high temp. as well as being insoluble in molten Al2O3. |