Gas processing system

Abstract

To enable the smooth and continuous operation of multiple separation membrane units in response to load fluctuations at the gas emission source. [Solution] The gas treatment system (1) comprises a plurality of separation membrane units (40) that separate CO2 from the exhaust gas of an engine (10) that undergoes load fluctuations, a booster (30) that increases the pressure of the exhaust gas supplied to the plurality of separation membrane units, and a control unit (70) that controls the drive of the booster. The engine is provided with a load detection unit (11) that detects the load and outputs it to the control unit. Each of the plurality of separation membrane units comprises a separation membrane (41a) that separates the exhaust gas supplied via the booster into permeable gas and impermeable gas, and a back pressure control valve (49) that controls the pressure of the impermeable gas that flows without passing through the separation membrane. Based on the detection results of the load detection unit, the control unit controls the drive of the booster and the opening degree of the back pressure control valves in the plurality of separation membrane units during operation.

Description

[Technical Field]

[0001] This invention relates to a gas treatment system. [Background technology]

[0002] Patent Document 1 discloses an exhaust gas treatment system equipped with multiple separation systems for separating carbon dioxide (CO2) from exhaust gas emitted from an engine. Each of these separation systems includes a control valve for switching the introduction and stopping of exhaust gas from the engine, a separation membrane for separating CO2 from the exhaust gas, and a measuring unit for measuring the CO2 concentration of the exhaust gas that has permeated the separation membrane. The operation of the control valves in the multiple separation systems is controlled based on the measurement value from the measuring unit. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-22710 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Patent Document 1 describes a problem in which, when exhaust gas is treated in multiple separation systems, if the engine load fluctuates and the exhaust gas flow rate and pressure change, the pressure of the exhaust gas introduced between the multiple separation systems becomes unstable. To resolve this problem, even if the opening of the control valve is adjusted based on the measurement value of the measuring unit, coordinated control between the multiple separation systems is required in response to the engine load fluctuations, which increases the control burden.

[0005] The present invention has been made in view of the above, and aims to provide a gas treatment system that can keep multiple separation membrane units running smoothly in response to load fluctuations of the gas emission source. [Means for solving the problem]

[0006] A gas treatment system according to one embodiment of the present invention is a gas treatment system comprising: a plurality of separation membrane units for separating desired components from exhaust gas of a gas emission source subject to load fluctuations; a booster for pressurizing the exhaust gas supplied to the plurality of separation membrane units; and a control unit for controlling the drive of the booster, wherein the gas emission source is provided with a load detection unit that detects the load and outputs it to the control unit, and each of the plurality of separation membrane units comprises a separation membrane for separating the exhaust gas supplied via the booster into permeable gas and impermeable gas, and a back pressure control valve for controlling the pressure of the impermeable gas that flows without permeating the separation membrane, and the control unit controls the drive of the booster and the opening degree of the back pressure control valves in the plurality of separation membrane units during operation based on the detection result of the load detection unit. [Effects of the Invention]

[0007] According to the present invention, the load detection unit detects the load of the gas emission source, and the booster controls the pressure of the exhaust gas supplied to multiple separation membrane units and the opening degree of the back pressure permeate valves of the multiple separation membrane units. This stabilizes the pressure of the exhaust gas supplied to the multiple separation membrane units. Furthermore, this control adjusts the back pressure of the permeate gas that has permeated through the separation membrane of each of the multiple separation membrane units to a predetermined pressure, maintaining good exhaust gas separation performance while eliminating the need for coordinated control between the multiple separation membrane units and reducing the control burden. As a result, the operation of the multiple separation membrane units in response to load fluctuations of the gas emission source can be maintained smoothly. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing an example of a gas treatment system according to an embodiment. [Figure 2] This is a functional block diagram of the pre-processing unit according to the embodiment. [Figure 3] Figure 3A is a graph showing the relationship between engine load and booster command value, and Figure 3B is a graph showing the relationship between booster command value and back pressure control valve opening command value. [Figure 4] This is a time chart illustrating an example of control for a booster and back pressure control valve. [Figure 5] This is a time chart illustrating an example of control in the event of a malfunction in the separation membrane. [Figure 6] This is a time chart illustrating another example of control in the event of a malfunction in the separation membrane. [Figure 7] This is an explanatory diagram of the backwashing process in the embodiment. [Figure 8] This is a time chart illustrating an example of control when performing a backwashing process. [Figure 9] This is a time chart illustrating an example of control when the engine load falls outside the standard range. [Figure 10] This graph shows the relationship between engine load, CO2 concentration, and CO2 recovery rate. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Figure 1 is a schematic diagram showing an example of a gas treatment system according to an embodiment. In this embodiment, the gas treatment system is considered to be a system for recovering CO2 (carbon dioxide) from exhaust gas emitted from an engine used in a ship as a gas emission source. However, it is not limited to this, and the gas treatment system according to this embodiment can be applied to the treatment of exhaust gas in thermal power plants, chemical industrial plants, and waste incineration facilities.

[0010] Figure 1 is a schematic diagram showing an example of a gas treatment system according to an embodiment. As shown in Figure 1, the gas treatment system 1 mainly comprises an engine (gas emission source) 10 which is the source of exhaust gas, a pre-processing unit 20, a booster 30, a plurality of separation membrane units 40, a liquefaction unit 60, and a control unit 70.

[0011] Engine 10 may be a main engine or an auxiliary generator. Alternatively, engine 10 may be both a main engine and an auxiliary generator. The main engine is primarily operated while the ship is underway. The auxiliary generator is primarily operated to supply electricity to the ship. Engine 10 is supplied with fuel stored in a fuel tank (not shown). Note that when applying the gas treatment system 1 of this embodiment to various plants, a boiler may be used instead of engine 10.

[0012] The engine 10 is equipped with a load detection unit 11 that performs load (operating load) fluctuations and detects the load and outputs it to the control unit 70. The load detected and output by the load detection unit 11 includes the rotational speed of the engine 10 and the amount of exhaust gas from the engine 10 (kg / h, m³). 3 In addition to / h, a percentage of rotational speed with the maximum rated rotational speed of engine 10 set to 100% can also be used as an example. Hereafter, this percentage will be referred to as the engine load rate (%).

[0013] The exhaust gas discharged from the engine 10 is introduced to the pre-processing unit 20 via line 12. Line 12 is equipped with a pre-processing unit booster 13. The pre-processing unit booster 13 increases the pressure of the exhaust gas before it is discharged from the engine 10 and introduced to the pre-processing unit 20.

[0014] The pre-treatment unit 20 performs pre-treatment of the exhaust gas flowing into the booster unit 30. The pre-treatment unit 20 processes at least some of the impurities other than CO2 contained in the exhaust gas. These impurities may include sulfur oxides (SOx), nitrogen oxides (NOx), or particulate matter (PM).

[0015] Figure 2 shows an example of the configuration of the pre-treatment unit. The pre-treatment unit 20 includes a nitrogen oxide treatment unit 22, a dust removal unit 23, a sulfur oxide treatment unit 24, and a mist removal unit 25. Note that the pre-treatment unit 20 may be modified to include at least one of the above-mentioned units 22 to 25.

[0016] The nitrogen oxide treatment device 22 treats nitrogen oxides (NOx) contained in the exhaust gas supplied from the engine 10. Treating nitrogen oxides (NOx) may mean removing nitrogen oxides (NOx). The nitrogen oxide treatment device 22 may be a denitrification device. The denitrification device may be, for example, a selective catalytic reduction (SCR) device. Alternatively, instead of the pre-treatment unit 20 having the nitrogen oxide treatment device 22, the engine 10 may have an exhaust gas recirculation (EGR) function.

[0017] The dust removal device 23 removes particulate matter (PM) contained in the exhaust gas after it has passed through the nitrogen oxide treatment device 22. The dust removal device 23 may be an electrostatic precipitator (ESP), a diesel particulate filter (DPF), or an activated carbon filter.

[0018] The sulfur oxide treatment device 24 treats sulfur oxides (SOx) contained in the exhaust gas after it has passed through the dust removal device 23. Treating sulfur oxides (SOx) may mean removing sulfur oxides (SOx). When the gas treatment system 1 is installed on a ship, the sulfur oxide treatment device 24 may be a wet scrubber installed on the ship.

[0019] The mist removal device 25 removes moisture contained in the exhaust gas after it has passed through the sulfur oxide treatment device 24. The mist removal device 25 may be a spray separator that collects, separates, and removes moisture contained in the exhaust gas using a demister.

[0020] Returning to Figure 1, the pre-processing unit 20 and the booster 30 are connected by a line 27 through which the exhaust gas, from which impurities have been removed in the pre-processing unit 20, flows. A heat exchanger 28 is provided downstream of the booster 30 in line 27. In other words, the heat exchanger 28 is provided between the booster 30 and the multiple separation membrane units 40. The heat exchanger 28 is provided so that the temperature of the exhaust gas can be adjusted by, for example, supplying a fluid that is hotter or colder than the exhaust gas flowing in line 27, thereby performing heat exchange between the fluid and the exhaust gas.

[0021] The booster 30 has the capability to compress the exhaust gas discharged from the engine 10 and passing through the pre-processing unit 20, thereby increasing the pressure of the exhaust gas to the receiving pressure in the separation membrane unit 40. In other words, the booster 30 increases the pressure of the exhaust gas supplied to the multiple separation membrane units 40. Therefore, the exhaust gas is supplied to the multiple separation membrane units 40 via the booster 30.

[0022] The booster 30 and the multiple separation membrane units 40 are connected by a branch line (branch piping) 31 through which the exhaust gas pressurized by the booster 30 flows. The branch line 31 is provided to distribute the exhaust gas pressurized by the booster 30 to the multiple separation membrane units 40 before delivery.

[0023] In this embodiment, the multiple separation membrane units 40 include first to nth separation membrane units 40A to 40N and a reserve separation membrane unit 40X. Here, "N" in the nth separation membrane unit is an integer of 2 or more, and is the same value as the number of separation membrane units 40 installed in the multiple separation membrane units 40 excluding the reserve separation membrane unit 40X. This number can be arbitrarily set according to the required performance of the gas treatment system 1. In Figure 1, for the sake of space, three separation membrane units 40 are shown: the first separation membrane unit 40A, the nth separation membrane unit 40N, and the reserve separation membrane unit 40X. Each of the separation membrane units 40A to 40N and 40X is enclosed by a dashed line in Figure 1, and is connected to a branch line 31 on the upstream side and to a converging line 32 on the downstream side. The converging line 32 merges into a single line 33, and is connected to the liquefaction section 60 via this line 33. Although not shown in the diagram, the second separation membrane unit may be referred to as "40B" in the description.

[0024] Each connecting line 35, which connects the downstream side of the branch line 31 to each of the separation membrane units 40A-40N and 40X, is provided with a switching valve 36. The switching valve 36 has the function of switching the introduction and stopping of exhaust gas from the branch line 31 to each of the separation membrane units 40A-40N and 40X by opening and closing drive. In addition, the switching valve 36 restricts the flow of gas from each of the separation membrane units 40A-40N to the branch line 31 side by closing during backwashing, which will be described later. In this embodiment, the switching valve 36 employs a valve structure that is used either fully open or fully closed, rather than being used at an intermediate opening, but this does not prevent it from being configured with a solenoid valve whose opening degree can be adjusted. In addition, such a valve structure is also used for the gate valve 42 and the circulation gate valve 54, which will be described later.

[0025] Downstream of the switching valve 36 in the connection line 35, a backwash discharge section 37, which will be used during backwashing as described later, is provided. The backwash discharge section 37 has a backwash discharge line 37a through which backwash purge gas flows, which is connected (branched) to the connection line 35, and a backwash discharge gate valve 37b that switches between discharging and stopping the backwash purge gas in the backwash discharge line 37a.

[0026] A pressure measuring unit 38 is provided downstream of the backwash discharge unit 37 in the connection line 35. The pressure measuring unit 38 consists of a pressure gauge that measures the pressure of the exhaust gas that is pressurized by the booster 30 and then introduced to each separation membrane unit 40A~40N, 40X via the branch line 31. The pressure measuring unit 38 continuously measures the pressure fluctuations of the exhaust gas before it is supplied upstream of each separation membrane unit 40A~40N, 40X and outputs the results to the control unit 70.

[0027] In this embodiment, the first to Nth separation membrane units 40A to 40N and the reserve separation membrane unit 40X employ the same configuration. Therefore, the first separation membrane unit 40A will be described below, and the other separation membrane units 40N and 40X will be denoted by the same reference numerals as the first separation membrane unit 40A, and their descriptions may be omitted.

[0028] The first separation membrane unit 40A includes a first separation section 41, a gate valve 42, a first negative pressure generator 43, a second separation section 44, and a second negative pressure generator 45, which are arranged in order from the upstream branch line 31 to the downstream collection line 32.

[0029] The first separation unit 41 is equipped with a separation membrane 41a and separates the exhaust gas, which has been pressurized by the booster 30 and introduced through the switching valve 36, into permeate gas and unpermeate gas using the separation membrane 41a. In the first separation unit 41, the unpermeate gas that did not permeate the separation membrane 41a becomes a gas mainly composed of oxygen and nitrogen with a lower CO2 concentration than the permeate gas that did permeate, and is discharged into the atmosphere via the discharge line 47. The permeate gas that permeates the separation membrane 41a contains CO2, and its CO2 concentration is higher than that of the exhaust gas before it was introduced into the first separation unit 41. Therefore, the first separation unit 41 reduces the flow rate by the amount of unpermeate gas discharged into the atmosphere via the separation membrane 41a, while increasing the CO2 concentration of the exhaust gas, and sends it to the first intermediate line 51 on the downstream side. In this way, the first separation membrane unit 40A, including the separation membrane 41a, separates CO2, which is the desired component, from the exhaust gas.

[0030] The first separation membrane unit 40A further includes a backwash inlet 48 and a back pressure control valve 49 provided in the discharge line 47. The backwash inlet 48 has a backwash inlet line 48a connected to (branched from) the discharge line 47 through which backwash purge gas flows, and a backwash inlet gate valve 48b that switches between discharging and stopping the backwash purge gas from the backwash inlet line 48a.

[0031] The first separation membrane unit 40A is equipped with a back pressure control valve 49 located downstream of the backwash inlet 48 in the discharge line 47. The back pressure control valve 49 controls the pressure of the unpermeated gas that flows without passing through the separation membrane 41a of the first separation unit 41. In other words, the pressure and discharge amount of the unpermeated gas are controlled by changing the opening degree of the back pressure control valve 49 in response to changes in the pressure of the unpermeated gas discharged into the atmosphere via the discharge line 47. The back pressure control valve 49 is also configured as a solenoid valve whose opening degree can be adjusted by an opening degree command from the control unit 70, and has the function of continuously outputting the change in opening degree to the control unit 70.

[0032] A gate valve 42 and a first negative pressure generating device 43 are provided in the first intermediate line 51 that connects the first separation section 41 and the second separation section 44.

[0033] The gate valve 42 has the function of switching between restricting and releasing the gas flow in the first intermediate line 51 by opening and closing it.

[0034] The first negative pressure generator 43 is provided downstream of the gate valve 42. The first negative pressure generator 43 is a suction pump that sucks the permeate gas separated by passing through the separation membrane 41a of the first separation unit 41 so that it flows from the first separation unit 41 to the first intermediate line 51. The exhaust gas is permeated through the separation membrane 41a of the first separation unit 41 by the negative pressure from the first negative pressure generator 43 and the positive pressure from the booster 30. The first negative pressure generator 43 and the second negative pressure generator 45 are composed of, for example, vacuum pumps.

[0035] The second separation unit 44 is configured similarly to the first separation unit 41. The second separation unit 44 is equipped with a separation membrane 44a and separates the permeate gas drawn in by the first negative pressure generator 43 as exhaust gas into permeate gas and unpermeate gas using the separation membrane 44a. In the second separation unit 44, the unpermeate gas that did not permeate the separation membrane 44a becomes a gas mainly composed of oxygen and nitrogen with a lower CO2 concentration than the permeate gas that did permeate, and is sent to the circulation line 52. The permeate gas that permeates the separation membrane 44a contains CO2, and its CO2 concentration is higher than that of the exhaust gas before it was introduced into the second separation unit 44. Therefore, the second separation unit 44 sends exhaust gas with a higher CO2 concentration to the collection line 32, while reducing the flow rate by the amount of unpermeate gas sent to the circulation line 52 via the separation membrane 44a.

[0036] Each separation membrane 41a, 44a can be composed of either an organic material or an inorganic material. Examples of organic separation membranes include hollow fiber porous materials made of polymers or resins, while examples of inorganic separation membranes include hollow fiber materials made of silicon oxide (SiO2) or aluminosilicate (so-called zeolite).

[0037] Specifically, it is preferable that the separation membrane 41a of the first separation section 41 is made of an inorganic material, and the separation membrane 44a of the second separation section 44 is made of an organic material. From the viewpoint of durability, it is preferable that the separation membrane 41a of the upstream first separation section 41 be made of an inorganic material.

[0038] The first separation membrane unit 40A further includes a circulation blower 53 and a circulation gate valve 54 provided in the circulation line 52. The circulation line 52 connects the second separation section 44 to the downstream side of the pressure measuring section 38 of the connecting line 35, which is the inlet of the first separation membrane unit 40A, and circulates the unpermeated gas that did not permeate the separation membrane 44a of the second separation section 44 to the first separation section 41. The circulation blower 53 has the function of sending the unpermeated gas in the circulation line 52 to the first separation section 41. The circulation gate valve 54 has the function of switching between restricting and releasing the gas flow in the circulation line 52 by opening and closing drive.

[0039] A second negative pressure generator 45 is provided in the second intermediate line 56, which connects the second separation unit 44 and the collection line 32. The second negative pressure generator 45 is a suction pump that sucks the permeate gas separated by passing through the separation membrane 44a of the second separation unit 44 so that it flows from the second separation unit 44 to the second intermediate line 56.

[0040] Here, the line 33 connecting the collection line 32 and the liquefaction unit 60 is provided with a concentration measuring unit 58 and a flow rate measuring unit 59, and the permeate gas measuring unit is formed by including the concentration measuring unit 58 and the flow rate measuring unit 59.

[0041] The concentration measurement unit 58 is a CO2 concentration meter, and is composed of, for example, a laser gas analyzer. The concentration measurement unit 58 continuously measures fluctuations in the CO2 concentration of exhaust gas sent from multiple separation membrane units 40 through the collection line 32 and outputs the results to the control unit 70.

[0042] The flow rate measuring unit 59 is composed of, for example, a flow meter (mass flow meter, etc.). The flow rate measuring unit 59 continuously measures fluctuations in the flow rate of exhaust gas sent from multiple separation membrane units 40 through the collection line 32 and outputs the results to the control unit 70.

[0043] The liquefaction unit 60 can be exemplified by being configured with a heat exchanger that performs heat exchange between the introduced exhaust gas and the refrigerant. In the liquefaction unit 60, at least the CO2 contained in the exhaust gas is condensed and liquefied, preferably in a state where the CO2 is liquefied and oxygen and nitrogen are maintained in gaseous form. The liquefaction unit 60 further includes a gas-liquid separator and a tank, which separate the exhaust gas in the above state into off-gas and liquefied CO2, discharge the off-gas into the atmosphere, and store the liquefied CO2 in the tank.

[0044] The control unit 70 includes a CPU that performs calculations according to a control program, and a storage medium such as memory. The control unit 70 executes various processes and provides overall control of each component of the gas processing system 1 connected via a wired or wireless communication path. For example, the control unit 70 is connected to each booster 13, 30, each negative pressure generating device 43, 45 of each of the multiple separation membrane units 40, and the motor (not shown) of the circulation blower 53, and has the function of controlling their drive. The control unit 70 has, for example, an inverter that controls the rotation speed of the motors. The control unit 70 is also connected to each of the valves 36, 37b, 42, 48b, 49, 54 mentioned above and controls their opening and closing drive.

[0045] The control unit 70 outputs the detected values ​​(detection results) and measured values ​​(measurement results) of the load detection unit 11 of the engine 10, the pressure measurement unit 29 (described later), each pressure measurement unit 38, the concentration measurement unit 58, and the flow rate measurement unit 59. For example, the control unit 70 controls the drive of the booster 30 and the opening degree of the back pressure control valves 49 of each of the multiple separation membrane units 40 based on the detected values ​​of the load detection unit 11 and the pressure measurement units 29 and 38. Specific examples of such control and other controls by the control unit 70 will be described later.

[0046] Next, an example of control when operating all of the separation membrane units 40 (the first to the Nth separation membrane units 40A to 40N) in the gas treatment system 1, excluding the preliminary separation membrane unit 40X, will be explained using Figures 3 and 4. Figure 3A is a graph showing the relationship between engine load and booster command value, and Figure 3B is a graph showing the relationship between booster command value and back pressure control valve opening command value.

[0047] In the graph of Figure 3A, the horizontal axis represents the engine load percentage (%), which is the load on engine 10, and the vertical axis represents the booster command value (rpm), which is the command value for the rotational speed (rpm) of the motor of booster 30. In the following explanation, the rotational speed of the motor of booster 30 may be referred to as "the rotational speed of booster 30". The control unit 70 stores the following calculation formula shown in the graph of Figure 3A. Booster command value (rpm) = Engine load rate (%) × Constant + Fluctuation margin

[0048] In the above arithmetic expression, the exhaust gas flow rate of the engine 10 depends on the engine load factor, and the constant is determined based on the test data of the exhaust gas flow rate and the booster command value. By adding a margin of variation to the above arithmetic expression, the control unit 70 calculates a booster command value that takes into account the delay caused by the distance between the engine 10 and the booster 30 and the capacity of the connection flow rate.

[0049] In the graph of FIG. 3B, the horizontal axis represents the booster command value (rpm), and the vertical axis represents the opening command value (%) of the back pressure control valve 49. The relationship shown in the graph of FIG. 3B is stored in the control unit 70. The control unit 70 calculates the opening command value of the back pressure control valve 49 based on the relationship shown in the graph of FIG. 3B and the booster command value calculated by the above arithmetic expression.

[0050] As shown in FIG. 3B, as the booster command value increases, the opening command value of the back pressure control valve 49 also increases, and as the booster command value decreases, the opening command value of the back pressure control valve 49 also decreases. By changing the opening of the back pressure control valve 49 via the control unit 70 according to such an opening command value, the supply pressure of the exhaust gas on the upstream (inlet) side of the separation membrane unit 40 is controlled to be a predetermined pressure.

[0051] Hereinafter, FIG. 4 is a time chart for explaining an example of the control of the booster and the back pressure control valve. Using FIG. 4, the control when operating all of the plurality of separation membrane units 40 (the first to Nth separation membrane units 40A to 40N) will be further described.

[0052] Here, a case where the rotational speed that becomes the load of the engine 10 varies as shown in FIG. 4 will be described as an example. In FIG. 4, the rotational speed of the engine 10 is constant at R1 (rpm) until time t 11 and gradually increases from time t 11 to time t 12 , t 13 and reaches time t 14 . It is constant at R4 (rpm) from time t 14 to time t 15 . Then, after the elapse of time t 15 , time t16 It gradually declines until time t 17 t 18 time t 16 From this point onward, the R6 (rpm) is considered constant.

[0053] The time t when the engine speed of engine 10 begins to increase 11 Time delayed from 12 Then, the control unit 70 controls the rotation speed of the booster 30 to increase from S1 (rpm) to S4 (rpm). Also, time t 12 A further delay from that time t 13 The control unit 70 controls the opening of the back pressure control valves 49 of the first to Nth separation membrane units 40A to 40N during operation to increase from VA1, VN1 (%) to VA4, VN4 (%). The time t when the engine speed of the 10 starts to increase 11 Time from t 12 t 13 The delay time is set by a timer in the control unit 70. By providing this delay time, the inertial gas corresponding to the line length and volume from the engine 10 to the booster 30 can be completely flowed.

[0054] Time t 14 When the engine speed becomes constant at R4 (rpm), time t 14 From time t 15 During this time, the control unit 70 controls the rotation speed of the booster 30 to remain constant at S4 (rpm). 14 From time t 15 During this time, the control unit 70 controls the opening degree of the back pressure control valve 49 of the first separation membrane unit 40A to be kept constant at VA4 (%), and the opening degree of the back pressure control valve 49 of the Nth separation membrane unit 40N to be kept constant at VN4 (%).

[0055] The exhaust gas supply pressure values ​​measured by each pressure measuring unit 38 on the upstream side (inlet side) of the first to Nth separation membrane units 40A to 40N are, time t 11 The P1 (kPaA) value is considered the same. The supply pressure value is the time t during which the opening degree of the back pressure control valve 49 is increased. 13 From time t 14The time until then varies as needed (shown by the dashed line in Figure 4). The time t for keeping the opening of the back pressure control valve 49 constant. 14 From time t 15 During this time, t is the time before the engine speed of 10 increases. 11 This results in the same value for P1(kPaA).

[0056] Time t 15 From time t 16 During this time, the engine speed of 10 decreases from R4 (rpm), and time t 16 From this point onward, R6 (rpm) remains constant. At this time, time t 16 Time delayed from 17 Then, the control unit 70 controls the rotation speed of the booster 30 to decrease from S4 (rpm) to S7 (rpm). Also, time t 17 A further delay from that time t 18 The control unit 70 controls the opening of the back pressure control valves 49 of the first to Nth separation membrane units 40A to 40N to decrease from VA4, VN4 (%) to VA8, VN8 (%). The time t when the decrease in the rotational speed of the engine 10 is completed. 16 Time from t 17 t 18 The delay time is set by a timer in the control unit 70.

[0057] According to the control shown in Figure 4 by the control unit 70, the rotational speed of the booster 30 can be adjusted in accordance with fluctuations in the rotational speed of the engine 10, thereby controlling the total flow rate of exhaust gas supplied to the entire set of separation membrane units 40A to 40N during operation. Furthermore, the opening degree of the back pressure control valve 49 of each of the separation membrane units 40A to 40N can be adjusted in accordance with fluctuations in the rotational speed of the engine 10, thereby controlling the back pressure of the unpermeated gas discharged from the first separation unit 41 to a predetermined pressure. As a result, the pressure value P1 (kPaA) measured at the pressure measuring unit 38 on the inlet side of the separation membrane units 40A to 40N can be made uniform, and the exhaust gas pressure in each of the separation membrane units 40A to 40N can be controlled to stabilize.

[0058] As described above, the control method suppresses variations in exhaust gas supply conditions across all of the separation membrane units 40A to 40N during operation, even when the load on the engine 10 fluctuates, allowing the operation of all of the separation membrane units 40A to 40N to continue smoothly. Therefore, even when the load on the engine 10 fluctuates, the system can continue supplying exhaust gas to all of the separation membrane units 40A to 40N without having to start or stop them in stages. This reduces the time required to adjust the exhaust gas pressure across the separation membrane units 40A to 40N, improving the engine 10's ability to respond to load fluctuations.

[0059] Furthermore, by controlling the rotational speed of the booster 30 and the opening degree of the back pressure control valves 49 of each of the multiple separation membrane units 40A to 40N during operation, the pressure of the exhaust gas supplied to the multiple separation membrane units 40A to 40N can be adjusted to follow the load fluctuations of the engine 10. This eliminates the need for coordinated control among the multiple separation membrane units 40A to 40N, reducing the control burden, and thus enabling the smooth and continuous operation of the multiple separation membrane units 40A to 40N.

[0060] Note that time t 14 , time t 15 In this system, the rotational speed of the booster 30, the opening degree of the back pressure control valves 49 of the first to Nth separation membrane units 40A to 40N, and the pressure values ​​measured by the pressure measuring units 38 at the inlet side of the multiple separation membrane units 40A to 40N all have a delay equal to the system capacity, and as shown in Figure 4, the changes begin to occur sequentially after a predetermined time has elapsed. 13 , time t 18 In this case, the pressure values ​​measured by the pressure measuring section 38 at the inlet side of the multiple separation membrane units 40A to 40N also have a delay equal to the system capacity, and as shown in Figure 4, the changes begin to occur sequentially after a predetermined time has elapsed.

[0061] In the control shown in Figure 4, the opening degree of each of the back pressure control valves 49 of the multiple separation membrane units 40A to 40N was controlled to a different value, but this is not the only option. For example, the control unit 70 may set the opening degree command value to be the same for each of the back pressure control valves 49 of the multiple separation membrane units 40A to 40N during operation, and control all of the back pressure control valves 49 to have the same opening degree.

[0062] With this control system, even if the load on the engine 10 fluctuates, the opening command value for the multiple back pressure control valves 49 can be made unified, further reducing the control burden. Also, as shown in Figure 1, by providing a pressure measuring unit 29 (shown by a dashed line) at one location upstream of the branching point of the branch line 31, the exhaust gas supply pressure in all of the multiple separation membrane units 40A to 40N can be measured and managed. This simplifies the equipment and reduces the management burden.

[0063] Next, an example of control by the control unit 70 when a malfunction occurs in the separation membrane 41a of some of the separation membrane units 40A to 40N will be explained using Figure 5. Figure 5 is a time chart to illustrate an example of control when a malfunction occurs in the separation membrane.

[0064] Here, we will explain an example of a malfunction occurring in the separation membrane 41a, specifically in the first separation membrane unit 40A of the multiple separation membrane units 40A to 40N, where dust and other debris accumulate on the separation membrane 41a, leading to an increase in pressure loss. In Figure 5, the rotational speed of the engine 10 is always kept constant at R1 (rpm). The rotational speed of the booster 30 is set over time t. 21 From time t 22 After time t 23 During this time, it is controlled to a constant value at S1 (rpm). The set value of the exhaust gas supply pressure on the upstream (inlet) side of the first to Nth separation membrane units 40A to 40N is set to time t 21 From time t 26 During this period, P1 (kPaA) is considered to be the same.

[0065] Due to the accumulation of dust on the separation membrane 41a, etc., the pressure loss of the first separation membrane unit 40A increases, over time t 21 From time t 22 During this time, the opening degree of the back pressure control valve 49 of the first separation membrane unit 40A is increased from VA1(%). Then, time t 22 When the opening degree VA2(%) of the back pressure control valve 49 reaches its upper limit, time t 22 Time t after a predetermined time has elapsed 23 From time t 24 During this time, the control unit 70 controls the rotational speed of the booster 30 to rapidly increase from S1 (rpm) to S4 (rpm). This rotational speed S4 (rpm) is pre-stored in the control unit 70 as the upper limit for the booster 30's rated operation.

[0066] Due to the rapid increase in the rotational speed of the booster 30, the exhaust gas supply pressure in the first separation membrane unit 40A increases, so time t 23 From time t 24 During this time, the opening degree of the back pressure control valve 49 is lowered.

[0067] The exhaust gas supply pressure value measured by the pressure measuring unit 38 upstream of the first separation membrane unit 40A is, time t 21 After time t 22 P1 (kPaA) remains constant until the time t reaches the upper limit of the opening degree VA2 (%) of the back pressure control valve 49. 22 From time t 23 During this time, the pressure rises due to pressure loss. Then, at time t 23 From time t 24 As the opening degree of the back pressure control valve 49 decreases during this time, the supply pressure value of exhaust gas to the first separation membrane unit 40A decreases, and time t 24 From this point onward, the system will return to a constant P1 (kPaA).

[0068] Time t 24 The time t after a predetermined time has elapsed since the rotation speed of the booster 30 became constant at S4 (rpm) is 25At this point, the opening of the back pressure control valve 49 of the first separation membrane unit 40A is increased again. This is because, due to the increase in the rotational speed of the booster 30, the exhaust gas flow rate remains increased even after the opening of the back pressure control valve 49 is decreased. Then, at time t 25 From time t 26 During this time, the opening degree of the back pressure control valve 49 of the first separation membrane unit 40A is increased, and time t 26 The opening degree VA6(%) of the back pressure control valve 49 reaches the upper limit again.

[0069] The time t when the opening degree VA6(%) of the back pressure control valve 49 reaches its upper limit 26 From time t 27 During this time, the exhaust gas supply pressure value measured by the pressure measuring unit 38 upstream of the first separation membrane unit 40A rises from P1 (kPaA) to P7 (kPaA) due to pressure loss. Then, at time t 27 The control unit 70 controls the exhaust gas supply pressure setting value in the first to Nth separation membrane units 40A to 40N to change from P1 (kPaA) to P7 (kPaA). This supply pressure setting value P7 (kPaA) is stored in the control unit 70 beforehand.

[0070] By changing the set value of the supply pressure to P7 (kPaA), the opening degree of the back pressure control valve 49 controlled by the control unit 70 is lowered from the upper limit VA6 (%), and time t 28 From this point onward, the control unit 70 controls the VA to remain constant at 8 (%). As a result, the exhaust gas supply pressure value to the first separation membrane unit 40A is controlled over time t 27 From this point onward, the pressure remains constant at P7 (kPaA).

[0071] The opening degree of the back pressure control valve 49 of the first separation membrane unit 40A is changed in accordance with the increase in the rotational speed of the booster 30 and the increase in the set value of the exhaust gas supply pressure in the first to the Nth separation membrane units 40A to 40N. Although the increase and decrease in this change is smaller than that of the back pressure control valve 49 of the first separation membrane unit 40A, it is performed at a similar timing. The exhaust gas supply pressure value measured by the pressure measuring unit 38 on the upstream side of the Nth separation membrane unit 40N is set at time t 27 Up to time t, P1 (kPaA) remains constant, 28 From this point onward, the pressure remains constant at P7 (kPaA). In other words, the exhaust gas supply pressure between the first separation membrane unit 40A and the nth separation membrane unit 40N can be made uniform.

[0072] In Figure 5, the pressure loss of the separation membrane 41a of the first separation membrane unit 40A increases due to the accumulation of dust and other debris, and the pressure value measured by the upstream pressure measuring unit 38 becomes the highest compared to the pressure values ​​measured by the other pressure measuring units 38. Under these conditions, according to the control shown in Figure 5 by the control unit 70, the opening degree of the back pressure control valves 49 of the second to Nth separation membrane units 40B to 40N is controlled to be the same in accordance with the opening degree of the back pressure control valve 49 of the first separation membrane unit 40A.

[0073] In other words, the control unit 70 controls the multiple pressure measuring units 38, specifically the time t 27 The opening degree of the back pressure control valve 49 in the first separation membrane unit 40A, which is downstream of the pressure measuring unit 38 that measured the highest pressure value P1 (kPaA), is controlled to be the same as the opening degree of the back pressure control valves 49 in the second to Nth separation membrane units 40B to 40N other than the first separation membrane unit 40A. This makes it possible to equalize the supply pressure of the separation membrane unit 40 with the highest exhaust gas supply pressure with the exhaust gas supply pressure in all other separation membrane units 40. Therefore, even if a malfunction occurs in some of the separation membranes 41a, the exhaust gas supply pressure in each of the separation membrane units 40A to 40N can be stabilized.

[0074] Note that time t23 , time t 24 In this system, the opening degree of the back pressure control valve 49 of the first to Nth separation membrane units 40A to 40N, and the pressure value measured by the pressure measuring unit 38 on the inlet side of the first separation membrane unit 40A, have a follow-up delay equal to the system capacity, and as shown in Figure 5, the changes begin to occur sequentially after a predetermined time has elapsed. 27 , time t 28 In this case, the pressure value measured at the pressure measuring unit 38 on the inlet side of the Nth separation membrane unit 40N also has a follow-up delay equal to the system capacity, and as shown in Figure 5, the change begins after a predetermined time has elapsed sequentially.

[0075] Next, using Figure 6, we will explain another example of control by the control unit 70 when a malfunction occurs in the separation membrane 41a of some of the separation membrane units 40A to 40N, as shown in Figure 5. Figure 6 is a time chart to explain another example of control when a malfunction occurs in the separation membrane.

[0076] Here, we will explain using the example of a malfunction occurring in the separation membrane 41a, specifically in the first separation membrane unit 40A of the multiple separation membrane units 40A to 40N, where aging deterioration or other issues occur in the separation membrane 41a, resulting in a decrease in its separation performance. In Figure 6, time t 31 From time t 32 During this time, due to the deterioration of the separation membrane 41a, the CO2 concentration value measured by the concentration measuring unit 58, which acts as a CO2 concentration meter, drops from G1 (%) to G2 (%), which falls below the lower limit. In other words, the flow rate of gases other than CO2 permeating through the separation membrane 41a increases, resulting in a decrease in the CO2 concentration value measured by the concentration measuring unit 58.

[0077] Time t 32 When the CO2 concentration value G2(%) measured by the concentration measurement unit 58 falls below the lower limit, the control unit 70 controls the system to emit an alarm via a sound-emitting device or display device (not shown). Furthermore, based on the condition that the CO2 concentration value G2(%) falls below the lower limit, time t 32 From time t 33During this period, the control unit 70 controls the rotational speed of the booster 30 to gently increase from S1 (rpm) to S3 (rpm). This rotational speed S3 (rpm) is calculated by the control unit 70 according to the measurement value of the concentration measurement unit 58.

[0078] Due to the increase in the rotational speed of the booster 30, in all the separation membrane units 40A to 40N, from time t 32 to time t 33 the control unit 70 controls the opening degree of the back pressure control valve 49 to increase from V1 (%) to V3 (%). As a result, the pressure and flow rate of the exhaust gas supplied to the separation membrane 41a increase, and by increasing the differential pressure across the separation membrane 41a, the CO2 concentration of the permeated gas increases. Therefore, between time t 32 and time t 33 the CO2 concentration value measured by the concentration measurement unit 58 increases from G2 (%) to G3 (%). At this time, when the pressure measurement unit 29 is provided at one location upstream of the branch position of the branch line 31 as described above, the supply pressure value of the exhaust gas measured by the pressure measurement unit 29 increases from P1 (kPaA) to P3 (kPaA).

[0079] Time t 33 to time t 34 If the second deterioration of the separation membrane 41a occurs during this period, the same flow as described above is repeated. First, the CO2 concentration value measured by the concentration measurement unit 58 decreases from G3 (%) to G5 (%) below the lower limit. When the CO2 concentration value G5 (%) measured by the concentration measurement unit 58 at time t 35 falls below the lower limit, the control unit 70 controls to issue an alarm as described above. And on the condition that the CO2 concentration value G5 (%) falls below the lower limit, between time t 35 and time t 36 the control unit 70 controls the rotational speed of the booster 30 to gently increase from S3 (rpm) to S6 (rpm). This rotational speed S6 (rpm) is calculated by the control unit 70 according to the measurement value of the concentration measurement unit 58.

[0080] Due to the increase in the rotational speed of the booster 30, in all the separation membrane units 40A to 40N, from time t 35From time t 36 During this time, the control unit 70 controls the opening of the back pressure control valve 49 to increase from V3 (%) to V6 (%). 35 From time t 36 During this time, the CO2 concentration value measured by the concentration measuring unit 58 increases from G5 (%) to G6 (%), and the exhaust gas supply pressure value measured by the pressure measuring unit 29 increases from P3 (kPaA) to P6 (kPaA).

[0081] According to the control shown in Figure 6 by the control unit 70, the drive of the booster 30 is controlled based on the CO2 concentration value measured by the concentration measurement unit 58, and the opening degree of the back pressure control valves 49 of each of the multiple separation membrane units 40A to 40N is adjusted to be the same during operation. As a result, even if deterioration occurs in some of the separation membranes 41a, the permeate gas can be set to a predetermined CO2 concentration value, and the exhaust gas supply pressure in each of the multiple separation membrane units 40A to 40N can be stabilized.

[0082] Note that time t 32 , time t 33 , time t 34 , time t 35 In this system, the rotational speed of the booster 30, the opening degree of the back pressure control valves 49 of all separation membrane units 40A to 40N, and the pressure value of the pressure measuring unit 29 all have a delay equal to the system capacity, and as shown in Figure 6, the changes begin to occur sequentially after a predetermined time has elapsed.

[0083] Next, the flow of the backwashing process for the separation membrane 41a in multiple separation membrane units 40 will be explained using Figure 7. Figure 7 is an explanatory diagram of the backwashing process in the embodiment. In the backwashing process, dust can be removed if it has accumulated on the separation membrane 41a of the separation membrane unit 40.

[0084] As shown in Figure 7, when a backwashing process is performed, a purge gas supply device 80 for backwashing is connected to the backwash inlet line 48a of the backwash inlet 48, and the purge gas PG, indicated by the thick arrow in Figure 7, is supplied at a predetermined pressure. Although Figure 7 illustrates the case where a purge gas supply device 80 is installed for each of the multiple separation membrane units 40, the purge gas PG may also be supplied using piping branched from a single purge gas supply device 80 or using multiple pipes.

[0085] The backwashing process can be similarly performed in all of the first to nth separation membrane units 40A to 40N and the reserve separation membrane unit 40X. In the backwashing process, before supplying purge gas PG from the purge gas supply device 80, the backwash inlet gate valve 48b of the backwash inlet 48 and the backwash discharge gate valve 37b of the backwash discharge 37 are opened. Furthermore, the upstream (inlet) side switching valve 36, gate valve 42, back pressure control valve 49, and circulation gate valve 54 are closed. Details of the opening and closing control of the back pressure control valve 49 will be described later.

[0086] In the backwashing process, as described above, after opening and closing valves 36, 37b, 42, 48b, 49, and 54, purge gas PG is supplied from the purge gas supply device 80 to the backwash introduction line 48a of the backwash introduction section 48. As a result, the purge gas PG, indicated by the thick arrows in Figure 7, is pumped to flow in the following order: backwash introduction line 48a of the backwash introduction section 48, discharge line 47, first separation section 41, connection line 35, and backwash discharge line 37a of the backwash discharge section 37. This flow of purge gas PG removes dust accumulated on the separation membrane 41a, which is then discharged through the connection line 35 and backwash discharge line 37a and recovered by a filter or the like.

[0087] In the backwashing process, the backwashing process is performed on each of the first to Nth separation membrane units 40A to 40N in that order, and exhaust gas treatment is performed in the same manner as normal operation when the backwashing process is not being performed on each of the separation membrane units 40A to 40N. In this case, the spare separation membrane unit 40X is used. Below, an example of control by the control unit 70 when the backwashing process is performed will be explained using Figure 8. Figure 8 is a time chart to explain an example of control when the backwashing process is performed.

[0088] In Figure 8, the backwash command for the entire gas treatment system 1 is given as time t. 41 From there, time t sequentially at predetermined time intervals 42 , time t 4N、 Time t 4N+1 The timer is set in the control unit 70. "N" is the same value as the number of separation membrane units 40 installed, excluding the spare separation membrane unit 40X. If "N" is 4 or greater, the backwashing from the third separation membrane unit to the (N-1) separation membrane unit is omitted from the illustration in Figure 8.

[0089] In Figure 8, the system-wide backwash command switches from "OFF" to "ON" at each time t, and then switches from "ON" to "OFF" midway between each time t and the next time t. Then, at the first time t 41 Then, the first separation membrane unit 40A switches from "OFF" to "ON" in the same way as the backwash command, and becomes subject to backwashing. Also, the second time t 42 Then, the second separation membrane unit 40B switches from "OFF" to "ON" in the same way as the backwash command, and becomes subject to backwashing, at the Nth time t 4N Next, the Nth separation membrane unit 40N will switch from "OFF" to "ON," just like the backwash command, and will become subject to backwashing.

[0090] In Figure 8, the back pressure control valve timer is set in the control unit 70. The back pressure control valve timer switches from "OFF" to "ON" a predetermined time before each time t set in the backwash command, and switches from "ON" to "OFF" a predetermined time after each time t.

[0091] First time t 41 Prior to the backwashing process that precedes this, the first to Nth separation membrane units 40A to 40N are in operation, and the reserve separation membrane unit 40X is stopped. In this state, the back pressure control valves 49 of the first to Nth separation membrane units 40A to 40N are set to the same opening degree V1 (%), and the back pressure control valve 49 of the reserve separation membrane unit 40X is controlled by the control unit 70 to 0 (%).

[0092] First time t 41 Prior to this, the back pressure control valve timer is switched to "ON," and the control unit 70 controls the opening of the back pressure control valve 49 of the auxiliary separation membrane unit 40X from 0 (%) to V1 (%), which is the same as the opening of the back pressure control valve 49 of the first to Nth separation membrane units 40A to 40N, and maintains it there. The opening of the back pressure control valve 49 of the auxiliary separation membrane unit 40X, V1 (%), is determined by time t 4N+1 It is controlled to maintain a constant value until after this time. While this opening degree V1(%) is maintained, the operation of the auxiliary separation membrane unit 40X continues and exhaust gas treatment is carried out. Therefore, time t 41 In addition to the first to Nth separation membrane units 40A to 40N, the reserve separation membrane unit 40X is also operated, resulting in one more separation membrane unit 40 being in operation compared to normal operation.

[0093] First time t 41 After this, the back pressure control valve timer switches to "OFF," and the control unit 70 controls the opening of the back pressure control valve 49 of the first separation membrane unit 40A to decrease from V1 (%) to 0 (%) and maintain that opening. While the opening of the back pressure control valve 49 of the first separation membrane unit 40A is maintained at 0 (%), the operation of the first separation membrane unit 40A is stopped, and the backwashing process described above is performed in the first separation membrane unit 40A. At this time, the first separation membrane unit 40A is stopped, but the backup separation membrane unit 40X is in operation, so the total number of operating separation membrane units 40 in the gas treatment system 1 remains the same as usual. In other words, the system is controlled so that the backup separation membrane unit 40X is operated in place of the first separation membrane unit 40A which is stopped.

[0094] second time t 42 Prior to this, after the backwashing process of the first separation membrane unit 40A is completed, the back pressure control valve timer is switched to "ON". This switch causes the control unit 70 to increase and maintain the opening degree of the back pressure control valve 49 of the first separation membrane unit 40A from 0 (%) to V1 (%). As a result, the operation of the first separation membrane unit 40A is restarted.

[0095] second time t 42 After this, the back pressure control valve timer is switched to "OFF," and the control unit 70 controls the opening of the back pressure control valve 49 of the second separation membrane unit 40B to decrease from V1 (%) to 0 (%) and maintain that opening. While the opening of the back pressure control valve 49 of the second separation membrane unit 40B is maintained at 0 (%), the operation of the second separation membrane unit 40B is stopped, and the backwashing process described above is performed in the second separation membrane unit 40B. At this time, the second separation membrane unit 40B is stopped, but the backup separation membrane unit 40X is in operation, so the total number of operating separation membrane units 40 in the gas treatment system 1 remains the same as usual. Furthermore, the operation of the backup separation membrane unit 40X continues in place of the first separation membrane unit 40A, and the first separation membrane unit 40A is controlled to operate in place of the stopped second separation membrane unit 40B.

[0096] In Figure 8, the Nth time t 4N Prior to this, the back pressure control valve timer switches to "ON". This switch causes the control unit 70 to increase and maintain the opening degree of the back pressure control valve 49 of the second separator membrane unit 40B from 0 (%) to V1 (%). As a result, the operation of the second separator membrane unit 40B resumes.

[0097] In Figure 8, the Nth time t 4NAfter this, the back pressure control valve timer is switched to "OFF," and the control unit 70 controls the opening of the back pressure control valve 49 of the Nth separation membrane unit 40N to decrease from V1(%) to 0(%) and maintain that opening. While the opening of the back pressure control valve 49 of the Nth separation membrane unit 40N is maintained at 0(%), the operation of the Nth separation membrane unit 40N is stopped, and the backwashing process described above is performed in the Nth separation membrane unit 40N. At this time, the Nth separation membrane unit 40N is stopped, but the backup separation membrane unit 40X is in operation, so the total number of operating separation membrane units 40 in the gas treatment system 1 remains the same as usual. Furthermore, the system is controlled to operate the previous separation membrane unit 40 in place of the Nth separation membrane unit 40N, which is stopped.

[0098] The (N+1)th time t 4N+1 Prior to this, the back pressure control valve timer is switched to "ON". This switch causes the control unit 70 to increase and maintain the opening degree of the back pressure control valve 49 of the Nth separation membrane unit 40N from 0 (%) to V1 (%). As a result, the operation of the Nth separation membrane unit 40N is restarted. With the restart of the Nth separation membrane unit 40N, the backwashing process is completed for all of the First to Nth separation membrane units 40A to 40N, and their operation is restarted.

[0099] The (N+1)th time t 4N+1 After this, the pressure control valve timer switches to "OFF," and the control unit 70 controls the opening of the back pressure control valve 49 of the auxiliary separation membrane unit 40X to decrease from V1 (%) to 0 (%) and maintain that opening. As a result, the operation of the auxiliary separation membrane unit 40X is stopped, and the control to perform the backwashing process on all of the first to Nth separation membrane units 40A to 40N in sequence is completed.

[0100] In Figure 8, in order to perform the backwash described above, the preliminary separation membrane unit 40X is operated, and then the first to the Nth separation membrane units 40A to 40N are stopped one by one in sequence. At this time, the control unit 70 controls the opening degree V1(%) of the back pressure control valve 49 of the operating preliminary separation membrane unit 40X to be the same as the opening degree and V1(%) of each back pressure control valve 49 in the multiple operating separation membrane units 40A to 40N. This makes it possible to stabilize the exhaust gas supply pressure in each of the multiple operating separation membrane units 40A to 40N, even when backwashing by rotating the multiple separation membrane units 40A to 40N. In addition, by controlling the opening degree V1(%) of each back pressure control valve 49 to be the same, the control burden when backwashing by rotating the multiple separation membrane units 40A to 40N can be reduced.

[0101] Furthermore, at each time point t, there is a delay equal to the system capacity between the timing when the back pressure control valve timer switches between "ON" and "OFF" and the timing when the opening degree of the back pressure control valve 49 begins to change, and a predetermined time elapses as shown in Figure 8.

[0102] Next, using Figure 9, we will explain examples of control by the control unit 70 when the load (rotational speed) of the engine 10 is higher or lower than the standard range, depending on the operating area of ​​the vessel on which the gas processing system 1 is installed. Figure 9 is a time chart to explain an example of control when the engine load is outside the standard range.

[0103] In the time chart of Figure 9, time can progress from left to right or from right to left. In Figure 9, the rotational speed of engine 10 is given by time t. a From time t d It rises as time progresses to the side, and time t d It is considered constant once it exceeds a certain value. Also, the rotational speed of engine 10 is determined by time t. d From time t a It descends as time progresses to the side, and time t aThe rotational speed of the booster 30 is considered constant once it exceeds a certain value. The control unit 70 controls the rotational speed of the booster 30 to rise and fall in accordance with the rotational speed of the engine 10.

[0104] In the fluctuation of the engine speed of engine 10 in Figure 9, time t b From time t c During this period, the standard operating range is defined as time t b more time t a side and time t c more time t d The side is considered to be within the non-standard range of operation.

[0105] The standard range is defined as the rotational speed of the engine 10 at which the CO2 concentration value measured by the concentration measuring unit 58 falls within a predetermined concentration control range, and the CO2 recovery rate calculated based on the CO2 concentration value and the flow rate measured by the flow rate measuring unit 59 falls within a predetermined recovery rate control range. Figure 10 is a graph showing the relationship between engine load, CO2 concentration value, and CO2 recovery rate.

[0106] In Figure 10, the range indicated by the dashed line represents the concentration control range for CO2 concentration. The median of the concentration control range is the design concentration value, and the upper and lower limits of the concentration control range are obtained by adding and subtracting predetermined control values ​​from the design concentration value. Similarly, in Figure 10, the range indicated by the dashed line represents the recovery rate control range for CO2 recovery rate. The median of the recovery rate control range is the design recovery rate, and the upper and lower limits of the recovery rate control range are obtained by adding and subtracting predetermined control values ​​from the design recovery rate.

[0107] In this embodiment, the separation membrane unit 40, when CO2 is separated from exhaust gas by the separation membrane 41a, as shown by the dashed line in Figure 10, tends to have a lower CO2 concentration and a higher CO2 recovery rate at high flow rates (when the engine 10 is under high load). Conversely, at low flow rates (when the engine 10 is under low load), tends to have a higher CO2 concentration and a lower CO2 recovery rate. Due to these tendencies, when the rotational speed of the engine 10 falls outside the standard range shown in Figure 9, the CO2 concentration falls outside the concentration control range, and the CO2 recovery rate falls outside the recovery rate control range, which presents a problem.

[0108] To resolve this problem, in this embodiment, the control unit 70 controls the exhaust gas temperature using the heat exchanger 28. In this control, as shown in Figure 9, time t c From time t d As the engine 10 progresses to the side, when its rotational speed increases and reaches a non-standard range, the control unit 70 controls the temperature command value of the heat exchanger 28 to increase in accordance with the increase in the rotational speed of the engine 10. This control increases the temperature of the exhaust gas before it passes through the heat exchanger 28 and is supplied to the separation membrane unit 40, and also increases the temperature of the separation membrane 41a. As a result, the permeability of the separation membrane 41a increases and the selectivity of the separation membrane 41a decreases, causing the CO2 concentration value and CO2 recovery rate to change from the state shown by the dashed line in the high-load range of Figure 10 to the state shown by the solid line.

[0109] Also, in Figure 9, time t b From time t a As the engine 10 moves toward the side, when its rotational speed decreases and reaches a non-standard range, the control unit 70 controls the temperature command value of the heat exchanger 28 to decrease in accordance with the decrease in the rotational speed of the engine 10. This control lowers the temperature of the exhaust gas before it passes through the heat exchanger 28 and is supplied to the separation membrane unit 40, and also lowers the temperature of the separation membrane 41a. As a result, the permeability of the separation membrane 41a decreases and the selectivity of the separation membrane 41a increases, causing the CO2 concentration value and CO2 recovery rate to change from the state shown by the dashed line in the low-load range of Figure 10 to the state shown by the solid line.

[0110] As a result, even if the rotational speed of engine 10 falls outside the standard range, the CO2 concentration value can be kept within the concentration control range, and the CO2 recovery rate can be kept within the recovery rate control range, allowing the CO2 recovery control to continue smoothly.

[0111] According to the control shown in Figure 9 by the control unit 70, the temperature of the exhaust gas from the heat exchanger 28 is adjusted based on the rotational speed of the engine 10, or in other words, the detection result of the load detection unit 11. This makes it possible to stabilize the CO2 concentration of the permeate gas and the CO2 recovery rate downstream of the multiple separation membrane units 40.

[0112] The embodiments of the present invention are not limited to those described above, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Furthermore, if the technical idea of ​​the present invention can be realized in a different way by advances in the art or by other derived arts, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea of ​​the present invention.

[0113] In the above embodiment, the separation membrane unit 40 is equipped with multiple separation membranes 41a, 44a to separate the exhaust gas in multiple stages, but it is not limited to this. For example, the separation section may be further increased in series, or the second separation section 44 may be omitted, and it is sufficient to have at least one separation membrane and to be able to control the back pressure with a back pressure control valve 49 at the upstreammost separation membrane.

[0114] Furthermore, at least one spare separation membrane unit 40X is sufficient, but it may be changed to more than one.

[0115] Furthermore, in the control shown in Figures 5 and 6, the malfunctioning separation membrane unit 40 is not limited to the first separation membrane unit 40A, but may be a different separation membrane unit 40 from the first separation membrane unit 40A, or it may be one of several separation membrane units 40.

[0116] Furthermore, in the control shown in Figure 6, the booster 30 and back pressure control valve 49 were controlled based on the CO2 concentration value measured by the concentration measuring unit 58, but this is not the only option. Instead of the CO2 concentration value, the control unit 70 may also perform control based on the flow rate measured by the flow rate measuring unit 59, or the CO2 recovery rate converted based on the flow rate and the CO2 concentration value.

[0117] Furthermore, the gas separated by the separation membrane unit 40 is not limited to CO2, but may also include, for example, SOx (sulfur oxides) containing gaseous SO2, NOx, etc., and includes not only gases that are discarded outside the device but also gases that can be reused. [Explanation of symbols]

[0118] 1: Gas processing system 10: Engine (gas emission source) 11: Load-damaged area 28: Heat exchanger 30: Voltage booster 38: Pressure measuring section 40: Separation membrane unit 40A: First separation membrane unit (separation membrane unit) 40N: Nth separation membrane unit (separation membrane unit) 40X: Spare separation membrane unit 41a: Separation membrane 49: Back pressure control valve 58: Concentration measurement unit (permeate gas measurement unit) 59: Flow rate measurement unit (permeation gas measurement unit) 70: Control Unit

Claims

1. Multiple separation membrane units for separating desired components from exhaust gas of a gas emission source subject to load fluctuations, A pressurizer for pressurizing the exhaust gas supplied to the plurality of separation membrane units, A gas processing system comprising a control unit that controls the drive of the aforementioned booster, The gas exhaust source is provided with a load detection unit that detects the load and outputs it to the control unit. Each of the plurality of separation membrane units comprises a separation membrane that separates the exhaust gas supplied via the booster into permeable gas and impermeable gas, and a back pressure control valve that controls the pressure of the impermeable gas that flows without passing through the separation membrane. The gas processing system is characterized in that the control unit controls the drive of the booster and the opening degree of the back pressure control valves in the plurality of separation membrane units during operation, based on the detection result of the load detection unit.

2. The gas processing system according to claim 1, characterized in that the control unit controls the opening degree of each of the multiple separation membrane units during operation to be the same.

3. Each of the plurality of separation membrane units is further provided with a pressure measuring unit for measuring the pressure of the exhaust gas upstream of the unit. The gas processing system according to claim 2, characterized in that the control unit controls the opening degree of the back pressure control valve in the separation membrane unit downstream of the pressure measuring unit that measured the highest pressure value among the plurality of pressure measuring units to be the same as the opening degree of the back pressure control valve in the separation membrane units other than the separation membrane unit.

4. The plurality of separation membrane units further comprises a permeate gas measuring unit that measures at least one of the concentration and flow rate of the permeate gas downstream of the plurality of separation membrane units, The gas processing system according to claim 2, characterized in that the control unit controls the drive of the booster and the opening degree of the back pressure control valves in the plurality of separation membrane units during operation, based on the measurement results of the permeate gas measuring unit.

5. It comprises at least one spare separation membrane unit, The aforementioned pre-separation membrane unit comprises a separation membrane that separates the exhaust gas supplied via the booster into permeable gas and impermeable gas, and a back pressure control valve that controls the pressure of the impermeable gas that flows without passing through the separation membrane. The gas processing system according to any one of claims 1 to 4, characterized in that when the preliminary separation membrane unit is operated and then the plurality of separation membrane units are sequentially shut down one by one, the control unit controls the opening degree of the back pressure control valve of the preliminary separation membrane unit to be the same as the opening degree of the back pressure control valve of the plurality of separation membrane units.

6. The system further comprises a heat exchanger provided between the booster and the plurality of separation membrane units for heat exchange with the exhaust gas, The gas treatment system according to any one of claims 1 to 4, characterized in that the control unit controls the temperature adjustment of the exhaust gas by the heat exchanger based on the detection result of the load detection unit.

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