KR20220099292A - Heterogeneous Liquefied Gas Storage Tank - Google Patents

Abstract

The present invention relates to a heterogeneous liquefied gas storage tank. The present invention relates to the liquefied gas storage tank having a tank-in-tank structure storing different types of cryogenic fluids. The heterogeneous liquefied gas storage tank according to the present embodiment comprises: an LNG storage tank for storing a liquefied natural gas; and a liquefied hydrogen storage tank installed inside the LNG storage tank and storing liquefied hydrogen.

Description

Heterogeneous Liquefied Gas Storage Tank}

The present invention relates to a liquefied gas storage tank having a tank-in-tank structure for storing different types of cryogenic fluids.

The International Maritime Organization (IMO), the European Union and the United States will significantly strengthen regulations on air pollutants emitted from ships. As international ship emission regulations are strengthened, countries around the world are focusing on developing eco-friendly low-carbon fuels and ships using the fuels. Accordingly, the share of zero-emission fuels and technologies for ships is expected to rapidly increase.

Until recently, natural gas has been considered the most promising as an eco-friendly fuel to replace the existing fossil fuel. In fact, more than 423 vessels fueled by natural gas are in operation as of September 2018, contributing greatly to reducing SO _x and NO _x emissions (SO _x 92% reduction compared to HFO, NO _x 80% reduction).

LNG (Liquefied Natural Gas) is obtained by cooling natural gas to a cryogenic temperature of about -163°C under normal pressure, and its volume is reduced to about 1/600 compared to that of natural gas in gaseous state, so it can be used as fuel for natural gas fueled ships. An LNG storage tank for storing natural gas in a cryogenic liquid state is provided.

The LNG storage tank is classified into an independent type tank and a membrane type tank depending on whether the insulation for storing LNG in a cryogenic state acts directly or indirectly on the load of the cargo.

Representative independent tanks are divided into MOSS type and SPB type, and membrane type tanks are divided into GTT NO 96, Mark Ⅲ and CSI.

In general, a free-standing tank is made by attaching a relatively rigid insulating panel such as polyurethane to a tank body made of an aluminum alloy, and is placed on a plurality of tank supports arranged on the inner bottom of the hull.

The membrane-type GTT NO 96 cargo hold includes a primary insulation box made of a plywood box and perlite, etc., arranged on the LNG side, and a secondary insulation box arranged on the inner wall side of the hull. A primary sealing wall (primary membrane) and a secondary sealing wall (secondary membrane) made of Invar steel (Invar 36% Ni) are installed above each of the primary insulation box and the secondary insulation box.

As such, the LNG storage tank has a thermal insulation structure so that cryogenic LNG maintains a liquid phase.

As the greenhouse gas emission regulations for ships will be strengthened in stages at each major point by 2050, it is expected that it will be difficult to comply with the regulations only with the existing engines and fuels.

Even in the case of LNG fuel, which has been verified as an alternative for reducing greenhouse gas emissions and is currently being applied as a real ship, it is the same as it is difficult to satisfy the stricter regulatory conditions in the future.

In particular, LNG fuel is only 15 to 25% effective in reducing carbon dioxide emissions compared to HFO, so it has a limitation in reducing carbon dioxide. . In addition, by 2050, the reduction of exhaust gas through LNG will not be effective in terms of the total amount due to the increase in vessel operation due to the increase in trade, and other adverse effects on atmospheric leakage of unburned methane gas such as engine methane slip will be reduced. There is also the prospect of offsetting it.

Even if the existing fossil fuels are converted to eco-friendly fuels such as LNG in the short to medium term, more future-oriented alternatives are needed in the long term, and it is very urgent to find alternative fuels that can satisfy the regulations to be strengthened in the future.

As an alternative to next-generation marine fuels, hydrogen, a zero-emission fuel, is in the spotlight. Hydrogen is clean and infinite, and it is the clean energy of the future that has about three times the amount of energy of gasoline based on the same weight. When hydrogen is used as a fuel, it is attracting attention because there is no emission of pollutants. The share of hydrogen as a fuel for ships is also expected to rise.

Hydrogen can be stored in any form of gas or liquid, but in the use of large-scale hydrogen, liquid hydrogen is recognized as advantageous because of its relatively high energy density and transport efficiency in terms of storage and transport. However, liquid hydrogen is an ultra-low temperature fluid with a boiling point of about -253°C, and its specific gravity is about 1/6 of that of LNG (Liquefied Natural Gas), so the BOR (Boil-Off Rate) per volume is about 10 times that of LNG. so high

For this reason, in storing and transporting liquid hydrogen, a large amount of flash gas is generated even during loading and unloading of liquid hydrogen. -Off Gas), which reduces the transport efficiency of liquid hydrogen. BOG generated in the liquid hydrogen storage tank is affected by energy transfer due to heat leakage of the liquid hydrogen storage tank itself and the shaking of the vessel, so that the fluid as a whole moves and a phase change occurs by this kinetic energy. fundamentally difficult to solve.

In addition, since it is expensive to manufacture a storage tank for storing cryogenic liquefied gas and a heat insulating material is provided, it is costly and spatially constrained to provide a storage tank for storing LNG and liquefied hydrogen on a ship, respectively.

Accordingly, the present invention is to solve the above problems, and to provide a heterogeneous liquefied gas storage tank of a tank-in-tank structure that can effectively store different types of cryogenic liquefied gas such as LNG and liquefied hydrogen.

According to one aspect of the present invention for achieving the above object, an LNG storage tank for storing liquefied natural gas; and a liquefied hydrogen storage tank installed inside the LNG storage tank and storing liquefied hydrogen.

Preferably, it is provided in the liquefied hydrogen storage tank and a heat insulating part designed to withstand the temperature difference between the temperature of the liquefied natural gas and the liquefied hydrogen; may further include.

Preferably, at least one support member connecting the outer wall of the liquid hydrogen storage tank and the inner wall of the LNG storage tank and fixing the liquid hydrogen storage tank inside the LNG storage tank; may further include.

Preferably, an LNG supply pump for discharging the LNG stored in the LNG storage tank to the outside of the LNG storage tank; and a liquid hydrogen supply pump for discharging the liquid hydrogen stored in the liquid hydrogen storage tank to the outside of the liquid hydrogen storage tank.

Preferably, it may further include an LNG dome providing a path through which a pipe connected to the LNG supply pump passes through the outside of the LNG storage tank.

Preferably, a liquid hydrogen dome providing a path through which a pipe connected to the liquid hydrogen supply pump passes through the outside of the LNG storage tank; may further include.

The heterogeneous liquefied gas storage tank according to the present invention, by providing a liquefied hydrogen storage tank inside the liquefied natural gas storage tank, can easily maintain the heterogeneous liquefied gas at a cryogenic temperature, and can effectively suppress the temperature rise, so that the liquefied gas can be stored at high density.

In addition, since the liquefied natural gas is blocked by the cryogenic temperature of the liquefied hydrogen, and the liquefied natural gas from the outside by the liquefied natural gas, it is possible to suppress the natural vaporization of the liquefied natural gas and liquefied hydrogen.

In addition, while liquefied natural gas and liquefied hydrogen can be stored in a ship as a fuel for a marine engine, space efficiency can be increased compared to when each of the liquefied natural gas storage tank and the liquefied hydrogen storage tank are provided.

In addition, it can be applied to eco-friendly ships that can be propelled by using hydrogen as a fuel and produce electricity, and can satisfy ship-related regulations such as Tier III.

In addition, since the thickness of the insulating material of the liquid hydrogen storage tank can be reduced, the weight of the storage tank can be reduced and the insulation cost can be reduced.

In addition, by exposing the dome of the liquefied hydrogen storage tank provided inside the liquefied natural gas storage tank to the outside of the liquefied natural gas storage tank, it is possible to facilitate installation or maintenance of a pump in the liquefied hydrogen storage tank.

1 is a schematic diagram illustrating a heterogeneous liquefied gas storage tank having a tank-in-tank structure according to an embodiment of the present invention.

In order to fully understand the operational advantages of the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, in adding reference signs to the elements of each drawing, it should be noted that only the same elements are indicated by the same reference numerals as much as possible even though they are indicated on different drawings.

Hereinafter, a heterogeneous liquefied gas storage tank according to an embodiment of the present invention will be described with reference to FIG. 1 .

In one embodiment of the present invention, the liquefied gas may be a gas obtained by liquefying a gas in a gaseous state at normal pressure and room temperature at a low temperature, for example, LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Gas). Petroleum Gas), liquefied ethylene gas (Liquefied Ethylene Gas), liquefied propylene gas (Liquefied Propylene Gas), etc. may be a liquefied hydrocarbon compound, in addition, liquid nitrogen (LN ₂ ), liquid hydrogen (LH ₂ ), liquid ammonia (LNH) ₃ ) Although it exists in a gaseous state under normal temperature and atmospheric pressure conditions, etc., it may be a liquefied gas that is stored after being liquefied into a liquid phase through processes such as compression and cooling.

In the embodiments to be described later, the liquefied gas is used as a fuel for propulsion or power generation or is loaded as a cargo, and will be described with LNG and liquefied hydrogen as examples.

In addition, the heterogeneous liquefied gas storage tank according to embodiments of the present invention may be applied to a ship or an offshore structure. However, the present invention is not limited thereto and may be applied to land.

Here, the vessel or offshore structure may be any type of vessel in which equipment such as an engine capable of using liquefied gas as a fuel for a propulsion engine or a fuel for an engine for power generation is installed. In addition, any type of vessel using liquefied gas as a fuel may be applied to the vessel according to an embodiment of the present invention. For example, including ships with self-propelled capabilities such as LNG carriers, liquid hydrogen carriers, and LNG RVs (Regasification Vessels), LNG Floating Production Storage Offloading (FPSO), LNG FSRU (Floating Storage Regasification Unit) and May include offshore structures that do not have the same propulsion capability but are floating in the sea.

However, in the embodiment to be described later, a liquefied gas carrier or a liquefied gas fuel vessel will be described as an example.

For example, in this embodiment, the ship may be an LNG carrier, a liquid hydrogen carrier, or an LNG-liquid hydrogen carrier using LNG, liquid hydrogen, and a mixed gas of natural gas and hydrogen gas as fuel.

In addition, in one embodiment of the present invention, the propulsion or power generation facility uses liquefied gas, that is, gas obtained by vaporizing LNG or liquefied hydrogen as a fuel, or produces propulsion or electric power by combustion by using it as a fuel as it is in a liquid state. It may be an engine that uses LNG or hydrogen as a fuel to generate electricity through an electrochemical reaction. In addition, the engine or fuel cell may use LNG, natural gas, liquid hydrogen, and hydrogen gas as fuel, respectively, and may mix natural gas and hydrogen gas.

The heterogeneous liquefied gas storage tank according to this embodiment stores both LNG and liquefied hydrogen.

The heterogeneous liquefied gas storage tank of this embodiment is a liquid hydrogen storage tank 200 in which liquid hydrogen (LH ₂ ) is stored as an inner tank, and an external tank of the type surrounding the liquid hydrogen storage tank 200 to store LNG. It has a tank-in-tank structure including the LNG storage tank 100 .

That is, the liquid hydrogen storage tank 200 is provided inside the LNG storage tank 100 .

As in this embodiment, the heterogeneous liquefied gas storage tank of the type in which the LNG storage tank 100 surrounds the liquefied hydrogen storage tank 200 is an external tank, an LNG storage tank 100, and an internal tank, a liquefied hydrogen storage tank ( 200) can be a means of insulating each other.

The boiling point of hydrogen is about -253°C, and the boiling point of LNG is about -163°C.

The conventional liquid hydrogen storage tank is designed to withstand a temperature difference of -253 ° C. inside the liquid hydrogen storage tank and room temperature (about 20 ° C.) outside the liquid hydrogen storage tank. In addition, the conventional LNG storage tank is designed to withstand a temperature difference of -163 ℃ inside the LNG storage tank and room temperature (about 20 ℃) outside the LNG storage tank.

That is, in the prior art, the insulation structure of the liquid hydrogen storage tank is configured to be very thick to withstand a temperature difference of about 270° C. or more, and an expensive material has to be used.

However, according to this embodiment, by installing the liquid hydrogen storage tank 200 inside the LNG storage tank 100 , the heat insulating part of the liquid hydrogen storage tank 200 has a temperature difference with LNG, that is, a temperature difference of about 90° C. Since it is designed to withstand

1 shows a heterogeneous liquefied gas storage tank having one liquefied hydrogen storage tank 200 inside the LNG storage tank 100, but one or more liquefied hydrogen storage tanks 200 inside the LNG storage tank 100 may be provided.

The LNG storage tank 100 of this embodiment includes an LNG supply pump 110 for discharging the LNG stored in the LNG storage tank 100 to the outside of the LNG storage tank 100 , and a pipe connected to the LNG supply pump 110 . An LNG dome 120 provided above the LNG storage tank 100 is provided to pass through.

In addition, the liquid hydrogen storage tank 200 of this embodiment is provided with a liquid hydrogen supply pump 210 for discharging the liquid hydrogen stored in the liquid hydrogen storage tank 200 to the outside of the liquid hydrogen storage tank 200, liquid hydrogen The liquid hydrogen dome 220 provided in the liquid hydrogen storage tank 200 is extended to be exposed to the outside of the LNG storage tank 100 as shown in FIG. 1 so that the pipe connected to the supply pump 210 passes through. do.

As such, by exposing the liquid hydrogen dome 220 to the outside of the LNG storage tank 100 , the installation of the liquid hydrogen supply pump 210 and the maintenance of the liquid hydrogen supply pump 210 and the liquid hydrogen storage tank 200 . It can make maintenance easier.

The LNG dome 120 and the liquid hydrogen dome 220 may be respectively provided as shown in FIG. 1 , and the LNG dome 120 may be jointly used together.

The liquid hydrogen storage tank 200 of this embodiment may be vertically installed inside the LNG storage tank 100 so that the liquid hydrogen dome 220 is easily exposed to the outside of the LNG storage tank 100 .

At this time, the liquid hydrogen storage tank 200 is manufactured to have a structure capable of reducing sloshing, or the liquid hydrogen storage tank 200 is provided with a sloshing reducing means (not shown) for reducing the sloshing of liquid hydrogen. may be

The liquid hydrogen storage tank 200 of this embodiment may be a cryogenic tank of a dual structure formed of an inner tank, a cooling layer and an outer tank. At this time, when the gas is filled in the cooling layer, the gas may be solidified or liquefied at the low temperature of liquid hydrogen, which is dangerous, so the cooling layer may be evacuated.

In addition, according to this embodiment, the support member 230 for connecting the outer wall of the outer tank of the liquid hydrogen storage tank 200 and the inner wall of the LNG storage tank 100 may be further included.

The liquid hydrogen storage tank 200 of this embodiment is not fixedly installed inside the LNG storage tank 100 by direct welding, but the liquid hydrogen storage tank 200 is stored in the LNG storage tank 200 by using the supports 230 . It can be fixed to the storage tank 100 so that it can be completely attached.

1, the support member 230 is shown as an example that a plurality of the lower and side surfaces of the liquid hydrogen storage tank 200 are provided, but the support member 230 is the left side and the right side of the liquid hydrogen storage tank 200, The liquid hydrogen storage tank 200 may be appropriately provided so as to be stably fixed inside the LNG storage tank 100, such as one or more provided on at least one of the upper side and the lower side, respectively.

In addition, although FIG. 1 illustrates that the liquid hydrogen storage tank 200 is provided to be biased toward one side of the interior of the LNG storage tank 100 as an example, the liquid hydrogen storage tank 200 is located in the middle of the LNG storage tank 100 . may be installed.

The position where the liquid hydrogen storage tank 200 is installed inside the LNG storage tank 100 is not particularly limited, but it is advantageous as it is located closer to the liquid hydrogen dome 220 or the LNG dome 120 , and in particular, LNG supply It is advantageous that the discharge part of the pump 110 is close to the position where it is connected to the outside of the tank through the LNG dome 120 .

The boiling point of hydrogen is about -253°C, and since the gas can be solidified or liquefied when in contact with most gases except for helium gas, etc., the liquid hydrogen storage tank 200 as well as various devices and components handling liquid hydrogen are connected. The piping and the like may be insulated.

In addition, the liquid hydrogen storage tank 200 of this embodiment may be a cylinder type or a spherical type tank. The cylinder-type liquid hydrogen storage tank 200 can be flexibly contracted at low temperature when liquid hydrogen is loaded and unloaded, and it is easy to install compared to the spherical type, so that the space in the LNG storage tank 100 can be utilized effectively. . The spherical type liquid hydrogen storage tank 200 has an advantageous structure to withstand the pressure increase caused by the generation of boil-off gas.

In addition, the liquid hydrogen storage tank 200 of the present embodiment may be a pressure tank capable of withstanding a pressure increase caused by the generation of boil-off gas. For example, the liquid hydrogen storage tank 200 has a structure that can withstand a pressure rise up to a set pressure of about 4 bar to 30 bar, and when the internal pressure exceeds the set pressure, the safety valve is automatically opened to store liquid hydrogen It may be controlled to discharge the boil-off gas from the tank 200 .

BOG generated in the LNG storage tank 100 and the liquefied hydrogen storage tank 200 may be supplied as fuel for an engine (not shown) or as fuel for a fuel cell (not shown), and a reliquefaction device ( (not shown) may be reliquefied and recovered back to each storage tank.

When the boil-off gas of LNG is re-liquefied and recovered again, the boil-off gas of liquefied hydrogen may be used as a refrigerant for cooling the boil-off gas of LNG.

The engine of this embodiment uses any one or more of LNG boil-off gas (ie, methane-rich gas), liquid hydrogen boil-off gas (ie, hydrogen-rich gas), and compressed gas of methane and hydrogen as fuel. It can be a high-pressure or low-pressure engine that can be used.

The high-pressure engine may be a MAN Electronic Gas Injection (ME-GI) engine or an eXtra long stroke Dual Fuel (X-DF) engine. The ME-GI engine is a two-stroke engine employing a diesel cycle, and is a high-pressure injection engine that requires a fuel pressure of about 150 to 300 bar as gas fuel. The X-DF engine is a 2-stroke engine adopting an auto cycle, and is a medium-pressure injection engine that requires a fuel pressure of about 12 to 18 bar.

The low pressure engine may be a Dual Fuel Diesel Electric (DFDE) or a Dual Fuel Diesel Generator (DFDG). The DFDE is a 4-stroke engine employing an Otto cycle, and is a low-pressure injection engine that requires a fuel pressure of about 4 to 8 bar as gas fuel.

The high-pressure engine and the low-pressure engine of this embodiment may use LNG boil-off gas, forced vaporization gas obtained by forcibly vaporizing LNG, or mixed boil-off gas obtained by mixing LNG boil-off gas and hydrogen boil-off gas, and LNG boil-off gas and hydrogen boil-off gas By using as fuel, it is possible to reduce pollutants contained in exhaust gas.

A fuel cell uses the reverse reaction of water electrolysis, and produces electricity and heat by reacting hydrogen and oxygen.

In this embodiment, the fuel cell may be a hydrogen fuel cell that directly uses boil-off gas of liquid hydrogen as a fuel, or a fuel cell that reforms the boil-off gas of LNG to produce hydrogen and then uses the produced hydrogen as a fuel. have. A hydrogen fuel cell is an eco-friendly energy source with high energy efficiency and less greenhouse gas generation than a method using fossil fuels. Therefore, according to this embodiment, it is possible to generate electric power in an environmentally friendly manner by using hydrogen as a fuel. At the same time, since the boil-off gas generated in the liquid hydrogen storage tank 200 is used as fuel, it is possible to prevent wasted hydrogen boil-off gas from being wasted.

As such, by providing the liquid hydrogen storage tank 200 in a tank-in-tank structure inside the LNG storage tank 100, it is possible to mutually maintain the cryogenic temperature of liquid hydrogen and LNG, and to simplify the insulation structure of liquid hydrogen can do it In ships that use liquid hydrogen and LNG as fuels, it is possible to increase the utilization of space in the ship.

The present invention is not limited to the above embodiments, and it is apparent to those skilled in the art that various modifications or variations can be implemented without departing from the technical gist of the present invention. did it

100: LNG storage tank 200: liquid hydrogen storage tank
110: LNG supply pump 210: Liquid hydrogen supply pump
120: LNG dome 220: liquid hydrogen dome
230: support member

Claims (6)

LNG storage tank for storing liquefied natural gas; and
A liquefied hydrogen storage tank installed inside the LNG storage tank and storing liquefied hydrogen; Containing, heterogeneous liquefied gas storage tank. The method according to claim 1,
A heterogeneous liquefied gas storage tank further comprising a; is provided in the liquefied hydrogen storage tank and is designed to withstand the temperature difference between the temperature of the liquefied natural gas and the liquefied hydrogen. The method according to claim 1,
At least one support member connecting the outer wall of the liquefied hydrogen storage tank and the inner wall of the LNG storage tank and fixing the liquefied hydrogen storage tank to the inside of the LNG storage tank; The method according to claim 1,
an LNG supply pump for discharging the LNG stored in the LNG storage tank to the outside of the LNG storage tank; and
A liquefied hydrogen supply pump for discharging the liquefied hydrogen stored in the liquefied hydrogen storage tank to the outside of the liquefied hydrogen storage tank; further comprising, a heterogeneous liquefied gas storage tank. 5. The method according to claim 4,
An LNG dome providing a path through which a pipe connected to the LNG supply pump passes through the outside of the LNG storage tank; further comprising, a heterogeneous liquefied gas storage tank. 5. The method according to claim 4,
A liquid hydrogen dome providing a path through which a pipe connected to the liquid hydrogen supply pump passes through the outside of the LNG storage tank; further comprising, a heterogeneous liquefied gas storage tank.

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