Deterioration checking device for gas separation system

Abstract

Provided is a deterioration checking device capable of checking for a deterioration in a gas separation system by using an existing sensor required for system operation. This deterioration checking device is for the gas separation system that has one or more gas separation membranes for the selective permeation of a specific gas, and controls an output of the gas separation membrane by using an output control valve. The deterioration checking device for the gas separation system is characterized in that the gas separation system is provided with: an input unit for capturing a process quantity affected by the deterioration of the gas separation membrane; a database for storing the process quantity when the gas separation system is operated by using the gas separation membrane in a new state (before deteriorated); and a separation membrane performance evaluation unit for evaluating the performance of the gas separation membrane from a difference between the captured process quantity at the current point in time and the process quantity in the new state.

Description

Gas separation system deterioration diagnostic device

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

[0002] One method for separating a specific gas from a mixture of multiple gases is to use a separation membrane that selectively permeates gases. Separation membranes include, for example, molecular sieve membranes, such as ceramic membranes, which separate gases based on differences in molecular diameter, and polymer membranes that 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 permeate. 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. Furthermore, the amount of gas permeation through a separation membrane decreases as the membrane deteriorates. To maintain separation efficiency, gas separation systems diagnose the state of membrane deterioration, and if the membrane deteriorates, maintenance such as replacing the membrane is performed.

[0004] An example of a method for diagnosing degradation of a separation membrane is Patent Document 1. Patent Document 1 describes a method for measuring the flow rate in a residual gas discharge channel and the flow rate in a permeate gas discharge channel of a separation membrane and evaluating the degradation state of the separation membrane using the ratio of these flow rates. The purpose of this patent document is to provide a membrane separation system and a method for evaluating degradation of a separation membrane that can inexpensively evaluate the degradation state of a separation membrane, and the method comprises: "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 has not permeated the separation membrane flows out; a permeate gas discharge channel through which permeate gas that has permeated the separation membrane flows out; a residual gas flow meter for measuring a flow rate F1 in the residual gas discharge channel; a permeate gas flow meter for measuring a flow rate F2 in the permeate gas discharge channel; and an arithmetic and control device, wherein the arithmetic and control device determines a ratio Rm between the flow rates F1 and F2 and compares the determined ratio Rm with a preset ratio Rk between the flow rates F1 and F2 to evaluate the degradation state of the separation membrane."

[0005] Japanese Patent Application Laid-Open No. 2022-127393

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

[0007] In this case, if the concentration of a specific gas cannot be controlled properly due to system deterioration or other reasons, and gas with a concentration outside the allowable range is supplied to the equipment, the equipment may malfunction. This could lead to a major accident in facilities such as production facilities and chemical plants, so deterioration diagnosis of gas separation systems must be carried out 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 such as concentration and flow rate, which requires multiple sensors such as gas concentration meters and flow meters, which increases 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 required for system operation, without the need to install additional sensors for the purpose.

[0010] In order to solve the above-mentioned 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 membranes is controlled by an output control valve, the deterioration diagnosis device comprising: an input unit that inputs process quantities affected by deterioration of the gas separation membrane; a database that stores the process quantities 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 quantity at the current time and the process quantity in the new state."

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

[0012] FIG. 1 is a schematic configuration example showing a gas separation system according to Example 1 of the present invention. FIG. 1 is a diagram showing the flow of signals in a control device in the gas separation system according to Example 1 of the present invention. FIG. 2 is a diagram showing the processing flow of a separation membrane performance evaluation unit in a control device in the gas separation system according to Example 1 of the present invention. FIG. 2 is a schematic configuration example showing a gas separation system according to Example 2 of the present invention. FIG. 3 is a diagram showing a schematic configuration example showing a gas separation system according to Example 3 of the present invention. FIG. 4 is a diagram showing an example of an operation schedule for the gas separation system according to Example 3 of the present invention. FIG. 5 is a diagram showing an example of a time change in the hydrogen concentration of the feed gas to the gas separation system according to Example 3 of the present invention. FIG. 6 is a diagram showing an example of a schematic configuration example showing a gas separation system according to Example 4 of the present invention. FIG. 7 is a diagram showing the flow of signals in a control device in the gas separation system according to Example 4 of the present invention. FIG. 8 is a diagram showing an example of a computer screen display for the gas separation system according to Example 4 of the present invention. FIG. 9 is a diagram showing an example of a computer screen display for the gas separation system according to Example 4 of the present invention. FIG. 10 is a diagram showing an example of a schematic configuration example showing a gas separation system according to Example 5 of the present invention. FIG. 11 is a diagram showing the characteristics of the mixed gas hydrogen concentration and the extracted gas hydrogen concentration. FIG. 12 is a diagram showing an example of a schematic configuration example showing a gas separation system according to Example 6 of the present invention. FIG. 13 is a diagram showing the characteristics of the primary and secondary pressure difference and the mixed gas flow rate. FIG. 10 is a diagram showing a schematic configuration example of a gas separation system according to a seventh embodiment of the present invention.

[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 can diagnose deterioration using existing sensors necessary for system operation.In this case, the existing sensors are sensors that detect process quantities that are affected by deterioration of separation membrane performance, and that can estimate deterioration from the change in 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 that are affected by deterioration and whose deterioration can be estimated from changes 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 Examples 1 to 4, the hydrogen concentration of the mixed gas is focused on in Examples 5 and 7, and the flow rate and pressure of the mixed gas is focused on in Example 6.

[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 a supply gas containing a mixture of hydrogen and methane is controlled so that the hydrogen concentration of the extracted gas is kept at a predetermined value even when the hydrogen concentration of the supply gas fluctuates around a certain value. For example, the hydrogen concentration may be controlled to a constant 20% (vol%), above or below a predetermined value, or within a predetermined range.

[0018] 1 , 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 from a main mixed gas pipe 2. Gas separation system 1 has a gas separation membrane module 11. 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 the separation membrane 12, but hydrogen permeates more easily than methane. For this reason, the hydrogen concentration is higher on the secondary side 14 than on the primary side 13. The permeation amount of each gas is proportional to the partial pressure difference between the primary side 13 and the secondary side 14.

[0020] The mixed gas pipe 3 is provided with a mixed gas flow rate control valve 21. The mixed gas flow rate control valve 21 adjusts the flow rate of the mixed gas supplied to the separation membrane. The display of the flow meter and the control method thereof will not be described here.

[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 in accordance with 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. Explanation of the pressure gauge display and its control method will be omitted.

[0022] The permeate gas pipe 5 is also provided with an extracted gas hydrogen concentration meter 31. The extracted gas hydrogen concentration meter 31 measures the hydrogen concentration of the permeate 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 and calculates the valve opening of the non-permeate gas pressure regulating valve 22 based on the hydrogen concentration signal so that the hydrogen concentration of the permeate gas (extracted gas) becomes a predetermined value. The manipulated variable calculation unit 42 transmits this to the non-permeate gas pressure regulating valve 22 via a control signal cable 52. Note that the manipulated variable calculation unit 42 may also calculate the valve opening manipulated variable of the non-permeate gas pressure regulating valve 22 from control to set the pressure or flow rate to a predetermined value instead of the hydrogen concentration signal.

[0024] The manipulated variable 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, the manipulated variable calculation unit 42 calculates the valve aperture of the non-permeate gas pressure regulating valve 22 to a small value, for example, when the concentration of the permeate gas is lower than a predetermined value. Reducing the valve aperture of the non-permeate gas pressure regulating valve 22 increases the pressure on the primary side 13, increases the gas partial pressure difference, increases the amount of hydrogen permeation through the separation membrane, and can increase the hydrogen concentration of the permeate gas. 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] The control device 41 includes a database 43 and a separation membrane performance evaluation unit 44 in addition to the operation amount calculation unit 42, and is connected to an external computer (user interface-equipped device). Figure 2 shows the flow of control signals between the operation amount calculation unit 42, database 43, and membrane separation performance evaluation unit 44 that constitute the control device 41, and the external computer (user interface-equipped device).

[0026] The following data is stored in advance in the database 43. 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 manipulated variable (valve opening) V0 (hereinafter referred to as the "initial value of the manipulated variable") when the gas separation system is operated using a separation membrane 12 in a brand new state (before deterioration). - The lower limit ΔVL of the difference between the current manipulated variable V(t) and the initial value of the manipulated variable. - The 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 manipulated variable V(t) calculated by the manipulated variable calculation unit 42 The initial value V0 of the manipulated variable, a lower limit ΔVL of the difference from the initial value of the manipulated variable, and an upper limit ΔVH thereof, which are stored in advance in the database 43. 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 results to the computer 45. The separation membrane performance evaluation results are, 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 results of the separation membrane performance evaluation unit 44 will be described. Figure 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 manipulated variable value V0 is calculated (processing step S1). The difference ΔV is compared with a lower limit ΔVL (processing step S2). If ΔV<lower limit ΔVL, it is determined that the separation membrane 12 has deteriorated, and this result is sent to the computer 45 (processing step S3).

[0028] On the other hand, if ΔV<lower limit ΔVL is not satisfied, the process proceeds to the next step, where the difference ΔV is compared with the upper limit ΔVH (step S4). If ΔV>upper limit ΔVH, it is determined that an abnormality has occurred, and this result is sent to the computer 45 (step S5). On the other hand, if ΔV>upper limit ΔVH is not satisfied, the process returns to step S1.

[0029] In the gas separation system 1, as the separation membrane 12 deteriorates, the amount of hydrogen permeated through the separation membrane decreases, resulting in a lower hydrogen concentration on the secondary side 14. The manipulated variable calculation unit 42 calculates the valve opening V(t) of the non-permeate gas pressure regulating valve 22 to a smaller value (V(t)<V0) so that the pressure on the primary side 13 increases (the gas partial pressure difference increases) in order to increase the hydrogen concentration on the secondary side 14 (set the hydrogen concentration on the secondary side 14 to a predetermined value). As a result, as the separation membrane 12 deteriorates, the valve opening of the non-permeate gas pressure regulating valve 22 is calculated to a smaller value.

[0030] According to the present invention, a performance degradation of the separation membrane 12 can be detected from such a change in the current manipulated variable V(t), and if V(t) - V0 < lower limit value ΔVL, it can be determined that the separation membrane has deteriorated and can be notified. Also, if V(t) - V0 > upper limit value ΔVH, it is considered that some abnormality has occurred in the gas separation system, such as a malfunction of the hydrogen concentration meter, and it can be notified that an abnormality has occurred in the gas separation system.

[0031] As described above, changes in the hydrogen permeation rate of the separation membrane, i.e., changes in the performance of the separation membrane, can be detected from changes in the manipulated variable calculated by the control device, and the deterioration state of the separation membrane can be diagnosed without installing additional sensors, which enables cost reductions in the gas separation system.

[0032] In this embodiment, the hydrogen concentration of the permeable gas is controlled by adjusting the pressure on the primary side 13 using the non-permeable gas pressure adjustment valve 22, but the hydrogen concentration of the permeable gas may also be controlled by adjusting the pressure on the secondary side 14 using the permeable gas pressure adjustment 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 operating variable and the lower limit value ΔVL and upper limit value ΔVH of the difference between the initial value of the operating variable may be corrected using a relational equation between the hydrogen concentration of the supply gas and the operating 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. Note that 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 installed for diagnosing the deterioration of the separation membrane can be reduced.

[0036] 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 the supply gas pipe 3 to the secondary side 14 of the 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 the valve opening degree of the branch gas flow rate control valve 24.

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

[0038] The non-permeate gas pressure regulating valve 22 regulates the pressure on the primary side 13 of the separation membrane 12. The pressure gauge display and its control method will not be described here.

[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 sends the calculated value to the branch gas flow rate control valve 24 through the control signal cable 52. For example, if 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 smaller 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 Example 1, the non-permeable gas pressure regulating valve 22 is the object of control, and in Example 2, the branch gas flow rate regulating valve 24 is the object 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 Example 2, the difference between the primary-side gas partial pressure and the secondary-side gas partial pressure, which is proportional to the amount of hydrogen permeated through the separation membrane, can be kept constant, and changes in separation membrane performance are more clearly reflected in the amount of hydrogen permeated. Therefore, changes in separation membrane performance are more clearly reflected in the manipulated variable calculated by the control device, and the deterioration state of the separation membrane can be accurately diagnosed.

[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 .

[0043] 5 is a diagram showing a schematic configuration example of a gas separation system according to Example 3. The difference from FIG. 4 is that a control device 41 includes a representative value calculation unit 46.

[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 from the control device 41. The database 43 stores an initial value VT0, a lower limit value ΔVTL of the difference, and an upper limit value ΔVTH for the representative values ​​of the manipulated variables. It also stores the manipulated variable V(t) calculated by the manipulated variable calculation unit 42 for 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 fluctuates over time, the period of fluctuation.

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

[0047] As Example 1, an example of an operation schedule for the gas separation system 1 is shown in Figure 7. For example, if the gas separation system 1 operates regularly for a certain period of time per 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 to t2) during the period from time t1 to time t2 as a representative value of the operation amount. Using such a representative value of the operation amount can reduce the processing load of the separation membrane performance evaluation unit 44.

[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) fluctuates periodically over time, the period from time t1 to time t2 is set based on that period. For example, if the hydrogen concentration fluctuates over a one-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 whether the hydrogen concentration is equivalent every week and whether fluctuations in the hydrogen concentration are relatively small. The representative value calculation unit 46 time-averages the manipulated variable V (t1 to t2) over the period from time t1 to time t2. Using such a representative value of the manipulated variable allows the manipulated variable to be compared under conditions of equivalent hydrogen concentrations (equivalent gas partial pressures) even if the hydrogen concentration of the supply gas fluctuates, thereby enabling more accurate diagnosis of the deterioration state of the separation membrane.

[0049] 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 Figure 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 from the control device 41. This differs from the flow of control signals from the control device 41 of the gas separation apparatus system according to Example 1 shown in FIG. 2 in that the separation membrane performance evaluation unit 48 calculates a degradation index value D(t) indicating the degradation state of the separation membrane 12. An example of a method for calculating the degradation index value D(t) is described below. As shown in equation (1), the degradation index value D(t) is calculated so that it is 0 in the initial state and 1 when the separation membrane is degraded. [Equation 1] D(t) = (V(t) - V0) / ΔVL (1) The computer 47 receives the separation membrane degradation index value D(t) and displays it on the screen. Examples of the display screen of the computer 47 are shown in FIGS. 11 and 12. FIG. 11 shows the current degree of degradation of the separation membrane. The "initial state" mark and the "state requiring maintenance" mark are connected by a straight line, and the current degradation state is displayed on the line with a triangular mark (△). When D(t) is 0, a triangle mark is positioned on the mark for "initial state" on the screen, and when D(t) is 1, a triangle mark is positioned on the mark for "state requiring maintenance" 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, the 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 when the "state requiring maintenance" will occur. Note that although manipulated variables are used in this embodiment, representative values ​​of the manipulated variables may also be used.

[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 Example 5 of the present invention. In Example 5, as shown in Fig. 13, the hydrogen concentration is monitored, and the mixed gas hydrogen concentration is detected by mixed gas hydrogen concentration sensor 32, and the extracted gas hydrogen concentration is detected by extracted gas hydrogen concentration sensor 31. These hydrogen concentration signals are input into separation membrane performance evaluation unit 44, which compares them with the stored contents of database 43 to evaluate the performance of the separation membrane, and the separation membrane performance evaluation results are sent to computer 45.

[0054] 14 shows the characteristics of the relationship between the hydrogen concentration of the mixed gas and the hydrogen concentration of the extracted gas, and although there is a proportional relationship in the low concentration range, as the concentration increases, there is a saturation relationship. Regarding this saturation characteristic, the solid line shows the characteristics of the hydrogen concentration of the mixed gas and the hydrogen concentration of the extracted gas obtained in the initial state, but with operation over time, the hydrogen concentration of the extracted gas when taken as the standard for the hydrogen concentration of the mixed gas fluctuates due to deterioration or abnormalities in the gas separation system.

[0055] For this reason, in Example 5, data representing the solid line indicating the initial state and the dotted line indicating the threshold for determining whether separation membrane performance has deteriorated or is abnormal 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 Figure 13. If there is an upward deviation, it is diagnosed as an abnormality in the center value, and if there is a downward deviation, it is diagnosed as deterioration of the separation membrane.

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

[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 flow meter 35. These detection signals are input into separation membrane performance evaluation unit 44, which compares them with the stored contents of database 43 to evaluate the performance of the separation membrane, and transmits the separation membrane performance evaluation results to computer 45.

[0058] 16 shows the relationship between the primary and secondary pressure difference and the mixed gas flow rate, which is basically proportional. Regarding this proportionality characteristic, the solid line indicates the relationship between the primary and secondary pressure difference and the mixed gas flow rate. However, with operation over time, the primary and secondary pressure difference when the mixed gas flow rate is used as the reference will fluctuate due to deterioration or abnormalities in the gas separation system.

[0059] For this reason, in Example 6, data representing the solid line indicating the initial state and the dotted line indicating a threshold for determining whether separation membrane performance is degraded or abnormal 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 Figure 16. If the deviation is above, it is diagnosed as a center value abnormality, and if the deviation is below, it is diagnosed as separation membrane degradation.

[0060] In Example 7, the function of a representative value calculation unit 46 is further added to Example 5. 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.

[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 an eighth embodiment.

[0062] In the above embodiment, the case where gas is extracted from the secondary side 14 of the separation membrane has been described, but gas may also 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 manipulated variable calculation unit 42 calculates the manipulated variable so that the concentration becomes a predetermined value.

[0063] Furthermore, although the deterioration state of the separation membrane is evaluated using the manipulated variable such as the valve opening of the regulating valve calculated by the manipulated variable calculation unit 42, the deterioration state of the separation membrane may also 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 evaluation is performed using the hydrogen concentration of the gas supplied to the separation membrane.

[0064] Although the case where one separation membrane is provided has been described, the separation membranes may be connected in parallel or in series.

[0065] Furthermore, 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 any 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 state of deterioration of the separation membrane.

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

[0067] DESCRIPTION OF SYMBOLS 1: Gas separation system 2: Mixed gas main pipe 3: Mixed gas pipe 4: Non-permeate gas pipe 5: Permeate gas pipe 6: Branch gas pipe 11: Separation membrane module 12: Separation membrane 13: Primary side 14: Secondary side 21: Mixed gas flow control valve 22: Non-permeate gas pressure control valve 23: Permeate gas pressure control valve 24: Branch gas flow control valve 31: Extracted gas hydrogen concentration meter 32: Mixed gas hydrogen concentration meter 33: Primary side gas pressure gauge 34: Secondary side gas pressure gauge 35: Mixed gas flow meter 41: Control device 42: Operation quantity calculation unit 43: Database 44, 48: Separation membrane performance evaluation unit 45, 47: Computer (equipment with user interface) 46: Representative value calculation unit 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 specific gases, the output of which is controlled by an output control valve, the deterioration diagnosis device comprising: an input unit that inputs process quantities affected by deterioration of the gas separation membrane; a database that stores the process quantities 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 current process quantity input and the process quantity in the new state.

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

3. A deterioration diagnosis device for a gas separation system as described in claim 2, wherein 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 judges deterioration and the occurrence of abnormalities in the gas separation membrane.

4. A deterioration diagnosis device for a gas separation system as described in claim 1, characterized in that the 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. A deterioration diagnosis device for a gas separation system as described in claim 1, characterized in that the separation membrane performance evaluation unit evaluates the performance of the gas separation membrane using a representative value of the process quantity at the current time point acquired over a certain period of time.

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

7. A deterioration diagnosis device for a gas separation system as described in claim 1, characterized in that 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. A deterioration diagnosis device for a gas separation system as described in claim 7, wherein 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 judges deterioration and abnormality of the gas separation membrane.

9. A deterioration diagnosis device for a gas separation system as described in claim 1, characterized in that the process variables affected by deterioration of the gas separation membrane are the pressure difference between the primary and secondary sides of the gas separation membrane and the mixed gas flow rate on the primary side.

10. A deterioration diagnosis device for a gas separation system as described in claim 7, wherein the database includes an initial value of the relationship between 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, and a threshold value for the pressure difference between the primary side and secondary side, and the separation membrane performance evaluation unit judges deterioration and abnormality occurrence of the gas separation membrane.

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

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