KR20190002846A - Selective catalytic reduction system - Google Patents

Abstract

The present invention relates to a selective catalytic reduction system, reducing nitrogen oxide (NOx) contained in exhaust gas of an engine, of which a portion of the entirety is discharged through a super-charger. According to an embodiment of the present invention, the system comprises: an exhaust flow path through which the exhaust gas which has passed through the super-charger flows; a reactor installed on the exhaust flow path and having a catalyst for reducing the NOx contained in the exhaust gas; a super-charger bypass flow path transferring the exhaust gas discharged from the engine to the exhaust flow path in front of the reactor passing around the super-charger; a first reducing agent injector injecting a reducing agent into the exhaust flow path in front of the reactor; and a second reducing agent injector injecting the reducing agent into the super-charger bypass flow path.

Description

{SELECTIVE CATALYTIC REDUCTION SYSTEM}

The present invention relates to a selective catalytic reduction system, and more particularly, to a selective catalytic reduction system used to reduce nitrogen oxides (NOx) contained in exhaust gases.

As industrialization has progressed rapidly, the use of various fossil fuels such as petroleum and coal has increased. As a result, various harmful gases emitted from the combustion process of fossil fuels cause serious air pollution. Typical examples are smog phenomenon and acid rain.

The main cause of air pollution is sulfur oxides (SOx) and nitrogen oxides (NOx) of exhaust gas emitted from engines of vehicles and ships, thermal power plants and factories. Among them, a selective catalytic reduction (SCR) system is a typical facility for reducing nitrogen oxides. The selective catalytic reduction system reacts the nitrogen oxides contained in the exhaust gas with the reducing agent while passing the exhaust gas and the reducing agent together in the reactor equipped with the catalyst, thereby reducing the nitrogen and the water vapor.

When this selective catalytic reduction system is used on ships, the emission of NOx from marine diesel engines is controlled by the International Maritime Organization's International Standard for the Prevention of Air Pollution (IMO Tier-III) And further energy is consumed for the operation of the selective catalytic reduction system. Therefore, an effective operation method is required together with a denitrification facility with a low cost and a high efficiency.

As a reducing agent for reducing nitrogen (N ₂ ) and water (H ₂ O) which are harmless to the human body by reacting with nitrogen oxides (NO x) in a selective catalytic reduction system, an aqueous urea solution, an aqueous ammonia solution, anhydrous ammonia . These reducing agents are injected into the exhaust gas moving toward the reactor. When urea aqueous solution is used as a reducing agent, urea is decomposed into ammonia by the temperature of the exhaust gas, and ammonia acts as a final reducing agent.

However, when the temperature of the exhaust gas is low, for example, when the temperature of the exhaust gas is less than 200 to 250 degrees Celsius, the urea is not completely converted into ammonia, and the efficiency of reducing nitrogen oxides is lowered or the residual urea or by- Thereby forming a deposit therein.

In order to improve the efficiency of the engine, a supercharger for supplying new external air to the engine by turning the turbine by the pressure of the exhaust gas discharged from the engine is widely used for marine or automotive power systems. And the exhaust gas passing through the supercharger is lowered in temperature and pressure. The temperature of the exhaust gas is reduced through the supercharger, and the temperature of the exhaust gas discharged from the engine changes depending on the engine operating conditions.

As described above, the temperature of the exhaust gas passing through the position where the reducing agent is injected varies from time to time due to various factors. Therefore, the reducing agent injected into the exhaust gas may not be completely decomposed depending on the situation, Problems are frequently generated.

An embodiment of the present invention provides a selective catalytic reduction system that improves decomposition production and mixing efficiency of a reducing agent.

According to the embodiment of the present invention, the selective catalytic reduction system reduces the nitrogen oxides (NOx) contained in the exhaust gas of the engine, all or part of which is exhausted through the supercharger. The selective catalytic reduction system includes an exhaust passage through which the exhaust gas passes through the supercharger, a reactor installed on the exhaust passage and containing a catalyst for reducing nitrogen oxides contained in the exhaust gas, A first reducing agent injecting unit injecting a reducing agent into the exhaust passage in front of the reactor, and a second reducing agent injecting unit injecting the reducing agent into the exhaust passage in front of the reactor, And a second reducing agent injecting unit for injecting a reducing agent into the interior of the second reducing agent injecting unit.

The selective catalytic reduction system may include a temperature sensor for measuring the temperature of the exhaust gas flowing along the exhaust passage, a temperature sensor for receiving the temperature information of the exhaust gas from the temperature sensor and measuring the temperature of the exhaust gas flowing from the first reducing agent injecting unit and the second reducing agent injecting unit And a controller for controlling whether the reducing agent is injected or not and the amount of the reducing agent injected.

The controller may control the ratio of the reducing agent sprayed through the first reducing agent spraying part and the second reducing agent spraying part according to the temperature of the exhaust gas measured by the temperature sensor.

Wherein the control unit injects a reducing agent through the second reducing agent injection unit when the temperature of the exhaust gas measured by the temperature sensor is less than a predetermined first reference temperature and the temperature of the exhaust gas is higher than the first reference temperature and the second reference temperature The reducing agent may be injected through the first reducing agent injecting unit and the second reducing agent injecting unit and the reducing agent may be injected through the first reducing agent injecting unit if the temperature of the exhaust gas is equal to or higher than the second reference temperature.

In addition, one region of the supercharger bypass passage provided with the second reducing agent injection portion may have a diameter larger than that of the other region.

The selective catalytic reduction system includes a supercharger bypass valve installed on the turbocharger flow path to regulate a flow rate of exhaust gas flowing along the supercharger bypass flow path and a supercharger bypass valve disposed in proportion to the flow rate of exhaust gas flowing along the supercharger bypass flow path And a controller for controlling the amount of the reducing agent injected by the second reducing agent injecting unit.

Wherein the selective catalytic reduction system includes a recirculation flow path branched from the rear end of the reactor or the exhaust flow path behind the reactor and joined to the exhaust flow path in front of the reactor or in front of the reactor, And a heating device for heating the fluid moving along the flow path.

The selective catalytic reduction system may further include a decomposition chamber disposed on the recirculation flow path and a third reducing agent injection unit injecting a reducing agent into the decomposition chamber.

The controller may control the ratio of the reducing agent sprayed through the first reducing agent spraying part and the third reducing agent spraying part according to the temperature of the exhaust gas measured by the temperature sensor.

Wherein the control unit injects the reducing agent through the third reducing agent injection unit when the temperature of the exhaust gas measured by the temperature sensor is less than a predetermined first reference temperature and the temperature of the exhaust gas is higher than the first reference temperature and the second reference temperature The reducing agent is injected through the first reducing agent spraying unit and the second reducing agent spraying unit when the temperature of the exhaust gas is lower than the second reference temperature and lower than the third reference temperature, When the temperature of the exhaust gas is equal to or higher than the third reference temperature, the reducing agent may be injected through the first reducing agent injecting unit.

The selective catalytic reduction system includes an auxiliary heat source supply flow path branched from the blower and the heating device and the exhaust flow path upstream of the reactor or upstream of the reactor and connected to the supercharger bypass flow path, And may further include an installed auxiliary heat source supply control valve. The second reducing agent injecting unit may be installed on the supercharger bypass flow path between the exhaust gas passage and a point where the auxiliary heat source supply passage is connected to the supercharger bypass passage.

The controller may control the ratio of the reducing agent sprayed through the first reducing agent spraying part and the reducing agent spraying part according to the temperature of the exhaust gas measured by the temperature sensor and may control the operation of the heating device and the blower .

If the temperature of the exhaust gas traveling along the supercharger bypass flow path is insufficient to decompose the reducing agent injected through the second reducing agent injection section, the control section may further supply thermal energy through the auxiliary heat source supply flow path.

According to the embodiment of the present invention, the selective catalytic reduction system can improve decomposition production and mixing efficiency of the reducing agent.

1 is a configuration diagram of a selective catalytic reduction system according to a first embodiment of the present invention.
2 is a block diagram of a selective catalytic reduction system according to a second embodiment of the present invention.
3 is a block diagram of a selective catalytic reduction system according to a third embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In addition, in the various embodiments, components having the same configuration are represented by the same reference symbols in the first embodiment, and in the other embodiments, only the configurations different from those of the first embodiment will be described do.

The drawings are schematic and not drawn to scale. The relative dimensions and ratios of the parts in the figures are exaggerated or reduced in size for clarity and convenience in the figures, and any dimensions are merely illustrative and not restrictive. And to the same structure, element or component appearing in more than one drawing, the same reference numerals are used to denote similar features.

The embodiments of the present invention specifically illustrate ideal embodiments of the present invention. As a result, various variations of the illustration are expected. Thus, the embodiment is not limited to any particular form of the depicted area, but includes modifications of the form, for example, by manufacture.

Hereinafter, the selective catalytic reduction system 101 according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

A selective catalytic reduction (SCR) system 101 according to the first embodiment of the present invention reduces nitrogen oxides (NOx) contained in the exhaust gas discharged from the engine 100. Here, the engine 100 may include at least one of a two-stroke low-speed diesel engine used as a main power source for supplying a propulsion force to a ship or a four-row medium-speed diesel engine used as a generator for generating power or auxiliary power for a ship.

However, the first embodiment of the present invention is not limited thereto. The engine 100 may be an internal combustion engine for a plant or an in-vehicle engine. That is, various kinds of engines 100 known to those skilled in the art can be used in the first embodiment of the present invention.

Further, in the first embodiment of the present invention, all or a part of the exhaust gas discharged from the engine 100 passes through the turbocharger 150. The supercharger 150 is connected to the exhaust port of the engine 100 to rotate the turbine with the pressure of the exhaust gas of the engine 100 to supply new external air to the engine 100 by compressing the fresh air. Thus, the efficiency of the engine 200 equipped with the turbocharger 150 is improved.

Further, in the first embodiment of the present invention, the exhaust gas discharged from the engine 100 has a temperature within a range of from 250 degrees Celsius to 600 degrees Celsius, and the temperature of the exhaust gas can be lowered through the supercharger 150. For example, the exhaust gas passing through the turbocharger 150 may be lowered to a temperature of not less than 150 degrees Celsius and less than 250 degrees Celsius.

1, a selective catalytic reduction (SCR) system 101 according to a first embodiment of the present invention includes an exhaust flow path 610, a reactor 300, a supercharger bypass flow path 650, A first reducing agent spraying unit 501, and a second reducing agent spraying unit 502.

The selective catalytic reduction system 101 according to the first embodiment of the present invention may further include a temperature sensor 710, a control unit 700, a supercharger bypass valve 750 and a reducing agent supply unit 550.

In addition, the selective catalytic reduction system 101 according to the first embodiment of the present invention may further include a recirculation passage 680, a blower 880, a heating device 830, and a mixer 400.

The exhaust passage 610 moves the exhaust gas containing nitrogen oxides (NOx) discharged from the engine 100. In addition, all or a part of the exhaust gas moving along the exhaust passage 610 passes through the turbocharger 150. The exhaust channel 610 is connected to the reactor 300 to be described later.

The reactor 300 is installed on the exhaust passage 610. That is, the reactor 300 receives the exhaust gas discharged from the engine 100 through the exhaust passage 610. The reactor 300 incorporates a catalyst 350 for reducing nitrogen oxides (NOx) contained in the exhaust gas. The catalyst 350 promotes the reaction of the reducing agent with the nitrogen oxides (NOx) contained in the exhaust gas to reduce the nitrogen oxides (NOx) to nitrogen and water vapor.

Also, in the first embodiment of the present invention, the catalyst 350 installed inside the reactor 300 may be arranged in a multi-layer structure based on the moving direction of the exhaust gas. That is, the catalyst 350 may be provided in the form of a plurality of catalyst modules, and the plurality of catalyst modules may be disposed along the moving direction of the exhaust gas.

Catalyst 350 may be made from a variety of materials known to those skilled in the art, such as zeolite, vanadium, and platinum. In one example, catalyst 350 may have an active temperature in the range of 250 degrees Celsius to 350 degrees Celsius. Here, the activation temperature refers to a temperature at which the catalyst 350 can be stably reduced without being poisoned. When the catalyst 350 reacts outside the activation temperature range, the catalyst 350 is poisoned and the efficiency is lowered.

For example, occurs the reduction reaction for reducing nitrogen oxide-containing exhaust gas at a relatively low temperature of less than ° C more than 250 ° C, 150, of the exhaust gas sulfur oxides (SOx) and ammonia (NH ₃₎ the reaction Thereby forming a catalyst poisoning substance.

Specifically, the poisoning substance that poisons the catalyst 350 may include at least one of ammonium sulfate (NH ₄ ) ₂ SO ₄ and ammonium hydrogen sulfite (NH ₄ HSO ₄ ). Such a catalyst poisoning material is adsorbed on the catalyst to lower the activity of the catalyst 350. Since the catalyst poisonous substance is decomposed at a relatively high temperature, that is, at a temperature within the range of 350 degrees Celsius to 450 degrees Celsius, the catalyst 350 in the reactor 300 can be heated to regenerate the poisoned catalyst 350.

Also, in the first embodiment of the present invention, the reactor 300 may be installed on the exhaust passage 610 in front of the turbocharger 150. In the following description, the term front means the upstream direction based on the moving direction of the exhaust gas, and the rear means the downstream direction based on the moving direction of the exhaust gas.

The supercharger bypass passage 650 bypasses the supercharger 150 and transfers some of the exhaust gas discharged from the engine 100 to the exhaust passage 610. The exhaust gas flowing into the exhaust passage 610 through the supercharger bypass passage 650 does not pass through the turbocharger 150 so that the temperature of the exhaust gas flowing through the turbocharger 150 is relatively higher than the exhaust gas flowing along the exhaust passage 610 . For example, the exhaust gas flowing along the exhaust passage 610 after passing through the turbocharger 150 has a temperature of not less than 150 degrees Celsius and less than 250 degrees Celsius, while the exhaust gas passage 610 through the supercharger bypass passage 650, May have a temperature in the range of 250 degrees Celsius to 600 degrees Celsius.

The first reducing agent spraying unit (501) injects a reducing agent into the exhaust passage (610) in front of the reactor (300). The second reducing agent spraying part 502 injects a reducing agent into the supercharger bypass flow path 650. For example, the first reducing agent spraying part 501 and the second reducing agent spraying part 502 are connected to urea, CO (NH ₂ ), and the like, respectively, in the exhaust gas flowing along the exhaust passage 610 and the turbocharger bypass passage 650, ₂ ) can be sprayed in the form of an aqueous solution.

In a first embodiment of the invention, the first reducing agent injection assembly 501 and the second and urea (urea, CO (NH _{2) 2)} aqueous solution is injected reducing agent injection assembly (502) corresponds to the reducing agent precursor, urea Ammonia (NH ₃ ) and isocyanic acid (HNCO) are produced by pyrolysis or hydrolysis, and isocyanic acid (HNCO) can be decomposed again into ammonia (NH ₃ ) and carbon dioxide (CO ₂ ). Finally, the ammonia (NH ₃ ) finally produced is used as a reducing agent to reduce nitrogen oxides (NOx) contained in the exhaust gas.

1, one region of the supercharger bypass passage 650 provided with the second reducing agent injection portion 502 may be relatively larger in diameter than the other regions. By providing the second reducing agent spraying portion 502 in the supercharging bypass passage 650 having a diameter smaller than that of the exhaust gas passage 610, the flow path resistance is increased or the pressure difference between the front and rear of the second reducing agent spraying portion 502 Can be minimized.

The reducing agent supply unit 550 supplies a reducing agent to be sprayed by the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502. One reducing agent supply unit 550 can supply the reducing agent to the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502 and the plurality of reducing agent supplying units 550 can supply the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502, A reducing agent may be supplied to the second reducing agent spraying unit 502.

Also, since the amount of exhaust gas discharged from the engine 100 varies depending on the load variation of the engine 100, the amount of the reducing agent required to reduce the nitrogen oxide contained in the exhaust gas also varies. The reducing agent supply unit 550 can adjust the supply amount of the reducing agent so that the reducing agent can be supplied in an appropriate amount depending on the operating condition of the engine 100 or the exhaust gas exhausting condition.

Specifically, the reducing agent supply unit 550 includes a reducing agent storage tank for storing the reducing agent to be supplied to the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502, a reducing agent supplying pump for supplying the reducing agent stored in the reducing agent storage tank, A module, a flow meter for measuring the supply flow rate, and a reducing agent supply line for moving the reducing agent. Here, the reducing agent supply pump module may include a pump for supplying the reducing agent, a filter necessary for installing the pump, a pressure gauge for the pump, a manual valve for the pump, and the like.

The supercharger bypass valve 750 is installed in the supercharger bypass passage 650. The supercharger bypass valve 750 not only opens and closes the supercharger bypass conduit 650 but also controls the flow rate of the exhaust gas passing through the supercharger bypass conduit 650. That is, the supercharger bypass valve 750 can control the total amount of heat energy to be supplied for decomposing the reducing agent injected by the second reducing agent injection portion 502 through the supercharger bypass passage 650.

The temperature sensor 710 can measure the temperature of the exhaust gas moving along the exhaust passage 610. [ Further, a plurality of temperature sensors 710 may be provided as needed. For example, the temperature sensor 710 may be installed on the exhaust flow path 610 between the supercharger 150 and the first reducing agent spraying unit 501. Further, in the first embodiment of the present invention, the selective catalytic reduction system 101 may further include an additional temperature sensor for measuring the temperature of the exhaust gas moving along the supercharger bypass flow path 650. [

The control unit 700 can receive the temperature information of the exhaust gas from the temperature sensor 710 and control the reductant injection amount or the reducing agent injection amount of the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502. The control unit 700 may adjust the ratio of the reducing agent injected through the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502 according to the temperature of the exhaust gas measured by the temperature sensor 710.

Depending on the operating conditions of the engine 100, the temperature of the exhaust gas may vary from time to time. For example, the temperature of the exhaust gas discharged from the engine 100 may be relatively low in an initial operation of the engine 100, a low load operation, or a very low temperature climate environment. On the other hand, when a sufficient time has elapsed after the engine 100 has been operated and the engine 100 is in a heated state, or in a high-temperature operation or in a very high temperature environment, the temperature of the exhaust gas discharged from the engine 100 may be relatively high have.

In the first embodiment of the present invention, the control unit 700 controls the exhaust passage 610 after passing through the turbocharger 150 in consideration of the temperature of the exhaust gas fluctuating according to the operating condition of the engine 100, The reducing agent can be injected through the second reducing agent spraying unit 502 when the temperature of the exhaust gas moving through the second reducing agent spraying unit 502 is lower than the reducing agent decomposable temperature. On the contrary, when the temperature of the exhaust gas passing through the turbocharger 150 is sufficiently higher than the decomposable temperature of the reducing agent, the reducing agent can be injected through the first reducing agent spraying unit 501.

The temperature of the exhaust gas flowing through the exhaust passage 610 after passing through the turbocharger 150 is the temperature at which the reducing agent can be decomposed, but when a large amount of reducing agent is injected, the first reducing agent injecting unit 501 And the second reducing agent spraying part 502 can spray the reducing agent together. In this case, the reducing agent injection ratio of the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502 can be adjusted according to the temperature of the exhaust gas passing through the turbocharger 150. For example, as the temperature of the exhaust gas passing through the supercharger 150 increases, the reducing agent injection ratio of the first reducing agent spraying unit 501 can be increased more than the second reducing agent spraying unit 502.

If the temperature of the exhaust gas measured by the temperature sensor 710 is lower than a predetermined first reference temperature, the control unit 700 may inject the reducing agent through the second reducing agent spraying unit 502. Here, the first reference temperature is the minimum temperature for decomposing the reducing agent. That is, the urea can not be decomposed below the first reference temperature. For example, the decomposable production temperature of the reducing agent may be in the range of about 250 degrees Celsius to about 600 degrees Celsius.

If the temperature of the exhaust gas measured by the temperature sensor 710 is lower than the first reference temperature by the second reducing agent injection unit 501 Reducing agent can be sprayed. That is, when the temperature of the exhaust gas is lower than the first reference temperature and lower than the second reference temperature, it is possible to decompose and generate the reducing agent even with the exhaust gas passing through the turbocharger 150. However, when a large amount of reducing agent is injected, It is possible. The first reference temperature and the second reference temperature may be set according to the type of the engine 100 and the overall performance of the selective catalytic reduction system 101.

The control unit 700 may inject the reducing agent through the first reducing agent spraying unit 501 when the temperature of the exhaust gas measured by the temperature sensor 710 exceeds the second reference temperature. That is, when the temperature of the exhaust gas is equal to or higher than the second reference temperature, it is possible to sufficiently supply the thermal energy required for decomposition and generation of the reducing agent with the exhaust gas passing through the turbocharger 150. Therefore, it is not necessary to inject the reducing agent through the second reducing agent spraying section 502 because of the lack of thermal energy. However, if necessary, a reducing agent may be injected together in the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502 to improve the mixing efficiency of the reducing agent.

On the other hand, the temperature of the exhaust gas discharged from the engine 100 decreases while passing through the turbocharger 150, and the temperature of the exhaust gas is decreased by a certain level according to the performance and operation state of the turbocharger 150. Accordingly, the controller 700 measures the temperature of the exhaust gas passing through the turbocharger 150, and estimates the temperature of the exhaust gas that has not passed through the turbocharger 150, that is, the temperature of the exhaust gas flowing along the turbocharger bypass passage 650 It is possible.

In addition, in the first embodiment of the present invention, the controller 700 can adjust the reducing agent injection amount of the second reducing agent spraying unit 502 in proportion to the flow rate of the exhaust gas flowing along the supercharger bypass flow path 650. That is, as the flow rate of the exhaust gas flowing along the supercharger bypass channel 650 increases, the controller 700 can increase the amount of the reducing agent injected from the second reducing agent injector 502.

The recirculation passage 680 may be branched from the rear end of the reactor 300 or the exhaust duct 610 behind the reactor 300 to join the exhaust duct 610 on the front side of the reactor 300 or in front of the reactor 300.

The blower 880 is installed on the recirculation passage 680 to regulate the flow rate of the exhaust gas flowing along the recirculation passage 680. That is, the blower 880 provides a suction force for circulating a part of the exhaust gas passing through the reactor 300 to the recirculation flow path 680. The heating device 830 can raise the temperature of the fluid moving along the recirculation flow path 680. In one example, the heating device 830 may be one of an electric heater, an oil burner, or a plasma burner. Depending on the type of the heating device 830, oxygen may be insufficient in the fluid moving through the recirculation flow path 680, so that additional oxygen may be required to operate the heating device 830. At this time, outside air may be supplied to the recirculation flow path 680 through an outside air supply device (not shown).

In the first embodiment of the present invention, the recycle flow path 680, the blower 880, and the heating device 830 are used to regenerate the catalyst 350 when the catalyst 350 installed in the reactor 300 is poisoned, To pre-heat the catalyst 350 in the reactor. As described above, when the catalyst 350 is heated while the exhaust gas passing through the reactor 300 is recirculated, the utilization efficiency of energy can be improved.

The mixer 400 may be installed on the exhaust flow path 610 between the first reducing agent spraying part 501 and the second reducing agent spraying part 502 and the reactor 300. The mixer 400 effectively mixes the reducing agent injected from the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502 with the exhaust gas.

With this configuration, the selective catalytic reduction system 101 according to the first embodiment of the present invention can improve decomposition generation and mixing efficiency of the reducing agent.

Specifically, the reducing agent can be sprayed in multiple directions at a plurality of positions according to the operating conditions of the engine 100 and the temperature of the exhaust gas, so that the reducing agent can be effectively decomposed and generated, and the mixing efficiency of the exhaust gas and the reducing agent can be improved.

Further, it is possible to effectively improve the mixing efficiency with the exhaust gas together with the decomposition efficiency while minimizing the space for decomposing urea to generate ammonia. That is, the urea can be injected into the exhaust passage 610 or the turbocharger bypass passage 650 without providing a separate decomposition chamber, thereby effectively decomposing the urea and generating ammonia. Therefore, it is possible to efficiently decompose urea without increasing the overall size of the selective catalytic reduction system 101 to produce ammonia as well as effectively mix ammonia and exhaust gas.

Also, it is possible to prevent a phenomenon that a urea is completely converted into ammonia and a deposit is generated in the exhaust flow path 610 and the reactor 300.

Hereinafter, a selective catalytic reduction system 102 according to a second embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 2, the selective catalytic reduction system 102 according to the second embodiment of the present invention further includes a decomposition chamber 850 and a third reducing agent injection unit 503. In addition, the selective catalytic reduction system 102 may further include an ammonia injector 580.

The decomposition chamber 850 is installed on the recirculation passage 680. Specifically, the decomposition chamber 850 can be installed behind the heating apparatus 830. [ The exhaust gas heated and heated by the heating unit 830 flows into the decomposition chamber 850 and the reducing agent spray unit 503 injects the reducing agent into the decomposition chamber 850. That is, the reducing agent injected from the third reducing agent spraying unit 503 can be decomposed in the decomposition chamber 850.

The ammonia injector 580 injects the ammonia produced in the decomposition chamber 850 to be effectively mixed with the exhaust gas moving along the exhaust gas passage 610.

In the second embodiment of the present invention, since the heating device 830 can sufficiently supply the thermal energy required for decomposition and generation of the reducing agent, the reducing agent injected from the third reducing agent spraying section 503 can affect the operating conditions of the engine 100 It can be stably decomposed without being affected.

In the second embodiment of the present invention, the control unit 700 controls the first reducing agent spraying unit 501, the second reducing agent spraying unit 502, and the third reducing agent spraying unit 502 according to the temperature of the exhaust gas measured by the temperature sensor 710. [ The ratio of the reducing agent sprayed through the reducing agent spraying unit 503 can be adjusted.

If the temperature of the exhaust gas measured by the temperature sensor 710 is lower than the predetermined first reference temperature, the control unit 700 may inject the reducing agent through the third reducing agent spraying unit 503. In the second embodiment of the present invention, the first reference temperature means the minimum temperature at which the exhaust gas discharged from the engine 100 before passing through the turbocharger 150 can decompose and produce the reducing agent. When the temperature of the exhaust gas in the exhaust passage 610 behind the turbocharger 150 is measured by the temperature sensor 710 and the temperature of the exhaust gas is measured in the exhaust passage in front of the turbocharger 150 It is divided as follows.

When the temperature sensor 710 measures the temperature of the exhaust gas at the rear of the supercharger 150, the first reference temperature is the temperature of the exhaust gas measured by the temperature sensor 710, and the exhaust gas temperature before the supercharger 150 It can mean the minimum temperature at which the exhaust gas temperature before the estimated supercharger 150 can decompose and produce the reducing agent.

When the temperature sensor 710 measures the temperature of the exhaust gas behind the supercharger 150, the first reference temperature is lowered through the supercharger 150 at a minimum temperature at which the reducing agent can not be decomposed and produced The temperature becomes lower by the temperature.

On the other hand, when the temperature sensor 710 measures the temperature of the exhaust gas in front of the turbocharger 150, the first reference temperature may be the minimum temperature at which the reducing agent can not be decomposed.

If the temperature of the exhaust gas is lower than the first reference temperature and lower than the second reference temperature, the control unit 700 may inject the reducing agent through the second reducing agent spraying unit 502. When the temperature of the exhaust gas is lower than the first reference temperature and lower than the second reference temperature, the reducing agent can not be decomposed by the temperature of the exhaust gas moving along the exhaust passage 610 after passing through the turbocharger 150, 650), the reducing agent can be decomposed by the temperature of the exhaust gas.

For example, when the temperature sensor 710 measures the temperature of the exhaust gas passing through the supercharger 150, the temperature of the exhaust gas traveling along the supercharger bypass flow path 650 can be indirectly estimated. However, the second embodiment of the present invention is not limited thereto, and the selective catalytic reduction system 102 may further include an additional temperature sensor for measuring the temperature of the exhaust gas flowing along the supercharger bypass passage 650 .

The control unit 700 may inject the reducing agent through the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502 when the temperature of the exhaust gas is lower than the second reference temperature and lower than the third reference temperature. That is, when the temperature of the exhaust gas is lower than the second reference temperature and lower than the third reference temperature, it is possible to decompose and produce the reducing agent even with the exhaust gas passing through the turbocharger 150. However, when a large amount of the reducing agent is injected, It is possible. The first reference temperature, the second reference temperature, and the third reference temperature may be set according to the type of engine 100 and the overall performance of the selective catalytic reduction system 102.

If the temperature of the exhaust gas is equal to or higher than the third reference temperature, the control unit 700 can inject the reducing agent through the first reducing agent spraying unit 501. When the temperature of the exhaust gas is equal to or higher than the third reference temperature, it is possible to sufficiently supply the thermal energy required for decomposition and generation of the reducing agent to the exhaust gas passing through the supercharger 150. Therefore, it is necessary to inject the reducing agent through the second reducing agent spraying unit 502 There is no. However, in order to improve the mixing efficiency of the reducing agent, a reducing agent may be injected together in the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502 as needed.

With this structure, the selective catalytic reduction system 102 according to the second embodiment of the present invention can improve decomposition generation and mixing efficiency of the reducing agent.

Specifically, the reducing agent can be sprayed in multiple directions at a plurality of positions according to the operating conditions of the engine 100 and the temperature of the exhaust gas, so that the reducing agent can be effectively decomposed and generated, and the mixing efficiency of the exhaust gas and the reducing agent can be improved.

Particularly, even when the temperature of the exhaust gas discharged from the engine 100 is low enough to decompose the reducing agent before passing through the turbocharger 150, the reducing agent can be decomposed and produced stably.

Hereinafter, a selective catalytic reduction system 103 according to a third embodiment of the present invention will be described with reference to FIG.

3, the selective catalytic reduction system 103 according to the third embodiment of the present invention further includes an auxiliary heat source supply passage 670 and an auxiliary heat source supply valve 770.

The auxiliary heat source supply passage 670 is branched from the blower 880 and the heating device 830 and the recirculation passage 680 between the front end of the reactor 300 or the exhaust passage 610 in front of the reactor 300, 650).

The auxiliary heat source supply valve 770 is provided in the auxiliary heat source supply passage 670 and regulates the flow rate of the fluid flowing through the auxiliary heat source supply passage 670 to the supercharger bypass passage 650.

In the third embodiment of the present invention, the second reducing agent spraying unit 502 is arranged so that the superheater bypass flow path 650 between the point where the auxiliary heat source supply flow path 670 is connected to the supercharger bypass flow path 650 and the exhaust flow path 610, As shown in FIG.

The control unit 700 controls the ratio of the reducing agent injected through the first reducing agent spraying unit 501 and the second reducing agent spraying unit 502 according to the temperature of the exhaust gas measured by the temperature sensor 710, The operation of the device 830 and the blower 880 can be controlled.

Specifically, when the temperature of the exhaust gas flowing along the supercharger bypass flow path 650 is insufficient to decompose the reducing agent injected through the second reducing agent injection part 502, the controller 700 controls the auxiliary heat source supply flow path 670 It is possible to additionally supply thermal energy to the supercharger bypass flow path 650. That is, when the temperature of the exhaust gas discharged from the engine 100 is low enough that the reducing agent can not be decomposed before passing through the turbocharger 150, the exhaust gas traveling along the turbocharger bypass passage 650 also decomposes the reducing agent It does not have enough temperature. In this case, the controller 700 operates the auxiliary heat source supply valve 770, the blower 880, and the heating device 830 so as to supplement the heat energy to the supercharger bypass flow path 650 through the auxiliary heat source supply flow path 670 Can supply.

Accordingly, even when the temperature of the exhaust gas discharged from the engine 100 is low enough to decompose the reducing agent before passing through the turbocharger 150, the reducing agent injected from the second reducing agent spraying unit 502 can be decomposed.

However, the present invention is not limited to the above-described embodiments. In another embodiment of the present invention, the decomposition chamber 850 of the second embodiment, the auxiliary heat source supply passage 670 of the third embodiment, (770) may be used together.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. will be.

It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, It is intended that all changes and modifications derived from the equivalent concept be included within the scope of the present invention.

101, 102, 103: selective catalytic reduction system
100: engine
150: supercharger
300: reactor
350: catalyst
400: Mixer
501: First reducing agent spraying part
502: Second reducing agent spraying part
503: Third reducing agent spraying part
550: Reducing agent supply unit
580: Ammonia injector
610:
650: Supercharger bypass channel
670: auxiliary heat source supply channel
680: Recirculation flow path
700:
710: Temperature sensor
750: Supercharger bypass valve
770: Auxiliary heat source supply valve
830: Heating device
850: decomposition chamber
880: Blower

Claims (13)

1. A selective catalytic reduction system for reducing nitrogen oxides (NOx) contained in an exhaust gas of an engine, all or part of which is exhausted through a supercharger,
An exhaust passage through which the exhaust gas passes through the supercharger;
A reactor provided on the exhaust flow path and containing a catalyst for reducing nitrogen oxides contained in the exhaust gas;
A supercharger bypass flow passage for bypassing the exhaust gas discharged from the engine to the exhaust passage in front of the reactor;
A first reducing agent spraying unit for spraying a reducing agent into the exhaust passage in front of the reactor; And
A second reducing agent spraying unit for spraying a reducing agent into the supercharger bypass passage,
≪ / RTI > The method according to claim 1,
A temperature sensor for measuring the temperature of the exhaust gas moving along the exhaust passage;
A control unit for receiving the temperature information of the exhaust gas from the temperature sensor and controlling the reductant injection amount or the reducing agent injection amount of the first reducing agent spraying unit and the second reducing agent spraying unit,
Further comprising a catalytic reduction catalyst. 3. The method of claim 2,
Wherein the control unit controls the ratio of the reducing agent injected through the first reducing agent injecting unit and the reducing agent injecting unit according to the temperature of the exhaust gas measured by the temperature sensor. 3. The method of claim 2,
Wherein,
A second reducing agent injecting unit injecting a reducing agent when the temperature of the exhaust gas measured by the temperature sensor is lower than a predetermined first reference temperature,
The reducing agent is injected through the first reducing agent spraying part and the second reducing agent spraying part when the temperature of the exhaust gas is lower than the first reference temperature and lower than the second reference temperature,
Wherein the reducing agent is injected through the first reducing agent injector when the temperature of the exhaust gas is equal to or higher than the second reference temperature. The method according to claim 1,
Wherein one region of the supercharger bypass passage provided with the second reducing agent injection portion has a larger diameter than that of the other region. The method according to claim 1,
A supercharger bypass valve installed on the turbocharger flow path to regulate the flow rate of the exhaust gas flowing along the supercharger bypass passage;
Further comprising a control unit for controlling the reducing agent injection amount of the second reducing agent injection unit in proportion to a flow rate of the exhaust gas flowing along the supercharger bypass flow path. 3. The method of claim 2,
A re-circulation flow path branched from the rear end of the reactor or the exhaust flow path behind the reactor and joined to the front end of the reactor or the exhaust flow path in front of the reactor;
A blower installed on the recirculation flow path; And
A heating device for heating the fluid moving along the recirculation flow path;
Further comprising a catalytic reduction catalyst. 8. The method of claim 7,
A decomposition chamber provided on the recirculation flow path;
And a third reducing agent spraying unit for spraying a reducing agent into the decomposition chamber
≪ / RTI > 9. The method of claim 8,
Wherein the controller controls the ratio of the reducing agent sprayed through the first reducing agent spraying part and the third reducing agent spraying part according to the temperature of the exhaust gas measured by the temperature sensor Reduction system. 9. The method of claim 8,
Wherein,
The reducing agent is injected through the third reducing agent injecting unit when the temperature of the exhaust gas measured by the temperature sensor is lower than a predetermined first reference temperature,
The reducing agent is injected through the second reducing agent injecting unit when the temperature of the exhaust gas is lower than the first reference temperature and lower than the second reference temperature,
The reducing agent is sprayed through the first reducing agent spraying part and the second reducing agent spraying part when the temperature of the exhaust gas is lower than the second reference temperature and lower than the third reference temperature,
Wherein the reducing agent is injected through the first reducing agent injector when the temperature of the exhaust gas is equal to or higher than the third reference temperature. 8. The method of claim 7,
An auxiliary heat source supply flow path branched from the recirculation flow path between the blower and the heating device and an exhaust flow path in front of the reactor or in front of the reactor and connected to the supercharger bypass flow path; And
The auxiliary heat source supply control valve
Further comprising:
Wherein the second reducing agent injection unit is installed on the supercharger bypass flow path between a point where the auxiliary heat source supply flow path is connected to the supercharger bypass flow path and the exhaust flow path. 12. The method of claim 11,
The controller controls the ratio of the reducing agent sprayed through the first reducing agent spraying part and the reducing agent spraying part according to the temperature of the exhaust gas measured by the temperature sensor and controls the operation of the heating device and the blower Gt; catalyst < / RTI > 13. The method of claim 12,
If the temperature of the exhaust gas flowing along the supercharger bypass flow path is insufficient to decompose the reducing agent injected through the second reducing agent injection section, the control section additionally supplies thermal energy to the supercharger bypass flow path through the auxiliary heat source supply flow path Characterized by a selective catalytic reduction system.

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