System and method for liquefaction of natural gas

Abstract

By controlling an excessive rise in the temperature of the material gas that is introduced into the liquefaction unit following the compression by a compressor, the temperature of the material gas may be adjusted to the temperature level at the introduction point of the liquefaction unit. A system ( 1 ) for the liquefaction of natural gas, comprises a first expander ( 3 ) for expanding natural gas under pressure as material gas; a first cooling unit ( 10, 11, 12 ) for cooling the material gas; a distillation unit ( 15 ) for reducing or eliminating a heavy component in the material gas by distilling the material gas cooled by the first cooler; a first compressor ( 4 ) for receiving a top fraction of the material gas from which the heavy component was reduced or eliminated by the distillation unit; and a liquefaction unit ( 21 ) for liquefying a gas phase component separated from the compressed material gas compressed by the first compressor by exchanging heat with a refrigerant.

1 . A system for the liquefaction of natural gas that cools the natural gas to produce liquefied natural gas, comprising:
 a first expander for expanding natural gas under pressure as material gas;   a first cooling unit for cooling the material gas;   a distillation unit for reducing or eliminating a heavy component in the material gas by distilling the material gas cooled by the first cooling unit;   a first compressor for receiving a top fraction of the material gas from which the heavy component was reduced or eliminated by the distillation unit; and   a liquefaction unit for liquefying a gas phase component separated from compressed material gas compressed by the first compressor by exchanging heat with a refrigerant.   
     
     
         2 . The system for the liquefaction of natural gas according to  claim 1 , wherein the compressed material gas is pre-cooled by being introduced into the liquefaction unit, and the system further comprises a first gas-liquid separation vessel for separating the gas phase component from the compressed material gas pre-cooled by the liquefaction unit. 
     
     
         3 . The system for the liquefaction of natural gas according to  claim 2 , further comprising a second cooling unit placed between the first compressor and the first gas-liquid separation vessel to cool the compressed material gas received from the first compressor. 
     
     
         4 . The system for the liquefaction of natural gas according to  claim 1 , further comprising a second gas-liquid separation vessel for receiving a part of the compressed material gas separated from the compressed material gas compressed by the first compressor, wherein a liquid phase component separated by the second gas-liquid separation vessel is recirculated to the distillation unit. 
     
     
         5 . The system for the liquefaction of natural gas according to  claim 1 , further comprising a heat exchanger for exchanging heat between the material gas to be introduced into the distillation unit and a top fraction from the distillation unit. 
     
     
         6 . The system for the liquefaction of natural gas according to  claim 1 , further comprising a heat exchanger for exchanging heat between the material gas to be introduced into the distillation unit and the compressed material gas compressed by the first compressor. 
     
     
         7 . The system for the liquefaction of natural gas according to  claim 1 , further comprising a heat exchanger for exchanging heat between the material gas at an upstream end of the first compressor and a top fraction from the distillation unit. 
     
     
         8 . A method for the liquefaction of natural gas by cooling the natural gas to produce liquefied natural gas, comprising:
 a first expansion step for expanding natural gas under pressure as material gas;   a first cooling step for cooling the material gas;   a distillation step for reducing or eliminating a heavy component in the material gas by distilling the material gas cooled in the first cooling step;   a first compression step for compressing a top fraction of the material gas from which the heavy component was reduced or eliminated in the distillation step; and   a liquefaction step for liquefying a gas phase component separated from the compressed material gas compressed in the first compression step by exchanging heat with a refrigerant.