KR20240008986A - Adsorption-storage and treatment system for Boil Off Gas of liquefied gas - Google Patents

Abstract

The present invention relates to a system for adsorption, storage and processing of boil-off gas of liquefied gas, which can safely and easily store the boil-off gas separately when excessive production of boil-off gas of liquefied gas occurs. A first transfer unit that transfers A heat exchange unit that cools the initial boil-off gas by exchanging heat with the cooling boil-off gas, the inlet end of which is connected to the outlet end of the low-temperature side of the heat exchange unit, and a secondary transfer that transfers the secondary boil-off gas, which is the boil-off gas cooled by the heat exchange unit. It includes a line, a secondary transfer unit that cools the secondary evaporation gas, and is connected to an outlet end of the secondary transfer unit in a branch structure, and at least some of the tertiary evaporation gas that is the evaporation gas cooled along the secondary transfer unit. A first adsorption storage tank that adsorbs and stores and a branched structure connected to the outlet end of the secondary transfer unit, and a tertiary transfer unit that supplies at least a portion of the tertiary evaporation gas to the high temperature part of the heat exchanger as the cooling evaporation gas. It is characterized by including.

Description

{Adsorption-storage and treatment system for Boil Off Gas of liquefied gas}

The present invention relates to a system for adsorption, storage and processing of boil-off gas of liquefied gas. More specifically, the present invention relates to a system for re-liquefying boil-off gas generated by vaporization of liquefied gas in a liquefied gas transport ship, which is a ship for transporting various liquefied gases, and further to This relates to a boil-off gas adsorption, storage and processing system for liquefied gas to separately store boil-off gas.

Liquefied gas, which is obtained by liquefying various gases in the gas phase, is widely used for various purposes such as power generation and fuel. An example of such liquefied gas is liquefied natural gas (LNG), and the demand for liquefied natural gas in various industrial and daily fields is rapidly increasing worldwide.

This type of liquefied natural gas is a colorless and transparent liquid obtained by liquefying natural gas containing methane as a main component by cooling it to about -163°C, and has a volume of about 1/600 of that of gaseous natural gas. Therefore, when natural gas is liquefied, its transportation and storage efficiency can be greatly improved.

However, the liquefaction temperature of natural gas is extremely low at -163°C at normal pressure, so the liquefied gas is sensitive to temperature changes and easily evaporates. For this reason, the storage tank that stores liquefied natural gas is insulated, but external heat is continuously transferred to the storage tank, so during the transportation of liquefied natural gas, liquefied natural gas is continuously naturally vaporized within the storage tank, producing boil-off gas (boil). -Off Gas, BOG) occurs. In addition, this phenomenon of evaporation gas generation easily occurs not only in liquefied natural gas, but also in other types of liquefied gases, such as liquefied air and liquefied hydrogen, which have extremely low liquefaction temperatures.

In addition, the above-described evaporation gas corresponds to a loss in transport efficiency, and its generation needs to be minimized.

Additionally, if evaporation gas accumulates in the storage tank, the pressure inside the tank may increase excessively, and in severe cases, there is a risk of tank damage. Therefore, various methods are being studied to treat boil-off gas generated within the storage tank. Recently, for the treatment of boil-off gas, a method of re-liquefying the boil-off gas and returning it to the storage tank, using the boil-off gas as fuel for ship engines, etc. Methods such as supplying to demand are being used.

As an example of such evaporative gas treatment technology, the preceding Korean Patent Publication No. 10-2017-0062227 discloses a fuel tank BOG treatment system for a gas-propelled ship. In addition, the prior literature discloses a design proposal for a fuel tank BOG processing system for a gas-propelled ship that can maximize the BOG cooling effect and treat it efficiently.

Meanwhile, the amount of BOG that can be operated is limited in various BOG processing/transfer equipment systems, such as reliquefaction facilities and BOG transfer facilities to engines, etc., so if excessive BOG is generated, it needs to be stored separately. However, the prior literature does not disclose any method for separately storing BOG, which may cause overload of the BOG processing/transportation system, and to prevent this overload, environmental pollution is prevented by discharging BOG into the atmosphere. Problems that may arise arise.

Korean Public Patent No. 10-2017-0062227

As part of solving the above-mentioned problems, the purpose of the present invention is to provide a system for adsorption, storage and processing of boil-off gas of liquefied gas that can safely and easily store the boil-off gas separately when the boil-off gas of liquefied gas is excessively generated. .

The liquefied gas boil-off gas adsorption, storage and processing system according to the present invention is a first transfer unit that transfers the initial boil-off gas of the liquefied gas generated from the liquefied gas storage tank, and the initial boil-off gas is supplied to the inlet end of the low temperature section, Cooling boil-off gas, which is a lower-temperature boil-off gas than the initial boil-off gas, is supplied to the inlet end of the high-temperature part, and a heat exchanger for cooling the initial boil-off gas by heat-exchanging the initial boil-off gas with the cooling boil-off gas, the inlet end. It is connected to the outlet end of the low-temperature side of the heat exchanger and includes a secondary transfer line for transferring secondary boil-off gas, which is the boil-off gas cooled by the heat exchange unit, a secondary transfer unit for cooling the secondary boil-off gas, and the secondary transfer unit. A first adsorption storage tank is connected to the outlet end of the branch structure and adsorbs and stores at least a portion of the tertiary boil-off gas, which is the cooled boil-off gas along the secondary transfer unit, and has a branch structure with the outlet end of the secondary transfer unit. It is characterized in that it includes a tertiary transfer unit that is connected and supplies at least a portion of the tertiary evaporation gas to the high temperature part of the heat exchanger as the cooling evaporation gas.

In addition, the secondary transfer unit is provided in series to alternate with a plurality of compressors provided along the secondary transfer line and each of the plurality of compressors to compress the secondary boil-off gas, and cools the secondary boil-off gas. It is characterized in that it includes a plurality of coolers.

In addition, the boil-off gas adsorption and storage and processing system of the liquefied gas has an inlet end connected to the outlet end of the high temperature part of the heat exchanger, and the fourth boil-off gas, which is the third boil-off gas, is heated through heat exchange with the initial boil-off gas. A fourth transfer part that transfers the fourth boil-off gas by adiabatically expanding it to cool and liquefy the fourth boil-off gas to increase the liquid specific gravity in the fourth boil-off gas, connected to the end of the fourth transfer part and the fourth boil-off gas It is characterized by comprising a first gas-liquid separator that separates the vapor-liquid gas and a second adsorption storage tank that adsorbs and stores at least a portion of the gaseous boil-off gas separated by the first gas-liquid separator.

In addition, the boil-off gas adsorption storage and processing system of the liquefied gas includes a second gas-liquid separator for gas-liquid separation of the fifth boil-off gas, which is a gas-liquid mixture discharged from the first gas-liquid separator or a boil-off gas having a gas phase, the second gas-liquid A reprocessing circulation unit that supplies the boil-off gas for reprocessing, which is the gaseous boil-off gas separated from the separator, to the inlet end of the low-temperature part of the heat exchanger, and the re-liquefied gas, which is the liquid-phase liquefied gas separated from the second gas-liquid separator, is supplied to the liquefied gas. It is characterized by comprising a liquefied gas supply unit supplied to the storage tank.

In addition, the secondary transfer unit may include an evaporative gas bypass unit that supplies at least a portion of the evaporative gas compressed and cooled by the plurality of compressors and the plurality of coolers as fuel for a marine engine.

According to the boil-off gas adsorption, storage and processing system for liquefied gas according to the present invention, the remaining amount of boil-off gas compressed to meet the requirements of consumers such as ship engines can be adsorbed and stored in a separate adsorption storage tank. In this way, as the above-mentioned separate evaporative gas storage means is provided, the excess evaporative gas does not need to continuously circulate within the system or be discharged to the outside air, preventing system overload and excess evaporative gas due to continuous circulation of the excess evaporative gas. This has the effect of minimizing environmental pollution caused by outdoor air emissions.

Figure 1 is a configuration diagram showing a system for adsorption, storage and processing of boil-off gas of liquefied gas according to the present invention.
FIG. 2 is a detailed configuration diagram showing the flow rate control unit shown in FIG. 1.
FIG. 3 is a flowchart showing an embodiment of the flow rate controller shown in FIG. 2.

Prior to the detailed description of the present invention, specific details for carrying out the present invention are included in the following embodiments and drawings, and the same reference numerals used throughout the specification refer to the same components.

Additionally, singular expressions in this specification will also include plural forms unless specifically stated in the phrase.

Hereinafter, the boil-off gas adsorption, storage and processing system for liquefied gas according to the present invention will be described with reference to the drawings.

Figure 1 is a configuration diagram showing a system for adsorption, storage and processing of boil-off gas of liquefied gas according to the present invention.

Referring to Figure 1, the boil-off gas adsorption storage and processing system 1000 of liquefied gas according to the present invention includes a first transfer unit 100, a heat exchange unit 200, a secondary transfer unit 300, and a first adsorption storage tank ( 400), a tertiary transfer unit 500, a reliquefaction processing unit 600, and a flow rate control unit 700.

The first transfer unit 100 is an initial boil-off gas (B1), which is a boil-off gas (BOG) generated by vaporizing the liquefied gas from the liquefied gas storage tank 10 in which the liquefied gas (LG) is stored. transport. Here, in addition to liquefied natural gas (LNG), the liquefied gas may be liquefied air, liquefied hydrogen, and various other liquefied gases not mentioned.

And, the heat exchange unit 200 may include a low temperature part 210 and a high temperature part 220.

More specifically, the inlet end of the low temperature unit 210 is connected to the outlet end of the first transfer unit 100 to receive the initial boil-off gas (B1). And, the cooling boil-off gas (B3), which is the boil-off gas that has undergone a separate cooling process, is supplied to the inlet end of the high temperature part 220. At this time, the flow directions of the boil-off gas in the low-temperature section 210 and the high-temperature section 220 may be opposite to each other.

In addition, the boil-off gas for cooling (B3) is composed of a relatively low temperature compared to the initial boil-off gas (B1), and the initial boil-off gas (B1) exchanges heat with the boil-off gas for cooling (B3) and is cooled. On the contrary, through the above-described heat exchange action, the temperature of the cooling boil-off gas (B3) is increased and transferred to another system through the outlet of the high temperature section 220.

In addition, the secondary transfer unit 300 includes a secondary transfer line 310, a compressor 320, a cooler 330, an evaporation gas bypass unit 340, a first branch control unit 351, and , may include a second branch control unit 352.

The secondary transfer line 310 has an inlet end connected to the outlet end of the low-temperature unit 210 of the heat exchange unit 200, and transfers the secondary boil-off gas (B2), which is the boil-off gas cooled by the heat exchange unit 200. .

In addition, the compressor 320 and the cooler 330 are alternately provided in series along the longitudinal direction of the secondary transfer line 310. Additionally, multiple compressors 320 and coolers 330 may be provided.

In addition, one end of the boil-off gas bypass unit 340 branches off from the secondary transfer line 310, and the end is connected to the demand source 20. In addition, the boil-off gas bypass unit 340 supplies the boil-off gas compressed and cooled by the compressor 320 and the cooler 330 to the demander 20.

Here, the demand source 20 may be an exhaust means. Also, preferably, the consumer 20 may be an engine that uses only boil-off gas as fuel, such as a ship's DFDE (Dual Fuel Diesel Electric) engine, or uses boil-off gas co-firing as fuel. Additionally, the demand source 20 may mean both an exhaust means and an engine, and an appropriate branch pipe structure, not shown, may be provided to supply evaporative gas to the exhaust means and the engine.

At this time, the evaporation gas bypass unit 340 is shown as branched between a plurality of compressors 320 and coolers 330, but this is only an example for explanation. For example, the evaporation gas bypass unit 340 may branch from another location of the secondary transfer line 310, or may branch from various locations such as the entrance or end of the secondary transfer line 310.

In addition, the first branch control unit 351, which is a type of branch valve, is provided in the secondary transfer line 310, and the boil-off gas bypass unit 340 is connected to the first branch control unit 351. A branch structure related to the evaporation gas bypass unit 340 described above may be provided.

In addition, the second branch control unit 352, which is a type of branch valve, is provided at the outlet end of the secondary transfer line 310.

And, the first adsorption storage tank 400 is connected to the second branch control unit 352 in a branch structure. In addition, the first adsorption storage tank 400 absorbs and stores at least a portion of the tertiary boil-off gas B3, which is the cooled boil-off gas along the secondary transfer unit 300.

At this time, the first adsorption storage tank 400 contains MOF (Metal Organic Framework)-based gas adsorption material, COF (Covalent Organic Framework)-based gas adsorption material, Zeolite 13X, HKUST-1, and various other gas adsorption materials not mentioned. The materials can be stored and used for evaporation gas adsorption. The boil-off gas adsorbed and stored in this way can be transferred to a boil-off gas treatment facility (not shown) provided on the ground.

In addition, the tertiary transfer unit 500 is connected in a branch structure from the second branch control unit 352, and at least part of the tertiary evaporation gas (B3) is used as the above-described cooling evaporation gas (B3) in the heat exchanger ( It is supplied to the high temperature part 220 of 200).

Here, the distribution amount of tertiary boil-off gas (B3) to each of the first adsorption storage tank 400 and the third transfer unit 500 is determined by the overall circulation amount of boil-off gas in the system, the remaining fuel amount of the engine, the pressure inside the system, and the temperature inside the system. , can be determined to various values in response to various other real-time variables not mentioned.

In addition, the reliquefaction processing unit 600 includes a fourth transfer unit 610, a first gas-liquid separator 620, a second adsorption storage tank 630, a second gas-liquid separator 640, and a reprocessing circulation unit. It may include (650) and a liquefied gas supply unit (660).

The inlet end of the 4th transfer unit 610 is connected to the outlet end of the high temperature part 220 of the heat exchange unit 200, and the 4th evaporation gas is the tertiary evaporation gas (B3) whose temperature is raised through heat exchange with the initial evaporation gas (B1). Transport gas (B4). In addition, the fourth transfer unit 610 may be provided with a first expansion valve (v1), and the first expansion valve (v1) adiabatically expands the fourth boil-off gas (B4) to form the fourth boil-off gas (B4). ) can be cooled and liquefied to increase the liquid specific gravity in the fourth boil-off gas (B4).

In addition, the first gas-liquid separator 620 is connected to the end of the fourth transfer unit 610 and separates the fourth boil-off gas (B4) into gas and liquid.

Here, at least a portion of the gaseous boil-off gas separated by the first gas-liquid separator 620 is stored in the second adsorption storage tank 630. Here, the second adsorption storage tank 630 is a means for storing boil-off gas by adsorption, like the first adsorption storage tank 400 described above.

In addition, the fifth boil-off gas (B5), which is a gas-liquid mixture or boil-off gas having a gas phase discharged from the first gas-liquid separator 620, is supplied to the second gas-liquid separator 640. At this time, a second expansion valve (v2) may be provided between the first gas-liquid separator 620 and the second gas-liquid separator 640, and the second expansion valve (v2) The specific gravity of the liquid in the 5th boil-off gas (B5) can be further increased by adiabatic expansion.

In addition, the boil-off gas for reprocessing (R), which is the gaseous boil-off gas separated from the second gas-liquid separator 640, passes through the reprocessing circulation unit 650 to the inlet end of the low-temperature unit 210 of the heat exchange unit 200. can be supplied.

At this time, the outlet side of the reprocessing circulation unit 650 is shown in FIG. 1 as being joined with the outlet side of the above-described first transfer unit 100, but this is only an example for explanation. As another example, the outlet side of the reprocessing circulation unit 650 may be directly connected to the inlet side of the low temperature unit 210 of the heat exchange unit 200 without passing through the first transfer unit 100.

And, the liquefied gas supply unit 660 supplies re-liquefied gas (L), which is a liquid liquefied gas separated from the second gas-liquid separator 640, to the liquefied gas storage tank 10. Here, some of the liquefied gas stored in the liquefied gas storage tank 10 is supplied to the demand source 30, such as a ME-GI (Main engine electronic control gas injection) engine, through the liquefied gas bypass unit 11, It can be used as fuel for engines.

Next, FIG. 2 is a detailed configuration diagram showing the flow rate control unit shown in FIG. 1. And, FIG. 3 is a flowchart showing an embodiment of the flow rate control unit shown in FIG. 2.

Referring further to FIGS. 2 and 3 , the flow rate control unit 700 may include a flow rate detection unit 710, a comparison calculation unit 720, and a distribution instruction unit 730. Additionally, in one embodiment of the flow rate control unit 700, a detection step (S100), a comparison step (S200), a tank capacity confirmation step (S300), and a distribution step (S400) may be performed.

First, the flow sensor 710 can perform the detection step (S100) by sensing the measurement amount, which is the amount of evaporation gas circulating throughout the system, in real time. At this time, preferably, the flow sensor 710 may be provided in the secondary transfer line 310, which is the section where the largest flow rate moves within the system. In addition, more preferably, the flow rate detection unit 710 may be provided between the outlet end of the low temperature unit 210 of the heat exchange unit 200 and the first branch control unit 351 in the secondary transfer line 310. .

In addition, the measured amount may also take into account the amount of evaporative gas scheduled to be branched and supplied to the evaporative gas bypass unit 340.

Next, the comparison calculation unit 720 may perform the comparison step (S200) by comparing the measured amount with a reference amount, which is a preset amount of evaporation gas, in real time. Here, the standard amount is a various value in response to the maximum amount of boil-off gas that can be operated in the entire system, the real-time storage amount of liquefied gas, the demand for liquefied gas-based co-fired fuel required by consumers (20, 30) such as various engines, and various other factors. It can be set variably.

At this time, when the measured amount is greater than or equal to the reference amount, the distribution indicator 730 calculates a storage demand amount, which is the amount of surplus boil-off gas corresponding to the difference between the measured amount and the reference amount. In addition, the tank capacity confirmation step (S300) can be performed by the distribution indicator 730 confirming the storable capacity, which is the amount of boil-off gas that can be additionally stored in each adsorption storage tank 400, 630.

Next, the distribution instruction unit 730 performs the distribution step (S400) to store boil-off gas in at least one adsorption storage tank (400, 630) in response to the storage demand. At this time, the amount of boil-off gas stored in each adsorption storage tank (400, 630) may be the storage demand divided by the relative ratio of each storage capacity. Here, the above-described distribution step (S400) can be performed by the distribution instruction unit 730 adjusting the opening related to flow rate distribution of the above-described second branch control unit 352.

As described above, the main technical idea of the present invention is to provide a system for adsorption, storage and processing of boil-off gas of liquefied gas, and the embodiment described above with reference to the drawings is only one embodiment and the right of the present invention is The scope will extend not only to the scope of the patent claims, but also to various equivalent embodiments that may exist.

10: Liquefied gas storage tank
11: Liquefied gas bypass unit
20, 30: Source of demand
1000: Evaporation gas adsorption, storage and processing system of liquefied gas according to the present invention
100: first transfer unit
200: heat exchange unit
210: low temperature section
220: high temperature part
300: Secondary transfer unit
310: Secondary transfer line
320: Compressor
330: cooler
340: Evaporative gas bypass unit
351: first branch control unit
352: second branch control unit
400: First adsorption storage tank
500: 3rd transfer unit
600: Reliquefaction processing unit
610: 4th transfer unit
620: First gas-liquid separator
630: Second adsorption storage tank
640: Second gas-liquid separator
650: Reprocessing circulation unit
660: Liquefied gas supply department
700: Flow control unit
710: Flow detection unit
720: Comparison calculation unit
730: Distribution instruction unit

Claims (5)

A first transfer unit that transfers the initial boil-off gas of the liquefied gas generated from the liquefied gas storage tank;
The initial boil-off gas is supplied to the inlet end of the low-temperature side, and the boil-off gas for cooling, which is a boil-off gas of a lower temperature than the initial boil-off gas, is supplied to the inlet end of the high-temperature side, and the initial boil-off gas is exchanged with the boil-off gas for cooling. a heat exchanger that cools the initial evaporation gas;
A secondary transfer unit having an inlet end connected to an outlet end of the low-temperature side of the heat exchange unit and including a secondary transfer line for transferring secondary boil-off gas, which is the boil-off gas cooled by the heat exchange unit, and cooling the secondary boil-off gas;
a first adsorption storage tank connected to the outlet end of the secondary transfer unit in a branched structure, and adsorbing and storing at least a portion of the tertiary boil-off gas, which is cooled boil-off gas along the secondary transfer unit; and
A tertiary transfer unit connected to the outlet end of the secondary transfer unit in a branched structure and supplying at least a portion of the tertiary boil-off gas to the high temperature part of the heat exchange unit as the cooling boil-off gas. Evaporative gas adsorption storage and processing system.

According to claim 1,
The secondary transfer unit,
a plurality of compressors provided along the secondary transfer line to compress the secondary boil-off gas; and
A boil-off gas adsorption storage and processing system for liquefied gas, comprising a plurality of coolers that are arranged in series to alternate with each of the plurality of compressors and cool the secondary boil-off gas.
According to claim 1,
The boil-off gas adsorption, storage and processing system of the liquefied gas is,
The inlet end is connected to the outlet end of the high temperature part of the heat exchange unit, and the fourth boil-off gas, which is the third boil-off gas whose temperature is raised through heat exchange with the initial boil-off gas, is transferred, and the fourth boil-off gas is adiabatically expanded to the fourth boil-off gas. A fourth transfer unit that cools and liquefies the primary boil-off gas to increase the liquid specific gravity in the fourth boil-off gas;
a first gas-liquid separator connected to an end of the fourth transfer unit and separating gas and liquid from the fourth boil-off gas; and
A boil-off gas adsorption storage and processing system for liquefied gas, comprising a second adsorption storage tank for adsorbing and storing at least a portion of the gaseous boil-off gas separated by the first gas-liquid separator.
According to claim 3,
The boil-off gas adsorption, storage and processing system of the liquefied gas is,
a second gas-liquid separator that separates the fifth boil-off gas, which is a gas-liquid mixture discharged from the first gas-liquid separator or a boil-off gas having a gas phase;
a reprocessing circulation unit that supplies boil-off gas for reprocessing, which is gaseous boil-off gas separated from the second gas-liquid separator, to the inlet end of the low-temperature section of the heat exchanger; and
A liquefied gas evaporation gas adsorption, storage and processing system comprising a liquefied gas supply unit that supplies re-liquefied gas, which is a liquid liquefied gas separated from the second gas-liquid separator, to the liquefied gas storage tank.
According to claim 2,
The secondary transfer unit,
A boil-off gas adsorption storage and processing system for liquefied gas, comprising a boil-off gas bypass unit that supplies at least a portion of the boil-off gas compressed and cooled by the plurality of compressors and the plurality of coolers as fuel for a marine engine.