Series Bosch System Development

Morgan Abney, Christopher Evans, Matt Mansell, Michael Swickrath
2012 42nd International Conference on Environmental Systems   unpublished
State-of-the-art (SOA) carbon dioxide (CO 2 ) reduction technology for the International Space Station produces methane as a byproduct. This methane is subsequently vented overboard. The associated loss of hydrogen ultimately reduces the mass of oxygen that can be recovered from CO 2 in a closed-loop life support system. As an alternative to SOA CO 2 reduction technology, NASA is exploring a Series-Bosch system capable of reducing CO 2 with hydrogen to form water and solid carbon. This results
more » ... n 100% theoretical recovery of oxygen from metabolic CO 2 . In the past, Bosch-based technology did not trade favorably against SOA technology due to a high power demand, low reaction efficiencies, concerns with carbon containment, and large resupply requirements necessary to replace expended catalyst cartridges. An alternative approach to Bosch technology, labeled "Series-Bosch," employs a new system design with optimized multi-stage reactors and a membrane-based separation and recycle capability. Multi-physics modeling of the first stage reactor, along with chemical process modeling of the integrated system, has resulted in a design with potential to trade significantly better than previous Bosch technology. The modeling process and resulting system architecture selection are discussed. In an attempt to facilitate ongoing hardware design efforts, modeling of both system level architecture and the RWGS sub-system were undertaken. The methodology for each effort is described in detail below. A. Series-Bosch System Architecture Model Development In order to begin understanding performance in the context of a system, a Series-Bosch model was developed. The model provides the capability to explore how system temperature and pressure influence the equilibrium composition. In addition, the system model was constructed in a modular format with specific subcomponent models H American Institute of Aeronautics and Astronautics 3 so that subcomponents can be easily added, removed, or re-located to explore design impacts. The following section serves to elaborate on sub-component models as well as demonstrate some results from the model. The model was constructed in the Aspen Custom Modeler® (ACM) software package (Aspen Tech, Inc.; Burlington, MA). The current schematic representation is illustrated in Error! Reference source not found.. As is evident in the illustration, a number of sub-components exist within the system including gas source tanks for CO 2 and H 2 introduction (CO 2 and H 2 O), gas reactors (RWGS and CFR), stream mixers (Mixer1 and Mixer2), regenerative heat exchangers (RegenHX1 and RegenHX2), heaters (Heater1 -Heater4) , a compressor, a condensing heat exchanger (CHX), a pre-compression cooling unit (PreCool), a stream splitter, and membrane separators (CO2Membrane and MembraneH 2 ). Each subcomponent represented in Figure 1Figure 1 has an associated model. The models for separate subcomponents vary in fidelity and will be discussed in the following sections.
doi:10.2514/6.2012-3554 fatcat:oeizbbdpengs7fc4pg34unyevm