Gas concentration control device

Abstract

The present invention is provided with: a plurality of gas separators that adjust the concentration of any gas component included in a mixed gas and output the adjusted mixed gas; and a control device that controls the concentration of the gas component of the mixed gas output from the gas separators and the flow rate of the mixed gas in response to a demand from a gas consumer, and detects the occurrence of an abnormality in any of the gas separators. When detecting the occurrence of an abnormality in any of the gas separators, the control device controls the output of the gas separator in which no abnormality has occurred, and uses the mixed gas output by the plurality of gas separators including the gas separator in which the abnormality has occurred to adjust the concentration of the gas component of the mixed gas to be supplied to the gas consumer and the flow rate of the mixed gas so as to satisfy the demand.

Description

Gas concentration control device

[0001] The present invention relates to a gas concentration control device.

[0002] In Europe and other regions, hydrogen is injected into existing gas lines to decarbonize gas consumption. Gas consumers can use either or both existing gases, such as natural gas, and hydrogen gas. Gas concentration control devices used in such grids require equipment to adjust the concentration of the gas used, such as hydrogen concentration, in line with the consumer's demand. However, if a sudden abnormality occurs, such as a malfunction in the gas separation device that separates hydrogen from the mixed gas or a malfunction in other equipment, the gas concentration control device may be unable to control the flow rate and hydrogen concentration of the product gas in line with demand. In other words, there is a concern that the state quantities (flow rate, concentration of gas components) of the mixed gas as the product gas may not be maintained.

[0003] Regarding gas supply and demand, a gas supply system equipped with an integrated supply and demand adjustment device that temporarily limits gas demand when gas supply capacity is temporarily insufficient compared to the amount of gas demand is disclosed in Patent Document 1. Patent Document 1 describes planning the storage amount of gas to be produced late at night when demand is low, stored in holders and gas pipelines, and delivered in the evening when demand increases, as well as the gas pressure in the pipelines for storage.

[0004] JP 2014-203276 A

[0005] As described above, the gas supply system described in Patent Document 1 discloses one of the control means that is effective when the gas supply capacity is insufficient relative to the demand amount. However, in a mixed gas supply system in which hydrogen or the like is injected into an existing gas line, the control means for when not only the supply amount of the mixed gas but also the concentration of any gas component of the mixed gas does not match the demand is not clearly stated.

[0006] In light of the above situation, there was a need for a configuration suitable for controlling the supply amount of mixed gas and the concentration of gas components of the mixed gas when some kind of sudden abnormality occurs and the state quantity of mixed gas supplied to a gas consumer does not match the demand.

[0007] In order to solve the above problems, one embodiment of the present invention provides a gas concentration control device that includes a plurality of gas separation devices that adjust the concentration of any gas component contained in a mixed gas and output the adjusted mixed gas, and a control device that controls the concentration of the gas component in the mixed gas output from the gas separation devices and the flow rate of the mixed gas in accordance with demand from gas consumers and detects the occurrence of an abnormality in the gas separation devices. When the control device detects an abnormality in a gas separation device, it controls the output of a gas separation device that is not experiencing an abnormality, and adjusts the concentration of the gas component in the mixed gas to be supplied to the gas consumer and the flow rate of the mixed gas to meet demand using the mixed gas output from the plurality of gas separation devices, including the gas separation device that has experienced the abnormality.

[0008] According to at least one aspect of the present invention, it is possible to provide a configuration suitable for controlling the supply amount of a mixed gas and the concentrations of gas components of the mixed gas when a sudden abnormality occurs and the state quantity of the mixed gas supplied to a gas consumer does not match the demand. This configuration makes it possible, for example, to minimize the impact of a sudden abnormality on gas consumers. Other problems, configurations, and effects will become clear from the following description of the preferred embodiment of the invention.

[0009] FIG. 1 is a diagram showing an example of the configuration of a gas concentration control device according to a first embodiment of the present invention. FIG. 2 is a diagram showing another example of the configuration of a gas concentration control device according to the first embodiment of the present invention. FIG. 3 is a diagram showing an example of the hardware configuration of a computer provided in the gas concentration control device according to the first embodiment of the present invention. FIG. 4 is a graph showing an example of a change in gas flow rate in the gas concentration control device according to the first embodiment of the present invention. FIG. 5 is a graph showing an example of a change in hydrogen concentration in the gas concentration control device according to the first embodiment of the present invention. FIG. 6 is a graph showing another example of a change in gas flow rate in the gas concentration control device according to the first embodiment of the present invention. FIG. 7 is a graph showing another example of a change in hydrogen concentration in the gas concentration control device according to the first embodiment of the present invention. A flowchart showing the processing flow of the gas concentration control device according to the first embodiment of the present invention. A flowchart showing an example of a procedure for evaluating whether operation can be continued according to the first embodiment of the present invention. A diagram showing an example of a display screen of the gas concentration control device according to a second embodiment of the present invention.

[0010] Hereinafter, examples of modes for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the accompanying drawings. In this specification and the accompanying drawings, common or similar components are given the same reference numerals, and duplicate explanations will be omitted. The number of each component may be singular or plural unless otherwise specified.

[0011] First Embodiment First, the configuration of a gas concentration control device according to a first embodiment of the present invention will be described with reference to Fig. 1. The gas concentration control device according to this embodiment is a device that manages and controls the supply status of existing gas and hydrogen when hydrogen produced by, for example, electrolysis of water using renewable energy or reforming of natural gas is mixed with existing gas and supplied to hydrogen users via a pipeline.

[0012] [Configuration of Gas Concentration Control Device] FIG. 1 is a diagram showing an example of the configuration of a gas concentration control device according to a first embodiment of the present invention. The gas concentration control device 100 shown in FIG. 1 is mainly composed of gas separation devices 1-3, a buffer tank 4, compressors 5-6, regulating valves 7-11, sensors 12-14, a control unit 15, a display device 16, and an input device 17. Generally, the gas concentration control device 100 is installed near a facility 200 that uses a gas consumer's product gas 26, but it may also be installed in a location remote from the facility 200. Note that the configuration of the gas concentration control device 100 is merely an example, and the number of gas separation devices, buffer tanks, regulating valves, and sensors may be changed. For example, the number of gas separation devices may be two or four or more. Furthermore, some of these may be installed external to the gas concentration control device 100.

[0013] Of these, gas separation devices 1 to 3 are devices that extract some gas components from a supply gas 21 (an example of a mixed gas) containing a plurality of different gas components. The different gas components are, for example, natural gas and hydrogen gas. Adjustment valves 7 to 9 are installed upstream of the gas separation devices 1 to 3 in the gas conduits through which the supply gas 21 passes. The gas separation devices 1 to 3 extract any gas component from the supply gas 21, adjust the concentration of the gas component to a target value, and output adjusted gases 23 to 25. When the gas separation devices 1 to 3 are operating normally, the concentrations of the gas components (e.g., hydrogen concentration) in the adjusted gases 23 to 25 output from the gas separation devices 1 to 3 are within a certain range of allowable error.

[0014] The gas concentration control device 100 then supplies a mixed gas obtained by mixing all of the regulated gases 23 to 25 as a product gas 26 to the gas consumer facility 200 via the regulating valve 10. Note that there are various gas separation means for the gas separation device, such as membrane separation and pressure swing separation, but the present invention is not limited to these gas separation means.

[0015] The buffer tank 4 is a tank that stores at least a portion of the product gas 26. The buffer tank 4 stores the product gas 26 that has been pressurized by the compressor 5. By storing the pressurized product gas 26, when the flow rate requested by a gas consumer for the product gas 26 temporarily exceeds the total flow rate of all the regulated gases 23 to 25, the shortfall in the product gas 26 is supplied from the buffer tank 4 via the regulating valve 11. Although the buffer tank 4 is not essential, providing the buffer tank 4 makes it possible to use the product gas 26 in the buffer tank 4 to make up for the shortfall when the flow rate requested by a gas consumer exceeds the maximum flow rate that can be output from the gas separation devices 1 to 3, as described above.

[0016] The buffer tank 4 in the configuration shown in Figure 1 is installed in parallel with a gas conduit that supplies product gas 26, a mixture of uncompressed regulated gases 23-25, to a gas consumer facility 200. The buffer tank 4 can be equipped with sensors that measure one or more of the remaining amount, pressure, temperature, composition, and concentration of the stored gas, and the flow rate of the input and output gases. The measured values ​​of these sensors may be transmitted to the control unit 15. Alternatively, the buffer tank 4 may be installed on the same gas conduit as the gas conduit that carries the product gas 26, as in the configuration shown in Figure 2.

[0017] [Another Configuration of Gas Concentration Control Device] Figure 2 is a diagram showing another example of the configuration of the gas concentration control device 100A according to the first embodiment of the present invention. In the configuration shown in Figure 1, between the gas separation devices 1 to 3 and the gas consumer facility 200, there are a gas conduit having an adjustment valve 10 and a gas conduit having a buffer tank 4. However, in the configuration of the gas concentration control device 100A shown in Figure 2, only a gas conduit having a buffer tank 4 is provided.

[0018] When the buffer tank 4 is disposed on the same gas conduit as the gas conduit carrying the product gas 26, as in the gas concentration control device 100A shown in FIG. 2, the regulating valve 10 and a portion of the gas conduit carrying the mixed gas (bypass portion) are not required, as compared to the configuration shown in FIG. 1. This has the advantage of simplifying the configuration of the gas concentration control device 100A. Furthermore, since the compressor 5 can be continuously operated while the product gas 26 is being supplied to the gas consumer's facility 200, the configuration of the system (including the control program algorithm) for controlling the operation of the compressor 5 can be further simplified. On the other hand, this has the disadvantage that, when the gas consumer's required concentration of each gas component in the product gas 26 fluctuates, it may not be possible to provide gas at the required concentration until the product gas 26 in the buffer tank 4 is depleted.

[0019] 1 can mix the product gas 26 in the buffer tank 4 with the adjusted gases 23-25 ​​output from the gas separation devices 1-3 even when the required concentrations of each gas component in the product gas 26 by the gas consumer fluctuate. This provides the gas concentration control device 100 with the advantage of being able to control the replacement of the product gas 26 in the buffer tank 4 while satisfying the required concentrations.

[0020] Returning to the explanation of FIG. 1 , the compressor 6 is a compressor that pressurizes the residual gas 22, which is the gas remaining in the gas separation units 1 to 3. The residual gas 22 is the difference between the supply gas 21 and the adjusted gases 23 to 25. The residual gas 22 is subjected to processing such as being returned to the pipeline from which the supply gas 21 is supplied, but the present invention does not limit the method for processing the residual gas 22. Furthermore, if it is not necessary to pressurize the gas by the compressor 6 in processing the residual gas 22, the compressor 6 may be omitted.

[0021] The regulating valves 7 to 9 are valves that regulate the flow rate of the supply gas 21 flowing into each of the gas separation devices 1 to 3. The valve opening degrees of the regulating valves 7 to 9 are controlled by a control unit 15. Although the same number of regulating valves 7 to 9 as the number of gas separation devices 1 to 3 are configured in FIG. 1, regulating valves that collectively control the flow rates of gas flowing into a plurality of gas separation devices may also be configured. The present invention does not limit the combination of gas separation devices and regulating valves.

[0022] The regulating valve 10 is a valve that controls the flow rate of the product gas 26. The valve opening degree of the regulating valve 10 is determined by the balance between the gas demand amount of the gas consumer and the total flow rate of the regulating gases 23 to 25. Although arrows are omitted in FIG. 1 for convenience of configuration, the valve opening degree of the regulating valve 10 can be controlled by the control unit 15. The valve opening degree of the regulating valve 10 can also be manually operated by an administrator or remotely controlled by a monitoring center of a gas supply company.

[0023] The regulating valve 11 is a valve that controls the flow rate of the product gas 26 output from the buffer tank 4. As described above, in the configuration of FIG. 1, when the flow rate required by a gas consumer for the product gas 26 temporarily exceeds the total output of all the regulated gases 23 to 25, the regulating valve 11 is opened to supply the shortage of product gas 26 from the buffer tank 4. The valve opening of the regulating valve 11 for supplying the shortage of product gas 26 is controlled by the control unit 15. In the configuration shown in FIG. 2, the regulating valve 11 also serves as the regulating valve 10 shown in FIG. 1.

[0024] The sensors 12 to 14 are devices that measure one or more of the composition, concentration of each gas component, flow rate, pressure, and temperature of the adjusted gases 23 to 25 output from the gas separation devices 1 to 3. The measured values ​​of the sensors 12 to 14 are transmitted to the control unit 15. The control unit 15 can use the measured values ​​of the sensors 12 to 14 to calculate the valve opening and the operation amount of the equipment.

[0025] The control unit 15 (an example of a control device) is a device that controls and monitors the operation variables of the equipment (gas separation device, valves, and other devices) equipped in the gas concentration control device 100, 100A, including the valve opening degrees of the regulating valves 7-11. The control unit 15 controls the flow rate of the mixed gas (regulated gases 23-25) output from the gas separation devices 1-3 and the concentrations of the gas components in the mixed gas according to the demand of gas consumers. The control unit 15 also detects the occurrence of an abnormality in the gas separation devices 1-3. The abnormality detection may be performed for each gas pipeline system. For example, if an abnormality occurs in the regulating valve 7 or the sensor 12, it will hinder the control of the regulated gas 23 output from the gas separation device 1. Therefore, an abnormality occurring in the regulating valve 7 or the sensor 12 may be broadly considered to be an abnormality in the gas separation device 1.

[0026] 1 and 2 for convenience of configuration, the measured values ​​of sensors 12 to 14 may be used to calculate the opening degree of valves and the operation amount of other equipment configured inside gas separation devices 1 to 3. As an example, the equipment is a heater of a gas heat exchanger provided in gas concentration control device 100, 100A. An abnormality in the gas separation device caused by equipment not operating normally is sometimes called an "equipment abnormality."

[0027] Similarly, although omitted for convenience of configuration, measurement values ​​other than those of sensors 12 to 14 may be used to calculate the valve opening and the operation amount of the equipment. Methods such as PID control, model predictive control, and AI (Artificial Intelligence) control can be applied as a method for calculating the valve opening and the operation amount of the equipment in control unit 15. However, the present invention does not limit the method for calculating the valve opening and the operation amount of the equipment.

[0028] The control unit 15 executes the following control when the buffer tank 4 is not used or when there is no remaining mixed gas (product gas 26) in the buffer tank 4. When the control unit 15 detects an abnormality in any of the gas separation devices 1-3, it controls the output of the gas separation device that is not experiencing an abnormality and adjusts the gas component concentration (e.g., hydrogen concentration) and flow rate of the mixed gas (product gas 26) to be supplied to the gas consumer using the mixed gas (adjusted gases 23-25) output from the multiple gas separation devices 1-3, including the gas separation device that has experienced an abnormality, to meet demand. With this configuration, the gas concentration control device 100, 100A of this embodiment can supply a mixed gas (product gas 26) that meets the demand of the gas consumer using the mixed gas output from the gas separation device that is not experiencing an abnormality, without using the mixed gas in the buffer tank 4. This minimizes the impact of a sudden abnormality on the gas consumer.

[0029] Furthermore, when the control unit 15 detects an abnormality in any of the gas separation devices 1-3, it controls the output of the buffer tank 4 and the gas separation device that is not experiencing an abnormality, thereby adjusting the concentration of gas components (e.g., hydrogen concentration) and the flow rate of the mixed gas to be supplied to the gas consumer (product gas 26) to meet demand. With this configuration, the gas concentration control device 100, 100A of this embodiment can supply a mixed gas (product gas 26) that meets the demand of the gas consumer using the mixed gas in the buffer tank 4 and the mixed gas output from the gas separation device that is not experiencing an abnormality. Therefore, the impact on the gas consumer due to a sudden abnormality can be minimized. At least, the product gas 26 stored in the buffer tank 4 can be used within its remaining amount to quickly replenish the shortage of the product gas 26 to be supplied to the gas consumer.

[0030] The display device 16 is a device used to present information to an administrator of the gas concentration control device 100, 100A. The display device 16 displays a GUI (Graphical User Interface) screen, the results of calculation processing by the CPU 31 shown in FIG. 3 (described later), etc. For example, the display device 16 is a liquid crystal display or a display unit of a terminal such as a smartphone or tablet.

[0031] The input device 17 is a device used by an administrator of the gas concentration control devices 100 and 100A to input management information and commands to the gas concentration control devices 100 and 100A. The input device 17 generates an input signal in response to an operation by the administrator and outputs the signal to the CPU 31. For example, the input device 17 is a keyboard, a mouse, a joystick, a touch panel, or the like.

[0032] [Hardware Configuration of Gas Concentration Control Device] Fig. 3 is a diagram showing an example of the hardware configuration of a computer included in the gas concentration control device 100, 100A according to the first embodiment. A calculator 30 shown in Fig. 3 is an example of hardware used as a computer. In the gas concentration control device 100, 100A, the calculator 30 (computer) executes a program to realize gas concentration control by the control unit 15.

[0033] The computer 30 includes a CPU (Central Processing Unit) 31, a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a non-volatile storage 36, and a communication interface 37, all of which are connected to a system bus. A display device 16 and an input device 17 are also connected to the computer 30.

[0034] The CPU 31 reads out program code of software that realizes each function according to this embodiment from the ROM 32, loads it into the RAM 33, and executes it. Variables, parameters, etc. generated during the calculation processing of the CPU 31 are temporarily written to the RAM 33, and these variables, parameters, etc. are read out as appropriate by the CPU 31. The functions of the gas concentration control device 100, 100A (control unit 15) are realized by the CPU 31 executing the program code read out from the ROM 32. However, another processor such as an MPU (Micro Processing Unit) may be used instead of the CPU 31.

[0035] The nonvolatile storage 36 is an example of a recording medium, and is capable of storing data used by a program, data obtained by executing a program, etc. An operating system (OS) or a program executed by the CPU 31 may also be recorded in the nonvolatile storage 36. The nonvolatile storage 36 may be a hard disk drive (HDD), a solid state drive (SSD), an optical (and magnetic) disk, a semiconductor memory card, or the like.

[0036] A communication device such as a network interface card (NIC) is used as the communication interface 37. The communication interface 37 is capable of transmitting and receiving various data to and from external devices via a communication network such as a LAN, a dedicated line, etc. The communication interface 37 may be used to realize communication between the control unit 15 and the equipment within the gas concentration control device 100, 100A.

[0037] The gas consumer facility 200 may employ the same hardware configuration as the computer 30 shown in Fig. 3. The terminals used by the administrators of the gas concentration control devices 100 and 100A and the administrators of the gas consumer facility 200 may also employ the same hardware configuration as the computer 30 shown in Fig. 3.

[0038] In the above-described gas concentration control devices 100 and 100A, even after detecting an abnormality in the gas separation device, the control unit 15 determines whether or not to continue operation of the gas consumer's facility 200 based on whether the concentration of gas components (e.g., hydrogen concentration) of the mixed gas (product gas 26) supplied to the gas consumer and the flow rate of the mixed gas can meet the demand of the gas consumer. Then, depending on the determination result of whether or not to continue operation, the control unit 15 stops the gas separation device in which the abnormality has occurred or the gas consumer's facility 200, and controls the output of the buffer tank 4 and the gas separation device in which the abnormality has not occurred.

[0039] In this manner, in this embodiment, the supply and stop of the product gas can be safely controlled by stopping the gas separation device or the gas consumer facility 200 in which an abnormality has occurred depending on the determination result of whether or not operation can be continued. In other words, the gas concentration control device 100 and the gas consumer facility 200 can be safely operated.

[0040] Hereinafter, a method for controlling the output of the buffer tank 4 and a gas separation device in which no abnormality has occurred will be specifically described with reference to two examples of gas concentration control, depending on the result of the determination as to whether operation can be continued.

[0041] [Gas concentration control (1)] Next, referring to Figures 4 and 5, an example of a control method will be described when some abnormality occurs in the gas separation device 1 of the gas concentration control device 100 and the gas concentration and gas flow rate of the adjusted gas 23 output from the gas separation device 1 can no longer be controlled.

[0042] In this example, the supply gas 21 is a mixed gas obtained by mixing natural gas with hydrogen, and the gas consumer's facility 200 supplies a mixed gas with a hydrogen concentration of 20% at 9 Nm ３ / h。 Figure 4 explains the flow rate control of the mixed gas, and Figure 5 explains the hydrogen concentration control. In this example, the concentration of hydrogen gas is adjusted, but it is also possible to adjust the concentration of natural gas.

[0043] (Changes in Gas Flow Rate) Figure 4 is a graph showing an example of changes in gas flow rate in the gas concentration control device 100. In the example of Figure 4, the demand amount (solid line) is the flow rate requested for product gas 26 from gas consumers, and the production flow rate (dash-dotted line) is the total flow rate of all regulated gases 23 to 25. Furthermore, gas flow rate A (dashed line with short intervals) is the flow rate of regulated gas 23 in gas separation device 1, and gas flow rate B (dashed line with long intervals) is the flow rate of regulated gases 24 and 25 in gas separation device 2 and gas separation device 3. Furthermore, the tank output (dash-dotted line) is the flow rate of product gas 26 output from buffer tank 4.

[0044] In this example, when an abnormality occurs in the gas separation device 1 (at time t1), the gas flow rate A is 3 Nm ３ / h to 1 Nm ３ / h over time, and the production flow rate also decreased to 9 Nm ３ / h to 7Nm ３ In response to this, the control unit 15 calculates the rate of decrease of the gas flow rate A or the predicted value for each hour. Then, based on the calculation result, the control unit 15 adjusts the valve opening of the adjustment valve 11 to reduce the output of the buffer tank 4 to 0 Nm / s. ３ / h to 2Nm ３ / h, the sum of the tank output and production flow rate is controlled to match the demand.

[0045] Furthermore, after the occurrence of an abnormality, the control unit 15 determines whether or not to continue operation of the gas consumer facility 200. To determine whether or not to continue operation, one or more of the maximum production flow rate of the product gas 26 after the occurrence of the abnormality, the demand amount, and the remaining amount of the product gas 26 in the buffer tank 4, which satisfy the gas composition and concentration required by the gas consumer facility 200, can be used. Whether or not to continue operation of the gas consumer facility 200 is determined depending on whether the state quantity of the product gas 26 can satisfy the demand of the gas consumer. In the examples of FIGS. 4 and 5 , the control unit 15 determines to continue operation of the gas consumer facility 200 and the gas concentration control device 100.

[0046] In Fig. 4, after determining to continue operation, the control unit 15 controls the production flow rate to increase by increasing the flow rates of the regulated gases 24 and 25 of the normal gas separation apparatus 2 and the gas separation apparatus 3 (time t2). In Fig. 4, during the same period, the gas flow rate B (the flow rates of the regulated gases 24 and 25) is 3 Nm ３ / h to 4Nm ３ / h, the production flow rate will increase by 7 Nm ３ / h to 9Nm ３ At this point, the production flow rate has met the demand, so the control unit 15 adjusts the valve opening of the regulating valve 11 to set the tank output to 0 Nm ３ / h, the buffer tank 4 is stopped (time t3).

[0047] After the buffer tank 4 is stopped, the control unit 15 adjusts the valve opening of the adjustment valve 7 to stop the gas separation device 1 in which the abnormality has occurred (time t4). In FIG. 4, the stop of the gas separation device in which the abnormality has occurred is described as "abnormal equipment stop". By stopping the gas separation device 1, the gas flow rate A (flow rate of the adjustment gas 23) becomes 0 Nm ３ Therefore, the control unit 15 simultaneously reduces the gas flow rate B (the flow rates of the adjusting gases 24 and 25) to 4 Nm ３ / h to 4.5 Nm ３ / h, the production flow rate will be increased to 9 Nm ３ The control unit 15 continues the operation of the gas concentration control device 100 using the gas separation devices 2 and 3.

[0048] There is no limitation on the order in which the gas separation device 1 is stopped and the output of the buffer tank 4 is stopped. Depending on the capacity of the buffer tank 4, the gas separation device 1 may be stopped before the output of the buffer tank 4 is stopped.

[0049] (Changes in Hydrogen Concentration) Figure 5 is a graph showing an example of changes in hydrogen concentration in the gas concentration control device 100. With reference to Figure 5, hydrogen concentration control under the same assumption as in Figure 4 will be described. In the example of Figure 5, the demand concentration (solid line) is the concentration of hydrogen gas (an example of a gas component) in the product gas 26 requested by the gas consumer. Furthermore, concentration A (dashed line with short intervals) is the hydrogen concentration of the adjusted gas 23 from gas separation device 1, and concentration B (dashed line with long intervals) is the hydrogen concentration of the adjusted gases 24 and 25 from gas separation device 2 and gas separation device 3.

[0050] In this example, when an abnormality occurs in gas separation apparatus 1 (time t1), the flow rate of regulated gas 23 (gas flow rate A) decreases, and at the same time, the hydrogen concentration of regulated gas 23 (concentration A) decreases from 20% to 8% (time t2). In response to this, control unit 15 increases the valve openings of regulating valves 8 and 9, and the valves through which hydrogen gas extracted from the mixed gas flows inside gas separation apparatus 2 and gas separation apparatus 3, thereby increasing the hydrogen concentration of concentration B from 20% to 22%. Through this adjustment, the hydrogen concentration of product gas 26 supplied to gas consumers is maintained at the desired concentration of 20%.

[0051] Thereafter, as the output of the buffer tank 4 approaches the stop (time t3), the gas flow rate B decreases to 3 Nm ３ / h to 4Nm ３ / h. In response to this, the control unit 15 reduces the hydrogen concentration of concentration B from 22% to 21.5% in order to maintain the hydrogen concentration of the product gas 26 at 20%.

[0052] Furthermore, after the output of the buffer tank 4 was stopped, the gas flow rate A decreased to 1 Nm as the gas separation device 1 in which the abnormality occurred approached shutdown (time t4). ３ / h to 0 Nm ３ / h, and the gas flow rate B is 4 Nm ３ / h to 4.5 Nm ３ / h. In response to this, the control unit 15 reduces the hydrogen concentration of concentration B from 21.5% to 20% in order to maintain the hydrogen concentration of the product gas 26 at 20%.

[0053] In this gas concentration control, when the concentration of a gas component (e.g., hydrogen concentration) in the mixed gas (product gas 26) requested by the gas consumer differs from the concentration of a gas component in the mixed gas output from a gas separation device in which an abnormality has occurred, the control unit 15 mixes the mixed gas (adjusted gas 23) output from the gas separation device in which an abnormality has occurred with either or both of the mixed gas (adjusted gases 24, 25) output from a gas separation device in which an abnormality has occurred and the mixed gas (product gas 26) in the buffer tank 4. This enables control to reduce the error between the concentration of a gas component in the mixed gas supplied to the gas consumer and the concentration of a gas component in the mixed gas requested by the gas consumer after an abnormality has occurred.

[0054] Furthermore, in this gas concentration control, when the determination result of whether or not to continue operation indicates that the gas consumer's facility 200 should continue operating, the control unit 15 stops the gas separation device in which the abnormality occurred and supplies a mixed gas (product gas 26) that satisfies the demand of the gas consumer using the mixed gas output from the buffer tank 4 and the gas separation device in which the abnormality occurred. According to this configuration, when the gas flow rate and hydrogen concentration of any gas separation device cannot be controlled due to some abnormality, the gas separation device in which the abnormality occurred is stopped and the operation of the gas consumer's facility 200 is continued using the mixed gas output from the buffer tank 4 and the gas separation device in which the abnormality occurred. As a result, this embodiment can quickly restore the state quantities (flow rate, gas component concentrations) of the product gas 26 to the state before the abnormality occurred, minimizing the impact on the gas consumer.

[0055] 4 and hydrogen concentration control as described above, when the gas flow rate and hydrogen concentration of the adjusted gas 23 become uncontrollable due to some abnormality, a control method is possible in which the gas separation device 1 is stopped while continuing operation of the gas consumer facility 200 by satisfying the demand amount of the product gas 26 and the demand concentration of the target gas component. Note that, although the concentration of hydrogen gas is adjusted in this example, a configuration in which the concentration of natural gas is adjusted may also be used.

[0056] [Gas Concentration Control (2)] Next, referring to Figures 6 and 7, an example of a control method for stopping the gas consumer's equipment 200 and the gas concentration control device 100 when the gas concentration and gas flow rate of the adjusted gas 23 cannot be controlled due to some abnormality in the gas separation device 1 of the gas concentration control device 100, and the demand amount and demand concentration of the product gas 26 cannot be met will be described.

[0057] In this example, the supply gas 21 is a mixed gas obtained by mixing natural gas with hydrogen, and the gas consumer's facility 200 supplies a mixed gas with a hydrogen concentration of 20% at a rate of 9 Nm ３ In addition, in an operation in which the gas consumer's facility 200 and the gas concentration control device 100 are stopped, the hydrogen concentration of the mixed gas is maintained at 20%, and the gas flow rate is set to 9 Nm ３ / h to 0 Nm ３ / h. Here, the maximum flow rate of the adjusted gas that can be output from each of the gas separation devices 1 to 3 is 4 Nm ３ / h. The flow rate control of the mixed gas is explained in Fig. 6, and the hydrogen concentration control is explained in Fig. 7. Note that in this example, the concentration of hydrogen gas is adjusted, but it may also be configured to adjust the concentration of natural gas.

[0058] (Changes in Gas Flow Rate) Figure 6 is a graph showing another example of changes in gas flow rate in the gas concentration control device 100. In the example of Figure 6, the meanings of the lines indicating the demand amount (solid line), the production flow rate (dash-dotted line), the gas flow rate A (dashed line with short intervals), the gas flow rate B (dashed line with long intervals), and the tank output (dashed line with two long intervals) are the same as in the example of Figure 4.

[0059] In this example, due to the occurrence of an abnormality in the gas separation device 1 (time t11), the gas flow rate A is 3 Nm ３ / h to 0 Nm ３ / h over time. In response to this, the control unit 15 reduces the gas flow rate B to 3 Nm ３ / h to 4Nm ３ / h, and the flow rate of the product gas 26 output from the buffer tank 4 is also increased to 0 Nm ３ / h to 1 Nm ３ / h, the sum of the tank output and production flow rate is controlled to match the demand.

[0060] As described above, after the occurrence of an abnormality, the control unit 15 determines whether or not the operation of the gas consumer facility 200 can be continued. In the examples of FIGS. 6 and 7, when the flow rate of the regulated gas 23 (gas flow rate A) is 0 Nm ３ / h (time t12), the flow rates of the adjusting gas 24 and the adjusting gas 25 (gas flow rate B) are increased to a maximum of 4 Nm ３ / h, the gas consumer's facility 200 requires 9 Nm ３ / h flow rate cannot be met. To satisfy the demands of the gas consumer, it is necessary to output the product gas 26 from the buffer tank 4. Therefore, the gas concentration control device 100 can only continue operation by utilizing the remaining amount of product gas 26 stored in the buffer tank 4. Therefore, in the examples of FIGS. 6 and 7, the control unit 15 determines to stop operation of the gas consumer's facility 200 and the gas concentration control device 100.

[0061] 6 , after determining to stop operation, the control unit 15 transmits the result of the determination to stop operation or a demand stop request signal to the gas consumer's facility 200. Upon receiving the result of the determination to stop operation or the demand stop request signal, the gas consumer's facility 200 starts operation toward stopping the facility 200 (hereinafter referred to as "stop operation"), and accordingly starts reducing the demand amount. The control unit 15 receives information about the changed demand amount from the gas consumer's facility 200, and prioritizes reducing the output of the buffer tank 4 in accordance with the changed demand amount, thereby causing the flow rate of the product gas 26 to follow the demand amount.

[0062] After that, the control unit 15 determines whether the output of the buffer tank 4 is 0 Nm ３ / h (time t13), the flow rate of the product gas 26 is made to follow the demand by reducing the gas flow rate B. Then, the control unit 15 controls the flow rate of the product gas 26 to follow the demand when the demand and the gas flow rate B (output of the gas separation devices 2 and 3) are equal to 0 Nm ３ / h, the gas concentration control device 100 is completely stopped.

[0063] In the above example, a request is made to the facility 200 of the gas consumer to stop demand, but it is also possible to request the gas consumer to reduce the demand of the facility 200. For example, if the flow rate of the product gas 26 requested by the gas consumer is 9 Nm ３ / h to 7Nm ３ / h, the gas concentration control device 100, 100A can continue operation using the adjusted gas 24 and the adjusted gas 25 without shutting down the gas consumer facility 200.

[0064] (Changes in Hydrogen Concentration) Figure 7 is a graph showing another example of changes in hydrogen concentration in the gas concentration control device 100. With reference to Figure 7, hydrogen concentration control under the same assumption as in Figure 6 will be described. In the example of Figure 7, the meanings of the lines indicating the demand concentration (solid line), concentration A (dashed line with short intervals), and concentration B (dashed line with long intervals) are the same as in the example of Figure 5.

[0065] In this example, the flow rate of the regulated gas 23 (gas flow rate A) decreases due to the occurrence of an abnormality in the gas separation device 1 (time t11), and at the same time, the hydrogen concentration of the regulated gas 23 (concentration A) increases from 20% to 30% over time. In response to this, the control unit 15 reduces the hydrogen concentration of concentration B (the hydrogen concentration of the regulated gases 24 and 25) from 20% to approximately 18% based on concentration A, gas flow rate A, and gas flow rate B so that the hydrogen concentration of the product gas 26 becomes the required concentration of 20%.

[0066] Thereafter, the control unit 15 sets the gas flow rate A to 0 Nm ３ / h (time t12), the hydrogen concentration of concentration B is gradually returned to 20%, and the hydrogen concentration of product gas 26 is maintained at 20%. Strictly speaking, in addition to these, the gas flow rate and hydrogen concentration of product gas 26 supplied from buffer tank 4 are also taken into consideration. The same can be said for the examples of the graphs shown in FIGS. 4 and 5.

[0067] Gas flow rate A is 0 Nm ３ / h and the output of the buffer tank 4 is stopped (time t13). Then, the production flow rate becomes 0 Nm3 as the gas flow rate B decreases. ３During this time, the control unit 15 maintains the hydrogen concentration of concentration B at 20% and supplies the product gas 26 that satisfies the demand concentration.

[0068] In this gas concentration control, when the determination result of whether or not operation can be continued indicates that operation of the gas consumer's facility 200 cannot be continued, the control unit 15 notifies the gas consumer's facility 200 of the determination result that operation cannot be continued. Then, until the gas consumer's facility 200 is shut down, the control unit 15 controls the output of the buffer tank 4 and the gas separation device in which no abnormality has occurred, and reduces the flow rate of the mixed gas (product gas 26) to zero while satisfying the concentration of the gas components in the mixed gas required by the gas consumer.

[0069] According to this embodiment having such a configuration, when the gas flow rate and hydrogen concentration of any gas separation device cannot be controlled due to some abnormality, it is possible to control the gas consumer's equipment 200 and gas concentration control device 100 to stop while satisfying the demand amount and demand concentration of product gas 26.

[0070] Furthermore, according to this embodiment, the gas consumer's facility 200 and the gas concentration control device 100 are stopped while satisfying the demand (particularly the demand concentration) for the product gas 26. This makes it possible to minimize the impact on the gas consumer while ensuring the safety of the facility 200 and the gas concentration control device 100.

[0071] [Processing of Gas Concentration Control Device] Next, processing of the gas concentration control device according to the first embodiment of the present invention will be described with reference to Fig. 8. Fig. 8 is a flowchart showing the flow of processing of the gas concentration control device 100. The example of Fig. 8 is an example of an algorithm of processing by the control unit 15. The same applies to processing of the gas concentration control device 100A. This processing will be described in conjunction with the examples of Figs. 4 and 5.

[0072] First, in processing step S1, the control unit 15 sets the control target values ​​of each facility of the gas concentration control device 100, including the regulating valves 7 to 11. For example, in the example of FIG. 4, the hydrogen concentration of the product gas required by the facility 200 of the gas consumer is 20%, and the gas flow rate is 9 Nm ３ / h, the target values ​​of the adjusted gases 23 to 25 of the gas separation devices 1 to 3 are also set to a hydrogen concentration of 20% and a gas flow rate of 9 Nm ３ / h.

[0073] However, if it is determined in the evaluation of whether operation can be continued in processing step S5 described below that an abnormality has occurred in some of the gas separation devices 1-3, the control target values ​​of each gas separation device 1-3 are adjusted so that the average values ​​(average concentrations) of the concentrations of each gas component of all adjusted gases 23-25 ​​and the total flow rate satisfy the target values ​​of the product gas 26. Here, the adjusted gases of all gas separation devices 1-3 are the target, regardless of whether an abnormality exists. However, the adjustment of the control target values ​​is targeted at gas separation devices that are not experiencing an abnormality. Furthermore, if there are updates to the target values, such as the demand amount and required concentration of the product gas 26 required by the gas consumer facility 200, the control unit 15 may receive updated target values ​​from the gas consumer facility 200 during this processing step.

[0074] Next, in process step S2, the control unit 15 calculates the operation amounts of the valves, devices, etc. of each of the gas separation devices 1 to 3 based on the control target values ​​of the gas concentrations of each of the gas separation devices 1 to 3. Then, the control unit 15 controls the concentrations of the gas components of the adjusted gases 23 to 25 output from each of the gas separation devices 1 to 3 based on the operation amounts of the valves, devices, etc. of each of the gas separation devices 1 to 3. The control target values ​​of the gas concentrations use the values ​​determined in process step S1.

[0075] Next, in process step S3, the control unit 15 calculates the manipulated variables of the valves, devices, etc. of each of the gas separation devices 1 to 3 based on the control target values ​​of the gas flow rates of each of the gas separation devices 1 to 3. Then, the control unit 15 controls the flow rates of the adjustment gases 23 to 25 output from each of the gas separation devices 1 to 3 based on the manipulated variables of the valves, devices, etc. of each of the gas separation devices 1 to 3. The value determined in process step S1 is used as the control target value of the gas flow rates. Note that in the present invention, there is no limitation on the order of calculations in process steps S2 and S3, and the order of calculation of the manipulated variables for flow rate control and concentration control of the adjustment gas may be changed as necessary.

[0076] Next, in processing step S4, the control unit 15 calculates the flow rate of the product gas 26 input to and output from the buffer tank 4, and further calculates the operation amounts of the compressor 5 and the regulating valve 11 based on the calculated flow rate of the product gas 26. Then, the control unit 15 controls the input and output of the product gas 26 to and from the buffer tank 4 based on the operation amounts of the compressor 5 and the regulating valve 11.

[0077] One mode for outputting product gas 26 from buffer tank 4 is when the total value of all regulated gases 23 to 25 is less than the demand for product gas 26. Conversely, one mode for storing product gas 26 in buffer tank 4 is when the total value of all regulated gases 23 to 25 exceeds the demand for product gas 26. There is no restriction on the order of calculations in process steps S2 to S4, and tank input / output control in process step S4 may be performed before process steps S2 and S3.

[0078] Next, in processing step S5, the control unit 15 evaluates whether or not the gas consumer facility 200 can continue to operate. In evaluating whether or not to continue operation, the control unit 15 determines whether or not the flow rate and concentration of each gas component of the product gas 26 supplied to the gas consumer can satisfy the demand of the gas consumer or its predicted value, even after the abnormality occurs. Details of the method for evaluating whether or not to continue operation will be described later with reference to FIG. 9.

[0079] Next, in processing step S6, it is determined whether or not to continue control of the gas concentration control device 100. For example, when the gas concentration control device 100 is stopped due to the shutdown of the gas consumer facility 200, and control of the gas concentration control device 100 is no longer necessary, the control unit 15 determines to stop control (NO determination) and ends the algorithm. Conversely, if control is to be continued (YES determination), the process proceeds to processing step S1, and processing steps S1 to S6 are executed again.

[0080] [Evaluation of whether operation can be continued] Next, evaluation of whether operation can be continued in processing step S5 of Fig. 8 will be described with reference to Fig. 9. Fig. 9 is a flowchart showing an example of the procedure for evaluation of whether operation can be continued in processing step S5 of Fig. 8.

[0081] First, in processing step S11 shown in FIG. 9 , the control unit 15 determines whether an abnormality has occurred in the equipment (such as a gas separation device) of the gas concentration control device 100. For example, if the error between the target value set in processing step S1 and the current value of the average concentration or total flow rate of each gas component of the adjustment gases 23 to 25 does not improve over a preset time, the control unit 15 determines whether an abnormality has occurred. However, the present invention does not limit the means for determining whether an abnormality has occurred. For example, an abnormality may be determined when the error is larger than a predetermined value and does not improve even after a preset time has elapsed, or when the error is so large that it is necessary to immediately shut down the gas concentration control device 100.

[0082] Next, in process step S12, the process branches based on the determination result of process step S11. If it is determined that an abnormality has occurred in the equipment of the gas concentration control device 100 (YES determination), the process proceeds to process step S13, and if it is determined that an abnormality has not occurred (NO determination), the process proceeds to process step S16.

[0083] In processing step S13, the control unit 15 evaluates the remaining amount of product gas 26 in the buffer tank 4 based on the measurement value of a sensor (not shown). Note that if the remaining amount of product gas 26 in the buffer tank 4 is not used in determining whether or not to continue operating the equipment in which an abnormality has occurred, as will be described later, the process may proceed to the next processing step without executing this processing step.

[0084] Next, in processing step S14, the control unit 15 acquires or predicts fluctuation information for the demand of the gas consumer facility 200, including the future, i.e., a predetermined time period into the future, and for the supply gas 21. The demand fluctuation may be acquired through communication with the gas consumer facility 200 or through an operation plan for the facility 200. Similarly, the fluctuation information for the supply gas 21 may be acquired through communication with an external facility of the gas concentration control device 100, such as a hydrogen generation plant.

[0085] Alternatively, a simulator or a model may be used to predict fluctuations in the demand amount and the supply gas 21. For example, a model-based estimation method for estimating fluctuations in the demand amount and the supply gas 21 may be used, such as a machine learning model such as a neural network model or a decision tree model, a statistical model, a plant model based on past data, or a numerical analysis model based on physical laws. However, the present invention is not limited to a method for estimating fluctuations in the demand amount and the supply gas.

[0086] If it is difficult to obtain or predict fluctuation information on the demand amount or supply gas 21, it may be assumed that the current demand amount and state quantities of supply gas 21 (concentration of gas components, flow rate, etc.) continue to be maintained at constant values. Furthermore, if the concentration of a gas component in the product gas required by a gas consumer fluctuates, the control unit 15 may be configured to obtain or predict fluctuation information on the concentration of the relevant gas component.

[0087] Next, in processing step S15, the control unit 15 determines whether or not the gas consumer's facility 200 can continue to operate. As described above, the control unit 15 determines whether or not the flow rate of the product gas 26 supplied to the gas consumer and the concentration of each gas component can meet the gas consumer's demand or its predicted value, even after the abnormality occurs. By using the predicted value of gas demand to determine whether or not the gas consumer's facility 200 can continue to operate, it is possible to determine whether or not the facility can continue to operate for a period extending from the present to the future. Therefore, the gas consumer's facility 200 and the gas concentration control device 100 can be operated safely into the future.

[0088] This determination of whether operation can be continued uses the concentrations of gas components in the mixed gas that can be output by multiple gas separation devices including the gas separation device where the abnormality occurred (average hydrogen concentration of regulated gases 23 to 25), and the concentration of gas components in the mixed gas requested by the gas consumer (hydrogen concentration of product gas 26), or a predicted value thereof. Alternatively, the flow rate of the mixed gas that can be output by multiple gas separation devices including the gas separation device where the abnormality occurred (total flow rate of regulated gases 23 to 25), and the flow rate of the mixed gas requested by the gas consumer (flow rate of product gas 26), or a predicted value thereof. Alternatively, both the concentration and the flow rate may be used.

[0089] For example, the control unit 15 compares the production volume and gas component concentrations of the product gas 26 after the abnormality has occurred with the demand volume, required concentration, or predicted values ​​of the product gas 26 required by the gas consumer facility 200, including future demand volumes. If the control unit 15 compares the demand volume, required concentration, or predicted values ​​and finds that the product gas 26 can be produced after the abnormality has occurred with an error in the production volume and gas component concentrations less than a preset threshold, it determines that operation can be continued. These thresholds are stored in the ROM 32 or the non-volatile storage 36.

[0090] Conversely, if the error is equal to or greater than the threshold, the control unit 15 determines that operation cannot be continued. Alternatively, if the error between the production amount of product gas 26 and the concentration of gas components after the occurrence of the abnormality is less than a preset threshold when the output of buffer tank 4 is included, the control unit 15 calculates the possible operation time from the remaining amount of product gas 26 in buffer tank 4. Then, the control unit 15 may determine to continue operation of the gas consumer facility 200 for the possible operation time.

[0091] Next, in processing step S16, the control unit 15 transmits the determination result of whether or not operation can be continued in processing step S15 to the gas consumer's facility 200 and the display device 16. Furthermore, if the determination result in processing step S12 is NO, the control unit 15 notifies the gas consumer's facility 200 and the display device 16 that there is no abnormality in the gas concentration control device 100 facility.

[0092] Here, if there are updates to target values ​​such as the demand amount and required concentration of product gas 26 required by gas consumer facility 200, control unit 15 may receive updated target values ​​from gas consumer facility 200 during this processing step. When control unit 15 receives updated target values, it again executes processing step S15 to determine whether operation can be continued.

[0093] <Second embodiment> Next, a display screen of a gas concentration control device according to a second embodiment of the present invention will be described with reference to Fig. 10. Fig. 10 is a diagram showing an example of a display screen of a gas concentration control device according to the second embodiment of the present invention. Fig. 10 shows an example of a screen displayed on either or both of the display device 16 of the gas concentration control device 100 shown in Fig. 1 and a display device (not shown) of the gas consumer facility 200. The same applies to the display screen of the gas concentration control device 100A.

[0094] 10 displays information (equipment abnormality information 301) about the equipment of the gas concentration control device 100 for which an abnormality was determined to have occurred in processing step S11. The notification screen 300 also displays a determination result 302 as to whether operation can be continued in processing step S15, a remaining amount 303 of product gas 26 in the buffer tank 4, a possible continuous operation time 304 calculated in processing step S15, and target values ​​305 (hydrogen concentration, gas flow rate) required for the current product gas 26. It is desirable to display one or more of the equipment abnormality information 301, the determination result 302 as to whether operation can be continued, the remaining amount 303 in the tank, the possible continuous operation time 304, and the target value 305 for the product gas on the notification screen 300.

[0095] The notification screen 300 may also be provided with a button 311 for instructing the gas consumer's facility 200 to continue operating, and a button 312 for instructing the gas consumer's facility 200 to stop operating. Aside from the determination result of whether or not to continue operation calculated in step S15, the administrator can decide whether or not to continue operation. A button 313 for adjusting the target value required for the current product gas 26 may also be provided. Pressing button 313, for example, causes the gas consumer's facility 200 to adjust the target value required for the product gas 26 based on the gas consumer's usage status of the product gas 26. Then, the display of the gas component concentration (e.g., hydrogen concentration) and the gas flow rate of the product gas 26 in the target value 305 on the notification screen 300 is updated.

[0096] With this notification screen 300, one or more of the administrators of the gas concentration control device 100 and the gas consumer's equipment 200 can determine whether or not to continue operating the gas consumer's equipment 200 based on the information displayed on the screen.

[0097] As described above, the present invention is not limited to the above-described embodiments, and various other modifications and applications are possible without departing from the spirit of the invention as set forth in the claims. For example, the above-described embodiments have been described in detail and specifically to clearly explain the present invention, and are not necessarily limited to those including all of the components described. Furthermore, it is also possible to add, replace, or delete other components to or from part of the configuration of each embodiment.

[0098] Furthermore, some or all of the above-described configurations, functions, processing units, etc. may be implemented in hardware, for example, by designing them as integrated circuits, etc. As the hardware, a broad processor device such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) may be used.

[0099] In the above-described embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are connected to each other.

[0100] DESCRIPTION OF SYMBOLS 1 to 3...Gas separation device, 4...Buffer tank, 5, 6...Compressor, 7 to 9...Regulating valve, 10, 11...Regulating valve, 12 to 14...Sensor, 15...Control unit, 16...Display device, 17...Input device, 21...Supply gas, 22...Residual gas, 23 to 25...Regulated gas, 26...Product gas, 30...Calculator, 31...CPU, 32...ROM, 33...RAM, 100, 100A...Gas concentration control device, 200...Gas consumer's facility, 300...Notification screen

Claims

1. A gas concentration control device comprising: a plurality of gas separation devices that adjust the concentration of any gas component contained in a mixed gas and output the adjusted mixed gas; and a control device that controls the concentration of the gas component of the mixed gas output from the gas separation devices and the flow rate of the mixed gas in accordance with the demand of gas consumers, and detects the occurrence of an abnormality in the gas separation devices, wherein when the control device detects the occurrence of an abnormality in a gas separation device, it controls the output of a gas separation device that is not experiencing an abnormality, and adjusts the concentration of the gas component of the mixed gas to be supplied to the gas consumer and the flow rate of the mixed gas using the mixed gas output from the plurality of gas separation devices, including the gas separation device that has experienced an abnormality, so as to meet the demand.

2. A gas concentration control device as described in claim 1, which is provided with a buffer tank that stores and outputs at least a portion of the mixed gas output from the plurality of gas separation devices, and when the control device detects an abnormality in one of the gas separation devices, it controls the output of the buffer tank and the gas separation devices that are not experiencing an abnormality, thereby adjusting the concentration of the gas components of the mixed gas supplied to the gas consumer and the flow rate of the mixed gas to meet the demand.

3. The gas concentration control device described in claim 2, wherein the control device determines whether or not the gas consumer's equipment can continue to operate after detecting an abnormality in the gas separation device, depending on whether the concentration of the gas components of the mixed gas supplied to the gas consumer and the flow rate of the mixed gas can meet the demand of the gas consumer, and stops the gas separation device in which an abnormality has occurred or the gas consumer's equipment depending on the result of the determination of whether or not operation can continue, and controls the output of the buffer tank and the gas separation device in which an abnormality has not occurred.

4. A gas concentration control device as described in claim 3, wherein the control device stops the gas separation device in which an abnormality has occurred when the judgment result is that the gas consumer's equipment should continue to operate, and supplies mixed gas that meets the demand of the gas consumer using mixed gas output from the buffer tank and the gas separation device in which an abnormality has not occurred.

5. The gas concentration control device described in claim 3, wherein, when the judgment result indicates that the gas consumer's equipment cannot continue operating, the control device notifies the gas consumer's equipment of the judgment result that operation cannot continue, and controls the output of the buffer tank and a gas separation device in which no abnormality is occurring until the gas consumer's equipment is stopped, thereby reducing the flow rate of the mixed gas to zero while satisfying the concentration of the gas components of the mixed gas required by the gas consumer.

6. A gas concentration control device as described in claim 3, wherein the control device acquires or predicts the future demand of the gas consumer, and determines whether or not the gas consumer's equipment can continue to operate, even after detecting an abnormality in the gas separation device, based on whether the concentration of the gas components of the mixed gas supplied to the gas consumer and the flow rate of the mixed gas can meet the demand of the gas consumer or its predicted value.

7. A gas concentration control device as described in claim 2, wherein, when the concentration of gas components in the mixed gas requested by the gas consumer differs from the concentration of gas components in the mixed gas output from a gas separation device in which an abnormality has occurred, the control device reduces the error between the concentration of gas components in the mixed gas supplied to the gas consumer and the concentration of gas components in the mixed gas requested by the gas consumer by mixing the mixed gas output from the gas separation device in which an abnormality has occurred with either or both of the mixed gas output from a gas separation device in which an abnormality has occurred.

8. A gas concentration control device as described in claim 2, wherein the buffer tank is installed in parallel with a gas pipe that supplies the mixed gas output from the plurality of gas separation devices to the gas consumer's equipment, and when the concentration of the gas components in the mixed gas required by the gas consumer fluctuates, the mixed gas output from the gas separation devices is mixed with the mixed gas in the buffer tank.

9. A gas concentration control device as described in claim 3, wherein the control device outputs information including one or more of the gas separation device in which an abnormality has been detected, the determination result of whether the gas consumer's equipment can continue to operate, the remaining amount of mixed gas in the buffer tank, and the possible continued operation time to either or both of a display device connected to the control device and a display device connected to the gas consumer's equipment.

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