Ionic Liquid CO2 Capture: CO2 Desorption Technology Review
Conference Proceeding
Overview
abstract
Historically, solid sorbents have removed carbon dioxide; (CO2) from space habitat atmospheres. For long-duration; human spaceflight, regenerable CO2 sorbents reduce system; mass compared to non-regenerable alternatives. To; regenerate a sorbent, CO2 and other adsorbed constituents; must be extracted (i.e., desorbed). The endothermic; thermal-vacuum desorption of CO2 from flight-proven; sorbents requires the following heats of desorption:; monoethanolamine-coated beads (solid-phase amines) ~ 1.7; MJ/kgCO2, 5A zeolites ~ 2.8 MJ/kgCO2, 13X zeolites ~ 2.0; MJ/kgCO2, and silver oxide (i.e., METOX) ~ 1.85 MJ/kgCO2.; More energy-efficient CO2 sorbents are being investigated; for technology readiness level maturation; ionic liquids; (ILs) are a candidate. One, 1-ethyl-3-methylimidazolium; acetate (EMIM [Ac]), experimentally requires ~ 0.62; MJ/kgCO2 for desorption. Room temperature ILs, those that; are liquid phase at room temperature, have negligible vapor; pressure, are chemically stable, and thus, are not expected; to degrade or produce toxic vapors at conditions favorable; for CO2 sorption. Further, ILs can be uniquely configured; within architectures to allow for continuous IL; regeneration and CO2 removal, rather than batch mode; operation. The most common architecture involves IL flowing; between two modules. The absorption module, typically a; hollow-fiber contactor, provides a contacting surface; between the IL and CO2-laden cabin airstream. The CO2-laden; ionic liquid subsequently flows into a desorption module; for IL regeneration. Thermal-vacuum swing can regenerate; the IL; however, at elevated temperatures, ILs can begin to; thermally decompose, degrading the CO2 removal performance; over time. The aim of this review article is to investigate; potential energy-efficient IL regeneration strategies that; could increase IL performance lifetime. Strategies; investigated include the following (and their possible; combinations): vacuum, sweep gas, ultrasonic, and microwave; CO2 desorption. This article will report and compare; aforementioned desorption technologies and their possible; applications, and it will recommend further experimental; investigations to advance IL desorption technologies.
