Compact, Lightweight Adsorber and Sabatier Reactor for CO2 Capture and Reduction for Consumable and Propellant Production
The utilization of CO2 to produce (or recycle) life support consumables, such as O2 and H2O, and to generate propellant fuels is an important aspect of NASA’s concept for future, long duration planetary exploration. One potential approach is to capture and use CO2 from the Martian atmosphere to generate the consumables and propellant fuels. Precision Combustion, Inc. (PCI), with support from NASA, continues to develop its regenerable adsorber technology for capturing CO2 from gaseous atmospheres (for cabin atmosphere revitalization and in-situ resource utilization applications) and its Sabatier reactor for converting CO2 to methane and water. Both technologies are based on PCI’s Microlith ® substrates and have been demonstrated to reduce size, weight, and power consumption during CO2 capture and methanation process. For adsorber applications, the Microlith substrates offer a unique resistive heating capability that shows potential for short regeneration time and reduced power requirements compared to conventional systems. For the Sabatier applications, the combination of the Microlith substrates and durable catalyst coating permits efficient CO2 methanation that favors high reactant conversion, high selectivity, and durability. Results from performance testing at various operating conditions will be presented. An effort to optimize the Sabatier reactor and to develop a bench-top Sabatier Development Unit (SDU) will be discussed. Nomenclature
Optimization and simulation of the Sabatier reaction process in a packed bed
The Sabatier reaction in a testing packed bed was investigated experimentally and theoretically, and was used to convert waste carbon dioxide and hydrogen to provide needed water for closing the life-support loop on orbit in space. A three-dimensional model including fluid flow, gas dispersion, heat and mass transfer, and chemical reaction was developed by coupling some semi-empirical correlated equations in chemical engineering science into computational fluid dynamics theory. Good agreements between the simulating results and experimental data for the effect of some parameters on reaction verified this model, for example, heat exchange between reactor and atmosphere, the material property of reactor, the catalyst deactivated and gas mass flux and so on. By using this model as the designing tools, an optimized packed bed is proposed. Compared with the testing packed bed, the relevant reactor length can be reduced from 220 to 150 mm with the same hydrogen conversion and lower pressure drop. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2879–2892, 2016
Simulation of a 25 kW Steam-Methanol Fuel Processor/PEM Fuel Cell System
The transition to a hydrogen economy will require an intermediate energy carrier until a sufficient hydrogen infrastructure can be implemented. A likely near-term candidate is the on-board or on-site production of hydrogen from steam-methanol reforming. The low tolerance of PEM fuel cell anode electrocatalyst, to the carbon monoxide produced during reforming, necessitates a hydrogen purification or carbon monoxide clean-up sub-system. Considerable advantages can be gained from the use of a steam-methanol reformer with a palladium-silver alloy membrane, hydrogen purification unit. In the present work we have examined such a system. A simulation comprised of a Polymer Electrolyte Membrane Fuel Cell electrochemical model, a membrane permeation model and a commercially available thermodynamics calculation package was constructed. The case investigated in this work is of a 25 kW nominal DC power generating system. A maximum efficiency of 40% was achieved at reformer and membrane unit conditions of 200°C and 300 psia with 97% conversion of the inlet methanol. The effects of variation in temperature and pressure where also investigated. It was found that the reformer and membrane unit pressure had the most significant effect on overall system efficiency. The system efficiency increases with pressure reaching a maximum at the upper limit of the operating region, 300 psia.Copyright © 2003 by ASME