Additional liquid natural gas plant and method of operating thereof

Abstract

The invention relates to a liquid natural gas plant for producing liquefied natural gas. The liquid natural gas plant comprises two or more parallel treatment and liquefaction trains, each train comprising a cooling stage arranged to receive a cleaned natural gas stream from a gas treatment stage, an NGL-extraction unit for extracting natural gas liquids, thereby generating a light natural gas stream. The liquid natural gas plant comprises an additional liquefaction train, comprising an additional cooling stage arranged to receive an additional feed stream for generating additional liquefied natural gas. The additional feed stream comprises two or more side streams taken from the light natural gas taken from the respective light natural gas streams of the one or more parallel treatment and liquefaction trains.

1 . A liquid natural gas plant for producing liquefied natural gas from a contaminated natural gas feed stream, the liquid natural gas plant comprising two or more parallel treatment and liquefaction trains arranged in process portions of the contaminated natural gas feed stream in parallel, the treatment and liquefaction trains each comprising:
 an inlet for receiving a portion of the contaminated natural gas feed stream,   a gas treatment stage for removing contaminants from the respective portion of the contaminated natural gas feed stream thereby generating a cleaned natural gas stream,   a cooling stage arranged to receive the cleaned natural gas stream from the gas treatment stage for cooling at least part of the cleaned natural gas stream, wherein the cooling stage comprises a NGL-extraction unit for extracting natural gas liquids, thereby generating a light natural gas stream to be at least partially further cooled by the cooling stage to be at least partially liquefied; and   an outlet for discharging liquefied natural gas,   wherein the liquid natural gas plant comprises at least one additional liquefaction train, the additional liquefaction train comprising:   an inlet for receiving an additional feed stream,   an additional cooling stage arranged to receive the additional feed stream for cooling the additional feed stream thereby generating additional liquefied natural gas, and   an outlet for discharging the additional liquefied natural gas,   wherein the additional feed stream comprises at least two or more side streams taken from the respective light natural gas streams, of the two or more parallel treatment and liquefaction trains.   
     
     
         2 . The liquid natural gas plant according to  claim 1 , wherein one or more of the parallel treatment and liquefaction trains comprise an end flash unit arranged to receive and flash at least part of the respective light natural gas streams to generate an end flash stream and liquefied natural gas, wherein the additional feed stream further comprises at least a portion of the one or more flash streams generated by the respective end flash units. 
     
     
         3 . The liquid natural gas plant according to  claim 1 , wherein the liquid natural gas plant comprises a collecting and compression unit, comprising a plurality of inlets to receive the respective streams to be comprised by the additional feed stream. The collecting and compression unit is arranged to pressurize and combine the different streams to form and discharge the additional feed stream. 
     
     
         4 . The liquid natural gas plant according to  claim 1 , wherein the liquid natural gas plant comprises a nitrogen removal stage, the nitrogen removal stage being arranged to receive one or more streams to be comprised by the additional feed stream and discharge one or more nitrogen depleted streams. 
     
     
         5 . The liquid natural gas plant according to  claim 1 , wherein the liquid natural gas plant comprises a fuel unit comprising a fuel inlet to receive a fuel stream, the fuel stream comprising a side stream of the contaminated natural gas feed stream. 
     
     
         6 . The liquid natural gas plant according to  claim 1 , wherein the liquid natural gas plant comprises at least four or more parallel treatment and liquefaction trains. 
     
     
         7 . A method of retrofitting an existing liquid natural gas plant to increase the liquefied natural gas production capacity thereof, wherein the existing liquid natural gas plant comprises two or more parallel treatment and liquefaction trains for producing liquefied natural gas from a contaminated natural gas feed stream, wherein the two or more parallel treatment and liquefaction trains are arranged to process portions of the contaminated natural gas feed stream in parallel and are each arranged to:
 receive a portion of a contaminated natural gas feed stream,   remove contaminants from the respective portion of the contaminated natural gas feed stream thereby generating a cleaned natural gas stream,   cool at least part of the cleaned natural gas stream and extract natural gas liquids, thereby generating a light natural gas stream to be at least partially further cooled by the cooling stage,   wherein the method of retrofitting comprises the steps of:   providing an additional liquefaction train, the additional liquefaction train comprising an additional cooling stage arranged to receive and liquefy an additional feed stream to generate additional liquefied natural gas,   fluidly connecting the additional liquefaction train to two or more of the light natural gas streams of two or more of the treatment and liquefaction trains to obtain side streams of the two or more light natural gas streams to be comprised in the additional feed stream, thereby creating a retrofitted liquid natural gas plant.   
     
     
         8 . The method of retrofitting according to  claim 7 , wherein the existing liquid natural gas plant comprises one or more parallel treatment and liquefaction trains comprising an end flash unit, the method of retrofitting comprising
 fluidly connecting the additional liquefaction train (C) to one or more of the end flash streams to receive at least a portion thereof to be comprised in the additional feed stream.   
     
     
         9 . The method of retrofitting according to  claim 7 , comprising
 providing a collecting and compression unit comprising a plurality of inlets to receive the respective streams to be comprised by the additional feed stream from the two or more parallel treatment and liquefaction trains, the collecting and compression unit comprising one or more compressors to compress the streams to be comprised by the additional feed stream to a predetermined additional feed pressure and combine the streams to be comprised by the additional feed stream to form the additional feed stream, the collecting and compression unit further comprising an outlet to discharge the additional feed stream,   fluidly connecting the respective inlets of the collecting and compression unit with the two or more parallel treatment and liquefaction trains and fluidly connecting the outlet of the collecting and compression unit with the additional liquefaction train.   
     
     
         10 . The method of retrofitting according to  claim 7 , wherein the existing liquid natural gas plant comprises a fuel unit, the fuel unit being arranged to receive and burn a fuel stream, thereby generating power and/or heat to provide the liquid natural gas plant with energy and/or heat,
 wherein the method of retrofitting comprises the step of:
 fluidly connecting the fuel unit to receive a side-stream of the contaminated natural gas feed stream or the cleaned natural gas stream. 
   
     
     
         11 . A method of operating a liquid natural gas comprising the steps of:
 operating the two or more parallel treatment and liquefaction trains whereby operating the two or more parallel treatment and liquefaction trains comprises receiving respective portions of the contaminated natural gas feed stream by the two or more parallel treatment and liquefaction trains at a feed pressure and processing said portions of the contaminated natural gas feed stream in parallel, and   operating the additional liquefaction train,   whereby operating the additional liquefaction train comprises providing an additional feed stream comprising at least two or more light natural gas streams taken from the two or more parallel treatment and liquefaction trains, wherein the additional feed stream is provided at an additional feed pressure, being at least 10 bar above the feed pressure.