Method and system for sterilization of a cryogen

Abstract

A system and method for sterilizing a cryogen is provided. In the disclosed embodiment a liquid cryogen is first vaporized and subsequently compressed prior to undergoing sterilization using biological filters. The compressed, sterilized cryogen vapor is then pre-cooled, preferably with the cryogen being vaporized, to produce a partially condensed, cool, sterile cryogen stream and then further condensed using the liquid cryogen to produce a sterilized liquid cryogen.

1 . A method of sterilizing a cryogen comprising the steps of:
 vaporizing a liquid cryogen to produce a cold cryogen vapor;   compressing the cold cryogen vapor to produce a compressed cryogen vapor;   sterilizing the compressed cryogen vapor to produce a compressed, sterile cryogen vapor;   pre-cooling the compressed, sterile cryogen vapor to produce a partially condensed, cool, sterile cryogen stream; and   further condensing the partially condensed, cool, sterile cryogen stream to produce a sterilized cryogen.   
     
     
         2 . The method of  claim 1  wherein the step of compressing the cold cryogen vapor further comprises compressing the cold cryogen vapor to a pressure greater than the saturation pressure of the liquid cryogen that is vaporized. 
     
     
         3 . The method of  claim 2  wherein the step of compressing the cold cryogen vapor further comprises compressing the cold cryogen vapor to a pressure of between about 70 psi and about 360 psi. 
     
     
         4 . The method of  claim 1  wherein the cold cryogen vapor is further warmed to a temperature of between about −20 degrees Centigrade to about 30 degrees Centigrade during the compressing step. 
     
     
         5 . The method of  claim 1  wherein the step of further condensing comprises passing the partially condensed, cool, sterile cryogen stream through an indirect heat exchanger together with a portion of the liquid cryogen. 
     
     
         6 . The method of  claim 1  wherein the cryogen is selected from the group consisting of nitrogen, hydrogen, helium, oxygen, and argon. 
     
     
         7 . The method of  claim 1  wherein the step of sterilizing the compressed cryogen vapor further comprises passing the compressed cryogen vapor through a biological filter. 
     
     
         8 . A cryogen sterilization system comprising:
 a source of cryogen vapor;   a compressor fluidically coupled to the source of cryogen vapor and adapted for compressing the cryogen vapor to a prescribed pressure;   a biological filter fluidically coupled to the compressor and adapted for sterilizing the compressed cryogen vapor;   a pre-cooler fluidically coupled to the biological filter and adapted to receive the compressed, sterile cryogen vapor and produce a partially condensed, cool, sterile cryogen stream; and   a secondary condenser fluidically coupled to the pre-cooler and adapted for further condensing the partially condensed, cool, sterile cryogen stream to produce a sterilized cryogen.   
     
     
         9 . The system of  claim 8  wherein the source of cryogen vapor further comprises:
 a source of liquid cryogen; and   an evaporator fluidically coupled to the source of liquid cryogen and adapted to vaporize the liquid cryogen.   
     
     
         10 . The system of  claim 9  wherein the pressure of the compressed, cryogen vapor is greater than the saturation pressure of the liquid cryogen that is vaporized. 
     
     
         11 . The system of  claim 8  wherein the pressure of the compressed, cryogen vapor is between about 70 psi and 360 psi. 
     
     
         12 . The system of  claim 8  wherein the cryogen vapor is at a temperature of between about −20 degrees Centigrade to about 30 degrees Centigrade prior to entering the biological filter. 
     
     
         13 . The system of  claim 8  wherein the cryogen is selected from the group consisting of nitrogen, hydrogen, helium, oxygen, and argon. 
     
     
         14 . The system of  claim 8  further comprising a storage tank fluidically coupled to the secondary condenser and adapted for storing the sterile cryogen. 
     
     
         15 . A method of sterilizing a cryogen comprising the steps of:
 compressing a cryogen vapor;   sterilizing the compressed cryogen vapor to produce a compressed, sterile cryogen vapor;   pre-cooling the compressed, sterile cryogen vapor to produce a partially condensed, cool sterile cryogen stream; and   further condensing the cool sterile cryogen stream to produce a sterilized cryogen.   
     
     
         16 . The method of  claim 15  wherein the step of compressing the cryogen vapor further comprises compressing the cryogen vapor to a pressure of between about 70 psi and about 360 psi. 
     
     
         17 . The method of  claim 15  wherein the cold cryogen vapor is further warmed to a temperature of between about −20 degrees Centigrade to about 30 degrees Centigrade during the compressing step. 
     
     
         18 . The method of  claim 15  wherein the cryogen is selected from the group consisting of nitrogen, hydrogen, helium, oxygen, and argon.