KR102067851B1 - Selective catalytic reduction system - Google Patents

Abstract

The SCR system receives an exhaust gas discharged from the engine and processes it through an SCR catalyst installed therein to remove nitrogen oxides in the exhaust gas; The operation mode is controlled to any one of the first mode, the second mode, and the third mode, in which the exhaust gas flowing into the SCR reactor is passed as it is, and in the second mode, the ammonia supply unit is driven to enter the SCR reactor. In the third mode, the exhaust gas treatment is performed by supplying ammonia to the exhaust gas, and in the third mode, a controller is configured to adjust the engine load to raise the temperature of the exhaust gas flowing into the SCR reactor above the vaporization temperature of ABS to perform catalyst regeneration. . Exhaust gas from the engine is configured to pass through the SCR reactor regardless of the operating mode.
Accordingly, the bypass line is omitted, thereby reducing installation space and material man-hours, simplifying system operation, and efficiently regenerating the SCR catalyst by adjusting the engine load in a structure without the bypass line.

Description

SCR system {SELECTIVE CATALYTIC REDUCTION SYSTEM}

The present invention relates to an SCR system, and more particularly, to an SCR system that can reduce installation space and material man-hours, simplify system operation, and efficiently recycle an SCR catalyst.

In general, a ship is installed with a main engine driving a propeller to propel a ship, and a plurality of power generation engines for supplying power to various equipment or equipment mounted on the ship.

Exhaust gas emitted after combustion in such a ship engine contains a number of suspended particulates and harmful substances such as NOx, which is a nitrogen oxide, and SOx, which are sulfur oxides.

Therefore, the exhaust line of the engine is equipped with a diesel particulate filter (DPF), a selective catalytic reduction (SCR), and a scrubber (SCRubber, SOx removal) to remove harmful components in the exhaust gas.

Among these, the SCR system includes an SCR reactor having an internal catalyst layer and installed on an exhaust line, and reacts nitrogen oxides (NOx) in the exhaust gas chemically with a reducing agent such as ammonia (NH3) and urea (Urea) in the catalyst layer. It is decomposed into harmless water and nitrogen and then discharged.

The SCR catalyst provided in the catalyst layer is composed of a porous catalyst filter formed by extrusion or metallic coating, and is implemented in a form in which one or several SCR catalysts are continuously installed in the SCR reactor.

When these SCR systems remove nitrogen oxides in the exhaust gas, by-products of ABS (Ammonium Bisulfate: NH4HSO4) are produced, which are gaseous above a certain temperature (eg 340 ° C), but liquid below a certain temperature. To adhere to the SCR catalyst.

ABS causes poisoning of the SCR catalyst and thus lowers the denitrification performance. As a result, the porous SCR catalyst is blocked, thereby increasing the back pressure and disturbing the flow of the exhaust gas.

In order to solve this problem, conventionally, the high temperature is provided to the SCR reactor as a separate heat source in a state in which the operation of the SCR reactor is stopped to perform a regeneration process in which ABS is melted and evaporated. There is a problem.

In addition, existing SCR systems for large engines generally have a bypass line that bypasses the SCR reactor, in which case the piping, valves and exhaust gas paths forming the bypass line can be selected as the SCR reactor side or the bypass line side. Since additional devices such as various valves must be installed, installation space and material maneuver are excessive, and system operation is complicated.

Korean Unexamined Patent Publication No. 10-2014-0041098 (Published: 2014.04.04.)

The present invention has been proposed to solve the problems of the prior art as described above, the bypass line can be omitted, can be installed while occupying limited space in the vessel, can save material maneuver, simplify the system operation It is an object of the present invention to provide an SCR system.

In addition, the present invention provides an SCR system capable of efficiently regenerating the SCR catalyst by adjusting the engine load in the SCR system in which the bypass line is omitted, and improving the thermal efficiency by reducing fuel consumption during the catalyst regeneration process. Has its purpose.

The technical problem to be achieved by the present invention is not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

SCR system according to the present invention for achieving the above object is an SCR reactor for receiving the exhaust gas discharged from the engine to process through the SCR catalyst installed therein to remove nitrogen oxides in the exhaust gas; An ammonia supply unit supplying ammonia to the SCR reactor for exhaust gas treatment; And controlling the operation mode to any one of a first mode, a second mode, and a third mode, in which the exhaust gas flowing into the SCR reactor is passed as it is, and in the second mode, the ammonia supply unit is driven to drive the SCR. The exhaust gas treatment is performed by supplying ammonia to the exhaust gas flowing into the reactor, and in the third mode, the engine load is adjusted to raise the temperature of the exhaust gas flowing into the SCR reactor above the vaporization temperature of ABS to perform catalyst regeneration. And an exhaust gas discharged from the engine passes through the SCR reactor regardless of the operation mode.

The SCR system according to the present invention may further include a temperature measuring unit for measuring the temperature of the exhaust gas flowing into the SCR reactor, in which case the control unit measures the difference between the temperature measured by the temperature measuring unit and the vaporization temperature of the ABS. On the basis of the increase in the engine load to increase the exhaust gas temperature, the catalyst can be carried out by heating the SCR reactor with a high temperature exhaust gas.

SCR system according to the present invention comprises a soot blower for removing the soot by injecting compressed air; And an ABS vaporizer that injects heated air or steam into the soot blower to increase the ambient temperature of the SCR catalyst, in which case the controller adjusts the engine load in a third mode and the soot. Catalyst regeneration may be performed by driving the blower and the ABS vaporizer together.

In the SCR system according to the present invention, the ammonia supply unit comprises a urea decomposition device for decomposing urea into ammonia gas; And an ammonia injector receiving ammonia gas from the urea cracker and injecting the ammonia gas into the front end of the SCR reactor.

In the SCR system according to the present invention, the controller may perform catalyst regeneration by generating a catalyst regeneration event at predetermined intervals.

The SCR system according to the present invention may further include a pressure measuring unit for measuring the differential pressure between the front end and the rear end of the SCR catalyst provided in the SCR reactor, in which case the control unit is a preset pressure differential measured through the pressure measuring unit If the value is equal to or greater than the value, the catalyst regeneration event is generated to enter the third mode, the engine load is adjusted by adjusting the engine load in the third mode, and the third mode may be terminated when the measured differential pressure becomes equal to or less than a predetermined value.

SCR system according to the present invention may further include a denitrification efficiency measuring unit for measuring the denitrification efficiency from the nitrogen oxide concentration difference between the front end and the rear end of the SCR catalyst provided in the SCR reactor, the control unit in this case the denitrification efficiency measurement When the denitrification efficiency measured through the negative value is less than or equal to a predetermined value, a catalyst regeneration event is generated to enter the third mode, and then the catalyst regeneration is performed by adjusting the engine load in the third mode, and the measured denitrification efficiency is greater than or equal to the preset value. If the third mode can be terminated.

In the SCR system according to the present invention, the control unit may drive the ammonia supply unit together in a third mode to perform the exhaust gas treatment operation and the catalyst regeneration operation through the SCR reactor.

In the SCR system according to the present invention, the control unit may perform a catalyst regeneration operation in a state in which the exhaust gas treatment operation through the SCR reactor is stopped by stopping driving of the ammonia supply unit in a third mode.

In the SCR system according to the present invention, the SCR reactor may be installed at the rear of the turbo charger (T / C).

SCR system according to the present invention can be installed while bypassing the bypass line occupies less space in the ship, can reduce the material maneuver, and can simplify the system operation.

In addition, the SCR system according to the present invention can efficiently recycle the SCR catalyst by adjusting the engine load in the SCR system in which the bypass line is omitted, and improve the thermal efficiency by reducing the fuel consumption in the catalyst regeneration process.

1 is a schematic structural diagram of an SCR system according to an embodiment of the present invention.
Figure 2 is an exemplary configuration for explaining in more detail the catalyst regeneration operation of the SCR reactor shown in FIG.
3 is a table illustrating the exhaust gas temperature according to the change of the engine load.
4 is a graph illustrating the change in denitrification efficiency to explain the catalyst regeneration effect.

Hereinafter, an SCR system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the SCR system according to the present invention, the bypass line bypassing the SCR reactor is eliminated, thereby reducing installation space and material man-hours that may be excessively related thereto.

As the bypass line is omitted entirely, the exhaust gas from the engine always passes through the SCR reactor without the need to select the exhaust gas path to the SCR reactor side or the bypass line side.

In addition, bypass lines are omitted, allowing the SCR catalyst to be efficiently regenerated by adjusting the engine load in a simplified SCR system to increase the exhaust gas temperature and raising the SCR reactor through this high temperature exhaust gas.

The catalyst regeneration operation may be performed in parallel with the exhaust gas treatment operation during operation of the SCR reactor, or may be performed while the operation of the SCR reactor is stopped to achieve a more complete catalyst regeneration effect.

1 is a schematic structural diagram of an SCR system according to an embodiment of the present invention.

Referring to FIG. 1, the exhaust gas discharged from the engine 10 is led to the SCR reactor 40 through an exhaust line after driving the turbo charger 20.

The SCR reactor 40 receives the exhaust gas flowing through the engine 10 and the T / C 20 and processes it through an SCR catalyst installed therein to remove nitrogen oxides in the exhaust gas.

The ammonia supply unit 30 supplies ammonia as a reducing agent to the SCR reactor 40 for exhaust gas treatment.

The ammonia supply unit 30 described above is a urea decomposition device 31 for decomposing urea into ammonia gas, and an ammonia injection device 32 receiving ammonia gas from the urea decomposition device 31 and injecting it into the front end of the SCR reactor 40. It can be configured to include).

The urea decomposition device 31 may convert urea into ammonia gas using a burner, an electric furnace, or an energy source such as a microwave.

In addition, one end of the ammonia injector 32 may be implemented in the form of an ammonia injection grid (AIG) so that ammonia gas may be directly injected to the exhaust line. In some embodiments, ammonia injector 32 in the form of a nozzle may be used.

As the reducing agent used in the ammonia supply unit 30, not only liquid urea but also solid phase materials, such as solid urea and ammonium carbonate, may be applied, and these materials are decomposed to form ammonia gas in the SCR reactor 40. It is injected at the shear.

The controller 100 may control the operation mode of the SCR system configured as described above in any one of the first mode, the second mode, and the third mode. Since the bypass line is not provided, the exhaust gas flowing into the exhaust line via the engine 10 and the T / C 20 is always in the SCR reactor 40 in both the first to third modes, that is, regardless of the operation mode. Is configured to pass through).

The controller 100 passes the exhaust gas flowing into the SCR reactor 40 as it is in the first mode, and drives the ammonia supply unit 30 while driving the SCR reactor 40 in the second mode, thereby driving the SCR reactor 40. Ammonia is supplied to the exhaust gas flowing into the exhaust gas, and the exhaust gas treatment is performed.In the third mode, the engine load is adjusted to adjust the temperature of the exhaust gas flowing into the SCR reactor 40 to the vaporization temperature of ABS (Ammonium Bisulfate: NH4HSO4). The catalyst regeneration is performed by raising above.

In the first mode, the operation of the SCR reactor 40 is stopped and the exhaust gas flowing into the SCR reactor 40 is allowed to pass through as it is without exhaust gas treatment and catalyst regeneration.

If the vessel enters the ECA (Emission Control Area) area while maintaining the first mode of simply passing the exhaust gas, the control unit 100 switches to the second mode and drives the ammonia supply unit 30 in the second mode. The SCR reactor 40 is operated while supplying ammonia to perform an exhaust gas treatment operation for removing nitrogen oxides in the exhaust gas.

Then, when the catalyst regeneration event occurs, the control unit 100 switches the operation mode of the SCR system to the third mode, and then the temperature of the exhaust gas flowing into the SCR reactor 40 in the third mode is higher than or equal to the vaporization temperature of the ABS. To increase the catalyst regeneration operation. At this time, the controller 100 can effectively increase the temperature of the exhaust gas above the vaporization temperature of the ABS by adjusting the engine load.

When switching to the third mode, the controller 100 may perform a catalyst regeneration operation regardless of whether the SCR reactor 40 is operated.

That is, in the third mode, the control unit 100 may drive the ammonia supply unit 30 together to perform exhaust gas treatment and catalyst regeneration through the SCR reactor 40, or stop the driving of the ammonia supply unit 30 to stop the SCR reactor. Only catalyst regeneration may be performed while the exhaust gas treatment through 40 is stopped.

For example, when a catalyst regeneration event occurs while driving the SCR reactor 40 while performing the exhaust gas treatment while driving the ammonia supply unit 30 in the second mode, the controller 40 may control the third mode from the second mode. Switch to to perform a catalyst regeneration operation, while continuing to drive the ammonia supply unit 30 in the third mode can continue the catalyst regeneration operation while continuing the exhaust gas treatment operation through the SCR reactor (40).

Alternatively, the controller 100 may stop the driving of the ammonia supply unit 30 when switching to the third mode to stop the exhaust gas treatment operation through the SCR reactor 40 for a more complete catalyst regeneration operation. You can also perform an operation.

Meanwhile, although FIG. 1 illustrates an SCR system in which the SCR reactor 40 is installed at the rear end of the T / C 20, the present invention is not limited thereto, and the SCR reactor 40 may include T / C ( It can also be applied to SCR systems installed at the front end of 20).

However, when the SCR reactor 40 is installed at the rear end of the T / C 20, as the exhaust gas is driven into the SCR reactor 40 after driving the T / C 20, the SCR reactor 40 is Since the exhaust gas is discharged at a relatively low temperature as compared to the case where it is installed at the front end of the T / C 20, the poisoning generation and the denitrification performance of the catalyst due to the deposition of ABS becomes a greater problem.

Therefore, the above-described catalyst regeneration operation can be applied more effectively.

FIG. 2 is an exemplary configuration diagram illustrating the catalyst regeneration operation of the SCR reactor shown in FIG. 1 in more detail.

Referring to FIG. 2, an SCR catalyst 41 for exhaust gas treatment is installed in the SCR reactor 40.

In addition, the SCR reactor 40 may be additionally provided with a temperature measuring unit 70, a pressure measuring unit 80 or a denitrification efficiency measuring unit 90.

The temperature measuring unit 70 is installed inside the SCR reactor 40, or at the front end or the rear end thereof, measures the temperature of the exhaust gas flowing into the SCR reactor 40, and applies the measured temperature to the controller 100. .

The pressure measuring unit 80 measures the differential pressure between the front end and the rear end of the SCR catalyst provided in the SCR reactor 40, and applies the measured differential pressure to the controller 100.

The denitrification efficiency measuring unit 90 measures the denitrification efficiency from the difference between nitrogen oxide concentrations at the front and rear ends of the SCR catalyst 41 provided in the SCR reactor 40, and applies the measured denitrification efficiency to the controller 100.

When the catalyst regeneration event occurs, the control unit 100 increases the engine load based on the difference between the current temperature measured by the temperature measuring unit 70 and the vaporization temperature of the ABS to increase the exhaust gas temperature, and Catalyst regeneration may be performed by raising the SCR reactor 40.

The controller 100 may periodically generate a catalyst regeneration event at predetermined intervals, for example, while the ship operates the high seas and the SCR reactor 40 is not operated.

 In addition, the controller 100 may generate a catalyst regeneration event when the differential pressure measured by the pressure measuring unit 80 is greater than or equal to a predetermined value.

In this case, as the catalyst regeneration event occurs, the controller 100 enters the third mode, adjusts the engine load in the third mode, increases the exhaust gas temperature, and performs the catalyst regeneration, and performs the pressure measurement unit 80. When the measured differential pressure is less than or equal to the preset value, the third mode is terminated. After the termination of the third mode, it may return to the original operation mode (first mode or second mode).

In addition, the control unit 100 may generate a catalyst regeneration event when the denitrification efficiency measured by the denitrification efficiency measurement unit 90 is equal to or less than a predetermined value.

In this case, as the catalyst regeneration event occurs, the controller 100 enters the third mode, adjusts the engine load in the third mode, increases the exhaust gas temperature, and performs the catalyst regeneration, and performs the denitrification efficiency measurement unit 90. The third mode is terminated when the denitrification efficiency measured through the reference value is greater than or equal to a preset value. After the termination of the third mode, it may return to the original operation mode (first mode or second mode).

In addition, in one embodiment, when the controller 100 enters the third mode and performs catalyst regeneration, the controller 100 may adjust the engine load and drive the soot blower 50 and the ABS vaporizer 60 together.

In addition to the ABS, the SCR catalyst 41 may deposit soot generated by incomplete combustion of fuel, which is also a major cause of deterioration of the catalyst performance.

The soot blower 50 injects compressed air to the SCR catalyst 41, and is installed at the front of the SCR catalyst 41 at a predetermined interval from the SCR catalyst 41, and operates under the control of the controller 100 to exhaust the air. By blowing compressed air in the same direction as the flow of gas, the soot deposited on the surface of the SCR catalyst 41 is removed.

The soot blower 50 described above is controlled by the nozzle unit 51 for injecting compressed air toward the SCR catalyst 41, the compressed air supply unit 53 for supplying the compressed air, and the control unit 100 under the control of the opening amount. It may include a valve 55 for controlling the amount of compressed air injected into the SCR catalyst 41 through the unit 51.

The ABS vaporizer 60 injects heated air or steam into the soot blower 50 to increase the ambient temperature of the SCR catalyst 41 to support the catalyst regeneration operation.

The above-described ABS vaporizer 60 is controlled by the hot gas supply unit 61 and the controller 100 to supply hot gas such as heated air or steam by using a burner, an electric furnace, radiant heat, and the like. And a valve 63 for adjusting the amount of hot gas provided through the blower 50 into the SCR reactor 40.

3 is a table illustrating an exhaust gas temperature according to an engine load change. And, Figure 4 is a graph illustrating a change in denitrification efficiency to explain the catalyst regeneration effect.

As described above, the control unit 100 may change the engine load to increase the exhaust gas temperature flowing into the SCR reactor 40 and thereby perform a catalyst regeneration operation.

Referring to the table illustrated in FIG. 3, as the operating load of the engine 10 increases to 25%, 50%, 70%, and 100%, the exhaust gas temperature rises to 230 ° C, 240 ° C, 260 ° C, and 280 ° C. do.

That is, it can be confirmed that the exhaust gas temperature can be increased by increasing the load of the engine 10 during the catalyst regeneration operation.

Status A, Status B, and Status C of FIG. 4 illustrate the denitrification efficiency (NOx Conversion) in the operation state (Fresh), poisoned state (Aged), and regeneration state of the SCR system, respectively.

For example, when the vessel enters the ECA (Emission Control Area) area, the controller 100 drives the ammonia supply unit 30 to drive the SCR reactor 40 while injecting ammonia as a reducing agent to process the exhaust gas.

At this time, since the exhaust gas discharged from the engine 10 in the configuration of the above-described SCR system is configured to always pass through the SCR reactor 40 without a separate bypass line, the control unit 100 is the operation of the SCR reactor 40 The catalyst regeneration operation can be performed independently of the above.

In other words, the catalyst regeneration operation may be performed while injecting ammonia and driving the SCR reactor 40 to continue the exhaust gas treatment operation, and the exhaust gas treatment operation is stopped by stopping the operation of the ammonia injection and the SCR reactor 40. It is also possible to perform a catalyst regeneration operation at.

Referring to FIG. 4, when the poisoning of the SCR catalyst 41 occurs and the denitrification efficiency is lowered (Status A → Status B), the controller 100 continuously operates the SCR reactor 40 in the ECA area while simultaneously operating the engine. The catalyst regeneration can be performed by changing the operating load of (10) to raise the exhaust gas temperature (Status B-> Status C).

Alternatively, the controller 100 enters the high seas out of the ECA region for more complete catalyst regeneration, and stops the operation of the SCR reactor 40 by stopping the ammonia injection, and in this state, the operating load of the engine 10 is stopped. It is also possible to carry out catalyst regeneration by changing the temperature by increasing the exhaust gas temperature (Status B-> Status C).

The configuration of the SCR system according to the present invention is not limited to the above-described embodiments, and may be variously modified and implemented within the range permitted by the technical idea of the present invention.

10: engine
20: T / C
30: ammonia supply
40: SCR reactor
50, 60: catalyst regeneration unit
100: control unit

Claims (10)

An SCR reactor receiving nitrogen gas from the exhaust gas by treating the exhaust gas discharged from the engine through an SCR catalyst installed therein;
An ammonia supply unit supplying ammonia to the SCR reactor for exhaust gas treatment; And
Control the operation mode to any one of the first mode, the second mode and the third mode, in the first mode to pass the exhaust gas flowing into the SCR reactor as it is, in the second mode to drive the ammonia supply unit in the SCR reactor Ammonia is supplied to the exhaust gas introduced into the exhaust gas, and the exhaust gas treatment is performed. In the third mode, the engine load is adjusted to increase the temperature of the exhaust gas flowing into the SCR reactor above the vaporization temperature of ABS to perform catalyst regeneration. It includes a control unit,
SCR system configured to allow the exhaust gas from the engine to pass through the SCR reactor regardless of the operating mode.
The method of claim 1,
Further comprising a temperature measuring unit for measuring the temperature of the exhaust gas flowing into the SCR reactor,
The control unit increases the engine load on the basis of the difference between the temperature measured by the temperature measuring unit and the vaporization temperature of the ABS to increase the exhaust gas temperature and the temperature of the SCR reactor with a high temperature exhaust gas to perform catalyst regeneration.
The method of claim 1,
A soot blower that blows compressed air to remove the soot; And
Including the ABS vaporizer to increase the ambient temperature of the SCR catalyst by injecting heated air or steam to the soot blower,
The control unit adjusts the engine load in the third mode and drives the soot blower and the ABS vaporizer together to perform catalyst regeneration.
The method of claim 1,
The ammonia supply unit,
A urea cracker for decomposing urea into ammonia gas; And
SCR system comprising an ammonia injector for receiving ammonia gas from the urea cracker and injecting the ammonia gas in front of the SCR reactor.
The method of claim 1,
The control unit generates a catalyst regeneration event every predetermined period to perform the catalyst regeneration.
The method of claim 1,
Further comprising a pressure measuring unit for measuring the differential pressure between the front end and the rear end of the SCR catalyst provided in the SCR reactor,
The control unit generates a catalyst regeneration event when the differential pressure measured by the pressure measuring unit is greater than or equal to a preset value, enters the third mode, adjusts the engine load in the third mode, and performs the catalyst regeneration. The SCR system terminates the third mode when the set value is less than the set value.
The method of claim 1,
Further comprising a denitrification efficiency measuring unit for measuring the denitrification efficiency from the nitrogen oxide concentration difference between the front end and the rear end of the SCR catalyst provided in the SCR reactor,
The control unit generates a catalyst regeneration event when the denitrification efficiency measured by the denitrification efficiency measuring unit is less than or equal to a predetermined value, enters the third mode, and adjusts the engine load in the third mode to perform catalyst regeneration. And the SCR system terminates the third mode when the efficiency reaches a predetermined value or more.
The method of claim 1,
The control unit,
SCR system for driving the ammonia supply unit together in the third mode to perform the exhaust gas treatment operation and the catalyst regeneration operation through the SCR reactor.
The method of claim 1,
The control unit,
SCR system for performing a catalyst regeneration operation in the state in which the exhaust gas treatment operation through the SCR reactor is stopped by stopping the drive of the ammonia supply unit in the third mode.
The method of claim 1,
The SCR reactor is installed in the rear end of the turbo charger (T / C) SCR system.

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