KR101732258B1 - Low-pressure selective catalytic reduction system and control method thereof - Google Patents

Abstract

A low pressure SCR system and a control method thereof are disclosed.
The low pressure SCR system is an SCR reactor; A bypass line installed in the SCR reactor; A bypass valve provided at a front end of the bypass line; A main exhaust passage in the SCR reactor partitioned with the bypass line and in which the catalyst is located; An inlet valve installed at an inlet of the SCR reactor for selectively opening and closing one side of the main exhaust passage and the bypass line; And an outlet valve installed at the outlet of the SCR reactor for selectively opening and closing the other side of the main exhaust passage and the bypass line, wherein the control unit selects one of the SCR mode, the bypass mode and the venting mode, Adjust the bypass valve, inlet valve and outlet valve.
Accordingly, the internal temperature of the SCR reactor can be maintained at a predetermined level or higher by the high-temperature exhaust gas, and the ABS decomposition and removal, the PM / soot removal, the corrosion prevention and the stable decomposition of the reducing agent can be achieved while consuming the minimum heat source.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a low-pressure SCR system and a control method thereof,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SCR system and a control method thereof, and more particularly, to a low-pressure SCR system and a control method thereof, in which an SCR reactor is installed at the rear end of an engine T / C (Turbo Charger).

The exhaust gas discharged after combustion in the marine engine contains a large number of suspended particulate matter, NOx which is nitrogen oxide, and SOx which is sulfur oxide.

Therefore, a diesel particulate filter, a selective catalytic reduction (SCR) system, a scrubber (SOx removal) and the like are installed in the exhaust line of the engine to remove harmful components in the exhaust gas.

Among them, the SCR system includes an SCR reactor having a catalyst built therein, and is configured to decompose nitrogen oxide in exhaust gas into water and nitrogen harmless to the human body by chemically reacting with the reducing agent in the catalyst layer.

Here, the catalyst is made of a porous catalyst filter formed with extrusion or metallic coating, and one or several SCR catalysts are continuously installed in the SCR reactor installed in the exhaust line.

When the SCR system is installed in front of the engine T / C (Turbo Charger), it is called a high-pressure SCR system because the pressure of the exhaust gas flowing into the SCR system is high.

In comparison, when the SCR system is installed downstream of the engine T / C with a relatively low exhaust gas temperature, it is called a low pressure SCR system.

1 is a schematic block diagram of a conventional low pressure SCR system.

The SCR reactor 40 is installed on the exhaust line 20 extending from the rear end of the engine T / C 10 and the bypass line 30 is branched at the front end of the SCR reactor 40.

Exhaust gas generated from the engine flows into the exhaust line 20 through the T / C 10 and the valves 21 and 22 and the bypass valve 31 provided at the front and rear ends of the SCR reactor 40 are selectively The exhaust gas is discharged via the SCR reactor 40 after the nitrogen oxide reduction or directly through the bypass line 30 without passing through the SCR reactor 40. [

In this low-pressure SCR system, the exhaust gas temperature at the rear end of the T / C 10 is about 190 to 300 ° C., the pressure is at the atmospheric pressure level, and the exhaust gas temperature at the rear end of the T / An excellent low-temperature catalyst is required.

2 is a graph illustrating the internal operating temperature of the SCR reactor shown in FIG.

The SCR system operates only within the emission control area (ECA) and uses the SCR reactor 40, in which case an expensive low sulfur fuel, typically less than 0.1% sulfur, is used. At the time of high-altitude navigation, exhaust gas is discharged through a separate bypass line (30) by using a fuel having a high sulfur content.

In Fig. 2, the operation of the SCR system is divided into the case of operating on the high seas (M1, M3) and the case of operating the exhaust regulating area (M2).

The valves 21 and 22 provided at the front and rear ends of the SCR reactor 40 are closed and the bypass valve 31 is closed when the engines M1 and M3 are operating, So that the exhaust gas is discharged through the bypass line 30 without passing through the SCR reactor 40.

During this bypass operation, the internal temperature of the SCR reactor 40 in use is lowered to about 25 캜 and the leakage of the exhaust gas due to the temperature difference between the bypass line 30 and the valves 21 and 22 SCR reactor 40, and sulfuric acid condensation is generated (R1 and R2 in FIG. 2).

Since condensed sulfuric acid causes internal corrosion of the SCR reactor 40, it is necessary to ventilate the sulfuric acid by continuously injecting ambient air at room temperature into the SCR reactor 40 (T11).

If the SCR system in which the operation is stopped is restarted, the temperature in the SCR reactor 40 is lowered to the room temperature of about 25 DEG C and the temperature of the SCR reactor 40 is raised to a predetermined SCR reaction temperature (about 200 to 250 DEG C) Time is delayed.

Therefore, in order to raise the internal temperature of the SCR reactor 40 before entering the emission control area, the external air is heated by an additional heat source such as a burner to warm the sealed SCR reactor 40 to about 200 캜 (T12).

On the other hand, in the case of operating the emission control area, the valves 21 and 22 provided at the front and rear ends of the SCR reactor 40 are opened and the bypass valve 31 is closed, thereby exhausting the exhaust gas to the SCR reactor 40 To react with the catalyst in the SCR reactor 40 to remove nitrogen oxides in the exhaust gas.

When the engine is stopped, the temperature in the SCR reactor 40 is lowered to a room temperature of about 25 캜 (T22).

Therefore, even in this case, the internal temperature of the SCR reactor 40 is reduced from an additional heat source such as a burner to about 200 (about 200) in the state where the valves 21 and 22 at the upstream and downstream stages are closed for preparation of condensation of sulfuric acid in the SCR reactor 40, Heating (T22) is required to maintain the temperature of the substrate at a temperature of 0 ° C.

(M3), an additional heat source is used for the removal of ABS (Ammonium Bisulfate) adhered to the catalyst in the SCR reactor 40. In this case, high temperature steam or high temperature compressed air is produced Thereby performing ABS decomposition and removal and regeneration (T31).

As described above, in the conventional low-pressure SCR system, since the exhaust line 20 and the bypass line 30 in which the SCR reactor 40 is installed are separated, the temperature in the SCR reactor 40 is frequently lowered to room temperature, Many heat sources are consumed.

Further, problems such as increase of ABS production amount causing corrosion due to low temperature inside the SCR reactor 40, deposition of PM (Particle Material) / soot, and reduction of the reducing agent occur.

To solve such a problem, it is necessary to provide a separate reducing agent supply device for hydrolyzing the additional heat source (burner, etc.), soot blower, and urea, so that the system configuration is complicated and installation is troublesome There is a problem.

Korean Patent Laid-Open Publication No. 10-2013-0016581 (published on February 23, 2013).

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems of the prior art, and it is an object of the present invention to provide a SCR reactor, which bypasses a bypass line to the inside of an SCR reactor, Pressure SCR system capable of maintaining the internal temperature at a predetermined level or higher, and a control method thereof.

Another object of the present invention is to optimize the opening and closing states of the valves installed on the upstream and downstream sides of the SCR reactor and the bypass line in accordance with the operation mode so as to reduce the decomposition of ABS and the removal of PM and suet while consuming a minimum heat source, A low-pressure SCR system and a control method thereof capable of achieving decomposition of a reducing agent, and the like.

It is still another object of the present invention to provide a low-pressure SCR system and a control method thereof that can modularize / downsize major components and simplify the configuration and maximize installation convenience.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not to be construed as limiting the invention as defined by the appended art. It will be possible.

According to an aspect of the present invention, there is provided a low pressure SCR system comprising: a SCR reactor; A bypass line installed in the SCR reactor; A bypass valve provided at a front end of the bypass line; A main exhaust passage in the SCR reactor partitioned with the bypass line and in which the catalyst is located; An inlet valve installed at an inlet of the SCR reactor for selectively opening and closing one of the main exhaust passage and the bypass line; And an outlet valve installed at an outlet of the SCR reactor for selectively opening and closing the main exhaust passage and the other side of the bypass line, wherein the control unit selects one of the SCR mode, the bypass mode, and the venting mode, And controls the bypass valve, the inlet valve, and the outlet valve according to the operation mode.

In the low pressure SCR system according to the present invention, in the SCR mode, the bypass valve is closed and the inlet valve and the outlet valve are opened to pass the exhaust gas to the catalyst of the main exhaust passage. In the bypass mode, The inlet valve and the outlet valve are closed to close the main exhaust passage and open the bypass valve to pass the exhaust gas through the bypass line. In the venting mode, the inlet valve is closed, The outlet valve may be throttled to discharge the residual exhaust gas from the main exhaust passage.

The low pressure SCR system according to the present invention can pass the exhaust gas discharged from the engine in all the operation modes into the inside of the SCR reactor so that the internal temperature of the SCR reactor is maintained above the exhaust gas temperature while the engine is running .

The low-pressure SCR system according to the present invention may further include a nozzle provided at a rear end of the bypass line.

The low pressure SCR system according to the present invention may further comprise a reducing agent supply device for generating ammonia gas from the solid ammonium carbonate and supplying the ammonia gas to the front end of the SCR reactor.

The low-pressure SCR system according to the present invention may further include a heater for generating high-temperature, high-pressure air for raising the internal temperature of the SCR reactor and supplying it to the main exhaust passage.

In the low pressure SCR system according to the present invention, in the bypass mode, high temperature and high pressure air generated from the heating device may be supplied to the main exhaust passage to raise the internal temperature of the SCR reactor to the ABS vaporization temperature or more.

The low-pressure SCR system according to the present invention supplies high-temperature, high-pressure air generated from the heating device to the main exhaust passage before entering the SCR mode or when the engine operation is temporarily stopped during the SCR mode, The internal temperature can be maintained above the SCR reaction temperature.

In the low-pressure SCR system according to the present invention, the SCR reactor may be installed for each engine T / C (Turbo Charger).

In the low-pressure SCR system according to the present invention, the bypass line is installed to pass through the catalyst in the center of the SCR reactor, and the main exhaust passage may be located in the periphery of the bypass line in the SCR reactor.

The control method of the low-pressure SCR system according to the present invention is a control method of a low-pressure SCR system including a bypass line and a main exhaust passage in which a catalyst is located, in which the SCR mode, the bypass mode, Selecting one operation mode; And an inlet valve installed at an inlet of the SCR reactor and selectively opening and closing one side of the main exhaust passage and the bypass line in accordance with the operation mode and an inlet valve disposed at an outlet of the SCR reactor, And adjusting an outlet valve installed to selectively open and close the main exhaust passage and the other side of the bypass line.

In the control method of the low-pressure SCR system according to the present invention, the valve control step includes closing the bypass valve and opening the inlet valve and the outlet valve to pass the exhaust gas through the catalyst of the main exhaust passage in the SCR mode ; Closing the inlet valve and the outlet valve to close the main exhaust passage and opening the bypass valve to pass the exhaust gas through the bypass line when the bypass mode is selected; And closing the inlet valve and throttling the bypass valve and the outlet valve to discharge residual exhaust gas from the main exhaust passage when the engine is in the venting mode.

According to the low pressure SCR system and the control method of the present invention, the bypass line is passed into the SCR reactor and the internal temperature of the SCR reactor can be maintained at a certain level or more by the high temperature exhaust gas even during the bypass operation of the exhaust gas have.

In addition, according to the low-pressure SCR system and the control method thereof according to the present invention, it is possible to optimally control the opening and closing states of the valves installed on the upstream and downstream sides of the SCR reactor and the bypass line according to the operation mode, Removal of soot, prevention of corrosion, stable decomposition of reducing agent, and the like.

Further, according to the low-pressure SCR system and the control method of the present invention, major components can be modularized / miniaturized, thereby simplifying the configuration and maximizing installation convenience.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a conventional low pressure SCR system. FIG.
Figure 2 is a graph illustrating the internal operating temperature of the SCR reactor shown in Figure 1;
3 is a configuration diagram of a low-pressure SCR system according to an embodiment of the present invention;
4 is a schematic view of an SCR reactor according to an embodiment of the present invention.
Figure 5 is an exploded perspective view of the SCR reactor shown in Figure 4;
6 illustrates operation of the SCR reactor according to the operation mode shown in FIG. 4; FIG.
FIG. 7 is a graph illustrating the internal temperature of the SCR reactor according to the operation mode shown in FIG. 4; FIG.
8 is a graph illustrating the internal pressure distribution according to the venting mode of the SCR reactor shown in FIG.
9 is a configuration diagram of a low-pressure SCR system according to another embodiment of the present invention.
10 is a flowchart illustrating a method of controlling a low pressure SCR system according to an embodiment of the present invention.

Hereinafter, a low pressure SCR system and a control method thereof according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a configuration diagram of a low pressure SCR system according to an embodiment of the present invention, and FIG. 4 is a configuration diagram of an SCR reactor according to an embodiment of the present invention.

In the low-pressure SCR system according to an embodiment of the present invention, the bypass line 133 is integrally disposed inside the SCR reactor 130 as shown, thereby simplifying the configuration and enabling miniaturization / modularization.

In Figure 3, the SCR reactor 130 is installed on the exhaust line 120 extending from the rear end of the engine T / C 110.

The exhaust gas generated from the engine is discharged to the exhaust line 120 through the T / C 110. [

The SCR reactor 130 is equipped with a catalyst 132 for SCR catalytic reaction with the exhaust gas and is provided at the front and rear ends of the SCR reactor 130 for passing and blocking the exhaust gas flowing through the exhaust line 120. [ An inlet valve 137 and an outlet valve 138 are provided.

4, the internal space of the SCR reactor 130 is largely divided into a bypass line 133 and a main exhaust passage 139 in which a catalyst 132 is installed.

At this time, the main exhaust passage 139 is a space where the SCR catalytic reaction for removing NOx in the exhaust gas occurs, whereas the bypass line 133 is a space for bypassing the exhaust gas without performing the SCR catalytic reaction.

The bypass line 133 is installed inside the SCR reactor 130 such that the bypass line 133 is partitioned from the main exhaust passage 139 in the SCR reactor 130 where the catalyst 132 is located.

A bypass valve 136 is provided at the front end of the bypass line 133.

In addition, a nozzle 134 may be installed at the rear end of the bypass line 133.

Referring again to FIG. 3, a reducing agent supply unit 150 is installed at the front end of the SCR reactor 130 to generate ammonia gas, which is a reducing agent, from solid ammonium carbonate and supplies the generated ammonia gas to the SCR reactor 130.

Since the reducing agent supplying device 150 can generate ammonia by vaporizing the solid ammonium carbonate at a relatively low temperature (for example, about 58 ° C or higher), the use of the reducing agent supplying device 150 can provide an additional heat source necessary for the decomposition of the reducing agent and a separate urea hydrolyzing device .

The control device 200 can implement the plurality of operation modes related to the exhaust gas treatment by operating the inlet valve 137, the bypass valve 136 and the outlet valve 138 described above.

That is, the control device 200 selects one of a plurality of operation modes including the SCR mode, the bypass mode, and the venting mode, and selects the bypass valve 136, the inlet valve 137, and the outlet valve 138 ) To adjust the opening and closing states of the valves 136, 137, 138 appropriately.

In such a configuration, in all the operation modes including the bypass mode, the exhaust gas discharged from the engine passes through the inside of the SCR reactor 130, so that while the exhaust gas acts as the main heat source and the engine is running, The internal temperature of the reactor 130 can always be maintained above the exhaust gas temperature (about 190 to 290 ° C).

The heating device 160 is an additional heat source of exhaust gas as a main heat source and generates high temperature and high pressure air under control of the control device 200 when necessary and supplies it to the main exhaust passage 139 where the catalyst 132 is located, Thereby raising the internal temperature of the heater 130.

5 is an exploded perspective view of the SCR reactor shown in FIG.

As shown, the SCR reactor 130 according to one embodiment includes a housing 131, a catalyst 132, a bypass line 133, a perforated plate 135, a main exhaust passage 139, and the like.

A bypass valve 136 is provided at a front end of the bypass line 133 and an inlet valve 137 and an outlet valve 138 are provided at the front and rear ends of the SCR reactor 130, respectively.

The bypass line 133 is installed to pass through the inside of the housing 131 and the front end of the bypass line 133 having the bypass valve 136 is inserted into the perforated plate 135, .

The bypass valve 136 is provided at the front end of the bypass line 133 and is opened and closed under the control of the control device 200.

The main exhaust passage 139 is formed by partitioning the bypass line 133 in the SCR reactor 130 into a space in which the catalyst 132 is located and causes an SCR catalytic reaction with the exhaust gas.

In one embodiment, the bypass line 133 described above can be installed to pass through the catalyst 132 in the middle of the SCR reactor 130, wherein the main exhaust passageway 139 is located within the SCR reactor 130 And is located at the periphery of the bypass line 133. [

The inlet valve 137 is installed at the inlet of the SCR reactor 130 and selectively opens and closes one side of the main exhaust passage 139 or one side of the bypass line 133 under the control of the control device 200.

The outlet valve 138 is installed at the outlet of the SCR reactor 130 and selectively opens and closes the other side of the main exhaust passage 139 or the bypass line 133 under the control of the control device 200.

6 is a view illustrating operation of the SCR reactor according to the operation mode shown in FIG.

6, (a) is an SCR mode, (b) is a bypass mode, and (c) is a venting mode.

the controller 200 closes the bypass valve 136 and opens the inlet valve 137 and the outlet valve 138 in the SCR mode of FIG. And passes through the catalyst 132 of the catalyst 139.

In this case, as the exhaust gas passes through the catalyst 132 of the main exhaust passage 139, the SCR catalytic reaction with the exhaust gas occurs, and the nitrogen oxide in the exhaust gas is removed.

the control device 200 closes the inlet valve 137 and the outlet valve 138 to close the exhaust passage 139 and the bypass valve 136 is closed in the bypass mode of FIG. So that the exhaust gas is passed through the bypass line 133.

In this case, the exhaust gas is directly discharged to the rear end of the SCR reactor 130 through the bypass line 133 without the SCR catalyst reaction, and is discharged at a high temperature exhaust gas (about 190 to 290 ° C) The interior of the SCR reactor 130 is always maintained at a high temperature, so that separate operation preparation and preheating are unnecessary.

Further, as the interior of the SCR reactor 130 is sealed during the bypass operation of the exhaust gas, the high-temperature high-pressure air is supplied from the heating device 160 to the additional heat source while utilizing the exhaust gas heat of high temperature, The internal temperature of the SCR reactor 130 may be raised to the ABS gasification temperature (about 350 ° C) or higher to decompose and remove the ABS and regenerate the catalyst (for example, when entering the pollution outside the emission control area).

In the conventional case in which the bypass line 30 is provided separately from the SCR reactor 40, the internal temperature of the SCR reactor 40 is maintained at a room temperature (for example, About 25 < 0 > C). In this case, it is necessary to raise the temperature by ΔT = 325 ° C. in order to raise the temperature from 25 ° C. to 350 ° C.

On the other hand, when the bypass line 133 is integrated into the SCR reactor 130 as in the embodiment of the present invention, even when the exhaust gas is bypassed, the internal temperature of the SCR reactor 130 becomes lower than the exhaust gas temperature, ° C., it is sufficient to raise the temperature by only ΔT = 150 ° C. in order to raise the temperature from 200 ° C. to 350 ° C.

the control device 200 closes the inlet valve 137 and throttles the bypass valve 136 and the outlet valve 138 so that the residual exhaust gas of the main exhaust passage 139 Thereby removing internal sulfur components, PM, soot, etc., which cause corrosion.

FIG. 7 is a graph illustrating an internal temperature distribution according to operation modes of the SCR reactor shown in FIG.

In FIG. 7, M1, M2, and M3 illustrate the venting mode (at the time of high sea operation), the SCR mode (when operating the emission control area), and the bypass mode (at the time of high sea operation).

T11 and T12 are the venting interval and the operation preparation interval in the venting mode, T21 and T22 are the driving interval and heating interval in the SCR mode, respectively, and T31 is the catalyst regeneration interval in the bypass mode.

The bypass line 30 is provided separately from the SCR reactor 40 so that the internal temperature of the SCR reactor 40 is maintained at room temperature (about 25 ° C.) during the bypass operation of the exhaust gas, (R1, R2), which causes corrosion.

In addition, a lot of additional heat sources are inevitably consumed due to the low internal temperature of the SCR reactor 40 in the operation preparation period T12, the catalyst regeneration period T31, and the like.

Compared to this prior art, the internal temperature of the SCR reactor 130 according to one embodiment of the present invention is the same as the temperature of the engine 100, except when the engine is paused (T22, e.g., Sulfuric acid condensation does not occur as it is always maintained at the exhaust gas temperature (about 200 캜 or above) during operation.

The SCR reactor 130 (also referred to as " SCR ") is connected to the operation preparation section T12, the operation section T21 and the catalyst regeneration section T31, including the heating section T22, ) Due to the small temperature difference between the present internal temperature and the target temperature.

At this time, the target temperatures of the activation preparation period T12, the activation period T21, the heating period T22 and the catalyst regeneration period T31 are, for example, a preheating temperature (about 180 to 200 DEG C) (About 230 to 250 DEG C), the SCR reaction temperature minimum threshold (about 200 DEG C), and the ABS vaporization temperature (about 350 DEG C).

On the other hand, in the case of the catalyst regeneration period T31 during the bypass mode M3, the control device 200 uses the heating device 160 as an additional heat source to heat the high temperature, high pressure air generated from the heating device 160, And may be supplied to the passage 139 to raise the internal temperature of the SCR reactor 130 to an ABS vaporization temperature (about 350 ° C) or higher.

At this time, since the internal temperature of the SCR reactor 130 is basically high due to the high temperature exhaust gas, the ABS gasification temperature can be easily satisfied with only a small heat source.

The control device 200 controls the heating device 160 to heat the heating device 160 in the heating period T22 during which the operation of the engine is suspended during the preparation period T12 before the SCR mode M2 is entered or during the SCR mode M2. Temperature high-pressure air generated therefrom can be supplied to the main exhaust passage 139 to maintain the internal temperature of the SCR reactor 130 at the SCR reaction temperature (about 200 to 250 ° C) or more.

8 is a graph illustrating the internal pressure distribution according to the venting mode of the SCR reactor shown in FIG.

8 (a) illustrates the internal pressure distribution of the SCR reactor 130 when the outlet valve 138 is opened in the bypass state, and (b) and (c) (X in (a)) and the vertical direction (y in (a)), respectively.

When the outlet valve 138 is throttled at the time of bypass operation of the exhaust gas, the flow rate of the SCR is increased by the nozzle 134 as shown in the figure and the SCR reactor 130 ) Acts like an ejector to exhaust the residual exhaust gas.

Further, as illustrated in FIGS. 13B and 13C, as the exhaust gas flow rate increases from 10 m / s to 20 m / s to 30 m / s, the differential pressure inside and outside the nozzle 134 at the rear end of the bypass line 133, The difference in pressure between the central portion and the surface portion of the heat exchanger 130 is increased.

In the venting mode, the bypass valve 136 and the outlet valve 138 are throttled in a state in which the inlet valve 137 is closed to generate an exhaust gas flow rate over a constant speed, The residual exhaust gas can be discharged to suck and remove the inner sulfur component, PM / soot, and the like.

9 is a configuration diagram of a low pressure SCR system according to another embodiment of the present invention.

The SCR reactor 130 can be miniaturized / modularized and can be installed in various ways. For example, the SCR reactor 130 can be installed for each engine T / C 110 as shown in FIG.

10 is a flowchart illustrating a method of controlling a low-pressure SCR system according to an embodiment of the present invention.

First, the control device 200 selects one of the SCR mode, the bypass mode, and the venting mode as the operation mode of the SCR reactor 130 (S110).

For example, the control device 200 may select the bypass mode when the ship is traveling on the high seas, and may select the bypass mode when the ship is traveling the emission regulating area.

When the measured differential pressure is equal to or greater than a predetermined value, the pressure difference between the upstream and downstream ends of the SCR reactor 130 in the bypass mode is measured. In order to remove the sulfur component, PM, or soot in the SCR reactor 130, It is possible to switch to the venting mode.

The controller 200 controls the bypass valve 136 at the upstream side of the bypass line 133 and the main exhaust passage 139 at the inlet of the SCR reactor 130 according to the operation mode selected at the above- An inlet valve 137 for selectively opening and closing one side of the bypass line 133 and an inlet valve 137 for selectively opening and closing the other side of the main exhaust passage 139 and the bypass line 133 provided at the outlet of the SCR reactor 130 The outlet valve 138 is adjusted (S120).

Specifically, when the SCR mode is selected in step S110, the controller 200 closes the bypass valve 136 and opens the inlet valve 137 and the outlet valve 138 to exhaust the exhaust gas to the main exhaust passage 139, (Step S121) so that the SCR catalytic reaction for removing the nitrogen oxides in the exhaust gas occurs.

When the bypass mode is selected in step S110, the control device 200 closes the inlet valve 137 and the outlet valve 138 to close the exhaust passage 139, opens the bypass valve 136, The exhaust gas is directly discharged to the rear end of the SCR reactor 130 through the bypass line 133 without catalytic reaction (S122).

The controller 200 closes the inlet valve 137 and throttles the bypass valve 136 and the outlet valve 138 so that the main exhaust passage 138 in the SCR reactor 130 is opened, (-) pressure state in the SCR reactor 130 by discharging the residual exhaust gas from the main exhaust passage 139 to the outside to suck and remove the sulfur component, PM, or soot in the SCR reactor 130 (S123) .

The configuration of the low-pressure SCR system and the control method thereof according to the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the technical idea of the present invention.

110: engine T / C, 120: exhaust line,
130: SCR reactor, 131: housing,
132: catalyst, 133: bypass line,
134: nozzle, 135: perforated plate,
136: bypass valve, 137: inlet valve,
138: outlet valve, 139: main exhaust passage,
150: Reducing agent supply device, 160: Heating device,
200: Control device

Claims (12)

SCR reactor;
A bypass line installed in the SCR reactor;
A bypass valve provided at a front end of the bypass line;
A main exhaust passage in the SCR reactor partitioned with the bypass line and in which the catalyst is located;
An inlet valve installed at an inlet of the SCR reactor for selectively opening and closing one of the main exhaust passage and the bypass line; And
And an outlet valve installed at an outlet of the SCR reactor for selectively opening and closing the main exhaust passage and the other side of the bypass line,
Wherein the bypass valve, the inlet valve, and the outlet valve are adjusted according to the operation mode by selecting one of the SCR mode, the bypass mode, and the venting mode. The method according to claim 1,
Closing the bypass valve and opening the inlet valve and the outlet valve to allow the exhaust gas to pass through the catalyst of the main exhaust passage,
Closing the inlet valve and the outlet valve to close the main exhaust passage and open the bypass valve to pass the exhaust gas through the bypass line,
Pressure SCR system in which the inlet valve is closed and the bypass valve and the outlet valve are throttled to discharge residual exhaust gas in the main exhaust passage in the venting mode. The method according to claim 1,
Wherein the exhaust gas discharged from the engine in all the operation modes is passed into the SCR reactor so that the internal temperature of the SCR reactor is maintained above the exhaust gas temperature while the engine is running. The method according to claim 1,
Further comprising a nozzle disposed downstream of the bypass line. The method according to claim 1,
Further comprising a reducing agent supply device for generating ammonia gas from the solid ammonium carbonate and feeding it to the front end of the SCR reactor. The method according to claim 1,
Further comprising a heating device for generating high-temperature, high-pressure air for raising the internal temperature of the SCR reactor and supplying it to the main exhaust passage. The method according to claim 6,
In the bypass mode, a low-pressure SCR system in which high-temperature, high-pressure air generated from the heating device is supplied to the main exhaust passage to raise the internal temperature of the SCR reactor to an ABS (Ammonium Bisulfate) gasification temperature or higher. The method according to claim 6,
Temperature high-pressure air generated from the heating device to the main exhaust passage before entering the SCR mode or when the engine operation is temporarily stopped during the SCR mode, the internal temperature of the SCR reactor is increased to the SCR reaction temperature or higher Low-pressure SCR system to maintain. The method according to claim 1,
Wherein the SCR reactor is installed for each engine T / C (Turbo Charger). The method according to claim 1,
Wherein the bypass line is installed to pass through the catalyst in a central portion of the SCR reactor and wherein the main exhaust passage is located at a periphery of the bypass line in the SCR reactor. A control method of a low-pressure SCR system in which an SCR reactor includes a bypass line and a main exhaust passage in which a catalyst is located,
Selecting one of an SCR mode, a bypass mode, and a venting mode; And
An inlet valve disposed at an inlet of the SCR reactor and selectively opening and closing one side of the main exhaust passage and the bypass line in accordance with the operation mode; And adjusting an outlet valve for selectively opening and closing the main exhaust passage and the other side of the bypass line. 12. The method of claim 11,
Closing the bypass valve and opening the inlet valve and the outlet valve to allow exhaust gas to pass through the catalyst in the main exhaust passage in the SCR mode;
Closing the inlet valve and the outlet valve to close the main exhaust passage and opening the bypass valve to pass the exhaust gas through the bypass line when the bypass mode is selected; And
And closing the inlet valve and throttle the bypass valve and the outlet valve to discharge residual exhaust gas in the main exhaust passage when the engine is in the venting mode.

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