KR102298854B1 - Fuel Gas Supply System for a Ship - Google Patents

Abstract

The present invention relates to a fuel supply system for a ship that can satisfy the emission gas regulations of a ship by effectively treating boil-off gas in a liquefied gas fuel ship and using it as a fuel for the ship. According to the present invention, the fuel supply system for a ship comprises: a liquefied gas storage tank for storing liquefied gas; a fuel supply unit for vaporizing the liquefied gas stored in the liquefied gas storage tank and supplying it as fuel for an engine; a hydrogen reformer for producing hydrogen by reforming boil-off gas generated in the liquefied gas storage tank; a fuel cell for generating electric power using the hydrogen generated by the hydrogen reformer; and a mixer for mixing the vaporized gas supplied to the engine and the hydrogen generated by the hydrogen reformer and supplying the mixture to the engine.

Description

{Fuel Gas Supply System for a Ship}

The present invention relates to a fuel supply system for a ship that can satisfy the emission gas regulation of a ship by effectively treating boil-off gas in a liquefied gas fuel ship and using it as a fuel for the ship.

The International Maritime Organization (IMO) has mandated the reduction of GHG (Green House Gas) emitted by ships from 2013. Based on 2008 emissions, a 10% reduction (step 1) from 2015, a 20% reduction (step 2) from 2020, and a 30% reduction (step 3) from 2025 are requested. In addition, the IMO is promoting to achieve a 50% reduction by 2050 (hereinafter referred to as IMO 2050).

As an indicator of carbon dioxide gas emission, EEDI (Energy Efficient Design Index), that is, the amount of carbon dioxide generated when transporting 1 ton of cargo for 1 nautical mile, is used. can be

On the other hand, when natural gas is used as a fuel, there is an effect of reducing greenhouse gas emission. A ship that uses natural gas as a fuel is called an LNG fueled ship (LFS).

As marine engines that can use LNG (Liquefied Natural Gas) as fuel, DF engines (DFDE (Dual Fuel Diesel Electric), DFDG (Dual Fuel Diesel Generator)), X-DF (eXtra long stroke Dual Fuel) engines, ME -There are dual fuel engines such as the GI engine (MAN Electronic Gas-Injection Engine). _{The engine applied to LFS reduces the generation of carbon dioxide, nitrogen oxides (NO x} ), sulfur oxides (SO _x ), etc. compared to diesel engines with the same output, and the price per unit of heat is considerably higher than that of ship fuel oil such as diesel fuel. It is inexpensive and economical as well.

On the other hand, since the liquefaction temperature of natural gas is a cryogenic temperature of -163°C at normal pressure, LNG is sensitive to temperature changes and evaporates easily. For this reason, the storage tank that stores the LNG is insulated, but since external heat is continuously transferred to the storage tank, the LNG is continuously naturally vaporized in the storage tank during the LNG transportation process, resulting in BOG (Boil-Off Gas). occurs

BOG is a type of loss and is an important problem in transport efficiency. In addition, when the boil-off gas is accumulated in the storage tank, the internal pressure of the tank may increase excessively, and in severe cases, there is a risk of damage to the tank. Therefore, various methods for treating boil-off gas generated in the storage tank are being studied.

As a method of treating BOG, there are a method of treating BOG by compression, a method of treating BOG by re-liquefaction/sub-cooling, and a method of treating BOG by incineration. have.

As a method of compressing and processing BOG, the method of storing the compressed BOG in a separate Type C tank is representative. Although this method has an advantage that it can be applied on a small scale, there is a problem in that the material and weight of the tank and the cost due to the insulation treatment increase.

As a method for re-liquefying BOG, BOG is liquefied using a liquid nitrogen cycle, or BOG is compressed and supplied as fuel for the engine while the rest is reliquefied using the cooling heat of BOG itself to recover. The method is applied with a solid line. This method requires a complex liquefaction cycle or high-pressure equipment for compressing boil-off gas, as well as a huge reliquefaction facility cost and the burden of increasing the generator capacity due to additional power consumption for operating the reliquefaction facility. have.

In addition, even if the method of re-liquefying BOG is applied, there is a situation in which BOG cannot be liquefied due to a sudden trip of the engine, a problem with the processing capacity of the re-liquefaction device, or safety reasons, so BOG is burned (incinerated). It is also inevitable to install a GCU (Gas Combustion Unit) for processing.

The method of incinerating and treating BOG not only causes environmental pollution, but also wastes BOG that can be used as an energy source, and has problems in that space and cost for installing an incineration facility are increased.

Therefore, research on how to use the boil-off gas in an environment-friendly and effective way without discharging it to the outside is continuously in progress.

As described above, when natural gas is used as a fuel, there is an effect of reducing greenhouse gas emissions. Specifically, it is known that there is a reduction effect of about 25% as of 2008. In addition, it is known that the operating efficiency of engines currently using natural gas as fuel has increased by about 20% compared to 2008.

In other words, the greenhouse gas reduction effect of the current LFS has improved by about 45% compared to 2008.

Therefore, to achieve the IMO 2050 target, the EEDI index must be lowered further. In addition, in the Emission Control Area (ECA), stricter regulations than the sulfur oxide and nitrogen oxide emission regulations suggested by the IMO are being applied.

Accordingly, the present invention is to solve the above problems, and it is a fuel supply system for a ship that can efficiently use boil-off gas as a fuel for a ship, achieve the IMO 2050 target, and also satisfy the demand for reducing emissions within the ECA area. is intended to provide.

According to one aspect of the present invention for achieving the above object, a liquefied gas storage tank for storing liquefied gas; a fuel supply unit for vaporizing the liquefied gas stored in the liquefied gas storage tank and supplying it as fuel for the engine; a hydrogen reformer for producing hydrogen by reforming the boil-off gas generated in the liquefied gas storage tank; a fuel cell for generating electric power using the hydrogen generated by the hydrogen reformer; and a mixer for mixing the gaseous gas supplied to the engine and hydrogen generated by the hydrogen reformer and supplying the mixture to the engine.

Preferably, the engine is a propulsion engine, and the electric power produced by the fuel cell may be supplied to a power demander in the ship.

Preferably, a boil-off gas compressor for compressing the boil-off gas generated in the liquefied gas storage tank; a first boil-off gas fuel line connecting the boil-off gas compressor and the mixer, and configured to supply boil-off gas as much as a flow rate required by the engine among the boil-off gases compressed by the boil-off gas compressor to the mixer; and a BOG supply line connecting the BOG compressor and the hydrogen reformer, and configured to supply the remaining BOG branched to the first BOG fuel line among BOG compressed by the BOG compressor to the hydrogen reformer. may further include.

Preferably, it is installed in the boil-off gas supply line downstream of the point where the first boil-off gas fuel line is branched from the downstream of the boil-off gas compressor, and the hydrogen reformer requires the boil-off gas supplied from the boil-off gas compressor to the hydrogen reformer. It may further include a reforming compressor that further compresses the pressure.

Preferably, it is provided in the first boil-off gas fuel line, the temperature controller for adjusting the boil-off gas supplied from the boil-off gas compressor to the mixer to a temperature required by the engine; may further include.

Preferably, a freshwater generator for producing fresh water required by the ship using seawater; and a steam boiler for heating the fresh water generated in the fresh water generator to generate steam and supplying the steam to the hydrogen reformer.

Preferably, as the fuel of the engine, a mixed gas of boil-off gas and hydrogen generated in the liquefied gas storage tank is preferentially used, and when the mixed gas is less than the demand amount required by the engine, the fuel supply unit is operated to vaporize It may further include; a control unit that generates a gas and controls to supply the generated gasified gas to the mixer.

The fuel supply system for a ship according to the present invention uses boil-off gas as a fuel for an engine, and uses the surplus boil-off gas to produce hydrogen, thereby effectively treating the boil-off gas without discharging the boil-off gas to the atmosphere.

In addition, since it is not necessary to provide a separate Type C tank or reliquefaction facility for treating BOG, installation and operation costs can be reduced, the generator capacity can be reduced, and the installation space can be reduced.

In addition, by producing hydrogen by using boil-off gas and using the produced hydrogen as fuel for fuel cells, it is possible to replace the existing power generation engine, thereby reducing fuel consumption and reducing the capacity of the power generation engine, and thus It can satisfy gas emission regulations.

In addition, by using hydrogen produced using boil-off gas as a fuel to generate electricity, and by using hydrogen mixed with natural gas fuel, the combustion stability of the engine is increased and the amount of nitrogen oxides and carbon dioxide in the exhaust gas is reduced, It can satisfy the strengthened international ship exhaust gas emission regulations.

It can also provide a cornerstone for technological development towards a hydrogen economy.

1 is a schematic diagram illustrating a fuel supply system for a ship according to an embodiment of the present invention.

In order to fully understand the operational advantages of the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, in adding reference signs to the elements of each drawing, it should be noted that only the same elements are indicated by the same reference signs as possible even if they are indicated on different drawings.

In addition, embodiments of the present invention may be applied on land or may be applied on a ship. The vessel may be any type of vessel in which an engine capable of using liquefied gas such as LNG, LPG, liquefied hydrogen, ammonia, etc. as a fuel for a propulsion engine or a fuel for an engine for power generation is installed. In addition, any type of vessel using liquefied gas as a fuel may be applied to the vessel according to an embodiment of the present invention. For example, ships include ships with self-propelled capabilities such as LNG carriers, liquid hydrogen carriers, and LNG regasification vessels (RVs), LNG Floating Production Storage Offloading (FPSO), and LNG FSRU (Floating Storage Regasification). Unit) may include offshore structures that do not have propulsion capabilities, but are floating in the sea.

In one embodiment of the present invention to be described later, the fuel supplied to the engine may be a compound containing hydrogen or a hydrocarbon compound. For example, hydrocarbon-based liquefied gas such as LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), Liquefied Ethylene Gas, Liquefied Propylene Gas, etc. It may be a natural or forced gas or liquefied gas containing hydrogen molecules in a chemical structure that can produce hydrogen by a process such as reforming or separation. However, in the embodiments to be described later, an example in which LNG is applied as a representative fuel will be described.

In addition, in embodiments of the present invention, the engine may be an engine capable of mixing liquefied gas and hydrogen gas.

Hereinafter, with reference to FIG. 1, a fuel supply system for a ship according to an embodiment of the present invention will be described.

A fuel supply system for a ship according to an embodiment of the present invention adjusts the LNG storage tank 100 for storing LNG and the LNG stored in the LNG storage tank 100 to the conditions required by the engines 710 and 720 to It includes a fuel supply unit 400 for supplying as fuel, and a boil-off gas processing unit for processing boil-off gas generated by natural vaporization of LNG in the LNG storage tank 100 .

In this embodiment, the LNG storage tank 100 may be an LNG storage tank for cargo provided in a ship, or may be an LNG storage tank for fuel. In addition, although only one LNG storage tank 100 is illustrated in FIG. 1 , in this embodiment, one or more LNG storage tanks 100 may be provided.

The engines 710 and 720 of this embodiment are dual fuel engines, and include a main engine 710 used for propulsion of a ship and a power generation engine 720 used for power generation.

Although only one power generation engine 720 is shown in FIG. 1 , in this embodiment, one or more power generation engines 720 may be provided according to the power generation demand capacity on board.

In this embodiment, the main engine 710, as a two-stroke engine, for example, may be an X-DF engine, in this embodiment, the power generation engine 720, as a four-stroke engine, for example, may be a DFDG. .

The X-DF (eXtra long stroke Dual Fuel) engine uses medium pressure natural gas of about 12 to 16 bar as a fuel, and operates based on an otto cycle. DFDG (Dual Fuel Diesel Generator) uses low-pressure natural gas of about 4 to 6.5 bar as a fuel, and operates based on an auto cycle.

The performance that the fuel used in an engine operating on the basis of Otto cycle does not pre-ignite, that is, anti-knocking, is defined by the Methane Number (MN) in the case of gaseous fuel, for example, X -For DF engines, a methane number of 80 or higher is required.

The fuel supply system according to the present embodiment is a semi-submersible pump provided inside the LNG storage tank 100 , and includes an LNG supply pump 110 and LNG for discharging LNG from the LNG storage tank 100 to the fuel supply unit 400 . A liquefied gas supply line LL connecting the supply pump 110 and the fuel supply unit 400 may be further included.

The fuel supply unit 400 vaporizes the LNG discharged from the LNG storage tank 100 to the LNG supply pump 110 and transferred along the liquefied gas supply line LL, and supplies it as fuel for the engines 710 and 720 . .

At least one LNG supply pump 110 may be provided. As shown in FIG. 1 , when two or more LNG supply pumps 110 are provided, at least one LNG supply pump 110 may be used for redundancy. can

The fuel supply unit 400 includes a vaporizer for vaporizing LNG (reference numeral not assigned), a gas-liquid separator for gas-liquid separation of the gas-liquid mixture generated in the vaporizer (reference number not given), and the gas fuel separated by the gas-liquid separator to the engine ( It may include a fuel heater (reference numeral not assigned) for heating to a temperature required by 710 and 720).

The gas discharged from the gas-liquid separator of this embodiment is a gas fuel having a methane number of 80 or more, and is supplied as a fuel of the engines 710 and 720 . In addition, the liquid discharged from the gas-liquid separator may be recovered to the LNG storage tank 100 as heavy hydrocarbons, or may be supplied to a separate heavy hydrocarbon treatment device (not shown).

The LNG supply pump 110 of this embodiment may be provided to compress LNG to a pressure required by the engines 710 and 720 . That is, the LNG supply pump 110 may supply the fuel supply unit 400 by compressing the LNG to the pressure required by the main engine 710 , that is, 12 to 16 bar or about 14 bar.

On the other hand, although not shown in the drawings, the fuel supply system according to the present embodiment is a pressure reducing device for reducing the gas fuel supplied from the fuel supply unit 400 to the power generation engine 720 to a pressure required by the power generation engine 720 . (not shown) may be further provided.

That is, the gas fuel enough to be supplied to the power generation engine 720 among the gas fuel vaporized in the carburetor of the fuel supply unit 400 is reduced to the pressure required by the power generation engine 720, that is, 4 to 6.5 bar by using a decompression device. can be supplied.

In addition, a high-pressure pump (not shown) is further provided in the fuel supply unit 400 , so that the LNG supply pump 110 serves only to discharge LNG from the LNG storage tank 100 , and transfers LNG from the high-pressure pump to the engine 710 , 720), it may be compressed to the required pressure and then supplied to the vaporizer.

The BOG processing unit of this embodiment includes a BOG preheater 210 for preheating BOG generated in the LNG storage tank 100 and discharged from the LNG storage tank 100, and BOG heated in the BOG preheater 210. The BOG compressor 220 for compressing the BOG, a hydrogen reformer 240 for reforming the BOG compressed by the BOG compressor 220 to generate hydrogen, and a hydrogen reformer 240 for storing the hydrogen generated by It may include a hydrogen storage tank 250 and a fuel cell 730 for generating electric power using hydrogen generated by the hydrogen reformer 240 as a fuel.

In addition, the LNG storage tank 100 and the boil-off gas processing unit are connected by a boil-off gas supply line (BL), and the boil-off gas discharged from the LNG storage tank 100 is sent to the boil-off gas processing unit through the boil-off gas supply line (BL). is supplied

The BOG preheater 210 of this embodiment preheats the BOG before supplying the cryogenic BOG to the BOG compressor 220 in order to prevent the problem that the BOG compressor 220 is damaged by the cryogenic temperature of BOG. can be a means.

The cooling heat of the BOG recovered from the BOG preheater 210 may be utilized in the inboard cooling heat demand.

The BOG compressor 220 may compress BOG to a pressure required by the hydrogen reformer 240 or a pressure required by the engines 710 and 720 .

When the BOG compressor 220 is provided to compress BOG to a pressure required by the main engine 710, the fuel supply system according to the present embodiment is provided in the BOG compressor 220 downstream of the BOG supply line BL. ), which is provided in the first BOG fuel line GL1 branching from It may further include a temperature controller 610 for heating or cooling.

Of the BOG compressed by the BOG compressor 220, the flow rate to be supplied to the engines 710 and 720 is branched to the first BOG fuel line GL1 and supplied to the engines 710 and 720, and the rest is BOG. It may be supplied to the hydrogen reformer 240 through the supply line BL.

The compressed BOG branched along the first BOG fuel line GL1 may be joined to the gas fuel flow supplied from the fuel supply unit 400 to the main engine 710 .

On the other hand, the compressed BOG branched to the first BOG fuel line GL1 may be supplied to the power generation engine 720. In this case, a BOG decompression device (not shown) is further provided to convert the compressed BOG into the power generation engine. (720) may be supplied under reduced pressure to the required pressure.

In this embodiment, based on the flow rate of BOG of 100 kg/hr, the pressure compressed by the BOG compressor 220 may be 14 bar, the temperature may be -130°C, and The compressed BOG may be heated to 35°C.

In addition, when the pressure required by the main engine 710 is lower than the pressure required by the hydrogen reformer 240 , the fuel supply system according to the present embodiment is located downstream of the point where the first boil-off gas fuel line GL1 is branched. The BOG supply line BL may further include a reforming compressor 230 for further compressing the compressed BOG to a pressure required by the hydrogen reformer 240 .

On the other hand, when the pressure required by the main engine 710 is higher than the pressure required by the hydrogen reformer 240 , the fuel supply system according to the present embodiment is downstream of the point where the first boil-off gas fuel line GL1 is branched. A pressure reducing device (not shown) for reducing the compressed BOG to the pressure required by the hydrogen reformer 240 may be further included in the BOG supply line BL.

According to the present embodiment, the BOG generated in the LNG storage tank 100 is compressed by the BOG compressor 220 and preferentially supplied to the first BOG fuel line GL1, thereby supplying BOG to the engines 710 and 720. ) may be supplied as fuel, and an excess BOG exceeding the required amount of the engines 710 and 720 may be supplied to the hydrogen reformer 240 to generate hydrogen.

The amount of BOG generated by a ship varies depending on the capacity of the LNG storage tank. In the case of a 3K class LNG fueled ship or a 7.5K class LNG bunkering shuttle, the BOG generated from the storage tank is about 200 kg/hr to 450 kg/hr. In addition, in the case of an 18K to 30K class small LNG carrier, it is 800 kg/hr to 1,200 kg/hr, and in the case of a 173K class LNG carrier, it reaches 3,100 kg/hr.

Considering the general operating conditions of ships, the surplus BOG remaining after being used as fuel for the engines 710 and 720 on average is about 30 to 50% of the BOG generation amount. In particular, BOG is additionally generated during the cool-down process carried out before/after bunkering of LNG fuel for every trip and during low-load operation. Generally, the cool-down process takes 1 day, and the low-load operation mode lasts for 3 to 5 days. This accounts for about 15 to 20% of the flight duration.

According to the present embodiment, the surplus BOG and BOG generated by the pre/post bunkering process are supplied to the hydrogen reformer 240 .

The hydrogen reformer 240 of this embodiment may generate boil-off gas into hydrogen using steam reforming. The reforming reaction equation occurring in the hydrogen reformer 240 of this embodiment is as follows.

2CH ₄ + 3H ₂ O ↔ 7H ₂ + CO ₂ + CO (-330.1 kJ/mol)(energy required)

According to the present embodiment, a hydrogen storage tank 250 for storing the hydrogen generated by the hydrogen reformer 240 and a hydrogen supply line HL connecting the hydrogen reformer 240 and the hydrogen storage tank 250 are further included. do. Hydrogen generated in the hydrogen reformer 240 by the above reaction may be transferred to the hydrogen storage tank 250 through the hydrogen supply line HL and stored in the hydrogen storage tank 250 .

The hydrogen gas stored in the hydrogen storage tank 250 is supplied as a fuel of the fuel cell 730 through the first hydrogen fuel line HL1 connecting the hydrogen storage tank 250 and the fuel cell 730 .

The fuel cell 730 is attracting attention in that it has high efficiency compared to other renewable energies and can store electrical energy in a chemical form. In particular, a hydrogen fuel cell using hydrogen as a fuel is expected to meet the greenhouse gas reduction efforts due to its high efficiency and low carbon dioxide emission compared to conventional fuel combustion engines.

One fuel cell 730 of this embodiment is provided with a capacity that can replace the capacity of one power generation engine 720 .

That is, according to this embodiment, instead of the power generation engine 720, which is a dual fuel engine, a fuel cell 730 using hydrogen as a fuel is provided, and hydrogen produced by reforming BOG is used in the ship. By generating electricity, it is possible to reduce the emission of greenhouse gases.

The fuel supply system according to the present embodiment may further include a steam boiler 260 for producing steam to be supplied to the hydrogen reformer 240 .

The steam boiler 260 of the present embodiment may produce steam by recovering waste heat from the hydrogen reformer 240 transferred through the reformer waste heat recovery line RL.

In addition, the ship is provided with a fresh water generator 300 that removes salts from seawater and produces fresh water for use as water for living in the ship or as cooling water for various devices in common.

According to this embodiment, the fresh water generator 300, which is an existing facility essential to a ship, produces fresh water for producing steam to be supplied to the hydrogen reformer 240, and at the same time, uses the generated fresh water using inboard waste heat. The fresh water preheated and preheated in the fresh water generator 300 is supplied to the steam boiler 260 to generate steam.

In the fresh water generator 300 , fresh water may be produced and preheated by using waste heat in the ship, such as the engines 710 and 720 or the fuel cell 730 .

Of the fresh water produced by the fresh water generator 300, the flow rate to be supplied to the hydrogen reformer 240 is heated using in-board waste heat such as the engines 710 and 720 or the fuel cell 730 using a fresh water preheating device (not shown). can do.

The fresh water preheated in the fresh water preheater is transferred to the steam boiler 260 through the first steam supply line SL1, and the steam generated in the steam boiler 260 is transferred to the hydrogen reformer through the second steam supply line SL2. 240) is supplied.

As described above, the load of the steam boiler 260 may be reduced by preheating the fresh water generated in the fresh water generator 300 using inboard waste heat and then supplying it to the steam boiler 260 .

In this embodiment, the fresh water preheating device may be an engine waste heat recovery device 711 that recovers waste heat of exhaust gas discharged from the main engine 710 through the engine waste heat recovery line EL. In addition, the engine waste heat recovery device 711 may be a means provided separately from the fresh water preheating device.

The engine waste heat recovery device 711 may directly produce steam using waste heat of exhaust gas discharged from the main engine 710 , and the steam produced by the engine waste heat recovery device 711 is a hydrogen reformer 240 , etc. It can be used in steam demand.

On the other hand, ships are provided with a gas boiler (not shown) that produces steam by heating fresh water by using gas as a fuel in common. According to this embodiment, the auxiliary supplying steam from the gas boiler to the hydrogen reformer 240 can be used as a means.

That is, the hydrogen reformer 240 mainly uses the steam generated by the steam boiler 260 , but may additionally receive steam generated by the gas boiler.

Also, according to the present embodiment, hydrogen stored in the hydrogen storage tank 250 may be used as a fuel for the fuel cell 730 or as a co-fired fuel for the engines 710 and 720, as described above.

Worldwide, regulations on ship emissions and greenhouse gases are being strengthened. For example, according to the recent air pollution regulation agreement of the Marine Environment Protection Committee (MEPC) under the International Maritime Organization (IMO), the amount of nitrogen oxides (NO _x ) in exhaust gas is about 14.4 g/ Tier II, which regulates to satisfy kWh, came into effect from 2011, and Tier III, which is more stringent than this, was applied restrictively from January 1, 2016.

That is, constructed on or after 2016 vessels flying the US ECA (Emission Control Area) area, which includes the North American and Caribbean waters must meet the Tier Ⅲ regulation, the NO _x emissions from existing 14.4g / kWh 3.4g / should be reduced to kWh. In addition, the designation of ECA regions will continue to expand in the future, and the regulatory value is also expected to be strengthened.

As a method to satisfy the nitrogen oxide emission regulations of ships, typically, a Selective Catalytic Reduction (SCR) system is installed to supply urea to the exhaust gas discharged from the engine to reduce nitrogen oxides to nitrogen (N ₂ ). and water (H ₂ O), or by installing an EGR (Exhaust Gas Recirculation) system to cool and purify a part of the exhaust gas discharged from the engine, mix it with combustion air, and supply it back to the engine for combustion. There is a method to suppress the formation of nitrogen oxides.

On the other hand, even when such a clean technology is applied, it is known that the effect is lower than that of using natural gas (NG), which is a clean fuel, as a fuel. When natural gas is used as a ship's propulsion fuel, compared to using diesel fuel such as HFO (Heavy Fuel Oil), _{there is almost no emission of fine dust and sulfur oxides (SO x} ), and nitrogen oxides (NO _x ) and Emissions of greenhouse gases such as carbon dioxide can be significantly reduced.

Nitrogen oxide (NO _x ) is mainly generated by a chemical reaction of _{nitrogen (N 2} ) and oxygen (O ₂ ) in the combustion process under high temperature and high pressure in the combustion chamber of the engine. The EGR system is a method of reducing the amount of nitrogen oxides produced by supplying only as much oxygen as necessary for combustion of fuel into the combustion chamber of the engine in order to suppress the production of nitrogen oxides, thereby minimizing the amount of oxygen used to generate nitrogen oxides. After combustion, exhaust gas containing a large amount of carbon dioxide is cooled and cleaned, mixed with combustion air, and supplied to the engine to increase the carbon dioxide concentration in the combustion air and lower the oxygen concentration to reduce the generation of nitrogen oxides. is to suppress

As described above, in the EGR system that recirculates a part of exhaust gas to the combustion air of the engine, the initial investment cost is high because there are a lot of additional equipment added to the engine. The disadvantage is that it is higher than this existing engine. In addition, there is a problem that a neutralizer (NaOH) supply is required while operating the EGR system, and residual substances such as sludge are generated and must be treated.

Similarly, when natural gas is used as an engine fuel, nitrogen oxides are generated in large amounts, and additional equipment must be installed to satisfy emission regulations. Accordingly, there is a need for a method capable of reducing the amount of nitrogen oxide emissions even in ships using LNG as fuel for engines.

Therefore, the fuel supply system according to the present embodiment further includes the mixers 510 and 520 , the hydrogen generated in the hydrogen reformer 240 , and the forced vaporization gas or boil-off gas transferred from the fuel supply unit 400 to the compressor ( 220) by mixing the boil-off gas, the mixed gas fuel of natural gas and hydrogen may be supplied to the engines 710 and 720.

According to the present embodiment, the main engine mixer 510 for supplying the mixed fuel mixed with hydrogen and natural gas to the main engine 710 and the mixed fuel mixed with hydrogen and natural gas are supplied to the power generation engine 720 . It may include a mixer 520 for the power generation engine.

The gas fuel of which the methane number, pressure and temperature required by the main engine 710 from the fuel supply unit 400 is adjusted is a first fuel supply line FL1 connecting the fuel supply unit 400 and the mixer 510 for the main engine. Hydrogen is transferred to the mixer 510 for the main engine through It is transferred to the mixer 510 for the engine.

In addition, the gas fuel of which the methane number, pressure, and temperature required by the power generation engine 720 from the fuel supply unit 400 is adjusted is a second fuel supply line FL2 connecting the fuel supply unit 400 and the mixer 520 for the power generation engine. ) is transferred to the mixer 520 for the power generation engine, and the hydrogen stored in the hydrogen storage tank 250 connects the hydrogen storage tank 250 and the mixer 520 for the power generation engine through a third hydrogen fuel line (HL3). It is transferred to the mixer 520 for the power generation engine.

The first fuel supply line FL1, the second fuel supply line FL2, and the first boil-off gas fuel line GL1 each have a natural gas flow transmitter that measures the flow rate of natural gas supplied to the mixers 510 and 520, respectively. (not shown) and a natural gas flow rate control valve (not shown) for controlling the flow rate of natural gas may be provided.

The control unit measures the flow rate of natural gas supplied to the mixers 510 and 520 using each natural gas flow transmitter, and adjusts the opening and closing of each natural gas flow control valve according to the measured value, thereby making the main engine mixer 510 ) and the flow rate of natural gas supplied to the mixer 520 for the power generation engine can be controlled.

In addition, in the second hydrogen fuel line HL2 and the third hydrogen fuel line HL3, a hydrogen flow transmitter (not shown) for measuring the flow rate of hydrogen supplied to the mixers 510 and 520, respectively, and the measured value Accordingly, a hydrogen flow rate control valve (reference numeral not assigned) capable of adjusting the flow rate of hydrogen supplied to the mixer 510 for the main engine and the mixer 520 for the power generation engine may be provided.

The control unit measures the flow rate of hydrogen supplied to each of the mixers 510 and 520 using each hydrogen flow transmitter, and adjusts the opening and closing of each hydrogen flow control valve according to the measured value, so that the main engine mixer 510 and It is possible to control the flow rate of hydrogen supplied to the mixer 520 for the power generation engine.

The engines 710 and 720 are capable of co-firing natural gas and hydrogen gas, and when combusting gas fuel in which natural gas and hydrogen are mixed in an appropriate ratio, nitrogen oxide (NO _x ), carbon dioxide ( CO ₂ ) generation is reduced. However, if the mixing ratio of hydrogen in the gas fuel is too high, incomplete combustion may occur and instead, environmental pollutants such as carbon monoxide (CO) may be discharged.

Therefore, according to the present embodiment, by controlling the flow rates of natural gas and hydrogen supplied to the mixers 510 and 520 , the mixing ratio of the mixed gas fuel to be supplied as the fuel of the engines 710 and 720 can be adjusted.

The mixing ratio of the gas fuel mixed in the mixers 510 and 520 may be a preset value or may be changed in real time according to the load of the engines 710 and 720 .

In addition, the mixers 510 and 520 of the present embodiment are connected to the engines 710 and 720 by the mixed fuel supply lines ML1 and ML2.

The main engine mixer 510 and the main engine 710 are connected by a first mixed fuel supply line ML1, and the mixed gas fuel mixed in the main engine mixer 510 is a first mixed fuel supply line ML1. ) is supplied to the main engine 710 along the

The power generation engine mixer 520 and the power generation engine 720 are connected by a second mixed fuel supply line ML2, and the mixed gas fuel mixed in the power generation engine mixer 520 is a second mixed fuel supply line ML2. ) is supplied to the power generation engine 720 along with it.

The flow rate of the mixed gas fuel supplied from the mixer 510 for the main engine to the main engine 710 may be adjusted according to the amount of gas fuel required by the main engine 710 .

The flow rate of the mixed gas fuel supplied from the power generation engine mixer 520 to the power generation engine 720 may be adjusted according to the amount of gas fuel required by the power generation engine 720 .

About 10 to 30% of hydrogen may be mixed in the mixed gas fuel supplied to the engines 710 and 720 from the mixers 510 and 520 of the present embodiment.

In this embodiment, hydrogen stored in the hydrogen storage tank 250 is preferentially used as a fuel of the fuel cell 730 , thereby replacing the capacity of at least one power generation engine 720 , and reducing the required amount of the fuel cell 730 . The excess hydrogen may be supplied to the mixers 510 and 520 and mixed with natural gas fuel to be used as fuel for the engines 710 and 720 .

In addition, the engines 710 and 720 of the present embodiment may preferentially use boil-off gas or a mixed gas fuel of boil-off gas and hydrogen as a fuel, and natural gas vaporized by the fuel supply unit 400 may be used as an auxiliary fuel.

Meanwhile, the unreacted gas discharged from the hydrogen reformer 240 is transferred through the second boil-off gas fuel line GL2 connecting the hydrogen reformer 240 and the first fuel supply line FL1, and the fuel supply unit 400 It may be joined to the gas fuel flow supplied to the main engine 710 from the.

In addition, the unreacted gas discharged from the hydrogen reformer 240 is transferred through the third boil-off gas fuel line GL3 connecting the hydrogen reformer 240 and the second fuel supply line FL2, and the fuel supply unit 400 It may be joined to the gas fuel flow supplied from the power generation engine 720 .

According to the present embodiment, the controller preferentially uses the mixed gas of boil-off gas and hydrogen generated in the LNG storage tank 100 as the fuel of the engines 710 and 720 , and the mixed gas is used in the engines 710 and 720 . When it is less than the required amount, the fuel supply unit 400 may be operated to generate vaporized gas and control it to be supplied to the mixers 510 and 520 .

In addition, in power production, the control unit operates the fuel cell 730 preferentially, and when the power production of the fuel cell 730 is less than the onboard power demand, the power generation engine 720 is operated to produce power. can

As described above, according to the present invention, by supplying a mixture of natural gas and hydrogen as fuel for the engine, it is possible to reduce the production amount of nitrogen oxides and carbon dioxide. In particular, the combustion safety of the engine can be improved by uniformly mixing natural gas and hydrogen gas at an appropriate mixing ratio in the mixing container and supplying the fuel as fuel.

As a mixed combustion engine of natural gas and hydrogen gas, by supplying a mixture of natural gas and hydrogen gas as fuel for the engine, it is possible to reduce the amount of nitrogen oxide and carbon dioxide produced. In particular, the combustion safety of the engine can be improved by uniformly mixing natural gas and hydrogen gas at an appropriate mixing ratio in the mixing container and supplying the fuel as fuel.

As described above, the embodiments according to the present invention have been reviewed, and the fact that the present invention can be embodied in other specific forms without departing from the spirit or scope of the present invention in addition to the above-described embodiments is recognized by those of ordinary skill in the art. It is self-evident to Therefore, the above-described embodiments are to be regarded as illustrative rather than restrictive, and accordingly, the present invention is not limited to the above description, but may be modified within the scope of the appended claims and their equivalents.

100: LNG storage tank
110: LNG supply pump
210: boil-off gas preheater
220: boil-off gas compressor
230 reforming compressor
240: hydrogen reformer
250: hydrogen storage tank
260: gas boiler
270: steam boiler
300: tide
400: fuel supply
510: mixer for main engine
520: mixer for power generation engine
610: thermostat
710: main engine
711: engine waste heat recovery device
720: power generation engine
BL : BOG supply line
GL1: 1st boil-off gas fuel line
GL2: 2nd BOG fuel line
GL3 : 3rd BOG fuel line
LL: liquefied gas supply line
FL1: first fuel supply line
FL2: Second fuel supply line
ML1: 1st mixed fuel supply line
ML2: 2nd mixed fuel supply line
HL1: 1st hydrogen fuel line
HL2: 2nd hydrogen fuel line
HL3 : 3rd hydrogen fuel line
SL1: first steam supply line
SL2: 2nd steam supply line
RL : Reformer waste heat recovery line
EL : Engine waste heat recovery line

Claims (7)

a liquefied gas storage tank for storing liquefied gas;
a fuel supply unit for vaporizing the liquefied gas stored in the liquefied gas storage tank and supplying it as fuel for the engine;
a hydrogen reformer for producing hydrogen by reforming the boil-off gas generated in the liquefied gas storage tank;
a fuel cell for generating electric power using the hydrogen generated by the hydrogen reformer;
a mixer for mixing the gaseous gas supplied to the engine and hydrogen generated by the hydrogen reformer and supplying the mixture to the engine;
a boil-off gas compressor for compressing the boil-off gas generated in the liquefied gas storage tank;
a first boil-off gas fuel line connecting the boil-off gas compressor and the mixer, and configured to supply boil-off gas as much as a flow rate required by the engine among the boil-off gases compressed by the boil-off gas compressor to the mixer; and
A boil-off gas supply line connecting the boil-off gas compressor and the hydrogen reformer, the boil-off gas branching to the first boil-off gas fuel line among the boil-off gas compressed by the boil-off gas compressor and supplying the remaining boil-off gas to the hydrogen reformer; Including, the fuel supply system of the ship. The method according to claim 1,
The engine is a propulsion engine,
The power produced by the fuel cell is supplied to a power demander on board, a fuel supply system of a ship. delete The method according to claim 1,
It is installed in the boil-off gas supply line downstream of the point where the first boil-off gas fuel line is branched from the downstream of the boil-off gas compressor, and further compresses the boil-off gas supplied from the boil-off gas compressor to the hydrogen reformer to the pressure required by the hydrogen reformer. A reforming compressor that further comprises, the ship's fuel supply system. The method according to claim 1,
A fuel supply system for a ship, further comprising a; provided in the first boil-off gas fuel line, the temperature controller for adjusting the boil-off gas supplied from the boil-off gas compressor to the mixer to a temperature required by the engine. The method according to claim 1,
a freshwater generator for producing fresh water required by the ship using seawater; and
The fuel supply system of a ship further comprising a; steam boiler for heating the fresh water generated in the fresh water generator to generate steam and supplying the steam to the hydrogen reformer. The method according to claim 1,
As the fuel of the engine, a mixed gas of boil-off gas and hydrogen generated in the liquefied gas storage tank is preferentially used, and when the mixed gas is less than the amount required by the engine, the fuel supply unit is operated to generate vaporized gas, , A control unit for controlling to supply the generated vaporized gas to the mixer; further comprising, the fuel supply system of the ship.

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