Apparatus for the liquefaction of a gas and methods relating to same

Abstract

Apparatuses and methods are provided for producing liquefied gas, such as liquefied natural gas. In one embodiment, a liquefaction plant may be coupled to a source of unpurified natural gas, such as a natural gas pipeline at a pressure letdown station. A portion of the gas is drawn off and split into a process stream and a cooling stream. The cooling stream may sequentially pass through a compressor and an expander. The process stream may also pass through a compressor. The compressed process stream is cooled, such as by the expanded cooling stream. The cooled, compressed process stream is expanded to liquefy the natural gas. A gas-liquid separator separates the vapor from the liquid natural gas. A portion of the liquid gas may be used for additional cooling. Gas produced within the system may be recompressed for reintroduction into a receiving line.

1 . A method of liquefying a gas, the method comprising:
 liquefying at least a portion of a source gas to provide a liquid natural gas;   precipitating a solid within the liquid natural gas; and   separating the solid from the liquid natural gas.   
   
   
       2 . The method of  claim 1 , further comprising subcooling the solid. 
   
   
       3 . The method of  claim 2 , wherein precipitating a solid within the liquid natural gas comprises precipitating solid carbon dioxide within the liquid natural gas. 
   
   
       4 . The method of  claim 3 , further comprising sublimating the solid carbon dioxide after separating the solid carbon dioxide from the liquid natural gas to form a gaseous carbon dioxide. 
   
   
       5 . The method of  claim 4 , further comprising directing the gaseous carbon dioxide into a natural gas pipeline. 
   
   
       6 . The method of  claim 1 , wherein liquefying at least a portion of the source gas to provide a liquid natural gas further comprises directing the source gas through at least one expansion valve. 
   
   
       7 . The method of  claim 1 , further comprising bubbling and agitating the solid precipitate within the liquid natural gas. 
   
   
       8 . The method of  claim 1 , wherein separating the solid from the liquid natural gas comprises directing a slurry comprising the solid and at least a portion of the liquid natural gas through a hydrocyclone. 
   
   
       9 . A liquefaction plant comprising:
 a product flow path defined and configured for delivery of a stream of gas through at least one expansion device and into a liquid-gas separator for producing a slurry of liquid natural gas and solid carbon dioxide from the at least a portion of a process stream within the liquid-gas separator; and   a hydrocyclone located and configured to receive a solid-liquid slurry from the liquid-gas separator.   
   
   
       10 . The liquefaction plant of  claim 9 , further comprising a transfer tank located and configured to receive a solid-liquid slurry from the liquid-gas separator and deliver a solid-liquid slurry from the liquid-gas separator to the hydrocyclone. 
   
   
       11 . The liquefaction plant of  claim 10 , further comprising an accumulator tank coupled to the transfer tank. 
   
   
       12 . The liquefaction plant of  claim 9 , wherein the liquid-gas separator further comprises a gas bubbler. 
   
   
       13 . The liquefaction plant of  claim 9 , further comprising a sublimation tank located and configured to receive and sublimate solid carbon dioxide from the hydrocyclone. 
   
   
       14 . The liquefaction plant of  claim 13 , further comprising a compressor located and configured to compress carbon dioxide gas from the sublimation tank and direct compressed carbon dioxide gas into a natural gas pipeline.