Navy

Energy efficient air contaminant removal system for enclosed spaces

Integrated system reduces total power consumption and generation of waste heat

Environmental

Navy submarines are necessarily equipped with devices for removing carbon monoxide (CO), carbon dioxide (CO2), and other contaminants from the air. This is done with catalytic burner and a COremoval system that are implemented as stand-alone configurations.

The catalytic burner breaks down airborne contaminants and converts them to non-hazardous molecules, namely COand water vapor. The catalyst within the burner system operates at an elevated temperature (450-600° Fahrenheit), and the system pulls a lot of electrical power from the submarine to maintain this operating temperature. The catalyst burner also generates waste-heat which requires additional energy from the submarine for waste-heat removal.

The COremoval unit that is currently onboard submarines is a scrubber system based on a solution of monoethanol amine (MEA). It operates at steady-state wherein COis removed from the air and absorbed into the MEA solution at a low temperature (˜70° F.) and removed from the MEA solution at a higher temperature (˜250° F.). Similar to the catalytic burner, the COremoval system also consumes energy and generates undesirable waste-heat. With the current operating parameters of these systems, there is no way to reduce the total amount of energy consumed and waste-heat generated by combining these systems.

A new CO2 removal system based on sorbents, known as the Advanced Carbon Dioxide Removal Unit (ACRU), is being developed by the Navy. The ACRU represents a type of temperature-swing adsorption system that is applicable to the removal of CO2 from confined spaces. With the ACRU, adsorption of COoccurs at room temperature (˜70° F.), and desorption of COoccurs at ˜180° F. Whereas the liquid MEA system operates at steady-state with the MEA in a continuous loop, the ACRU must cycle two or more sorbent beds between the low adsorption temperature and high desorption temperature in a non-steady state manner. When a sorbent bed must be regenerated, heat input is required to raise its temperature from the adsorption temperature to the desorption temperature. When the sorbent bed must be cooled, heat removal is required.

In light of the above, Navy researcher Franklin Gulian developed an air contaminant removal system that reduces the total power consumption and waste heat generated.

Total energy consumption is reduced by transferring some of the waste heat generated by the catalytic system into the adsorption system during the sorbent heat-up portion of the sorbent regeneration cycle. The heat is transferred using a thermal reservoir, which accumulates heat from the catalytic apparatus and transfers it to the adsorption apparatus at a later time, and which is repeatedly cycled as the sorbent is cycled. The catalytic system and the adsorption system are integrated to further reduce the total energy consumed, modify the sorbent regeneration temperature profile, and to obtain an optimum power load profile.

Uses for this air scrubbing solution include mining operations, underground shelters, high CO2 environments, and submarines.

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