Steam generation system for combined heat and power, combined heat and power system, and method for generating steam for combined heat and power

Abstract

Provided is a steam generation system for combined heat and power that can be used as a combined heat and power system even with warm water below 100°C. 【Solution means】The steam generation system 9 includes a steam generator 27 that heats negative pressure water with warm water below 100°C obtained from the cooling water that cools the gas engine 3 to generate negative pressure steam, a steam supply path 31 that supplies the negative pressure steam generated by the steam generator 27 to the demand destination, a water supply path 29 that supplies water to the steam generator 27, and a pressure reducing valve 35 provided in the water supply path 29 that reduces the pressure of the water to below atmospheric pressure.

Description

Technical Field

[0001] The present disclosure relates to a steam generation system for combined heat and power, a combined heat and power system, and a method for generating steam for combined heat and power.

Background Art

[0002] Patent Document 1 discloses a cogeneration system (combined heat and power system) that generates steam using engine cooling water for cooling the engine jacket of a power generation engine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the cogeneration system described in Cited Document 1, engine cooling water at 100°C or higher is required to generate steam. Therefore, when the engine cooling water is less than 100°C, heating means for raising the temperature to 100°C or higher is required.

[0005] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a steam generation system for combined heat and power, a combined heat and power system, and a method for generating steam for combined heat and power that can be used as a combined heat and power system even with warm water at less than 100°C.

Means for Solving the Problems

[0006] A steam generation system for combined heat and power according to an aspect of the present disclosure includes a steam generator that generates steam by heating negative-pressure water with warm water obtained from cooling water for cooling a power generation engine, a steam supply unit that supplies the steam generated by the steam generator to a demand destination, a water supply unit that supplies water to the steam generator, a pressure reducing valve provided in the water supply unit that reduces the pressure of water to below atmospheric pressure, a steam compressor provided in the steam supply unit that increases the pressure of the steam to above atmospheric pressure, and a control unit that controls the depressurization of a flow path in a range from the upstream side of the steam compressor to the downstream side of the pressure reducing valve by adjusting the operation of the steam compressor. , the control unit adjusts the steam flow rate by coordinating the capacity control of the steam compressor and the opening degree control of the pressure reducing valve 。

[0007] A combined heat and power system according to an aspect of the present disclosure includes the above-described steam generation system for combined heat and power, a power generation engine, and a generator that generates electricity by the power generation engine.

[0008] A method for generating steam for combined heat and power according to an aspect of the present disclosure includes a steam generation step of generating steam by heating negative-pressure water with warm water obtained from cooling water for cooling a power generation engine, a steam supply step of supplying the steam generated in the steam generation step to a demand destination, a water supply step of supplying water to the steam generator, a pressure reducing step of reducing the pressure of the water supplied to the steam generator to below atmospheric pressure with a pressure reducing valve, and a steam compression step of increasing the pressure of the steam obtained in the steam supply step to above atmospheric pressure with a steam compressor. The operation of the steam compressor controls the depressurization of a flow path in a range from the upstream side of the steam compressor to the downstream side of the pressure reducing valve. At the same time, the steam flow rate is adjusted by coordinating the capacity control of the steam compressor and the opening degree control of the pressure reducing valve 。

Advantages of the Invention

[0009] Even warm water below 100°C can be used as a combined heat and power system.

Brief Description of the Drawings

[0010]

Figure 1

Modes for Carrying Out the Invention

[0011] Hereinafter, an embodiment according to the present disclosure will be described with reference to FIG. 1. FIG. 1 shows a cogeneration system 1 according to this embodiment. The cogeneration system 1 includes a gas engine (power generation engine) 3, an exhaust gas boiler 5, a CO2 recovery device 7, and a steam generator (cogeneration steam generation system) 9.

[0012] The gas engine 3 is operated using a gas fuel such as city gas as fuel. A generator (not shown) is driven by the gas engine 3 to generate electric power. The electric power generated by the generator is supplied to the demand side. Instead of the gas engine 3, other power generation engines such as a gas turbine engine or a diesel engine using oil fuel may be used. Also, a plurality of gas engines 3 may be provided.

[0013] The exhaust gas boiler 5 generates steam using the exhaust gas discharged from the gas engine 3. The exhaust gas that has completed heat exchange in the exhaust gas boiler 5 is guided to the CO2 recovery device through the exhaust gas flow path 11. The steam generated in the exhaust gas boiler 5 is guided to the boiler steam supply path 13 and supplied to an external demand side.

[0014] The CO2 recovery device 7 recovers CO2 (carbon dioxide) from the exhaust gas guided from the gas engine 3. The CO2 recovery device 7 uses a chemical absorption method using an absorption liquid that chemically absorbs CO2, such as an amine absorption liquid.

[0015] The CO2 recovery device 7 includes an absorption tower 15 and a regeneration tower 16. In the absorption tower 15, an amine absorption liquid is brought into contact with the exhaust gas to absorb CO2 in the exhaust gas. A lean solution supply unit 15a that supplies a lean solution from which CO2 has been desorbed and the CO2 concentration has been made lean is connected to the absorption tower 15. While the amine absorption liquid (lean solution) supplied from the lean solution supply unit 15a flows through the absorption tower 15, it absorbs CO2 in the exhaust gas. The rich solution having absorbed CO2 in the absorption tower 15 and having a rich CO2 concentration is sent to the rich solution supply unit 16a via the heat exchanger 20 by the absorption tower pump 22.

[0016] The heat exchanger 20 is a non-contact type heat exchanger, and performs heat exchange between the lean solution supplied from the regeneration tower pump 18 and the rich solution supplied from the absorption tower pump 22.

[0017] The exhaust gas from which CO2 has been removed by the amine absorbent is discharged from the absorption tower 15 to the outside.

[0018] In the regeneration tower 16, CO2 is desorbed from the rich solution that has absorbed CO2. The amine absorbent (rich solution) supplied into the regeneration tower 16 from the rich solution supply section 16a is heated by the heat exchanger 20, thereby providing the amount of heat required for the endothermic reaction of desorbing CO2. CO2 is desorbed from the rich solution while the amine absorbent (rich solution) supplied from the rich solution supply section 16a flows through the regeneration tower 16. The CO2 desorbed from the rich solution is discharged from the regeneration tower 16 and led to a CO2 storage section (not shown).

[0019] A reboiler 17 for heating the amine absorbent is connected to the regeneration tower 16. The amine absorbent taken out from the regeneration tower 16 through the absorbent recovery path 16b is heated by the reboiler 17. As the heating source of the reboiler 17, the steam led from a boiler steam branch path (steam supply section) 13a branched from the boiler steam supply path 13 is used. The amine absorbent heated by the reboiler 17 is returned to the regeneration tower 16 through the absorbent return path 16c. The heated amine absorbent (lean solution) is taken out from the bottom of the regeneration tower 16 and sent to the heat exchanger 20 by the regeneration tower pump 18.

[0020] The steam generation system 9 is connected to the gas engine 3. The steam generation system 9 includes a hot water circuit 25 in which hot water circulates between the gas engine 3, and a steam generator 27 to which the hot water circuit 25 is connected.

[0021] The warm water circuit 25 is a closed-loop flow path for circulating the warm water led from the gas engine 3. The warm water is heated by exchanging heat with the cooling water that cools the gas engine 3 and is set to a temperature of less than 100°C. A warm water pump 33 is provided in the warm water circuit 25. The operation of the warm water pump 33 is controlled by a control unit (not shown). Note that the cooling water that has cooled the gas engine 3 may be directly supplied to the warm water circuit 25, or the warm water circuit 25 may be constituted by the circulation path of the cooling water itself. Also, the cooling water that cools the gas engine 3 may be drawn out to the outside of the gas engine 3 by a water supply pipe, and the warm water inside the warm water circuit 25 may be heated by a heat exchanger provided outside the gas engine 3. Here, the cooling water that cools the gas engine 3 includes the cooling water that cools the oil circulating or passing through the inside of the gas engine 3. Note that the engine for power generation is not limited to a gas engine, and a gas turbine engine may be used.

[0022] The steam generator 27 is a non-contact heat exchanger in which warm water and feed water exchange heat without contact, and for example, a partition type heat exchanger such as a plate type heat exchanger, a shell & plate heat exchanger, or a shell & tube heat exchanger can be used.

[0023] Also, the steam generation system 9 may have bypass means for adjusting the amount of heat supplied to the heat exchanger that heats the warm water in the steam generator 27 or the warm water circuit 25. Specifically, the warm water circuit 25 may have a warm water bypass flow path 25a for circulating the warm water led from the gas engine 3 without passing through the steam generator 27. It has a warm water bypass control valve 25b for adjusting the amount of warm water passing through the warm water bypass flow path 25a. By setting the warm water bypass control valve 25b to an arbitrary opening degree, the amount of heat input to the steam generator 27 can be controlled. When returning the warm water to the gas engine without passing through the steam generator 27, it is also possible to maintain the heat balance by providing heat dissipation means such as a cooling tower on the warm water circuit.

[0024] Furthermore, when the cooling water for cooling the gas engine 3 exchanges heat with the hot water in the hot water circuit 25 through a heat exchanger, it may have a bypass flow path for bypassing the cooling water so that it does not pass through this heat exchanger. Also in this case, a bypass control valve having the same function as the hot water bypass control valve 25b on the hot water circuit 25 can be further provided.

[0025] A water supply path (water supply section) 29 for supplying feed water to be heated is connected to the steam generator 27. A pressure reducing valve 35 is provided in the water supply path 29. The pressure reducing valve 35 reduces the pressure of the feed water at normal temperature (for example, 20°C) and atmospheric pressure to negative pressure water. The opening degree of the pressure reducing valve 35 is controlled by a control section (not shown). The pressure reducing valve 35 is controlled so that the inside of the steam generator 27 reaches a desired pressure in coordination with the operation of each steam compressor 37 as necessary.

[0026] A steam supply path (steam supply section) 31 through which the negative pressure steam generated in the steam generator 27 flows out is connected to the steam generator 27. The negative pressure steam generated in the steam generator 27 is generated by the hot water below 100°C supplied from the hot water circuit 25. For example, when the pressure of the feed water is -0.054 MPaG, the saturated steam is 80°C, so negative pressure steam can be generated with hot water of about 85°C.

[0027] A plurality of steam compressors 37 and a supply amount adjustment section 39 are provided in the steam supply path 31. Each steam compressor 37 compresses the negative pressure steam to a pressure equal to or higher than atmospheric pressure. As the steam compressor 37, for example, in addition to positive displacement compressors such as screw compressors and claw compressors, turbo compressors and the like are used. Also, due to the operation of the steam compressor 37, the flow path in the range from its upstream side to the downstream side of the pressure reducing valve 35 is depressurized. The steam compressor 37 is driven by, for example, an electric motor, and its rotation speed is controlled by a control section (not shown). Note that the capacity of the steam compressor 37 may be increased or decreased by increasing or decreasing the rotation speed of the electric motor, or with the rotation speed fixed, a pipeline for bypassing from the protruding side to the suction side of the compressor may be provided, and a control valve for changing the pressure loss of the pipeline may be provided on the pipeline to increase or decrease it. In addition, in the present embodiment shown in FIG. 1, four vapor compressors 37 are arranged in series, but the number thereof is not limited and may be one, two, three, or five or more.

[0028] The supply amount adjustment unit 39 separates the pressurized vapor into gas and liquid and adjusts the vapor flow rate to be discharged. The vapor flow rate discharged from the supply amount adjustment unit 39 is controlled by a control unit (not shown).

[0029] In addition, the vapor flow rate can be adjusted by coordinating the capacity control of the vapor compressor 37 and the opening degree control of the pressure reducing valve 35. For example, by increasing the capacity of the vapor compressor 37 and increasing the opening degree of the pressure reducing valve 35, the amount of vapor can be increased. Thereby, the vapor flow rate can be increased while keeping the circulation flow rate of the hot water circuit 25 and the amount of heat input to the steam generator 27 constant. Further, by increasing the capacity of the vapor compressor 37, the total amount of heat energy input per unit time by vapor compression also increases.

[0030] At this time, the valve opening degree provided in the above-described hot water bypass means may be adjusted. For example, the opening degree of the hot water bypass control valve 25b provided in the hot water circuit 25 may be further coordinated with the capacity control of the vapor compressor 37 or the opening degree control of the pressure reducing valve 35 according to a command from the control unit. For example, when increasing the capacity of the vapor compressor 37 and increasing the opening degree of the pressure reducing valve 35, by increasing the opening degree of the hot water bypass control valve 25b to increase the amount of heat input to the steam generator 27, the vapor flow rate can be increased and the heat energy per unit time supplied can be maintained or increased.

[0031] In addition, the steam flow rate or temperature can also be adjusted by using a steam bypass flow path 31a provided with a steam bypass valve 31b that bypasses a predetermined stage among a plurality of stages of steam compressors 37. For example, when it is desired to decrease the steam temperature, the steam bypass valve 31b is opened according to a command from the control unit to bypass the low-stage steam compressor 37 and utilize the compression capacity of the steam compressor 37 on the subsequent stage side, thereby reducing the temperature rise range. In this case, the operation of the low-stage steam compressor 37 can be stopped. As a result, without controlling the hot water bypass control valve 25b of the hot water circuit 25 (that is, without discarding heat in the cooling tower), the temperature rise range can be reduced by decreasing the number of operating compressors, leading to an improvement in the efficiency of the entire system. Further, even when retrofitting the steam generation system 9 to an existing engine heat utilization system and it is difficult to finely control the existing hot water circuit 25 according to the operating conditions of the steam generation system 9, it is relatively easy to correspond to a desired steam amount or temperature only by the operation or control on the steam generation system 9 side.

[0032] A part of the feed water is guided from the feed water path 29 to the downstream side of each steam compressor 37 and the supply amount adjustment unit 39 via a water injection pipe 41. By injecting the feed water guided from the water injection pipe 41, the pressurized steam and the steam guided to the supply amount adjustment unit 39 are cooled. Note that a pressure boosting means (such as a pump) may be provided in the water injection pipe 41 to obtain the pressure required for injection.

[0033] The pressurized steam flowing out from the supply amount adjustment unit 39 passes through the steam supply path 31 and merges into the boiler steam branch path 13a. Thus, the steam guided from the supply amount adjustment unit 39 merges into the boiler steam branch path 13a and is guided to the reboiler 17 of the CO2 recovery device 7.

[0034] A turbine 14 is provided on the upstream side of the confluence position P1 where the steam supply path 31 merges into the boiler steam branch path 13a. The turbine 14 reduces the pressure of the steam and recovers the pressure energy. Note that an expansion valve may be provided instead of the turbine 14.

[0035] The control unit is composed of, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium, etc. And a series of processes for realizing various functions are stored in a storage medium, etc. in the form of a program as an example. The CPU reads this program into the RAM, etc. and executes information processing and arithmetic processing, thereby realizing various functions. Note that the program may be in a form pre-installed in the ROM or other storage media, a form provided in a state stored in a computer-readable storage medium, a form distributed via wired or wireless communication means, etc. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, etc.

[0036] The above-described cogeneration system 1 operates as follows. Power generation is performed by the operation of the gas engine 3, and the exhaust gas discharged from the gas engine 3 is led to the CO2 recovery device 7 through the exhaust gas boiler 5. The steam generated in the exhaust gas boiler 5 is supplied to the demand side through the boiler steam supply path 13. A part of the steam generated in the exhaust gas boiler 5 is branched at the boiler steam branch path 13a, depressurized by the turbine 14, and then led to the reboiler 17 of the CO2 recovery device 7. The steam generated by the steam generator 27 and pressurized by each steam compressor 37 also merges into the boiler steam branch path 13a.

[0037] Cooling water that cools the gas engine 3 circulates warm water below 100°C that is heated through the warm water circuit 25. The warm water below 100°C heats the negative pressure water in the steam generator 27 that has been depressurized by the pressure reducing valve 35 to generate negative pressure steam. The negative pressure steam generated by the steam generator 27 passes through the steam supply line 31 and is pressurized to above atmospheric pressure by a plurality of steam compressors 37 before being led to the supply amount adjustment unit 39. The steam whose flow rate has been adjusted by the supply amount adjustment unit 39 passes through the steam supply line 31 and merges with the boiler steam branch line 13a. The steam after merging at the boiler steam branch line 13a is led to the reboiler 17 and used as a heat source.

[0038] In the CO2 recovery device 7, CO2 is recovered from the exhaust gas led from the gas engine 3 in the absorption tower 15, and the exhaust gas after CO2 absorption is discharged to the outside. In the regeneration tower 16, the amine absorption liquid is heated by the reboiler 17. The CO2 desorbed from the amine absorption liquid is discharged from the regeneration tower 16 and sent to the CO2 storage section.

[0039] The functions and effects of the present embodiment described above are as follows. In the steam generator 27, negative pressure water is heated from warm water below 100°C obtained from the cooling water that cools the gas engine 3 to generate negative pressure steam. The generated negative pressure steam is supplied to the place of demand via the steam supply line 31. Thereby, even if the warm water obtained from the engine cooling water is below 100°C, steam can be generated and combined heat and power supply is possible.

[0040] A pressure reducing valve 35 is provided in the water supply line 29 that supplies water to the steam generator 27, and the water supply is made into negative pressure water below atmospheric pressure. Thereby, even water above atmospheric pressure can be supplied to the steam generator 27 as negative pressure water.

[0041] The steam compressor 37 is used to boost the negative pressure steam to above atmospheric pressure and supply it to the place of demand. Thereby, it is possible to flexibly respond to the required pressure at the place of demand.

[0042] The CO2 recovery device 7 for recovering CO2 from exhaust gas uses a chemical absorption method in which CO2 is chemically absorbed and recovered using an amine absorption liquid, and heating (absorption heat) is required to desorb CO2 from the absorption liquid that has absorbed CO2 and regenerate the absorption liquid. By supplying the steam generated by the steam generator 27 to the reboiler 17 of the CO2 recovery device 7, it can be used as a heat source for regenerating the amine absorption liquid.

[0043] The cogeneration steam generation system, cogeneration system, and cogeneration steam generation method described in each of the embodiments described above can be understood as follows, for example.

[0044] The cogeneration steam generation system (9) according to the first aspect of the present disclosure includes a steam generator (27) that generates steam by heating negative-pressure water with warm water obtained from cooling water for cooling a power generation engine (3), a steam supply unit (31) that supplies the steam generated by the steam generator to a demand destination, a water supply unit (29) that supplies water to the steam generator, a pressure reducing valve (35) provided in the water supply unit that reduces the pressure of water to below atmospheric pressure, a steam compressor (37) provided in the steam supply unit that boosts the pressure of steam to above atmospheric pressure, and a control unit that controls the pressure reduction of the flow path in the range from the upstream side of the steam compressor to the downstream side of the pressure reducing valve by adjusting the operation of the steam compressor.

[0045] In the steam generator, negative-pressure water is heated from the warm water obtained from the cooling water that has cooled the power generation engine to generate negative-pressure steam. The generated negative-pressure steam is supplied to the demand destination by the steam supply unit. As a result, even if the warm water obtained from the engine cooling water is less than 100°C, steam can be generated and cogeneration becomes possible.

[0046] A pressure reducing valve is provided in the water supply unit that supplies water to the steam generator to make the water negative-pressure water below atmospheric pressure. As a result, even water above atmospheric pressure can be supplied to the steam generator as negative-pressure water.

[0047] The negative-pressure steam is boosted to a pressure above atmospheric pressure by a steam compressor and supplied to the demand destination. As a result, it is possible to flexibly respond to the required pressure of the demand destination.

[0048] By adjusting the operation of the steam compressor, the pressure reduction in the flow path in the range from the upstream side of the steam compressor to the downstream side of the pressure reducing valve is controlled. As a result, the pressure of the steam generator can be adjusted to a desired value.

[0049] In the steam generation system (9) for combined heat and power according to the second aspect of the present disclosure, in the first aspect, the control unit controls the steam flow rate by adjusting the operation of the steam compressor and the opening degree of the pressure reducing valve.

[0050] The steam generation system (9) for combined heat and power according to the third aspect of the present disclosure includes, in the first aspect or the second aspect, a hot water circuit (25) that supplies hot water to the steam generator, and a bypass flow path (25a) that is provided in the hot water circuit and bypasses the hot water supplied to the steam generator.

[0051] In the steam generation system for combined heat and power according to the fourth aspect of the present disclosure, in the first aspect, the demand destination is a CO2 recovery device that recovers carbon dioxide from the exhaust gas discharged from the power generation engine.

[0052] For example, in the case of a chemical absorption method in which a CO2 recovery device that recovers carbon dioxide (CO2) from exhaust gas chemically absorbs and recovers CO2 using an absorption liquid (for example, an amine absorption liquid), heating is required to desorb CO2 from the absorption liquid that has absorbed CO2 and regenerate the absorption liquid. By making the demand destination a CO2 recovery device, the negative-pressure steam generated in the steam generator can be used as a heat source for regenerating the absorption liquid. Note that it is preferable that the negative-pressure steam is compressed by a steam compressor to a desired pressure.

[0053] The combined heat and power system according to the first aspect of the present disclosure includes the steam generation system for combined heat and power described in any of the above, a power generation engine, and a generator that generates electricity by the power generation engine.

[0054] The steam generation method for combined heat and power according to the first aspect of the present disclosure includes a steam generation step of heating negative pressure water with warm water obtained from cooling water for cooling a power generation engine to generate steam, a steam supply step of supplying the steam generated in the steam generation step to a demand destination, a water supply step of supplying water to the steam generator, a pressure reduction step of reducing the pressure of the water supplied to the steam generator with a pressure reducing valve to below atmospheric pressure, and a steam compression step of boosting the pressure of the steam obtained in the steam supply step with a steam compressor to above atmospheric pressure. By operating the steam compressor, the pressure reduction of the flow path in the range from the upstream side of the steam compressor to the downstream side of the pressure reducing valve is controlled.

Explanation of Signs

[0055] 1 Combined heat and power system 3 Gas engine (power generation engine) 5 Exhaust gas boiler 7 CO2 recovery device 9 Steam generation system (steam generation system for combined heat and power) 11 Exhaust gas flow path 13 Boiler steam supply path 13a Boiler steam branch path (steam supply section) 14 Turbine 15 Absorption tower 15a Lean solution supply section 16 Regeneration tower 16a Rich solution supply section 16b Absorbent recovery path 16c Absorbent return path 17 Reboiler 18 Regeneration tower pump 20 Heat exchanger 22 Absorption tower pump 25 Warm water circuit 25a Warm water bypass flow path 25b Warm water bypass control valve 27 Steam generator 29 Water supply path (water supply section) 31 Steam supply path (steam supply section) 31a Steam bypass flow path 31b Steam bypass valve 33 Warm water pump 35 Pressure reducing valve 37 Steam compressor 39 Supply amount adjustment unit 41 Water injection pipe

Claims

1. A steam generator that heats negative-pressure water with warm water obtained from cooling water for cooling a power generation engine to generate steam, A steam supply unit that supplies the steam generated by the steam generator to a demand destination, A water supply unit that supplies water to the steam generator, A pressure reducing valve provided in the water supply unit for reducing the pressure of water to below atmospheric pressure, A steam compressor provided in the steam supply unit for boosting the pressure of steam to above atmospheric pressure, A control unit that controls the pressure reduction of the flow path in the range from the upstream side of the steam compressor to the downstream side of the pressure reducing valve by adjusting the operation of the steam compressor, Comprising, The control unit is a cogeneration steam generation system that adjusts the steam flow rate by coordinating the capacity control of the steam compressor and the opening degree control of the pressure reducing valve.

2. The cogeneration steam generation system according to claim 1, wherein the control unit controls the steam flow rate by adjusting the operation of the steam compressor and the opening degree of the pressure reducing valve.

3. A hot water circuit that supplies hot water to the steam generator, A bypass flow path provided in the hot water circuit for bypassing the hot water supplied to the steam generator, The cogeneration steam generation system according to claim 1, comprising.

4. The cogeneration steam generation system according to claim 1, wherein the demand destination is a CO2 recovery device that recovers carbon dioxide from the exhaust gas discharged from the power generation engine.

5. The cogeneration steam generation system according to any one of claims 1 to 4, A power generation engine, A generator that generates electricity by the power generation engine, A cogeneration system comprising.

6. A steam generation step of heating negative-pressure water with warm water obtained from cooling water for cooling a power generation engine to generate steam in a steam generator, A steam supply step of supplying the steam generated in the steam generation step to a demand destination, A water supply step of supplying water to the steam generator, A pressure reduction step of reducing the pressure of the water supplied to the steam generator with a pressure reducing valve to below atmospheric pressure, A steam compression step of boosting the negative-pressure steam obtained in the steam supply step to above atmospheric pressure with a steam compressor, Having, By operating the steam compressor, the pressure reduction of the flow path in the range from the upstream side of the steam compressor to the downstream side of the pressure reducing valve is controlled, and the steam flow rate is adjusted by coordinating the capacity control of the steam compressor and the opening degree control of the pressure reducing valve. A method for generating steam for cogeneration.

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