KR20200034882A - Fuel gas supplying system in ships - Google Patents

Abstract

According to the present invention, a fuel gas supply system includes: a storage tank storing liquefied gas and evaporation gas; a first fuel gas supply line including a compression part for pressing the evaporation gas of the storage tank, and supplying the evaporation gas, which is compressed through the compression part, to a consumer; a re-liquefaction line receiving and re-liquefying some of the compressed evaporation gas; a gas-liquid separator provided on the re-liquefaction line and separating the evaporation gas in a gas-liquid mixture state into a gas component and a liquid component; an evaporation gas circulation line supplying the gas component separated by the gas-liquid separator to the consumer; a first collection line including an ejector supplying the liquid component separated by the gas-liquid separator to the storage tank; a second fuel gas supply line compressing the gas of the storage tank with a high-pressure pump and gasifying the gas through a heat exchanger to supply the liquefied gas to the consumer; and an ejector line supplying the liquefied gas in a high-pressure state at the rear end of the high-pressure pump to the ejector. Therefore, the fuel gas supply system can prevent the gas-liquid separator from getting into a vacuum state.

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 ship fuel gas supply system capable of efficient use and management of fuel gas.

As the regulations of the International Maritime Organization (IMO) for the emission of greenhouse gases and various air pollutants have been strengthened, the shipbuilding and shipping industry has replaced natural fuels such as heavy fuels and diesel oils, and used natural gas, a clean energy source, as fuel for ships. There are many cases where it is used.

Natural gas is typically phased with Liquefied Natural Gas, a colorless, transparent, cryogenic liquid that cools natural gas to approximately -162 degrees Celsius and reduces its volume to 1/600 for ease of storage and transportation. It is changing and performing management and operation.

The liquefied natural gas is accommodated in a storage tank installed insulated on the hull and stored and transported. However, since it is practically impossible to completely insulate and receive the liquefied natural gas, the external heat is continuously transferred to the inside of the storage tank, and the evaporated gas generated by the natural vaporization of the liquefied natural gas accumulates inside the storage tank. . Since the boil-off gas may increase the internal pressure of the storage tank and cause deformation and damage of the storage tank, it is necessary to treat and remove the boil-off gas.

Accordingly, in the related art, a method of flowing evaporation gas to a vent mast provided on the upper side of a storage tank or burning gas using a gas combustion unit (GCU) has been used. However, this is not desirable in terms of energy efficiency, so a method of supplying liquefied gas with liquefied natural gas or fuel gas to the engine of each ship or using a liquefaction device such as a refrigeration cycle to re-liquefy the volatile gas is utilized. It is being used.

Meanwhile, 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 (-161.5 degrees Celsius) and ethane (-89 degrees Celsius).

Accordingly, the boil-off gas generated naturally by vaporization in the storage tank contains a lot of nitrogen components having a relatively low boiling point, which causes a decrease in the re-liquefaction efficiency of the boil-off gas and affects the utilization and treatment of the boil-off gas. I go 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 deterioration of the calorific value of the fuel gas, thereby improving the reliquefaction efficiency of the boil-off gas and the calorific value of the fuel gas. A method for citation and management is required.

Republic of Korea Patent Publication No. 10-2010-0035223 (2010. 04. 05. published)

The present invention is to provide a fuel gas supply system that can efficiently use and manage the fuel gas.

According to an aspect of the present invention, a storage tank containing liquefied gas and evaporated gas; A first fuel gas supply line having a compression unit for pressurizing the evaporation gas of the storage tank, and supplying the pressurized evaporation gas through the compression unit to a consumer; A re-liquefaction line receiving and re-liquefying a part of the pressurized evaporation gas; A gas-liquid separator provided on the re-liquefaction line and separating a gas-liquid mixed vapor gas into a gas component and a liquid component; An evaporation gas circulation line supplying gas components separated from the gas-liquid separator to a demand source; A first recovery line provided with an ejector for supplying the liquid component separated from the gas-liquid separator to the storage tank; A second fuel gas supply line that pressurizes the liquefied gas of the storage tank with a high pressure pump and vaporizes it with a heat exchanger to supply it to the demand destination; A fuel gas supply system may be provided, including; an ejector line that supplies liquefied gas in a high pressure state at the rear end of the high pressure pump to the ejector.

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

A second flow rate control valve is provided, and a second recovery line for supplying the liquid component separated from the gas-liquid separator to the storage tank, wherein the control unit includes one of the first flow rate control valve or the second flow rate control valve. The flow rate of the first recovery line may be controlled by controlling at least one.

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

The reliquefaction line may include a cooling unit that cools the pressurized evaporation gas, and an expansion valve that depressurizes the evaporation gas that has passed through the cooling unit and supplies it to the gas-liquid separator.

The fuel gas supply system according to the present invention can easily recover liquid components remaining in the gas-liquid separator or accumulated in the piping through a first recovery line provided with an ejector to a storage tank.

In addition, when the internal pressure of the gas-liquid separator falls below a certain level, it is possible to prevent the gas-liquid separator from becoming a vacuum by closing the first flow control valve provided in the first recovery line.

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 of ordinary skill in the art. The present invention is not limited to the embodiments presented herein, but may be embodied in other forms. The drawings may omit the illustration of parts irrelevant to the description in order to clarify the present invention, and the size of components may be exaggerated to facilitate 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 that pressurizes the evaporation gas of the storage tank 110 and the compression unit 121 It is provided in the first fuel gas supply line 120 for supplying the pressurized evaporation gas to the customer through the passage, a reliquefaction line 130 for receiving and re-liquefying a part of the pressurized evaporation gas, and the gas liquid The gas-liquid separator 133 for separating the vaporized gas in the mixed state into gas components and liquid components, separated from the gas-liquid circulation line 134 and gas-liquid separator 133 that supply the gas components separated from the gas-liquid separator 133 to the customer. The first recovery line 170, which is provided with an ejector 171 for supplying the liquid components to the storage tank 110, pressurizes the liquefied gas of the storage tank 110 to the high pressure pump 152 and the heat exchanger 153. After the second fuel gas supply line 150 and the high pressure pump 152 that vaporize and supply it to the customer It may include an ejector line 180 for supplying the liquefied gas of the high-pressure state to the ejector (171).

In the following examples, as an example to help understanding of the present invention, liquefied natural gas and evaporation gas generated therefrom have been described, but the present invention is not limited thereto, and various liquefied gases such as liquefied ethane gas, liquefied hydrocarbon gas, and the like When the generated evaporation gas is applied, it should be understood in the same way with the same technical idea. In addition, the demand destination includes a first demand destination 10, which is an engine that requires a fuel gas in a relatively high pressure state, and a second demand destination 20, which is an engine that requires a fuel gas in a low pressure state. It may refer to.

The storage tank 110 is provided to receive or store liquefied natural gas and evaporated 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 a place of production of natural gas and stably stores liquefied natural gas and evaporated gas until it unloads to reach its destination, but as described below, the propulsion engine or ship of the 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 insulated, but since it is practically difficult to completely block external heat intrusion, there is an evaporation gas generated by naturally vaporizing liquefied natural gas inside the storage tank 110. do. Since this evaporation gas increases the internal pressure of the storage tank 110 and potentially poses a risk of deformation and explosion of the storage tank 110, it is necessary to remove or process the evaporation 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 reliquefaction line 130 ) Can be re-liquefied and re-supplied to the storage tank 110. In addition, although not shown in the drawing, it may be supplied to a vent mast (not shown) provided on the upper portion of the storage tank 110 to process or consume evaporated gas.

The engine may receive fuel gas such as liquefied natural gas and evaporated gas accommodated in the storage tank 110 to generate propulsion power of the ship or generate power for power generation of internal equipment of the ship. The engine may be composed of a first demand source 10 for generating output by receiving a relatively high pressure fuel gas, and a second demand source 20 for generating output by receiving a relatively low pressure fuel gas. For example, the first demand destination 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 demand destination 20 is output with relatively low pressure fuel gas. It can be made of a DFDE engine, etc. that can generate. However, the present invention is not limited thereto, and should be understood in the same way when various numbers of engines and various types of engines are used.

The first fuel gas supply line 120 pressurizes the boil-off gas existing in the storage tank 110 and supplies it to the first demand source 10 and the reliquefaction line 130. The first fuel gas supply line 120 is provided with an inlet end connected to the inside of the storage tank 110, and an outlet side end connected to the first demand source 10 through the first fuel gas supply line 120. It can be provided. The first fuel gas supply line 120 is provided with a compression unit 121 having a plurality of stages of compressors 121a so that the evaporated gas can be processed according to the 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 by branching from the first fuel gas supply line 120.

The compression unit 121 may include a compressor 121a for compressing the evaporation gas and a cooler 121b for cooling the heated evaporation gas while being compressed. When the engine is composed of a plurality of engines having different pressure conditions, the branch line 140 to be described later is branched from the middle of the compression unit 121 to supply partially pressurized evaporation gas to the second demand source 20 Can be.

In FIG. 1, the compression unit 121 is shown to be composed of a five-stage compressor 121a and a cooler 121b, but this is, for example, the compression unit 121 according to the required pressure condition and temperature of the engine. It may be made of (121a) and a cooler (121b). In addition, the cooling unit 131 of the reliquefaction line 130, which will be described later, may be installed at the front end of the compression unit 121 on the first fuel gas supply line 120, and detailed description thereof will be described later.

The reliquefaction line 130 passes through the compression part 121 of the first fuel gas supply line 120 and is provided to receive a portion of the pressurized evaporation gas and reliquefy it.

The reliquefaction line 130 includes a cooling unit 131 for cooling the pressurized evaporation gas, an expansion valve 132 for primarily depressurizing the pressurized evaporation gas that has passed through the cooling unit 131, and an expansion valve 132. A gas-liquid separator 133 that passes through and separates the gas-liquid mixed state into gas components and liquid components, and an evaporation gas circulation line 134 that supplies the gas components separated from the gas-liquid separator 133 to the second customer 20 , It may include a first recovery line 170 and the second recovery line 160 for re-supplying the liquid components separated from the gas-liquid separator 133 to the storage tank (110).

The cooling unit 131 is provided to cool the pressurized evaporation gas supplied to the reliquefaction line 130. The cooling unit 131 is a gas-liquid separator transported along the boil-off gas before the compression unit 121 and the boil-off gas circulation line 134, which will be transported along the pressurized boil-off gas along the first fuel gas supply line 120 ( 133) may be made of a heat exchanger to exchange heat with the separated gas component. Since the pressurized evaporation gas is pressurized by the compression unit 121, the temperature and pressure are elevated, and thus the low temperature evaporation gas and the evaporation gas circulation line before passing through the compression unit 121 of the first fuel gas supply line 120 By heat exchange with the low-temperature gas component transferred along (134), it is possible to cool the hot pressurized evaporation gas supplied to the reliquefaction line 130. By providing the cooling unit 131 as a heat exchanger in this way, since the pressurized evaporation gas can be cooled without a separate cooling device, unnecessary waste of power is prevented and the equipment is simplified, thereby improving the efficiency of operation of the equipment.

The expansion valve 132 may be provided at a rear end of the cooling unit 131. The expansion valve 132 may firstly depressurize the pressurized evaporation gas that has passed through the cooling unit 131, thereby cooling and expanding to realize reliquefaction. The expansion valve 132 may be, for example, a Joule-Thomson Valve. The expansion valve 132 may depressurize the pressurized evaporation gas that has passed through the cooling unit 131 to a pressure level corresponding to the fuel gas pressure condition required by the second demand source 20. This will be described in detail later.

The gas-liquid separator 133 is provided to be cooled and depressurized through the expansion valve 132 to separate the vaporized 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 depressurized to re-liquefy, but flash gas may be generated in the process of depressurizing. Accordingly, the gas-liquid separator 133 receives the evaporated gas that has passed through the expansion valve 132 and has become a gas-liquid mixture, and separates it into a gas component and a liquid component, thereby improving the reliability of the re-liquefaction process and handling each component separately. can do.

On the other hand, natural gas is a mixture containing ethane, propane, butane, nitrogen (Nitrogen), etc. in addition to the main component methane (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 (-161.5 degrees Celsius) and ethane (-89 degrees Celsius). As the nitrogen component has a very low boiling point, the boil-off gas generated by vaporization naturally inside the storage tank 110 contains a lot of nitrogen components as the nitrogen component is vaporized relatively first, and furthermore, the nitrogen component of the boil-off gas There is a problem that the reliquefaction efficiency of the boil-off gas decreases as the concentration of increases.

In particular, for re-liquefying the boil-off gas, after pressurizing the boil-off gas by the compression unit 121 and cooling the pressurized boil-off gas by the cooling unit 131, the gas-liquid separator when depressurizing the boil-off gas pressed by the expansion valve 132 A gas component such as a flash gas separated at (133) contains a high concentration of nitrogen components having a low boiling point. When the gas component containing the high concentration of the nitrogen component is circulated again in the fuel gas system 100, the reliquefaction efficiency of the evaporated gas is lowered, and the compressor 121a of the compression unit 121 is circulated by the circulated gas component. There is a problem in that a load is caused on the back or the installation of the compressor 121a having a high specification is required, resulting in inefficiency in equipment operation.

The boil-off gas circulation line 134 is separated from the gas-liquid separator 133 and is provided to supply a gas component containing a high concentration of nitrogen components to the second demand source 20 as fuel gas. As described above, a relatively high concentration of nitrogen component is contained in the gas component generated in the process of depressurizing the vaporized gas cooled and pressurized through the expansion valve 132. Accordingly, the boil-off gas circulation line 134 is supplied with a gas component having a low re-liquefaction efficiency, and supplies and uses it as a fuel gas to the second demand source 20, and at the same time promotes efficient use of fuel gas, and a gas-liquid separator 133 ) To increase the reliquefaction efficiency of liquid components containing relatively low concentrations of nitrogen components.

The expansion valve 132 is provided to depressurize the pressurized evaporation gas that has passed through the cooling unit 131 to a level corresponding to the pressure condition required by the second demand source 20, and the evaporation gas circulation line 134 is separately compressed. The gas component separated from the gas-liquid separator 133 can be directly supplied to the second customer 20 as a fuel gas without an apparatus.

The boil-off gas circulation line 134 is provided to pass through the cooling unit 131 made of a heat exchanger. Cooling of the pressurized evaporation gas flowing along the reliquefaction line 130 by using cold heat of gas components containing a high concentration of nitrogen components flowing along the evaporation gas circulation line 134, and at the same time, the reliquefaction line 130 The temperature of the gas component flowing along the evaporation gas circulation line 134 is increased to a level corresponding to the temperature condition of the fuel gas required by the second demand source 20 by receiving the hot heat of the pressurized evaporation gas flowing along the You can.

The boil-off gas circulation line 134 is provided with a flow rate control valve 134a, which will be described later, to supply the amount of fuel gas transported along the boil-off gas circulation line 134.

The branch line 140 is branched from the middle of the compression unit 121 of the first fuel gas supply line 120 and is provided to supply some pressurized evaporation gas to the second demand source 20. The branch line 140 is provided with an inlet end connected to the middle of the compression unit 121, and an outlet end connected to the evaporation gas circulation line 134 to be connected to the second demand source 20. have. A valve 140a is provided in the branch line 140, and the flow rate flowing along the branch line 140 can be adjusted.

Since the second demand source 20 receives a relatively low pressure fuel gas and generates an output, it is branched from the middle of the compression unit 121 that compresses the evaporation gas to receive some pressurized evaporation gas as fuel gas. It can be operated, and can be supplied with fuel gas along with a gas component containing a high concentration of nitrogen components transported along the above-described boil-off gas circulation line 134. Meanwhile, although not shown in FIG. 1, when the supply amount of the fuel gas supplied through the branch line 140 and the evaporation gas circulation line 134 is greater than the supply amount of the fuel gas required by the second demand source 20, it is surplus. A gas combustion unit (GCU) that receives and consumes fuel gas is provided, and an end portion of the branch line 140 may be branched to be connected to the GCU.

 The second fuel gas supply line 150 may be a fuel transport line connecting the storage tank 110 and the first customer 10. In addition, the second fuel gas supply line 150 includes a tank pump 151 provided inside the storage tank 110, a high pressure pump 152 to pressurize the liquefied gas, and a heat exchange to vaporize the 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 pump that pumps 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 pressurized pump device, and the heat exchanger 153 may be a vaporizer that changes the liquefied gas that has passed through the high pressure pump 152 into a gas phase.

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

For example, the gas-liquid separator 133 operates only during laden voyage. When switching to the ballast Voyage, the high-pressure pump 152 is driven and remains inside the gas-liquid separator 133 or in the piping. The accumulated liquid component may be drained to the storage tank 110 through the first recovery line 170.

The ejector 171 uses a high-pressure fuel gas flowing through the second fuel gas supply line 150 as a driving force to suction the low-pressure liquid component contained in the gas-liquid separator 133 to store the storage tank ( 110). At this time, the control unit controls at least one of the first flow rate control valve 170a or the second flow rate control valve 160a provided in the first recovery line 170 according to the pressure state of the gas-liquid separator 133, and the first recovery line. Flow rate flowing to the 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 falls below a certain level, the first flow control valve 170a can be closed to prevent the gas-liquid separator 133 from becoming a vacuum.

The ejector line 180 is 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, the ejector line 180 is provided with a third flow control valve 180a, and the control unit controls at least one of the first to third flow control valves 160a, 170a, 180a to control the first recovery line 170. Flow rate can be adjusted. That is, the control unit, when the liquid component is not enough to escape naturally through the second recovery line 160 based on the internal pressure value of the gas-liquid separator 133, the ejector 171 provided in the first recovery line 170 The liquid component can be forcibly sent out using.

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

10: first consumer 20: second consumer
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 evaporated gas;
A first fuel gas supply line having a compression unit for pressurizing the evaporation gas of the storage tank, and supplying the pressurized evaporation gas through the compression unit to a consumer;
A re-liquefaction line receiving and re-liquefying a part of the pressurized evaporation gas;
A gas-liquid separator provided on the re-liquefaction line and separating a gas-liquid mixed vapor gas into gas components and liquid components;
An evaporation gas circulation line for supplying gas components separated from the gas-liquid separator to the customer;
A first recovery line provided with an ejector for supplying the liquid component separated from the gas-liquid separator to the storage tank;
A second fuel gas supply line that pressurizes the liquefied gas of the storage tank with a high-pressure pump and vaporizes it with a heat exchanger to supply it to the customer;
And an ejector line for supplying liquefied gas in a high pressure state to the ejector at the rear end of the high pressure pump. According to claim 1,
A fuel gas supply system for controlling the internal pressure of the gas-liquid separator by closing the first flow control valve provided in the first recovery line when the internal pressure of the gas-liquid separator falls below a certain level. According to claim 2,
A second flow rate control valve is provided, further comprising a second recovery line for supplying the liquid component separated from the gas-liquid separator to the storage tank,
The control unit controls at least one of the first flow control valve or the second flow control valve to control the flow rate of the fuel gas supply system to the first recovery line. According to claim 3,
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 control the flow rate of the fuel gas supply system to the first recovery line. According to claim 1,
The reliquefaction line
A fuel gas supply system including a cooling unit for cooling the pressurized evaporation gas, and an expansion valve for reducing the evaporation gas that has passed through the cooling unit and supplying it to the gas-liquid separator.

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