Boil-off gas reliquefaction system

Abstract

Disclosed is a BOG reliquefaction system. The BOG reliquefaction system includes: a compressor compressing BOG; a heat exchanger cooling the BOG compressed by the compressor through heat exchange using BOG not compressed by the compressor as a refrigerant; a pressure reducer disposed downstream of the heat exchanger and reducing a pressure of fluid cooled by the heat exchanger; and a second oil filter disposed downstream of the pressure reducer, wherein the compressor includes at least one oil-lubrication type cylinder and the second oil filter is a cryogenic oil filter.

1 . A boil-off gas (BOG) reliquefaction system comprising:
 a compressor compressing BOG;   a heat exchanger cooling the BOG compressed by the compressor through heat exchange using the BOG not compressed by the compressor as a refrigerant;   a pressure reducer disposed downstream of the heat exchanger and reducing a pressure of fluid cooled by the heat exchanger; and   a second oil filter disposed downstream of the pressure reducer,   wherein the compressor comprises at least one oil-lubrication type cylinder and the second oil filter is a cryogenic oil filter.   
     
     
         2 . The BOG reliquefaction system according to  claim 1 , further comprising:
 a gas/liquid separator disposed downstream of the pressure reducer and separating the BOG into liquefied gas generated through reliquefaction and gaseous BOG;   wherein the second oil filter is disposed on a fifth supply line through which the liquefied gas separated by the gas/liquid separator is discharged.   
     
     
         3 . The BOG reliquefaction system according to  claim 1 , further comprising:
 a gas/liquid separator disposed downstream of the pressure reducer and separating the BOG into liquefied gas generated through reliquefaction and gaseous BOG;   wherein the second oil filter is disposed on a sixth supply line through which the gaseous BOG separated by the gas/liquid separator is discharged.   
     
     
         4 . The BOG reliquefaction system according to  claim 1 , wherein the second oil filter separates lubricant oil having a solid phase. 
     
     
         5 . The BOG reliquefaction system according to  claim 1 , further comprising:
 a gas/liquid separator disposed downstream of the pressure reducer and separating the BOG into liquefied gas generated by reliquefaction and gaseous BOG,   wherein the second oil filter is disposed between the pressure reducer and the gas/liquid separator.   
     
     
         6 . The BOG reliquefaction system according to  claim 1 , wherein the second oil filter is an upward discharge type. 
     
     
         7 - 17 . (canceled) 
     
     
         18 . The BOG reliquefaction system according to  claim 3 , wherein the second oil filter is an upward discharge type. 
     
     
         19 . The BOG reliquefaction system according to  claim 5 , wherein the second oil filter is an upward discharge type. 
     
     
         20 . The BOG reliquefaction system according to  claim 2 , wherein the second oil filter is a downward discharge type. 
     
     
         21 . The BOG reliquefaction system according to  claim 2 , wherein the liquefied gas separated by the gas/liquid separator and discharged along the fifth supply line is sent to a storage tank. 
     
     
         22 . The BOG reliquefaction system according to  claim 21 , wherein the second oil filter is a downward discharge type. 
     
     
         23 . The BOG reliquefaction system according to  claim 1 , wherein the compressor compresses the BOG to a pressure of 150 bar to 350 bar. 
     
     
         24 . The BOG reliquefaction system according to  claim 1 , wherein the compressor compresses the BOG to a pressure of 80 bar to 250 bar. 
     
     
         25 . The BOG reliquefaction system according to  claim 1 , wherein the heat exchanger comprises a micro-channel type fluid channel. 
     
     
         26 . The BOG reliquefaction system according to  claim 25 , wherein the heat exchanger is a printed circuit heat exchanger (PCHE). 
     
     
         27 . The BOG reliquefaction system according to  claim 1 , further comprising:
 a bypass line through which the BOG is supplied to the compressor after bypassing the heat exchanger.   
     
     
         28 . The BOG reliquefaction system according to  claim 27 , further comprising:
 a first valve disposed upstream of a cold fluid channel of the heat exchanger and regulating a flow rate of fluid and opening/closing of a corresponding supply line,   wherein the bypass line is branched from the corresponding supply line upstream of the first valve.   
     
     
         29 . The BOG reliquefaction system according to  claim 27 , further comprising:
 a second valve disposed downstream of a cold fluid channel of the heat exchanger and regulating a flow rate of fluid and opening/closing of a corresponding supply line,   wherein the bypass line is joined to the corresponding supply line downstream of the second valve.   
     
     
         30 . The BOG reliquefaction system according to  claim 1 , further comprising:
 a first oil filter disposed downstream of the compressor and separating lubricant oil from the BOG.   
     
     
         31 . The BOG reliquefaction system according to  claim 30 , wherein the first oil filter separates lubricant oil having a vapor phase or mist phase.