Steam supply system and steam supply method

Abstract

Provided is a steam supply system that enables effective utilization of generated negative pressure steam at a heat utilization location. A steam supply unit (1A) comprises a water circulation path (3). The water circulation path (3) comprises: flow rate adjustment valve (7) that decompresses water to a negative pressure to generate negative pressure water, a first heat exchanger (9) that transfers heat between the negative pressure water and a heating medium to generate negative steam, a second heat exchanger (11) that generates condensed water from the negative pressure steam by transferring heat between the negative pressure steam and heat utilization destination (15); and a water pump (5) that supplies the condensed water to the flow rate adjustment valve (7).

Description

Technical Field

[0001] The present disclosure relates to a steam supply system and a steam supply method.Background Art

[0002] In recent years, initiatives toward carbon neutrality have been actively pursued in the industrial field. In the industrial field, about 85% of the consumed energy used for thermal applications. As a main heat source for performing heat supply, a fuel-burning boiler has been used in the related art. On the other hand, substituting heat pumps for decarbonization is being keenly studied.

[0003] It is known that a heat pump is used to generate negative pressure steam (for example, PTL 1). Since steam can be generated by heating at a low temperature of less than 100°C, it is advantageous in terms of energy saving.

[0004] In addition, in a case where steam is supplied to each process of a plant, a centralized disposition method in which a fuel-burning boiler of about 650 kW is installed at one location in the plant and steam is distributed to each process through a header is widely used.Citation ListPatent Literature

[0005] [PTL 1] Japanese Unexamined Patent Application Publication No. 2014-102062Summary of InventionTechnical Problem

[0006] In PTL 1, although a negative pressure steam is generated, the negative pressure steam is used by being pressurized by a steam compressor, and there is no consideration of using the negative pressure steam itself.

[0007] For example, in a surface treatment tank in a plant or the like, steam is used to maintain a temperature, and there are many processes in which a temperature on a user side is less than 100°C (furthermore, 80°C or lower). As described above, there is a certain demand for the negative pressure steam itself having a saturation temperature of lower than 100°C.

[0008] In addition, instead of the above-described centralized disposition method, in a case where a distributed disposition is adopted in which the capacity of a steam utilization side and the capacity of a steam supply side are matched one-to-one corresponded to each other and the equipment is installed in the vicinity of each process, a steam transportation loss as in the centralized disposition method can be reduced.

[0009] The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a steam supply system and a steam supply method capable of effectively using generated negative pressure steam at a heat use destination.

[0010] Another object of the present disclosure is to provide the steam supply system and the steam supply method in which a distributed disposition is realizable.Solution to Problem

[0011] A steam supply system according to an aspect of the present disclosure includes: a decompression unit that decompresses water to a negative pressure to generate negative pressure water; a first heat exchanger that exchanges heat between the negative pressure water and a heating medium to generate negative pressure steam; a second heat exchanger that generates condensate of the negative pressure steam by exchanging heat between the negative pressure steam and a heat use destination; and a water supply unit that supplies the condensate to the decompression unit.

[0012] A steam supply method comprising: a decompression step of decompressing water to a negative pressure to generate negative pressure water in a decompression unit; a first heat exchange step of exchanging heat between the negative pressure water and a heating medium to generate negative pressure steam; a second heat exchange step of generating condensate of the negative pressure steam by exchanging the heat between the negative pressure steam and a heat use destination; and a water supply step of supplying the condensate to the decompression unit.Advantageous Effects of Invention

[0013] The generated negative pressure steam can be effectively used at the heat use destination.

[0014] In addition, since it is sufficient to install equipment having a capacity of supplying a heating medium to the extent of generating negative pressure steam, the equipment can be disposed in the distributed disposition.Brief Description of Drawings

[0015] FIG. 1 is a schematic configuration diagram showing a steam supply system according to a first embodiment of the present disclosure. FIG. 2 is a schematic configuration diagram showing a steam supply system according to a second embodiment of the present disclosure. FIG. 3 is a schematic configuration diagram showing a steam supply system according to a third embodiment of the present disclosure. FIG. 4 is a schematic configuration diagram showing a steam supply system according to a fourth embodiment of the present disclosure. Description of Embodiments

[0016] Embodiments according to the present disclosure will be described below with reference to the drawings.[First Embodiment]

[0017] Hereinafter, a first embodiment of the present disclosure will be described with reference to FIG. 1.

[0018] The steam supply system 1A includes a water circulation passage 3 that is closed. The water pump (water supply unit) 5, the flow rate control valve (decompression unit) 7, the first heat exchanger 9, and the second heat exchanger 11 are provided in the water circulation passage 3.

[0019] The water pump 5 is controlled by a control unit (not shown), and sucks the negative pressure water of the water circulation passage 3 and discharges the negative pressure water to the flow rate control valve 7. The water discharged at this time is pressurized and remains at the negative pressure or is the positive pressure. As the water pump 5, for example, a self-priming vortex pump, a gear pump, or the like can be used.

[0020] The control unit (not shown) includes, for example, a central processing unit (CPU), a random-access memory (RAM), a read-only memory (ROM), a computer-readable storage medium, and the like. A series of pieces of processing for achieving various functions is stored in, for example, a storage medium or the like in the form of a program, and the CPU reads out the program to the RAM or the like, and executes processing for information processing and arithmetic processing of information, to achieve various functions. The program may adopt a form in which the program is installed in advance in the ROM or another storage medium, a form in which the program is provided in a stored state in the computer-readable storage medium, or a form in which the program is distributed via wired or wireless communication means. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

[0021] The flow rate control valve 7 is controlled by a controller (not shown), adjusts a flow rate of water sent from the water pump 5, and decompresses the water. The pressure is reduced by the flow rate control valve 7 to make the negative pressure water about 30~70 kPa, for example.

[0022] In the first heat exchanger 9, the negative pressure water supplied from the flow rate control valve 7 and a heating medium flowing through the heating medium flow passage 13 perform heat exchange. As the heating medium, hot water, a refrigerant compressed by a compressor and heated, or the like can be used. In the first heat exchanger 9, the negative pressure water is heated and vaporized by the heating medium to generate the negative pressure steam. For example, in a case where the temperature of the negative pressure water flowing into the first heat exchanger 9 is 80°C, for example, the heating medium of 95 °C, which is lower than 100 °C, is used.

[0023] As the first heat exchanger 9, a non-contact heat exchanger in which the negative pressure water and the heating medium exchange the heat without contact is used, and for example, a partitioned heat exchanger such as a plate-type heat exchanger, a shell and plate heat exchanger, and a shell and tube heat exchanger can be used.

[0024] The second heat exchanger 11 is installed at a heat use destination 15. The heat use destination 15 is heated through the heat medium (for example, water or air) that is heated by the negative pressure steam of lower than 100°C. A pressurization unit such as the steam compressor 10 is not provided between the second heat exchanger 11 and the first heat exchanger 9, and the negative pressure steam generated by the first heat exchanger 9 is directly led to the second heat exchanger.

[0025] As the second heat exchanger 11, the non-contact heat exchanger in which the negative pressure steam and the heat medium of the heat use destination 15 exchange the heat without contact is used, and for example, the partition wall type heat exchanger such as the plate type heat exchanger, a fin and tube heat exchanger, or an immersion heat exchanger can be used.

[0026] The negative pressure steam is condensed by releasing the heat to the heat medium of the heat use destination 15 by the second heat exchanger 11 to be the negative pressure water. The negative pressure water is led to the suction side of the water pump 5 through the water circulation passage 3.

[0027] As described above, in the water circulation passage 3, the flow rate control valve (decompression unit) 7, the first heat exchanger 9, the second heat exchanger 11, and the water pump (water supply unit) 5 are provided in this order along a circulation direction of the water. The water circulation passage 3 comprises these configurations, and thus a passage from a downstream side of the decompression unit 7 to a suction side of the water pump 5 in the passage can be set to be negative pressure. Since the first heat exchanger 9 and the second heat exchanger 11 are provided in the section, the latent heat associated with a change in the state of water can be exchanged with another medium at a temperature lower than 100°C in the heat exchangers.

[0028] The operation and effects of the present embodiment described above are as follows.

[0029] After the water is decompressed to the negative pressure by the flow rate control valve 7, the water is subjected to exchange the heat with the heating medium is heated by the first heat exchanger 9 in the first heat exchanger to generate negative pressure steam of less than 100°C. As a result, the heating medium 9 supplied to the first heat exchanger can be set to lower than 100°C.

[0030] The negative pressure steam of less than 100°C generated by the first heat exchanger 9 exchange with the heat use destination 15 in the second heat exchanger 11 to be condensed, so that heat of less than 100°C can be supplied to the heat use destination 15. Thus, it is possible to meet the demand of the heat use destination 15 requiring heat of less than 100°C.

[0031] In a case where the negative pressure steam is used as it is in the second heat exchanger 11, it is not necessary to install the steam compressor for compressing the negative pressure steam supplied to the second heat exchanger 11, which is advantageous from the viewpoint of cost and maintenance.

[0032] The negative pressure water that is condensed by releasing the latent heat of condensation in the second heat exchanger 11 is supplied to the flow rate control valve 7 by the water pump 5 to form a circulation system of the water. As a result, the effective use of the water can be achieved.

[0033] In order to supply the heat medium for generating the negative pressure steam in the first heat exchanger 9, for example, a heat pump of about several tens to several hundreds of kW can be used. By using the heat pump of this capacity, the capacity of the heat use destination 15 and the capacity of the supply side (heat pump) can be matched one-to-one corresponded to each other, so that the steam supply system 1A can be disposed in the distributed disposition at each position in the plant. As a result, the steam transportation loss can be reduced as compared with a centralized disposition method in which a boiler is installed at one location in the plant and steam is distributed to each process through a header, and heat efficiency can be improved.

[0034] By using the water pump 5 that transfers the negative pressure water led from the second heat exchanger 11 to the flow rate control valve 7, the water circulation passage 3 having a simple configuration can be formed.[Second Embodiment]

[0035] Next, a second embodiment of the present disclosure will be described with reference to FIG. 2. The present embodiment differs in that a different water supply unit is employed instead of the water pump 5 (see FIG. 1) of the first embodiment. The same configurations will be designated by the same reference numerals, and the description thereof will not be repeated.

[0036] As shown in FIG. 2, a steam supply system 1B of the present embodiment comprises a water supply unit 17. The water supply unit 17 comprises a water pump 19, an aspirator 21, and a water tank 23. The water tank 23 is open to the atmosphere. Therefore, the water stored in the water tank 23 is atmospheric pressure. The water pump 19 is controlled by a control unit (not shown), and sucks up the water stored in the water tank 23 and supplies the water to the aspirator 21. The aspirator 21 sucks the negative pressure water led from the second heat exchanger 11 by the low pressure generated by the Venturi effect, and supplies the water to the water tank 23 from the discharge pipe 25 of the water circulation passage 3. The negative pressure water is atmospheric pressure by being led to the water tank 23.

[0037] A water supply pipe 27 of the water circulation passage 3 is provided to be immersed in the water stored in the water tank 23. The water stored in the water tank 23 is led to the flow rate control valve 7 via the water supply pipe 27. As described above, in the water circulation passage 3 according to the present embodiment, the flow rate control valve (decompression unit) 7, the first heat exchanger 9, the second heat exchanger 11, and the aspirator 21 are provided in this order along the circulation direction of the water. By providing the water circulation passage 3 with these configurations, it is possible to create a negative pressure at least in the passage from the downstream side of the decompression unit 7 to the suction side of the aspirator 21. Since the first heat exchanger 9 and the second heat exchanger 11 are provided in the section, the latent heat associated with a change in the state of water can be exchanged with another medium at a temperature lower than 100°C in the heat exchangers.

[0038] The operation and the effects of the present embodiment are as follows in addition to the first embodiment.

[0039] Since the water flowing through the water circulation passage 3 or the steam is set to be negative pressure, in a case in which the water circulation passage 3 is closed, it is difficult to discharge the air that has entered. Therefore, the water tank 23 that opens the negative pressure water to the atmosphere is provided, and the stored water of the water tank 23 set to the atmospheric pressure is led to the flow rate control valve 7 using the water supply pipe 27. As a result, even in a case in which the air enters the water circulation passage 3, the entered air can be discharged.[Third Embodiment]

[0040] Next, a third embodiment of the present disclosure will be described with reference to FIG. 3. In the present embodiment, a specific configuration of the heating medium supplied to the first heat exchanger 9 of the first embodiment is added. The same configurations will be designated by the same reference numerals, and the description thereof will not be repeated. The present embodiment can also be applied to the steam supply system comprising the water supply unit 17 (refer to FIG. 2) as in the second embodiment.

[0041] As shown in FIG. 3, a steam supply system 1C according to the present embodiment includes a heat pump 30. The heat pump 30 includes a refrigerant circulation passage 32 through which the refrigerant circulates. The refrigerant circulation passage 32 is connected to the first heat exchanger 9, and corresponds to the heating medium flow passage 13 in FIG. 1.

[0042] The refrigerant circulation passage 32 includes the compressor 34 that compresses the refrigerant supplied to the first heat exchanger 9, the expansion valve 36 that decompresses the refrigerant that has been subjected to the heat exchange in the first heat exchanger 9, and the evaporator 38 that exchanges heat between the refrigerant decompressed by the expansion valve 36 and the heat source medium to evaporate the refrigerant.

[0043] As the compressor, for example, a scroll compressor or a rotary compressor is used. As the refrigerant, a substitute for fluorocarbon refrigerant or a natural refrigerant such as CO2 is used. As the heat source medium led to the evaporator 38, water or air is used.

[0044] According to the present embodiment, since the heating medium to be supplied to the first heat exchanger 9 is generated by using the heat pump 30, the heating medium heated to the desired temperature can be generated from the heat source medium that is the low-temperature heat source such as water or air.[Fourth Embodiment]

[0045] Next, a fourth embodiment of the present disclosure will be described with reference to FIG. 4. The present embodiment is different from the heat pump 30 of the third embodiment (see FIG. 3) is of a cascade type. The same configurations will be designated by the same reference numerals, and the description thereof will not be repeated. The present embodiment can also be applied to the steam supply system comprising the water supply unit 17 (refer to FIG. 2) as in the second embodiment.

[0046] As shown in FIG. 4, a steam supply system 1D of the present embodiment includes a cascade-type heat pump 40. The cascade-type heat pump 40 includes a high-stage heat pump 40A and a low-stage heat pump 40B.

[0047] The high-stage heat pump 40A includes the high-stage refrigerant circulation passage 42A through which the refrigerant circulates, the high-stage compressor 44A that compresses the refrigerant to be supplied to the first heat exchanger 9, the high-stage expansion valve 46A that decompresses the refrigerant after the heat exchange in the first heat exchanger 9, and the high-stage evaporator 48A that evaporates the refrigerant decompressed by the high-stage expansion valve 46A.

[0048] The low-stage heat pump 40B includes the low-stage refrigerant circulation passage 42B through which the refrigerant circulates, the low-stage compressor 44B that compresses the refrigerant to be supplied to the high-stage evaporator 48A, the low-stage expansion valve 46B that decompresses the refrigerant after the heat exchange in the high-stage evaporator 48A, and the low-stage evaporator 48B that exchanges heat between the refrigerant decompressed by the low-stage expansion valve 46B and the heat source medium to evaporate the refrigerant.

[0049] As the high-stage compressor 44A and the low-stage compressor 44B, for example, a scroll compressor or a rotary compressor is used. Since the required pressure range is different between the high stage and the low stage, it is preferable to use a compressor having high efficiency in the operating pressure range.

[0050] As the refrigerant, a substitute for fluorocarbon refrigerant or a natural refrigerant such as CO2 is used. It is preferable that the refrigerant is different between the high-stage refrigerant circulation passage 42A and the low-stage refrigerant circulation passage 42B. For example, the efficiency can be improved by using the high-pressure refrigerant and the low-pressure refrigerant in a divided manner.

[0051] As the heat source medium led to the low-stage evaporator 48B, water or air is used. In a case in which air is used as the heat source medium, a commercially available air-source heat pump can be used as the low-stage heat pump 40B.

[0052] According to the present embodiment, since the cascade-type heat pump 40 including the high-stage heat pump 40A and the low-stage heat pump 40B is used, the heating medium can be generated from the heat source medium that is a low-temperature heat source such as water or air. Since the heat can be extracted from the heat source medium by the heat pumps 40A and 40B of a plurality of stages as the cascade type, the heat pump 40 can be operated with high efficiency.

[0053] One or a plurality of heat pumps may be provided between the high-stage heat pump 40A and the low-stage heat pump 40B to form a cascade type of three or more stages.

[0054] The steam supply system and the steam supply method according to each embodiment described above are understood as follows.

[0055] A first aspect of the present disclosure relates to a steam supply system including a decompression unit (7) that decompresses water to a negative pressure to generate negative pressure water; a first heat exchanger (9) that exchanges heat between the negative pressure water and a heating medium to generate negative pressure steam; a second heat exchanger (11) that generates condensate of the negative pressure steam by exchanging heat between the negative pressure steam and a heat use destination; and a water supply unit (5) that supplies the condensate to the decompression unit.

[0056] After the water is decompressed to the negative pressure by the decompression unit, the water is subjected to exchange the heat with the heating medium is heated by the first heat exchanger in the first heat exchanger to generate negative pressure steam of less than 100°C. As a result, the heating medium supplied to the first heat exchanger can be set to less than 100°C.

[0057] The negative pressure steam of less than 100°C generated by the first heat exchanger exchange with the heat use destination in the second heat exchanger to be condensed, so that heat of less than 100°C can be supplied to the heat use destination. As a result, it is possible to meet the demand of the heat use destination that requires heat of less than 100°C.

[0058] In a case where the negative pressure steam is used as it is in the second heat exchanger, it is not necessary to install the steam compressor for compressing the negative pressure steam supplied to the second heat exchanger, which is advantageous from the viewpoint of cost and maintenance.

[0059] The condensate that is condensed by releasing the latent heat of condensation in the second heat exchanger is supplied to the decompression unit by the water supply unit to form a circulation system of water. As a result, the effective use of the water can be achieved.

[0060] In addition, since it is sufficient to install an apparatus having a capacity of supplying the heat medium of less than 100°C for generating the negative pressure steam in the first heat exchanger, the apparatus can be disposed in the distributed disposition.

[0061] As the first heat exchanger, for example, a partition type heat exchanger such as a plate-type heat exchanger, a shell and plate heat exchanger, or a shell and tube heat exchanger can be used such that the negative pressure water and the heat medium can exchange the heat without contact.

[0062] As the second heat exchanger, for example, a partition type heat exchanger such as a plate type heat exchanger, a fin-and-tube heat exchanger, or an immersion heat exchanger can be used such that the negative pressure steam and the heat use destination can perform heat exchange without contact.

[0063] As the heating medium, hot water, a refrigerant that is compressed and heated, or the like can be used.

[0064] A second aspect of the present disclosure relates to the steam supply system according to the first aspect, in which the water supply unit includes a water pump (5) that transfers the condensed water led from the second heat exchanger to the decompression unit.

[0065] By using the water pump that transfers the condensate led from the second heat exchanger to the decompression unit, it is possible to form a water circulation passage having a simple configuration.

[0066] As the water pump, for example, a self-priming spiral pump or a gear pump can be used.

[0067] A third aspect of the present disclosure relates to the steam supply system according to the first aspect, in which the water supply unit (17) includes a water tank (23) that opens the condensed water led from the second heat exchanger to an atmosphere, and a water supply pipe (27) that guides the condensed water stored in the water tank and set to atmospheric pressure to the decompression unit.

[0068] Since the water flowing through the water circulation passage or the steam is at a negative pressure, in a case in which the water circulation passage is closed, it is difficult to discharge the air that has entered. Therefore, the water tank that opens the condensate of negative pressure to the atmosphere is provided, and the condensate of the water tank set to the atmospheric pressure is led to the decompression unit using the water supply pipe. As a result, even in a case in which air enters the water circulation passage, the air can be discharged to the atmosphere.

[0069] A fourth aspect of the present disclosure relates to the steam supply system according to any one of the first to third aspects, further including a heat pump (30) that supplies a refrigerant as the heating medium to be supplied to the first heat exchanger, in which the heat pump includes a refrigerant circulation passage (32) for circulating the refrigerant, a compressor (34) that compresses the refrigerant to be supplied to the first heat exchanger, an expansion valve (36) that decompresses the refrigerant after the heat is exchanged in the first heat exchanger, and an evaporator (38) that exchanges heat between a refrigerant decompressed by the expansion valve and heat source medium to evaporate the refrigerant.

[0070] Since the heat pump is used, the heating medium can be generated from the heat source medium that is a low-temperature heat source such as water or air.

[0071] A fourth aspect of the present disclosure relates to the steam supply system according to any one of the first to third aspects, further including a heat pump that supplies a refrigerant as the heating medium to be supplied to the first heat exchanger, in which the heat pump includes a high-stage heat pump (40A) and a low-stage heat pump (40B), the high-stage heat pump includes a high-stage refrigerant circulation passage (42A) for circulating the refrigerant, a high-stage compressor (44A) that compresses the refrigerant to be supplied to the first heat exchanger, a high-stage expansion valve (46A) that decompresses the refrigerant after the heat is exchanged in the first heat exchanger, and a high-stage evaporator (48A) that evaporates a refrigerant decompressed by the high-stage expansion valve, and the low-stage heat pump includes a low-stage refrigerant circulation passage (42B) for circulating the refrigerant, a low-stage compressor (44B) that compresses the refrigerant to be supplied to the high-stage evaporator, a low-stage expansion valve (46B) at decompresses a refrigerant after the heat is exchanged in the high-stage evaporator, a low-stage evaporator (48B) that exchanges heat between a refrigerant decompressed by the low-stage expansion valve and heat source medium to evaporate the refrigerant.

[0072] The heating medium can be generated from the heat source medium that is the low-temperature heat source such as water or air by the cascade-type heat pump including the high-stage heat pump and the low-stage heat pump. Since the heat can be extracted from the heat source medium by a plurality of stages of heat pumps as the cascade type, the heat pump can be operated with high efficiency.

[0073] It should be noted that one or a plurality of heat pumps may be provided between the high-stage heat pump and the low-stage heat pump to form a three-stage or more cascade type.

[0074] A first aspect of the present disclosure relates to a steam supply method including a decompression step of decompressing water to a negative pressure to generate negative pressure water in a decompression unit; a first heat exchange step of exchanging heat between the negative pressure water and a heating medium to generate negative pressure steam; a second heat exchange step of generating condensate of the negative pressure steam by exchanging heat between the negative pressure steam and a heat use destination; and a water supply step of supplying the condensate to the decompression unit.Reference Signs List

[0075] 1A, 1B, 1C, 1D: steam supply system 3: water circulation passage 5: water pump (water supply unit) 7: flow rate control valve (decompression unit) 9: first heat exchanger 11: second heat exchanger 29: heating medium flow passage 15: heat use destination 17: water supply unit 19: water pump 21: aspirator 23: water tank 25: discharge pipe 27: water supply pipe 30: heat pump 32: refrigerant circulation passage 34: compressor 36: expansion valve 38: evaporator 40: heat pump 40A: high-stage heat pump 40B: low-stage heat pump 42A: high-stage refrigerant circulation passage 42B: low-stage refrigerant circulation passage 44A: high-stage compressor 44B: low-stage compressor 46A: high-stage expansion valve 46B: low-stage expansion valve 48A: high-stage evaporator 48B: low-stage evaporator

Claims

1. A steam supply system comprising: a decompression unit that decompresses water to a negative pressure to generate negative pressure water; a first heat exchanger that exchanges heat between the negative pressure water and a heating medium to generate negative pressure steam; a second heat exchanger that generates condensate of the negative pressure steam by exchanging heat between the negative pressure steam and a heat use destination; and a water supply unit that supplies the condensate to the decompression unit.

2. The steam supply system according to claim 1, wherein the water supply unit includes a water pump that transfers the condensate led from the second heat exchanger to the decompression unit.

3. The steam supply system according to claim 1, wherein the water supply unit includes a water tank that opens the condensate led from the second heat exchanger to an atmosphere, and a water supply pipe that guides the condensate stored in the water tank and set to atmospheric pressure to the decompression unit.

4. The steam supply system according to claim 1, further comprising: a heat pump that supplies a refrigerant as the heating medium to be supplied to the first heat exchanger, wherein the heat pump includes a refrigerant circulation passage for circulating the refrigerant, a compressor compressing the refrigerant to be supplied to the first heat exchanger, an expansion valve decompressing the refrigerant after the heat is exchanged in the first heat exchanger, and an evaporator that exchanges heat between a refrigerant decompressed by the expansion valve and heat source medium to evaporate the refrigerant.

5. The steam supply system according to claim 1, further comprising: a heat pump that supplies a refrigerant as the heating medium to be supplied to the first heat exchanger, wherein the heat pump includes a high-stage heat pump and a low-stage heat pump, the high-stage heat pump includes a high-stage refrigerant circulation passage for circulating the refrigerant, a high-stage compressor compressing the refrigerant to be supplied to the first heat exchanger, a high-stage expansion valve decompressing the refrigerant after the heat is exchanged in the first heat exchanger, and a high-stage evaporator that evaporates a refrigerant decompressed by the high-stage expansion valve, and the low-stage heat pump includes a low-stage refrigerant circulation passage for circulating the refrigerant, a low-stage compressor that compresses the refrigerant to be supplied to the high-stage evaporator, a low-stage expansion valve that decompresses a refrigerant after the heat is exchanged in the high-stage evaporator, and a low-stage evaporator that exchanges heat between a refrigerant decompressed by the low-stage expansion valve and heat source medium to evaporate the refrigerant.

6. A steam supply method comprising: a decompression step of decompressing water to a negative pressure to generate negative pressure water in a decompression unit; a first heat exchange step of exchanging heat between the negative pressure water and a heating medium to generate negative pressure steam; a second heat exchange step of generating condensate of the negative pressure steam by exchanging heat between the negative pressure steam and a heat use destination; and a water supply step of supplying the condensate to the decompression unit.

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