KR102535970B1 - Hydrogen-Enriched Compressed Natural Gas Fuel Supply System and Method for Low Pressure Gas Engine of a Ship - Google Patents

Abstract

In the present invention, in supplying gas fuel to a marine low-pressure gas engine, a hydrogen mixture fuel supply system for a marine low-pressure gas engine capable of reducing methane slip by supplying a mixture of hydrogen to natural gas supplied as fuel of the engine and methods.
A method for supplying hydrogen mixed fuel to a marine low-pressure gas engine according to the present invention analyzes methane slip of exhaust gas discharged from a marine low-pressure gas engine using liquefied gas as fuel, and according to the degree of methane slip included in the exhaust gas Methane slip of the marine low-pressure gas engine is prevented by controlling the amount of hydrogen added to the gas fuel supplied to the marine low-pressure gas engine, and the hydrogen mixed with the liquefied gas is compressed and stored in a hydrogen storage tank on board, and the hydrogen As a storage tank, hydrogen can be supplied using an onshore hydrogen supply infrastructure.

Description

Hydrogen-Enriched Compressed Natural Gas Fuel Supply System and Method for Low Pressure Gas Engine of a Ship}

The present invention, in supplying gas fuel to a marine low-pressure gas engine, hydrogen of a marine low-pressure gas engine capable of reducing methane slip of the low-pressure gas engine by supplying a mixture of hydrogen to natural gas supplied as fuel of the engine It relates to a mixed fuel supply method and system.

Ship emission and greenhouse gas regulations are being strengthened worldwide. For example, according to the recent air pollution control agreement of the Marine Environment Protection Committee (MEPC) under the International Maritime Organization (IMO), the emission of nitrogen oxides (NO _x ) in exhaust gas is about 14.4g/ Tier II, which regulates to be satisfied with kWh, went into effect from 2011, and more stringent Tier III was applied on a limited basis from January 1, 2016.

In other words, ships built after 2016 and operating in the US ECA (Emission Control Area) including North America and Caribbean waters must satisfy Tier Ⅲ regulations and reduce NO _x emissions from the existing 14.4g/kWh to 3.4g/kWh. reduced to kWh. In addition, the designation of ECA areas will continue to expand in the future, and the regulation is expected to be strengthened as well.

As international interest in preventing marine air pollution increases, as a green-ship, a ship using liquefied natural gas (LNG) as fuel (LFS; Liquefied Gas Fueled Ship) has been developed, Approval In Principle (AIP) has been approved by the classification society of each country, and it is meeting the demand for conversion to clean energy due to environmental regulations. Such an LFS has been developed a technology that can be applied not only to LNG carriers equipped with LNG storage tanks and transporting LNG cargoes, but also to general merchant ships including container ships and tanker ships.

Natural gas is relatively environmentally friendly because it does not produce sulfur compounds and soot when burned due to its low sulfur content. Among the engines used in ships, dual fuel engines that can use natural gas as fuel include ME-GI (MAN Electronic Gas Injection) engines and X-DF (eXtra long stroke Dual Fuel) engines. , DFDE (Dual Fuel Diesel Electric) engine, etc.

The ME-GI engine uses a 2-stroke cycle and is mainly used for propulsion. In addition, the ME-GI engine adopts a diesel cycle in which high-pressure natural gas of about 300 bar is directly injected into the combustion chamber near the top dead center of the piston.

On the other hand, the X-DF engine uses a 2-stroke cycle, is mainly used for propulsion, and, like the ME-GI engine, directly drives a propeller for propulsion of a ship. In addition, the X-DF engine uses medium-pressure natural gas at about 16 bar as fuel and adopts an otto cycle.

The DFDE engine uses a 4-stroke cycle and is mainly used for power generation. In addition, the DFDE engine adopts an Otto cycle in which low-pressure natural gas of about 6.5 bar is injected into the combustion air inlet and compressed as the piston rises.

The Otto cycle follows a static process in which the volume of combustion occurs near top dead center, where a mixture of fuel and combustion air is introduced into the cylinder prior to the upstroke and compressed together. The mixture introduced into the cylinder is adiabatically compressed and the temperature rises. If the mixture reaches too high a temperature, premature ignition may occur. Therefore, the compression ratio of the Otto cycle is set lower than that of the diesel cycle.

A high-pressure gas engine that follows a diesel cycle, that is, an ME-GI engine, has high efficiency, but in order to satisfy nitrogen oxide emission regulations, a nitrogen oxide treatment system such as SCR (Selective Catalytic Reduction) or EGR (Exhaust Gas Recirculation) is additionally installed. It has to be done.

On the other hand, in the case of a low-pressure gas engine following the Otto cycle, that is, an X-DF engine or a DFDE, the efficiency is lower than that of the ME-GI engine, but the combustion temperature of the fuel is not high, so the amount of nitrogen oxides (NO _x ) generated due to high heat Since this is small, there is an advantage in that it satisfies IMO Tier III, the currently in effect nitrogen oxide regulation, without additionally installing a separate nitrogen oxide treatment system such as SCR or EGR.

However, since the low-pressure gas engine using the Otto cycle injects fuel into the middle of the cylinder, unlike the high-pressure gas engine, there is a disadvantage in that a methane slip phenomenon in which gas leaks before fuel explosion occurs. The amount of methane slip in the low-pressure gas engine is about 2 g/kWh, which is about 10 times more than the amount of methane slip (about 0.2 g/kWh) generated in the high-pressure gas engine.

As methane slip, that is, unburned methane (CH ₄ ) is discharged as exhaust gas, it becomes a factor in rapidly increasing the Global Warming Potential (GWP) of low-pressure gas engine exhaust gas.

Accordingly, an object of the present invention is to provide a hydrogen fuel mixture supply method and a hydrogen mixture fuel supply system for a marine low pressure gas engine, which can reduce methane slip and increase combustion efficiency of the marine low pressure gas engine.

According to one aspect of the present invention for achieving the above object, methane slip of exhaust gas discharged from a marine low-pressure gas engine using liquefied gas as fuel is analyzed, and according to the degree of methane slip included in the exhaust gas, the methane slip Methane slip of the marine low-pressure gas engine is prevented by controlling the amount of hydrogen added to the gas fuel supplied to the marine low-pressure gas engine, and the hydrogen to be mixed with the liquefied gas is obtained by compressing the hydrogen supplied from the land using a hydrogen compressor. Provided is a method for supplying hydrogen mixed fuel to a low-pressure gas engine for a ship, which is stored in a hydrogen storage tank on board.

Preferably, a plurality of hydrogen storage tanks are installed, and when the pressure of hydrogen discharged from the hydrogen storage tank is lower than the pressure required for mixing with the liquefied gas or the pressure required by the marine low-pressure gas engine, the low After storing pressure hydrogen in the hydrogen temporary storage tank, it can be compressed by the hydrogen compressor and re-supplied to the hydrogen storage tank.

Preferably, the ship is provided with a liquefied gas storage tank, and after compressing boil-off gas generated in the liquefied gas storage tank using a second fuel compressor, it is mixed with compressed hydrogen to be used as fuel for the low-pressure gas engine for ships. can supply

Preferably, among the boil-off gas compressed using the second fuel compressor, the remaining compressed boil-off gas supplied as fuel for the marine low-pressure gas engine is supplied by using a first fuel compressor provided separately from the second fuel compressor. After compression, the evaporated gas cooled and expanded can be re-liquefied by the cooling heat of the refrigerant and recovered to the liquefied gas storage tank.

According to another aspect of the present invention for achieving the above object, a fuel supply device for supplying liquefied gas to the fuel of the low-pressure gas engine for ships; A hydrogen storage tank for storing compressed hydrogen; a hydrogen mixing device for mixing the liquefied gas and hydrogen stored in the hydrogen storage tank; a low-pressure gas engine for ships using the liquefied gas as fuel; a methane slip analyzer for analyzing methane slip of exhaust gas discharged from the marine low-pressure gas engine; And a controller for controlling the amount of hydrogen supplied from the hydrogen storage tank to the hydrogen mixing device by using the measured value measured by the methane slip analyzer, wherein the marine low-pressure gas engine is mixed with the liquefied gas. Provided is a hydrogen mixture fuel supply system for a low-pressure gas engine for ships in which methane slip is controlled by using mixed gas fuel with a controlled amount of hydrogen as fuel, and the hydrogen storage tank is detachable from the hydrogen infrastructure on land.

Preferably, a plurality of hydrogen storage tanks are installed, and a hydrogen compressor for compressing and supplying the hydrogen supplied from the land to the hydrogen storage tank; a pressure gauge for measuring the pressure of hydrogen discharged from the hydrogen storage tank; a hydrogen recirculation valve for supplying hydrogen to the hydrogen compressor when the pressure of the hydrogen discharged from the hydrogen storage tank is lower than the pressure required by the hydrogen mixing device or the marine low-pressure gas engine; and a hydrogen temporary storage tank for storing hydrogen supplied to the hydrogen compressor, wherein the control unit controls the hydrogen compressor and a hydrogen recirculation valve according to the measured value of the pressure gauge and compresses the low-pressure hydrogen. It can be re-supplied to the hydrogen storage tank.

Preferably, the fuel supply device includes a second fuel compressor for compressing boil-off gas generated by natural vaporization of liquefied gas to a pressure required by the marine low-pressure gas engine and supplying the compressed gas to the hydrogen mixing device; a re-liquefaction device for re-liquefying the remaining compressed boil-off gas supplied to the hydrogen mixing device among the compressed boil-off gas compressed by the second fuel compressor and recovering the compressed boil-off gas into a liquefied gas storage tank; and a first fuel compressor for compressing the boil-off gas and supplying it as a refrigerant for liquefying the boil-off gas in the re-liquefaction device.

Preferably, the re-liquefaction device includes a boost compressor further compressing the compressed boil-off gas compressed by the second fuel compressor to a pressure required for re-liquefaction; A cold box for liquefying the boil-off gas compressed by the boost compressor with cooling heat of the boil-off gas refrigerant whose temperature is lowered by expansion after being compressed by the first fuel compressor.

The method and system for supplying hydrogen mixed fuel to a low-pressure gas engine for ships according to the present invention can satisfy the emission regulations of ships without additionally installing a separate exhaust gas treatment system, and reduce methane slip of low-pressure gas engines for ships It can be done so it is eco-friendly.

In addition, by reducing methane slip, the global warming potential of ship exhaust gas can be lowered.

In addition, by using a mixture of natural gas and hydrogen as a fuel supplied to a low-pressure gas engine for ships, it is possible to improve combustion speed and combustion stability compared to using only natural gas as fuel.

In addition, the combustion efficiency of the engine can be increased by improving the combustion speed and combustion stability of the fuel.

In addition, it is effective because it is possible to directly apply commercially available hydrogen storage tanks and hydrogen supply control systems on land without separately building expensive hydrogen infrastructure, which is an unverified stage.

In addition, the hydrogen mixture gas fuel can be used as the fuel of the low-pressure gas engine without using a separate marine hydrogen mixture fuel engine.

1 is a block diagram schematically showing a hydrogen fuel mixture supply system for a low-pressure gas engine for ships 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 a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are marked with the same numerals as much as possible, even if they are displayed on different drawings.

In one embodiment of the present invention described later, the vessel may be any type of vessel equipped with an engine capable of using liquefied gas as a fuel for a propulsion engine or a fuel for a power generation engine. In addition, any ship using liquefied gas as fuel can be applied to a ship according to an embodiment of the present invention regardless of its shape. For example, ships with self-propelled capabilities such as LNG carriers, liquid hydrogen carriers, and LNG RVs (Regasification Vessel), LNG FPSOs (Floating Production Storage Offloading), LNG FSRUs (Floating Storage Regasification Units) and It may include offshore structures that do not have the same propulsion capability but are floating on the sea. However, in an embodiment to be described later, a liquefied gas carrier or a liquid hydrogen carrier will be described as an example.

In addition, the liquefied gas may be a liquefied gas that can be transported by liquefying the gas at a low temperature, for example, LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), liquefied ethylene gas It may be a liquefied petrochemical gas such as (Liquefied Ethylene Gas) or liquefied propylene gas (Liquefied Propylene Gas). However, in the embodiment to be described later, it will be described as an example in which LNG, which is a representative liquefied gas, is applied.

That is, in an embodiment of the present invention to be described later, the liquefied gas fuel will be described by taking LNG as an example, and the ship will be described by taking an LNG carrier as an example.

1 is a block diagram schematically showing a hydrogen fuel mixture supply system for a low-pressure gas engine for ships according to an embodiment of the present invention. Hereinafter, a hydrogen mixture fuel supply method and a hydrogen mixture fuel supply system for a low pressure marine low pressure gas engine according to an embodiment of the present invention will be described with reference to FIG. 1 .

A hydrogen mixed fuel supply system according to an embodiment of the present invention is installed in an LNG carrier and includes an LNG storage tank 100 for storing LNG; A fuel supply device for supplying LNG fuel from the LNG storage tank 100 as fuel of the engine; and a low-pressure gas engine 410.

The LNG storage tank 100 of this embodiment may be an LNG cargo tank for storing LNG as cargo or an LNG fuel tank for storing LNG as fuel. Although only one LNG storage tank is shown in the drawing, , One or more LNG storage tanks 100 may be installed.

In addition, the LNG storage tank 100 may be insulated so that cryogenic LNG maintains a liquid state. However, even if the LNG storage tank 100 is insulated, heat intrusion from the outside cannot be completely blocked, so that LNG is naturally vaporized in the LNG storage tank 100 to generate boil-off gas (BOG). When BOG is continuously generated, the internal pressure of the LNG storage tank 100 eventually rises. A safety valve (not shown) may be installed in the LNG storage tank 100 to automatically discharge BOG when the internal pressure of the LNG storage tank 100 exceeds a set value to adjust the internal pressure of the LNG storage tank 100.

In addition, an LNG pump 110 may be installed in the LNG storage tank 100 to pressurize the LNG stored in the LNG storage tank 100 and discharge it to the outside. When the LNG storage tank 100 is an LNG cargo tank, the LNG pump 110 may be a cargo pump installed to unload LNG. Alternatively, it may be a fuel pump (not shown) installed separately from the cargo pump in order to discharge LNG to be supplied as fuel from the LNG storage tank 100. Hereinafter, the LNG pump 110 will be described as an example of a cargo pump.

In this embodiment, the fuel supplied as fuel for the engine is a mixed gas of natural gas and hydrogen forcibly vaporized from LNG stored in the LNG storage tank 100 or a mixed gas of BOG and hydrogen generated in the LNG storage tank 100. It is a concept including, and may be a mixed gas of natural gas, BOG, and hydrogen.

The engine 410 of this embodiment, as a low-pressure gas engine, may be a dual fuel engine capable of using both gas fuel such as natural gas and oil fuel such as diesel as fuel, and is installed as an engine for propulsion or power generation in a ship. it could be

The engine 410 may be operated by an Otto cycle, and may be, for example, an X-DF engine, a DFDE using LNG and diesel as fuel, or a DFDE using LPG and diesel as fuel. In this embodiment, the engine 410 is a propulsion engine and will be described as an example in which an X-DF engine is applied.

The X-DF engine 410 is a propulsion engine that uses a 2-stroke cycle and directly drives a propeller 412 for propulsion of a ship. In addition, medium-pressure gas fuel of about 16 bar is used as fuel.

Since an engine using an Otto cycle introduces a mixture of fuel and combustion air into a cylinder before an upstroke, premature ignition may occur before ignition by an ignition source, resulting in a knocking phenomenon.

The performance of the fuel used in engines using the Otto cycle to prevent premature ignition, i.e. anti-knocking, is determined by the octane number in the case of liquid fuel and the methane number in the case of gas fuel. , and, for example, in the case of the X-DF engine 410, a methane number of 80 or more is required.

LNG is about 95% methane (CH ₄ ), about 2% or less ethane (C ₂ H ₆ ) and propane (C ₃ H ₈ ), about 95%, based on mole fraction. It is typical to include an inert gas such as nitrogen at 1% or less. That is, BOG has methane, which has the highest boiling point, as its main component among the components constituting LNG.

Therefore, in the X-DF engine 410 of the present embodiment, BOG having a high methane number is preferentially used as fuel, and when the amount of BOG is insufficient, LNG may be forcibly vaporized and used as fuel.

The X-DF engine 410 of the present embodiment can use diesel oil, natural gas forcibly vaporized from LNG, or BOG generated by naturally vaporizing LNG in the LNG storage tank 100 as fuel, and can use natural gas and hydrogen as fuel. Both the mixed gas and the mixed gas of BOG and hydrogen can be used as fuel, but in this embodiment, BOG or a mixed gas of BOG and hydrogen will be used as an example as a fuel.

In addition, in the following embodiments, natural gas and BOG will not be specifically referred to, and natural gas or BOG refers to BOG and LNG storage tank 100 generated by natural vaporization of LNG in the LNG storage tank 100 It can be understood as a concept that includes all natural gas that is forcibly vaporized from LNG stored in. In addition, natural gas or BOG may be a concept including flash gas generated in the process of loading and unloading LNG or re-liquefying BOG.

The fuel supply device of this embodiment includes a fuel compressor (210a, 210b) for compressing BOG or natural gas to a pressure required by the X-DF engine (410); a hydrogen storage tank 750 for storing hydrogen; and a hydrogen mixing device 300 for mixing BOG or natural gas compressed in the fuel compressors 210a and 210b with hydrogen.

The fuel compressors 210a and 210b of the present embodiment may be screw-type compressors, and as shown in FIG. 1, first fuel compressors 210a installed in parallel and operated at a load of 100% or less, respectively. ; and a second fuel compressor 210b.

In the present embodiment, two fuel compressors are installed in parallel as an example, but it is not limited thereto, and two or more fuel compressors 210a and 210b may be installed in parallel, or two or more fuel compressors 210a and 210b may be installed in series. Two or more sets of fuel compressors installed in parallel may be installed.

However, among the fuel compressors installed in parallel, at least one fuel compressor is used to compress BOG or natural gas to be supplied as fuel for the X-DF engine 410, and at least one fuel compressor is used to re-liquefy BOG described later It can be used to compress BOG or natural gas as the working fluid of the refrigerant cycle for

The first fuel compressor 210a of this embodiment may compress BOG or natural gas as a refrigerant for re-liquefying BOG, and the second fuel compressor 210b may supply BOG or Natural gas can be compressed.

The first fuel compressor 210a and the second fuel compressor 210b may have the same capacity or different capacities, and compress BOG or natural gas at different pressures.

The LNG storage tank 100, the second fuel compressor 210b, and the hydrogen mixing device 300 of this embodiment may be connected by a BOG line BL1; BOG is connected from the LNG storage tank 100 to the BOG line BL1 ) and is supplied to the hydrogen mixing device 300.

In the BOG line BL1, one or more flow control valves (not given reference numerals) are installed upstream and downstream of the second fuel compressor 210b to adjust the flow rate of BOG flowing along the BOG line BL1, respectively. It can be. In particular, the flow rate control valve installed downstream of the second fuel compressor 210b may be installed together with a check valve (not given a reference numeral) to prevent a reverse flow of BOG. By installing the flow control valve and the check valve together, it is possible to prevent the compressed BOG from flowing back toward the second fuel compressor 210b by controlling the opening or closing of the flow control valve.

In addition, in the BOG line BL1, a flow control valve (not given a reference numeral) may be installed upstream of the hydrogen mixing device 300. A flow control valve installed upstream of the hydrogen mixing device 300 may also be installed with a check valve (not given a reference numeral) for preventing reverse flow of BOG or natural gas supplied to the hydrogen mixing device 300.

The hydrogen mixing device 300 of this embodiment is connected to the second fuel compressor 210b through the BOG line BL1 and connected to the hydrogen storage tank 750 through the hydrogen line HL.

The hydrogen storage tank 750 may be a compression tank for storing compressed hydrogen. Although four hydrogen storage tanks 750 have been described as an example in FIG. 1 , the present invention is not limited thereto, and one or more hydrogen storage tanks 750 may be installed.

Although the pressure of the compressed hydrogen stored in the hydrogen storage tank 750 is not particularly limited, the hydrogen storage tank 750 of this embodiment may be applied as it is to a commercially available land-use compressed hydrogen tank. For example, compressed hydrogen stored in the hydrogen storage tank 750 may be about 700 bar.

The compressed hydrogen stored in the hydrogen storage tank 750 flows along the hydrogen line HL and is transferred to the hydrogen mixing device 300.

In the hydrogen mixing device 300, compressed BOG transferred from the LNG storage tank 100 through the BOG line BL1 and compressed hydrogen transferred from the hydrogen storage tank 750 through the hydrogen line HL are mixed to form HCNG (Hydrgen-enriched Compressed Natural Gas) fuel is produced. The HCNG fuel generated in the hydrogen mixing device 300 is supplied as fuel for the X-DF engine 410 along the mixed fuel line FL connecting the hydrogen mixing device 300 and the X-DF engine 410. .

The hydrogen content of the HCNG fuel generated in the mixed fuel line (FL) is higher than when hydrogen is not added, because hydrocarbon emissions, that is, the amount of methane slip and carbon emissions such as carbon monoxide and carbon dioxide, are reduced. The higher the value, the better, but depending on the amount of excess air (oxygen) for burning the fuel supplied to the engine 410, the higher the hydrogen content, the higher the emission of nitrogen oxides than when hydrogen is not added. can Therefore, the hydrogen content of the HCNG fuel generated from the mixed fuel line (FL) can be selected in consideration of these factors.

Since hydrogen is highly reactive and has a high flame propagation speed, the burning duration is short. Therefore, even if a small amount of hydrogen is added to the natural gas or BOG fuel supplied to the low-pressure gas engine such as the X-DF engine 410, the combustion of the fuel is promoted, thereby increasing the stability of combustion and reducing methane slip. .

Hydrogen-enriched Compressed Natural Gas (HCNG) fuel is a clean alternative fuel and has the advantages of both natural gas fuel and hydrogen fuel. By adding hydrogen, the burning velocity and poor combustion stability of natural gas fuel can be improved. Natural gas fuel has received a lot of attention as an alternative fuel because of its low emission of pollutants such as particulate matters and hydrocarbons. HCNG fuel has value as a clean fuel that exceeds the benefits of natural gas in that it increases engine efficiency and power and reduces pollutant emissions through improved engine control.

Hydrogen is an abundant element in the air and is considered an ideal alternative fuel. However, at present, hydrogen infrastructure such as hydrogen production, distribution, supply, and storage is insufficient, and the cost required to build infrastructure to meet a wide range of demand is also high, so the economic feasibility is evaluated as low.

According to the present embodiment, by using the existing marine fuel supply infrastructure such as the X-DF engine 410 and the fuel supply device, and the onshore hydrogen supply infrastructure such as the compressed hydrogen storage tank 750 and the compressed hydrogen supply system, Even if a new system such as an HCNG engine is not applied, hydrogen mixed fuel can be used as a fuel for low-pressure gas engines for ships, so problems related to cost, efficiency, and safety can be overcome.

In this embodiment, even if only a small amount of hydrogen is added to the mixed gas fuel supplied to the X-DF engine 410, the methane slip reduction effect can be expected, and the onshore hydrogen infrastructure can be applied as it is.

For example, when only natural gas or BOG fuel is supplied to a low-pressure gas engine, about 0.34% of hydrogen is added under the same conditions, based on the amount of unburned hydrocarbons in the exhaust gas, that is, methane slip, which is about 960 ppm. When the mixed gas fuel is supplied to the low-pressure gas engine, the amount of methane slip contained in the exhaust gas is about 120 ppm or less, and the methane slip can be reduced by about 91%.

On the other hand, when only natural gas or BOG fuel is supplied to the low-pressure gas engine, about 0.34% of hydrogen under the same conditions is based on the amount of carbon monoxide (CO), which is a by-product of incomplete combustion, contained in the exhaust gas of about 720 ppm. When the added mixed gas fuel is supplied to the low-pressure gas engine, the amount of carbon monoxide contained in the exhaust gas is reduced by about 92%, and when the mixed gas fuel with about 1.2% of hydrogen added to the low-pressure gas engine is supplied to the low-pressure gas engine, the amount of carbon monoxide is reduced by about 92%. The amount of carbon monoxide included has a reduction effect of about 97% compared to when the hydrogen addition amount is 0%.

That is, according to the present embodiment, by supplying a hydrogen mixed fuel gas in which hydrogen is mixed with natural gas or BOG fuel as the fuel of the low pressure gas engine 410, methane slip is reduced, incomplete combustion of the fuel is reduced, and exhaust It is possible to significantly reduce the emission of pollutants in the gas.

According to this embodiment, the exhaust gas discharged from the X-DF engine 410 is discharged from the X-DF engine 410 to the outside along the exhaust gas line EL. A methane slip analyzer 411 for analyzing the amount of methane slip; may be installed.

The combustion state of the X-DF engine 410 is determined according to the amount of methane slip or carbon monoxide measured or analyzed by the methane slip analyzer 411, and accordingly, the control unit 800 detects hydrogen from the hydrogen storage tank 750 The flow rate and pressure of hydrogen supplied to the mixing device 300 or the flow rate and pressure of hydrogen stored in the hydrogen storage tank 750 may be adjusted.

The hydrogen storage tank 750 of this embodiment may be detachable from the hydrogen infrastructure 700 on land. The onshore hydrogen infrastructure 700 may include a hydrogen storage means, a hydrogen supply means, and the like installed on land.

The onshore hydrogen infrastructure 700 and the hydrogen storage tank 750 are connected by a hydrogen line HL, and the hydrogen line HL controls a flow path of hydrogen flowing through the hydrogen line HL, a flow rate of hydrogen, and the like. a hydrogen supply valve 710 to; And hydrogen distribution valve 740; may be installed one or more, respectively.

As shown in FIG. 1 , one or more hydrogen distribution valves 740 may be installed upstream of one or more hydrogen storage tanks 750, respectively.

In addition, in the hydrogen line (HL) connecting the onshore hydrogen infrastructure 700 and the hydrogen storage tank 750, a hydrogen compressor 720 for compressing hydrogen transferred from the onshore hydrogen infrastructure 700 to the hydrogen storage tank 750 ; and a hydrogen cooler 730 for cooling the hydrogen compressed in the hydrogen compressor 720.

The hydrogen compressor 720 of this embodiment may be controlled by the controller 800. For example, the control unit 800 uses the pressure of hydrogen supplied from the hydrogen storage tank 760 to the hydrogen mixing device 300, the measured or analyzed value of the methane slip analyzer 411, etc. It is possible to control the discharge pressure of hydrogen.

The pressure of hydrogen compressed in the hydrogen compressor 720 may be the operating pressure of the hydrogen storage tank 750 or the hydrogen pressure required by the hydrogen mixing device 300. It can be compressed up to bar.

The hydrogen cooler 730 of the present embodiment may cool the compressed hydrogen, the temperature of which has risen by compression in the hydrogen compressor 720, to a temperature required by the hydrogen storage tank 750.

Water or seawater may be used as a refrigerant for cooling the compressed hydrogen in the hydrogen cooler 730 of the present embodiment.

In the hydrogen line HL connecting the hydrogen storage tank 750 and the hydrogen mixing device 300, a pressure gauge 760 for measuring the pressure or flow rate of hydrogen supplied from the hydrogen storage tank 750 to the hydrogen mixing device 300 ; may be installed downstream of one or more hydrogen storage tanks 750, respectively.

Based on the measured value measured by the pressure gauge 760, the control unit 800 may include any one or more of the hydrogen supply valve 710, the hydrogen compressor 720, and one or more hydrogen distribution valves 740; Any one or more of one or more hydrogen recirculation valves 770 to be described later; may be controlled.

According to this embodiment, the hydrogen temporary storage tank 780; and a hydrogen branch line HL1 branched from the hydrogen line HL downstream of the hydrogen storage tank 750 and connected to the hydrogen line HL upstream of the hydrogen compressor 720.

The hydrogen temporary storage tank 780 is provided separately from the hydrogen storage tank 750, and may be used as a redundancy of the hydrogen storage tank 750, and the pressure or flow rate of hydrogen flowing through the hydrogen line HL, hydrogen storage It may be used as a safety means for controlling the pressure of the tank 750 or as a buffer means for stabilizing hydrogen according to changes in pressure or flow rate of hydrogen flowing through the hydrogen line HL.

The hydrogen temporary storage tank 780 of the present embodiment has a pressure required by the hydrogen mixing device 300 or the X-DF engine 410 among the plurality of hydrogen storage tanks 750 supplying hydrogen to the hydrogen mixing device 300. The hydrogen discharged from the hydrogen storage tank 750 having a lower internal pressure is stored.

When hydrogen is filled with the hydrogen storage tank 750, since hydrogen compressed at high pressure, for example, compressed hydrogen of 700 bar is stored, the internal pressure of the hydrogen storage tank 750 is a high pressure of about 700 bar, but the hydrogen storage tank As hydrogen is supplied from 750 to the hydrogen mixing device 300, the internal pressure of the hydrogen storage tank 750 gradually decreases.

If the pressure of hydrogen discharged from the hydrogen storage tank 750 is lower than the pressure required by the hydrogen mixing device 300 or the X-DF engine 410, hydrogen cannot be supplied as fuel for the X-DF engine 410. .

According to the present embodiment, the internal pressure of the hydrogen storage tank 750 or the pressure of hydrogen discharged from the hydrogen storage tank 750 downstream of the hydrogen storage tank 750 is measured using the pressure gauge 750, and the measured value is to control the flow of hydrogen.

If the pressure measurement value is lower than the pressure required by the hydrogen mixing device 300 or the X-DF engine 410, the control unit 800 controls the hydrogen recirculation valve 770 so that hydrogen is supplied to the hydrogen branch line HL1. ), and the hydrogen branched to the hydrogen branch line HL1 is stored in the hydrogen temporary storage tank 780.

The hydrogen recirculation valve 770 is installed downstream of one or more hydrogen storage tanks 750, and when the hydrogen recirculation valve 770 is opened, hydrogen flows into the hydrogen branch line HL1 and the hydrogen recirculation valve 770 is closed. When it is, hydrogen is installed in a position so that it is supplied to the hydrogen mixing device 300 along the hydrogen line HL.

In addition, a safety valve (reference numeral not given) may be installed in the hydrogen branch line HL1. By installing a safety valve in the hydrogen branch line (HL1), when the pressure downstream of the hydrogen storage tank 750 exceeds a set value, the safety valve is automatically opened, and the hydrogen line (HL) downstream of the hydrogen storage tank 750 is opened. Flowing hydrogen may be controlled to automatically flow into the hydrogen branch line HL1.

The hydrogen temporarily stored in the hydrogen temporary storage tank 780 is recycled to the hydrogen compressor 720 and compressed in the hydrogen compressor 720 so that the internal pressure among the plurality of hydrogen storage tanks 750 is reduced to the hydrogen mixing device 300 or X - It can be recovered to the hydrogen storage tank 750 that is lower than the pressure required by the DF engine 410.

As such, even hydrogen that cannot be supplied to the hydrogen mixing device 300 as a mixed gas fuel to be supplied to the X-DF engine 410 due to low pressure can be used as fuel for the entire X-DF engine 410.

In addition, according to the present embodiment, hydrogen is installed between the hydrogen storage tank 750 and the hydrogen mixing device 300, and is supplied from the hydrogen storage tank 750 to the hydrogen mixing device 300 along the hydrogen line HL. It may further include a hydrogen heater 790 for adjusting the temperature required by the X-DF engine 410.

The hydrogen heater 790 of this embodiment may adjust the temperature of the hydrogen gas supplied to the hydrogen mixing device 300 to the temperature required by the X-DF engine 410, and the HCNG generated by the hydrogen mixing device 300 The temperature of the fuel may be adjusted to a temperature required by the X-DF engine 410.

The fuel supply device of the present embodiment includes a re-liquefaction device for re-liquefying BOG or natural gas remaining after being supplied to the X-DF engine 410 and recovering it to the LNG storage tank 100; and a refrigerant cycle for circulating BOG or natural gas as a refrigerant in order to re-liquefy BOG or natural gas in the re-liquefying device.

The re-liquefaction apparatus of this embodiment includes a boost compressor 610 for pressurizing the compressed BOG compressed in the second fuel compressor 210b; a heat exchange unit 620 for recovering and liquefying cold heat of the compressed BOG compressed in the boost compressor 610 before compression supplied to the fuel compressors 210a and 210b; and a cold box 510 further cooling the liquefied BOG in the heat exchange unit 620 by heat exchange with methane refrigerant circulating in the refrigerant cycle. Joule-Thomson valve 630 for reducing the re-liquefied BOG cooled in the cold box 510 to the storage pressure of the LNG storage tank 100; and a gas-liquid separator 640 that supplies only the re-liquefied BOG in a liquid state to the LNG storage tank 100 by gas-liquid separation of flash gas generated while depressurizing the re-liquefied BOG in the Joule-Thomson valve 630.

Among the compressed BOG compressed by the second fuel compressor 210b, the boost compressor 610 pressurizes the remaining compressed BOG supplied as fuel for the X-DF engine 410 and transfers it to the heat exchange unit 620. The compressed BOG is compressed to a pressure suitable for re-liquefaction by the boost compressor 610, and the compressed BOG compressed in the boost compressor 610 may be liquefied while passing through the heat exchange unit 620.

The heat exchange unit 620 liquefies the compressed BOG transferred by the boost compressor 610 by recovering the cold heat of the BOG before compression supplied to the fuel compressor 210 .

That is, before the BOG supplied to the fuel compressors 210a and 210b is introduced into the fuel compressors 210a and 210b, the heat exchange unit 620 cools the compressed BOG to be reliquefied and the temperature rises. According to this embodiment, by recovering cold heat before compressing BOG in the fuel compressors 210a and 210b, the fuel compressors 210a and 210b do not need to be equipped for expensive cryogenic temperatures, and the compression efficiency is improved by increasing the compressor introduction temperature. can increase

The heat exchange unit 620 of this embodiment may be a diffusion-bonded compact heat exchanger (DCHE). A diffusion bonding type heat exchanger is a heat exchanger having a structure in which welding between plates is excluded by stacking and diffusion bonding a plurality of heat exchange plates. By using a heat exchanger excluding welding, it can be applied to various temperatures and pressures, and has excellent heat exchange performance per unit area, so that BOG compressed at high pressure can be cooled to a low temperature.

The cold box 510 further cools the liquefied BOG in the heat exchange unit 620 by using the cooling heat of the methane refrigerant branched from some of the BOG or natural gas flowing through the BOG line BL.

In this embodiment, the methane refrigerant circulates through a refrigerant cycle to be described later, and may be BOG compressed in the first fuel compressor 210a, natural gas, or a mixture of BOG and natural gas.

If there are components that are not liquefied in the heat exchange unit 620, all of them may be liquefied by heat exchange in the cold box 510. That is, according to the present embodiment, the compressed BOG transported by the boost compressor 610 may be re-liquefied while passing through the heat exchange unit 620 or the heat exchange unit 620 and the cold box 510 .

The Joule-Thomson valve 630 of this embodiment reduces the re-liquefied BOG cooled in the cold box 510 to the storage pressure of the LNG storage tank 100. While passing through the Joule-Thomson valve 630, the re-liquefied BOG expands adiabatically, and the temperature of the fluid can be lowered due to the Joule-Thomson effect.

In addition, during the depressurization process by the Joule-Thomson valve 630, some of the re-liquefied BOG may flash, and thus a gas-liquid mixture may be formed. The flash gas generated in the depressurization process may be gas-liquid separated in the gas-liquid separator 650. The gaseous flash gas separated in the gas-liquid separator 650 is supplied to the fuel compressors 210a and 210b through the BOG recovery line BL3 connecting the gas-liquid separator 650 and the BOG line BL. can join the flow.

According to this embodiment, branched off from the BOG line BL downstream of the second fuel compressor 210b, the boost compressor 610, the heat exchange unit 620, the cold box 510, and the Joule-Thompson valve 630 , A re-liquefaction line (RL) connecting the gas-liquid separator 640 and the LNG storage tank 100; includes. That is, among the compressed BOG compressed in the second fuel compressor 210b, the compressed BOG remaining after being supplied to the hydrogen mixing device 300 may be introduced into the reliquefaction line RL, and introduced into the reliquefaction line RL. Compressed BOG is liquefied in its entirety while passing through the boost compressor 610, heat exchange unit 620 and cold box 510, depressurized while passing through the Joule-Thomson valve 630, and then gas-liquid separator 640 for gas-liquid separation And, the re-liquefied BOG in a liquid state separated in the gas-liquid separator 640 can be recovered to the LNG storage tank 100.

Since the re-liquefaction process of the present embodiment may not always proceed in real time, according to the present embodiment, an accumulator (reference numeral not given) is provided in the re-liquefaction line RL upstream of the boost compressor 610. In this way, compressed BOG is accumulated, and when a certain amount of compressed BOG is collected, re-liquefaction may be performed.

According to this embodiment, BOG or natural gas generated in the LNG storage tank 100 may be used as a refrigerant for re-liquefying BOG.

That is, the methane refrigerant used as a refrigerant for re-liquefying BOG in the cold box 510 of the present embodiment is BOG or natural gas (hereinafter referred to as 'BOG refrigerant) circulating in a refrigerant cycle including the first fuel compressor 210a. '.) is.

BOG or natural gas to be used as a refrigerant is introduced into the first fuel compressor 210a through a second BOG line BL2 branched from the BOG line BL at the upstream of the fuel compressors 210a and 210b. The first fuel compressor 210a compresses the compressed BOG introduced through the second BOG line BL2 to a pressure suitable for circulating the refrigerant cycle.

The first fuel compressor 210a of this embodiment can be operated only when it is necessary to supply, replenish, or circulate the BOG refrigerant in the refrigerant cycle.

First, the BOG refrigerant compressed in the first fuel compressor 210a flows into the cold box 510 and is cooled by heat exchange in the cold box 510 .

The refrigerant cycle of this embodiment further includes an expander 520 that expands the compressed BOG refrigerant compressed in the first fuel compressor 210a and cooled in the cold box 510 .

The compressed BOG refrigerant expanded while passing through the expander 520 has a lowered temperature and may be partially or entirely condensed. The BOG refrigerant whose temperature is lowered while passing through the expander 520 is recycled to the first fuel compressor 210a.

In the cold box 510 of this embodiment, after being cooled in the compressed BOG refrigerant and heat exchange unit 620 by the cooling heat of the BOG refrigerant whose temperature is lowered while passing through the expander 520, the cold box along the reliquefaction line RL The reliquefied BOG, introduced at 510, is cooled.

Since the refrigerant cycle of the present embodiment may not always operate in real time, according to the present embodiment, an accumulator (no reference numeral is given) is provided between the first fuel compressor 210a and the cold box 510 to compress BOG When the refrigerant is accumulated and a certain amount of the compressed BOG refrigerant is collected, or when a demand occurs in the cold box 510, the compressed BOG refrigerant may be supplied to the cold box 510.

The fuel supply device of the present embodiment is branched from the BOG line BL1 downstream of the second fuel compressor 210b and supplied to the hydrogen mixing device 300 and requires a fuel demand source 420 that requires the remaining compressed BOG; And a flow path branched from the BOG line BL1 downstream of the second fuel compressor 210b, connected to the fuel consumer 420, supplied to the hydrogen mixing device 300, and supplying the remaining compressed BOG to the fuel consumer 420 A third BOG line (BL4) provided; may be further included.

The fuel demand place of this embodiment may include an integrated IGG/GCU, a power generation engine, an auxiliary boiler, and the like.

The combined inert gas generator/gas combustion unit (IGG/GCU) burns compressed BOG to generate inert gas or burns compressed BOG to generate combustion heat.

In addition, the engine for power generation generates electric power using compressed BOG as fuel, and may include, for example, a turbine-generator, a DFDE, and the like.

In addition, the auxiliary boiler burns the compressed BOG to generate steam or high-temperature water with the heat of combustion, and the generated steam or high-temperature water can be supplied to a steam customer or a hot water customer on board.

According to this embodiment, BOG generated on board can be used to generate mixed gas fuel to be supplied to the X-DF engine 410, or to be re-liquefied and recovered, or to be used as a refrigerant required for re-liquefaction of BOG. It can also be supplied as fuel for demand. Therefore, BOG, the main component of which is methane, can be efficiently utilized onboard the ship without being discharged into the atmosphere or thrown away.

In addition, in the fuel supply device of this embodiment, the amount of BOG to be supplied to the X-DF engine 410 is insufficient, natural gas is additionally required for operation of BOG re-liquefaction, or the amount of BOG required as a refrigerant is insufficient, A vaporizer 120 for forcibly vaporizing the LNG stored in the LNG storage tank 100 when the amount to be supplied as fuel for the fuel demand is insufficient; and an LNG pump 110 that pressurizes the LNG stored in the LNG storage tank 100 and supplies it to the vaporizer 120.

The natural gas forcedly vaporized in the vaporizer 120 of this embodiment may be supplied to the fuel compressors 210a and 210b by joining the BOG line BL.

In addition, the fuel supply device of the present embodiment may further include a mist separator 130 for removing liquid components in the natural gas forcedly vaporized in the vaporizer 120.

Only gas components from which liquid components are separated and removed in the mist separator 130 of the present embodiment may be supplied to the fuel compressor 210 .

By separating and removing liquid components in the natural gas supplied to the fuel compressor 210, such as droplets, by the mist separator 130 of the present embodiment, the liquid components are mixed into the fuel compressor 210 to prevent failure of the fuel compressor 210. problems can be prevented.

In addition, the mist separator 130 of the present embodiment may be a methane number control means for adjusting the methane number of natural gas supplied to the fuel compressors 210a and 210b, particularly the second fuel compressor 210b.

As described above, the X-DF engine 410 of this embodiment, that is, the low-pressure gas engine, has a fuel methane number limitation. Since methane is the main component of BOG, methane number control may not be required, but natural gas vaporized in the vaporizer 120 may have a lower methane number than conditions required for a low pressure gas engine.

Therefore, according to the present embodiment, in the mist separator 130, heavy hydrocarbons such as propane, which is a component that lowers the methane number, are condensed in the natural gas vaporized in the vaporizer 120, and the condensed heavy hydrocarbons are gas-liquid separated to obtain methane as the main component To, only natural gas in a gaseous state having a high methane number is supplied to the second fuel compressor 210b, and heavy hydrocarbons separated in a liquid state can be separately discharged. The heavy hydrocarbon gas-liquid separated in the mist separator 130 is supplied to the purging unit 140, purged in the purging unit 140, and then supplied to the LNG storage tank 100 along the liquid recovery line LL.

As described above, by supplying hydrogen-mixed gas fuel as fuel to the marine low-pressure gas engine, methane slip of the engine can be reduced, and combustion stability and combustion efficiency can be improved, such as preventing incomplete combustion. In addition, the proven commercialization technology can be applied as it is without having a separate hydrogen infrastructure.

It is obvious to those skilled in the art that the present invention is not limited to the above embodiments, and can be variously modified or modified without departing from the technical gist of the present invention. it did

100: LNG storage tank
210: fuel compressor
300: hydrogen mixing device
410: low pressure gas engine
411: methane slip analyzer
700: onshore hydrogen infrastructure
720: hydrogen compressor
730: hydrogen cooler
750: hydrogen storage tank
780: hydrogen temporary storage tank
790: hydrogen heater
610: boost compressor
620: heat exchange unit
630: Joule-Thompson valve
640: gas-liquid separator
510: cold box
520: expander

Claims (8)

Analyze the methane slip of the exhaust gas discharged from the low-pressure gas engine for ships using liquefied gas as fuel,
Preventing methane slip of the marine low-pressure gas engine by controlling the amount of hydrogen added to the gas fuel supplied to the marine low-pressure gas engine according to the degree of methane slip included in the exhaust gas,
The hydrogen to be mixed with the liquefied gas is compressed using a hydrogen compressor and stored in a hydrogen storage tank on board,
A plurality of hydrogen storage tanks are installed,
When the pressure of hydrogen discharged from the hydrogen storage tank is lower than the pressure required for mixing with the liquefied gas or the pressure required by the marine low-pressure gas engine,
After storing the low-pressure hydrogen in a hydrogen temporary storage tank, compressing the hydrogen with the hydrogen compressor and resupplying it to the hydrogen storage tank. delete The method of claim 1,
The vessel is provided with a liquefied gas storage tank,
After compressing the boil-off gas generated in the liquefied gas storage tank using a second fuel compressor, mixing it with compressed hydrogen and supplying it as fuel for the marine low-pressure gas engine, a method for supplying hydrogen mixed fuel to a marine low-pressure gas engine. The method of claim 3,
Of the boil-off gas compressed using the second fuel compressor, the compressed boil-off gas remaining after being supplied as fuel for the marine low-pressure gas engine is compressed using a first fuel compressor provided separately from the second fuel compressor, and then cooled. and reliquefying the expanded boil-off gas refrigerant by cooling heat and recovering it to a liquefied gas storage tank. A fuel supply device for supplying liquefied gas as fuel to a marine low-pressure gas engine;
A hydrogen storage tank for storing compressed hydrogen;
a hydrogen mixing device for mixing the liquefied gas and hydrogen stored in the hydrogen storage tank;
a low-pressure gas engine for ships using the liquefied gas as fuel;
a methane slip analyzer for analyzing methane slip of exhaust gas discharged from the marine low-pressure gas engine; and
A controller for controlling the amount of hydrogen supplied from the hydrogen storage tank to the hydrogen mixing device using the measured value measured by the methane slip analyzer; includes,
In the marine low-pressure gas engine, methane slip is controlled by using a mixed gas fuel in which the amount of hydrogen mixed with the liquefied gas is controlled as fuel,
The hydrogen storage tank is detachable from the onshore hydrogen infrastructure,
A plurality of hydrogen storage tanks are installed,
a hydrogen compressor that compresses the hydrogen supplied from the land and supplies it to the hydrogen storage tank;
a pressure gauge for measuring the pressure of hydrogen discharged from the hydrogen storage tank;
a hydrogen recirculation valve for supplying hydrogen to the hydrogen compressor when the pressure of the hydrogen discharged from the hydrogen storage tank is lower than the pressure required by the hydrogen mixing device or the marine low-pressure gas engine; and
Further comprising a hydrogen temporary storage tank for storing hydrogen supplied to the hydrogen compressor,
The control unit controls the hydrogen compressor and the hydrogen recirculation valve according to the measured value of the pressure gauge, and compresses the low pressure hydrogen and resupplies it to the hydrogen storage tank. delete The method of claim 5,
The fuel supply device,
a second fuel compressor for compressing boil-off gas generated by natural vaporization of liquefied gas to a pressure required by the marine low-pressure gas engine and supplying the compressed gas to the hydrogen mixing device;
a re-liquefaction device for re-liquefying the remaining compressed boil-off gas supplied to the hydrogen mixing device among the compressed boil-off gas compressed by the second fuel compressor and recovering the compressed boil-off gas into a liquefied gas storage tank; and
A hydrogen mixture fuel supply system for a marine low-pressure gas engine comprising a; first fuel compressor for compressing the boil-off gas and supplying it as a refrigerant for liquefying the boil-off gas in the re-liquefaction device. The method of claim 7,
The re-liquefaction device,
a boost compressor further compressing the compressed boil-off gas compressed in the second fuel compressor to a pressure required for re-liquefaction;
A hydrogen mixture fuel supply system for a marine low-pressure gas engine comprising a; cold box for liquefying the boil-off gas compressed in the boost compressor with the cold heat of the boil-off gas refrigerant whose temperature is lowered by expansion after being compressed in the first fuel compressor. .

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