KR20140052818A - 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 in response to a methane number required by an engine which can compress and vaporize liquefied natural gas (LNG), and can receive the LNG to use as fuel. According to the present invention, a system for supplying fuel gas for a ship and a method for supplying fuel gas using the system are provided. The system for supplying fuel gas for a ship comprises a storage tank which stores LNG, and an engine which receives the LNG stored in the storage tank to use as fuel. More specifically, the system 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 pump line which compresses LNG contained in the storage tank by a pump and supplies the LNG as fuel to the engine; and a vapor-liquid separator which is provided on the pump line to adjust a methane number of LNG to a value required by the engine by separating hydrocarbon components from the LNG.

Description

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

More particularly, the present invention relates to a system and method for supplying a fuel gas to ship, and more particularly, to a DF (Dual Fuel) engine that can be used as fuel after compressed and vaporized LNG is supplied with methane number The present invention relates to a fuel gas supply system and method for supplying a fuel gas to a ship.

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.

In addition to methane, liquefied natural gas includes ethane, propane, and butane, and the composition varies depending on the place of production. In order to vaporize liquefied natural gas and supply it to the DF engine as fuel, the methane number and temperature conditions You have to supply them together.

In order for the engine to produce a normal output, the methane required by the engine must be met. If the methane level is lower than the proper methane level, explosion and combustion occur before the piston of the engine reaches the top dead center, Lt; / RTI >

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide a DF engine for ships capable of compressing and vaporizing LNG, And to provide a marine fuel gas supply system and method.

According to an aspect of the present invention, there is provided a fuel gas supply system for a ship having a storage tank storing liquefied natural gas, and an engine used as fuel supplied with liquefied natural gas stored in the storage tank, 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 pump line for compressing the LNG stored in the storage tank by a pump (exhaust pump) and supplying the LNG as fuel to the engine; A gas-liquid separator installed in the pump line for separating the heavy hydrocarbon component from the LNG to adjust the methane value of the LNG to a value required by the engine; A fuel gas supply system for a marine vessel is provided.

The marine fuel gas supply system of the present invention preferably further comprises a vaporizer provided upstream of the gas-liquid separator and partially vaporizing the LNG by applying heat to the LNG supplied to the gas-liquid separator.

Preferably, the marine fuel gas supply system of the present invention further comprises a return line for returning the liquid component separated in the gas-liquid separator to the storage tank.

Preferably, the engine includes a main engine and a sub-engine, and at least one of the main engine and the sub-engine is required to be controlled in methane.

Preferably, the main engine is an ME-GI engine that does not require methane control, and the sub-engine is a DF engine that requires methane control.

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 Do.

Preferably, 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 BOG on the way being compressed by the compressor can be branched.

The pump line preferably 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 Do.

Wherein the LNG main supply line includes a high-pressure pump that compresses LNG at a pressure required by the main engine, the LNG portion supply line includes the gas-liquid separator, and the LNG portion supply line is located upstream of the high- Is branched from the LNG main supply line.

According to another aspect of the present invention, there is provided a fuel gas supply system for a ship, comprising: a storage tank storing liquefied natural gas; and a fuel gas supply system for a ship having an engine used as fuel supplied with liquefied natural gas stored in the storage tank, Wherein the fuel gas supply system includes a compressor line that compresses the BOG generated in the storage tank by a compressor and supplies the compressed BOG to the engine as fuel and an LNG accommodated in the storage tank by a high pressure pump And a pump line supplying the engine as fuel, wherein when the LNG is supplied to the engine through the pump line, a methane-regulating step of adjusting the methane price of the LNG to a value required by the engine by separating the heavy hydrocarbon component from the LNG A method for supplying a marine fuel gas is provided.

According to the present invention, there can be provided a marine fuel gas supply system and method capable of supplying fuel gas by matching methane demanded by the engine to a marine DF engine that can be used as a fuel after compression and vaporization of LNG have.

Thus, according to the fuel gas supply system and method of the present invention, not only the evaporation gas (BOG), which is high in methane content and can be supplied as fuel, but also the LNG is supplied to the engine as fuel, You will be able to match methane.

1 is a schematic view showing a ship fuel gas supply system according to the present invention, and
Fig. 2 is a schematic configuration diagram showing a marine fuel gas supply system according to the present invention , which is equipped with a methane- regulating means .

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.

When supplying natural gas as a fuel, it is not necessary to match methane in case of ME-GI engine, but in case of DF engine, it is necessary to match methane.

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. However, in the case of LNG, the methane content is relatively low, which is lower than the methane demanded by the DF engine, and the ratio of the hydrocarbon components (methane, ethane, propane, butane, etc.) It is not suitable to be supplied as fuel to the DF engine.

To regulate methane, the liquefied natural gas can be forcedly vaporized and then cooled to remove liquefied heavy hydrocarbons (HHC), which have a higher liquefaction point than methane. After adjusting the methane, additional methane-regulated natural gas may be added to meet the temperature requirements of the engine. The middle hydrocarbon component means a hydrocarbon component such as ethane, propane or butane having a higher carbon number than methane.

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.

Figure 1 is a cross- In the embodiment  Following hybrid  Fig. 2 is a configuration diagram showing a fuel supply system. The hybrid  The fuel supply system is a propulsion main engine, MEGI  Engine-mounted LNG  Carrier and the like.

Referring to Figure 1, In the embodiment  Following hybrid  The fuel supply system 100 includes a storage tank (not shown) cargo tank ; 1) LNG To the main engine ( main engine ; 3, a fuel supply line 110 for providing a path for transferring fuel from the storage tank 1 Generated BOG ( Boil Off Gas ) To the main engine (3) BOG  Line < / RTI > In addition, In the embodiment  Following BOG Using hybrid  The fuel supply system 100 is connected through a fuel supply line 110 LNG To LNG  Pump( LNG  pump; 120) and LNG In the vaporizer (LNG vaporizer) 130  To the main engine 1 as fuel, BOG  Through line 140 BOG To BOG  compressor( BOG compressor ; 150 to supply it to the main engine 1 as fuel, BOG  From the compressor 150, BOG Integrated IGG / GCU  To the system (200).

The main engine 1 can be used MEGI  The engine is approximately 150-400 bara It is necessary to supply the fuel at a high pressure of about (absolute pressure). Therefore, In the embodiment  The LNG pump 120 and the BOG  As the compressor 150, MEGI  From engine to required pressure LNG And a high-pressure pump that can compress the BOG, respectively.

The fuel supply line 110 is, for example, LNGC Is supplied from the storage tank 1 of the transfer pump 2 by the driving of the transfer pump 2 LNG As a fuel to the main engine 3, LNG  The pump 120 LNG The vaporizer 130  Respectively.

LNG  The pump 120 is connected to the fuel supply line 110 LNG Required for transport Pumping power  Provided, for example, LNG HP  Pump( LNG High Pressure pump ) Can be used, As in the embodiment  And can be installed in parallel.

LNG The vaporizer 130  In the fuel supply line 110 LNG  By being installed at the rear end of the pump 120 LNG  And is conveyed by the pump 120 LNG , ≪ / RTI > LNG For example, LNG Is vaporized by heat exchange with the fruit circulated and supplied through the fruit circulation line 131, and as another example, LNG To provide the heat of vaporization of The heating means  Can be used. Also, LNG The vaporizer 130 LNG Which can be used at high pressure for vaporization of HP A high pressure vaporizer  Can be used. On the other hand, the fruit circulated and supplied to the fruit circulation line 131 is, for example, Generated  Steam can be used.

BOG  The line 140 is naturally discharged from the storage tank 1 Generated BOG To the main engine 3, As in the embodiment  By being connected to the fuel supply line 110 BOG To be supplied to the main engine 3 as fuel, or alternatively, BOG To the main engine (3).

BOG  The compressor (150) BOG  Installed in line 140 BOG  Through line 140 BOG . 1, BOG  Although only the compressor 150 is shown, BOG  Compressors are designed in a binary design (as in conventional conventional fuel supply systems) redundancy ), The system can be configured so that two compressors of the same specification are connected in parallel. However, As in the embodiment BOG  In line 140, BOG  In the branch of line 160, BOG  When the compressor 150 is installed, BOG  It is possible to obtain an additional effect that the economical burden due to the installation of the compressor 150 and the burden on maintenance and repair can be reduced.

Surplus BOG  The line 160 BOG  From the compressor 150, BOG Integrated IGG / GCU  To the system 200, IGG / GCU  In addition to the system 200, DF  Surplus by auxiliary engine such as engine BOG Can be supplied as fuel.

Integrated IGG / GCU  The system 200 IGG ( Inert Gas Generator ) And GCU ( Gas  Combustion Unit ) Is an integrated system.

Meanwhile, BOG  The line 160 and the fuel supply line 110 may be connected to each other by a connection line 170. Thus, the surplus line (s) BOG To be used as the fuel of the main engine 1, LNG Integrated IGG / GCU  So that the system 200 can be used as fuel. The connection line 170 is provided with a through- BOG I vaporized LNG A heater 180 may be installed for heating the heater 180, BOG I vaporized LNG By adjusting the pressure by Abate  Pressure reducing valve ( Pressure Reduction Valve ; (PRV) 190 may be installed. On the other hand, the heater 180 may be a gas heater using the heat of combustion of gas, or may include a heat-generating circulation supply unit for supplying a heat source for heating by circulation of heat, The heating means  Can be used.

According to the present invention hybrid  The operation of the fuel supply system will be described.

When the pressure in the storage tank 1 is equal to or higher than a predetermined pressure BOG The BOG compressor 150 is driven BOG And supplies it to the main engine 1 as fuel. Further, if the pressure in the storage tank 1 is less than the predetermined pressure BOG  When the amount of generated gas is small, LNG  The pump 120 LNG The vaporizer 130  By driving LNG To be supplied to the main engine 1 as fuel.

Meanwhile, BOG  From the compressor 150, BOG Surplus BOG  Integrated line < RTI ID = 0.0 > IGG / GCU  The system 200 or DF  An auxiliary engine such as an engine, BOG To be supplied to the consuming or storage tank (1) Inert gas  So that it can be used as a fuel for an auxiliary engine or the like.

BOG Integrated type IGG / GCU  The system 200 includes a main body 210, BOG  By combustion, continuously from the storage tank 1 Generated BOG And to supply it to the storage tank 1 as needed, As an inert gas  It is also possible to generate combustion gas.

Fig. 2 shows a schematic configuration diagram of a marine fuel gas supply system according to a preferred embodiment of the present invention, which is equipped with a methane- regulating means .

Figure 2, an example is a fuel gas supply system of the present invention the high-pressure gas injection engine to use LNG as fuel, i.e., with metanga adjusting means for an LNG carrier is installed a ME-GI engine is applied is shown, but the present invention 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 marine fuel gas supply system according to the present invention includes a high-pressure natural gas injection engine such as an ME-GI engine as a main engine and a DF engine (e.g., DF Generator: DFDG) as a sub engine. 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. A plurality of main engines and sub engines may be installed, respectively.

The marine fuel gas supply system according to the present invention is a system in which the natural gas (that is, the gas BOG in the gaseous state) accommodated in the storage tank 11 for the engines (that is, the ME-GI engine as the main engine and the DF engine as the sub engine) And LNG in a liquid state) as fuel.

In order to supply gaseous BOG as fuel gas, the fuel gas supply system of the present invention includes a BOG main supply line L1 for supplying BOG stored in the storage tank 11 to the main engine, And a BOG part supply line L2 branching from the line L1 and supplying the BOG to the sub engine.

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

According to the present invention, the BOG main feed line L1 is provided with a compressor 13 for compressing 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. Further, in addition to the structure in which a plurality of compression cylinders are arranged in one compressor, the structure may be changed to have a structure in which a plurality of compressors are 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 as the sub engine is branched from the main BOG supply line L1. More specifically, the sub-BOG supply line L2 branches from the main BOG supply line L1 so that the vaporized gas in the middle of the multi-stage compression process can be branched in the compressor 13. [ 2 shows the illustrated and can, but this merely one example, one-stage or a three to five-stage compressing BOG by supplying the sub-engine via a BOG feed line (L2) portion of any portion to branch the compressed BOG 2 dan The system can be configured so that it can be branched and supplied to the sub engine via the sub BOG supply line L2 . 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 inefficient because it must be supplied to the engine.

As described above, when the LNG is heated, since the methane component having a relatively low liquefaction temperature is preferentially vaporized, in the case of the evaporated gas, the methane content is high and can be supplied as fuel to the DF engine as it is. Therefore, there is no need to separately provide a device for methane control in the BOG main supply line and the BOG part supply line.

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- The vaporized gas on the way can be used in the BOG consumption means by branching through the BOG branch line L7. As means for consuming the evaporative gas, a GCU, a gas turbine, etc., which can use a relatively low pressure natural gas as fuel compared to the ME-GI engine, can be used. BOG branch line (L7) is, as shown in Figure 2, it is preferable that the branch unit in the BOG feed line (L2).

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 for each storage tank 11. Although only one high-pressure pump 23 is shown in FIG. 2 , a plurality of high-pressure pumps may be connected in parallel if necessary.

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 an ME-GI engine. Since the pressure required by the ME-GI engine is supercritical, LNG compressed at high pressure is neither gas nor liquid. 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 which is the sub engine is branched from the main LNG supply line L3. More specifically, the secondary LNG supply line L4 branches from the main LNG supply line L3 so that the LNG before the high-pressure pump 23 can be branched.

A vaporizer 25, a gas-liquid separator 26, and a heater 27 are provided in the secondary LNG supply line L4 to adjust the methane temperature and the temperature of the LNG supplied as fuel to a value required by the DF engine.

As described above, in the case of LNG, the methane content is relatively low, which is lower than the methane price required by the DF engine, and the ratio of the hydrocarbon components (methane, ethane, propane, butane, etc.) It is not suitable for vaporizing it as it is and supplying it to the DF engine as fuel.

To regulate the methane gas, the LNG is heated in the vaporizer 25 and partially vaporized. The fuel gas, which is partially vaporized and mixed with the gaseous state (i.e., natural gas) and the liquid state (i.e., LNG), is supplied to the gas-liquid separator 26 to be separated into gas and liquid. Since the vaporization temperature of the high-calorific heavy hydrocarbon (HHC) component is relatively high, the proportion of the heavy hydrocarbon component in the remaining liquid LNG that is not vaporized in the partially vaporized fuel gas becomes relatively high. Therefore, by separating the liquid component from the gas-liquid separator 26, that is, by separating the heavy hydrocarbon component, the methane gas of the fuel gas can be increased.

The heating temperature in the vaporizer 25 can be adjusted in order to obtain an appropriate methane gas in consideration of the ratio of the hydrocarbon component contained in the LNG and the methane demanded by the engine. The heating temperature in the vaporizer 25 can be set within a range of approximately -80 to -120 degrees centigrade. The liquid component separated from the fuel gas in the gas-liquid separator 26 is returned to the storage tank 11 through the return line L5. Although not shown in the drawings, instead of returning the liquid component separated from the fuel gas in the gas-liquid separator 26 to the storage tank, the piping may be configured to supply the ME-GI engine, which does not require methane adjustment, as fuel.

The methane-regulated fuel gas is supplied to the heater 27 through the LNG portion feed line L4 and is further heated to the temperature required by the sub-engine and supplied to the sub-engine as fuel. If the sub-engine is, for example, DFDG, the methane required is generally greater than 80. For example, in the case of General LNG (typically methane: 89.6%, nitrogen: 0.6%), the methane level before the separation of the heavy hydrocarbon component is 71.3 and the lower heating value at that time is 48,872.8 kJ / kg atm, saturated vapor standard). When this General LNG is pressurized to 7 bara and heated to -120 ° C to remove the heavy hydrocarbon component, the methane gas is increased to 95.5, and the LHV at that time is 49,265.6 kJ / kg.

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 (that is, L1 and L2 in Fig. 2 ) and the 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 preferable that the fuel gas is supplied to the engines through the compressor line and the fuel gas is supplied to the engines through the pump line in the ballast state where the amount of the generated 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 may be efficient to use the vaporized gas as a fuel in the DF engine by branching the vapor through the BOG branch line L7 during compression. That is, for example, if evaporative gas is supplied to the DF engine through only the second-stage compression cylinder of the five-stage compressor, the remaining three-stage compression cylinders are idle. 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 at the time of use, and a fuel gas supply system using two pump lines may have a problem that a large amount of energy is consumed in processing (i.e., liquefying) evaporative gas. The fuel gas supply system of the present invention, in which the compressor line and the 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, of it it is possible while using less compressor to the first drying, as well as cost and reduced operation cost can be operated by appropriately selecting the optimum fuel gas supply method according to the amount of boil-off gas may also achieve additional effects.

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, 25: vaporizer
26: gas-liquid separator 27: heater
L1: BOG main supply line L2: BOG supply line
L3: LNG main supply line L4: LNG subsidiary supply line
L5: return line L7: BOG branch line

Claims (10)

1. A fuel gas supply system for a ship having a storage tank storing liquefied natural gas and an engine used as fuel supplied with liquefied natural gas stored in the storage tank,
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 pump line for compressing the LNG stored in the storage tank by a pump and supplying the LNG as fuel to the engine;
A gas-liquid separator installed in the pump line for separating the heavy hydrocarbon component from the LNG to adjust the methane value of the LNG to a value required by the engine;
The fuel gas supply system comprising: The method according to claim 1,
Further comprising a vaporizer disposed upstream of the gas-liquid separator and partially vaporizing the LNG by applying heat to the LNG supplied to the gas-liquid separator. The method of claim 2,
And a return line for returning the liquid component separated in the gas-liquid separator to the storage tank. The method according to claim 1,
Wherein the engine includes a main engine and a sub-engine, wherein at least one of the main engine and the sub-engine requires methane-charge control. The method of claim 4,
Wherein the main engine is an ME-GI engine that does not require methane control, and the sub-engine is a DF engine requiring methane control. The method of claim 4,
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. The method of claim 6,
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 as to divide the BOG on the way being compressed by the compressor Ship fuel gas supply system. The method of claim 4,
The 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 Fuel gas supply system. The method of claim 8,
Wherein the LNG main supply line includes a high-pressure pump for compressing LNG at a pressure required by the main engine, the LNG portion supply line includes the gas-liquid separator,
And the LNG portion supply line is branched from the LNG main supply line on the upstream side of the high-pressure pump. 1. A method for supplying a fuel gas to a fuel cell by a fuel gas supply system for a ship having a storage tank storing liquefied natural gas and an engine used as fuel supplied with liquefied natural gas stored in the storage tank,
Wherein the fuel gas supply system includes a compressor line that compresses the BOG generated in the storage tank by a compressor and supplies the BOG to the engine as fuel, and a fuel supply system that compresses the LNG stored in the storage tank by a pump and supplies the compressed LNG as fuel to the engine Pump line,
And adjusting the methane price of the LNG to a value required by the engines by separating the heavy hydrocarbon component from the LNG when the LNG is supplied to the engine through the pump line.

Images