Natural gas liquefaction system including an integrally-geared turbo-compressor

Abstract

According to one aspect of the present disclosure, a natural gas liquefaction system (100) is provided. The system comprises an integrally-geared turbo-compressor (150) with a plurality of compressor stages; a prime mover (160) for driving the compressor; a pre-cooling loop (110), through which a first refrigerant is adapted to circulate, wherein one or more first compressor stages (151) of the plurality of compressor stages are adapted to pressurize the first refrigerant; a cooling loop (130), through which a second refrigerant is adapted to circulate, wherein one or more second compressor stages (155) of the plurality of compressor stages are adapted to pressurize the second refrigerant; a first heat exchanger device (170) for transferring heat from a natural gas and/or from the second refrigerant to the first refrigerant; and a second heat exchanger device (180) for transferring heat from the natural gas to the second refrigerant. A further aspect relates to a compressor arrangement for a natural gas liquefaction system. A yet further aspect relates to a method of liquefying natural gas.

1 . A natural gas liquefaction system ( 100 ), comprising:
 an integrally-geared turbo-compressor ( 150 ) with a plurality of compressor stages;   a single prime mover ( 160 ) for driving the compressor ( 150 );   a pre-cooling loop ( 110 ), through which a first refrigerant is adapted to circulate, wherein one or more first compressor stages ( 151 ) of the plurality of compressor stages are adapted to pressurize the first refrigerant;   a cooling loop ( 130 ), through which a second refrigerant is adapted to circulate, wherein one or more second compressor stages ( 155 ) of the plurality of compressor stages are adapted to pressurize the second refrigerant;   a first heat exchanger device ( 170 ) for transferring heat from a natural gas and/or from the second refrigerant to the first refrigerant; and   a second heat exchanger device ( 180 ) for transferring heat from the natural gas to the second refrigerant;   wherein said single prime mover ( 160 ) drives each of the one or more first compressor stages ( 151 ) and second compressor stages ( 155 ).   
     
     
         2 . The system of  claim 1 , wherein the compressor ( 150 ) comprises a plurality of first compressor stages ( 151 ), particularly four sequentially arranged first compressor stages, for pressurizing the first refrigerant, and/or a plurality of second compressor stages ( 155 ), particularly three or four sequentially arranged second compressor stages, for pressurizing the second refrigerant. 
     
     
         3 . The system of  claim 1 , wherein the compressor ( 150 ) comprises:
 a transmission mechanism ( 301 ), particularly including a gear, configured to be driven into rotation by said prime mover;   at least one first shaft ( 303 ) configured to be driven into rotation by said transmission mechanism ( 301 ) and configured for driving at least one of the first compressor stages; and   at least one second shaft ( 305 ) configured to be driven into rotation by said transmission mechanism ( 301 ) and configured for driving at least one of the second compressor stages.   
     
     
         4 . The system of  claim 3 , wherein the transmission mechanism ( 301 ) comprises a first gear wheel ( 307 ) meshing at least one first pinion connected to the at least one first shaft ( 303 ) for driving the at least one first compressor stage. 
     
     
         5 . The system of  claim 3 , wherein the first gear wheel ( 307 ) further meshes at least one second pinion connected to the at least one second shaft ( 305 ) for driving the at least one second compressor stage. 
     
     
         6 . The system of  claim 3 , wherein the transmission mechanism ( 301 ) comprises a first gear wheel ( 307 ) configured for driving the at least one first shaft ( 303 ), and a second gear wheel ( 308 ) configured for driving the at least one second shaft ( 305 ), particularly wherein the diameter of the second gear wheel ( 308 ) is smaller than the diameter of the first gear wheel ( 307 ) and/or wherein the first gear wheel and the second gear wheel are directly meshing gear wheels. 
     
     
         7 . The system of  claim 3 , wherein at least one of the at least one first shaft and the at least one second shaft drives two compressor stages arranged on opposite ends of the respective shaft. 
     
     
         8 . The system of  claim 1 , wherein the compressor ( 150 ) comprises a plurality of first compressor stages ( 151 ), and wherein the pre-cooling loop ( 110 ) is configured to divide the first refrigerant into a plurality of precooling streams, which are guided to a respective one of said plurality of first compressor stages ( 151 ). 
     
     
         9 . The system of  claim 8 , comprising:
 a plurality of first expansion elements ( 241 ,  243 ,  245 ,  247 ) sequentially arranged in the pre-cooling loop ( 110 ) and configured for expanding the first refrigerant at a plurality of decreasing pressure levels;   a plurality of first heat exchangers ( 249 ,  251 ,  253 ,  255 ) of the first heat exchanger device ( 170 ,  270 ) for receiving respective precooling streams of the first refrigerant expanded through at least one of said plurality of first expansion elements ( 241 ,  243 ,  245 ,  247 ) and for transferring heat from the natural gas to the first refrigerant; and   a plurality of return paths ( 261 ,  263 ,  265 ,  267 ) configured for returning said precooling streams of the first refrigerant from the plurality of first heat exchangers ( 249 ,  251 ,  253 ,  255 ) to a respective one of the plurality of first compressor stages ( 151 ).   
     
     
         10 . The system of  claim 1 , comprising at least one first auxiliary expansion element arranged in the pre-cooling loop ( 110 ) and at least one first auxiliary heat exchanger of the first heat exchanger device ( 170 ,  270 ) configured for receiving a portion of said first refrigerant expanded through the at least one first auxiliary expansion element and for transferring heat from the second refrigerant to the first refrigerant. 
     
     
         11 . The system of  claim 10 , comprising:
 a plurality of first auxiliary expansion elements ( 221 ,  223 ,  225 ,  227 ) sequentially arranged in the pre-cooling loop ( 110 ) and configured for expanding the first refrigerant at a plurality of decreasing pressure levels;   a plurality of first auxiliary heat exchangers ( 229 ,  231 ,  233 ,  235 ) of the first heat exchanger device ( 170 ,  270 ) configured for receiving respective portions of said first refrigerant expanded through at least one of said plurality of first auxiliary expansion elements ( 221 ,  223 ,  225 ,  227 ) and for transferring heat from the second refrigerant to the first refrigerant; and   a plurality of return paths ( 261 ,  263 ,  265 ,  267 ) configured for returning said portions of the first refrigerant from the plurality of first auxiliary heat exchangers ( 229 ,  231 ,  233 ,  235 ) to a respective one of said plurality of first compressor stages ( 151 ).   
     
     
         12 . The system of  claim 1 , wherein the first refrigerant comprises a gas with a molecular weight of 40 or more, particularly propane, and/or wherein the second refrigerant is a mixed refrigerant, particularly a mixture comprising methane, ethane, propane and/or nitrogen. 
     
     
         13 . The system  claim 1 , wherein said prime mover ( 160 ) comprises an electric motor or an internal combustion engine, particularly a gas turbine. 
     
     
         14 . A method of liquefying natural gas, comprising:
 providing an integrally-geared turbo-compressor ( 150 ) having a plurality of compressor stages;   driving the compressor ( 150 ) with a single prime mover ( 160 );   circulating a first refrigerant through one or more first compressor stages ( 151 ) of the plurality of compressor stages, each of the one or more first compressor stages ( 151 ) being driven by said single prime mover ( 160 );   circulating a second refrigerant through one or more second compressor stages ( 155 ) of the plurality of compressor stages, each of the one or more second compressor stages ( 155 ) being driven by said single prime mover ( 160 );   cooling at least one of natural gas and the second refrigerant by heat exchange against the first refrigerant; and   cooling the natural gas by heat exchange against the second refrigerant.   
     
     
         15 . The method of  claim 14 , further comprising:
 expanding the first refrigerant through a plurality of sequentially arranged first expansion elements ( 241 ,  243 ,  245 ,  247 ) at a plurality of decreasing pressure levels;   circulating portions of the first refrigerant from the plurality of sequentially arranged first expansion elements through a plurality of first heat exchangers ( 249 ,  251 ,  253 ,  255 ) to remove heat from the natural gas; and   returning the portions of the first refrigerant from the plurality of first heat exchangers to respective ones of said one or more first compressor stages.   
     
     
         16 . The method of  claim 14 , wherein a transmission mechanism ( 301 ) of the compressor is driven by the prime mover ( 160 ),
 at least one first shaft ( 303 ) is driven into rotation by said transmission mechanism ( 301 ) at a rotation speed of 3.000 rpm or more and 7.000 rpm or less and drives at least one of the first compressor stages; and   at least one second shaft ( 305 ) is driven into rotation by said transmission mechanism ( 301 ) at a rotation speed of 8.000 rpm or more and 20.000 rpm or less and drives at least one of the second compressor stages.   
     
     
         17 . The method of  claim 14 , wherein the first refrigerant is sequentially circulated through three, four or more first compressor stages and compressed to an exit pressure ranging from 10 bar to 40 bar absolute, and/or wherein the second refrigerant is sequentially circulated through three, four or more second compressor stages and compressed to an exit pressure ranging from 50 bar to 100 bar absolute. 
     
     
         18 . The method of  claim 14 , further comprising controlling independently movable inlet guide vanes to regulate partial flows at a suction side of the one or more first compressor stages, particularly as a function of flow conditions of respective partial flows.