System and method for treating gas resulting from the evaporation of a cryogenic liquid

Abstract

The proposed system comprises a supply line for at least one engine, on which line is situated a first compression unit (3) for said gas and a bypass to a return line on which are successively situated cooling means (10) and reliquefaction means (30). The cooling means successively comprise a second compression unit (11, 12, 13) and a heat exchanger (17). Downstream of the second compression unit (11, 12, 13) a bypass to a loop (18, 20, 21) comprises first expansion means (14), the loop rejoining the return line upstream of the second compression unit (11, 12, 13) after having passed through the heat exchanger (17) in the opposite direction with respect to the gas fraction not bypassed via the loop.

1 - 16 . (canceled) 
     
     
         17 . A system for the supply of an engine on the basis of a gas arising from the evaporation of a cryogenic liquid and for the reliquefaction of this gas, said system comprising: a supply line for at least one engine, on which line is situated a first compression unit ( 3 ) for said gas and a bypass to a return line on which are successively situated cooling means ( 10 ) and first expansion means ( 30 ),
 characterized in that the cooling means successively comprise a second compression unit ( 11 ,  12 ,  13 ) and a heat exchanger ( 17 ) as well as downstream of the second compression unit ( 11 ,  12 ,  13 ) a bypass to a loop ( 18 ,  20 ,  21 ) comprising second expansion means ( 14 ), the loop rejoining the return line upstream of the second compression unit ( 11 ,  12 ,  13 ) after having passed through the heat exchanger ( 17 ) in the opposite direction with respect to the gas fraction not bypassed via the loop.   
     
     
         18 . The supply and reliquefaction of  claim 17 , characterized in that it comprises a recycling line ( 35 ) making it possible to send a non-reliquefied fraction of the gas exiting the first expansion means ( 30 ) to the supply line ( 2 ) for the engine upstream of the first compression unit ( 3 ). 
     
     
         19 . The supply and reliquefaction system of  claim 18 , characterized in that the recycling line ( 35 ) passes through the heat exchanger ( 17 ). 
     
     
         20 . The supply and reliquefaction system of  claim 17 , characterized in that the bypass is performed within the heat exchanger ( 17 ). 
     
     
         21 . The supply and reliquefaction system of  claim 17 , characterized in that the first expansion means comprise an expansion valve ( 30 ) emerging in a balloon ( 40 ) intended to separate the liquid formed and the unliquefied gas fraction. 
     
     
         22 . The supply and reliquefaction system of  claim 21 , characterized in that the upper part of the balloon ( 40 ) is linked to the heat exchanger ( 17 ) in such a way that the gas originating from the balloon ( 40 ) enters the exchanger ( 17 ) on the same side as the bypass, and in that the lower part of the balloon ( 40 ) is linked to a cryogenic liquid tank ( 1 ). 
     
     
         23 . The supply and reliquefaction system of  claim 17 , characterized in that the second compression unit comprises several compression stages ( 11 ,  12 ,  13 ) each with a compression wheel, in that the second expansion means comprise an expansion turbine ( 14 ), and in that each compression wheel and the expansion turbine ( 14 ) are associated with one and the same mechanical transmission ( 15 ). 
     
     
         24 . The supply and reliquefaction system of  claim 17 , characterized in that it furthermore comprises means ( 62 ) for injecting gas into the bypass loop of the circuit. 
     
     
         25 . The supply and reliquefaction system of  claim 24 , characterized in that the means ( 62 ) for injecting gas into the bypass loop comprise a pump ( 60 ) for cryogenic liquid, a vaporizer ( 63 ) and a control valve ( 64 ). 
     
     
         26 . The supply and reliquefaction system of  claim 17 , characterized in that it furthermore comprises a collector for the recovery of the evaporated gases of a set of cryogenic liquid tanks ( 1 ), and in that the collector is linked directly, that is to say in particular with no intermediate device for heat exchange with another gas pipe, to the first compression unit ( 3 ). 
     
     
         27 . A ship for transporting cryogenic liquid, characterized in that the ship comprises a supply and reliquefaction system of  claim 17 . 
     
     
         28 . The ship of  claim 27 , characterized in that said ship is a methane carrier. 
     
     
         29 . A method for managing a gas stream arising from the evaporation of a cryogenic liquid, in which:
 said gas stream being compressed within a first compression unit before being sent either to an engine, or to reliquefaction means,   the gas fraction sent to the reliquefaction means passes through cooling means ( 10 ) and then expansion means ( 30 ) and finally through a separator ( 40 ) from which the liquid part is sent to a cryogenic liquid tank ( 1 ),   characterized in that the cooling means are means of mechanical refrigeration within which:   a gas stream is compressed in a second compression unit ( 11 ,  12 ,  13 ), and then cooled within a heat exchanger ( 17 ) before being expanded in such a way that a gas fraction reliquefies,   after its compression, the gas stream is separated into a first gas stream part and a second gas stream part,   the first part of the gas stream is cooled and then sent to the reliquefaction means so as to be at least partially liquefied, and   the second part of the stream of the gas is fed into a loop ( 18 ,  20 ,  21 ) in which said second gas stream part is expanded, and then is used to cool the first part of the gas stream before rejoining the gas stream so as to be compressed again in the second compression unit ( 11 ,  12 ,  13 ).   
     
     
         30 . The method of  claim 29 , characterized in that the gas arising from the evaporation is compressed without prior heat exchange with another gas pipe. 
     
     
         31 . The method of  claim 29 , characterized in that the unliquefied gas exiting the first expansion means ( 30 ) is conducted by a recycling line ( 35 ) upstream of the first compression unit ( 3 ). 
     
     
         32 . The method of  claim 31 , characterized in that the unliquefied gas exiting the first expansion means ( 30 ) passes through the heat exchanger ( 17 ) before being compressed again in the first compression unit ( 3 ).