Deterioration diagnostic device for gas separation system

Abstract

Provided is a deterioration diagnostic device for a gas separation system capable of diagnosing deterioration using an existing sensor required for normal operation of the system without additional installation of a sensor for deterioration diagnosis of a separation membrane. A deterioration diagnostic device (41) for a gas separation system (1) has one or more gas separation membranes (12) that selectively transmit a specific gas, and controls an output of the gas separation membrane(s) (12) by output control valves (22, 23). The deterioration diagnostic device (41) comprises an input unit (42) that captures a process amount affected by deterioration of the gas separation membrane(s) (12), and a separation membrane performance evaluation unit (43) that evaluates the performance of the gas separation membrane(s) (12) from the process amount at the point in time of the capture.

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 allows gas to permeate. 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 be permeated. Gases that pass through without passing through the separation membrane are called non-permeating gases, and gases that permeate the separation membrane are called non-permeating gases.

[0003] The amount of gas permeation through a separation membrane is proportional to the difference between the partial pressure of the supply gas and the partial pressure of the permeating gas multiplied by the membrane area. Furthermore, the amount of gas permeation through a separation membrane decreases as the membrane deteriorates. In gas separation systems, to maintain the quality of the product gas, the deterioration state of the separation membrane is diagnosed, and if the separation membrane deteriorates, maintenance such as replacing the membrane is performed.

[0004] An example of a method for diagnosing deterioration 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 deterioration 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 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 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 deterioration state of the separation membrane."

[0005] JP 2022-127393 A

[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 different from natural gas is mixed with natural gas and transported using an existing gas grid containing natural gas, such as natural gas mainly composed of methane, and a deterioration diagnosis method for a system for controlling the concentration of a specified gas in a gas separation facility, a chemical plant, etc.

[0007] In this case, if the concentration of a specific gas in the product gas cannot be controlled properly due to deterioration of the separation membrane, etc., and gas outside the allowable range of the product specification gas concentration is supplied to the equipment, the equipment may break down. This could lead to a major accident in consumer facilities such as chemical plants, so deterioration diagnosis of the gas separation system must be carried out regularly.

[0008] For this reason, it is necessary to diagnose deterioration of the gas separation system. However, deterioration diagnosis of the separation membrane in a typical gas separation system requires many measurements such as concentration and flow rate, so it is necessary to add many sensors such as gas concentration meters and flow meters for deterioration diagnosis, which increases costs, which is an issue.

[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 normal operation of the system, without the need to install additional sensors for the purpose.

[0010] In order to solve the above problem, 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 takes in process quantities that are affected by the deterioration of the gas separation membrane; and a separation membrane performance evaluation unit that evaluates the performance of the gas separation membrane from the taken-in process quantities at the current time."

[0011] According to the present invention, deterioration diagnosis can be performed using existing sensors required for normal operation of the system without installing additional sensors for deterioration diagnosis of the separation membrane, thereby reducing the need to install sensors for deterioration diagnosis of the separation membrane.

[0012] FIG. 1 is a diagram showing a schematic configuration example of 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 diagram showing a schematic configuration example of a gas separation system according to Example 2 of the present invention. FIG. 3 is a diagram showing the flow of signals in a control device in the gas separation system according to Example 2 of the present invention. FIG. 4 is a diagram showing an example of a computer screen display of a gas separation system according to Example 3 of the present invention. FIG. 5 is a diagram showing the characteristics of the difference between the permeate side pressure and the non-permeate side pressure of a separation membrane and the flow rate of the mixed gas supplied to the system. FIG. 6 is a diagram showing a schematic configuration example of a gas separation system according to Example 5 of the present invention. FIG. 7 is a diagram showing the flow of signals in a control device in a gas separation system according to Example 5 of the present invention.

[0013] Hereinafter, examples of the present invention will be described with reference to the drawings. Note that the same components are designated by the same reference numerals, and if a description is redundant, that description may be omitted. Furthermore, the present invention is not limited to the following examples.

[0014] The present invention aims to provide a method and apparatus for diagnosing deterioration in a gas separation system that enables deterioration diagnosis using existing sensors required for the operation of the gas separation system. In this case, the existing sensors are sensors required to control the concentration of a specific gas to the product gas specification during normal operation, and simultaneously detect process variables that are affected by deterioration of separation membrane performance. The present invention makes it possible to estimate deterioration from the change in the process variables measured by these sensors between the current process variables and the initial process variables before operation begins.

[0015] 1 is a diagram showing a schematic configuration example of a gas separation system 1 and a control device 41 according to a first embodiment of the present invention. The gas separation system 1 is mainly composed of a mixed gas supply pipe 3 connected to a mixed gas main pipe 2, a mixed gas flow rate control valve 21, separation membrane modules 11a to 11c, a non-permeate gas pressure control valve 22a, a permeate gas pressure control valve 22b, a non-permeate gas concentration control valve 23a, a permeate gas concentration control valve 23b, a non-permeate gas pressure gauge 31a, a permeate gas pressure gauge 31b, a product gas concentration meter 32, and a control device 41. The non-permeate gas is a gas that does not permeate the separation membrane 12 of the separation membrane module 11, passes through the non-permeate side 13, and is discharged from the separation membrane module 11. The permeate gas is a gas that permeates the separation membrane 12 of the separation membrane module 11, passes through the permeate side 14, and is discharged from the separation membrane module 11.

[0016] The above configurations are the instruments and devices necessary for explaining the embodiments of the present invention, but instruments and devices may be added as needed during actual operation. Furthermore, while the gas separation system 1 in FIG. 1 shows an example in which three separation membrane modules 11 are connected in parallel, the number of separation membrane modules may be one or more, and they may be connected in series or in a series-parallel combination instead of in parallel. Furthermore, the gas separation system 1 in FIG. 1 may be a large-scale facility having multiple separation membrane module groups.

[0017] The gas separation system 1 controls the hydrogen concentration of the product gas, which is a mixture of hydrogen and methane, to a predetermined value according to product specifications, even if the hydrogen concentration of the gas supplied to the gas separation system from the mixed gas main pipe 2 fluctuates. For example, the hydrogen concentration may be controlled to a constant 20 vol% or within a predetermined range. A mixed gas of hydrogen and methane is supplied to the separation membrane module 11 through the mixed gas supply pipe 3 connected to the mixed gas main pipe 2. Of the mixed gas supplied from the mixed gas supply pipe 3, mainly hydrogen permeates the separation membrane 12 and is discharged from the separation membrane module 11 as a permeated gas. Methane also permeates the separation membrane 12, but hydrogen permeates more easily than methane. Therefore, the permeated gas discharged from the permeate side 14 has a higher hydrogen concentration than the non-permeated gas passing through the non-permeated side 13. The permeation rate of each gas is proportional to the partial pressure difference between the feed gas or non-permeated gas and the permeated gas. The mixed gas supply pipe 3 is provided with a mixed gas flow control valve 21. The mixed gas flow rate control valve 21 adjusts the flow rate of the mixed gas supplied to the separation membrane 12. A description of the control method will be omitted. The mixed gas return pipe 4a is provided with a non-permeate gas pressure control valve 22a. The non-permeate gas pressure control valve 22a adjusts the pressure on the non-permeate side 13 of the separation membrane according to the value on the non-permeate gas pressure gauge 31a, depending on the hydrogen concentration of the permeate gas. Details will be described later. The mixed gas return pipe 4b is provided with a permeate gas pressure control valve 22b. The permeate gas pressure control valve 22b adjusts the pressure on the permeate side 14 according to the value on the permeate gas pressure gauge 31b. A description of the control method will be omitted.

[0018] These mixed gas return gas pipes 4 may be connected to, for example, the mixed gas main pipe 2 and returned as unused gas; there are no further connection restrictions. The product gas pipe 5 is also provided with a product gas hydrogen concentration meter 32. The product gas hydrogen concentration meter 32 measures the hydrogen concentration of the gas in the product gas pipe 5 and adjusts the valve openings of the non-permeate gas concentration control valve 23a and the permeate gas concentration control valve 23b so that a predetermined product gas hydrogen concentration is achieved. The adjustment method will be described later. The hydrogen concentration of the gas in the product gas pipe obtained from the product gas hydrogen concentration meter 32 is transmitted to the operation amount calculation unit 42 of the control device 41 via a hydrogen concentration signal cable 52. The mixed gas flow rate control valve 21, non-permeate gas pressure control valve 22a, permeate gas pressure control valve 22b, non-permeate gas concentration control valve 23a, and permeate gas concentration control valve 23b control the output of the gas separation membrane, and therefore can be considered "output control valves."

[0019] The control device 41 has two main functions. One is to control the gas separation system 1, and the other is to monitor the gas separation system 1. The manipulated variable calculation unit 42 functions for control, and the separation membrane performance evaluation unit 43 functions for monitoring. Of these, the manipulated variable calculation unit 42 receives a hydrogen concentration signal and calculates the valve opening of each concentration control valve 23 based on the hydrogen concentration signal so that the hydrogen concentration of the product gas becomes a predetermined value. The manipulated variable calculation unit 42 transmits the calculated valve opening to each concentration control valve 23 via a control signal cable 51. The manipulated variable calculation unit 42 may also calculate the valve opening manipulated variable of the non-permeate gas pressure control valve 22 by controlling the pressure or flow rate to a predetermined value instead of the hydrogen concentration signal. As will be described later, the control device 41 can be said to be a "deterioration diagnosis device" because it also performs deterioration diagnosis of the gas separation system 1, and the manipulated variable calculation unit 42 can be said to be an "input unit" (also performing the functions of an input unit) because it takes in process variables.

[0020] The manipulated variable calculation unit 42 will be further described. Based on the characteristic that the amount of hydrogen permeation through the separation membrane 12 is proportional to the gas partial pressure difference between the non-permeate side 13 and the permeate side 14, the manipulated variable calculation unit 42 calculates a smaller valve aperture of the non-permeate gas pressure regulating valve 22a, for example, to increase the hydrogen concentration of the permeate gas. Reducing the valve aperture of the non-permeate gas pressure regulating valve 22a increases the pressure on the permeate side 13, increasing the gas partial pressure difference, increasing the amount of hydrogen permeation through the separation membrane 12, and increasing the hydrogen concentration of the permeate gas. The method for calculating the valve aperture based on the hydrogen concentration may be any conventional method, such as proportional control or proportional-integral control. Here, in this embodiment, the hydrogen concentration of the permeate gas is controlled by adjusting the pressure on the non-permeate side 13 via the non-permeate gas pressure regulating valve 22a. However, the hydrogen concentration of the permeate gas may also be controlled by adjusting the pressure on the permeate side 14 via the permeate gas pressure regulating valve 22b, or the hydrogen concentration may be controlled by adjusting both simultaneously.

[0021] In addition to the manipulated variable calculation unit 42, the control device 41 also includes a separation membrane performance evaluation unit 43 and a database 45, and is connected to an external output computer 44. Figure 2 shows the flow of control signals between the manipulated variable calculation unit 42, separation membrane performance evaluation unit 43, database 45, and external output computer 44 that constitute the control device 41.

[0022] The database 45 stores the following data in advance. The separation membrane performance evaluation unit 43 receives all of this data. (1) The manipulated variable (valve opening) Vi0 (hereinafter referred to as the "initial value of the manipulated variable") when the gas separation system 1 is operated using a new (before deterioration) separation membrane 12. (2) The current manipulated variable Vi(t) calculated by the manipulated variable calculation unit 42. (3) The lower limit ΔViL of the difference between the current manipulated variable Vi(t) and the initial value of the manipulated variable. (4) The upper limit ΔViH of the difference between the current manipulated variable Vi(t) and the initial value of the manipulated variable.

[0023] The subscript i indicates each pressure regulating valve 22 a, b and each concentration regulating valve 23 a, b. The lower limit ΔViL and upper limit ΔViH of the difference between the current manipulated variable Vi(t) and the initial value of the manipulated variable can be set by analysis or experiment based on constraints such as the product gas specifications and the specifications of the constituent equipment of the gas separation system 1.

[0024] The separation membrane performance evaluation unit 43 evaluates the performance of the separation membranes 12a-c of the multiple separation membrane modules 11a-c based on the received data, and transmits the separation membrane performance evaluation results to an external output computer 44. The results of the separation membrane performance evaluation are, for example, a signal notifying that the separation membrane has deteriorated or that an abnormality has occurred. Hereinafter, the separation membranes 12a-c will be referred to as separation membranes 12.

[0025] Next, an example of the separation membrane performance evaluation method and results of the separation membrane performance evaluation unit 43 will be described. Figure 3 shows the process flow of the separation membrane performance evaluation unit 43 when i represents the non-permeable gas pressure regulating valve 22a. In the gas separation system 1, if the separation membrane 12 exhibits deterioration behavior such that the amount of target gas permeated decreases due to clogging or other reasons, the hydrogen concentration on the permeate side 14 decreases. To increase the hydrogen concentration on the permeate side 14, the manipulated variable calculation unit 42 calculates a smaller valve opening Vi(t) of the non-permeable gas pressure regulating valve 22a (Vi(t) < Vi0) so that the pressure on the non-permeable side 13 increases. As a result, as the separation membrane 12 deteriorates, the valve opening of the non-permeable gas pressure regulating valve 22a is calculated to a smaller value. Therefore, the separation membrane performance evaluation unit 43 first calculates the difference ΔVi between the current manipulated variable Vi(t) and the initial manipulated variable Vi0 (processing step S1). The difference ΔVi is compared with a lower limit ΔViL (processing step S2). If ΔVi < the lower limit ΔViL, the separation membrane 12 is determined to be degraded, and the result is sent to the external output computer 44 (processing step S3). If ΔVi < the lower limit ΔViL, the difference ΔVi is compared with an upper limit ΔViH (processing step S4). If ΔVi > the upper limit ΔViH, it is assumed that some abnormality has occurred in the gas separation system 1, such as a malfunction of the hydrogen concentration meter. The result is sent to the external output computer 44 (processing step S5). If the separation membrane performance evaluation unit 43 determines that the separation membrane 12 is in an inoperable degraded or abnormal state, i.e., that the product gas specifications cannot be met, the operation of the gas separation system 1 is stopped. In this case, if there are multiple separation membrane module groups, as described above, it is sufficient to stop only the group in which degradation or abnormality is detected. Furthermore, to maintain the customer's demand, the product gas flow rate may be secured by supplying the treated gas volume of the stopped group to other groups.

[0026] While the above example describes an example in which deterioration or abnormality of the separation membrane 12 is diagnosed based on the operation amount of the non-permeate gas pressure regulating valve 22a, the other valves, such as the permeate gas pressure regulating valve 22b, the non-permeate gas concentration regulating valve 23a, and the permeate gas concentration regulating valve 23b, can also be diagnosed by setting upper and lower limits in a similar manner. Each valve can be diagnosed independently, or information from multiple regulating valves can be combined to set upper and lower limits for diagnosis; the present invention is not limited to the above-mentioned example. Furthermore, while the above example primarily assumes clogging of the separation membrane 12, deterioration of the separation membrane is not limited to clogging; deterioration such as a decrease in the permeation ratio due to an increase in the permeation rate of gas species other than the target gas caused by swelling can also be assumed. Therefore, the performance of the separation membrane 12 can be evaluated by changing or adding upper and lower limits as needed.

[0027] In addition, if the hydrogen concentration of the gas supplied to the separation membrane 12 fluctuates, the initial value Vi0 of the manipulated variable and the lower limit ΔViL and upper limit ΔViH of the difference from 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.

[0028] According to this embodiment, a change in the hydrogen permeation rate of the separation membrane 12, i.e., a change in the performance of the separation membrane 12, can be detected from a change in the manipulated variable calculated by the control device 41, and the deterioration state of the separation membrane 12 can be diagnosed without installing an additional sensor, thereby reducing the cost of the gas separation system.

[0029] 4 is a diagram showing a schematic configuration example of a gas separation system 1 and a control device 41 according to a second embodiment of the present invention. The difference from FIG. 1 is that the control device 41 includes a representative value calculation unit 46.

[0030] In Example 2, the operation amount calculated by the operation amount calculation unit 42 is stored in the database 45, the representative value calculation unit 46 calculates a representative value from the stored operation amount, and the separation membrane performance evaluation unit 43 evaluates the deterioration state of the separation membrane 12 using the representative value.

[0031] FIG. 5 shows the flow of control signals from the control device 41. The database 45 stores an initial value VTi0, a lower limit value ΔVTiL for the difference, and an upper limit value ΔVTiH for the representative values ​​of the manipulated variables. It also stores the manipulated variables Vi (t1-t2) calculated by the manipulated variable calculation unit 42 for the period from time t1 to time t2. The periods such as time t1 and time t2 are set in advance based on the gas supply rate to the gas separation system 1 in 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 fluctuation period. Note that the subscript i used above indicates information on each pressure regulating valve 22a, b and each concentration regulating valve 23a, b, as in the first embodiment.

[0032] The representative value calculation unit 46 calculates a representative value of the manipulated variables using the manipulated variables Vi (t1 to t2) in the period from time t1 to time t2. Two examples of the method for calculating the representative value of the manipulated variables will be described below.

[0033] As Example 1, an example of an operation schedule for the gas separation system 1 is shown in Figure 6. For example, if the gas separation system 1 regularly operates under steady conditions 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 Vi (t1 to t2) during the period from time t1 to time t2, and calculates the average as a representative value of the operation amount.

[0034] As Example 2, FIG. 7 shows an example of the time variation of 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, 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 9:00 AM to 10:00 AM on Monday. Points to consider when setting the period include whether the hydrogen concentration is equivalent for each period and whether the fluctuations in the hydrogen concentration are relatively small. The representative value calculation unit 46 time-averages the manipulated variable Vi (t1 to t2) over the period from time t1 to time t2. Note that even if the hydrogen concentration fluctuations in the mixed gas main pipe 2 in Example 2 fluctuate irregularly rather than periodically, t1 and t2 may be set by referring to periods of hydrogen concentration fluctuations that exhibit similar behavior from past manipulated variables stored in the database 45, and the representative value may be calculated.

[0035] In this embodiment, by using a representative value of the operating variable, the operating variable can be compared under equivalent conditions even if the supply gas flow rate varies due to the operating schedule or the hydrogen concentration in the mixed gas main pipe 2 varies, so it is possible to diagnose the deterioration state of the separation membrane 12 while reducing the processing of the separation membrane performance evaluation unit 44.

[0036] In this embodiment, instead of determining deterioration or abnormality as in Examples 1 and 2, the separation membrane performance evaluation unit 43 calculates a deterioration index value indicating the performance state of the separation membrane 12 and outputs the deterioration index value to the external output computer 44.

[0037] 8 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 system 1 according to Example 1 shown in FIG. 2 in that the separation membrane performance evaluation unit 43 calculates a deterioration index value Di(t) indicating the deterioration state of the separation membrane 12. An example of a method for calculating the deterioration index value Di(t) for the non-permeable gas pressure regulating valve 22a will be described below. As shown in the following equation (1), the deterioration index value Di(t) is calculated so that it is 0 in the initial state and 1 when the separation membrane is deteriorated. [Equation 1] Di(t)=(Vi(t)-Vi0) / ΔViL (1) Note that equation (1) can be said to be a "deterioration index calculation equation" because it is a calculation equation used to calculate the performance of the separation membrane 12 at the current time from the operation amount of the non-permeable gas pressure regulating valve 22a.

[0038] The external output computer 44 receives the separation membrane degradation index value Di(t) and displays it on the screen. Examples of the display screen of the computer 44 are shown in Figures 9 and 10. Figure 9 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 with a triangle mark (△) on the line. When Di(t) is 0, a triangle mark is located on the "initial state" mark on the screen, and when Di(t) is 1, a triangle mark is located on the "state requiring maintenance" mark on the screen. Figure 10 shows the change in the degradation state of the separation membrane 12 over time. The vertical axis represents the degradation state of the separation membrane, and the horizontal axis represents time. In this case, the external output computer 44 saves and graphs the received degradation state Di(t) of the separation membrane. From the graph of the change in the degradation state of the separation membrane over time, it is possible to predict when the "state requiring maintenance" will occur.

[0039] While the above example describes an example in which deterioration or abnormality of the separation membrane 12 is diagnosed from the manipulated variable of the non-permeate gas pressure regulating valve 22a, the deterioration indexes of the other valves, namely the permeate gas pressure regulating valve 22b, the non-permeate gas concentration regulating valve 23a, and the permeate gas concentration regulating valve 23b, may also be calculated using a similar approach. While each valve may be diagnosed individually, a deterioration index calculation formula may be established by combining information on multiple regulating valves to calculate the deterioration index, and the present invention is not limited to the above-mentioned example. Furthermore, while the manipulated variable was used in this example, a representative value of the manipulated variable may also be used, as in the approach of Example 3.

[0040] According to this embodiment, it is possible not only to judge the deterioration or abnormality of the separation membrane 12 but also to grasp the current performance status.

[0041] In this example, a method for evaluating performance degradation will be described in which the object of control is not changed, and the objects of monitoring separation membrane performance are the pressure on the non-permeate side and the pressure on the permeate side of the separation membrane, which are related to performance. Although the illustration of the control valve control signal cable 51 and the hydrogen concentration signal cable 52 connected to the manipulated variable calculation unit as in Figures 1 and 4 is omitted in this example, they are connected as shown in Figures 1 and 4, and product gas concentration control is performed as described in Example 1.

[0042] 11 is a diagram showing a schematic configuration example of a gas separation system 1 according to this embodiment. In this embodiment, as shown in FIG. 11 , the objects monitored by the separation membrane performance evaluation unit 43 are the non-permeate side pressure of the separation membrane 12, the permeate side pressure, and the mixed gas flow rate (hereinafter referred to as the supply gas flow rate) supplied to the system from the mixed gas supply pipe 3, with the non-permeate side pressure detected by a non-permeate gas pressure gauge 31 a, the permeate side pressure detected by a permeate gas pressure gauge 31 b, and the supply gas flow rate detected by a supply gas flow meter 33. These detection signals are input into the separation membrane performance evaluation unit 43 and compared with the contents stored in a database 45 to evaluate the performance of the separation membrane. The separation membrane performance evaluation results are then sent to an external output computer 45.

[0043] 12 shows the relationship between the difference between the non-permeate side pressure and the permeate side pressure and the feed gas flow rate, which are basically proportional to each other. Regarding this proportionality characteristic, the solid line shows the relationship between the difference between the non-permeate side pressure and the permeate side pressure and the feed gas flow rate in the initial state. In contrast, with long-term operation of the gas separation system 1, the difference between the non-permeate side pressure and the permeate side pressure relative to the feed gas flow rate fluctuates due to deterioration or abnormalities in the performance of the separation membrane 12. For example, if the plot of the difference between the non-permeate side pressure and the permeate side pressure relative to the current feed gas flow rate falls above the solid line, this indicates that the separation membrane 12 is clogged, making it difficult for the target gas to permeate. If this plot falls below the solid line, this indicates that the separation membrane 12 has deteriorated, such as by perforation or swelling, increasing the permeability of gases other than the target gas, and decreasing the permeability ratio. In this embodiment, data representing the solid line indicating the initial state and the dotted line indicating a threshold value for determining whether the separation membrane performance has deteriorated or is abnormal are stored in advance as stored contents in database 45, and it is monitored whether the plot of the difference between the non-permeation side pressure and the permeation side pressure versus the supply gas flow rate at the current time is within the range of the dotted line in Figure 12 or deviates from the threshold value.

[0044] According to this embodiment, even if pressure is the object of performance degradation monitoring, it is possible to evaluate the degradation of the separation membrane 12 without installing an additional sensor.

[0045] In Examples 1 to 4, the performance of the separation membrane 12 was evaluated using the database 45 provided in the control device 41, but in this example, the performance of the separation membrane 12 is evaluated using a simulator 47 and a separation membrane performance evaluation unit 43 provided in the control device 41. An example of this will be described below.

[0046] 13 is a diagram showing an example of a schematic configuration of a gas separation system 1 according to this embodiment. Although not shown, a simulator 47 installed in the control device 41 incorporates a calculation model for calculating the process quantities of the gas separation system 1 and the operation quantities of the pressure regulating valve 22 and the concentration regulating valve 23. The process quantities of the gas separation system 1 in this embodiment refer to the flow rate, pressure, temperature, composition, etc. of the gas before and after the equipment. Note that density, molecular weight, etc. may be added to the process quantities, and the items are not limited as long as the items necessary for performance evaluation are calculated.

[0047] FIG. 14 shows the flow of control signals from the control device 41. Input conditions for the calculation model in the simulator 47 include, for example, information on the supply gas process quantity supplied from the mixed gas supply pipe 3, information on the product gas process quantity specified in the product gas pipe 5 as product specifications, and the initial performance of the separation membrane 12, such as the permeability coefficient of the separation membrane. Based on this information, the current process quantities and the manipulated variables of each control valve are calculated. In particular, the process quantities on the non-permeate side 13 and the permeate side 14 of the separation membrane 12 are not shown, but are calculated using the initial performance of the separation membrane 12, such as the initial value of the permeability coefficient of the separation membrane. Here, the current manipulated variables of each control valve calculated using the initial performance of the separation membrane 12 are designated ViS(t). The simulator 47 then outputs to the separation membrane performance evaluation unit 43 the lower limit ΔViSL and upper limit ΔViSH of the difference between the current manipulated variable Vi(t) and the current manipulated variable ViS(t) calculated from the initial performance of the separation membrane, which are stored in advance. The separation membrane performance evaluation unit 43 calculates the difference between ViS(t) output from this simulator 47 and Vi(t) output from the operation amount calculation unit 42, and if this value is within the range of the upper limit value ΔViSH of the lower limit value ΔViSL output from the simulator 47, it is determined that operation that meets the product gas specifications is possible, but if it is below the lower limit value ΔViSL or above the upper limit value ΔViSH, it is determined that deterioration or an abnormality has occurred. This information is output to the external output computer 44 and displayed on the external output computer 44.

[0048] The above example of performance evaluation of the separation membrane 12, in which the deterioration state is determined based on information calculated from the simulator 47, has been explained using the same concept as in Example 1. However, the evaluation method in the separation membrane performance evaluation unit 43 may be similar to that in Example 3, in which a deterioration evaluation index is calculated, the current performance of the separation membrane 12 is evaluated, and the performance status is output to an external output computer. Furthermore, in this example, the performance of the separation membrane 12 is evaluated using the manipulated variables of the pressure control valve 22 and the concentration control valve 23, but as in the concept of Example 4, the performance may also be evaluated by calculating the pressure on the non-permeation side 13 and the permeation side 14 based on the initial performance of the separation membrane using the simulator 47 and comparing the pressure with the current value of the pressure gauge 31.

[0049] By using this embodiment, it is possible to compare the difference between the operating amount calculated by the simulator based on the initial performance of the separation membrane and the actual operating amount, making it possible to accurately evaluate the performance of the separation membrane 12 even if the hydrogen concentration in the main mixed gas pipe 3 or the amount of gas processed in the gas separation system fluctuates.

[0050] 1 Gas separation system 2 Mixed gas main pipe 3 Mixed gas supply pipe 4a, 4b Mixed gas return gas pipe 5 Product gas pipe 11a to 11c Separation membrane module 12a to 12c Separation membrane 13a to 13c Non-permeate side 14a to 14c Permeate side 21 Mixed gas flow rate control valve 22a Non-permeate gas pressure control valve 22b Permeate gas pressure control valve 23a Non-permeate gas concentration control valve 23b Permeate gas concentration control valve 31a Non-permeate gas pressure gauge 31b Permeate gas pressure gauge 32 Product gas hydrogen concentration meter 33 Supply gas flow meter 41 Control device 42 Operation quantity calculation unit 43 Separation membrane performance evaluation unit 44 External output computer 45 Database 46 Representative value calculation unit 47 Simulator 51a to 51d Control valve control signal cable 52 Hydrogen concentration signal cable 53 Pressure signal cable 54 Flow Signal Cable

Claims

1. A deterioration diagnosis device for a gas separation system having one or more gas separation membranes that selectively allow specific gases to pass through, and in which the output of the gas separation membranes is controlled by an output control valve, characterized in that the deterioration diagnosis device comprises an input unit that takes in process variables that are affected by the deterioration of the gas separation membrane, and a separation membrane performance evaluation unit that evaluates the performance of the gas separation membrane from the currently taken in process variables.

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 1 or 2, characterized in that the deterioration diagnosis device further comprises a database that stores initial operating values ​​of the process variables, and the separation membrane performance evaluation unit evaluates the performance of the gas separation membrane from the difference between the initial operating values ​​of the process variables in the database and the current process variables imported from the input unit.

4. A deterioration diagnosis device for a gas separation system as described in claim 1 or 2, wherein the deterioration diagnosis device further comprises a database that stores a gas separation membrane deterioration index calculation formula used to calculate the current performance of the gas separation membrane from the operation amount of the output control valve, and the separation membrane performance evaluation unit evaluates the current performance of the gas separation membrane from the deterioration index calculation formula and the operation amount of the output control valve.

5. A deterioration diagnosis device for a gas separation system according to claim 1 or 2, characterized in that the deterioration diagnosis device comprises a simulator that calculates the process quantity of the gas separation system, and the separation membrane performance evaluation unit evaluates the performance of the gas separation membrane from the difference between the process quantity at the current time calculated by the simulator from the initial performance of the gas separation membrane and the process quantity at the current time taken in from the input unit.

6. A deterioration diagnosis device for a gas separation system according to claim 1 or 2, wherein the separation membrane performance evaluation unit converts the state of deterioration 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 or 2, characterized in that the separation membrane performance evaluation unit evaluates the performance of the gas separation membrane using a representative value of the current process quantity acquired over a certain period of time.

8. A deterioration diagnosis device for a gas separation system according to claim 1 or 2, characterized in that the process variables affected by the deterioration of the gas separation membrane are the pressure on the non-permeation side and the pressure on the permeation side of the gas separation membrane.

9. A deterioration diagnosis device for a gas separation system as described in claim 8, characterized in that the deterioration diagnosis device includes a database that stores an initial value of the relationship between the difference in non-permeation side pressure and permeation side pressure relative to the supply gas flow rate of the gas separation membrane, and a threshold value for the measured difference in non-permeation side pressure and permeation side pressure, and the separation membrane performance evaluation unit determines the deterioration and abnormality of the gas separation membrane.

10. A deterioration diagnosis device for a gas separation system according to claim 1 or 2, characterized in that the output control valve controls the hydrogen concentration in the gas in the gas separation system.

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