Investigation of microgravity vortex phase separator for spacecraft liquid amine CO2 removal system

Abstract

Spacecraft cabin atmosphere revitalization, more specifically CO2 removal, is a key technology to pursue long-duration, crewed space missions, such as the ones to the Moon and Mars. The ISS currently uses the Carbon Dioxide Removal Assembly (CDRA) as the primary system that employs solid sorbent (zeolite) to remove CO2 from cabin air. However, CDRA cannot meet high reliability and low maintenance requirements. Liquid sorbents may be used as an alternative to solid sorbents and are estimated to attain 65 % less power, weight, and volume than solid based CO2 scrubbers. Liquid amines (liquid sorbent) are currently being researched by NASA for CO2 capture, however their implementation for space applications depends on an effective gas-liquid separation method under microgravity conditions. The Vortex Phase Separator (VPS) offers a new approach for a liquid amine CO2 removal system, and initial investigation of the prototype VPS system demonstrated up to 90.3 % CO2 removal from a humid CO2 stream at 1.47 l/min flow rate. Tests were conducted to determine the CO2 removal efficiency considering several operating parameters, including the liquid amine flow rate, initial fill (charge) level, and temperature; CO2 flow rate; extended-time operation; and CO2-amine pre-mixing length. Results provided key insights on design, operation, and performance aspects of a subscale system, and demonstrated the feasibility of the microgravity VPS for liquid amine CO2 removal system as an alternative, novel spacecraft air revitalization approach.