"flexible liquefied natural gas plant"

Abstract

The present techniques are directed to a flexible liquefied natural gas (LNG) plant that may be tied to an external electric grid for importing or exporting electric power. Exemplary embodiments provide a method for producing LNG that includes producing a base load capacity of refrigeration capacity for LNG production from a first compression system. Electricity may be produced from a second compressor string if electricity is needed by an external power grid, or a second amount of refrigeration capacity may be provided by the second compressor string is natural gas feed is available and the external grid does not need power.

What is claimed is: 
     
         1 . A method for producing liquefied natural gas (LNG), comprising:
 producing a base load refrigeration capacity for LNG production from a first compression system; and   producing electricity from a second compression system, wherein the second compression system is configured to export the electricity to an external power grid when needed.   
     
     
         2 . The method of  claim 1 , further comprising producing a second amount of refrigeration capacity from the second compression system if electricity is not needed by an external power grid and natural gas feed is available. 
     
     
         3 . The method of  claim 2 , comprising producing a third amount of refrigeration capacity from a third compression system if electricity is available from the external power grid and natural gas feed is available. 
     
     
         4 . The method of  claim 3 , wherein the first compression system, the second compression system, and the third compression system share inlet and outlet manifolds for a refrigerant. 
     
     
         5 . The method of  claim 1 , further comprising increasing compression power in the first compression system by powering a motor/generator from the external power grid, wherein the motor/generator is in parallel with a gas turbine coupled to a compressor string. 
     
     
         6 . The method of  claim 1 , further comprising increasing compression power in the second compressor string by powering a motor/generator from the external power grid, wherein the motor/generator is in parallel with a gas turbine coupled to a compressor string. 
     
     
         7 . A compression system, comprising:
 a gas turbine engine;   a motor/generator sized to match an output power from the gas turbine engine, wherein the motor/generator is configured to be powered by the gas turbine engine;   a compressor string sized match the output power from the gas turbine engine, wherein the compressor string is configured to be powered by the gas turbine engine; and   a decoupling device located between the motor/generator and the compressor string, wherein when the decoupling device is disengaged, the gas turbine engine is configured to directly drive the motor/generator without transferring energy to the compressor string.   
     
     
         8 . The compression system of  claim 7 , wherein the decoupling device comprises a clutch. 
     
     
         9 . The compression system of  claim 7 , further comprising a second decoupling device located between the gas turbine engine and the motor/generator, wherein when the second decoupling is disengaged, the motor/generator is configured to directly drive the compressor string without transferring energy to the gas turbine engine. 
     
     
         10 . A flexible liquefied natural gas (LNG) plant comprising:
 a first gas turbine-driven gas compression system comprising a gas turbine, a motor/generator, and a first compressor string, wherein:
 the motor/generator is sized to match the power output of the gas turbine; and 
 the motor/generator is configured to provide electricity to an outside utility grid; and 
   an electric motor-driven compression system, comprising an electric motor and a second compressor string, wherein:
 an inlet line of the second compressor string shares a common manifold with the first compressor string; and 
 an outlet line of the second compressor string shares a common manifold with the first compressor string. 
   
     
     
         11 . The flexible LNG plant of  claim 10 , further comprising a second gas turbine-driven compression system, wherein the second gas turbine-driven compression system comprises a third compressor string configured to provide a base load refrigerant compression capacity for a LNG plant, wherein:
 an inlet line of the third compressor string shares a common inlet manifold with the first compressor string and the second compressor string; and   an outlet line of the third compressor string shares a common outlet manifold with the first compressor string and the second compressor string.   
     
     
         12 . The flexible LNG plant of  claim 10 , wherein the electric motor-driven compression system is configured to be powered from an outside utility grid. 
     
     
         13 . The flexible LNG plant of  claim 10 , wherein a refrigerant is propane, a mixed hydrocarbon refrigerant, nitrogen, or any combinations thereof. 
     
     
         14 . The flexible LNG plant of  claim 10 , wherein the gas turbine is coupled to the motor/generator and is decoupled from the first compressor string. 
     
     
         15 . The flexible LNG plant of  claim 10 , wherein the first gas turbine-driven gas compression system comprises a clutch located on a shaft between the motor/generator and the first compressor string. 
     
     
         16 . The flexible LNG plant of  claim 15 , wherein the clutch is configured to disengage the first compressor string from the gas turbine, allowing the gas turbine to drive the motor/generator. 
     
     
         17 . The flexible LNG plant of  claim 15 , further comprising a clutch located between the gas turbine and the motor/generator. 
     
     
         18 . The flexible LNG plant of  claim 10 , wherein the electric motor-driven compression system is at least partially powered by the motor/generator from a parallel compression system. 
     
     
         19 . The flexible LNG plant of  claim 18 , wherein the clutch is configured to disengage the gas turbine from the motor/generator to allow the motor/generator to drive the second compressor string. 
     
     
         20 . The flexible LNG plant of  claim 10 , further comprising a variable speed drive located between the motor/generator and the second compressor string. 
     
     
         21 . The flexible LNG plant of  claim 10 , further comprising a heat recovery unit on an exhaust from a gas turbine. 
     
     
         22 . The flexible LNG plant of  claim 20 , further comprising a steam turbine driven from steam generated by heat recovered from the heat recovery unit.