The Development of Models for Carbon Dioxide Reduction Technologies for Spacecraft Air Revitalization

Abstract

Through the respiration process, humans consume oxygen (O2) while producing carbon dioxide (CO2) and water (H2O) as byproducts. For long term space exploration, CO2 concentration in the atmosphere must be managed to prevent hypercapnia. Moreover, CO2 can be used as a source of oxygen through chemical reduction serving to minimize the amount of oxygen required at launch. Reduction can be achieved through a number of techniques. The National Aeronautics and Space Administration (NASA) is currently exploring the Sabatier reaction, the Bosch reaction, and co-electrolysis of CO2 and H2O for this process. Proof-of-concept experiments and prototype units for all three processes have proven capable of returning useful commodities for space exploration.While all three techniques have demonstrated the capacity to reduce CO2 in the laboratory, there is interest in understanding how all three techniques would perform at a system-level within a spacecraft. Consequently, there is an impetus to develop predictive models for these processes that can be readily re-scaled and integrated into larger system models. Such analysis tools provide the ability to evaluate each technique on a comparable basis with respect to processing rates. This manuscript describes the current models for the carbon dioxide reduction processes under parallel developmental efforts. Comparison to experimental data is provided were available for verification purposes.

Use of Photobioreactors in Regenerative Life Support Systems for Human Space Exploration

“…Consequently, a system is needed to remove excess CO 2 and provide a sufficient partial O 2 pressure. The partial O 2 pressure depends on the total cabin pressure and should range between 18 and 23.1 kPa or 21–50% per volume, respectively ( Lange et al, 2003 ; Swickrath and Anderson, 2012 ; Anderson et al, 2018 ). On the ISS, the total pressure is set at 101.3 kPa (with 21% O 2 ), so it resembles the pressure on Earth (101.325 kPa on sea level).…”

Kinetic Modelling of the Aqueous-Phase Reforming of Fischer-Tropsch Water over Ceria-Zirconia Supported Nickel-Copper Catalyst

“…The activation energy of the WGS reaction was fixed to 85 kJ•mol −1 based on the value reported by Wheeler et al [32] for a nickel catalyst. The equilibrium constant was calculated for the WGS reaction at the operating conditions using a temperature dependent equation published by Swickrath and Anderson [33]. According to the calculated equilibrium constants included in Supplementary Section 2, the WGS reaction was not limited by chemical equilibrium at the operating temperatures applied in the present work.…”

“…The activation energy of the methanation reaction was fixed to 95 kJ•mol −1 based on the value obtained over a nickel-based catalyst and reported in [35]. The equilibrium constant was calculated for the methanation reaction at the operating conditions using a temperature dependent equation published in [33]. As well as the WGS reaction, the methanation reaction was not limited by chemical equilibrium at the reaction temperatures applied in the present work, according to the calculated equilibrium constants included in Supplementary Section 2.…”

Assessment of 1-Dimensional Catalytic Reactors Using Constrained Gibbs Free Energy Minimization Method: Water Gas Shift and Carbon Monoxide Methanation Case

“…Modeling and simulation of chemical reactors are advantageous as they enable the easy study of the influence of the operation conditions on the reactor performance, while the experimental work is limited to validation experiments . Robust models are the first step toward optimization of reactors and, consequently, the chemical process.…”

“…Extensive work has been done in order to improve these reactions. Among them, Swickrath and Anderson explored potential Sabatier reactions to convert CO–CO 2 into water and methane, aiming for carbon dioxide recycling and water reuse in space technology improvement; Kopyscinski et al performed an extensive study of methanation in a nickel-alumina catalytic plate reactor, using a sophisticated apparatus to collect data over several points of the bed. In both works, WGS took place to some extent.…”