DEVICE AND METHOD FOR PROCESSING BOIL-OFF GAS IN LIQUEFIED GAS REGASIFICATION SYSTEM
A device for processing boil-off gas in a liquefied gas regasification system includes a fuel compressor for compressing boil-off gas at a pressured required by a fuel consumer; a high-pressure compressor installed at the rear end of the fuel compressor in series with the fuel compressor so as to compress the low-pressure boil-off gas, which has been compressed by the fuel compressor, at a pressure required by a regasified gas consumer; a low-temperature heat exchanger for cooling the high-pressure boil-off gas compressed by the high-pressure compressor; a pressure-reducing device for reducing the pressure of the high-pressure boil-off gas, which has been cooled by the low-temperature heat exchanger, to the inner pressure of a liquefied gas storage tank for storing the liquefied gas; and a liquefied gas drum for separating flash gas generated by the pressure-reducing device in the pressure-reducing process.
1 . A device for processing boil-off gas in a liquefied gas regasification system, the device comprising:
a fuel compressor compressing boil-off gas to a pressure required for a fuel demand site;
a high-pressure compressor disposed in series with the fuel compressor downstream of the fuel compressor and compressing the low-pressure boil-off gas compressed by the fuel compressor to a pressure required for a regasified gas demand site;
a low-temperature heat exchanger cooling the high-pressure boil-off gas compressed by the high-pressure compressor;
a decompression unit decompressing the high-pressure boil-off gas cooled by the low-temperature heat exchanger to an internal pressure of a liquefied gas storage tank; and
a liquefied gas drum separating flash gas generated during decompression by the decompression unit,
wherein reliquefied boil-off gas separated by the liquefied gas drum is returned to the liquefied gas storage tank.
2 . The device according to claim 1 , further comprising:
an expander expanding and cooling some of the high-pressure boil-off gas to be supplied to the low-temperature heat exchanger,
wherein the low-temperature heat exchanger cools the high-pressure boil-off gas through heat exchange with the boil-off gas expanded and cooled by the expander.
3 . The device according to claim 2 , further comprising:
a high-temperature heat exchanger precooling the high-pressure boil-off gas to be supplied to the low-temperature heat exchanger to an inlet temperature of the expander,
wherein some of the high-pressure boil-off gas to be supplied to the low-temperature heat exchanger from the high-temperature heat exchanger is sent to the expander.
4 . The device according to claim 3 , wherein the high-temperature heat exchanger cools the high-pressure boil-off gas to be supplied to the low-temperature heat exchanger and the expander through heat exchange with the expanded boil-off gas heated through heat exchange in the low-temperature heat exchanger and discharged from the low-temperature heat exchanger.
5 . The device according to claim 3 , further comprising:
a gas compressor compressing the expanded boil-off gas subjected to heat exchange in the low-temperature heat exchanger and discharged from the low-temperature heat exchanger to a pressure of a flow of the boil-off gas compressed by the fuel compressor,
wherein the boil-off gas compressed by the gas compressor is joined with the flow of the boil-off gas compressed by the fuel compressor.
6 . The device according to claim 5 , wherein the gas compressor is connected to the expander via a common shaft.
7 . The device according to claim 5 , further comprising:
a gas cooler regulating a temperature of the boil-off gas compressed and heated by the gas compressor.
8 . The device according to claim 3 , wherein the flash gas separated by the liquefied gas drum is joined with a flow of the expanded boil-off gas to be supplied to the low-temperature heat exchanger.
9 . A method for processing boil-off gas in a liquefied gas regasification system, comprising:
compressing boil-off gas to a low pressure required for a fuel demand site,
compressing the low-pressure boil-off gas to a high pressure required for a regasified gas demand site,
cooling the high-pressure boil-off gas,
decompressing the cooled high-pressure boil-off gas to an internal pressure of a liquefied gas storage tank; and
separating flash gas generated during decompression of the cooled high-pressure boil-off gas and returning reliquefied boil-off gas to the liquefied gas storage tank.
10 . The method according to claim 9 , wherein cooling the high-pressure boil-off gas comprises:
expanding and cooling some of the high-pressure boil-off gas before cooling the high-pressure boil-off gas; and
liquefying at least part of the high-pressure boil-off gas through heat exchange between the expanded and cooled boil-off gas and the high-pressure boil-off gas.
11 . The method according to claim 10 , further comprising:
precooling the high-pressure boil-off gas through heat exchange with the expanded boil-off gas heated while cooling the high-pressure boil-off gas, before performing heat exchange between the expanded and cooled boil-off gas and the high-pressure boil-off gas.
12 . The method according to claim 11 , wherein precooling the high-pressure boil-off gas comprises:
cooling the high-pressure boil-off gas to an inlet temperature of an expander expanding the high-pressure boil-off gas.
13 . The method according to claim 11 , wherein the expanded boil-off gas heated while cooling the high-pressure boil-off gas is compressed to a pressure of a flow of boil-off gas to be compressed by a fuel compressor before being joined with the flow of the boil-off gas.
14 . The method according to claim 13 , wherein expansion work in expanding the high-pressure boil-off gas is recovered as compression work in compressing the expanded boil-off gas.
15 . The method according to claim 11 , wherein the separated flash gas is joined with a flow of the expanded boil-off gas exchanging heat with the high-pressure boil-off gas.