Degradation diagnosis apparatus for gas separation system

Abstract

To provide a degradation diagnosis apparatus for a gas separation system that enables degradation diagnosis using existing sensors required for system operation.SOLUTION: A degradation diagnosis apparatus for a gas separation system includes one or more gas separation membranes that selectively transmit specific gases and control the output of the gas separation membranes using an output control valve. The degradation diagnosis apparatus includes: an input unit that acquires a process amount affected by degradation of the gas separation membrane; a database that stores a process amount when the gas separation system is operated using a new (non-degraded) gas separation membrane; and a separation membrane performance evaluation unit that evaluates the performance of the gas separation membrane from a difference between the acquired current process amount and the process amount using the new gas separation membrane.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a deterioration diagnosis device for a gas separation system. [Background technology]

[0002] As a method for separating a specific gas from a mixture of multiple gases, there is a method that uses a separation membrane that selectively permeates gas. Separation membranes include, for example, molecular sieve membranes, such as ceramic membranes, which separate gases based on differences in molecular diameter, and polymer membranes, which utilize differences in the solubility of gases in the membrane. These separation membranes also allow a certain amount of gases other than the specific gas to be permeated. The side before permeation through the separation membrane is called the primary side, and the side after permeation is called the secondary side.

[0003] The amount of gas permeation through a separation membrane is proportional to the difference between the gas partial pressure on the primary side and the gas partial pressure on the secondary side multiplied by the membrane area. The amount of gas permeation through a separation membrane also decreases as the separation membrane deteriorates. In gas separation systems, in order to maintain separation efficiency, the deterioration state of the separation membrane is diagnosed, and if the separation membrane deteriorates, maintenance such as replacing the separation membrane is performed.

[0004] An example of a method for diagnosing deterioration of a separation membrane is Patent Document 1. Patent Document 1 is a method for measuring the flow rate of a residual gas discharge channel and the flow rate of a permeation gas discharge channel of a separation membrane and evaluating the deterioration state of the separation membrane using the flow rate ratio, and aims to provide a membrane separation system and a method for evaluating the deterioration of a separation membrane that can inexpensively evaluate the deterioration state of a separation membrane, and the method includes "a membrane separation device having a separation membrane, a multicomponent gas supply channel for supplying a multicomponent gas to the membrane separation device, a residual gas discharge channel through which residual gas that does not permeate the separation membrane flows out, a permeation gas discharge channel through which permeation gas that permeates the separation membrane flows out, a residual gas flowmeter for measuring the flow rate F1 of the residual gas discharge channel, a permeation gas flowmeter for measuring the flow rate F2 of the permeation gas discharge channel, and an arithmetic and control device, and the arithmetic and control device calculates a ratio Rm between the flow rates F1 and F2, and compares the calculated ratio Rm with a preset ratio Rk between the flow rates F1 and F2 to evaluate the deterioration state of the separation membrane." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-127393 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention relates to a system for controlling the concentration of a specific gas required by a specific gas user at the usage location when a specific gas different from natural gas is mixed with natural gas and transported using an existing gas grid for natural gas mainly composed of methane, and a deterioration diagnosis device for a system for controlling the concentration of a specific gas in gas production facilities, chemical plants, etc.

[0007] In this case, if the concentration of a specific gas cannot be controlled normally due to deterioration of the system, and gas with a concentration outside the allowable range is supplied to the equipment, the equipment may break down. In facilities such as production facilities and chemical plants, this may lead to a major accident, so deterioration diagnosis of the gas separation system must be performed regularly.

[0008] For this reason, it is necessary to achieve highly accurate deterioration diagnosis of gas separation systems. However, deterioration diagnosis of separation membranes requires multiple measurements of concentration, flow rate, etc., which requires multiple sensors such as gas concentration meters and flow meters, resulting in high costs.

[0009] An object of the present invention is to provide a deterioration diagnosis device for a gas separation system that can diagnose deterioration of a separation membrane using existing sensors necessary for system operation, without the need for additional sensors to diagnose deterioration of the separation membrane. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a deterioration diagnosis device for a gas separation system having one or more gas separation membranes that selectively permeate specific gases, and in which the output of the gas separation membrane is controlled by an output control valve, the deterioration diagnosis device comprising: an input unit that inputs process amounts affected by deterioration of the gas separation membrane; a database that stores the process amounts when the gas separation system is operated using a gas separation membrane in a new state (before deterioration); and a separation membrane performance evaluation unit that evaluates the performance of the gas separation membrane from the difference between the input process amount at the current time and the process amount in the new state. Effect of the Invention

[0011] According to the present invention, the number of sensors required for diagnosing deterioration of the separation membrane can be reduced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a schematic configuration example of a gas separation system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a signal flow in the control device in the gas separation system according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing a process flow of a separation membrane performance evaluation unit of the control device in the gas separation system according to the first embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing a schematic configuration example of a gas separation system according to a second embodiment of the present invention. [Diagram 5] FIG. 1 is a diagram showing a schematic configuration example of a gas separation system according to a third embodiment of the present invention. [Figure 6] FIG. 11 is a diagram showing the flow of signals in a control device in a gas separation system according to a third embodiment of the present invention. [Figure 7] FIG. 11 is a diagram showing an example of an operation schedule of a gas separation system according to a third embodiment of the present invention. [Figure 8] FIG. 11 is a diagram showing an example of the change over time in hydrogen concentration in the supply gas of the gas separation system according to Example 3 of the present invention. [Figure 9] FIG. 1 is a diagram showing a schematic configuration example of a gas separation system according to a fourth embodiment of the present invention. [Figure 10] FIG. 11 is a diagram showing the flow of signals in a control device in a gas separation system according to Example 4 of the present invention. [Figure 11] FIG. 11 is a diagram showing an example of a screen display of a computer in a gas separation system according to Example 4 of the present invention. [Figure 12] FIG. 11 is a diagram showing an example of a screen display of a computer in a gas separation system according to Example 4 of the present invention. [Figure 13] FIG. 13 is a diagram showing a schematic configuration example of a gas separation system according to a fifth embodiment of the present invention. [Figure 14] FIG. 4 is a graph showing the characteristics of mixed gas hydrogen concentration and extracted gas hydrogen concentration. [Figure 15] FIG. 13 is a diagram showing a schematic configuration example of a gas separation system according to a sixth embodiment of the present invention. [Figure 16] A diagram showing the characteristics of the primary and secondary pressure difference and the mixed gas flow rate. [Figure 17] FIG. 13 is a diagram showing a schematic configuration example of a gas separation system according to a seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] The present invention is intended to provide a deterioration diagnosis device for a gas separation system that enables deterioration diagnosis using existing sensors necessary for system operation.In this case, the existing sensor is a sensor in which the process quantity detected by the sensor is affected by deterioration of the separation membrane performance, and which makes it possible to estimate deterioration from the change between the initial process quantity before operation begins and the process quantity at the current time.

[0015] In the embodiments of the present invention, several process variables are exemplified which are affected by deterioration and whose deterioration can be estimated from the change between before the start of operation and the present time. Here, examples will be described in which the valve operation variable is focused on in the first to fourth embodiments, the hydrogen concentration of the mixed gas is focused on in the fifth and seventh embodiments, and the flow rate and pressure of the mixed gas is focused on in the sixth embodiment. EXAMPLES

[0016] In the first to fourth embodiments, examples of diagnosing deterioration by focusing on the amount of valve operation will be described.

[0017] 1 is a diagram showing a schematic configuration example of a gas separation system according to a first embodiment of the present invention. In this embodiment, a case will be described in which the hydrogen concentration of the extracted gas is controlled to a predetermined value even if the hydrogen concentration of the supply gas fluctuates around a certain value, for a supply gas that is a mixture of hydrogen and methane. For example, there are cases in which the hydrogen concentration is controlled to a constant 20% (vol%), to be above or below a predetermined value, or to be within a predetermined range.

[0018] 1, a gas separation system 1 is configured to receive a supply of a mixed gas of hydrogen and methane through a mixed gas pipe 3 branched off from a main mixed gas pipe 2. The gas separation system 1 has a gas separation membrane module 11. The separation membrane module 11 is separated into a primary side 13 and a secondary side 14 by a separation membrane 12.

[0019] The mixed gas pipe 3 is connected to the primary side 13. A non-permeate gas pipe 4 is connected to the primary side 13. A permeate gas pipe 5 is connected to the secondary side 14. Of the mixed gas supplied from the mixed gas main pipe 2 to the primary side 13 of the hydrogen separation device 1, mainly hydrogen permeates through the separation membrane 12. Methane also permeates through the separation membrane 12, but hydrogen permeates more easily than methane. For this reason, the secondary side 14 has a higher hydrogen concentration than the primary side 13. The amount of permeation of each gas is proportional to the partial pressure difference between the primary side 13 and the secondary side 14 of each gas.

[0020] The mixed gas pipe 3 is provided with a mixed gas flow rate adjustment valve 21. The mixed gas flow rate adjustment valve 21 adjusts the flow rate of the mixed gas supplied to the separation membrane. Description of the flow meter indication and its control method will be omitted.

[0021] The non-permeable gas pipe 4 is provided with a non-permeable gas pressure regulating valve 22. The non-permeable gas pressure regulating valve 22 regulates the pressure on the primary side of the separation membrane according to the hydrogen concentration of the permeable gas. Details will be described later. The permeable gas pipe 5 is provided with a permeable gas pressure regulating valve 23. The permeable gas pressure regulating valve 23 regulates the pressure on the secondary side. An explanation of the pressure gauge display and its control method will be omitted.

[0022] In addition, the permeable gas pipe 5 is provided with an extracted gas hydrogen concentration meter 31. The extracted gas hydrogen concentration meter 31 measures the hydrogen concentration of the permeable gas, and transmits a hydrogen concentration signal to the control device 41 through a hydrogen concentration signal cable 51.

[0023] The control device 41 has two main functions. One is to control the gas separation system, and the other is to monitor the gas separation system. The manipulated variable calculation unit 42 functions for control, and the separation membrane performance evaluation unit functions for monitoring. Of these, the manipulated variable calculation unit 42 receives a hydrogen concentration signal, calculates the valve opening of the non-permeable gas pressure regulating valve 22 based on the hydrogen concentration signal so that the hydrogen concentration of the permeable gas (extracted gas) becomes a predetermined value, and transmits the calculated value to the non-permeable gas pressure regulating valve 22 through a control signal cable 52. Note that the manipulated variable calculation unit 42 may calculate the valve opening manipulated variable of the non-permeable gas pressure regulating valve 22 from the control of the pressure or flow rate to a predetermined value instead of the hydrogen concentration signal.

[0024] The operation amount calculation unit 42 will be further described. Based on the characteristic that the amount of hydrogen permeation through the separation membrane is proportional to the gas partial pressure difference between the primary side 13 and the secondary side 14, for example, when the concentration of the permeable gas is lower than a predetermined value, the operation amount calculation unit 42 calculates the valve aperture of the non-permeable gas pressure regulating valve 22 to a small value. When the valve aperture of the non-permeable gas pressure regulating valve 22 is reduced, the pressure on the primary side 13 increases, the gas partial pressure difference increases, the amount of hydrogen permeation through the separation membrane increases, and the hydrogen concentration of the permeable gas can be increased. The method of calculating the valve aperture based on the hydrogen concentration may be any conventional method such as proportional control or proportional integral control.

[0025] In addition to the operation amount calculation unit 42, the control device 41 also includes a database 43 and a separation membrane performance evaluation unit 44, and is connected to an external computer (a device equipped with a user interface). Fig. 2 shows the flow of control signals between the operation amount calculation unit 42, the database 43, and the separation membrane performance evaluation unit 44 constituting the control device 41, and the external computer (a device equipped with a user interface).

[0026] The following data is stored in advance in the database 43. Note that the lower limit ΔVL and upper limit ΔVH of the difference between the current manipulated variable V(t) and the initial value of the manipulated variable can be set by analysis or experimentation based on constraints such as the required separation efficiency of the gas separation system and the specifications of the constituent equipment. The operation amount (valve opening) V0 (hereinafter referred to as the "initial value of the operation amount") when the gas separation system is operated using a new (before deterioration) separation membrane 12. · Lower limit ΔVL of the difference between the current manipulated variable V(t) and the initial value of the manipulated variable Upper limit ΔVH of the difference between the current manipulated variable V(t) and the initial value of the manipulated variable The separation membrane performance evaluation unit 44 receives the following data. The current operation amount V(t) calculated by the operation amount calculation unit 42 The initial value V0 of the manipulated variable, the lower limit ΔVL of the difference from the initial value of the manipulated variable, and the upper limit ΔVH The separation membrane performance evaluation unit 44 evaluates the performance of the separation membrane based on the received data, and transmits the separation membrane performance evaluation result to the computer 45. The separation membrane performance evaluation result is, for example, a signal notifying that the separation membrane has deteriorated or that an abnormality has occurred.

[0027] Next, an example of the separation membrane performance evaluation method and the results thereof by the separation membrane performance evaluation unit 44 will be described. Fig. 3 shows the processing flow of the separation membrane performance evaluation unit 44. First, the difference ΔV between the current manipulated variable V(t) and the initial value V0 of the manipulated variable is calculated (processing step S1). The difference ΔV is compared with a lower limit value ΔVL (processing step S2), and if ΔV<lower limit value ΔVL, it is determined that the separation membrane 12 has deteriorated, and the result is sent to the computer 45 (processing step S3).

[0028] On the other hand, if ΔV is not less than the lower limit value ΔVL, the process proceeds to the next process, and the difference ΔV is compared with the upper limit value ΔVH (processing step S4). If ΔV > the upper limit value ΔVH, it is determined that an abnormality has occurred, and the result is transmitted to the computer 45 (processing step S5). On the other hand, if ΔV is not greater than the upper limit value ΔVH, the process returns to the process of processing step S1.

[0029] In the gas separation system 1, when the separation membrane 12 deteriorates, the hydrogen permeation amount of the separation membrane decreases, and the hydrogen concentration on the secondary side 14 decreases. The operation amount calculation unit 42 calculates a smaller valve opening degree V(t) of the non-permeable gas pressure regulating valve 22 (V(t) < V0) so that the pressure on the primary side 13 becomes higher (the gas partial pressure difference becomes larger) in order to increase the hydrogen concentration on the secondary side 14 (to make the hydrogen concentration on the secondary side 14 a predetermined value). As a result, as the separation membrane 12 deteriorates, the valve opening degree of the non-permeable gas pressure regulating valve 22 is calculated to be a smaller value.

[0030] According to the present invention, it is possible to detect a decrease in the performance of the separation membrane 12 from such a change in the current operation amount V(t), and when V(t) - V0 < the lower limit value ΔVL, it can be determined that the deterioration of the separation membrane has progressed and notified. Also, when V(t) - V0 > the upper limit value ΔVH, it is considered that some abnormality has occurred in the gas separation system such as a failure of the hydrogen concentration meter, so it is possible to notify that an abnormality has occurred in the gas separation system.

[0031] As described above, from the change in the operation amount calculated by the control device, it is possible to detect the change in the hydrogen permeation amount of the separation membrane, that is, the change in the performance of the separation membrane, and it is possible to diagnose the deterioration state of the separation membrane without adding an additional sensor. As a result, it is possible to reduce the cost of the gas separation system.

[0032] In this embodiment, the hydrogen concentration of the permeated gas is controlled by adjusting the pressure on the primary side 13 from the non-permeable gas pressure regulating valve 22. However, the hydrogen concentration of the permeated gas may also be controlled by adjusting the pressure on the secondary side 14 from the permeated gas pressure regulating valve 23.

[0033] In addition, if the hydrogen concentration of the gas supplied to the separation membrane 12 fluctuates, the initial value V0 of the manipulated variable and the lower limit ΔVL and upper limit ΔVH of the difference between the initial value of the manipulated variable may be corrected using a relational equation between the hydrogen concentration of the supply gas and the manipulated variable.

[0034] In addition, in this embodiment, the manipulated variable calculated from the control for adjusting the concentration of the extracted gas to a predetermined value is used, but the manipulated variable calculated from the control for adjusting the pressure or flow rate to a predetermined value may also be used. The deterioration diagnosis device for the gas separation system is preferably configured using a computer.

[0035] According to the present invention, the number of sensors required for diagnosing deterioration of the separation membrane can be reduced. EXAMPLES

[0036] Fig. 4 is a diagram showing a schematic configuration example of a gas separation system according to a second embodiment of the present invention. The difference from Fig. 1 is that a branch gas pipe 6 that branches gas from a supply gas pipe 3 to a secondary side 14 of a separation membrane 12, and a branch gas flow rate control valve 24 are provided in the branch gas pipe 6. Also, an operation amount calculation unit 42 transmits a valve opening degree of the branch gas flow rate control valve 24.

[0037] The branched gas flow rate control valve 24 adjusts the flow rate of the branched gas branched from the supply gas pipe 3 to the secondary side 14 of the separation membrane 12. On the secondary side 14, the permeated gas (high hydrogen concentration) of the separation membrane is diluted with the branched gas (low hydrogen concentration). In other words, the flow rate of the branched gas is adjusted by the branched gas flow rate control valve 24, thereby adjusting the concentration on the secondary side 14.

[0038] The non-permeating gas pressure regulating valve 22 regulates the pressure on the primary side 13 of the separation membrane 12. An explanation of the pressure gauge display and its control method will be omitted.

[0039] Based on the hydrogen concentration signal of the permeable gas received from the hydrogen concentration signal cable 51, the manipulated variable calculation unit 42 calculates the branch gas flow rate control valve 24 so that the hydrogen concentration of the permeable gas becomes a predetermined value, and transmits the calculated value to the branch gas flow rate control valve 24 through the control signal cable 52. For example, when the concentration of the extracted gas is lower than a predetermined value, the manipulated variable calculation unit 42 calculates the valve aperture of the branch gas flow rate control valve 24 to a small value. Reducing the valve aperture of the branch gas flow rate control valve 24 reduces the flow rate of the branch gas, and the concentration of the extracted gas can be increased. The method of calculating the valve aperture based on the hydrogen concentration may be any conventional method such as proportional control or proportional integral control.

[0040] In addition, in embodiment 1, the non-permeable gas pressure regulating valve 22 and in embodiment 2, the branch gas flow rate regulating valve 24 are the objects of control and their operating amounts are the objects of deterioration monitoring. These determine the output of the gas separation system, and in this sense, they can be called output control valves.

[0041] In the second embodiment, the difference between the gas partial pressure on the primary side and the gas partial pressure on the secondary side, which is proportional to the amount of hydrogen permeated through the separation membrane, can be kept constant, and the performance change of the separation membrane is more clearly reflected as the amount of hydrogen permeated. Therefore, the performance change of the separation membrane is more clearly reflected in the operation amount calculated by the control device, and the deterioration state of the separation membrane can be diagnosed with high accuracy.

[0042] In this embodiment, the gas is branched from the supply gas pipe 3 to the secondary side 14 of the separation membrane 12 , but the gas may be branched from the non-permeation gas pipe 4 to the secondary side 14 of the separation membrane 12 . EXAMPLES

[0043] 5 is a diagram showing a schematic configuration example of a gas separation system according to Example 3. The difference from FIG.

[0044] In Example 3, the operation amounts calculated by the operation amount calculation unit 42 are stored in the database 43, the representative value calculation unit 46 calculates a representative value from the stored operation amounts, and the separation membrane performance evaluation unit 44 evaluates the deterioration state of the separation membrane using the representative value.

[0045] 6 shows the flow of control signals of the control device 41. The database 43 has an initial value VT0, a lower limit value ΔVTL of the difference, and an upper limit value ΔVTH for the representative value of the manipulated variable. In addition, the database 43 stores the manipulated variable V(t) calculated by the manipulated variable calculation unit 42 during the period from time t1 to time t2 (V(t1-t2)). Times t1 and t2 are set in advance based on the operation schedule of the gas separation system 1 and, if the hydrogen concentration in the mixed gas main pipe 2 varies over time, the period of the variation.

[0046] The representative value calculation unit 46 calculates a representative value of the operation amounts using the operation amounts V(t1 to t2) in the period from time t1 to time t2. Two examples of the method of calculating the representative value of the operation amounts will be described below.

[0047] As Example 1, an example of an operation schedule of the gas separation system 1 is shown in Fig. 7. For example, if the gas separation system 1 operates regularly for a certain period of time each day, time t1 is set as the operation start time, and time t2 is set as the operation end time. The representative value calculation unit 46 calculates a time average of the operation amount V (t1-t2) during the period from time t1 to time t2 as a representative value of the operation amount. By using such a representative value of the operation amount, the processing load of the separation membrane performance evaluation unit 44 can be reduced.

[0048] As Example 2, FIG. 8 shows an example of the change over time in the hydrogen concentration of the supply gas of the gas separation system 1. For example, if the hydrogen concentration of the supply gas (mixed gas main pipe 2) varies periodically over time, the period is set from time t1 to time t2 based on the period. For example, if the hydrogen concentration varies over a week period, the period from time t1 to time t2 is set to be between 9:00 and 10:00 on Mondays. Points to consider when setting the period include the fact that the hydrogen concentration is the same every week and that the fluctuation in the hydrogen concentration is relatively small. The representative value calculation unit 46 calculates a time average of the operation amount V (t1 to t2) during the period from time t1 to time t2. If such a representative value of the operation amount is used, the operation amount can be compared under the condition of the same hydrogen concentration (same gas partial pressure) even if the hydrogen concentration of the supply gas varies, so that the deterioration state of the separation membrane can be diagnosed more accurately. EXAMPLES

[0049] Fig. 9 is a diagram showing a schematic configuration example of a gas separation system according to Example 4 of the present invention. The difference from Fig. 5 is that a separation membrane performance evaluation unit 48 calculates a deterioration index value D(t) indicating the deterioration state of the separation membrane 12, and a computer 47 displays the deterioration index value D(t) on a screen.

[0050] Fig. 10 shows the flow of control signals of the control device 41. The difference from the flow of control signals of the control device 41 of the gas separation device system according to Example 1 shown in Fig. 2 is that the separation membrane performance evaluation unit 48 calculates a deterioration index value D(t) indicating the deterioration state of the separation membrane 12. An example of a method for calculating the deterioration index value D(t) will be described below. As shown in formula (1), the deterioration index value D(t) is calculated so that it is 0 in the initial state and 1 when the separation membrane is deteriorated. [Number 1] D(t)=(V(t)-V0) / ΔVL (1) The computer 47 receives the separation membrane deterioration index value D(t) and displays it on the screen. Examples of the display screen of the computer 47 are shown in Figures 11 and 12. Figure 11 shows the current degree of deterioration of the separation membrane. The "initial state" mark and the "state requiring maintenance" mark are connected in a straight line, and the current deterioration state is displayed with a triangular mark (△) on the line. When D(t) is 0, the triangular mark is located on the "initial state" mark on the screen, and when D(t) is 1, the triangular mark is located on the "state requiring maintenance" mark on the screen.

[0051] FIG. 12 shows the change over time in the deterioration state of the separation membrane. The vertical axis represents the deterioration state of the separation membrane, and the horizontal axis represents time. In this case, computer 45 stores the received deterioration state D(t) of the separation membrane and graphs it. From the graph of the change over time in the deterioration state of the separation membrane, it is possible to predict the time when the "state requiring maintenance" will be reached. Note that, although the manipulated variable is used in this embodiment, a representative value of the manipulated variable may also be used. EXAMPLES

[0052] In the first to fourth embodiments, the system output is controlled by the gas separation system output control valve, and the manipulated variable is monitored. In contrast, in the fifth embodiment, the control side is left as it is, and the monitoring target is the hydrogen concentration.

[0053] 13 is a diagram showing a schematic configuration example of a gas separation system according to a fifth embodiment of the present invention. In the fifth embodiment, as shown in FIG. 13, the hydrogen concentration is monitored, the mixed gas hydrogen concentration is detected by a mixed gas hydrogen concentration sensor 32, and the extracted gas hydrogen concentration is detected by an extracted gas hydrogen concentration sensor 31. These hydrogen concentration signals are input to a separation membrane performance evaluation unit 44 and compared with the stored contents of a database 43 to evaluate the performance of the separation membrane. The separation membrane performance evaluation result is then transmitted to a computer 45.

[0054] Figure 14 shows the characteristics showing the relationship between the hydrogen concentration in the mixed gas and the hydrogen concentration in the extracted gas, which is proportional in the low concentration range, but becomes saturated as the concentration increases. Regarding this saturation characteristic, the solid line shows the characteristics of the hydrogen concentration in the mixed gas and the hydrogen concentration in the extracted gas in the initial state, whereas with operation over time, the hydrogen concentration in the extracted gas when the hydrogen concentration in the mixed gas is used as the standard fluctuates due to deterioration or abnormalities in the gas separation system.

[0055] For this reason, in the fifth embodiment, data on the solid line indicating the initial state and the dotted line indicating a threshold for judging deterioration or abnormality in separation membrane performance are stored in advance as stored contents in database 43, and the relationship between the detected mixed gas hydrogen concentration and the extracted gas hydrogen concentration is monitored for deviations above or below the range of the dotted line in Fig. 13. Deviations above are diagnosed as a center value abnormality, and deviations below are diagnosed as deterioration of the separation membrane. EXAMPLES

[0056] In the sixth embodiment, the control side remains the same, and the flow rate and pressure of the mixed gas are monitored.

[0057] 15 is a diagram showing a schematic configuration example of a gas separation system according to Example 6 of the present invention. In Example 6, as shown in Fig. 15, the primary and secondary pressures and the mixed gas flow rate are monitored, and the primary and secondary pressures are detected by pressure gauges 33 and 34, and the mixed gas flow rate is detected by flowmeter 35. These detection signals are input to separation membrane performance evaluation unit 44 and compared with the stored contents of database 43 to evaluate the performance of the separation membrane. The separation membrane performance evaluation result is then transmitted to computer 45.

[0058] Figure 16 shows the characteristics showing the relationship between the primary and secondary pressure difference and the mixed gas flow rate, which are basically proportional. Regarding this proportionality characteristic, the solid line shows the characteristics showing the relationship between the primary and secondary pressure difference and the mixed gas flow rate, but with aging operation, the primary and secondary pressure difference when the mixed gas flow rate is used as the standard fluctuates due to deterioration or abnormalities in the gas separation system.

[0059] For this reason, in the sixth embodiment, data on the solid line indicating the initial state and the dotted line indicating a threshold for judging deterioration or abnormality in the separation membrane performance are stored in advance as stored contents in database 43, and the relationship between the detected primary / secondary pressure difference and the mixed gas flow rate is monitored for deviation above or below the range of the dotted line in Fig. 16. If there is an upward deviation, it is diagnosed as a center value abnormality, and if there is a downward deviation, it is diagnosed as deterioration of the separation membrane. EXAMPLES

[0060] In the seventh embodiment, the function of a representative value calculation unit 46 is further added to the components of the fifth embodiment. The representative value calculation unit 46 has basically the same function as that described in Fig. 5, and obtains the time average value of the measurement values ​​at regular time intervals to obtain the characteristics of the mixed gas hydrogen concentration and the extracted gas hydrogen concentration. EXAMPLES

[0061] Various embodiments of the present invention have been described above, but each part of these processes can be further modified and implemented as follows, which will be collectively described as embodiment 8.

[0062] In the above embodiment, the gas is extracted from the secondary side 14 of the separation membrane, but the gas may be extracted from the primary side 13 of the separation membrane. In this case, the hydrogen concentration in the non-permeate gas pipe 4 is measured, and the operation amount calculation unit 42 calculates the operation amount so that the concentration becomes a predetermined value.

[0063] In addition, the deterioration state of the separation membrane is evaluated using the operation amount such as the valve opening of the regulating valve calculated by the operation amount calculation unit 42, but the deterioration state of the separation membrane may be evaluated using measured values ​​such as pressure, flow rate, and hydrogen concentration. When pressure and flow rate are used, the evaluation is performed using a value normalized by dividing the pressure by the flow rate. When hydrogen concentration is used, the hydrogen concentration is corrected by the hydrogen concentration of the gas supplied to the separation membrane.

[0064] Further, although the embodiment has been described with one separation membrane, the separation membranes may be connected in parallel or in series.

[0065] In addition, the mixed gas flow control valve 21, the non-permeate gas pressure control valve 22, the permeate gas pressure control valve 23, and the branch gas flow control valve 24 may be devices that adjust flow rate or pressure, and the compressor discharge pressure may be adjusted according to the pressure distribution, and the compressor discharge pressure may be used as an operating variable to evaluate the deterioration state of the separation membrane.

[0066] Furthermore, the mixed gas pipe 3, the non-permeate gas pipe 4, the permeate gas pipe 5, the branch gas pipe 6, and the separation membrane module 11 may each be provided with a heater or a cooler for adjusting the temperature of the fluid. [Explanation of symbols]

[0067] 1: Gas separation system 2:Mixed gas main pipe 3: Mixed gas piping 4: Non-permeable gas piping 5: Permeation gas piping 6: Branch gas piping 11: Separation membrane module 12: Separation membrane 13: Primary side 14: Secondary side 21: Mixed gas flow control valve 22: Non-permeable gas pressure regulating valve 23: Permeation gas pressure regulating valve 24: Branch gas flow control valve 31: Extracted gas hydrogen concentration meter 32: Mixed gas hydrogen concentration meter 33: Primary gas pressure gauge 34: Secondary gas pressure gauge 35: Mixed gas flow meter 41: Control device 42: Operation amount calculation section 43: Database 44, 48: Separation Membrane Performance Evaluation Section 45, 47: Computer (equipment with user interface) 46: Representative value calculation section 51: Hydrogen concentration signal cable 52: Flow control valve control signal cable

Claims

1. A deterioration diagnosis device for a gas separation system having one or more gas separation membranes that selectively permeate a specific gas, the output of the gas separation membranes being controlled by an output control valve, The deterioration diagnosis device for a gas separation system is characterized by comprising an input unit that inputs process quantities affected by deterioration of the gas separation membrane, a database that stores the process quantities when a gas separation system is operated using a gas separation membrane in a new state (before deterioration), and a separation membrane performance evaluation unit that evaluates the performance of the gas separation membrane based on the difference between the input process quantities at the current time and the process quantities in the new state.

2. The deterioration diagnosis device for a gas separation system according to claim 1, A deterioration diagnosis device for a gas separation system, wherein a process variable affected by deterioration of the gas separation membrane is an operation variable of the output control valve.

3. The deterioration diagnosis device for a gas separation system according to claim 2, A deterioration diagnosis device for a gas separation system, characterized in that the database includes an initial value of the process quantity and a threshold value for the difference between the process quantities, and the separation membrane performance evaluation unit determines deterioration and abnormality occurrence of the gas separation membrane.

4. The deterioration diagnosis device for a gas separation system according to claim 1, A deterioration diagnosis device for a gas separation system, characterized in that an output control valve that controls the output of the gas separation membrane is a non-permeable gas pressure regulating valve that adjusts the non-permeable gas pressure of the gas separation membrane, or a branch gas flow rate regulating valve that branches a specific gas to the secondary side of the gas separation membrane.

5. The deterioration diagnosis device for a gas separation system according to claim 1, The deterioration diagnosis device for a gas separation system, wherein the separation membrane performance evaluation unit evaluates the performance of the gas separation membrane using a representative value of the process amount at the current time point that is acquired over a certain period of time.

6. The deterioration diagnosis device for a gas separation system according to claim 1, The deterioration diagnostic device for a gas separation system, wherein the separation membrane performance evaluation unit converts a deterioration state into an index and outputs the index to an external device.

7. The deterioration diagnosis device for a gas separation system according to claim 1, A deterioration diagnosis device for a gas separation system, wherein the process variables affected by deterioration of the gas separation membrane are the hydrogen concentration in the mixed gas on the primary side of the gas separation membrane and the hydrogen concentration in the extracted gas on the secondary side.

8. The deterioration diagnosis device for a gas separation system according to claim 7, The database includes an initial value of the relationship between the mixed gas hydrogen concentration on the primary side of the gas separation membrane and the extracted gas hydrogen concentration on the secondary side, and a threshold value for the difference between the mixed gas hydrogen concentration and the extracted gas hydrogen concentration, and the separation membrane performance evaluation unit determines deterioration and abnormality of the gas separation membrane.

9. The deterioration diagnosis device for a gas separation system according to claim 1, A deterioration diagnosis device for a gas separation system, wherein process variables affected by deterioration of the gas separation membrane are the pressure difference between the primary side and secondary side of the gas separation membrane and the mixed gas flow rate on the primary side.

10. The deterioration diagnosis device for a gas separation system according to claim 7, The database includes an initial value of the relationship between the pressure difference between the primary side and the secondary side of the gas separation membrane and the mixed gas flow rate on the primary side, and a threshold value for the pressure difference between the primary side and the secondary side, and the separation membrane performance evaluation unit determines deterioration and abnormality occurrence of the gas separation membrane, characterized in that the database includes an initial value of the relationship between the pressure difference between the primary side and the secondary side of the gas separation membrane and a threshold value for the pressure difference between the primary side and the secondary side of the gas separation membrane.

11. The deterioration diagnosis device for a gas separation system according to claim 1, The deterioration diagnosis device for a gas separation system, wherein the output control valve controls the gas hydrogen concentration in the gas separation system.

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