Production of liquid natural gas and other cryogens using a multi-stage active magnetic regenerative liquefier

Abstract

Apparatus and processes for liquefying process gases using multi-stage active magnetic regenerative refrigerators are disclosed. The apparatus and processes can be configured to liquefy process streams that liquefy below ˜200 K, such as ethane, methane, argon, nitrogen, neon, hydrogen and/or helium process gases. Active magnetic regenerative liquefiers use multiple successive active magnetic regenerator stages, with each stage using a compositionally distinct magnetic refrigerant material having a distinct Curie temperature. In some aspects, the refrigerant material in each successive stage has a Curie temperature of about 20 K-40K different from that of neighboring stages. Heat transfer fluid flows are directed to improve system efficiency.

We claim: 
     
         1 . A process for liquefying process gases comprising:
 introducing a high-pressure helium or liquid propane heat transfer fluid into each stage of a multi-stage active magnetic regenerative refrigerator apparatus, wherein each active magnetic regenerative refrigerator stage comprises: (i) a high magnetic field portion in which the heat transfer fluid flows from a cold side to a hot side through at least one magnetized regenerator having at least one magnetic refrigerant, (ii) a first no heat transfer fluid flow portion in which the regenerator is demagnetized, (iii) a low magnetic field portion in which the heat transfer fluid flows from a hot side to a cold side through at least one demagnetized regenerator, and (iv) a second no heat transfer fluid flow portion in which the regenerator is magnetized;   within each stage of the multi-stage active magnetic regenerative refrigerator apparatus, continuously introducing a separate flow of the heat transfer fluid from the cold side of the low magnetic field portion into the cold side of the high magnetic field portion; and   continuously separating a portion of the cold heat transfer fluid flowing from the cold side of the low magnetic field portion of each stage to generate an unbalanced flow stream from each stage, returning the separated cold heat transfer fluid at each stage through a process gas heat exchanger to cool the process gas before the heat transfer fluid rejoins the primary heat transfer stream near the hot temperature of each stage near the inlet to a fluid circulating means.   
     
     
         2 . The process of  claim 1 , wherein each active magnetic regenerative refrigerator stage comprises a different magnetic refrigerant material having a different Curie temperature and each magnetic refrigerant material comprises at least one of the following materials: Gd, Gd 0.90 Y 0.10 , Gd 0.83 Dy 0.17 , Gd 0.30 Tb 0.70 , Gd 0.69 Er 0.31 , Gd 0.02 Tb 0.98 , Gd 0.32 Dy 0.68 , Gd 0.66 Y 0.34 , Gd 0.39 Ho 0.61 , Gd 0.59 Y 0.41 , Gd 0.15 Dy 0.85 , Gd 0.42 Er 0.58 , Gd 0.27 Ho 0.73 , Gd 0.16 Ho 0.84 , Gd 0.34 Er 0.66 , Gd 0.23 Er 0.77 . 
     
     
         3 . A process for liquefying a process gas comprising:
 introducing a heat transfer fluid into an active magnetic regenerative refrigerator apparatus that comprises from about 4 to about 13 successive stages, wherein each stage comprises an independently compositionally distinct magnetic refrigerant material having an independent Curie temperature, and wherein the first stage has the highest Curie temperature and the last stage has the lowest Curie temperature.   
     
     
         4 . The process of  claim 3 , additionally comprising:
 flowing different rates of heat transfer fluid through each stage of the active magnetic regenerative refrigerator apparatus to cool each stage during start up until the magnetic refrigerants in each stage are cooled below their respective Curie temperatures.   
     
     
         5 . The process of  claim 3 , additionally comprising:
 flowing bypass heat transfer fluid flow from each stage through a process heat exchanger and removing sensible heat from the process stream in each stage; and cooling the bypass fluid flow by the same temperature as an operating temperature range for each stage.   
     
     
         6 . The process of  claim 3 , additionally comprising:
 flowing a primary heat transfer fluid from each stage through a thermal load heat exchanger and absorbing reject heat from the next lower stage and, in stages where the process stream liquefies, absorbing latent heat of liquefaction and parasitic heat leaks into the stage where liquefaction occurs.   
     
     
         7 . The process of  claim 5 , wherein the bypass flow comprises from about 3% to 12% of the heat transfer fluid flow. 
     
     
         8 . The process of  claim 5 , wherein the bypass flow comprises more than about 2% and less than about 20% of the heat transfer fluid flow. 
     
     
         9 . The process of  claim 5 , further comprising introducing a non-bypassed portion of the heat transfer fluid into the cold side of the magnetized bed in the high magnetic field section. 
     
     
         10 . The process of  claim 3 , wherein the overall process achieves a Figure of Merit (FOM) of at least 0.6. 
     
     
         11 . The process of  claim 3 , wherein each distinct magnetic regenerative refrigerator material comprises at least one of the following materials: Gd, Gd 0.90 Y 0.10 , Gd 0.83 Dy 0.17 , Gd 0.30 Tb 0.70 , Gd 0.69 Er 0.31 , Gd 0.02 Tb 0.98 , Gd 0.32 Dy 0.68 , Gd 0.66 Y 0.34 , Gd 0.39 Ho 0.81 , Gd 0.59 Y 0.41 , Gd 0.15 Dy 0.85 , Gd 0.42 Er 0.58 , Gd 0.27 Ho 0.73 , Gd 0.16 Ho 0.84 , Gd 0.34 Er 0.66 , Gd 0.23 Er 0.77 . 
     
     
         12 . An active magnetic regenerative liquefier comprising:
 multiple successive active magnetic regenerator stages, wherein each stage comprises an independently compositionally distinct magnetic refrigerant material having an independent Curie temperature, and wherein the first stage has the highest Curie temperature and the last stage has the lowest Curie temperature.   
     
     
         13 . The active magnetic regenerative liquefier of  claim 12 , wherein each successive stage has a Curie temperature from about 20 to about 40K different from the neighboring stages, and the stages are arranged in successive Curie temperature order with a first stage having the highest Curie temperature and highest magnetic refrigerant material mass and a final stage having the lowest Curie temperature and lowest magnetic refrigerant material mass. 
     
     
         14 . The active magnetic regenerative liquefier of  claim 12 , wherein each magnetic refrigerant is constrained to operate near and below its Curie temperature throughout an active magnetic regeneration cycle. 
     
     
         15 . The active magnetic regenerative liquefier of  claim 12 , wherein temperature ranges across the highest to lowest Curie temperature stages range from about 285 K to about 120 K. 
     
     
         16 . The active magnetic regenerative liquefier of  claim 12 , wherein each stage comprises a unique magnetocaloric alloy. 
     
     
         17 . The active magnetic regenerative liquefier of  claim 12 , wherein each distinct magnetic refrigerator material comprises at least one of the following materials: Gd, Gd 0.90 Y 0.10 , Gd 0.83 Dy 0.17 , Gd 0.30 Tb 0.70 , Gd 0.69 Er 0.31 , Gd 0.02 Tb 0.98 , Gd 0.32 Dy 0.68 , Gd 0.66 Y 0.34 , Gd 0.39 Ho 0.61 , Gd 0.59 Y 0.41 , Gd 0.15 Dy 0.85 , Gd 0.42 Er 0.58 , Gd 0.27 Ho 0.73 , Gd 0.16 Ho 0.84 , Gd 0.34 Er 0.66 , Gd 0.23 Er 0.77 . 
     
     
         18 . The active magnetic regenerative liquefier of  claim 12 , comprising eight stages, each stage having a different magnetocaloric alloy refrigerant material.