FFC Cambridge Process
Contents
Introduction
The FFC Cambridge Process reduces oxides to their metal components by electrolysis in a bath of molten calcium chloride. The process has potential to directly produce oxygen and metal from virtually any oxide. The process works by placing the oxide to be refined into a bath of molten calcium chloride and creating a voltage differential between the oxide component (which forms the cathode) and an anode which is also placed in the bath. Oxygen is stripped off the cathode, where it forms calcium oxide, which is soluble in the calcium chloride bath. This oxide is split at the anode, producing oxygen. The cathode meanwhile is gradually reduced to a porous metallic sponge.
The process is currently being developed by Metalysis for terrestrial metal production, specifically for the production of titanium; the developers hope it will eventually replace the Kroll Process.
Application To Lunar Colonization
In a lunar environment, this process could enable much simpler resource extraction. Experiments have already been done using pellets of sintered lunar regolith stimulant, producing metalized pellets and oxygen.
Aluminum/Silicon/Calcium Production from Anorthite
Anorthite (CaAl2Si2O8), which makes up much of the Lunar Highlands, could be separated from the regolith by electrostatic/magnetic benefication, and then sintered into an appropriate cathode. As the process progresses, the oxygen is stripped off, and metallic calcium is produced, which is soluble in the calcium chloride bath. To keep the calcium concentration from becoming too high (which can reduce current efficiencies), a distillation unit is set up to continuously remove the metallic calcium from the mix. Once the Anorthite cathode is completely reduced, a sponge consisting of approximately 49% Aluminum, 51% Silicon remains. This sponge could then be melted and distilled under partial vacuum to produce pure aluminum and silicon. For every metric ton of Anorthite processed in this manner, approximately 460 kg oxygen, 193 kg aluminum, 201 kg silicon, and 144 kg calcium would be obtained.
Iron/Titanium Production from Ilmenite
Ilmenite (FeTiO3), is found in abundance on the lunar Maria and is easily separated through magnetic means. This substance would be processed in the same fashion as Anorthite, resulting in a 54% Iron, 46% Titanium alloy, which could then be distilled to produce Iron and Titanium. The end result for each ton would be approximately 316 kg Oxygen, 316 kg Titanium, and 368 kg Iron.
Other Products
Lunar Chromite could also be reduced in the same fashion, producing Ferrochrome, which could be used to add Chromium content to Iron alloys. Many of the above listed reductions would also contain amounts of Magnesium and Sodium (Lunar Ilmenite in particular is known to be highly enriched with Magnesium), which could be distilled out fairly easily due to their low melting points.
Chlorine Recovery
The only substance used which is not readily available on the Lunar surface is chlorine. Chlorine is avalible on the lunar surface in the form of Apatite (Ca10(PO4)6(OH, F, Cl, Br)2), but only in trace quantities. If a viable procedure for concentrating apatite out of the lunar regolith is not found, then a high degree of chlorine recycling would be necessary for the FFC Cambridge process to be useful in a lunar environment.
Chlorine losses from the system would come in the form of calcium chloride trapped in the pores of the metallic sponge produced in the reduction process, as well as any amount lost from the distillation of calcium metal out of the bath during anorthite processing. The latter losses could be reduced to acceptable levels through careful design of the distillation equipment.
In terrestrial applications, the salt trapped in the pores of the sponge is removed by grinding the sponge and washing the resulting powder with water, as calcium chloride is highly water soluble. The same procedure could be followed in a lunar environment, followed by reverse osmosis and distillation to recover the dissolved salt.
A simpler method is to simply melt the sponge, as is required for most of the described processes already. Since calcium chloride is not soluble in most metals, it should separate into a distinct layer, where it can be easily drained off.
