KR102506297B1 - Selective catalytic reduction system - Google Patents

Abstract

An embodiment of the present invention relates to a selective catalytic reduction system, wherein the selective catalytic reduction system for removing nitrogen oxides contained in exhaust gas is installed on a main flow path through which the exhaust gas passes, and a catalyst therein. An installed reactor, a bypass passage branched from the main flow passage in front of the reactor and allowing the exhaust gas to bypass the reactor and join the main flow passage at the rear of the reactor, and exhaust gas branched from the main flow passage at the rear of the reactor and passing through the reactor A recirculation passage for recirculating gas to flow into the main passage in front of the reactor, a recirculation blower installed in the recirculation passage to introduce the exhaust gas passing through the reactor into the recirculation passage, and a reducing agent for supplying a reducing agent to the recirculation passage A supply line, a washing water supply unit for supplying washing water toward the reducing agent supply line, and a reducing agent or foreign matter remaining in the reducing agent supply line by controlling the washing water supply unit after blocking the supply of the reducing agent to the reducing agent supply line To remove It includes a reducing agent purge mode and a passage purge mode for operating the recirculation blower to remove exhaust gas remaining in the reactor and the recirculation passage, and sequentially performing the reducing agent purge mode and the passage purge mode.

Description

Selective catalytic reduction system {SELECTIVE CATALYTIC REDUCTION SYSTEM}

Embodiments of the present invention relate to a selective catalytic reduction system, and more particularly, to a selective catalytic reduction system for reducing nitrogen oxides contained in exhaust gas.

In general, a selective catalytic reduction system reduces nitrogen oxides (NOx) contained in exhaust gas. Specifically, the selective catalytic reduction system injects a reducing agent into the exhaust gas so that the exhaust gas mixed with the reducing agent passes through the catalyst and is discharged as nitrogen or water.

And the exhaust gas contains sulfur oxides. Specifically, exhaust gas from an engine that generates power by burning fuel contains sulfur oxides as well as nitrogen oxides.

Sulfur oxides contained in the exhaust gas combine with water generated when the exhaust gas reaches the dew point due to the lowered temperature of the exhaust passage when the engine is stopped, thereby corroding the inside of the exhaust passage. And the reactor also has a problem of corrosion.

Due to the corrosion of the exhaust flow path and the reactor, the lifespan of the exhaust flow path and the reactor is reduced, and there is a problem in that a lot of cost and time are required to replace them. And when such sulfuric acid is discharged to the outside, it can cause serious damage to the human body and the external environment.

An embodiment of the present invention provides a selective catalytic reduction system capable of removing a reducing agent remaining in a reducing agent supply line and exhaust gas remaining in a reactor and a recirculation passage.

According to an embodiment of the present invention, a selective catalytic reduction system for removing nitrogen oxides contained in exhaust gas includes a main flow path through which the exhaust gas passes, a reactor installed on the main flow path and a catalyst installed therein, and the reactor. A bypass passage branched from the front main flow passage and allowing the exhaust gas to bypass the reactor and join the main flow passage at the rear of the reactor; A recirculation passage for recirculation to flow into the main passage, a recirculation blower installed in the recirculation passage to introduce the exhaust gas passing through the reactor into the recirculation passage, a reducing agent supply line for supplying a reducing agent to the recirculation passage, and the reducing agent A washing water supply unit for supplying washing water toward the supply line, and a reducing agent purge mode for removing the reducing agent or foreign substances remaining in the reducing agent supply line by controlling the washing water supply unit after blocking the supply of the reducing agent to the reducing agent supply line; and a flow path purge mode for operating a recirculation blower to remove exhaust gas remaining in the reactor and the recirculation flow path, and a control unit for sequentially performing the reducing agent purge mode and the flow path purge mode.

In addition, the selective catalytic reduction system described above may further include an air supply unit supplying air to the reactor or the recirculation passage.

In addition, the control unit may further include a flow path venting mode in which the pressure inside the reactor and the recirculation flow path is maintained at a predetermined pressure by operating the air supply unit after completion of the flow path purge mode.

In addition, the selective catalytic reduction system described above may further include a cleaning air supply unit supplying cleaning air to the reducing agent supply line, and the control unit controls the cleaning air supply unit after the washing water supply unit operates in the reducing agent purge mode. Washing water or foreign substances remaining in the reducing agent supply line may be removed.

In addition, the above-described selective catalytic reduction system is installed in the recirculation passage and is controlled by a decomposition chamber in which a reducing agent is injected through the reducing agent supply line, and a washing control unit that controls the supply of washing water supplied to the reducing agent supply line. It may further include a water control valve, and a cleaning air control valve controlled by the control unit and controlling supply of cleaning air supplied to the reducing agent supply line.

In addition, the selective catalytic reduction system described above includes a bypass valve capable of selectively blocking the inflow of exhaust gas into the bypass passage, a first valve installed in the main passage in front of the reactor, and a second valve installed in the main passage in the rear of the reactor. It may further include, and the control unit may operate the recirculation blower after opening the bypass valve, closing the first valve, and partially opening the second valve in the flow path purge mode.

In addition, the control unit may operate the air supply unit during operation of the recirculation blower so that exhaust gas remaining on the front side of the reactor and on the recirculation passage passes through the reactor and is discharged to a main passage at the rear of the reactor.

In addition, the control unit operates the recirculation blower for a preset recirculation blower operation time, stops the operation of the recirculation blower, closes the second valve, stops the operation of the air supply unit, and then completes the passage purge mode. can do.

In addition, the selective catalytic reduction system described above may further include a pressure detection sensor for detecting an internal pressure of the main flow path or the recirculation flow path between the closed first valve and the closed second valve.

In addition, the selective catalytic reduction system described above may further include a heating member installed on the recirculation passage and capable of increasing the temperature of the exhaust gas passing through the recirculation passage.

In addition, the air supply unit is a combustion air supplying member for supplying outside air necessary for combustion of the heating member, and atomizing air for supplying air for atomization of the reducing agent supplied to the recirculation passage or atomization of fuel injected into the heating member. It may be any one of the supply members.

In addition, the air supply unit may be any one of a soot blower for supplying fluid toward the catalyst inside the reactor or a fresh air supply valve for supplying fresh air to the recirculation passage.

According to embodiments of the present invention, the selective catalytic reduction system can effectively prevent ammonia from being discharged to the outside of the reactor by effectively removing the reducing agent remaining in the reducing agent supply line, and removing exhaust gas remaining in the reactor and the recirculation passage. Thus, corrosion of the inside of the reactor and the recirculation passage can be effectively prevented.

1 is a view showing a selective catalytic reduction operation in which a selective catalytic reduction system according to an embodiment of the present invention reduces nitrogen oxides contained in exhaust gas.
FIG. 2 is a diagram illustrating a case where the selective catalytic reduction system of FIG. 1 performs a reducing agent purge mode.
FIG. 3 is a diagram illustrating a case where the selective catalytic reduction system of FIG. 1 performs a flow path purge mode.
4 is a view showing a case where the selective catalytic reduction system of FIG. 1 performs a flow path venting mode.
5 is a flow chart sequentially illustrating the operation of a control unit of a selective catalytic reduction system according to an embodiment of the present invention.
6 is a flowchart illustrating the operation of the control unit of FIG. 5 in detail.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. This invention may be embodied in many different forms and is not limited to the embodiments set forth herein.

It is advised that the drawings are schematic and not drawn to scale. Relative dimensions and proportions of parts in the drawings are shown exaggerated or reduced in size for clarity and convenience in the drawings, and any dimensions are illustrative only and not limiting. In addition, the same reference numerals are used to indicate similar features in the same structural elements or parts appearing in two or more drawings.

The embodiments of the present invention specifically represent ideal embodiments of the present invention. As a result, various variations of the diagram are expected. Therefore, the embodiment is not limited to the specific shape of the illustrated area, and includes, for example, modification of the shape by manufacturing.

Hereinafter, with reference to FIGS. 1 to 4, a selective catalytic reduction system 101 according to an embodiment of the present invention will be described.

As shown in FIG. 1, the selective catalytic reduction system 101 includes a main flow path 100, a reactor 200, a bypass flow path 300, a recirculation flow path 350, a recirculation blower 400, and a reducing agent supply line ( 630), a washing water supply unit 640, and a controller 900.

Exhaust gas passes through the main flow path 100 . Specifically, as shown in FIG. 1 , the main flow path 100 is connected to the engine 10 and guides the exhaust gas discharged from the engine 10 to be discharged to the outside.

Reactor 200 has a catalyst disposed therein. Specifically, the catalyst may be a selective reduction catalyst capable of reducing nitrogen oxides (NOx) included in exhaust gas. In addition, the reactor 200 is installed on the main flow path 100. Thus, the exhaust gas passing through the main flow path 100 can pass through the reactor 200 and be discharged.

The bypass passage 300 branches from the main passage 100 in front of the reactor 200 so that the exhaust gas bypasses the reactor 200 and joins the main passage 100 at the rear of the reactor 200. Specifically, the branching point of the bypass passage 300 is connected to the main passage 100 in front of the reactor 200, and the junction of the bypass passage 300 is connected to the main passage 100 at the rear of the reactor 200.

The recirculation passage 350 branches from the main passage 100 at the rear of the reactor 200 and guides the exhaust gas passing through the reactor 200 to flow into the main passage 100 at the front of the reactor 200 . Specifically, the branching point of the recirculation passage 350 is between the junction of the main passage 100 and the bypass passage 300 at the rear of the reactor 200, and the junction of the recirculation passage 350 is the main passage in front of the reactor 200 ( 100) and the branch point of the bypass passage 300. In other words, one side of the recirculation passage 350 is connected to the main passage 100 between the main passage 100 in front of the reactor 200 and one side of the bypass passage 300, and the other side of the recirculation passage 350 is the reactor ( 200) It may be connected to the main flow path 100 between the rear main flow path 100 and the other side of the bypass flow path 300.

The recirculation blower 400 is installed on the recirculation passage 350. In addition, the recirculation blower 400 introduces exhaust gas that has passed through the reactor 200 into the recirculation passage 350 . Specifically, the recirculation blower 400 forms a flow of fluid inside the recirculation passage 350 so that the exhaust gas passing through the reactor 200 is introduced into the recirculation passage 350 and moves along the recirculation passage 350 to the reactor. (200) can be supplied forward.

The reducing agent supply line 630 supplies the reducing agent to the recirculation passage 350 . Specifically, the reducing agent supply unit 600 may include a reducing agent storage unit 620 and a reducing agent supply line 630 . The reducing agent stored in the reducing agent storage unit 620 may move along the reducing agent supply line 630 and be supplied to the recirculation passage 350 . That is, one end of the reducing agent supply line 630 may be connected to a reducing agent injection nozzle (not shown). Therefore, the reducing agent supply line 630 guides the reducing agent stored in the reducing agent storage unit 620 to be supplied to the reducing agent injection nozzle.

The washing water supply unit 640 supplies washing water to the reducing agent supply line 630 . In addition, the washing water supplied from the washing water supply unit 640 moves along the reducing agent supply line 630 and the reducing agent injection nozzle, and can remove the reducing agent and foreign substances remaining in the reducing agent supply line 630 and the reducing agent injection nozzle. . For example, the washing water may be water.

The control unit 900 includes a reducing agent purge mode and a passage purge mode, and sequentially performs the reducing agent purge mode and passage purge mode.

In the reducing agent purge mode, as shown in FIG. 2 , the control unit 900 operates the washing water supply unit 640 to supply the washing water to the reducing agent supply line 630 . At this time, the supply of the reducing agent to the reducing agent supply line 630 is blocked. That is, in the reducing agent purge mode, the controller 900 cuts off the supply of the reducing agent supplied to the reducing agent supply line 630 and then operates the washing water supply unit 640 to supply the washing water to the reducing agent supply line 630.

In addition, the controller 900 operates the recirculation blower 400 in the passage purge mode, as shown in FIG. 3 , to remove the exhaust gas remaining in the reactor 200 and the recirculation passage 350. Specifically, the controller 900 operates the recirculation blower 400 so that the exhaust gas remaining in the recirculation passage 350 passes through the reactor 200 and is discharged to the rear of the reactor 200. to operate

Then, the controller 900 performs the flow path purge mode after completing the reducing agent purge mode, and sequentially performs the reducing agent purge mode and the flow path purge mode.

Therefore, in the reducing agent purge mode of the control unit 900, the reducing agent remaining in the reducing agent supply line 630 is diluted and supplied to the recirculation passage 350 by the washing water supplied from the washing water supply unit 640, and this recirculation passage ( The reducing agent supplied to 350) may be discharged to the outside after passing through the reactor 200 in the passage purge mode.

That is, when the reducing agent remaining in the reducing agent supply line 630 is discharged to the outside without passing through the reactor 200, the control unit 900 can effectively prevent a problem that ammonia or the like has a harmful effect on the human body. In addition, the control unit 900, in the passage purge mode, the exhaust gas remaining on the reactor 200 and the recirculation passage 350 is condensed due to the low temperature of the reactor 200 or the recirculation passage 350, and the water and Corrosion of the reactor 200 and the recirculation flow path 350 due to sulfuric acid generated when combined with the sulfur compound included in the exhaust gas can be effectively prevented.

In addition, the selective catalytic reduction system 101 according to an embodiment of the present invention, as shown in FIGS. 3 and 4, may further include an air supply unit 550.

The air supply unit 550 may supply air to the reactor 200 or the recirculation passage 350 . Specifically, the air supply unit 550 may supply external air into the reactor 200 . Alternatively, the air supply unit 550 may supply external air into the recirculation passage 350 .

In addition, the selective catalytic reduction system 101 according to an embodiment of the present invention, as shown in FIG. 4, may further include a flow path venting mode for operating the air supply unit 550 after completing the flow path purge mode.

The control unit 900 operates after completing the passage venting mode and the passage purge mode. Accordingly, the control unit 900 may sequentially perform the reducing agent purge mode, flow path purge mode, and flow path venting mode.

The controller 900 may operate the air supply unit 550 to maintain the pressure inside the reactor 200 and the recirculation passage 350 at a preset pressure. Specifically, a pressure range may be preset in the control unit 900 .

In addition, the selective catalytic reduction system 101 according to an embodiment of the present invention, as shown in FIG. 2, may further include a cleaning air supply unit 650.

The cleaning air supplier 650 may supply cleaning air to the reducing agent supply line 630 . For example, the cleaning air supply unit 650 may supply compressed air to the inside of the reducing agent supply line 630 so that washing water or foreign substances remaining inside the reducing agent supply line 630 may be removed.

In the reducing agent purge mode, the controller 900 stops the cleaning water supply unit 640 after operation, and then operates the cleaning air supply unit 650 to effectively remove the washing water or foreign substances remaining in the reducing agent supply line 630. there is. Specifically, after the operation of the cleaning air supply unit 650 is completed, the cleaning air supply unit 650 may be operated to supply cleaning air to the reducing agent supply line 630 . Therefore, the cleaning air supply unit 650 can effectively remove the cleaning water and foreign substances remaining in the reducing agent supply line 630 and the reducing agent nozzle.

In addition, the control unit 900 may operate the cleaning air supply unit 650 after the operation of the washing water supply unit 640, so that if foreign substances remain in the reducing agent supply line 630 or the reducing agent nozzle, they are melted through the washing water and then cleaned. Air may be supplied and blown into the recirculation passage 350 .

In addition, the selective catalytic reduction system 101 according to an embodiment of the present invention may include a decomposition chamber 610, a washing water control valve 642, and a washing air control valve 652.

The decomposition chamber 610 may be installed on the recirculation passage 350. Specifically, the decomposition chamber 610 may be disposed at a location relatively adjacent to the confluence of the recirculation flow path 350 rather than the recirculation blower 400 .

The decomposition chamber 610 may decompose the reducing agent injected through the reducing agent supply line 630 into ammonia using thermal energy of the exhaust gas passing through the recirculation passage 350 . Therefore, in order to reduce nitrogen oxides contained in the exhaust gas of the present invention, urea passing through the reducing agent supply line 630 may be decomposed into ammonia inside the decomposition chamber 610 and injected into the exhaust gas. Specifically, an ammonia injection grid (AIG) 680 may be installed in the main flow path 100 in front of the reactor 200, and a branch point of the recirculation flow path 350 may be connected thereto. That is, ammonia passing through the recirculation passage 350 may be injected into the exhaust gas through the ammonia injection grid 680 .

The washing water control valve 642 is operated by the control unit 900 . Specifically, the washing water supply unit 640 may include a washing water supply line 641 and a washing water control valve 642 . The washing water supply line 641 may guide washing water to be supplied to the reducing agent supply line 630 from a previously stored washing water storage unit (not shown). The washing water control valve 642 is installed on the washing water supply line 641 to control the inflow and flow of the washing water supplied to the washing water supply line 641 . Accordingly, when the controller 900 controls the washing water supply unit 640, it is possible to control the amount of opening or closing of the washing water control valve 642.

The cleaning air control valve 652 is operated by the control unit 900. Specifically, the cleaning air supply unit 650 may include a cleaning air supply line 651 and a cleaning air control valve 652. The cleaning air supply line 651 may compress a pre-stored cleaning air storage unit (not shown) or external air to guide the cleaning air to be supplied to the reducing agent supply line 630 . The cleaning air control valve 652 is installed on the cleaning air supply line 651 to adjust the inflow and flow rate of the cleaning air supplied to the cleaning air supply line 651 . Accordingly, when the control unit 900 controls the cleaning air supply unit 650, the amount of opening and closing of the cleaning air control valve 652 may be adjusted.

In addition, the selective catalytic reduction system 101 according to an embodiment of the present invention, as shown in FIGS. 1 to 4, the bypass valve 310, the first valve 110, and the second valve 120 can include more.

The bypass valve 310 may selectively block the inflow of exhaust gas flowing into the bypass passage 300 . Specifically, the bypass valve 310 may be installed on the bypass passage 300 .

That is, when the bypass valve 310 is closed, the exhaust gas discharged from the engine 10 may flow into the reactor 200 through the main flow path 100 . Alternatively, when the bypass valve 310 is opened, exhaust gas discharged from the engine 10 may flow into the bypass passage 300 .

The first valve 110 may be installed on the main flow path 100 in front of the reactor 200. Specifically, the first valve 110 may be installed between the branching point of the bypass passage 300 and the junction of the recirculation passage 350 . Specifically, the first valve 110 may selectively control the inflow of exhaust gas flowing into the reactor 200 .

The second valve 120 may be installed on the main flow path 100 behind the reactor 200 . Specifically, the second valve 120 may be installed between the junction of the bypass passage 300 and the branching point of the recirculation passage 350 . Specifically, the second valve 120 may control the introduction of the exhaust gas passing through the bypass passage 300 into the reactor 200 and the recirculation passage 350 . For example, the second valve 120 is controlled by the controller 900 and can control the amount of opening of the flow path inside the main flow path 100 .

The control unit 900 may open the bypass valve 310 as shown in FIG. 3 in the flow path purge mode. Specifically, in the passage purge mode, exhaust gas may pass through the bypass passage 300 .

Also, in the flow path purge mode, the controller 900 may close the first valve 110 . Specifically, exhaust gas is blocked from entering the reactor 200 . That is, in the passage purge mode, the exhaust gas may bypass the reactor 200 .

And, in the flow path purge mode, as shown in FIG. 3 , the controller 900 opens at least a portion of the second valve 120 (within a range of 1% to 45% of the total area of the entire main flow path 100). can That is, the second valve 120 may be controlled to open at least a portion of the inside of the main flow path 100 so that the exhaust gas passing through the reactor 200 is discharged to the main flow path 100 . In other words, the second valve 120 may be controlled to open at least a portion of the inside of the main flow path 100 and close the remaining main flow path 100 . Also, the control unit 900 may operate the recirculation blower 400 . Therefore, after passing through the reactor 200, the remaining exhaust gas moving along the recirculation passage 350 may be discharged to the outside through the main passage 100 at the rear of the reactor 200. That is, the control unit 900 passes the remaining exhaust gas between the main flow path 100 between the first valve 110 and the second valve 120 and the recirculation flow path 350 through the reactor 200, and then the reactor ( 200) can be effectively discharged to the outside.

At this time, since the residual exhaust gas passing through the reactor 200 by the recirculation blower 400 is discharged through between the second valve 120 and the main flow path 100, the exhaust gas passing through the bypass flow path 300 is discharged through the recirculation flow path. 350 and the reactor 200 can be effectively prevented.

That is, since the second valve 120 is partially open, the flow rate of the exhaust gas passing between the second valve 120 and the main flow path 100 increases, so that the exhaust gas passing through the bypass flow path 300 passes through the recirculation flow path. Backflow flowing into the reactor 350 and the reactor 200 can be effectively prevented.

In addition, the controller 900 of the selective catalytic reduction system 101 according to an embodiment of the present invention may operate the air supply unit 550 when the recirculation blower 400 operates.

The controller 900 may operate the recirculation blower 400 and the air supply unit 550 in the passage purge mode. Accordingly, sulfur oxides contained in the exhaust gas remaining in the reactor 200 and the recirculation passage 350 can be effectively discharged to the outside of the reactor 200 . Specifically, when external air is introduced into the reactor 200 or the recirculation passage 350 by the operation of the air supply unit 550, the concentration of sulfur oxides included in the exhaust gas may be reduced. In addition, the air supply unit 550 can effectively discharge the exhaust gas remaining in the recirculation passage 350 and the reactor 200 to the main passage 100 at the rear of the reactor 200 together with the operation of the recirculation blower 400. there is.

In addition, the control unit 900 of the selective catalytic reduction system 101 according to an embodiment of the present invention, as shown in FIG. 4, stops the operation of the recirculation blower 400 and closes the second valve 120. and stop the operation of the air supply unit 550 to complete the passage purge mode.

The control unit 900 may have a recirculation blower operation time set in advance. Accordingly, the control unit 900 may count the operating time of the recirculating blower 400 based on a timer (not shown) or a signal that drives the recirculating blower 400 and compare it with a predetermined operating time of the recirculating blower. Specifically, the control unit 900 may stop the operation of the recirculation blower 400 when the operation time of the recirculation blower 400 reaches the preset operating time of the recirculation blower.

Also, the control unit 900 may close the second valve 120 and stop the operation of the air supply unit 550 after stopping the operation of the recirculation blower 400 . Specifically, the controller 900 may control the second valve 120 to close the main flow path 100 . Also, the controller 900 may stop the operation of the air supply unit 550 .

Accordingly, the controller 900 may stop the operation of the recirculation blower 400 and the air supply unit 550 and control the second valve 120 to close the main flow path 100 when the passage purge is completed.

In addition, the selective catalytic reduction system 101 according to an embodiment of the present invention may further include a pressure detection sensor 750 for detecting the internal pressure of the recirculation flow path 350 in the flow path vent mode.

When the flow path venting mode of the control unit 900 is performed, the first valve 110 and the second valve 120 are closed and the bypass valve 310 is open. At this time, when external air is introduced into the reactor 200 or the recirculation passage 350 due to the air supply unit 550, the main passage between the closed first valve 110 and the closed second valve 120 ( 100) and the pressure between the recirculation passage 350 is increased.

Therefore, even when the airtightness due to repeated use of the first valve 110 or the second valve 120 occurs, the main flow path between the closed first valve 110 and the closed second valve 120 Since the internal pressure between the reactor 100 and the recirculation passage 350 is relatively higher than the pressure of the exhaust gas discharged from the engine 10 or the exhaust gas passing through the bypass passage 300, the reactor 200 and the recirculation passage 350 ) can effectively prevent the exhaust gas from flowing backward.

The pressure detection sensor 750 may detect internal pressure between the main flow path 100 between the closed first valve 110 and the closed second valve 120 and the recirculation flow path 350 . A pressure setting range is preset in the control unit 900 . Specifically, a first set pressure and a second set pressure are preset in the control unit 900 . For example, the first set pressure value is a higher value than the second set pressure value.

Accordingly, the control unit 900 may control the operation of the air supply unit 550 according to a preset pressure setting range. Specifically, the internal pressure between the main flow path 100 and the recirculation flow path 350 between the closed first valve 110 and the closed second valve 120 detected by the pressure sensor 750 is the first setting If the pressure is less than the pressure, the control unit 900 may stop the operation of the air supply unit 550 .

In addition, the internal pressure between the main flow path 100 and the recirculation flow path 350 between the closed first valve 110 and the closed second valve 120 detected by the pressure detection sensor 750 is the second set pressure. If less than, the control unit 900 operates the air supply unit 550 so that the internal pressure between the main flow path 100 between the closed first valve 110 and the closed second valve 120 and the recirculation flow path 350 The pressure of the exhaust gas discharged from the engine 10 or the pressure of the exhaust gas passing through the bypass passage 300 may be formed higher.

That is, the control unit 900 controls between the main flow path 100 and the recirculation flow path 350 between the closed first valve 110 and the closed second valve 120 according to the pressure detected by the pressure detection sensor 750. It is possible to operate the air supply unit 550 so that the internal pressure of is formed between the first set pressure and the second set pressure.

In addition, the selective catalytic reduction system 101 according to an embodiment of the present invention may further include a heating member 500.

During the operation of the heating member 500, fuel is supplied and exhaust gas passing through the recirculation passage 350 may be heated. Specifically, the heating member 500 may be operated to effectively decompose the urea injected inside the decomposition chamber 610 into ammonia. Also, the heating member 500 may be operated by the controller 900 .

In addition, the air supply unit 550 of the selective catalytic reduction system 101 according to an embodiment of the present invention includes a combustion air supply member 510, an atomization air supply member 800 for supplying air for atomization of a reducing agent or atomization of fuel , It may be any one of the soot blower 700 or the fresh air supply valve 410.

The combustion air supply member 510 supplies outside air required during combustion of the heating member 500 . In the passage purge mode or passage venting mode, the control unit 900 operates the combustion air supply member 510 while stopping the supply of fuel to the heating member 500 to supply outside air to the heating member 500 to recirculate the passage. Outside air may be introduced through (350). Specifically, the combustion air supply member 510 may include an outside air supply valve 512 controlled by the controller 900 and an outside air supply blower 511 .

The atomization air supply member 800 may atomize the reducing agent supplied to the recirculation passage 350 or supply compressed air for atomization of the fuel injected into the heating member 500 . Also, the atomization air supply member 800 may be operated by the control unit 900 . Specifically, the atomization air supply member 800 may help atomization of the reducing agent injected into the decomposition chamber 610 or atomization of the fuel injected into the heating member 500 . In addition, when the atomization air supply member 800 is operated as the air supply unit 550, injection of the reducing agent into the decomposition chamber 610 may be stopped and fuel supply to the heating member 500 may be stopped.

Therefore, the atomized air supply member 800 may supply compressed air to the decomposition chamber 610 or the heating member 500 so that the compressed air is introduced through the recirculation passage 350 .

The soot blower 700 supplies fluid toward the catalyst inside the reactor 200. Specifically, the fluid supplied into the reactor 200 through the soot blower 700 may cause foreign substances attached to the catalyst to be discharged to the outside of the reactor 200 . Also, the soot blower 700 may be operated by the control unit 900. Specifically, when the soot blower 700 operates as the air supply unit 550, fluid may be supplied into the reactor 200.

The new supply valve 410 is connected to the recirculation passage 350 . Specifically, the new supply valve 410 may be connected to a branch point of the recirculation flow path 350 and relatively adjacent to the recirculation blower 400 . Also, the fresh air supply valve 410 can be selectively controlled by the control unit 900 to supply fresh air to the recirculation passage 350 . Therefore, when the control unit 900 operates in the passage purge mode, when the air supply unit 550 is the fresh air supply valve 410, the recirculation blower 400 effectively removes the fresh air supply supplied to the recirculation passage 350. ) can be transferred along. That is, fresh air supplied over the entire area of the recirculation passage 350 is moved, and sulfur oxides contained in the exhaust gas remaining in the recirculation passage 350 can be removed and diluted.

Hereinafter, with reference to FIGS. 1 and 5, the operation process of the controller 900 of the selective catalytic reduction system 101 according to an embodiment of the present invention will be described.

The control unit stops a selective catalytic reduction (SCR) operation for reducing nitrogen oxides contained in the exhaust gas of the selective catalytic reduction system. That is, the control unit performs the process described below after stopping the supply of the reducing agent.

Although the supply of the reducing agent is stopped, a reducing agent purge mode is performed to remove the reducing agent remaining in the reducing agent supply line (S100). That is, the foreign substances attached to the reducing agent supply line or the reducing agent nozzle connected thereto or the reducing agent remaining therein are removed.

Thereafter, a passage purge mode is performed to remove the exhaust gas remaining in the reactor and the recirculation passage (S200). That is, when sulfur oxides contained in the exhaust gas remaining inside the reactor and inside the recirculation passage remain, sulfuric acid generated when combined with water condensed inside the reactor and the recirculation passage due to the lowered temperature after the SCR operation is stopped is added to the reactor and The recirculation flow path is corroded. Therefore, the passage purge mode removes the exhaust gas remaining inside the reactor and the recirculation passage.

Thereafter, a flow path venting mode is performed in which the inside of the reactor and the recirculation flow path are relatively higher than the pressure of the exhaust gas discharged from the engine (S300). Specifically, before the passage venting mode or after completion of the passage purge mode, the front and rear portions of the reactor are closed, and a closed loop is established between the reactor and the recirculation passage.

Therefore, in the flow path venting mode, the pressure inside the reactor and the recirculation flow path in which the closed loop is formed is relatively higher than the pressure of the exhaust gas outside, thereby preventing the exhaust gas from flowing into the closed loop.

Hereinafter, the operation process of the controller 900 of the selective catalytic reduction system 101 described above based on FIGS. 1 to 6 will be described in more detail.

The control unit of the selective catalytic reduction system 101 installed in the ship performs a selective catalytic reduction (SCR) operation to remove nitrogen oxides contained in the exhaust gas when entering a sea area where exhaust gas emission regulations exist. However, when the operation of the ship is stopped or when the ship passes through a sea area where there is no emission regulation of exhaust gas, the control unit stops the selective catalytic reduction (SCR) operation.

Hereinafter, the selective catalytic reduction system 101 described describes a process after the selective catalytic reduction (SCR) operation is stopped.

Priority is given to performing the reducing agent purge mode (S100) of the control unit, and the process thereof will be sequentially described.

The injection of the reducing agent is stopped (S100). Specifically, injection of a reducing agent that can be mixed with exhaust gas to reduce nitrogen oxides is stopped.

The washing water supply valve is opened (S120). Specifically, the control unit supplies washing water to the reducing agent supply line to remove the reducing agent remaining in the reducing agent supply line or the reducing agent nozzle connected thereto. In addition, the washing water passing through the reducing agent supply line and the reducing agent nozzle is supplied to the recirculation passage through the decomposition chamber. Therefore, the remaining reducing agent can be supplied to the recirculation passage instead of being discharged to the outside, so that it can be mixed with the exhaust gas remaining in the recirculation passage and the reactor, pass through the reactor, and then be discharged to the outside.

It is compared whether the opening time of the washing water supply valve reaches the predetermined opening time of the washing water supply valve (S130). Until the opening time of the washing water supply valve stored in the control unit is reached, the control unit continues counting the opening time of the washing water supply valve.

When the opening time of the washing water supply valve is less than the preset opening time of the washing water supply valve, the washing water supply valve is kept open.

Alternatively, when the opening time of the washing water supply valve exceeds the preset opening time of the washing water supply valve, the washing water supply valve is closed (S140).

The cleaning air supply valve is opened (S150). Specifically, the control unit supplies cleaning air to the reducing agent supply line to remove washing water or foreign substances remaining in the reducing agent supply line or the reducing agent nozzle connected thereto. That is, cleaning air may be supplied to the reducing agent supply line to dry the inside of the reducing agent supply line or the reducing agent nozzle connected thereto.

It is compared whether the opening time of the cleaning air supply valve reaches the preset opening time of the cleaning air supply valve (S160). Until the cleaning air supply valve opening time stored in the controller is reached, the controller continues counting the cleaning air supply valve opening time.

When the opening time of the cleaning air supply valve is less than the preset opening time of the cleaning air supply valve, the cleaning air supply valve is kept open.

Alternatively, when the opening time of the cleaning air supply valve exceeds the predetermined opening time of the cleaning air supply valve, the cleaning air supply valve is closed (S170).

Thus, the control unit completes the operation of the reducing agent purge mode (S100). Then, the flow path purge mode (S200) is performed.

Hereinafter, the flow path purge mode (S200) will be described. And, the operating process of the flow path purge mode (S200) will be sequentially described.

The bypass valve is opened (S210). Specifically, the controller opens the bypass valve to allow the exhaust gas discharged from the engine to pass through the bypass passage.

The first valve is closed (S220). Therefore, the exhaust gas discharged from the engine bypasses the reactor and is discharged through the bypass passage. In addition, the introduction of exhaust gas into the reactor toward the front of the reactor is restricted.

Air is supplied to the reactor or the recirculation passage (S230). The air supplied to the reactor or the recirculation passage reduces the concentration of sulfur oxides contained in the exhaust gas remaining in the reactor and the recirculation passage.

Part of the second valve is opened (S240). The control unit opens a part of the second valve so that the exhaust gas that has passed through the bypass passage is not re-introduced to the rear of the reactor, and the exhaust gas remaining in the recirculation passage and the reactor is discharged through the rear of the reactor together with supplied air.

Operate the recirculation blower (S250). Accordingly, the air supplied between the recirculation passage and the reactor and the remaining exhaust gas have a flow from the recirculation passage toward the front of the reactor by the operated recirculation blower. That is, the exhaust gas remaining between the reactor and the recirculation passage is discharged to the outside of the reactor after passing through the reactor.

It is compared whether the operation time of the recirculation blower reaches the predetermined operation time of the recirculation blower (S260). Until the operating time of the recirculating blower stored in the controller is reached, the controller continues to count the operating time of the recirculating blower.

If the operating time of the recirculating blower is less than the predetermined operating time of the recirculating blower, the operation of the recirculating blower is continuously maintained.

Alternatively, when the operating time of the recirculating blower exceeds the predetermined operating time of the recirculating blower, the operation of the recirculating blower is stopped (S270).

The second valve is closed (S280). In addition, the supply of air supplied to the reactor or the recirculation passage is stopped (S290).

Thus, the control unit completes the operation of the flow path purge mode (S200). Then, the euro venting mode (S300) is performed.

Hereinafter, the passage venting mode (S300) will be described. And, the operation process of the flow venting mode (S300) will be sequentially described. As described above, the first valve and the second valve are closed before the passage venting mode (S300) is performed.

Air is supplied into the reactor and the inside of the recirculation passage between the closed first valve and the closed second valve (S310). At this time, the pressure inside the reactor and the recirculation passage between the first valve closed by the supplied air and the second valve closed is higher than the pressure of the exhaust gas passing through the bypass passage and passing through the main passage.

The pressure detection sensor detects the pressure inside the reactor and the recirculation passage between the closed first valve and the closed second valve (S320).

The detected pressure is compared with the first set pressure preset in the control unit (S330).

When the detected pressure is less than the first set pressure, the pressure is detected while maintaining the air supply into the reactor and the inside of the recirculation passage between the closed first valve and the closed second valve.

Alternatively, when the detected pressure exceeds the first set pressure, the supply of air into the reactor and the inside of the recirculation passage between the closed first valve and the closed second valve is stopped (S340).

After the air supply is stopped, the re-detection pressure inside the reactor and the recirculation passage between the closed first valve and the closed second valve is compared with the second set pressure preset in the control unit (S350).

When the re-detection pressure exceeds the second set pressure, air supply between the closed first valve and the closed second valve into the reactor and into the recirculation passage is stopped.

Alternatively, when the re-detection pressure is less than the second set pressure, the supply of air to the inside of the reactor and the recirculation passage between the closed first valve and the closed second valve is resumed (S310).

Therefore, the control unit maintains the pressure inside the reactor and the recirculation passage between the closed first valve and the closed second valve at 1.1 bar to 1.6 bar.

The flow path venting mode (S300) may be stopped by an operator or when a ship enters an emission regulated sea area.

With this configuration, the selective catalytic reduction system 101 according to an embodiment of the present invention can effectively remove the reducing agent remaining in the reducing agent supply line and the exhaust gas remaining in the reactor and the recirculation passage. Therefore, the selective catalytic reduction system 101 can effectively prevent corrosion in the reactor and inside the recirculation passage.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art to which the present invention pertains can understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. will be.

Therefore, the embodiments described above should be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the claims described below, the meaning and scope of the claims, and All changes or modified forms derived from the equivalent concept should be construed as being included in the scope of the present invention.

100: main flow 101: selective catalytic reduction system
110: first valve 120: second valve
200: reactor 300: bypass
310: bypass valve 350: recirculation flow path
400: recirculation blower 410: new supply valve
500: heating member 510: combustion air supply member
550: air supply unit 610: decomposition chamber
630: reducing agent supply line 640: washing water supply unit
650: cleaning air supply unit 700: soot blower
800: atomization air supply member 900: control unit

Claims (12)

In the selective catalytic reduction system for removing nitrogen oxides contained in exhaust gas,
a main flow path through which the exhaust gas passes;
a reactor installed on the main flow path and having a catalyst installed therein;
a bypass passage branched from the main passage in front of the reactor and allowing the exhaust gas to bypass the reactor and join the main passage in the rear of the reactor;
a recirculation passage branched from the main passage at the rear of the reactor and recirculating the exhaust gas passing through the reactor to flow into the main passage at the front of the reactor;
a recirculation blower installed in the recirculation passage to introduce the exhaust gas passing through the reactor into the recirculation passage;
a reducing agent supply line supplying a reducing agent to the recirculation passage;
a washing water supply unit supplying washing water toward the reducing agent supply line; and
A reducing agent purge mode in which the reducing agent supply line is cut off and then the washing water supply unit is controlled to remove the reducing agent or foreign substances remaining in the reducing agent supply line, and the recirculation blower is operated to clean the inside of the reactor and the recirculation passage It includes a flow path purge mode for removing remaining exhaust gas, and a control unit that performs the flow path purge mode after completion of the reducing agent purge mode.
Selective catalytic reduction system comprising a. In paragraph 1,
The selective catalytic reduction system further comprising an air supply unit for supplying air to the reactor or the recirculation passage. In paragraph 2,
The control unit,
After completing the flow path purge mode, the selective catalytic reduction system further comprises a flow path venting mode in which the pressure inside the reactor and the recirculation flow path is maintained at a predetermined pressure by operating the air supply unit. In paragraph 2,
Further comprising a cleaning air supply unit for supplying cleaning air to the reducing agent supply line,
The control unit,
In the reducing agent purge mode, after the washing water supply unit operates, the selective catalytic reduction system is characterized in that to remove the washing water or foreign substances remaining in the reducing agent supply line by controlling the cleaning air supply unit. In paragraph 4,
a decomposition chamber installed in the recirculation passage and in which a reducing agent is injected through the reducing agent supply line;
a washing water control valve controlled by the controller and controlling the supply of washing water supplied to the reducing agent supply line; and
A cleaning air control valve controlled by the controller and controlling the supply of cleaning air supplied to the reducing agent supply line.
Selective catalytic reduction system comprising a. In paragraph 3,
a bypass valve capable of selectively blocking the inflow of exhaust gas into the bypass passage;
A first valve installed in the main flow path in front of the reactor; and
Further comprising a second valve installed in the main flow path behind the reactor,
The control unit,
In the flow path purge mode, the bypass valve is opened, the first valve is closed, and the second valve is partially opened, and then the recirculation blower is operated. In paragraph 6,
The control unit,
When the recirculation blower operates, the air supply unit is operated so that the exhaust gas remaining on the front side of the reactor and on the recirculation flow path passes through the reactor and is discharged to the main flow path at the rear of the reactor. In paragraph 7,
The control unit,
After operating the recirculation blower for a predetermined recirculation blower operation time, stopping the operation of the recirculation blower, closing the second valve, and stopping the operation of the air supply unit, and then completing the flow path purge mode. catalytic reduction system. In paragraph 8,
The selective catalytic reduction system further comprising a pressure detection sensor for detecting the internal pressure of the main flow path or the recirculation flow path between the closed first valve and the closed second valve. In paragraph 2,
The selective catalytic reduction system further comprises a heating member installed on the recirculation passage and capable of raising the temperature of the exhaust gas passing through the recirculation passage. In paragraph 10,
The air supply unit,
Combustion air supply member for supplying outside air required during combustion of the heating member, and atomization air supply member for supplying air for atomization of the reducing agent supplied to the recirculation passage or atomization of the fuel injected into the heating member. Selective catalytic reduction system, characterized in that. In paragraph 2,
The air supply unit,
Selective catalytic reduction system, characterized in that any one of a soot blower for supplying fluid toward the catalyst inside the reactor, or a fresh air supply valve for supplying fresh air to the recirculation passage.

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