KR102231812B1 - Gas Treatment System, Method of Gas Treatment using the same and Ship having the same - Google Patents

Abstract

A gas treatment system according to the present invention, relates to a gas treatment method using the same, and a ship including the same, the gas treatment system of the present invention, the cargo tank; A first fuel supply line for supplying the boil-off gas generated from the cargo tank to a customer; A gas-liquid separator provided in the first fuel supply line; A boil-off gas compression unit for compressing the boil-off gas that has passed through the gas-liquid separator; A boil-off gas recovery line for branching off the boil-off gas that has passed through the boil-off gas compression unit; A buffer tank for condensing the boil-off gas branched through the boil-off gas recovery line; And a boil-off gas supplement line for moving the boil-off gas generated in the buffer tank to the gas-liquid separator.

Description

Gas treatment system, method of gas treatment using the same, and ship including the same {Gas Treatment System, Method of Gas Treatment using the same and Ship having the same}

The present invention relates to a gas treatment system, a gas treatment method using the same, and a ship including the same.

A ship is a transportation means for sailing the ocean carrying a large amount of minerals, crude oil, natural gas, or more than a few thousand containers, etc., made of steel, and the thrust generated by the rotation of the propeller while floating on the water surface by buoyancy. Go to.

Such ships generate thrust by driving an engine or a gas turbine. At this time, the engine uses oil fuel such as gasoline or diesel to move the piston so that the crankshaft is rotated by the reciprocating motion of the piston, and the shaft connected to the crankshaft Is rotated to drive the propeller, whereas gas turbines burn fuel with compressed air and rotate the turbine blades through the temperature/pressure of the combustion air to generate power and transmit power to the propeller.

However, in recent years, LNG carriers that carry Liquefied Natural Gas, which is a kind of liquefied gas, use LNG as fuel to drive customers such as engines and turbines, and the LNG fuel supply method is being used, and LNG is a clean fuel. And because the reserves are richer than petroleum, the method of using LNG as a fuel for customers is also applied to other ships other than LNG carriers.

However, compared to the conventional case of using oil fuel such as diesel, in the case of using gas fuel LNG, LNG is continuously vaporized in the LNG cargo tank while LNG is transported by the LNG carrier and evaporated in the LNG cargo tank. Boil-off gas (BOG) is generated, and the generated boil-off gas increases the pressure in the cargo tank and accelerates the flow of liquefied gas according to the fluctuation of the ship, thereby causing structural problems. There are a number of problems to be solved, such as the need to suppress the problem, so continuous research and development is being made on the technology to supply customers in ships using LNG, a clean fuel.

The present invention was created to solve the problems of the prior art as described above, an object of the present invention, in a ship using the liquefied gas stored in the cargo tank as a fuel, the boil-off gas naturally occurring in the cargo tank is a buffer tank It is intended to provide a gas treatment system capable of efficiently treating boil-off gas, a gas treatment method using the same, and a ship including the same.

A gas treatment system according to an aspect of the present invention includes a cargo tank; A first fuel supply line for supplying the boil-off gas generated from the cargo tank to a customer; A gas-liquid separator provided in the first fuel supply line; A boil-off gas compression unit for compressing the boil-off gas that has passed through the gas-liquid separator; A boil-off gas recovery line for branching off the boil-off gas that has passed through the boil-off gas compression unit; A buffer tank for condensing the boil-off gas branched through the boil-off gas recovery line; And a boil-off gas supplement line for moving the boil-off gas generated in the buffer tank to the gas-liquid separator.

Specifically, it may include a first liquefied gas recovery line for recovering the liquefied gas phase-separated in the gas-liquid separator to the cargo tank.

Specifically, it may include a heat exchanger for exchanging the boil-off gas of the boil-off gas recovery line and the boil-off gas of the first fuel supply line.

Specifically, it may include a second liquefied gas recovery line for moving the liquefied gas from the buffer tank to the cargo tank.

Specifically, the second liquefied gas recovery line may be connected to the first liquefied gas recovery line.

Specifically, a second fuel supply line for supplying the liquefied gas stored in the cargo tank to the customer may be provided, and a pump and a forced vaporizer may be provided in the second fuel supply line.

Specifically, it may include a liquefied gas filling line provided to move the liquefied gas stored in the cargo tank to the buffer tank.

Specifically, the liquefied gas filling line may be branched from the second fuel supply line.

Specifically, the buffer tank, when the boil-off gas discharged from the cargo tank exceeds the amount of boil-off gas consumption of the customer, receives and stores the excess boil-off gas through the boil-off gas recovery line, and discharges it from the cargo tank. When the generated boil-off gas does not reach the consumption of the boil-off gas of the customer, at least a part of the stored boil-off gas may be supplemented with the gas delivered to the customer through the boil-off gas supplement line.

Specifically, the buffer tank may be provided independently from a flow of supplying liquefied gas as fuel from the cargo tank to the customer.

Specifically, the buffer tank may be a Type-C pressure tank.

Specifically, the liquefied gas stored in the cargo tank may be supplied as fuel to the customer without passing through the buffer tank, and may be joined upstream of the boil-off gas compression unit in a state of boil-off gas forced by a forced carburetor.

Specifically, the customer is an XDF engine that is a low-pressure engine while it is necessary to adjust the methane number, and the boil-off gas compression unit is a centrifugal gas containing droplets while compressing so as to correspond to the required pressure of the XDF engine. It may be a type low compressor.

Specifically, the gas-liquid separator is a forced evaporation gas obtained by forcibly evaporating the liquefied gas discharged from the cargo tank through the first fuel supply line and forcibly evaporating the liquefied gas discharged from the cargo tank. Is introduced through the second fuel supply line, the boil-off gas stored in the buffer tank is introduced through the boil-off gas replenishing line, and removes the droplets contained in the boil-off gas and adjusts the methane number to the boil-off gas compression unit. Can supply.

Specifically, it further comprises a condensation structure installed at the end of the boil-off gas recovery line extending to the inner bottom of the buffer tank so that the boil-off gas recovered to the buffer tank is condensed into the liquefied gas filled in the buffer tank. I can.

Specifically, a pressure generating unit installed in the buffer tank and operated when supplying the boil-off gas stored in the buffer tank to the customer's fuel to increase the amount of boil-off gas and to increase the internal pressure of the buffer tank. I can.

Specifically, a decompression means provided between the buffer tank and the boil-off gas compression unit may further include a decompression means for decompressing the boil-off gas supplied from the buffer tank to the boil-off gas compression unit.

A ship according to another aspect of the present invention is characterized in that it includes the gas treatment system described above.

A gas treatment system according to the present invention, a gas treatment method using the same, and a ship including the same, in a ship using liquefied gas stored in a cargo tank as fuel, a naturally vaporized boil-off gas supplied from a cargo tank as a fuel of a customer and/ Alternatively, by treating the forcibly evaporated boil-off gas using a buffer tank, the boil-off gas can be efficiently treated.

In addition, the gas treatment system according to the present invention, a gas treatment method using the same, and a ship including the same, are stored in the buffer tank when the amount of boil-off gas naturally occurring in the cargo tank is greater or temporarily greater than the amount of fuel required by the customer. By configuring so that it is possible to reduce the amount of boil-off gas burned by the gas combustion unit or discharged to the outside, unnecessary waste of the boil-off gas can be prevented, and the internal pressure stability of the cargo tank can be ensured.

In addition, the gas treatment system according to the present invention, a gas treatment method using the same, and a ship including the same constitute a buffer tank independently from the flow of supplying liquefied gas as fuel from the cargo tank to the customer, but the boil-off gas stored in the buffer tank Unlike a fuel tank as an example for explaining the effect of the present invention, a fuel pump for supplying liquefied gas to a consumer, a fuel carburetor, etc., should be provided by configuring to selectively supply the liquefied gas to the consumer as needed. Peripheral devices for fuel supply can be simplified.

In addition, the gas treatment system according to the present invention, the gas treatment method using the same, and the ship including the same, supply the natural vaporized boil-off gas in the cargo tank as the main fuel of the customer, but the boil-off gas stored in the buffer tank is used as the auxiliary fuel of the customer. Since the buffer tank does not require a fuel pump for supplying the liquefied gas fuel, the buffer tank does not require a fuel pump to supply the liquefied gas fuel, so even if the flow rate and the internal pressure of the buffer tank are lowered, unlike the fuel tank as an example for explaining the effect of the present invention, There is no need to consider the problem of fuel supply interruption and cooldown due to insufficient effective suction head and inlet pressure required for operation.

In addition, the gas treatment system according to the present invention, a gas treatment method using the same, and a ship including the same, are configured to supply only boil-off gas as the fuel of the customer without supplying the liquefied gas as the fuel of the customer from the buffer tank, so that the buffer tank is Unlike the fuel tank as an example for explaining the effect of the present invention, in order to use liquefied gas as a fuel of a consumer, it is not necessary to maintain a certain range of flow rate and internal pressure, and thus it can be free from maintaining the flow rate and internal pressure of the liquefied gas.

In addition, the gas treatment system according to the present invention, the gas treatment method using the same, and the ship including the same, the buffer tank is filled with liquefied gas irrespective of the fuel of the customer, so that the internal boil-off gas can be condensed into the liquefied gas and stored. , When discharge from the buffer tank is required, such as expansion of the filled liquefied gas, it is configured to return to the cargo tank, thereby liquefying the liquefied gas compared to the absence of the discharge configuration of the liquefied gas from the fuel tank as an example for explaining the effect of the present invention. The stability of the buffer tank can be secured from the expansion of gas.

1 is a conceptual diagram of a gas treatment system according to a first embodiment of the present invention.
2 is a conceptual diagram of a gas treatment system according to a second embodiment of the present invention.
3 is a conceptual diagram of a gas treatment system according to a third embodiment of the present invention.
4 is a conceptual diagram of a gas treatment system according to a fourth embodiment of the present invention.
5 is a conceptual diagram of a gas treatment system according to a fifth embodiment of the present invention.
6 is a flowchart illustrating a gas treatment method using the gas treatment system according to the first to fifth embodiments of the present invention.
7 is a first partial flow chart for explaining a gas treatment method using the gas treatment system according to the first to fifth embodiments of the present invention.
8 is a second partial flow chart for explaining a gas treatment method using the gas treatment system according to the first to fifth embodiments of the present invention.
9 is a third partial flow chart for explaining a gas treatment method using the gas treatment system according to the first to fifth embodiments of the present invention.

Objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments associated with the accompanying drawings. In adding reference numerals to elements of each drawing in the present specification, it should be noted that, even though they are indicated on different drawings, only the same elements are to have the same number as possible. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. For reference, in the present specification, the gas is forcibly liquefied for storage because the boiling point is lower than room temperature as well as LNG, and it can be used to encompass all materials generally stored in a liquid state, such as LPG, ethylene, ammonia, etc. having a calorific value.

In addition, the gas may include liquefied gas, natural evaporated evaporated gas, forced evaporated evaporated gas, and excess evaporated gas.

However, the evaporated gas may mean not only the evaporated gas in a gaseous state, but also a liquefied evaporated gas, and the liquefied gas may mean not only the liquefied gas in the liquid state but also the vaporized liquefied gas.

The present invention includes a ship (S) provided with any one of the gas treatment system (1, 2, 3, 4, 5) according to various embodiments described below, wherein the ship (S) is a gas carrier, gas It should be noted that it is a concept that includes all of the commercial ships, FSRU, FLNG, bunkering vessels, offshore plants, etc. that carry cargo or people.

1 is a conceptual diagram of a gas treatment system according to a first embodiment of the present invention.

As shown in Figure 1, the gas treatment system 1 according to the first embodiment of the present invention, in the ship S using the liquefied gas stored in the cargo tank 10 as fuel without a separate fuel tank, It may be provided to treat the boil-off gas naturally occurring inside the cargo tank 10 in the buffer tank 80.

One or more cargo tanks 10 may be installed in the hull of the ship S to store cargo and liquefied gas as fuel, and any known type of tank such as a membrane type tank or an independent tank may be used.

In general, in a cargo tank, the stored liquefied gas is continuously evaporated to generate boil-off gas (BOG) inside, and the generated boil-off gas increases the pressure in the cargo tank and is liquefied according to the fluctuation of the ship. Since the flow of gas can be accelerated to cause a structural problem of the tank, it is necessary to suppress the generation of boil-off gas.

Accordingly, conventionally, as a method to suppress and treat boil-off gas in the cargo tank of a ship, a method of discharging boil-off gas to the outside of the cargo tank and incineration, and a reliquefaction device by discharging the boil-off gas to the outside of the cargo tank. The method of returning to the cargo tank after reliquefaction by means of the vessel, the method of using evaporative gas as fuel used in the propulsion engine of the ship, and the method of suppressing the generation of evaporative gas by maintaining the internal pressure of the cargo tank high are independent. It is used as or in combination.

In the case of a ship equipped with a boil-off gas re-liquefaction device, the boil-off gas inside the cargo tank is discharged to the outside of the cargo tank in order to maintain the proper pressure of the cargo tank, and the boil-off gas is reliquefied through the re-liquefaction device. At this time, the discharged boil-off gas is re-liquefied through heat exchange with a refrigerant cooled to an ultra-low temperature in a re-liquefaction device including a refrigeration cycle, for example, nitrogen and mixed refrigerant, and then returned to the cargo tank.

In the case of ships equipped with a low-pressure engine propulsion system, the fuel consumption of the engine is fuel consumption by supplying the boil-off gas as fuel to the low-pressure engine after processing the boil-off gas by only heating the boil-off gas compression unit without installing a reliquefaction facility. When the amount of boil-off gas is less than the generated amount, the boil-off gas must be burned in a gas combustion unit (GCU) or vented to the atmosphere.

In addition, ships equipped with reliquefaction facilities and low-pressure engines can process boil-off gas by the reliquefaction facility, but due to the complexity of operating the reliquefaction device using nitrogen gas, the control of the entire system is complicated and a considerable amount of power is required. Is consumed.

As described above, in order to suppress and treat the boil-off gas in the cargo tank of the ship, a gas combustion unit or a reliquefaction device must be used. In the case of using a gas combustion unit, fuel gas loss occurs and ash In the case of using a liquefier, the system becomes large, and considerable installation and maintenance costs are incurred.

Therefore, there is a need to continuously research and develop a system and method for efficiently treating liquefied gas, including boil-off gas naturally occurring from the cargo tank. In this embodiment, naturally from the cargo tank 10 A system including a buffer tank 80 is provided as a method for efficiently treating the generated boil-off gas and liquefied gas, which will be described in detail below.

The gas treatment system 1 of this embodiment includes a cargo tank 10, a customer 20a, a pump 30, a forced vaporizer 40a, a gas-liquid separator 50, an evaporative gas compression unit 60a, and an evaporative gas cooler. 70, a buffer tank 80, a pressure reducing means 90, may include a gas combustion unit (100).

The cargo tank 10 may store liquefied gas. The liquefied gas stored in the cargo tank 10 and the boil-off gas naturally generated therein may be used as fuel for the customer 20a.

The boil-off gas naturally vaporized in the cargo tank 10 may be supplied to the customer 20a through the first fuel supply line L1 in which the gas-liquid separator 50 and the boil-off gas compression unit 60a are provided. In addition, the liquefied gas stored in the cargo tank 10 and used as fuel may be supplied to the customer 20a through the second fuel supply line L2 provided with the pump 30 and the forced carburetor 40a. . Also,

In addition to the above-described first fuel supply line (L1) and second fuel supply line (L2), the boil-off gas replenishment line (L3), the boil-off gas recovery line (L4), and the first liquefied gas recovery line (L5) to be mentioned below. ), the liquefied gas filling line (L6), the second liquefied gas recovery line (L7), the boil-off gas discharge line (L8), etc., all gas lines have a valve (not shown) that controls the flow rate of the liquefied gas or boil-off gas. It goes without saying that a number of check valves (not shown) may be provided for preventing the liquefied gas or evaporative gas from flowing backward.

Liquefied gas supplied as fuel from the cargo tank 10 to the customer 20a, as will be described later, does not pass through the buffer tank 80. It goes without saying that this liquefied gas is forcibly vaporized by the forced vaporizer 40a before being supplied to the consumer 20a.

In this embodiment, when the boil-off gas naturally occurring inside the cargo tank 10 is more than or temporarily generated more than the fuel amount required by the customer 20a, the boil-off gas is used in the buffer tank for safety of the cargo tank 10 ( 80) can be recovered and stored. In this way, the gas treatment system 1 converts the excess boil-off gas from the cargo tank 10 to the fuel of the customer 20a, which remains larger than the fuel consumption of the customer 20a. ), it is possible to reduce the amount that is burned or discharged to the outside, thereby preventing unnecessary waste of boil-off gas, as well as ensuring the internal pressure stability of the cargo tank 10.

The liquefied gas stored in the cargo tank 10 is a buffer tank through the liquefied gas filling line L6 branched from the second fuel supply line L2 so that the boil-off gas inside the buffer tank 80 can be condensed and stored. 80) can be charged. When the liquefied gas filled in the buffer tank 80 expands and acts as a risk factor, etc., when discharge is required, it can be returned from the buffer tank 80 to the cargo tank 10 through the second liquefied gas recovery line L7. have. Here, the second liquefied gas recovery line (L7), as shown, one end is connected to the lower portion of the buffer tank 80 and the other end is connected to the cargo tank 10, to the inside of the cargo tank 10 Can be extended. In addition, although not shown, the second liquefied gas recovery line L7 may be connected to the first liquefied gas recovery line L5 to return the liquefied gas to the cargo tank 10.

The liquefied gas returned to the cargo tank 10 from the buffer tank 80 through the second liquefied gas recovery line L7 is not provided with a liquefied gas transfer means such as a pump in the second liquefied gas recovery line L7. It can be restored by free flow due to gravity, which is possible by installing the buffer tank 80 on a deck that is at a higher level than the cargo tank 10 installed in the hull. When the buffer tank 80 has a level similar to that of the cargo tank 10, that is, when installed in the hull, a liquefied gas transfer means such as a pump can be installed in the second liquefied gas recovery line L7 to return the liquefied gas. Of course.

The demander 20a may mean a device such as an engine installed for propulsion or power generation of the ship S, for example, a MEGI engine, an XDF engine, a DF engine included in DFDE, a DF boiler engine, a turbine engine. , A power generation engine, and the like.

The consumer 20a is fueled by forcibly vaporized evaporated gas generated by forcibly evaporating the liquefied gas stored in the cargo tank 10 or the natural evaporated evaporated gas generated by the natural evaporation of the liquefied gas in the cargo tank 10. Power can be generated by using.

In addition, the customer (20a), when the boil-off gas forcibly evaporated from the cargo tank 10 and / or the boil-off gas that is natural evaporated does not reach the consumption of the boil-off gas of the customer (20a), the boil-off gas stored in the buffer tank (80) At least some of them may be transmitted through the boil-off gas supplement line L3 to generate power.

In this embodiment, the consumer 20a may be an XDF engine, which is a type of low-pressure engine that needs to adjust the methane number and operates at a low pressure in the range of 10 bar to 20 bar. Due to the application of such an XDF engine, in the present embodiment, a low compressor (LD Compressor) is applied as the boil-off gas compression unit 60a, and a gas-liquid separator 50 that controls methane number is applied. In this embodiment, a case of applying the XDF engine to the customer 20a is described, but it is not limited thereto, and other low-pressure engines driven at low pressure can be applied while the need to adjust the methane number is not limited thereto. In addition, in addition to the XDF engine, which is the main engine that propels the ship S, the demander 20a in the present embodiment may, of course, include a power generation engine that generates electricity.

The pump 30 may be installed inside the cargo tank 10 to pressurize the liquefied gas discharged to the outside, and may be installed in the second fuel supply line L2 extending to the bottom of the cargo tank 10. have.

This pump 30 may be a fuel pump for compressing and transferring liquefied gas.

The liquefied gas compressed by the pump 30 will be supplied as fuel to the customer 20a through the forced vaporizer 40a, the gas-liquid separator 50, and the boil-off gas compression unit 60a without going through the buffer tank 80. I can. In addition, the liquefied gas compressed by the pump 30 is a liquefied gas filling line (L6) branched from the second fuel supply line (L2) as necessary, such as for the purpose of condensing and storing the boil-off gas inside the buffer tank (80). ) May also be supplied to the buffer tank 80.

The forced vaporizer 40a may be provided in the second fuel supply line L2 and may forcibly vaporize the liquefied gas transferred from the pump 30.

The forced vaporization gas obtained by forcibly vaporizing the liquefied gas in the forced vaporizer 40a may be joined upstream of the vaporized gas compression unit 60a through the gas-liquid separator 50 without passing through the buffer tank 80.

In addition to the methane component, the forced evaporation gas contains other components (propane, butane, etc.) in addition to the methane component, and contains droplets, so that the type of engine that needs to control the methane number as a customer 20a is applied, and the evaporation gas compression unit (60a) When a type of centrifugal compressor that does not allow boil-off gas containing droplets to enter is applied, it is necessary to remove droplets while adjusting the methane number to improve the performance of the customer (20a) and the boil-off gas compression unit (60a). There is, by providing a gas-liquid separator 50 between the forced vaporizer (40a) and the boil-off gas compression unit (60a), it can be solved.

In this embodiment, the forced carburetor 40a is an XDF engine, which is a type of low-pressure engine driven at a low pressure in the range of 10 bar to 20 bar, and the boil-off gas compression unit 60a is an LD compressor, It may be a low pressure vaporizer (LP Vaporizer).

The gas-liquid separator 50 is provided upstream of the boil-off gas compression unit 60a to phase-separate the boil-off gas supplied to the boil-off gas compression unit 60a into a liquid phase and a gas phase, so that only the boil-off gas in the gas phase is transferred to the boil-off gas compression unit 60a. Can be supplied. In addition, the gas-liquid separator 50 may be supplied to the customer 20a by adjusting the methane number of the boil-off gas.

In the gas-liquid separator 50, the forced vaporized boil-off gas obtained by forcibly vaporizing the liquefied gas in the forced vaporizer 40a may be introduced through the second fuel supply line L2. The forced evaporation gas contains components such as propane and butane in addition to methane, and contains a large amount of droplets, and the methane number can be adjusted and the droplets can be removed in the gas-liquid separator 50.

In addition, in the gas-liquid separator 50, the naturally vaporized boil-off gas in the cargo tank 10 may be introduced through the first fuel supply line L1. The naturally vaporized boil-off gas is mostly composed of methane, but contains some droplets, so that droplets can be removed from the gas-liquid separator 50.

In addition, the gas-liquid separator 50 may introduce excess boil-off gas stored in the buffer tank 80 through the boil-off gas supplement line L3. At this time, the excess boil-off gas may be introduced into the gas-liquid separator 50 after being depressurized by the decompression means 90 provided in the boil-off gas supplement line L3. The excess evaporation gas is mostly composed of methane, but contains some droplets, so that the droplets can be removed in the gas-liquid separator 50.

The boil-off gas from which the methane number has been adjusted and the liquid phase has been removed in the gas-liquid separator 50 may be supplied to the boil-off gas compression unit 60a through the first fuel supply line L1.

The boil-off gas that flows into the gas-liquid separator 50 includes both naturally-evaporated boil-off gas (including excess boil-off gas) and forcibly evaporated boil-off gas. Is contained, and all boil-off gases contain droplets, so the type of engine that needs to control the methane number as the customer 20a is applied as in this embodiment, and the evaporation containing droplets as the boil-off gas compression unit 60a When a type of centrifugal compressor that does not allow gas to enter is applied, it is necessary to remove droplets while adjusting the methane number using the gas-liquid separator 50 to improve the performance of the customer 20a and the boil-off gas compression unit 60a. have. In particular, in this embodiment, the gas-liquid separator 50 must be provided because the forcibly vaporized boil-off gas obtained by forcibly vaporizing the liquefied gas in the forced vaporizer 40a is joined upstream of the boil-off gas compression unit 60a. do.

The gas-liquid separator 50 is filled with a liquid boil-off gas phase-separated from the boil-off gas, that is, liquefied gas, and the filled liquefied gas is recovered to the cargo tank 10 through the first liquefied gas recovery line L5. . One end of the first liquefied gas recovery line L5 may be connected to the lower portion of the gas-liquid separator 50 and the other end may extend to the inside of the cargo tank 10.

The boil-off gas compression unit 60a may mean a pressurizing device installed to supply boil-off gas as fuel to the customer 20a, and may be, for example, a centrifugal compressor, a screw compressor, a reciprocating compressor, or the like. This boil-off gas compression unit (60a) may be configured in multiple stages as shown, for example, four stages are composed of one set, and two sets are arranged in parallel so that at least one set can be selectively operated. I can.

A cooler (not shown) may be provided between the multi-stage boil-off gas compression units 60a. The cooler lowers the temperature of the boil-off gas raised by the upstream boil-off gas compressor (60a) to facilitate the operation of the downstream boil-off gas compressor (60a).

The boil-off gas compression unit 60a may compress boil-off gas supplied from the gas-liquid separator 50 provided in the first fuel supply line L1 so as to correspond to the required pressure of the customer 20a.

In this embodiment, the boil-off gas compression unit 60a is an XDF engine, which is a type of low-pressure engine that is driven at a low pressure in the range of 10 bar to 20 bar while the customer 20a needs to adjust the methane number, and the boil-off gas in the gas-liquid separator 50 Since the droplets contained in can be removed, it may be a centrifugal type LD Compressor that compresses at a low pressure without allowing the evaporation gas containing the droplets to enter.

Downstream of the boil-off gas compression unit (60a) is branched from the first fuel supply line (L1) and extends to the buffer tank (80), and is discharged from the cargo tank (10) to at least one stage of the boil-off gas compression unit (60a). A boil-off gas recovery line L4 for branching out some of the compressed boil-off gas may be provided.

The boil-off gas recovery line (L4), when the naturally vaporized boil-off gas in the cargo tank (10) is more than the amount of fuel required by the customer (20a) or temporarily occurs, a constant flow rate supplied as the fuel of the customer (20a). It serves as a passage through which excess boil-off gas other than the boil-off gas can be recovered and stored in the buffer tank 80. This boil-off gas recovery line (L4), although not shown, recovers some of the boil-off gas discharged from the cargo tank 10 and compressed by at least one stage of the boil-off gas compression unit (60a) to the buffer tank (80). Of course it can be configured to store.

In addition, a boil-off gas discharge line L8 branched from the first fuel supply line L1 and extending to the gas combustion unit 100 may be provided downstream of the boil-off gas compression unit 60a. When the amount of boil-off gas supplied as fuel from the cargo tank 10 is greater than the amount of fuel consumption of the customer 20a, and the excess boil-off gas can no longer be stored in the buffer tank 80 , It serves as a passage for allowing some of the boil-off gas to be burned in the gas combustion unit (100).

The boil-off gas cooler 70 is provided in the first fuel supply line L1 downstream of the boil-off gas compression unit 60a, and the temperature of the boil-off gas increased while being pressurized by the boil-off gas compression unit 60a is stored at the customer 20a. It can be adjusted to the required temperature.

In addition, the boil-off gas cooler 70, when the boil-off gas in a state in which the temperature is increased by being pressurized by the boil-off gas compression unit 60a is recovered to the buffer tank 80 through the boil-off gas recovery line L4, the buffer tank ( In order to prevent the internal pressure of the 80) from rapidly increasing, the first fuel supply line (L1) upstream rather than the boil-off gas recovery line (L4) branched from the first fuel supply line (L1) and extended to the buffer tank (80). It is prepared.

The buffer tank 80 may be manufactured as a type-C pressure tank, and may be installed on the deck of the ship (S). The buffer tank 80 may be installed inside the hull.

The buffer tank 80 branches off from the first fuel supply line L1 the naturally vaporized vaporized gas in the cargo tank 10 and/or the forced vaporized vaporized gas obtained by forcibly vaporizing the liquefied gas in the forced vaporizer 40a. It can be recovered and stored through the evaporated gas recovery line (L4).

In the buffer tank 80 of this embodiment, when the boil-off gas discharged from the cargo tank 10 exceeds the boil-off gas consumption of the customer 20a, the excess boil-off gas is delivered and stored through the boil-off gas recovery line L4. And, when the boil-off gas discharged from the cargo tank 10 does not reach the consumption of the boil-off gas of the customer 20a, at least some of the stored boil-off gas is supplied to the boil-off gas supplement line (L3), the boil-off gas compression unit (60a), and 1 It is possible to supplement the gas delivered to the consumer 20a through the fuel supply line L1.

In addition, the buffer tank 80, when the boil-off gas discharged from the cargo tank 10 does not reach the boil-off gas consumption amount of the customer 20a, although not shown, at least a portion of the stored boil-off gas is supplied to the boil-off gas supplement line (L3). Of course, it is possible to supplement the gas delivered to the demander 20a having a low required pressure, such as a power generation engine, or supply it directly or indirectly to the demander 20a having a low required pressure. The boil-off gas replenishment line L3 may serve as a passage for replenishing the boil-off gas stored in the buffer tank 80 to the fuel gas supplied to the customer 20a.

The boil-off gas stored in the buffer tank 80 is, when the boil-off gas discharged from the cargo tank 10 exceeds the consumption of the boil-off gas of the customer 20a, the boil-off gas of a certain flow rate supplied to the fuel of the customer 20a. It may be excess boil-off gas except for.

The excess boil-off gas is compressed in the boil-off gas compression unit (60a) to correspond to the demanded pressure of the customer (20a).For example, when the customer (20a) is an XDF engine, it is evaporated in a pressurized state at a pressure in the range of 10 bar to 20 bar. It is supplied to the buffer tank 80 through the gas recovery line L4, and even though the pressure decreases slightly while passing through the boil-off gas recovery line L4, it will be stored in the buffer tank 80 while still having a pressure of around 10 bar. I can. Since the buffer tank 80 is a Type-C pressure tank and the pressure of the stored excess evaporation gas is high, the reliquefaction rate of the stored excess evaporation gas can be higher than that in the case of a non-pressure tank, so that the reliquefaction function can also be performed. There is.

In this way, by storing the excess boil-off gas in the buffer tank 80, it is possible to reduce the amount of the excess boil-off gas being burned or discharged to the outside by the gas combustion unit 100, thereby preventing unnecessary waste of the excess boil-off gas. In addition, it is possible to ensure the stability of the internal pressure of the cargo tank 10.

As described above, the buffer tank 80, in addition to supplying the naturally vaporized boil-off gas in the cargo tank 10 and/or the liquefied gas stored in the cargo tank 10 as fuel of the customer 20a, therein The stored excess boil-off gas can be supplied as the fuel of the consumer 20a. That is, the buffer tank 80, when the boil-off gas discharged from the cargo tank 10 does not reach the consumption of the boil-off gas of the customer 20a, supplements at least part of the stored boil-off gas to the gas delivered to the customer 20a. can do. Of course, when the fuel gas is sufficiently supplied from the buffer tank 80 to the customer 20a, the fuel gas may not be supplied from the cargo tank 10 to the customer 20a.

Since the excess boil-off gas stored in the buffer tank 80 is stored in a state having a pressure of about 10 bar as described above, the boil-off gas replenishment line (L3) from the buffer tank 80 to the gas-liquid separator 50 When supplied, the high pressure of the excess boil-off gas supplied to the boil-off gas compression unit 60a via the gas-liquid separator 50 may be transmitted as it is to the boil-off gas compression unit 60a to cause a problem. ) Must be supplied after reducing pressure.

In addition, the excess boil-off gas stored in the buffer tank 80 may be condensed and stored. The excess boil-off gas inside the buffer tank 80 may be condensed by filling the liquefied gas of the cargo tank 10 through the liquefied gas filling line L6 branched from the second fuel supply line L2. The liquefied gas filled in the buffer tank 80 is not used as fuel for the customer 20a, but serves to condense the excess evaporation gas, so it can be filled with a small amount, and if there is no need to condense the excess evaporation gas, it is charged. You do not have to do.

In addition, the liquefied gas filled in the buffer tank 80 is a second liquefied gas recovery line L7 when discharge from the buffer tank 80 is required, such as when the liquid level of the liquefied gas is higher than the set level value or the liquefied gas expands. ) Can be returned to the cargo tank 10 from the buffer tank 80. Here, the second liquefied gas recovery line (L7), as shown, one end is connected to the lower portion of the buffer tank 80 and the other end is connected to the cargo tank 10, to the inside of the cargo tank 10 Can be extended. In addition, although not shown, the second liquefied gas recovery line L7 may be connected to the first liquefied gas recovery line L5 to return the liquefied gas to the cargo tank 10.

As described above, the buffer tank 80, unlike a fuel tank that fills liquefied gas from the cargo tank 10 and supplies it as fuel to the customer 20a, stores excess boil-off gas and stores excess boil-off gas as needed. Since it is configured to be used as the fuel of (20a), it is configured independently from the flow of supplying liquefied gas as fuel from the cargo tank 10 to the customer 20a.

That is, in this embodiment, the flow of the liquefied gas supplied from the cargo tank 10 to the customer 20a is that the liquefied gas stored in the cargo tank 10 does not pass through the buffer tank 80 and the second fuel supply line ( Since it is forcibly vaporized in the forced vaporizer 40a provided in L2 and is supplied to the consumer 20a through the gas-liquid separator 50 and the boil-off gas compression unit 60a, it is irrelevant to the buffer tank 80.

The buffer tank 80 according to the present invention can condensate and store the excess boil-off gas remaining after being oversupplied to the customer 20a by using liquefied gas, as well as converting the liquefied gas into the cargo tank 10. By configuring so that it can be restored, the boil-off gas inside the cargo tank 10 is discharged to the outside of the cargo tank 10 to reliquefy the cargo tank 10 in order to maintain the proper pressure, or the customer 20a from the cargo tank 10 If the amount of boil-off gas supplied as fuel of) is greater than the amount of fuel consumed by the consumer 20a, it may serve as a reliquefaction device for re-liquefying it. For this reason, since the gas treatment system 1 according to the present embodiment includes the buffer tank 80, it is possible to efficiently process excess boil-off gas without installing a reliquefaction device. The gas treatment systems 2, 3, 4, and 5 according to another exemplary embodiment described below are also provided with a buffer tank 80, so it is of course not necessary to install a reliquefaction device.

In addition, the buffer tank 80 according to the present invention stores the excess boil-off gas remaining in excess of the amount of fuel required by the customer 20a in the boil-off gas supplied from the cargo tank 10 as the fuel of the customer 20a. Of course, since it is possible to selectively use excess boil-off gas as the fuel of the customer 20a as needed, the gas treatment system 1 including the buffer tank 80 of the present invention is an example for explaining the effect of the present invention. It is inevitable to be structurally different from a gas treatment system including a fuel tank as a fuel tank, but it will be more apparent by comparing and explaining the fuel tank as an example for explaining the effect of the present invention below.

In general, in a ship having a cargo tank storing liquefied gas and a fuel tank storing liquefied gas as fuel, the fuel tank receives the liquefied gas directly from the cargo tank and fills it with a bunker ring.

The flow configuration for supplying liquefied gas as fuel from the fuel tank to the consumer is to fill the liquefied gas from the cargo tank, pressurize the filled liquefied gas using a pump, and vaporize the pressurized liquefied gas with a fuel vaporizer for forced vaporization. The evaporated evaporated gas is generated, and the forcibly vaporized evaporated gas is compressed to correspond to the demanded pressure of the consumer through the evaporation gas compression unit and supplied to the consumer.

However, as described above, the buffer tank 80 of the present invention is not configured to receive liquefied gas from the cargo tank 10 and supply it as fuel to the customer 20a.

That is, the fuel tank must be equipped with a pump, a fuel carburetor, etc. as a peripheral device for supplying liquefied gas as fuel, but the buffer tank 80 of the present invention is used as fuel from the cargo tank 10 to the customer 20a. It is configured independently of the flow of supplying the liquefied gas, and there is no need for a peripheral device for supplying the liquefied gas as fuel, so the operation is relatively simple.

Particularly, a pump, which is a peripheral device of a fuel tank, has complicated operations such as having to meet an inflow flow rate and an inflow pressure in order to operate without a problem, as is well known.

For example, when the flow rate of the fuel tank decreases, it must be replenished in the cargo tank, and at this time, there is a problem that the fuel supply from the fuel tank must be temporarily stopped, and a cooldown is required to restart the operation. There is a hassle.

In addition, if the internal pressure of the fuel tank is lowered, it is necessary to receive more boil-off gas from the cargo tank to increase the internal pressure, but the lowered internal pressure means that there is not enough boil-off gas in the cargo tank. There is a problem that the fuel supply from the fuel tank must be temporarily stopped due to the need to wait for natural evaporation or to use the pressure generating unit, and there is a hassle such as having to cool down in order to operate again.

In addition, when the fuel supply is temporarily stopped, a diesel fuel engine can be used, but it causes an exhaust gas environmental problem, so an exhaust gas treatment system must be provided. Is wasted, and if the operation is stopped, the liquefied gas fuel engine has to be operated after a cooldown.

Since the buffer tank 80 of the present invention does not require a pump for pressurizing fuel gas, even if the flow rate and internal pressure are lowered, unlike the fuel tank described above, the effective suction head and inlet pressure required for driving the pump are not met. There is no need to consider fuel supply interruption and cooldown issues, and it can be free from maintenance of flow rate and internal pressure.

In addition, there is a line in the fuel tank for filling liquefied gas from the cargo tank, but there is no line for returning the liquefied gas from the fuel tank to the cargo tank. Although it is impossible to discharge from the tank, the buffer tank 80 of the present invention can return the liquefied gas filled in the buffer tank to the cargo tank 10 through the second liquefied gas recovery line L7. It is possible to secure the stability of the buffer tank 80 from the expansion of the liquefied gas compared to that there is no configuration for discharging the liquefied gas.

The decompression means 90 reduces the pressure of the excess boil-off gas stored in the buffer tank 80 and supplies it to the boil-off gas compression unit 60a.

The depressurization means 90 may be provided in the boil-off gas supplement line L3 between the buffer tank 80 and the gas-liquid separator 50. The pressure reducing means 90 may be an expansion valve such as a Joule-Thomson valve, an expander, or the like.

The reason for supplying the excess boil-off gas by decompressing it with the decompression means 90 is that the excess boil-off gas is supplied to the buffer tank 80 while being compressed in the boil-off gas compression unit 60a and has a pressure of about 10 bar. When it is stored as, and is supplied to the gas-liquid separator 50 from the buffer tank 80 through the boil-off gas supplement line (L3), the excess boil-off gas supplied to the boil-off gas compression unit 60a through the gas-liquid separator 50 This is because the high pressure of the boil-off gas compression unit (60a) is transmitted as it is to cause problems such as lowering the driving efficiency of the boil-off gas compression unit (60a).

The gas combustion unit 100 may be installed in the boil-off gas discharge line L8 branched from the first fuel supply line L1 downstream of the boil-off gas compression unit 60a, and is less than the fuel consumption of the customer 20a. When the amount of boil-off gas supplied as fuel from the cargo tank 10 is large and the excess boil-off gas cannot be stored in the buffer tank 80 any more, a part of the boil-off gas can be burned. In this embodiment, since most of the excess boil-off gas can be stored in the buffer tank 80, the amount of boil-off gas burned by the gas combustion unit 100 or discharged to the outside can be greatly reduced.

2 is a conceptual diagram of a gas treatment system according to a second embodiment of the present invention.

Hereinafter, a second embodiment will be described with reference to FIG. 2, but the configurations using the same reference numerals as in the first embodiment in the present embodiment do not necessarily mean the same configuration.

As shown in Figure 2, the gas treatment system 2 according to the second embodiment of the present invention, a ship that uses the liquefied gas stored in the cargo tank 10 as fuel without a separate fuel tank (S ), it may be provided to treat the boil-off gas naturally occurring inside the cargo tank 10 in the buffer tank 80.

The gas treatment system 2 according to the second embodiment of the present invention includes a cargo tank 10, a customer 20a, a pump 30, a forced vaporizer 40a, a gas-liquid separator 50, a boil-off gas compression unit ( 60a), a boil-off gas cooler (70), a buffer tank (80), a decompression means (90), a gas combustion unit (100), a heat exchanger (110), a condensation structure (120), a pressure generating unit (130). I can.

Here, the cargo tank 10, the customer (20a), the pump 30, the forced vaporizer (40a), the gas-liquid separator (50), the boil-off gas compression unit (60a), the boil-off gas cooler (70), the buffer tank (80) , The decompression means 90, and the gas combustion unit 100 are the same as or similar to those described in the first embodiment, so a detailed description thereof will be omitted, and the heat exchanger 110, which is a component different from the first embodiment of the present invention , The condensation structure 120, the pressure generating unit 130, and only the parts that are different due to this will be described.

The heat exchanger 110 is connected to a first fuel supply line (L1) connecting the cargo tank 10 and the gas-liquid separator 50, and a first fuel supply line (L1) downstream of the boil-off gas compression unit (60a). Thus, it may be provided in the boil-off gas recovery line L4 extending to the buffer tank 80.

The heat exchanger 110 includes a relatively low temperature (for example, about -100°C at 1 bar) naturally vaporized boil-off gas supplied to the gas-liquid separator 50 through the first fuel supply line L1, and a customer ( Before being supplied to 20a), heat exchange is performed with excess boil-off gas of relatively high temperature (for example, about 40° C. at 10 bar to 20 bar) supplied to the buffer tank 80 through the boil-off gas recovery line L4. At this time, in the heat exchanger 110, the excess boil-off gas may be cooled and partially re-liquefied by obtaining cold heat from the naturally-evaporated boil-off gas and stored in the buffer tank 80.

The condensation structure 120 is a structure that condenses excess boil-off gas flowing into the buffer tank 80 through the boil-off gas recovery line L4 to the liquefied gas filled in the buffer tank 80, so that it can be immersed in the liquefied gas. It may be provided near the bottom of the buffer tank 80.

The condensation structure 120 may be installed at an end of the boil-off gas recovery line L4, and may be formed in a structure capable of dispersing and delaying the flow of excess boil-off gas. At this time, the boil-off gas recovery line L4 may further extend from the ceiling of the buffer tank 80 to the floor so that the condensation structure 120 may be installed near the bottom of the buffer tank 80.

The pressure generating unit 130 may be installed in the buffer tank 80.

The pressure generating unit 130 is operated when the buffer tank 80 supplies excess boil-off gas as fuel to the customer 20a, thereby increasing the amount of excess boil-off gas and increasing the internal pressure of the buffer tank 80. .

In this embodiment, unlike the first embodiment, since the excess boil-off gas is stored in the buffer tank 80 in a state cooled and reliquefied by the heat exchanger 110, not in a gaseous state before being supplied to the customer 20a. In addition, the amount of stored excess boil-off gas is inevitably small, and the internal pressure is also lowered, thereby creating pressure to increase the pressure while increasing the amount of excess boil-off gas when it is necessary to supply it as an auxiliary fuel of the customer (20a). Unit 130 is required.

3 is a conceptual diagram of a gas treatment system according to a third embodiment of the present invention.

Hereinafter, a third embodiment will be described with reference to FIG. 3, but configurations using the same reference numerals as in the first embodiment in this embodiment do not necessarily mean the same configuration.

As shown in Figure 3, the gas treatment system 3 according to the third embodiment of the present invention, a ship that uses the liquefied gas stored in the cargo tank 10 as fuel without a separate fuel tank (S ), it may be provided to treat the boil-off gas naturally occurring inside the cargo tank 10 in the buffer tank 80.

The gas treatment system 3 according to the third embodiment of the present invention includes a cargo tank 10, a customer 20a, a pump 30, a forced vaporizer 40a, a first gas-liquid separator 50a, and a second gas-liquid. It may include a separator 50b, a boil-off gas compression unit 60a, an boil-off gas cooler 70, a buffer tank 80, a decompression means 90, and a gas combustion unit 100.

Here, the cargo tank 10, the customer (20a), the pump 30, the forced vaporizer (40a), the boil-off gas compression unit (60a), the boil-off gas cooler (70), the buffer tank (80), the decompression means (90) , Since the gas combustion unit 100 is the same as or similar to that described in the first embodiment, a detailed description will be omitted, and the first gas-liquid separator 50a and the second gas-liquid are components different from the first embodiment of the present invention. Only the separator 50b and the parts that are different due to this will be described.

The first gas-liquid separator (50a) is provided upstream of the boil-off gas compression unit (60a) and separates the boil-off gas supplied to the boil-off gas compression unit (60a) into a liquid phase and a gas phase. ) Can be supplied.

In the first gas-liquid separator 50a, the naturally vaporized boil-off gas in the cargo tank 10 may be introduced through the first fuel supply line L1. The natural evaporation gas is mostly composed of methane, but contains some droplets, so that the droplets can be removed in the first gas-liquid separator 50a.

In addition, the first gas-liquid separator 50a may be connected to the boil-off gas supplement line L3 so that the excess boil-off gas stored in the buffer tank 80 is decompressed by the decompression means 90 and then introduced. The excess boil-off gas is mostly composed of methane.

In addition, in the first gas-liquid separator 50a, excess boil-off gas stored in the buffer tank 80 may be introduced through the boil-off gas supplement line L3. At this time, the excess boil-off gas may flow into the first gas-liquid separator 50a after being depressurized by the decompression means 90 provided in the boil-off gas supplement line L3. The excess evaporation gas is mostly composed of methane, but contains some droplets, so that the droplets can be removed in the first gas-liquid separator 50a.

In this way, the boil-off gas from which the liquid phase has been removed in the first gas-liquid separator 50a may be supplied to the boil-off gas compression unit 60a through the first fuel supply line L1.

The naturally vaporized boil-off gas and/or excess boil-off gas flowing into the first gas-liquid separator 50a contains droplets, and thus boil-off gas containing droplets enters as the boil-off gas compression unit 60a as in the present embodiment. When a centrifugal compressor of a type that does not work is applied, it is necessary to remove droplets in order to improve the performance of the boil-off gas compression unit 60a. Accordingly, in this embodiment, the first gas-liquid separator 50a must be provided upstream of the boil-off gas compression unit 60a to prevent droplets from flowing into the boil-off gas compression unit 60a, which is a centrifugal compressor.

In addition, the first gas-liquid separator 50a is filled with a liquid boil-off gas phase-separated from the boil-off gas, that is, liquefied gas, and the filled liquefied gas is transferred to the cargo tank 10 through the first liquefied gas recovery line L5. Is recovered. The first liquefied gas recovery line L5 may have one end connected to the lower portion of the first gas-liquid separator 50a, and the other end may extend to the inside of the cargo tank 10.

The second gas-liquid separator 50b is provided in the second fuel supply line L2 connected to the first fuel supply line L1 between the boil-off gas compression unit 60a and the customer 20a, and the forced vaporizer 40a The forced evaporation gas obtained by forcibly evaporating the liquefied gas can be phase-separated into a liquid phase and a gas phase. In addition, the second gas-liquid separator 50b removes components such as propane and butane contained in the forcibly evaporated evaporation gas, and merges the evaporated gas whose methane number is adjusted to the downstream of the evaporated gas compression unit 60a, and the customer 20a Can be supplied to. The second gas-liquid separator 50b may be provided in the second fuel supply line L2 downstream of the forced vaporizer 40a.

The second fuel supply line L2 of this embodiment supplies the first fuel downstream of the boil-off gas compression unit 60a from the cargo tank 10, unlike the first embodiment connected to the upstream side of the boil-off gas compression unit 60a. It may extend to the line L1.

The peripheral line of the second gas-liquid separator 50b may be similar to the first gas-liquid separator 50a, and detailed descriptions of the peripheral lines will be omitted here.

The forced vaporized boil-off gas to be used as the fuel of the customer 20a obtained by the forced vaporizer 40a and the second gas-liquid separator 50b is supplied through the second fuel supply line L2. Since it is joined to the first fuel supply line L1, the branch point of the boil-off gas recovery line L4 branched from the first fuel supply line L1 is the second fuel supply line connected to the first fuel supply line L1. It is preferable to be located downstream of the connection point of L2).

In the above, the forced evaporation gas flowing into the second gas-liquid separator 50b contains other components (propane, butane, etc.) in addition to the methane component. When the necessary XDF engine is applied, it is necessary to adjust the methane number to improve the performance of these engines. Therefore, in the present embodiment, the second gas-liquid separator 50b must be provided in order to supply fuel having an increased methane number to the consumer 20a, which is an XDF engine, to the downstream of the boil-off gas compression unit 60a.

4 is a conceptual diagram of a gas treatment system according to a fourth embodiment of the present invention.

Hereinafter, a fourth embodiment will be described with reference to FIG. 4, but configurations using the same reference numerals as in the third embodiment in the present embodiment do not necessarily mean the same configuration.

As shown in Figure 4, the gas treatment system 4 according to the fourth embodiment of the present invention, a ship that uses the liquefied gas stored in the cargo tank 10 as fuel without a separate fuel tank (S ), it may be provided to treat the boil-off gas naturally occurring inside the cargo tank 10 in the buffer tank 80.

The gas treatment system 4 according to the fourth embodiment of the present invention includes a cargo tank 10, a customer 20a, a pump 30, a forced vaporizer 40a, a second gas-liquid separator 50b, and boil-off gas compression. A unit 60b, an evaporative gas cooler 70, a buffer tank 80, a decompression means 90, and a gas combustion unit 100 may be included.

Here, the cargo tank 10, the customer (20a), the pump 30, the forced vaporizer (40a), the boil-off gas cooler (70), the buffer tank (80), the pressure reducing means (90), the gas combustion unit (100) Since it is the same or similar to that described in the third embodiment, a detailed description will be omitted, and the boil-off gas compression unit 60b, which is a component different from the third embodiment of the present invention, and the first gas-liquid separator 50a, which is an omitted component. Only the parts that change due to) will be described.

The boil-off gas compression unit (60b) is a screw-type low-pressure compressor (LD Compressor) that compresses to a low pressure while the boil-off gas containing droplets, which is a different type from the boil-off gas compression unit 60a of the third embodiment, can enter, or a reciprocating low pressure. It may be a compressor (LD Compressor). This boil-off gas compression unit (60b) may be configured in multiple stages as shown, for example, four stages are composed of one set, and two sets are arranged in parallel so that at least one set can be selectively operated. I can. A cooler (not shown) may be provided between the multi-stage boil-off gas compression units 60b, and the cooler lowers the temperature of the boil-off gas raised by the boil-off gas compressor 60b on the upstream side, thereby lowering the boil-off gas compressor 60b at the downstream side. ) To facilitate the operation.

Downstream of the boil-off gas compression unit (60b) of the present embodiment, the same or similar to the boil-off gas compression unit (60a) of the third embodiment is branched from the first fuel supply line (L1) and extends to the buffer tank (80), A boil-off gas recovery line L4 may be provided for branching out some of the boil-off gas discharged from the cargo tank 10 and compressed by at least one stage of the boil-off gas compression unit 60b.

As described above, the boil-off gas compression unit 60b of this embodiment differs in type compared to the boil-off gas compression unit 60a of the third embodiment, as described above, and the surrounding elements are the same or similar to those of the third embodiment. In order to avoid redundant description, detailed description will be omitted.

In this embodiment, the first gas-liquid separator 50a, which is a component of the third embodiment, is omitted. As described above, the first gas-liquid separator 50a of the third embodiment is the boil-off gas compression unit 60a of the third embodiment. ) It is essentially provided because a type of centrifugal type low compressor that does not allow boil-off gas containing droplets to enter is applied, but in the present embodiment, the boil-off gas compression unit 60b is a type in which boil-off gas containing droplets can enter Since the screw type low compressor or the reciprocating type low compressor is applied, there is no need to provide the first gas-liquid separator 50a, which is a component of the third embodiment.

That is, in this embodiment, as in the third embodiment, the boil-off gas (natural vaporization) introduced into the boil-off gas compression unit 60a, which is a centrifugal low-pressure compressor, through the first fuel supply line L1 and the boil-off gas supplement line L3. There is no need to provide a first gas-liquid separator 50a for preventing the inflow of droplets to remove droplets contained in the evaporated gas and/or excess evaporated gas).

In this embodiment, since the first gas-liquid separator 50a of the third embodiment is omitted, the first fuel supply line L1 is provided with an evaporative gas supplement line L3 between the depressurization means 90 and the boil-off gas compression unit 60b. ) Is directly connected to the boil-off gas compression unit 60b through the boil-off gas of the cargo tank 10 and boil-off gas replenishment line (L3) supplied to the boil-off gas compression unit (60b) through the first fuel supply line (L1). The boil-off gas of the buffer tank 80 supplied to) may be joined in the first fuel supply line L1 upstream of the boil-off gas compression unit 60b.

As described above, in this embodiment, by applying a screw type low compressor or a reciprocating type low pressure compressor in which the boil-off gas containing droplets may enter the boil-off gas compression unit 60b, the cargo tank 10 and the boil-off gas compression unit ( No gas-liquid separator is provided between 60b) and between the buffer tank 80 and the boil-off gas compression unit 60b, and the excess boil-off gas in the buffer tank 80 and the naturally vaporized boil-off gas in the cargo tank 10 are separated by gas-liquid separation. It may be configured to be joined without being introduced into the evaporative gas compression unit 60b.

5 is a conceptual diagram of a gas treatment system according to a fifth embodiment of the present invention.

Hereinafter, a fifth embodiment will be described with reference to FIG. 5, but configurations using the same reference numerals as in the third embodiment in the present embodiment do not necessarily mean the same configuration.

As shown in Figure 5, the gas treatment system 5 according to the fifth embodiment of the present invention, a ship that uses the liquefied gas stored in the cargo tank 10 as fuel without a separate fuel tank (S ), it may be provided to treat the boil-off gas naturally occurring inside the cargo tank 10 in the buffer tank 80.

The gas treatment system 5 according to the fifth embodiment of the present invention includes a cargo tank 10, a customer 20b, a first pump 30a, a second pump 30b, a forced vaporizer 40b, and a boil-off gas. It may include a compression unit (60c), a boil-off gas cooler (70), a buffer tank (80), a decompression means (90), a gas combustion unit (100).

Here, the cargo tank 10, the boil-off gas cooler 70, the buffer tank 80, the pressure reducing means 90, and the gas combustion unit 100 are the same as or similar to those described in the third embodiment, so a detailed description thereof will be omitted. And, the customer (20b), the first pump (30a), the second pump (30b), the forced vaporizer (40b), the boil-off gas compression unit (60c) and the other components from the third embodiment of the present invention are omitted. Only the parts that change due to the first gas-liquid separator 50a and the second gas-liquid separator 50b, which are constituents, will be described.

The consumer (20b) fuels the forced evaporation gas generated by forcibly evaporating the liquefied gas stored in the cargo tank 10 or the natural evaporated evaporated gas generated by the natural evaporation of the liquefied gas in the cargo tank 10. Power can be generated by using.

In addition, the customer (20b), when the boil-off gas forcibly vaporized from the cargo tank (10) and / or the boil-off gas is less than the boil-off gas consumption of the customer (20a), the boil-off gas stored in the buffer tank (80) At least some of them may be transmitted through the boil-off gas supplement line L3 to generate power.

In this embodiment, the consumer 20b may be a MEGI engine, which is a type of high-pressure engine that is driven at a high pressure in the range of 250 bar or more, for example, 250 bar to 400 bar without the need to adjust the methane number. By applying such a MEGI engine, in this embodiment, a high-pressure compressor is applied as the boil-off gas compression unit 60c, and a high-pressure pump is applied as the second pump 30b. In this embodiment, a case of applying the MEGI engine to the customer 20b is described, but it is not limited thereto, and other high-pressure engines capable of driving at a high pressure of 250 bar or more can be applied without the need to adjust the methane number. In addition, in addition to the MEGI engine, which is the main engine that propels the ship S, the demander 20b in the present embodiment may, of course, include a power generation engine that generates electricity.

The first pump 30a is installed inside the cargo tank 10 to pressurize the liquefied gas discharged to the outside, and is installed in the second fuel supply line L2 extending to the bottom of the cargo tank 10 Can be.

The first pump 30a extracts liquefied gas from the cargo tank 10 and pressurizes the liquefied gas so as to prevent cavitation of the second pump 30b, which is a high-pressure pump. ) To supply a sufficient amount of liquefied gas.

In addition, the first pump 30a is also supplied to the buffer tank 80 through the liquefied gas filling line L6 as necessary, such as for the purpose of condensing and storing the boil-off gas of the buffer tank 80. Here, the liquefied gas filling line L6 may be connected to the second fuel supply line L2 between the first pump 30a and the second pump 30b.

The second pump 30b may be a high-pressure pump provided in the second fuel supply line L2, and pressurizes the liquefied gas supplied from the first pump 30a to a high pressure required by the high-pressure engine, the consumer 20b. Thus, it is possible to supply the liquefied gas to the customer (20b).

The second fuel supply line L2 of the present embodiment extends from the inside of the cargo tank 10 to the first fuel supply line L1 downstream of the boil-off gas compression unit 60a in the same or similar to the third embodiment. I can.

After being discharged from the cargo tank 10, the liquefied gas is first pressurized by the first pump 30a, and the second pump 30b collects the liquefied gas in the liquid state first pressurized by the first pump 30a. It is pressurized secondarily and is forcibly vaporized through the forcible vaporizer 40b, and the forcibly vaporized boil-off gas is joined to the downstream of the boil-off gas compression unit 60c and supplied to the customer 20b.

At this time, the second pump 30b pressurizes the liquefied gas to a pressure required by the customer 20b, for example, 250 bar or more, and supplies it to the customer 20b, so that the customer 20b, a high-pressure engine, generates power through the liquefied gas. Can be produced.

The second pump 30b pressurizes the liquid liquefied gas discharged from the first pump 30a to a high pressure, so that the liquefied gas is in a supercritical state having a higher temperature and higher pressure than a critical point. It can be phase-changed. At this time, the temperature of the liquefied gas in the supercritical state may be relatively higher than the critical temperature.

In addition, the second pump 30b may pressurize the liquefied gas in a liquid state at high pressure to change it into a supercooled liquid state. Here, the liquefied gas in the subcooled liquid state is a state in which the pressure of the liquefied gas is higher than the critical pressure and the temperature is lower than the critical temperature.

Specifically, the second pump 30b pressurizes the liquefied gas in a liquid state discharged from the first pump 30a to a high pressure of 250 bar or higher, but makes the temperature of the liquefied gas lower than the critical temperature, thereby subcooling the liquefied gas. It can phase change to a liquid state. Here, the temperature of the liquefied gas in the state of the supercooled liquid may be -140°C to -60°C, which is relatively lower than the critical temperature.

In this embodiment, the liquefied gas compressed by the second pump 30b is joined to the downstream of the boil-off gas compression unit 60c through the forced vaporizer 40b without passing through the buffer tank 80, Supplied as fuel.

The forced vaporizer 40b may be provided in the second fuel supply line L2 downstream of the second pump 30b, which is a high-pressure pump, and may forcibly vaporize the liquefied gas transferred from the second pump 30b. .

The forced vaporization gas obtained by forcibly vaporizing the liquefied gas in the forced vaporizer 40b may be joined to the downstream of the vaporized gas compression unit 60c without passing through the buffer tank 80.

The forced evaporation gas contains other components (propane, butane, etc.) in addition to the methane component, but in this embodiment, a kind of engine that does not need to adjust the methane number as the customer 20b is applied, so that the forced vaporizer 40b There is no need to install a gas-liquid separator for controlling the methane number downstream.

In this embodiment, the forced carburetor 40b applies a MEGI engine, which is a type of high-pressure engine in which the second pump 30b pressurizes at a high pressure of 250 bar or more and the customer 20b drives at a high pressure of 250 bar or more. It may be a vaporizer (HP Vaporizer).

The boil-off gas compression unit 60c is provided in the first fuel supply line L1 to compress the boil-off gas so as to correspond to the required pressure of the customer 20b.

In this embodiment, the boil-off gas compression unit 60c may be a reciprocating compressor in which boil-off gas containing droplets of a different type from the boil-off gas compression unit 60a of the third embodiment may enter. However, in this embodiment, since the demander 20b does not need to adjust the methane number and is a MEGI engine, which is a type of high-pressure engine driven at a high pressure of 250 bar or more, the boil-off gas compression unit 60c is a reciprocating type high-pressure compressor (HD) composed of multiple stages. Compressor). A cooler (not shown) may be provided between the multi-stage boil-off gas compression units 60c, and the cooler lowers the temperature of the boil-off gas raised by the upstream boil-off gas compressor 60c to lower the boil-off gas compressor ( It makes it possible to facilitate the operation of 60c).

In the case of a multi-stage boil-off gas compression unit (60c) with an intermediate stage, for example, a 5-stage compressor, the first fuel is downstream of the cooler provided between the second compressor and the third compressor, specifically at the rear end of the second compressor. A boil-off gas recovery line L4 branched from the supply line L1 and extending to the buffer tank 80 may be provided. The boil-off gas recovery line (L4), when the naturally vaporized boil-off gas in the cargo tank (10) is more than the amount of fuel required by the customer (20b) or temporarily occurs, a constant flow rate supplied as the fuel of the customer (20b). It serves as a passage for storing excess boil-off gas excluding boil-off gas in the buffer tank (80).

In this embodiment, the first gas-liquid separator 50a, which is a component of the third embodiment, is omitted. As described above, the first gas-liquid separator 50a of the third embodiment is the boil-off gas compression unit 60a of the third embodiment. ) It is essentially provided because a type of centrifugal type low compressor that does not allow boil-off gas containing droplets to enter is applied, but in this embodiment, the boil-off gas compression unit 60c is a type in which boil-off gas containing droplets can enter At the same time, since the reciprocating type high pressure compressor having multiple stages is applied to generate high pressure, there is no need to provide the first gas-liquid separator 50a, which is a component of the third embodiment.

In addition, in this embodiment, the second gas-liquid separator 50b, which is a component of the third embodiment, is omitted. As described above, the second gas-liquid separator 50b of the third embodiment is the customer 20a of the third embodiment. Since the XDF engine, which needs to adjust the methane number, is applied, it was essentially provided, but in this embodiment, the customer 20b applies the MEGI engine, which is a high-pressure engine, without needing to adjust the methane number. There is no need to provide a two-gas-liquid separator (50b).

That is, in this embodiment, as in the third embodiment, the boil-off gas (natural vaporization) introduced into the boil-off gas compression unit 60a, which is a centrifugal low-pressure compressor, through the first fuel supply line L1 and the boil-off gas supplement line L3. It is not necessary to provide a first gas-liquid separator (50a) for preventing the inflow of droplets to remove droplets contained in the evaporated gas and/or excess evaporation gas), but also a second gas-liquid separator (50b) for controlling methane number. none.

In addition to the first to fifth embodiments described above, the present invention encompasses all embodiments generated by a combination of at least two or more of the above embodiments or a combination of at least one or more of the above embodiments and known techniques.

Hereinafter, a gas treatment method using the gas treatment systems 1, 2, 3, 4, 5 according to the first to fifth embodiments of the present invention will be described with reference to FIGS. 6 to 9 as follows.

6 is a flow chart illustrating a gas treatment method using a gas treatment system according to the first to fifth embodiments of the present invention, and FIG. 7 is a flowchart illustrating a gas treatment method using the gas treatment system according to the first to fifth embodiments of the present invention. A first partial flow chart for explaining a gas treatment method, FIG. 8 is a second partial flow chart for explaining a gas treatment method using a gas treatment system according to the first to fifth embodiments of the present invention, and FIG. 9 is A third partial flow chart for explaining a gas treatment method using a gas treatment system according to the first to fifth embodiments of the present invention.

6 to 9, the gas treatment systems 1, 2, 3, 4, 5 according to the first to fifth embodiments of the present invention are cargo supplied as fuel of the customers 20a and 20b. It can be operated in various ways depending on the amount of the naturally vaporized boil-off gas in the tank 10.

6, a gas treatment method using a gas treatment system (1, 2, 3, 4, 5) according to the first to fifth embodiments of the present invention includes a cargo tank 10 for storing liquefied gas and , When the boil-off gas discharged from the cargo tank 10 exceeds the boil-off gas consumption of the customers 20a, 20b including the propulsion engine, the buffer tank 80 for storing the surplus boil-off gas and the boil-off gas propelling engine In the gas treatment system (1, 2, 3, 4, 5) that includes the boil-off gas compression units (60a, 60b, 60c) for compressing to correspond to the required pressure of the propulsion engine, and operates according to the boil-off gas consumption of the propulsion engine, the cargo When the boil-off gas discharged from the tank 10 exceeds the consumption of the boil-off gas of the propulsion engine, the step of storing the excess boil-off gas in the buffer tank 80 (S210), the internal pressure of the buffer tank 80 is a limit set value When it is determined that it is reached, the step of stopping the storage of the boil-off gas in the buffer tank 80 and increasing the speed of the ship to increase the boil-off gas consumption of the propulsion engine (S220), and the boil-off gas discharged from the cargo tank 10 If the evaporation gas consumption amount of the propulsion engine is not reached, at least a part of the boil-off gas stored in the buffer tank 80 is delivered to the propulsion engine (S230).

Referring to Figure 7, in step S220, the boil-off gas discharged from the cargo tank 10 even after stopping the storage of boil-off gas in the buffer tank 80 and increasing the amount of boil-off gas consumption of the propulsion engine by increasing the ship speed at a high speed. If it is determined that the evaporation gas consumption of the propulsion engine is exceeded, the step of increasing the load of the power generation engine included in the demanders 20a and 20b or consuming the evaporation gas through the gas combustion unit 100 (S221) is further performed. Can include.

Referring to Figure 8, in S230, even after delivering at least a portion of the boil-off gas stored in the buffer tank 80 to the propulsion engine, it is determined that the boil-off gas discharged from the cargo tank 10 does not reach the consumption of the boil-off gas of the propulsion engine. If so, it may further include a step (S231) of supplying the forced vaporized boil-off gas obtained by forcibly vaporizing the liquefied gas of the cargo tank 10 to the propulsion engine.

Referring to FIG. 9, when it is determined that the liquid level of the liquefied gas is lowered due to exhaustion of the boil-off gas stored in the buffer tank 80 as at least part of the boil-off gas stored in the buffer tank 80 is delivered to the propulsion engine in S230, , It may further include a step (S232) of maintaining a certain level by filling the liquefied gas of the cargo tank 10 in the buffer tank 80.

As described above, in this embodiment, in the ship S using the liquefied gas stored in the cargo tank 10 as fuel, the naturally vaporized boil-off gas supplied from the cargo tank 10 as fuel of the customers 20a and 20b, and / Or by treating the forcibly evaporated boil-off gas using the buffer tank 80, it is possible to efficiently process the boil-off gas.

In addition, this embodiment is configured to be stored in the buffer tank 80 when the boil-off gas naturally occurring in the cargo tank 10 is more than or temporarily generated more than the amount of fuel required by the customers 20a and 20b. , It is possible to reduce the amount of boil-off gas burned by the gas combustion unit 100 or discharged to the outside, thereby preventing unnecessary waste of boil-off gas, as well as ensuring the internal pressure stability of the cargo tank 10. .

In addition, in this embodiment, the buffer tank 80 is configured independently of the flow of supplying the liquefied gas as fuel from the cargo tank 10 to the customers 20a and 20b, but the boil-off gas stored in the buffer tank 80 is Explaining the effect of the present invention in which a fuel pump, a fuel carburetor, etc. for supplying liquefied gas to the consumers 20a and 20b should be provided by configuring to be selectively supplied as fuel to the consumers 20a and 20b as needed. Unlike the fuel tank as an example, it is possible to simplify a peripheral device for supplying liquefied gas fuel.

In addition, in this embodiment, the boil-off gas that is naturally vaporized in the cargo tank 10 is supplied as the main fuel of the customers 20a and 20b, but the boil-off gas stored in the buffer tank 80 is supplemented by the customers 20a and 20b. By configuring to supply as fuel, since the buffer tank 80 does not require a fuel pump for supplying liquefied gas fuel, even if the flow rate and internal pressure of the buffer tank 80 are lowered, as an example for explaining the effect of the present invention. Unlike the fuel tank, there is no need to consider the problem of fuel supply interruption and cooldown due to insufficient effective suction head and inlet pressure required for driving the fuel pump.

In addition, in the present embodiment, the buffer tank 80 is configured to supply only the boil-off gas as the fuel of the customers 20a and 20b without supplying the liquefied gas as the fuel of the customers 20a and 20b from the buffer tank 80. Unlike the fuel tank as an example for explaining the effect of the present invention, in order to use liquefied gas as fuel for the customers 20a and 20b, it is not necessary to maintain a certain range of flow rate and internal pressure, and thus from maintaining the flow rate and internal pressure of the liquefied gas. You can be free.

In addition, this embodiment allows the buffer tank 80 to be filled with liquefied gas regardless of the fuel of the customer (20a, 20b) so that the internal boil-off gas can be condensed and stored in the liquefied gas, but the filled liquefied gas is expanded. When discharge from the buffer tank 80 is required, such as, by configuring it to return to the cargo tank 10, liquefied gas compared to that there is no discharge configuration of liquefied gas from the fuel tank as an example for explaining the effect of the present invention. It is possible to ensure the stability of the buffer tank 80 from the expansion of the.

In the above, the present invention has been described based on the embodiments of the present invention, but this is only an example and does not limit the present invention, and those of ordinary skill in the field to which the present invention pertains will not depart from the essential technical content of the present embodiment. It will be appreciated that various combinations or modifications and applications not illustrated in the embodiments are possible in the range. Accordingly, technical contents related to modifications and applications that can be easily derived from the embodiments of the present invention should be interpreted as being included in the present invention.

1, 2, 3, 4, 5: gas treatment system
10: cargo tank 20a, 20b: customer
30, 30a, 30b: pump 40a, 40b: forced carburetor
50, 50a, 50b: gas-liquid separator 60a, 60b, 60c: boil-off gas compression unit
70: boil-off gas cooler 80: buffer tank
90: decompression means 100: gas combustion unit
110: heat exchanger 120: condensation structure
130: pressure generating unit L1: first fuel supply line
L2: second fuel supply line L3: boil-off gas replenishment line
L4: Boiled gas recovery line L5: First liquefied gas recovery line
L6: liquefied gas filling line L7: second liquefied gas recovery line
L8: Evaporative gas emission line S: Ship

Claims (18)

Cargo tank;
A first fuel supply line for supplying the boil-off gas generated from the cargo tank to a customer;
A gas-liquid separator provided in the first fuel supply line;
A second fuel supply line for supplying the liquefied gas stored in the cargo tank to the customer;
A boil-off gas compression unit for compressing the boil-off gas that has passed through the gas-liquid separator;
A boil-off gas recovery line for branching off the boil-off gas that has passed through the boil-off gas compression unit;
A buffer tank for condensing the boil-off gas branched through the boil-off gas recovery line;
A boil-off gas supplement line for moving the boil-off gas generated in the buffer tank to the gas-liquid separator; And
And a liquefied gas filling line branched from the second fuel supply line and provided to move the liquefied gas stored in the cargo tank to the buffer tank,
A pump and a forced vaporizer are provided in the second fuel supply line, and supplying the forced vaporized boil-off gas to the gas-liquid separator. The method of claim 1,
And a first liquefied gas recovery line for recovering the liquefied gas phase-separated in the gas-liquid separator to the cargo tank. The method of claim 1,
And a heat exchanger for exchanging the boil-off gas of the boil-off gas recovery line and the boil-off gas of the first fuel supply line. The method of claim 2,
And a second liquefied gas recovery line for moving the liquefied gas from the buffer tank to the cargo tank. The method of claim 4, wherein the second liquefied gas recovery line,
Gas processing system, characterized in that connected to the first liquefied gas recovery line. delete delete delete The method of claim 1, wherein the buffer tank,
When the boil-off gas discharged from the cargo tank exceeds the amount of boil-off gas consumption of the customer, the excess boil-off gas is delivered and stored through the boil-off gas recovery line,
When the boil-off gas discharged from the cargo tank does not reach the consumption of the boil-off gas of the customer, at least part of the stored boil-off gas is supplemented to the gas delivered to the customer through the boil-off gas supplement line. . The method of claim 1, wherein the buffer tank,
A gas treatment system, characterized in that it is provided independently from a flow of supplying liquefied gas as fuel from the cargo tank to the customer. The method of claim 1, wherein the buffer tank,
Gas treatment system, characterized in that the type-C pressure tank. The method of claim 1, wherein the liquefied gas stored in the cargo tank,
A gas processing system, characterized in that the gas processing system is supplied as fuel to the customer without passing through the buffer tank, and is joined upstream of the boil-off gas compression unit in a state of boil-off gas forcibly evaporated by a forced vaporizer. The method of claim 1, wherein the customer is
It is an XDF engine that is a low-pressure engine that needs to adjust the methane number,
The boil-off gas compression unit,
A gas processing system, characterized in that it is a centrifugal type low compressor that does not allow boil-off gas containing droplets to enter while compressing to correspond to the required pressure of the XDF engine. The method of claim 13, wherein the gas-liquid separator,
The naturally vaporized boil-off gas in the cargo tank is introduced through the first fuel supply line, and the forced vaporized boil-off gas obtained by forcibly evaporating the liquefied gas discharged from the cargo tank in a forced vaporizer through the second fuel supply line. Gas treatment, characterized in that the boil-off gas is introduced and stored in the buffer tank is introduced through the boil-off gas supplement line, and the droplets contained in the boil-off gas are removed, and the methane number is adjusted to supply the boil-off gas compression unit system. The method of claim 1,
Characterized in that it further comprises a condensation structure installed at an end of the boil-off gas recovery line extending to the inner bottom of the buffer tank so that the boil-off gas recovered to the buffer tank is condensed into the liquefied gas filled in the buffer tank. Gas treatment system. The method of claim 1,
And a pressure generating unit installed in the buffer tank and operated when supplying the boil-off gas stored in the buffer tank as the fuel of the customer to increase the amount of boil-off gas and to increase the internal pressure of the buffer tank. Gas treatment system. The method of claim 1,
And a decompression means provided between the buffer tank and the boil-off gas compression unit, and depressurizing the boil-off gas supplied from the buffer tank to the boil-off gas compression unit. A ship, characterized in that the gas treatment system according to any one of claims 1 to 5 and 9 to 17 is provided.

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