Liquefaction of Natural Gas

Abstract

Systems and a method for the formation of a liquefied natural gas (LNG) are disclosed herein. The system includes a first fluorocarbon refrigeration system configured to chill a natural gas using a first fluorocarbon refrigerant and a second fluorocarbon refrigeration system configured to further chill the natural gas using a second fluorocarbon refrigerant. The system also includes a nitrogen refrigeration system configured to cool the natural gas using a nitrogen refrigerant to produce LNG and a nitrogen rejection unit configured to remove nitrogen from the LNG. As an alternative embodiment, the nitrogen refrigeration system can be replaced by a methane autorefrigeration system.

What is claimed is: 
     
         1 . A hydrocarbon processing system for formation of a liquefied natural gas (LNG), comprising:
 a first fluorocarbon refrigeration system configured to chill a natural gas using a first fluorocarbon refrigerant;   a second fluorocarbon refrigeration system configured to further chill the natural gas using a second fluorocarbon refrigerant;   a nitrogen refrigeration system configured to cool the natural gas using a nitrogen refrigerant to produce LNG; and   a nitrogen rejection unit configured to remove nitrogen from the LNG.   
     
     
         2 . The hydrocarbon processing system of  claim 1 , wherein the first fluorocarbon refrigeration system is configured to cool the second fluorocarbon refrigerant of the second fluorocarbon refrigeration system. 
     
     
         3 . The hydrocarbon processing system of  claim 1 , wherein the first fluorocarbon refrigeration system or the second fluorocarbon refrigeration system, or both, is configured to cool the nitrogen refrigerant of the nitrogen refrigeration system. 
     
     
         4 . The hydrocarbon processing system of  claim 1 , wherein the first fluorocarbon refrigeration system or the second fluorocarbon refrigeration system, or both, comprises multiple cooling cycles. 
     
     
         5 . The hydrocarbon processing system of  claim 1 , wherein the nitrogen refrigeration system comprises a plurality of heat exchangers configured to allow for cooling of the natural gas via an indirect exchange of heat between the natural gas and the nitrogen refrigerant. 
     
     
         6 . The hydrocarbon processing system of  claim 1 , wherein the first fluorocarbon refrigeration system comprises:
 a compressor configured to compress the first fluorocarbon refrigerant to provide a compressed first fluorocarbon refrigerant;   a chiller configured to cool the compressed first fluorocarbon refrigerant by indirect heat exchange with a cooling fluid;   a valve configured to expand the compressed first fluorocarbon refrigerant to cool the compressed first fluorocarbon refrigerant, thereby producing a cooled first fluorocarbon refrigerant; and   a heat exchanger configured to cool the natural gas via indirect heat exchange with the cooled first fluorocarbon refrigerant.   
     
     
         7 . The hydrocarbon processing system of  claim 1 , wherein the second fluorocarbon refrigeration system comprises:
 a compressor configured to compress the second fluorocarbon refrigerant to provide a compressed second fluorocarbon refrigerant;   a chiller configured to cool the compressed second fluorocarbon refrigerant by indirect heat exchange with a cooling fluid;   a valve configured to expand the compressed second fluorocarbon refrigerant to cool the compressed second fluorocarbon refrigerant, thereby producing a cooled second fluorocarbon refrigerant; and   a heat exchanger configured to cool the natural gas via indirect heat exchange with the cooled second fluorocarbon refrigerant.   
     
     
         8 . The hydrocarbon processing system of  claim 1 , wherein the first fluorocarbon refrigerant comprises R-410A. 
     
     
         9 . The hydrocarbon processing system of  claim 1 , wherein the second fluorocarbon refrigerant comprises R-508B. 
     
     
         10 . The hydrocarbon processing system of  claim 1 , wherein the first fluorocarbon refrigerant or the second fluorocarbon refrigerant, or both, comprises a nontoxic, nonflammable refrigerant. 
     
     
         11 . The hydrocarbon processing system of  claim 1 , wherein the first fluorocarbon refrigeration system or the second fluorocarbon refrigeration system, or both, comprises two or more chillers and two or more compressors. 
     
     
         12 . The hydrocarbon processing system of  claim 1 , wherein the first fluorocarbon refrigeration system and the second fluorocarbon refrigeration system are implemented in series. 
     
     
         13 . The hydrocarbon processing system of  claim 1 , wherein the nitrogen refrigerant is in a gas phase. 
     
     
         14 . The hydrocarbon processing system of  claim 1 , wherein the nitrogen refrigeration system comprises two or more chillers, two or more expanders, and two or more compressors. 
     
     
         15 . The hydrocarbon processing system of  claim 1 , wherein the hydrocarbon processing system is configured to chill the natural gas for hydrocarbon dew point control. 
     
     
         16 . The hydrocarbon processing system of  claim 1 , wherein the hydrocarbon processing system is configured to chill the natural gas for natural gas liquid extraction. 
     
     
         17 . The hydrocarbon processing system of  claim 1 , wherein the hydrocarbon processing system is configured to separate methane and lighter gases from carbon dioxide and heavier gases. 
     
     
         18 . The hydrocarbon processing system of  claim 1 , wherein the hydrocarbon processing system is configured to prepare hydrocarbons for liquefied petroleum gas production storage. 
     
     
         19 . The hydrocarbon processing system of  claim 1 , wherein the hydrocarbon processing system is configured to condense a reflux stream. 
     
     
         20 . A method for formation of a liquefied natural gas (LNG), comprising:
 cooling a natural gas in a first fluorocarbon refrigeration system;   cooling the natural gas in a second fluorocarbon refrigeration system;   liquefying the natural gas to form LNG in a nitrogen refrigeration system; and   removing nitrogen from the LNG in a nitrogen rejection unit.   
     
     
         21 . The method of  claim 20 , comprising cooling a second fluorocarbon refrigerant of the second fluorocarbon refrigeration system within the first fluorocarbon refrigeration system. 
     
     
         22 . The method of  claim 20 , comprising cooling a nitrogen refrigerant of the nitrogen refrigeration system within the first fluorocarbon refrigeration system or the second fluorocarbon refrigeration system, or both. 
     
     
         23 . The method of  claim 20 , wherein cooling the natural gas in the first fluorocarbon refrigeration system comprises:
 compressing a first fluorocarbon refrigerant to provide a compressed first fluorocarbon refrigerant;   optionally cooling the compressed first fluorocarbon refrigerant by indirect heat exchange with a cooling fluid;   expanding the compressed first fluorocarbon refrigerant to cool the compressed first fluorocarbon refrigerant, thereby producing an expanded, cooled first fluorocarbon refrigerant;   passing said expanded, cooled first fluorocarbon refrigerant to a first heat exchange area;   optionally compressing the natural gas;   optionally cooling the natural gas by indirect heat exchange with an external cooling fluid; and   heat exchanging the natural gas with the expanded, cooled first fluorocarbon refrigerant.   
     
     
         24 . The method of  claim 20 , wherein cooling the natural gas in the second fluorocarbon refrigeration system comprises:
 compressing a second fluorocarbon refrigerant to provide a compressed second fluorocarbon refrigerant;   optionally cooling the compressed second fluorocarbon refrigerant by indirect heat exchange with a cooling fluid;   expanding the compressed second fluorocarbon refrigerant to cool the compressed second fluorocarbon refrigerant, thereby producing an expanded, cooled second fluorocarbon refrigerant;   passing said expanded, cooled second fluorocarbon refrigerant to a first heat exchange area;   optionally compressing the natural gas;   optionally cooling the natural gas by indirect heat exchange with an external cooling fluid; and   heat exchanging the natural gas with the expanded, cooled second fluorocarbon refrigerant.   
     
     
         25 . The method of  claim 20 , comprising maintaining a nitrogen refrigerant of the nitrogen refrigeration system in a gas phase using one or more expansion turbines. 
     
     
         26 . The method of  claim 20 , comprising chilling the natural gas in the first fluorocarbon refrigeration system or the second fluorocarbon refrigeration system, or both, using two or more refrigeration stages. 
     
     
         27 . The method of  claim 20 , comprising liquefying the natural gas in the nitrogen refrigeration system using one or more refrigeration stages. 
     
     
         28 . A hydrocarbon processing system for formation of a liquefied natural gas (LNG), comprising:
 a first refrigeration system configured to cool a natural gas using a first fluorocarbon refrigerant, wherein the first refrigeration system comprises a plurality of first heat exchangers configured to allow for cooling of the natural gas via an indirect exchange of heat between the natural gas and the first fluorocarbon refrigerant;   a second refrigeration system configured to chill the natural gas using a second fluorocarbon refrigerant, wherein the second refrigeration system comprises a plurality of second heat exchangers configured to allow for cooling of the natural gas via an indirect exchange of heat between the natural gas and the second fluorocarbon refrigerant;   a third refrigeration system configured to form LNG from the natural gas using a nitrogen refrigerant, wherein the third refrigeration system comprises a plurality of third heat exchangers configured to allow for cooling of the natural gas via an indirect exchange of heat between the natural gas and the nitrogen refrigerant; and   a nitrogen rejection unit configured to remove nitrogen from the LNG.   
     
     
         29 . The hydrocarbon processing system of  claim 28 , wherein the nitrogen refrigerant is in a gas phase. 
     
     
         30 . The hydrocarbon processing system of  claim 28 , wherein the plurality of first heat exchangers comprise evaporators configured to cool the natural gas by at least partially vaporizing the first fluorocarbon refrigerant via a transfer of heat from the natural gas to the first fluorocarbon refrigerant. 
     
     
         31 . The hydrocarbon processing system of  claim 28 , wherein the plurality of second heat exchangers comprise evaporators configured to chill the natural gas by at least partially vaporizing the second fluorocarbon refrigerant via a transfer of heat from the natural gas to the second fluorocarbon refrigerant. 
     
     
         32 . A hydrocarbon processing system for formation of a liquefied natural gas (LNG), comprising:
 a first fluorocarbon refrigeration system configured to chill a natural gas using a first fluorocarbon refrigerant;   a second fluorocarbon refrigeration system configured to further chill the natural gas using a second fluorocarbon refrigerant; and   a methane autorefrigeration system configured to cool the natural gas to produce LNG.   
     
     
         33 . The hydrocarbon processing system of  claim 32 , comprising a nitrogen rejection unit upstream of the methane autorefrigeration system, and wherein the methane autorefrigeration system comprises a plurality of expansion valves and a plurality of flash drums.