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

Abstract

The present invention relates to a multiple-loop power generation system and method using cold energy of liquefied gas whereby waste cold energy of liquefied gas is recovered and power is generated by using multiple loops. A multiple-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 using a main refrigerant stream and generates power; a main refrigerant branching portion which branches the main refrigerant stream expanded while driving the turbine into two or more main refrigerant streams including a first main refrigerant stream and a second main refrigerant stream; two or more main refrigerant economizers which respectively cool-down the two or more main refrigerant streams, comprising a first main refrigerant economizer which recovers cold energy of the liquefied gas by exchanging heat between the first main refrigerant stream and the liquefied gas; a main refrigerant compressor which supplies a main refrigerant stream that is cooled by any one of the two or more main refrigerant economizers as a refrigerant for another main refrigerant economizer; an auxiliary refrigerant turbine-generator which drives the turbine using an auxiliary refrigerant stream and generates power; and an auxiliary refrigerant economizer which exchanges heat between the auxiliary refrigerant stream that is expanded while driving the turbine and one or more main refrigerant streams discharged after the heat exchange in the two or more main refrigerant economizers, so that the auxiliary refrigerant stream is cooled by the remaining cold energy of the main refrigerant stream.

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, forming liquefied natural gas (LNG). This is then transported long distances to its intended destination. Natural gas is liquefied by cooling it from atmospheric pressure to the cryogenic temperature of approximately -163°C, 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 turbine-generator comprising: a primary refrigerant turbine-generator for generating electric power by driving a turbine with a primary refrigerant stream; a primary refrigerant branching section for branching a primary refrigerant stream expanded while driving the turbine into two or more primary refrigerant streams including a first primary refrigerant stream and a second primary refrigerant stream; a first primary refrigerant economizer for heat-exchanging the first primary refrigerant stream with a liquefied gas to recover cold heat of the liquefied gas, and two or more primary refrigerant economizers for cooling the two or more primary refrigerant streams respectively; a primary refrigerant compressor for supplying the primary refrigerant stream cooled in one of the primary refrigerant economizers as the refrigerant of another primary refrigerant economizer; an auxiliary refrigerant turbine-generator for generating electric power by driving a turbine with an auxiliary refrigerant stream; A multi-loop power generation system utilizing the cold heat of liquefied gas is provided, including an auxiliary refrigerant economizer that heat-exchanges an expanded auxiliary refrigerant stream while driving the turbine and at least one main refrigerant stream discharged after heat exchange in the two or more main refrigerant economizers, thereby cooling the auxiliary refrigerant stream with the residual cold heat of the main refrigerant stream.

[0016] Preferably, the system may further include a primary refrigerant heater for heating the primary refrigerant stream from which cold heat has been recovered in the two or more primary refrigerant economizers and the auxiliary refrigerant economizers and recirculating the heated primary refrigerant stream to the primary refrigerant turbine-generator.

[0017] Preferably, the system may further include a residual heat combining unit that combines two or more primary refrigerant streams supplied as refrigerant to the auxiliary refrigerant economizer from the two or more primary refrigerant economizers into one stream.

[0018] Preferably, the system further includes an auxiliary refrigerant branching section for branching the expanded auxiliary refrigerant stream into at least one auxiliary refrigerant stream including at least one of a first auxiliary refrigerant stream and a second auxiliary refrigerant stream, wherein at least one auxiliary refrigerant economizer is provided to cool each of the at least one auxiliary refrigerant streams.

[0019] Preferably, one or more primary refrigerant streams supplied as refrigerant to the auxiliary refrigerant economizer from one or more of the two or more primary refrigerant economizers can be supplied to each of the one or more auxiliary refrigerant economizers.

[0020] Preferably, the auxiliary refrigerant economizer is provided in two or more numbers, and may further include an auxiliary refrigerant compressor that supplies an auxiliary refrigerant stream cooled in one of the two or more auxiliary refrigerant economizers as the refrigerant of another auxiliary refrigerant economizer.

[0021] Preferably, the system may further include an auxiliary refrigerant compressor for compressing the auxiliary refrigerant stream cooled in the auxiliary refrigerant economizer; and an auxiliary refrigerant heater for heating the auxiliary refrigerant stream compressed in the auxiliary refrigerant compressor and recirculating it to the auxiliary refrigerant turbine-generator.

[0022] Preferably, the main refrigerant stream and the auxiliary refrigerant stream 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] Preferably, the primary refrigerant economizer and the secondary refrigerant economizer may be provided as a plate type heat exchanger, a plate-fin type heat exchanger, a printed circuit board type heat exchanger, an aluminum bonded type heat exchanger, a coil wound type heat exchanger, or one or more multi-stream heat exchangers.

[0027] According to another aspect of the present invention for achieving the above-described object, there is provided 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 two or more primary refrigerant streams including a first primary refrigerant stream and a second primary refrigerant stream; a liquefied gas cold heat recovery step for cooling the first primary refrigerant stream using liquefied gas as a refrigerant; a primary refrigerant cooling step for cooling one or more primary refrigerant streams including the second primary refrigerant stream, wherein one of the cooled primary refrigerant streams is used as a refrigerant for cooling another primary refrigerant stream; an auxiliary refrigerant power generation step for generating electric power by driving a turbine with an auxiliary refrigerant stream; A multi-loop power generation method using cold heat from liquefied gas is provided, comprising: a residual cold heat recovery step of cooling the auxiliary refrigerant stream using the cold heat of the liquefied gas, by heat-exchanging the expanded auxiliary refrigerant stream while driving the turbine and at least one main refrigerant stream from which cold heat has been recovered in the main refrigerant cooling step;

[0028] Preferably, the method may further include a primary refrigerant heating step of heating the primary refrigerant stream from which cold heat has been recovered in the primary refrigerant cooling step and the residual cold heat recovery step and recycling the heated primary refrigerant stream to the primary refrigerant power generation step.

[0029] Preferably, the residual heat recovery step may further include a residual heat combining step of combining two or more primary refrigerant streams supplied as refrigerants into one stream.

[0030] Preferably, the method may further include: an auxiliary refrigerant branching step for branching the expanded auxiliary refrigerant stream into at least two auxiliary refrigerant streams including a first auxiliary refrigerant stream and a second auxiliary refrigerant stream; a step for cooling each of one or more auxiliary refrigerant streams including the second auxiliary refrigerant stream, wherein one of the cooled one or more auxiliary refrigerant streams is supplied as a refrigerant for cooling another auxiliary refrigerant stream; and an auxiliary refrigerant heating step for heating the auxiliary refrigerant stream cooled in the auxiliary refrigerant cooling step or the auxiliary refrigerant stream used as a refrigerant in the auxiliary refrigerant cooling step and recirculating the heated auxiliary refrigerant stream to the auxiliary refrigerant power generation step.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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 can be cooled and power can be generated by using only the cold heat of the liquefied gas without having a separate cooling cycle.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] FIG. 1 is a schematic diagram illustrating a multi-loop power generation system using the cold energy of liquefied gas according to one embodiment of the present invention.

[0041] FIG. 2 is a schematic drawing illustrating a modified example of a multi-loop power generation system using cold energy from liquefied gas according to one embodiment of the present invention illustrated in FIG. 1.

[0042] 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.

[0043] FIG. 4 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] In the embodiments of the present invention described below, the liquefied gas will be described as liquefied hydrogen (LH2) as an example.

[0048] 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.

[0049] 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.

[0050] 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).

[0051]

[0052] 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.

[0053] First, referring to FIGS. 1 and 2, a multi-loop power generation system using cold heat of liquefied gas according to the present embodiment includes a multi-loop cycle including a main refrigerant cycle (100) that recovers cold heat of liquefied hydrogen to generate power, and an auxiliary refrigerant cycle (200) that is provided downstream of the main refrigerant cycle (100) based on the flow direction of the main refrigerant stream and recovers residual cold heat of the main refrigerant while the auxiliary refrigerant circulates.

[0054] 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 the main refrigerant stream, but is not limited thereto.

[0055] That is, the multi-loop power generation system according to the present invention may be equipped with two or more auxiliary refrigerant cycles (200) including two or more auxiliary refrigerant cycles (200) sequentially connected downstream of the main refrigerant cycle to form a two-stage or more multi-loop cycle.

[0056] According to a two-stage loop power generation system in which two loop cycles, such as a main refrigerant cycle (100) and an auxiliary refrigerant cycle (200), are sequentially connected as in this embodiment, first, as the first stage, the main refrigerant circulating in the main refrigerant cycle (100) primarily recovers the cold heat of liquefied hydrogen to generate power, and as the second stage, the auxiliary refrigerant circulating in the auxiliary refrigerant cycle recovers the residual cold heat of the main refrigerant supplied from the main refrigerant cycle (100) to generate power.

[0057] Meanwhile, in the case of a three-stage loop power generation system in which three loop cycles, including a main refrigerant cycle (100), a first auxiliary refrigerant cycle (200), and a second auxiliary refrigerant cycle (not shown), are sequentially connected, in the first stage, the main refrigerant circulating in the main refrigerant cycle (100) primarily recovers the cold heat of liquefied hydrogen to generate power, in the second stage, the first auxiliary refrigerant circulating in the first auxiliary refrigerant cycle (200) recovers the remaining cold heat of the main refrigerant 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 can further recover the remaining cold heat of the main refrigerant from which the cold heat was first recovered in the first auxiliary refrigerant cycle to generate power.

[0058] Each sequentially connected loop cycle may include a turbine-generator (110, 210) that generates power by driving a turbine using refrigerant circulating in each loop cycle, an economizer (130, 140b, 140c, 140d, 140e, 140f, 140g, 230, 240b, 240c) 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, 250c) 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 can be recycled back to the turbine-generator.

[0059] Each loop cycle constituting the multi-loop power generation system according to the present embodiment can operate as a Brayton cycle.

[0060] 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.

[0061] 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.

[0062] 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).

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] The drawing illustrates, as an example, a primary refrigerant cycle (100) having seven stages including seven economizers (130, 140b, 140c, 140d, 140e, 140f, 140g), and an auxiliary refrigerant cycle (200) having three stages including three economizers (230, 240b, 240c). In describing the present embodiments, the primary refrigerant cycle (100) having seven stages and the auxiliary refrigerant cycle (200) having three stages will be described with reference to the drawing.

[0073] However, the number is not limited to this, and as described later, the main refrigerant cycle (100) may be provided with at least one stage, including the first stage economizer (the first main refrigerant economizer (130) of the present embodiment) in which liquefied hydrogen and the main refrigerant exchange heat.

[0074] In addition, the auxiliary refrigerant cycle (200) may be equipped with one or more stages including an economizer in which the main refrigerant supplied from the main refrigerant cycle (100) and the auxiliary refrigerant exchange heat.

[0075] 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.

[0076] 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.

[0077] In these embodiments, the primary and secondary refrigerants may be fluids of different substances or the same substance. In describing these embodiments, the terms "primary" and "auxiliary" are merely used to distinguish between the primary and secondary refrigerants, and do not imply that one refrigerant is primarily used and the other is used as an auxiliary refrigerant.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] Additionally, nitrogen is an inert gas that is easily obtained from the air, is cheap to purchase, is safe, and does not contain carbon, so it can be vented into the air, which has the advantage of not requiring a flare device.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] Referring to the drawing, the primary refrigerant cycle according to the present embodiment comprises 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 (130, 140b, 140c, 140d, 140e, 140f, 140g) that cools each primary refrigerant stream, a primary refrigerant compressor (150a, 150b, 150c, 150d, 150e, 150f, 150g) 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 It may include at least one of the main refrigerant heaters (170) that heat the main refrigerant stream (RL) joined at the joining portion (160).

[0092] In explaining this embodiment, it is assumed that the main refrigerant cycle (100) is provided with 7 stages, so the main refrigerant stream (RL) expanded in the main refrigerant turbine-generator (110) can 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).

[0093] 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).

[0094] In addition, 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).

[0095] 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).

[0096] 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.

[0097] 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.

[0098] 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.

[0099] According to this embodiment, a primary refrigerant stream cooled in one of the primary refrigerant economizers among a plurality of primary refrigerant economizers can be compressed in a primary refrigerant compressor and then supplied as refrigerant to a primary refrigerant economizer of the next stage or to an auxiliary refrigerant cycle (200).

[0100] 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).

[0101] 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).

[0102] 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) or the auxiliary refrigerant stream supplied to the auxiliary refrigerant economizer of the auxiliary refrigerant cycle (200).

[0103] 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.

[0104] 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.

[0105] In addition, among the primary refrigerant streams that have been used as refrigerants in a plurality of primary refrigerant economizers and whose temperature has increased, at least one primary refrigerant stream, particularly a primary refrigerant stream with sufficient residual cold heat, may be supplied to an auxiliary refrigerant cycle (200) before being transferred to the primary refrigerant junction (160) and used as a refrigerant so that the residual cold heat is further recovered, and then transferred to the primary refrigerant junction (160).

[0106] Here, sufficient residual cooling may mean that the temperature of the primary refrigerant stream discharged after being used as refrigerant in the primary refrigerant economizer is lower than a preset first set temperature.

[0107] Here, the first set temperature is not limited, but the first set temperature may be a temperature at which the energy generated by expansion through heating is sufficiently large compared to the energy consumed when the auxiliary refrigerant receives residual cold heat from the main refrigerant and compresses it.

[0108] Additionally, the first set temperature will be a temperature at which the auxiliary refrigerant can be liquefied by compression when the means for compressing the auxiliary refrigerant stream discharged after heat exchange from the auxiliary refrigerant economizer is a pump.

[0109] In addition, the first set temperature may be the lowest temperature at which the power generation generated in the auxiliary refrigerant cycle is reasonably economical when the means for compressing the auxiliary refrigerant stream discharged after heat exchange from the auxiliary refrigerant economizer is a compressor, by transferring the residual cold heat of the main refrigerant stream to the auxiliary refrigerant stream.

[0110] The first set temperature may be lower when the means for compressing the auxiliary refrigerant stream discharged from the auxiliary refrigerant economizer after heat exchange is a pump, compared to when the means is a compressor.

[0111] The first set temperature can be determined based on the composition, operating pressure, temperature, and flow rate of the main refrigerant stream and the composition, operating pressure, and temperature of the auxiliary refrigerant stream.

[0112] The available residual enthalpy of cooling is determined based on the flow rate and temperature of the primary refrigerant stream, and accordingly, the auxiliary refrigerant flow rate to meet the target temperature of the auxiliary refrigerant stream will be determined, i.e., the flow rate of the auxiliary refrigerant can be determined based on the flow rate and temperature of the primary refrigerant.

[0113] In this embodiment, among the primary refrigerant streams that have been used as refrigerants in a plurality of primary refrigerant economizers and whose temperature has increased, a first primary refrigerant stream (RL1) used as refrigerant in a second primary refrigerant economizer (140b) and a second primary refrigerant stream (RL2) used as refrigerant in a third primary refrigerant economizer (140c) are supplied as refrigerants in an auxiliary refrigerant cycle (200), and after cooling the secondary refrigerant stream by heat exchange in the auxiliary refrigerant economizer, they are transferred to a primary refrigerant junction (160).

[0114] Referring to FIG. 1, the operating method of the main refrigerant cycle (100) according to one embodiment of the present invention will be described in more detail as follows.

[0115] The expanded main refrigerant stream (RL) in the main refrigerant turbine-generator (110) can be branched into at least two streams, including a first main refrigerant stream (RL1) and a second main refrigerant stream (RL2), and in this embodiment, seven streams.

[0116] In the first main refrigerant economizer (130), the first main refrigerant stream (RL1) branched from the main refrigerant branch (120) and liquefied hydrogen undergo heat exchange, so that the first main refrigerant stream (RL1) that has recovered the cold heat of the liquefied hydrogen is cooled, and the liquefied hydrogen can be heated and discharged.

[0117] The first primary refrigerant stream (RL1) cooled by heat exchange in the first primary refrigerant economizer (130) can be compressed by the first primary refrigerant compressor (150a) and supplied to the second primary refrigerant economizer (140b).

[0118] In this embodiment, the first primary refrigerant stream (RL1) cooled by heat exchange 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) as an example.

[0119] However, if the temperature of the first main refrigerant stream (RL1) cooled by heat exchange in the main refrigerant economizer (130) is lower than the first set temperature, the cooled first main refrigerant stream (RL1) may also be supplied as a refrigerant to the auxiliary refrigerant cycle (200). The first main refrigerant stream (RL1) from which residual cold heat is further recovered while being used as a refrigerant in the auxiliary refrigerant cycle (200) may be transferred to the main refrigerant junction (160). If the temperature of the cooled first main refrigerant stream (RL1) is higher than the first set temperature, it may not be supplied to the auxiliary refrigerant cycle (200) but may be transferred to the main refrigerant junction (160).

[0120] In the second main refrigerant economizer (140b), the second main refrigerant stream (RL2) branched from the main refrigerant branch section (120) and the first main refrigerant stream (RL1) cooled in the first main refrigerant economizer (130) exchange heat so that the second main refrigerant stream (RL2) can be cooled.

[0121] The second main refrigerant stream (RL2) cooled by heat exchange in the second main refrigerant economizer (140b) can be compressed in the second main refrigerant compressor (150b) and then supplied to the third main refrigerant economizer (140c).

[0122] In addition, if the temperature of the first main refrigerant stream (RL1) from which cold heat is recovered by heat exchange in the second main refrigerant economizer (140b) is lower than the first set temperature, it is supplied to the auxiliary refrigerant cycle (200) and the remaining cold heat is further recovered and then transferred to the main refrigerant junction (160). If it is higher than the first set temperature, it may not be supplied to the auxiliary refrigerant cycle (200) but may be transferred to the main refrigerant junction (160).

[0123] According to the embodiment illustrated in FIG. 1, the temperature of the first primary refrigerant stream (RL1) from which cold heat has been recovered by heat exchange in the second primary refrigerant economizer (140b) is lower than the first set temperature, and the remaining cold heat can be further recovered to cool the secondary refrigerant stream circulating in the secondary refrigerant cycle (200) before being transferred to the primary refrigerant junction (160).

[0124] 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 so that the third main refrigerant stream (RL3) can be cooled.

[0125] The third main refrigerant stream (RL3) cooled by heat exchange in the third main refrigerant economizer (140c) can be compressed in the third main refrigerant compressor (150c) and then supplied to the fourth main refrigerant economizer (140d).

[0126] In addition, if the temperature of the second main refrigerant stream (RL2) from which cold heat is recovered by heat exchange in the third main refrigerant economizer (140c) is lower than the first set temperature, it is supplied to the auxiliary refrigerant cycle (200) and the remaining cold heat is further recovered and then transferred to the main refrigerant junction (160). If it is higher than the first set temperature, it may not be supplied to the auxiliary refrigerant cycle (200) but may be transferred to the main refrigerant junction (160).

[0127] According to the embodiment illustrated in FIG. 1, the temperature of the second main refrigerant stream (RL2) from which cold heat has been recovered by heat exchange in the third main refrigerant economizer (140c) is lower than the first set temperature, and the remaining cold heat can be further recovered to cool the auxiliary refrigerant stream circulating in the auxiliary refrigerant cycle (200) before being transferred to the main refrigerant junction (160).

[0128] 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 so that the fourth main refrigerant stream (RL4) can be cooled.

[0129] The fourth main refrigerant stream (RL4) cooled by heat exchange in the fourth main refrigerant economizer (140d) can be compressed in the fourth main refrigerant compressor (150d) and then supplied to the fifth main refrigerant economizer (140e).

[0130] In addition, if the temperature of the third main refrigerant stream (RL3) from which cold heat is recovered by heat exchange in the fourth main refrigerant economizer (140d) is lower than the first set temperature, it is supplied to the auxiliary refrigerant cycle (200) so that the remaining cold heat is further recovered and then transferred to the main refrigerant junction (160). If it is higher than the first set temperature, it may not be supplied to the auxiliary refrigerant cycle (200) but may be transferred to the main refrigerant junction (160).

[0131] According to the embodiment illustrated in FIG. 1, the temperature of the third primary refrigerant stream (RL3) from which cold heat is recovered by heat exchange in the fourth primary refrigerant economizer (140d) exceeds the first set temperature, and may be transferred to the primary refrigerant junction (160) without being supplied to the auxiliary refrigerant cycle (200).

[0132] 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 so that the fifth main refrigerant stream (RL5) can be cooled.

[0133] The fifth main refrigerant stream (RL5) cooled by heat exchange in the fifth main refrigerant economizer (140e) can be compressed in the fifth main refrigerant compressor (150e) and then supplied to the sixth main refrigerant economizer (140f).

[0134] In addition, if the temperature of the fourth main refrigerant stream (RL4) from which cold heat is recovered by heat exchange in the fifth main refrigerant economizer (140e) is lower than the first set temperature, it is supplied to the auxiliary refrigerant cycle (200) so that the remaining cold heat is further recovered and then transferred to the main refrigerant junction (160). If it is higher than the first set temperature, it may not be supplied to the auxiliary refrigerant cycle (200) but may be transferred to the main refrigerant junction (160).

[0135] According to the embodiment illustrated in FIG. 1, the temperature of the fourth primary refrigerant stream (RL4) from which cold heat is recovered by heat exchange in the fifth primary refrigerant economizer (140e) exceeds the first set temperature, and may be transferred to the primary refrigerant junction (160) without being supplied to the auxiliary refrigerant cycle (200).

[0136] 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) exchange heat so that the sixth main refrigerant stream (RL6) can be cooled.

[0137] The sixth main refrigerant stream (RL6) cooled by heat exchange in the sixth main refrigerant economizer (140f) can be compressed in the sixth main refrigerant compressor (150f) and then supplied to the seventh main refrigerant economizer (140g).

[0138] In addition, if the temperature of the fifth main refrigerant stream (RL5) from which cold heat is recovered by heat exchange in the sixth main refrigerant economizer (140f) is lower than the first set temperature, it is supplied to the auxiliary refrigerant cycle (200) so that the remaining cold heat is further recovered and then transferred to the main refrigerant junction (160). If it is higher than the first set temperature, it may not be supplied to the auxiliary refrigerant cycle (200) but may be transferred to the main refrigerant junction (160).

[0139] According to the embodiment illustrated in FIG. 1, the temperature of the fifth primary refrigerant stream (RL5) from which cold heat is recovered by heat exchange in the sixth primary refrigerant economizer (140f) exceeds the first set temperature, and may be transferred to the primary refrigerant junction (160) without being supplied to the auxiliary refrigerant cycle (200).

[0140] In the seventh main refrigerant economizer (140g), which is the last stage, the seventh main refrigerant stream (RL7) branched from the main refrigerant branch (120) and the sixth main refrigerant stream (RL6) cooled in the sixth main refrigerant economizer (140f) undergo heat exchange so that the seventh main refrigerant stream (RL7) can be cooled.

[0141] The seventh main refrigerant stream (RL7) cooled by heat exchange in the seventh main refrigerant economizer (140g) can be compressed in the seventh main refrigerant compressor (150g) and then transferred to the main refrigerant junction (160).

[0142] In addition, if the temperature of the sixth main refrigerant stream (RL6) from which cold heat is recovered by heat exchange in the seventh main refrigerant economizer (140g) is lower than the first set temperature, it is supplied to the auxiliary refrigerant cycle (200) so that the remaining cold heat is further recovered and then transferred to the main refrigerant junction (160). If it is higher than the first set temperature, it may not be supplied to the auxiliary refrigerant cycle (200) but may be transferred to the main refrigerant junction (160).

[0143] According to the embodiment illustrated in FIG. 1, the temperature of the sixth main refrigerant stream (RL6) from which cold heat is recovered by heat exchange in the seventh main refrigerant economizer (140g) exceeds the first set temperature, and can be transferred to the main refrigerant junction (160) without being supplied to the auxiliary refrigerant cycle (200).

[0144] The residual 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) is further recovered in several stages using the second main refrigerant economizer (140b) and other subsequent main refrigerant economizers, while 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.

[0145] Seven primary refrigerant streams transferred to the primary refrigerant junction (160) may be combined into one primary refrigerant stream (RL) and transferred to the primary refrigerant heater (170). The primary refrigerant stream (RL) may be heated in the primary refrigerant heater (170) and then recycled to the primary refrigerant turbine-generator (110).

[0146] 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.

[0147] 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).

[0148] 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.

[0149] 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.

[0150] 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.

[0151] Meanwhile, among the plurality of primary refrigerant streams from which cold heat is recovered in the primary refrigerant economizer, at least one primary refrigerant stream is supplied to the auxiliary refrigerant cycle, so that the remaining cold heat of the primary refrigerant stream is further recovered in the auxiliary refrigerant cycle (200), thereby improving the power generation efficiency of the power generation system.

[0152] The auxiliary refrigerant cycle (200) can additionally recover the remaining cold heat of the main refrigerant stream that is transferred after the cold heat is recovered from the first main refrigerant economizer (130).

[0153] The auxiliary refrigerant cycle (200) of the present embodiment can be provided one or more stages downstream of the main refrigerant cycle (100), and the main refrigerant stream from which cold heat has been recovered while sequentially passing through the main refrigerant cycle and the auxiliary refrigerant cycle can be combined at the main refrigerant junction (160) and recycled to the main refrigerant turbine-generator (110).

[0154] The auxiliary refrigerant cycle (200) 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, 240c) that cools each of the plurality of auxiliary refrigerant streams, an auxiliary refrigerant compressor (250a, 250b, 250c) that pressurizes the auxiliary refrigerant stream cooled in the auxiliary refrigerant economizer (230, 240b, 240c), an auxiliary refrigerant joining unit (260) that joins the plurality of auxiliary refrigerant streams compressed in the auxiliary refrigerant compressors (250a, 250b, 250c) into one auxiliary refrigerant stream (NL), and an auxiliary refrigerant It may include at least one auxiliary refrigerant heater (270) that heats the auxiliary refrigerant stream (NL) joined at the joining portion (260) and recirculates it to the auxiliary refrigerant turbine-generator (210).

[0155] This embodiment will be described based on the assumption that the auxiliary refrigerant cycle is equipped with three stages. However, the number of stages of the auxiliary refrigerant cycle is not limited.

[0156] 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), a second auxiliary refrigerant stream (NL2), and a third auxiliary refrigerant stream (NL3) in the auxiliary refrigerant branch section (220).

[0157] The first auxiliary refrigerant stream (NL1), the second auxiliary refrigerant stream (NL2), and the third auxiliary refrigerant stream (NL3) are names used to distinguish and describe streams that are branched off from the auxiliary refrigerant stream (NL). Each of the branched auxiliary refrigerant streams may be the same substance that flows along 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.

[0158] Since this embodiment is described based on the auxiliary refrigerant cycle having three stages, the auxiliary refrigerant economizer according to this embodiment may include three auxiliary refrigerant economizers, including a first auxiliary refrigerant economizer (230) that cools a first auxiliary refrigerant stream (NL1), a second auxiliary refrigerant economizer (240b) that cools a second auxiliary refrigerant stream (NL2), and a third auxiliary refrigerant economizer (240c) that cools a third auxiliary refrigerant stream (NL3).

[0159] Additionally, downstream of the three auxiliary refrigerant economizers, three auxiliary refrigerant compressors corresponding to each auxiliary refrigerant economizer may be provided.

[0160] The auxiliary refrigerant compressor of the present embodiment may include three 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), a second auxiliary refrigerant compressor (250b) that compresses a second auxiliary refrigerant stream (NL2) cooled in a second auxiliary refrigerant economizer (240b), and a third auxiliary refrigerant compressor (250c) that compresses a third auxiliary refrigerant stream (NL3) cooled in a third auxiliary refrigerant economizer (240c).

[0161] 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.

[0162] In at least one auxiliary refrigerant economizer among a plurality of auxiliary refrigerant economizers, the auxiliary refrigerant stream and the main refrigerant stream transferred after the cold heat is recovered in the main refrigerant cycle (100) are heat-exchanged, and the auxiliary refrigerant stream can be cooled by recovering the remaining cold heat of the main refrigerant stream through the heat exchange.

[0163] Among the multiple auxiliary refrigerant economizers, the auxiliary refrigerant economizer provided at least in the first stage, i.e., the first auxiliary refrigerant economizer (230), can use the main refrigerant stream transferred after the cold heat is first recovered in the main refrigerant cycle (100) as a refrigerant for cooling the auxiliary refrigerant stream.

[0164] In the primary refrigerant cycle (100), the number of auxiliary refrigerant economizers that use the transferred primary refrigerant stream as a refrigerant for cooling the secondary refrigerant stream, i.e., among a plurality of auxiliary refrigerant economizers, is not limited to which auxiliary refrigerant economizer is installed in which stage the primary refrigerant stream is used as a refrigerant.

[0165] The main refrigerant stream to be supplied as the refrigerant to the auxiliary refrigerant economizer provided in which stage can be determined by the composition, pressure, temperature and flow rate of the main refrigerant stream transferred to the auxiliary refrigerant cycle (200), and the target temperature of the auxiliary refrigerant stream downstream of each auxiliary refrigerant economizer (hereinafter referred to as “second set temperature”).

[0166] That is, the main refrigerant stream transferred to the auxiliary refrigerant cycle (200) can be supplied to the auxiliary refrigerant economizer of the stage where the temperature of the auxiliary refrigerant stream cooled by heat exchange when the main refrigerant stream and the auxiliary refrigerant stream are heat-exchanged becomes lower than the second set temperature.

[0167] However, the second set temperature must be higher than the freezing point of the auxiliary refrigerant stream.

[0168] The above-described embodiment is explained as an example in which the first main refrigerant stream (RL1) from which cold heat is recovered in the second main refrigerant economizer (140b) and the second main refrigerant stream (RL2) from which cold heat is recovered in the third main refrigerant economizer (140c) are used as refrigerants in the auxiliary refrigerant cycle (200).

[0169] The temperature of the first main refrigerant stream (RL1) transferred to the auxiliary refrigerant cycle (200) is lower than the temperature of the second main refrigerant stream (RL2), and the first main refrigerant stream (RL1) can be supplied as the refrigerant of the auxiliary refrigerant economizer of the stage preceding the second main refrigerant stream (RL2).

[0170] Referring to FIG. 1, in the present embodiment, the first main refrigerant stream (RL1) transferred to the auxiliary refrigerant cycle (200) after the cold heat is recovered in the main refrigerant cycle (100) may be supplied as the refrigerant of the auxiliary refrigerant economizer provided in the first stage among a plurality of auxiliary refrigerant economizers, i.e., the first auxiliary refrigerant economizer (230), and the second main refrigerant stream (RL2) transferred to the auxiliary refrigerant cycle (200) after the cold heat is recovered in the main refrigerant cycle (100) may be supplied as the refrigerant of the auxiliary refrigerant economizer provided in the last stage among a plurality of auxiliary refrigerant economizers, i.e., the third auxiliary refrigerant economizer (240c).

[0171] In the first auxiliary refrigerant economizer (230), the first auxiliary refrigerant stream (NL1) branched from the auxiliary refrigerant branch (220) and the first main refrigerant stream (RL1) transferred after the cooling heat is first recovered in the main refrigerant cycle (100) undergo heat exchange, and the first auxiliary refrigerant stream (NL1) can be cooled by recovering the remaining cooling heat of the first main refrigerant stream (RL1) through the heat exchange.

[0172] In the third auxiliary refrigerant economizer (240c), the third auxiliary refrigerant stream (NL3) branched from the auxiliary refrigerant branch (220) and the second main refrigerant stream (RL2) transferred after the cooling heat is first recovered from the main refrigerant cycle (100) undergo heat exchange, and the third auxiliary refrigerant stream (NL3) can be cooled by recovering the remaining cooling heat of the second main refrigerant stream (RL2) through the heat exchange.

[0173] The main refrigerant stream, from which residual cold heat has been recovered while being used as a refrigerant to cool the auxiliary refrigerant stream in the auxiliary refrigerant economizer, can be recycled to the main refrigerant turbine-generator (110) through the main refrigerant junction (160) or through another route.

[0174] In this way, by recovering the remaining cold heat of the main refrigerant stream, which is used as a refrigerant in the main refrigerant cycle (100) and from which cold heat is recovered, as cold heat for cooling the auxiliary refrigerant stream in the auxiliary refrigerant cycle (200), the cold heat of the liquefied hydrogen can be utilized to the maximum extent, and furthermore, the effect of reducing the energy load for heating the main refrigerant stream for recycling to the main refrigerant turbine-generator (110) can be expected.

[0175] Meanwhile, the first auxiliary refrigerant stream (NL1) cooled while recovering the remaining cold heat of the main refrigerant stream 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.

[0176] 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 may be compressed in an auxiliary refrigerant compressor and then supplied as a refrigerant to an auxiliary refrigerant economizer of the next stage.

[0177] Additionally, the auxiliary refrigerant stream cooled in one of the auxiliary refrigerant economizers among the plurality of auxiliary refrigerant economizers may be heated in the auxiliary refrigerant heater (270) through the auxiliary refrigerant junction (260) and recycled to the auxiliary refrigerant turbine-generator (210).

[0178] In the present embodiment, 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.

[0179] By branching the expanded auxiliary refrigerant stream (NL) in the auxiliary refrigerant turbine-generator (110) into at least two streams including a first auxiliary refrigerant stream (NL1) and a second auxiliary refrigerant stream (NL2), and further recovering the residual cold heat of the first auxiliary refrigerant stream (NL1) from which the residual cold heat of the main refrigerant stream is recovered in the first auxiliary refrigerant economizer (230) through heat exchange with the second auxiliary refrigerant stream (NL2) in the second auxiliary refrigerant economizer (240b), there is an 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.

[0180] The second auxiliary refrigerant stream (NL2) cooled by heat exchange in the second auxiliary refrigerant economizer (240b) may 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), or may be supplied as a refrigerant for cooling the third auxiliary refrigerant stream (NL3) in the third auxiliary refrigerant economizer (240c), which is the auxiliary refrigerant economizer of the next stage.

[0181] Each auxiliary refrigerant stream branched from the auxiliary refrigerant branch section (220) of the present embodiment may be cooled by heat exchange with the main refrigerant stream transferred after the cold heat has been recovered in the main refrigerant cycle (100) 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).

[0182] Additionally, the auxiliary refrigerant stream cooled by heat exchange in each auxiliary refrigerant economizer may 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.

[0183] 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.

[0184] In this embodiment, since the auxiliary refrigerant economizer is provided in three stages as an example, the third main refrigerant stream (NL3) cooled in the third auxiliary refrigerant economizer (240c), which is the auxiliary refrigerant economizer of the last stage, can be transferred to the auxiliary refrigerant junction (260) through a compression process.

[0185] 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.

[0186] 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).

[0187] 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.

[0188] 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.

[0189] 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.

[0190] In this embodiment, liquefied hydrogen can be supplied to a gas consumer through a liquefied gas line (LL) after the cold heat is recovered in the main refrigerant cycle.

[0191] 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.

[0192] Although not shown in the drawing, according to the present embodiment, a liquefied gas heater (not shown) may be further included, which is provided downstream of the first main refrigerant economizer (130) and heats liquefied hydrogen that is heated by heat exchange in the first main refrigerant economizer (130) and supplied to a gas demand source.

[0193] The heat source for heating liquefied hydrogen in a liquefied gas heater may be, but is not limited to, seawater, fresh water, combustion gas, or the atmosphere.

[0194]

[0195] *Liquefied hydrogen introduced into the liquefied gas heater in a liquid state can be heated and completely vaporized by the liquefied gas heater. Furthermore, liquefied hydrogen introduced into the liquefied gas heater in a gaseous state, i.e., regasified gas, can be heated by the liquefied gas heater to the temperature required by the gas demand source. The regasified gas transported from the liquefied gas heater to the gas demand source can satisfy the temperature requirements of the gas demand source.

[0196]

[0197] Meanwhile, the power generation system according to an embodiment of the present invention illustrated in FIG. 2 is a modified example of the power generation system illustrated in FIG. 1 described above, and differs from the embodiment illustrated in FIG. 1 in that it further includes a residual heat merging unit (180) and has a two-stage auxiliary refrigerant cycle (200). Hereinafter, only the differences will be mainly described.

[0198] By further including the residual heat merging unit (180), compared to the embodiment illustrated in FIG. 1 in which two or more primary refrigerant streams are supplied to two or more auxiliary refrigerant economizers without the residual heat merging unit (180), the number of stages of the auxiliary refrigerant cycle (200) is reduced. That is, compared to the embodiment illustrated in FIG. 1 in which the auxiliary refrigerant cycle (200) is provided in three stages, the power generation efficiency can be improved to a similar level with only the auxiliary refrigerant cycle (200) provided in two stages.

[0199] According to this modified example, it may further include a residual heat combining unit (180) for combining one or more primary refrigerant streams transferred from one or more primary refrigerant economizers to the auxiliary refrigerant cycle (200) into one stream.

[0200] In the case where a residual heat merging unit (180) is further included, the first primary refrigerant stream (RL1) from which cold heat is recovered by heat exchange with the second primary refrigerant stream (RL2) in the second primary refrigerant economizer (140b), and the second primary refrigerant stream (RL2) from which cold heat is recovered by heat exchange with the third primary refrigerant stream (RL3) in the third primary refrigerant economizer (140c) may be combined into one primary refrigerant residual heat stream (RLa) in the residual heat merging unit (180) and supplied as a refrigerant for cooling the first secondary refrigerant stream (NL1) in the first secondary refrigerant economizer (230).

[0201] However, it is not limited thereto, and the primary refrigerant streams from which cold heat has been recovered from one or more primary refrigerant economizers among a plurality of primary refrigerant economizers may be combined at a residual heat merging portion (180) to generate one primary refrigerant residual heat stream (RLa).

[0202] Additionally, the primary refrigerant residual heat stream (RLa) generated in the residual heat junction (180) can be supplied as a refrigerant to one of the plurality of secondary refrigerant economizers, depending on the temperature of the primary refrigerant residual heat stream (RLa).

[0203] The supply of the primary refrigerant residual heat stream (RLa) as the refrigerant of the auxiliary refrigerant economizer provided in which stage can be determined by the composition, pressure, temperature and flow rate of the primary refrigerant residual heat stream (RLa), and the second set temperature.

[0204] That is, the primary refrigerant residual heat stream (RLa) transferred to the secondary refrigerant cycle (200) can be supplied to the secondary refrigerant economizer of the stage where the temperature of the secondary refrigerant stream cooled by heat exchange when the primary refrigerant residual heat stream (RLa) and the secondary refrigerant stream are heat-exchanged becomes lower than the second set temperature.

[0205] In one of the plurality of auxiliary refrigerant economizers, the main refrigerant residual heat stream (RLa) from which residual cold heat has been recovered by heat exchange with the auxiliary refrigerant stream can be recycled to the main refrigerant turbine-generator (110) through the main refrigerant junction (160) or another path.

[0206] Referring to FIG. 2, this modified example is explained by way of example in which the main refrigerant residual heat stream (RLa) is supplied to the first auxiliary refrigerant economizer (230).

[0207] In this modified example, in the first auxiliary refrigerant economizer (230), the first auxiliary refrigerant stream (NL1) branched from the auxiliary refrigerant branch (220) and the main refrigerant residual heat stream (RLa) exchange heat, and through the heat exchange, the first auxiliary refrigerant stream (NL1) can be cooled by recovering the residual cold heat of the main refrigerant residual heat stream (RLa).

[0208] The first auxiliary refrigerant stream (NL1) cooled while recovering the residual cold heat of the main refrigerant residual heat stream (RLa) 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.

[0209] The main refrigerant residual heat stream (RLa) from which residual cold heat is recovered in the first auxiliary refrigerant economizer (230) can be recycled to the main refrigerant turbine-generator (110) through the main refrigerant junction (160) or through a separate path.

[0210] 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.

[0211] The second auxiliary refrigerant stream (NL2) cooled by heat exchange in the second auxiliary refrigerant economizer (240b) may 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), or, if there is an auxiliary refrigerant economizer in the next stage, may be supplied as a refrigerant to the auxiliary refrigerant economizer in the next stage.

[0212] In this modified example, since the second auxiliary refrigerant economizer (240b) is the last-stage auxiliary refrigerant economizer, the second auxiliary refrigerant stream (NL2) cooled by heat exchange in the second auxiliary refrigerant economizer (240b) and the first auxiliary refrigerant stream (NL1) from which cold heat has been recovered by heat exchange can be supplied to the auxiliary refrigerant heater (270) through the auxiliary refrigerant junction (260), heated, and then recycled to the auxiliary refrigerant turbine-generator (210).

[0213]

[0214] According to one embodiment of the present invention described above, after recovering the cold heat of liquefied hydrogen in the main refrigerant cycle (100), the remaining cold heat of the main refrigerant stream from which the cold heat has been recovered is further recovered in the auxiliary refrigerant cycle (200), thereby recovering and utilizing the cold heat of liquefied hydrogen to the maximum extent possible.

[0215] When the cold heat of the liquid hydrogen is recovered in multiple stages in the main refrigerant cycle (100) using the main refrigerant and the remaining cold heat of the main refrigerant is further recovered in the auxiliary refrigerant cycle (200) 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 (100) and auxiliary refrigerant cycle (200) is greater than the power consumption required to operate the increased number of equipment such as the compressor, and as a result, the power generation efficiency is improved.

[0216] In this embodiment, the primary refrigerant and the auxiliary refrigerant are circulated in the primary refrigerant cycle (100) and the auxiliary refrigerant cycle (200), respectively, such that the pressure does not fall below or above the critical pressure. In other words, no phase change occurs in the primary refrigerant and the auxiliary refrigerant during the cycle, regardless of the temperature.

[0217] 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.

[0218] Since the primary refrigerant and the auxiliary refrigerant are maintained above the critical pressure while circulating in the primary refrigerant cycle (100) and the auxiliary refrigerant cycle (200), respectively, the pinch points of the primary refrigerant economizer and the auxiliary refrigerant economizer do not exist inside the device, or at least the effect occurs at a low temperature near the end of the heat exchanger, so that heat exchange performance can be maximized. In addition, since slugging does not occur, there is almost no piping stress applied to the piping through which the working fluid flows.

[0219] Additionally, in the present embodiment, the primary refrigerant and auxiliary refrigerant may be maintained in a supercritical state while circulating the primary refrigerant cycle (100) and auxiliary refrigerant cycle (200), respectively. When the primary refrigerant and auxiliary refrigerant are maintained in a supercritical state, the primary refrigerant and auxiliary refrigerant flow in a high-density state, thereby enabling the size of the power generation system to be reduced.

[0220]

[0221] 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 6.3% or more 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. 4).

[0222] In Fig. 4, 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.

[0223] The multi-loop power generation system using the cold energy of liquefied gas according to the present embodiment illustrated in FIGS. 1 and 2 increases the total number of stages and thus the initial cost, compared to the single-loop power generation system equipped with the 7-stage main refrigerant cycle illustrated in FIG. 4.

[0224] 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).

[0225]

[0226] 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.

[0227] <Explanation of symbols>

[0228] 110: Main refrigerant turbine-generator

[0229] 120: Main refrigerant branch

[0230] 130, 140b, 140c, 140d, 140e, 140f, 140g: Main refrigerant economizer

[0231] 150a, 150b, 150c, 150d, 150e, 150f, 150g: Main refrigerant compressor

[0232] 160: Main refrigerant junction

[0233] 170: Main refrigerant heater

[0234] 180: Residual heat junction

[0235] RL, RL1, RL2, RL3, RL4, RL5, RL6, RL7: Main refrigerant streams

[0236] RLa: Main refrigerant residual heat stream

[0237] 210: Auxiliary refrigerant turbine-generator

[0238] 220: Auxiliary refrigerant branch

[0239] 230, 240b, 240c: Auxiliary refrigerant economizer

[0240] 250a, 250b, 250c: Auxiliary refrigerant compressor

[0241] 260: Auxiliary refrigerant junction

[0242] 270: Auxiliary refrigerant heater

[0243] NL, NL1, NL2, NL3: Auxiliary refrigerant stream

[0244] LL: Liquefied gas line

Claims

1. A primary refrigerant turbine-generator that generates electricity by driving a turbine with a primary refrigerant stream; A main refrigerant branch unit for branching the expanded main refrigerant stream while driving the turbine into two or more main refrigerant streams including a first main refrigerant stream and a second main refrigerant stream; A first primary refrigerant economizer for recovering cold heat of the liquefied gas by heat-exchanging the first primary refrigerant stream and the liquefied gas, and two or more primary refrigerant economizers for cooling the two or more primary refrigerant streams, respectively; A primary refrigerant compressor that supplies a primary refrigerant stream cooled in one of the two or more primary refrigerant economizers as a refrigerant for another primary refrigerant economizer; An auxiliary refrigerant turbine-generator that generates electric power by driving a turbine with an auxiliary refrigerant stream; and A multi-loop power generation system utilizing the cold heat of liquefied gas, comprising an auxiliary refrigerant economizer that cools the auxiliary refrigerant stream by heat-exchanging an expanded auxiliary refrigerant stream while driving the turbine and one or more main refrigerant streams discharged after heat exchange in the two or more main refrigerant economizers; 2. In claim 1, A multi-loop power generation system utilizing the cold heat of liquefied gas, further comprising a primary refrigerant heater for heating the primary refrigerant stream from which cold heat has been recovered in the two or more primary refrigerant economizers and the auxiliary refrigerant economizers and recirculating the heated primary refrigerant stream to the primary refrigerant turbine-generator.

3. In claim 1, A multi-loop power generation system utilizing cold heat of liquefied gas, further comprising a residual heat combining unit that combines two or more primary refrigerant streams supplied as refrigerant of an auxiliary refrigerant economizer from the two or more primary refrigerant economizers into one stream and supplies them.

4. In claim 1, Further comprising an auxiliary refrigerant branch section for branching the expanded auxiliary refrigerant stream into at least one auxiliary refrigerant stream including at least one of a first auxiliary refrigerant stream and a second auxiliary refrigerant stream; A multi-loop power generation system utilizing the cold energy of liquefied gas, wherein at least one auxiliary refrigerant economizer is provided to cool each of the at least one auxiliary refrigerant streams.

5. In claim 4, A multi-loop power generation system utilizing the cold heat of liquefied gas, wherein one or more primary refrigerant streams supplied as refrigerant to an auxiliary refrigerant economizer from one or more of the above two or more primary refrigerant economizers are each supplied to one or more of the above auxiliary refrigerant economizers.

6. In claim 4, The above auxiliary refrigerant economizer is equipped with two or more, A multi-loop power generation system utilizing the cold energy of liquefied gas, further comprising an auxiliary refrigerant compressor that supplies an auxiliary refrigerant stream cooled in one of the two or more auxiliary refrigerant economizers as the refrigerant of another auxiliary refrigerant economizer.

7. In claim 1, An auxiliary refrigerant compressor for compressing an auxiliary refrigerant stream cooled in the above auxiliary refrigerant economizer; and A multi-loop power generation system utilizing cold energy from liquefied gas, further comprising an auxiliary refrigerant heater for heating the auxiliary refrigerant stream compressed in the auxiliary refrigerant compressor and recirculating it to the auxiliary refrigerant turbine-generator.

8. 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.

9. 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.

10. Primary refrigerant power generation stage that generates electricity by driving a turbine with the primary refrigerant stream; A primary refrigerant branching step for branching the expanded primary refrigerant stream into two or more primary refrigerant streams including a first primary refrigerant stream and a second primary refrigerant stream while driving the turbine; A liquefied gas cold heat recovery step for cooling the first main refrigerant stream using liquefied gas as a refrigerant; A primary refrigerant cooling step in which one or more primary refrigerant streams including the second primary refrigerant stream are cooled, wherein one primary refrigerant stream among the cooled primary refrigerant streams is used as a refrigerant for cooling another primary refrigerant stream; An auxiliary refrigerant generation step that generates electricity by driving a turbine with an auxiliary refrigerant stream; and A multi-loop power generation method using cold heat from liquefied gas, comprising: a residual cold heat recovery step of cooling the auxiliary refrigerant stream by heat-exchanging the expanded auxiliary refrigerant stream while driving the turbine and one or more main refrigerant streams from which cold heat has been recovered in the main refrigerant cooling step; 11. In claim 10, A multi-loop power generation method using cold heat from liquefied gas, further comprising a primary refrigerant heating step for heating the primary refrigerant stream from which cold heat has been recovered in the primary refrigerant cooling step and the residual cold heat recovery step and recirculating the heated primary refrigerant stream to the primary refrigerant power generation step.

12. In claim 10, A multi-loop power generation method using cold heat from liquefied gas, further comprising a residual heat combining step for combining two or more primary refrigerant streams supplied as refrigerant to the residual cold heat recovery step into one stream and supplying them.

13. In claim 10, An auxiliary refrigerant branching step for branching the expanded auxiliary refrigerant stream into at least two auxiliary refrigerant streams including a first auxiliary refrigerant stream and a second auxiliary refrigerant stream; A step of cooling one or more auxiliary refrigerant streams including the second auxiliary refrigerant stream, wherein one of the cooled one or more auxiliary refrigerant streams is supplied as a refrigerant to cool another auxiliary refrigerant stream, thereby cooling the auxiliary refrigerant stream; and A multi-loop power generation method using cold energy from liquefied gas, further comprising an auxiliary refrigerant heating step of heating the auxiliary refrigerant stream cooled in the auxiliary refrigerant cooling step or the auxiliary refrigerant stream used as a refrigerant in the auxiliary refrigerant cooling step and recirculating it to the auxiliary refrigerant power generation step.

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