KR20140052887A - System and method for supplying fuel gas for a ship - Google Patents

Abstract

The present invention relates to a system and a method for supplying fuel gas for a ship, which are capable of supplying fuel gas to an engine which compresses and vaporizes LNG and receives and use the LNG as fuel according to the fuel supply conditions of a main engine and a sub engine. According to the present invention, the system for supplying fuel gas for a ship having an engine which receives LNG from a storage tank for storing LNG and uses the LNG as fuel includes: a compressor line which compresses BOG generated in the storage tank by a compressor and supplies the BOG as fuel to the engine; a high-pressure pump line which compresses LNG stored in the storage tank by a high-pressure pump and supplies the LNG as fuel to the engine; an expansion valve which is provided on the high-pressure pump line to decompress the LNG compressed by the high-pressure pump to pressure required by the engine; and a heater which heats the LNG decompressed through the expansion valve to a temperature required by the engine.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a fuel gas supply system for a ship,

[0001] The present invention relates to a system and a method for supplying fuel gas for ships, and more particularly, to a DF (Dual Fuel) engine which can be used as fuel after compressed and vaporized LNG, To a fuel gas supply system and a method for supplying fuel gas to a ship in accordance with fuel requirements of a DF engine.

In recent years, consumption of liquefied gas such as LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas) has been rapidly increasing worldwide. The liquefied gas is transported in a gaseous state via land or sea gas piping, or is transported to a distant consumer site stored in a liquefied gas carrier in a liquefied state. Liquefied gas such as LNG or LPG is obtained by cooling natural gas or petroleum gas at a very low temperature (approximately -163 ° C. in the case of LNG), and its volume is significantly reduced compared to when it is in a gaseous state, .

The liquefied gas carrier, such as an LNG carrier, is used to load the liquefied gas with the liquefied gas to the sea and to unload the liquefied gas to the onshore site. For this purpose, a storage tank capable of withstanding the extremely low temperature of the liquefied gas ).

Examples of maritime structures having storage tanks capable of storing liquefied gas at cryogenic temperatures include ships such as LNG RV (Regasification Vessel), LNG FSRU (Floating Storage and Regasification Unit), LNG FPSO (Floating, Production, Storage and off-loading), and the like.

LNG RV is a LNG regeneration facility installed on a liquefied natural gas carrier capable of self-propulsion and floating. LNG FSRU stores liquefied natural gas unloaded from LNG carrier offshore at sea, It is an offshore structure that vaporizes liquefied natural gas and supplies it to the customers on land. The LNG FPSO is a marine structure used to purify the natural gas mined in the sea, directly liquefy it, store it in the storage tank, and transfer the LNG stored in the storage tank to the LNG transport if necessary. In this specification, a vessel is a concept including a liquefied gas carrier such as an LNG carrier, an LNG RV, an LNG FPSO, and an LNG FSRU.

Since the liquefaction temperature of natural gas is a cryogenic temperature of about -163 ° C at normal pressure, LNG is evaporated even if its temperature is slightly higher than -163 ° C at normal pressure. For example, in the case of a conventional LNG carrier, the LNG storage tank of the LNG carrier is heat-treated, but since the external heat is continuously transferred to the LNG, LNG is transported by the LNG carrier, The LNG storage tank is constantly vaporized and boil-off gas (BOG) is generated in the LNG storage tank.

BACKGROUND ART [0002] Conventionally, in order to suppress and treat evaporation gas in a storage tank of a liquefied gas carrier, a method of discharging evaporation gas to the outside of the storage tank and incinerating it, a method of discharging evaporation gas to the outside of the storage tank, A method of returning to the storage tank after re-liquefying, a method of using evaporation gas as fuel used in a propulsion engine of the ship, a method of suppressing the generation of evaporation gas by keeping the internal pressure of the storage tank high, Have been used in combination.

In order to prevent environmental pollution caused by ships, international standards and regulations of each country are increasingly complicated. As a result, there is a growing concern about the environmentally friendly and highly efficient fuels of ships. One of them is natural gas which is natural vaporized or forced vaporized from LNG DFDE (Dual Fuel Diesel Electric) system which is mixed with diesel oil and used as fuel of engine (that is, DF engine) has been developed and used.

Application No. 10-2010-0116987

DF engines are being used as propulsion systems for ships, and engines that use high-pressure gas injection are being developed. In such a propulsion system of the ship, the fuel supply device of the engine may be provided in a binary manner in preparation for the shutdown of the engine in the event of a failure of the apparatus.

When a high-pressure gas injection engine is configured as a propulsion system in an LNG carrier and the BOG generated during LNG transportation is supplied as fuel for a marine engine, two sets of compressors are provided. When the LNG is filled in the cargo tank, It is possible to supply the fuel by compressing it. However, it is difficult to supply sufficient fuel because the amount of BOG generated when the amount of LNG loaded on the cargo tank is small due to unloading of LNG.

Compressed and vaporized LNG instead of BOG, which constitutes a high-pressure gas injection engine that is supplied as fuel, consumes LNG stored in a cargo tank, so that stable fuel supply is possible. However, a large amount of BOG generated under full loading of LNG is not utilized The cargo tank of the ship is equipped with a pump for unloading the liquefied gas, a stripping pump for raising the liquefied gas remaining in the cargo tank after unloading, and an FG pump for transferring the liquefied gas for fueling the engine There is a problem that the number of constituent devices becomes large, so that a lot of space is occupied in the cargo tank, and equipment is difficult to manage.

Therefore, it is an object of the present invention to provide a fuel supply system capable of reducing the number of equipment installed in the system and simplifying the fuel supply path while making sufficient use of the generated BOG, capable of stably supplying fuel even when the amount of generated BOG is small, System.

According to an aspect of the present invention, there is provided a fuel gas supply system for a ship having an engine that receives a liquefied natural gas from a storage tank for storing liquefied natural gas and uses the liquefied natural gas as a fuel,

A compressor line for compressing the BOG generated in the storage tank by a compressor and supplying the compressed BOG as fuel to the engine;

A high-pressure pump line which compresses the LNG stored in the storage tank by a high-pressure pump and supplies the compressed LNG as fuel to the engine;

An expansion valve installed in the high-pressure pump line for reducing the pressure of the LNG compressed by the high-pressure pump to a pressure required by the engine; And

And a heater that heats the LNG that has been reduced while passing through the expansion valve to a temperature required by the engine.

Preferably, the engine includes a main engine and a sub-engine, the high-pressure pump line includes an LNG main supply line for supplying LNG discharged from the storage tank to the main engine, And an LNG portion supply line for supplying the LNG portion to the sub engine, wherein the heater may be provided in the LNG portion supply line.

The LNG supply line may further include a vaporizer installed at an upstream side of a branch point of the LNG main supply line and the LNG supply line in the high pressure pump line for heating and vaporizing the LNG compressed by the high pressure pump.

Advantageously, said main engine comprises at least one ME-GI engine and said sub engine may comprise a DF engine.

Preferably, the compressor line includes a BOG main supply line for supplying the BOG discharged from the storage tank to the main engine, and a BOG part supply line for supplying the BOG discharged from the storage tank to the sub engine can do.

Preferably, the BOG main feed line includes a compressor having a multi-stage compression process, and the BOG feed line is branched from the BOG main feed line to branch the compressed BOG through at least a portion of the multi- .

According to another aspect of the present invention, there is provided a method of supplying a fuel gas to a ship equipped with an engine supplied with the liquefied natural gas from a storage tank for storing liquefied natural gas and used as fuel,

The BOG generated in the storage tank is compressed by a compressor and supplied as fuel to the main engine of the ship, or the LNG stored in the storage tank is compressed by a high-pressure pump and supplied as fuel to the main engine,

A step of branching the LNG compressed by the high-pressure pump to a pressure required by the sub-engine of the ship, and a heating step of adjusting the pressure-reduced LNG to a temperature required by the sub-engine, There is provided a method for supplying a marine fuel gas.

Preferably, the compressor has a multi-stage compression process, and can branch the compressed BOG through at least a portion of the multi-stage compressors to supply the compressed BOG to the sub-engine.

Preferably, the LNG to be supplied to the sub engine of the ship may be branched on the downstream side of the vaporizer which heats and vaporizes the compressed LNG.

According to the present invention, there is provided a marine fuel gas supply system capable of supplying fuel gas in accordance with conditions such as temperature and pressure demanded by a corresponding engine, for a marine DF engine that can be used as a fuel after compression and vaporization of LNG, A method can be provided.

The present invention can supply both BOG and LNG, so that stable fuel supply to the engine of the ship can be achieved. In addition, the LNG supplied to the main engine can be depressurized and heated to be supplied to the DF engine. By sharing the fuel supply system between the main engine and the sub engine, the space and efficiency of the ship can be improved by reducing equipment and pipelines, .

1 is a schematic structural view showing a marine fuel gas supply system according to a first embodiment of the present invention, and Fig.
2 is a schematic configuration diagram showing a marine fuel gas supply system according to a second embodiment of the present invention.

In general, among the waste gases emitted from vessels, those regulated by the International Maritime Organization are nitrogen oxides (NOx) and sulfur oxides (SOx), and in recent years they have also been trying to regulate the emission of carbon dioxide (CO ₂ ) have. Particularly, in the case of nitrogen oxide (NOx) and sulfur oxides (SOx), it was submitted through the Protocol of the Maritime Pollution Prevention Convention (MARPOL) in 1997, In May, the requirements for the fermentation were satisfied and the regulations are being implemented.

Accordingly, various methods for reducing nitrogen oxide (NOx) emissions have been studied in order to meet these requirements. Of these methods, a high-pressure natural gas injection engine for ships such as LNG carrier, for example, ME-GI engine . The ME-GI engine is seen as an environmentally friendly next-generation engine that can reduce pollutant emissions by 23%, nitrogen compounds 80%, and sulfur compounds 95% or more, compared with diesel engines of the same class.

Such an ME-GI engine can be used for a ship such as an LNG carrier which stores and transports LNG in a cryogenic storage tank (in the present specification, a vessel means an LNG carrier, an LNG RV, etc., a marine plant such as an LNG FPSO, an LNG FSRU, In this case, natural gas is used as the fuel, and depending on the load, a high gas supply pressure of about 150 to 400 bara (absolute pressure) is required for the engine do.

The ME-GI engine can be used directly on the propeller for propulsion, and the ME-GI engine consists of a two-stroke engine that rotates at low speed. That is, the ME-GI engine is a low-speed two-stroke high-pressure natural gas injection engine.

Further, in order to reduce nitrogen oxide emissions, a DF engine (for example, DFDG: Dual Fuel Diesel Generator) which is a mixture of diesel oil and natural gas and used as fuel has been developed and used for propulsion and power generation. The DF engine is an engine that can mix oil and natural gas or use only one selected from oil and natural gas as fuel. The sulfur content in the exhaust gas is smaller than the sulfur content in the fuel, little.

The DF engine does not need to supply the fuel gas at a high pressure such as the ME-GI engine, but can supply the fuel gas by compressing it to approximately several to several tens of bara. The DF engine obtains power by driving the generator by the driving force of the engine, and drives the propulsion motor or operates various devices or equipments by using this electric power.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the following examples can be modified in various forms, and the scope of the present invention is not limited to the following examples.

1 is a configuration diagram showing a fuel supply system according to a first embodiment of the present invention. The fuel supply system of this embodiment can be applied to, for example, an LNG carrier equipped with a MEGI engine as the main engine for propulsion.

Referring to FIG. 1, a fuel supply system 100 according to a first embodiment of the present invention provides a path for transferring an LNG from a cargo tank 1 to a main engine 3 A fuel supply line 110 and a BOG line 140 providing a path for transferring BOG generated from the storage tank 1 to the main engine 3. In the hybrid fuel supply system 100 using the BOG according to an embodiment of the present invention, the LNG is supplied to the LNG pump 120 and the LNG vaporizer 130 through the fuel supply line 110 The BOG compressor 140 compresses the BOG through the BOG line 140 and supplies the compressed BOG to the main engine 1. The BOG compressor 150 compresses the BOG from the BOG compressor 140 to the main engine 1, And supplies the surplus BOG to the integrated IGG / GCU system 200.

The MEGI engine which can be used as the main engine 1 needs to be supplied with fuel at a high pressure of about 150 to 400 bara (absolute pressure). Therefore, as the LNG pump 120 and the BOG compressor 150 according to the present embodiment, a high-pressure pump and a high-pressure compressor capable of compressing LNG and BOG, respectively, to a pressure required by the MEGI engine are used.

The fuel supply line 110 provides a path for transferring the LNG supplied by the drive of the transfer pump 2 from the storage tank 1 of the LNGC as fuel to the main engine 3, And an LNG vaporizer 130 are installed.

The LNG pump 120 is installed to supply the pumping force necessary for transferring the LNG to the fuel supply line 110. For example, the LNG HP pump (LNG High Pressure pump) may be used. In the present embodiment, .

The LNG vaporizer 130 is installed at the rear end of the LNG pump 120 in the fuel supply line 110 to vaporize the LNG conveyed by the LNG pump 120. In order to vaporize the LNG, Various kinds of heating means may be used for providing heat of vaporization of LNG including heaters as another example. In addition, the LNG vaporizer 130 may be a high pressure vaporizer that can be used at a high pressure for vaporizing the LNG. On the other hand, steam generated from a boiler or the like can be used as the fruit to be circulated and supplied to the fruit circulation line 131, for example.

The BOG line 140 provides a path for transferring the BOG generated naturally from the storage tank 1 to the main engine 3 and is connected to the fuel supply line 110 as in the present embodiment, To the engine 3, or alternatively it may provide a path for supplying the BOG directly to the main engine 3.

The BOG compressor 150 is installed in the BOG line 140 to compress the BOG through the BOG line 140. Although only one BOG compressor 150 is shown in FIG. 1, the BOG compressor is configured such that the two compressors of the same specification are connected in parallel to meet redundancy requirements, as in a conventional fuel supply system. Lt; / RTI > However, in the case where a single BOG compressor 150 is installed in the branch of the redundant BOG line 160 in the BOG line 140 as in the present embodiment, an economical burden due to the installation of the expensive BOG compressor 150, And reduce the burden on the repairer.

The redundant BOG line 160 provides a path for supplying surplus BOG from the BOG compressor 150 to the integrated IGG / GCU system 200, which may include an integrated IGG / GCU system 200 as well as an auxiliary The surplus BOG can be supplied as fuel by an engine or the like.

The integrated IGG / GCU system 200 is an integrated system of IGG (Inert Gas Generator) and GCU (Gas Combustion Unit).

The surplus BOG line 160 and the fuel supply line 110 may be connected to each other by a connection line 170. Thus, the surplus BOG can be used as the fuel for the main engine 1 by the connection line 170, or the vaporized LNG can be used as fuel for the integrated IGG / GCU system 200. [ The connection line 170 may be provided with a heater 180 for heating BOG or vaporized LNG passing therethrough and may be provided with a pressure reduction valve (Pressure Reduction) for reducing excessive pressure by controlling the pressure by BOG or vaporized LNG. (PRV) 190 may be installed. Meanwhile, the heater 180 may be a gas heater using heat of combustion of gas, or various heating means may be used as well as a heat circulation supply unit that provides a heat source for heating by circulation of the heat.

The operation of the fuel supply system according to this embodiment will now be described.

When the pressure in the storage tank 1 is equal to or higher than a predetermined pressure or the amount of generated BOG is large, BOG is compressed by driving the BOG compressor 150 and supplied to the main engine 1 as fuel. When the pressure in the storage tank 1 is less than the predetermined pressure or the BOG generation amount is small, the LNG pump 120 and the LNG vaporizer 130 are driven to transfer and vaporize the LNG to supply the main engine 1 as fuel .

The surplus BOG from the BOG compressor 150 is supplied to the auxiliary IGG / GCU system 200 or the auxiliary engine such as the DF engine through the surplus BOG line 160 to the BOG consuming or storing tank 1 To be used for the purpose of producing an inert gas to be supplied, and further to be used as fuel for an auxiliary engine or the like.

The integrated IGG / GCU system 200 to which the BOG is supplied can consume BOG continuously generated from the storage tank 1 by BOG combustion in the main body 210 and supply the BOG to the storage tank 1 It is also possible to generate a combustion gas as an inert gas.

Fig. 2 shows a schematic configuration diagram of a marine fuel gas supply system according to a second embodiment of the present invention.

2 shows an example in which the fuel gas supply system of the present invention is applied to a LNG carrier equipped with a high-pressure natural gas injection engine capable of using LNG as fuel, that is, an ME-GI engine, The fuel gas supply system can be applied to all kinds of ships equipped with an engine using LNG as fuel. That is, the present invention can be applied to LNG carriers, LNG RVs, and other offshore plants such as LNG FPSO and LNG FSRU.

The DF engine (for example, DF Generator: DFDG) is used as the sub-engine 32. The DF engine (DFDG) . Generally, the main engine is used for propulsion for the ship's operation, and the sub-engine is used for power generation to supply power to various devices and facilities installed inside the ship. However, But is not limited thereto. The main engine and the sub engine may be installed in plural, respectively.

The marine fuel gas supply system according to the present embodiment is a system in which the natural gas (that is, the gaseous state (that is, the gaseous state) accommodated in the storage tank 11 for the engines (that is, the ME- Of BOG and liquid LNG) as fuel.

The fuel gas supply system of the present embodiment for supplying the gaseous BOG as the fuel gas includes a BOG main supply line L1 for supplying BOG stored in the storage tank 11 to the main engine 31, And a BOG part supply line L2 branched from the main supply line L1 to supply the BOG to the sub engine 32. [

In order to supply the LNG in the liquid state as the fuel gas, the fuel gas supply system of this embodiment includes an LNG main supply line L3 for supplying the LNG stored in the storage tank 11 to the main engine 31, And an LNG portion supply line L4 branching from the LNG main supply line L3 and supplying the LNG to the sub engine 32. [

According to the present embodiment, the BOG main feed line L1 is provided with a compressor 13 for compressing the BOG, and the LNG main feed line L3 is provided with a high-pressure pump 23 for compressing the LNG.

The evaporated gas NBOG generated in the storage tank 11 storing the liquefied gas and discharged through the BOG discharge valve 12 is conveyed along the BOG main supply line L1 and compressed in the compressor 13, A natural gas injection engine, such as an ME-GI engine. The evaporation gas is compressed by the compressor (13) to a high pressure of about 150 to 400 bara and then supplied to the high pressure natural gas injection engine.

The storage tank has a sealing and thermal barrier to store liquefied gases such as LNG in cryogenic conditions, but it can not completely block the heat transmitted from the outside. Accordingly, evaporation of the liquefied gas is continuously performed in the storage tank 11, and the evaporation gas in the storage tank 11 is discharged to maintain the pressure of the evaporated gas at a proper level.

The compressor 13 may include one or more compression cylinders 14 and one or more intercoolers 15 for cooling the evaporated gas as it is being compressed. The compressor 13 may be configured, for example, to compress the evaporation gas to about 400 bara. In Fig. 2, a multi-stage compression compressor 13 including five compression cylinders 14 and five intermediate coolers 15 is illustrated, but the number of compression cylinders and intercoolers can be changed as needed. In addition to a structure in which a plurality of compression cylinders are arranged in one compressor, a plurality of compressors may be connected in series.

The evaporated gas compressed in the compressor 13 is supplied to the high-pressure natural gas injection engine through the BOG main supply line L1. In accordance with the amount of fuel required in the high-pressure natural gas injection engine, Gas injection engine, or may supply only a part of the compressed evaporated gas to the high-pressure natural gas injection engine.

The sub BOG supply line L2 for supplying the fuel gas to the DF engine 32 which is the sub engine is branched from the main BOG supply line L1. More specifically, the sub-BOG supply line L2 branches off from the main BOG supply line L1 so that the compressed vaporized gas can be diverted through a part of the multi-stage compression in the compressor 13. 2 is an example in which the evaporation gas is branched through a part of the multi-stage compression. In this case, the BOG is branched in any of the first to fifth stages and is supplied to the sub-engine via the sub BOG supply line L2. Can be configured. As the compressor, for example, a compressor of Burckhardt can be used. The compressor of Bochard Inc. Comprises a total of five cylinders, the three cylinders in the front are operated in an oil-free manner and the two cylinders in the rear are operated in an oil-lubricated manner. Therefore, when the compressor of the subsidiary company is used as the compressor 13 for compressing the BOG, it is necessary to configure the BOG to be transferred through the oil filter when branching the BOG in four or more stages. However, It may be advantageous in that there is no need to use a filter.

Since the required pressure of the DF engine (for example, DFDG) as the sub engine is lower than that of the ME-GI engine, when the BOG in the compressed state at the high pressure is branched at the rear end of the compressor 13, It may be supplied to the engine.

When the LNG is heated, the methane component having a relatively low liquefaction temperature is preferentially vaporized. Therefore, in the case of the vaporized gas, the methane content is high and can be supplied as fuel to the DF engine as it is.

On the other hand, when the amount of evaporative gas generated in the storage tank 11 is higher than the amount of fuel required by the main engine and the sub engine, and a surplus of evaporative gas is expected to be generated, the compressed or step- It can be used in other BOG consumption means. As such evaporative gas consumption means, GCU, gas turbine, etc., which can use natural gas relatively low in pressure as compared with ME-GI engine, can be used.

The LNG main supply line L3 is provided with a discharge pump 21 installed inside the storage tank 11 for discharging the LNG to the outside of the storage tank 11, A high-pressure pump 23 for secondarily compressing the LNG to a pressure required by the ME-GI engine is provided. The discharge pumps 21 may be installed one by one in each storage tank 11. The high-pressure pump 23 can be used by providing a plurality of high-pressure pumps in parallel.

As described above, the pressure of the fuel gas required in the ME-GI engine is as high as about 150 to 400 bara (absolute pressure). As used herein, "high pressure" should be taken to mean a pressure of 150-400 bara (absolute pressure) required by the ME-GI engine.

The LNG discharged from the storage tank 11 storing the liquefied gas through the discharge pump 21 is transferred along the LNG main supply line L3 and supplied to the high pressure pump 23. [ Subsequently, the LNG is compressed to a high pressure by the high-pressure pump 23, and then supplied to the vaporizer 24 to be vaporized. The vaporized LNG is supplied as fuel to a high-pressure natural gas injection engine, such as the ME-GI engine 31. At pressures required by the ME-GI engine, LNG is supercritical. Therefore, the expression of vaporizing the LNG compressed at the high pressure in the vaporizer 24 should be regarded as meaning that the temperature of the LNG in the supercritical state is raised to the temperature required by the ME-GI engine.

The sub LNG supply line L4 for supplying the fuel gas to the DF engine 32 which is the sub engine is branched from the main LNG supply line L3. More specifically, the secondary LNG supply line L4 branches off from the main LNG supply line L3 on the downstream side of the vaporizer 24 or on the downstream side of the high-pressure pump 23.

The secondary LNG supply line L4 is provided with an expansion valve 25 and a heater 26 so that the pressure and temperature of the LNG supplied as fuel can be adjusted to a value required by the DF engine.

In the case of LNG, the methane content is relatively lower than that of BOG and may be lower than the methane demanded by the DF engine. Since the ratio of hydrocarbon components (methane, ethane, propane, butane, etc.) It is not suitable to supply the DF engine as fuel as it is. Therefore, a separator (not shown) for controlling the DF engine may be further provided.

The LNG branched from the main LNG supply line L3 to the sub LNG supply line L4 via the high pressure pump and the vaporizer passes through the expansion valve 25 and is decompressed to the pressure required by the DF engine. The fuel gas that has been thermally expanded while passing through the expansion valve 25 is introduced into the heater 26, heated to the temperature required by the sub engine, and then supplied to the sub engine as fuel.

The DF engine requires a fuel gas supply of 3 to 10 bar, preferably 5 to 7 bar and a temperature of 30 to 70 ° C, preferably 40 to 50 ° C, so that the fuel is supplied to the DF engine through the expansion valve 25 and the heater 26 The fuel is supplied according to such fuel supply conditions.

According to the present invention, there are two paths for supplying the fuel gas to the engines (main engine and sub engine). That is, the fuel gas may be supplied to the engine after being compressed through the compressor (13), or may be supplied to the engine after being compressed through the high-pressure pump (23).

In particular, ships such as LNG carriers and LNG RVs are used to transport LNG from the production site to the consumer site. Therefore, when operating from the production site to the consumer site, it is necessary to operate Laden as a storage tank full of LNG, When returning to production site, the storage tank is operated in a ballast state with almost empty space. Since the amount of LNG is large in the laid-in state, the amount of evaporation gas is relatively large, and in the ballast state, the amount of LNG is small and the amount of evaporation gas is relatively small.

For example, in the case of an LNG carrier having a storage capacity of 150000 m < 3 >, the amount of BOG generated in the layun state is 3 to 4 ton / h, The BOG generation amount is 0.3 to 0.4 ton / h. It is known that ME-GI engines can use 1 to 4 ton / h of natural gas as fuel depending on the load. On the other hand, since the BOR (Boil Off Rate) is gradually lowered as the insulation performance of the storage tank is improved recently, the amount of BOG generated is also decreasing.

Therefore, when the compressor line (i.e., L1 and L2 in Fig. 2) and the high-pressure pump line (i.e., L3 and L4 in Fig. 2) are provided together as in the fuel gas supply system of the present invention, It is desirable to supply the fuel gas to the engines through the compressor line in the laundering state and to supply the fuel gas to the engines through the high pressure pump line in the ballast state where the generation amount of the evaporation gas is small.

Generally, the energy required to compress the gas (BOG) by the compressor to a high pressure of 150 to 400 bara (absolute pressure) required by the ME-GI engine is less than the energy required to compress the liquid (LNG) It is considered economical to use only a high pressure pump line without a compressor line since a considerable amount of energy is required and the compressor for compressing the gas at a high pressure is considerably expensive and takes up a large volume. For example, 2MW of power is consumed to fuel a ME-GI engine by driving a set of multi-stage compressors. Only 100kW of power is consumed by using a high-pressure pump. However, when the fuel gas is supplied to the engines using only the high-pressure pump line in the laid-open state, a liquefaction device for re-liquefying the BOG in order to treat BOG continuously occurring in the storage tank is indispensable, , It is advantageous to install a compressor line and a high-pressure pump line together.

On the other hand, when the amount of evaporative gas generated in the storage tank does not meet the amount of fuel required by the ME-GI engine, such as a ballast state, the evaporated gas in the multi-stage compressor is not compressed to the high pressure required by the ME- It is effective to branch off the evaporation gas during compression and use it as fuel in the DF engine, and idle the remaining compression cylinders. When the evaporator is driven by compressing the entire 5-stage compressor, the required power is 2MW. If only the second stage is used and the remaining three stages are idle, the required power is 600kW. The required power is 100 kW. Therefore, when the BOG generation amount is less than the fuel amount required in the ME-GI engine, such as the ballast condition, it is advantageous from the energy efficiency standpoint that the BOG consumes the entire amount in the DF engine and supplies the LNG as fuel through the high pressure pump.

However, even if the BOG generation amount is less than the fuel requirement amount in the ME-GI engine, the BOG may be supplied as fuel to the ME-GI engine through the compressor while supplying the LNG by the deficient amount. Instead of discharging the BOG every time the BOG is generated, the BOG is collected without releasing the BOG until the storage tank reaches a certain pressure, and then discharged intermittently to the DF engine or ME-GI And may be supplied as fuel to the engine.

In addition, in ships where equipment repair and replacement is not easy, it is necessary to install two important facilities in case of an emergency (redundancy; that is, dual design). In other words, the ship is provided with an extra facility that can perform the same function as the main facility, so that when the main facility is in normal operation, It is required to design redundantly important facilities. Examples of facilities requiring dual design include rotary-driven equipment such as compressors and pumps.

In this way, the ship needs to be equipped with a plurality of facilities in order to satisfy only the dual requirement without being usually used. The fuel gas supply system using two compressor lines requires a great deal of cost There is a problem that a space is consumed and a lot of energy is consumed in use, and a fuel gas supply system using two high-pressure pump lines may have a problem that a large amount of energy is consumed in processing (i.e., re-liquefying) evaporative gas. In contrast, the fuel gas supply system of the present invention, in which a compressor line and a high-pressure pump line are installed together, can continue normal operation through the other supply line even if a problem occurs in one of the supply lines. If only one compressor line is installed It is possible to reduce the cost of the first drying operation as well as the operation cost by appropriately selecting and operating the optimum fuel gas supplying method according to the amount of generated evaporation gas while using less expensive compressor.

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 will be.

11: Storage tank 12: Discharge valve
13: compressor 14: compression cylinder
15: Intermediate cooler 21: Discharge pump
23: high-pressure pump 24: vaporizer
25: expansion valve 26: heater
L1: BOG main supply line
L2: BOG feed line
L3: LNG main supply line
L4: LNG part supply line

Claims (9)

There is provided a fuel gas supply system for a ship having an engine that receives the liquefied natural gas from a storage tank for storing liquefied natural gas and uses the liquefied natural gas as a fuel,
A compressor line for compressing the BOG generated in the storage tank by a compressor and supplying the compressed BOG as fuel to the engine;
A high-pressure pump line which compresses the LNG stored in the storage tank by a high-pressure pump and supplies the compressed LNG as fuel to the engine;
An expansion valve installed in the high-pressure pump line for reducing the pressure of the LNG compressed by the high-pressure pump to a pressure required by the engine; And
And a heater for heating the reduced LNG to a temperature required by the engine while passing through the expansion valve. The method according to claim 1,
The engine includes a main engine and a sub engine,
The high pressure pump line includes an LNG main supply line for supplying the LNG discharged from the storage tank to the main engine and an LNG portion supply line for supplying the LNG discharged from the storage tank to the sub engine,
And the heater is provided in the LNG portion supply line. 3. The method of claim 2,
Further comprising a vaporizer installed upstream of a branch point of the LNG main supply line and the LNG supply line in the high pressure pump line for heating and vaporizing the compressed LNG in the high pressure pump. 3. The method of claim 2,
Wherein the main engine comprises at least one ME-GI engine,
Wherein the secondary engine includes a DF engine. 3. The method of claim 2,
The compressor line includes a BOG main supply line for supplying the BOG discharged from the storage tank to the main engine and a BOG part supply line for supplying the BOG discharged from the storage tank to the sub engine Fuel gas supply system. 6. The method of claim 5,
Wherein the BOG main supply line includes a compressor having a multi-stage compression process, and the BOG supply line is branched from the BOG main supply line so that the compressed BOG is branched through at least a part of the multi- Ship fuel gas supply system. There is provided a method of supplying a fuel gas of a vessel equipped with an engine that receives the liquefied natural gas from a storage tank for storing liquefied natural gas and uses the liquefied natural gas as a fuel,
The BOG generated in the storage tank is compressed by the compressor and supplied to the main engine of the ship as fuel or the LNG stored in the storage tank is compressed and vaporized by the high pressure pump and supplied to the main engine as fuel,
A step of branching the LNG compressed by the high-pressure pump to a pressure required by the sub-engine of the ship, and a heating step of adjusting the pressure-reduced LNG to a temperature required by the sub-engine, Method of supplying fuel gas for ship. 8. The method of claim 7,
Wherein the compressor compresses the BOG through at least a portion of the compressors in a multi-stage compression process, and supplies the compressed BOG to the sub-engine. 9. The method according to claim 7 or 8,
Wherein the LNG to be supplied to the secondary engine of the ship is branched on the downstream side of the vaporizer for heating and vaporizing the compressed LNG.

Images