A Continuous Hydrogen Reduction Process for the Production of Water on the Moon

Abstract

A continuous screw reactor for hydrogen reduction of lunar soil simulant was assembled. The water production rates were measured with different reduction conditions. Reduced simulants were analyzed by XRD (X-ray Diffraction), SEM (Scanning Electron Microscope), and EDS (Energy dispersive X-ray spectroscopy). The effect of reduction temperatures in the range of 1173-1373 K in 3 vol% hydrogen was clarified. The highest water production rate at the steady-state is obtained at 1273 K. The water production rate becomes higher with the higher reduction temperature up to 1273 K. It becomes lower at the temperature above 1273 K because Na-rich components in lunar simulant melt and it inhibits the hydrogen diffusion. The impact of hydrogen concentrations between 3-10 vol% was revealed with the fixed reduction temperature of 1273 K. The reaction rate has linear relationship to the hydrogen concentration. The reduced lunar simulant contain α-Fe, and the amount increases with higher hydrogen concentrations. The reduced ilmenite has porous structures due to the vacancy of oxygen. This work suggests the continuous hydrogen reduction system as a promising process to acquire oxygen on the moon.