KR101814439B1 - System for supplying fuel gas - Google Patents

Abstract

Disclosed is a fuel gas supply system. According to the present invention, the fuel gas supply system comprises: a storage tank for storing liquefied gas and evaporated gas generated therefrom; a first supply line including a first compressor for pressurizing the evaporated gas, and supplying the evaporated gas to a demand; a recovery line extending toward a gas-liquid separator from a rear end of the first compressor, and receiving the evaporated gas to divide the same into flash gas and liquid components; a heat exchanger for performing heat exchange between the evaporated gas passing through the first supply line and the evaporated gas passing through the recovery line; a re-supply line extending toward the first supply line from the gas-liquid separator to supply the flash gas to the first supply line; and a second supply line extending toward the demand from the gas-liquid separator to supply the flash gas to the demand. According to the present invention, energy consumed for pressurization can be reduced.

Description

[0001] SYSTEM FOR SUPPLYING FUEL GAS [0002]

The present invention relates to a fuel gas supply system capable of using liquefied gas stored in a liquefied gas storage tank of a ship as a fuel.

As IMO regulations on the emission of greenhouse gases and various air pollutants are strengthened, shipbuilding and marine industries are replacing the use of heavy fuel oil and diesel oil, In many cases.

Natural gas, which is widely used in fuel gas, is mainly stored as methane and is stored and transported in a liquefied gas state where the volume thereof is reduced to 1/600.

The ship carrying the liquefied gas has a storage tank which is insulated to store the liquefied gas. In addition, such a vessel can provide a fuel gas supply system that vaporizes naturally occurring boiling off gas in the storage tank or liquefied gas in the storage tank and supplies it to the fuel of the engine. The vessel's engine is equipped with a high-pressure (approx. 150 to 700 bar) or medium-pressure (low-pressure) injection system, such as a low-pressure (approx. 5-8 bar) injection engine such as a DFDE (Dual Fuel Disel Electric) engine and a ME- GI engine (Man B & W's Gas Injection engine) A medium pressure gas injection engine capable of combusting with fuel gas of about 16 to 18 bar may be used.

This fuel gas supply system can compress the evaporated gas supplied from the storage tank through the fuel gas supply line by the compression unit and supply it to the fuel of the ME-GI engine. At this time, when more evaporation gas than the fuel consumption amount required by the engine is supplied, the surplus evaporation gas is heat-exchanged with the evaporation gas supplied from the storage tank by the heat exchanger and is liquefied, and then supplied to the gas-liquid separator. The gas-liquid separator separates the evaporated gas of the excess heat-exchanged gas into gas and liquid components. The liquid components separated by the gas-liquid separator are stored in a storage tank, and the gas components are mixed again with the evaporation gas of the storage tank and then circulated.

In this system, since the liquid must be transported from the gas-liquid separator to the storage tank without using the pump, the pressure in the gas-liquid separator is maintained at about 3 to 4 barA in consideration of the internal pressure of the LNG tank and the LNG level in the tank, To the tank. Conventionally, a pressure or level sensor of a valve and a gas-liquid separator is installed at the upper and lower ends of a gas-liquid separator, a liquid component is regulated through a valve of a liquid outlet of a gas-liquid separator, and a pressure is regulated through a valve of a gas- Method.

Meanwhile, the gas component separated from the gas-liquid separator, that is, the flash gas is a state (about 40 to 50%) in which a large amount of un-liquefied nitrogen gas is contained in the evaporation gas. The flash gas is supplied to the evaporation gas % Content), the nitrogen gas content is reduced to about 15%. In this case, if the flash gas and the evaporation gas are once mixed, the engine can not be separated until the re-liquefaction. Therefore, even though the engine can use the evaporation gas having the higher nitrogen gas content as the fuel, There is a problem to use.

In this case, the nitrogen gas circulating in the fuel gas supply line is continuously accumulated, which causes the size of major equipment such as a compressor and a heat exchanger to increase. Also, as the nitrogen gas content increases, the flow rate passing through the compressor increases and energy is required. In addition, there is a problem in that the re-liquefaction rate is low due to a high nitrogen gas content during the re-liquefaction.

Korean Patent Laid-Open No. 10-2014-0052898 (published on May 4, 2014)

The present invention aims to provide a fuel gas supply system which can easily adjust the nitrogen gas content supplied to a demand place of an engine or the like.

The present invention aims to reduce the capital expenditure (CAPEX) and the operating cost (OPEX) by reducing the energy consumption of the compressor or the heat exchanger.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a storage tank for storing liquefied gas and evaporative gas generated therefrom; A first supply line having a first compressor for pressurizing the evaporation gas and supplying the evaporation gas to a customer; A recovery line extending from the rear end of the first compressor toward the gas-liquid separator and separating the evaporated gas into a flash gas and a liquid component; A heat exchanger for performing heat exchange between the evaporation gas passing through the first supply line and the evaporation gas passing through the recovery line; A re-supply line extending from the gas-liquid separator to the first supply line and supplying the flash gas to the first supply line; And a second supply line extending from the gas-liquid separator toward the customer and supplying the flash gas to the customer.

The second supply line is provided to pass through the heat exchanger and the heat exchanger can perform heat exchange between the first supply line, the recovery line, and the fluid passing through the second supply line, respectively.

The customer includes a first customer requesting an evaporation gas in a high pressure state and a second customer requesting an evaporation gas in a low pressure state and a first valve for reducing pressure is provided between the first customer and the second customer .

The first supply line connects the storage tank and the first demander, and the second supply line connects the gas-liquid separator and the second demander.

The second supply line may be provided with a third compressor for raising the flash gas to a pressure required by the second customer.

And a second compressor for condensing the evaporated gas may be provided in the recovery line.

And a return line for supplying the liquid component separated in the gas-liquid separator to the storage tank.

The second supply line may be provided with a third valve for controlling the amount of nitrogen supplied to the customer.

A second valve, a fourth valve, and a fifth valve for regulating flow rate or pressure are respectively provided in the recovery line, the re-supply line, and the return line, and a measurement sensor provided in the gas-liquid separator or the customer And a controller for controlling the operation of the first valve to the fifth valve based on the information transmitted.

Wherein the customer includes a first customer requesting an evaporation gas in a high pressure state and a second customer requesting an evaporation gas in a low pressure state and the second customer is provided in a branch line branching from the interruption of the first compressor .

The first supply line may connect the storage tank and the first demander, and the second supply line may connect the gas-liquid separator and the branch line.

The fuel gas supply system according to the present invention is characterized in that the content of the nitrogen gas flowing into the second customer is checked through a measuring sensor provided in the second customer, and based on this information, 2 It is possible to control the nitrogen gas content supplied to the customer. This reduces the nitrogen gas content circulating through the first supply line and the re-supply line, reduces the re-liquefaction rate of the evaporation gas, makes it possible to design the first compressor compact, and also reduces the energy consumed in pressurization.

The second supply line is provided to pass through the heat exchanger. In the heat exchanger, heat exchange is performed between the evaporated gas flowing along the second supply line and the compressed evaporated gas passing through the recovered line, It is possible to increase the liquefaction efficiency of the compressed evaporative gas supplied to the evaporator.

1 schematically shows a fuel gas supply system according to a first embodiment of the present invention.
2 schematically shows a fuel gas supply system according to a second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below are provided by way of example so that those skilled in the art will be able to fully understand the spirit of the present invention. The present invention is not limited to the embodiments described below, but may be embodied in other forms. In order to clearly explain the present invention, parts not related to the description are omitted from the drawings, and the width, length, thickness, etc. of the components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

Also, terms including ordinals such as " first, " " second, " and the like can be used to describe various elements, but the elements are not limited by terms. Terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terms used in the present application are used to illustrate the embodiments and are not intended to limit or limit the invention, and the singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprise", "comprising", and the like are intended to specify the presence of stated features, integers, steps, components, or combinations thereof, and may include one or more other features, Steps, elements, or combinations thereof, as a matter of convenience, without departing from the spirit and scope of the invention. Also, when a part is referred to as being "connected" to another part, it includes not only a direct connection but also an indirect connection between the other parts.

1 schematically shows a fuel gas supply system according to a first embodiment of the present invention.

Referring to FIG. 1, a fuel gas supply system according to a first embodiment of the present invention includes a storage tank 1 provided in a ship and storing liquefied gas and evaporative gas generated therefrom, A first supply line L1 provided with a compressor 20 for supplying the evaporation gas to a customer and a gas-liquid separator 40 for supplying the evaporation gas at the downstream end of the first compressor 20 and separating the flash gas into a liquid component A heat exchanger 10 for performing heat exchange between the evaporation gas passing through the first supply line L1 and the evaporation gas passing through the recovery line L2, A second supply line L4 extending to the supply line L1 and supplying the flash gas to the first supply line L1 and a second supply line L4 extending from the gas-liquid separator 40 to the customer, (L3).

The ship includes a liquefied gas carrier, a liquefied gas RV (regasification vessel), a container ship, a general merchant vessel, an LNG FPSO (Floating, Production, Storage and Off-loading), an LNG FSRU (Floating Storage and Regasification Unit) Liquefied gases may include liquefied ethane, LNG, liquefied ethylene, LPG, liquefied propane, liquefied butane, which may be stored in a liquefied state.

The storage tank 1 may have a suitable thermal insulation structure for storing and transporting the liquefied gas. For example, the storage tank 1 may be formed of various types of known thermal insulation tanks such as a MOSS type and a membrane type. The storage tank 1 has a thermal insulation structure capable of storing the liquefied gas stored therein at a cryogenic temperature, but evaporation gas (BOG) due to the evaporation of the liquefied gas is continuously generated in the storage tank 1.

The consumers 2 and 3 may include a first consumer 2 requesting a relatively high-pressure fuel gas and a second consumer 3 requesting a low-pressure fuel gas. At this time, the first customer 2 requests the fuel gas of 10 bar or more as the X-DF engine, and the second customer 3 can demand the fuel gas of about 7 bar as the power generation engine.

In the first embodiment, the first customer 2 may be an engine requiring supply of the fuel gas at a pressure of about 10 bar or more, for example, an X-DF engine. In addition, the first customer 2 may be a dual fuel engine that can utilize NG as well as heavy fuel oil (HFO) as fuel. The first customer (2) may be a consumption means such as a consumer on the land, an industrial complex or the like, or various engines using natural gas as a fuel gas. However, the present invention is not limited to this, and includes a case of a facility of various structures and systems.

The second demander (3) may be an engine which requires supply of the fuel gas at a relatively low pressure as compared with the first demander (2). For example, it may be a power generation engine such as a DFDE engine using fuel gas of about 5 to 7 bar. At this time, the second customer 3 may be a dual fuel engine using not only NG but also heavy fuel oil (HFO) as fuel, as in the case of the first customer 2.

The branch line L6 may be branched from the first supply line L1 toward the first demanding party 2 toward the second demanding party 3. [ The branch line L6 may be provided with a first valve V1 for regulating or reducing the flow rate of the fuel gas. In particular, the first valve V1 acts as a pressure reducing valve to convert the relatively high-pressure fuel gas required by the first customer 2 into a low-pressure fuel gas required by the second customer 3 can do.

The first supply line L1 is a pipe for supplying the evaporation gas in the storage tank 1 and supplying the supplied evaporation gas at a gas pressure suitable for the first customer 2. The first supply line L1 is connected to the first supply line L1, A multi-stage first compressor 20 for pressurizing the evaporation gas supplied from the storage tank 1 to a pressure required by the first customer 2 may be connected.

The heat exchange unit 10 can perform heat exchange between the first supply line L1 and the recovery line L2 and the second supply line L3 passing therethrough using the heating medium. That is, the heat exchange unit 10 is provided with the evaporation gas supplied from the storage tank 1 through the first supply line L1, the gas flowing toward the second demand point 3 through the recovery line L2, (L3) is performed.

The heating medium circulating in the heat exchange unit 10 is heated through heat exchange with the recovery line L2 to heat the evaporation gas passing therethrough through heat exchange with the first supply line L1. The heat medium collects the cold heat of the flash gas separated from the gas-liquid separator 40 through heat exchange with the second supply line L2, and uses the vaporized gas passing through the first supply line L1 You can preheat. As described above, the heat exchange unit 10 performs heat exchange between the first supply line L1 and the recovery line L2 and the second supply line L3, thereby enabling efficient use of energy, thereby preventing waste of energy .

The first compressor 20 can deliver the evaporation gas supplied from the storage tank 1 to the first supply line L1 and can simultaneously compress the evaporation gas to meet the required pressure of the first customer 2 . For example, the first compressor 20 includes five compressors 21a to 21e and five coolers 22a to 22e connected to the output ends of the respective stages. The five compressors 21a to 21e are arranged in a stepwise manner The evaporation gas can be compressed to meet the required pressure of the first customer 2. [ In order to improve the compression efficiency, the coolers 22a to 22e connected between the respective stages interim cool each discharge gas to prevent the temperature of the evaporation gas from being increased due to compression.

The evaporated gas compressed by the first compressor 20 to meet the required pressure of the first customer 2 is discharged through the first supply line L1 to the first customer 2 or the first valve V1, And can be supplied to the second demander (3). At this time, when the evaporation gas is supplied in an amount larger than the amount required by the customer 2 or 3, or when the nitrogen content needs to be regulated, a part of the evaporation gas is supplied to the recovery line L2 branched from the first supply line L1. Lt; / RTI >

The recovery line (L2) recovers the evaporated gas pressurized by the first compressor (20) at the required pressure of the consumers (2, 3), and further pressurizes it with a pressure suitable for liquefaction. The recovered refrigerant is cooled, decompressed and liquefied, (40). The recovery line L2 is provided with a heat exchanger 10 for cooling and liquefying the evaporated gas and a second valve for discharging the evaporated gas liquefied through the heat exchanger 10 to the gas-liquid separator 40 V2) may be installed. In other words, the evaporation gas supplied to the gas-liquid separator 40 through the recovery line L2 passes through the second compressor 30, the heat exchanger 10, and the second valve V2 in sequence, Liquid separator 40 in a vapor-liquid mixed state.

The evaporation gas supplied to the gas-liquid separator 40 can be separated into a flash gas as a gas component and a remaining liquid component. The liquid component separated in the gas-liquid separator 40, that is, the liquefied gas can be stored in the storage tank 1 through the return line L5 and the evaporated gas separated in the gas-liquid separator 40 can be stored in the second supply line L3 to the second customer 3 or may be supplied to the first supply line L1 again through the re-supply line L4. In this case, the flash gas may be a part of the refrigerant which is condensed in the second compressor 30 or the like, which is less supercooled and flows to the expanding side, as a gas.

The second compressor 30 is provided in the second supply line L3 and is provided for converting the compressed evaporated gas moving toward the gas-liquid separator 40 into a liquid state, and can perform a condenser function. The second compressor (30) may be provided with a second cooler (31) at the rear end of the compressor, like the first compressor (20).

The second supply line L3 may pass through the heat exchanger 10 to increase the liquefaction efficiency of the compressed evaporative gas supplied to the gas-liquid separator 40 through the recovery line L2. In the heat exchanger 10, the heat exchange between the evaporated gas separated by the gas-liquid separator 40 and flowing along the second supply line L3 and the compressed evaporated gas supplied to the gas-liquid separator 40 through the recovery line L2 .

The third compressor 50 and the third cooler 51 can be provided on the second supply line L3 to raise the flash gas discharged from the gas-liquid separator 40 to a pressure required by the second customer 3. [ The flash gas having a low pressure of about 3 to 4 bar is compressed to about 7 to 8 bar required by the second customer 3.

The re-supply line L4 may be provided to connect the upper end of the gas-liquid separator 40 and the first supply line L1. A part of the flash gas separated by the gas-liquid separator 40 is sent to the second supply line L3 for supplying to the customer 2 and the other is recirculated to the first supply line L1.

The return line L5 allows the liquid phase fuel separated in the gas-liquid separator 40 to be stored again in the storage tank 1. At this time, the return line L5 may be provided with a fifth valve V5 for reducing the liquefied gas supplied to the storage tank 1 to atmospheric pressure.

At this time, the fourth valve V4 and the fifth valve V5 are provided respectively in the re-supply line L4 and the return line L5, and the pressure P or the water level L, measured by the gas-liquid separator 40, Whether or not the opening / closing operation can be determined. The amount of the flash gas filled in the gas-liquid separator 40 is measured from the pressure level. If the size of the flash gas is greater than necessary, the fourth valve V4 is opened to transfer the flash gas to the re-supply line L4, (Water level) is measured, the fifth valve (V5) is opened to recover the liquid fuel filled in the gas-liquid separator (40) to the storage tank (1) through the return line (L5) .

The third valve (V3) is provided in the second supply line (L3) and can control the amount of nitrogen supplied to the second customer (3). The content of the nitrogen gas flowing into the second consumer 3 can be confirmed through a calorific value measuring device (not shown) included in the second consumer 3 or a component measuring device (not shown) before the second consumer 3 The third valve V3 adjusts the flow rate between the gas-liquid separator 40 and the heat exchanger 10 based on this information to control the content of the nitrogen gas supplied to the second customer 3. [ This can reduce the amount of nitrogen gas circulating through the first supply line (L1) to reduce the re-liquefaction ratio and the size of the first compressor (20), and also reduce the energy consumed in pressurizing the evaporation gas.

Further, a control unit (not shown) may be provided to control the valves including the third valve V3. For example, a third valve V3, a fourth valve V4 and a fifth valve V5 for regulating the flow rate or pressure are connected to the recovery line L2, the re-supply line L4 and the return line L5 And a control unit (not shown) is provided for each of the first to fifth valves V1 to V5 based on the information (nitrogen content) transmitted from the measurement sensor provided in the gas-liquid separator 40 or the customer 2 or 3. [ The amount of nitrogen gas N2 consumed in the first consumer 2 or the second consumer 3 can be controlled.

A gas sensor (not shown) is a component analyzer for measuring the nitrogen content. The gas sensor is provided in the gas-liquid separator 40 to analyze components of the flash gas discharged from the gas-liquid separator 40, So that it is possible to analyze the components of the fluid flowing into the customers 2 and 3. The control unit (not shown) can adjust the nitrogen content of the fuel gas transferred to each customer 2 or 3 based on the component information transmitted from the measurement sensor.

Hereinafter, a fuel gas supply system according to a second embodiment of the present invention will be described with reference to FIG. Hereinafter, the same reference numerals are assigned to constituent elements having the same function, and a detailed description thereof will be omitted.

2 schematically shows a fuel gas supply system according to a second embodiment of the present invention. The second embodiment shows that the present fuel gas system can be applied to an engine in which the first customer 2 'requires high-pressure fuel gas such as the ME-GI engine. At this time, the customer 2 'may be an engine requiring fuel gas supply at a pressure of about 150 to 300 bar, for example, an ME-GI engine. Also, the first customer 2 'may be a dual fuel engine that can utilize NG as well as heavy fuel oil (HFO) as fuel.

In the second embodiment, the recovery line L2 'may be branched at the downstream of the fourth compressor of the first compressor 20' to extend to the gas-liquid separator 40 as shown. Unlike the first embodiment, the first consumer 2 'requires high-pressure fuel gas, and thus the first compressor 20' also has a higher rise pressure at each stage than the first embodiment, Liquid separator 40 'in the first compressor 20' to supply the low-pressure fuel gas to the second consumer 3 through the second supply line L3 '. Here, the second valve V2 can reduce the pressure of the fluid passing through the recovery line L2 'by the pressure required by the gas-liquid separator 40.

The branch line L6 'may be branched from the end of the first compressor 20', for example, at the downstream end of the second compressor to extend to the second consumer 3 side. The second demander 3 requires a relatively low-pressure fuel gas as compared with the first demander 2 ', because such low-pressure fuel gas can be pressurized by only passing the two gases through the two compressors. Here, the stop position of the first compressor 20 'may mean a position where only a part of the compressors of the first compressor 20' configured as a multi-stage compressor type of the evaporation gas passes.

As described above, in the second embodiment, the second customer 3 is provided in the branch line L6 'branching from the interruption of the first compressor 20', the second supply line L3 'is provided in the gas-liquid separator 40, The third valve V3 provided in the second supply line L3 'can be adjusted to adjust the nitrogen gas content supplied to the second customer 3 in the same manner as in the first embodiment by connecting the branch line L6' have. This reduces the nitrogen gas content circulating through the first feed line L1 and the re-feed line L4, which reduces the re-liquefaction rate of the evaporated gas to enable the first compressor 20 'to be compactly designed, Thereby reducing energy consumption.

The foregoing has shown and described specific embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined in the appended claims.

L1: first supply line L2: recovery line
L3: second supply line L4: re-supply line
L5: return line L6: branch line
V1: first valve V2: second valve
V3: third valve V4: fourth valve
V5: fifth valve 1: storage tank
2: First Demand Point 3: Second Demand Point
10: heat exchanger 20: first compressor
21a: No. 1 compressor 21b: No. 2 compressor
21c: No. 3 compressor 21d: No. 4 compressor
21e: No. 5 compressor 22a: No. 1 condenser
22b: Cooler No. 2 22c: Cooler No. 3
22d: Cooler No. 4 22e: Cooler No. 5
30: second compressor 31: second cooler
40: gas-liquid separator 50: third compressor
51: third cooler 2 ': first demand customer
20 ': first compressor L2': recovery line
L3 ': second supply line L6': branch line

Claims (11)

A storage tank for storing liquefied gas and evaporative gas generated therefrom;
A first supply line provided with a first compressor for pressurizing the evaporative gas and supplying the evaporative gas to a first customer;
A recovery line connected to the gas-liquid separator for separating the flash gas into a liquid component and supplied to the evaporator at a downstream end of the first compressor;
A second supply line extending from the gas-liquid separator to a second customer and supplying the flash gas to the second customer;
A heat exchanger for performing heat exchange between the first supply line, the collection line, and the fluid passing through the second supply line, respectively;
A re-supply line extending from the gas-liquid separator to the first supply line and supplying the flash gas to the first supply line; And
And a return line for supplying the liquid component separated in the gas-liquid separator to the storage tank,
A first valve for reducing pressure is provided in a branch line connecting the first demander and the second demander,
Wherein the second supply line is provided with a third valve for controlling the amount of nitrogen supplied to the second customer,
A second valve, a fourth valve, and a fifth valve for regulating the flow rate or the pressure are provided in the recovery line, the re-supply line, and the return line,
Further comprising a control unit for controlling operation of the first valve to the fifth valve based on information transmitted from the gas-liquid separator or the measurement sensor provided in the customer. delete delete delete The method according to claim 1,
The second supply line
And a third compressor for raising the flash gas to a pressure required by the second customer. The method according to claim 1,
Wherein the recovery line is provided with a second compressor for condensing the evaporated gas. delete delete delete A storage tank for storing liquefied gas and evaporative gas generated therefrom;
A first supply line provided with a first compressor for pressurizing the evaporative gas and supplying the evaporative gas to a first customer;
A recovery line connected to the gas-liquid separator for separating the flash gas into a liquid component and supplied to the evaporator at a downstream end of the first compressor;
A second supply line extending from the gas-liquid separator to a second customer and supplying the flash gas to the second customer;
A heat exchanger for performing heat exchange between the fluid passing through the first supply line, the collection line and the second supply line, respectively;
A re-supply line extending from the gas-liquid separator to the first supply line and supplying the flash gas to the first supply line; And
And a return line for supplying the liquid component separated in the gas-liquid separator to the storage tank,
Wherein the second supply line is provided with a third valve for controlling the amount of nitrogen supplied to the second customer,
A second valve, a fourth valve, and a fifth valve for regulating the flow rate or the pressure are provided in the recovery line, the re-supply line, and the return line,
Further comprising a control unit for controlling operations of the second valve to the fifth valve based on information transmitted from the gas-liquid separator or the measurement sensor provided in the customer,
And the second demand point is provided in a branch line branching from the interruption of the first compressor. delete

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