Natural gas adsorption storage system

Abstract

To provide a natural gas adsorption storage system that not only provides simple heat exchange but also avoids increase in weight of the system.SOLUTION: An adsorption storage system 100 includes: a first gas storage part (first gas tank 11) capable of storing and discharging a natural gas and filled with a first adsorbent 111; and a second gas storage part (second gas tank 22) capable of storing and discharging carbon dioxide and filled with a second adsorbent 222, where the first gas storage part (first gas tank 11) and the second gas storage part (second gas tank 22) are thermally connected to each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an adsorptive storage system for natural gas. [Background technology]

[0002] Patent Document 1 discloses a technology for a vehicle that is equipped with a tank filled with an adsorbent capable of adsorbing and releasing natural gas and that runs on natural gas supplied from the tank as fuel, in which the tank is heated using engine cooling water to prevent an endothermic reaction that occurs when the natural gas is released from the adsorbent and the associated decrease in the natural gas release capacity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-146092 A Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional vehicles such as those described in Patent Document 1, the tank is generally disposed at the rear of the vehicle and the engine is generally disposed at the front of the vehicle. Therefore, when heating the tank, it is necessary to extend the cooling water piping from the front of the vehicle to the rear of the vehicle, which not only complicates the heat exchange system but also increases the weight of the system including the cooling water.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a natural gas adsorption storage system that realizes simple heat exchange and avoids an increase in the weight of the system. [Means for solving the problem]

[0006] A natural gas adsorption storage system according to one aspect of the present invention includes a first gas storage unit filled with a first adsorbent capable of storing and releasing natural gas, a second gas storage unit filled with a second adsorbent capable of storing and releasing carbon dioxide, A generator that consumes natural gas to generate electricity and emits carbon dioxide;The first gas storage unit and the second gas storage unit are thermally connected to each other. The first gas storage unit communicates with a natural gas inlet side of the generator, and the second gas storage unit communicates with a carbon dioxide exhaust side of the generator, and when natural gas is discharged from the first gas storage unit to the generator, carbon dioxide discharged from the generator is stored in the second gas storage unit, and when natural gas supplied from the outside is stored in the first gas storage unit, carbon dioxide is discharged to the outside from the second gas storage unit. . Effect of the Invention

[0007] In the above embodiment, when natural gas is adsorbed to the first adsorbent, heat of adsorption (heat generation) is generated, which reduces the adsorption capacity of the natural gas. In addition, when natural gas is released from the first adsorbent, heat of release (endotherm) is generated, which reduces the release capacity of the natural gas. On the other hand, when carbon dioxide is adsorbed to the second adsorbent, heat of adsorption (heat generation) is generated, and when carbon dioxide is released from the second adsorbent, heat of release (endotherm) is generated. Therefore, by filling the gas tank with carbon dioxide when releasing natural gas and releasing carbon dioxide when filling the gas tank with natural gas, it is possible to exchange heat between the heat of adsorption generated in the first gas storage unit and the heat of release generated in the second gas storage unit, and between the heat of release generated in the first gas storage unit and the heat of adsorption generated in the second gas storage unit. Therefore, it is possible to suppress the decrease in the adsorption capacity when natural gas is adsorbed to the first adsorbent and the decrease in the release capacity when natural gas is released from the first adsorbent. Furthermore, a flow path for supplying carbon dioxide to the second gas storage unit is necessary, but the flow path through which carbon dioxide flows is lighter than the flow path through which cooling water flows because there is no cooling water. As a result, it is possible to realize simple heat exchange while preventing the system from becoming heavy. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram for simply explaining the natural gas adsorption storage system of the first embodiment. [Diagram 2] FIG. 2 is a block diagram showing a main configuration of the natural gas adsorption storage system of the first embodiment. [Diagram 3] FIG. 3 is a flow diagram when natural gas is released from the first gas tank and carbon dioxide is filled into the second gas tank in the natural gas adsorption storage system of the first embodiment. [Figure 4] FIG. 4 is a graph showing the relationship between the discharge pressure of natural gas and carbon dioxide and the loading amount into the adsorbent. [Diagram 5] Figure 5 shows the energy balance when the heat released when natural gas is released from the first gas tank is supplied from outside, and is a graph showing the relationship between the amount of heat that can be supplied from the second gas tank to the first gas tank and the vehicle speed, with the carbon dioxide recovery rate as a parameter, and a pie chart showing the ratio of the heat of carbon dioxide adsorption to the power consumption of the compressor. [Figure 6] FIG. 6 is a flow diagram showing a process for filling the first gas tank with natural gas and releasing carbon dioxide from the second gas tank in the natural gas adsorption storage system of this embodiment. [Figure 7] Figure 7 is a graph showing the relationship between the amount of natural gas filled, the natural gas filling time, and the temperature of the first gas tank in a case where the amount of heat to be extracted from the first gas tank when filling the first gas tank with natural gas is covered by the heat released from carbon dioxide, with the carbon dioxide recovery rate used as a parameter. [Figure 8] FIG. 8 is a cross-sectional view (vertical direction) of the first gas tank (second gas tank) in the natural gas adsorption storage system of the second embodiment. [Figure 9] FIG. 9 is a cross-sectional view (horizontal direction) of the first gas tank (second gas tank) in the natural gas adsorption storage system of the second embodiment. [Figure 10] FIG. 10 is a schematic diagram showing a flow path of a refrigerant flow passage in a natural gas adsorption storage system according to the second embodiment. [Figure 11] FIG. 11 is a schematic diagram showing a modified example of the flow path of the refrigerant flow passage in the natural gas adsorption storage system of the second embodiment. [Figure 12] FIG. 12 is a schematic diagram of a first gas tank in the natural gas adsorption storage system of the third embodiment. [Figure 13] FIG. 13 is a schematic diagram showing a flow path of a refrigerant flow passage in a natural gas adsorption storage system according to the third embodiment. [Figure 14] FIG. 14 is a block diagram for simply explaining the natural gas adsorption storage system of the fourth embodiment. [Figure 15]FIG. 15 is a block diagram for simply explaining the natural gas adsorption storage system of the fifth embodiment. [Figure 16] FIG. 16 is a diagram showing the structure of the adsorbent. [Figure 17A] FIG. 17A is a diagram showing a modified example of the adsorbent structure (before synthesis). [Figure 17B] FIG. 17B shows a modified example of the adsorbent structure (after synthesis). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] [Overview of the first embodiment] FIG. 1 is a block diagram for simply explaining a natural gas adsorptive storage system 100 according to the first embodiment.

[0011] A natural gas adsorption storage system 100 (hereinafter referred to as the adsorption storage system 100) of the first embodiment is mounted on a vehicle that uses natural gas as fuel. The adsorption storage system 100 includes a first gas tank 11 (first gas storage unit) that can be filled with and released from natural gas, a second gas tank 22 (second gas storage unit) that can be filled with and released from carbon dioxide (CO2), a compressor 21 (pressure boosting means) that pressurizes and supplies carbon dioxide to the second gas tank 22, and a circulation pump 31 that circulates a refrigerant between the first gas tank 11 and the second gas tank 22.

[0012] The first gas tank 11 can be filled with natural gas from an external source (gas station) at a predetermined pressure (e.g., 3.5 [Mpa]) and the filled natural gas can be supplied to the generator 9 (fuel cell, engine). That is, when V3 is opened with V4 closed, natural gas is supplied to the first gas tank 11, and when V4 is opened with V3 closed, the natural gas stored in the first gas tank 11 is supplied to the generator 9.

[0013] The first gas tank 11 is filled with a first adsorbent 111 (FIG. 8) that adsorbs and releases (desorbs) natural gas. Therefore, when natural gas is supplied to the first gas tank 11, the natural gas is adsorbed into the first adsorbent 111. The amount of natural gas adsorbed (adsorption density) varies depending on the pressure of the natural gas in the first gas tank 11 and the temperature of the first adsorbent 111 (see FIG. 4).

[0014] When V4 is opened and the pressure inside the first gas tank 11 drops, natural gas is released from the first adsorbent 111, and at that time the first adsorbent 111 generates released heat (endothermic heat). If the temperature of the first adsorbent 111 drops due to this released heat, the release efficiency of the natural gas decreases. Therefore, when releasing natural gas from the first gas tank 11, it is necessary to supply from the outside an amount of heat equivalent to the released heat generated when the natural gas is released from the first adsorbent 111.

[0015] Furthermore, when V3 is opened and natural gas is filled into the first gas tank 11, the first adsorbent 111 adsorbs the natural gas, and in the process, the first adsorbent 111 generates heat of adsorption (heat). If the temperature of the first adsorbent 111 rises due to this heat of adsorption, the adsorption efficiency of the natural gas decreases. Therefore, when filling the first gas tank 11 with natural gas, it is necessary to extract the heat of adsorption generated when the natural gas is adsorbed into the first adsorbent 111 from the outside.

[0016] The second gas tank 22 is filled with a second adsorbent 222 (FIG. 8) that adsorbs and releases (desorbs) carbon dioxide. Therefore, when carbon dioxide is supplied to the second gas tank 22, the carbon dioxide is adsorbed by the second adsorbent 222. The amount of carbon dioxide adsorbed (adsorption density) varies depending on the pressure of carbon dioxide in the second gas tank 22 and the temperature of the second adsorbent 222.

[0017] When V2 is opened and the pressure inside the second gas tank 22 drops, carbon dioxide is released from the second adsorbent 222, and at that time, the second adsorbent 222 generates released heat (endothermic heat). If the temperature of the second adsorbent 222 drops due to this released heat, the carbon dioxide release efficiency decreases. Therefore, when carbon dioxide is released from the second gas tank 22, it is necessary to supply from the outside an amount of heat equivalent to the released heat generated when carbon dioxide is released from the second adsorbent 222.

[0018] Furthermore, when the compressor 21 is turned on with V2 closed and V1 open, carbon dioxide is supplied to the second gas tank 22 at a predetermined pressure (for example, 0.5 [Mpa]) and the carbon dioxide is adsorbed to the second adsorbent 222, and at that time, the second adsorbent 222 generates adsorption heat (heat generation). If the temperature of the second adsorbent 222 rises due to this adsorption heat, the adsorption efficiency of carbon dioxide decreases. Therefore, when filling the second gas tank 22 with carbon dioxide, it is necessary to extract the adsorption heat generated when the carbon dioxide is adsorbed to the second adsorbent 222 from the outside.

[0019] Here, the generator 9 (fuel cell, engine) consumes natural gas to generate electricity and emits carbon dioxide. Furthermore, the first gas tank 11 and the second gas tank 22 are capable of exchanging heat with each other via a refrigerant.

[0020] Therefore, when natural gas is released from the first gas tank 11, the second gas tank 22 can be filled with carbon dioxide. This allows the second gas tank 22 to supply an amount of heat that offsets the released heat generated in the first gas tank 11 via the refrigerant, and it is possible to suppress a decrease in the release capacity of natural gas from the first adsorbent 111. At the same time, the first gas tank 11 can extract, via the refrigerant, the heat of adsorption generated when carbon dioxide is adsorbed by the second adsorbent 222 in the second gas tank 22, and it is possible to suppress a decrease in the adsorption efficiency of carbon dioxide to the second adsorbent 222.

[0021] Furthermore, when filling the first gas tank 11 with natural gas, the carbon dioxide filled in the second gas tank 22 can be released. This allows the second gas tank 22 to extract the heat of adsorption generated in the first gas tank 11 via the refrigerant, and it is possible to suppress a decrease in the adsorption capacity of the natural gas to the first adsorbent 111. At the same time, the first gas tank 11 can supply to the second gas tank 22 via the refrigerant an amount of heat that offsets the heat released when carbon dioxide is released from the second adsorbent 222 in the second gas tank 22, and it is possible to suppress a decrease in the efficiency of release of carbon dioxide from the second adsorbent 222.

[0022] As the first adsorbent 111 and the second adsorbent 222, for example, a gas adsorbent such as a metal organic framework (MOF, regular porous metal complex), a porous coordination polymer (PCP), activated carbon, or zeolite is applied. The structures of the first adsorbent 111 and the second adsorbent 222 will be described later.

[0023] Examples of adsorbents that have a higher heat of adsorption / heat of release per mole of carbon dioxide than those of methane, natural gas, etc. include adsorbents such as MOFs, activated carbon, zeolites, etc. Many of the commonly available MOFs, such as Basolite C-300, have a high adsorption capacity for both methane and carbon dioxide, and also have a high heat of adsorption for carbon dioxide, and their application is preferable from the viewpoint of enabling the miniaturization of the entire system.

[0024] For example, when MOFs are used as the first adsorbent 111 and the second adsorbent 222, the heat of adsorption / heat of release of methane is 12.5 [kJ / mol], and the heat of adsorption / heat of release of carbon dioxide is 15 [kJ / mol]. Furthermore, when one mole of methane is burned, one mole of carbon dioxide is generated. Therefore, the heat of adsorption / heat of release of one mole of methane can be covered by the heat of adsorption / heat of release of one mole of carbon dioxide. Furthermore, by using the same material (e.g., MOF) for the first adsorbent 111 and the second adsorbent 222, costs can be reduced.

[0025] Natural gas is mostly composed of methane, but also contains small amounts of other hydrocarbons such as ethane, propane, and butane. For example, the heat of adsorption of butane (n-butane) is 36 [kJ / mol], but 4 moles of carbon dioxide are generated when butane is burned. Therefore, the heat of adsorption / heat of release of 1 mole of butane (36 [kJ / mol]) can be covered by the heat of release / heat of adsorption of 4 moles of carbon dioxide (15 x 4 = 60 [kJ / mol]). The above values ​​of the heat of adsorption / heat of release of carbon dioxide, methane, and butane (n-butane) are quoted from a non-patent document ("Heats of Adsorption for Seven Gases in Three Metal - Organic Frameworks: Systematic Comparison of Experimental and Simulation", David Farrusseng etc, Langmuir 2009, 25(13), 7383-7388, Published on Web 06 / 04 / 2009).

[0026] Considering the heat of adsorption / heat of desorption of methane and butane, the heat of adsorption / heat of desorption of ethane is about 20 [kJ / mol], and the heat of adsorption / heat of desorption of propane is about 28 [kJ / mol]. In addition, burning 1 mole of ethane produces 2 moles of carbon dioxide, and burning 1 mole of propane produces 3 moles of carbon dioxide.

[0027] Therefore, the heat of adsorption / heat of release of 1 mole of ethane (approximately 20 kJ / mol) can be covered by the heat of release / heat of adsorption of 2 moles of carbon dioxide (15 x 2 = 30 kJ / mol), and the heat of adsorption / heat of release of 1 mole of propane (approximately 28 kJ / mol) can be covered by the heat of release / heat of adsorption of 3 moles of carbon dioxide (15 x 3 = 45 kJ / mol).

[0028] A fuel cell or an engine is applied as the generator 9. In a fuel cell, natural gas is converted into a reformed gas, which is used in a power generation reaction, and a mixed gas of carbon dioxide and water vapor is discharged. Therefore, a configuration for recovering carbon dioxide from exhaust gas can be, for example, a configuration in which the mixed gas is supplied to a condenser (separator 91 (Figure 2)) and the water vapor is removed to recover carbon dioxide. In particular, a fuel cell can recover carbon dioxide with a high recovery rate, so that the second gas tank 22 can be efficiently filled with carbon dioxide.

[0029] On the other hand, in an engine, natural gas is directly burned to discharge exhaust gas containing carbon dioxide. Therefore, as a configuration for recovering carbon dioxide from exhaust gas, for example, a configuration in which exhaust gas is supplied to a device (separator 91 (FIG. 2)) equipped with a trapping agent such as a lean absorption liquid or a solution of an alkali metal carbonate, the exhaust gas is blown onto the trapping agent to absorb carbon dioxide, and then the trapping agent is heated in the device to recover carbon dioxide. Note that hydrofluoroether (HFE) used as a refrigerant, etc. (see, for example, US9267415B2) can also be used as a trapping agent. Another configuration for recovering carbon dioxide from exhaust gas can also be a configuration in which exhaust gas is supplied to an FT polymer for carbon dioxide separation (see, for example, JP2015-536814A) to separate carbon dioxide from the exhaust gas.

[0030] As mentioned above, the heat of adsorption / heat of desorption of methane is 12.5 [kJ / mol], and the heat of adsorption / heat of desorption of carbon dioxide is 15 [kJ / mol]. The proportion of methane in natural gas is about 90 [%], but even if we assume that it is all methane, if the carbon dioxide recovery rate is (12.5 [kJ / mol]) / (15 [kJ / mol]) x 100 = 83.3 [%] or more, the heat of adsorption / heat of desorption of methane can be covered by the heat of desorption / heat of carbon dioxide.

[0031] Considering the volume ratio between the first gas tank 11 and the second gas tank 22, if the carbon dioxide recovery rate from the generator 9 is 100%, the heat of adsorption / heat of release of methane is 12.5 [kJ / mol], and the heat of adsorption / heat of release of carbon dioxide is 15 [kJ / mol], so the second gas tank 22 can be designed with a volume of 12.5 / 15 x 100 = 83.3 [%] of the first gas tank 11.

[0032] In addition, it is also preferable to design the ratio of the volumes of the first gas tank 11 and the second gas tank 22 so that the total adsorption capacity is approximately equal, taking into consideration the natural gas adsorption capacity per unit volume of the first adsorbent 111 and the carbon dioxide adsorption capacity per unit volume of the second adsorbent 222. For example, when the adsorption capacity per unit volume of the second adsorbent 222 is twice the adsorption capacity per unit volume of the first adsorbent 111, the second gas tank 22 can be designed with a volume half that of the first gas tank 11. Of course, the capacities of the first gas tank 11 and the second gas tank 22 may be the same, and the carbon dioxide adsorption capacity per unit volume of the second adsorbent 222 may be larger than the natural gas adsorption capacity per unit volume of the first adsorbent 111.

[0033] As described above, it is preferable to set the volume ratio between the first gas tank 11 and the second gas tank 22 so that the total amount of heat adsorption / discharge heat due to natural gas in the first gas tank 11 is approximately equal to the total amount of heat adsorption / discharge heat due to carbon dioxide in the second gas tank 22, or so that the natural gas adsorption capacity of the first gas tank 11 is approximately equal to the carbon dioxide adsorption capacity of the second gas tank 22. This allows the second gas tank 22 to be designed smaller than the first gas tank 11, and the load (power consumption) on the compressor 21 can be reduced.

[0034] Furthermore, it is also preferable to appropriately select the materials of the first adsorbent 111 and the second adsorbent 222 so that the adsorption capacity of the same number of moles of carbon dioxide as methane can be achieved at a lower pressure than that of methane in natural gas. This also reduces the load (power consumption) on the compressor 21.

[0035] [Main configuration of the first embodiment] 2 is a block diagram showing the main configuration of a natural gas adsorption storage system 100 according to the first embodiment. As described above, the adsorption storage system 100 according to the first embodiment is mounted on a vehicle that generates power using natural gas as fuel. The vehicle is equipped with a generator 9 (fuel cell, engine), a battery (not shown), and a motor (not shown), and the power generated by the generator 9 is charged into the battery, and the motor receives power from the battery to drive the drive wheels of the vehicle. The motor also generates regenerative power during deceleration, which can be charged into the battery.

[0036] The adsorption storage system 100 of the first embodiment includes a supply line 1 that stores natural gas supplied from the outside and supplies the natural gas to a gas inlet side of a generator 9, and a discharge line 2 that stores or discharges carbon dioxide recovered from the gas exhaust side of the generator 9. A separator 91 that separates carbon dioxide from the exhaust gas and a heat exchanger 92 (for example, a radiator mounted on a vehicle) that cools the carbon dioxide discharged from the separator 91 are connected to the generator 9.

[0037] The supply line 1 can be detachably connected to an external gas station. In the supply line 1, a valve V3, a first gas tank 11, a reserve tank 12, a pressure sensor P2, and a valve V4 are arranged in this order from upstream. The valve V3 is connected to an external gas station via a pressure reducing valve 8. The first gas tank 11 and the reserve tank 12 are housed in a tank case 231 described below. The reserve tank 12 temporarily stores the natural gas discharged from the first gas tank 11, reduces the pressure, and supplies it to the valve V4.

[0038] The discharge line 2 is connected to a heat exchanger 92, and carbon dioxide is supplied from the heat exchanger 92. In the discharge line 2, a temperature sensor T0, a compressor 21, a valve V1, a second gas tank 22, and a valve V2 are arranged in this order from the upstream side.

[0039] In addition, a branch flow path 23 branches off from a position on the discharge line 2 between the compressor 21 and the valve V1. The branch flow path 23 merges with the discharge line 2 at a position on the discharge line 2 between the valve V1 and the second gas tank 22. A valve V5 is disposed in the branch flow path 23. The tank case 231 is integrally incorporated in the branch flow path 23.

[0040] A circulation line 3 for circulating the refrigerant is disposed between the first gas tank 11 and the second gas tank 22. A temperature sensor T1, a circulation pump 31, and a heater 32 are disposed in the flow path of the circulation line 3 from the second gas tank 22 to the first gas tank 11. The temperature sensor T1 detects the temperature of the refrigerant discharged from the second gas tank 22.

[0041] The circulation pump 31 circulates the refrigerant between the first gas tank 11 and the second gas tank 22, and here it is driven in a direction to supply the refrigerant discharged from the second gas tank 22 to the first gas tank 11.

[0042] The heater 32 heats the refrigerant supplied to the first gas tank 11. A temperature sensor T2 is disposed in the flow path of the circulation line 3 from the first gas tank 11 to the second gas tank 22, and detects the temperature of the refrigerant discharged from the first gas tank 11.

[0043] The controller 4 (control unit) is a computer including, for example, a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 4 is a component that constitutes the natural gas adsorption storage system 100 of this embodiment and is provided with a program for executing the system. The controller 4 can also control the on / off and output of the generator 9, and can also operate according to commands from an ECU or the like that controls the entire vehicle.

[0044] [Control flow when releasing natural gas] FIG. 3 is a flow diagram when natural gas is released from the first gas tank 11 and carbon dioxide is filled into the second gas tank 22 in the natural gas adsorption storage system 100 of the first embodiment.

[0045] In step S101, the controller 4 opens the valve V4. As a result, natural gas is supplied to the generator 9 from the first gas tank 11 via the reserve tank 12. At this time, the natural gas begins to desorb from the first adsorbent 111, and heat release (heat absorption) is generated.

[0046] In step S102, the controller 4 (or the ECU) starts up the generator 9.

[0047] In step S103, the controller 4 opens the valve V1 and closes the valve V2, and then starts the compressor 21. As a result, the second gas tank 22 is filled with carbon dioxide and begins to be adsorbed by the second adsorbent 222, generating heat of adsorption (heat generation).

[0048] In step S104, the controller 4 starts the circulation pump 31. This starts heat exchange between the first gas tank 11 and the second gas tank 22. The controller 4 may simultaneously perform steps S101, S102, S103, and S104.

[0049] In step S105, the controller 4 adjusts the output of the circulation pump 31 so that the difference ΔT1 (ΔT1=T1-T2) between the temperature (T1) detected by the temperature sensor T1 and the temperature (T2) detected by the temperature sensor T2 is equal to or less than a predetermined temperature difference (e.g., 10°C). This suppresses a decrease in temperature of the first gas tank 11, and suppresses a decrease in the release efficiency of the natural gas from the first adsorbent 111. At the same time, the temperature increase of the second gas tank 22 is also suppressed, and suppresses a decrease in the adsorption efficiency of the carbon dioxide to the second adsorbent 222.

[0050] In step S106, the controller 4 determines whether or not the temperature detected by the temperature sensor T0 exceeds a predetermined maximum temperature Tmax, and if YES, the process proceeds to step S107, and if NO, the process proceeds to step S109.

[0051] In step S107, the controller 4 determines whether or not the next step S108 has already been executed, and if YES, the process proceeds to step S109, and if NO, the process proceeds to step S108.

[0052] In step S108, the controller 4 closes the valve V1 and opens the valve V5. As a result, carbon dioxide is introduced from the compressor 21 into the branch flow path 23, cooled by the first gas tank 11 in the tank case 231, and supplied to the second gas tank 22. This suppresses an increase in the temperature of the carbon dioxide, and suppresses a decrease in the adsorption efficiency of the carbon dioxide to the second adsorbent 222. Note that in step S108, the controller 4 may control the opening degrees of the valves V5 and V1 so that the flow rate of the carbon dioxide flowing through the valve V1 and the flow rate of the carbon dioxide flowing through the valve V5 are a predetermined ratio (for example, 1:1).

[0053] In step S109, the controller 4 determines whether the pressure (P2) detected by the pressure sensor P2 is smaller than a predetermined lower limit pressure Pmin (the pressure required for the generator 9 to generate rated power), and if the answer is YES, proceeds to step S110, and if the answer is NO, proceeds to step S112.

[0054] In step S110, the controller 4 determines whether or not the next step S111 has already been executed. If YES, the process proceeds to step S113, and if NO, the process proceeds to step S111.

[0055] In step S111, the controller 4 activates the heater 32 and increases the rotation speed (output) of the circulation pump 31. This causes the temperature of the first gas tank 11 to increase (for example, from room temperature (20° C.) to 40° C.), and the pressure detected by the pressure sensor P2 increases.

[0056] In step S112, it is determined whether or not the pressure detected by the pressure sensor P1 has exceeded the maximum allowable pressure P1max. If YES, the process proceeds to step S114, and if NO, the process returns to step S106.

[0057] In step S113, the controller 4 determines that the natural gas in the first gas tank 11 is insufficient, and outputs a signal to warn the driver.

[0058] In step S114, the controller 4 opens the valve V2 at a predetermined rate so that the pressure detected by the pressure sensor P1 becomes equal to or lower than the maximum pressure P1max, or the controller 4 closes the valves V1, V2, and V5 and then stops the compressor 21.

[0059] Regardless of the above flow, when the ECU stops the generator 9, the controller 4 closes the valves V1-V5 and stops the compressor 21, the circulation pump 31, and the heater 32.

[0060] [Natural gas discharge pressure and filling volume] 4 is a graph showing the relationship between the discharge pressure of natural gas and carbon dioxide and the amount of carbon dioxide filled into the adsorbent. Consider the case where natural gas is discharged from the first gas tank 11 and carbon dioxide is filled into the second gas tank 22, where heat exchange takes place between the first gas tank 11 and the second gas tank 22, and where both tanks are maintained at room temperature (20° C.).

[0061] In this case, the natural gas in the first gas tank 11 initially has a pressure of P2min or more (here, this is considered to be equal to the pressure (P2) detected by the pressure sensor P2 and the pressure in the first gas tank 11), and as shown in Figure 4, the pressure and filling amount of the natural gas in the first gas tank 11 move toward the origin of the coordinates in Figure 4 (pressure, filling amount) following the line [20[℃]_FUEL(CH4)].

[0062] In addition, the carbon dioxide in the second gas tank initially has a pressure approximately equal to atmospheric pressure (AP: 101.3 kPa), but as the second gas tank 22 is filled with carbon dioxide, the pressure and filling amount of carbon dioxide in the second gas tank 22 have the characteristic of moving away from the origin of the coordinate system along the line [20[℃]_CO2] in the coordinate system (pressure, filling amount) of Figure 4.

[0063] 3 is not executed, the generator 9 will be unable to perform rated power generation when the pressure of the natural gas in the first gas tank 11 falls below P2min, but power generation itself can continue. However, when the pressure and fill amount of the natural gas in the first gas tank 11 finally drops to the coordinates (AP, A2) on the [20[℃]_FUEL(CH4)] line, it will be impossible to extract any more natural gas and generate any more power.

[0064] On the other hand, if step S111 in Fig. 3 is executed and the temperature of the first gas tank 11 (natural gas) becomes 40 degrees, for example, the natural gas in the first gas tank 11 is released while maintaining its pressure, decreasing the filling amount. That is, the pressure and filling amount of the natural gas in the first gas tank 11 decrease along the vertical axis from the coordinate (P2min, A3) on the line of [20[°C]_FUEL(CH4)], and finally move to the coordinate (P2min, A1) on the line of [40[°C]_FUEL(CH4)]. Therefore, during this movement, the natural gas is released at a pressure of P2min, and the generator 9 can continue to generate rated power.

[0065] When the pressure and filling amount of natural gas reach the coordinates (P2min, A1), the vehicle stops running (generating electricity by generator 9). At this time, valve V3 and valve V4 are closed and heater 32 also stops, so the temperature of natural gas returns to room temperature (20 [°C]), and for example, the pressure of natural gas also becomes a value below atmospheric pressure (P2n < AP). That is, the pressure and filling amount of natural gas in the first gas tank 11 move to the coordinates (P2n, A1) on the line of [20 [°C]_FUEL(CH4)].

[0066] Therefore, by executing step S111 in FIG. 3, until the filling amount A1 becomes lower than the minimum value A3 of the filling rate of natural gas at which rated power generation is possible when step S111 is not executed, and the minimum value A2 of the filling rate of natural gas at which minimum power generation is possible when step S111 is not executed, natural gas can be used for rated power generation, increasing the usage amount of natural gas and extending the driving distance of the vehicle.

[0067] [Energy balance during natural gas release] FIG. 5 shows the energy balance when the heat of release generated when releasing natural gas from the first gas tank 11 is supplied from the outside, which is a graph showing the relationship depending on the heat amount that can be supplied from the second gas tank 22 to the first gas tank 11 and the vehicle speed with the carbon dioxide recovery rate as a parameter, and a pie chart showing the ratio of the heat of adsorption of carbon dioxide to the power consumption of the compressor 21.

[0068] As described above, if the carbon dioxide recovery rate is approximately = 83.3 [%] or more, the heat of adsorption / release of methane can be covered by the heat of release / adsorption of carbon dioxide. Therefore, from the perspective of heat balance, if the carbon dioxide recovery rate is the above value or more, it is possible to cover the heat amount to be supplied to the first gas tank 11 when releasing natural gas from the first gas tank 11 with the heat of adsorption of carbon dioxide.

[0069] However, from the perspective of energy balance including power consumption, when filling the second gas tank 22 with carbon dioxide, it is necessary to consider excluding the compression of carbon dioxide by the compressor 21 (power consumption of the compressor 21) and the output of the circulation pump 31 (power consumption).

[0070] In addition, while the natural gas is being released, the vehicle is running, and as the vehicle speed increases, the flow rate of the natural gas, i.e., the amount of heat released when the natural gas is released from the first adsorbent 111, increases. Correspondingly, the power consumption of the compressor 21 increases, and the heat of adsorption when the carbon dioxide is adsorbed by the second adsorbent 222 increases.

[0071] Furthermore, when the vehicle speed increases, the amount of heat (discharged heat) to be supplied to the first gas tank 11 increases, and the heat of adsorption generated in the second gas tank 22 also increases, but the amount of heat to be cooled in the second gas tank 22 also increases in order to suppress a decrease in the efficiency of adsorption of carbon dioxide to the second adsorbent 222. For this reason, it is necessary to achieve a heat balance between the two (bringing the temperature of the first gas tank 11 and the temperature of the second gas tank 22 closer together), and the flow rate of the refrigerant, i.e., the output (power consumption) of the circulation pump 31 increases.

[0072] From the above, the energy balance when natural gas is released from the first gas tank 11 and carbon dioxide is filled into the second gas tank 22 can be calculated as follows. Note that, since the power consumption of the circulation pump 31 is sufficiently smaller than the power consumption of the compressor 21, the influence of the circulation pump 31 is ignored in FIG. 5.

[0073] As shown in FIG. 5, the line showing the energy balance increases in the negative direction as the vehicle speed increases. The line of α=0 shows the energy balance when the heat of carbon dioxide adsorption is not used at all, and is −567 [W] at a vehicle speed of 180 km / h, for example. However, in this case, it is equivalent to not using the compressor 21, and the power consumption of the compressor 21 can be set to zero. Also, in this case, if the amount of heat to be supplied to the first gas tank 11 is entirely provided by the heater 32 (FIG. 2), the heater 32 will consume 567 [W].

[0074] For example, when the carbon dioxide recovery rate α=0.5 and the speed is 180 km / h, the energy balance is −391 [W], and the net amount of heat that can be supplied to the first gas tank 11 is calculated as −391-(−567)=176 [W]. On the other hand, the power consumption of the compressor 21 is calculated as 164 [W]. Therefore, as shown in the pie chart (center) of FIG. 5, the net amount of heat (Heat) supplied to the first gas tank 11 exceeds the power consumption (Comp) of the compressor 21.

[0075] In this case, the amount of heat to be supplied to the first gas tank 11 by the heater 32 (FIG. 2) is 391 W, which is a reduction of ((567-391) / 567)×100=31% compared to the case where the entire amount is supplied by the heater 32.

[0076] For example, when the carbon dioxide recovery rate α=0.9 and the energy balance at a speed of 180 km / h is -250 [W], the net amount of heat that can be supplied to the first gas tank 11 is calculated as -250-(-567)=317 [W]. On the other hand, the power consumption of the compressor 21 is calculated as 295 [W]. Therefore, as shown in the pie chart (right) of FIG. 5, the net amount of heat (Heat) supplied to the first gas tank 11 exceeds the power consumption (Comp) of the compressor 21.

[0077] In this case, the amount of heat to be supplied to the first gas tank 11 by the heater 32 is 391 [W], which is a reduction of ((567-250) / 567)×100=56 [%] compared to the case where the heater 32 supplies the entire amount.

[0078] For example, when the carbon dioxide recovery rate α=0 and the speed is 20 km / h, the energy balance is -63 [W]. When the carbon dioxide recovery rate α=0.5 and the speed is 20 km / h, the energy balance is -43 [W]. As a result, the net amount of heat that can be supplied to the first gas tank 11 is calculated as -43-(-63)=20 [W]. On the other hand, the power consumption of the compressor 21 is calculated as 18 [W]. Therefore, as shown in the pie chart (left) of FIG. 5, the net amount of heat (Heat) supplied to the first gas tank 11 is greater than the power consumption (Comp) of the compressor 21.

[0079] In this case, the amount of heat supplied to the first gas tank 11 by the heater 32 is 43 W, which is a reduction of ((63-43) / 63) x 100 = 32% compared to the case where the entire amount is supplied by the heater 32 (63 W). Therefore, it can be seen that in either case, the energy balance is improved and energy consumption can be reduced compared to the case where carbon dioxide is directly heated by the heater 32 or the like.

[0080] [Control flow when filling natural gas] FIG. 6 is a flow diagram when natural gas is filled into the first gas tank 11 and carbon dioxide is released from the second gas tank 22 in the natural gas adsorption storage system 100 of this embodiment.

[0081] In step S201, the controller 4 closes the valves V1, V3, and V4, and then opens the valve V2. As a result, carbon dioxide starts to be released from the second gas tank 22, and the carbon dioxide is released from the second adsorbent 222, generating released heat (endothermic heat).

[0082] In step S202, the controller 4 starts the circulation pump 31 and detects the temperatures from the temperature sensors T1 and T2. By starting the circulation pump 31, heat exchange between the first gas tank 11 and the second gas tank 22 is started.

[0083] In step S203, the controller 4 opens the valve V3 to start filling the first gas tank 11 with natural gas, and detects the pressure (P2) from the pressure sensor P2. As the first gas tank 11 is filled with natural gas, the natural gas begins to be adsorbed by the first adsorbent 111, which generates heat of adsorption (heat generation). The controller 4 may simultaneously perform steps S201, S202, and S203.

[0084] In step S204, the controller 4 performs control to increase the opening of the valve V2 within a range in which the difference ΔT2 (ΔT2=T2-T1) between the temperature (T2) detected by the temperature sensor T2 and the temperature (T1) detected by the temperature sensor T1 is equal to or less than a predetermined temperature difference (e.g., 10°C). By increasing the opening of the valve V2, the amount of carbon dioxide released from the second adsorbent 222 is increased, and the amount of heat extracted from the first gas tank 11 by the second gas tank 22 is increased by the release.

[0085] In step S205, the controller 4 increases the opening of the valve V3 to increase the flow rate of the natural gas filled into the first gas tank 11.

[0086] In step S206, the controller 4 controls the rotation speed of the circulation pump 31 so that the difference ΔT3 (ΔT3 = T2 - T1) between the temperature (T2) detected by the temperature sensor T2 and the temperature (T1) detected by the temperature sensor T1 is equal to or less than a predetermined temperature difference (e.g., 10 [°C]).

[0087] In step S207, the controller 4 judges whether the pressure (P2) detected by the pressure sensor P2 has reached a predetermined maximum pressure P2max (for example, the pressure detected by the pressure sensor P2 when the pressure in the first gas tank 11 is 3.5 [Mpa]) or whether the temperature (T2) detected by the temperature sensor T2 has reached a predetermined upper limit temperature (T2max, for example, 40 [°C]), and if YES, proceeds to step S208, and if NO, returns to step S204. The judgment (YES) in step S207 is either to judge that the first gas tank 11 is sufficiently filled with natural gas.

[0088] By repeatedly executing the above steps S204, S205, S206, and S207 (NO), natural gas can be rapidly filled into the first gas tank 11 while suppressing the temperature rise of the first gas tank 11, thereby suppressing the decrease in the adsorption capacity of the natural gas to the first adsorbent 111.

[0089] In step S208, the controller 4 closes the valves V1-V4. This ends the filling of the first gas tank 11 with natural gas and the release of carbon dioxide from the second gas tank 22. Meanwhile, the circulation pump 31 remains activated.

[0090] In step S209, the controller 4 determines whether the difference ΔT4 (ΔT4=T2-T1) between the temperature (T2) detected by the temperature sensor T2 and the temperature (T1) detected by the temperature sensor T1 has become equal to or less than a predetermined temperature difference (e.g., 2°C), and if the result is YES, the controller 4 proceeds to S210, and if the result is NO, the controller 4 maintains step S209.

[0091] In step S210, the controller 4 determines that the natural gas has been sufficiently and uniformly adsorbed into the first adsorbent 111, and stops the circulation pump 31.

[0092] [Relationship between rapid filling of natural gas and carbon dioxide capture rate] Figure 7 is a graph showing the relationship between the amount of natural gas filled, the natural gas filling time, and the temperature of the first gas tank 11 when the amount of heat to be extracted from the first gas tank 11 when filling the first gas tank 11 with natural gas is covered by the heat released from carbon dioxide when the carbon dioxide recovery rate is used as a parameter.

[0093] 7, assuming a case where natural gas is rapidly filled into the first gas tank 11 in a short time (e.g., 10 minutes), the carbon dioxide recovery rate was considered to prevent the natural gas from exceeding the upper limit temperature (e.g., 40°C) at which the natural gas can be rapidly adsorbed by the first adsorbent 111 within that time. Note that the recovery rate represents the recovery rate of carbon dioxide from the generator 9 as described above, but is synonymous with the molar ratio of the flow rate of natural gas filled into the first gas tank 11 and the flow rate of carbon dioxide released from the second gas tank 22. In addition, when calculating the temperature of the first gas tank 11, the amount of heat dissipated from the first gas tank 11 to the outside is taken into consideration.

[0094] If the recovery rate α=0, that is, when filling the first gas tank 11 with natural gas and no heat exchange is performed between the first gas tank 11 and the second gas tank 22, it can be seen that about one minute after filling begins, when the filling rate reaches about 10%, the temperature of the first gas tank 11 will reach the upper limit temperature (e.g., 40°C), and any further rapid filling will become difficult.

[0095] When the recovery rate α is 0.75, it can be seen that about 5 minutes after the start of filling, when filling is about 50%, the temperature of the first gas tank 11 reaches the upper limit temperature (e.g., 40°C), and any further rapid filling becomes difficult.

[0096] When the recovery rate α is 0.80, it can be seen that about 9 minutes after the start of filling, when filling is about 90%, the temperature of the first gas tank 11 reaches the upper limit temperature (e.g., 40°C), and any further rapid filling becomes difficult.

[0097] When the recovery rate α is 0.90, the temperature of the first gas tank 11 decreases slowly but monotonically immediately after the start of filling. Even when about 10 minutes after the start of filling, when about 100% filling is completed, the temperature of the first gas tank 11 does not exceed the upper limit temperature (e.g., 40°C). Therefore, it can be seen that rapid filling is fully possible when the recovery rate α is 0.90.

[0098] As mentioned above, if the carbon dioxide recovery rate is 83.3% or more, the curve shown in FIG. 7 does not increase monotonically with the filling time, and rapid filling is considered possible.

[0099] [Effects of the first embodiment] The natural gas adsorption storage system 100 of the first embodiment includes a first gas storage unit (first gas tank 11) filled with a first adsorbent 111 capable of storing and releasing natural gas, and a second gas storage unit (second gas tank 22) filled with a second adsorbent 222 capable of storing and releasing carbon dioxide, and the first gas storage unit (first gas tank 11) and the second gas storage unit (second gas tank 22) are thermally connected to each other.

[0100] According to the above configuration, when natural gas is adsorbed to the first adsorbent 111, heat of adsorption (heat generation) is generated, which reduces the adsorption capacity of the natural gas. In addition, when natural gas is released from the first adsorbent 111, heat of release (endotherm) is generated, which reduces the release capacity of the natural gas. On the other hand, when carbon dioxide is adsorbed to the second adsorbent 222, heat of adsorption (heat generation) is generated, and when carbon dioxide is released from the second adsorbent 222, heat of release (endotherm) is generated. Therefore, by filling the tank with carbon dioxide when releasing natural gas and by releasing carbon dioxide when filling the tank with natural gas, heat exchange between the heat of adsorption generated in the first gas storage unit (first gas tank 11) and the heat of release generated in the second gas storage unit (second gas tank 22), and heat exchange between the heat of release generated in the first gas storage unit (first gas tank 11) and the heat of adsorption generated in the second gas storage unit (second gas tank 22) are possible. Therefore, it is possible to suppress a decrease in the adsorption capacity when the natural gas is adsorbed into the first adsorbent 111, and a decrease in the release capacity when the natural gas is released from the first adsorbent 111. Furthermore, although a flow path (discharge line 2) for supplying carbon dioxide to the second gas storage unit (second gas tank 22) is required, the flow path through which carbon dioxide flows is lighter than the flow path through which cooling water flows since no cooling water is used. As a result, it is possible to realize simple heat exchange and avoid an increase in the weight of the system.

[0101] According to the first embodiment, the first gas storage unit (first gas tank 11) is connected to the gas inlet side of the generator 9, and the second gas storage unit (second gas tank 22) is connected to the gas exhaust side of the generator 9.

[0102] When the generator 9 consumes natural gas, it discharges carbon dioxide. Therefore, the amount of heat required to offset the heat of release generated when discharging natural gas can be provided by the heat of adsorption of carbon dioxide supplied from the generator 9, and a decrease in the ability of discharging natural gas from the first adsorbent 111 can be suppressed. At the same time, the amount of heat required to offset the heat of adsorption generated when filling the carbon dioxide supplied from the generator 9 can be provided by the heat of release of natural gas, and a decrease in the ability of adsorbing carbon dioxide into the second adsorbent 222 can be suppressed. Conversely, the amount of heat required to offset the heat of adsorption generated when filling natural gas can be provided by the heat of release of carbon dioxide through heat exchange, and a decrease in the ability of filling the first adsorbent 111 with natural gas can be suppressed. At the same time, the amount of heat required to offset the heat of release generated when discharging carbon dioxide can be provided by the heat of adsorption of natural gas through heat exchange, and a decrease in the ability of discharging carbon dioxide from the second adsorbent 222 can be suppressed.

[0103] In this embodiment, the system includes a refrigerant flow path (circulation line 3) arranged so that a refrigerant circulates between a first gas storage unit (first gas tank 11) and a second gas storage unit (second gas tank 22), and a circulation pump 31 that circulates the refrigerant, and the first gas storage unit (first gas tank 11) and the second gas storage unit (second gas tank 22) are thermally connected via the refrigerant.

[0104] With the above-described configuration, heat exchange between the first gas storage unit (first gas tank 11) and the second gas storage unit (second gas tank 22) can be performed with a simple configuration.

[0105] In this embodiment, the system includes a branch flow path 23 that branches off from a second gas supply flow path (exhaust line 2) through which carbon dioxide supplied to the second gas storage unit (second gas tank 22) flows and is connected to the second gas storage unit (second gas tank 22), a tank case 231 that forms part of the branch flow path 23 and accommodates the first gas storage unit (first gas tank 11), and a bypass valve (valve V5) that is arranged in the branch flow path 23 and opens and closes the branch flow path 23.

[0106] With the above configuration, the carbon dioxide to be filled into the second gas storage unit (second gas tank 22) can be cooled in advance by heat exchange with the first gas storage unit (first gas tank 11), thereby suppressing a decrease in the adsorption capacity of the carbon dioxide into the second adsorbent 222.

[0107] In this embodiment, a first gas supply valve (valve V4) is arranged in a first gas supply flow path (supply line 1) that supplies natural gas stored in a first gas storage unit (first gas tank 11) to a generator 9, a second gas supply valve (valve V1) is arranged in a second gas supply flow path (discharge line 2) that supplies carbon dioxide discharged from the generator 9 to a second gas storage unit (second gas tank 22), and a second gas supply valve (valve V2) is arranged in the second gas supply flow path (discharge line 2) to pressurize the carbon dioxide discharged from the generator 9. The gas supply system further includes a pressure increasing means (compressor 21) for supplying the carbon dioxide gas to a second gas storage unit (second gas tank 22), a second gas exhaust valve (valve V2) arranged in an external exhaust path (exhaust line 2) for exhausting carbon dioxide from the second gas storage unit (second gas tank 22), a refrigerant flow path (circulation line 3) arranged so that a refrigerant circulates between the first gas storage unit (first gas tank 11) and the second gas storage unit (second gas tank 22), a circulation pump 31 for circulating the refrigerant, and a second gas storage unit (second gas tank 22). a first temperature sensor (temperature sensor T1) that detects the temperature of the refrigerant immediately after it is discharged from a first gas storage unit (first gas tank 22), a second temperature sensor (temperature sensor T2) that detects the temperature of the refrigerant immediately after it is discharged from a first gas storage unit (first gas tank 11), and a control unit (controller 4) that controls a first gas supply valve (valve V4), a second gas supply valve (valve V1), a second gas discharge valve (valve V2), a pressure boosting means (compressor 21), and a circulation pump 31. The control unit (controller 4) controls the generator 9. At startup, the first gas supply valve (valve V4) and the second gas supply valve (valve V1) are opened, the second gas exhaust valve (valve V2) is closed, the pressure boosting means (compressor 21) is driven, the circulation pump 31 is driven, and the output of the circulation pump 31 is controlled so that the temperature difference (T1-T2) between the temperature (T1) detected by the first temperature sensor (temperature sensor T1) and the temperature (T2) detected by the second temperature sensor (temperature sensor T2) is equal to or less than a predetermined temperature difference (ΔT1).

[0108] With the above configuration, natural gas can be released from the first gas storage unit (first gas tank 11) and supplied to the generator 9 while appropriately performing heat exchange between the first gas storage unit (first gas tank 11) and the second storage unit (second gas tank 22), and carbon dioxide discharged from the generator 9 can be filled into the second gas storage unit (second gas tank 22).

[0109] In this embodiment, the system includes a branch flow path 23 that branches off from the second gas supply flow path (discharge line 2) and communicates with a second gas storage unit (second gas tank 22), a tank case 231 that forms part of the branch flow path 23 and houses the first gas storage unit (first gas tank 11), a bypass valve (valve V5) that is arranged in the branch flow path 23 and opens and closes the branch flow path 23, and a third temperature sensor (temperature sensor T0) that detects the temperature of carbon dioxide discharged from the generator 9, and a control unit (controller 4) opens the bypass valve (valve V5) based on the temperature detected by the third temperature sensor (temperature sensor T0).

[0110] With the above configuration, the carbon dioxide to be filled into the second gas storage unit (second gas tank 22) can be cooled in advance by heat exchange with the first gas storage unit (first gas tank 11) based on the temperature detected by the third temperature sensor (temperature sensor T0), thereby suppressing a decrease in the adsorption ability of the carbon dioxide to the second adsorbent 222.

[0111] In this embodiment, the first gas storage unit (first gas tank 11) is provided with a pressure sensor (pressure sensor P2) that detects the pressure of natural gas supplied thereto, and a heater 32 that heats the refrigerant, and the control unit (controller 4) controls the output of the heater 32 and the circulation pump 31 so that the pressure detected by the pressure sensor (pressure sensor P2) is equal to or higher than a predetermined pressure (P2min).

[0112] The above configuration can increase the amount of natural gas that can be released from the first gas storage unit (first gas tank 11). In addition, while the vehicle is running, the heater 32 supplies a heat amount that offsets the heat released from the first gas tank 11, but since heat exchange occurs between the second gas tank 22 and the first gas tank 11, the power consumption of the heater 32 can be reduced accordingly.

[0113] In this embodiment, an external supply valve (valve V3) is disposed in an external supply flow path (supply line 1) that supplies natural gas from the outside to a first gas storage unit (first gas tank 11), a first gas supply valve (valve V4) is disposed in a first gas supply flow path (supply line 1) that supplies natural gas stored in the first gas storage unit (first gas tank 11) to a generator 9, a second gas supply valve (valve V1) is disposed in a second gas supply flow path (discharge line 2) that supplies carbon dioxide discharged from the generator 9 to a second gas storage unit (second gas tank 22), and The device includes a second gas discharge valve (valve V2) arranged in an external discharge path (discharge line 2) for discharging carbon dioxide from a gas storage unit (second gas tank 22), a refrigerant flow path (circulation line 3) arranged so that a refrigerant circulates between the first gas storage unit (first gas tank 11) and the second gas storage unit (second gas tank 22), a circulation pump 31 for circulating the refrigerant, a first temperature sensor (temperature sensor T1) for detecting the temperature of the refrigerant immediately after being discharged from the second gas storage unit (second gas tank 22), and a temperature sensor (temperature sensor T2) for detecting the temperature of the refrigerant immediately after being discharged from the first gas storage unit (first gas tank 11). a pressure sensor P2 that detects the pressure of the natural gas supplied to the generator 9; and a control unit (controller 4) that controls the external supply valve (valve V3), the first gas supply valve (valve V4), the second gas supply valve (valve V1), the second gas exhaust valve (valve V2), and the circulation pump 31. The control unit (controller 4) closes the first gas supply valve (valve V4) and the second gas supply valve (valve V1), opens the second gas exhaust valve (valve V2), and opens the external supply valve (valve V3) to operate the circulation pump 31. While driving the valve, the aperture of the second gas exhaust valve (valve V2) is controlled so that the temperature difference (T2-T1) between the temperature (T1) detected by the first temperature sensor (temperature sensor T1) and the temperature (T2) detected by the second temperature sensor (temperature sensor T2) is equal to or less than a first predetermined temperature difference (ΔT2). Thereafter, the aperture of the external supply valve (valve V3) is controlled, and the output of the circulation pump 31 is controlled so that the temperature difference (T2-T1) is equal to or less than a second predetermined temperature difference (ΔT3). When the pressure detected by the pressure sensor P2 reaches the predetermined pressure (P2max),Or, when the temperature (T2) detected by the second temperature sensor (temperature sensor T2) reaches a predetermined temperature (T2max), the external supply valve (valve V3) and the second gas exhaust valve (valve V2) are closed, and then, when the temperature difference (T2-T1) becomes equal to or less than a third predetermined temperature difference (ΔT4), the circulation pump 31 is stopped.

[0114] With the above configuration, natural gas can be filled into the first gas storage unit (first gas tank 11) while properly performing heat exchange between the first gas storage unit (first gas tank 11) and the second storage unit (second gas tank 22), and carbon dioxide can be released from the second gas storage unit (second gas tank 22).

[0115] [Second embodiment] Fig. 8 is a cross-sectional view (vertical direction) of the first gas tank 11 (second gas tank 22) in the natural gas adsorption storage system 100 of the second embodiment. Fig. 9 is a cross-sectional view (horizontal direction) of the first gas tank 11 (second gas tank 22) in the natural gas adsorption storage system 100 of the second embodiment. Fig. 10 is a schematic diagram showing the flow path of the refrigerant flow path (circulation line 3) in the natural gas adsorption storage system 100 of the second embodiment.

[0116] In the following embodiments, components common to the first embodiment are denoted by the same reference numerals, and their description will be omitted unless necessary. Also, the control in the following embodiments is similar to that in the first embodiment, and therefore the description will be omitted.

[0117] As shown in Fig. 8, in the second embodiment, the first gas tank 11 is divided into a plurality (10) of tubular compartments. As shown in Fig. 8, each compartment has a substantially rectangular cross section. Then, each compartment is filled with a first adsorbent 111 to form a plurality (10, only five are shown in Fig. 9) of first gas storage sections 5A-5J.

[0118] In the center of the first gas storage unit 5A-5J, a first distribution channel 51 is formed through which natural gas flows along the longitudinal direction (horizontal direction) of the tube. As natural gas flows through this first distribution channel 51, the natural gas diffuses from the first distribution channel 51 to the first adsorbent 111 and is adsorbed by the first adsorbent 111. In addition, the natural gas released from the first adsorbent 111 is guided to the first distribution channel 51 and released to the outside of the first gas tank 11.

[0119] 9, the first flow passages 51 can be connected in series with adjacent other first flow passages 51, thereby connecting the first gas storage units 5A-5J in series with respect to the first flow passages 51. Note that it is also possible to connect some or all of the first flow passages 51 in parallel.

[0120] The first gas tank 11 also has a first refrigerant flow path 33 through which the refrigerant flows. The first refrigerant flow path 33 constitutes the circulation line 3. For example, as shown in FIG. 9, a large number of first refrigerant flow paths 33 are formed inside the walls forming the compartments, and are adjacent to the first gas storage units 5A-5J so as to be able to exchange heat. Here, the walls forming the compartments (first gas storage units 5A-5J) are formed thick at the positions where the first refrigerant flow paths 33 are formed, and are formed thin at other portions. As shown in FIG. 8, the first refrigerant flow paths 33 are disposed at positions facing the corners of the compartments, but may be disposed at positions facing the centers of the sides of the compartments. Furthermore, the first refrigerant flow paths 33 may be formed at the centers of the compartments (first gas storage units 5A-5J) in the same manner as the first circulation path 51. In the following description, for example, the "first refrigerant flow path 33 adjacent to the first gas storage unit 5A" will be expressed as the "first refrigerant flow path 33 disposed in the first gas storage unit 5A".

[0121] As shown in Fig. 8, the second gas tank 22 has a structure similar to that of the first gas tank 11. The second gas tank 22 is divided into a plurality (10) of tubular compartments. A plurality (10, only five are shown in Fig. 9) of second gas storage sections 6A-6J are formed by filling each compartment with a second adsorbent 222. Similarly to the first gas tank 11, a second flow path 61 and a second refrigerant flow path 34 are also formed.

[0122] As shown in FIG. 10, in the first gas tank 11, the first refrigerant flow path 33 has the first gas storage unit 5J as the refrigerant inlet and the first gas storage unit 5I as the refrigerant outlet, and is arranged so as to pass through the first gas storage unit 5J, the first gas storage unit 5E, the first gas storage unit 5D, the first gas storage unit 5C, the first gas storage unit 5B, the first gas storage unit 5A, the first gas storage unit 5F, the first gas storage unit 5G, the first gas storage unit 5H, and the first gas storage unit 5I in that order, all in series.

[0123] As shown in FIG. 10, in the second gas tank 22, the second refrigerant flow path 34 has the second gas storage section 6D as the refrigerant inlet and the second gas storage section 6E as the refrigerant outlet, and is arranged so as to pass through the second gas storage section 6D, the second gas storage section 6C, the second gas storage section 6B, the second gas storage section 6A, the second gas storage section 6F, the second gas storage section 6G, the second gas storage section 6H, the second gas storage section 6I, the second gas storage section 6J, and the second gas storage section 6E in that order, all in series.

[0124] The first refrigerant flow path 33 and the second refrigerant flow path 34 are connected by a first connection flow path 37 and a second connection flow path 38 which constitute the circulation line 3. The first connection flow path 37 connects the upstream end of the first refrigerant flow path 33 and the downstream end of the second refrigerant flow path 34, and a temperature sensor T1, a circulation pump 31, and a heater 32 are disposed in the first connection flow path 37. The second connection flow path 38 connects the downstream end of the first refrigerant flow path 33 and the upstream end of the second refrigerant flow path 34, and a temperature sensor T2 is disposed in the second connection flow path 38.

[0125] In Figure 10, the first flow path 51 (not shown in Figure 10) in the first gas tank 11 is connected arbitrarily, but the first gas storage section 5A at the lower right of the first gas tank 11 in the figure is the most upstream of the first flow path 51, and the first gas storage section 5J at the upper left of the figure is the most downstream of the first flow path 51.

[0126] Similarly, in Figure 10, the second flow path 61 (not shown) in the second gas tank 22 is connected arbitrarily, but the second gas storage section 6J in the upper left of the figure of the second gas tank 22 is the most upstream of the second flow path 61 (not shown), and the second gas storage section 6A in the lower right of the figure is the most downstream of the second flow path 61 (not shown).

[0127] Here, the first connection flow path 37 is connected to the first refrigerant flow path 33 arranged in the first gas storage unit 5J. That is, in the first gas tank 11, the first refrigerant flow path 33 is arranged such that the first gas storage unit 5J is the most upstream.

[0128] As described above, the heat of adsorption / heat of desorption of ethane, propane, and butane (hereinafter referred to as butane, etc.) is higher than the heat of adsorption / heat of desorption of methane. Therefore, butane, etc. is more easily adsorbed by and more difficult to desorb from the first adsorbent 111 than methane.

[0129] For example, when natural gas is filled into the first gas tank 11 as shown in Fig. 10, butane and the like are intensively adsorbed into the first gas storage section 5J, and a large amount of adsorption heat is generated in the first gas storage section 5J. However, when natural gas is filled into the first gas tank 11, carbon dioxide is released from the second gas tank 22, and the refrigerant is cooled by the heat released at that time. Therefore, the refrigerant is first supplied to the first refrigerant flow path 33 arranged in the first gas storage section 5J in the first gas tank 11, so that the heat of adsorption generated in the first adsorbent 111 by the low-temperature refrigerant can be efficiently extracted, and a decrease in the adsorption efficiency of butane and the like can be suppressed.

[0130] Conversely, when releasing natural gas from the second gas tank 22, a large amount of heat is required to release butane, etc. from the first gas storage unit 5J. However, when releasing natural gas from the first gas tank 11, the second gas tank 22 is filled with carbon dioxide, and the refrigerant is heated by the heat of adsorption at that time. Therefore, since the refrigerant is first supplied to the first refrigerant flow path 33 arranged in the first gas storage unit 5J in the first gas tank 11, the high-temperature refrigerant can efficiently cover the amount of heat required to release butane, etc. from the first adsorbent 111, and a decrease in the release efficiency of butane, etc. can be suppressed.

[0131] [Modification of the second embodiment] FIG. 11 is a schematic diagram showing a modified example of the flow path of the refrigerant flow passage in the natural gas adsorption storage system 100 according to the second embodiment.

[0132] As shown in FIG. 11, the first refrigerant flow path 33 is arranged in the first gas tank 11, with the first gas storage unit 5J as the refrigerant inlet and the first gas storage unit 5F as the refrigerant outlet, and passing through the first gas storage unit 5J, the first gas storage unit 5E, the first gas storage unit 5D, the first gas storage unit 5C, the first gas storage unit 5B, the first gas storage unit 5A, and the first gas storage unit 5F in that order in series.

[0133] Furthermore, a third refrigerant flow path 35 is arranged in the first gas tank 11. The third refrigerant flow path 35 is arranged in the first gas tank 11 such that the first gas storage unit 5I serves as a refrigerant inlet and the first gas storage unit 5G serves as a refrigerant outlet, and the third refrigerant flow path 35 passes through the first gas storage unit 5I, the first gas storage unit 5H, and the first gas storage unit 5G in this order in series.

[0134] Correspondingly, the circulation line 3 branches into two, for example, at a position between the heater 32 and the first gas tank 11, one of which is connected to a first refrigerant flow path 33 arranged in the first gas storage unit 5J, and the other of which is connected to a third refrigerant flow path 35 arranged in the first gas storage unit 5I.

[0135] In addition, the circulation line 3 branches into two at a position between the temperature sensor T2 and the first gas tank 11, one of which is connected to a first refrigerant flow path 33 arranged in the first gas storage unit 5F, and the other of which is connected to a third refrigerant flow path 35 arranged in the first gas storage unit 5G.

[0136] The third refrigerant flow path 35 has a shorter path length than the first refrigerant flow path 33. Therefore, the amount of heat exchange differs between the downstream vicinity of the first refrigerant flow path 33 and the downstream vicinity of the third refrigerant flow path 35, and the temperatures therebetween differ. Therefore, in FIG. 11, at least the temperatures of the first gas storage unit 5F and the first gas storage unit 5G differ from each other. By forming refrigerant flow paths with different path lengths in this way, it is possible to form an arbitrary temperature distribution in the first gas tank 11. A similar configuration is also possible for the second gas tank 22.

[0137] [Effects of the second embodiment] According to the second embodiment of the natural gas adsorption storage system 100, a plurality of first gas storage units 5A-5J are arranged in series to form a distribution path (first distribution path 51) through which natural gas flows, and a portion (first connection flow path 37) of the refrigerant flow path (circulation line 3) that supplies the refrigerant discharged from the second gas storage unit 6A-6J to the first gas storage unit 5A-5J is connected to the first gas storage unit 5J among the first gas storage units 5A-5J that is arranged furthest upstream of the distribution path (first distribution path 51).

[0138] With the above-described configuration, it is possible to suppress a decrease in the adsorption efficiency and the release efficiency of butane and the like contained in natural gas, and to effectively utilize butane and the like.

[0139] Furthermore, according to a modified example of this embodiment, the refrigerant flow path (first refrigerant flow path 33, third refrigerant flow path 35) branches into multiple paths in at least one of the first gas storage section 5A-5J and the second gas storage section 6A-6J, and the branched refrigerant flow paths (first refrigerant flow path 33, third refrigerant flow path 35) have different lengths.

[0140] This makes it possible to form an arbitrary temperature distribution in the first gas tank 11 and / or the second gas tank 22.

[0141] [Third embodiment] Fig. 12 is a schematic diagram of the first gas tank 11 in the natural gas adsorption storage system 100 of the third embodiment. Fig. 13 is a schematic diagram showing the flow path of the refrigerant flow path (circulation line 3) in the natural gas adsorption storage system 100 of the third embodiment.

[0142] As shown in Fig. 12, in the third embodiment, the structure of the first gas tank 11 is similar to that of the second embodiment, but the fourth refrigerant flow path 36 is disposed adjacent to the first gas storage unit 5J. In Fig. 12, for example, the fourth refrigerant flow path 36 is disposed adjacent to the four corners of the first gas storage unit 5J, but the fourth refrigerant flow path 36 may be disposed in the center of the first gas storage unit 5J similarly to the first circulation path 51. In the following, for example, "the fourth refrigerant flow path 36 adjacent to the first gas storage unit 5J" will be expressed as "the fourth refrigerant flow path 36 disposed in the first gas storage unit 5J".

[0143] The fourth refrigerant flow path 36 is set to have a smaller diameter than the first refrigerant flow path 33 (and the second refrigerant flow path 34).

[0144] 13, the fourth refrigerant flow path 36 is branched off from the first refrigerant flow path 33, except for the circulation pump 31. The circulation pump 31 is disposed in the second connection flow path 38, and the second gas tank 22 side is the refrigerant output direction.

[0145] As shown in Fig. 13, the fourth refrigerant flow path 36 branches off from the second refrigerant flow path 34 at the second gas storage section 6D, and is arranged so as to pass through the second gas storage section 6D, the second gas storage section 6C, the second gas storage section 6B, the second gas storage section 6A, the second gas storage section 6F, the second gas storage section 6G, the second gas storage section 6H, the second gas storage section 6I, the second gas storage section 6J, and the second gas storage section 6E in this order in series, in the same manner as the second refrigerant flow path 34. The fourth refrigerant flow path 36 then extends from the second gas storage section 6E to the outside of the second gas tank 22 and connects to the first gas storage section 5J of the first gas tank 11 via the heater 32. After that, the fourth refrigerant flow path 36 extends from the first gas storage section 5J only via the first gas storage section 5J, and merges with the second connection flow path 38 at a position between the temperature sensor T2 of the second connection flow path 38 and the circulation pump 31, for example.

[0146] In addition, the fourth refrigerant flow path 36 may branch off from the second connection flow path 38 at a position on the output side of the circulation pump 31 of the second connection flow path 38, and may also merge with the first refrigerant flow path 33 arranged in the first gas storage section 5I.

[0147] The first refrigerant flow path 33 is arranged in the first gas tank 11, with the first gas storage unit 5E as the refrigerant inlet and the first gas storage unit 5I as the refrigerant outlet, passing through the first gas storage unit 5E, the first gas storage unit 5D, the first gas storage unit 5C, the first gas storage unit 5B, the first gas storage unit 5A, the first gas storage unit 5F, the first gas storage unit 5G, the first gas storage unit 5H, and the first gas storage unit 5I in that order.

[0148] As shown in FIG. 12, in the first gas tank 11, the first refrigerant flow path 33 has the first gas storage section 5A-5J as the object of heat exchange, and the fourth refrigerant flow path 36 has the first gas storage section 5J as the object of heat exchange.

[0149] As described above, the fourth refrigerant flow path 36 is designed to have a smaller diameter than the second refrigerant flow path 34. Therefore, in the second gas tank 22, the fourth refrigerant flow path 36 is heated / cooled more than the second refrigerant flow path 34.

[0150] Therefore, when natural gas is filled into the first gas tank 11, carbon dioxide is released from the second gas tank 22, and the heat released at this time causes the refrigerant in the fourth refrigerant flow path 36 to be cooled more than the refrigerant in the second refrigerant flow path 34. Therefore, the refrigerant cooled by the fourth refrigerant flow path 36 exchanges heat with the first gas storage section 5J, so that the adsorption heat generated in the first adsorbent 111 can be efficiently extracted and a decrease in the adsorption efficiency of butane and the like can be suppressed.

[0151] Conversely, when natural gas is released from the first gas tank 11, the second gas tank 22 is filled with carbon dioxide, and due to the heat of adsorption generated at that time, the refrigerant in the fourth refrigerant flow path 36 is heated more than the refrigerant in the second refrigerant flow path 34. Therefore, the refrigerant heated by the fourth refrigerant flow path 36 exchanges heat with the first gas storage section 5J, so that the amount of heat required to release butane, etc. from the first adsorbent 111 can be efficiently supplied, and a decrease in the release efficiency of butane, etc. can be suppressed.

[0152] Furthermore, since the fourth refrigerant flow path 36 has a smaller diameter than the first refrigerant flow path 33 and the second refrigerant flow path 34, the heat capacity is accordingly smaller; however, since the only object of heat exchange in the first gas tank 11 is the first gas storage section 5J, heat exchange can be performed sufficiently.

[0153] [Effects of the third embodiment] According to the third embodiment of the natural gas adsorption storage system 100, a plurality of first gas storage units 5A-5J are arranged in series to form a distribution path (first distribution path 51) through which natural gas flows, and are provided with a branched refrigerant flow path (fourth refrigerant flow path 36) that branches off from the refrigerant flow path (circulation line 3, first refrigerant flow path 33, second refrigerant flow path 34) and has a smaller diameter than the refrigerant flow path (circulation line 3, first refrigerant flow path 33, second refrigerant flow path 34), and the branched refrigerant flow path (fourth refrigerant flow path 36) is connected to the second gas storage unit 6A-6J, and a portion of the branched refrigerant flow path (fourth refrigerant flow path 36) that supplies the refrigerant discharged from the second gas storage unit 6A-6J to the first gas storage unit 5A-5J side is connected to the first gas storage unit 5J that is arranged most upstream of the distribution path (first distribution path 51) among the first gas storage units 5A-5J.

[0154] With the above configuration, the refrigerant supplied through the branched refrigerant flow path (fourth refrigerant flow path 36) suppresses the decrease in adsorption efficiency and release efficiency of butane and the like contained in natural gas, thereby enabling effective use of butane and the like.

[0155] [Fourth embodiment] Fig. 14 is a block diagram for simply explaining a natural gas adsorption storage system 100 of the fourth embodiment. In the fourth embodiment, a plurality of first gas storage sections 5A-5E and second gas storage sections 6A-6E are formed in one gas tank 10. The structure of the gas tank 10 is similar to that shown in Fig. 8, but the lower five compartments in the figure are filled with the first adsorbent 111, and the upper five compartments are filled with the second adsorbent 222.

[0156] Supply line 1 (first flow path 51 (FIG. 8) in gas tank 10) is arranged, for example, to pass through first gas storage units 5A-5E in series. Discharge line 2 (second flow path 61 (FIG. 8) in gas tank 10) is arranged, for example, to pass through second gas storage units 6A-6E in series.

[0157] The circulation line 3 has, for example, a refrigerant inlet and outlet at a position in the gas tank 10 that communicates with the first gas storage section 5A, and is arranged to pass through the first gas storage section 5A, the second gas storage section 6A, the second gas storage section 6B, the second gas storage section 6C, the second gas storage section 6D, the second gas storage section 6E, the first gas storage section 5E, the first gas storage section 5D, the first gas storage section 5C, the first gas storage section 5B, and the first gas storage section 5A in that order.

[0158] The gas tank 10 is made of a material having high thermal conductivity, such as aluminum, stainless steel, etc. Therefore, heat exchange between the first gas storage sections 5A-5E and the second gas storage sections 6A-6E is possible through at least one wall surface of the compartments of the gas tank 10.

[0159] 14, efficient heat exchange is possible between the first gas storage section 5A and the second gas storage section 6A, between the first gas storage section 5B and the second gas storage section 6B, between the first gas storage section 5C and the second gas storage section 6C, between the first gas storage section 5D and the second gas storage section 6D, and between the first gas storage section 5E and the second gas storage section 6AE. Therefore, if sufficient heat exchange can be performed through the wall surfaces, the circulation line 3 (circulation pump 31) can be omitted.

[0160] [Effects of the fourth embodiment] According to the natural gas adsorption storage system 100 of the fourth embodiment, a part of the outer wall of the first gas storage unit 5A-5E and a part of the second gas storage unit 6A-6E are connected to each other, so that the first gas storage unit 5A-5E and the second gas storage unit 6A-6E are thermally connected to each other. This enables heat exchange without using a refrigerant.

[0161] [Fifth embodiment] Fig. 15 is a block diagram for simply explaining a natural gas adsorption storage system 100 of the fifth embodiment. The fifth embodiment is similar to the fourth embodiment, but the first gas storage units 5A-5E and the second gas storage units 6A-6E are arranged in a staggered manner in the gas tank 10 (storage facility). Of course, it is not necessary for all of them to be arranged in a staggered manner, and at least one of the first gas storage units 5A-5E and the second gas storage units 6A-6E may be alternately replaced, for example, the first gas storage unit 5C and the second gas storage unit 6C in Fig. 14 may be replaced.

[0162] The supply line 1 (first flow path 51 (FIG. 8) in the gas tank 10) has a zigzag path in the gas tank 10 so as to serially pass through the first gas storage units 5A-5E. Similarly, the discharge line 2 (second flow path 61 (FIG. 8) in the gas tank 10) has a zigzag path in the gas tank 10 so as to serially pass through the second gas storage units 6A-6E.

[0163] The circulation line 3 is arranged, for example, to pass through the first gas storage section 5A, the second gas storage section 6A, the first gas storage section 5B, the second gas storage section 6C, the first gas storage section 5D, the second gas storage section 6E, the first gas storage section 5E, the second gas storage section 6D, the first gas storage section 5C, the second gas storage section 6B, and the first gas storage section 5A in that order.

[0164] With this arrangement, for example, the first gas storage unit 5C can exchange heat with the three wall surfaces surrounding the first gas storage unit 5C, i.e., the second gas storage unit 6B, the second gas storage unit 6C, and the second gas storage unit 6D. Therefore, even in this embodiment, if heat exchange through the wall surfaces can be sufficiently performed, the circulation line 3 (circulation pump 31) can be omitted.

[0165] [Effects of the fifth embodiment] According to the fifth embodiment of the natural gas adsorption storage system 100, a storage facility (gas tank 10) is provided that houses the first gas storage unit 5A-5E and the second gas storage unit 6A-6E, and the first gas storage unit 5A-5E and the second gas storage unit 6A-6E are arranged in a plurality of units in the storage facility (gas tank 10), and at least one of the first gas storage unit 5A-5E and the second gas storage unit 6A-6E are arranged alternately (staggered) in the storage facility (gas tank 10), and the first gas storage unit 5A-5E and the second gas storage unit 6A-6E are in contact with each other, so that the first gas storage unit 5A-5E and the second gas storage unit 6A-6E are thermally connected to each other. This makes it possible to efficiently perform heat exchange without using a refrigerant.

[0166] [Adsorbent structure] Fig. 16 is a diagram showing the structure of an adsorbent. Fig. 17A is a diagram showing a modified example of the structure of the adsorbent (before synthesis). Fig. 17B is a diagram showing a modified example of the structure of the adsorbent (after synthesis). The first adsorbent 111 and the second adsorbent 222 are formed of, for example, a metal-organic framework as described above, and as shown in Fig. 16, have a shape obtained by solidifying particles having a predetermined particle size. Therefore, the filling rate is not very high, and voids exist. The larger the volume of the voids, the lower the adsorption capacity per unit volume.

[0167] Therefore, as shown in Figure 17A, particles with a large average particle size are packed in a planar manner, and particles with a small average particle size are filled into the gaps, thereby forming a layer filled with particles with a large average particle size and particles with a small average particle size, as shown in Figure 17B. By stacking multiple such layers, a first adsorbent 111 or second adsorbent 222 with a high filling rate can be constructed.

[0168] It is also preferable to mix the first adsorbent 111 and the second adsorbent 222 to integrally form a first gas storage section (first adsorbent 111) and a second gas storage section (second adsorbent 222), and to configure a mixed adsorbent having a structure in which the first adsorbent 111 and the second adsorbent 222 have different average particle sizes.

[0169] For example, it is conceivable to fill one of the first gas storage units 5A-5E and the second gas storage units 6A-6E (or all of them) in the gas tank 10 shown in Fig. 14 or 15 with the mixed adsorbent. In this case, a three-way valve is disposed before and after the flow path constituting the storage unit, and the three-way valve is driven so that when filling the storage unit with natural gas, the flow path communicates with the first flow path 51 (Fig. 8) through which natural gas flows, and when filling the storage unit with carbon dioxide, the flow path communicates with the second flow path 61 (Fig. 8) through which carbon dioxide flows.

[0170] As a result, the heat of adsorption generated in the first adsorbent 111 by the filled natural gas can be used as the heat required when releasing carbon dioxide from the second adsorbent 222, and the heat of adsorption generated in the second adsorbent 222 by the filled carbon dioxide can be used as the heat required when releasing natural gas from the first adsorbent 111. Therefore, heat exchange on a micro scale is possible without using the circulation line 3 (circulation pump 31), and uniform heat exchange can be performed at least in the storage section.

[0171] Here, the first adsorbent 111 is preferably one that has a greater heat of adsorption / heat of release of methane than that of carbon dioxide, and the second adsorbent 222 is preferably one that has a greater heat of adsorption / heat of release of methane than that of carbon dioxide. This makes it easier for the first adsorbent 111 to adsorb methane than carbon dioxide, and easier for the second adsorbent 222 to adsorb carbon dioxide than methane.

[0172] The first adsorbent 111 may have a large average particle size, and the second adsorbent 222 may have a small average particle size, or vice versa. The average particle sizes may be three or more, not just three large and small. Furthermore, the volume ratio of the first adsorbent 111 and the second adsorbent 222 may be appropriately adjusted so that their adsorption capacities or their total amounts of adsorption heat / release heat are approximately equal.

[0173] This application claims priority based on Japanese Patent Application No. 2020-113046, filed with the Japan Patent Office on June 30, 2020, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0174] 11 Gas Tank No. 1 111 1st adsorbent 22 Second Gas Tank 222 Second adsorbent

Claims

1. a first gas storage unit filled with a first adsorbent capable of storing and releasing natural gas; a second gas storage section filled with a second adsorbent capable of storing and releasing carbon dioxide; a generator that consumes natural gas to generate electricity and emits carbon dioxide; The first gas storage unit and the second gas storage unit are thermally connected to each other; the first gas storage unit is in communication with a natural gas introduction side of the generator; the second gas storage unit is in communication with a carbon dioxide exhaust side of the generator; carbon dioxide discharged from the generator when releasing natural gas from the first gas storage unit to the generator is stored in the second gas storage unit; A natural gas adsorption storage system in which carbon dioxide is released to the outside from the second gas storage section when natural gas supplied from outside is stored in the first gas storage section.

2. a coolant flow path arranged so that a coolant circulates between the first gas storage portion and the second gas storage portion; and a circulation pump that circulates the coolant, The natural gas adsorption storage system according to claim 1 , wherein the first gas storage unit and the second gas storage unit are thermally connected via the refrigerant.

3. The natural gas adsorption storage system according to claim 2 , wherein the refrigerant flow path branches into a plurality of paths in at least one of the first gas storage section and the second gas storage section, and the lengths of the branched refrigerant flow paths are different from each other.

4. The first gas storage unit is arranged in plurality to form a flow path through which the natural gas flows in series, 3. The natural gas adsorption storage system according to claim 2, wherein a portion of the refrigerant flow path that supplies the refrigerant discharged from the second gas storage unit to the first gas storage unit is connected to the first gas storage unit that is located most upstream of the distribution path among the first gas storage units.

5. The first gas storage unit is arranged in plurality so as to form a flow path through which the natural gas flows in series. And, a branch refrigerant flow path that branches off from the refrigerant flow path and has a diameter smaller than that of the refrigerant flow path; 3. The natural gas adsorption storage system of claim 2, wherein the branched refrigerant flow path is connected to the second gas storage section, and a portion of the branched refrigerant flow path that supplies the refrigerant discharged from the second gas storage section to the first gas storage section is connected to the first gas storage section that is located most upstream of the distribution path among the first gas storage sections.

6. a branch flow path branching from a second gas supply flow path through which carbon dioxide supplied to the second gas storage portion flows; a tank case that forms a part of the branch flow path and accommodates the first gas storage portion; The natural gas adsorption storage system according to claim 1 , further comprising: a bypass valve disposed in the branch passage for opening and closing the branch passage.

7. a first gas supply valve disposed in a first gas supply passage that supplies the natural gas stored in the first gas storage unit to the generator; a second gas supply valve disposed in a second gas supply passage that supplies carbon dioxide discharged from the generator to the second gas storage section; a pressure increasing means disposed in the second gas supply passage and configured to increase the pressure of carbon dioxide discharged from the generator and supply the carbon dioxide to the second gas storage section; a second gas exhaust valve disposed in an external exhaust path for exhausting carbon dioxide from the second gas storage portion; a refrigerant flow path arranged so that a refrigerant circulates between the first gas storage portion and the second gas storage portion; A circulation pump that circulates the refrigerant; a first temperature sensor that detects a temperature of the refrigerant immediately after it is discharged from the second gas storage section; a second temperature sensor that detects the temperature of the refrigerant immediately after it is discharged from the first gas storage section; a control unit that controls the first gas supply valve, the second gas supply valve, the second gas exhaust valve, the pressure boosting means, and the circulation pump, The control unit is When the generator is started, the first gas supply valve and the second gas supply valve are opened, the second gas exhaust valve is closed, and the pressure boosting means is driven.

2. The natural gas adsorption storage system according to claim 1, wherein the output of the circulation pump is controlled while driving the circulation pump so that the temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is equal to or less than a predetermined temperature difference.

8. a branch flow path branching from the second gas supply flow path and communicating with the second gas storage portion; a tank case that forms a part of the branch flow path and accommodates the first gas storage portion; a bypass valve disposed in the branch passage and configured to open and close the branch passage; and a third temperature sensor that detects the temperature of the carbon dioxide discharged from the generator. The control unit is 8. The natural gas adsorptive storage system according to claim 7, wherein the bypass valve is opened based on a temperature detected by the third temperature sensor.

9. a pressure sensor that detects the pressure of the natural gas supplied to the first gas storage unit; a heater for heating the refrigerant; The control unit is 9. The natural gas adsorptive storage system according to claim 7, wherein outputs of the heater and the circulating pump are controlled so that the pressure detected by the pressure sensor is equal to or higher than a predetermined pressure.

10. an external supply valve disposed in an external supply passage for supplying natural gas to the first gas storage unit from the outside; a first gas supply valve disposed in a first gas supply passage that supplies the natural gas stored in the first gas storage unit to the generator; a second gas supply valve disposed in a second gas supply passage that supplies carbon dioxide discharged from the generator to the second gas storage section; a second gas exhaust valve disposed in an external exhaust path for exhausting carbon dioxide from the second gas storage portion; a refrigerant flow path arranged so that a refrigerant circulates between the first gas storage portion and the second gas storage portion; A circulation pump that circulates the refrigerant; a first temperature sensor that detects a temperature of the refrigerant immediately after it is discharged from the second gas storage section; a second temperature sensor that detects the temperature of the refrigerant immediately after it is discharged from the first gas storage section; a pressure sensor that detects the pressure of the natural gas supplied to the generator; a control unit that controls the external supply valve, the first gas supply valve, the second gas supply valve, the second gas exhaust valve, and the circulation pump, The control unit is closing the first gas supply valve and the second gas supply valve and opening the second gas exhaust valve; opening the external supply valve to drive the circulation pump, and controlling an opening degree of the second gas exhaust valve so that a temperature difference between a temperature detected by the first temperature sensor and a temperature detected by the second temperature sensor is equal to or smaller than a first predetermined temperature difference; Thereafter, the opening degree of the external supply valve is controlled, and the output of the circulating pump is controlled so that the temperature difference becomes equal to or smaller than a second predetermined temperature difference. when the pressure detected by the pressure sensor reaches a predetermined pressure or when the temperature detected by the second temperature sensor reaches a predetermined temperature, the external supply valve and the second gas exhaust valve are closed; 2. The natural gas adsorptive storage system according to claim 1, wherein the circulation pump is stopped when the temperature difference thereafter becomes equal to or smaller than a third predetermined temperature difference.

11. 2. The natural gas adsorption storage system of claim 1, wherein a portion of an outer wall of the first gas storage section and a portion of the second gas storage section are connected to each other, thereby thermally connecting the first gas storage section and the second gas storage section to each other.

12. a storage facility that accommodates the first gas storage unit and the second gas storage unit; The first gas storage unit and the second gas storage unit are A plurality of each of the storage facilities are arranged in the storage facility, At least one of the first gas storage units and the second gas storage units are alternately arranged in the storage facility; 2. The natural gas adsorption storage system of claim 1, wherein the first gas storage unit and the second gas storage unit are in contact with each other, thereby thermally connecting the first gas storage unit and the second gas storage unit to each other.

13. 2. The natural gas adsorptive storage system of claim 1, wherein the first adsorbent and the second adsorbent are metal-organic frameworks.

14. The natural gas adsorption storage system of claim 13, wherein the first gas storage section and the second gas storage section are integrally formed by mixing the first adsorbent and the second adsorbent, and the first adsorbent and the second adsorbent have different average particle sizes.

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