Gas processing system

Abstract

To provide a gas processing system that can reduce energy consumption.SOLUTION: A gas processing system comprises: an electric dust collector that collects impurities in combustion exhaust gas including CO2; a first flow path through which the combustion exhaust gas including ozone passing through the electric dust collector is flown; a storage tank in which the combustion exhaust gas flowing through the first flow path is temporarily stored; a second flow path through which the combustion exhaust gas passing through the storage tank is flown; a third flow path branching from the second flow path. through which at least part of the combustion exhaust gas flowing through the second flow path is refluxed to the first flow path; a first adjustment valve for adjusting an aperture of the third flow path; a detection part that detects a first flow volume relating to the combustion exhaust gas that is supplied to the electric dust collector; and a control part that controls an aperture of the first adjustment valve on the basis of the first flow volume detected by the first detection part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a gas treatment system.

Background Art

[0002] Conventionally, an ozone decomposition device for thermally decomposing ozone has been known. For example, Patent Document 1 discloses an ozone decomposition treatment device provided with a heat exchanger that has a passage through which ozone gas after heat treatment by a heater passes, and that lengthens the residence time of the ozone gas before heat treatment.

[0003] Further, Patent Document 2 discloses a CO2 separation system provided with an electrostatic precipitator that collects impurities in combustion exhaust gas containing CO2. In the CO2 separation system disclosed in Patent Document 2, ozone may be generated from oxygen molecules in the combustion exhaust gas due to corona discharge accompanying the operation of the electrostatic precipitator.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] There is a demand for reducing the energy consumption in a CO2 separation system. The same applies to the case of using the ozone decomposition treatment device disclosed in Patent Document 1 for decomposing ozone generated in a CO2 separation system provided with an electrostatic precipitator. However, since the ozone decomposition treatment device disclosed in Patent Document 1 heats ozone only with a heater, there is room for improvement from the viewpoint of reducing energy consumption.

[0006] The present disclosure provides a gas treatment system that reduces energy consumption.

Means for Solving the Problem

[0007] In the first aspect, an electrostatic precipitator for collecting impurities in combustion exhaust gas containing CO2, a first flow path through which the combustion exhaust gas containing ozone flows after passing through the electrostatic precipitator, a storage tank for temporarily storing the combustion exhaust gas that has flowed through the first flow path, a second flow path through which the combustion exhaust gas that has passed through the storage tank flows, a third flow path that branches from the second flow path and recirculates at least a part of the combustion exhaust gas flowing through the second flow path to the first flow path, a first regulating valve for adjusting the opening degree of the third flow path, a first detection unit for detecting a first flow rate of the combustion exhaust gas supplied to the electrostatic precipitator, and a control unit for controlling the opening degree of the first regulating valve based on the first flow rate detected by the first detection unit.

Effect of the Invention

[0008] According to the technology of the present disclosure, the energy consumption can be reduced.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0010] Hereinafter, an example of the gas treatment system according to the embodiment will be described with reference to the drawings. Here, the "connection" described in this specification is not limited to the case where one member A and the other member B are directly connected, but includes the case where the member A and the member B are connected via one or more other members.

[0011] [First Embodiment] [Overall Configuration] With reference to FIGS. 1 to 4, a configuration example of the gas treatment system 1 according to the first embodiment is shown. FIG. 1 is a schematic diagram showing an example of the overall configuration of the gas treatment system 1 according to the first embodiment. FIG. 2 is a graph for explaining the outline of the temporal change of the ozone concentration under a plurality of different temperature conditions. FIG. 3 is a schematic side view showing a configuration example of the storage tank 30 of the gas treatment system 1 according to the first embodiment. FIG. 4 is a block diagram showing a configuration example of the control unit 60 of the gas treatment system 1 according to the first embodiment.

[0012] The gas treatment system 1 is supplied with combustion exhaust gas containing CO2 discharged from various devices and / or facilities. For example, the gas treatment system 1 is supplied with combustion exhaust gas discharged from an engine 100E provided in a ship. As an example, a case where the gas treatment system 1 is supplied with combustion exhaust gas discharged from the engine 100E will be described. However, the combustion exhaust gas supplied to the gas treatment system 1 is not limited to that discharged from the engine 100E provided in the ship. For example, the combustion exhaust gas supplied to the gas treatment system 1 may be discharged from a combustion facility that burns fossil fuels, such as a boiler in a coal-fired power plant. In the following description, the side closer to the engine 100E is referred to as "upstream" as the flow direction of the fluid containing the combustion exhaust gas. On the other hand, the side away from the engine 100E is referred to as "downstream". The engine 100E and the aforementioned combustion facility are examples of a "combustion exhaust gas discharge source".

[0013] Combustion exhaust gas contains impurities such as dust. Impurities derived from the combustion exhaust gas can adsorb to a CO2 separation unit such as a separation membrane module or a CO2 absorption tower, for example, thereby inhibiting these CO2 separation operations. Therefore, in the gas treatment system 1, an electrostatic precipitator 10 for collecting impurities contained in the combustion exhaust gas is disposed upstream of the CO2 separation unit. Further, ozone (O3) can be generated from oxygen molecules (O2) contained in the combustion exhaust gas by corona discharge in the electrostatic precipitator 10. The generated ozone flows downstream of the electrostatic precipitator 10 together with the combustion exhaust gas treated by the electrostatic precipitator 10. Since ozone is a compound with high oxidizing power, it can deteriorate resin packings provided in the flow path in the gas treatment system 1, separation membranes made of polymer materials, and the like. Therefore, the gas treatment system 1 includes a component for treating ozone to reduce the ozone concentration. That is, the gas treatment system 1 treats, for example, ozone contained in the combustion exhaust gas. Note that the impurities in the combustion exhaust gas are not limited to dust.

[0014] As shown in FIG. 1, the gas treatment system 1 includes an electrostatic precipitator 10, a first flow path 21, a storage tank 30, a second flow path 22, a third flow path 23, a first control valve 40, a first detection unit 51, and a control unit 60. Further, the gas treatment system 1 may include a second detection unit 52, a third detection unit 53, a blower 71, a heat exchanger 72 for heat removal, a denitration and desulfurization device 73, a separation membrane module 80, and a vacuum pump 82. Furthermore, the gas treatment system 1 may include other components such as an economizer and a filter for adsorbing impurities. Note that the separation membrane module is an example of the "CO2 separation unit". Another example of the CO2 separation unit includes a CO2 absorption tower that brings an absorption liquid (lean liquid) into contact with the combustion exhaust gas and recovers the CO2 absorbed by the absorption liquid. Hereinafter, the components included in the gas treatment system 1 will be described.

[0015] <Electrostatic Precipitator 10> The electrostatic precipitator 10 is connected to the engine 100E via, for example, a pipe 11. The electrostatic precipitator 10 collects impurities in the combustion exhaust gas supplied from the engine 100E. The electrostatic precipitator 10 is supplied with combustion exhaust gas at a high temperature exceeding, for example, 300 degrees from the engine 100E. Hereinafter, the flow rate of the combustion exhaust gas supplied from the engine 100E to the electrostatic precipitator 10 is referred to as the "first flow rate F1".

[0016] The electrostatic precipitator 10 includes a discharge electrode, a dust collecting electrode, and a collection chamber that houses the discharge electrode and the dust collecting electrode. When a high voltage is applied between the discharge electrode and the dust collecting electrode, a corona discharge occurs in the opposing space where the discharge electrode and the dust collecting electrode face each other. As a result, the impurities in the combustion exhaust gas introduced into the collection chamber become charged. Further, the charged impurities are collected by the dust collecting electrode. Ozone can be generated from oxygen molecules in the impurities by the corona discharge generated between the discharge electrode and the dust collecting electrode.

[0017] <First flow path 21> The first flow path 21 is a flow path through which the combustion exhaust gas that has passed through the electrostatic precipitator 10 flows. The combustion exhaust gas flowing through the first flow path 21 contains ozone generated within the electrostatic precipitator 10. As shown in FIG. 1, the first flow path 21 connects the electrostatic precipitator 10 and the storage tank 30. As an example of the first flow path 21, a pipe excellent in corrosion resistance can be mentioned. Further, a blower 71 such as a fan may be arranged in the first flow path 21. By blowing the combustion exhaust gas flowing through the first flow path 21, the blower 71 can increase the flow velocity of the combustion exhaust gas downstream.

[0018] <Storage tank 30> The storage tank 30 temporarily stores the combustion exhaust gas flowing through the first flow path 21. For example, the combustion exhaust gas introduced into the storage tank 30 stays in the storage tank 30 for a time determined by the first flow rate F1 or the like. Here, the decomposition rate of ozone in the combustion exhaust gas changes according to the temperature conditions to which the ozone is exposed. Specifically, when ozone is exposed to a relatively high-temperature environment, the decomposition rate of ozone is fast. On the other hand, when ozone is exposed to a relatively low-temperature environment, the decomposition rate of ozone is slow. For example, as shown in FIG. 2, the decomposition rate of ozone under the temperature condition of about 350 degrees is faster than the decomposition rate of ozone under the temperature condition of about 250 degrees.

[0019] The combustion exhaust gas is introduced into the storage tank 30 while maintaining a relatively high temperature when discharged from the engine 100E, for example. By temporarily retaining such high-temperature combustion exhaust gas in the storage tank 30, ozone can be decomposed using the temperature of the combustion exhaust gas. Thereby, the ozone concentration in the combustion exhaust gas can be reduced. That is, the ozone concentration can be reduced without separately supplying thermal energy from the heater to the ozone. Further, even if a heater is used, the combustion exhaust gas has a relatively high temperature at a stage before heating by the heater. Therefore, the energy consumption for raising the temperature of the combustion exhaust gas to a desired temperature can be reduced. From these facts, the energy consumption in the operation of the gas treatment system 1 can be reduced.

[0020] As shown in FIG. 3, the storage tank 30 includes a storage section 31 that temporarily stores the combustion exhaust gas containing ozone, an introduction pipe 32 for introducing the combustion exhaust gas into the storage section 31, and a discharge pipe 33 for discharging the combustion exhaust gas from the storage section 31.

[0021] The introduction pipe 32 is connected to the first flow path 21. The discharge pipe 33 is connected to the second flow path 22. Also, the introduction pipe 32 is preferably arranged near the bottom wall of the storage section 31, and the discharge pipe 33 is preferably arranged near the upper wall of the storage section 31. In this way, by providing the discharge pipe 33 above the introduction pipe 32 and increasing the height difference between the discharge pipe 33 and the introduction pipe 32, the residence time of the combustion exhaust gas in the storage section 31 can be lengthened. As a result, the ozone concentration in the combustion exhaust gas can be further reduced.

[0022] However, the configuration of the storage tank 30 is not limited to this. As another example, there is a configuration provided with a spiral flow path for flowing the combustion exhaust gas introduced into the storage section 31 from the introduction pipe 32, for example, along the inner wall of the storage section 31 in a spiral shape. By providing a spiral flow path in the storage section 31, the residence time of the combustion exhaust gas in the storage section 31 can be lengthened.

[0023] <Second flow path 22> The second flow path 22 is a flow path through which the combustion exhaust gas that has passed through the storage tank 30 flows. As shown in FIG. 1, the second flow path 22 connects the storage tank 30 and the separation membrane module 80. As an example of the second flow path 22, a pipe excellent in corrosion resistance can be mentioned.

[0024] A heat exchanger 72 for heat removal may be arranged in the second flow path 22. The heat exchanger 72 for heat removal lowers the temperature of the combustion exhaust gas heading towards the separation membrane module 80 by heat exchange between the combustion exhaust gas and the refrigerant. As a result, the temperature of the combustion exhaust gas can be lowered to a relatively low temperature range below 100 degrees. As a result, damage and deterioration of the separation membrane module 80 due to the introduction of high-temperature combustion exhaust gas can be suppressed.

[0025] Furthermore, a denitration and desulfurization device 73 may be arranged in the second flow path 22. In the example shown in FIG. 1, the denitration and desulfurization device 73 is arranged downstream of the heat exchanger 72 for heat removal. However, the position of the denitration and desulfurization device 73 is not limited to this. For example, the denitration and desulfurization device 73 may be arranged upstream of the electrostatic precipitator 10.

[0026] The denitration and desulfurization device 73 removes nitrogen oxides (NOx) and sulfur oxides (SOx) in the combustion exhaust gas heading towards the separation membrane module 80. Thereby, the concentrations of NOx and SOx in the combustion exhaust gas introduced into the separation membrane module 80 can be reduced. As a result, it is possible to suppress NOx and SOx in the combustion exhaust gas from adsorbing to the separation membrane of the separation membrane module 80 and inhibiting the CO2 separation operation of the separation membrane module 80.

[0027] <The third flow path 23> The third flow path 23 is a flow path that branches from the second flow path 22. Also, the third flow path 23 recirculates at least a part of the combustion exhaust gas flowing through the second flow path 22 to the first flow path 21. That is, the third flow path 23 recirculates the combustion exhaust gas that has passed through the storage tank 30 to the first flow path 21. Thereby, the combustion exhaust gas that has passed through the storage tank 30 once can be introduced into the storage tank 30 again. As a result, the residence time of the combustion exhaust gas in the storage tank 30 can be extended. Note that the combustion exhaust gas recirculated to the first flow path 21 via the third flow path 23 is referred to as "recirculation gas". Also, the flow rate of the recirculation gas is hereinafter referred to as "the second flow rate F2".

[0028] As an example of the third flow path 23, a pipe excellent in corrosion resistance can be cited. Also, the third flow path 23 merges with the first flow path 21 at a predetermined position upstream of the blower 71. Thereby, the flow velocity of the recirculation gas can be increased. However, the merging position of the third flow path 23 and the first flow path 21 is not limited to this.

[0029] <The first control valve 40> The first control valve 40 adjusts the opening degree of the third flow path 23. That is, by adjusting the opening degree of the third flow path 23 by the first control valve 40, the second flow rate F2 related to the recirculation gas is adjusted. The opening degree of the first control valve 40 is controlled by the control unit 60. Therefore, the first control valve 40 has a processing unit that processes the control signal from the control unit 60.

[0030] As an example of the first control valve 40, a two-way valve having two ports and a valve body that opens and closes an internal space connecting the two ports can be mentioned. However, the first control valve 40 may have other configurations.

[0031] <First detection unit 51> The first detection unit 51 detects a first flow rate F1 of the combustion exhaust gas supplied to the electrostatic precipitator 10. When the reflux gas does not reflux to the first flow path 21, the first flow rate F1 corresponds to the flow rate of the combustion exhaust gas passing through the electrostatic precipitator 10 and heading toward the storage tank 30. The first detection unit 51 outputs a detection signal corresponding to the detected first flow rate F1 to the control unit 60.

[0032] Examples of the first detection unit 51 include flow sensors such as electromagnetic flow meters, thermal flow meters, and ultrasonic flow meters. However, the configuration of the first detection unit 51 is not limited to these. The first detection unit 51 shown in FIG. 1 is arranged upstream of the electrostatic precipitator 10. However, the first detection unit 51 may be arranged downstream of the electrostatic precipitator 10.

[0033] <Second detection unit 52> The second detection unit 52 detects the temperature of the storage tank 30. Through the temperature detected by the second detection unit 52, the temperature of the combustion exhaust gas stored in the storage tank 30 (that is, the ambient temperature of ozone) can be estimated. The second detection unit 52 outputs a detection signal corresponding to the detected temperature to the control unit 60. Examples of the second detection unit 52 include temperature sensors such as resistance temperature detectors, linear resistors, and thermistors. However, the configuration of the second detection unit 52 is not limited to these.

[0034] <Third detection unit 53> The third detection unit 53 detects a second flow rate F2 of the reflux gas flowing through the third flow path 23. The third detection unit 53 outputs a detection signal corresponding to the detected second flow rate F2 to the control unit 60. Examples of the third detection unit 53 include flow sensors such as electromagnetic flow meters, thermal flow meters, and ultrasonic flow meters. However, the configuration of the third detection unit 53 is not limited to these. As shown in FIG. 1, the third detection unit 53 is disposed in the third flow path 23 at a position closer to the first flow path 21 than the first regulating valve 40.

[0035] <Separation membrane module 80> The separation membrane module 80 separates CO2 in the combustion exhaust gas. The separation membrane module 80 includes a separation membrane and a container that houses the separation membrane. The separation membrane is, for example, a polymer membrane that selectively permeates CO2. Examples of the polymer membrane include a hollow fiber membrane bundle in which a plurality of hollow fiber membranes from several hundred to several hundred thousand are bundled.

[0036] The combustion exhaust gas supplied to the separation membrane module 80 is introduced into the inner space of the hollow fiber membrane bundle from an opening on one side of the hollow fiber membrane bundle. At this time, CO2 in the combustion exhaust gas permeates through the hollow fiber membrane and moves to the outer space of the hollow fiber membrane bundle. That is, CO2 in the combustion exhaust gas permeates through the separation membrane. After permeating through the separation membrane, the gas discharged from the separation membrane module 80 is referred to as "permeated gas". The permeated gas is discharged from a first discharge port provided in the container that houses the separation membrane.

[0037] On the other hand, other components in the combustion exhaust gas are introduced into the inner space of the hollow fiber membrane bundle from an opening on one side of the hollow fiber membrane bundle, and then discharged from an opening on the other side of the hollow fiber membrane bundle. That is, other components in the combustion exhaust gas do not permeate through the separation membrane. The gas that does not permeate through the separation membrane and is discharged from the separation membrane module 80 is referred to as "non-permeated gas". The non-permeated gas is discharged from a second discharge port provided in the container that houses the separation membrane. Note that the non-permeated gas may contain CO2 that did not permeate through the separation membrane.

[0038] A vacuum pump 82 may be connected to the first discharge port of the separation membrane module 80. By using the vacuum pump 82 to reduce the pressure on the first discharge port side of the separation membrane module 80, a high pressure difference can be generated between the inside and outside of the separation membrane. Thereby, the CO2 separation function of the separation membrane can be enhanced.

[0039] <Control unit 60> The control unit 60 controls various operations in the gas treatment system 1. As shown in FIG. 4, the control unit 60 is communicably connected to each of the first regulating valve 40, the first detection unit 51, the second detection unit 52, and the third detection unit 53.

[0040] The control unit 60 is an information processing device including, for example, an arithmetic processing unit 61, a storage unit 62, and a communication unit 63. Each of the arithmetic processing unit 61, the storage unit 62, and the communication unit 63 is electrically connected to each other via a bus 68.

[0041] The arithmetic processing unit 61 is a processor that executes control and processing of various operations in the control unit 60. As an example of the arithmetic processing unit 61, a CPU (Central Processing Unit) can be mentioned. Further, the arithmetic processing unit 61 may be composed of other electronic circuits that perform the same functions as a processor such as a CPU.

[0042] The storage unit 62 stores a program executed by the arithmetic processing unit 61 and various data necessary for the execution of the program. As an example of the storage unit 62, a non-volatile storage medium such as a ROM (Read Only Memory) can be mentioned.

[0043] Further, the storage unit 62 stores, for example, data related to the volume of the storage tank 30 and data for calculating various threshold values set by the arithmetic processing unit 61. The storage unit 62 stores data related to the temporal change of the ozone concentration under each of a plurality of different temperature conditions. For example, the storage unit 62 stores the ozone concentration C1-1 at an elapsed time of 1 second, the ozone concentration C1-2 at an elapsed time of 2 seconds, ···, the ozone concentration C1-n at an elapsed time of n seconds at a temperature of 250 degrees, the ozone concentration C2-1 at an elapsed time of 1 second, the ozone concentration C2-2 at an elapsed time of 2 seconds, ···, the ozone concentration C2-n at an elapsed time of n seconds at a temperature of 350 degrees, and the like. The data stored in the storage unit 62 may be theoretical values related to the temporal change of the ozone concentration or measured values measured in advance. Hereinafter, the data related to the temporal change of the ozone concentration under a plurality of different temperature conditions is referred to as "ozone concentration data DO".

[0044] The communication unit 63 is a communication interface including members such as a communication circuit and an antenna for performing communication with each of the first control valve 40, the first detection unit 51, the second detection unit 52, and the third detection unit 53.

[0045] Next, various functions in the arithmetic processing unit 61 will be described. As shown in FIG. 4, the arithmetic processing unit 61 functions as means such as an acquisition means 611, a residence time calculation means 612, a first threshold value calculation means 613, a first determination means 614, a second threshold value calculation means 615, a second determination means 616, an opening degree adjustment means 617, a third determination means 618, and the like. The arithmetic processing unit 61 executes a program stored in the storage unit 62 to cause the control unit 60 to function as these means. The program may be stored and provided in a computer-readable storage medium or provided via a communication network such as the Internet.

[0046] The acquisition means 611 receives detection signals from each of the first detection unit 51, the second detection unit 52, and the third detection unit 53 through the communication unit 63. Thereby, the acquisition means 611 acquires various information such as the first flow rate F1, the second flow rate F2, and the temperature K1 of the storage tank 30 related to the combustion exhaust gas, respectively.

[0047] The residence time calculation means 612 calculates the residence time T1 of the combustion exhaust gas in the storage tank 30 based on the first flow rate F1 acquired by the acquisition means 611 and the volume V of the storage tank 30. For example, the residence time calculation means 612 calculates the residence time T1 by dividing the volume V of the storage tank 30 by the flow rate value corresponding to the first flow rate F1.

[0048] The first threshold value calculation means 613 calculates a first threshold value Th1 regarding the temperature necessary to reduce the ozone concentration in the combustion exhaust gas to the target concentration at the time when the residence time T1 has elapsed. When calculating the first threshold value Th1, the first threshold value calculation means 613 refers to the information on the residence time T1 input from the residence time calculation means 612 and the ozone concentration data DO stored in the storage unit 62. Here, the "target concentration" can be set as appropriate. Also, the "target concentration" may be the relative value of the target concentration when the ozone concentration in the combustion exhaust gas at the start time of introduction into the storage tank 30 is set to "1".

[0049] For example, when the target concentration is set to "0.01", the first threshold value calculation means 613 uses the ozone concentration data DO to calculate the first threshold value Th1 necessary for the ozone concentration in the combustion exhaust gas to be reduced to "0.01" during the period of the residence time T1.

[0050] The first determination means 614 determines whether or not the temperature K1 of the storage tank 30 acquired by the acquisition means 611 is equal to or higher than the first threshold value Th1. That is, the first determination means 614 determines whether or not the temperature K1 of the storage tank has reached the first threshold value Th1.

[0051] The second threshold value calculation means 615 calculates a second threshold value Th2 regarding the required time for the ozone concentration in the combustion exhaust gas to reach the target concentration under the temperature condition at the temperature K1 of the storage tank 30. When calculating the second threshold value Th2, the second threshold value calculation means 615 refers to the information on the residence time T1 input from the residence time calculation means 612 and the ozone concentration data DO stored in the storage unit 62.

[0052] The second determination means 616 determines whether or not the residence time T1 is equal to or greater than a second threshold value Th2. That is, the second determination means 616 determines whether or not it is necessary to introduce the reflux gas into the storage tank 30 to extend the residence time of the combustion exhaust gas.

[0053] When it is necessary to extend the residence time of the combustion exhaust gas, the opening degree adjustment means 617 adjusts the opening degree of the first control valve 40 and introduces the reflux gas necessary to make the new residence time T3 equal to or greater than the second threshold value Th2 into the storage tank 30.

[0054] Specifically, the opening degree adjustment means 617 calculates an additional flow rate value FL required for the combustion exhaust gas to stay in the storage tank 30 during the residence time T3. Further, the opening degree adjustment means 617 adjusts the opening degree of the first control valve 40 so that the second flow rate F2 related to the reflux gas becomes the flow rate value FL.

[0055] The third determination means 618 determines whether or not the second flow rate F2 is equal to or greater than the flow rate value FL with reference to the information on the second flow rate F2 acquired by the acquisition means 611. When the second flow rate F2 is equal to or greater than the flow rate value FL, it is estimated that the reflux gas stays in the storage tank 30 for at least the residence time T3. Thereby, the ozone concentration in the combustion exhaust gas can be further reduced.

[0056] <Opening degree adjustment operation of the first control valve 40> Next, with reference to FIG. 5, the flow of the opening degree adjustment operation of the first control valve 40 in the control unit 60 will be described. FIG. 5 is a flowchart showing an example of the flow of the opening degree adjustment operation of the first control valve 40 in the control unit 60. At the start time of introducing the combustion exhaust gas, it is assumed that the first control valve 40 is closed.

[0057] First, in step S11, the control unit 60 acquires information on the first flow rate F1 and the temperature K1 of the storage tank 30 related to the combustion exhaust gas supplied to the electrostatic precipitator 10 from the first detection unit 51 and the second detection unit 52.

[0058] Subsequently, in step S12, the control unit 60 calculates the residence time T1 of the combustion exhaust gas in the storage tank 30 based on the first flow rate F1 and the volume V of the storage tank 30.

[0059] Subsequently, in step S13, the control unit 60 calculates a first threshold value Th1 related to the temperature required to reduce the ozone concentration in the combustion exhaust gas to the target concentration at the time when the residence time T1 elapses.

[0060] Subsequently, in step S14, the control unit 60 determines whether the temperature K1 of the storage tank 30 is equal to or higher than the first threshold value Th1. As a result of the determination, if the temperature K1 of the storage tank 30 is equal to or higher than the first threshold value Th1, the control unit 60 does not output a control signal to the first control valve 40. That is, the first control valve 40 remains in a closed state. The reflux gas is not introduced into the storage tank 30.

[0061] On the other hand, as a result of the determination in step S14, if the temperature K1 of the storage tank 30 is lower than the first threshold value Th1, in step S15, the control unit 60 calculates a second threshold value Th2 related to the time required for the ozone concentration in the combustion exhaust gas to reach the target concentration under the temperature condition at the temperature K1 of the storage tank 30.

[0062] Subsequently, in step S16, the control unit 60 determines whether the residence time T1 is equal to or longer than the second threshold value Th2. As a result of the determination, if the residence time T1 is equal to or longer than the second threshold value Th2, the control unit does not output a control signal to the first control valve 40. That is, the first control valve 40 remains in a closed state. The reflux gas is not introduced into the storage tank 30.

[0063] On the other hand, if as a result of the determination in step S16 the residence time T1 is less than the second threshold value Th2, in step S17 the control unit 60 calculates the flow rate value FL of the reflux gas necessary for the new residence time T3 to be equal to or greater than the second threshold value Th2. Further, the control unit 60 adjusts the opening degree of the first regulating valve 40 so that the second flow rate F2 of the reflux gas becomes the flow rate value FL. Specifically, the control unit 60 outputs a control signal indicating the opening degree information to the first regulating valve 40. Thereby, the reflux gas flows through the third flow path 23 into the first flow path 21 and is introduced into the storage tank 30. As a result, the residence time regarding the reflux gas is extended. It is determined whether the second flow rate F2 is equal to or greater than the flow rate value FL.

[0064] Subsequently, in step S18, the control unit 60 determines whether the second flow rate F2 acquired from the third detection unit 53 is equal to or greater than the flow rate value FL. As a result of the determination, if the second flow rate F2 is equal to or greater than the flow rate value FL, the opening degree of the first regulating valve 40 is maintained. On the other hand, if the second flow rate F2 is less than the flow rate value FL, the series of steps according to steps S17 and S18 is repeated until the second flow rate F2 becomes equal to or greater than the flow rate value FL.

[0065] In this way, by the control unit 60 controlling the flow rate value of the reflux gas, the probability that the ozone concentration reaches the target concentration can be further increased.

[0066] [Second Embodiment] [Overall Configuration] Referring to FIG. 6, a configuration example of the gas treatment system 1A according to the second embodiment is shown. FIG. 6 is a schematic diagram showing an example of the overall configuration of the gas treatment system 1A according to the second embodiment. In the second embodiment, the same reference numerals are given to the constituent parts similar to those in the first embodiment, and the description is omitted as appropriate.

[0067] As shown in FIG. 6, the gas treatment system 1A according to the second embodiment is different from the first embodiment in that it includes a heater 91. The control unit 60 of the gas treatment system 1A may further function as heater temperature control means. Note that the other components included in the gas treatment system 1A according to the second embodiment may be the same as those of the gas treatment system 1 according to the first embodiment.

[0068] The heater 91 raises the temperature inside the storage tank 30. That is, the heater 91 heats the combustion exhaust gas containing ozone introduced into the storage tank 30. The configuration of the heater 91 is not limited as long as it can raise the temperature inside the storage tank 30.

[0069] For example, when an economizer or the like is arranged upstream of the storage tank 30 and the temperature of the combustion exhaust gas when introduced into the storage tank 30 is lower than the temperature when discharged from the engine 100E, the combustion exhaust gas can be heated by the heater 91. As a result, the thermal energy applied to the ozone in the combustion exhaust gas increases, and the decomposition of ozone is promoted. As a result, the ozone concentration can be reduced.

[0070] <Control operation of heater temperature> Next, with reference to FIG. 7, the control operation of the heater temperature in the control unit 60 will be described. FIG. 7 is a flowchart for explaining the control operation of the heater temperature in the control unit 60.

[0071] First, in step S31, the control unit 60 acquires information on the first flow rate F1 of the combustion exhaust gas supplied to the electrostatic precipitator 10 and the temperature K1 of the storage tank 30 from the first detection unit 51 and the second detection unit 52.

[0072] Subsequently, in step S32, the control unit 60 calculates the residence time T1 of the combustion exhaust gas in the storage tank 30 based on the first flow rate F1 and the volume V of the storage tank 30.

[0073] Subsequently, in step S33, the control unit 60 calculates a first threshold value Th1 regarding the temperature necessary to reduce the ozone concentration in the combustion exhaust gas to the target concentration at the time when the residence time T1 has elapsed.

[0074] Subsequently, in step S34, the control unit 60 determines whether or not the temperature K1 of the storage tank 30 is equal to or higher than the first threshold value Th1. As a result of the determination, if the temperature K1 of the storage tank 30 is equal to or higher than the first threshold value Th1, the control unit 60 does not output a control signal to the heater 91. That is, the combustion exhaust gas in the storage tank 30 is not heated.

[0075] As a result of the determination in step S34, if the temperature K1 of the storage tank 30 is lower than the first threshold value Th1, in step S35, the control unit 60 calculates a heating amount Q1 necessary for the ozone concentration in the combustion exhaust gas to reach the target concentration at the time when the residence time T1 has elapsed. Further, the control unit 60 outputs a control signal regarding the heating amount Q1 to the heater 91. The heater 91 performs a heating operation in response to the control signal from the control unit 60.

[0076] Subsequently, in step S36, the control unit 60 acquires the temperature information of the storage tank 30 again from the second detection unit 52. Further, the control unit 60 determines whether or not the temperature K1 of the storage tank 30 is equal to or higher than the first threshold value Th1 based on the acquired temperature information. As a result of the determination, if the temperature K1 of the storage tank 30 is equal to or higher than the first threshold value Th1, the control unit 60 stops the heating operation of the heater 91.

[0077] As a result of the determination in step S36, if the temperature K1 of the storage tank 30 is lower than the first threshold value Th1, the series of steps according to step S35 and step S36 are repeated.

[0078] In this way, the control unit 60 operates the heater 91 as necessary. Thereby, compared with a configuration in which the combustion exhaust gas in the storage tank 30 is constantly heated by the heater 91, the energy consumption consumed in the operation of the gas treatment system 1A can be reduced.

[0079] [Third Embodiment] <Overall Configuration> Referring to FIG. 8, a configuration example of the gas treatment system 1B according to the third embodiment is shown. FIG. 8 is a schematic diagram showing an example of the overall configuration of the gas treatment system 1B according to the third embodiment. In the third embodiment, the same reference numerals are given to the components similar to those in the first and second embodiments, and the description thereof will be omitted as appropriate.

[0080] As shown in FIG. 8, the gas treatment system 1B according to the third embodiment is different from the above-described embodiments in that it includes a fourth flow path 24 connected to the engine 100E and a second regulating valve 45. The control unit 60 of the gas treatment system 1B may function as means for controlling the opening and closing of the second regulating valve 45 based on the first flow rate F1 acquired from the first detection unit 51 and the temperature of the storage tank 30 acquired from the second detection unit 52. Other constituent members included in the gas treatment system 1B according to the third embodiment may be the same as those in the above-described embodiments.

[0081] The fourth flow path 24 is a flow path for flowing the combustion exhaust gas discharged from the engine 100E, which is different from the first flow path 21. The fourth flow path 24 is continuous with the storage tank 30. The fourth flow path 24 shown in FIG. 8 merges into the first flow path 21 after passing through the inside of the storage tank 30. However, the fourth flow path 24 does not necessarily have to pass through the inside of the storage tank 30 and may contact the storage tank 30. Further, the fourth flow path 24 does not have to merge into the first flow path 21.

[0082] For example, high-temperature combustion exhaust gas exceeding 300 degrees discharged from the engine 100E flows through the fourth flow path 24. By providing the fourth flow path 24, the combustion exhaust gas staying in the storage tank 30 can be heated without using a heating means such as the heater 91. Thereby, while reducing the energy consumption in the operation of the gas treatment system 1B, the ozone concentration in the combustion exhaust gas can be reduced.

[0083] The second control valve 45 adjusts the opening and closing of the fourth flow path 24. The opening and closing operation of the second control valve 45 may be controlled by the control unit 60. For example, when the control unit 60 determines that the ozone concentration is not reduced to the target concentration at the residence time T1 at the temperature of the storage tank 30, the control unit 60 controls the second control valve 45 to open. As a result, high-temperature combustion exhaust gas flows through the fourth flow path 24, and the storage tank 30 is heated. Accordingly, the combustion exhaust gas staying in the storage tank 30 is heated, and the ozone concentration in the combustion exhaust gas is reduced.

[0084] As described above, the embodiments have been described. However, the above embodiments are presented as examples, and the present invention is not limited by the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, replacements, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0085] 1, 1A, 1B Gas treatment system 10 Electrostatic precipitator 21 First flow path 22 Second flow path 23 Third flow path 24 Fourth flow path 30 Storage tank 40 First control valve 45 Second control valve 51 First detection unit 52 Second detection unit 53 Third detection unit 60 Control unit 80 Separation membrane module 82 Vacuum pump

Claims

1. CO ２ An electrostatic precipitator that collects impurities in combustion exhaust gas containing A first flow path through which the combustion exhaust gas containing ozone flows after passing through the electrostatic precipitator; A storage tank for temporarily storing the combustion exhaust gas that has flowed through the first flow path; A second flow path through which the combustion exhaust gas that has passed through the storage tank flows; A third flow path that branches off from the second flow path and recirculates at least a part of the combustion exhaust gas flowing through the second flow path to the first flow path; A first control valve for adjusting the opening degree of the third flow path; A first detection unit for detecting a first flow rate of the combustion exhaust gas supplied to the electrostatic precipitator; A control unit for controlling the opening degree of the first control valve based on the first flow rate detected by the first detection unit; A gas treatment system comprising:

2. Further comprising a second detection unit for detecting the temperature of the storage tank, The control unit controls the opening degree of the first control valve so as to adjust a second flow rate flowing through the third flow path based on the first flow rate detected by the first detection unit and the temperature of the storage tank detected by the second detection unit. The gas treatment system according to claim 1.

3. The control unit stores ozone concentration data regarding the time change of the ozone concentration under each of a plurality of different temperature conditions, and based on the first flow rate detected by the first detection unit, the temperature of the storage tank detected by the second detection unit, and the ozone concentration data, controls the opening degree of the first control valve so as to adjust a second flow rate flowing through the third flow path. The gas treatment system according to claim 2.

4. The first flow path is connected to an engine as a combustion exhaust gas discharge source. The gas treatment system according to claim 1 or claim 2.

5. Further comprising a heater for increasing the temperature inside the storage tank. The gas treatment system according to claim 1 or claim 2.

6. A fourth flow path connected to the storage tank; A second control valve for adjusting the opening and closing of the fourth flow path; Further comprising: The combustion exhaust gas discharged from the combustion exhaust gas discharge source flows through the first flow path and the fourth flow path respectively; The control unit controls the opening and closing of the second control valve based on the first flow rate detected by the first detection unit and the temperature of the storage tank detected by the second detection unit. The gas treatment system according to claim 2.

7. CO from the combustion exhaust gas flowing through the second flow path ２ separating CO ２ further comprising a separation unit The gas treatment system according to claim 1 or claim 2.

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