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The Trace Contaminant Control Subassembly (TCCS) to be used onboard the International Space Station (ISS) uses expendable adsorption beds and a conventional high temperature catalytic oxidizer to control trace chemical contaminants in the cabin air. Although effective, the current design has a high life cycle operating cost associated with maintaining the expendable beds and heating the catalytic oxidizer. In order to improve the TCCS's process economics, a retrofit to its primary design is being studied which utilizes an advanced technology lightweight, long-life Microlith™ catalytic converter (MCC). Development and testing of MCC prototypes for application to the TCCS have been conducted on a bench scale. Results from these studies are presented that show the converter's destruction performance for representative trace chemical contaminants found in a spacecraft cabin atmosphere.

This paper reports test results of a compact, high pollutant conversion efficiency, catalytic muffler developed for utility engines (<19kW/25hp). Tests were conducted in-house, and at an independent laboratory under EPA supervision and funding, using a four-stroke engine generator set. The specific HC, CO and NOx emissions were reduced by 98%, 97%, and 19%, respectively. This level of reduction is thought to be sufficient for reducing such emissions from utility engines to the level of future standards such as 1999 CARB. A total of 200 hours of performance and limited durability testing were accumulated on the catalytic muffler. The prototype demonstrated successful operation by entraining fresh air and mixing with exhaust gas, converting pollutants, maintaining acceptable skin and exhaust gas temperatures, and muffling noise.