Method of cooling a hydrocarbon stream and apparatus therefor

Abstract

Method and apparatus for cooling a hydrocarbon stream ( 520 ) to produce an at least partially liquefied hydrocarbon stream ( 530 ). A cooled main refrigerant stream ( 245 ) is further cooled against at least a part of one or more expanded cooled pre-cooling refrigerant streams ( 155 ). A hydrocarbon stream ( 520 ) is at least partially liquefied in one or more main heat exchangers ( 220 ) against an expanded cooled main refrigerant stream ( 255 ), to provide an at least partially, preferably fully, liquefied hydrocarbon stream ( 530 ). The air inlet stream ( 45 ) of a first gas turbine ( 50 ) is cooled using cooling duty from the main refrigerant in the main refrigerant circuit ( 200 ) to provide a cooled air inlet stream ( 55 ) to the first gas turbine ( 50 ).

1 . A method of cooling a hydrocarbon stream to produce a liquefied hydrocarbon stream, comprising at least the steps of:
 (a) cooling a compressed pre-cooling refrigerant stream comprising a pre-cooling refrigerant in one or more pre-cooling ambient coolers to provide a cooled pre-cooling refrigerant stream;   (b) cooling a cooled main refrigerant stream against at least a part of one or more expanded cooled pre-cooling refrigerant streams, said expanded pre-cooling refrigerant stream derived from the cooled pre-cooling refrigerant stream to provide a pre-cooled main refrigerant stream and one or more pre-cooling refrigerant streams, wherein said pre-cooling refrigerant is circulated in a pre-cooling refrigerant circuit;   (c) at least partially liquefying a hydrocarbon stream in one or more main heat exchangers against an expanded cooled main refrigerant stream, said expanded cooled main refrigerant stream derived from the pre-cooled main refrigerant stream, to provide an at least partially liquefied hydrocarbon stream and a main refrigerant stream, wherein said main refrigerant is circulated in a main refrigerant circuit;   (d) cooling an air inlet stream of a first gas turbine using cooling duty from the main refrigerant in the main refrigerant circuit to provide a cooled air inlet stream to the first gas turbine; and   (e) driving a first compressor with the first gas turbine.   
     
     
         2 . The method according to  claim 1 , wherein step (a) further comprises cooling a hydrocarbon feed stream against at least a part of the expanded cooled pre-cooling refrigerant stream to provide the hydrocarbon stream. 
     
     
         3 . The method according to  claim 1 , wherein the first gas turbine is a pre-cooling gas turbine and the first compressor is a pre-cooling compressor in the pre-cooling refrigerant circuit. 
     
     
         4 . The method according to  claim 1 , wherein the first gas turbine is a main cooling gas turbine and the first compressor is a main refrigerant compressor in the main refrigerant circuit. 
     
     
         5 . The method according to  claim 1 , wherein the cooling of the air inlet stream of the first gas turbine in step (d) is provided by the further steps of:
 cooling a thermal transfer fluid in a thermal transfer fluid stream against the main refrigerant in the main refrigerant circuit to provide a cooled thermal transfer fluid stream; and   cooling the air inlet stream against the cooled thermal transfer fluid stream to provide the cooled air inlet stream and the thermal transfer fluid stream.   
     
     
         6 . The method according to  claim 5 , wherein the thermal transfer fluid is selected from one or more of the group consisting of: water and a glycol. 
     
     
         7 . The method according to  claim 5 , wherein the main refrigerant in the main refrigerant circuit used in the heat exchange with the thermal transfer fluid stream is a part of the main refrigerant stream drawn from at least one of the main heat exchangers. 
     
     
         8 . The method according to  claim 5 , wherein the main refrigerant in the main refrigerant circuit used in the heat exchange with the thermal transfer fluid stream is a part of the pre-cooled main refrigerant stream. 
     
     
         9 . The method according to  claim 5 , wherein the cooling of the cooled main refrigerant stream in step (b) is carried out sequentially in two or more pre-cooling heat exchangers in series and the main refrigerant in the main refrigerant circuit used in the heat exchange with the thermal transfer fluid stream is drawn from between two of said pre-cooling heat exchangers. 
     
     
         10 . The method according to  claim 5 , where in the main refrigerant in the main refrigerant circuit used in the heat exchange with the thermal transfer fluid stream is a mixed refrigerant and is provided by the further steps of:
 separating the pre-cooled main refrigerant stream in a main gas/liquid separator to provide an overhead gaseous stream and a liquid bottom stream; and   withdrawing a part of the liquid bottom stream to cool the thermal transfer fluid stream.   
     
     
         11 . The method according to  claim 1 , wherein the pre-cooling refrigerant circuit comprises one or more pre-cooling compressors, one or more pre-cooling heat exchangers, one or more pre-cooling ambient coolers and one or more pre-cooling expansion devices, and wherein the main refrigerant circuit comprises one or more main refrigerant compressors, one or more main heat exchangers, one or more said main ambient coolers and one or more main expansion devices. 
     
     
         12 . An apparatus for liquefying a hydrocarbon stream comprising at least:
 a pre-cooling refrigerant circuit comprising:   one or more pre-cooling heat exchangers to cool a cooled main refrigerant stream against a pre-cooling refrigerant in at least a part of one or more expanded cooled pre-cooling refrigerant streams to provide a pre-cooled main refrigerant stream and one or more pre-cooling refrigerant streams, one or more pre-cooling compressors to compress the one or more pre-cooling refrigerant streams to provide a compressed pre-cooling refrigerant stream, one or more pre-cooling ambient coolers to cool the compressed main refrigerant stream to provide a cooled pre-cooling refrigerant stream, and one or more pre-cooling expansion devices to expand the cooled pre-cooling refrigerant stream to provide the expanded cooled pre-cooling refrigerant stream;   and   a main refrigerant circuit comprising:   one or more main heat exchangers to:   at least partially liquefy a hydrocarbon stream against a main refrigerant in at least a part of one or more expanded cooled main refrigerant streams to provide an at least partially liquefied hydrocarbon stream and one or more main refrigerant streams,   one or more main refrigerant compressors to compress the one or more main refrigerant streams, or a stream derived therefrom, to provide a compressed main refrigerant stream, one or more main ambient coolers to cool the compressed main refrigerant stream to provide the cooled main refrigerant stream, and   one or more main expansion devices to expand the pre-cooled main refrigerant stream, or a stream derived therefrom, to provide the expanded cooled main refrigerant stream;   a first gas turbine having a first air inlet stream; and   cooling means to cool the first air inlet stream using cooling duty from the main refrigerant in the main refrigerant circuit.   
     
     
         13 . The apparatus according to  claim 12 , wherein the pre-cooling refrigerant circuit further cools a hydrocarbon feed stream against a pre-cooling refrigerant in at least a part of one or more expanded cooled pre-cooling refrigerant streams to provide the hydrocarbon stream and one or more pre-cooling refrigerant streams. 
     
     
         14 . The apparatus according to  claim 12 , further comprising one or more pre-cooling gas turbines arranged to drive said pre-cooling compressors, each of said pre-cooling gas turbines having a pre-cooling turbine air inlet stream, and whereby the first gas turbine is at least one of the pre-cooling gas turbines and the first air inlet stream is the pre-cooling turbine air inlet stream. 
     
     
         15 . The apparatus according to  claim 12 , further comprising one or more main gas turbines arranged to drive said main refrigerant compressors, each of said main gas turbines having a main turbine air inlet stream, and whereby the first gas turbine is at least one of the main gas turbines and the first air inlet stream is the main turbine air inlet stream.