Dynamic Maintenance of CO ₂ Levels in Closed Environments 2004-01-2376

Carbon dioxide (CO₂) management is critical for all life forms and certainly for all human space-flight missions. CO₂ must be extracted and removed or recycled safely, reliably, and rapidly while maintaining CO₂ levels within allowable limits independent of crew activity. In view of ESM considerations the system should minimize mass, volume, energy and crew maintenance. Such considerations favor regenerable systems.

Our efforts in this direction are focused on a contained liquid membrane design enzyme catalyzed by carbonic anhydrase that exhibits high permeance, ca. 5*10⁻⁷ molesCO₂/m² s Pa, very high selectivity vs. nitrogen and is non-responsive to a wide variety of VOCs. Over the last year we have addressed five issues: scale-up, integrated water management, enzyme immobilization, system modeling, and process engineering design. We have developed a membrane element (10 cm × 10 cm × 0.67 cm) capable of removing 0.09 kg/d CO₂ from a 0.5% feed stream. The overall reactor includes a Nafion membrane dehumidifier allowing regulation of return gas humidity level. We have expanded our 1-Dimensional Reactive Transport efforts to introduce enzyme kinetic equations. Finally, we have generated a full-up process engineering design that allows calculation of pressure drops, enthalpy changes, and energy requirements for this isothermal, catalyzed reactor design.