Energy-saving liquefied gas fueled ship and evaporation gas treatment method for said liquefied gas fueled ship

Abstract

The present invention relates to a power-saving evaporated gas treatment system for a ship that uses liquefied gas as fuel, which can reduce the power consumption of a re-liquefaction system when treating evaporated gas generated by natural evaporation of liquefied gas, and a method for treating evaporated gas in such a liquefied gas-fueled ship. The energy-saving liquefied gas-fueled ship of the present invention includes a liquefied gas storage tank for storing liquefied gas; an engine that uses as fuel the liquefied gas stored in the liquefied gas storage tank or the evaporated gas generated by natural evaporation of the liquefied gas; a fuel supply means for supplying the liquefied gas as fuel for the engine; a compressor for compressing the evaporated gas at a pressure required by the engine; a heat exchanger for cooling the remaining evaporated gas compressed by the compressor that is not supplied to the engine; a refrigerant circulation line through which a refrigerant supplied to the heat exchanger circulates; a refrigerant compression section that is provided in the refrigerant circulation line and compresses the refrigerant discharged after heat exchange in the heat exchanger; and a cold energy recovery device that recovers cold energy from the liquefied gas to be supplied as fuel for the engine and cools the refrigerant compressed by the refrigerant compression section.

Description

[Technical field]

[0001] The present invention relates to an energy-saving liquefied gas-fueled ship that can reduce the power consumption of a re-liquefaction system when treating evaporated gas generated by the natural evaporation of liquefied gas in a ship that uses liquefied gas as fuel, and a method for treating evaporated gas for such a liquefied gas-fueled ship. [Background technology]

[0002] As international interest in preventing marine air pollution grows, there is an increasing demand for ships (LFS; Liquefied Gas Fueled Ships) that use liquefied natural gas (LNG) as fuel as environmentally friendly ships (Green-ships). LFS have been officially certified (AIP; Approval In Principle) by ship classification systems in each country and meet the demand for switching to clean energy required by environmental regulations. LFS are equipped with LNG storage tanks and are being applied not only to LNG carriers that transport LNG cargo, but also to general commercial ships such as container ships and tankers.

[0003] Natural gas is relatively environmentally friendly because it contains little sulfur and does not produce sulfur compounds or soot when burned. Representative dual fuel engines that can use natural gas as fuel for ships include ME-GI (MAN Electronic Gas Injection) engines, X-DF (eXtra long stroke Dual Fuel) engines, and DF engines (DFDE (Dual Fuel Diesel Electric), DFDG (Dual Fuel Diesel Generator)).

[0004] ME-GI engines are two-stroke cycle engines that are primarily used for propulsion and operate on the basis of the diesel cycle, in which high-pressure natural gas (approximately 300 bar) is directly injected into the combustion chamber near the top dead center of the piston.

[0005] Meanwhile, the X-DF engine is a two-stroke cycle engine that is mainly used for propulsion, and like the ME-GI engine, it directly drives the propeller to propel the ship.The X-DF engine also uses heavy natural gas at about 16 bar as fuel and operates based on the Otto cycle.

[0006] The DF engine is a four-stroke cycle engine mainly used for generating electricity. The DF engine operates based on the 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.

[0007] Meanwhile, natural gas, which is mainly composed of methane, has been drawing attention as an environmentally friendly fuel as it emits almost no environmental pollutants when burned. LNG is obtained by liquefying natural gas by cooling it to about -163℃ under normal pressure, and as its volume is reduced to about 1 / 600 of that of its gaseous state, it is highly suitable for long-distance transportation by sea. Therefore, natural gas is mainly stored and transported in the form of liquefied natural gas, which is easy to store and transport.

[0008] Since the liquefaction point of natural gas is an extremely low temperature of about -163℃ at normal pressure, LNG storage tanks are generally insulated to keep LNG in a liquid state. However, even though LNG storage tanks are insulated, they have a limit to blocking external heat, and external heat is continuously transferred to the LNG storage tank, so that LNG naturally vaporizes continuously inside the LNG storage tank during the LNG transportation process, generating boil-off gas (BOG).

[0009] Continuous generation of evaporative gas in an LNG storage tank increases the pressure resistance of the LNG storage tank. If the pressure resistance of the storage tank exceeds a set safety pressure, it may lead to an emergency situation such as tank damage, so the evaporative gas must be discharged to the outside of the storage tank using a safety valve. However, since evaporative gas is a type of LNG loss and is a significant problem in terms of LNG transportation efficiency and fuel efficiency, various methods are used to treat the evaporative gas generated in the storage tank.

[0010] In recent years, methods have been developed and applied in which the evaporated gas is used at fuel demand destinations such as ship engines, the evaporated gas is reliquefied and then collected in storage tanks, or a combination of these two methods is used. Summary of the Invention [Problem to be solved by the invention]

[0011] Methods for re-liquefying the evaporated gas include a method in which the evaporated gas is re-liquefied by heat exchange with the refrigerant using a refrigeration cycle that uses a separate refrigerant, and a method in which the evaporated gas itself is used as the refrigerant without using a separate refrigerant.

[0012] The applicant has invented a method for re-liquefying evaporated gas using the evaporated gas itself as a refrigerant without a separate refrigerant. The evaporated gas compressed by the compressor is cooled by heat exchange with the evaporated gas before being compressed by the compressor, and then expanded by a JT valve or the like to re-liquefy a portion of the evaporated gas. This system is called a PRS (Partial Re-liquefaction System).

[0013] As a method of re-liquefying evaporated gas by using the evaporated gas itself as a refrigerant without a separate refrigerant, an improved PRS technology has been developed in which compressed evaporated gas is cooled by heat exchange with uncompressed evaporated gas, and then re-liquefied by adiabatic expansion, and this technology is being applied to ships.

[0014] When a large amount of evaporated gas needs to be reliquefied, such as when there is a large amount of liquefied gas inside the storage tank and a large amount of evaporated gas is generated, or when the ship is at anchor or operating at a slow speed and only a small amount of evaporated gas is used by the engine, the PRS alone may not be able to satisfy the required amount of reliquefaction, and the applicant has invented technology to improve the PRS so that even more evaporated gas can be reliquefied.

[0015] As an improved technology of PRS, a system that can further cool the evaporated gas by a refrigerant cycle that uses the evaporated gas itself as a refrigerant is called MRS (Methane Refrigeration System).

[0016] Representative examples of systems using separate refrigeration cycles include processes using an SMR cycle and a C3MR cycle, and processes using a single refrigerant.

[0017] The process using the C3MR cycle (Propane-precooled Mixed Refrigerant Cycle) is a process in which natural gas is cooled using a single propane refrigerant, and then liquefied and supercooled using a mixed refrigerant. The process using the SMR cycle (Single Mixed Refrigerant Cycle) is a process in which natural gas is liquefied using a mixed refrigerant consisting of multiple components, and the process using a single refrigerant is a process in which natural gas is liquefied using a nitrogen refrigerant system (NRS).

[0018] Both the SMR cycle and the C3MR cycle use a mixed refrigerant. As the liquefaction process progresses, refrigerant leakage occurs and the composition ratio of the mixed refrigerant changes, reducing the liquefaction efficiency. Therefore, the composition ratio of the mixed refrigerant must be continuously measured and the missing refrigerant components must be filled in to maintain the refrigerant composition.

[0019] On the other hand, the nitrogen refrigerant is relatively less efficient than a cycle using a mixed refrigerant, but has the advantages of being highly safe since the refrigerant is inactive and easy to apply to ships since there is no phase change of the refrigerant.

[0020] The reliquefaction system, which uses a refrigeration cycle using nitrogen refrigerant, has a nitrogen refrigeration cycle in which the nitrogen refrigerant discharged after heat exchange in a heat exchanger is compressed through a compander, cooled, expanded and cooled again, and circulated to the heat exchanger.

[0021] An object of the present invention is to provide an energy-saving liquefied gas fuel ship that can reduce power consumption through effective heat exchange when treating evaporated gas using a nitrogen refrigerant system. [Means for solving the problem]

[0022] According to one aspect of the present invention for achieving the above-mentioned object, there is provided a liquefied gas storage tank for storing liquefied gas; an engine that uses as fuel the liquefied gas stored in the liquefied gas storage tank or the evaporated gas generated by natural evaporation of the liquefied gas; a fuel supply means for supplying the liquefied gas as fuel to the engine; and a pressure regulator for supplying the evaporated gas to the engine at a pressure required by the engine. Ma a compressor for compressing the evaporative gas by the compressor; a heat exchanger for cooling the remaining evaporated gas that is not supplied to the engine among the evaporated gas compressed by the compressor; a refrigerant circulation line through which the refrigerant to be supplied to the heat exchanger circulates; from the heat exchanger Discharged Ta The present invention includes a refrigerant compression unit that compresses a refrigerant; and a cold energy recovery device that recovers cold energy from a liquefied gas that is supplied as fuel for the engine and cools the refrigerant compressed by the refrigerant compression unit. the refrigerant compressed in the refrigerant compression unit is cooled in the heat exchanger by heat exchange with uncompressed evaporated gas discharged from the liquefied gas storage tank and not yet compressed by the compressor; a refrigerant cooling line for branching the refrigerant compressed in the refrigerant compression unit from the refrigerant circulation line before being supplied to the heat exchanger and supplying the branched refrigerant to the cold heat recovery device; and a flow rate adjusting means for adjusting the flow rate of the refrigerant branched from the refrigerant circulation line to the refrigerant cooling line. A power-saving liquefied gas fuelled ship is provided.

[0023] Preferably, the fuel supply means includes a high-pressure pump that compresses the liquefied gas to a pressure required by the engine; and a high-pressure vaporizer that vaporizes the liquefied gas compressed by the high-pressure pump; and the cold energy recovery device may be provided between the high-pressure pump and the high-pressure vaporizer.

[0024] Preferably, a refrigerant expansion device is provided in the refrigerant circulation line, and expands and cools the refrigerant supplied to the heat exchanger; The flow rate adjusting means includes: The refrigerant circulation system may further include a first valve provided in the refrigerant circulation line for controlling a flow path such that the refrigerant compressed in the refrigerant compression unit is cooled through the heat exchanger and then introduced into the refrigerant expansion device; and a second valve provided in the refrigerant circulation line for controlling a flow path such that the refrigerant compressed in the refrigerant compression unit is cooled through the cold heat recovery device and then introduced into the refrigerant expansion device.

[0025] Preferably, The flow rate adjusting means is The cold energy recovery device may further include a first temperature sensor that measures a temperature of the liquefied gas supplied to the cold energy recovery device; a second temperature sensor that measures a temperature of the liquefied gas discharged from the cold energy recovery device; and a control unit that controls the opening / closing and opening amount of the second valve using the temperature measurements of the first temperature sensor and the second temperature sensor.

[0026] Preferably, The flow rate adjusting means is The cold energy recovery device may further include a third temperature sensor that measures a temperature of the refrigerant supplied to the cold energy recovery device; a fourth temperature sensor that measures a temperature of the refrigerant discharged from the cold energy recovery device; and a control unit that controls opening / closing and the opening degree of the second valve using the temperature measurements of the third temperature sensor and the fourth temperature sensor.

[0027] Preferably, in the heat exchanger, four flows can be heat exchanged, including the compressed gas compressed in the compressor, the refrigerant expanded and cooled in the refrigerant expansion device, the uncompressed evaporated gas introduced from the storage tank to the compressor, and the refrigerant compressed in the refrigerant compression section.

[0028] Preferably, The flow rate adjusting means isThe refrigerant compressor may further include a control unit that measures a temperature of the refrigerant supplied to the refrigerant compression unit and adjusts a total flow rate of the refrigerant circulating through the refrigerant circulation line.

[0029] According to another aspect of the present invention for achieving the above object, there is provided a method for treating evaporated gas in a liquefied gas fuel ship, which uses liquefied gas stored in a liquefied gas storage tank or evaporated gas generated by natural evaporation of the liquefied gas as fuel for an engine. And The evaporative gas is then pumped to the engine. but Required pressure Ma Compress with To the engine and the remaining evaporated gas not being supplied to the engine. of reliquefaction Let me Collected in the liquefied gas storage tank In what , Compressed Re-liquefying evaporated gas Let Ruta eye, heat exchanger in, The compression was done Evaporation gas and uncompressed gas discharged from the liquefied gas storage tank before compression of Heat exchange between the evaporated gas and the refrigerant circulating in the refrigerant circulation line Let me , the compression was done Cooling of evaporative gas By doing The heated refrigerant is compressed, and the compressed refrigerant of from the liquefied gas storage tank The above Supply to engine Be Heat exchange with liquefied gas and at least one of heat exchange with the uncompressed evaporated gas. cooling and adjusting the flow rate of the compressed refrigerant that is subjected to heat exchange with the liquefied gas and the uncompressed evaporated gas. A method for treating vapors of a liquefied gas fuelled ship is provided.

[0030] Preferably, the remaining refrigerant, excluding the refrigerant that exchanges heat with the liquefied gas, among the compressed refrigerant, may be supplied to the heat exchanger and cooled.

[0031] Preferably, the flow rate of the refrigerant exchanging heat with the liquefied gas can be controlled by a temperature measurement of the liquefied gas exchanging heat with the refrigerant and a temperature measurement of the liquefied gas discharged after exchanging heat with the refrigerant.

[0032] Preferably, the flow rate of the refrigerant exchanging heat with the liquefied gas can be controlled by a temperature measurement of the refrigerant exchanging heat with the liquefied gas and a temperature measurement of the refrigerant discharged after exchanging heat with the liquefied gas. Effect of the Invention

[0033] The energy-saving liquefied gas-fueled ship and the evaporative gas treatment method for the liquefied gas-fueled ship of the present invention can effectively cool the evaporative gas to be re-liquefied using the cold energy of the evaporative gas itself and the cold energy of the refrigerant cycle, thereby increasing the re-liquefaction rate, and by compressing the refrigerant using the expansion energy of the refrigerant in the refrigerant cycle, the power required to compress the refrigerant in the refrigerant cycle can be reduced, thereby improving the energy efficiency of the ship.

[0034] In addition, since the unused cold energy of the liquefied gas fuel is recovered and the evaporated gas is liquefied, the flow rate of the nitrogen refrigerant used to liquefy the evaporated gas can be reduced, the capacity of each device for compressing and expanding the refrigerant can be reduced, power consumption can be reduced, installation and operating costs can be reduced, and as a result, re-liquefaction efficiency can be improved. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is a schematic diagram showing an evaporation gas treatment system for a liquefied gas fuel ship to which a nitrogen refrigerant cycle is applied. [Diagram 2] 1 is a schematic diagram showing an evaporation gas treatment system for an energy-saving liquefied gas fuel ship according to one embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] For a fuller understanding of the operating advantages and objects attained by the practice of the present invention, reference should be had to the accompanying drawings, in which preferred embodiments of the invention are illustrated and the contents thereof.

[0037] Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, in assigning reference numerals to the components of each drawing, it should be noted that the same components are represented by the same numerals as much as possible even if they are shown in different drawings.

[0038] Hereinafter, the term "ship" in the present invention refers to any type of liquefied gas fueled ship (LFS) that is equipped with an engine that can use liquefied gas and evaporated gas generated from liquefied gas as fuel for propulsion or power generation engines, or that uses liquefied gas or evaporated gas as fuel for onboard engines. Representative examples include ships with their own propulsion capabilities, such as LNG carriers, liquid hydrogen carriers, and LNG RVs (regasification vessels), as well as offshore structures that do not have propulsion capabilities but float on the sea, such as LNG FPSOs (floating production storage offloading) and LNG FSRUs (floating storage regasification units).

[0039] In addition, in the present invention, the liquefied gas may include all kinds of liquefied gases that can liquefy gas at low temperatures for transportation, generate evaporated gas in a stored state, and can be used as fuel for engines, etc. Such liquefied gases may be, for example, liquefied petrochemical gases such as LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), liquefied ethylene gas, and liquefied propylene gas. However, in the embodiment described below, an example will be described in which LNG, one of the representative liquefied gases, is applied.

[0040] Meanwhile, the fluid flowing through each line of the present embodiment may be in any one of a liquid state, a gas-liquid mixture state, a gas state, and a supercritical fluid state, depending on the operating conditions of the system.

[0041] In addition, in one embodiment of the present invention described below, the engine may be a gas fuel engine that can use natural gas as fuel as a dual fuel engine among engines used in ships, and may include any one or more of a high pressure gas injection engine, a heavy pressure gas injection engine, and a low pressure gas injection engine.

[0042] The high pressure gas injection engine is described as an engine using gas fuel at about 100 bar to 400 bar, or about 150 bar or more, preferably about 300 bar, such as an ME-GI engine, for example. The heavy pressure gas injection engine may be an engine using gas fuel at about 10 bar to 20 bar, preferably about 16 bar, such as an X-DF engine, and the low pressure gas injection engine may be an engine using gas fuel at about 5 bar to 10 bar, preferably about 6.5 bar, such as a DF engine, a DFDG engine, or a DFGE engine.

[0043] In one embodiment of the present invention described below, an ME-GI engine is applied as the main propulsion engine, and a DFDE is applied as the auxiliary power generation engine.

[0044] First, referring to FIG. 1, the liquefied gas fueled ship includes a storage tank T for storing liquefied gas, a compressor 100 for compressing evaporated gas generated by natural evaporation of the liquefied gas fuel in the storage tank T, and a heat exchanger 200 for cooling all or a part of the evaporated gas compressed by the compressor 100 by heat exchange with uncompressed evaporated gas and a refrigerant introduced from the storage tank T to the compressor 100.

[0045] In addition, an evaporated gas supply line GL connecting the storage tank T to the compressor 100, and a re-liquefaction line RL connecting the rear end of the compressor 100 to the heat exchanger 200 and from the heat exchanger 200 to the storage tank T are provided.

[0046] In addition, a refrigerant circulation line CL is further provided through which the refrigerant supplied to the heat exchanger 200 circulates. The refrigerant circulation line CL is provided with a refrigerant expansion device 510 for expanding and cooling the refrigerant supplied to the heat exchanger 200, and a refrigerant compression unit 500 for compressing the refrigerant discharged after heat exchange in the heat exchanger 200.

[0047] The refrigerant compression unit 500 may be a compander, and may be connected to the refrigerant expansion device 510 via a shaft, and may be driven by receiving the expansion energy of the refrigerant. Alternatively, the refrigerant compression unit 500 may be driven by a motor, and the motor may be connected to the refrigerant expansion device 510, and may be configured to compress the refrigerant while being driven by receiving the expansion energy of the refrigerant.

[0048] The refrigerant compressed in the refrigerant compression section 500 is introduced into the heat exchanger 200 and cooled, and then supplied to the refrigerant expansion device 510 along the refrigerant circulation line CL, where it is expanded and cooled, and is then supplied to the heat exchanger 200 again as a refrigerant.

[0049] In the heat exchanger 200 of this embodiment, four flows are heat exchanged, including all or a portion of the compressed evaporative gas, the uncompressed evaporative gas introduced into the compressor 100, the refrigerant expanded and cooled in the refrigerant expansion device 510, and the refrigerant compressed in the refrigerant compression section 500.

[0050] That is, the refrigerant is compressed, cooled by its own cold energy, expanded, and then supplied to heat exchanger 200 for circulation. This refrigerant cycle is combined with the applicant's PRS system, in which compressed evaporative gas is cooled by uncompressed evaporative gas introduced into compressor 100, and configured so that four streams are heat exchanged in the heat exchanger.

[0051] The refrigerant that circulates through the refrigerant circulation line CL and is supplied to the heat exchanger 200 may be, for example, nitrogen (N2).

[0052] When a refrigerant cycle is formed in which compressed refrigerant is supplied to heat exchanger 200, cooled using the cold energy of the refrigerant itself, expanded, and then supplied to heat exchanger 200 for circulating, and the evaporated gas is cooled by heat exchange, a large amount of nitrogen refrigerant is required to cool the evaporated gas to a liquefaction temperature due to the difference in heat capacity between the evaporated gas, whose main component is methane, and nitrogen. As a result, most of the cold energy of the refrigerant cycle must be used to cool the nitrogen refrigerant itself, which results in an increase in the capacity of the device that compresses the refrigerant and the device that expands the refrigerant, and therefore an increase in power consumption.

[0053] In order to solve this problem, in this embodiment, the extremely low temperature uncompressed evaporated gas generated from the storage tank T is also introduced into the compressor 100 via the heat exchanger 200, thereby reducing the flow rate of refrigerant required in the refrigerant cycle.

[0054] This allows the capacity of each device for compressing and expanding the refrigerant to be reduced, power consumption to be reduced, and installation and operation costs to be saved.

[0055] When the heat exchanger is configured to exchange heat between four flows in this way, power consumption is reduced by about 25% compared to when the refrigerant cycle is configured to cool the refrigerant using the cold heat of the refrigerant itself.

[0056] In addition, in order to process the evaporated gas, the system may further include a pressure reducing device 300 that reduces the pressure of the compressed evaporated gas cooled by the heat exchanger 200, and a gas-liquid separator 400 that separates the evaporated gas reduced in pressure by the pressure reducing device 300 into gas and liquid and sends only the reliquefied evaporated gas in liquid form to the storage tank T.

[0057] Here, the pressure reducing device 300 may be configured with an expander or an expansion valve such as a Joule-Thomson valve that reduces the pressure of the compressed and cooled evaporated gas. Through the reduction in pressure, the evaporated gas is cooled by adiabatic expansion or isentropic expansion.

[0058] In addition, the evaporated gas that has been depressurized and additionally cooled in the pressure reducing device 300 is introduced into the gas-liquid separator 400, and the liquid separated in the gas-liquid separator 400 is supplied to the storage tank T along the re-liquefaction line RL and re-stored.

[0059] However, even if the gas-liquid separator 400 is used, the flash gas, which is a gas, and the liquefied gas, which is a liquid, may not be 100% phase-separated, so the separated liquid or liquefied gas may contain unseparated flash gas.

[0060] The flash gas separated in the gas-liquid separator 400 is merged with the flow of uncompressed evaporated gas at the front end of the heat exchanger 200 via an uncondensed gas line NL connected from the upper end of the gas-liquid separator 400 to an evaporated gas supply line GL at the front end of the heat exchanger 200, and can be introduced into the refrigerant of the heat exchanger 200.

[0061] On the other hand, if the ship is a liquefied gas-fueled ship, when the ship gains speed, the liquefied gas stored in the storage tank T can be used as fuel for the engine E, and in this case, the storage tank T may be a fuel tank that stores liquefied gas as fuel.

[0062] As means for supplying the liquefied gas fuel stored in the storage tank T to the engine E, there are provided a low-pressure pump (not shown) that discharges the liquefied gas fuel stored in the storage tank T from the storage tank T, a high-pressure pump 600 that pressurizes the liquefied gas fuel discharged from the storage tank T by the low-pressure pump so that it can be supplied at the pressure required by the engine E, and a high-pressure carburetor 700 that vaporizes the liquefied gas fuel compressed by the high-pressure pump 600 at the state required by the engine E.

[0063] Here, the engine E includes a first engine E1 which is a propulsion engine used for propelling the ship, and a second engine E2 which is a generator used for producing electric power to be supplied to onboard electric power consumers. In this embodiment, the propulsion engine E1 will be described as an ME-GI engine, as an example.

[0064] In this embodiment, the high-pressure pump 600 pumps the liquefied gas transferred from the storage tank T so that the liquefied gas supplied to the engine E satisfies the pressure conditions required by the first engine E1. Pressurization It is possible.

[0065] The gas fuel vaporized by the high-pressure vaporizer 700 may be supplied to the first engine E1 via a first fuel supply line FL1, or may be supplied to the second engine E2 via a second fuel supply line FL2 branched off from the first fuel supply line FL1 between the high-pressure vaporizer 700 and the first engine E1 and connected to the second engine E2.

[0066] A fuel heater 800 is provided in the second fuel supply line FL2 to adjust the temperature of the gas fuel supplied to the second engine E2 to a temperature condition required by the second engine E2.

[0067] In addition, a part or all of the evaporated gas compressed by the compressor 100 can also be supplied as fuel to the engine E via a third fuel supply line FL3 that connects the compressor 100 and the engine E.

[0068] In this embodiment, a third fuel supply line FL3 is provided to be connected to the second engine E2 downstream of the compressor 100, and the compressed evaporative gas compressed by the compressor 100 is supplied as fuel to the second engine E2.

[0069] That is, in this embodiment, the compressor 100 can compress the evaporative gas to a pressure required by the second engine E2.

[0070] However, the present invention is not limited thereto, and the compressor 100 can compress the fuel at, for example, the fuel supply pressure of the ship's main engine. When a DF engine is provided, the fuel can be compressed at 5.5 barg, when an X-DF engine is provided, and when an ME-GI engine is provided, the fuel can be compressed at 15 barg, and when an ME-GI engine is provided, the fuel can be compressed at 300 barg. The compressed evaporated gas can also be supplied as fuel to the ship's main engine (not shown). Also, evaporated gas that is not supplied to the fuel can be reliquefied.

[0071] According to ship regulations, the compressor that supplies fuel to the engine must be designed for redundancy in case of an emergency, and redundancy design means that when one compressor cannot be used due to breakdown, maintenance, etc., the other compressor can be used instead. Although one compressor is shown in the drawing, the compressor may be configured to include a main compressor and a redundancy compressor.

[0072] Of the evaporated gas compressed by the compressor 100, the remaining compressed evaporated gas that is not supplied as fuel to the engine E flows into the heat exchanger 200 via a re-liquefaction line RL.

[0073] Of the evaporated gas compressed by the compressor 100, the compressed evaporated gas that flows into the reliquefaction line RL is cooled in the heat exchanger 200. The evaporated gas that is compressed and reliquefied and the refrigerant compressed in the refrigerant compression unit become the hot stream of the heat exchanger, while the uncompressed evaporated gas and the refrigerant expanded and cooled in the refrigerant expansion device become the cold stream. In the heat exchanger 200, four streams are heat exchanged, and the hot stream is cooled by heat exchange with the cold stream.

[0074] In a liquefied gas fuel ship equipped with a high-pressure engine such as an ME-GI engine as a propulsion engine, for the purpose of cost reduction, instead of applying a high-pressure compressor as a liquefied gas fuel supply means, the liquefied gas is supplied to the high-pressure required by the ME-GI engine using a high-pressure pump 600. Ma in Pressurization and supply them.

[0075] This is a process in which liquefied gas is vaporized and then the gas is compressed under high pressure. Ma Compared to the cost of installing and operating a high-pressure compressor to compress liquefied gas at high pressure, Ma in Pressurization Equipped with a high pressure pump to liquefy gas Pressurization This is because it is more economical to vaporize the high pressure liquid after the evaporation.

[0076] However, with this method, when the ship speed is generated and liquefied gas fuel is supplied from the storage tank T to the first engine E1, the cold energy of the liquefied gas transferred from the storage tank T to the high-pressure vaporizer 700 via the first fuel supply line FL1 is wasted without being recovered at all.

[0077] Meanwhile, the nitrogen refrigerant in a gaseous state used as a refrigerant for liquefying the evaporated gas in the heat exchanger 200 is compressed in the refrigerant compression unit 500 and its temperature is increased by the compression process. According to the method shown in FIG. 1, the compressed nitrogen refrigerant is expanded in the refrigerant expansion device 510 to lower its temperature, and is therefore cooled in the heat exchanger 200 before the expansion process.

[0078] This embodiment is an improvement over the evaporative gas processing system shown in FIG. 1 so as to reduce power consumption.

[0079] Referring to FIG. 2, a first fuel supply line FL1 between the high-pressure pump 600 and the high-pressure carburetor 700 supplies fuel from the high-pressure pump 600 to the high-pressure carburetor 700. Pressurization The system further includes a cold heat recovery device 900 for recovering cold heat from the liquefied gas, and a refrigerant cooling line CL1 that branches off from a refrigerant circulation line CL connected to the heat exchanger 200 from the rear end of the refrigerant compression unit 500 and supplies a part or all of the nitrogen refrigerant compressed in the refrigerant compression unit 500 to the cold heat recovery device 900.

[0080] In the cold heat recovery device 900, the fuel flows along the first fuel supply line FL1 and is pumped by the high-pressure pump 600. Pressurization The liquefied gas is heated and the nitrogen refrigerant is cooled by heat exchange between the high-pressure liquid or supercritical liquefied gas and the nitrogen refrigerant in a gaseous state that flows along the refrigerant cooling line CL1 and is compressed in the refrigerant compression section 500.

[0081] The liquefied gas heated by heat exchange in the cold heat recovery device 900 is supplied to the high-pressure vaporizer 700 , and the nitrogen refrigerant cooled by heat exchange in the cold heat recovery device 900 is supplied to the refrigerant expansion device 510 .

[0082] In this manner, all or a part of the nitrogen refrigerant is sent to the cold energy recovery device 900 before being supplied to the heat exchanger 200 as a refrigerant for liquefying the compressed evaporated gas, and cooled by recovering the cold energy of the liquefied gas fuel at the rear end of the high-pressure pump 600. By providing the cold energy recovery device 900, the flow rate of the nitrogen refrigerant required for liquefying the evaporated gas can be reduced compared to a case in which the process of recovering the cold energy of the liquefied gas fuel is not included, and as a result, the power consumption of the refrigerant compression unit 500 can be reduced.

[0083] In addition, the system may further include a refrigerant flow rate adjusting means for controlling the flow rate of the nitrogen refrigerant compressed in the refrigerant compression unit 500 that is supplied to the refrigerant expansion device 510 after being cooled in the cold heat recovery device 900, i.e., the flow rate branched to the refrigerant cooling line CL1, and the flow rate of the nitrogen refrigerant compressed in the refrigerant compression unit 500 that is supplied to the refrigerant expansion device 510 after being cooled in the heat exchanger 200, i.e., the flow rate branched to the refrigerant circulation line CL.

[0084] The refrigerant flow rate adjusting means includes a first valve CV1 provided in the refrigerant circulation line CL between the refrigerant compression unit 500 and the heat exchanger 200 downstream of the point where the refrigerant cooling line CL1 branches off, a second valve CV2 provided in the refrigerant cooling line CL1 between the refrigerant compression unit 500 and the cold heat recovery device 900, and a controller 1000 that controls the opening / closing and opening amount of the first valve CV1 and the second valve CV2.

[0085] A low-temperature fuel is supplied to the cold heat recovery device 900 through a first fuel supply line FL1 between the high-pressure pump 600 and the cold heat recovery device 900. Pressurization A first temperature sensor TT1 for measuring the temperature of the liquefied gas and a high-temperature gas flowing toward the high-pressure vaporizer 700 after the cold energy recovery device 900 recovers the cold energy are provided in the first fuel supply line FL1 between the cold energy recovery device 900 and the high-pressure vaporizer 700. Pressurization The system may further include a second temperature sensor TT2 for measuring the temperature of the liquefied gas, a third temperature sensor TT3 for measuring the temperature of the high-temperature nitrogen refrigerant supplied to the cold heat recovery device 900, and a fourth temperature sensor TT4 for measuring the temperature of the low-temperature nitrogen refrigerant supplied to the refrigerant expansion device 510 after being cooled in the cold heat recovery device 900.

[0086] The temperature measurement values ​​measured by the first temperature sensing unit TT1, the second temperature sensing unit TT2, the third temperature sensing unit TT3 and the fourth temperature sensing unit TT4 are transmitted to the controller 1000, which receives the temperature measurement values ​​and transmits output values ​​based on the measurement values, i.e., valve opening / closing and opening rate indication values, to the first valve CV1 and the second valve CV2, thereby controlling the first valve CV1 and the second valve CV2.

[0087] In other words, the flow rate of the nitrogen refrigerant compressed in the refrigerant compression section 500 to be branched to the cold heat recovery device 900 is controlled based on the temperature measurement values ​​of the liquefied gas fuel at the front and rear ends of the cold heat recovery device 900 and / or the temperature measurement values ​​of the refrigerant at the front and rear ends of the cold heat recovery device 900.

[0088] Meanwhile, the flow rate of the nitrogen refrigerant circulating through the refrigerant circulation line CL to liquefy the evaporated gas in the heat exchanger 200 can be adjusted based on the temperature of the nitrogen refrigerant measured upstream of the refrigerant compression unit 500 .

[0089] This can be derived using the temperature measurements of the second temperature sensing unit TT2, the third temperature sensing unit TT3 and the fourth temperature sensing unit TT4.

[0090] In this manner, by gradually opening the second valve CV2, the flow rate of the refrigerant flowing into the cold heat recovery device 900 is increased, and at the same time, the total flow rate of the refrigerant circulating through the refrigerant cycle, i.e., the refrigerant circulation line CL, is gradually decreased, thereby reducing the load (power) of the refrigerant expansion device 510.

[0091] For example, a portion of the flow rate of the refrigerant circulating through the refrigerant cycle is temporarily stored in a separate refrigerant tank (not shown) depending on the temperature measurement value upstream of the pressure reducing device 300.

[0092] On the other hand, when the supply of LNG fuel decreases, i.e., when the flow rate of LNG flowing into the cold heat recovery device 900 decreases, the temperature measurement value of the fourth temperature sensing unit TT4 increases, and as a result, the second valve CV2 is gradually closed and the first valve CV1 is gradually opened.

[0093] Conversely, when the supply of LNG fuel increases, i.e., when the flow rate of LNG flowing into the cold heat recovery device 900 increases, the temperature measurement value of the second temperature sensing unit TT2 decreases, and as a result, at this time, the second valve CV2 is controlled to gradually open and the first valve CV1 is controlled to gradually close.

[0094] Similarly, at this time, the heat exchange performance of the cold energy recovery device 900 can be confirmed using the temperature measurement values ​​of the first temperature sensing unit TT1, the second temperature sensing unit TT2, the third temperature sensing unit TT3 and the fourth temperature sensing unit TT4, and it is possible to double-check that all recoverable cold energy is being recovered.

[0095] The present invention is not limited to the above-described embodiments, and it is obvious to a person having ordinary skill in the art to which the present invention pertains that the present invention can be implemented with various modifications or variations without departing from the technical gist of the present invention.

Claims

1. Liquefied gas storage tanks for storing liquefied gas; An engine that uses as fuel the liquefied gas stored in the liquefied gas storage tank or the evaporated gas generated by natural evaporation of the liquefied gas; a fuel supply means for supplying the liquefied gas as fuel for the engine; a compressor for compressing the evaporative gas to a pressure required by the engine; a heat exchanger for cooling the remaining evaporated gas that is not supplied to the engine among the evaporated gas compressed by the compressor; a refrigerant circulation line through which the refrigerant supplied to the heat exchanger circulates; A refrigerant compression section that is provided in the refrigerant circulation line and compresses the refrigerant discharged from the heat exchanger after heat exchange in the heat exchanger; and a cold energy recovery device that recovers cold energy from the liquefied gas supplied as fuel for the engine and cools the refrigerant compressed by the refrigerant compression unit; The refrigerant compressed in the refrigerant compression unit is cooled in the heat exchanger by heat exchange with uncompressed evaporated gas discharged from the liquefied gas storage tank and before being compressed by the compressor, a refrigerant cooling line that branches the refrigerant compressed in the refrigerant compression unit from the refrigerant circulation line before being supplied to the heat exchanger, and supplies the branched refrigerant to the cold heat recovery device; and The energy-saving liquefied gas fueled ship further includes a flow rate adjusting means for adjusting a flow rate of the refrigerant branched from the refrigerant circulation line to the refrigerant cooling line.

2. The fuel supply means includes: a high pressure pump for compressing the liquefied gas to a pressure required by the engine; and a high-pressure vaporizer for vaporizing the liquefied gas compressed by the high-pressure pump; The energy-saving liquefied gas fueled ship according to claim 1 , wherein the cold heat recovery device is provided between the high-pressure pump and the high-pressure vaporizer.

3. a refrigerant expansion device provided in the refrigerant circulation line for expanding and cooling the refrigerant supplied to the heat exchanger; The flow rate adjusting means is a first valve provided in the refrigerant circulation line for controlling a flow path so that the refrigerant compressed in the refrigerant compression unit is cooled through the heat exchanger and then introduced into the refrigerant expansion device; and 2. The energy-saving liquefied gas-fueled ship as described in claim 1, further comprising: a second valve provided in the refrigerant circulation line for controlling a flow path so that the refrigerant compressed in the refrigerant compression section is cooled through the cold heat recovery device and then introduced into the refrigerant expansion device.

4. The flow rate adjusting means is a first temperature sensor for measuring a temperature of the liquefied gas supplied to the cold heat recovery device; A second temperature sensor for measuring the temperature of the liquefied gas discharged from the cold heat recovery device; and 4. The energy-saving liquefied gas fueled ship according to claim 3, further comprising: a control unit that controls opening / closing and an opening degree of the second valve using the temperature measurements of the first temperature sensing unit and the second temperature sensing unit.

5. The flow rate adjusting means is a third temperature sensor for measuring a temperature of the refrigerant supplied to the cold heat recovery device; A fourth temperature sensor for measuring the temperature of the refrigerant discharged from the cold heat recovery device; and 5. The energy-saving liquefied gas fueled ship according to claim 3 or 4, further comprising: a control unit that controls the opening / closing and the opening degree of the second valve using the temperature measurement values ​​of the third temperature sensing unit and the fourth temperature sensing unit.

6. In the heat exchanger, 4. The energy-saving liquefied gas-fueled ship according to claim 3, wherein four flows are heat exchanged, including the compressed gas compressed in the compressor, the refrigerant expanded and cooled in the refrigerant expansion device, the uncompressed evaporated gas, and the refrigerant compressed in the refrigerant compression section.

7. The flow rate adjusting means is 4. The energy-saving liquefied gas-fueled ship according to claim 3, further comprising: a control unit that measures a temperature of the refrigerant supplied to the refrigerant compression unit and adjusts a total flow rate of the refrigerant circulating through the refrigerant circulation line.

8. A method for treating evaporated gas in a liquefied gas fueled ship that uses liquefied gas stored in a liquefied gas storage tank or evaporated gas generated by natural evaporation of the liquefied gas as fuel for an engine, comprising the steps of: The evaporative gas is compressed to a pressure required by the engine and supplied to the engine, and the remaining evaporative gas not supplied to the engine is re-liquefied and collected in the liquefied gas storage tank, In order to re-liquefy the compressed evaporated gas, a heat exchanger is used to exchange heat between the compressed evaporated gas, the uncompressed evaporated gas discharged from the liquefied gas storage tank, and the refrigerant circulating in a refrigerant circulation line; compressing a refrigerant heated by cooling the compressed evaporative gas, and cooling the compressed refrigerant by at least one of heat exchange with a liquefied gas supplied from the liquefied gas storage tank to the engine and heat exchange with the uncompressed evaporative gas; A method for treating evaporated gas in a liquefied gas fuel ship, comprising adjusting a flow rate of the compressed refrigerant that is subjected to heat exchange with the liquefied gas and the uncompressed evaporated gas.

9. 9. The method for treating evaporated gas in a liquefied gas fueled ship according to claim 8, wherein the remaining refrigerant, excluding the refrigerant that exchanges heat with the liquefied gas, out of the compressed refrigerant, is supplied to the heat exchanger and cooled.

10. The flow rate of the refrigerant exchanging heat with the liquefied gas is The method for treating evaporated gas in a liquefied gas fuelled ship according to claim 9, wherein control is performed based on a measured value of the temperature of the liquefied gas before heat exchange with the refrigerant and a measured value of the temperature of the liquefied gas after heat exchange with the refrigerant.

11. The flow rate of the refrigerant exchanging heat with the liquefied gas is 11. An evaporative gas treatment method for a liquefied gas fueled ship as described in claim 9 or 10, wherein control is performed based on a measured value of the temperature of the refrigerant before heat exchange with the liquefied gas and a measured value of the temperature of the refrigerant after heat exchange with the liquefied gas.

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