US 11,724,781 B2
Boil-off gas reliquefaction system and method for discharging lubricanting oil in boil-off gas reliquefaction system
Joon Chae Lee, Seoul (KR); Dong Kyu Choi, Seongnam-si (KR); and Hyun Jun Shin, Seoul (KR)
Assigned to DAEWOO SHIPBUILDING & MARINE ENGINEERING CO., LTD., Geoje-si (KR)
Appl. No. 16/635,962
Filed by DAEWOO SHIPBUILDING & MARINE ENGINEERING CO., LTD., Geoje-si (KR)
PCT Filed Aug. 3, 2017, PCT No. PCT/KR2017/008374
§ 371(c)(1), (2) Date Jan. 31, 2020,
PCT Pub. No. WO2019/027065, PCT Pub. Date Feb. 7, 2019.
Claims priority of application No. 10-2017-0097316 (KR), filed on Jul. 31, 2017.
Prior Publication US 2020/0239109 A1, Jul. 30, 2020
Int. Cl. F17C 9/00 (2006.01); B63B 25/16 (2006.01); F17C 9/02 (2006.01); B63H 21/38 (2006.01); F17C 6/00 (2006.01)
CPC B63B 25/16 (2013.01) [F17C 9/02 (2013.01); B63H 21/38 (2013.01); F17C 6/00 (2013.01); F17C 2227/0339 (2013.01); F17C 2265/017 (2013.01); F17C 2265/031 (2013.01); F17C 2265/033 (2013.01); F17C 2265/038 (2013.01)] 11 Claims
OG exemplary drawing
 
1. A boil-off gas (BOG) reliquefaction system comprising:
a compressor configured to compress BOG;
a heat exchanger configured to cool the BOG compressed by the compressor through heat exchange using BOG not compressed by the compressor as a refrigerant;
a bypass line configured to supply BOG to the compressor bypassing the heat exchanger;
a pressure reducer disposed downstream of the heat exchanger and configured to reduce a pressure of fluid cooled by the heat exchanger; and
at least one of a combination of a first temperature sensor disposed upstream of a cold fluid channel of the heat exchanger and a fourth temperature sensor disposed downstream of a hot fluid channel of the heat exchanger, a combination of a second temperature sensor disposed downstream of the cold fluid channel of the heat exchanger and a third temperature sensor disposed upstream of the hot fluid channel of the heat exchanger, and a combination of a first pressure sensor disposed upstream of the hot fluid channel of the heat exchanger and a second pressure sensor disposed downstream of the hot fluid channel of the heat exchanger,
wherein the compressor comprises at least one oil-lubrication cylinder,
wherein the heat exchanger comprises a micro-channel fluid channel,
wherein the BOG reliquefaction system further comprises:
a controller configured to:
determine whether the heat exchanger is clogged by lubricant oil based on a detection result obtained by at least one of the first temperature sensor, the second temperature sensor, the third temperature sensor, the fourth temperature sensor, the first pressure sensor, and the second pressure sensor, and
responsive to determining that it is time to discharge condensed or solidified lubricant oil, supply the BOG to the compressor by bypassing the heat exchanger through the bypass line, wherein when the heat exchanger is bypassed through the bypass line, the BOG is not supplied to a cold fluid channel of the heat exchanger, wherein the reliquefaction system is configured so that the BOG compressed by the compressor is supplied to the hot fluid channel of the heat exchanger, thereby increasing a temperature of the hot fluid channel of the heat exchanger, while the heat exchanger is bypassed through the bypass line.