JP2014059028A - Gas replacement method and gas replacement apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of shortening time required for replacing the inside of a tank with gas.SOLUTION: A gas replacement method includes: a step (a) for performing several times a supply/exhaust step including a supply step for supplying second-class gas into the tank so that pressure in the tank becomes a predetermined value or more and an exhaust step for exhausting the gas in the tank to the outside after the supply step; and a step (b) for reducing pressure in the tank to a level less than the predetermined value after the step (a). In the step (a), the exhaust step is switched to the supply step at a point of time when an inflection point appears in a graph expressing the pressure in the tank by a vertical axis and lapsed time by a horizontal axis to express a change of the pressure in the tank during execution of the exhaust step.

Description

  The present invention relates to a technique for replacing gas in a tank.

  Conventionally, a technique is known in which the atmosphere in a processing chamber is replaced with an inert gas and then evacuated to replace the processing chamber with hydrogen (for example, Patent Document 1).

JP 2001-289400 A Japanese Patent Laid-Open No. 2000-220795 JP-A-2005-054963

  Here, in recent years, an automobile (fuel cell automobile) having a fuel cell as a drive source has been developed. In addition, a tank filled with hydrogen at a high pressure has been developed as a hydrogen source for fuel cell vehicles. When manufacturing this tank, it is necessary to perform an airtight test (for example, a set test determined by the High Pressure Gas Safety Association) to determine whether or not the tank has airtightness. In this case, it is necessary to replace the inert gas in the tank filled in the airtight test with hydrogen after the test is completed. Further, from the viewpoint of safety, it is desirable that the hydrogen after substitution is of high purity (for example, purity 99.9% or more) and low pressure (for example, 1 MPa or less). For example, when a tank for storing hydrogen at high pressure (a high-pressure hydrogen tank) is assembled to a fuel cell vehicle, the tank internal pressure needs to be 1 MPa or less for safety.

  In existing hydrogen replacement methods, it may take a long time to perform hydrogen replacement that satisfies the above conditions (purity and pressure). For example, in the replacement method using the differential pressure as the driving force, when the differential pressure between the atmospheric pressure and the tank internal pressure becomes small, the release speed for releasing the gas in the tank to the outside decreases.

  The demand as described above is not limited to the technique of replacing the inside of the tank containing the inert gas with hydrogen, but the second type gas different from the first type gas in the tank containing the first type gas. This was a common request for the technology to replace

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, there is provided a gas replacement method for replacing the first type gas stored in the tank with the second type gas so that the pressure in the tank is less than a predetermined value. Provided. In this gas replacement method, (a) a supply step of supplying the second type gas into the tank containing the first type gas so that the pressure in the tank becomes equal to or higher than the predetermined value; A step of performing a plurality of supply / exhaust steps after the supply step, and a step of exhausting the gas in the tank to the outside; (b) after the step (a), the pressure in the tank is The step (a) includes a step of changing the pressure in the tank with the pressure in the tank as the vertical axis and the elapsed time as the horizontal axis during the discharging step. Is switched to the supplying step when an inflection point appears.
According to the gas replacement method of this aspect, since the discharge process can be performed in a range where the gas discharge speed is relatively high, the time for replacing the inside of the tank with the second type gas can be shortened.

(2) In the gas replacement method of the above aspect, in the step (a), at least the tank is heated to increase the temperature in the tank, thereby increasing the internal pressure of the tank above the predetermined value. It may be performed in the state.
According to the gas replacement method of the above aspect, since the supply / discharge process is performed by increasing the internal pressure of the tank, the gas discharge speed in the discharge process using the differential pressure between the atmospheric pressure and the tank internal pressure can be increased. Thereby, the time for replacing the inside of the tank with the second type gas can be further shortened.

(3) In the gas replacement method of the above aspect, the step (b) is a step of reducing the internal pressure of the tank to less than the predetermined value by lowering the temperature in the tank than before the heating. It may be.
According to the gas replacement method of the above aspect, the internal pressure of the tank can be easily made less than the predetermined value by lowering the temperature in the tank.

(4) According to another embodiment, there is provided a gas replacement device that replaces the first type gas accommodated in the tank with the second type gas so that the pressure in the tank becomes less than a predetermined value. Provided. The gas replacement device includes a gas source for storing the second type gas, a supply line for supplying the second type gas stored in the gas source into the tank, and a gas in the tank. A discharge line for discharging, a pressure measuring unit for measuring the pressure in the tank, and a control unit for controlling the operation of the gas replacement device, wherein the control unit controls the pressure in the tank. When the vertical axis represents the elapsed time and the horizontal axis represents the change in pressure in the tank, and when the gas is discharged through the discharge line, an inflection point appears in the graph. Then, switching to the supply of the second type gas using the supply line.
According to the gas replacement device of the other embodiment, the control unit reduces the time for replacing the inside of the tank with the second type gas by discharging the gas in a range where the gas discharge speed is relatively high. it can.

(5) In the gas replacement device of the above aspect, the gas replacement device includes at least a heating unit that heats the tank, and the control unit heats the tank by the heating unit to increase the temperature in the tank. The supply of the second type gas by the supply line and the discharge of the gas by the discharge line may be executed in a state where the internal pressure of the tank is raised above the predetermined value.
According to the gas replacement device of the above aspect, the control unit supplies the second type gas and discharges the gas in a state where the internal pressure of the tank is increased by the heating unit. Thereby, the gas discharge speed using the differential pressure between the atmospheric pressure and the tank internal pressure can be increased. Thereby, the time for replacing the inside of the tank with the second type gas can be further shortened.

(6) In the gas replacement device according to the above aspect, the control unit repeatedly performs the supply of the second type gas and the discharge of the gas, and then stops the heating of the tank by the heating unit. Then, the internal pressure of the tank may be less than the predetermined value by lowering the temperature in the tank.
According to the hydrogen substitution apparatus of the above aspect, the control unit can easily reduce the internal pressure of the tank below a predetermined value by lowering the temperature in the tank.

  The present invention can be realized in various forms. For example, in addition to a gas replacement method and a gas replacement device, a tank manufactured using the gas replacement method and the gas replacement device, and a fuel cell equipped with the tank It can be realized in the form of a vehicle or the like.

It is a figure which shows the mode of gas replacement. It is a flow of the gas replacement method of 1st Embodiment. It is a pressure change graph at the time of using the gas replacement method of this embodiment. It is a pressure change graph at the time of using the gas replacement method of a reference example. It is a figure for demonstrating the gas replacement apparatus of 2nd Embodiment. It is a flow of the gas replacement method of 2nd Embodiment. It is an experimental result using the gas replacement method of this embodiment. It is an experimental result using the gas replacement method of a reference example.

Next, embodiments of the present invention will be described in the following order.
A. First embodiment:
B. Second Embodiment C. Variations:

A. First embodiment:
FIG. 1 is a diagram showing a state of gas replacement. As shown in FIG. 1, the tank 10 includes a tank body 12 and a valve portion 14. The tank 10 is disposed on a fixing base 20 for fixing the position of the tank 10. A discharge line 46 for discharging the gas inside the tank 10 and a supply line 44 for supplying the second type gas are connected to the valve unit 14. Then, by repeatedly supplying the second type gas to the tank 10 using the supply line 44 and discharging the gas in the tank 10 using the discharge line 46, the inside of the tank 10 is filled with the second type gas. Replace. Further, the internal pressure of the tank 10 after replacement with the second type gas is less than 1 MPa. The supply line 44 and the discharge line 46 are each provided with a valve for opening and closing the line. The supply line 44 communicates with a gas source 42 containing the second type gas.

  FIG. 2 is a flow of the gas replacement method of the first embodiment. By this gas replacement method, the first type gas (for example, inert gas) contained in the tank 10 is changed so that the pressure in the tank 10 is less than a predetermined value of 1 MPa (the second type gas ( For example, hydrogen).

  First, a supply / discharge process is performed (step S20). The supply / discharge process is a process in which the supply process into the first type tank 10 using the supply line 44 and the gas discharge process in the tank 10 using the discharge line 46 are repeated. The supplying step is a step of supplying the second type gas into the tank 10 in which the first type gas is accommodated so that the pressure in the tank 10 becomes a first set value that is a predetermined value (1 MPa) or more. is there. The discharging step is a step of discharging the gas in the tank 10 to the outside by a differential pressure between the outside and the internal pressure of the tank 10. The supply / discharge process is a graph ("pressure change graph") representing a change in pressure in the tank 10 with the vertical axis representing the pressure in the tank 10 and the elapsed time representing the horizontal axis during the discharge process. Or in the “pressure change curve”), when the inflection point appears, the supply process is switched. For example, a pressure change graph is calculated by a control device that executes the gas replacement method, and when the inflection point appears, the control device controls the valve to switch from the discharge process to the supply process.

After the inside of the tank 10 is replaced with the second type gas having a predetermined concentration (for example, 99.9% or more) by the supply / discharge process, the pressure reduction process is performed (step S30). The pressure lowering step is a step of reducing the pressure in the tank 10 to be lower than a predetermined value lower than the first set value by continuing the discharging step regardless of the inflection point (step S30). The concentration of the second type gas (for example, hydrogen or helium) in the tank 10 can be calculated using, for example, the following equation (1). The concentration of the second type gas (replacement gas) in the tank 10 can be calculated using a concentration sensor or the like in addition to the calculation using the equation (1).
Formula (1)
M2 = 1− (P1 / P2) × (1−M1) (1)
Here, M1 is the second type gas concentration in the tank before the supply process, M2 is the second type gas concentration in the tank after one supply process, P1 is the tank internal pressure after the supply process, and P2 is It is the tank internal pressure after the discharge process.

  FIG. 3 is a pressure change graph when the gas replacement method of the present embodiment is used. The vertical axis is the pressure in the tank 10, and the horizontal time is the elapsed time. As shown in FIG. 3, when the gas in the tank 10 is being discharged (released), when the inflection point Q1 appears in the pressure change graph (when the pressure P2 is reached), the supply process starts from the discharge process. Switch to. In this pressure change graph, the pressure reduction process is performed after the supply / discharge process consisting of one supply process and one discharge process is repeated five times. Here, the first set value is the pressure P1, and the pressure less than the predetermined value is about atmospheric pressure (0 MPa).

  FIG. 4 is a pressure change graph when the gas replacement method of the reference example is used. In the gas replacement method of the reference example, the supply process is performed until the internal pressure of the tank 10 reaches P1 regardless of the appearance of the inflection point, and then the internal pressure of the tank 10 is close to atmospheric pressure (in this embodiment, 0 MPa). This is a method of replacing the gas in the tank 10 by performing the discharge process until it becomes.

  In the gas replacement method of the reference example, P1 is set to 2 MPa, the supply / exhaust process of 0 MPa to 2 MPa is repeated three times, and the air (first gas) in the tank 10 is helium (second type) with a predetermined concentration. Gas). In this case, the time T1 required for the replacement was about 30 minutes. “Substitution” means that the concentration of the substitution gas in the tank 10 is 99.9% or more.

  On the other hand, in the gas replacement method of this embodiment, P1 is set to 2 MPa, P2 is set to 0.2 MPa, and the supply / exhaust process is repeated five times, and the air (first gas) in the tank 10 is helium having a predetermined concentration. Replaced with (second type gas). Then, the pressure reduction process was performed and the pressure in the tank 10 was set to 0 MPa. In this case, the time T2 required for the replacement is about 10 minutes, and the time required for replacing the gas in the tank 10 and setting the pressure in the tank 10 to 0 MPa as compared with the gas replacement method of the reference example. Was shortened.

  When the gas replacement method of the present embodiment is performed with P2 of 0.4 MPa, the time T2 is 12 minutes. When the gas replacement method of the present embodiment is performed with P2 of 0.2 MPa, the time T2 is 14 minutes. Minutes.

  As described above, in the gas replacement method of the present embodiment, the discharge process is switched to the supply process when an inflection point of the pressure change graph appears. Thereby, since the discharge process can be performed in a range where the gas discharge speed is relatively high, the time for replacing the inside of the tank 10 with the second type gas can be shortened.

B. Second embodiment:
FIG. 5 is a diagram for explaining the gas replacement device of the second embodiment. The gas replacement device 100 includes a control unit 90, a supply / discharge device 40, a heating unit 85, and a gas source 42. The control unit 90 controls operations of the supply / discharge device 40 and the heating unit 85. The gas source 42 is filled with a replacement gas (second type gas) for replacing the inside of the tank 10 at a predetermined pressure (for example, 10 MPa or more). The gas replacement apparatus 100 can also be used when performing the gas replacement method of the first embodiment.

  The supply / exhaust device 40 includes a supply line 44 for supplying the second type gas, which is a replacement gas, to the tank 10, and a discharge line 46 for discharging the gas in the tank 10 to the outside. The supply line 44 supplies the second type gas from the gas source 42 to the tank 10. The discharge line 46 discharges the gas in the tank 10 to the outside. The discharge by the discharge line 46 is performed by the differential pressure between the pressure outside the tank 10 (atmospheric pressure) and the pressure in the tank 10 as in the discharge process of the first embodiment. Further, the downstream side of the supply line 44 and the upstream side of the discharge line 46 are common lines located in the valve unit 14.

  The supply line 44 includes valves 62 and 54, a connection port 83, a supply port 81, a temperature sensor 74, and a pressure sensor 77. The connection port 83 is configured to be able to separate the upstream side and the downstream side of the connection port 83. The supply port 81 is configured to be able to separate the upstream side and the downstream side from the supply port 81. The pressure sensor 77 measures the pressure (internal pressure) in the tank 10 and outputs the measurement result to the control unit 90. The temperature sensor 74 measures the temperature in the tank 10 and outputs the measurement result to the control unit 90.

  The discharge line 46 includes valves 61 and 52, a connection port 84, and a discharge port 82. The connection port 84 is configured to be able to separate the upstream side and the downstream side of the connection port 84. The discharge port 82 is configured to be able to separate the upstream side and the downstream side of the discharge port 82.

  The supply / discharge device 40 further includes a bypass line 86 that connects the supply line 44 and the discharge line 46. The bypass line 86 includes a valve 63 and pressure sensors 71 and 72. Before the supply / discharge device 40 is connected to the tank 10 and the second type gas is supplied and discharged, the valve 63 is opened to connect the supply line 44 and the discharge line 46 with the second type gas. Fill. Note that the bypass line 86 is blocked by the valve 63 when the supply / discharge process is performed.

  The heating unit 85 is configured to be able to heat the tank 10 and the lines (piping) 44 and 46 connected to the tank 10. The heating unit 85 is, for example, a heater. In the present embodiment, the heating unit 85 heats the tank 10 and the supply line 44. Specifically, the inside of the region R1 in FIG. 5 is heated. The control unit 90 receives the signal from the supply / exhaust device 40 and controls the valves 62, 54, 52, 61 to supply the second type gas into the tank 10 and from the tank 10. Control gas emissions.

  FIG. 6 is a flow of the gas replacement method of the second embodiment. By this gas replacement method, the first type gas (in this embodiment, helium) accommodated in the tank 10 is converted into the second type gas (in this embodiment, so that the pressure in the tank 10 is less than 1 MPa. Nitrogen).

  This gas replacement method is executed by the control unit 90. The gas replacement method includes a heating process (step S10). In the heating process, the tank 10 and the supply line 44 are heated by the heating unit 85, and the temperature in the supply line 44 and the tank 10 is higher than room temperature (15 ° C.) (for example, 85 ° C. to 100 ° C.). Let the temperature rise. As the temperature in the tank 10 rises, the pressure in the tank 10 rises due to expansion. For example, the pressure in the tank 10 increases from 0.8 MPa to 1 MPa. In the heating process, at least the temperature in the tank 10 may be increased.

  After step S10, a supply / discharge process is performed (step S20a). The supply / discharge process is a process of repeatedly supplying the second type gas into the tank 10 using the supply line 44 and discharging the gas in the tank 10 using the discharge line 46. Step S20 is performed in a state where the temperature in the supply line 44 and the tank 10 is raised to a temperature higher than room temperature (15 ° C.) (for example, 85 ° C. to 100 ° C.). The supply / discharge process is performed, for example, when the pressure in the tank 10 is in the range of 1 MPa to 3 MPa.

  After the inside of the tank 10 is replaced with the second type gas in step S20, a pressure reduction process is performed (step S30a). The pressure lowering step is a step of setting the pressure in the tank 10 to less than 1 MPa. In the present embodiment, the pressure reduction process is performed by stopping heating by the heating unit 85 and lowering the supply / discharge device 40 and the tank 10 to room temperature (for example, 15 ° C.). By reducing the temperature in the tank 10, the pressure in the tank 10 is reduced to a pressure before heating (before step S10). Thereby, the pressure in the tank 10 can be made less than 1 MPa.

  FIG. 7 shows the experimental results using the gas replacement method of the present embodiment. In this experimental result, helium as the first type gas is accommodated (filled) in the tank 10 before replacement, and this helium is replaced with nitrogen as the second type gas. Details of each step of the gas replacement method are as follows.

  In step S10, the temperature in the supply line 44 and the tank 10 is raised from normal temperature (15 ° C.) to high temperature (range of 85 ° C. to 100 ° C.). As a result, the internal pressure of the tank 10 increases from 0.8 MPa to 1 MPa due to thermal expansion. Next, the supply / discharge process is repeated in the range of 3 MPa to 1 MPa. That is, after step S10, nitrogen is supplied into the tank 10 until the internal pressure becomes 3 MPa. When the internal pressure becomes 3 MPa, the supply process is stopped, and the discharge process is performed until the internal pressure becomes 1 MPa. After the inside of the tank 10 is replaced with nitrogen, a pressure reduction process is performed. That is, by stopping the heating by the heating unit 85 and lowering the inside of the tank 10 to room temperature (15 ° C.), the pressure in the tank 10 is made less than 1 MPa. Note that the temperature in the tank 10 may be lowered by blowing cool air or the like onto the tank 10. As shown in FIG. 7, the time Tp of the supply / discharge process required until the inside of the tank 10 was replaced with helium was about 15 minutes.

  FIG. 8 shows the experimental results using the gas replacement method of the reference example. The gas replacement method of the reference example performs the supply / exhaust process without starting the heating unit 85. That is, the temperature in the tank 10 is set to room temperature (15 ° C.), helium is supplied into the tank 10 until the pressure in the tank 10 reaches approximately 2.5 MPa to 3.0 MPa, and then the pressure in the tank 10 reaches approximately 0 MPa. The gas in the tank 10 is discharged. In the gas replacement method of the reference example, the time Tp of the supply / discharge process required to replace the inside of the tank 10 with helium was about 35 minutes.

  As described above, in the gas replacement method of the second embodiment, the discharge rate is performed in the discharge step performed using the differential pressure inside and outside the tank 10 by performing the supply step with the temperature inside the tank 10 raised. The gas release in the region where the internal pressure of the tank 10 where the pressure becomes low is 1 MPa or less can be omitted. Thereby, the gas replacement time can be shortened.

  In the second embodiment, the time point when the discharge process is switched to the supply process may be the time point when the inflection point of the pressure change graph appears. By so doing, gas replacement can be performed using only the differential pressure with a high discharge rate, and therefore the gas replacement time can be further shortened. In this case, the control unit 90 generates a pressure change graph.

C. Variations:
In addition, elements other than the elements described in the independent claims of the claims in the constituent elements in the embodiment are additional elements and can be omitted as appropriate. Further, the present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist thereof. For example, the following modifications are possible.

C-1. First modification:
In the above embodiment, an example in which nitrogen or helium is used as the replacement gas (second type gas) has been described, but other gases may be used. For example, the present invention can be applied to a case where a high pressure gas tank that has been subjected to an airtight test with an inert gas such as helium is replaced with hydrogen.

DESCRIPTION OF SYMBOLS 10 ... Tank 12 ... Tank main body 14 ... Valve part 20 ... Fixed stand 40 ... Supply / discharge device 42 ... Gas source 44 ... Supply line 46 ... Discharge line 61 ... Valve 62 ... Valve 63 ... Valve 71 ... Pressure sensor 74 ... Temperature sensor 77 ... Pressure sensor 81 ... Supply port 82 ... Discharge port 83 ... Connection port 84 ... Connection port 85 ... Heating part 86 ... Bypass line 90 ... Control part 100 ... Gas displacement device Q1 ... Inflection point

Claims (6)

A gas replacement method for replacing the first type gas stored in the tank with the second type gas so that the pressure in the tank becomes less than a predetermined value,
(A) a supply step of supplying the second type gas into the tank in which the first type gas is accommodated so that a pressure in the tank is equal to or higher than the predetermined value; and after the supply step, A step of discharging the gas in the tank to the outside, and a step of performing a supply and discharge step having a plurality of times,
(B) after the step (a), the step of making the pressure in the tank less than the predetermined value,
The step (a)
In the graph showing the change in pressure in the tank with the pressure in the tank as the vertical axis and the elapsed time as the horizontal axis when performing the discharge step, the supply step when the inflection point appears Switch to the gas replacement method. The gas replacement method according to claim 1,
The gas replacement method, wherein the step (a) is performed in a state where the internal pressure of the tank is raised above the predetermined value by heating at least the tank to raise the temperature in the tank. The gas replacement method according to claim 2,
The gas replacement method, wherein the step (b) is a step of lowering the internal pressure of the tank to less than the predetermined value by lowering the temperature in the tank than before the heating. A gas replacement device that replaces the first type gas stored in the tank with the second type gas so that the pressure in the tank becomes less than a predetermined value,
A gas source containing the second type gas;
A supply line for supplying the second type gas stored in the gas source into the tank in which the first type gas is stored;
A discharge line for discharging the gas in the tank;
A pressure measuring unit for measuring the pressure in the tank;
A control unit for controlling the operation of the gas replacement device,
The controller is
The pressure in the tank is plotted on the vertical axis, the elapsed time is plotted on the horizontal axis, and a graph representing the change in pressure in the tank is generated, and the graph changes when the gas is discharged through the discharge line. A gas replacement device that switches to the supply of the second type gas using the supply line when a bending point appears. The gas replacement device according to claim 4, further comprising a heating unit that heats at least the tank,
The controller is
In the state where the internal pressure of the tank is raised above the predetermined value by heating the tank by the heating unit and increasing the temperature in the tank, the supply of the second type gas by the supply line A gas replacement device that performs the discharge of the gas by the discharge line. The gas replacement device according to claim 5,
The controller is
After repeatedly performing the supply of the second type gas and the discharge of the gas, the heating of the tank by the heating unit is stopped and the temperature in the tank is decreased, thereby reducing the internal pressure of the tank. A gas replacement device that is less than the predetermined value.

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