Method and apparatus for cooling a gaseous hydrocarbon stream

Abstract

A gaseous hydrocarbon stream ( 10 ) is cooled to produce a liquefied hydrocarbon stream ( 20 ). The gaseous hydrocarbon stream ( 10 ) is cooled in one or more heat exchangers ( 140 a ) using a first refrigerant from a first refrigerant circuit ( 100 ) in which said first refrigerant is compressed in a first compressor ( 110 ) driven by a first gas turbine ( 120 ) having a first inlet air stream ( 125 ) and liquefied using a second refrigerant circuit ( 200 ) wherein a second refrigerant is compressed in a second compressor ( 210 ) driven by a second gas turbine ( 220 ) and having a second inlet air stream ( 225 ). The cooling duty available in a stream of a chilled coolant ( 320 ) is divided over at least first ( 340 ) and second ( 350 ) parts in accordance with a common input parameter, and one or both of said first and second inlet air streams ( 125, 225 ) are cooled with the chilled coolant ( 320 ), whereby the cooling duty available in the first part ( 340 ) is used to cool the first inlet air stream ( 125 ), and the cooling duty available in the second part ( 350 ) is used to cool the second inlet air stream ( 225 ).

1 . A method of cooling a gaseous hydrocarbon stream to produce a liquefied hydrocarbon stream, comprising:
 cooling the gaseous hydrocarbon stream in one or more heat exchangers using a first refrigerant from a first refrigerant circuit in which said first refrigerant is compressed in a first compressor driven by a first gas turbine having a first inlet air stream, said cooling providing a cooled hydrocarbon stream;   20 liquefying the cooled hydrocarbon stream using a second refrigerant, which second refrigerant is compressed in a second compressor driven by a second gas turbine having a second inlet air stream, and cooled at least by heat exchanging with said first refrigerant from the first refrigerant circuit, said liquefying providing a liquefied hydrocarbon stream;   providing a stream of a chilled coolant, comprising chilling a fluid;   dividing the cooling duty available in the chilled coolant over at least first and second parts in accordance with a common input parameter;   cooling one of both of said first and second inlet air streams with the chilled coolant, whereby the cooling duty available in the first part is used to cool the first inlet air stream, and the cooling duty available in the second part is used to cool the second inlet air stream,   
       wherein said providing of the cooled hydrocarbon stream comprises producing a partially condensed hydrocarbon stream from the gaseous hydrocarbon stream and passing the partially condensed hydrocarbon stream through a gas/liquid phase separator and drawing a liquid bottom stream and a vaporous overhead stream from the gas/liquid phase separator, and wherein the fluid is actively chilled using refrigeration duty taken from the liquid bottom stream. 
     
     
         2 . The method of  claim 1 , wherein the common input parameter is used to divide the cooling duty available in the chilled coolant such as to provide relatively more chilling duty to the inlet air stream of the gas turbine that drives the most constraining refrigerant circuit of the first and second refrigerant circuits. 
     
     
         3 . The method of  claim 1 , wherein the common input parameter includes one or more parameters indicative of at least one the group consisting of: ambient temperature; first compressor discharge pressure; first gas turbine load/poweroutput; second gas turbine load/poweroutput; first gas turbine fuel gas valve opening; second gas turbine fuel gas valve opening; cut point temperature between first and second refrigerant cycle; first compressor adsorbed power; second compressor absorbed power; difference between first and second gas turbine power output; flow rate of liquefied hydrocarbon stream. 
     
     
         4 . The method of  claim 1 , wherein the common input parameter includes one or more parameter indicative of at least ambient temperature. 
     
     
         5 . (canceled) 
     
     
         6 . The method of  claim 1 , wherein the fluid is actively chilled using refrigeration duty taken from one or more of the first and second refrigerant circuits. 
     
     
         7 . The method of  claim 1 , wherein the fluid is actively chilled using refrigeration duty taken from the first refrigerant circuit. 
     
     
         8 . (canceled) 
     
     
         9 . The method of  claim 1 , wherein the fluid comprises the chilled coolant after it has been used for said cooling of the one or both of said first and second inlet air streams. 
     
     
         10 . The method of  claim 1 , dividing the cooling duty available in the chilled coolant over at least first and second parts in accordance with a common input parameter comprises determining an optimum division of the cooling duty available in the chilled refrigerant over the first and second parts based on the common input parameter and dividing the cooling duty in accordance with the determined optimum division. 
     
     
         11 . The method of  claim 10 , wherein the optimum division is the division whereby the liquefied hydrocarbon stream production rate is maximized. 
     
     
         12 . The method of  claim 10 , wherein the optimum division is defined as the division whereby the first and second refrigerant circuits are equally constraining for maximising liquefied hydrocarbon production 
     
     
         13 . An apparatus for cooling a gaseous hydrocarbon stream to produce a liquefied hydrocarbon stream, comprising:
 a first refrigerant circuit comprising a first refrigerant, a first compressor, a first gas turbine coupled to the first compressor to drive the first compressor, and a first inlet air stream to the first gas turbine; the first compressor arranged to compress said first refrigerant;   a second refrigerant circuit comprising a second refrigerant, a second compressor, a second gas turbine coupled to the second compressor to drive the second compressor, and a second inlet air stream to the second gas turbine; the second compressor arranged to compress said second refrigerant;   one or more first heat exchangers arranged to receive and cool the gaseous hydrocarbon stream and the second refrigerant, using said first refrigerant from said cooling providing a cooled hydrocarbon stream and a cooled second refrigerant stream;   one or more second heat exchangers arranged to receive and liquefy the cooled hydrocarbon stream using the cooled second refrigerant stream, so as to provide a liquefied hydrocarbon stream;   a stream of a chilled coolant composed of a chilled fluid;   a divider to divide the chilled coolant over at least first and second parts in accordance with a common input parameter;   a first inlet air cooling heat exchanger arranged in the first inlet air stream to cool the first inlet air stream with the first part of the chilled coolant;   a second inlet air cooling heat exchanger arranged in the second inlet air stream to cool the second inlet air stream with the second part of the chilled coolant,   a gas/liquid phase separator arranged to receive the hydrocarbon stream, connected to a vaporous overhead stream line and connected to a liquid bottom stream line;   a bottom stream heat exchanger arranged in the liquid bottom stream line and arranged to add heat to at least part of the liquid bottom stream in the liquid bottom stream line, wherein the fluid is a heat source for adding the heat whereby the fluid is actively chilled using refrigeration duty taken from the liquid bottom stream.   
     
     
         14 . The apparatus of  claim 13 , further comprising a controller arranged to receive a signal representative of the common input parameter, and to determine an optimum division of the cooling duty available in the chilled refrigerant over the first and second parts based on the common input parameter. 
     
     
         15 . The apparatus of  claim 14 , wherein the optimum division is determined by which of the first and second refrigerant circuits is the most constraining of the two for maximising liquefied hydrocarbon production. 
     
     
         16 . A method of producing a liquefied hydrocarbon stream, comprising:
 indirect heat exchanging a hydrocarbon stream in one or more heat exchangers against one or more refrigerants from one or more refrigerant circuits, at least one of which refrigerant circuits comprising a compressor driven by a gas turbine by which compressor the refrigerant of that refrigerant circuit is compressed;   withdrawing a fraction from the hydrocarbon stream after it has been heat exchanged in at least one of the one or more heat exchangers, wherein said withdrawing comprises producing a partially condensed hydrocarbon stream from the gaseous hydrocarbon stream; passing the partially condensed hydrocarbon stream through a gas/liquid phase separator; and drawing a liquid bottom stream and a vaporous overhead stream from the gas/liquid phase separator, and wherein said fraction from the hydrocarbon stream comprises at least the liquid bottom stream withdrawn from the gas/liquid separator;   providing a stream of a chilled coolant by indirect heat exchanging the chilled coolant against at least a part of the withdrawn fraction of the hydrocarbon stream that is not cycled in a refrigerant circuit;   chilling an inlet air stream comprising heat exchanging with the chilled coolant to produce a chilled inlet air stream, and feeding the chilled inlet air stream to the gas turbine;   wherein the produced liquefied hydrocarbon stream comprises at least part of the hydrocarbon stream that has not been withdrawn.   
     
     
         17 . The method of  claim 16 , wherein cooling duty for providing the chilled coolant is supplemented by cooling duty obtained from refrigerant cycled in a refrigerant circuit. 
     
     
         18 . The method of  claim 16 , further comprising drawing off a fuel gas stream from the vaporous overhead stream, and wherein said liquefied hydrocarbon stream is produced from the vaporous overhead stream remaining after the fuel gas stream has been withdrawn therefrom. 
     
     
         19 . The method of  claim 16 , wherein said indirect heat exchanging of the hydrocarbon stream in one or more heat exchangers against one or more refrigerants from one or more refrigerant circuits may comprise:
 cooling the hydrocarbon stream by heat exchanging against a first refrigerant from a first refrigerant circuit in which said first refrigerant is compressed in a first compressor driven by a first gas turbine having a first inlet air stream, said cooling providing a cooled hydrocarbon stream;   liquefying at least part of the cooled hydrocarbon stream using a second refrigerant, which second refrigerant is compressed in a second compressor driven by a second gas turbine having a second inlet air stream, and cooled at least by heat exchanging with said first refrigerant from the first refrigerant circuit, said liquefying providing a liquefied hydrocarbon stream;   wherein said chilling of said inlet air stream comprises cooling one or both of said first and second inlet air streams with at least a part of the chilled coolant.   
     
     
         20 . The method of  claim 19 , further comprising:
 dividing the cooling duty available in the chilled coolant over at least first and second parts, whereby the cooling duty available in the first part is used to cool the first inlet air stream, and the cooling duty available in the second part is used to cool the second inlet air stream.   
     
     
         21 . The method of  claim 20 , wherein said cooling duty is divided in accordance with a common input parameter. 
     
     
         22 . An apparatus for producing a liquefied hydrocarbon stream, comprising:
 one or more refrigerant circuits each comprising a refrigerant, at least one of which refrigerant circuits comprising a compressor driven by a gas turbine, for compressing the refrigerant of that refrigerant circuit;   an inlet air stream to the gas turbine;   one or more heat exchangers for indirectly heat exchanging a hydrocarbon stream against one or more refrigerants from the one or more refrigerant circuits, including said at least one;   withdrawing means for withdrawing a fraction of the hydrocarbon stream downstream of at least one of the one or more heat exchangers and providing a remaining hydrocarbon stream from which the fraction has been withdrawn, wherein the withdrawing means comprises a gas/liquid separator having an overhead outlet for discharging a vaporous overhead stream and a bottom outlet for discharging a liquid bottom stream, whereby said fraction of the hydrocarbon stream comprises the liquid bottom stream and said remaining stream comprises the vaporous overhead stream;   a chiller connected to the withdrawing means and arranged to receive at least part of the withdrawn fraction from the withdrawing means, and further arranged to indirectly heat exchange a coolant fluid against the at least part of the withdrawn fraction to produce a stream of a chilled coolant from the coolant fluid;   an inlet air cooling heat exchanger arranged in the inlet air stream to cool the inlet air stream with the chilled coolant;   a feed duct to feed the cooled inlet air stream from the inlet air cooling heat exchanger into the gas turbine;   conduit means for conveying a liquefied hydrocarbon stream that comprises at least part of the remaining hydrocarbon stream.