KR102379500B1 - Fuel gas treating system in ships - Google Patents

Abstract

A fuel gas management system for a ship is disclosed. In the fuel gas management system of a ship according to this embodiment, a storage tank for accommodating liquefied gas and boil-off gas, a first compressor for pressurizing boil-off gas of the storage tank is provided, and means for consuming the boil-off gas pressurized by the first compressor A boil-off gas supply line supplied to the The line includes a heat exchanger for exchanging a portion of the pressurized BOG with BOG at the front end of the first compressor on the BOG supply line, and a first gas-liquid separator for receiving BOG cooled by the heat exchanger but separating it into a gas component and a liquid component; , a gas component circulation line for depressurizing the gas component of the first gas-liquid separator via an expander, and a second gas-liquid separator for receiving the decompressed gas component transferred along the gas component circulation line but separating it into a gas component and a liquid component; It may be provided, including a liquid component circulation line for supplying the liquid component of the first gas-liquid separator to the second gas-liquid separator, and a pressure control line for supplying a portion of the boil-off gas cooled by the heat exchanger to the second gas-liquid separator.

Description

Fuel gas management system for ships {FUEL GAS TREATING SYSTEM IN SHIPS}

The present invention relates to a fuel gas management system for a ship, and more particularly, to a fuel gas management system for a ship that can promote efficient use and management of fuel gas.

As the International Maritime Organization (IMO)'s regulations on the emission of greenhouse gases and various air pollutants are strengthened, the shipbuilding and shipping industry replaces the existing fuels such as heavy oil and diesel oil, and uses natural gas, a clean energy source, as fuel gas for ships. is being used more and more.

For ease of storage and transportation, natural gas is usually reduced to 1/600 in volume by cooling natural gas to about -162 degrees Celsius. It has changed and is being managed and operated.

Such liquefied natural gas is stored and transported by being accommodated in a storage tank installed after being insulated on the hull. However, since it is practically impossible to completely insulate and accommodate the liquefied natural gas, external heat is continuously transferred to the inside of the storage tank, and the boil-off gas generated by the natural vaporization of the liquefied natural gas is accumulated in the storage tank. . BOG raises the internal pressure of the storage tank and may cause deformation and damage to the storage tank, so it is necessary to process and remove BOG.

For this reason, conventionally, a method of flowing the boil-off gas through a vent mast provided on the upper side of the storage tank or burning the boil-off gas using a gas combustion unit (GCU) has been used. However, since this is undesirable in terms of energy efficiency, a method of supplying BOG together with liquefied natural gas or as fuel gas to the engine of a ship, or reliquefying BOG using a reliquefaction device consisting of a refrigeration cycle, etc. is not recommended. is being used

Republic of Korea Patent Publication No. 10-2010-0035223 (published on April 05, 2010)

This embodiment intends to provide a fuel gas management system for a ship capable of efficiently using and managing fuel gas.

This embodiment is intended to provide a fuel gas management system for a ship that can promote efficient facility operation with a simple structure.

This embodiment intends to provide a fuel gas management system for a ship capable of improving energy efficiency.

This embodiment intends to provide a fuel gas management system for a ship capable of stably performing a reliquefaction process of boil-off gas.

This embodiment intends to provide a fuel gas management system for a ship that can improve structural stability of facilities through effective re-liquefaction and treatment of BOG.

According to one aspect of the present invention, a storage tank for accommodating liquefied gas and boil-off gas, a first compressor for pressurizing boil-off gas of the storage tank is provided, and the boil-off gas pressurized by the first compressor is supplied to a consumption means a boil-off gas supply line, a reliquefaction line for receiving and re-liquefying a portion of the boil-off gas pressurized by the first compressor, and a compander having the first compressor and an expander for decompressing the boil-off gas; The liquefaction line includes a heat exchanger for exchanging a portion of the pressurized BOG with BOG at the front end of the first compressor on the BOG supply line, and a second heat exchanger that receives BOG cooled by the heat exchanger but separates it into a gas component and a liquid component A gas-liquid separator, a gas component circulation line for decompressing the gas component of the first gas-liquid separator via the expander, and a gas component transferred along the gas component circulation line are accommodated, but separated into a gas component and a liquid component a second gas-liquid separator, a liquid component circulation line for supplying the liquid component of the first gas-liquid separator to the second gas-liquid separator, and a pressure for supplying a portion of the boil-off gas cooled by the heat exchanger to the second gas-liquid separator It may be provided including a control line.

The reliquefaction line may be provided by further comprising a first valve provided in the pressure control line to control the supply amount of boil-off gas.

The reliquefaction line includes a gas component recovery line for supplying the gas component of the second gas-liquid separator to the front end of the first compressor on the storage tank or the boil-off gas supply line, and a liquid component of the second gas-liquid separator to the storage tank It may be provided by further comprising a liquid component recovery line for supplying to the

The reliquefaction line includes a pressure sensor for measuring the internal pressure of the second gas-liquid separator, a level sensor for measuring the water level of the second gas-liquid separator, and a second provided in the liquid component recovery line to adjust the supply amount of the liquid component a valve and a third valve provided in the gas component recovery line to control the supply amount of gas components, and control the operation of the first to third valves based on information measured by the pressure sensor and the level sensor It may be provided by further comprising a control unit.

The reliquefaction line may further include a pressure reducing valve provided in the liquid component circulation line to depressurize the liquid component.

The gas component circulation line and the liquid component circulation line are joined to be connected to the second gas-liquid separator, and the reliquefaction line is provided at the rear end of the point where the gas component circulation line and the liquid component circulation line meet. It may be provided by further comprising a check valve to prevent.

The compander may further include a second compressor provided at a rear end of the first compressor to additionally pressurize the boil-off gas introduced into the reliquefaction line.

It may further include an emergency drive line that operates when the compander is stopped, and the emergency drive line may include a preliminary compressor for pressurizing the boil-off gas in the storage tank.

The fuel gas management system of the ship according to this embodiment has the effect of efficiently using and managing fuel gas.

The fuel gas management system of the ship according to this embodiment has the effect of improving energy efficiency.

The fuel gas management system of the ship according to the present embodiment has a simple structure and has the effect of promoting efficient facility operation.

The fuel gas management system of the ship according to this embodiment has the effect of improving the structural stability of the facility.

The fuel gas management system of the ship according to this embodiment has the effect of stably and continuously performing the reliquefaction process of boil-off gas.

1 is a conceptual diagram illustrating a fuel gas management system of a ship according to this embodiment.

Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings. The following examples are presented to sufficiently convey the spirit of the present invention to those of ordinary skill in the art to which the present invention pertains. The present invention is not limited to the embodiments presented herein, and may be embodied in other forms. The drawings may omit the illustration of parts not related to the description in order to clarify the present invention, and slightly exaggerate the size of the components to help understanding.

1 is a conceptual diagram illustrating a fuel gas management system 100 of a ship according to the present embodiment.

Referring to FIG. 1 , in the fuel gas management system 100 of a ship according to an embodiment of the present invention, a storage tank 110 , a first compressor 121 for pressurizing boil-off gas of the storage tank 110 is provided, and the second 1 A boil-off gas supply line 120 for supplying boil-off gas pressurized through the compressor 121 to a consumption means, a first compressor 121 and a second compressor 122 for pressurizing boil-off gas, and pressure reduction of boil-off gas The compander 130 having the expander 144, the reliquefaction line 140 for receiving and re-liquefying a part of the pressurized BOG, and the valves 146a, 147a, 148a based on measurement information of the sensors 145a and 145b ) may be provided including a control unit 150 for controlling the opening/closing operation, and an emergency driving line 160 driven during an emergency operation.

In the following embodiments, liquefied natural gas and boil-off gas generated therefrom have been applied as an example to aid understanding of the present invention, but the present invention is not limited thereto, and various liquefied gases such as liquefied ethane gas and liquefied hydrocarbon gas and this It should be understood in the same way with the same technical idea even when the boil-off gas generated from the gas is applied.

The storage tank 110 is provided to accommodate or store liquefied natural gas and boil-off gas generated therefrom. The storage tank 110 may be provided as a membrane-type cargo hold insulated to minimize vaporization of liquefied natural gas due to external heat intrusion. The storage tank 110 receives or stores liquefied natural gas supplied from a natural gas production area, etc., and stably stores the liquefied natural gas and BOG until it reaches its destination and is unloaded, but as will be described later, a propulsion engine of a ship or a ship It may be provided to be used as a fuel gas, such as an engine for power generation.

The storage tank 110 is generally installed with thermal insulation, but it is practically difficult to completely block the intrusion of external heat. do. Since such BOG raises the internal pressure of the storage tank 110 and poses a risk of deformation and explosion of the storage tank 110 , there is a need to remove or process BOG from the storage tank 110 . Accordingly, the boil-off gas generated inside the storage tank 110 is used as fuel gas of the engine by the boil-off gas supply line 120 or is reliquefied by the re-liquefaction line 140 as in this embodiment, and the storage tank 110 ) can be resupplied. In addition, although not shown in the drawings, the boil-off gas may be treated or consumed by supplying it to a vent mast (not shown) provided on the upper portion of the storage tank 110 .

The consumption means may be supplied with fuel gas such as liquefied natural gas and boil-off gas accommodated in the storage tank 110 to generate propulsive force of the ship or to generate power for power generation such as internal facilities of the ship. The consuming means includes a first consuming means 11 for receiving a relatively high pressure fuel gas to generate an output, a second consuming means 12 for receiving a relatively low pressure fuel gas to generate an output, and surplus fuel gas. It may include a third defense means 13 made of a GCU (Gas Combustion Unit) for receiving and consuming. For example, the first consuming means 11 is made of a ME-GI engine or an X-DF engine capable of generating an output with relatively high-pressure fuel gas, and the second consuming means 12 is a relatively low-pressure fuel. It may consist of a DFDE engine capable of generating an output with gas, or the like. However, the present invention is not limited thereto, and it should be understood that the same number of engines and various types of engines are used.

The boil-off gas supply line 120 may be provided to pressurize the boil-off gas existing in the storage tank 110 and supply it to the consumption means 11 , 12 , 13 and the reliquefaction line 140 . The boil-off gas supply line 120 is provided with an inlet end connected to the inside of the storage tank 110 , and an outlet end end may be branched and connected to the consumption means 11 , 12 , 13 , respectively. In particular, at the front end of the second consuming means 12 and the third consuming means 13 on the boil-off gas supply line 120 , the pressure of the pressurized boil-off gas is adjusted according to the required pressure level of each of the consumption means 12 and 13 . A pressure reducing valve (not shown) may be provided, respectively.

A plurality of first compressors 121 of the compander 130 are provided in the BOG supply line 120 to process BOG according to the conditions required by the engine, the first compressor 121 and the second At the rear end of the compressor 122 , a reliquefaction line 140 , which will be described later, may be provided branching from the boil-off gas supply line 120 .

The first compressor 121 provided in the compander 130 may be provided in a plurality of stages to compress the boil-off gas in stages. In addition, it may further include a cooler (not shown) for cooling the boil-off gas heated while being compressed by the compressor. In FIG. 1 , the first compressor 121 is illustrated as being composed of a three-stage compressor, but this is an example, and the first compressor 121 may be composed of a variable number of compressors and coolers depending on the required pressure condition and temperature of the consumption means. can In addition, a heat exchanger 142 of the reliquefaction line 140 to be described later may be installed at the front end of the first compressor 121 on the boil-off gas supply line 120 , and a detailed description thereof will be provided later.

The second compressor 122 is provided at the rear end of the first compressor 121 to additionally pressurize the boil-off gas flowing into the reliquefaction line 140 . Like the first compressor 121 , the second compressor 122 may be disposed in multiple stages to compress the boil-off gas in stages. The second compressor 122 may further include a cooler (not shown) for cooling the boil-off gas heated while being compressed. In FIG. 1 , the second compressor 122 is illustrated as being composed of a two-stage compressor, but this is an example, and the second compressor 122 may be composed of various number of compressors and coolers depending on the required pressure condition and temperature of the consumption means. The compander 130 includes a first compressor 121 and a second compressor 122 for pressurizing the supplied boil-off gas, and an expander 144 for decompressing the supplied boil-off gas, and the first The compressor 121 may pressurize the BOG by using the BOG expansion force in the expander 144 . For example, the expander 144 is provided as a turbine type, and the expander 144 rotates the turbine with the expansion force obtained in the process of decompressing and expanding the boil-off gas, and energy generated by the rotation of the turbine By utilizing the first compressor 121 can pressurize the boil-off gas. The first compressor 121 of the compander 130 may pressurize the introduced BOG to a pressure level of about 12 to 17 bar, and the second compressor 122 may pressurize the BOG introduced into the reliquefaction line 140 . can be pressurized to a pressure level of about 40 to 60 bar. In addition, the expander 144 may reduce the introduced boil-off gas to a pressure level of about 4 bar. However, the numerical value is an example to help the understanding of the present invention, and the first compressor 121 and the second compressor 121 and 2 The pressure value of the compressor 122 and the pressure value of the expander 144 may be variously changed.

The re-liquefaction line 140 passes through the first compressor 121 and the second compressor 122 of the boil-off gas supply line 120 and is provided to receive and reliquefy the pressurized boil-off gas.

The reliquefaction line 140 includes a heat exchanger 142 that cools the pressurized BOG, and a first gas-liquid separator 143 that receives BOG cooled through the heat exchanger 142 and separates it into a gas component and a liquid component. ), the gas component circulation line 143a for supplying the gas component of the first gas-liquid separator 143 to the expander 144 of the compander 130 to reduce pressure, and the liquid component of the first gas-liquid separator 143 is supplied A liquid component circulating line 143c for receiving and depressurizing, a gas component circulating line 143a and a liquid component receiving the decompressed gas component and liquid component supplied along the liquid component circulation line 143c, but separating the gas component and the liquid component 2 gas-liquid separator 145, a liquid component recovery line 146 for supplying the liquid component of the second gas-liquid separator 145 to the storage tank 110, and a storage tank 110 for the gas component of the second gas-liquid separator 145 Alternatively, a pressure control line 148 for directly supplying a portion of the BOG cooled through the gas component recovery line 147 and the heat exchanger 142 supplied to the BOG supply line 120 to the second gas-liquid separator 145 . may include

The heat exchanger 142 is provided to cool the boil-off gas pressurized through the first compressor 121 and the second compressor 122 . The heat exchanger 142 transfers the pressurized boil-off gas along the boil-off gas supply line 120 to heat exchange with the boil-off gas before the pressurization of the front end of the first compressor 121, so that the first compressor 121 and the second compressor 122 ), while cooling the pressurized BOG, the BOG before the pressurization of the front end of the first compressor 121 may be heated. Since the pressurized BOG is pressurized by the first compressor 121 and the second compressor 122 to increase the temperature and pressure, the low temperature before passing through the first compressor 121 of the BOG supply line 120 is By exchanging heat with BOG, the high-temperature pressurized BOG supplied to the reliquefaction line 140 can be cooled. As described above, since the pressurized BOG can be cooled without a separate cooling device by the heat exchanger 142, unnecessary waste of power is prevented, the facility is simplified, and the efficiency of facility operation can be promoted.

The first gas-liquid separator 143 is provided to separate the boil-off gas in a gas-liquid mixed state cooled by passing through the heat exchanger 142 into a gas component and a liquid component. As the pressurized BOG is cooled while passing through the heat exchanger 142, some reliquefaction is performed, but an unliquefied gas component may also exist. Accordingly, the first gas-liquid separator 143 receives the boil-off gas cooled by passing through the heat exchanger 142, and separates it into a gas component and a liquid component to facilitate easy handling and management of each component.

The gas component circulation line 143a is provided to supply and pass through the gas component separated in the first gas-liquid separator 143 to the expander 144 of the compander 130 . To this end, the inlet side end of the gas component circulation line 143a communicates with the inner upper side of the first gas-liquid separator 143, and the outlet side end joins with the liquid component circulation line 143c to be described later to the second gas-liquid separator 145 ), but the middle portion may be provided to pass through the expander 144 of the compander 130 .

The expander 144 of the compander 130 is provided to depressurize and expand the gas component of the first gas-liquid separator 143 transferred along the gas component circulation line 143a. The expander 144 is pressurized through the first compressor 121 and the second compressor 122, and by decompressing the cooled boil-off gas through the heat exchanger 142, it is cooled and expanded to realize re-liquefaction of the gas component. there is. The expander 144 may reduce the gas component to a pressure level corresponding to the internal pressure of the second gas-liquid separator 145 , and a detailed description thereof will be provided later.

The liquid component circulation line 143c is provided to supply the liquid component separated in the first gas-liquid separator 143 by re-liquefaction through the heat exchanger 142 to the second gas-liquid separator 145 to be described later. To this end, the inlet side end of the liquid component circulation line 143c communicates with the inner lower side of the first gas-liquid separator 143, and the outlet side end joins the gas component circulation line 143a to the second gas-liquid separator 145. A pressure reducing valve (143d) for decompressing the liquid component transferred along the liquid component circulation line (143c) may be provided at the middle part.

The pressure reducing valve 143d may reduce the pressure to a pressure level corresponding to the internal pressure of the liquid component second gas-liquid separator 145 provided in the liquid component circulation line 143c and transferred thereto. As described above, the boil-off gas flowing into the reliquefaction line 140 is pressurized while passing through the first compressor 121 and the second compressor 122, and the pressure reducing valve 143d is the first gas-liquid separator 143. By depressurizing the separated liquid component, cooling and expansion can be implemented. The pressure reducing valve 143d may be, for example, a Joule-Thomson valve.

In addition, between the point where the gas component circulation line 143a and the liquid component circulation line 143c join and the second gas-liquid separator 145, the counterflow of the gas flow, specifically, the gas component circulation line from the second gas-liquid separator 145 ( 143a) and a check valve (143b) for preventing gas flow from occurring to the liquid component circulation line (143c) may be provided.

The second gas-liquid separator 145 receives the boil-off gas in a gas-liquid mixed state supplied from the gas component circulation line 143a and the liquid component circulation line 143c, but is provided to separate the gas component into a gas component and a liquid component. Most of the gas components of the first gas-liquid separator 143 are reliquefied as they are reduced and cooled while passing through the expander 144 , but gas components such as flash gas may be generated during the decompression process. In addition, as the liquid component of the first gas-liquid separator 143 is depressurized via the pressure reducing valve 143d, some gas components may be generated. Accordingly, the second gas-liquid separator 145 receives the gas flows respectively transferred along the gas component circulation line 143a and the liquid component circulation line 143c, but separates them into gas components and liquid components for easy handling and management can be facilitated. The second gas-liquid separator 145 may be provided with a level sensor 145a for measuring the water level and a pressure sensor 145b for measuring the internal pressure, which will be described in detail later.

The liquid component recovery line 146 may connect the second gas-liquid separator 145 and the storage tank 110 to re-supply the liquid component separated by the second gas-liquid separator 145 to the storage tank 110 . The liquid component recovery line 146 may have an inlet-side end connected to the inner lower side of the second gas-liquid separator 145 , and an outlet-side end connected to the inside of the storage tank 110 .

The liquid component recovery line 146 may be provided with a second valve 146a for controlling the supply amount of the liquid component recovered to the storage tank 110 . The second valve 146a can be opened and closed based on the water level information of the second gas-liquid separator 145 measured by the level sensor 145a, and the degree of opening and closing can be adjusted, and the second valve 146a is the control unit 150 The opening/closing operation may be automatically controlled by the operator, or the opening/closing operation may be manually controlled by an operator.

The gas component recovery line 147 includes a second gas-liquid separator 145 and a storage tank ( 110) or the second gas-liquid separator 145 and the boil-off gas supply line 120 may be provided. In FIG. 1 , the gas component recovery line 147 is illustrated as resupplying the gas component of the second gas-liquid separator 145 to the front end of the first compressor 121 on the boil-off gas supply line 120 , but in addition to this, the second This includes all cases of re-supplying from the gas-liquid separator 145 to the storage tank 110 or re-supplying the boil-off gas supply line 120 and the storage tank 110 together.

The gas component recovery line 147 may be provided with a third valve 147a for controlling the supply amount of the gas component recovered to the storage tank 110 or the boil-off gas supply line 120 . The third valve 147a can be opened and closed based on the internal pressure information of the second gas-liquid separator 145 measured by the pressure sensor 145b, and the degree of opening and closing can be adjusted, and the third valve 147a is the control unit 150 ) to automatically control the opening/closing operation, or manually controlling the opening/closing operation by an operator.

Meanwhile, the internal pressure of the second gas-liquid separator 145 is greater than the internal pressure of the storage tank 110 . This is to effectively supply the liquid component separated by the second gas-liquid separator 145 , that is, the reliquefied BOG to the storage tank 110 . For example, when the internal pressure of the storage tank 110 is operated at the atmospheric pressure level, the expander 144 and the pressure reducing valve 143d of the compander 130 respectively convert the gas component and the liquid component to a pressure level of about 4 bar. The pressure is reduced, and the internal pressure of the second gas-liquid separator 145 is also operated at a pressure level corresponding thereto. However, it is practically impossible to constantly maintain the operating pressure of the expander 144 at 4 bar due to the structural limit or operational limit of the compander 130 . Accordingly, there is a fear that the pressure level of the gas component pressurized by the expander 144 of the compander 130 is lower than 4 bar. In this case, the internal pressure of the second gas-liquid separator 145 is also reduced, so that the second gas-liquid There is a problem in that it becomes difficult to re-supply the gas component and the liquid component accommodated in the separator 145 to the storage tank 110 and the like.

Accordingly, the reliquefaction line 140 may include a pressure control line 148 for adjusting the internal pressure of the second gas-liquid separator 145 and a first valve 148a provided therefor to adjust the BOG supply amount.

The pressure control line 148 is provided to directly supply a portion of the pressurized BOG at the front end of the first gas-liquid separator 143 to the second gas-liquid separator 145 to adjust the internal pressure of the second gas-liquid separator 145 . To this end, the inlet end of the pressure control line 148 is branched between the heat exchanger 142 and the first gas-liquid separator 143 on the reliquefaction line 140 , and the outlet-side end is the second gas-liquid separator 145 . It may be connected to the inside, and the pressure control line 148 may be provided with a first valve 148a for controlling the supply amount of the pressurized boil-off gas transferred along it. Whether the first valve 148a is opened or closed based on the internal pressure information of the second gas-liquid separator 145 measured by the pressure sensor 145b and the degree of opening and closing can be adjusted, and the first valve 148a is the control unit 150 ) to automatically control the opening/closing operation, or manually controlling the opening/closing operation by an operator.

In this way, the pressure control line 148 directly supplies a portion of the boil-off gas pressurized through the first compressor 121 and the second compressor 122 to the second gas-liquid separator 145 , thereby forming the second gas-liquid separator 145 . ) can be adjusted and raised, and thus the liquid component recovery line 146 and the gas component recovery line 147 can be used as a power source by using the internal pressure of the second gas-liquid separator 145 as a power source without a separate compressor or pump. ), the liquid component and gas component can be re-supplied, respectively, so that the efficiency of facility operation can be promoted.

The control unit 150 may automatically control the opening and closing operations of the first to third valves 146a, 147a, and 148a based on information measured by the level sensor 145a and the pressure sensor 145b. Specifically, when the level of the second gas-liquid separator 145 measured by the level sensor 145a exceeds a preset value, the controller 150 disconnects the liquid component recovery line 146 from the second gas-liquid separator 145 . Accordingly, it is judged that the resupply of the liquid component is not smooth. In other words, it is determined that the internal pressure of the second gas-liquid separator 145 is low and it is insufficient to utilize it as a power source for supplying gas and liquid components. Then, the control unit 150 controls the operation to open the first valve 148a to increase the flow rate of the pressurized BOG supplied to the second gas-liquid separator 145 through the flow rate control line 148, thereby 2 As the internal pressure of the gas-liquid separator 145 rises, the liquid component may be smoothly supplied through the liquid component recovery line 146 . At this time, the control unit 150 may close the third valve 147a of the gas component recovery line 147a in order to effectively and quickly control the internal pressure of the second gas-liquid separator 145 .

After that, when the water level of the second gas-liquid separator 145 measured by the level sensor 145a is lower than a preset value, the control unit 150 determines that the normal operation of the reliquefaction line 140 is possible, and the first By controlling the operation to close the valve 148a again, the gas flow transferred along the gas component circulation line 143a and the liquid component circulation line 143c flows back into the second gas-liquid separator 145, and The reliquefaction process may be performed again.

On the other hand, even in the case of malfunction of the compander 130 or stoppage for maintenance, continuous operation of the consumption means 11 , 12 , 13 such as the engine may be required depending on the operating environment of the ship, in particular, When the operation of the first compressor 121 of the panda 130 is stopped, there is a fear that the internal pressure of the storage tank 110 may rise as the boil-off gas inside the storage tank 110 accumulates. As described above, since there is a risk of safety accidents such as deformation or explosion of the storage tank 110 as the internal pressure of the storage tank 110 rises, the boil-off gas in the storage tank 110 must be continuously removed and treated.

Accordingly, when the compander 130 malfunctions or is stopped for maintenance, an emergency driving line 160 for removing and processing boil-off gas in the storage tank 110 may be provided.

The emergency driving line 160 is branched from the front end of the first compressor 121 on the boil-off gas supply line 120 and may be provided to rejoin at the rear end of the first compressor 121, and is configured to auxiliaryly pressurize the boil-off gas. A preliminary compressor 161 may be included. Like the first compressor 121 , the preliminary compressor 161 may be provided in multiple stages to compress the BOG in stages, and may further include a cooler (not shown) for cooling the BOG heated while being compressed. In this way, since the boil-off gas of the storage tank 110 can be removed and treated in any operating situation by the emergency drive line 160 and the preliminary compressor 161 provided therein, it is unnecessary to promote the stability of facility operation and at the same time Energy efficiency can be improved by minimizing the boil-off gas that must be consumed.

100: fuel gas management system 110: storage tank
120: boil-off gas supply line 121: first compressor
122: second compressor 130: compander 140: re-liquefaction line
142: heat exchanger
143: first gas-liquid separator 143a: gas component circulation line
143c: liquid component circulation line 144: expander
145: second gas-liquid separator 145a: level sensor
145b: pressure sensor 146: liquid component recovery line
147: gas component recovery line 148: pressure control line
150: control unit 160: emergency drive line

Claims (8)

a storage tank for accommodating liquefied gas and boil-off gas;
a boil-off gas supply line provided with a first compressor for pressurizing the boil-off gas in the storage tank and supplying the boil-off gas pressurized by the first compressor to a consumption means;
a re-liquefaction line for receiving and re-liquefying a portion of the boil-off gas pressurized by the first compressor; and
a compander including the first compressor and an expander for decompressing the boil-off gas;
The reliquefaction line is
A heat exchanger for exchanging a portion of the pressurized BOG with BOG at the front end of the first compressor on the BOG supply line, and a first gas-liquid separator for receiving BOG cooled by the heat exchanger but separating it into a gas component and a liquid component and a gas component circulation line for depressurizing the gas component of the first gas-liquid separator via the expander, and a second second for accommodating the decompressed gas component transferred along the gas component circulation line and separating it into a gas component and a liquid component A gas-liquid separator, a liquid component circulation line for supplying the liquid component of the first gas-liquid separator to the second gas-liquid separator, and a pressure control line for supplying a portion of the boil-off gas cooled by the heat exchanger to the second gas-liquid separator A ship's fuel gas management system, including. According to claim 1,
The reliquefaction line is
The fuel gas management system of a ship further comprising a first valve provided in the pressure control line to control the supply amount of boil-off gas. 3. The method of claim 2,
The reliquefaction line is
A gas component recovery line for supplying the gas component of the second gas-liquid separator to the front end of the first compressor on the storage tank or the boil-off gas supply line, and a liquid component for supplying the liquid component of the second gas-liquid separator to the storage tank A fuel gas management system for a ship further comprising a recovery line. 4. The method of claim 3,
The reliquefaction line is
A pressure sensor for measuring the internal pressure of the second gas-liquid separator, a level sensor for measuring the water level of the second gas-liquid separator, a second valve provided in the liquid component recovery line to control the supply amount of the liquid component; Further comprising a third valve provided in the component recovery line to control the supply amount of the gas component,
The fuel gas management system of a ship further comprising a; a control unit for controlling the operation of the first to third valves based on the information measured by the pressure sensor and the level sensor. 5. The method of claim 4,
The reliquefaction line is
A fuel gas management system for a ship further comprising a pressure reducing valve provided in the liquid component circulation line to reduce the liquid component. 6. The method of claim 5,
The gas component circulation line and the liquid component circulation line join and are connected to the second gas-liquid separator,
The reliquefaction line is
The fuel gas management system of a ship further comprising a check valve provided at a rear end of a point where the gas component circulation line and the liquid component circulation line merge to prevent a reverse flow of the gas flow. 7. The method of claim 6,
The compander is
The fuel gas management system of a ship further comprising a second compressor provided at the rear end of the first compressor to additionally pressurize the boil-off gas introduced into the reliquefaction line. 8. The method of claim 7,
It further includes; an emergency drive line that operates when the compander is stopped.
The emergency driving line is a fuel gas management system for a ship including a preliminary compressor for pressurizing the boil-off gas of the storage tank.

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