Preliminary Investigation of Microgravity Vortex Phase Separator for Liquid Amine CO2 Removal System

Innovative, reliable, and cost-effective life support systems, such as CO2 removal technologies, are key to support human exploration of deep space. ISS currently uses solid sorbent (granules of synthetic rock (zeolite)) to capture CO2. NASA seeks to replace these solid sorbents as they have large volume, high desorption temperatures causing high power usage, and long-term reliability issues. Liquid sorbents may be used as an alternative to solid sorbents and are estimated to consume 65% less power. Liquid amines 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. This study investigates the Vortex Phase Separator (VPS) technology as a new approach for a liquid amine CO2 removal system. The microgravity VPS uses a nozzle attached to a right circular cylinder so that cabin air with high CO2 levels enters tangentially along the separator wall. The injected stream breaks into very small bubbles and coalesces with a swirling liquid amine layer which is also tangentially injected by another nozzle on the opposite side of the separator. As the bubbles flow through and interact with the colder liquid amine layer, CO2 is absorbed, and water vapor is condensed. Since the bubbles are subjected to a centrifugal acceleration field normal to the z-axis of the separator volume, gas (CO2-lean air) moves to the gas column in the center of the separator and liquid (liquid amine with increasing CO2 and water content) remains on the separator walls, effectively causing the liquid and gas phases to separate. A prototype VPS system is tested to demonstrate the separation of CO2 from a warm, humid, CO2-rich air stream and measure the system performance. Initial testing showed VPS capability for reducing water content in a humid air stream up to 49%.