High Capacity Adsorbent Development for Carbon Dioxide Removal System Efficiency Improvements

Abstract

Regenerable carbon dioxide removal is a key element for successful, long-term manned space flight missions. Currently, the International Space Station (ISS) utilizes zeolite molecular sieves as part of its regenerable carbon dioxide removal system. The zeolite molecular sieve utilized in this system was based on 1980’s technology. Since then molecular sieve technology has improved significantly with the advent of adsorbents with greater carbon dioxide adsorption capacity and reduced attrition through immobilization. A carbon dioxide removal system that incorporates these new zeolite molecular sieve technologies would provide improved crew health through lower cabin carbon dioxide partial pressures and improved system performance through reduced system equivalent mass. Honeywell has conducted preliminary evaluations of Ion Exchanged X (IEX) zeolite molecular sieves for carbon dioxide removal, which have shown increased carbon dioxide capacities compared to those used in the ISS CDRA. To further improve the adsorbent’s attrition properties, this IEX zeolite can be used in conjunction with Honeywell’s immobilization technology, developed for the adsorbent beds used in the On-Board Oxygen Generation System (OBOGS) units. This technology uses a polymeric binder and forms the adsorbent into a molded porous bed, which resists attrition and dust generation. Since the polymeric binder replaces the clay binder normally used in zeolites, a significant increase in the dynamic capacity of the adsorbent bed also results.