TECHNOLOGY AREA(S): Ground/Sea Vehicles

ACQUISITION PROGRAM: PMS 397, Columbia Class Program Office

OBJECTIVE: Develop a compact high-energy efficient forced-air (100 cfm) system for removing hazardous levels (less than 50 ppm) of carbon monoxide (CO) from ambient air on submarines.

DESCRIPTION: Nuclear submarines in the U.S. fleet use a central catalytic oxidation system to remove carbon monoxide (CO), hydrogen (H2), and volatile organic compounds (VOC) from air by converting them to carbon dioxide (CO2) and water vapor. A high ventilation rate is generally used to prevent hazardous gases from accumulating at their sources and is usually sufficient to prevent unsafe concentrations. However, some isolated or poorly ventilated spaces within the submarine would benefit from local removal of CO. Where contamination may accumulate to hazardous levels, if not removed locally, the severity would increase if there was a fire or failure of the central catalytic oxidation system. This SBIR topic seeks to develop an energy efficient, compact, portable, stable, and stand-alone system to prevent the build-up of CO in such isolated and poorly ventilated spaces. The current �CO and H2 Burner� draws a large volume of air from the Auxiliary Machinery Room (AMR) and catalytically removes CO by conversion to CO2. The catalyst is only sufficiently active at elevated temperature (500�F) in the presence of humidity. No room temperature or portable systems exist. The proposed portable system would continually monitor its local space and activate when necessary (i.e., greater than 50 ppm CO) to continuously remove the CO until a local concentration of 5 ppm is attained.� The airflow through the system must be at least 100 cubic feet per minute (cfm). The catalyst must achieve 95% removal rate over a temperature range of 15�C to 25�C and humidity in the range of 50%-80% relative humidity (RH). The confined spaces do not have access to cooling water but will have access to electrical power for running a fan and operating a CO sensor (115 VAC, 100 Watt maximum). The system must operate for 10,000 hours without requiring maintenance when 115 VAC power is available. Battery backup must be included to allow the system to remove CO for one hour if 115 VAC electrical power is not available. The final target maximum system weight and volume are 50 pounds (lbs.) and 2 cubic feet, respectively. In addition, the final design must pass shock (MIL-S-901) and vibration (MIL-STD-167) testing making it suitable for shipboard application.

References 2 - 4 provide a sufficient overview of the conditions present on submarines and the contaminants found in submarine air. Currently available sorbents are not suitable for this system because they do not have sufficient absorption capacity for low concentrations of CO and would require frequent regeneration or change-out. Platinum- and palladium-based catalysts are not active at room temperature and would require energy to maintain an elevated catalyst temperature. Air-to-air heat exchangers (recuperators) will not eliminate the energy requirement because their efficiency is too low for a lightweight and compact system.� Compact high efficiency heat exchangers have a high-pressure drop, which would then require an unacceptably noisy fan or regenerative blower. A room temperature CO oxidation catalyst may be the most feasible option for this system and must be stable in the presence of moisture and other contaminants.� Moisture sorbent guard beds that could require maintenance or noisy blowers are not permitted.

Hopcalite is commonly used for short-term room temperature oxidation of CO, but is not suitable for this topic because it rapidly deactivates in the presence of water vapor. Nano-gold has shown extraordinary activity for CO oxidation at sub-ambient temperatures but is not stable in the long-term submarine environment and has been observed to also deactivate in the presence of water vapor. Catalysts activated by ultra-violet light would be suitable if an overall system requiring less than 100 Watts could be designed.

PHASE I: Develop a concept for a catalytic material formulation that can achieve the CO removal under the conditions of flow, temperature and humidity specified in the requirements above. Demonstrate the feasibility of the concept catalyst material to achieve the required CO removal capacity for 10,000 hours continuous operation. The Phase I Option, if exercised, will include the initial design concepts and plan to build a prototype in Phase II.

PHASE II: Develop a non-dusting engineered prototype form of the material to enable a system design comprising a low-pressure fan as detailed in the Description. Provide a report documenting the results of MIL-S-901D and MIL-STD-167 testing and internal testing showing 90% removal of 50 ppm CO in an air stream at room temperature at 80% RH (relative humidity) for 1000 hours. Conduct shock and vibration testing at a suitable certified laboratory chosen by the proposer and approved by NAVSEA. Provide a sample (engineered form) of the material for Navy testing under the same conditions for 10,000 hours. (Note: Technical requirements will be satisfied if a 90% removal rate is maintained at room temperature for 10,000 hours with no increase in pressure drop.) Ensure that the performance of the engineered form does not decrease if the temperature is increased to 200�C for up to 10 minutes. Develop and submit a Phase III plan for Navy approval.

PHASE III DUAL USE APPLICATIONS: Assist the Navy in transitioning the system for Navy use. The company may want to offer a non-militarized version for commercial or residential use. One possible use would be in automotive repair garages. The material developed in this SBIR topic will be useful for any system designed to remove CO from commercial or residential buildings.

REFERENCES:

1. Trent, R.W. �Air Conditioning in Submarines.� ASHRAE Journal, January 2001. https://www.documentweb.org/22866-Ar-Condtonng-n-Submarnes-pdf.html

2. Carhart, H.W. and Thompson, J.K. �Removal of Contaminants from Submarine Atmospheres.� U.S Naval Research Laboratory, Washington, D.C.
�http://pubs.acs.org/doi/pdf/10.1021/bk-1975-0017.ch001

3. �Submarine Air Treatment,� http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=16&cad=rja&uact=8&ved=2ahUKEwjDzqP7wqfgAhXQUt8KHd41AAwQFjAPegQIAhAC&url=http%3A%2F%2Fweb.mit.edu%2F12.000%2Fwww%2Fm2005%2Fa2%2F8%2Fpdf1.pdf&usg=AOvVaw3Wi50hkskLJAVgwcIFkPte

4. Choudhary, T.V. and Goodman, D.W. "Oxidation catalysis by supported gold nano-clusters." Topics in Catalysis, Vol. 21, Nos. 1-3, October 2002.� https://link.springer.com/article/10.1023/A:1020595713329

5. Fleck, M. and Benda, G. "Carbon Monoxide Air Filter." US Patent 5,564,065, October 1996. http://www.freepatentsonline.com/5564065.html

KEYWORDS: Room Temperature Oxidation; Carbon Monoxide; Moisture Resistant Catalyst; Poison Resistant Catalyst; Nano-Gold; Indoor Air Quality