Dehydrating and Sterilizing Wastes Using Supercritical CO2

A relatively low-temperature process for dehydrating and sterilizing biohazardous wastes in an enclosed life-support system exploits (1) the superior mass-transport properties of supercritical fluids in general and (2) the demonstrated sterilizing property of supercritical CO2 in particular. The wastes to be treated are placed in a chamber. Liquid CO2, drawn from storage at a pressure of 850 psi (˜5.9 MPa) and temperature of 0 °C, is compressed to pressure of 2 kpsi (˜14 MPa) and made to flow into the chamber. The compression raises the temperature to 10 °C. The chamber and its contents are then further heated to 40 °C, putting the CO2 into a supercritical state, in which it kills microorganisms in the chamber. Carrying dissolved water, the CO2 leaves the chamber through a back-pressure regulator, through which it is expanded back to the storage pressure. The expanded CO2 is refrigerated to extract the dissolved water as ice, and is then returned to the storage tank at 0 °C.

This work was done by Ian J. Brown of Lynntech, Inc. for Johnson Space Center. For further information, contact the Johnson Technology Transfer Office at (281) 483-3809. MSC-23495

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