DESCRIPTION: Current submarine Carbon Dioxide (CO2) removal technologies include both liquid and solid amine-based systems.  The materials use amine chemistry to capture CO2 at room temperature and the material is regenerated using heat and vacuum to remove the captured CO2 and restore the material back to the chemical state where it can repeat the process of capturing additional CO2.  Legacy hardware, using the liquid based system, is prone to scaling and other complications from the use of a liquid (Ref. 1).  Additionally, the material has a short lifetime, requiring replacement underway, and hazmat wastes are complicated to handle.  The use of solid CO2 capture sorbent technologies improves the maintainability of the system and improves the quality of life for the sailor.  Both systems, however, are relatively energy intensive and only harness a portion of the full theoretical CO2 capture capacity of the sorbent.  Space and volume constraints dictate the need to maximize the amount of CO2 capacity for a minimum of volume, and an advanced system that could offer the full CO2 removal capacity of a material would be advantageous to the Navy.

A new and innovative solid material capable of higher CO2 loading per unit mass of sorbent could offer space and volume savings to the submarine, using less power and reduce the load on the ship’s chilled water system.  For example, Metal Organic Framework (MOF) materials have shown to offer a unique CO2 capture mechanism that can potentially maximize the full working capacity of the material with only a small change in pressure (Ref. 2 and 3).  Current technologies operate within a range of cyclic capacities, between approximately 3-5% by weight, and preliminary research has demonstrated that MOF materials may be able to achieve weight capacities of up to 13%.  Additionally, existing solid CO2 removal technologies are sensitive to moisture level in the air stream.  MOF have shown to be stable under a wide range of operating parameters, which could provide increased reliability to the submarine. All other materials that may have similar characteristics should be considered.

The Navy is looking for an advanced CO2 capture system capable of harnessing the full cyclic capacity of the material that will improve the CO2 scrubbing performance of the submarine and offer additional capabilities of longer durations or increased crew sizes.  The product would offer additional CO2 removal capacity within the same footprint and volume of legacy systems.  Alternatively, a higher capacity material would offer space and weight savings by providing the same CO2 removal capacity in a smaller footprint. In either case, a new system would be considered more energy efficient by requiring less energy to accomplish the same capability.  A new system would be more affordable by requiring significantly less material to capture typical submarine levels of CO2.  Additionally, a new system may reduce total operating costs, both by reducing the draw on ships’ power and chilled water systems and/or maximizing the amount of time between required sorbent replacement.

Any material under consideration for CO2 capture would need to work within the typical submarine operating environment and must be robust. Materials must be stable under a range of humidity conditions, typically between 30-60% relative humidity, and maintain a background level of 0.5% CO2.  A granular product in the 200-1000 micron range is preferable for this application.  Materials must offer a high cyclic stability over extended durations in a typical environment—0.5% CO2 in a balance of air.
 

PHASE I: The company will develop a concept for a material appropriate for CO2 capture meeting the requirements described in the above description.  The company will demonstrate the feasibility of the concept through modeling or analytical methods in meeting Navy needs and will establish that the material can be reasonably developed into a useful system for the Navy.   The Phase I Option, if awarded, should include initial material layout and capabilities description of how to incorporate the material in Phase II.
 

PHASE II: Based on the results of Phase I and the Phase II Statement of Work (SOW), the company will develop a functionalized form of the material and test it on a lab scale under the appropriate conditions to simulate a submarine environment.  The material will be evaluated to determine its capability in meeting the performance goals defined in Phase II SOW and the Navy requirements for CO2 removal materials.  CO2 removal material system performance will be demonstrated through material evaluation and analytical methods over the required range of parameters including numerous deployment cycles.  Evaluation results will be used to finalize and deliver a sample of prototype material that will meet Navy requirements.  The company will prepare a Phase III development plan to transition the technology to Navy use.
 

PHASE III DUAL USE APPLICATIONS: The company will be expected to support the Navy in transitioning the CO2 removal system into Navy use on the Ohio Replacement Submarines and potentially backfit onto prior classes of submarines. The company will finalize and fabricate   the CO2 removal material system to determine its effectiveness in an operationally relevant environment. The company will support the Navy for test and validation to certify and qualify the system for transition into operational Navy use. Following performance testing and validation, the system is expected to produce results outperforming the current CO2 capacity in regards to meeting the Navy’s requirements for CO2 removal materials which offer more space and volume savings for the submarine while using less power and load on the ship’s chilled water system. CO2 capture materials have many commercial applications, the most common being “green” technologies and stripping CO2 from power plant stack gasses.  These applications operate under a higher CO2 background level, but the technologies operate under the same basic principles and technology developed under this SBIR would directly apply to commercial applications.
 

REFERENCES:

1. Mason, John T. “LOS ANGELES CLASS and OHIO CLASS Carbon Dioxide Removal System – System Health Report,” 30 May 2007.
 

2. Demessence, Aude, D’Allesandro, Deanna M., Foo, Maw Lin, Long, Jeffery R., “Strong CO2 Binding in a Water-Stable, Triazolate-Bridged Metal-Organic Framework Functionalized with Ethylenediamine.” J. Am. Chem. Soc., 2009, 131 (25) pp 8784-8786. http://pubs.acs.org/doi/full/10.1021/ja903411w
 

3. Sumida, Kenji, and others, “Carbon Dioxide Capture in Metal-Organic Frameworks”, Chem. Reviews, 2012, 112 (2), pp 724-781; http://pubs.acs.org/doi/pdfplus/10.1021/cr2003272