Waste heat utilization system and control method for waste heat utilization system

Abstract

To provide an exhaust heat utilization system capable of more effectively using exhaust heat and a control method for the exhaust heat utilization system.SOLUTION: A chemical heat pump 12 includes a heat accumulator 21, a recovery device 31, a condenser 41 and an evaporator 51. The heat accumulator 21 includes a chemical thermal storage medium HM that performs dehydration reaction during a heat storage operation and hydration reaction during a heat radiation operation. The recovery device 31 includes an absorber LM that absorbs steam and recovers steam generated from the chemical thermal storage medium HM. The condenser 41 condenses the steam to be discharged from the absorber LM during a regeneration operation for performing the dehydration reaction of the absorber LM. The evaporator 51 supplies steam to be caused to react with the chemical thermal storage medium HM to the heat accumulator 21. A control section 13 includes a heat radiation operation control section 13b for switching from a first heat radiation operation to a second heat radiation operation. In the first heat radiation operation, the steam to be discharged from the absorber LM in the regeneration operation is supplied to the heat accumulator 21. In the second heat radiation operation, the steam generated by the evaporator 51 is supplied to the heat accumulator 21.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a waste heat utilization system and a control method for the waste heat utilization system. [Background technology]

[0002] As disclosed in Patent Document 1, a chemical heat pump is known as a device that can be used to reuse exhaust heat generated in factories and the like. The chemical heat pump includes a heat accumulator, a recovery device, a condenser, and an evaporator. The heat accumulator contains a chemical heat storage material that stores heat through a dehydration reaction and releases heat through a hydration reaction. The recovery device recovers steam generated by the dehydration reaction of the chemical heat storage material. The recovery device of such a chemical heat pump contains an absorbent that undergoes a hydration reaction with steam generated by the dehydration reaction of the chemical heat storage material, thereby making it possible to easily proceed with the dehydration reaction of the chemical heat storage material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-158299 Summary of the Invention [Problem to be solved by the invention]

[0004] The absorbent material used in the recovery unit of a chemical heat pump is reused by being regenerated in a regeneration operation after the heat storage operation of the chemical heat pump. In this regeneration operation, the absorbent material is heated using exhaust heat to cause a dehydration reaction in the absorbent material. At this time, the steam generated by the dehydration reaction in the absorbent material is condensed in a condenser, which can promote the dehydration reaction in the absorbent material. However, in this type of absorbent regeneration operation, the heat of the steam introduced into the condenser is not actually used effectively. [Means for solving the problem]

[0005] A waste heat utilization system that solves the above problem is a waste heat utilization system comprising a chemical heat pump that stores waste heat and a control unit that controls the operation of the chemical heat pump, wherein the chemical heat pump comprises a heat accumulator having a chemical heat storage material that undergoes a dehydration reaction during heat storage operation and a hydration reaction during heat dissipation operation, a recovery device having an absorbent material that absorbs water vapor and recovers water vapor generated from the chemical heat storage material, a condenser that condenses water vapor discharged from the absorbent material during a regeneration operation in which a dehydration reaction of the absorbent material occurs, and an evaporator that supplies water vapor to the heat accumulator to react with the chemical heat storage material, and the control unit comprises a heat dissipation operation control unit that switches from a first heat dissipation operation to a second heat dissipation operation, and in the first heat dissipation operation, water vapor discharged from the absorbent material during the regeneration operation is supplied to the heat accumulator, and in the second heat dissipation operation, water vapor generated by the evaporator is supplied to the heat accumulator.

[0006] According to this configuration, the first heat dissipation operation, which is part of the heat dissipation operation, can be performed by utilizing the water vapor discharged from the absorbent material during the regeneration operation. Therefore, in the entire heat dissipation operation, it is possible to reduce the amount of water vapor used in the evaporator by utilizing the exhaust heat. In other words, it is possible to reduce the amount of exhaust heat used when extracting heat from the chemical thermal storage medium HM.

[0007] In the above-described exhaust heat utilization system, the heat dissipation operation control unit may switch from the first heat dissipation operation to the second heat dissipation operation based on the temperature or pressure of the heat storage device. According to this configuration, the hydration reaction of the chemical heat storage material is suitably continued, thereby making it possible to stably perform the heat dissipation operation.

[0008] In the above-described exhaust heat utilization system, the recovery device has a heat exchanger, and the control device includes a heat storage operation control device that controls the replenishment of water that has passed through the heat exchanger of the recovery device to the evaporator during the heat storage operation. With this configuration, water that has been heated by passing through the heat exchanger of the recovery device can be replenished to the evaporator during the heat storage operation. This makes it possible to reduce the use of exhaust heat to heat the water in the evaporator. Therefore, exhaust heat can be used more effectively.

[0009] In the above-described exhaust heat utilization system, water cooled by the condenser may be supplied to the heat exchanger of the recovery unit during the heat storage operation. With this configuration, for example, water condensed by the condenser during the regeneration operation can be effectively used to cool the recovery unit. Also, it becomes possible to supply relatively clean water to the evaporator.

[0010] A control method for a waste heat utilization system that solves the above-mentioned problems is a control method for a waste heat utilization system that includes a chemical heat pump that stores waste heat, wherein the chemical heat pump includes a heat accumulator having a chemical heat storage material that undergoes a dehydration reaction during heat storage operation and a hydration reaction during heat dissipation operation, a recovery device having an absorbent material that absorbs water vapor and recovers water vapor generated from the chemical heat storage material, a condenser that condenses water vapor discharged from the absorbent material during a regeneration operation that causes a dehydration reaction of the absorbent material, and an evaporator that supplies water vapor to the heat accumulator to react with the chemical heat storage material, and the control method includes a step of switching from a first heat dissipation operation to a second heat dissipation operation, wherein in the first heat dissipation operation, water vapor discharged from the absorbent material during the regeneration operation is supplied to the heat accumulator, and in the second heat dissipation operation, water vapor generated by the evaporator is supplied to the heat accumulator. [Effects of the Invention]

[0011] According to the present invention, it is possible to more effectively utilize exhaust heat. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram illustrating a waste heat utilization system according to an embodiment. [Figure 2] FIG. 4 is a schematic diagram illustrating a first heat storage operation of the exhaust heat utilization system. [Figure 3] FIG. 4 is a schematic diagram illustrating a second heat storage operation of the exhaust heat utilization system. [Figure 4] FIG. 3 is a schematic diagram illustrating a first regeneration operation and a first heat dissipation operation of the exhaust heat utilization system. [Figure 5] FIG. 4 is a schematic diagram illustrating a second regeneration operation and a second heat dissipation operation of the exhaust heat utilization system. [Figure 6] FIG. 3 is a flow diagram illustrating control of the exhaust heat utilization system. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the exhaust heat utilization system will be described with reference to the drawings. <Overall configuration of the waste heat utilization system> As shown in FIG. 1, the exhaust heat utilization system 11 includes a chemical heat pump 12 that stores exhaust heat, and a control unit 13 that controls the operation of the chemical heat pump 12.

[0014] The chemical heat pump 12 includes a heat accumulator 21, a recovery device 31, a condenser 41, and an evaporator 51. The waste heat utilization system 11 stores heat using a waste heat source HS, and then releases heat at a temperature higher than that of the waste heat source HS. The waste heat utilization system 11 of this embodiment can send water vapor to a heating target 61 during heat release operation.

[0015] <Thermal storage device> The heat accumulator 21 has a chemical heat storage material HM that undergoes a dehydration reaction during heat storage operation of the exhaust heat utilization system 11 and a hydration reaction during heat dissipation operation of the exhaust heat utilization system 11. A well-known solid material can be used as the chemical heat storage material HM. The chemical heat storage material HM may be composed of only a chemical heat storage substance, or may be a material in which a particulate chemical heat storage substance is bound with a water vapor permeable binder such as a water vapor permeable resin. Examples of chemical heat storage materials include alkaline earth metal halides and calcium sulfate. One type of chemical heat storage material HM may be used, or multiple types may be used in combination.

[0016] The dehydration reaction and hydration reaction of calcium chloride, which is a type of chemical heat storage material, are represented by, for example, the following formula (A). CaCl2·H2O+H2O⇔CaCl2·2H2O···(A) The heat accumulator 21 includes a first heat exchanger 22 that exchanges heat with the chemical heat storage material HM. The heat accumulator 21 generates saturated steam in a flow path of the first heat exchanger 22 by utilizing heat generated from the chemical heat storage material HM. The heat accumulator 21 includes a first container 23 that accommodates the chemical heat storage material HM and the first heat exchanger 22. The first container 23 of the heat accumulator 21 is configured so that water vapor used in the hydration reaction of the chemical heat storage material HM can be introduced. Furthermore, the first container 23 of the heat accumulator 21 is configured so that water vapor generated in the dehydration reaction of the chemical heat storage material HM can be discharged.

[0017] Examples of the first heat exchanger 22 of the heat accumulator 21 include a fin-tube type heat exchanger and a finless heat exchanger. Note that similar heat exchangers can also be used for the heat exchangers described below.

[0018] <Collector> The recovery device 31 has an absorbent material LM that absorbs water vapor. The absorbent material LM recovers the water vapor generated from the chemical thermal storage material HM of the heat accumulator 21. The recovery device 31 is equipped with a second heat exchanger 32 that exchanges heat with the absorbent material LM, and a second container 33 that houses the absorbent material LM and the second heat exchanger 32.

[0019] The absorbent material LM is used to lower the temperature at which the dehydration reaction of the chemical heat storage material HM occurs. By using the absorbent material LM, it becomes possible to promote the dehydration reaction of the chemical heat storage material HM and store heat even with waste heat at a lower temperature. Furthermore, the absorbent material LM is made of a substance that can undergo a dehydration reaction at the temperature of the heating medium of the waste heat source HS. This allows the absorbent material LM to be regenerated using the waste heat source HS.

[0020] The equilibrium vapor pressure VP2C of the absorbent material LM at the temperature of the cooling source CS is lower than the equilibrium vapor pressure VP1H of the chemical heat storage material HM at the temperature of the exhaust heat source HS, thereby suitably promoting the dehydration reaction of the chemical heat storage material HM. On the other hand, the equilibrium vapor pressure VP2H of the absorbent material LM at the temperature of the exhaust heat source HS is preferably higher than the equilibrium vapor pressure VP1H of the chemical heat storage material HM at the same temperature of the exhaust heat source HS. Such an absorbent material LM is easier to dehydrate than the chemical heat storage material HM, so by regenerating the absorbent material LM using the exhaust heat source HS, it can be efficiently used for the next heat storage operation. Furthermore, the equilibrium vapor pressure VP2H of the absorbent material LM at the temperature of the exhaust heat source HS is preferably higher than the equilibrium vapor pressure VP3C of water at the temperature of the cooling source CS. As a result, the water vapor generated by heating the absorbent material LM with the exhaust heat source HS is condensed by cooling with the cooling source CS, thereby efficiently regenerating the absorbent material LM.

[0021] Examples of the absorbent material LM include zeolite, lithium hydroxide, magnesium sulfate, strontium bromine, activated carbon, and porous metal complexes (MOFs). One type of absorbent material LM may be used, or multiple types may be used in combination.

[0022] The dehydration reaction and hydration reaction of strontium bromide, which is one type of absorbent material LM, are represented by, for example, the following formula (B). SrBr2·H2O+5H2O⇔SrBr2·6H2O···(B) <Condenser> The condenser 41 condenses the water vapor discharged from the absorbent material LM. The condenser 41 includes a third heat exchanger 42 to which a cooling medium is supplied from a cooling source CS, and a third container 43 that houses the third heat exchanger 42. The third heat exchanger 42 of the condenser 41 condenses the water vapor introduced into the condenser 41. The third heat exchanger 42 of the condenser 41 also cools the water W2 in the third container 43 of the condenser 41. That is, the third heat exchanger 42 of the condenser 41 includes a water vapor condensing section that condenses the water vapor and a water cooling section that cools the water. The third heat exchanger 42 can be composed of one or more heat exchangers.

[0023] <Evaporator> The evaporator 51 supplies water vapor to be reacted with the chemical thermal storage material HM to the heat accumulator 21. The evaporator 51 includes a fourth heat exchanger 52 to which a heating medium is supplied from the exhaust heat source HS, and a fourth container 53 that houses the fourth heat exchanger 52. In the evaporator 51, water W1 in the fourth container 53 can be heated by the fourth heat exchanger 52 to generate water vapor.

[0024] <Flow path configuration> Next, the main flow path configuration of the exhaust heat utilization system 11 will be described. First, there will be described the flow paths used in the heat storage operation of the exhaust heat utilization system 11. The heat storage operation of this embodiment includes a first heat storage operation and a second heat storage operation.

[0025] Fig. 2 shows the flow paths used in the first heat storage operation. As shown in Fig. 2, the exhaust heat utilization system 11 has a water vapor recovery flow path L1 that sends water vapor WV1 from the heat accumulator 21 to the recovery device 31. The exhaust heat utilization system 11 has a heat accumulator heating flow path L2 that sends water W1 heated in the evaporator 51 to the first heat exchanger 22 of the heat accumulator 21 by a pump 71, and a first evaporator flow path L3 that returns the water that has passed through the first heat exchanger 22 to the evaporator 51. The exhaust heat utilization system 11 also has a recovery device cooling flow path L4 that sends water W2 cooled in the condenser 41 to the second heat exchanger 32 of the recovery device 31 by a pump 72, and a supply flow path L5A that supplies the evaporator 51 with water that has passed through the second heat exchanger 32.

[0026] Fig. 3 shows the flow paths used in the second heat storage operation. As shown in Fig. 3, the exhaust heat utilization system 11 has a first condenser flow path L5B that returns water that has passed through the second heat exchanger 32 of the recovery device 31 to the condenser 41. The second heat storage operation is performed without using the supply flow path L5A used in the first heat storage operation shown in Fig. 2.

[0027] Next, we will explain the flow paths used in the regeneration operation and heat dissipation operation of the exhaust heat utilization system 11. The regeneration operation includes a first regeneration operation and a second regeneration operation. The heat dissipation operation includes a first heat dissipation operation and a second heat dissipation operation.

[0028] Fig. 4 shows the flow paths used in the first regeneration operation and the first heat dissipation operation. As shown in Fig. 4, the exhaust heat utilization system 11 has a first heat accumulator flow path L6A that sends water vapor WV2 from the recovery device 31 to the heat accumulator 21. The exhaust heat utilization system 11 also has a recovery device heating flow path L7 that sends water W1 heated in the evaporator 51 to the second heat exchanger 32 of the recovery device 31 by a pump 71, and a second evaporator flow path L8 that returns the water that has passed through the second heat exchanger 32 to the evaporator 51.

[0029] The exhaust heat utilization system 11 is configured to be switchable between the collector cooling flow path L4 shown in Fig. 3 and the collector heating flow path L7 shown in Fig. 4. Switching between the collector cooling flow path L4 and the collector heating flow path L7 can be performed by opening and closing a valve.

[0030] Fig. 5 shows the flow paths used in the second regeneration operation and the second heat dissipation operation. As shown in Fig. 5, the exhaust heat utilization system 11 has a second condenser flow path L6B that sends steam WV2 from the recovery unit 31 to the condenser 41. The second regeneration operation and the second heat dissipation operation use the recovery unit heating flow path L7 and the second evaporator flow path L8.

[0031] The exhaust heat utilization system 11 has a heat accumulator steam flow path L9 that sends steam WV3 from the evaporator 51 to the heat accumulator 21. The exhaust heat utilization system 11 also has a steam supply flow path L10 that sends steam from the first heat exchanger 22 of the heat accumulator 21 to an object to be heated 61. The object to be heated 61 is not particularly limited. Examples of the object to be heated 61 include a steam generator and a thermoelectric converter.

[0032] <Control unit> As shown in FIG. 1, the control unit 13 has a heat storage operation control unit 13a, a heat dissipation operation control unit 13b, and a regeneration operation control unit 13c. The control unit 13 secures the flow paths used in each operation by controlling the opening and closing of on-off valves provided in the flow paths. The heat storage operation control unit 13a switches from the first heat storage operation to the second heat storage operation. The heat dissipation operation control unit 13b switches from the first heat dissipation operation to the second heat dissipation operation. The regeneration operation control unit 13c switches from the first regeneration operation to the second regeneration operation. The control unit 13 can be configured, for example, so that a CPU performs the above-mentioned controls in accordance with a program stored in memory.

[0033] <Control of waste heat utilization system> 6, the exhaust heat utilization system 11 first performs a determination step of determining whether or not there is a demand for heat (step S11). If it is determined in the determination step of step S11 that there is a demand for heat (step S11: YES), the system proceeds to a first heat storage operation of step S12 and a second heat storage operation of step S13. After such a heat storage operation, the exhaust heat utilization system 11 proceeds to a first heat dissipation operation of step S14 and a first regeneration operation of step S15. The first heat dissipation operation of step S14 and the first regeneration operation of step S15 are performed simultaneously.

[0034] On the other hand, if it is determined in the determination process of step S11 that there is no heat demand (step S11: NO), the determination process of step S11 is repeated. Next, in the operation of the exhaust heat utilization system 11, a determination step is performed in which it is determined whether or not the temperature of the heat accumulator 21 has reached a predetermined temperature in the first heat dissipation operation of step S14 (step S16). The temperature of the heat accumulator 21 can be measured by, for example, a temperature sensor arranged in the first container 23 of the heat accumulator 21.

[0035] In the determination process of step S16, if it is determined that the temperature of the heat accumulator 21 has reached the predetermined temperature (step S16: YES), the process proceeds to a second heat dissipation operation of step S17 and a second regeneration operation of step S18.

[0036] The second heat dissipation operation in step S17 and the second regeneration operation in step S18 are performed simultaneously. On the other hand, if it is determined in the determination step of step S16 that the temperature of the heat accumulator 21 has not reached the predetermined temperature (step S16: NO), the determination step of step S16 is repeated.

[0037] After the second heat dissipation operation in step S17 and the second regeneration operation in step S18, the determination step in step S11 is repeated. <Operation of the waste heat utilization system> Next, an example of each operation of the exhaust heat utilization system 11 will be described.

[0038] (First heat storage operation of the exhaust heat utilization system) As shown in FIG. 2, in the first heat storage operation, water vapor WV1 discharged from the chemical thermal storage material HM of the heat accumulator 21 is recovered by the recovery device 31. In detail, the water vapor WV1 discharged from the chemical thermal storage material HM of the heat accumulator 21 is sent to the recovery device 31 through a recovery steam flow path L1. Water W2 cooled in the condenser 41 is sent to the second heat exchanger 32 of the recovery device 31 through a recovery device cooling flow path L4. The water sent to the second heat exchanger 32 of the recovery device 31 is heated by heat exchange with the absorbent material LM. The water that has passed through the second heat exchanger 32 of the recovery device 31 is replenished to the evaporator 51 through the replenishment flow path L5A. In this way, the water that has been heated by passing through the second heat exchanger 32 of the recovery device 31 can be replenished to the evaporator 51 through the replenishment flow path L5A, making it possible to reduce the use of exhaust heat to heat the water in the evaporator 51.

[0039] In the first heat storage operation, water vapor WV1 discharged from the chemical heat storage material HM of the heat storage device 21 is sent to the recovery device 31, and a dehydration reaction of the chemical heat storage material HM occurs. Here, as the dehydration reaction of the chemical heat storage material HM progresses, the temperature of the chemical heat storage material HM decreases. When the temperature of the chemical heat storage material HM becomes lower than the temperature of the heating medium of the exhaust heat source HS, the heat storage device 21 is heated using water W1 heated in the evaporator 51. More specifically, the water W1 heated in the evaporator 51 is sent to the first heat exchanger 22 of the heat storage device 21 through the heat storage device heating flow path L2. The water that has passed through the first heat exchanger 22 is sent to the evaporator 51 through the evaporator first flow path L3. In this way, the water W1 heated in the evaporator 51 circulates between the evaporator 51 and the first heat exchanger 22 of the heat storage device 21. The water W1 in the evaporator 51 is heated by supplying a heating medium from the exhaust heat source HS to the fourth heat exchanger 52 of the evaporator 51.

[0040] In this way, the dehydration reaction of the chemical heat storage material HM is advanced by using the exhaust heat source HS to heat the chemical heat storage material HM in the heat storage device 21. The heat storage operation of the exhaust heat utilization system 11 can be stopped by closing the valve between the heat storage device 21 and the recovery device 31.

[0041] (Second heat storage operation of the exhaust heat utilization system) 3, in the second heat storage operation, the supply of water to the evaporator 51 through the second heat exchanger 32 of the recovery device 31 is stopped. In the second heat storage operation of this embodiment, the water sent from the condenser 41 to the second heat exchanger 32 of the recovery device 31 is returned to the condenser 41 through the first condenser flow path L5B. The water W2 cooled in the condenser 41 in this manner circulates between the condenser 41 and the second heat exchanger 32 of the recovery device 31.

[0042] Switching from the first heat storage operation to the second heat storage operation is performed based on the amount of water replenished from the recovery device 31 to the evaporator 51. The amount of water replenished from the recovery device 31 to the evaporator 51 can be measured using a flow meter or a liquid level meter.

[0043] (First heat dissipation operation and first regeneration operation of the exhaust heat utilization system) As shown in Fig. 4, in the first heat dissipation operation, water vapor WV2 discharged from the absorbent material LM of the recovery device 31 is supplied to the heat accumulator 21. More specifically, the water vapor WV2 in the recovery device 31 is sent to the heat accumulator 21 through the first heat accumulator flow path L6A. This causes a hydration reaction of the chemical heat storage material HM in the heat accumulator 21. At this time, the water in the flow path of the first heat exchanger 22 of the heat accumulator 21 can be heated by the heat generated by the hydration reaction of the chemical heat storage material HM. Note that it is preferable to supply water into the flow path of the first heat exchanger 22 before the first heat dissipation operation. Water W1 heated in the evaporator 51 can be supplied into the flow path of the first heat exchanger 22.

[0044] In the first regeneration operation, the absorbent LM in the recovery device 31 is subjected to a dehydration reaction. As a result, water vapor WV2 is discharged from the absorbent LM. More specifically, in the first regeneration operation, water W1 heated in the evaporator 51 is sent to the second heat exchanger 32 of the recovery device 31 through the recovery device heating flow path L7. The water that has passed through the second heat exchanger 32 is sent to the evaporator 51 through the evaporator second flow path L8. The water W1 heated in the evaporator 51 in this manner circulates between the evaporator 51 and the second heat exchanger 32.

[0045] (Second heat dissipation operation and second regeneration operation of the exhaust heat utilization system) As shown in FIG. 5 , in the second heat release operation, a heating medium is supplied from the exhaust heat source HS to the fourth heat exchanger 52 of the evaporator 51, thereby generating steam WV3 in the evaporator 51. The steam WV3 generated in the evaporator 51 is sent to the heat accumulator 21 through the heat accumulator steam flow path L9. This causes a hydration reaction of the chemical heat storage material HM in the heat accumulator 21. The water in the flow path of the first heat exchanger 22 of the heat accumulator 21 is heated by heat generated by the hydration reaction of the chemical heat storage material HM. This makes it possible to generate steam in the flow path of the first heat exchanger 22. The steam in the flow path of the first heat exchanger 22 is sent to the heating target 61 through the steam supply flow path L10. The heat release operation of the exhaust heat utilization system 11 can be stopped by closing the valve between the evaporator 51 and the heat accumulator 21.

[0046] In the second regeneration operation, the water vapor WV2 discharged from the absorbent LM of the recovery device 31 is condensed using the condenser 41. More specifically, the water vapor WV2 discharged from the absorbent LM of the recovery device 31 is sent to the condenser 41 through the second condenser flow path L6B. A cooling medium is supplied to the third heat exchanger 42 of the condenser 41 from the cooling source CS. The second regeneration operation can be stopped by closing the valve between the recovery device 31 and the condenser 41.

[0047] <Improving the waste heat utilization rate> Next, an example of improving the exhaust heat utilization rate will be described. One condition for the chemical heat pump 12 is shown below.

[0048] Chemical heat storage material HM: calcium chloride Absorber LM: Strontium bromide ·Exhaust heat source HS temperature: 80[℃] -Temperature of cooling source CS: 30[℃] Heat capacity of heat accumulator 21: 80 [kJ / K] Steam conditions output to heating target 61: 140°C, 9 MJ In the first heat storage operation, the absorbent material LM was cooled by supplying a cooling medium from the cooling source CS to the second heat exchanger 32 of the recovery device 31 at a flow rate of 14 [L / min]. At this time, the temperature difference ΔT between the inlet temperature and outlet temperature of the second heat exchanger 32 was 20 [°C]. In this first heat storage operation, water was replenished to the evaporator 51 through the second heat exchanger 32. The amount of water replenished at this time was 8 [kg].

[0049] By supplying water from the recovery vessel 31 to the evaporator 51 in this way, the amount of heat required to heat the water in the evaporator 51 can be reduced. The amount of heat reduction in this case is 0.67 [MJ] (= 4.2 [kJ / K / kg] × 8 [kg] × 20 [°C] / 1000), where 4.2 [kJ / K / kg] is the specific heat of water.

[0050] In the first regeneration operation, the equilibrium vapor pressure when the absorbent LM undergoes a dehydration reaction using the exhaust heat source HS is 15 [kPa]. In the first heat dissipation operation, the water vapor WV2 discharged from the absorbent LM is supplied to the heat accumulator 21.

[0051] When the pressure condition of the water vapor inside the heat accumulator 21 is 15 [kPa], the equilibrium temperature of the chemical heat storage material HM is 120 [°C], so the temperature inside the heat accumulator 21 rises from 80 [°C], which is the temperature of the exhaust heat source HS, to 120 [°C]. At this time, the amount of heat required for the above temperature rise is 3.2 [MJ] (= 80 [kJ / K] × (120 [°C] - 80 [°C]) / 1000). It can be seen that this amount of heat of 3.2 [MJ] can be generated using the water vapor WV2 discharged from the absorbent material LM.

[0052] Here, when the water vapor is output to the external heating target 61 by only the second heat dissipation operation without performing the first heat dissipation operation as described above, the amount of heat required by the evaporator 51 is 11.3 [MJ]. However, this amount of heat is calculated assuming that the temperature difference ΔT due to the temperature rise in the heat storage device 21 is 60 [°C], the reaction heat of the chemical heat storage material HM is 51 [kJ / mol], the molar mass of water is 18 [g / mol], and the latent heat of vapor at 80 [°C] is 2308 [kJ / kg].

[0053] When the first heat dissipation operation is performed, the amount of heat required by the evaporator 51 is 8.6 [MJ], which is a value obtained by subtracting 2.6 [MJ], which is the amount of heat of the evaporator 51 required for the first heat dissipation operation, from 11.3 [MJ]. This amount of heat of the evaporator 51, 2.6 [MJ], is calculated as follows based on the amount of heat, 3.2 [MJ], supplied from the absorbent material LM to the chemical thermal storage material HM.

[0054] 3.2[MJ] / 51[kJ / mol]×18[g / mol] / 1000×2308[kJ / kg]=2.6[MJ] Here, it is assumed that the total amount of heat input from the exhaust heat source HS in the heat storage operation and the regeneration operation is 25 [MJ]. When the first heat dissipation operation and the second heat dissipation operation are performed as in this embodiment to output the above-mentioned water vapor to the external heating target 61, the calculated result of the exhaust heat utilization rate is 0.27 (= 9 [MJ] / (25 [MJ] + 8.6 [MJ])).

[0055] On the other hand, if the above-mentioned water vapor is output to the external heating target 61 using only the second heat dissipation operation without performing the first heat dissipation operation, the calculated exhaust heat utilization rate is 0.25 (= 9 [MJ] / (25 [MJ] + 11.3 [MJ])).

[0056] In other words, by performing the first heat dissipation operation and the second heat dissipation operation as in this embodiment, it is possible to improve the exhaust heat utilization rate by about 10% compared to when only the second heat dissipation operation is performed without the first heat dissipation operation.

[0057] The operation and effects of this embodiment will be described. (1) The chemical heat pump 12 of the exhaust heat utilization system 11 includes a heat accumulator 21, a recovery device 31, a condenser 41, and an evaporator 51. The control unit 13 of the exhaust heat utilization system 11 includes a heat dissipation operation control unit 13b that switches from a first heat dissipation operation (step S14) to a second heat dissipation operation (step S17). In the first heat dissipation operation, water vapor WV2 discharged from the absorbent material LM during the first regeneration operation (step S15) is supplied to the heat accumulator 21. In the second heat dissipation operation, water vapor WV3 generated in the evaporator 51 is supplied to the heat accumulator 21.

[0058] According to this configuration, the first heat dissipation operation, which is part of the heat dissipation operation, can be performed by utilizing the water vapor WV2 discharged from the absorbent material LM during the first regeneration operation. Therefore, in the entire heat dissipation operation, it is possible to reduce the amount of water vapor WV3 used that is generated in the evaporator 51 by utilizing the exhaust heat. In other words, it is possible to reduce the amount of exhaust heat used when extracting heat from the chemical thermal storage medium HM. This allows for more effective use of the exhaust heat.

[0059] (2) The heat dissipation operation control unit 13b switches from the first heat dissipation operation to the second heat dissipation operation based on the temperature of the heat storage device 21. In this case, the hydration reaction of the chemical heat storage material HM is continued in a favorable manner, thereby enabling the heat dissipation operation to be performed stably. For example, when the absorbent material LM is strontium bromide, the equilibrium vapor pressure is 15 kPa when a dehydration reaction is performed using an exhaust heat source HS of 80°C. When the water vapor pressure condition is 15 kPa, the equilibrium temperature of calcium chloride, which is the chemical heat storage material HM, is 120°C. Therefore, for example, when the temperature of the chemical heat storage material HM reaches 120°C by the first heat dissipation operation, the operation can be switched to the second heat dissipation operation. As a result, the hydration reaction of calcium chloride is performed under higher vapor pressure conditions, allowing the heat dissipation operation to be performed at a higher temperature.

[0060] (3) The control unit 13 of the exhaust heat utilization system 11 is equipped with a heat storage operation control unit 13a that controls the supply of water that has passed through the second heat exchanger 32 of the recovery device 31 to the evaporator 51. In this case, during the heat storage operation, water that has been heated by passing through the second heat exchanger 32 of the recovery device 31 can be supplied to the evaporator 51. This makes it possible to reduce the use of exhaust heat to heat the water in the evaporator 51. This allows for more effective use of exhaust heat.

[0061] (4) In the heat storage operation of the exhaust heat utilization system 11, water cooled using the condenser 41 is supplied to the second heat exchanger 32 of the recovery device 31. In this case, for example, the water condensed by the condenser 41 during the regeneration operation can be effectively used to cool the recovery device 31. In addition, it becomes possible to supply water with a relatively high degree of purity to the evaporator 51. Therefore, for example, it becomes possible to reduce the maintenance work of the evaporator 51.

[0062] (5) The exhaust heat utilization system 11 includes a collector cooling flow path L4 that sends water W2 cooled in the condenser 41 to the second heat exchanger 32 of the collector 31, and a collector heating flow path L7 that sends water W1 heated in the evaporator 51 to the second heat exchanger 32 of the collector 31. In the exhaust heat utilization system 11, the collector cooling flow path L4 and the collector heating flow path L7 are configured to be switchable.

[0063] In this case, the collector 31 can be cooled and heated by water W2 flowing through the collector cooling flow path L4, which is independent of the cooling medium flow path of the cooling source CS, and water W1 flowing through the collector heating flow path L7, which is independent of the heating medium flow path of the exhaust heat source HS. Therefore, in the second heat exchanger 32 of the collector 31, mixing of the heating medium of the exhaust heat source HS with the cooling medium of the cooling source CS can be prevented. This prevents the system of the cooling source CS from being affected by the properties of the heating medium of the exhaust heat source HS. Furthermore, in the second heat exchanger 32 of the collector 31, mixing of the cooling medium of the cooling source CS with the heating medium of the exhaust heat source HS can be prevented. This prevents the system of the exhaust heat source HS from being affected by the properties of the cooling medium of the cooling source CS. Therefore, it is possible to maintain the systems of the cooling source CS and the exhaust heat source HS in an independent state in the installation location of the exhaust heat utilization system 11.

[0064] (6) The control method for the exhaust heat utilization system 11 includes a step of switching from the first heat dissipation operation to the second heat dissipation operation. According to this method, the functions and effects described in the above section (1) are achieved.

[0065] (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.

[0066] The supply passage L5A may be omitted from the exhaust heat utilization system 11. That is, the first heat storage operation may be omitted, and the heat storage operation may be performed only by the second heat storage operation. In the first and second heat storage operations shown in FIGS. 2 and 3, the water W2 in the condenser 41 is supplied to the second heat exchanger 32 of the recovery device 31, but this can also be changed so that the cooling medium of the cooling source CS is supplied.

[0067] 2 and 3, the first heat exchanger 22 of the heat accumulator 21 is supplied with water W1 heated by the evaporator 51, but this is not limiting. For example, the first heat exchanger 22 of the heat accumulator 21 may be changed so that a heating medium from the exhaust heat source HS is supplied to the first heat exchanger 22 of the heat accumulator 21. Furthermore, for example, the first heat exchanger 22 of the heat accumulator 21 may be changed so that water vapor generated by the evaporator 51 is supplied to the first heat exchanger 22 of the heat accumulator 21.

[0068] 4 and 5, the second heat exchanger 32 of the recovery device 31 is supplied with water W1 from the evaporator 51, but this is not limiting. The second heat exchanger 32 of the recovery device 31 may be changed to be supplied with a heating medium from the exhaust heat source HS, for example. The second heat exchanger 32 of the recovery device 31 may also be changed to be supplied with water vapor generated in the evaporator 51, for example.

[0069] The heat dissipation operation control unit 13b is configured to switch from the first heat dissipation operation to the second heat dissipation operation based on the temperature of the heat accumulator 21, but is not limited to this. The heat dissipation operation control unit 13b can also be configured to switch from the first heat dissipation operation to the second heat dissipation operation based on, for example, the pressure of the heat accumulator 21. In this case, the pressure of the heat accumulator 21 can be measured by, for example, a pressure sensor disposed in the first container 23 of the heat accumulator 21. The heat dissipation operation control unit 13b can also be configured to switch to the second heat dissipation operation after a predetermined time has elapsed since the first heat dissipation operation.

[0070] The exhaust heat utilization system 11 is configured to send water vapor from the heat accumulator 21 to the object to be heated 61 during heat dissipation operation, but it can also be configured to transport heat from the heat accumulator 21 to the object to be heated 61 using a heat pipe, for example.

[0071] During the first heat storage operation shown in FIG. 2 , the exhaust heat utilization system 11 may use the inverter of the pump 72 to control the flow rate of water sent from the condenser 41 to the second heat exchanger 32 of the recovery device 31 and to the evaporator 51 through the supply flow path L5A. For example, the flow rate of water sent to the evaporator 51 can be controlled based on the measurement results of the temperature of the water flowing out of the second heat exchanger 32 of the recovery device 31. More specifically, the water flow rate is controlled so that the temperature of the water flowing out of the second heat exchanger 32 is higher than a predetermined temperature. In other words, by slowing down the flow rate of water through the second heat exchanger 32 of the recovery device 31, the temperature of the water at the outlet of the second heat exchanger 32 can be further increased. This makes it possible to stably supply water at a temperature higher than a predetermined temperature to the evaporator 51. [Explanation of symbols]

[0072] 11...Waste heat utilization system 12...Chemical heat pump 13...Control unit 13a...Heat storage operation control section 13b...Heat dissipation operation control section 21... Heat storage device 31...Collector 32…Second heat exchanger 41...Condenser 51...Evaporator HM…Chemical heat storage material LM...Absorbent material L5A…supply channel WV1, WV2, WV3...Water vapor

Claims

1. A waste heat utilization system comprising: a chemical heat pump that stores waste heat; and a control unit that controls the operation of the chemical heat pump, The chemical heat pump comprises: a heat storage device having a chemical heat storage material that undergoes a dehydration reaction during heat storage operation and a hydration reaction during heat release operation; A recovery device having an absorbent material that absorbs water vapor and recovers water vapor generated from the chemical heat storage material; a condenser that condenses water vapor discharged from the absorbent during a regeneration operation in which a dehydration reaction of the absorbent is performed; an evaporator that supplies water vapor to the heat storage device to react with the chemical heat storage material, the control unit includes a heat dissipation operation control unit that switches from a first heat dissipation operation to a second heat dissipation operation, In the first heat release operation, water vapor discharged from the absorbent material during the regeneration operation is supplied to the heat accumulator, In the second heat dissipation operation, the water vapor generated in the evaporator is supplied to the heat storage device.

2. The exhaust heat utilization system according to claim 1 , wherein the heat dissipation operation control unit switches from the first heat dissipation operation to the second heat dissipation operation based on a temperature or a pressure of the heat storage device.

3. The recovery vessel has a heat exchanger, 3. The exhaust heat utilization system according to claim 1, wherein the control unit includes a heat storage operation control unit that controls the replenishment of the evaporator with water that has passed through the heat exchanger of the recovery device during the heat storage operation.

4. The exhaust heat utilization system according to claim 3 , wherein in the heat storage operation, water cooled by the condenser is supplied to the heat exchanger of the recovery unit.

5. A control method for a waste heat utilization system including a chemical heat pump that stores waste heat, The chemical heat pump comprises: a heat storage device having a chemical heat storage material that undergoes a dehydration reaction during heat storage operation and a hydration reaction during heat release operation; A recovery device having an absorbent material that absorbs water vapor and recovers water vapor generated from the chemical heat storage material; a condenser that condenses water vapor discharged from the absorbent during a regeneration operation in which a dehydration reaction of the absorbent is performed; an evaporator that supplies water vapor to the heat storage device to react with the chemical heat storage material, The control method includes switching from a first heat dissipation operation to a second heat dissipation operation; In the first heat release operation, water vapor discharged from the absorbent material during the regeneration operation is supplied to the heat accumulator, In the second heat dissipation operation, the water vapor generated in the evaporator is supplied to the heat storage device.

Images