# US 10,767,921 B2 · Liquefied gas treatment system

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- Number: US 10,767,921 B2
- Document ID: US10767921B2
- Status: Granted
- Kind: B2
- Application number: 15/191,486
- Filed: 2016-06-23
- Published: 2016-10-20
- Granted: 2020-09-08
- Earliest claimed: 2013-05-30
- Assignees: Hyundai Heavy Industries Co., Ltd.
- Applicants: Hyundai Heavy Industries Co., Ltd.
- Inventors: Eun Sung Baek
- Web page: https://patentgrep.com/patent/US10767921B2

## CPC

- F25J 1/023: {for the combustion as fuels, i.e. integration with the fuel gas system}
- F17C 7/04: with change of state, e.g. vaporisation
- F17C 9/02: with change of state, e.g. vaporisation
- F25J 1/0025: {Boil-off gases "BOG" from storages}
- F25J 1/0035: {by gas expansion with extraction of work}
- F25J 1/004: {by flash gas recovery (F25J1/0267 takes precedence)}
- F25J 1/0045: {by vaporising a liquid return stream}
- F25J 1/0202: {in a quasi-closed internal refrigeration loop (F25J1/0208, F25J1/0219, F25J1/0224 take precedence)}
- F25J 1/0254: {controlling particular process parameter, e.g. pressure, temperature}
- F25J 1/0298: {Safety aspects and control of the refrigerant compression system, e.g. anti-surge control}
- F02M 21/0221: {Fuel storage reservoirs, e.g. cryogenic tanks}
- F17C 2201/0157: Polygonal
- F17C 2201/052: large (>1000 m3)
- F17C 2203/0391: by vacuum
- F17C 2203/0629: Two walls
- F17C 2203/0639: Steels
- F17C 2221/033: Methane, e.g. natural gas, CNG, LNG, GNL, GNC, PLNG
- F17C 2223/0161: cryogenic, e.g. LNG, GNL, PLNG
- F17C 2223/033: Small pressure, e.g. for liquefied gas
- F17C 2223/035: High pressure (>10 bar)
- F17C 2223/043: in the gas
- F17C 2225/0123: gaseous, e.g. CNG, GNC
- F17C 2225/033: Small pressure, e.g. for liquefied gas
- F17C 2225/035: High pressure, i.e. between 10 and 80 bars
- F17C 2227/0164: with specified compressor type, e.g. piston or impulsive type
- F17C 2227/0306: using the same fluid
- F17C 2227/0309: using another fluid
- F17C 2227/036: "Joule-Thompson" effect
- F17C 2250/0443: Flow or movement of content
- F17C 2265/036: with heating
- F17C 2265/037: with pressurising
- F17C 2265/066: for feeding engines for propulsion
- F17C 2270/0105: Ships
- F25J 2240/02: Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
- F25J 2240/40: Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
- F25J 2290/62: Details of storing a fluid in a tank
- Y02T 10/30: Use of alternative fuels, e.g. biofuels
- F25J: LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS {OR LIQUEFIED GASEOUS} MIXTURES BY PRESSURE AND COLD TREATMENT {OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE (cryogenic pumps F04B37/08; gas storage vessels, gas holders F17; filing vessels with, or discharging from vessels, compressed, liquefied or solidified gases F17C; refrigeration machines, plants, or systems F25B)}
- F17C: VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES (storing fluids in natural or artificial cavities or chambers in the earth B65G5/00; construction or assembling of bulk storage containers employing civil-engineering techniques E04H7/00; variable-capacity gas-holders F17B; liquefaction or refrigeration machines, plants, or systems F25)
- F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A liquefied gas treatment system according to an embodiment of the present invention includes a boil-off gas heat exchanger exchanging heat between boil-off gas, pressurized by a boil-off gas compressor and recovered along a boil-off gas supply line branching off upstream of a liquefied gas-consuming unit, and the boil-off gas supplied from a liquefied gas storage tank, wherein the boil-off gas heat exchanger cools the boil-off gas, recovered along the boil-off gas supply line, with the boil-off gas, supplied from the liquefied gas storage tank, or flash gas, supplied through a vapor recovery line.

## Claims

### Claim 1

A liquefied gas treatment system, comprising:
a boil-off gas supply line connected from a liquefied gas storage tank to a liquefied gas-consuming unit;
a boil-off gas compressor provided on the boil-off gas supply line and pressurizing boil-off gas generated from the liquefied gas storage tank;
a boil-off gas heat exchanger provided upstream of the boil-off gas compressor on the boil-off gas supply line and exchanging heat between the boil-off gas, pressurized by the boil-off gas compressor and recovered along the boil-off gas supply line branching off upstream of the liquefied gas-consuming unit, and the boil-off gas supplied from the liquefied gas storage tank;
a boil-off gas decompressor provided downstream of the boil-off gas heat exchanger on a flow of the boil-off gas, recovered along the boil-off gas supply line, and decompressing the boil-off gas pressurized by the boil-off gas compressor;
a vapor-liquid separator separating flash gas from the boil-off gas decompressed by the boil-off gas decompressor;
a vapor recovery line connected from the vapor-liquid separator to the boil-off gas heat exchanger and supplying the flash gas to the boil-off gas heat exchanger;
a flash gas recovery line extending the vapor recovery line from the boil-off gas heat exchanger to a mixer;
the mixer provided upstream of the boil-off gas heat exchanger on the boil-off gas supply line, configured to mix the boil-off gas, supplied from the liquefied gas storage tank, with the flash gas, heat-exchanged by the boil-off gas heat exchanger, and supplying mixed gases to the boil-off gas heat exchanger;
a first valve positioned between the boil-off gas heat exchanger and the mixer and configured to control flow of the flash gas supplied to the boil-off gas compressor by exhausting the flash gas to an outside of the liquefied gas treatment system;
a flash gas bypass line branching off from the vapor recovery line and connected to a position between the first valve and the boil-off gas heat exchanger; and
a second valve configured to control flow of the flash gas supplied to the position between the first valve and the boil-off gas heat exchanger through the flash gas bypass line.

### Claim 2 (depends on 1)

The liquefied gas treatment system of claim 1, wherein the first valve is a three-way valve configured to discharge the flash gas to an outside of the liquefied gas treatment system.

### Claim 3 (depends on 1)

The liquefied gas treatment system of claim 1, wherein the second valve is a three-way valve provided between the vapor-liquid separator and the heat exchanger on the vapor recovery line.

### Claim 4 (depends on 1)

The liquefied gas treatment system of claim 1, wherein the boil-off gas, heat-exchanged by the boil-off gas heat exchanger, is supplied to the boil-off gas decompressor or the boil-off gas compressor.

### Claim 5 (depends on 1)

The liquefied gas treatment system of claim 1, wherein the flash gas, heat-exchanged by the boil-off gas heat exchanger, is supplied to and combusted in a gas combustion unit combusting fuel.

### Claim 6 (depends on 1)

The liquefied gas treatment system of claim 1, further comprising a liquid recovery line connected from the vapor-liquid separator to the liquefied gas storage tank and recovering the boil-off gas in liquid state, separated by the vapor-liquid separator, to the liquefied gas storage tank.

### Claim 7 (depends on 1)

The liquefied gas treatment system of claim 1, wherein the boil-off gas decompressor is a Joule-Thomson valve.

### Claim 8 (depends on 1)

The liquefied gas treatment system of claim 1, wherein the boil-off gas compressor comprises a plurality of boil-off gas compressors.

### Claim 9 (depends on 1)

The liquefied gas treatment system of claim 1, further comprising a boil-off gas cooler associated with the boil-off gas compressor.

### Claim 10 (depends on 8)

The liquefied gas treatment system of claim 8, further comprising at least one boil-off gas cooler provided between the plurality of boil-off gas compressors.

### Claim 11 (depends on 1)

The liquefied gas treatment system of claim 1, further comprising a third valve provided at a position where the boil-off gas supply line branches off to the boil-off gas heat exchanger.

### Claim 12 (depends on 1)

The liquefied gas treatment system of claim 1, wherein the vapor recovery line connected from the vapor-liquid separator to the boil-off gas heat changer is connected through the boil-off gas heat exchanger to the flash gas recovery line connecting the boil-off gas heat exchanger to the mixer provided upstream of the boil-off gas heat exchanger.

### Claim 13 (depends on 1)

The liquefied gas treatment system of claim 1, wherein the liquefied gas-consuming unit comprises a dual fuel engine to which boil-off gas or oil is selectively supplied without mixing the boil off gas and oil with each other.