Gas liquefaction system and method

Abstract

A system and a method for liquefaction of gases which are utilized in their liquid state as refrigerants in applications that require low temperatures, throughout various pressure ranges, from slightly above atmospheric pressures to pressures near the critical point. The system and method are based on closed-cycle cryocoolers and utilize the thermodynamic properties of the gas to achieve optimal liquefaction rates.

1 . A gas liquefaction system for liquefying gas, comprising:
 a gas intake module adapted to be connected to a gas source and configured to provide gas to the system;   a thermally isolated container;   at least one interior tank in the container having at least one neck extending therefrom;   at least one refrigeration coldhead having a cold finger portion located inside the neck and extending toward the interior tank;   a gas compressor configured to provide compressed gas to the refrigeration coldhead for the operation of the cryocooler;   at least one gas pressure control mechanism configured to dynamically adjust pressure and flow of the gas between the gas intake module and the interior tank; and   at least one control device for controlling liquefaction performance of the system, said at least one gas pressure control mechanism and said at least one control device being configured to control pressure within the interior tank to achieve up to an optimal liquefaction performance by maintaining pressure inside the interior tank near a critical pressure of the gas being liquefied for providing liquefaction conditions capable of utilizing maximum cooling power of the refrigeration coldhead.   
     
     
         2 . The gas liquefaction system of  claim 1 , wherein the gas pressure control mechanism comprises:
 one or more pressure regulators adapted to regulate the pressure of the gas flowing from the gas intake module;   one or more mass flow meters configured to measure a volume of the gas from the pressure regulators;   one or more electronically controlled valves;   one or more pressure sensors;   means for coupling said pressure regulators, mass flow meters, valves, and pressure sensors to said control device; and   means for coupling signals from said at least one control device to dynamically configure said pressure regulators, mass flow meters, valves, and pressure sensors to enable said gas pressure control mechanism to adjust pressure of the gas entering the interior tank.   
     
     
         3 . The gas liquefaction system of  claim 1 , further comprising one or more mechanical valves configured to control the passage of gas through the gas pressure control mechanism. 
     
     
         4 . The gas liquefaction system of  claim 1 , wherein the gas is helium. 
     
     
         5 . The gas liquefaction system of  claim 4 , wherein the critical pressure of the gas being liquefied is greater than 1.0 bar and no more than about 2.27 bar. 
     
     
         6 . A gas liquefaction method that makes use of a gas liquefaction system according to  claim 1 , the method comprising:
 supplying gas to the gas liquefaction system through the gas intake module;   regulating the power of the refrigeration coldhead by means of the control devices to achieve a desired rate of liquefaction;   adjusting the flow of gas entering the interior tank by means of the gas pressure control mechanism and the control devices for achieving a constant pressure within the interior tank;   for a period of time during which liquefaction is performed, maintaining the pressure within the interior tank at a liquefaction pressure above atmospheric pressure and up to the critical pressure of the gas being liquefied by means of the gas pressure control mechanism and the control devices; and   dynamically modulating the power of the refrigeration coldhead, the flow of gas entering the interior tank and the pressure within the interior tank by the control device to achieve desired liquefaction performance.   
     
     
         7 . The gas liquefaction method according to  claim 9 , and further comprising the determination of the level of liquefied gas inside the interior tank from the total mass of the gas in the interior tank and/or the determination of the gas and liquid densities by measuring the pressure or temperature at thermodynamic equilibrium. 
     
     
         8 . The gas liquefaction method according to  claim 6 , and further comprising:
 triggering an input valve to close, preventing the flow of gas into the system;   determining and maintaining the pressure in the interior tank; and   performing on/off cycles of the refrigeration coldhead, forcing the temperatures of refrigeration coldhead stages to exceed temperatures of fusion and sublimation of impurities present in the interior of the interior tank, making such impurities precipitate and fall into the bottom of the interior tank and thus cleansing the zone where the gas is pre-cooled and liquefied.   
     
     
         9 . The gas liquefaction method according to  claim 6 , and further comprising:
 a stand-by mode in which the volume of liquefied gas is indefinitely conserved in equilibrium with an amount of vapor in the interior tank, the standby mode being initiated by:   closing the gas intake into the gas liquefaction system by the control devices triggering of the input valve by means of the gas pressure control mechanism.   
     
     
         10 . The gas liquefaction method according to  claim 6 , including direct liquefaction of recovered gas above atmospheric pressure, comprising:
 storing gas in a buffer storage tank prior to its passage through the gas intake module above atmospheric pressure; and   maintaining the gas liquefaction system at a pressure above atmospheric pressure by means of the gas pressure control mechanism.   
     
     
         11 . The gas liquefaction method according to  claim 6 , wherein the gas pressure control mechanism, the gas intake module, and the control devices are governed by means of a software program in at least one data storage means. 
     
     
         12 . The gas liquefaction method according to  claim 11 , wherein the data storage means is connected to a programmable device in charge of executing said software program. 
     
     
         13 . The gas liquefaction method according to  claim 6 , wherein said gas is selected from the group consisting of: helium, nitrogen, oxygen, hydrogen, and neon. 
     
     
         14 . A method for achieving high-performance liquefaction of cryogen gas within a liquefier, the method comprising:
 using a computer control device coupled to one or more pressure regulators, electronically controlled valves, one or more mass flow meters and one or more pressure sensors:   monitoring pressure within a liquefaction region of the liquefier; and   dynamically adjusting a flow of gas entering the liquefaction region of the liquefier to achieve a constant liquefaction pressure therein;   wherein said constant liquefaction pressure is greater than 1.00 bar.   
     
     
         15 . The method of  claim 14 , wherein said gas is helium and said constant liquefaction pressure is greater than 1.00 bar and no more than about 2.27 bar. 
     
     
         16 . The method of  claim 14 , wherein said gas is selected from the group consisting of helium, nitrogen, oxygen, hydrogen, and neon. 
     
     
         17 . The method of  claim 16 , wherein said constant liquefaction pressure is greater than 1.00 bar and up to a critical pressure of said gas. 
     
     
         18 . The method of  claim 14 , further comprising:
 using said computer control device to control power of a cryocooler being at least partially disposed within said liquefaction region for achieving a desired liquefaction rate.   
     
     
         19 . The method of  claim 18 , wherein the power of the cryocooler, the flow of gas entering the liquefaction region, and the pressure within the liquefaction region are each dynamically modulated by the computer control device to achieve desired liquefaction performance.