KR102142114B1 - Fuel gas supplying system in ships - Google Patents

Abstract

A fuel gas supply system is disclosed. The fuel gas supply system according to an embodiment of the present invention includes a storage tank for receiving liquefied gas and boil-off gas, and a compression unit for pressurizing the evaporation gas of the storage tank, and supplies the pressurized evaporation gas to the first engine through the compression unit. A first fuel gas supply line, a second fuel gas supply line that branches off from the middle of the compression part and supplies partially pressurized evaporation gas to the second engine, and re-liquefies a part of the pressurized evaporation gas A liquefaction line and a heating value control unit for measuring and controlling the heating value of the fuel gas supplied to the second engine, wherein the re-liquefaction line primarily cools the pressurized evaporation gas and the pressurized evaporation gas that has passed through the cooling unit. A first expansion valve to reduce the pressure, a first gas-liquid separator that passes through the first expansion valve to separate vaporized gas in a gas-liquid state into a gas component and a liquid component, and the gas component separated from the first gas-liquid separator to the second engine. It may be provided, including a liquefied gas circulation line receiving the liquid component separated from the first gas-liquid separator and the evaporation gas circulation line supplied to the.

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) on the emission of greenhouse gases and various air pollutants have been strengthened, the shipbuilding and shipping industry has replaced natural fuels, such as heavy fuel oil and diesel oil, with natural gas, which is a clean energy source, as fuel gas for ships. It is often used as a.

Natural gas is typically phased with Liquefied Natural Gas, a colorless and transparent cryogenic liquid whose natural gas is cooled to about -162 degrees Celsius and reduced in 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 liquefied natural gas, the external heat is continuously transferred to the interior of the storage tank, so that the liquefied natural gas vaporizes naturally and accumulates inside the storage tank. . The evaporated gas may increase the internal pressure of the storage tank and cause deformation and damage of the storage tank, so it is necessary to treat and remove the evaporated gas.

Accordingly, in the related art, a method has been used in which evaporation gas is flowed through a vent mast provided on the upper side of a storage tank or a gas combustion unit (GCU) is used to burn the evaporation gas. 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 each ship's engine or using a liquefaction device consisting of 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 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 a fuel gas to the engine of a ship, the nitrogen component of the boil-off gas affects the decrease in the calorific value of the fuel gas. There is a need for a way to promote use and management.

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

An embodiment of the present invention is to provide a fuel gas supply system capable of improving the reliquefaction efficiency of the boil-off gas.

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

An embodiment of the present invention is to provide a fuel gas supply system that can effectively control and maintain the heating value of the fuel gas supplied to the engine.

An embodiment of the present invention is to provide a fuel gas supply system capable of promoting efficient facility operation with a simple structure.

An embodiment of the present invention is to provide a fuel gas supply system capable of improving energy efficiency.

According to an aspect of the present invention, a storage tank for receiving liquefied gas and boil-off gas, a compression unit for pressurizing the boil-off gas of the storage tank, and a first for supplying the pressurized boil-off gas to the first engine through the compression unit Fuel gas supply line, a second fuel gas supply line that is branched from the middle of the compression part and supplies partially pressurized boil-off gas to the second engine, and re-liquefies a part of the pressurized boil-off gas A liquefaction line and a calorific value control unit for measuring and adjusting the calorific value of the fuel gas supplied to the second engine, wherein the re-liquefaction line is a cooling unit for cooling the pressurized evaporation gas, and the pressurized pressure passing through the cooling unit A first expansion valve that primarily depressurizes the evaporation gas, a first gas-liquid separator that passes through the first expansion valve to separate the gas-liquid mixed vapor gas into a gas component and a liquid component, and is separated from the first gas-liquid separator. It may be provided, including a boil-off gas circulation line for supplying the gas components to the second engine and a liquefied gas circulation line for receiving the liquid components separated from the first gas-liquid separator.

The calorific value control unit may be provided with a calorific value measuring device for measuring the calorific value of the fuel gas supplied to the second engine, and a flow rate control valve respectively provided in the second fuel gas supply line and the boil-off gas circulation line.

The flow control valve may be provided to control operation based on the fuel gas calorific value information measured by the calorimeter.

The re-liquefaction line is provided on the liquefied gas circulation line, and a second expansion valve for secondarily depressurizing the liquid component separated from the first gas-liquid separator, and passing through the second expansion valve to vaporize gaseous mixed state vaporized gas. A second gas-liquid separator for separating components and liquid components, and a vaporized gas recovery line for supplying gas components separated from the second gas-liquid separator to the front end of the compression section on the storage tank or the first fuel gas supply line and the agent It may be provided further comprising a liquefied gas recovery line for supplying the liquid components separated from the two-liquid separator to the storage tank.

The cooling unit may include a heat exchanger for exchanging the pressurized evaporation gas with at least one of the evaporation gas at the front end of the compression unit and the gas component separated from the first gas-liquid separator.

The first expansion valve may be provided to depressurize the pressurized evaporation gas to a pressure condition corresponding to the pressure of the fuel gas pressure or the partially pressurized evaporation gas required by the second engine.

The fuel gas supply system according to an embodiment of the present invention has an effect of improving the reliquefaction efficiency and performance of the evaporated gas.

The fuel gas supply system according to an embodiment of the present invention has an effect of efficiently using and managing fuel gas.

The fuel gas supply system according to an embodiment of the present invention has an effect of effectively controlling and maintaining the heat value of the fuel gas.

The fuel gas supply system according to an embodiment of the present invention has an effect of improving energy efficiency.

The fuel gas supply system according to an embodiment of the present invention has a simple structure, and has an effect of promoting efficient facility operation.

1 is a conceptual diagram showing a fuel gas supply system according to an embodiment of the present invention.
2 is a conceptual diagram showing a fuel gas supply system according to another 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. To clarify the present invention, the illustration of parts irrelevant to the description may be omitted, 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.

1, the fuel gas supply system 100 according to an embodiment of the present invention includes a storage tank 110, a compression unit 121 to pressurize the boil-off gas of the storage tank 110, and the compression unit ( 121) to the first fuel gas supply line 120 for supplying the pressurized boil-off gas to the first engine, the re-liquefaction line 130 for receiving and re-liquefying a part of the pressurized boil-off gas, to the compression unit 121 It may be provided by a second fuel gas supply line 140 for supplying the partially pressurized boil-off gas to the second engine, a heating value control unit for measuring and controlling the heating value of the fuel gas supplied to the second engine.

In the following embodiments, 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 boil-off gas generated from is applied, it should be understood with the same technical idea.

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 stores the liquefied natural gas and the evaporated gas stably until it receives or stores liquefied natural gas from a production site of natural gas and unloads it to its destination to unload, but as described later, the propulsion engine or ship of the ship It may be provided to be used as a fuel gas, such as a power generation engine.

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 or re-used as the fuel gas of the engine by the first fuel gas supply line 120 or the second fuel gas supply line 140 as in the embodiment of the present invention. It can be re-liquefied by the liquefaction line 130 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 engine that receives a relatively high pressure fuel gas and generates an output, and a second engine that receives a relatively low pressure fuel gas and generates an output. For example, the first engine is composed of a ME-GI engine or an X-DF engine capable of generating output with a relatively high pressure fuel gas, and the second engine is a DFDE capable of generating output with a relatively low pressure fuel gas. It may be made of an engine or the like. 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 may be provided to pressurize the boil-off gas present in the storage tank 110 and supply it to the first engine and the reliquefaction line 130. The first fuel gas supply line 120 is provided so that the inlet end is connected to the inside of the storage tank 110, and the outlet end is provided to be connected to the first engine via the first fuel gas supply line 120. Can. 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 evaporated gas and a cooler 121b for cooling the heated evaporated gas while being compressed. When the engine is composed of a plurality of engines having different pressure conditions, the second fuel gas supply 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 engine. Can be prepared.

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 an example, according to the required pressure condition and temperature of the engine, the compression unit 121 may have various numbers. Compressor (121a) and may be made of 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 part of the pressurized evaporation gas and reliquefy it.

The reliquefaction line 130 includes a cooling unit 131 for cooling the pressurized evaporation gas, a first expansion valve 132 for firstly depressurizing the pressurized evaporation gas that has passed through the cooling unit 131, and a first expansion valve. The first gas-liquid separator 133 that passes through the 132 and separates the gas-liquid mixed evaporation gas into a gas component and a liquid component, and the evaporation gas that supplies the gas components separated from the first gas-liquid separator 133 to the second engine Gas is passed through the second expansion valve 136 and the second expansion valve 136 to secondarily depressurize the liquid components separated from the circulation line 134 and the first gas-liquid separator 133 to gaseous gas in a gas-liquid mixed state. The second gas-liquid separator 137, which separates the components from the liquid components, and the gas components separated from the second gas-liquid separator 137 are recovered from the evaporated gas re-supplied to the storage tank 110 or the first fuel gas supply line 120. Line 138, the second gas-liquid separator 137 may include a liquefied gas recovery line 139 for re-supplying the liquid components 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 the first gaseous liquid transported along the boil-off gas circulating line 134 and the boil-off gas before the compression unit 121 is transferred along the pressurized boil-off gas along the first fuel gas supply line 120 The separator 133 may be formed of a heat exchanger that exchanges heat with gas components separated from the separator. Since the pressurized boil-off gas is pressurized by the compression unit 121, the temperature and pressure are elevated, so the low-temperature evaporation gas and the boil-off gas circulation line before passing through the compression unit 121 of the first fuel gas supply line 120 By exchanging heat 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, the pressurized evaporation gas can be cooled without a separate cooling device, thereby preventing unnecessary waste of power and simplifying the facility, thereby improving the efficiency of facility operation.

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

The first gas-liquid separator 133 is first cooled and depressurized by passing through the first expansion valve 132 and is provided to separate the vaporized gas in the gas-liquid mixed state into gas components and liquid components. When the pressurized evaporation gas passes through the first expansion valve 132, it is cooled and depressurized to re-liquefy, but flash gas may be generated in the process of depressurizing. Accordingly, the first gas-liquid separator 133 receives the evaporated gas that has passed through the first expansion valve 132 and is in a gas-liquid mixed state, and simultaneously separates the gas component and the liquid component to promote the reliability of the re-liquefaction process. Ingredients can be handled separately.

On the other hand, natural gas is a mixture containing ethane, propane, butane, nitrogen, etc. in addition to the main component 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 natural vaporization inside the storage tank 110, the nitrogen component is vaporized relatively first and contains a lot of nitrogen components, 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, after the pressurization of the pressurized vaporization gas by the compression unit 121 and the cooling of the pressurized vaporization gas by the cooling unit 131 for re-liquefaction of the vaporization gas, when the depressurization of the pressurized vaporization gas by the first expansion valve 132 The gas component, such as flash gas, separated from the first gas-liquid separator 133 contains a high concentration of nitrogen components having a low boiling point. When the gas component containing a high concentration of nitrogen components 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 components. There is a problem in that a load is caused on the back or the installation of the compressor 121a of a high specification is required, resulting in inefficiency of equipment operation.

The evaporation gas circulation line 134 is separated from the first gas-liquid separator 133 and is provided to supply a gas component containing a relatively high concentration of nitrogen components to the second engine as fuel gas. As described above, the gas component generated in the process of depressurizing the cooled and pressurized evaporation gas through the first expansion valve 132 contains a relatively high concentration of nitrogen components. 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 engine, thereby promoting efficient use of the fuel gas and at the same time, the first gas-liquid separator 133 By separating by, it is possible to increase the reliquefaction efficiency of a liquid component containing a relatively low concentration of nitrogen components.

The first expansion valve 132 is provided to depressurize the pressurized evaporation gas that has passed through the cooling unit 131 to a level corresponding to a pressure condition required by the second engine, and the evaporation gas circulation line 134 is a separate compression device. Without it, the gas component separated from the first gas-liquid separator 133 can be directly supplied to the second engine as fuel gas.

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 a gas component containing a high concentration of nitrogen component flowing along the evaporation gas circulation line 134, and at the same time, the reliquefaction line 130 It is possible to increase the temperature of the gas component flowing along the evaporation gas circulation line 134 to a level corresponding to the temperature condition of the fuel gas required by the second engine by receiving the hot heat of the pressurized evaporation gas flowing along.

The boil-off gas circulation line 134 is provided with a flow rate control valve 152, which will be described later, to supply the amount of fuel gas transported along the boil-off gas circulation line 134, and detailed description thereof will be described later. do.

The liquid component containing the relatively low concentration of nitrogen components separated by the first gas-liquid separator 133 is transferred along the liquefied gas circulation line 135, and a second expansion valve provided in the liquefied gas circulation line 135 ( 136) may be secondarily depressurized and re-liquefied. As described above, as the nitrogen content of the low concentration is improved, the reliquefaction efficiency of the evaporation gas is improved. As the liquid component separated by the first gas-liquid separator 133 contains the nitrogen component of the low concentration, the second expansion valve 136 ) Even if decompression is performed, generation of gas components such as flash gas is reduced, and reliquefaction efficiency may be improved. The second expansion valve 136 may be formed of, for example, a Joule-Thomson Valve, and the second expansion valve 136 may be reduced to a pressure level corresponding to the internal pressure of the storage tank 110. have.

The second gas-liquid separator 137 passes through the second expansion valve 136 and is secondarily cooled and depressurized to separate the vaporized gas in the gas-liquid mixed state into gas components and liquid components. The liquid component of the first gas-liquid separator 133, which is additionally depressurized by the second expansion valve 136, contains nitrogen components at a low concentration, so that most of the liquid components are re-liquefied, but a small amount of nitrogen components is present as well as complete re-liquefaction. It is practically impossible to achieve. Accordingly, the evaporation gas that has passed through the second expansion valve 136 and is in a gas-liquid mixed state is separated into a gas component and a liquid component in the second gas-liquid separator 137 to promote the reliability of the re-liquefaction process, and each component is handled separately. can do.

The boil-off gas recovery line 138 is stored with the second gas-liquid separator 137 to re-supply the gas components separated by the second gas-liquid separator 137 to the storage tank 110 or the first fuel gas supply line 120. It may be provided between the tank 110 or the second gas-liquid separator 137 and the first fuel gas supply line 120. In FIG. 1, the boil-off gas recovery line 138 is illustrated as re-supplying the gas component of the second gas-liquid separator 137 to the front end of the compression unit 121 on the first fuel gas supply line 120. This includes both re-supply from the two-liquid separator 137 to the storage tank 110 or re-supply to the first fuel gas supply line 120 and the storage tank 110 together.

The liquefied gas recovery line 139 may be provided between the second gas-liquid separator 137 and the storage tank 110 to re-supply the liquid component separated by the second gas-liquid separator 137 to the storage tank 110. . The liquefied gas recovery line 139 may be provided at its inlet end in communication with the lower side of the second gas-liquid separator 137, and at its outlet end in communication with the interior of the storage tank 110. The liquefied gas recovery line 139 may be provided with an on-off valve (not shown) for adjusting the supply amount of the liquefied natural gas recovered to the storage tank 110.

The second fuel gas supply 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 engine. The second fuel gas supply 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 engine. Can.

Since the second engine is supplied with 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, so that some pressurized evaporation gas can be supplied and operated as fuel gas. In addition, the fuel gas may be supplied together with a gas component containing a high concentration of nitrogen components transferred along the above-described evaporation gas circulation line 134. Meanwhile, although not shown in FIG. 1, when the supply amount of the fuel gas supplied through the second fuel gas supply line 140 and the evaporation gas circulation line 134 is greater than the supply amount of the fuel gas required by the second engine, it is surplus. A gas combustion unit (GCU) for receiving and consuming fuel gas is provided, and an end portion of the second fuel gas supply line 140 may be branched to be connected to the GCU.

The calorific value adjusting unit is provided to measure and regulate the calorific value of the fuel gas supplied to the second engine.

The heating value (heating value) means the amount of heat released when a unit mass of fuel gas is completely burned. Methane, butane and propane in natural gas have relatively high calorific value, which increases the calorific value of fuel gas (The calorific value of methane: about 12,000 kcal/kg, the calorific value of butane: about 11,863 kcal/kg, the calorific value of propane: about 2,000 kcal /kg), while the calorific value of nitrogen is very low (the calorific value of nitrogen: about 60kcal/kg), the higher the absolute content or concentration of the nitrogen component, the lower the total calorific value of fuel gas. At this time, if the total amount of heat generated by the fuel gas supplied to the engine is excessively low and the minimum heat value required by the engine is not satisfied, it affects the output of the engine and causes unnecessary load on the engine.

As described above, in order to increase the reliquefaction efficiency of the reliquefaction line 130, a liquid component separated from the first gas-liquid separator 133 and containing a relatively low concentration of nitrogen components is supplied to the second expansion valve 136 side. , The gas component containing a relatively high concentration of nitrogen components is supplied to the second engine through the evaporation gas circulation line 134, and the high concentration nitrogen component flowing along the evaporation gas circulation line 134 to the second engine There is a concern that the calorific value of the supplied fuel gas is lower than the condition calorific value required by the second engine.

Referring to FIG. 1, the calorific value control unit of the fuel gas supply system 100 according to an embodiment of the present invention measures or calculates the calorific value of the fuel gas supplied to the second engine, and the calorific value meter 150 and the second fuel gas It may include flow control valves 151 and 152 installed in the supply line 140 and the boil-off gas circulation line 134, respectively.

The calorimeter 150 is a first gas-liquid separator 133 supplied to the second engine through the partially pressurized evaporation gas and the evaporation gas circulation line 134 supplied to the second engine through the second fuel gas supply line 140 ) Can measure the calorific value of fuel gas containing gas component in real time. The calorimeter 150 transmits the calorific value information of the fuel gas measured by a display unit (not shown) made of a display or the like to inform the occupant of the ship, or transmits the calorific value of the measured fuel gas to a control unit (not shown) , The control unit may control the opening and closing degree of the flow control valve, which will be described later, by comparing and analyzing the conditional heating value of the previously input second engine and the heating value information of the fuel gas transmitted from the calorimeter 150.

In FIG. 1, the calorimeter 150 is provided at the rear end of the point where the evaporation gas circulation line 134 on the second fuel gas supply line 140 joins, and is shown to measure the calorific value of the fuel gas. If the calorific value of the supplied fuel gas can be measured, its position can be variously modified.

Flow control valves 151 and 152 may be installed on the second fuel gas supply line 140 and the evaporation gas circulation line 134, respectively. Each of the flow control valves 151 and 152 automatically adjusts the degree of opening and closing by manual or control by the operator based on the calorific value information of the fuel gas measured by the calorimeter 150 and the conditional calorific value information of the second engine. It is possible to control the heating value of the fuel gas.

For example, if the calorific value of the fuel gas measured by the calorimeter 150 is less than the condition calorific value of the second engine, the flow control valve 151 installed in the second fuel gas supply line 140 is opened, and the evaporated gas is circulated. The flow control valve 152 installed in the line 134 may be completely closed or partially closed to increase the heating value of the fuel gas. Conversely, when the calorific value of the fuel gas measured by the calorimeter 150 is greater than the conditional heat value of the second engine, the evaporation gas circulation line is provided so as to preferentially consume the nitrogen component of the evaporation gas in the fuel gas supply system 100 ( The flow control valve 152 installed in 134 may be opened, and the flow control valve 151 installed in the second fuel gas supply line 140 may be completely closed or partially closed.

2 is a conceptual diagram showing a fuel gas supply system 100 according to another embodiment of the present invention. Referring to Figure 2, the calorific value control unit of the fuel gas supply system 100 according to another embodiment of the present invention is a calorific value measuring instrument 150 for measuring or calculating the calorific value of the fuel gas supplied to the second engine, the evaporation gas circulation line ( 134), the calorific value control line 153 for recovering the gas components supplied to the liquefied gas circulation line 135, the second fuel gas supply line 140, the evaporation gas circulation line 134, the calorific value control line 153 It may include a flow control valve (151, 152, 154) are respectively installed.

Among the descriptions of the fuel gas supply system 100 according to another embodiment of the present invention described below, except for a configuration additionally described with reference to a separate reference number, the same description as the above-described embodiment is provided to prevent overlapping of contents. Omitted.

The calorific value control line 153 is provided with an inlet end connected to the evaporation gas circulation line 134 and an outlet end connected to the front end of the second expansion valve 136 on the liquefied gas circulation line 135. Can be. As described above, the gas component flowing along the boil-off gas circulation line 134 contains a high concentration of nitrogen components, and has a lower calorific value than some pressurized boil-off gas flowing along the second fuel gas supply line 140. Accordingly, a part of gas components flowing along the evaporation gas circulation line 134 may be recovered to the liquefied gas circulation line 135 to increase and control the total heating value of the fuel gas supplied to the second engine. At the same time, the calorific value control line 153 recovers a portion of the gas component flowing through the evaporation gas circulation line 134 to the liquefied gas circulation line 135, thereby responding to the required supply amount of the fuel gas of the second engine. It is possible to efficiently adjust the supply amount.

In the calorific value regulating line 153, a flow rate regulating valve 154 for regulating the supply amount of some gas components flowing along the calorific value regulating line 153 may be provided. The flow control valve 154 automatically adjusts the amount of opening and closing by controlling the opening/closing degree automatically or manually by the operator based on the calorific value information of the fuel gas measured by the calorimeter 150 and the conditional calorific value information of the second engine. It is possible to control the supply amount of some gas components flowing along the line 153. Also, unlike this, although not shown in the drawing, the heating value control line 153 is based on the fuel gas supply amount information measured by the second fuel gas supply line 140 or the flow sensor installed in the second engine (not shown). The opening/closing degree of the provided flow control valve 154 may be controlled.

Fuel gas supply system 100 according to an embodiment of the present invention having such a configuration is a gas component containing a relatively high concentration of nitrogen components generated in the process of decompressing the pressurized evaporation gas for the re-liquefaction process of the evaporation gas By using the gas as a fuel gas to the second engine, and supplying a liquid component containing a relatively low concentration of nitrogen components to the reliquefaction process, efficient consumption of nitrogen components in the fuel gas supply system 100 and the fuel gas system 100 ) Has the effect of improving the reliquefaction efficiency of the evaporation gas and the reliquefaction performance of the reliquefaction line through continuous reduction of the total nitrogen content in ).

In addition, by measuring and regulating the calorific value of the fuel gas by the calorific value control unit, it has the effect of promoting efficient use and management of the fuel gas by controlling the calorific value of the fuel gas in response to the condition calorific value required by the engine.

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.

100: fuel gas supply system 110: storage tank
120: first fuel gas supply line 121: compression unit
130: reliquefaction line 131: cooling unit
132: first expansion valve 133: first gas-liquid separator
134: evaporation gas circulation line 135: liquefied gas circulation line
136: second expansion valve 137: second gas-liquid separator
138: evaporation gas recovery line 139: liquefied gas recovery line
140: second fuel gas supply line 150: calorimeter
151, 152, 154: Flow control valve
153: calorific value control line

Claims (6)

A storage tank accommodating liquefied gas and evaporated gas;
A first fuel gas supply line having a compression part to pressurize the evaporation gas of the storage tank and supplying the pressurized evaporation gas to the first engine through the compression part;
A second fuel gas supply line branched from the middle of the compression unit and supplies partially pressurized evaporation gas to the second engine;
A reliquefaction line receiving and re-liquefying a part of the pressurized evaporation gas; And
It includes a heating value control unit for measuring and controlling the heating value of the fuel gas supplied to the second engine,
The reliquefaction line
A cooling unit for cooling the pressurized evaporation gas, a first expansion valve for firstly depressurizing the pressurized evaporation gas that has passed through the cooling unit, and passing through the first expansion valve to vaporize the vaporized gas in a gas-liquid mixed state. A first gas-liquid separator for separating components and liquid components, an evaporation gas circulation line for supplying gas components separated from the first gas-liquid separator to the second engine, and receiving liquid components separated from the first gas-liquid separator A liquefied gas circulation line, a second expansion valve provided on the liquefied gas circulation line to secondarily depressurize the liquid component separated from the first gas-liquid separator, and passing through the second expansion valve to collect vaporized gas in a gas-liquid mixed state. A fuel gas supply system comprising a second gas-liquid separator that separates gas components and liquid components. According to claim 1,
The heating amount control unit
A calorimeter measuring the calorific value of the fuel gas supplied to the second engine, and
A fuel gas supply system including a flow control valve provided on each of the second fuel gas supply line and the boil-off gas circulation line. According to claim 2,
The flow control valve
A fuel gas supply system controlled according to the fuel gas calorific value information measured by the calorimeter. According to claim 3,
The reliquefaction line
The gaseous component separated from the second gas-liquid separator is supplied to the storage tank or the first fuel gas supply line before the compression part, and an evaporation gas recovery line and the liquid component separated from the second gas-liquid separator are transferred to the storage tank. A fuel gas supply system further comprising a liquefied gas recovery line to supply. According to claim 1,
The cooling unit
And a heat exchanger for exchanging the pressurized boil-off gas with at least one of the boil-off gas at the front end of the compression part and the gas component separated from the first gas-liquid separator. According to claim 1,
The first expansion valve
A fuel gas supply system for depressurizing the pressurized boil-off gas to a pressure condition corresponding to the pressure of the fuel gas required by the second engine or a pressure of the partially pressurized boil-off gas.

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