Electrochemical and Steam-Desorbed Amine CO2 Concentration: Subsystem Comparison

There are two techniques being considered for carbon dioxide (CO₂) removal and concentration for application in a regenerable Environmental Control and Life Support Systems (EC/LSS) aboard the projected Space Station. One uses the continuous Electrochemical Depolarized CO₂ Concentration (EDC) technique while the second uses the cyclic absorption and desorption (with steam) from an amine resin bed. While the technologies involved with these techniques are substantially different, each must interface with other elements of a regenerable EC/LSS. This paper presents a comparison of the two competing technologies and includes the design and sizing of the respective subsystems for a Space Station application. The analysis includes identification of assumptions and groundrules with particular attention given to defining subsystem boundaries. These boundaries are defined as all the hardware required for each technique to replace the nonregenerable (i.e., lithium hydroxide, LiOH) approach to CO₂ removal used on prior space missions. The analysis determined total equivalent weight which includes fixed hardware weight and weight penalties for power needs and heat rejection requirements. Data for the subsystems was acquired through NASA and other published sources. While not a detailed discussion of the respective technologies, this paper examines the various merits including the advantages and disadvantages and operational impacts (e.g., light and dark cycle operation) of the subsystems.