Multi-loop power generation system and method using cold energy of liquefied gas

Abstract

The present invention relates to a multi-loop power generation system and method using cold energy of liquefied gas, the system and the method using multiple loops to recover waste cold energy of liquefied gas and generate power. The multi-loop power generation system using cold energy of liquefied gas, according to the present invention, comprises: a main refrigerant turbine-generator which drives a turbine with a main refrigerant stream so as to generate power; a main refrigerant branch part which causes the main refrigerant stream that expands while the turbine is driven, to branch off into at least two main refrigerant streams including a first main refrigerant stream and a second main refrigerant stream; a first main refrigerant economizer which allows heat exchange between the first main refrigerant stream and the liquefied gas so that the cold energy of the liquefied gas is recovered; an auxiliary refrigerant turbine-generator which drives the turbine with an auxiliary refrigerant stream so as to generate power; an auxiliary refrigerant branch part which causes the auxiliary refrigerant stream that expands while the turbine is driven, to branch off into at least two auxiliary refrigerant streams including a first auxiliary refrigerant stream and a second auxiliary refrigerant stream; and a first auxiliary refrigerant economizer which allows heat exchange between the first auxiliary refrigerant stream and the liquefied gas from which cold energy was recovered in the first main refrigerant economizer, so that the residual cold energy of the liquefied gas is recovered.

Description

Multi-loop power generation system and method using cold energy from liquefied gas

[0001] The present invention relates to a multi-loop power generation system and method using the cold heat of liquefied gas, which recovers the waste cold heat of liquefied gas and generates power using a multi-loop.

[0002] Natural gas is liquefied at extremely low temperatures at its production site, becoming liquefied natural gas (LNG). This is then transported long distances to its intended destination. Natural gas is liquefied by cooling it to the cryogenic temperature of approximately -163°C at atmospheric pressure, creating LNG. Liquid natural gas, or LNG, has a volume roughly 1 / 600th that of gaseous natural gas, making it ideal for storage and transportation.

[0003] Natural gas stored in a liquid state is regasified using a regasification facility to produce natural gas in a gaseous state, and is supplied to each demander in a gaseous state.

[0004] Basically, the regasification facility is composed of a high-pressure pump that compresses natural gas, i.e. LNG, in a liquid state stored in a storage tank to the pressure required by the demander, and a vaporizer that vaporizes the high-pressure LNG compressed by the high-pressure pump into natural gas.

[0005] Seawater, which is readily available, is primarily used as a heat source for vaporizing LNG in vaporizers. The low-temperature seawater, which recovers its cold energy through direct or indirect heat exchange with the LNG, is then discharged back into the sea.

[0006] The energy required to transform liquid LNG into gaseous natural gas reaches 200 kcal per kg. A significant amount of energy is wasted in the process of vaporizing liquid natural gas, leaving it largely unused and being dumped into the ocean by seawater.

[0007] These problems occur equally even if the regasification target is replaced with another liquefied gas, such as liquefied hydrogen or liquefied ammonia.

[0008] Cold thermal power generation is one of the technologies that effectively utilizes the cold energy of LNG. A typical commercial cold thermal power generation system operates in a closed loop, where high-temperature, high-pressure gaseous refrigerant is reduced to low pressure through an expander, which then drives a turbine to generate electricity. The low-pressure refrigerant is liquefied through heat exchange with LNG, pressurized using a pump, and vaporized through heat exchange with seawater to create a high-temperature, high-pressure gas. This high-temperature, high-pressure gaseous refrigerant is then circulated back to the expander, a process that repeats.

[0009] A basic LNG cold-heat power generation system is composed of a vaporizer that vaporizes LNG by exchanging heat with a refrigerant, a pump that pressurizes the refrigerant discharged from the vaporizer after heat exchange with the LNG, a heat exchanger that heat-exchanges the refrigerant pressurized by the pump with a heat source, a turbine that expands the refrigerant discharged from the heat exchanger after heat exchange, and a generator that generates electricity from the expansion work generated by driving the turbine.

[0010] Here, the refrigerant circulates through a closed cycle consisting of a vaporizer, pump, heat exchanger, and turbine, undergoing a phase change in which it condenses while exchanging heat with LNG in the vaporizer and vaporizes while exchanging heat with seawater in the heat exchanger.

[0011] The conventional LNG cold power generation system, which consists of a single cycle, has the disadvantage of low power generation efficiency due to the relatively large loss caused by latent heat as the refrigerant undergoes phase change, and the system becomes large due to the low density of the working fluid in the low-pressure section.

[0012] In addition, the LNG cold power generation system, which is composed of a conventional single cycle, has to control the operating pressure and temperature of the cycle so that the refrigerant can be completely condensed in the vaporizer and completely vaporized in the heat exchanger, and the temperature of the refrigerant must be kept as low as possible to maximize the expansion ratio while maintaining a temperature above the freezing point, making it difficult to control and limiting improvements in efficiency.

[0013] Accordingly, the present invention aims to achieve the above-described object by providing a multi-loop power generation system and method using the cold energy of liquefied gas, which improves the power generation efficiency of a conventional liquefied gas cold energy power generation system composed of a single cycle.

[0014] The challenges addressed by the present invention are not limited to those mentioned above. Other technical challenges not mentioned will be readily apparent to those skilled in the art, as described below.

[0015] According to an aspect of the present invention for achieving the above-described object, there is provided a main refrigerant turbine-generator for generating electric power by driving a turbine with a main refrigerant stream; and a main refrigerant branch unit for branching an expanded main refrigerant stream while driving the turbine into at least two or more main refrigerant streams including a first main refrigerant stream and a second main refrigerant stream; a first main refrigerant economizer for heat-exchanging the first main refrigerant stream with a liquefied gas to recover cold heat of the liquefied gas; an auxiliary refrigerant turbine-generator for generating electric power by driving a turbine with an auxiliary refrigerant stream; and an auxiliary refrigerant branch unit for branching an expanded auxiliary refrigerant stream while driving the turbine into at least two or more auxiliary refrigerant streams including a first auxiliary refrigerant stream and a second auxiliary refrigerant stream. A multi-loop power generation system utilizing the cold heat of liquefied gas is provided, including a first auxiliary refrigerant economizer that recovers the remaining cold heat of the liquefied gas by heat-exchanging the first auxiliary refrigerant stream and the liquefied gas from which the cold heat has been recovered in the first main refrigerant economizer.

[0016] Preferably, the system may further include a second main refrigerant economizer that heat-exchanges the first main refrigerant stream cooled in the first main refrigerant economizer with the second main refrigerant stream branched from the main refrigerant branch to cool the second main refrigerant stream; and a main refrigerant heater that heats the first main refrigerant stream and the second main refrigerant stream discharged after heat-exchange from the second main refrigerant economizer and recirculates them to the main refrigerant turbine-generator.

[0017] Preferably, at least one main refrigerant heater is provided, and when two or more main refrigerant heaters are provided, the main refrigerant heaters may be provided in series or in parallel.

[0018] Preferably, the system may further include a second auxiliary refrigerant economizer that heat-exchanges the first auxiliary refrigerant stream cooled in the first auxiliary refrigerant economizer with the second auxiliary refrigerant stream branched from the auxiliary refrigerant branch to cool the second auxiliary refrigerant stream; and an auxiliary refrigerant heater that heats the first auxiliary refrigerant stream and the second auxiliary refrigerant stream discharged after heat-exchange from the second auxiliary refrigerant economizer and recirculates them to the auxiliary refrigerant turbine-generator.

[0019] Preferably, at least one auxiliary refrigerant heater is provided, and when two or more auxiliary refrigerant heaters are provided, the auxiliary refrigerant heaters may be provided in series or in parallel.

[0020] Preferably, the first primary refrigerant economizer and the first secondary refrigerant economizer may be one or more multi-stream heat exchangers.

[0021] Preferably, the system may further include a liquefied gas heater that heats the liquefied gas recovered from the residual refrigerant heat in the first auxiliary refrigerant economizer and supplies the heat to a gas demand source.

[0022] Preferably, the first primary refrigerant economizer and the first auxiliary refrigerant economizer may be a plate-type heat exchanger, a plate-fin type heat exchanger, a printed circuit board type heat exchanger, an aluminum bonded heat exchanger, or a coil wound type heat exchanger.

[0023] Preferably, the main refrigerant stream and the auxiliary refrigerant stream may be a single refrigerant selected from the group consisting of hydrogen, helium, nitrogen, oxygen, neon, argon, carbon compounds having 5 or fewer carbon atoms, and freon refrigerants, or a mixed refrigerant of two or more of these.

[0024] Preferably, the primary refrigerant stream and the auxiliary refrigerant stream can be maintained above a critical pressure while circulating the primary refrigerant cycle and the auxiliary refrigerant cycle, respectively.

[0025] According to another aspect of the present invention for achieving the above-described object, a multi-loop power generation method using cold heat of liquefied gas is provided, comprising: a primary refrigerant power generation step for generating electric power by driving a turbine with a primary refrigerant stream; a primary refrigerant branching step for branching an expanded primary refrigerant stream while driving the turbine into at least two primary refrigerant streams including a first primary refrigerant stream and a second primary refrigerant stream; a first cold heat recovery step for recovering cold heat of the liquefied gas by heat-exchanging the first primary refrigerant stream with the liquefied gas; an auxiliary refrigerant power generation step for generating electric power by driving the turbine with an auxiliary refrigerant stream; an auxiliary refrigerant branching step for branching an expanded secondary refrigerant stream while driving the turbine into at least two auxiliary refrigerant streams including a first auxiliary refrigerant stream and a second auxiliary refrigerant stream; and a second cold heat recovery step for recovering residual cold heat of the liquefied gas by heat-exchanging the first secondary refrigerant stream with the liquefied gas from which cold heat has been recovered in the first cold heat recovery step.

[0026] Preferably, the method may further include a primary refrigerant heat recovery step of heat-exchanging the first primary refrigerant stream cooled in the first cold heat recovery step with the second primary refrigerant stream branched in the primary refrigerant branching step to cool the second primary refrigerant stream; and a primary refrigerant heating step of heating the first primary refrigerant stream and the second primary refrigerant stream discharged after heat-exchange from the primary refrigerant cold heat recovery step and recirculating them to the primary refrigerant power generation step.

[0027] Preferably, the method may further include an auxiliary refrigerant cold heat recovery step of heat-exchanging the first auxiliary refrigerant stream cooled in the second cold heat recovery step with the second auxiliary refrigerant stream branched in the auxiliary refrigerant branching step to cool the second auxiliary refrigerant stream; and an auxiliary refrigerant heating step of heating the first main refrigerant stream and the second main refrigerant stream discharged after heat-exchange from the auxiliary refrigerant cold heat recovery step and recirculating them to the auxiliary refrigerant power generation step.

[0028] Preferably, the second cold heat recovery step may further include a liquefied gas heating step for heating the liquefied gas from which the remaining cold heat has been recovered and supplying the heated gas to a gas demand source.

[0029] The multi-loop power generation system and method using the cold energy of liquefied gas according to the present invention can produce clean energy using the ultra-low temperature cold energy that is wasted without consuming fuel or causing an oxidation reaction of the fuel.

[0030] In addition, by applying multiple loops, the cold energy of the liquefied gas is recovered over multiple cycles, thereby further improving energy production efficiency compared to a system that applies a single loop.

[0031] In particular, since the cold heat of the liquefied gas is recovered over two or more stages using two or more refrigerant cycles, the overall power generation efficiency can be further improved compared to the case where the cold heat of the liquefied gas is recovered using one refrigerant cycle.

[0032] In addition, by branching the expanded refrigerant stream from the turbine-generator, cooling some of it by recovering the cold heat of the liquefied gas in a heat exchanger and then compressing it, and cooling the remaining part by recovering the remaining cold heat of the compressed refrigerant stream after recovering the cold heat of the liquefied gas and then compressing it, the refrigerant before compression can be cooled using only the cold heat of the liquefied gas without having a separate cooling cycle.

[0033] In addition, by cooling the refrigerant introduced into the compressor, the energy consumed for compression can be reduced, the expansion ratio can be maximized, the system can be optimized, and the cold heat utilization efficiency, i.e., the power generation efficiency, of the cold heat power generation system can be improved.

[0034] In addition, since the refrigerant is maintained in a supercritical state while circulating through the cycle, the system can be made smaller compared to equipment used in conventional cold and heat power generation systems that involve phase change of the refrigerant based on the same capacity.

[0035] In addition, if it is replaced with another refrigerant that is appropriate for the operating temperature, it is economical because it can be replaced with a pump that compresses the liquid phase instead of a compressor that compresses the gas phase as a compression means that compresses the refrigerant that circulates the refrigerant cycle, and the installation and operation costs are much lower.

[0036] In addition, since refrigerants that are easily available at the site where the present invention is applied, such as nitrogen and evaporated gas, can be applied, the operating costs (OPEX) required for refrigerant replenishment, etc. can also be reduced.

[0037] The effects of the present invention are not limited to those described above. Other effects not mentioned will be readily apparent to those skilled in the art from this specification and the accompanying drawings.

[0038] FIG. 1 is a drawing schematically illustrating the basic configuration of a multi-loop power generation system using the cold energy of liquefied gas according to one embodiment of the present invention.

[0039] FIG. 2 is a schematic diagram illustrating a comparative example of a multi-loop power generation system using the cold energy of liquefied gas according to one embodiment of the present invention.

[0040] FIG. 3 is a PT diagram for explaining the phases while the refrigerant circulates through a cycle according to one embodiment of the present invention.

[0041] In order to fully understand the operational advantages of the present invention and the objects achieved by the embodiments 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.

[0042] Hereinafter, the configuration and operation of preferred embodiments of the present invention will be described in detail with reference to the attached drawings. When adding reference numerals to components in each drawing, it should be noted that, as much as possible, identical components are indicated with the same numerals even if they are shown in different drawings. In addition, the following embodiments may be modified in various different forms, and the scope of the present invention is not limited to the following embodiments.

[0043] In the embodiments of the present invention described below, the liquefied gas may be a liquefied gas that can be transported by liquefying gas at a low temperature, and may be, for example, a hydrocarbon-based liquefied gas such as LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), liquefied ethylene gas, or liquefied propylene gas. Alternatively, it may be a non-hydrocarbon-based liquefied gas such as liquefied carbon dioxide, liquefied hydrogen, or liquefied ammonia.

[0044] In the embodiments of the present invention described below, the liquefied gas will be described as liquefied hydrogen (LH2) as an example.

[0045] In addition, the multi-loop power generation system and method using the cold heat of liquefied gas according to the embodiments of the present invention described below can be applied on land where a heat exchanger for recovering the cold heat of liquefied gas is provided, such as a liquefied gas introduction terminal, a liquefied gas thermal power generation plant, a liquefied gas filling station, and a liquefied gas fuel-propelled mobility.

[0046] In explaining the embodiments of the present invention described below, the present system and method will be described by way of example as being equipped in a liquefied gas introduction terminal.

[0047] In addition, the power generation system and method using cold energy from liquefied gas according to embodiments of the present invention described below can also be applied to ships or oceans. Here, the term "ship" may include all types of ships equipped with LNG regasification facilities capable of regasifying LNG and supplying it to gas demanders, including ships with self-propulsion capabilities such as LNG RVs (Regasification Vessels) and liquefied gas fuel-propelled ships, as well as offshore structures floating on the sea such as LNG FSRUs (Floating Storage Regasification Units).

[0048]

[0049] Hereinafter, a multi-loop power generation system and method using liquefied gas cooling according to embodiments of the present invention will be described with reference to the attached drawings.

[0050] First, referring to FIG. 1, a multi-loop power generation system using cold heat from liquefied gas according to the present embodiment may include a main refrigerant cycle that recovers cold heat from liquefied hydrogen to generate power, and an auxiliary refrigerant cycle that is provided downstream of the main refrigerant cycle based on the flow direction of liquefied hydrogen and recovers residual cold heat from liquefied hydrogen, the cold heat of which has been recovered in the main refrigerant cycle, while the auxiliary refrigerant circulates to generate power.

[0051] In this embodiment, the multi-loop power generation system is described as a two-stage loop cycle in which two loop cycles, a main refrigerant cycle and an auxiliary refrigerant cycle, are connected in series based on the flow direction of liquefied hydrogen, but is not limited thereto.

[0052] That is, the multi-loop power generation system according to the present invention may be equipped with two or more auxiliary refrigerant cycles, including two or more auxiliary refrigerant cycles, which are sequentially connected downstream of the main refrigerant cycle, to form a two-stage or more multi-loop cycle.

[0053] According to a two-stage loop power generation system in which two loop cycles, such as a main refrigerant cycle and an auxiliary refrigerant cycle, are sequentially connected as in this embodiment, in the first stage, the main refrigerant circulating in the main refrigerant cycle primarily recovers the cold heat of liquefied hydrogen to generate power, and in the second stage, the auxiliary refrigerant circulating in the auxiliary refrigerant cycle primarily recovers the remaining cold heat of liquefied hydrogen from which the cold heat was first recovered in the main refrigerant cycle to generate power.

[0054] Meanwhile, in the case of a three-stage loop power generation system in which three loop cycles, including a main refrigerant cycle, a first auxiliary refrigerant cycle, and a second auxiliary refrigerant cycle, are sequentially connected, in the first stage, the main refrigerant circulating in the main refrigerant cycle primarily recovers the cold heat of the liquid hydrogen to generate power, in the second stage, the first auxiliary refrigerant circulating in the first auxiliary refrigerant cycle primarily recovers the remaining cold heat of the liquid hydrogen from which the cold heat was first recovered in the main refrigerant cycle to generate power, and in the third stage, the second auxiliary refrigerant circulating in the second auxiliary refrigerant cycle further recovers the remaining cold heat of the liquid hydrogen from which the cold heat was secondarily recovered in the first auxiliary refrigerant cycle to generate power.

[0055] Each sequentially connected loop cycle may include a turbine-generator (110, 210) that generates electricity by driving a turbine using a refrigerant circulating in each loop cycle, an economizer (130, 140b, 140c, 140d, 140e, 140f, 140g, 230, 240b) that cools the refrigerant expanded in the turbine-generator with the cold heat of liquefied hydrogen, a compressor (150a, 150b, 150c, 150d, 150e, 150f, 150g, 250a, 250b) that compresses the refrigerant cooled in the economizer, and a heater (170, 270) that heats the refrigerant compressed in the compressor. The refrigerant heated in the heater may be recycled back to the turbine-generator.

[0056] Each loop cycle constituting the multi-loop power generation system according to the present embodiment can operate as a Brayton cycle.

[0057] Each loop cycle may include one or more economizers that recover the cooling heat of the liquefied hydrogen or the self-cooling heat of the refrigerant circulating in each loop cycle to cool the refrigerant expanded in the turbine-generator. The process of recovering the self-cooling heat of the refrigerant in the economizer may be performed in one or more stages.

[0058] Each loop cycle is equipped with N economizers, which can recover the cold heat or residual cold heat of liquefied hydrogen across N stages. In addition, a compressor corresponding to each economizer can be equipped one-to-one at the rear of each of the N economizers.

[0059] In this embodiment, the economizer may be a plate type heat exchanger, a plate-fin type heat exchanger, a printed circuit heat exchanger (PCHE), a brazed aluminum heat exchanger (BAHX), or a coil-wound heat exchanger (CWHX).

[0060] The drawings attached to this specification illustrate an example in which multiple economizers are provided as individual heat exchangers, but at least two of the multiple economizers may be provided as a multi-stream heat exchanger as a single cold box.

[0061] Additionally, multiple economizers may be provided as one cold box, such as the economizers of each refrigerant cycle, for example, the main refrigerant economizers of the main refrigerant cycle, or the economizers of different cycles, for example, at least one main refrigerant economizer among the main refrigerant economizers of the main refrigerant cycle and at least one auxiliary refrigerant economizer among the auxiliary refrigerant economizers of the auxiliary refrigerant cycle, may be provided as one cold box.

[0062] Meanwhile, each loop cycle may further include a branching portion (120, 220) that branches the refrigerant circulating in the cycle into N refrigerant streams upstream of the economizer, and a joining portion (160, 260) that joins the N refrigerant streams back into one stream downstream of each economizer.

[0063] The branch section of this embodiment may be provided downstream of the turbine-generator and upstream of the economizer, or may be provided upstream of the turbine-generator.

[0064] That is, the branch section may distribute and supply the expanded refrigerant stream from one or more turbine-generators to each economizer, or may distribute the refrigerant stream from the branch section into N refrigerant streams and then supply them to each of N turbine-generators. If the branch section is installed upstream of the turbine-generator, N turbine-generators may be installed in one-to-one correspondence with N economizers.

[0065] The drawing illustrates an example in which a branch (120, 220) of each loop cycle is provided downstream of a turbine-generator (110, 210) to branch the refrigerant stream expanded from one turbine-generator (110, 210) into N refrigerant streams and supply them to each economizer. This embodiment is described based on this.

[0066] However, the refrigerant branch (120, 220) of each loop cycle may be provided upstream of the turbine-generator (110, 210) of each loop cycle, and may be configured such that the refrigerant streams are branched into N refrigerant streams at the refrigerant branch (120, 220), and each refrigerant stream is divided and supplied to N turbine-generators, expanded respectively, and then divided and supplied to N economizers respectively.

[0067] In this embodiment, the branch section (120, 220) may mean a point where the line through which the expanded refrigerant stream flows in the turbine-generator (110, 210) is divided into N. The branch section (120, 220) may be equipped with a distributor or valve.

[0068] Meanwhile, the joining portion (160, 260) of the present embodiment is not limited to joining N refrigerant streams into one refrigerant stream, and the joining portion may join the same number of refrigerant streams as the number of heaters (170, 270) that heat the N streams. For example, if two heaters are provided in parallel, the joining portion may join N refrigerant streams into two refrigerant streams and supply them to the two heaters respectively.

[0069] As the temperature of a fluid decreases, its density increases, thus reducing the energy consumed for compression. According to the present embodiment, the refrigerant stream discharged from the turbine-generator is divided into two or more streams at a branch point, supplied to each economizer, and cooled and then compressed in each economizer, thereby reducing the energy consumed for compression.

[0070] Meanwhile, the higher the temperature of the fluid introduced into the turbine, the more energy generated by expansion. According to the present embodiment, by providing a heater to heat the refrigerant stream compressed by the compressor before supplying it to the turbine-generator, the energy generated by expansion, i.e., the amount of power generated, can be increased.

[0071] In Fig. 1, the main refrigerant cycle according to the present embodiment is illustrated as an example in which it is provided in seven stages including seven economizers (130, 140b, 140c, 140d, 140e, 140f, 140g), and the auxiliary refrigerant cycle is provided in two stages including two economizers (230, 240b). However, the number of stages is not limited thereto.

[0072] Additionally, in the present embodiments, the primary and secondary refrigerants may be fluids of different substances or the same substance. In describing the present embodiments, the terms "primary" and "auxiliary" are merely used to distinguish the primary and secondary refrigerants, and do not imply that one refrigerant is primarily used and the other is used as an auxiliary refrigerant.

[0073] The operating pressure of the primary refrigerant cycle of the present embodiment may be 5 barg or higher or the critical pressure of the primary refrigerant circulating in the primary refrigerant cycle. In addition, the operating temperatures of the primary refrigerant cycle and the auxiliary refrigerant cycle of the present embodiment may be -60°C or lower or 0°C or lower.

[0074] The main refrigerant and auxiliary refrigerant of the present embodiment may each be a single refrigerant selected from the group consisting of hydrogen, helium, nitrogen, oxygen, neon, argon, carbon compounds having 5 or fewer carbon atoms, and freon refrigerants, or a mixed refrigerant of two or more of these.

[0075] Additionally, in this embodiment, the primary refrigerant and the secondary refrigerant may be substances that do not reach the freezing point even at the point where the lowest temperature is reached during each cycle.

[0076] Additionally, the primary refrigerant may be a liquefied gas, i.e., in this embodiment, a vaporized gas of liquefied hydrogen or a mixture containing a vaporized gas of liquefied hydrogen, and the secondary refrigerant may be a single or mixture having a boiling point higher than that of the primary refrigerant.

[0077] When nitrogen is used as a primary or auxiliary refrigerant, the freezing point of nitrogen is an extremely low temperature of approximately -210°C at normal pressure, and the storage temperature of liquid hydrogen is below the liquid point of liquid hydrogen, that is, approximately -253°C, so nitrogen can be used as a refrigerant that does not reach the freezing point while circulating the refrigerant cycle while recovering the cold heat of liquid hydrogen.

[0078] Additionally, nitrogen is an inert gas that is easily obtained from the air, is cheap to purchase, safe, and does not contain carbon, so it can be vented into the air, which has the advantage of not requiring a flare device.

[0079] In any case, when the multi-loop power generation system according to the present embodiment is applied on land equipped with liquefied gas regasification facilities such as liquefied gas terminals, or when it is applied at sea equipped with liquefied gas regasification facilities such as FSRUs, equipment for generating and supplying nitrogen is provided for the purpose of purging or maintenance of the regasification facilities.

[0080] That is, if the working fluid of the power generation system according to this embodiment is used as nitrogen, the working fluid can be easily supplied even without a separate nitrogen generation / supply device, and installation and operating costs can be reduced by using the existing equipment.

[0081] Meanwhile, in the case of using the Brayton Cycle (Supercritical CO2Brayton Cycle) that uses supercritical carbon dioxide as a working fluid, the freezing point of carbon dioxide used as a refrigerant is approximately -78.5℃ at normal pressure, so the problem of freezing may occur during the process of recovering the cold heat of liquefied hydrogen at approximately -253℃, making it unsuitable for recovering cold heat.

[0082] In addition, carbon dioxide is a greenhouse gas that causes environmental pollution, is an acid gas that causes equipment corrosion, and is dangerous to the human body when exposed to a certain concentration or higher for a long period of time. In addition, in order to maintain carbon dioxide at a pressure higher than the critical pressure, the operating pressure of the system must be maintained in a high-pressure environment of 200 barg or more, making it difficult to apply in practice.

[0083] In this embodiment, the boil-off gas (BOG; Boil-Off Gas), i.e., hydrogen (H2), which is generated by natural vaporization of liquefied hydrogen, the liquefied gas of this embodiment, is used as a single refrigerant, or a mixed refrigerant of hydrogen and nitrogen is used, as an example, and the boil-off gas of LNG, i.e., methane (CH4), is used as a single refrigerant, as an auxiliary refrigerant, as an example, will be explained.

[0084] By using the evaporation gas of the liquefied gas, which is the target of cold heat recovery, as the main refrigerant, not only can the cold heat of vaporization of the liquefied gas be recovered without reaching the freezing point while the main refrigerant circulates through the main refrigerant cycle (100), but also the cost of processing the evaporation gas can be reduced and there is the advantage of easy supply.

[0085] In addition, the above-described embodiment was explained using the example of being equipped in a liquefied hydrogen terminal. If the liquefied hydrogen terminal is built near an LNG terminal and existing infrastructure such as a city gas pipeline network can be utilized as is, using LNG boil-off gas as an auxiliary refrigerant not only facilitates supply and demand but also has the effect of efficiently processing LNG boil-off gas.

[0086] Referring to FIG. 1, the primary refrigerant cycle according to the present embodiment may include at least one of a primary refrigerant turbine-generator (110) that generates power by driving a turbine using a primary refrigerant stream (RL), a primary refrigerant branching unit (120) that branches the primary refrigerant stream (RL) expanded in the primary refrigerant turbine-generator (110) into a plurality of streams, a primary refrigerant economizer that cools each primary refrigerant stream, a primary refrigerant compressor that compresses each primary refrigerant stream cooled in the primary refrigerant economizer, a primary refrigerant joining unit (160) that joins the primary refrigerant streams compressed in the primary refrigerant compressor into one stream, and a primary refrigerant heater (170) that heats the primary refrigerant streams (RL) joined in the primary refrigerant joining unit (160).

[0087] Since this embodiment is described based on the main refrigerant cycle having 7 stages, the main refrigerant stream (RL) expanded in the main refrigerant turbine-generator (110) may be branched into 7 streams including a first main refrigerant stream (RL1), a second main refrigerant stream (RL2), a third main refrigerant stream (RL3), a fourth main refrigerant stream (RL4), a fifth main refrigerant stream (RL5), a sixth main refrigerant stream (RL6), and a seventh main refrigerant stream (RL7) in the main refrigerant branch section (120).

[0088] The first main refrigerant stream (RL1), the second main refrigerant stream (RL2), the third main refrigerant stream (RL3), the fourth main refrigerant stream (RL4), the fifth main refrigerant stream (RL5), the sixth main refrigerant stream (RL6), and the seventh main refrigerant stream (RL7) are names used to distinguish and describe streams that are divided by branching the main refrigerant stream (RL). Each of the branched main refrigerant streams may be the same material that is compressed in different compressors after branching off from the main refrigerant branching section (120) and joins into one main refrigerant stream (RL) upstream of the main refrigerant heater (170) to circulate the main refrigerant cycle (100).

[0089] Since this embodiment is described based on the main refrigerant cycle having 7 stages, the main refrigerant economizer according to this embodiment includes a first main refrigerant economizer (130) that cools the first main refrigerant stream (RL1), a second main refrigerant economizer (140b) that cools the second main refrigerant stream (RL2), a third main refrigerant economizer (140c) that cools the third main refrigerant stream (RL3), a fourth main refrigerant economizer (140d) that cools the fourth main refrigerant stream (RL4), a fifth main refrigerant economizer (140e) that cools the fifth main refrigerant stream (RL5), a sixth main refrigerant economizer (140f) that cools the sixth main refrigerant stream (RL6), and a seventh main refrigerant economizer (140f) that cools the seventh main refrigerant stream (RL7). It can include 7 main refrigerant economizers including economizer (140g).

[0090] In addition, downstream of the seven primary refrigerant economizers, seven primary refrigerant compressors corresponding to each primary refrigerant economizer are provided, and the primary refrigerant compressors of the present embodiment include a first primary refrigerant compressor (150a) that compresses a first primary refrigerant stream (RL1) cooled in a first primary refrigerant economizer (130), a second primary refrigerant compressor (150b) that compresses a second primary refrigerant stream (RL2) cooled in a second primary refrigerant economizer (140b), a third primary refrigerant compressor (150c) that compresses a third primary refrigerant stream (RL3) cooled in a third primary refrigerant economizer (140c), a fourth primary refrigerant compressor (150d) that compresses a fourth primary refrigerant stream (RL4) cooled in a fourth primary refrigerant economizer (140d), and a fifth primary refrigerant compressor (150a) that compresses a first primary refrigerant stream (RL1) cooled in a first primary refrigerant economizer (130), a second primary refrigerant compressor (150b) that compresses a second primary refrigerant stream (RL2) cooled in a second primary refrigerant economizer (140b), a fourth primary refrigerant compressor (150d) that compresses a fourth primary refrigerant stream (RL4) cooled in a fourth primary refrigerant economizer (140d). It may include seven main refrigerant compressors, including a fifth main refrigerant compressor (150e) that compresses a fifth main refrigerant stream (RL5) cooled in an economizer (140e), a sixth main refrigerant compressor (150f) that compresses a sixth main refrigerant stream (RL6) cooled in a sixth main refrigerant economizer (140f), and a seventh main refrigerant compressor (150g) that compresses a seventh main refrigerant stream (RL7) cooled in a seventh main refrigerant economizer (140g).

[0091] In this embodiment, the explanation is based on the assumption that the main refrigerant is evaporated gas of liquefied hydrogen, and the main refrigerant compressor here may be a compressor that compresses a gaseous fluid.

[0092] In the first stage of the plurality of primary refrigerant economizers, i.e., the first primary refrigerant economizer (130), the first primary refrigerant stream (RL1) and the liquefied hydrogen transported through the liquefied gas line (LL) exchange heat, and the first primary refrigerant stream can be cooled by recovering the cold heat of the liquefied hydrogen through the heat exchange.

[0093] In addition, the first main refrigerant stream (RL1) cooled by the cold heat of liquefied hydrogen in the first main refrigerant economizer (130) can be compressed in the first main refrigerant compressor (150a) and then supplied as the refrigerant of the second main refrigerant economizer (140b), which is the main refrigerant economizer of the next stage.

[0094] That is, according to the present embodiment, a primary refrigerant stream cooled in a primary refrigerant economizer of one stage among a plurality of primary refrigerant economizers can be compressed in a primary refrigerant compressor and then supplied as a refrigerant to a primary refrigerant economizer of the next stage.

[0095] In the second main refrigerant economizer (140b), the second main refrigerant stream (RL2) and the first main refrigerant stream (RL1) cooled in the first main refrigerant economizer (130) can exchange heat to cool the second main refrigerant stream (RL2).

[0096] Each of the main refrigerant streams branched from the main refrigerant branch section (120) of the present embodiment may be cooled by heat exchange with liquid hydrogen directly or by heat exchange with the main refrigerant stream cooled in the main refrigerant economizer of the previous stage in each main refrigerant economizer, and then may be joined at the main refrigerant joining section (160).

[0097] In addition, the main refrigerant stream cooled by heat exchange in each main refrigerant economizer can be supplied to the main refrigerant economizer of the next stage and used as a refrigerant to cool the main refrigerant stream supplied to the main refrigerant economizer of the next stage from the main refrigerant branch (120).

[0098] However, since the main refrigerant stream cooled in the main refrigerant economizer provided in the last stage among multiple main refrigerant economizers does not have a main refrigerant economizer in the next stage, the process of being used as a refrigerant is omitted and the main refrigerant stream can be transferred to the main refrigerant junction (160) through a compression process.

[0099] In this embodiment, since the main refrigerant economizer is provided in 7 stages as an example, the 7th main refrigerant stream (RL7) cooled in the 7th main refrigerant economizer (140g), which is the main refrigerant economizer of the last stage, can be directly transferred to the main refrigerant junction (160) after going through a compression process.

[0100] More specifically, the expanded main refrigerant stream (RL) in the main refrigerant turbine-generator (110) is branched into at least two streams, seven streams in this embodiment, including a first main refrigerant stream (RL1) and a second main refrigerant stream (RL2).

[0101] The first primary refrigerant stream (RL1) cooled by heat exchange with liquefied hydrogen in the first primary refrigerant economizer (130) is compressed by the first primary refrigerant compressor (150a) and supplied to the second primary refrigerant economizer (140b).

[0102] In the second main refrigerant economizer (140b), the second main refrigerant stream (RL2) branched from the main refrigerant branch (120) and the first main refrigerant stream (RL1) cooled in the first main refrigerant economizer (130) undergo heat exchange, thereby cooling the second main refrigerant stream (RL2).

[0103] The first main refrigerant stream (RL1) from which cold heat has been recovered by heat exchange in the second main refrigerant economizer (140b) is transferred to the main refrigerant junction (160), and the second main refrigerant stream (RL2) cooled by heat exchange is compressed in the second main refrigerant compressor (150b) and then supplied to the third main refrigerant economizer (140c).

[0104] In the third main refrigerant economizer (140c), the third main refrigerant stream (RL3) branched from the main refrigerant branch (120) and the second main refrigerant stream (RL2) cooled in the second main refrigerant economizer (140b) undergo heat exchange, thereby cooling the third main refrigerant stream (RL3).

[0105] The second main refrigerant stream (RL2) from which cold heat has been recovered by heat exchange in the third main refrigerant economizer (140c) is transferred to the main refrigerant junction (160), and the third main refrigerant stream (RL3) cooled by heat exchange is compressed in the third main refrigerant compressor (150c) and then supplied to the fourth main refrigerant economizer (140d).

[0106] In the fourth main refrigerant economizer (140d), the fourth main refrigerant stream (RL4) branched from the main refrigerant branch (120) and the third main refrigerant stream (RL3) cooled in the third main refrigerant economizer (140c) undergo heat exchange, thereby cooling the fourth main refrigerant stream (RL4).

[0107] The third main refrigerant stream (RL3) from which cold heat has been recovered by heat exchange in the fourth main refrigerant economizer (140d) is transferred to the main refrigerant junction (160), and the fourth main refrigerant stream (RL4) cooled by heat exchange is compressed in the fourth main refrigerant compressor (150d) and then supplied to the fifth main refrigerant economizer (140e).

[0108] In the fifth main refrigerant economizer (140e), the fifth main refrigerant stream (RL5) branched from the main refrigerant branch (120) and the fourth main refrigerant stream (RL4) cooled in the fourth main refrigerant economizer (140d) undergo heat exchange, thereby cooling the fifth main refrigerant stream (RL5).

[0109] The fourth main refrigerant stream (RL4) from which cold heat has been recovered by heat exchange in the fifth main refrigerant economizer (140e) is transferred to the main refrigerant junction (160), and the fifth main refrigerant stream (RL5) cooled by heat exchange is compressed in the fifth main refrigerant compressor (150e) and then supplied to the sixth main refrigerant economizer (140f).

[0110] In the sixth main refrigerant economizer (140f), the sixth main refrigerant stream (RL6) branched from the main refrigerant branch (120) and the fifth main refrigerant stream (RL5) cooled in the fifth main refrigerant economizer (140e) undergo heat exchange, thereby cooling the sixth main refrigerant stream (RL6).

[0111] The fifth main refrigerant stream (RL5) from which cold heat has been recovered by heat exchange in the sixth main refrigerant economizer (140f) is transferred to the main refrigerant junction (160), and the sixth main refrigerant stream (RL6) cooled by heat exchange is compressed in the sixth main refrigerant compressor (150f) and then supplied to the seventh main refrigerant economizer (140g).

[0112] In the seventh main refrigerant economizer (140g), which is the last stage, the seventh main refrigerant stream (RL7) branched from the main refrigerant branch section (120) and the sixth main refrigerant stream (RL6) cooled in the sixth main refrigerant economizer (140f) undergo heat exchange, thereby cooling the seventh main refrigerant stream (RL7).

[0113] The sixth main refrigerant stream (RL6) from which cold heat has been recovered by heat exchange in the seventh main refrigerant economizer (140g) is transferred to the main refrigerant junction (160), and the seventh main refrigerant stream (RL7) cooled by heat exchange can be compressed in the seventh main refrigerant compressor (150g) and then transferred to the main refrigerant junction (160).

[0114] By further recovering the remaining cold heat of the first main refrigerant stream (RL1) from which cold heat is recovered from liquefied hydrogen in the first main refrigerant economizer (130) in several stages using the second main refrigerant economizer (140b) and other subsequent main refrigerant economizers, the heat exchange flow rate of the circulating refrigerant is increased, and thus the amount of electricity generated by the turbine can be increased.

[0115] Seven primary refrigerant streams transferred to the primary refrigerant junction (160) are combined into one primary refrigerant stream (RL) and transferred to the primary refrigerant heater (170). The primary refrigerant stream (RL) can be heated in the primary refrigerant heater (170) and then recycled to the primary refrigerant turbine-generator (110).

[0116] The heat source for heating the main refrigerant stream (RL) in the main refrigerant heater (170) of the present embodiment may be seawater, fresh water, combustion gas, or the atmosphere, but is not limited thereto.

[0117] By heating the main refrigerant stream (RL) introduced into the main refrigerant turbine-generator (110) using a main refrigerant heater (170), the inlet temperature of the turbine-generator (110) can be increased, and the volume of the main refrigerant stream (RL) can be increased, thereby increasing the power generation of the main refrigerant cycle (100).

[0118] The drawing illustrates an example in which one main refrigerant heater (170) is provided. However, this is not limited to this, and one or more main refrigerant heaters (170) may be provided in series or in parallel.

[0119] For example, two main refrigerant heaters (170) are installed in series, and the main refrigerant streams that have been branched into multiple flows are combined into one main refrigerant stream (RL) at the main refrigerant junction (160), and can be heated in two stages while sequentially passing through the two main refrigerant heaters (170) connected in series.

[0120] As another example, two primary refrigerant heaters (170) may be installed in parallel, and the primary refrigerant streams that have been branched into multiple flows may be combined into two primary refrigerant streams at the primary refrigerant junction (160), and the two combined primary refrigerant streams may be distributed and supplied to two primary refrigerant heaters (170) installed in parallel.

[0121] Meanwhile, the liquefied hydrogen heated through heat exchange with the first main refrigerant stream (RL1) in the first main refrigerant economizer (130) is supplied to the auxiliary refrigerant cycle through the liquefied gas line (LL), so that further cold heat can be recovered.

[0122] The auxiliary refrigerant cycle can additionally recover the cold heat of the liquefied hydrogen that is transferred after the cold heat is recovered in the first main refrigerant economizer (130).

[0123] The auxiliary refrigerant cycle of the present embodiment can be provided one or more stages downstream of the main refrigerant cycle, and the liquefied gas line (LL) can be extended to a gas demand source through the main refrigerant cycle and the auxiliary refrigerant cycle sequentially.

[0124] The auxiliary refrigerant cycle of the present embodiment comprises an auxiliary refrigerant turbine-generator (210) that generates power by driving a turbine using an auxiliary refrigerant stream (NL), an auxiliary refrigerant branching unit (220) that branches the auxiliary refrigerant stream (NL) expanded in the auxiliary refrigerant turbine-generator (210) into a plurality of auxiliary refrigerant streams, an auxiliary refrigerant economizer (230, 240b) that cools each of the plurality of auxiliary refrigerant streams, an auxiliary refrigerant compressor (250a, 250b) that pressurizes the auxiliary refrigerant stream cooled in the auxiliary refrigerant economizer (230, 240b), an auxiliary refrigerant joining unit (260) that joins the plurality of auxiliary refrigerant streams compressed in the auxiliary refrigerant compressor (250a, 250b) into one auxiliary refrigerant stream (NL), and an auxiliary refrigerant joining unit (260) that heats the auxiliary refrigerant stream (NL) joined in the auxiliary refrigerant joining unit (260) to form an auxiliary refrigerant. It may include one or more auxiliary refrigerant heaters (270) that recirculate to the turbine-generator (210).

[0125] This embodiment will be described based on the assumption that the auxiliary refrigerant cycle is equipped with two stages. However, the number of stages of the auxiliary refrigerant cycle is not limited.

[0126] In the auxiliary refrigerant turbine-generator (210) of the present embodiment, the expanded auxiliary refrigerant stream (NL) may be branched into a first auxiliary refrigerant stream (NL1) and a second auxiliary refrigerant stream (NL2) in the auxiliary refrigerant branch section (220).

[0127] The first auxiliary refrigerant stream (NL1) and the second auxiliary refrigerant stream (NL2) are names used to distinguish and describe the streams into which the auxiliary refrigerant stream (NL) is branched. Each of the branched auxiliary refrigerant streams may be the same substance that flows through different paths after branching off from the auxiliary refrigerant branching section (220), is compressed, and joins into one auxiliary refrigerant stream (NL) upstream of the auxiliary refrigerant heater (270) to circulate the auxiliary refrigerant cycle.

[0128] Since this embodiment is described based on the assumption that the auxiliary refrigerant cycle is provided in two stages, the auxiliary refrigerant economizer according to this embodiment may include two auxiliary refrigerant economizers, such as a first auxiliary refrigerant economizer (230) that cools a first auxiliary refrigerant stream (NL1) and a second auxiliary refrigerant economizer (240b) that cools a second auxiliary refrigerant stream (NL2).

[0129] Additionally, downstream of the two auxiliary refrigerant economizers, two auxiliary refrigerant compressors corresponding to each auxiliary refrigerant economizer are provided.

[0130] The auxiliary refrigerant compressor of the present embodiment may include two auxiliary refrigerant compressors, including a first auxiliary refrigerant compressor (250a) that compresses a first auxiliary refrigerant stream (NL1) cooled in a first auxiliary refrigerant economizer (230), and a second auxiliary refrigerant compressor (250b) that compresses a second auxiliary refrigerant stream (NL2) cooled in a second auxiliary refrigerant economizer (240b).

[0131] In this embodiment, the auxiliary refrigerant is described as being evaporated gas of liquefied natural gas (LNG), i.e., methane, and the auxiliary refrigerant compressor may be a pump that compresses a liquid fluid.

[0132] Among the multiple auxiliary refrigerant economizers, the auxiliary refrigerant economizer provided in the first stage, i.e., the first auxiliary refrigerant economizer (230), exchanges heat between the first auxiliary refrigerant stream (NL1) and the liquefied hydrogen transferred from the main refrigerant cycle through the liquefied gas line (LL), and the first auxiliary refrigerant stream (NL1) can be cooled by recovering the remaining cold heat of the liquefied hydrogen heated while recovering the cold heat from the main refrigerant cycle through the heat exchange.

[0133] In addition, the first auxiliary refrigerant stream (NL1) cooled by the cold heat of liquefied hydrogen in the first auxiliary refrigerant economizer (230) can be compressed in the first auxiliary refrigerant compressor (250a) and then supplied as the refrigerant of the second auxiliary refrigerant economizer (240b), which is the auxiliary refrigerant economizer of the next stage.

[0134] That is, according to the present embodiment, an auxiliary refrigerant stream cooled in one of the auxiliary refrigerant economizers among a plurality of auxiliary refrigerant economizers can be compressed in an auxiliary refrigerant compressor and then supplied as a refrigerant to an auxiliary refrigerant economizer of the next stage.

[0135] In the second auxiliary refrigerant economizer (240b), the second auxiliary refrigerant stream (NL2) and the first auxiliary refrigerant stream (NL1) cooled in the first auxiliary refrigerant economizer (230) undergo heat exchange so that the second auxiliary refrigerant stream (NL2) can be cooled.

[0136] According to the present embodiment, the expanded auxiliary refrigerant stream (NL) in the auxiliary refrigerant turbine-generator (110) is branched into at least two streams including a first auxiliary refrigerant stream (NL1) and a second auxiliary refrigerant stream (NL2), and the residual cold heat of the first auxiliary refrigerant stream (NL1), from which the residual cold heat of the liquefied hydrogen is recovered in the first auxiliary refrigerant economizer (230), is further recovered through heat exchange with the second auxiliary refrigerant stream (NL2) in the second auxiliary refrigerant economizer (240b), thereby having the effect of increasing the heat exchange flow rate of the circulating refrigerant, and thus, the amount of electricity generated by the turbine can be increased.

[0137] The first auxiliary refrigerant stream (NL1) heated by heat exchange in the second auxiliary refrigerant economizer (240b) and the second auxiliary refrigerant stream (NL2) cooled by heat exchange in the second auxiliary refrigerant economizer (240b) can be combined into one auxiliary refrigerant stream (NL) in the auxiliary refrigerant junction (260), heated in the auxiliary refrigerant heater (270), and then recycled to the auxiliary refrigerant turbine-generator (210).

[0138] Each auxiliary refrigerant stream branched from the auxiliary refrigerant branch section (220) of the present embodiment may be cooled by direct heat exchange with liquefied hydrogen or by heat exchange with the auxiliary refrigerant stream cooled in the auxiliary refrigerant economizer of the previous stage in each auxiliary refrigerant economizer, and then may be joined at the auxiliary refrigerant joining section (260).

[0139] Additionally, the auxiliary refrigerant stream cooled by heat exchange in each auxiliary refrigerant economizer can be supplied to the auxiliary refrigerant economizer of the next stage and used as a refrigerant to cool the auxiliary refrigerant stream supplied to the auxiliary refrigerant economizer of the next stage.

[0140] Meanwhile, the auxiliary refrigerant stream cooled in the auxiliary refrigerant economizer provided in the last stage among multiple auxiliary refrigerant economizers can be omitted from the process of being used as a refrigerant because there is no auxiliary refrigerant economizer in the next stage, and can be transferred to the auxiliary refrigerant junction (260) after going through a compression process.

[0141] In this embodiment, since the auxiliary refrigerant economizer is provided in two stages as an example, the second main refrigerant stream (NL2) cooled in the second auxiliary refrigerant economizer (240b), which is the auxiliary refrigerant economizer of the last stage, can be directly compressed and transferred to the auxiliary refrigerant junction (260).

[0142] The heat source for heating the auxiliary refrigerant stream (NL) in the auxiliary refrigerant heater (270) of the present embodiment may be seawater, fresh water, combustion gas, or the atmosphere, but is not limited thereto.

[0143] By heating the auxiliary refrigerant stream (NL) introduced into the auxiliary refrigerant turbine-generator (210) by providing an auxiliary refrigerant heater (270), the inlet temperature of the auxiliary refrigerant turbine-generator (210) can be increased, and the volume of the auxiliary refrigerant stream (NL) can be increased, thereby increasing the expansion work that can be generated through the turbine, i.e., the amount of power generated by the auxiliary refrigerant turbine-generator (210).

[0144] The drawing illustrates an example in which one auxiliary refrigerant heater (270) is provided. However, this is not limited to this, and one or more auxiliary refrigerant heaters (270) may be provided in series or in parallel.

[0145] For example, two auxiliary refrigerant heaters (270) are installed in series, and auxiliary refrigerant streams that have been branched into multiple flows are combined into one auxiliary refrigerant stream (NL) at an auxiliary refrigerant junction (260), and can be heated in two stages while sequentially passing through two auxiliary refrigerant heaters (270) connected in series.

[0146] As another example, two auxiliary refrigerant heaters (270) may be installed in parallel, and the auxiliary refrigerant streams that were branched into multiple flows may be combined into two auxiliary refrigerant streams at the auxiliary refrigerant junction (260), and the two combined auxiliary refrigerant streams may be distributed and supplied to two auxiliary refrigerant heaters (270) installed in parallel.

[0147] The liquefied hydrogen of this embodiment can be supplied to a gas consumer through a liquefied gas line (LL) after the cold heat is recovered in the main refrigerant cycle and the auxiliary refrigerant cycle.

[0148] According to the present embodiment, the liquefied hydrogen supplied to the first primary refrigerant economizer (130) along the liquefied gas line (LL) may be heated by losing cold heat while exchanging heat with the first primary refrigerant stream (RL1) in the first primary refrigerant economizer (130), or at least part of it may be vaporized.

[0149] In addition, the liquefied hydrogen supplied from the first primary refrigerant economizer (130) to the first auxiliary refrigerant economizer (230) along the liquefied gas line (LL) may be heated by losing cold heat while exchanging heat with the first auxiliary refrigerant stream (NL1) in the first auxiliary refrigerant economizer (230), or at least part of it may be vaporized.

[0150] The multi-loop power generation system according to the present embodiment may further include a liquefied gas heater (300) provided downstream of the first auxiliary refrigerant economizer (230) and heating liquefied hydrogen that is heated by heat exchange in the first auxiliary refrigerant economizer (230) and supplied to a gas demand source.

[0151] The heat source for heating liquefied hydrogen in the liquefied gas heater (300) of this embodiment may be seawater, fresh water, combustion gas, or the atmosphere, but is not limited thereto.

[0152] Liquefied hydrogen introduced in a liquid state from the first auxiliary refrigerant economizer (230) to the liquefied gas heater (300) can be heated in the liquefied gas heater (300) and completely vaporized. In addition, liquefied hydrogen introduced in a gaseous state from the first auxiliary refrigerant economizer (230) to the liquefied gas heater (300), i.e., regasified gas, can be heated in the liquefied gas heater (300) to a temperature required by the gas demander.

[0153] The regasified gas transferred from the liquefied gas heater (300) to the gas demand source can satisfy the temperature conditions required by the gas demand source.

[0154] The drawing illustrates an example in which one liquefied gas heater (300) is provided. However, this is not limited to this, and one or more liquefied gas heaters (300) may be provided in series or in parallel.

[0155] For example, two liquefied gas heaters (300) are installed in series, and liquefied hydrogen can be heated in two stages by sequentially passing through the two liquefied gas heaters (300) connected in series.

[0156] As another example, two liquefied gas heaters (300) may be installed in parallel, and liquefied hydrogen may be distributed and supplied to the two liquefied gas heaters (300) installed in parallel.

[0157] According to one embodiment of the present invention described above, the remaining cold heat of the liquefied hydrogen, from which cold heat has been recovered in the main refrigerant cycle, is further recovered in the auxiliary refrigerant cycle, thereby allowing the cold heat of the liquefied hydrogen to be recovered and utilized to the maximum extent possible.

[0158] If the cold heat of the liquid hydrogen is recovered in multiple stages in the main refrigerant cycle using the main refrigerant, and the remaining cold heat of the liquid hydrogen is further recovered in multiple stages in the auxiliary refrigerant cycle using the auxiliary refrigerant, the number of required equipment may increase compared to the case where the cold heat of the liquid hydrogen is recovered using only one cycle, but the amount of power generated from the turbine-generator of each main refrigerant cycle and auxiliary refrigerant cycle is greater than the power consumption required to operate the increased number of equipment such as the compressor, resulting in improved power generation efficiency.

[0159] In this embodiment, the primary refrigerant and auxiliary refrigerant are designed so that the pressure does not fall below or below the critical pressure during the primary refrigerant cycle and auxiliary refrigerant cycle, respectively. In other words, no phase change occurs in the primary refrigerant and auxiliary refrigerant during the cycle, regardless of the temperature.

[0160] Referring to Figure 3, the primary refrigerant and auxiliary refrigerant remain in the critical region (CA) where the pressure is maintained above the critical pressure during each cycle, and therefore the phase of the primary refrigerant and auxiliary refrigerant becomes a compressible fluid or a supercritical fluid.

[0161] Since the primary and auxiliary refrigerants are maintained above their critical pressures during the primary and auxiliary refrigerant cycles, respectively, the pinch points of the primary and auxiliary refrigerant economizers do not exist within the device, or at least occur at low temperatures near the ends of the heat exchanger, maximizing heat exchange performance. Furthermore, since slugging does not occur, there is virtually no piping stress applied to the piping through which the working fluid flows.

[0162] Additionally, in this embodiment, the primary and auxiliary refrigerants may be maintained in a supercritical state during the primary and auxiliary refrigerant cycles, respectively. Maintaining the primary and auxiliary refrigerants in a supercritical state allows them to flow in a high-density state, thereby enabling a smaller power generation system.

[0163] In the case of a power generation system with a total of 9 stages, in which the liquefied gas is liquefied hydrogen, the main refrigerant is hydrogen vaporization gas, the auxiliary refrigerant is LNG vaporization gas, the main refrigerant cycle is a 7-stage process including 7 economizers to recover the cold heat of the liquefied hydrogen, and the auxiliary refrigerant cycle is a 2-stage process including 2 economizers to recover the remaining cold heat of the liquefied hydrogen, it was confirmed that the efficiency was improved by approximately 4% compared to the process of recovering the cold heat of the liquefied hydrogen using a single 7-stage cycle of the main refrigerant (see Fig. 2).

[0164] In Fig. 2, the drawing symbol TG represents a turbine-generator that generates power by expanding refrigerant, BR represents a distribution unit that distributes and supplies the expanded refrigerant to each economizer, EC1 to EC7 represent economizers of each stage, C1 to C7 represent compressors that compress the refrigerant cooled in each economizer and supply it to the next stage's economizer or junction unit, S and S1 to S7 represent refrigerant streams, CB represents a junction unit that combines the refrigerant cooled in the economizer or the refrigerant from which cold heat has been recovered and sends it to a heater, and HT represents a heater for heating the refrigerant from which cold heat has been recovered in the economizer of each stage or the cooled refrigerant and resupplying it to the turbine-generator.

[0165] The multi-loop power generation system using the cold energy of liquefied gas according to the present embodiment illustrated in FIG. 1 has a total of 9 stages, and compared to the single-loop power generation system equipped with a 7-stage main refrigerant cycle illustrated in FIG. 2, the total number of stages increases, resulting in an increase in initial cost.

[0166] However, in the additional auxiliary refrigerant cycle, since the auxiliary refrigerant circulates in a critical state close to the liquid phase, a pump that is cheaper than a compressor can be adopted as a means of compressing the refrigerant, and at the pump inlet, the auxiliary refrigerant is in a supercritical state close to the liquid phase characteristics, and its density increases compared to the main refrigerant at the compressor inlet close to the gas phase. Since the heat transfer efficiency increases as the density increases, it is expected that the heat exchanger area and equipment size of the auxiliary refrigerant in a multi-loop power generation system will be much smaller than those of the main refrigerant even though the number of stages increases compared to a single-loop power generation system. As a result, the power generation efficiency is improved because the power generation of the auxiliary refrigerant turbine-generator is greater than the increase in capital investment cost (CAPEX) and operating cost (OPEX).

[0167]

[0168] As described above, embodiments of the present invention have been described. It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms, in addition to the embodiments described above, without departing from the spirit or scope thereof. Therefore, the above-described embodiments should be considered illustrative rather than restrictive, and accordingly, the present invention is not limited to the above description, but may be modified within the scope of the appended claims and their equivalents.

[0169] <Explanation of symbols>

[0170] 110: Main refrigerant turbine-generator

[0171] 120: Main refrigerant branch

[0172] 130, 140b, 140c, 140d, 140e, 140f, 140g: Main refrigerant economizer

[0173] 150a, 150b, 150c, 150d, 150e, 150f, 150g: Main refrigerant compressor

[0174] 160: Main refrigerant junction

[0175] 170: Main refrigerant heater

[0176] RL, RL1, RL2, RL3, RL4, RL5, RL6, RL7: Main refrigerant streams

[0177] 210: Auxiliary refrigerant turbine-generator

[0178] 220: Auxiliary refrigerant branch

[0179] 230, 240b: Auxiliary refrigerant economizer

[0180] 250a, 250b: Auxiliary refrigerant compressor

[0181] 260: Auxiliary refrigerant junction

[0182] 270: Auxiliary refrigerant heater

[0183] NL, NL1, NL2: Auxiliary refrigerant stream

[0184] LL: Liquefied gas line

[0185] 300: Liquefied gas heater

Claims

1. A primary refrigerant turbine-generator that generates electricity by driving a turbine with a primary refrigerant stream; and A main refrigerant branch unit for branching the expanded main refrigerant stream while driving the turbine into at least two main refrigerant streams including a first main refrigerant stream and a second main refrigerant stream; A first main refrigerant economizer that recovers cold heat from the liquefied gas by heat-exchanging the first main refrigerant stream and the liquefied gas; Auxiliary refrigerant turbine-generator that generates electricity by driving a turbine with an auxiliary refrigerant stream; An auxiliary refrigerant branch unit that branches the expanded auxiliary refrigerant stream while driving the turbine into at least two auxiliary refrigerant streams including a first auxiliary refrigerant stream and a second auxiliary refrigerant stream; and A multi-loop power generation system utilizing the cold heat of liquefied gas, comprising a first auxiliary refrigerant economizer that recovers the remaining cold heat of the liquefied gas by heat-exchanging the liquefied gas from which the cold heat has been recovered in the first main refrigerant economizer with the first auxiliary refrigerant stream.

2. In claim 1, A second main refrigerant economizer that cools the second main refrigerant stream by heat-exchanging the first main refrigerant stream cooled in the first main refrigerant economizer and the second main refrigerant stream branched from the main refrigerant branch; and A multi-loop power generation system utilizing cold energy from liquefied gas, further comprising a primary refrigerant heater for heating the first primary refrigerant stream and the second primary refrigerant stream discharged after heat exchange from the second primary refrigerant economizer and recirculating them to the primary refrigerant turbine-generator.

3. In claim 2, At least one of the above main refrigerant heaters is provided, A multi-loop power generation system utilizing the cold energy of liquefied gas, wherein when two or more of the above-mentioned main refrigerant heaters are provided, the main refrigerant heaters are provided in series or parallel.

4. In claim 1, A second auxiliary refrigerant economizer that cools the second auxiliary refrigerant stream by heat-exchanging the first auxiliary refrigerant stream cooled in the first auxiliary refrigerant economizer and the second auxiliary refrigerant stream branched from the auxiliary refrigerant branch; and A multi-loop power generation system utilizing cold energy from liquefied gas, further comprising an auxiliary refrigerant heater for heating the first auxiliary refrigerant stream and the second auxiliary refrigerant stream discharged after heat exchange from the second auxiliary refrigerant economizer and recirculating them to the auxiliary refrigerant turbine-generator.

5. In claim 4, At least one auxiliary refrigerant heater is provided, A multi-loop power generation system utilizing the cold energy of liquefied gas, wherein when two or more auxiliary refrigerant heaters are provided, the auxiliary refrigerant heaters are provided in series or parallel.

6. In claim 1, A multi-loop power generation system utilizing the cold energy of liquefied gas, wherein the first main refrigerant economizer and the first auxiliary refrigerant economizer are one or more multi-stream heat exchangers.

7. In claim 1, A multi-loop power generation system utilizing the cold heat of liquefied gas, further comprising a liquefied gas heater that heats the liquefied gas from which residual cold heat has been recovered in the first auxiliary refrigerant economizer and supplies the heat to a gas demand source.

8. In claim 1, A multi-loop power generation system utilizing cold energy from liquefied gas, wherein the first main refrigerant economizer and the first auxiliary refrigerant economizer are plate-type heat exchangers, plate-fin-type heat exchangers, printed circuit board-type heat exchangers, aluminum-bonded heat exchangers, or coil-wound heat exchangers.

9. In claim 1, A multi-loop power generation system utilizing the cold energy of liquefied gas, wherein the above-mentioned main refrigerant stream and auxiliary refrigerant stream are each a single refrigerant selected from the group consisting of hydrogen, helium, nitrogen, oxygen, neon, argon, carbon compounds having 5 or fewer carbon atoms, and freon refrigerants, or a mixed refrigerant comprising two or more of these.

10. In claim 1, A multi-loop power generation system utilizing the cold heat of liquefied gas, wherein the above-mentioned main refrigerant stream and auxiliary refrigerant stream are maintained above the critical pressure while circulating the main refrigerant cycle and auxiliary refrigerant cycle, respectively.

11. A primary refrigerant power generation stage that generates electricity by driving a turbine with a primary refrigerant stream; A main refrigerant branching step for branching the expanded main refrigerant stream into at least two main refrigerant streams including a first main refrigerant stream and a second main refrigerant stream while driving the turbine; A first cold heat recovery step for recovering cold heat of the liquefied gas by heat-exchanging the first main refrigerant stream and the liquefied gas; Auxiliary refrigerant generation stage that generates electricity by driving a turbine with an auxiliary refrigerant stream; An auxiliary refrigerant branching step for branching the expanded auxiliary refrigerant stream while driving the turbine into at least two auxiliary refrigerant streams including a first auxiliary refrigerant stream and a second auxiliary refrigerant stream; and A multi-loop power generation method using cold heat from liquefied gas, comprising: a second cold heat recovery step for recovering residual cold heat from the liquefied gas by heat-exchanging the first auxiliary refrigerant stream and the liquefied gas from which cold heat has been recovered in the first cold heat recovery step; 12. In claim 11, A primary refrigerant heat recovery step for cooling the second primary refrigerant stream by heat-exchanging the first primary refrigerant stream cooled in the first primary refrigerant heat recovery step and the second primary refrigerant stream branched in the primary refrigerant branch step; and A multi-loop power generation method using cold heat from liquefied gas, further comprising a primary refrigerant heating step for heating the first primary refrigerant stream and the second primary refrigerant stream discharged after heat exchange from the primary refrigerant cold heat recovery step and recirculating them to the primary refrigerant power generation step.

13. In claim 11, An auxiliary refrigerant heat recovery step for cooling the second auxiliary refrigerant stream by heat-exchanging the first auxiliary refrigerant stream cooled in the second refrigerant heat recovery step and the second auxiliary refrigerant stream branched in the auxiliary refrigerant branch step; and A multi-loop power generation method using cold heat from liquefied gas, further comprising an auxiliary refrigerant heating step for heating the first main refrigerant stream and the second main refrigerant stream discharged after heat exchange from the auxiliary refrigerant cold heat recovery step and recirculating them to the auxiliary refrigerant power generation step.

14. In claim 11, A multi-loop power generation method using cold heat from liquefied gas, further comprising a liquefied gas heating step of heating the liquefied gas from which the remaining cold heat has been recovered in the second cold heat recovery step and supplying the heated liquefied gas to a gas demand source.

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