Thermodynamic modelling of ultra-high vacuum thermal decomposition for lunar resource processing

Shaw, Matthew; Brooks, Geoffrey; Rhamdhani, M. Akbar; Duffy, Alan R.; Pownceby, Mark I.

doi:10.1016/j.pss.2021.105272

Cited by 16 publications

(3 citation statements)

References 33 publications

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“…Given the computationally heavy nature of evaluating all the combinations of binary and ternary oxide systems, focus was placed on the evaluation of Fe, Na, and K, these being the most volatile oxides in the feed composition [11].…”

Section: Saturated Vapor Pressurementioning

confidence: 99%

“…Thermodynamic equilibrium modelling of a sublimation process acting under ultrahigh vacuum conditions (3 × 10 −15 atm) predicted that for Fe sublimation, a minimum temperature of 800 • C was required [11]. In the current work, partial melting of the regolith simulant material was observed at 1200 • C. As such, for the investigation of the sublimation kinetics of regolith material presented in the current work, the temperature range from 800 • C to 1200 • C was considered.…”

Section: Introductionmentioning

confidence: 95%

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Metal and Oxide Sublimation from Lunar Regolith: A Kinetics Study

et al. 2023

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When considering the extraction of metals from lunar regolith for use in space, one reductive method of interest is vacuum thermal dissociation. Given the high vacuum environment on the Moon, the sub-liquidus operation of such a process, i.e., sublimation, warrants investigation. In the current work, the kinetics of the vacuum sublimation of the more volatile major oxides found in the lunar regolith, Na2O, K2O, and FeO, are evaluated. Two distinct factors are accounted for in the current work: the change in the evaporation flux due to temperature; and the reduction in available surface area for evaporation due to sintering of the feedstock. Surface area change due to the sintering of compressed LMS-1 regolith simulant pellets was quantified via a Brunauer–Emmett–Teller analysis. The surface area of the samples was measured to vary from 3.29 m2/g in the unsintered sample, to 1.04 m2/g in the samples sintered at 800 °C, and down to 0.09 m2/g in the sample sintered at 1150 °C. Evaporation flux was calculated using the Hertz–Knudsen–Langmuir equation using saturated vapor pressures predicted from the FactSage thermochemical package and verified against Knudsen Effusion Mass Spectroscopy data from tests conducted on lunar regolith sample #12022. The combination of these studies resulted in the conclusion that no local maxima in evaporation rate below the melting point was found for the current system, as such the highest rate of sublimation was determined to be 1200 °C for all species, at temperatures of 1200 °C and above, partial melting of the material occurs. The predicted maximum rate of sublimation for the species Fe, Na, and K at 1200 °C was 0.08, 1.38, and 1.02 g/h/g of regolith, respectively. It is noted that significant variation was seen between FactSage predictions of saturated vapor pressures and the measured values. Future work generating detailed thermochemical databases to predict the behavior of complex systems similar in composition to lunar regolith would benefit the accuracy of similar kinetic studies in the future.

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Section: Saturated Vapor Pressurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Metal and Oxide Sublimation from Lunar Regolith: A Kinetics Study

et al. 2023

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“…A carbothermal reduction process has also been extensively studied, and the reducing agents mainly include solid carbon, CO gas, methane, etc. − Thermodynamically, the efficiency of chemical reduction depends on the limited oxides such as FeTiO 3 and Fe 2 O 3 of the lunar regolith. The second way is to decompose lunar regolith by vacuum thermal dissociation. − High temperatures (>2000 °C) and ultrahigh vacuum (<10 –14 atm) are needed to drive the spontaneous thermodynamic decomposition of oxides to metals and oxygen . The vacuum thermal decomposition has been well modeled a the practical demonstration has not yet been performed.…”

Section: Introductionmentioning

confidence: 99%

Extracting Oxygen from Chang’e-5 Lunar Regolith Simulants

Shi

Yang

Zheng

et al. 2022

ACS Sustainable Chem. Eng.

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Harvesting oxygen and metals from the local resources of the Moon is a key step to advancing outer space exploration. A large amount of oxygen is stored in the lunar regolith in the form of oxides. Many efforts have been devoted to electrochemically splitting oxides to oxygen and metals in molten oxides and molten salts. However, a cheap oxygen-evolution inert anode is still a serious challenge, especially in the supercorrosive molten halides. Herein, we combine a molten CaCl 2 electrolyzer that can convert Chang'e-5 lunar regolith simulants to metals and CO 2 using a carbon anode and a molten carbonate electrolyzer that can convert the generated CO 2 to carbon and oxygen using a cheap Ni11Fe10Cu oxygen-evolution anode. Further, the electrolytic carbon is reused as the anode in the molten CaCl 2 electrolyzer, thereby closing the carbon cycle. Hence, the overall electrochemical reaction of the dual-electrolyzer system is to convert lunar regolith to metals and oxygen. More broadly, this system can convert the CO 2 generated by humans living on the Moon and Mars to oxygen and carbon materials.

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