Heat pump system

Abstract

To provide a technique for improving energy consumption efficiency in a heat pump system.SOLUTION: A heat pump system includes: a generation part for generating an inclusion hydrate; a decomposition part where the inclusion hydrate is decomposed and a decomposition product is sent out; a first main passage in which a heat medium flows from the generation part to the decomposition part; a second main passage in which the heat medium flows from the decomposition part to the generation part; a mixed solvent separation part for separating a mixed solvent from the heat medium flowing in the first main passage; a liquid-liquid separation part in which an auxiliary agent in a water-soluble liquid in the mixed solvent separated by the mixed solvent separation part is separated by a reverse osmosis membrane or an ion exchange membrane; a gas-liquid separation part for separating the gas in the decomposition product sent out from the decomposition part from the mixed solvent; and a first sub passage for supplying, to the generation part, the mixed solvent in which the auxiliary agent separated by the liquid-liquid separation part is added.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat pump system. [Background technology]

[0002] Conventionally, heat pumps that combine gas compression / expansion and heat exchange have been used. For example, Patent Document 1 discloses a vehicle air conditioning system that includes an expansion valve that expands condensed refrigerant and is interconnected via a refrigerant line, an evaporator that evaporates the expanded refrigerant through heat exchange with air, and a compressor that compresses the evaporated gaseous refrigerant.

[0003] Although heat pumps are characterized by their ability to efficiently obtain thermal energy using little electrical energy, with the recent rise in awareness of environmental issues, there is a demand for even greater improvements in energy consumption efficiency. To address this, heat pump systems utilizing the decomposition / formation of clathrate hydrates have been proposed (see, for example, Patent Documents 2 and 3 and Non-Patent Document 1). The heat of decomposition / formation of clathrate hydrates is more than 10 times the latent heat of evaporation / condensation of ordinary refrigerants, such as those used in the heat pump described in Patent Document 1, and therefore, improvements in energy consumption efficiency are expected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-076792 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-101140 [Patent Document 3] Japanese Patent Publication No. 2022-087404 [Non-patent literature]

[0005] [Non-Patent Document 1] T. Ogawa et al., Applied Energy, 26, 2157 (2006). Summary of the Invention [Problem to be solved by the invention]

[0006] In the heat pump systems that utilize the decomposition / generation of clathrate hydrates disclosed in Patent Documents 2 and 3 and Non-Patent Document 1, further improvements in energy consumption efficiency are desired.

[0007] The present invention has been made to solve the above-mentioned problems, and has an object to provide a technique for improving energy consumption efficiency in a heat pump system. [Means for solving the problem]

[0008] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0009] (1) According to one aspect of the present invention, there is provided a heat pump system in which a heat medium transports heat by repeating the decomposition process and the formation process of clathrate hydrate. This heat pump system includes a production section into which a mixed liquid of a mixed solvent of a water-soluble liquid auxiliary agent and water and a gas is introduced to produce clathrate hydrates, a decomposition section into which decomposition of the clathrate hydrates is carried out and a decomposition product, which is a mixed phase of the gas and the mixed solvent, is discharged, a first main flow path through which the heat medium flows from the production section to the decomposition section, a second main flow path through which the heat medium flows from the decomposition section to the production section, a heat dissipation section which causes the heat medium in the production section to dissipate heat by heat exchange between the heat medium and a heat source outside the heat pump system, a pressure reduction section which reduces the pressure of the heat medium in the decomposition section, a heat absorption section which causes the heat medium in the decomposition section to absorb heat by heat exchange between the heat medium and a heat source outside the heat pump system, a mixed solvent separation section which is connected to the production section via the first main flow path and which separates the mixed solvent from a mixture containing at least the clathrate hydrates and the mixed solvent produced in the production section, and a flow path through which the decomposition a gas-liquid separation section connected to the decomposition section via the second main flow path and configured to separate the gas in the decomposition product delivered from the decomposition section from the mixed solvent; a compression section connected to the gas-liquid separation section via the second main flow path and configured to compress the gas separated by the gas-liquid separation section; a mixing section connected to the compression section and the production section via the second main flow path and connected to the gas-liquid separation section via a first sub-flow path and configured to generate the mixed liquid containing the mixed solvent separated by the gas-liquid separation section and the gas compressed by the compression section; a liquid-liquid separation section connected to the mixed solvent separation section and the decomposition section via the second sub-flow path and configured to separate water and the auxiliary in the mixed solvent separated by the mixed solvent separation section using a reverse osmosis membrane or an ion exchange membrane; and a third sub-flow path connected to the liquid-liquid separation section and configured to supply the auxiliary separated by the liquid-liquid separation section to the mixing section.

[0010] According to this configuration, since the liquid-liquid separation unit includes a reverse osmosis membrane or an ion exchange membrane, the auxiliary agent can be separated from a mixed solvent of a water-soluble liquid auxiliary agent and water, and the mixed solvent with a reduced auxiliary agent concentration can be supplied to the decomposition unit. The reduced auxiliary agent concentration in the decomposition unit shifts the stability boundary curve of clathrate hydrates to the lower temperature side, thereby accelerating the decomposition of clathrate hydrates in the decomposition unit. Furthermore, the liquid-liquid separation unit supplies the mixed solvent with concentrated auxiliary agent to the production unit, thereby accelerating the production of clathrate hydrates. In other words, according to this configuration, the auxiliary agent concentration can be controlled between the production unit and the decomposition unit, thereby increasing the temperature difference between the high-temperature side and the low-temperature side during refrigeration cycle operation and improving the energy consumption efficiency (COP: coefficient of performance).

[0011] (2) The heat pump system of the above aspect may further include a gas / solid-liquid separation unit connected to the generation unit via the first main flow path and configured to separate the gas from a gas-solid-liquid mixture containing the clathrate hydrate, the gas, and the mixed solvent generated in the generation unit; and a fourth sub-flow path for supplying the gas separated by the gas / solid-liquid separation unit to the mixing unit.

[0012] According to this configuration, a gas / solid-liquid separation section is provided between the generation section and the decomposition section, so that gas can be separated / removed from a mixture containing clathrate hydrate solids (also called "slurry"), and a mixture containing mainly clathrate hydrate solids with a reduced gas content can be supplied to the decomposition section. The heat transfer medium (a mixed phase of gas, water, and auxiliary agent) on the outlet side of the decomposition section is at low temperature and pressure. According to this configuration, the amount of gas supplied to the decomposition section is reduced, and therefore the amount of low-pressure gas supplied to the compression section can be reduced, thereby suppressing a decrease in compressor efficiency. As a result, energy consumption efficiency can be further improved.

[0013] (3) The heat pump system of the above aspect may further include a transport pump disposed in the first main flow path and transporting the heat medium. In this way, the flow rate can be adjusted by the transport pump, and therefore the decomposition rate in the decomposition section can be adjusted.

[0014] (4) The heat pump system of the above aspect further includes a confluence section disposed in the first sub-channel and confluences the third sub-channel with the first sub-channel, and a concentration adjustment section configured to adjust the concentration of the auxiliary agent in the mixed solvent supplied to the mixing section, wherein the concentration adjustment section includes a concentration meter disposed in the first sub-channel and detecting the concentration of the auxiliary agent in the mixed solvent flowing between the confluence section and the mixing section, a flow meter disposed in the first sub-channel and detecting the flow rate of the mixed solvent supplied to the mixing section, and a gas-liquid separation section of the first sub-channel. and the confluence section and configured to control the flow rate of the mixed solvent separated by the gas-liquid separation section; a reservoir section configured in the third sub-channel and capable of storing the auxiliary agent separated by the liquid-liquid separation section; and a second pump configured in the third sub-channel and configured to control the flow rate of the auxiliary agent flowing from the reservoir section to the first sub-channel, and the concentration of the mixed solvent supplied to the mixing section may be adjusted to a predetermined target value by controlling the first pump and the second pump based on detection results of the concentration meter and the flow meter.

[0015] In this way, the concentration of the auxiliary agent in the mixed solvent supplied to the production section can be adjusted, and by setting the auxiliary agent concentration appropriate for the production of clathrate hydrate in the production section, the energy consumption efficiency (COP) can be further improved.

[0016] (5) The heat pump system of the above aspect further comprises: a confluence section disposed in the first sub-channel and converging the third sub-channel into the first sub-channel; and a concentration adjustment section configured to adjust the concentration of the auxiliary agent in the mixed solvent supplied to the mixing section, wherein the concentration adjustment section comprises: a first pump disposed between the gas-liquid separation section and the confluence section in the first sub-channel and configured to control the flow rate of the mixed solvent separated by the gas-liquid separation section; a first concentration meter disposed between the gas-liquid separation section and the confluence section in the first sub-channel and configured to detect the concentration of the auxiliary agent in the mixed solvent separated by the gas-liquid separation section; and a concentration adjustment section disposed between the gas-liquid separation section and the confluence section in the first sub-channel and configured to adjust the flow rate of the mixed solvent separated by the gas-liquid separation section. a storage section disposed in the third sub-channel and capable of storing the auxiliary agent separated by the liquid-liquid separation section; a second pump disposed in the third sub-channel and controlling the flow rate of the mixed solvent containing the auxiliary agent flowing from the storage section to the first sub-channel; a second concentration meter disposed in the third sub-channel and detecting the concentration of the auxiliary agent in the mixed solvent; and a second flow meter disposed in the third sub-channel and detecting the flow rate of the mixed solvent, and the first pump is controlled based on detection results from the first concentration meter and the first flow meter, and the second pump is controlled based on detection results from the second concentration meter and the second flow meter to adjust the concentration of the mixed solvent supplied to the mixing section to a predetermined target value.

[0017] In this way, the concentration of the adjuvant in the mixed solvent supplied to the generation unit can be adjusted more accurately in a short time, thereby further improving the energy consumption efficiency (COP).

[0018] (6) The heat pump system of the above aspect may further include a dehydration unit disposed between the gas-liquid separation unit and the compression unit, and configured to adsorb the mixed solvent in the gas separated by the gas-liquid separation unit. This allows the mixed solvent mixed in the gas separated by the gas-liquid separation unit to be removed. This reduces energy consumption by the compression unit, thereby further improving the energy consumption efficiency of the heat pump system.

[0019] The present invention can be realized in various forms, for example, in the form of a heat utilization device having a heat pump system, a control method for a heat pump system, a method for generating cold heat, a method for generating hot heat, etc. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is an explanatory diagram schematically illustrating a basic configuration of a heat pump system according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram schematically illustrating a normal mode in the heat pump system. [Figure 3] FIG. 10 is an explanatory diagram schematically illustrating a temperature difference expansion mode in the heat pump system. [Figure 4] FIG. 1 is an explanatory diagram conceptually showing the stability boundary curve of a clathrate hydrate. [Figure 5] FIG. 1 is an explanatory diagram showing an example of the shift of the stability boundary curve of a clathrate hydrate by an auxiliary agent. [Figure 6] FIG. 1 is an explanatory diagram showing an example of the relationship between the concentration of an auxiliary agent and the stable boundary temperature of a clathrate hydrate. [Figure 7] 10 is a flowchart showing a flow of mode switching control in a control unit. [Figure 8] FIG. 10 is an explanatory diagram showing a comparison of energy consumption efficiencies. [Figure 9] FIG. 10 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system according to a second embodiment. [Figure 10] 10 is a flowchart showing the flow of a density adjustment process. [Figure 11] 10 is a flowchart showing the flow of density adjustment processing. [Figure 12] 10 is a flowchart showing a flow of a flow rate adjustment process. [Figure 13] FIG. 10 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system according to a third embodiment. [Figure 14] 10 is a flowchart showing the flow of a density adjustment process. [Figure 15]FIG. 10 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] First Embodiment FIG. 1 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system 100 according to a first embodiment. The heat pump system 100 transports heat by using a heat medium to repeatedly undergo decomposition and formation processes of clathrate hydrates. Clathrate hydrates are ice-like compounds (clathrate compounds) in which gas molecules are enclosed in cages formed by hydrogen bonds between water molecules. Heat is generated during the formation process in which clathrate hydrates are formed from water and gas, and heat is absorbed during the decomposition process in which the clathrate hydrates are separated into water and gas. The heat pump system 100 according to this embodiment transports heat by utilizing the latent heat (heat of decomposition and formation) of clathrate hydrates.

[0022] The heat pump system 100 includes a production section 10 into which a mixture of a gas and a mixed solvent of water and an auxiliary agent is introduced to produce clathrate hydrates; a decomposition section 20 into which the clathrate hydrates are decomposed and a decomposition product, which is a mixed phase of gas and the mixed solvent, is delivered; a first main flow path 30 through which a heat transfer medium flows from the production section 10 to the decomposition section 20; and a second main flow path 40 through which the heat transfer medium flows from the decomposition section 20 to the production section 10. FIG. 1 shows the phase changes of the heat transfer medium flowing through the first main flow path 30 and the second main flow path 40, with the clathrate hydrates indicated by dashed lines, the decomposition product (gas / mixed solvent mixed phase) indicated by dashed lines, the mixed liquid of gas and mixed solvent indicated by double lines, the gas phase indicated by dashed lines, and the aqueous phase (mixed solvent) indicated by solid lines. The clathrate hydrates emerge from the production section 10 in the form of a gas-solid-liquid mixture containing clathrate hydrate solids, unreacted gas, and the mixed solvent (water / auxiliary agent). In the following description, the gas-solid-liquid mixture containing the clathrate hydrate solid is also referred to as a clathrate hydrate slurry.

[0023] Gases that can be used to produce clathrate hydrates include hydrocarbon gases such as methane, ethane, propane, ethylene, and acetylene; fluorocarbon gases such as HFCs (hydrofluorocarbons) and HCFCs (hydrochlorofluorocarbons); rare gases such as argon and krypton; carbon dioxide (CO2), nitrogen, air, ammonia, and xenon (Xe). Gases with properties such as a high maximum equilibrium temperature, a low equilibrium pressure, and a small change in pressure relative to temperature are preferred because they can achieve a high COP. These gases may be used alone or in combination to achieve desired properties. Combining different gases allows for the adjustment of the phase change conditions of clathrate hydrates.

[0024] As described above, in the heat pump system 100 of this embodiment, a mixture of a mixed solvent of water and an auxiliary agent and a gas is supplied to the generator 10. The auxiliary agent is added to the water to adjust the phase change conditions of the clathrate hydrate (described in detail later). The auxiliary agent is not particularly limited as long as it is a water-soluble liquid, but it is preferable that it has a molecular size (5.8 to 8.6 Å) that can form a clathrate hydrate. Examples of such auxiliary agents include ammonium salts such as tetrabutylammonium fluoride and tetrapentylammonium chloride.

[0025] As shown in the figure, the heat pump system 100 includes a heat dissipation section 12 that causes the heat medium to dissipate heat by heat exchange between the heat medium in the generation section 10 and a heat source outside the heat pump system 100, and a heat absorption section 22 that causes the heat medium to absorb heat by heat exchange between the heat medium in the decomposition section 20 and a heat source outside the heat pump system. Heat exchangers are used as the heat dissipation section 12 and the heat absorption section 22.

[0026] The heat pump system 100 includes, in order from upstream, a gas / solid-liquid separation section 52 that separates gas from the clathrate hydrate slurry, a mixed solvent separation section 53 that separates liquid (mixed solvent) from the clathrate hydrate slurry (a solid-liquid mixture containing clathrate hydrate solids and a mixed solvent) that has passed through the gas / solid-liquid separation section 52, and a pressure reduction section 24 that reduces the pressure of the heat medium in the decomposition section 20. The heat pump system 100 also includes a second main flow path 30. 40 includes, in order from upstream, a first gas-liquid separation section 14 that separates the decomposition product, which is a mixed phase of gas and water (mixed solvent) sent out from the decomposition section 20, into gas and liquid, a compression section 16 that compresses the gas separated by the first gas-liquid separation section 14, and a mixer 18 that mixes the water (mixed solvent) separated by the first gas-liquid separation section 14 with the gas compressed by the compression section 16 to produce a mixed liquid. The mixer 18 and the first gas-liquid separation section 14 are connected to the first sub-channel 4. 3. The heat pump system 100 further includes a liquid-liquid separation unit 54 connected to the mixed solvent separation unit 53 and the decomposition unit 20 via a second sub-flow path 62. The liquid-liquid separation unit 54 separates the water and the auxiliary agent in the mixed solvent separated by the mixed solvent separation unit 53 using a reverse osmosis membrane or an ion exchange membrane. The heat pump system 100 also includes a third sub-flow path 63 connected to the liquid-liquid separation unit 54 and used to supply the auxiliary agent separated by the liquid-liquid separation unit 54 to the mixer 18. In this embodiment, the third sub-flow path 63 merges with the first sub-flow path 43 via a junction 69. The heat pump system 100 also includes a second gas-liquid separation unit 56 in the second flow path 42 between the compressor 16 and the mixer 18. The compressor oil separated by the second gas-liquid separation unit 56 is returned to the compressor 16 via a fifth sub-flow path 80. The first gas-liquid separation unit 14 in this embodiment is also referred to simply as the "gas-liquid separation unit."

[0027] The second main flow path 40 includes a first flow path 41 connecting the decomposition section 20 and the first gas-liquid separation section 14, a second flow path 42 connecting the first gas-liquid separation section 14 and the compression section 16, a third flow path 48 connecting the compression section 16 and the second gas-liquid separation section 56, a fourth flow path 44 connecting the second gas-liquid separation section 56 and the mixing section 18, and a fifth flow path 45 connecting the mixing section 18 and the generation section 10.

[0028] The first sub-channel 43 includes a tenth sub-channel 43a upstream of the junction 69 and an eleventh sub-channel 43b downstream of the junction 69. In the first sub-channel 43, the tenth sub-channel 43a and the eleventh sub-channel 43b are provided with a liquid feed pump 15 and a liquid feed pump 58, respectively, which feed the mixed solvent separated in the first gas-liquid separation section 14 toward the mixing section 18. A high-pressure pump with a higher pressure than the liquid feed pump 15 is used as the liquid feed pump 58.

[0029] The gas / solid-liquid separation section 52 separates the gas from a gas-solid-liquid mixture (clathrate hydrate slurry) containing clathrate hydrate solids, unreacted gas, water, and auxiliary agent. Here, the solid-liquid mixture from which the gas has been separated is also referred to as clathrate hydrate slurry. The separated gas flows into the compression section 16 via the fourth sub-flow path 60 and the second flow path 42. The fourth sub-flow path 60 is provided with an on-off valve 66 and a blower 67. During operation of the heat pump system 100, the on-off valve 66 is opened and the blower 67 is operated. The gas / solid-liquid separation section can be of a surface tension type, centrifugal force type, multi-stage filter type, cyclone type, or other type. In the case of a cyclone-type gas / solid-liquid separation section, it is expected that the solid-liquid phase and the gas phase will be 100% (volume ratio) after separation. The clathrate hydrate slurry flowing out from the gas / solid-liquid separation section 52 may contain a small amount of gas.

[0030] Because the gas / solid-liquid separation section 52 is located upstream of the pressure reduction section 24, the gas separated in the gas / solid-liquid separation section 52 is in a high-pressure state. If the gas / solid-liquid separation section 52 were not provided, the excess gas in the gas-solid-liquid mixture mainly containing clathrate hydrate solids would be decompressed in the pressure reduction section 24 and flow into the compression section 16 in a low-pressure state, where it would be compressed. In contrast, in the heat pump system 100A of this embodiment, before the clathrate hydrate slurry flowing through the first main flow path 30 is decompressed, the excess gas in the clathrate hydrate slurry is separated by the gas / solid-liquid separation section 52 and supplied to the compression section 16. This reduces the workload in the compression section 16, thereby further improving the energy consumption efficiency (COP).

[0031] In this embodiment, the mixed solvent separation section 53 is a solid-liquid separator that separates a liquid (mixed solvent) from the clathrate hydrate slurry (a solid-liquid mixture containing clathrate hydrate solids and mixed solvent) flowing out of the gas / solid-liquid separation section 52. The separated mixed solvent flows into the liquid-liquid separation section 54 via the second sub-channel 62. Here, the solid phase from which the mixed solvent has been separated also contains a liquid and is also referred to as clathrate hydrate slurry. The mixed solvent separation section 53 can be of a surface tension type, centrifugal force type, cyclone type, or other type. In the case of a cyclone type mixed solvent separation section, it is expected that the liquid phase side after separation will be 100% mixed solvent, and the solid phase side will be 10 / 90% mixed solvent / clathrate hydrate solid (volume ratio). Note that the clathrate hydrate slurry flowing out of the mixed solvent separation section 53 may contain a small amount of gas.

[0032] The pressure reducing section 24 may be an expansion valve, a capillary tube, or the like. Liquid-liquid separation unit 54 is equipped with a reverse osmosis membrane or an ion exchange membrane, and separates the water and auxiliary agent from a mixed solvent of water and a water-soluble auxiliary agent. The mixed solvent in which the auxiliary agent concentration has been reduced by liquid-liquid separation unit 54 is supplied to decomposition unit 20 via second sub-channel 62, and the mixed solvent in which the auxiliary agent has been concentrated by liquid-liquid separation unit 54 flows into first sub-channel 43 via third sub-channel 63. When liquid-liquid separation unit 54 having a reverse osmosis membrane is used, the auxiliary agent concentration of the mixed solvent that has passed through liquid-liquid separation unit 54 (mixed solvent flowing through second sub-channel 62) is expected to be 10 ppm or less.

[0033] The heat transfer medium discharged from the decomposition unit 20 is a mixed phase containing gas resulting from the decomposition of clathrate hydrates, water, and an auxiliary agent. Although the heat transfer medium flowing through the first flow path 41 is a mixed phase containing gas, water, and an auxiliary agent, it is not actively mixed, and the gas is not mixed as uniformly in the mixed solvent as in the heat transfer medium flowing through the fifth flow path 45. In this specification, a solution in which high-pressure gas and a mixed solvent are actively mixed is referred to as a "mixed liquid," and a solution containing gas, water, and an auxiliary agent produced by the decomposition of clathrate hydrates in the decomposition unit 20 and not actively mixed is referred to as a "decomposed product."

[0034] The first gas-liquid separation unit 14 separates the decomposition product (a mixed phase of gas and mixed solvent) supplied from the decomposition unit 20 into a gas phase and an aqueous phase (mixed solvent), supplies the gas phase to the compression unit 16 via the second flow path 42, and supplies the mixed solvent to the mixing unit 18 via the first sub-flow path 43. Various types of gas-liquid separators can be used as the first gas-liquid separation unit 14, such as surface tension, cyclone, filter, centrifugal, cooling, multi-stage filter, and cyclone. In the case of a surface tension gas-liquid separator, it is expected that the gas phase after separation will be 100% refrigerant gas, and the liquid phase will be 30 / 70% refrigerant gas / mixed solvent (volume ratio). In this embodiment, an electric compressor is used as the compression unit 16.

[0035] The second gas-liquid separation unit 56 separates lubricating oil mixed into the gas phase as it passes through the compression unit 16. The second gas-liquid separation unit 56 can be, for example, a surface tension type, a centrifugal force type, a multi-stage filter type, or a cyclone type. When a centrifugal force type gas-liquid separation unit is used, it is expected that the gas phase after separation will be 100% refrigerant gas, and the liquid phase will be 10% refrigerant gas / compressor lubricating oil (volume ratio) 90%. The compressor oil separated by the second gas-liquid separation unit 56 is returned to the compression unit 16 via the fifth sub-flow path 80. This makes it possible to prevent damage to the compression unit 16 and a deterioration in sealing performance.

[0036] The mixing section 18 actively mixes water (mixed solvent) with the high-pressure gas. The type of the mixing section 18 that can be used includes internal mixing, external mixing, and collision types. The mixed solvent and the high-pressure gas can be mixed, for example, by stirring the gas and mixed solvent, or by supplying the gas into the mixed solvent through a filter. Mixing the mixed solvent and the gas in the mixing section 18 results in finer gas bubbles in the mixed solvent. The size of the bubbles is not particularly limited, but is preferably micro- to nano-sized. Reducing the bubble size increases the contact area between the gas and water, improving the efficiency of clathrate hydrate production. Nano-sized bubbles improve the efficiency of clathrate hydrate production, but require more energy. Therefore, it is preferable to set the bubble size in consideration of the balance with energy consumption.

[0037] The heat pump system 100 of this embodiment includes a liquid-liquid separation unit 54, and can control the concentration of the auxiliary agent in the mixed liquid supplied to the generation unit 10 and the concentration of the auxiliary agent in the decomposition unit by controlling the opening and closing of on-off valves 64 and 65. In the normal mode, the on-off valves 64 and 65 are closed, and in the temperature difference expansion mode, the on-off valves 64 and 65 are opened (described in detail later).

[0038] Fig. 2 is an explanatory diagram schematically showing the normal mode in the heat pump system 100 of this embodiment. Heat transport in the heat pump system 100 of this embodiment will be described using Fig. 2. In the normal mode, as described above, the on-off valves 64 and 65 are closed.

[0039] The heat medium at the outlet of the decomposition section 20 in FIG. 2 is in a decomposed state (a mixed phase of gas, water, and auxiliary agent) and is at low temperature and low pressure. The decomposition product as the heat medium flows through the first flow path 41 into the first gas-liquid separation section 14. The decomposition product is decomposed into gas and the mixed solvent in the first gas-liquid separation section 14. The gas flows through the second flow path 42 into the compression section 16, is pressurized by the compression section 16, the lubricating oil is separated by the second gas-liquid separation section 56, and flows through the fourth flow path 44 into the mixing section 18. The gas is pressurized and heated by compression in the compression section 16. Meanwhile, the mixed solvent is forced through the first sub-flow path 43 by the liquid feed pumps 15 and 58 and flows into the mixing section 18. In the mixing section 18, the high-pressure gas and the mixed solvent are mixed to produce a high-pressure mixed liquid, which flows into the production section 10 through the fifth flow path 45. That is, the heat medium (liquid mixture) on the inlet side of the generation unit 10 is at high temperature and pressure.

[0040] The high-pressure mixed liquid (heat medium) that flows into the generation section 10 is cooled by heat dissipation in the heat dissipation section 12. Specifically, the heat exchanger that serves as the heat dissipation section 12 exchanges heat between the heat medium in the generation section 10 and a heat source outside the heat pump system, cooling the heat medium. When heat equivalent to the heat of generation is released from the heat medium, the state of the heat medium crosses the phase equilibrium line of the heat medium and becomes a clathrate hydrate state (high pressure) at the outlet side of the generation section 10. The clathrate hydrate discharged from the generation section 10 is in a slurry state containing unreacted water (mixed solvent) and gas. The heat medium flows from the generation section 10 to the decomposition section 20 due to the pressure difference between the generation section 10 and the decomposition section 20.

[0041] The clathrate hydrate slurry as a heat transfer medium flows through the first main flow path 30, at least a portion of the gas is separated by the gas / solid-liquid separation section 52, the pressure is reduced by the pressure reduction section 24, and the clathrate hydrate slurry flows into the decomposition section 20. The clathrate hydrate slurry is reduced in pressure and temperature by the pressure reduction section 24. That is, at the inlet side of the decomposition section 20, the heat transfer medium is a low-pressure clathrate hydrate slurry. The low-pressure clathrate hydrate slurry (heat transfer medium) that flows into the decomposition section 20 is heated by the heat absorption section 22. Specifically, the heat exchanger serving as the heat absorption section 22 exchanges heat between the heat transfer medium in the decomposition section 20 and a heat source external to the heat pump system, and the heat transfer medium absorbs the external heat and is heated. When the heat transfer medium absorbs heat equivalent to the heat of decomposition, the state of the heat transfer medium crosses the phase equilibrium line of the heat transfer medium and reaches a low-temperature, low-pressure decomposition state (a mixed phase of gas and mixed solvent) at the outlet side of the decomposition section 20.

[0042] In this way, in the heat pump system 100 of this embodiment, heat equivalent to the heat of decomposition and formation of clathrate hydrates can be pumped from an object outside the heat pump system 100 and provided to another object outside the heat pump system 100. The heat exchanger serving as the heat release section 12 and the heat exchanger serving as the heat absorption section 22 may perform heat exchange inside or outside the generation section 10 and the decomposition section 20, respectively.

[0043] Fig. 3 is an explanatory diagram schematically showing the temperature difference expansion mode in the heat pump system 100 of this embodiment. Fig. 4 is an explanatory diagram conceptually showing the stability boundary curve of a clathrate hydrate. As described above, in the temperature difference expansion mode in the heat pump system 100 of this embodiment, the on-off valves 64 and 65 are opened (described in detail later).

[0044] As shown in FIG. 3 , when the on-off valves 64 and 65 are opened in the temperature difference expansion mode, at least a portion of the mixed solvent is separated from the solid-liquid mixed-phase clathrate hydrate slurry in the mixed solvent separation section 53, and the mixed solvent flows into the liquid-liquid separation section 54. In the liquid-liquid separation section 54, the auxiliary agent is separated, and the mixed solvent with a reduced auxiliary agent concentration (e.g., an auxiliary agent concentration of 10 ppm or less) is supplied to the decomposition section 20 via the second sub-channel 62. This reduces the auxiliary agent concentration in the heat transfer medium in the decomposition section 20. As shown in FIG. 4 , the stability boundary curve of the clathrate hydrate shifts to the lower temperature side in the absence of the auxiliary agent compared to the presence of the auxiliary agent. As a result, even if the temperature in the decomposition section 20 is the same, the decomposition reaction is promoted more than when the auxiliary agent is present.

[0045] On the other hand, in the temperature difference enlarging mode, when the on-off valves 64 and 65 are opened, in the liquid-liquid separation section 54, a mixed solvent in which the auxiliary agent is concentrated (for example, 100% auxiliary agent) is added to the mixed solvent flowing through the eleventh sub-channel 43b via the third sub-channel 63, and is supplied to the mixing section 18. That is, because the auxiliary agent is added to the mixed liquid, the stability boundary curve of the clathrate hydrate shifts to the higher temperature side compared to when no auxiliary agent is present, as shown in FIG. 4. As a result, even if the temperature in the production section 10 is the same, the production reaction is promoted more than when no auxiliary agent is present.

[0046] In this way, in the heat pump system 100, since the production section 10 operates at a high temperature, an auxiliary agent is added to facilitate the production of clathrate hydrates, while the decomposition section 20 operates at a low temperature, so the auxiliary agent is removed to facilitate the decomposition of clathrate hydrates. That is, according to the heat pump system 100 of this embodiment, it is possible to control the temperatures at which clathrate hydrates are produced and decomposed by adding or removing the auxiliary agent.

[0047] FIG. 5 is an explanatory diagram showing an example of the shift of the stability boundary curve of clathrate hydrates due to an auxiliary agent. FIG. 5 shows an example in which HFC-32 (HFC is a hydrofluorocarbon) is used as the gas and tetrabutylammonium fluoride (TBAF) is used as the auxiliary agent. HFC-32 is also commonly known as R32. In FIG. 5, the stabilization curve without the addition of an auxiliary agent is shown by a solid line, the stabilization curve with the addition of an auxiliary agent is plotted by a black circle, and the vapor pressure curve is shown by a dashed line. In addition, FIG. 5 shows an example of the temperature ranges on the generator side and the decomposer side by a circle. As shown in FIG. 5, the addition of an auxiliary agent shifts the stability curve of clathrate hydrates to a higher temperature side, promoting the formation of clathrate hydrates.

[0048] The stability boundary curve in the presence of an adjuvant changes continuously depending on the proportion of adjuvant added, but coincides with the stability boundary curve in the absence of adjuvant below a certain concentration. Figure 5 shows an example in which the adjuvant concentration is 0.035. Here, the adjuvant concentration is in mol%, and is calculated as the number of moles of adjuvant (TBAF) / (number of moles of adjuvant + number of moles of water). The stability boundary curve of the clathrate hydrate shown in Figure 5 was created as follows. 1) Water (and an auxiliary agent) is sealed in a vacuumed high-pressure cell, and the pressure is increased to the desired level with gas. 2) When the cell is cooled to a desired temperature and the contents are stirred, the formation of clathrate compounds begins spontaneously. 3) The temperature and pressure stop changing and reach a constant value, reaching equilibrium. 4) Determine the equilibrium point by changing the temperature or pressure.

[0049] Figure 6 is an explanatory diagram showing an example of the relationship between the auxiliary agent concentration and the stable boundary temperature of a clathrate hydrate. Figure 6 shows an example in which TBAF is used as the auxiliary agent and the pressure is 0.1 MPa. The auxiliary agent concentration is in mol%. In Figure 6, ● is a quote from the following paper, and ■ is the result of an experiment conducted by the inventors. Paper:Thermodynamic and Raman spectroscopic studies on hydrogen+ tetra-n-butyl ammonium fluoride semi-clathrate hydrates J Sakamoto, S Hashimoto, T Tsuda, T Sugahara, Y Inoue, K Ohgaki Chemical engineering science 63 (24), 5789-5794 As shown in the figure, the stability boundary temperature increases with increasing auxiliary agent concentration up to an auxiliary agent concentration of 0.03, remains approximately constant up to an auxiliary agent concentration of 0.04, and decreases with increasing auxiliary agent concentration above 0.04. From this result, it is considered that the stability boundary temperature of clathrate hydrates can be controlled by the auxiliary agent concentration.

[0050] The heat pump system 100 of this embodiment can be applied to, for example, an air conditioner having at least one of the functions of cooling, heating, dehumidification, and humidification. It can also be applied to various heat utilization devices (including plants and systems) that transfer heat to and from a heat source, such as cooling devices (such as heat sinks), heating devices (such as floor heating devices), hot water supply devices, refrigeration devices, dehydration devices, heat storage devices, snow melting devices, and drying devices. High energy efficiency can be achieved in these heat utilization devices by using the heat pump of this embodiment.

[0051] The switching between the normal mode and the temperature difference widening mode, i.e., the opening and closing of the on-off valves 64 and 65, may be configured to be performed manually by a user, or may be configured to be controlled by a control unit (not shown). When a control unit is provided, the control unit is a computer including a ROM, a RAM, and a CPU, and controls the entire heat pump system 100, including the switching between the normal mode and the temperature difference widening mode. Here, the computer may include a PLC (programmable logic controller), a PC (personal computer), etc.

[0052] 7 is a flowchart showing the flow of mode switching control in the control unit. The mode switching control is control for switching between the normal mode and the temperature difference widening mode described above. When the control unit starts the mode switching control, in step S102, the control unit operates the heat pump system 100 in the normal mode. That is, the control unit closes the on-off valves 64 and 65.

[0053] In step S104, the control unit compares the low-temperature side target value with the threshold value, and operates in normal mode until the low-temperature side target value becomes equal to or less than the threshold value (NO in step S104). When the low-temperature side target value becomes equal to or less than the threshold value (YES in step S104), the process proceeds to step S106. Here, the low-temperature side target value is the temperature of the decomposition unit (the value detected by a temperature sensor, not shown). The threshold value can be set arbitrarily, and in this embodiment, it is set to 15°C.

[0054] In step S106, the control unit operates the heat pump system 100 in the temperature difference expansion mode. That is, the control unit opens the on-off valves 64 and 65. In step S108, the control unit compares the low temperature side target value with the threshold value, and operates in the wide temperature difference mode until the low temperature side target value becomes larger than the threshold value (NO in step S108). When the low temperature side target value becomes larger than the threshold value (YES in step S108), the process returns to step S102. Here, the threshold value is the same as the threshold value used in step S104.

[0055] Figure 8 is an explanatory diagram showing a comparison of energy consumption efficiencies. In Figure 8, the case where the heat of decomposition and formation of clathrate hydrate is utilized is described as "clathrate hydrate," and the case where the heat associated with the condensation and evaporation of the refrigerant is utilized is described as "R32." Here, R32 refers to the refrigerant R32, which is characterized by its low global warming potential among HFCs (hydrofluorocarbons). The gas that generates the clathrate hydrate shown in Figure 8 is the refrigerant R32.

[0056] As shown in the figure, in the case of a heat pump system using clathrate hydrates, the amount of heat gained is approximately 6 to 7 times that of a conventional refrigerant (R32). As shown in the figure, the compressor work when using clathrate hydrates is equivalent to that when using a conventional refrigerant (R32). The COP can be roughly calculated using the following equation (1). COP = heat gain / (compressor work + auxiliary equipment work) ... (Equation 1) When clathrate hydrates are used, for example, if auxiliary equipment such as a pump for transporting clathrate hydrate slurry is added, even if the required power (compressor work + auxiliary equipment work) becomes twice that of conventional equipment, a COP of about 10 can be expected. On the other hand, when a conventional refrigerant is used, even if no additional auxiliary equipment is required, the COP is about 4.

[0057] As described above, the heat pump system 100 of this embodiment transports heat by utilizing the latent heat (heat of decomposition and formation) of clathrate hydrates. Because the heat of decomposition and formation of clathrate hydrates is greater than the heat associated with the condensation and evaporation of the refrigerant, the energy consumption efficiency can be improved compared to conventional heat pumps that utilize the exchange of heat associated with the condensation and evaporation processes of the refrigerant.

[0058] Furthermore, the heat pump system 100 of this embodiment includes a liquid-liquid separation unit 54 equipped with a reverse osmosis membrane or an ion exchange membrane, which allows separation of the water-soluble liquid auxiliary agent from the mixed solvent. Therefore, the mixed solvent with a reduced auxiliary agent concentration by the liquid-liquid separation unit 54 can be supplied to the decomposition unit 20. The reduction in the auxiliary agent concentration in the decomposition unit 20 shifts the stability boundary curve of clathrate hydrates toward the lower temperature side, thereby promoting decomposition of clathrate hydrates in the decomposition unit. Furthermore, supplying the mixed solvent with concentrated auxiliary agent by the liquid-liquid separation unit 54 to the production unit 10 promotes the production of clathrate hydrates. In other words, this configuration allows the auxiliary agent concentration to be controlled between the production unit and the decomposition unit, thereby increasing the temperature difference between the high-temperature side and the low-temperature side during refrigeration cycle operation and improving energy consumption efficiency.

[0059] Furthermore, because the gas / solid-liquid separation section 52 is located upstream of the pressure reduction section 24, the gas separated in the gas / solid-liquid separation section 52 is in a high-pressure state. If the gas / solid-liquid separation section 52 were not provided, the excess gas in the gas-solid-liquid mixture mainly containing clathrate hydrate solids would be decompressed in the pressure reduction section 24 and flow into the compression section 16 in a low-pressure state, where it would be compressed. In contrast, in the heat pump system 100 of this embodiment, before the clathrate hydrate slurry flowing through the first main flow path 30 is decompressed, the excess gas in the clathrate hydrate slurry is separated by the gas / solid-liquid separation section 52 and supplied to the compression section 16 in a high-pressure state. This makes it possible to suppress a decrease in compressor efficiency in the compression section 16, thereby further improving the energy consumption efficiency (COP).

[0060] Furthermore, according to the heat pump system 100 of this embodiment, the water and the adjuvant can be separated from the decomposition product, which is a mixed phase of gas, water, and the adjuvant, by the first gas-liquid separation unit 14, and the gas from which the water has been separated can be compressed by the compression unit 16. Therefore, compared to a case where the first gas-liquid separation unit 14 is not provided, the work of the compression unit 16 is reduced by the work of compressing the water, and the energy consumption efficiency of the heat pump system can be improved.

[0061] Furthermore, according to this configuration, the mixed solvent and compressed gas are mixed in advance by mixing unit 18, and the resulting mixed liquid is sent to production unit 10. Therefore, compared to a case where mixing unit 18 is not provided and the gas and mixed solvent are sent directly to production unit 10 without being mixed, the contact area between the gas and water is increased, and the efficiency of clathrate hydrate production in production unit 10 can be improved. As a result, the energy consumption efficiency of the heat pump system can be improved.

[0062] Second Embodiment FIG. 9 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system 100A according to a second embodiment. The heat pump system 100A according to the second embodiment includes a concentration adjuster 70 in addition to the configuration of the heat pump system 100 according to the first embodiment. The concentration adjuster 70 includes a storage unit 71 disposed in the third sub-channel 63 and capable of storing the auxiliary agent separated by the liquid-liquid separator 54, a liquid feed pump 72, a concentration meter 73 and a flow meter 74 disposed in the eleventh sub-channel 43b, and a liquid feed pump 15 (also included in the heat pump system 100 according to the first embodiment). In this embodiment, a medium-pressure pump having a higher pressure than the liquid feed pump 15 but a lower pressure than the liquid feed pump 58 is used as the liquid feed pump 72. The concentration meter 73 detects the concentration of the auxiliary agent in the mixed solvent flowing through the eleventh sub-channel 43b, and the flow meter 74 detects the flow rate of the mixed solvent flowing through the eleventh sub-channel 43b. The same components as those in the first embodiment are designated by the same reference numerals, and the preceding description is referred to. In this embodiment, the liquid feed pump 15 is also referred to as a "first pump," and the liquid feed pump 72 is also referred to as a "second pump."

[0063] FIG. 10 is a flowchart showing the flow of concentration adjustment processing performed by the concentration adjuster 70. In the temperature difference enlarging mode described above, the concentration adjuster 70 adjusts the concentration of the mixed solvent supplied to the mixer 18 by repeating concentration adjustment S200 and flow rate adjustment S300 as shown in the figure. In the heat pump system 100A of this embodiment, the concentration adjuster 70 controls the liquid feed pump 72 and the liquid feed pump 15 so that a predetermined concentration target and flow rate target are achieved. In this embodiment, a control unit that controls the entire heat pump system 100A performs concentration adjustment control and functions as part of the concentration adjuster 70B. In other embodiments, the liquid feed pump 72 and the liquid feed pump 15 may each be configured to include a control unit that receives detection values from the concentration meter 73 and the flow meter 74 and performs concentration adjustment control.

[0064] FIG. 11 is a flowchart showing the flow of the concentration adjustment S200 process performed by the concentration adjuster 70. If the measured value (current) of the concentration meter 73 is the same as the target concentration ("=" in step S202), no change is made (step S206). If the measured value (current) of the concentration meter 73 is smaller (diluted) than the target concentration (">" in step S202), the flow rate of the liquid feed pump 72 is increased (step S204). This increases the concentration of the mixed solvent flowing through the eleventh sub-path 43b. If the measured value (current) of the concentration meter 73 is larger (diluted) than the target concentration ("<" in step S202), the flow rate of the liquid feed pump 72 is decreased (step S208). This decreases the concentration of the mixed solvent flowing through the eleventh sub-path 43b. When the concentration adjustment S200 is completed, the process proceeds to flow rate adjustment S300 (FIG. 10).

[0065] FIG. 12 is a flowchart showing the flow of the flow rate adjustment S300 process performed in the concentration adjuster 70. If the measurement value (current) of the flow meter 74 is the same as the target flow rate ("=" in step S302), no change is made (step S306). If the measurement value (current) of the flow meter 74 is greater than (higher than) the target flow rate ("<" in step S302), the flow rate of the liquid feed pump 15 is reduced (step S304). This reduces the flow rate of the mixed solvent flowing through the eleventh sub-path 43b. If the measurement value (current) of the flow meter 74 is smaller than (lower than) the concentration target (">" in step S302), the flow rate of the liquid feed pump 15 is increased (step S308). This increases the flow rate of the mixed solvent flowing through the eleventh sub-path 43b. When the flow rate adjustment S300 is completed, the process returns to the concentration adjustment S200 (FIG. 10).

[0066] For example, if the measured value (current) of the concentration meter 73 is smaller (diluted) than the target concentration, increasing the flow rate of the liquid feed pump 72 will increase the concentration of the mixed solvent flowing through the eleventh sub-channel 43b. As a result, the flow rate of the mixed solvent flowing through the eleventh sub-channel 43b increases, which may cause the measured value (current) of the flow meter 74 to exceed the target flow rate. In this case, reducing the flow rate of the liquid feed pump 15 reduces the flow rate of the mixed solvent flowing through the eleventh sub-channel 43b, thereby approaching the target flow rate. In this manner, the concentration adjuster 70 repeats concentration adjustment S200 and flow rate adjustment S300 to adjust the concentration of the mixed solvent supplied to the mixer 18 to the target value. In this embodiment, the increase / decrease amounts of the flow rates of the liquid feed pump 15 and the liquid feed pump 72 are preset. The increase / decrease amounts may be fixed, such as 10 L / min, or may vary depending on the detection results of the concentration meter 73.

[0067] As described above, the heat pump system 100A of this embodiment is equipped with the concentration adjusting unit 70, and therefore is capable of adjusting the concentration of the auxiliary agent in the mixed solvent supplied to the mixing unit 18. As described above, the stability boundary temperature of the clathrate hydrate can be controlled by the concentration of the auxiliary agent ( FIG. 6 ). Therefore, by supplying the mixed solvent with an appropriate auxiliary agent concentration to the mixing unit 18 in accordance with the operating conditions (temperature range) of the production unit 10, it is possible to promote the production of clathrate hydrate in the production unit 10. As a result, the energy efficiency of the heat pump system 100A can be improved.

[0068] Third Embodiment 13 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system 100B according to a third embodiment. The heat pump system 100B according to the third embodiment includes a concentration adjuster 70B instead of the concentration adjuster 70 of the heat pump system 100A according to the second embodiment. The concentration adjuster 70B includes a reservoir 71 disposed in the third sub-channel 63 and capable of storing the auxiliary agent separated by the liquid-liquid separator 54, a liquid feed pump 72, a concentration meter 75, a flow meter 76, a liquid feed pump 15 disposed in the tenth sub-channel 43a, a concentration meter 77, and a flow meter 78. The concentration meter 75 and the flow meter 76 detect the auxiliary agent concentration and flow rate, respectively, of the mixed solvent flowing downstream of the reservoir 71 of the third sub-channel 63, and the concentration meter 77 and the flow meter 78 detect the auxiliary agent concentration and flow rate, respectively, of the mixed solvent flowing through the tenth sub-channel 43a. The same components as those in the second embodiment are designated by the same reference numerals, and reference is made to the preceding description. In this embodiment, the liquid feed pump 15 is also referred to as the "first pump," the concentration meter 73 as the "first concentration meter," the flow meter 74 as the "first flow meter," the liquid feed pump 72 as the "second pump," the concentration meter 75 as the "second concentration meter," and the flow meter 76 as the "second flow meter."

[0069] 14 is a flowchart showing the flow of the concentration adjustment process performed in the concentration adjuster 70B. In this embodiment, a control unit that controls the entire heat pump system 100B performs concentration adjustment control and functions as part of the concentration adjuster 70B. In other embodiments, the liquid feed pump 72 and the liquid feed pump 15 may each be configured to include a control unit that receives detection values from the concentration meter 73, the flow meter 74, the concentration meter 75, and the flow meter 76 and performs concentration adjustment control. In the heat pump system 100B of this embodiment, the concentration of the mixed solvent supplied to the mixer 18 is also adjusted in the above-mentioned temperature difference expansion mode.

[0070] In step S402, the concentration meter 77 detects the concentration Cn1 of the auxiliary agent in the mixed solvent flowing through the tenth sub-channel 43a. In step S404, the concentration meter 75 detects the concentration Cn2 of the auxiliary agent in the mixed solvent flowing through the third sub-channel 63.

[0071] In step S406, the concentration adjuster 70B calculates a target flow rate Fg1 of the mixed solvent flowing through the tenth sub-channel 43a and a target flow rate Fg2 of the mixed solvent flowing downstream of the reservoir 71 in the third sub-channel 63. <<Calculation method for target flow rates Fg1 and Fg2>> Formula for calculating molar concentration in a solution Cn1×Fg1+Cn2×Fg2=Cg×Fg3…(Formula 1) Fg1+Fg2=Fg3…(Formula 2) From (Equation 1) and (Equation 2), Fg1 = (Cg - Cn2) / (Cn1 - Cn2) × Fg3 Fg2=Fg3-Fg1 where: Fg1: target flow rate [L / min] of the mixed solvent flowing through the tenth sub-channel 43a Fg2: Target flow rate [L / min] of the mixed solvent flowing through the third sub-channel 63 Fg3: Target flow rate [L / min] (set value) of mixed solvent (after concentration adjustment) sent to mixing section 18 Cn1: Molar concentration [mol / L] of the mixed solvent flowing through the tenth sub-channel 43a (measured value) Cn2: Molar concentration [mol / L] of the mixed solvent flowing through the third sub-channel 63 (measured value) Cg: Target concentration [mol / L] (set value) of the mixed solvent (after concentration adjustment) sent to the mixing unit 18 is. The molar concentrations (Cn1 and Cn2) can be determined from the conductivity of the mixed solvent by calculating in advance the relational expression between the conductivity of the mixed solvent and the molar concentration.

[0072] In step S408, the concentration adjuster 70B controls the liquid feed pump 15 so that the detection result by the flow meter 78 becomes the target flow rate Fg1. In step S410, the concentration adjuster 70B controls the liquid feed pump 72 so that the detection result by the flow meter 76 becomes the target flow rate Fg2.

[0073] In the heat pump system 100B of this embodiment, the concentration adjuster 70B can adjust the concentration of the mixed solvent sent to the mixer 18 to the target concentration Cg by repeating the above-described steps S402 to S410.

[0074] As described above, according to the heat pump system 100B of this embodiment, target values for the flow rates of the mixed solvent flowing through the tenth sub-channel 43a and the third sub-channel 63 are calculated based on the molar concentration of the mixed solvent (lower auxiliary agent concentration) flowing through the tenth sub-channel 43a and the molar concentration of the mixed solvent (higher auxiliary agent concentration) flowing through the third sub-channel 63, respectively, and the increase / decrease in the flow rates by the liquid feed pump 15 and the liquid feed pump 72 is controlled. Therefore, compared to when the increase / decrease in the flow rates by the liquid feed pump 15 and the liquid feed pump 72 are set to fixed values in advance, the auxiliary agent concentration of the mixed solvent supplied to the mixer 18 can be set to the target value in a shorter time. As a result, the energy efficiency of the heat pump system 100B can be further improved.

[0075] <Fourth embodiment> 15 is an explanatory diagram schematically illustrating the basic configuration of a heat pump system 100C according to a fourth embodiment. In addition to the configuration of the heat pump system 100 according to the first embodiment, the heat pump system 100C according to the fourth embodiment is equipped with a slurry pump 39 in the first main flow path 30 and a dehydration unit 17 in the second flow path 42. The same components as those in the first embodiment are denoted by the same reference numerals, and reference is made to the preceding description.

[0076] The slurry pump 39 transports the clathrate hydrate slurry delivered from the production section 10. By providing the slurry pump 39, the heat pump system 100C can adjust the flow rate of the heat medium flowing through the first main flow path 30, and therefore can adjust the decomposition rate in the decomposition section 20. The slurry pump 39 in this embodiment is also referred to as a "transport pump."

[0077] The dehydration section 17 adsorbs water and the auxiliary agent in the gas separated in the first gas-liquid separation section 14. The dehydration section 17 can perform dehydration using an adsorbent such as silica gel. This can remove the water (mixed solvent) mixed in the gas separated in the first gas-liquid separation section 14, thereby further reducing the energy consumption by the compression section 16 and further improving the energy consumption efficiency of the heat pump system 100C. The adsorbent is not limited to silica gel, and any known adsorbent can be used. The adsorbent can be easily regenerated by heat treatment.

[0078] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0079] Although the above embodiment shows an example in which the gas / solid-liquid separation unit 52 is provided, the gas / solid-liquid separation unit 52 does not have to be provided. When the gas / solid-liquid separation unit 52 is not provided, a gas / solid-liquid separator can be used as the mixed solvent separation unit 53. Furthermore, the clathrate hydrate slurry flowing out from the production unit 10 does not have to contain gas.

[0080] In the above embodiment, the gas separated in the gas / solid-liquid separation section 52 is supplied to the compression section 16, but it may also be supplied to the mixer 18. Even in this case, the same effects as those of the above embodiment can be obtained.

[0081] In the above embodiment, the auxiliary agent separated in the liquid-liquid separator 54 flows into the first sub-channel 43. However, the third sub-channel 63 may be directly connected to the liquid-liquid separator 54 and the mixing section 18, and the auxiliary agent separated in the liquid-liquid separator 54 may flow directly into the mixing section 18 via the third sub-channel 63.

[0082] In the first embodiment, the first sub-channel 43 is provided with two liquid feed pumps, the liquid feed pump 15 and the liquid feed pump 58, but the first sub-channel 43 may be provided with only one of them. For example, the liquid feed pump 15 may not be provided.

[0083] The pressure reduction section 24 may be provided in the first main flow path 30 through which the heat transfer medium flows from the production section 10 to the decomposition section 20, or may be provided between the decomposition section 20 and the first gas-liquid separation section 14 in the second main flow path 40 through which the heat transfer medium flows from the decomposition section 20 to the production section 10. Alternatively, the decomposition section 20 may be provided with the pressure reduction section 24, or the compression section 16 may be provided with the pressure reduction section 24. In this case, the pressure inside the decomposition section 20 can be reduced and the decomposition of clathrate hydrates in the decomposition section 20 can be promoted.

[0084] In the fourth embodiment, an example was shown in which the heat pump system was provided with the slurry pump 39, but the slurry pump 39 may also be provided in the heat pump systems of the first to third embodiments.

[0085] In the fourth embodiment, an example was shown in which the heat pump system was provided with the dehydration unit 17, but the dehydration unit 17 may also be provided in the heat pump systems of the first to third embodiments.

[0086] Although the above embodiment illustrates a configuration in which the second gas-liquid separation unit 56 is provided, the second gas-liquid separation unit 56 does not necessarily have to be provided.

[0087] In the above embodiment, a concentration meter may be provided in the second sub-channel 62 between the liquid-liquid separation section 54 and the decomposition section 20. In this way, the concentration of the diluted mixed solvent can be confirmed.

[0088] The present disclosure has been described above based on embodiments and modifications, but the above-described embodiments are intended to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. The present disclosure may be modified or improved without departing from the spirit and scope of the claims, and the present invention includes equivalents thereof. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0089] The present invention can also be realized as the following application examples. [Application example 1] A heat pump system in which a heat transfer medium transports heat by repeating a decomposition process and a formation process of a clathrate hydrate, a generation section into which a mixed solvent of a water-soluble liquid adjuvant and water and a gas are introduced and into which clathrate hydrates are generated; a decomposition section into which the clathrate hydrate is decomposed and into which a decomposition product, which is a mixed phase of the gas and the mixed solvent, is delivered; a first main flow path through which the heat transfer medium flows from the generation section to the decomposition section; a second main flow path through which the heat transfer medium flows from the decomposition section to the generation section; a heat dissipation unit that dissipates heat from the heat medium by heat exchange between the heat medium in the generation unit and a heat source outside the heat pump system; a pressure reducing section that reduces the pressure of the heat medium in the decomposition section; a heat absorption unit that absorbs heat into the heat medium by heat exchange between the heat medium in the decomposition unit and a heat source outside the heat pump system; a mixed solvent separation section connected to the production section via the first main channel and configured to separate the mixed solvent from a mixture containing at least the clathrate hydrate produced in the production section and the mixed solvent; a gas-liquid separation section connected to the decomposition section via the second main flow path, which separates the gas in the decomposition product sent out from the decomposition section from the mixed solvent; a compression section connected to the gas-liquid separation section via the second main flow path and configured to compress the gas separated by the gas-liquid separation section; a mixing section connected to the compression section and the production section via the second main flow path and connected to the gas-liquid separation section via a first sub-flow path, and configured to produce the mixed liquid containing the mixed solvent separated by the gas-liquid separation section and the gas compressed by the compression section; a liquid-liquid separation section connected to the mixed solvent separation section and the decomposition section via a second sub-channel, which separates the water and the auxiliary in the mixed solvent separated by the mixed solvent separation section using a reverse osmosis membrane or an ion exchange membrane; a third sub-flow path connected to the liquid-liquid separation unit for supplying the auxiliary agent separated by the liquid-liquid separation unit to the mixing unit; Equipped with Heat pump system. [Application example 2] The heat pump system according to Application Example 1, a gas / solid-liquid separation section disposed between the production section and the mixed solvent separation section, which separates the gas from a gas-solid-liquid mixture containing the clathrate hydrate, the gas, and the mixed solvent produced in the production section; a fourth sub-channel for supplying the gas separated by the gas / solid-liquid separation unit to the mixing unit; Further provided with Heat pump system. [Application example 3] The heat pump system according to Application Example 1 or Application Example 2, Further provided is a transport pump disposed in the first main flow path and transporting the heat medium. Heat pump system. [Application example 4] The heat pump system according to any one of Application Examples 1 to 3, moreover, a junction portion disposed in the first sub-channel and merging the third sub-channel into the first sub-channel; a concentration adjusting unit that adjusts the concentration of the auxiliary agent in the mixed solvent supplied to the mixing unit; Equipped with The concentration adjusting unit a concentration meter disposed in the first sub-channel and configured to detect the concentration of the auxiliary agent in the mixed solvent flowing between the junction and the mixing section; a flow meter disposed in the first sub-channel and configured to detect a flow rate of the mixed solvent supplied to the mixing section; a first pump disposed between the gas-liquid separation unit and the junction unit in the first sub-channel, the first pump controlling the flow rate of the mixed solvent separated by the gas-liquid separation unit; a storage section disposed in the third sub-channel and capable of storing the auxiliary agent separated by the liquid-liquid separation section; a second pump disposed in the third sub-channel and configured to control the flow rate of the auxiliary agent flowing from the reservoir to the first sub-channel; Equipped with controlling the first pump and the second pump based on the detection results of the concentration meter and the flow meter to adjust the concentration of the mixed solvent supplied to the mixing section to a predetermined target value; Heat pump system. [Application example 5] The heat pump system according to any one of Application Examples 1 to 4, moreover, a junction portion disposed in the first sub-channel and merging the third sub-channel into the first sub-channel; a concentration adjusting unit that adjusts the concentration of the auxiliary agent in the mixed solvent supplied to the mixing unit; Equipped with The concentration adjusting unit a first pump disposed between the gas-liquid separation unit and the junction unit in the first sub-channel, the first pump controlling the flow rate of the mixed solvent separated by the gas-liquid separation unit; a first concentration meter disposed between the gas-liquid separation unit and the junction unit in the first sub-channel, the first concentration meter detecting the concentration of the auxiliary agent in the mixed solvent separated by the gas-liquid separation unit; a first flow meter disposed between the gas-liquid separation unit and the junction unit in the first sub-channel, the first flow meter detecting a flow rate of the mixed solvent separated by the gas-liquid separation unit; a storage section disposed in the third sub-channel and capable of storing the auxiliary agent separated by the liquid-liquid separation section; a second pump disposed in the third sub-channel and configured to control the flow rate of the mixed solvent containing the auxiliary agent flowing from the reservoir to the first sub-channel; a second concentration meter disposed in the third sub-channel and configured to detect the concentration of the auxiliary agent in the mixed solvent; a second flow meter disposed in the third sub-channel and configured to detect a flow rate of the mixed solvent; Equipped with controlling the first pump based on the detection results of the first concentration meter and the first flow meter, and controlling the second pump based on the detection results of the second concentration meter and the second flow meter, thereby adjusting the concentration of the mixed solvent supplied to the mixing section to a predetermined target value. Heat pump system. [Application Example 6] The heat pump system according to any one of Application Examples 1 to 5, a dehydration unit disposed between the gas-liquid separation unit and the compression unit, which adsorbs the mixed solvent in the gas separated by the gas-liquid separation unit. Heat pump system. [Explanation of symbols]

[0090] 10...Generation section 12...Heat radiation part 14...First gas-liquid separation section 15...Liquid transfer pump 16...Compression section 17...Dehydration section 18…Mixing section 20…Disassembly part 22...heat absorption part 24...Decompression section 30...First main channel 39...Slurry pump 40…Second main flow path 43...First sub-channel 52...Gas / solid-liquid separation section 53... Mixed solvent separation section 54...Liquid-liquid separation section 56...Second gas-liquid separation section 58...Liquid transfer pump 60…4th sub-channel 62…Second sub-channel 63…Third sub-channel 64, 65, 66...Shut-off valve 67...Blower 69...Confluence 70, 70B...Concentration adjustment section 71...Storage section 72...Liquid transfer pump 73, 75, 77...densitometer 74, 76, 78...flow meter 80...5th sub-channel 100, 100A, 100B, 100C...Heat pump system

Claims

1. A heat pump system in which a heat transfer medium transports heat by repeating a decomposition process and a formation process of a clathrate hydrate, a generation section into which a mixed solvent of a water-soluble liquid adjuvant and water and a gas are introduced and into which clathrate hydrates are generated; a decomposition section into which the clathrate hydrate is decomposed and into which a decomposition product, which is a mixed phase of the gas and the mixed solvent, is delivered; a first main flow path through which the heat transfer medium flows from the generation section to the decomposition section; a second main flow path through which the heat medium flows from the decomposition section to the generation section; a heat dissipation unit that dissipates heat from the heat medium by heat exchange between the heat medium in the generation unit and a heat source outside the heat pump system; a pressure reducing section that reduces the pressure of the heat medium in the decomposition section; a heat absorption unit that absorbs heat into the heat medium by heat exchange between the heat medium in the decomposition unit and a heat source outside the heat pump system; a mixed solvent separation section connected to the production section via the first main flow path and configured to separate the mixed solvent from a mixture containing at least the clathrate hydrate and the mixed solvent produced in the production section; a gas-liquid separation section connected to the decomposition section via the second main flow path, which separates the gas in the decomposition product delivered from the decomposition section from the mixed solvent; a compression section connected to the gas-liquid separation section via the second main flow path and configured to compress the gas separated by the gas-liquid separation section; a mixing section connected to the compression section and the production section via the second main flow path and connected to the gas-liquid separation section via a first sub-flow path, and configured to produce the mixed liquid containing the mixed solvent separated by the gas-liquid separation section and the gas compressed by the compression section; a liquid-liquid separation section connected to the mixed solvent separation section and the decomposition section via a second sub-flow path, which separates the water and the auxiliary in the mixed solvent separated by the mixed solvent separation section using a reverse osmosis membrane or an ion exchange membrane; a third sub-flow path connected to the liquid-liquid separation section, for supplying the auxiliary agent separated by the liquid-liquid separation section to the mixing section; Equipped with Heat pump system.

2. The heat pump system according to claim 1, a gas / solid-liquid separation section disposed between the production section and the mixed solvent separation section, which separates the gas from a gas-solid-liquid mixture containing the clathrate hydrate, the gas, and the mixed solvent produced in the production section; a fourth sub-flow passage for supplying the gas separated by the gas / solid-liquid separation section to the mixing section; Further provided with Heat pump system.

3. The heat pump system according to claim 1, The heat transfer system further includes a transport pump disposed in the first main flow path and configured to transport the heat transfer medium. Heat pump system.

4. The heat pump system according to claim 1, moreover, a junction portion disposed in the first sub-channel and merging the third sub-channel into the first sub-channel; a concentration adjusting unit that adjusts the concentration of the auxiliary agent in the mixed solvent supplied to the mixing unit; Equipped with The concentration adjusting unit a concentration meter disposed in the first sub-channel and configured to detect a concentration of the auxiliary agent in the mixed solvent flowing between the junction and the mixing section; a flow meter disposed in the first sub-channel and configured to detect a flow rate of the mixed solvent supplied to the mixing section; a first pump disposed between the gas-liquid separation unit and the junction unit in the first sub-channel, the first pump controlling a flow rate of the mixed solvent separated by the gas-liquid separation unit; a reservoir portion disposed in the third sub-channel and capable of storing the auxiliary agent separated by the liquid-liquid separation portion; a second pump disposed in the third sub-channel and configured to control the flow rate of the auxiliary agent flowing from the reservoir to the first sub-channel; Equipped with controlling the first pump and the second pump based on the detection results of the concentration meter and the flow meter to adjust the concentration of the mixed solvent supplied to the mixing section to a predetermined target value; Heat pump system.

5. The heat pump system according to claim 1, moreover, a junction portion disposed in the first sub-channel and merging the third sub-channel into the first sub-channel; a concentration adjusting unit that adjusts the concentration of the auxiliary agent in the mixed solvent supplied to the mixing unit; Equipped with The concentration adjusting unit a first pump disposed between the gas-liquid separation unit and the junction unit in the first sub-channel, the first pump controlling a flow rate of the mixed solvent separated by the gas-liquid separation unit; a first concentration meter disposed between the gas-liquid separation section and the junction section of the first sub-channel, the first concentration meter detecting a concentration of the auxiliary agent in the mixed solvent separated by the gas-liquid separation section; a first flow meter disposed between the gas-liquid separation unit and the junction unit in the first sub-channel, the first flow meter detecting a flow rate of the mixed solvent separated by the gas-liquid separation unit; a reservoir portion disposed in the third sub-channel and capable of storing the auxiliary agent separated by the liquid-liquid separation portion; a second pump disposed in the third sub-channel and configured to control a flow rate of the mixed solvent containing the auxiliary agent flowing from the reservoir to the first sub-channel; a second concentration meter disposed in the third sub-channel and configured to detect the concentration of the auxiliary agent in the mixed solvent; a second flow meter disposed in the third sub-channel and configured to detect a flow rate of the mixed solvent; Equipped with controlling the first pump based on the detection results of the first concentration meter and the first flow meter, and controlling the second pump based on the detection results of the second concentration meter and the second flow meter, thereby adjusting the concentration of the mixed solvent supplied to the mixing section to a predetermined target value. Heat pump system.

6. The heat pump system according to any one of claims 1 to 5, a dehydration unit disposed between the gas-liquid separation unit and the compression unit, which adsorbs the mixed solvent in the gas separated by the gas-liquid separation unit. Heat pump system.

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