Method for producing sterile cryogenic liquid

Abstract

A method for producing a sterile cryogenic fluid from a cryogenic gas by sterilizing the cryogenic gas and using a heat exchanger to liquefy the sterile cryogenic stream. The discharge rate of the sterile cryogenic fluid is controlled by sizing the discharge orifice and setting a predetermined pressure of the sterile cryogenic fluid.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a method and apparatus for the production of a sterile cryogenic fluid such as liquid nitrogen. The invention employs an improved pressure and flow control arrangement which significantly reduces the complexity of the system and the validation requirements for steam sterilization.[0002]Earlier methods for the production of sterile cryogenic fluids such as liquid nitrogen have generally used two broad approaches. The first method uses direct liquid filtration (down to about 0.2 micron or less) to remove microbial or other contaminants. The second method also uses filtration to about 0.2 micron or less, but starts by filtering warm gas. This sterile warm gas is then liquefied in an indirect heat exchange process with a suitable low temperature refrigerant. This low temperature refrigerant is generally liquid having the same chemical composition as the sterile gas (e.g., nitrogen). In this case it is necessary to maintai...

AI Technical Summary

Benefits of technology

[0009]An important property that the discharge orifice should possess is its ability to be steam sterilized. Unlike a needle valve, the orifice should have no traps or pockets like a needle valve and can be readily sterilized with steam. The orifice should provide a reproducible and constant flow restriction that will offer a controlled pressure drop along the line leading to the orifice.

Problems solved by technology

This generally introduces piping and valve complexities, and makes it difficult to pre-sterilize the system (typically using steam).

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