Steam generator and method for controlling a steam generator

Abstract

A steam generator that makes it possible to effectively utilize the heat of a reactor after a heat dissipation operation, and a method for controlling the steam generator are provided. [Solution] A chemical heat pump 21 of a steam generator 12 includes a heat recovery flow path 25 and a circulation flow path 26. The heat recovery flow path 25 recovers heat in the heat exchanger into the storage tank 24 by introducing steam in the heat exchanger of a reactor 23 into the storage tank 24. The circulation flow path 26 circulates water in the storage tank 24 through the heat exchanger of the reactor 23. A control unit 41 of the steam generator 12 controls switching of the operation of the chemical heat pump 21. In the heat recovery operation, after a heat dissipation operation, heat in the heat exchanger of the reactor 23 is recovered into the storage tank 24 through the heat recovery flow path 25. In the preheating operation, after a heat storage operation, the heat exchanger of the reactor 23 is preheated through the circulation flow path 26 before starting the heat dissipation operation.

Description

[Technical Field]

[0001] The present disclosure relates to a steam generating device and a method for controlling a steam generating device. [Background technology]

[0002] As described in Patent Document 1, a steam generator equipped with a chemical heat pump is known. The chemical heat pump includes a reactor having a chemical heat storage material and a heat exchanger that is capable of exchanging heat with the chemical heat storage material. The chemical heat storage material stores heat through a dehydration reaction and releases heat through a hydration reaction. In the heat storage operation of the chemical heat pump, a dehydration reaction of the chemical heat storage material is carried out using exhaust heat. In the heat release operation of the chemical heat pump, steam is generated by a hydration reaction of the chemical heat storage material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-159571 Summary of the Invention [Problem to be solved by the invention]

[0004] In the steam generation system as described above, there is still room for improvement in terms of effectively utilizing the heat of the reactor after the heat dissipation operation. [Means for solving the problem]

[0005] The steam generating device that solves the above problem is a steam generating device that includes a chemical heat pump that generates steam by utilizing exhaust heat, a steam supply unit that supplies the steam to a supply destination, and a control unit that controls the chemical heat pump, wherein the chemical heat pump includes a reactor having a chemical heat storage material that stores heat by a dehydration reaction and releases heat by a hydration reaction and a heat exchanger that is provided so as to be able to exchange heat with the chemical heat storage material, a storage tank that stores water to be supplied into the heat exchanger of the reactor, and a control unit that controls the chemical heat pump to transfer heat from the heat exchanger to the chemical heat storage material by introducing steam from the heat exchanger of the reactor into the storage tank. The reactor is provided with a heat recovery flow path that recovers water into the storage tank, and a circulation flow path that circulates the water in the storage tank into the heat exchanger of the reactor, and the control unit controls to switch between a heat dissipation operation that sends steam to the steam supply unit by performing a hydration reaction of the chemical heat storage material in the reactor, a heat recovery operation that recovers heat in the heat exchanger of the reactor into the storage tank through the heat recovery flow path after the heat dissipation operation, a heat storage operation that performs a dehydration reaction of the chemical heat storage material in the reactor, and a preheating operation that preheats the heat exchanger of the reactor through the circulation flow path after the heat storage operation and before starting the heat dissipation operation.

[0006] According to this configuration, the heat in the heat exchanger of the reactor after the heat dissipation operation of the chemical heat pump can be recovered into the storage tank by the heat recovery operation. Also, the heat recovered in the storage tank by the preheating operation can be used to preheat the heat exchanger of the reactor before the heat dissipation operation starts. [Effects of the Invention]

[0007] The present disclosure exhibits the effect of making it possible to effectively utilize the heat of the reactor after the heat dissipation operation. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a steam generating system according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating the heat dissipation operation. [Figure 3] FIG. 3 is a schematic diagram illustrating the heat recovery operation. [Figure 4] FIG. 4 is a schematic diagram illustrating the heat storage operation. [Figure 5] FIG. 5 is a schematic diagram illustrating the preheating operation. [Figure 6] FIG. 6 is a flowchart illustrating the operation of the steam generating device. [Figure 7] FIG. 7 is a time chart illustrating the operation of the steam generating device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of a steam generating device and a method for controlling a steam generating device will be described with reference to the drawings. As shown in FIG. 1, a steam generator 12 constituting a part of a steam generating system 11 includes a chemical heat pump 21, a steam supply unit 31, and a control unit 41.

[0010] <Chemical Heat Pump 21> The chemical heat pump 21 generates steam by utilizing exhaust heat. The chemical heat pump 21 includes an exhaust heat recovery section 22, a reactor 23, and a storage tank 24. The chemical heat pump 21 further includes a heat recovery flow path 25 and a circulation flow path 26.

[0011] The exhaust heat recovery section 22 includes a heat exchanger into which exhaust heat is introduced from the outside. The form of the exhaust heat recovered by the exhaust heat recovery section 22 may be liquid (such as wastewater) or gas. Examples of the heat exchanger of the exhaust heat recovery section 22 include a fin-tube heat exchanger and a finless heat exchanger. Note that similar heat exchangers can be used for the heat exchangers described below unless otherwise specified.

[0012] The reactor 23 has a chemical heat storage material HM that stores heat through a dehydration reaction and releases heat through a hydration reaction, and a heat exchanger that is provided so as to be able to exchange heat with the chemical heat storage material HM. The chemical heat storage material HM and the heat exchanger are housed in a container.

[0013] The chemical heat storage material HM undergoes a dehydration reaction during the heat storage operation of the chemical heat pump 21, and a hydration reaction during the heat release operation of the chemical heat pump 21. The chemical heat storage material HM is preferably a powdered material. The chemical heat storage material HM may be composed only of a chemical heat storage substance that undergoes a dehydration reaction and a hydration reaction, or may be a material in which the chemical heat storage substance is bound with a water vapor permeable binder such as a water vapor permeable resin. Examples of chemical heat storage substances include alkaline earth metal halides. One type of chemical heat storage material HM may be used, or multiple types may be used in combination. The dehydration reaction and hydration reaction of calcium chloride, which is a type of chemical heat storage substance, are represented, for example, by the following formula (A):

[0014] CaCl2·H2O+H2O⇔CaCl2·2H2O···(A) The reactor 23 generates saturated steam in the flow path of the heat exchanger by utilizing heat generated from the chemical heat storage material HM. The container of the reactor 23 is configured to be able to introduce water vapor used in the hydration reaction of the chemical heat storage material HM. In addition, the container of the reactor 23 is configured to discharge water vapor generated by the dehydration reaction of the chemical heat storage material HM.

[0015] The storage tank 24 stores water to be supplied to the heat exchanger of the reactor 23. The storage tank 24 stores water condensed in the heat exchanger of the reactor 23. The storage tank 24 is configured to allow water to be replenished from the outside. The storage tank 24 is preferably configured to be able to be maintained in an airtight state. Specifically, the storage tank 24 can be maintained in an airtight state by closing an on-off valve such as a control valve provided in a flow path connected to the storage tank 24.

[0016] The heat recovery flow path 25 introduces steam in the heat exchanger of the reactor 23 into the storage tank 24. This recovers heat in the heat exchanger of the reactor 23 into the storage tank 24. The circulation flow path 26 circulates water in the storage tank 24 through the heat exchanger of the reactor 23. The circulation flow path 26 includes a part of the heat recovery flow path 25. The circulation flow path 26 is equipped with a liquid transfer pump 26a that transfers water in the storage tank 24.

[0017] The chemical heat pump 21 has flow paths used for the heat dissipation operation and the heat storage operation. The flow path used for the heat dissipation operation includes a flow path that supplies water in the storage tank 24 into the heat exchanger of the reactor 23. This flow path can be configured from a part of the heat recovery flow path 25 and a part of the circulation flow path 26. The flow path used for the heat dissipation operation further includes a flow path that supplies steam to be reacted with the chemical heat storage material HM to the reactor 23. The flow path used for the heat dissipation operation further includes a flow path that transports heat in the heat exchanger of the reactor 23 towards the steam supply unit 31.

[0018] The flow path used for the heat storage operation includes a heat transport path 27 that sends heat recovered by the exhaust heat recovery unit 22 to the heat exchanger of the reactor 23. The heat transport path 27 can be configured, for example, by a heat pipe. In this embodiment, the heat transport path 27 includes a first heat pipe section 27a included in the heat exchanger of the exhaust heat recovery unit 22 and a second heat pipe section 27b included in the heat exchanger of the reactor 23. The heat transport path 27 also includes an intermediate heat pipe section 27c that transports heat between the first heat pipe section 27a and the second heat pipe section 27b. Well-known heat pipes can be used for each of the first heat pipe section 27a, the second heat pipe section 27b, and the intermediate heat pipe section 27c. The heat pipe may be, for example, a loop-type heat pipe that circulates water in the storage tank 24 in one direction as the working fluid. The heat transport path 27 may also be configured by ordinary piping that transports a heat medium.

[0019] <Steam supply unit 31> The steam supply unit 31 is connected to a steam header SH as a supply destination. The steam supply unit 31 includes a detector P1 that detects the pressure of the steam sent from the chemical heat pump 21, and a control valve 32 that controls the supply of steam to the supply destination.

[0020] <Control unit 41> The control unit 41 switches between the heat storage operation and the heat release operation of the chemical heat pump 21. The control unit 41 also switches between the heat recovery operation and the preheating operation (described later) of the chemical heat pump 21. The switching between the operations of the chemical heat pump 21 can be performed by controlling the opening and closing of a control valve provided in the chemical heat pump 21.

[0021] The control unit 41 of this embodiment is further configured to control the steam supply unit 31. More specifically, the control unit 41 controls the control valve 32 provided in the flow path of the steam supply unit 31. This allows the start and stop of steam supply to the destination steam header SH. The control valve 32 is opened and closed based on, for example, a pressure threshold detected by a detector P1. The control valve 32 may be opened and closed based on a comparison result between the pressure detected by the detector P1 and the pressure in the steam header SH. The pressure in the steam header SH is detected by a detector P2. The control valve 32 may be opened, for example, when the steam pressure in the steam supply unit 31 becomes higher than the steam pressure in the steam header SH. Furthermore, the control valve 32 may be closed, for example, when the steam pressure in the steam supply unit 31 becomes lower than the steam pressure in the steam header SH.

[0022] <Steam Generation System 11> Next, the steam generating system 11 will be described. The steam generating system 11 includes an introduction path L1 that introduces steam that advances the hydration reaction of the chemical thermal storage medium HM into the reactor 23, and a recovery path L2 that recovers steam generated by the dehydration reaction of the chemical thermal storage medium HM from the reactor 23. The introduction path L1 of this embodiment includes an ejector EJ and a boiler B. The recovery path L2 of this embodiment includes a steam recovery section SR.

[0023] The steam to be drawn into the ejector EJ may be generated, for example, by providing a separate evaporator that utilizes exhaust heat. However, from the viewpoint of simplifying and miniaturizing the steam generation system 11, it is preferable to generate the steam using the exhaust heat recovery section 22 in the steam generator 12. That is, the steam generation system 11 has a flow path for drawing the steam generated in the heat exchanger of the exhaust heat recovery section 22 into the ejector EJ. The ejector EJ is equipped with a nozzle, a diffuser, and the like. A portion of the steam generated in the boiler B can be used as the driving steam for the ejector EJ. The boiler B can be a boiler already installed for another purpose in a facility such as a factory. The driving steam for the ejector EJ can also be supplied from an existing steam pipe.

[0024] The vapor recovery section SR recovers vapor generated by a dehydration reaction of the chemical heat storage material HM in the reactor 23 during heat storage operation of the chemical heat pump 21. As the vapor recovery section SR, for example, a vapor recovery vessel containing a recovery material or a pressure reduction pump can be used. Here, an example will be described in which a vapor recovery vessel is used as the vapor recovery section SR. As the recovery material, a material that can undergo a hydration reaction with the vapor (water) generated by the dehydration reaction of the chemical heat storage material HM in the reactor 23 can be used. A heat exchanger into which a heat medium such as waste hot water or cold water from the outside flows is provided within the vapor recovery vessel, and the recovery material is arranged in the vapor recovery vessel so as to be heated or cooled by the heat exchanger. The recovery of steam by the recovery material is promoted by, for example, cooling the recovery material with cold water.

[0025] The pressure inside the vapor recovery vessel can be reduced by causing a hydration reaction of the recovery material inside the vapor recovery vessel. As a result, even if the vapor generated from the chemical thermal storage medium HM in the reactor 23 is at a relatively low pressure (low temperature), by using a recovery material that can undergo a hydration reaction with the low-pressure steam, the dehydration reaction of the chemical thermal storage medium HM can be favorably promoted.

[0026] The recovery material may be a known solid material, which may consist solely of a recovery substance capable of undergoing hydration and dehydration reactions, or may be a material in which particulate recovery substances are bound together with a water vapor-permeable binder such as a water vapor-permeable resin.

[0027] As the recovery material (recovery substance), for example, a substance that undergoes a hydration reaction at a temperature higher than the temperature at which steam condenses under pressure conditions below atmospheric pressure can be suitably used. This makes it possible to recover steam in the steam recovery unit even if the operating conditions of the chemical heat pump 21 are set below atmospheric pressure (reduced pressure) and cold water at a temperature higher than the temperature at which steam can condense is supplied to the heat exchanger of the steam recovery unit. Furthermore, by setting the operating conditions (heat storage operation conditions) within the chemical heat pump 21 system to below atmospheric pressure (reduced pressure), it is possible to reduce the cost of safety measures for the chemical heat pump 21.

[0028] Here, the hydration reaction of the recovery material referred to in this specification also includes the adsorption of steam (moisture) using a porous material as a recovery material. In other words, the dehydration reaction of the recovery material also includes the desorption of steam (moisture) using a porous material as a recovery material. Examples of recovery materials include zeolite, lithium hydroxide, magnesium sulfate, strontium oxalate, activated carbon, and porous metal oxides (MOFs). One type of recovery material may be used, or multiple types may be used in combination. It is preferable that the recovery material has heat resistance of 200°C or higher.

[0029] The recovered material can be reused by dehydrating it. For example, by using the exhaust heat to dehydrate the recovered material during the heat dissipation operation of the chemical heat pump 21, the recovered material can be regenerated into a state where it can undergo a hydration reaction, and can be reused.

[0030] <Operation of the steam generator 12 and the steam generation system 11> Next, the operation of the steam generator 12 and the steam generation system 11 will be described. (heat dissipation operation) 2, 6, and 7, in the heat dissipation operation of step S1, a hydration reaction of the chemical thermal storage medium HM is carried out in the reactor 23. In detail, the steam discharged from the ejector EJ described above is introduced into the reactor 23. The steam introduced into the reactor 23 causes a hydration reaction of the chemical thermal storage medium HM in the reactor 23.

[0031] In the reactor 23, steam is generated by heating the water in the heat exchanger of the reactor 23 due to the heat generated by the hydration reaction of the chemical thermal storage medium HM. The steam generated in the heat exchanger of the reactor 23 is sent to a steam supply unit 31. When the steam sent to the steam supply unit 31 reaches a predetermined pressure, the control valve 32 is opened to supply the steam to the supply destination (steam header SH).

[0032] (Heat recovery operation) 3, 6, and 7, in the heat recovery operation of step S2, after the heat dissipation operation of step S1, heat in the heat exchanger of the reactor 23 is recovered into the storage tank 24 through the heat recovery flow path 25. In detail, the introduction of steam into the reactor 23 is stopped, that is, in a state in which the heat dissipation operation of step S1 is stopped, the heat recovery flow path 25 is opened, and the steam in the heat exchanger of the reactor 23 is introduced into the storage tank 24. At this time, the temperature of the reactor 23 (the temperature of the chemical thermal storage medium HM) decreases, and the temperature of the storage tank 24 (the temperature of the water in the storage tank 24) increases. During this heat recovery operation, water may be replenished into the storage tank 24 from the outside. This makes it possible to efficiently raise the temperature of the water replenished from the outside.

[0033] (heat storage operation) 4, 6, and 7, in the heat storage operation of step S3, a dehydration reaction of the chemical heat storage material HM occurs in the reactor 23. In detail, the chemical heat storage material HM in the reactor 23 undergoes a dehydration reaction by being heated by the heat transported from the exhaust heat recovery section 22. The steam generated by the dehydration reaction of the chemical heat storage material HM is recovered by the steam recovery section SR of the recovery path L2.

[0034] (Preheating operation) 5, 6, and 7, the preheating operation in step S4 preheats the heat exchanger of the reactor 23 through the circulation flow path 26 after the heat storage operation in step S3 and before the heat dissipation operation in step S1 is started. In detail, hot water is stored in the storage tank 24 due to the heat recovery operation in step S2. This hot water in the storage tank 24 is circulated to the heat exchanger of the reactor 23 through the circulation flow path 26. At this time, the temperature of the hot water in the storage tank 24 decreases, and the temperature of the reactor 23 (the temperature of the chemical thermal storage material HM) increases. This makes it possible to effectively utilize the heat recovered in the heat recovery operation in step S2.

[0035] It is preferable that the storage tank 24 be maintained in an airtight state after the heat recovery operation of step S2 until the preheating operation of step S4 begins. Furthermore, it is preferable that the control unit 41 described above be configured to switch from the preheating operation of step S4 to the heat dissipation operation of step S1 based on the temperature of the water in the storage tank 24. Specifically, the chemical heat pump 21 includes a temperature detection unit (not shown) that detects the temperature of the water in the storage tank 24. During the preheating operation of step S4, the temperature of the water in the storage tank 24 decreases. In other words, the progress of preheating of the reactor 23 can be directly confirmed by the temperature of the water in the storage tank 24. Therefore, by switching from the preheating operation of step S4 to the heat dissipation operation of step S1 based on the temperature of the water in the storage tank 24 as described above, it becomes easy to switch the operation at an appropriate timing.

[0036] <Action and effect> The operation and effects of this embodiment will be described. (1) The steam generator 12 includes a chemical heat pump 21 that generates steam by utilizing exhaust heat, a steam supply unit 31 that supplies the steam to a supply destination, and a control unit 41 that controls the chemical heat pump 21. The chemical heat pump 21 includes a reactor 23, a storage tank 24, a heat recovery flow path 25, and a circulation flow path 26. The reactor 23 houses a chemical heat storage material HM that stores heat through a dehydration reaction and releases heat through a hydration reaction, and a heat exchanger that is provided so as to be able to exchange heat with the chemical heat storage material HM. The storage tank 24 stores water to be supplied to the heat exchanger of the reactor 23. The heat recovery flow path 25 recovers heat in the heat exchanger into the storage tank 24 by introducing steam in the heat exchanger of the reactor 23 into the storage tank 24. The circulation flow path 26 circulates the water in the storage tank 24 through the heat exchanger of the reactor 23. The control unit 41 performs control to switch between a heat dissipation operation (step S1), a heat recovery operation (step S2), a heat storage operation (step S3), and a preheating operation (step S4). In the heat dissipation operation of step S1, steam is sent to the steam supply unit 31 by performing a hydration reaction of the chemical heat storage material HM in the reactor 23. In the heat recovery operation of step S2, after the heat dissipation operation of step S1, heat in the heat exchanger of the reactor 23 is recovered into the storage tank 24 through the heat recovery flow path 25. In the heat storage operation of step S3, a dehydration reaction of the chemical heat storage material HM is performed in the reactor 23. In the preheating operation of step S4, after the heat storage operation of step S3, the heat exchanger of the reactor 23 is preheated through the circulation flow path 26 before starting the heat dissipation operation of step S1.

[0037] According to this configuration, the heat recovery operation in step S2 allows the heat in the heat exchanger of the reactor 23 after the heat dissipation operation in step S1 to be recovered into the storage tank 24. Furthermore, the preheating operation in step S4 allows the heat recovered in the storage tank 24 to be used to preheat the heat exchanger of the reactor 23 before the start of the heat dissipation operation in step S1. Therefore, it becomes possible to effectively utilize the heat in the reactor 23 after the heat dissipation operation in step S1.

[0038] (2) It is preferable that the control unit 41 is configured to switch from the preheating operation of step S4 to the heat dissipation operation of step S1 based on the temperature of the water in the storage tank 24. In this case, it becomes easy to switch from the preheating operation of step S4 to the heat dissipation operation of step S1 at an appropriate timing. Therefore, it is possible to avoid complicated settings when switching from the preheating operation of step S4 to the heat dissipation operation of step S1.

[0039] (3) After the heat recovery operation in step S2, the storage tank 24 is preferably maintained in an airtight state until the preheating operation in step S4 is started. In this case, the heat recovered in the storage tank 24 by the heat recovery operation in step S2 can be prevented from being released to the outside. Therefore, the utilization rate of the heat recovered in the storage tank 24 can be further increased.

[0040] (4) It is preferable to supply water from the outside to the storage tank 24 during the heat recovery operation in step S2. In this case, it is possible to effectively use the heat recovered from the reactor 23 to increase the temperature of the water supplied to the storage tank 24. Furthermore, by supplying water from the outside to the storage tank 24 during the heat recovery operation in step S2, it is possible to increase the amount of heat recovered from the reactor 23.

[0041] <Example of change> The above embodiment may be modified as follows: The above embodiment and the following modifications may be implemented in combination with each other within the scope of technical compatibility.

[0042] The supply of water from the outside to the storage tank 24 can also be performed at a timing other than the heat recovery operation in step S2. After the heat recovery operation in step S2, the storage tank 24 may be partially open instead of being sealed until the preheating operation in step S4 is started.

[0043] The wall portion constituting the storage tank 24 may have a heat insulating structure in which a heat insulating material or the like is arranged in order to improve the heat retention of the storage tank 24 . The control unit 41 is configured to switch from the preheating operation of step S4 to the heat dissipation operation of step S1 based on the temperature of the water in the storage tank 24. This is not limiting, and for example, the control unit 41 may be configured to switch to the heat dissipation operation of step S1 after a predetermined time has elapsed since the start of the preheating operation of step S4.

[0044] The steam supply unit 31 includes a control valve 32 controlled by the control unit 41, but may be configured as a pressure regulating valve that opens when a predetermined pressure is reached. In the heat dissipation operation in step S1, steam generated by the exhaust heat recovery unit 22 is used, but instead of using the exhaust heat recovery unit 22, a separately prepared evaporator may be used.

[0045] In the heat storage operation in step S3, steam generated in the exhaust heat recovery section 22 is used, but it is also possible to configure the system so that exhaust heat is directly introduced from the exhaust heat source to the heat exchanger of the reactor 23 without using the exhaust heat recovery section 22.

[0046] When a vapor recovery unit SR is used that contains a recovery material that undergoes a hydration reaction, the vapor recovery capacity can be increased by providing an additional auxiliary recovery unit that does not contain a recovery material. The auxiliary recovery unit can be configured to include a heat exchanger that is supplied with a refrigerant such as cold water, and to condense and recover the vapor.

[0047] The steam generator 12 can also be used in a steam generation system other than the steam generation system 11 described above. [Explanation of symbols]

[0048] 12...Steam generator 21...Chemical heat pump 23...Reactor 24...Storage tank 25...Heat recovery channel 26...Circulation flow path 31...Steam supply section 41...Control unit HM…Chemical heat storage material

Claims

1. A steam generating device comprising: a chemical heat pump that generates steam by utilizing exhaust heat; a steam supply unit that supplies the steam to a supply destination; and a control unit that controls the chemical heat pump, The chemical heat pump comprises: A reactor having a chemical heat storage material that stores heat through a dehydration reaction and releases heat through a hydration reaction and a heat exchanger that is provided so as to be able to exchange heat with the chemical heat storage material; a storage tank for storing water to be supplied to the heat exchanger of the reactor; a heat recovery flow path that recovers heat in the heat exchanger into the storage tank by introducing steam in the heat exchanger of the reactor into the storage tank; a circulation flow path that circulates the water in the storage tank through the heat exchanger of the reactor, The control unit A heat dissipation operation of sending steam to the steam supply unit by performing a hydration reaction of the chemical heat storage material in the reactor; a heat recovery operation of recovering heat in the heat exchanger of the reactor into the storage tank through the heat recovery flow path after the heat dissipation operation; A heat storage operation in which a dehydration reaction of the chemical heat storage material is performed in the reactor; a preheating operation for preheating the heat exchanger of the reactor through the circulation flow path after the heat storage operation and before starting the heat release operation, and

2. The steam generating apparatus according to claim 1 , wherein the control unit is configured to switch from the preheating operation to the heat dissipation operation based on a temperature of the water in the storage tank.

3. The steam generating apparatus according to claim 1 , wherein the storage tank is maintained in an airtight state after the heat recovery operation and until the preheating operation is started.

4. The steam generating apparatus according to claim 1 , wherein water is replenished from the outside into the storage tank during the heat recovery operation.

5. A method for controlling a steam generating device including a chemical heat pump that generates steam by utilizing exhaust heat, a steam supply unit that supplies the steam to a supply destination, and a control unit that controls the chemical heat pump, The chemical heat pump comprises: A reactor having a chemical heat storage material that stores heat through a dehydration reaction and releases heat through a hydration reaction and a heat exchanger that is provided so as to be able to exchange heat with the chemical heat storage material; a storage tank for storing water to be supplied to the heat exchanger of the reactor; a heat recovery flow path that recovers heat in the heat exchanger into the storage tank by introducing steam in the heat exchanger of the reactor into the storage tank; a circulation flow path that circulates the water in the storage tank through the heat exchanger of the reactor, The control unit A heat dissipation operation of sending steam to the steam supply unit by performing a hydration reaction of the chemical heat storage material in the reactor; a heat recovery operation of recovering heat in the heat exchanger of the reactor into the storage tank through the heat recovery flow path after the heat dissipation operation; A heat storage operation in which a dehydration reaction of the chemical heat storage material is performed in the reactor; a preheating operation for preheating the heat exchanger of the reactor through the circulation flow path after the heat storage operation and before starting the heat release operation,

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