JP2024089990A - Heat medium circulation system - Google Patents

Abstract

To provide a heat medium circulation system which can stably supply heat to a device which needs heat even if the heat which is collected due to variation in load on a reactor, in the heat medium circulation system which performs a heat exchange by making the heat medium circulate in the reactor in which a heat generation reaction is performed and the device which needs heat.SOLUTION: A heat medium circulation system 10 comprises a reactor 21 in which a heat generation reaction is performed, a device 22 which needs heat, a constant temperature tank 11, a first flow passage 12, and a second flow passage 13. The constant temperature tank 11 stores a heat medium HM, and maintains it within a prescribed temperature range. The first flow passage 12 makes a heat medium HM circulate between the reactor 21 and the constant temperature tank 11, and transfers the heat of the reactor 21 to the heat medium HM. The second flow passage 13 makes the heat medium HM circulate between the device 22 and the constant temperature tank 11, and transfers the heat of the heat medium HM to the device 22. The heat medium HM circulates in the first flow passage 12 and the second flow passage 13 through the single constant temperature tank 11.SELECTED DRAWING: Figure 2

Description

This disclosure relates to a heat transfer medium circulation system.

Power generation systems that can effectively utilize the heat generated in dehydrogenation and hydrogenation reactions have been known for some time (see Patent Document 1 below). The power generation system described in Patent Document 1 includes an electric heating device, a heat exchanger, a generator, and an electricity storage device (paragraph 0006, claim 1, abstract, and figure 1 of the same document).

The electric heating device heats at least one of the first passage and the first catalyst in a hydrogenation system having a hydrogenation reactor including a first passage provided with a first catalyst that promotes the hydrogenation reaction of aromatic compounds, and a first exhaust pipe extending from the first passage to the outside of the hydrogenation reactor.

The heat exchange unit cools at least one of the first passage, the first catalyst, and the first exhaust pipe. The generator generates electricity using heat obtained in the heat exchange unit. The power storage device stores the electricity obtained by the generator. In this power generation system, the electric heating device is driven based on at least the electricity from the power storage device.

An invention related to a heat output technology that uses a chemical heat storage material is also known (see Patent Document 2 below). The heat output method described in Patent Document 2 includes a first steam generation step, a preheating step, a first heating step, and a second steam generation step (paragraph 0008, claim 1, abstract, and figure 1 of the same document).

In the first steam generation process, the first steam is generated using the heat of the first exhaust gas from the heat source device, and the second exhaust gas is discharged. In the preheating process, the solid chemical heat storage material is preheated by exchanging heat between the second exhaust gas and the solid chemical heat storage material, which absorbs heat through a dehydration reaction and generates heat through a hydration reaction.

In the first heating step, the water in the water container connected to the heat storage tank storing the solid chemical heat storage material is heated by heat exchange between the water in the water container and at least the second exhaust gas. In the second water vapor generation step, the second water vapor is generated by the heat output from the solid chemical heat storage material.

JP 2020-078104 A JP 2014-105926 A

As a measure against global warming, the use of green hydrogen, which is hydrogen produced using electricity derived from renewable energy sources, is being promoted. However, when electricity derived from renewable energy sources such as solar or wind power is used as the power input to a hydrogen production device, the power input to the device is likely to fluctuate depending on weather conditions and the time of day. Fluctuations in the power input to the device in this way may, for example, fluctuate the load on a reactor downstream of the device where an exothermic reaction takes place, reducing the stability of the reactor and the device that utilizes its heat, and may reduce the efficiency of heat exchange between the reactor and the device that utilizes its heat.

The present disclosure provides a heat medium circulation system that performs heat exchange by circulating a heat medium between a reactor in which an exothermic reaction takes place and a device requiring heat, and that can stably supply heat to the device requiring heat even if the load on the reactor fluctuates and the heat recovered fluctuates.

One aspect of the present disclosure is a heat medium circulation system that includes a reactor in which an exothermic reaction takes place and a device that requires heat, and that circulates a heat medium between the reactor and the device, the heat medium circulation system including a thermostatic chamber that stores the heat medium and maintains it at a predetermined temperature range, a first flow path that circulates the heat medium between the reactor and the thermostatic chamber to transfer heat from the reactor to the heat medium, and a second flow path that circulates the heat medium between the device and the thermostatic chamber to transfer heat from the heat medium to the device, and the heat medium circulates between the first flow path and the second flow path via the single thermostatic chamber.

According to the above aspect of the present disclosure, it is possible to provide a heat medium circulation system that can stably supply heat to a device that requires heat, even if the load on the reactor in which the exothermic reaction takes place fluctuates and the heat recovered fluctuates.

FIG. 1 is a block diagram illustrating an embodiment of a heat medium circulation system according to the present disclosure. FIG. 2 is a schematic cross-sectional view of the heat transfer medium circulation system of FIG. 1 . Block diagram of an SOEC methanation system including the heat transfer medium circulation system of Figure 1. FIG. 2 is a block diagram of an SOEC methanation system according to Comparative Example 1. FIG. 4 is a block diagram of an SOEC methanation system according to Comparative Example 2.

Below, an embodiment of the heat transfer medium circulation system according to the present disclosure will be described with reference to the drawings.

Figure 1 is a block diagram showing an embodiment of a heat transfer medium circulation system according to the present disclosure. Figure 2 is a schematic cross-sectional view of the heat transfer medium circulation system 10 of the present embodiment shown in Figure 1. Figure 3 is a block diagram of a solid oxide electrolysis cell (SOEC) methanation system 100 including the heat transfer medium circulation system 10 of the present embodiment shown in Figure 1. Below, first, the details of the heat transfer medium circulation system 10 of the present embodiment will be described, and then the details of the SOEC methanation system 100 including the heat transfer medium circulation system 10 of the present embodiment will be described.

(Heat medium circulation system)
The heat medium circulation system 10 of this embodiment includes a reactor 21 in which an exothermic reaction takes place, a device 22 that requires heat, a thermostatic chamber 11, a first flow path 12, and a second flow path 13, and is configured so that the heat medium HM circulates through the first flow path 12 and the second flow path 13 via a single thermostatic chamber 11. The heat medium circulation system 10 further includes, for example, a temperature control device 14. That is, the heat medium HM is circulated to the reactor 21 and the device 22 via the thermostatic chamber 11, the first flow path 12, and the second flow path 13, and heat exchange between the reactor 21 and the device 22 is realized by recovering heat from the reactor 21 and supplying heat to the device 22.

The heat medium HM is preferably one with a larger heat capacity per unit volume, and the latent heat generated during the phase change may be utilized to recover and supply heat. By utilizing the latent heat generated during the phase change of the heat medium HM, the heat medium HM at a constant temperature can be circulated to the reactor 21 and the device 22, and the reactor 21 and the device 22 can be maintained within an appropriate temperature range. In addition, the heat medium HM may be, for example, a two-phase flow with a high heat transfer rate, or a heat medium oil capable of circulating in the liquid phase at a temperature of 300°C or higher.

The efficiency of heat exchange between the reactor 21 and the device 22 depends, for example, on the heat transfer coefficient of the heat medium HM in addition to the heat exchange method. The heat transfer coefficient of the heat medium HM varies greatly depending on, for example, the phase of the heat medium HM. In general, the heat transfer coefficient of the heat medium HM is two-phase flow, liquid, and gas, in descending order. In addition, the heat medium HM used is, for example, one that corresponds to the pressure of the system used, does not corrode the device, and is non-flammable.

The thermostatic bath 11 is, for example, a device that stores the heat medium HM and maintains it within a predetermined temperature range. More specifically, the thermostatic bath 11 has, for example, a heat medium storage section 11a that stores the heat medium HM. The volume of the heat medium HM stored in the heat medium storage section 11a is, for example, larger than the volume of the heat medium HM filling the first flow path 12 and the second flow path 13, and specifically, for example, is 10 times or more, or 100 times or more.

This allows the heat medium HM whose temperature has increased by passing through the first flow path 12 and the heat medium HM whose temperature has decreased by passing through the second flow path 13 to merge with the heat medium HM stored in the heat medium storage section 11a, and the temperature of the heat medium HM flowing out of the heat medium storage section 11a can be maintained within a predetermined temperature range. In addition, the thermostatic bath 11 may have a thermal insulating material that keeps the heat medium HM stored in the heat medium storage section 11a warm.

The thermostatic bath 11 has, for example, a first heat medium outlet 11b and a first heat medium inlet 11c, and a second heat medium outlet 11d and a second heat medium inlet 11e that open to the heat medium storage section 11a. The first heat medium outlet 11b allows the heat medium HM to flow out from the heat medium storage section 11a to the first heat exchange section 12a, and the first heat medium inlet 11c allows the heat medium HM that has passed through the first heat exchange section 12a to flow into the heat medium storage section 11a. The second heat medium outlet 11d allows the heat medium HM to flow out from the heat medium storage section 11a to the second heat exchange section 13a, and the second heat medium inlet 11e allows the heat medium HM that has passed through the second heat exchange section 13a to flow into the heat medium storage section 11a.

The first flow path 12, for example, circulates a heat medium HM between the reactor 21 and the thermostatic bath 11 to transfer heat from the reactor 21 to the heat medium HM. The reactor 21 in which the exothermic reaction takes place is, but is not particularly limited to, for example, a methanation reactor 121 constituting the SOEC methanation system 100 described below. The first flow path 12 has, for example, a first heat exchanger 12a and a first pump 12b.

The first heat exchanger 12a transfers heat from the reactor 21 to the heat medium HM. More specifically, the first heat exchanger 12a is provided, for example, adjacent to the catalyst housing section 21a of the reactor 21, and transfers heat generated by an exothermic reaction mediated by a catalyst inside the catalyst housing section 21a to the heat medium HM flowing inside the first heat exchanger 12a.

The first pump 12b is provided, for example, between the heat medium storage section 11a and the first heat exchange section 12a of the thermostatic bath 11, and pumps the heat medium HM to circulate it between the heat medium storage section 11a and the first heat exchange section 12a. The first pump 12b is controlled, for example, by a control section, and can adjust the flow rate of the heat medium HM flowing through the first flow path 12 by adjusting the flow rate of the heat medium HM being pumped, thereby adjusting the flow rate of the heat medium HM passing through the first heat exchange section 12a.

The second flow path 13, for example, circulates the heat medium HM between the device 22 and the thermostatic bath 11 to transfer the heat of the heat medium HM to the device 22. The device 22 that requires heat is, but is not particularly limited to, for example, the evaporator 122 that constitutes the SOEC methanation system 100. The second flow path 13 has, for example, a second heat exchanger 13a and a second pump 13b.

The second heat exchange unit 13a transfers the heat of the heat medium HM to the device 22. More specifically, the second heat exchange unit 13a is provided, for example, inside the device 22 in which water W is stored, and transfers the heat of the heat medium HM to the water W inside the device 22. This allows the water W to be evaporated to generate water vapor S in the device 22, such as the evaporator 122, which requires heat.

The second pump 13b is provided, for example, between the heat medium storage section 11a and the second heat exchange section 13a of the thermostatic bath 11, and pumps the heat medium HM to circulate it between the heat medium storage section 11a and the second heat exchange section 13a. The second pump 13b is controlled, for example, by the control section, and can adjust the flow rate of the heat medium HM flowing through the second flow path 13 by adjusting the flow rate of the heat medium HM being pumped, thereby adjusting the flow rate of the heat medium HM passing through the second heat exchange section 13a.

The type of the first pump 12b and the second pump 13b is not particularly limited, and for example, a non-positive displacement pump or a positive displacement pump can be used. By using a non-positive displacement pump as the first pump 12b and the second pump 13b, the heat medium HM can be circulated continuously through the first flow path 12 and the second flow path 13. In addition, by using a positive displacement pump as the first pump 12b and the second pump 13b, the stability of the discharge pressure and discharge flow rate of the heat medium HM can be improved.

The heat exchange method in the first heat exchange section 12a and the second heat exchange section 13a is not particularly limited. For example, depending on the type of heat medium HM and the type and size of the reactor 21 and the device 22, a heat exchange method that allows for highly efficient heat recovery and heat supply and can maintain each device within an appropriate temperature range can be selected. Specifically, for example, a shell-and-tube type, a plate type, a coil type, a spiral type, or a fin tube type can be individually adopted as the heat exchange method for the first heat exchange section 12a and the second heat exchange section 13a.

The shell-and-tube type has a simple structure, can be used in a wide range of pressures from low to high, is easy to maintain, and can easily handle replacement of the catalyst inside the reactor 21. In the plate type, heat exchange is performed through a heat transfer plate made of thin plates with a complex pressed shape, so the contact area with the heat medium HM is large and high heat exchange efficiency is obtained. Therefore, by adopting the plate type, it is possible to reduce the size of the first heat exchange section 12a or the second heat exchange section 13a.

In the coil type, the heat transfer medium HM is circulated inside a heat transfer tube wound in a coil shape, and heat is exchanged with the fluid outside the heat transfer tube. The coil type has a very simple structure, and it is possible to use the heat transfer tube by immersing it in a water tank. In the spiral type, heat exchange occurs with a spirally wound flat plate as the boundary. In the fin tube type, fins are attached to a metal tube, making it possible to exchange heat through a large heat transfer area.

The temperature control device 14, for example, maintains the heat medium HM stored in the thermostatic bath 11 within a predetermined temperature range. The temperature control device 14 includes, for example, a control unit, a temperature sensor that detects the temperature of the heat medium HM stored in the thermostatic bath 11, and an electric heater that heats the heat medium HM stored in the thermostatic bath 11. The control unit of the temperature control device 14 controls the electric heater so as to maintain the temperature of the heat medium HM detected by the temperature sensor within a predetermined temperature range. The heating method of the electric heater can be, for example, resistance heating, induction heating, or infrared heating.

By adopting an induction heating method for the electric heater, it is possible to miniaturize the electric heater and quickly control the temperature of the heat medium HM. Furthermore, by adopting an infrared heating method for the electric heater, it is possible to increase the efficiency of the electric heater and quickly heat the heat medium HM. The heating method of the electric heater can be appropriately selected depending on, for example, the volume of the heat medium HM stored in the thermostatic chamber 11 and the type of heat medium HM. Furthermore, the temperature control device 14 may include, in addition to the electric heater, a latent heat storage material or a chemical heat storage material for maintaining the heat medium HM within a predetermined temperature range.

The predetermined temperature range of the heat medium HM stored in the thermostatic bath 11 is set, for example, to a temperature range that can maintain the exothermic reaction of the reactor 21 at an appropriate temperature range and can supply the necessary heat to the device 22. More specifically, for example, there is an overlapping temperature range between the appropriate temperature range of the exothermic reaction of the reactor 21 and the temperature range that can supply the necessary heat to the device 22, and this overlapping temperature range can be set to the predetermined temperature range of the heat medium HM stored in the thermostatic bath 11.

Here, the reactor 21 and the device 22 are, for example, the methanation reactor 121 and the evaporator 122 constituting the SOEC methanation system 100 shown in FIG. 3, respectively. When the pressure inside the device 22 is 10 atm, the boiling point of water W is about 180°C, and the temperature range capable of supplying the necessary heat to the device 22 is, for example, 200°C or higher. In addition, the activation temperature of the Ni-based catalyst used in the methanation reactor 121 is about 230°C, and the appropriate temperature range for the exothermic reaction of the reactor 21 is, for example, 230°C or higher and 250°C or lower.

In such a case, the predetermined temperature range of the heat transfer medium HM stored in the thermostatic chamber 11 can be set to, for example, 230°C or more and 250°C or less. This allows the heat transfer medium HM to be supplied from the thermostatic chamber 11 to the first flow path 12 and the second flow path 13, so that the exothermic reaction in the methanation reactor 121 can be maintained within an appropriate temperature range and the necessary heat can be supplied to the evaporator 122.

(SOEC methanation system)
Next, a detailed description will be given of the configuration of the SOEC methanation system 100 including the heat medium circulation system 10 of this embodiment. As shown in Fig. 3, the SOEC methanation system 100 of this embodiment includes a heat medium circulation system 110 corresponding to the heat medium circulation system 10 described above, as well as a methanation reactor 121, an evaporator 122, a flow rate control device 123, a solid oxide electrolysis cell (SOEC) 124, a condenser 125, and a flow rate control device 126.

The flow control device 123 is provided, for example, between a source of water W and the evaporator 122, and controls the flow rate of the water W supplied to the evaporator 122. More specifically, the flow control device 123 includes, for example, a flow control valve 123a that controls the flow rate of the water W supplied to the evaporator 122, as shown in FIG. 2. The flow control device 123 may also include, for example, a pump capable of controlling the discharge flow rate.

The evaporator 122 corresponding to the above-mentioned device 22 requiring heat, for example, evaporates water W supplied via a flow control device 123 and supplies water vapor S to the SOEC 124. More specifically, the evaporator 122 evaporates the water W to generate water vapor S by heating the water W with heat supplied via the second heat exchanger 13a from the heat medium HM circulating through the second flow path 113 of the heat medium circulation system 110, for example.

The SOEC 124 uses electric power EP derived from renewable energy such as solar power or wind power to generate gas containing hydrogen (H ₂ ) from a mixed gas of carbon dioxide (CO ₂ ) supplied from a carbon dioxide supplier and water vapor S supplied from the evaporator 122. The SOEC 124 generates hydrogen by, for example, electrolyzing the water vapor S. In addition, in the SOEC 124, for example, a portion of the carbon dioxide is electrolyzed into carbon monoxide (CO).

The carbon dioxide supplied from the carbon dioxide supply source may be merged downstream of the SOEC 124 and mixed with the hydrogen generated in the SOEC 124. The gas containing hydrogen and carbon dioxide discharged from the SOEC 124, or the mixed gas of hydrogen and carbon dioxide discharged from the SOEC 124, is introduced, for example, into the condenser 125. The gas introduced into the condenser 125 has moisture contained in the gas removed, and is introduced into the flow control device 126.

The flow rate control device 126 controls the flow rate of the gas introduced from the condenser 125. The gas whose flow rate is controlled by the flow rate control device 126 is introduced into the methanation reactor 121. The gas introduced into the methanation reactor 121 passes through a catalyst layer contained in the catalyst containing section 21a, causing a methanation reaction in which hydrogen contained in the gas reacts with carbon dioxide. The methanation reaction is an exothermic reaction represented, for example, by the following reaction formula (1).

4H ₂ + CO ₂ → CH ₄ + 2H ₂ O (ΔH = -165 kJ/mol) ... (1)

The methane-containing gas produced by the methanation reaction that passes through the catalyst layer contained in the catalyst containing section 21a inside the methanation reactor 121 is, for example, recovered and purified for use. Thus, the reactor 21 in which the exothermic reaction described above takes place is, for example, the methanation reactor 121 into which the hydrogen-containing gas produced in the SOEC 124 is introduced to produce the methane-containing gas.

The heat medium circulation system 110 constituting the SOEC methanation system 100 circulates the heat medium HM to the methanation reactor 121, which is the reactor 21 where the exothermic reaction takes place, and the evaporator 122, which is the device 22 that requires heat, in the same manner as the heat medium circulation system 10 described above. The heat medium circulation system 110, for example, includes the methanation reactor 121 as the reactor 21 and the evaporator 122 as the device 22. The heat medium circulation system 110 also includes a constant temperature bath 111, a first flow path 112, a second flow path 113, and a temperature control device 114 that correspond to the constant temperature bath 11, the first flow path 12, the second flow path 13, and the temperature control device 14 of the heat medium circulation system 10 described above.

The operation of the heat transfer medium circulation system 10 of this embodiment is described below.

As a measure against global warming, the use of green hydrogen, which is hydrogen produced using electricity EP derived from renewable energy sources, is being promoted. For example, the SOEC methanation system 100 recovers the reaction heat of the methanation reaction in the methanation reactor 121 using the heat medium circulation system 110, and supplies the recovered heat to the evaporator 122 to evaporate the water W and generate water vapor S. This theoretically makes the efficiency of the methanation reaction 100%, and the overall efficiency of the SOEC methanation system 100 is expected to be around 80 to 90%.

However, when electricity EP derived from renewable energy sources such as solar or wind power is used as the power input to the SOEC 124 that produces hydrogen, it is conceivable that the electricity EP input to the device will fluctuate depending on weather conditions and the time of day. Fluctuations in the electricity EP input to the SOEC 124 will, for example, fluctuate the load on the methanation reactor 121 downstream of the SOEC 124 where the exothermic reaction takes place. As a result, there is a risk that the stability of the methanation reactor 121 and the evaporator 122 that utilizes the heat from the methanation reactor 121 will decrease, and the efficiency of heat exchange between the methanation reactor 121 and the evaporator 122 will decrease.

More specifically, if the renewable energy-derived electricity EP supplied to the SOEC 124 suddenly decreases, the amount of hydrogen generated in the SOEC 124 decreases, and the load on the methanation reactor 121 decreases. If the load on the methanation reactor 121 decreases and the reaction rate of the methanation reaction decreases, the heat recovered from the methanation reactor 121 via the heat medium HM may decrease, and the heat supplied to the evaporator 122 via the heat medium HM may decrease. If the heat supplied to the evaporator 122 decreases in this way, the water vapor S supplied from the evaporator 122 to the SOEC 124 may decrease, and the amount of hydrogen generated in the SOEC 124 may further decrease.

In this way, the decrease in the amount of hydrogen produced in the SOEC 124 caused by a sudden decrease in the electricity EP derived from renewable energy can be returned to a stable state by, for example, readjusting conditions such as the temperature and flow rate of the heat medium HM. However, it takes a certain amount of time for the amount of hydrogen produced in the SOEC 124 to return to a stable state after the decrease occurs, and there is a risk of significant losses during that time.

In contrast, the heat medium circulation system 10 of this embodiment is a system that includes a reactor 21 in which an exothermic reaction such as a methanation reactor 121 takes place, and a device 22 that requires heat such as an evaporator 122, and circulates the heat medium HM between the reactor 21 and the device 22. The heat medium circulation system 10 includes a thermostatic chamber 11, a first flow path 12, and a second flow path 13. The thermostatic chamber 11 stores the heat medium HM and maintains it at a predetermined temperature range. The first flow path 12 circulates the heat medium HM between the reactor 21 and the thermostatic chamber 11 to transfer heat from the reactor 21 to the heat medium HM. The second flow path 13 circulates the heat medium HM between the device 22 and the thermostatic chamber 11 to transfer heat from the heat medium HM to the device 22. In the heat medium circulation system 10 of this embodiment, the heat medium HM circulates between the first flow path 12 and the second flow path 13 via a single thermostatic chamber 11.

With this configuration, the heat medium circulation system 10 of this embodiment can efficiently recover heat by transferring heat from the reactor 21, where an exothermic reaction takes place, to the heat medium HM circulated in the first flow path 12. In addition, the heat of the heat medium HM circulated in the second flow path 13 can be efficiently supplied by transferring the heat from the heat medium HM to the device 22 that requires heat, thereby improving the efficiency of heat exchange between the reactor 21 and the device 22.

In addition, the heat medium HM that flows out of the same thermostatic bath 11 storing the heat medium HM maintained at a predetermined temperature range and has increased in temperature by recovering heat from the reactor 21, and the heat medium HM that has decreased in temperature by supplying heat to the device 22, each flow into the same thermostatic bath 11. As a result, the heat medium HM whose temperature has increased above the predetermined temperature range and the heat medium HM whose temperature has decreased below the predetermined temperature range join and mix with the heat medium HM stored in the thermostatic bath 11 in the predetermined temperature range, and each becomes at a temperature within the predetermined temperature range.

Therefore, according to the heat medium circulation system 10 of this embodiment, even if the heat recovery from the reactor 21 fluctuates due to fluctuations in the electric power EP derived from renewable energy, the heat medium HM in a predetermined temperature range can be circulated in the second flow path 13, making it possible to stably supply heat to the device 22 that requires heat. In other words, the fluctuations in the heat recovery from the reactor 21 can be absorbed by the thermostatic chamber 11 to stabilize the operation of the device 22. In addition, by circulating the heat medium HM between the same thermostatic chamber 11 in which the heat medium HM in a predetermined temperature range is stored and the first flow path 12 and the second flow path 13, the efficiency of heat exchange between the reactor 21 and the device 22 is improved, and an energy saving effect is obtained.

In the heat medium circulation system 10 of this embodiment, the thermostatic bath 11 has a heat medium storage section 11a that stores the heat medium HM. The first flow path 12 has a first heat exchange section 12a that transfers heat from the reactor 21 to the heat medium HM, and a first pump 12b that is provided between the heat medium storage section 11a and the first heat exchange section 12a and adjusts the flow rate of the heat medium HM flowing through the first flow path 12. The second flow path 13 has a second heat exchange section 13a that transfers heat from the heat medium HM to the device 22, and a second pump 13b that is provided between the heat medium storage section 11a and the second heat exchange section 13a and adjusts the flow rate of the heat medium HM flowing through the second flow path 13.

With this configuration, according to the heat medium circulation system 10 of this embodiment, the flow rate of the heat medium HM circulating between the heat medium storage section 11a of the thermostatic bath 11 and the first heat exchange section 12a can be controlled by controlling the flow rate of the heat medium HM pumped by the first pump 12b. In addition, the flow rate of the HM circulating between the heat medium storage section 11a of the thermostatic bath 11 and the second heat exchange section 13a can be controlled by controlling the flow rate of the heat medium HM pumped by the second pump 13b. Therefore, the flow rate of the heat medium HM circulating between the heat medium storage section 11a of the thermostatic bath 11 and each of the first flow path 12 and the second flow path 13 can be increased or decreased according to the fluctuation of the load of the reactor 21, thereby maintaining the temperature of the reactor 21 and the device 22 within an appropriate temperature range.

In addition, in the heat medium circulation system 10 of this embodiment, the volume of the heat medium HM stored in the heat medium storage section 11a of the thermostatic bath 11 is larger than the volume of the heat medium HM filling the first flow path 12 and the second flow path 13. With this configuration, the heat medium circulation system 10 of this embodiment can suppress temperature changes in the heat medium HM in the heat medium storage section 11a, where the heat medium HM whose temperature has risen above a predetermined temperature range and the heat medium HM whose temperature has fallen below the predetermined temperature range merge, and maintain the heat medium HM within the predetermined temperature range.

In the heat medium circulation system 10 of this embodiment, the device 22 requiring heat is, for example, an evaporator 122, and the reactor 21 in which the exothermic reaction takes place is, for example, a methanation reactor 121. With this configuration, the heat medium HM stored in the thermostatic bath 11 can be circulated to the first flow path 12, and the heat generated by the methanation reaction in the methanation reactor 121 can be recovered and transferred to the heat medium HM stored in the thermostatic bath 11. In addition, the heat medium HM stored in the thermostatic bath 11 can be circulated to the second flow path 13, and heat can be supplied to the evaporator 122 to generate water vapor.

In the heat medium circulation system 10 of this embodiment, the evaporator 122 supplies water vapor to a solid oxide electrolysis cell, i.e., SOEC 124, which generates a gas containing hydrogen from carbon dioxide and water vapor using electricity EP derived from renewable energy. The methanation reactor 121 receives the hydrogen-containing gas generated in the solid oxide electrolysis cell, i.e., SOEC 124, and generates a gas containing methane.

In this embodiment of the heat medium circulation system 10, when the renewable energy-derived electric power EP fluctuates, the amount of hydrogen generated by the SOEC 124, which uses the electric power to generate hydrogen, fluctuates. As a result, the amount of hydrogen contained in the gas introduced into the methanation reactor 121 decreases, and the amount of heat generated by the methanation reaction, which is an exothermic reaction in the methanation reactor 121, decreases. However, by circulating the heat medium HM of a predetermined temperature range stored in the thermostatic bath 11 through the first flow path 12, the necessary heat can be transferred from the heat medium HM to the methanation reactor 121, and the methanation reactor 121 can be maintained in a temperature range appropriate for the methanation reaction.

In addition, even if the amount of heat generated in the methanation reactor 121 decreases and the heat recovery from the methanation reactor 121 decreases, the heat medium HM stored in the thermostatic bath 11 and maintained at a predetermined temperature range is circulated between the thermostatic bath 11 and the second flow path 13. This allows the necessary heat supply to the evaporator 122 to be continued, the water vapor S to be stably supplied from the evaporator 122 to the SOEC 124, the decrease in the amount of hydrogen generated in the SOEC 124 to be suppressed, and the stability of the methanation reaction in the methanation reactor 121 to be improved.

In addition, in the heat medium circulation system 10 of this embodiment, the predetermined temperature range of the heat medium HM stored in the thermostatic bath 11 is set to a temperature range that can maintain the exothermic reaction of the reactor 21 at an appropriate temperature range and can supply the necessary heat to the device 22. With this configuration, the heat medium circulation system 10 of this embodiment can suppress a decrease in the stability of the reactor 21 and the device 22 even if, for example, the electric power EP derived from renewable energy fluctuates and the amount of heat generated by the exothermic reaction of the reactor 21 decreases.

The heat medium circulation system 10 of this embodiment further includes a temperature control device 14 that maintains the heat medium HM stored in the thermostatic bath 11 within a predetermined temperature range. As described above, when the amount of heat generated by the exothermic reaction in the reactor 21 decreases and the temperature of the heat medium HM flowing from the first flow path 12 into the thermostatic bath 11 drops, the temperature of the heat medium HM stored in the thermostatic bath 11 may drop below the predetermined temperature range depending on the conditions. However, even in such cases, the heat medium circulation system 10 of this embodiment allows the heat medium HM stored in the thermostatic bath 11 to be heated by the temperature control device 14 and maintained within the predetermined temperature range.

The above describes in detail an embodiment of the heat transfer medium circulation system according to the present disclosure using the drawings, but the specific configuration is not limited to this embodiment, and even if there are design changes, etc., within the scope that does not deviate from the gist of this disclosure, they are included in this disclosure.

For example, in the above embodiment, the heat medium circulation system 10 has one reactor 21 in which an exothermic reaction takes place and one device 22 that requires heat. However, there may be two or more reactors 21 and devices 22. In this case, the first flow path 12 may be provided in each reactor 21, and the second flow path 13 may be provided in each device 22. The heat medium circulation system 10 may also be provided with a second flow path 13 for the reactor in which an endothermic reaction takes place to supply heat, or with a first flow path 12 for a device that requires heat dissipation to recover heat. The heat medium circulation system 10 may also have a heat-retaining flow path that circulates the heat medium between the thermostatic bath 11 and the device that requires heat retention.

Below, comparative examples of heat medium circulation systems different from the heat medium circulation system according to the present disclosure will be described in comparison with the embodiment of the heat medium circulation system according to the present disclosure. Note that in each comparative example, configurations similar to those described in the above-mentioned embodiment will be assigned the same reference numerals as in the above-mentioned embodiment, and descriptions thereof will be omitted.

[Comparative Example 1]
4 is a block diagram of a heat medium circulation system 110X of Comparative Example 1 included in the SOEC methanation system 100X. The heat medium circulation system 110X of Comparative Example 1 includes a first heat medium passage 111X, a second heat medium passage 112X, a heat medium circulation pump 113X, a heat medium heater 114X, and a temperature control device 115X. In this Comparative Example 1, it is assumed that the evaporator 122 requires a heat amount equal to or greater than the heat generation amount of the methanation reactor 121.

The first heat medium flow path 111X is a flow path for the heat medium HM that connects the methanation reactor 121 and the evaporator 122, and allows the heat medium HM that has undergone heat recovery in the methanation reactor 121 to flow into the evaporator 122. The second heat medium flow path 112X is a flow path for the heat medium HM that connects the evaporator 122 and the methanation reactor 121, and allows the heat medium HM that has undergone heat supply to the evaporator 122 to flow into the methanation reactor 121 via the heat medium heater 114X.

The heat medium circulation pump 113X is provided, for example, midway through the first heat medium passage 111X or the second heat medium passage 112X to pump the heat medium HM. As a result, the heat medium HM circulates from the methanation reactor 121 to the evaporator 122, from the evaporator 122 to the heat medium heater 114X, and from the heat medium heater 114X to the methanation reactor 121. The heat medium heater 114X heats the heat medium HM whose temperature has been reduced by supplying heat to the evaporator 122, and adds the amount of heat that is insufficient due to the heat supply to the evaporator 122 to the heat medium HM. The temperature control device 115X controls the heat medium heater 114X to control the temperature of the heat medium HM.

[Comparative Example 2]
5 is a block diagram of a heat medium circulation system 110Y of Comparative Example 2 included in the SOEC methanation system 100Y. The heat medium circulation system 110Y of Comparative Example 2 includes a first heat medium passage 111Y, a second heat medium passage 112Y, a heat medium circulation pump 113Y, a heat medium heater 114Y, and a temperature control device 115Y, similar to the heat medium circulation system 110X of Comparative Example 1. Each of these parts is similar to the parts of the heat medium circulation system 110X of Comparative Example 1, so a description thereof will be omitted.

The heat medium circulation system 110Y of Comparative Example 2 has the same configuration as the heat medium circulation system 110X of Comparative Example 1, and further includes a heat medium cooling device 116Y, a temperature control device 117Y, and a heat exchanger 118Y. In Comparative Example 2, it is assumed that the heat value of the methanation reactor 121 is equal to or greater than the heat value required in the evaporator 122.

The heat medium cooling device 116Y is provided in the middle of the first heat medium flow path 111Y, and cools the heat medium HM whose temperature has risen due to heat recovery in the methanation reactor 121 to lower the temperature. The temperature control device 117Y controls the heat medium cooling device 116Y to control the temperature of the heat medium HM. The heat exchange unit 118Y includes, for example, a heat medium that recovers heat in the heat medium cooling device 116Y and supplies heat to the heat medium heater 114Y, a flow path for circulating the heat medium, and a pump for pumping the heat medium.

Below, the operation of the heat medium circulation system 110 according to this embodiment will be explained by comparing the heat medium circulation system 110 according to the above-mentioned embodiment with the heat medium circulation systems 110X and 110Y according to comparative examples 1 and 2.

Here, the heat required by the evaporator 122 is 600 [kW], the heat generation amount of the methanation reactor 121 is 400 [kW], the flow rate of the heat medium HM is 0.01 [ ^m3 /s], the density of the heat medium HM is 868.7 [kg/ ^m3 ], the specific heat of the heat medium HM is 2.35 [kJ/kg/K], and the total pressure of the heat medium HM is 1 [MPa]. Also, the evaporator 122 is required to flow in the heat medium HM of 250 [°C] or more, and the methanation reactor 121 is required to flow in the heat medium HM of 250 [°C].

The assumptions for the calculation are as follows. In the heat medium circulation system 110 of this embodiment, the same flow rate of the heat medium HM is circulated in the first flow path 112 and the second flow path 113. The temperature dependence of the density and specific heat of the heat medium HM are not taken into consideration and are set to constant values. In the heat medium circulation system 110Y of Comparative Example 2, the indirect heat exchange rate between the heat medium heater 114Y and the heat medium cooling device 116Y via the heat exchange section 118Y is 80%.

In the heat medium circulation system 110 of the above embodiment, the direct heat exchange rate between the heat medium HM flowing from the first flow path 112 into the thermostatic bath 111 and the heat medium HM flowing from the second flow path 113 into the thermostatic bath 111 is 100%. The flow path through which the heat medium HM circulates is an adiabatic system. In the heat medium circulation system 110 of the above embodiment and the heat medium circulation system 110Y of Comparative Example 2, the temperature of the heat medium HM flowing into the evaporator 122 is controlled to 250°C.

Under the above assumptions, we will explain the steady state of the SOEC methanation system, the first transient state in which the load on the methanation reactor 121 has decreased to 50% of the steady state, and the second transient state in which the load on the evaporator 122 has decreased to 50% of the steady state.

(steady state)
In a steady state, the temperature of the heat medium HM decreases by 29.4 [° C.] due to the heat supply to the evaporator 122 and increases by 19.6 [° C.] due to the heat recovery from the methanation reactor 121.

In the heat medium circulation system 110X of Comparative Example 1 shown in FIG. 4, the temperature of the heat medium HM flowing into the methanation reactor 121 is controlled to 250 [°C] by the heat medium heater 114X and the temperature control device 115X. Then, the temperature of the heat medium HM flowing into the evaporator 122 after heat recovery in the methanation reactor 121 becomes 269.6 [°C], and the temperature of the heat medium HM flowing into the heat medium heater 114X after heat supply in the evaporator 122 becomes 240.2 [°C]. Therefore, the performance required to heat the heat medium HM to 250 [°C] in the heat medium heater 114X is 200 [kW].

In the heat medium circulation system 110Y of Comparative Example 2 shown in FIG. 5, the temperature of the heat medium HM flowing into the methanation reactor 121 and the evaporator 122 is controlled to 250 [°C] by the heat medium heater 114Y and the temperature control device 115Y, and the heat medium cooling device 116Y and the temperature control device 117Y, respectively. Then, the temperature of the heat medium HM flowing out of the evaporator 122 is 220.6 [°C], and the temperature of the heat medium HM flowing out of the methanation reactor 121 is 269.6 [°C], and the performance required for the heat medium heater 114Y and the heat medium cooling device 116Y is 600 [kW] and 400 [kW], respectively. Taking into account the heat exchange by the heat exchanger 118Y, the required performance is 360 [kW].

In the heat medium circulation system 110 of the embodiment shown in FIG. 3, the heat medium HM stored in the thermostatic chamber 111 is controlled to 250°C. As a result, the temperature of the heat medium HM flowing into the methanation reactor 121 and the evaporator 122 is also 250°C. Then, the temperature of the heat medium HM flowing out of the evaporator 122 is 220.6°C, and the temperature of the heat medium HM flowing out of the methanation reactor 121 is 269.6°C, and each of the heat medium HM flows into the thermostatic chamber 111 to perform direct heat exchange.

As a result, even when the heat medium HM stored in the thermostatic bath 111 is heated by the temperature control device 114 to maintain the temperature of the heat medium HM at 250°C, the required heating performance is 200 kW. Therefore, in a steady state, the heat medium circulation system 110 according to the above-mentioned embodiment and the heat medium circulation system 110X of Comparative Example 1 have the same energy efficiency, and the heat medium circulation system 110Y of Comparative Example 2 has the lowest energy efficiency.

(First Transient State)
The first transient state is a state in which the load of the methanation reactor 121 becomes 200 [kW], which is 50 [%] of the steady state. In this first transient state, the temperature of the heat medium HM decreases by 29.4 [°C] due to the heat supply to the evaporator 122, and increases by 9.8 [°C] due to the heat recovery from the methanation reactor 121.

In the heat medium circulation system 110X of Comparative Example 1 shown in FIG. 4, the temperature of the heat medium HM flowing into the methanation reactor 121 is controlled to 250 [°C] by the heat medium heater 114X and the temperature control device 115X. Then, the temperature of the heat medium HM flowing into the evaporator 122 after heat recovery in the methanation reactor 121 becomes 259.8 [°C], and the temperature of the heat medium HM flowing into the heat medium heater 114X after heat supply in the evaporator 122 becomes 230.4 [°C]. Therefore, the performance required to heat the heat medium HM to 250 [°C] in the heat medium heater 114X is 400 [kW].

In the heat medium circulation system 110Y of Comparative Example 2 shown in FIG. 5, the temperature of the heat medium HM flowing into the methanation reactor 121 and the evaporator 122 is controlled to 250 [°C] by the heat medium heater 114Y and the temperature control device 115Y, and the heat medium cooling device 116Y and the temperature control device 117Y, respectively. Then, the temperature of the heat medium HM flowing out of the evaporator 122 is 220.6 [°C], and the temperature of the heat medium HM flowing out of the methanation reactor 121 is 259.8 [°C], and the performance required for the heat medium heater 114Y and the heat medium cooling device 116Y is 600 [kW] and 200 [kW], respectively. Taking into account the heat exchange by the heat exchanger 118Y, the required performance is 480 [kW].

In the heat medium circulation system 110 of the embodiment shown in FIG. 3, the heat medium HM stored in the thermostatic bath 111 is controlled to 250°C. As a result, the temperature of the heat medium HM flowing into the methanation reactor 121 and the evaporator 122 is also 250°C. Then, the temperature of the heat medium HM flowing out of the evaporator 122 is 220.6°C, and the temperature of the heat medium HM flowing out of the methanation reactor 121 is 259.8°C, and each of the heat medium HM flows into the thermostatic bath 111 to perform direct heat exchange.

As a result, even when the heat medium HM stored in the thermostatic bath 111 is heated by the temperature control device 114 to maintain the temperature of the heat medium HM at 250°C, the required heating performance is 400 kW. Therefore, similar to the steady state, in the first transient state, the heat medium circulation system 110 according to the above-mentioned embodiment and the heat medium circulation system 110X of Comparative Example 1 have the same energy efficiency, and the heat medium circulation system 110Y of Comparative Example 2 has the lowest energy efficiency.

(Second Transient State)
The second transient state is a state in which the load of the evaporator 122 becomes 300 [kW], which is 50 [%] of the steady state. In this second transient state, the temperature of the heat medium HM decreases by 14.7 [°C] due to the heat supply to the evaporator 122, and increases by 19.6 [°C] due to the heat recovery from the methanation reactor 121.

In the heat medium circulation system 110X of Comparative Example 1 shown in FIG. 4, the temperature of the heat medium HM flowing into the methanation reactor 121 is controlled to 250 [°C] by the heat medium heater 114X and the temperature control device 115X. Then, the temperature of the heat medium HM flowing into the evaporator 122 after heat recovery in the methanation reactor 121 becomes 269.6 [°C], and the temperature of the heat medium HM flowing into the heat medium heater 114X after heat supply in the evaporator 122 becomes 254.9 [°C]. Here, it is necessary to lower the heat medium HM flowing into the methanation reactor 121 to 250 [°C], but the heat medium heater 114X cannot cool the heat medium HM, so the required temperature conditions cannot be met.

In the heat medium circulation system 110Y of Comparative Example 2 shown in FIG. 5, the temperature of the heat medium HM flowing into the methanation reactor 121 and the evaporator 122 is controlled to 250 [°C] by the heat medium heater 114Y and the temperature control device 115Y, and the heat medium cooling device 116Y and the temperature control device 117Y, respectively. Then, the temperature of the heat medium HM flowing out of the evaporator 122 is 235.3 [°C], and the temperature of the heat medium HM flowing out of the methanation reactor 121 is 269.6 [°C], and the performance required for the heat medium heater 114Y and the heat medium cooling device 116Y is 300 [kW] and 400 [kW], respectively. Taking into account the heat exchange by the heat exchanger 118Y, the required performance is 220 [kW].

In the heat medium circulation system 110 of the embodiment shown in FIG. 3, the heat medium HM stored in the thermostatic bath 111 is controlled to 250°C. As a result, the temperature of the heat medium HM flowing into the methanation reactor 121 and the evaporator 122 is also 250°C. Then, the temperature of the heat medium HM flowing out of the evaporator 122 is 235.3°C, and the temperature of the heat medium HM flowing out of the methanation reactor 121 is 269.6°C, and each of the heat medium HM flows into the thermostatic bath 111 to perform direct heat exchange.

As a result, even when the heat medium HM stored in the thermostatic bath 111 is heated by the temperature control device 114 to maintain the temperature of the heat medium HM at 250°C, the required heating performance is 100 kW. Therefore, in the second transient state, the heat medium circulation system 110 according to the above-mentioned embodiment has higher energy efficiency than the heat medium circulation system 110Y of Comparative Example 2. Moreover, the heat medium circulation system 110X of Comparative Example 1 cannot satisfy the temperature conditions of the heat medium HM, and the system does not function.

As described above, the heat transfer medium circulation system 110 of the above-mentioned embodiment can achieve energy efficiency equivalent to and higher than either of the heat transfer medium circulation systems 110X and 110Y of Comparative Examples 1 and 2 in any of the steady state, the first transient state, and the second transient state.

In contrast, the heat medium circulation system 110X of Comparative Example 1 does not have a means for controlling the temperature of the heat medium HM flowing into the evaporator 122, so if the load of either the methanation reactor 121 or the evaporator 122 fluctuates, there is a risk that the heat supply and demand relationship will no longer be established. Furthermore, in the heat medium circulation system 110X of Comparative Example 1, if the electricity EP derived from renewable energy suddenly decreases and the hydrogen generated in the SOEC 124 decreases, the heat recovery in the methanation reactor 121 decreases, and the heat supply in the evaporator 122 decreases. In other words, the fluctuation in the load of the methanation reactor 121 affects the evaporator 122.

The heat medium circulation system 110Y of Comparative Example 2 has a heat medium cooling device 116Y in addition to the heat medium heater 114Y, and therefore consumes more energy than the heat medium circulation system 110 of this embodiment. It is also possible to improve energy efficiency by using the heat exchanger 118Y. However, since the heat exchanger 118Y performs indirect heat exchange via the heat medium flow path, the efficiency is lower than that of direct heat exchange between heat media HM of different temperatures in the thermostatic bath 111 of the heat medium circulation system 110 of this embodiment.

Furthermore, in the heat medium circulation system 110Y of Comparative Example 2, if the electricity EP derived from renewable energy suddenly decreases and the hydrogen generated in the SOEC 124 decreases, the heat recovery in the methanation reactor 121 decreases and the heat supply in the evaporator 122 decreases. In other words, fluctuations in the load of the methanation reactor 121 affect the evaporator 122.

In contrast, the heat medium circulation system 110 of the above-described embodiment has a thermostatic bath 111 that stores the heat medium HM and maintains it within a predetermined temperature range, so that the effect of fluctuations in the load of either the methanation reactor 121 or the evaporator 122 on the other can be reduced. Therefore, according to the above-described embodiment, even if the load of the methanation reactor 121 or the evaporator 122 fluctuates, it is possible to provide a heat medium circulation system 110 that is more energy efficient than Comparative Examples 1 and 2, can meet the temperature conditions of the heat medium HM, and does not require changes to the control conditions.

10 Heat medium circulation system 11 Thermostatic bath 11a Heat medium storage section 12 First flow path 12a First heat exchange section 12b First pump 13 Second flow path 13a Second heat exchange section 13b Second pump 14 Temperature control device 21 Reactor 22 Apparatus 110 Heat medium circulation system 111 Thermostatic bath 112 First flow path 113 Second flow path 114 Temperature control device 121 Methanation reactor (reactor)
122 Evaporator (apparatus)
124 SOEC (Solid Oxide Electrolysis Cell)
EP Electric power HM Heat transfer medium S Steam

Claims (7)

A heat transfer medium circulation system comprising a reactor in which an exothermic reaction takes place and a device requiring heat, and circulating a heat transfer medium between the reactor and the device,
a thermostatic bath for storing the heat transfer medium and maintaining the heat transfer medium at a predetermined temperature range;
a first flow path that circulates the heat medium between the reactor and the thermostatic chamber to transfer heat of the reactor to the heat medium;
a second flow path that circulates the heat medium between the device and the thermostatic chamber to transfer heat of the heat medium to the device;
A heat medium circulation system, characterized in that the heat medium circulates through the first flow path and the second flow path via a single thermostatic chamber. The thermostatic bath has a heat medium reservoir that reserves the heat medium,
2. The heat medium circulation system according to claim 1, wherein the first flow path comprises a first heat exchange unit that transfers heat from the reactor to the heat medium, and a first pump that is provided between the heat medium storage unit and the first heat exchange unit and that adjusts a flow rate of the heat medium flowing through the first flow path; and the second flow path comprises a second heat exchange unit that transfers heat of the heat medium to the device, and a second pump that is provided between the heat medium storage unit and the second heat exchange unit and that adjusts a flow rate of the heat medium flowing through the second flow path. The heat medium circulation system according to claim 2, characterized in that the volume of the heat medium stored in the heat medium storage section is greater than the volume of the heat medium filling the first flow path and the second flow path. the device is an evaporator;
2. The heat medium circulation system according to claim 1, wherein the reactor is a methanation reactor. The evaporator supplies water vapor to a solid oxide electrolysis cell that produces a gas containing hydrogen from carbon dioxide and water vapor using electricity derived from renewable energy;
5. The heat medium circulation system according to claim 4, wherein the methanation reactor receives the hydrogen-containing gas produced in the solid oxide electrolysis cell and produces a methane-containing gas. The heat transfer medium circulation system according to claim 1, characterized in that the predetermined temperature range of the heat transfer medium stored in the thermostatic bath is set to a temperature range capable of maintaining the exothermic reaction in the reactor at an appropriate temperature range and capable of supplying the necessary heat to the device. The heat transfer medium circulation system according to claim 1, further comprising a temperature control device that maintains the heat transfer medium stored in the thermostatic bath within the predetermined temperature range.

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