JP7434682B2 - Hydrogen filling system - Google Patents

Description

The present invention relates to a hydrogen filling system for filling hydrogen fuel into a fuel cell vehicle or the like, and particularly relates to a thermal process technology in the hydrogen filling system.

As shown in Figure 1(a), conventional hydrogen stations, in the case of regular-sized fuel cell vehicles (hereinafter referred to as "FCVs"), supply hydrogen gas as fuel to the onboard hydrogen installed in the FCV. Designed, constructed, and constructed as equipment for high-pressure filling up to 70 MPa (G) (or 87.5 MPa (G)) for gas tanks (capacity approximately 155 L in the case of regular car class) (hereinafter referred to as "FCV tanks"). It is in operation.
Currently, the design indicator for this filling is to complete filling up to 70 MPa (G) (or 87.5 MPa (G)) (equivalent to about 5 kg of hydrogen mass) in about 3 minutes.

Generally, in a hydrogen station, the hydrogen gas to be filled is boosted to about 82 MPa (G) (or more) using a pressure boosting means such as a compressor, and is temporarily stored in a high pressure accumulator. Then, an operation is performed in which this high-pressure hydrogen gas is charged into the FCV tank, which is the filling destination, using a differential pressure from the primary side (pressure accumulator).
Currently, due to insufficient demand from the market and the frequency of filling operations being infrequent, batch-type differential pressure filling is performed from a pressure accumulator installed on the primary side, but in the future, full-volume compressors will be used. It is also necessary to consider a gas supply process that is close to continuous operation.

By the way, the filling operation of high-pressure hydrogen gas itself is an unsteady adiabatic compression process with hydrogen gas continuously flowing into the FCV tank, which is a closed space. gas temperature increases. Current FCV tanks use special resins that can withstand high pressure due to their structure, so the upper limit temperature during filling is set at 85° C. for safety reasons due to the heat resistance temperature of the adhesive for fixing them. Currently, in order to complete the filling operation of the FCV tank at 85°C or lower, a mechanism is used in which the hydrogen gas to be filled is pre-cooled to -40°C and then supplied to the FCV tank. Therefore, hydrogen stations are equipped with pre-cooling equipment to cool the high-pressure hydrogen gas. This pre-cooling equipment generally cools the hydrogen gas indirectly to about -40°C using a heat exchanger using a low-temperature fluid generated by -45°C class external refrigeration equipment.

As shown in FIG. 1(a), the pre-cool equipment includes a pre-cooler heat exchanger that exchanges heat between high-pressure hydrogen gas and low-temperature brine, a circuit that circulates brine through the pre-cooler, pre-cool refrigeration equipment that freezes and cools the brine to a predetermined temperature, It consists of the heat removal section, etc.
In conventional hydrogen stations that require such pre-cool refrigeration equipment, that is, an external refrigerator, when filling the FCV tank with hydrogen gas compressed to high pressure using external energy such as electricity, external energy is used again. Because the system is frozen and cooled indirectly, it is a very wasteful system from a thermal process perspective. This pre-cooling refrigeration equipment has an installed capacity of approximately 30 kW at an average hydrogen station for standard-sized FCVs. For this reason, there is room for improvement in the power consumption of auxiliary equipment such as pre-cool refrigerator equipment and air-cooled chillers from the perspective of operating costs of hydrogen stations.

By the way, the present applicant has previously incorporated an expansion turbine 6 as an improved type of pre-cool equipment, as shown in FIG. A new method (expansion turbine method) was proposed (see Patent Document 1).
If this expansion turbine method is planned based on the throughput of an average hydrogen station for ordinary car class FCVs, the mass flow rate of the hydrogen gas to be processed is relatively small, so the expansion turbine itself is very difficult to operate. Due to the small size, there were issues with manufacturing precision and ensuring effective efficiency. Furthermore, since this expansion turbine rotates at a very high speed, the inclusion of a high-speed rotating machine in the system was predicated on ensuring the reliability of the machine.

In addition, a vortex tube (vortex tube device) is used in pre-cooling equipment. Compressed gas is supplied into the tube, the gas is rotated at high speed within the tube, and cold air flows from one end (cold end) in the form of a central flow (secondary swirl flow). The vortex tube is generated at the cold end of the vortex tube by taking out the body and taking out the hot gas flowing in the form of peripheral swirling flow (primary swirling flow) from the other end (hot end) through a throttle valve. A method (vortex tube method) using hydrogen gas as filling gas has been proposed (for example, see Patent Documents 2 and 3).
In the configuration disclosed in Patent Document 2, this vortex tube method requires energy to drive a compressor, etc. to cool and pressurize the hydrogen gas generated at the warm end of the vortex tube and return it to the storage tank. There was an issue.
Furthermore, in the configuration disclosed in Patent Document 3, after the hydrogen gas generated on the warm end side of the vortex tube is cooled, it is used as the filling gas together with the hydrogen gas generated on the cold end side. The problem was that the control method was complicated.
In addition, a proposal has been proposed in which the hot end of the vortex tube is slow-heated and then merges with the filling gas side to fill the tank, but this method does not sufficiently lower the enthalpy (temperature) of the combined gas itself sent to the tank side. There was an issue.

Patent No. 6231245 Publication number 7-50639 Japanese Patent Application Publication No. 2007-309375

As described above, conventional hydrogen stations equipped with pre-cooling equipment have the following problems.
(1) Conventional hydrogen stations (Figure 1(a)) require -45°C class refrigeration equipment, accompanying low-temperature brine piping, and pre-cooled heat exchangers, making the plant equipment complex and expensive. was.
(2) Conventional hydrogen stations (Figure 1(a)) require power from -45°C class refrigeration equipment for plant operation.
(3) In the conventional hydrogen station (FIG. 1(a)), the plant installation area is large and the construction cost is high.
(4) At conventional hydrogen stations (Figure 1(a)), periodic maintenance inspections of -45°C refrigeration equipment are required by law as part of plant maintenance costs.
(5) Conventional hydrogen stations (Figure 1 (a)) have poor scalability (-45℃ refrigerated (The equipment must also have four times the capacity.)
(6) A hydrogen station with an expansion turbine-type high-pressure hydrogen filling system (Figure 1(b)) can solve the above problems (1) to (5), but the average When planning based on the throughput of a hydrogen station, the mass flow rate of the hydrogen gas to be processed is relatively small, so the expansion turbine itself would be extremely small, posing problems in terms of manufacturing and efficiency.
(7) A hydrogen station with an expansion turbine-type high-pressure hydrogen filling system (Figure 1(b)) can solve the above problems (1) to (5), but the expansion turbine rotates at a very high speed. , it was necessary to ensure sufficient reliability to include high-speed rotating machinery within the system.
(8) In the vortex tube method, the hydrogen gas generated at the warm end of the vortex tube is normally operated in a large proportion (30 to 40% of the total), and the temperature drop of the hydrogen gas generated at the cold end is reduced. There is a limit to the amount of gas, and if the hydrogen gas generated at the warm end of the vortex tube is cooled, pressurized, and returned to the storage tank, energy is required to drive the compressor, etc.
(9) In the vortex tube method, the hydrogen gas generated at the warm end of the vortex tube is normally extracted at a high proportion (30 to 40% of the total), and the temperature drop of the hydrogen gas generated at the cold end is reduced. There is a limit to the amount of gas, and if the hydrogen gas generated at the warm end of the vortex tube is cooled and then used as the filling gas together with the hydrogen gas generated at the cold end, the filling gas control method becomes complicated.
(10) A typical vortex tube used in the vortex tube method consists of cold gas flowing in the center flow (secondary swirl flow) inside the vortex tube, and warm gas flowing in the outer circumferential swirl flow (primary swirl flow). As turbulence occurs near the interface with the two, the energy efficiency decreases in the areas where they are in internal contact with each other.
(11) A method has also been proposed in which the hot end gas is cooled using a vortex tube method and then merged with the filling gas again. However, in this method, the enthalpy (temperature) of the gas supplied to the tank after merging is equal to that of the hot single gas. As the temperature rises, it is difficult to keep the temperature below -40°C.
(12) A method has also been proposed in which the hot end gas is cooled using a vortex tube method and then merged with the filling gas again, but in this method, the heat transfer area required for heat reduction is larger than in the present invention. The reason is that the heat transfer coefficient inside the pipe is proportional to the 0.8th power of the flow velocity of the internal fluid, but in a vortex tube, the internal vortex rotates at high speed (1 million rpm), and the inner wall contact While the flow velocity reaches 400 to 600 m/s, the gas flow velocity inside the piping after normal hot gas extraction is at most 20 to 30 m/s, and it is difficult to provide a compact slow heating structure.

In view of the above problems of conventional hydrogen stations equipped with pre-cooling equipment, the present invention provides a hydrogen filling system for filling tanks as fuel for fuel cells, using a vortex tube for cooling hydrogen gas in the pre-cooling equipment. A first object of the present invention is to provide a hydrogen filling system that can reduce the amount of hydrogen gas extracted on the warm end side of the vortex tube.

Further, the present invention provides a hydrogen filling system that can eliminate the decrease in energy efficiency due to turbulence near the interface between the outer circumferential swirl flow (primary swirl flow) and the center flow (secondary swirl flow) of the vortex tube. This is the second purpose.

In order to achieve the above first object, the hydrogen filling system of the present invention includes a pre-cooling facility using a vortex tube for cooling hydrogen gas to be filled into a tank as fuel for fuel cell use. The vortex tube is characterized by being provided with a heat removal means connected to an external cooling means via a heat removal circuit.
That is, the hydrogen filling system of the present invention is suitable for high-pressure hydrogen filling processes at hydrogen stations, etc. by gradually reducing the heat from the vortex tube body (high temperature part), and as a result, lowering the gas temperature at the cold end further than usual. is its biggest feature. In addition, if heat removal of the hot end outlet gas of the vortex tube is performed at a later stage, as in the existing example, not only the slow heat transfer performance will be poor, but also it will be difficult to provide a compact heat removal structure. .

In this case, the heat removal means of the vortex tube may include a heat transfer promoting structure.

Furthermore, in order to achieve the second object, the hydrogen filling system of the present invention can be configured such that the vortex tube has a double pipe structure that partitions a center flow and an outer circumferential swirl flow.

Further, a plurality of the vortex tubes may be connected in series.

According to the hydrogen filling system of the present invention, by providing the vortex tube with a heat removal means connected via an external cooling means and a heat removal circuit, the amount of hydrogen gas generated on the warm end side of the vortex tube is reduced. (bleed air amount) can be reduced.

Moreover, energy efficiency can be improved by providing the heat removal means of the vortex tube with a heat transfer promoting structure.

Furthermore, by providing the vortex tube with a double pipe structure that partitions the center flow and the outer circumferential swirl flow, the outer circumference swirl flow (primary swirl flow) and the center flow (secondary swirl flow) of the vortex tube can be separated. It is possible to eliminate the decrease in energy efficiency due to turbulence near the interface and further improve energy efficiency.

Further, by connecting a plurality of the vortex tubes in series, a larger cooling capacity can be obtained.

1 shows a hydrogen station equipped with conventional pre-cooling equipment, (a) is an explanatory diagram showing an example of a hydrogen station equipped with pre-cooling refrigeration equipment, and (b) is an explanatory diagram showing an example of a hydrogen station equipped with an expansion turbine. . BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a first embodiment of a hydrogen filling system equipped with pre-cooling equipment using a vortex tube of the present invention. It is an explanatory view showing an example of the same vortex tube. It is an explanatory view showing a first modification of the same vortex tube. It is an explanatory view showing a second modification of the same vortex tube. FIG. 2 is an explanatory diagram showing a second embodiment of a hydrogen filling system equipped with pre-cooling equipment using a vortex tube of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiments of the hydrogen filling system of the present invention will be described based on the drawings.

2 and 3 show a first embodiment of the hydrogen filling system of the present invention.
This hydrogen filling system consists of a vortex tube 20 (vortex tube device) for cooling hydrogen gas to be filled into a tank 5 as fuel for fuel cells. Compressed gas is supplied into the tube, rotated at high speed within the tube, and one end ( Cold gas flowing in the form of a central flow (secondary swirling flow) is extracted from the cold end (cold end) side, and hot gas flowing in the form of an outer swirling flow (primary swirling flow) is taken out from the other end (hot end) through a throttle valve. In a hydrogen filling system equipped with a pre-cooling facility using a vortex tube 20, the vortex tube 20 is provided with a heat removal means 26 connected to an external cooling means 3 via a heat removal circuit. .
That is, this hydrogen filling system is suitable for high-pressure hydrogen filling processes such as hydrogen stations, and heats up directly from the main body (high temperature part) of the vortex tube 20, resulting in lowering the gas temperature at the cold end further than usual. Its biggest feature is that it does.

High-pressure hydrogen gas supplied from the hydrogen gas source 1 is directly led to the inlet port 21 of the vortex tube 20 provided in the vortex tube unit 2, and is converted into a high-speed swirling flow (primary swirling flow) inside the tangential nozzle 24. At the collision point (throttle valve 25 in FIG. 3), the gas is separated into a hot gas component and a center flow (secondary swirl flow) consisting of a cold gas component. The cooled central flow, which has a temperature lower than the inlet temperature, is metered by the metering discharge unit 4 from the outlet port 23 of the vortex tube 20 and then sent to the tank 5 side.
Here, for each filling pressure condition, the outlet port 23 of the vortex tube 20 is adjusted so that the temperature on the tank side satisfies the safe temperature of 85° C. when the tank pressure after filling reaches 70 MPa. Adjust gas temperature.
This adjustment is performed by the throttle valve 25, but in normal filling, the amount of gas (bleeded air amount) discharged from the outlet port 22 on the warm end side of the vortex tube 20 is almost zero (or about several percent). , adjust the throttle valve 25.
Specifically, when applying the vortex tube 20 to a hydrogen station, as shown in FIG. 3, in order to maximize its cooling functionality, as an example, a cooling jacket is installed around the outer periphery of the vortex tube 20 as a heat removal means. 26, and by forcibly cooling and slowing the temperature with chiller water (for example, about 5 to 7°C) flowing through the cooling jacket 26, the temperature at the warm end of the vortex tube 20 can be adjusted by adjusting the throttle valve 25. To make the amount of gas (extracted air amount) discharged from the outlet port 22 almost zero (or about several percent) and to further reduce the temperature of the cold gas component that makes up the central flow (secondary swirl flow). We are making it possible to do so.
In this way, heat is forcibly exchanged with chiller water (cold water) (or cold air) from the tangential nozzle 24 of the vortex tube 20 to the outlet port 22 on the hot end side where the temperature increases, and the heat is gradually removed to the outside. The feature is that it has a circuit.
Here, chiller water (cold water) (or cold air) flowing through the cooling jacket 26 is introduced from the inlet port 26a of the cooling jacket 26, and after exchanging heat, is discharged from the outlet port 26b, and is discharged from the external chiller unit (or The heat is radiated by the cooling means 3 consisting of a cooler unit) and circulated to the inlet port 26a of the cooling jacket 26.
This minimizes gas bleed from the outlet port 22 on the hot end side of the vortex tube 20 (almost zero (or about a few percent)), and at the same time reduces the temperature of the gas discharged from the outlet port 23 on the opposite side. An increase in quantity can be achieved.

In this way, gas bleed from the hot end outlet port 22 of the vortex tube 20 can be minimized (almost zero (or on the order of several percent)), but the minimized hot end outlet When the vortex tube 20 consists of a single-stage vortex tube unit 2 as in this embodiment, the bleed gas from the port 22 is collected in the low-pressure buffer bank of the hydrogen station and sent to the suction side of the hydrogen gas compressor. In a hydrogen station where liquid hydrogen is returned or evaporated for use, this extracted gas can be used as a heat source in the liquid hydrogen evaporator.
Furthermore, as shown in FIG. 5 described later, when the vortex tube unit 2 is composed of two-stage (high pressure stage/low pressure stage) vortex tube units 2A and 2B, the vortex tube unit 2 is a one-stage type vortex tube unit 2, and Although similar processing can be performed, the bleed gas from the outlet port 22 on the hot end side of the vortex tube 20 of the vortex tube unit 2A of the high pressure stage is transferred to the inlet port of the vortex tube 20 of the vortex tube unit 2B of the low pressure stage. 21, it is also possible to mix the gas into the gas supplied from the outlet port 23 of the vortex tube 20 in the high pressure stage.

Here, an advantage of applying this slow heating method to a hydrogen station is that, like air, hydrogen gas has a very high temperature level at the warm end portion of the vortex tube 20 (90° C. or higher). This is because when hydrogen gas expands at room temperature, the temperature of the gas increases due to the Joule-Thompson coefficient. A higher temperature than normal means that heat is more easily removed to the outside, and the gas temperature on the outlet side is lowered by the amount of energy extracted as heat to the outside.

As shown in FIG. 2, the system has a very simple configuration and does not include an expansion turbine that rotates at high speed, so it is possible to reduce costs and improve reliability.
The cooling performance of the vortex tube 20 depends on how the temperature of the gas is raised by the internal swirling vortex flow and how the heat is gradually transferred to the outside. As in the second embodiment of the hydrogen filling system of the invention, it is also possible to use a two-stage (or multi-stage) expansion type in which each vortex tube 20 is operated at an optimal pressure difference.
This vortex method has an extremely simple structure, so it is extremely advantageous in increasing the capacity of the plant. For example, expansion to a hydrogen station for large vehicles (with a flow rate of approximately 4 times or more) can be achieved by incorporating n times the number of vortex tube units, which is much more efficient than the conventional -45℃ refrigeration system. Become an advantage.

In addition, as shown in FIG. 4, a heat transfer promoting mechanism such as a fin structure 27 is added to the cooling outer surface of the vortex tube 20, and as the amount of heat transfer increases, the gas from the outlet port 23 of the vortex tube 20 is temperature drops further.
Here, since the flow velocity inside the tube of the vortex tube 20 is an extremely high-speed eddy flow (usually a flow rate of 400 to 600 m/s), the heat transfer coefficient inside the tube is extremely large, and heat is not transferred to the outside in this part. , it is also advantageous in terms of structure and mechanism.

Furthermore, as shown in FIG. 5, the vortex tube 20 can be provided with a double pipe structure 28 that partitions the center flow and the outer circumferential swirl flow.
This minimizes and optimizes the mutual interference of the opposing swirling flows inside the vortex tube 20, thereby increasing the cooling efficiency of the gas from the outlet port 23 of the vortex tube 20 (temperature rise of the primary flow swirling vortex outside). can be raised).

As above, the hydrogen filling system of the present invention has been explained based on a plurality of examples, but the present invention is not limited to the configurations described in the above examples, and the configurations described in each example may be combined as appropriate. , the configuration may be changed as appropriate without departing from the spirit thereof.

The hydrogen filling system of the present invention uses a vortex tube for cooling hydrogen gas in the pre-cooling equipment in a hydrogen filling system that fills a tank as fuel for fuel cells, and the hydrogen gas generated at the warm end side of the vortex tube. Since it has the property of being able to reduce the amount of gas, it can be suitably used for hydrogen filling equipment such as hydrogen stations.

1 Hydrogen gas source 2 Vortex tube unit 2A Vortex tube unit (high pressure stage)
2B Vortex tube unit (low pressure stage)
20 Vortex tube 21 Inlet port 22 Outlet port (hot end side)
23 Outlet port (cold end side)
24 Tangential nozzle 25 Throttle valve 26 Heat removal means (cooling jacket)
27 Fin structure 28 Double pipe structure 3 Cooling means 4 Fixed amount discharge unit 5 Tank

Claims (4)

In a hydrogen filling system equipped with pre-cooling equipment using a vortex tube to cool hydrogen gas to be filled into a tank as fuel for fuel cells, hydrogen gas is supplied into the tube to the vortex tube, and hydrogen gas is fed into the tube at high speed. The vortex tube is rotated to take out cold gas flowing in a central flow form from one end and hot gas flowing in an outer circumferential swirl form from the other end via a throttle valve. A heat removal means connected to an external cooling means through a heat removal circuit was installed , and by adjusting the opening degree of the throttle valve, the temperature of the hydrogen gas filled into the tank was kept at 85 degrees Celsius or less. A hydrogen filling system featuring: The hydrogen filling system according to claim 1, wherein the heat removal means of the vortex tube includes a heat transfer promoting structure. 3. The hydrogen filling system according to claim 1, wherein the vortex tube has a double pipe structure that partitions a center flow and an outer swirling flow. 4. The hydrogen filling system according to claim 1, wherein a plurality of said vortex tubes are connected in series.

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