Oxygen from Lunar Regolite with Solar Concentrating Energy
Thorsten Denk; thorsten.denk.psa.es
ERA-STAR Regions DeMoLOP Project (ERA – Space Technologies Applications & Research for the Regions and Medium-Sized Countries -CA-515793-ERA-STAR REGIONS), EC 6th Framework Programme. Total budget: 100 k€.
December 1, 2008 – December 30, 2009
The US National Space Agency (NASA) is planning to again focus manned space exploration on the moon as the precursor of possible trips to Mars in the next two decades. The most important resource that will be required there is oxygen, for human consumption and for rocket fuel. If in situ oxygen could be achieved on the moon, a very substantial and costly part of the load that has to be transported from the earth would be saved.
Lunar regolite (powder) is rich in oxygen (up to 45% of its mass), but the chemical bonds are very strong, which means that for it to be extracted, very high temperatures over 1000ºC are necessary. As a consequence of prior studies, reduction of the lunar regolite component called ilmenite to water with hydrogen, followed by electrolysis to obtain oxygen and recover the hydrogen, is considered the most favorable chemical reaction.
FeTiO3 + H2 -> TiO2 + H2O + Fe
2 H2O -> 2 H2 + O2
An attractive way to supply the energy necessary is using concentrating solar radiation systems, which provide high energy flux densities and would make it feasible to reach the temperatures necessary to carry out the process.
The DeMoLOP Project is intended to study how to obtain oxygen from lunar regolite using concentrating solar energy, developing a complete demonstration system consisting of:
A regolite extraction system
A reaction system for obtaining oxygen
An oxygen post-processing system
The contribution of the ORESOL project concentrates on execution of Point 2), development, construction, testing and characterization of a device able to carry out the chemical reaction with concentrating solar radiation to gain oxygen from a “lunar soil stimulant” made by NASA.
The two main achievements in the Oresol Project are complete process development and the solar reactor design.
The simplified basic ORESOL process diagram is shown in Figure 1. Radiation from the sun is concentrated by the solar concentrator (1). The reactor is located in the focus (2). This reactor is fed by lunar regolite and hydrogen. The products are regolite slag and gas composed mostly of the excess feed hydrogen and the rest is steam, the desired solar thermal reactor product. Due to the low useful reagent (ilmenite) content in regolite, a large amount of solids will inevitably have to be processed with their associated energy consumption to heat them. Therefore, to simplify post-processing of the slag, a (partial) waste-heat recovery system is recommendable. (3) While solid waste is being ejected (8), the volatile components are sent to the water treatment system (4). In this step, excess hydrogen is separated from the water obtained, and, if necessary, the water is purified and stored. While the hydrogen reenters the process, the water goes to the electrolyzer (5). This equipment, which is the largest consumer of electrical energy in the process, dissociates the water into hydrogen and oxygen. While this hydrogen is also recycled, oxygen is the desired final product of the process (9). The diagram is completed by grounding (12), a heat rejection system (11), a regolite gate system (7) and slag (8), other regolite pretreatment systems (7) and various subsystems, especially for pumping and storing hydrogen.
The Oresol project is only the first step toward a lunar oxygen production plant, and therefore, the process has been greatly simplified. Research is concentrating first on the key step in the process, which is the solar reactor (2). The Solar Furnace of the Plataforma Solar de Almería is being used as the solar concentrator (1). A low-expansion fluidized bed in continuous operation was chosen as the Oresol reactor concept vertically concentrated solar radiation and direct absorption through a quartz window. The reactor is designed for operation with pure hydrogen to produce up to 700 g water per hour, consuming approximately 120 kg of regolite during this time. The most important tasks pending for 2010 are completion of reactor installation and testing.