Gas separation system

Abstract

The present invention is applied to a system in which an adjustment valve that controls the flow rate of a gas separated by a separation membrane for separating a specific gas from a mixed gas, and a pressure gauge for measuring the pressure between the separation membrane and the adjustment valve are used to evaluate the performance of the separation membrane. This gas separation system comprises: a pressure temporal change rate calculation unit that calculates the pressure temporal change rate at a predetermined valve opening state by using the degree of valve opening of the adjustment valve and time-series data of measured values from the pressure gauge; and a separation membrane performance evaluation unit that compares the calculated pressure temporal change rate to an initial value to evaluate the performance of the separation membrane.

Description

Gas Separation Systems

[0001] The present invention relates to 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 gas to permeate in addition to the specific gas you want 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 separation membrane deteriorates. To maintain separation efficiency, gas separation systems must diagnose the deterioration state of the separation membrane, and if the separation membrane deteriorates, maintenance such as replacing the separation membrane must be performed.

[0004] One example of a method for diagnosing deterioration of a separation membrane is the technology described in Patent Document 1. Patent Document 1 describes a technology that detects pressure changes in the downstream path of the product gas and determines when to replace the separation membrane based on the pressure change after the device is shut down. When the device is shut down, the inlet valve on the upstream side of the separation membrane and the outlet valve on the downstream side close, so the technology described in Patent Document 1 reduces the pressure between these valves and determines when to replace them based on this change.

[0005] Japanese Patent Application Laid-Open No. 2000-102717

[0006] However, when a specific gas other than natural gas is mixed with natural gas and transported using an existing gas grid containing methane as the main component, the concentration of the specific gas cannot be controlled properly, and if gas with a concentration outside the allowable range is supplied to the equipment, the equipment may break down. In such cases, it may lead to a major accident in facilities such as production facilities and chemical plants, so it is necessary to regularly perform deterioration diagnosis of the gas separation system.

[0007] Therefore, it is necessary to achieve high-precision deterioration diagnosis of gas separation systems. However, because deterioration diagnosis of separation membranes requires multiple measurements such as concentration and flow rate, it requires multiple sensors such as gas concentration meters and flow meters, which results in high costs. Furthermore, when multiple separation membranes are used, only an overall evaluation can be performed, making it impossible to identify the deteriorated separation membrane.

[0008] An object of the present invention is to provide a gas separation system that minimizes the need for additional equipment for diagnosing deterioration of separation membranes and that can identify a deteriorated separation membrane when multiple separation membranes are used.

[0009] To solve the above problems, for example, the configuration described in the claims is adopted. The present application includes multiple means for solving the above problems, and one example is a gas separation system that uses a regulator valve to control the flow rate of gas separated by a separation membrane that separates a gas of a specific component from a mixed gas, and a pressure gauge that measures the pressure between the separation membrane and the regulator valve to evaluate the performance of the separation membrane. The gas separation system is configured to include a pressure time change rate calculation unit that calculates the pressure time change rate at a predetermined valve opening state using the valve opening of the regulator valve and time series data of the measurement value of the pressure gauge, and a separation membrane performance evaluation unit that compares the pressure time change rate calculated by the pressure time change rate calculation unit with an initial value to evaluate the performance of the separation membrane.

[0010] According to the present invention, it is possible to reduce the need for additional equipment for diagnosing the deterioration of separation membranes and to appropriately evaluate the performance of separation membranes. For example, when multiple separation membranes are used, it is possible to identify a deteriorated separation membrane. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments.

[0011] FIG. 1 is a configuration diagram showing an example of a gas separation system according to a first embodiment of the present invention. FIG. 2 is a diagram showing the flow of signals in a control device of a gas separation system according to a first embodiment of the present invention. FIG. 3 is a diagram showing an example of pressure measurement value time series data in a gas separation system according to a first embodiment of the present invention. FIG. 4 is a flowchart showing an example of processing of a separation membrane performance evaluation unit in a gas separation system according to a first embodiment of the present invention. FIG. 4 is a configuration diagram showing an example of a gas separation system according to a first embodiment of the present invention. FIG. 5 is a diagram showing an example of pressure measurement value time series data in a gas separation system according to a second embodiment of the present invention. FIG. 6 is a diagram showing an example (Example 1) of a display screen of a gas separation system according to a second embodiment of the present invention. FIG. 7 is a diagram showing an example (Example 2) of a display screen of a gas separation system according to a second embodiment of the present invention. FIG. 8 is a configuration diagram showing an example of a gas separation system according to a third embodiment of the present invention. FIG. 9 is a configuration diagram showing an example of a gas separation system according to a fourth embodiment of the present invention. FIG. 10 is a configuration diagram showing an example of a gas separation system according to a fifth embodiment of the present invention. FIG. 11 is a diagram showing the flow of signals in a control device of a gas separation system according to a fifth embodiment of the present invention.

[0012] <First Embodiment> A gas separation system according to a first embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG.

[0013] [Configuration of Gas Separation System] Figure 1 shows an example of the configuration of a gas separation system 1 according to this embodiment. In this embodiment, a mixture of hydrogen and methane is used as the supply gas, and hydrogen is separated from this mixture using a separation membrane. In such a case, the gas separation system 1 according to this embodiment controls the hydrogen concentration of the extracted gas to a predetermined value even if the hydrogen concentration of the supply gas fluctuates around a certain value. For example, the gas separation system 1 controls the hydrogen concentration to a constant value such as 20% (vol%), or to a value above or below a predetermined value, or to a value within a predetermined range.

[0014] In the example shown in Fig. 1, gas separation system 1 is configured to receive a supply of a mixed gas of hydrogen and methane through mixed gas supply piping 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. The primary side is the side where gas does not permeate the separation membrane, and the secondary side is the side where gas has permeated the separation membrane.

[0015] The mixed gas supply pipe 2 is connected to the primary side 13. The non-permeate gas pipe 3 is connected to the primary side 13. The permeate gas pipe 4 is connected to the secondary side 14. Of the mixed gas supplied from the mixed gas supply pipe 2 to the primary side 13, mainly hydrogen permeates 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.

[0016] The permeate gas pipe 4 is provided with a control valve 21. The control valve 21 receives commands from a valve opening command unit 42 of the control device 41 and adjusts the valve opening. Typically, the valve opening of the control valve 21 is calculated by the control device 41 so as to control the pressure, flow rate, or concentration of the permeate gas. In addition, a pressure gauge 31 is provided between the control valve 21 and the secondary side 14. The pressure gauge 31 measures the permeate gas pressure and transmits the pressure measurement value to a measurement value input unit 43 of the control device 41.

[0017] The control device 41 is composed of a valve opening command unit 42, a measurement value input unit 43, a database 44, a pressure time rate of change calculation unit 45, and a separation membrane performance evaluation unit 46. The processing performed by these components is explained in FIG. 2. In the drawing, the database is abbreviated as "DB." The results of evaluation by the separation membrane performance evaluation unit 46 of the control device 41 are sent to a terminal 47 and displayed on a display unit of the terminal 47. The valve opening command unit 42 sets the valve opening based on a command sent from the terminal 47.

[0018] The control device 41 can be configured, for example, by a computer. The hardware configuration of the control device 41 is shown in the lower right of Fig. 1. The computer that functions as the control device 41 is configured by a CPU (Central Processing Unit) 41a, a memory 41b, a storage 41c, an input unit 41d, an output unit 41e, and a communication interface 41f.

[0019] The CPU 41a executes programs stored in the memory 41b or the storage 41c. The memory 41b is configured as, for example, a random access memory (RAM), and stores computer programs and calculation result data, and also provides the CPU 41a with a work area required for each process.

[0020] In this embodiment, the CPU 41a executes a program, which configures a valve opening command unit 42, a measurement value input unit 43, a pressure time rate of change calculation unit 45, and a separation membrane performance evaluation unit 46 in a work area in the memory 41b. The storage 41c stores computer programs as well as data required for calculations and calculation result data. The storage 41c stores data as a database 44, for example.

[0021] The input unit 41d performs input processing required for control. For example, measurement values ​​from the pressure gauge 31 and the like are input to the input unit 41d. The output unit 41e performs output processing required for control. For example, the output unit 41e outputs a valve opening command value from the valve opening command unit 42. The communication interface 41f performs communication processing with other devices via a connected network.

[0022] Note that configuring the control device 41 as a computer is just one example, and for example, part or all of the processing may be configured as hardware such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The terminal 47 shown in Fig. 1 is also configured as a computer with the same hardware configuration as the control device 41. Alternatively, the control device 41 may incorporate the functions and configuration of the terminal 47.

[0023] [Signal Flow in the Control Device] Figure 2 is a diagram showing the flow of signals in the control device 41 of the gas separation system 1 of this embodiment. The valve opening command unit 42 receives a performance evaluation implementation command from the terminal 47 and sends a command to the control valve 21 to set the valve opening to zero (step S14). When the pressure on the primary side of the separation membrane is higher than the secondary side and gas is permeating the separation membrane, the administrator may operate the terminal 47 to issue a performance evaluation implementation command. Furthermore, the start-up process, shutdown process, and load change process of the gas separation system 1 may be incorporated into a single process.

[0024] The measurement value input unit 43 receives the measurement value of the pressure gauge 31 and transmits it to the database 44 (step S12). The database 44 stores a predetermined initial value of the pressure time rate of change, upper and lower limits of the difference between the measurement value and the initial value, and time-series data of the pressure measurement value. The pressure time rate of change calculation unit 45 receives from the database 44 time-series data of the pressure measurement value from the time when a command to set the valve opening to zero is sent to the control valve 21 until a certain period of time has elapsed (step S13). The pressure time rate of change calculation unit 45 then calculates the pressure time rate of change K and transmits the calculated pressure time rate of change K to the separation membrane performance evaluation unit 46 (step S15).

[0025] Figure 3 is a diagram showing an example of pressure measurement time series data handled by the gas separation system 1 of this embodiment. The vertical axis of Figure 3 represents pressure, and the horizontal axis represents time. Data d0 shown in Figure 3 represents an initial value, and data d1 represents a measured value. The pressure measured by the pressure gauge 31 is a certain constant value, but when the valve opening of the control valve 21 becomes zero, the amount of gas permeated accumulates without being discharged from the secondary side, so the pressure of the permeated gas on the secondary side of the separation membrane rises and approaches the pressure on the primary side.

[0026] The pressure time change rate K can be calculated by a known method. For example, as shown in Fig. 3, it can be calculated by dividing the difference between the pressure P(t1) at time t1 when a command to set the valve opening to zero is sent to the regulator valve 21 and the pressure P(t1+Δt) at time (t1+Δt) after a certain period has elapsed by the certain period Δt. Alternatively, the time from the pressure P(t1) at time t1 to the time when the pressure reaches P(t1)+ΔP can be measured, and the pressure time change rate K can be calculated by the following formula: [Math 1] K = (P(t1+Δt) - P(t1)) / Δt

[0027] 2 , the separation membrane performance evaluation unit 46 acquires an initial value K0 of the pressure time rate of change, and an upper limit ΔKH and a lower limit ΔKL of the difference from the initial value from the database 44 (step S11). Then, the separation membrane performance evaluation unit 46 evaluates the performance of the separation membrane using the acquired pressure time rate of change K, the initial value K0 of the pressure time rate of change, and the upper limit ΔKH and lower limit ΔKL of the difference from the initial value, and transmits the performance evaluation results to the terminal 47 (step S16).

[0028] [Processing Performed by Separation Membrane Performance Evaluation Unit] Figure 4 is a flowchart showing an example of processing by the separation membrane performance evaluation unit 46 of the control device 41 of the gas separation system 1 of this embodiment. First, the separation membrane performance evaluation unit 46 calculates the difference ΔK between the pressure time rate of change K calculated by the pressure time rate of change calculation unit 45 and the initial value K0 of the pressure time rate of change (Step S1). Next, the separation membrane performance evaluation unit 46 compares the difference ΔK with a lower limit value ΔKL (Step S2). If the comparison in Step S2 shows that the difference ΔK is smaller than the lower limit value ΔKL (ΔK < ΔKL) (YES in Step S2), the separation membrane performance evaluation unit 46 determines that the separation membrane 12 has deteriorated and transmits the result to the terminal 47 (Step S3).

[0029] On the other hand, if the comparison in step S2 finds that the difference ΔK is not smaller than the lower limit ΔKL (ΔK≧ΔKL) (NO in step S2), the separation membrane performance evaluation unit 46 proceeds to the next process and compares the difference ΔK with the upper limit ΔKH (step S4). If the comparison in step S4 finds that the difference ΔK is greater than the upper limit ΔKH (ΔK>ΔKH) (YES in step S4), the separation membrane performance evaluation unit 46 determines that an abnormality has occurred and transmits the result to the terminal 47 (step S5). On the other hand, if the comparison in step S4 finds that the difference ΔK is not greater than the upper limit ΔKH (ΔK≦ΔKH) (NO in step S4), the separation membrane performance evaluation unit 46 transmits the value (ΔK / ΔKL) obtained by dividing the difference ΔK by the lower limit ΔKL to the terminal 47 (step S6).

[0030] [Effects of the First Embodiment] In the gas separation system 1, when the separation membrane 12 deteriorates, the amount of gas permeating through the separation membrane decreases even when the partial pressure difference between the gases on the primary side 13 and the secondary side 14 is the same. When the amount of gas permeating through the separation membrane decreases, the rate of pressure increase slows after the valve opening of the control valve 21 becomes zero. That is, as shown in Fig. 3, the measured value d1 after a certain amount of gas permeation has occurred shows a slower rate of pressure increase than the initial value d0 of pressure increase through the separation membrane, and the degree to which the rate of increase slows increases in response to deterioration of the separation membrane 12.

[0031] Here, the gas separation system 1 of this embodiment detects a deterioration in the performance of the separation membrane 12 from such a change in the pressure change rate, and if the pressure time change rate is ΔK<lower limit value ΔKL, it can notify the terminal 47 that the separation membrane has deteriorated. Also, if the pressure time change rate is ΔK>upper limit value ΔVH, it is considered that some kind of abnormality has occurred in the gas separation system 1, such as a malfunction of the hydrogen concentration meter, and the gas separation system 1 can notify the terminal 47 that an abnormality has occurred.

[0032] As described above, the gas separation system of this embodiment can detect changes in the gas permeation rate of the separation membrane, i.e., changes in the performance of the separation membrane, from changes in the pressure time rate of change of the separation membrane, so that the deterioration state of the separation membrane can be diagnosed without the need for additional concentration sensors or flow rate sensors, thereby reducing the cost of diagnosing the deterioration state of the separation membrane.

[0033] <Second Embodiment> A gas separation system according to a second embodiment of the present invention will be described below with reference to Figures 6 to 8. In Figures 6 to 8 showing the second embodiment, parts corresponding to those in Figures 1 to 5 described in the first embodiment are given the same reference numerals, and duplicate explanations will be omitted.

[0034] [Configuration of Gas Separation System] Figure 5 is a diagram showing an example of the configuration of a gas separation system 1 according to a second embodiment of the present invention. As shown in Figure 5, the gas separation system 1 in this embodiment has two modules: a first separation membrane module 11 and a second separation membrane module 11a. The internal structure and characteristics of each separation membrane module 11, 11a are the same as those of the separation membrane module 11 described in the first embodiment. The first separation membrane module 11 has a first separation membrane 12, and the second separation membrane module 11a has a second separation membrane 12a.

[0035] The two separation membrane modules 11, 11a are connected in parallel. Specifically, the mixed gas supply pipe 51 branches at a branch point 101 into a mixed gas supply pipe 52 and a mixed gas supply pipe 52a, each of which is connected to the primary sides of the separation membrane modules 11, 11a. Non-permeate gas pipes 53, 53a are connected to the primary sides of the separation membrane modules 11, 11a, respectively. Permeate gas pipes 56, 56a are connected to the secondary sides of the separation membrane modules 11, 11a, respectively.

[0036] The non-permeate gas pipes 53, 53a connected to the primary sides of the separation membrane modules 11, 11a merge with the non-permeate gas pipe 54 at a junction 102. The permeate gas pipes 56, 56a connected to the secondary sides of the separation membrane modules 11, 11a merge with the permeate gas pipe 57 at a junction 103.

[0037] The permeate gas pipe 57 is provided with a first control valve 21. Similar to the control valve 21 of the first embodiment, the first control valve 21 receives commands from the valve opening command unit 42 of the control device 41 and adjusts the valve opening. The permeate gas pipe 56 is provided with a first check valve 22 that prevents backflow. A first pressure gauge 31 that measures the pressure between the secondary side of the separation membrane module 11 and the first check valve 22 is also provided. The measurement value of the first pressure gauge 31 is transmitted to the measurement value input unit 43 of the control device 41. Similarly, the permeate gas pipe 56a is provided with a second check valve 22a that prevents backflow. A second pressure gauge 31a that measures the pressure between the secondary side of the separation membrane module 11a and the second check valve 22a is also provided. The measurement value of the second pressure gauge 31a is transmitted to the measurement value input unit 43 of the control device 41.

[0038] The control device 41 is the same as in the first embodiment in that it is composed of a valve opening command unit 42, a measurement value input unit 43, a database 44, a pressure time rate of change calculation unit 45, and a separation membrane performance evaluation unit 46. In the control device 41 of this embodiment, the measurement value input unit 43 receives measurement values ​​from multiple pressure gauges 31, 31a. The database 44 of the control device 41 stores time series data of multiple pressure measurement values ​​from the pressure gauges 31, 31a. The pressure time rate of change calculation unit 45 of the control device 41 calculates multiple pressure time rates. Furthermore, the separation membrane performance evaluation unit 46 in the control device 41 evaluates the performance of each of the multiple separation membranes and transmits the performance evaluation results of the multiple separation membranes to a terminal 47.

[0039] [Example of Pressure Measurement Time Series Data] Figure 6 is a diagram showing an example of pressure measurement time series data for the gas separation system 1 according to the second embodiment. The vertical axis of Figure 6 represents pressure, and the horizontal axis represents time. It can be seen from Figure 6 that when the second separation membrane 12a is more deteriorated than the first separation membrane 12, and when the valve opening of the control valve 21 becomes zero, the pressure on the secondary side of the second separation membrane 12a (pressure d12 on the second pressure gauge 31a) increases later than the pressure on the secondary side of the first separation membrane 12 (pressure d11 on the first pressure gauge 31). The pressure d10 indicated by the dashed line in Figure 6 is the initial value.

[0040] [Display Screen Example] Figures 7 and 8 show examples of the display screen 47a of the terminal 47. The terminal 47 receives the separation membrane degradation index value ΔK / ΔKL and displays it on the screen. The display screen 47a shown in Figure 7 shows the current degree of degradation of each separation membrane. The display screen 47a connects the "initial state" mark and the "state requiring maintenance" mark with a straight line, and displays the performance of the first separation membrane 12 and the second separation membrane 12a, i.e., the current degradation state, with two triangular marks (△ and ▽) on the line. When each degradation index value ΔK / ΔKL is 0, the triangular mark △ representing the first separation membrane is located at the "initial state" mark on the screen, and when the degradation index value ΔK / ΔKL is 1, the triangular mark ▽ representing the second separation membrane is located at the "state requiring maintenance" mark on the screen.

[0041] Figure 8 shows the change over time in the deterioration state of the separation membrane. The vertical axis of Figure 8 represents the deterioration state of the separation membrane, and the horizontal axis represents time. Display screen 47a in Figure 8 is a graph of the separation membrane deterioration index value ΔK / ΔKL received by terminal 47. In this case, the graph on display screen 47a displays the position of the deterioration state where separation membrane maintenance is required. From the graph of the change over time in the deterioration state of the separation membrane, it is possible to predict the time when each of the first separation membrane 12 and the second separation membrane 12a will reach a "state requiring maintenance."

[0042] [Effects of the Second Embodiment] In the gas separation system 1 of the second embodiment, the permeation gas pipes 56, 56a connected to the secondary sides of the separation membranes 12, 12a join at the junction 103, and the permeation gas pipes 56, 56a are provided with check valves 22, 22a. This prevents pressure increases due to backflow, making it possible to evaluate only the pressure increases due to the permeation rate of the separation membrane for each separation membrane 12, 12a. Thus, according to the second embodiment, the pressure time change rate for each separation membrane can be obtained, enabling the individual performance evaluation of each separation membrane. This reduces the frequency of separation membrane replacement and reduces maintenance costs.

[0043] <Third embodiment> A gas separation system according to a third embodiment of the present invention will now be described with reference to Fig. 9. In Fig. 9, parts corresponding to those in Figs. 1 to 8 described in the first and second embodiments are given the same reference numerals, and duplicated explanations will be omitted.

[0044] [Configuration of Gas Separation System] Fig. 9 is a diagram showing a configuration example of a gas separation system 1 according to a third embodiment. As shown in Fig. 9, the gas separation system 1 has two separation membrane modules 11, 11a, and the internal structure and characteristics of the separation membrane modules 11, 11a are the same as those of the separation membrane modules 11, 11a described in the second embodiment.

[0045] However, in this embodiment, the two separation membrane modules 11, 11a are connected in series on their primary sides and in parallel on their secondary sides. Specifically, the mixed gas supply pipe 51 is connected to the primary side of the first separation membrane module 11. A pipe 53 is connected to the primary side of the first separation membrane module 11, and the other end of the pipe 53 is connected to the primary side of the second separation membrane module 11a.

[0046] Furthermore, a non-permeate gas pipe 54 is connected to the primary side of the second separation membrane module 11a. A permeate gas pipe 56 is connected to the secondary side of the first separation membrane module 11, and a permeate gas pipe 56a is connected to the secondary side of the second separation membrane module 11a. The permeate gas pipes 56 and 56a merge into a permeate gas pipe 57 at a junction 103. A control valve 21 is provided in the permeate gas pipe 57. The control valve 21 is the same as the control valve 21 in the second embodiment.

[0047] The permeate gas pipe 56 is provided with a check valve 22, and a first pressure gauge 31 is provided between the first check valve 22 and the secondary side of the first separation membrane module 11. The pipe 56a is provided with a second check valve 22a, and a second pressure gauge 31a is provided between the second check valve 22a and the secondary side of the second separation membrane module 11a. The measured values ​​of the pressure gauges 31 and 31a are sent to a measured value input unit 43 of the control device 41. The configuration and processing of the control device 41 are the same as those of the second embodiment.

[0048] [Effects of the third embodiment] As shown in the third embodiment, even in a configuration in which the primary sides of two separation membrane modules 11, 11a are connected in series, the pressure time change rate on the secondary side of each of the multiple separation membranes 11, 11a can be calculated simultaneously, making it possible to evaluate the performance of each individual separation membrane.

[0049] <Fourth embodiment> A gas separation system according to a fourth embodiment of the present invention will now be described with reference to Fig. 10. In Fig. 10, parts corresponding to those shown in Figs. 1 to 9 described in the first to third embodiments are given the same reference numerals, and duplicated explanations will be omitted.

[0050] [Configuration of Gas Separation System] Fig. 10 is a diagram showing a configuration example of a gas separation system 1 according to a fourth embodiment. In Fig. 10, the gas separation system 1 has two separation membrane modules 11, 11a, and the internal structure and characteristics of the two separation membrane modules 11, 11a are the same as those of the separation membrane modules 11, 11a described in the second and third embodiments.

[0051] In the example of Figure 10, two separation membrane modules 11, 11a are connected in series. Specifically, a mixed gas supply pipe 51 is connected to the primary side of the first separation membrane module 11. The primary side of the first separation membrane module 11 is connected to a non-permeate gas pipe 53, and the other end of the non-permeate gas pipe 53 is connected to the primary side of the second separation membrane module 11a. A non-permeate gas pipe 54 is connected to the primary side of the second separation membrane module 11a. A permeate gas pipe 56a is connected to the secondary side of the second separation membrane module 11a, and the other end of the permeate gas pipe 56a is connected to the secondary side of the first separation membrane module 11. A permeate gas pipe 56 is connected to the secondary side of the first separation membrane module 11.

[0052] A first control valve 21 is provided in the permeate gas pipe 56. A first pressure gauge 31 is provided between the first control valve 21 and the first separation membrane module 11. A second control valve 21a is provided in the second permeate gas pipe 56a. A second pressure gauge 31a is provided between the second control valve 21a and the second separation membrane module 11a. The control valves 21, 21a receive commands from a valve opening command unit 42 of the control device 41 and adjust their valve openings.

[0053] The first pressure gauge 31 and the second pressure gauge 31a transmit their measurement values ​​to a measurement value input unit 43 of the control device 41. The control device 41 has the same configuration and processing as the control device 41 of the second embodiment, except for the following points: That is, the control device 41 of this embodiment differs from the control device 41 of the second embodiment in that the valve position command unit 42 simultaneously transmits the same command to multiple (two) control valves 21, 21a.

[0054] [Effects of the Fourth Embodiment] In the fourth embodiment as well, the pressure time change rate on the secondary side of each of the plurality of separation membranes 12, 12a can be calculated simultaneously, enabling performance evaluation of each individual separation membrane.

[0055] Fifth Embodiment A gas separation system according to a fifth embodiment of the present invention will now be described with reference to Figures 11 and 12. In Figures 11 and 12 showing the fifth embodiment, parts corresponding to those shown in Figures 1 to 10 described in the first to fourth embodiments are designated by the same reference numerals, and duplicated explanations will be omitted.

[0056] [Configuration of Gas Separation System] Fig. 10 is a diagram showing an example of the configuration of a gas separation system 1 according to a fifth embodiment. In Fig. 11, the gas separation system 1 has two separation membrane modules 11, 11a, and the internal structure and characteristics of each of the separation membrane modules 11, 11a are the same as those of the separation membrane modules 11, 11a described in the second to fourth embodiments.

[0057] The two separation membrane modules 11, 11a are connected in series. Specifically, the mixed gas supply pipe 51 is connected to the primary side of the first separation membrane module 11. The primary side of the first separation membrane module 11 is connected to a non-permeate gas pipe 53. A permeate gas pipe 56 is connected to the secondary side of the first separation membrane module 11, and the other end of the permeate gas pipe 56 is connected to the primary side of the second separation membrane module 11a. A non-permeate gas pipe 53a is connected to the primary side of the second separation membrane module 11a. A permeate gas pipe 56a is connected to the secondary side of the second separation membrane module 11a.

[0058] The permeate gas pipe 56 is provided with a first pressure gauge 31. The non-permeate gas pipe 53a is provided with a first control valve 21. The permeate gas pipe 56a is provided with a second control valve 21a. In addition, a second pressure gauge 31a is provided between the second control valve 21a and the second separation membrane module 11a.

[0059] The first control valve 21 and the second control valve 21a receive commands from a valve position command unit 42 of the control device 41 to adjust the valve opening. The first pressure gauge 31 and the second pressure gauge 31a send measurement values ​​to a measurement value input unit 43 of the control device 41. The control device 41 has the same configuration and processing as the control device 41 of the fourth embodiment, except for the following points. That is, the control device 41 of this embodiment differs from the control device 41 of the fourth embodiment in that the valve position command unit 42 sends a command to the second control valve 21a to set the valve opening to zero, and then sends a similar command to the first control valve 21 after a certain time has elapsed.

[0060] [Signal Flow of the Control Device] FIG. 12 is a diagram showing the signal flow of the control device 41 of the gas separation system 1 according to the embodiment of the present invention. The valve position command unit 42 receives a performance evaluation implementation command from the terminal 47 and transmits a command to the second control valve 21a to set the valve position to zero (step S24). Here, when the pressure on the primary side of the second separation membrane module 11a is higher than that on the secondary side and gas is permeating the separation membrane, the administrator may operate the terminal 47 so that the terminal 47 issues a performance evaluation implementation command. The startup process, shutdown process, and load change process of the gas separation system 1 may be integrated into a single process. Furthermore, after a certain time has elapsed since transmitting a command to the second control valve 21a to set the valve position to zero, the valve position command unit 42 transmits a command to the first control valve 21 to set the valve position to zero (step S27).

[0061] The measurement value input unit 43 receives the measurement values ​​of the two pressure gauges 31, 31a and transmits them to a database 44 (step S22). The database 44 stores a predetermined initial value of the pressure time rate of change, upper and lower limits of the difference between the measurement value and the initial value, and time-series data of the pressure measurement values. The data stored in the database 44 is transmitted to the separation membrane performance evaluation unit 46 (step S21). The pressure time rate of change calculation unit 45 receives from the database 44 the time-series data of the pressure measurement values ​​of the second pressure gauge 31a from the time when a command to set the valve opening to zero is sent to the second control valve 21a until a certain period of time has elapsed (step S23).

[0062] The pressure time rate of change calculation unit 45 then calculates the pressure time rate of change of the second pressure gauge 31a and transmits the calculated pressure time rate of change to the separation membrane performance evaluation unit 46 (step S25). The pressure time rate of change calculation unit 45 also receives from the database 44 time series data of the pressure measurement value of the first pressure gauge 31 from the time when a command to set the valve opening to zero was sent to the first control valve 21 until a certain period of time has elapsed (step S28). The pressure time rate of change calculation unit 45 then calculates the pressure time rate of change of the first pressure gauge 31 and transmits the calculated pressure time rate of change to the separation membrane performance evaluation unit 46 (step S29).

[0063] The separation membrane performance evaluation unit 46 evaluates the performance of the second separation membrane 12a using the pressure time change rate of the second pressure gauge 31a and transmits the performance evaluation results to the terminal 47 (step S26).The separation membrane performance evaluation unit 46 also evaluates the performance of the separation membrane 12 using the pressure time change rate of the pressure gauge 31 and transmits the performance evaluation results to the terminal 47 (step S30).

[0064] [Effects of the Fifth Embodiment] In the fifth embodiment, the secondary pressure time change rate can be calculated simultaneously for each of the plurality of separation membranes 12, 12a, and the performance of each separation membrane can be evaluated.

[0065] <Modifications> Note that the embodiments described so far have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described.

[0066] For example, the display examples shown in Figures 7 and 8 show examples of displaying the performance of multiple separation membranes, but the display format of the performance of multiple separation membranes is not limited to the examples shown in these figures. For example, the performance of each separation membrane may be displayed as a numerical value. Furthermore, although the display example shows only the second embodiment, similar display formats can be applied to other embodiments.

[0067] Furthermore, in the configuration diagrams shown in Figures 1, 5, 9, 10, and 11, only control lines and information lines considered necessary for explanation are shown, and not all control lines and information lines are necessarily shown in the product. In reality, it can be assumed that almost all components are interconnected. Furthermore, the control flows shown in Figures 2 and 12 and the flowchart shown in Figure 4 are also examples, and as long as the processing results are the same, the order of some processes may be changed or multiple processes may be executed simultaneously. Furthermore, in each of the above-described embodiments, the control device 41 is shown to include a pressure time rate of change calculation unit and a separation membrane performance evaluation unit. However, the pressure time rate of change calculation unit and the separation membrane performance evaluation unit are configured, for example, by executing a program implemented in a computer. In this case, the program may be stored in a memory or storage device within the computer, or may be stored and transferred on an external memory, IC card, SD card, optical disk, or other recording medium.

[0068] REFERENCE SIGNS LIST 1...gas separation system, 2...mixed gas supply pipe, 3...non-permeate gas pipe, 4...permeate gas pipe, 11...gas separation membrane module (first separation membrane module), 11a...gas separation membrane module (second separation membrane module), 12...separation membrane (first separation membrane), 12a...separation membrane (second separation membrane), 13...primary side, 14...secondary side, 21...control valve (first control valve), 21a...control valve (second control valve), 22, 22a...check valve, 31...pressure gauge (first pressure gauge), 31a...pressure gauge (second pressure gauge), 41...control device, 41a...CPU, 41b...memory, 41c...storage, 41d...input unit, 41e...output unit, 41f...communication interface, 42...valve opening command unit, 43...measured value input unit, 44...Database, 45...Pressure time change rate calculation unit, 46...Separation membrane performance evaluation unit, 47...Terminal, 47a...Display screen, 51, 52, 52a...Mixed gas supply pipe, 53, 53a, 54...Non-permeating gas pipe, 56, 56a, 57...Permeating gas pipe, 101...Branch point, 102, 103...Confluence point

Claims

1. A gas separation system that evaluates the performance of a separation membrane that separates a specific component gas from a mixed gas using a regulation valve that controls the flow rate of gas separated by the separation membrane and a pressure gauge that measures the pressure between the separation membrane and the regulation valve, the gas separation system comprising: a pressure time rate of change calculation unit that calculates the pressure time rate of change in a predetermined valve opening state using the valve opening of the regulation valve and time series data of the measurement value of the pressure gauge; and a separation membrane performance evaluation unit that compares the pressure time rate of change calculated by the pressure time rate of change calculation unit with an initial value to evaluate the performance of the separation membrane.

2. The gas separation system according to claim 1, wherein the separation membrane comprises a plurality of separation membranes, a pressure gauge is also installed for each of the separation membranes, the regulating valve controls the flow rate of gas discharged from the plurality of separation membranes and merges at a junction, and each of the pressure gauges measures the pressure on the side that has permeated each of the separation membranes.

3. The gas separation system according to claim 2, wherein the pressure time rate of change calculation unit calculates the pressure time rate of change in a predetermined valve opening state using the valve opening of the control valve and time series data of the measurement values ​​of each of the pressure gauges, and the separation membrane performance evaluation unit evaluates the performance of each of the plurality of separation membranes.

4. A gas separation system as described in claim 3, which has an on-off valve that cuts off the flow rate of the pipe in which each of the pressure gauges is installed, and the separation membrane performance evaluation unit stores pressure measurement values ​​for a certain period of time using the pressure gauge installed in the closed pipe when the on-off valve is changed from open to closed as a database, and evaluates the performance of each of the multiple separation membranes based on the pressure measurement values ​​stored in the database and the time series data actually measured.

5. The gas separation system according to claim 2, wherein the plurality of separation membranes include a first separation membrane and a second separation membrane connected in series to the first separation membrane for separating gas discharged from the primary side of the first separation membrane; the pressure gauges include a first pressure gauge for measuring the pressure in a pipe connected to the secondary side of the first separation membrane and a second pressure gauge for measuring the pressure in a pipe connected to the secondary side of the second separation membrane; and the separation membrane performance evaluation unit evaluates the performance of the first separation membrane and the performance of the second separation membrane connected in series based on the pressure measurement values ​​obtained by the first pressure gauge and the pressure measurement values ​​obtained by the second pressure gauge.

6. The gas separation system described in claim 5, wherein the secondary side of the first separation membrane is also connected in series with the secondary side of the second separation membrane via piping, the pressure time rate of change calculation unit simultaneously acquires the valve opening of the control valve and time series data of the measurement values ​​of each of the pressure gauges to calculate the pressure time rate of change in a predetermined valve opening state, and the separation membrane performance evaluation unit evaluates the performance of each of the plurality of separation membranes.

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