KR102477625B1 - Fuel gas supplying system in ships - Google Patents

Abstract

A fuel gas supply system according to the present invention includes a storage tank for accommodating liquefied gas and boil-off gas; a first fuel gas supply line having a compression unit for pressurizing the boil-off gas of the storage tank and passing through the compression unit to supply the pressurized boil-off gas to a consumer; a re-liquefaction line for receiving and re-liquefying a part of the pressurized boil-off gas; a gas-liquid separator provided in the re-liquefaction line and separating boil-off gas in a gas-liquid mixed state into a gas component and a liquid component; a boil-off gas circulation line supplying the gas component separated in the gas-liquid separator to a consumer; a first recovery line provided with an ejector for supplying liquid components separated by the gas-liquid separator to the storage tank; a second fuel gas supply line for pressurizing the liquefied gas in the storage tank with a high-pressure pump, vaporizing it with a heat exchanger, and supplying the liquefied gas to the consumer; An ejector line for supplying liquefied gas under high pressure at the rear end of the high-pressure pump to the ejector may be included.

Description

Fuel gas supply system {FUEL GAS SUPPLYING SYSTEM IN SHIPS}

The present invention relates to a fuel gas supply system, and more particularly, to a fuel gas supply system for ships capable of promoting efficient use and management of fuel gas.

As the regulations of the International Maritime Organization (IMO) on the emission of greenhouse gases and various air pollutants are strengthened, the shipbuilding and shipping industries use natural gas, a clean energy source, as fuel gas for ships instead of using heavy oil and diesel oil, which are existing fuels. are increasingly being used.

Natural gas is usually liquefied natural gas, a colorless and transparent cryogenic liquid that is reduced to 1/600 of its volume by cooling natural gas to about -162 degrees Celsius for ease of storage and transportation. It changes and manages and operates.

This liquefied natural gas is stored and transported in a storage tank that is insulated and installed on the hull. However, since it is practically impossible to completely insulate and accommodate liquefied natural gas, external heat is continuously transferred to the inside of the storage tank, and liquefied natural gas is naturally vaporized, and evaporated gas is accumulated inside the storage tank. . Boiled gas increases the internal pressure of the storage tank and may cause deformation and damage of the storage tank, so it is necessary to treat and remove the boil-off gas.

Accordingly, in the prior art, a method of sending the boil-off gas to a vent mast provided on the upper side of the storage tank or burning the boil-off gas using a GCU (Gas Combustion Unit) has been used. However, this is not desirable in terms of energy efficiency, so a method of re-liquefying the boil-off gas by supplying the boil-off gas together with liquefied natural gas or as fuel gas to the ship's engine, or using a re-liquefaction device consisting of a refrigeration cycle, etc. It is being used.

On the other hand, natural gas is a mixture containing ethane, propane, butane, and nitrogen in addition to methane. Among them, the boiling point of nitrogen is about -195.8 degrees Celsius, which is very low compared to other components such as methane (boiling point -161.5 degrees Celsius) and ethane (boiling point -89 degrees Celsius).

As a result, the boil-off gas generated by vaporization naturally inside the storage tank contains a lot of nitrogen components with a relatively low boiling point, which reduces the re-liquefaction efficiency of the boil-off gas, which affects the utilization and treatment of boil-off gas. going crazy

In addition, when the boil-off gas is supplied as fuel gas to the engine of a ship, the nitrogen component of the boil-off gas affects the lowering of the calorific value of the fuel gas, thereby improving the re-liquefaction efficiency of the boil-off gas and the calorific value of the fuel gas. A plan to promote citation and management is required.

Republic of Korea Patent Publication No. 10-2010-0035223 (published on April 5, 2010)

The present invention is to provide a fuel gas supply system capable of efficiently using and managing fuel gas.

According to one aspect of the present invention, a storage tank for accommodating liquefied gas and boil-off gas; a first fuel gas supply line having a compression unit for pressurizing the boil-off gas of the storage tank and passing through the compression unit to supply the pressurized boil-off gas to a consumer; a re-liquefaction line for receiving and re-liquefying a part of the pressurized boil-off gas; a gas-liquid separator provided in the re-liquefaction line and separating boil-off gas in a gas-liquid mixed state into a gas component and a liquid component; a boil-off gas circulation line supplying the gas component separated in the gas-liquid separator to a consumer; a first recovery line provided with an ejector for supplying liquid components separated by the gas-liquid separator to the storage tank; a second fuel gas supply line for pressurizing the liquefied gas in the storage tank with a high-pressure pump, vaporizing it with a heat exchanger, and supplying the liquefied gas to the consumer; A fuel gas supply system including an ejector line for supplying liquefied gas under high pressure at the rear end of the high pressure pump to the ejector may be provided.

When the internal pressure of the gas-liquid separator falls below a predetermined level, the internal pressure of the gas-liquid separator may be adjusted by closing the first flow control valve provided in the first recovery line.

A second flow control valve is provided and a second recovery line for supplying the liquid component separated in the gas-liquid separator to the storage tank; further comprising a control unit of the first flow control valve or the second flow control valve. A flow rate flowing through the first recovery line may be adjusted by controlling at least one of them.

A third flow control valve is provided in the ejector line, and the control unit controls at least one of the first to third flow control valves to adjust the flow rate flowing through the first recovery line.

The re-liquefaction line may include a cooling unit for cooling the pressurized boil-off gas, and an expansion valve for reducing the boil-off gas passing through the cooling unit and supplying it to the gas-liquid separator.

The fuel gas supply system according to the present invention can easily recover the liquid component remaining inside the gas-liquid separator or stagnant in the pipe to the storage tank through the first recovery line provided with the ejector.

In addition, when the internal pressure of the gas-liquid separator falls below a certain level, the first flow control valve provided in the first recovery line is closed to prevent the gas-liquid separator from being in a vacuum state.

1 is a conceptual diagram showing a fuel gas supply system according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention 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 skilled in the art. The present invention may be embodied in other forms without being limited to only the embodiments presented herein. In the drawings, in order to clarify the present invention, illustration of parts irrelevant to the description may be omitted, and the size of components may be slightly exaggerated to aid understanding.

1 is a conceptual diagram showing a fuel gas supply system 100 according to an embodiment of the present invention. Referring to this, the fuel gas supply system 100 according to an embodiment of the present invention includes a storage tank 110 and a compression unit 121 for pressurizing the boil-off gas of the storage tank 110, and the compression unit 121 The first fuel gas supply line 120 for supplying the pressurized boil-off gas through the gas-liquid supply line 120, the re-liquefaction line 130 for receiving and re-liquefying a part of the pressurized boil-off gas, and provided in the re-liquefaction line 130 and gas-liquid The gas-liquid separator 133 separates the boil-off gas in the mixed state into gas and liquid components, the boil-off gas circulation line 134 supplies the gas components separated in the gas-liquid separator 133 to the consumer, and the gas-liquid separator 133. The first recovery line 170 provided with an ejector 171 for supplying the liquid component to the storage tank 110, the liquefied gas in the storage tank 110 is pressurized by the high pressure pump 152 and transferred to the heat exchanger 153. It may include a second fuel gas supply line 150 for vaporizing and supplying it to a consumer, and an ejector line 180 for supplying high-pressure liquefied gas at the rear of the high-pressure pump 152 to the ejector 171 .

In the following embodiments, as an example to aid understanding of the present invention, liquefied natural gas and boil-off gas generated therefrom have been applied and described, but the present invention is not limited thereto, and various liquefied gases such as liquefied ethane gas and liquefied hydrocarbon gas and Even when the generated evaporation gas is applied, it should be equally understood in the same technical spirit. In addition, the consumer includes a first consumer 10, which is an engine requiring fuel gas in a relatively high-pressure state, and a second consumer 20, which is an engine requiring fuel gas in a low-pressure state, either of which can refer to

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 an insulated membrane-type cargo hold to minimize vaporization of liquefied natural gas due to external heat intrusion. The storage tank 110 receives and stores liquefied natural gas from natural gas producers, etc., and stably stores liquefied natural gas and boil-off gas until reaching the destination and unloading. It may be provided to be used as a fuel gas for an engine for power generation of.

Although the storage tank 110 is generally insulated and installed, it is practically difficult to completely block external heat intrusion, so that evaporation gas generated by naturally evaporating liquefied natural gas exists inside the storage tank 110. do. Since this boil-off gas raises the internal pressure of the storage tank 110 and poses a risk of deformation and explosion of the storage tank 110, it is necessary to remove or treat the boil-off gas from the storage tank 110. Accordingly, the boil-off gas generated inside the storage tank 110 is used as the fuel gas of the engine by the first fuel gas supply line 120 or the branch line 140 as in the embodiment of the present invention, or the re-liquefaction line 130 It can be re-liquefied by ) and re-supplied to the storage tank 110. 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 above the storage tank 110.

The engine may receive fuel gas such as liquefied natural gas and boil-off gas contained in the storage tank 110 to generate propulsion of the ship or generate power for power generation such as internal facilities of the ship. The engine may include a first consumer 10 receiving relatively high-pressure fuel gas and generating output, and a second consumer 20 receiving relatively low-pressure fuel gas and generating output. For example, the first consumer 10 is composed of a ME-GI engine or an X-DF engine capable of generating output with relatively high-pressure fuel gas, and the second consumer 20 outputs with relatively low-pressure fuel gas. It can be made up of a DFDE engine that can generate . However, it is not limited thereto, and it should be understood the same even when various numbers of engines and various types of engines are used.

The first fuel gas supply line 120 pressurizes the boil-off gas present in the storage tank 110 and supplies it to the first consumer 10 and the re-liquefaction line 130 . The first fuel gas supply line 120 has an inlet end connected to the inside of the storage tank 110, and an outlet end connected to the first consumer 10 via the first fuel gas supply line 120. can be arranged so that In the first fuel gas supply line 120, a compression unit 121 having a plurality of stages of compressors 121a is provided to process boil-off gas according to conditions required by the engine, and at the rear end of the compression unit 121 A reliquefaction line 130 to be described later may be provided branched from the first fuel gas supply line 120 .

The compression unit 121 may include a compressor 121a for compressing the boil-off gas and a cooler 121b for cooling the heated boil-off gas while being compressed. When the engine is composed of a plurality of engines having different pressure conditions, a branch line 140 to be described later is branched from the stop of the compression unit 121 to supply partially pressurized boil-off gas to the second consumer 20. It can be.

In FIG. 1, the compression unit 121 is shown as consisting of a 5-stage compressor 121a and a cooler 121b, but this is an example. (121a) and a cooler (121b). In addition, a cooling unit 131 of a reliquefaction line 130 to be described later may be installed at the front end of the compression unit 121 on the first fuel gas supply line 120, and a detailed description thereof will be described later.

The re-liquefaction line 130 passes through the compression unit 121 of the first fuel gas supply line 120 and is provided to receive and re-liquefy some of the pressurized boil-off gas.

The reliquefaction line 130 includes a cooling unit 131 for cooling the pressurized boil-off gas, an expansion valve 132 for primarily reducing the pressurized boil-off gas passing through the cooling unit 131, and an expansion valve 132. A gas-liquid separator 133 that passes through and separates the boil-off gas in a gas-liquid mixture into gas and liquid components, and a boil-off gas circulation line 134 that supplies the separated gas components in the gas-liquid separator 133 to the second consumer 20 , It may include a first recovery line 170 and a second recovery line 160 for re-supplying the liquid component separated in the gas-liquid separator 133 to the storage tank 110.

The cooling unit 131 is provided to cool the pressurized boil-off gas supplied to the reliquefaction line 130 . The cooling unit 131 is a gas-liquid separator that transfers the pressurized boil-off gas along the first fuel gas supply line 120, the boil-off gas at the front end of the compression unit 121, and the boil-off gas circulation line 134 to be described later ( 133) may consist of a heat exchanger that exchanges heat with the separated gas component. Since the pressurized boil-off gas is pressurized by the compression unit 121 and the temperature and pressure are elevated, the low-temperature boil-off gas before passing through the compression part 121 of the first fuel gas supply line 120 and the boil-off gas circulation line By exchanging heat with the low-temperature gas component transported along the 134, the high-temperature pressurized boil-off gas supplied to the re-liquefaction line 130 can be cooled. In this way, by providing the cooling unit 131 as a heat exchanger, since the pressurized boil-off gas can be cooled without a separate cooling device, unnecessary waste of power is prevented and facilities are simplified, thereby improving facility operation efficiency.

The expansion valve 132 may be provided at a rear end of the cooling unit 131 . The expansion valve 132 may implement re-liquefaction by first reducing the pressurized boil-off gas that has passed through the cooling unit 131, cooling and expanding it. The expansion valve 132 may be formed of, for example, a Joule-Thomson valve. The expansion valve 132 may reduce the pressurized boil-off gas that has passed through the cooling unit 131 to a pressure level corresponding to the fuel gas pressure condition required by the second consumer 20 . A detailed description of this will be described later.

The gas-liquid separator 133 passes through the expansion valve 132 to cool and depressurize, and is provided to separate boil-off gas in a gas-liquid mixed state into a gas component and a liquid component. When the pressurized evaporation gas passes through the expansion valve 132, it is cooled and decompressed to be re-liquefied, but flash gas may be generated during the depressurization process. Accordingly, the gas-liquid separator 133 receives the boil-off gas that passes through the expansion valve 132 and becomes a gas-liquid mixture, and at the same time separates it into a gas component and a liquid component to promote the reliability of the re-liquefaction process and treat each component separately. can do.

On the other hand, natural gas is a mixture containing ethane, propane, butane, nitrogen, and the like in addition to methane, which is the main component. Among them, the boiling point of nitrogen is about -195.8 degrees Celsius, which is very low compared to other components such as methane (boiling point -161.5 degrees Celsius) and ethane (boiling point -89 degrees Celsius). As the nitrogen component has a very low boiling point, the evaporation gas generated by naturally evaporating inside the storage tank 110 is vaporized relatively first and contains a large amount of nitrogen, and furthermore, the nitrogen component of the evaporation gas There is a problem in that the re-liquefaction efficiency of the boil-off gas decreases as the concentration of is increased.

In particular, after pressurizing the boil-off gas by the compression unit 121 and cooling the pressurized boil-off gas by the cooling unit 131 to re-liquefy the boil-off gas, the gas-liquid separator when reducing the pressure of the boil-off gas pressurized by the expansion valve 132 Gas components such as flash gas separated in 133 contain a high concentration of nitrogen components having a low boiling point. When the gas component containing a high concentration of nitrogen component is circulated again in the fuel gas system 100, not only the re-liquefaction efficiency of the boil-off gas is lowered, but also the compressor 121a of the compression unit 121 due to the circulated gas component. There is a problem that causes a load on the back or requires the installation of a high-spec compressor 121a, resulting in inefficiency in facility operation.

The boil-off gas circulation line 134 is provided to supply a gas component separated from the gas-liquid separator 133 and containing a high-concentration nitrogen component to the second consumer 20 as fuel gas. As described above, a relatively high concentration of nitrogen is contained in the gas component generated in the process of reducing the pressure of the boil-off gas cooled and pressurized through the expansion valve 132. Accordingly, the boil-off gas circulation line 134 receives a gas component having low re-liquefaction efficiency and supplies and uses it as fuel gas to the second consumer 20, thereby promoting efficient use of the fuel gas and at the same time, the gas-liquid separator 133 ), it is possible to increase the re-liquefaction efficiency of the liquid component containing a relatively low concentration of nitrogen component.

The expansion valve 132 is provided to reduce the pressurized boil-off gas that has passed through the cooling unit 131 to a level corresponding to the pressure condition required by the second consumer 20, and the boil-off gas circulation line 134 is a separate compression The gas component separated in the gas-liquid separator 133 can be directly supplied to the second consumer 20 as fuel gas without a device.

The boil-off gas circulation line 134 is provided to pass through the cooling unit 131 made of a heat exchanger. At the same time as cooling the pressurized boil-off gas flowing along the re-liquefaction line 130 using the cooling heat of the gas component containing a high concentration of nitrogen flowing along the boil-off gas circulation line 134, the re-liquefaction line 130 The temperature of the gas component flowing along the boil-off gas circulation line 134 is raised to a level corresponding to the temperature condition of the fuel gas required by the second consumer 20 by receiving the high-temperature heat of the pressurized boil-off gas flowing along the can

The boil-off gas circulation line 134 is provided with a flow rate control valve 134a of the calorific value control unit, which will be described later, so that the supply amount of the fuel gas transported along the boil-off gas circulation line 134 can be adjusted.

The branch line 140 is provided to be branched from the interruption portion of the compression unit 121 of the first fuel gas supply line 120 to supply some pressurized boil-off gas to the second consumer 20. The branch line 140 has an inlet end connected to the stop of the compression unit 121, and an outlet end connected to the boil-off gas circulation line 134 and connected to the second consumer 20. there is. A valve 140a is provided in this branch line 140, and the flow rate flowing along it can be adjusted.

Since the second consumer 20 receives relatively low-pressure fuel gas and generates output, it is provided branched off from the middle portion of the compression unit 121 for compressing the boil-off gas, thereby receiving some pressurized boil-off gas as fuel gas. It can be operated, and fuel gas can be supplied together with the gas component containing a high concentration of nitrogen component transported along the boil-off gas circulation line 134 described above. On the other hand, although not shown in FIG. 1, when the supply amount of fuel gas supplied through the branch line 140 and the boil-off gas circulation line 134 is greater than the supply amount of fuel gas required by the second consumer 20, the surplus A Gas Combustion Unit (GCU) for receiving and consuming fuel gas may be provided, and an outlet side end of the branch line 140 may be branched and connected to the GCU.

The second fuel gas supply line 150 may be a fuel transportation line connecting the storage tank 110 and the first consumer 10 . In addition, in the second fuel gas supply line 150, a tank pump 151 provided inside the storage tank 110, a high pressure pump 152 for pressurizing liquefied gas, and a heat exchanger for vaporizing liquefied gas at the rear end of the high pressure pump 152 Group 153 may be included. At this time, the tank pump 151 is a water pump that pumps the liquefied gas stored in the storage tank 110 from a low place to a high place, and the high pressure pump 152 converts the liquefied gas pulled up by the tank pump 151 into a high pressure state. It is a pump device that pressurizes, and the heat exchanger 153 may be a vaporizer that phase-changes the liquefied gas that has passed through the high-pressure pump 152 into a gaseous state.

The first recovery line 170 and the second recovery line 160 are provided to supply the liquid component separated in the gas-liquid separator 133 to the storage tank 110, and each has a first flow control valve for adjusting the flow rate ( 170a) and the second flow control valve 160a may be installed. At this time, an ejector 171 is installed in the first recovery line 170, and when the internal pressure of the gas-liquid separator 133 is insufficient, liquid components inside the gas-liquid separator 133 may be ejected using high-pressure liquefied gas.

For example, the gas-liquid separator 133 operates only during laden voyage, but remains inside the gas-liquid separator 133 at the same time as driving the high-pressure pump 152 or in the pipe when switching to ballast voyage. The stagnant liquid component may be drained to the storage tank 110 through the first recovery line 170 .

The ejector 171 uses the high-pressure fuel gas flowing through the second fuel gas supply line 150 as a driving force to suction the low-pressure liquid component accommodated in the gas-liquid separator 133 to store the tank ( 110) can be discharged. At this time, the control unit controls at least one of the first flow control valve 170a or the second flow control valve 160a provided in the first recovery line 170 according to the pressure state of the gas-liquid separator 133 to control the first recovery line. The flow rate flowing to (170) can be adjusted.

Meanwhile, the first recovery line 170 using the ejector 171 may be selectively used only when natural recovery through the second recovery line 160 is not possible. Furthermore, when the internal pressure of the gas-liquid separator 133 drops below a certain level, the first flow control valve 170a is closed to prevent the gas-liquid separator 133 from entering a vacuum state.

The ejector line 180 may be connected to the rear end of the high-pressure pump 152 on the second fuel gas supply line 150 to supply fuel gas to the ejector 171 . At this time, a third flow control valve 180a is provided in the ejector line 180, and the control unit controls at least one of the first to third flow control valves 160a, 170a, and 180a to generate the first recovery line 170. flow rate can be adjusted. That is, when the liquid component is not sufficient to naturally escape through the second recovery line 160 based on the internal pressure value of the gas-liquid separator 133, the controller 171 provided in the first recovery line 170 It is possible to forcibly send the liquid component to the outside by using.

The present invention has been described with reference to an embodiment shown in the accompanying drawings, but this is only exemplary, and those skilled in the art can make various modifications and equivalent other embodiments therefrom. You will understand. Therefore, the true scope of the present invention should be defined only by the appended claims.

10: first demand place 20: second demand place
100: fuel gas supply system 110: storage tank
120: first fuel gas supply line 121: compression unit
121a: compressor 121b: cooler
130: reliquefaction line 131: cooling unit
132: expansion valve 133: gas-liquid separator
134: boil-off gas circulation line 134a: flow control valve
140: branch line 140a: valve
150: second fuel gas supply line 151: tank pump
152: high pressure pump 153: heat exchanger
160: second recovery line 160a: second flow control valve
170: first recovery line 170a: first flow control valve
171: ejector 180: ejector line
180a: third flow control valve

Claims (5)

A storage tank accommodating liquefied gas and boil-off gas;
a first fuel gas supply line having a compression unit for pressurizing the boil-off gas of the storage tank and passing through the compression unit to supply the pressurized boil-off gas to a consumer;
a re-liquefaction line for receiving and re-liquefying a part of the pressurized boil-off gas;
a gas-liquid separator provided in the re-liquefaction line and separating boil-off gas in a gas-liquid mixed state into a gas component and a liquid component;
a boil-off gas circulation line for supplying the gas components separated by the gas-liquid separator to the consumer;
a first recovery line provided with an ejector for supplying liquid components separated by the gas-liquid separator to the storage tank;
a second fuel gas supply line for pressurizing the liquefied gas in the storage tank with a high-pressure pump, vaporizing it with a heat exchanger, and supplying the liquefied gas to the consumer;
an ejector line supplying high-pressure liquefied gas to the ejector at a rear end of the high-pressure pump; and
A second recovery line having a second flow control valve and supplying the liquid component separated in the gas-liquid separator to the storage tank; includes,
When the internal pressure of the gas-liquid separator falls below a certain level, the first flow control valve provided in the first recovery line is closed to adjust the internal pressure of the gas-liquid separator,
The control unit controls at least one of the first flow control valve and the second flow control valve to adjust the flow rate flowing through the first recovery line. delete delete According to claim 1,
A third flow control valve is provided in the ejector line,
The control unit controls at least one of the first to third flow control valves to adjust the flow rate flowing into the first recovery line. According to claim 1,
The reliquefaction line
A fuel gas supply system comprising a cooling unit for cooling pressurized boil-off gas, and an expansion valve for reducing the boil-off gas passing through the cooling unit and supplying it to the gas-liquid separator.

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