KR20220064440A - Selective catalytic reduction system - Google Patents

Abstract

The present invention provides a selective catalytic reduction system which suppresses malfunction and can stably clean a residual reducing agent while having simple components. According to the present invention, the selective catalytic reduction system comprises: a reducing agent decomposition chamber decomposing a reducing agent to reduce nitrogen oxide; an injection nozzle injecting a reducing agent into the reducing agent decomposition chamber; a reducing agent storage unit storing a reducing agent to be injected by the injection nozzle; a reducing agent supply line connecting the reducing agent storage unit and the injection nozzle; a reducing agent supply pump installed on the reducing agent supply line; a cleaning water supply line connected to the reducing agent supply line between the reducing agent supply pump and the reducing agent storage unit; a cleaning water supply unit supplying cleaning water to the cleaning water supply line; an air supply unit supplying compressed air to be injected by the injection nozzle; an air supply line connecting the air supply unit and the injection nozzle; and a purge line branching from the air supply line to merge with the reducing agent supply line between the reducing agent supply pump and the injection nozzle.

Description

Selective Catalytic Reduction System {SELECTIVE CATALYTIC REDUCTION SYSTEM}

The present invention relates to a selective catalytic reduction system for reducing nitrogen oxides contained in exhaust gas using a selective catalytic reduction reaction.

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

In addition, in the case of existing fossil fuels, carbon (Carbon, C) is included, and carbon dioxide (CO ₂ ) is generated during combustion, which greatly affects the greenhouse gas effect. For example, a main fuel component of a diesel engine is cetane (C1 ₆ H ₃₄ ), a main fuel component of an LNG engine is methane (CH ₄ ), and a main fuel component of a methanol engine is methanol (CH ₃ OH). Accordingly, a ship using a diesel engine emits nitrogen oxide (NOx), an air pollutant, during operation.

In recent years, with the increasing awareness of environmental conservation, emission regulations for nitrogen oxides have been introduced. A representative facility for reducing such nitrogen oxides is a selective catalytic reduction (SCR) system. In the selective catalytic reduction system, the exhaust gas and the reducing agent pass together through a reactor in which the catalyst is installed, and the nitrogen oxides and the reducing agent contained in the exhaust gas are reacted to reduce the nitrogen and water vapor.

In the selective catalytic reduction system, ammonia (NH ₃ ) is used as a reducing agent for reducing nitrogen oxides. That is, ammonia reacts with nitrogen oxides. However, since ammonia itself is not easy to store and transport as a contaminant, it is common to use a stable aqueous solution of urea, which is a reducing agent precursor, rather than directly using ammonia. That is, after spraying an aqueous solution of urea (urea, CO(NH ₂ ) ₂ ), it is hydrolyzed or thermally decomposed to generate ammonia (NH ₃ ) and then used as a reducing agent.

However, when urea is directly injected into the exhaust gas having a temperature of less than 250 degrees Celsius, biuret, cyanuric acid, melamine, and ammeline, etc., which are generated as urea is decomposed, are There is a problem in that the injection nozzle is clogged by by-products or the flow of exhaust gas is obstructed.

Accordingly, in order to improve the pyrolysis and hydrolysis efficiency of urea, a separate decomposition chamber is provided, and a heated fluid is supplied to the decomposition chamber to raise the internal temperature of the decomposition chamber to the hydrolysis reaction temperature, and urea is stably produced in the decomposition chamber. A method of supplying ammonia (NH ₃ ) and isocyanic acid (HNCO) produced by decomposition to the reactor is used.

On the other hand, when the operation of the selective catalytic reduction system is stopped and the supply of the reducing agent is stopped, the urea aqueous solution remaining in the injection nozzle or the reducing agent supply pipe is solidified, and there is a problem in that the injection nozzle or the reducing agent supply pipe is blocked.

Accordingly, when the operation of the selective catalytic reduction system is stopped and the supply of the reducing agent is stopped, washing water is supplied to the reducing agent supply line, the remaining reducing agent is injected into the high-temperature gas through the injection nozzle, and air is supplied again to the reducing agent supply line. The process of removing the residual reducing agent and water through the spray nozzle is being performed.

However, when washing water is used for cleaning the reducing agent supply line and the spray nozzle, if the cleaning water is supplied while air is being sprayed to the spray nozzle, the reverse pressure to the reducing agent supply line is applied by the pressure of the air. do. Therefore, only when the supply pressure of the washing water is higher than the pressure acting in the reverse direction of the air, the reverse flow of the washing water can be prevented and washing can be performed smoothly.

However, when the supply pressure of the washing water that can be supplied from the ship is low, there is a problem in that a separate pump for supplying the washing water must be additionally provided for smooth washing.

In addition, the flow measurement device used to control the supply amount of the reducing agent has an electronic type and a mechanical type. If the electronic flow measurement device is used, the flow of the fluid is reduced by the characteristics of the sensor when the tube is emptied by the above-described air cleaning Even if there is no output value, a problem may occur. And when a mechanical flow measurement device is used, if the reducing agent is not completely removed by washing with washing water due to the complicated internal structure, when washing is performed with air, the compressed air expands as it moves and the temperature drops. At this time, the residual The temperature of the reducing agent being used is lowered to generate solids, which may cause a malfunction of the flow measuring device as well as other parts such as valves.

An embodiment of the present invention provides a selective catalytic reduction system capable of stably cleaning the residual reducing agent even with a simple configuration and suppressing the occurrence of a malfunction.

According to an embodiment of the present invention, the selective catalytic reduction system includes a reducing agent decomposition chamber for decomposing a reducing agent to reduce nitrogen oxides, a spray nozzle for spraying a reducing agent to the reducing agent decomposition chamber, and a reducing agent to be sprayed by the spray nozzle. a reducing agent storage unit, a reducing agent supply line connecting the reducing agent storage unit and the injection nozzle, a reducing agent supply pump installed on the reducing agent supply line, and the reducing agent supply line between the reducing agent supply pump and the reducing agent storage unit A washing water supply line connected to the washing water supply line, a washing water supply unit supplying washing water to the washing water supply line, an air supply unit supplying compressed air to be sprayed by the injection nozzle, and an air supply connecting the air supply unit and the injection nozzle a line, and a purge line branching from the air supply line and joining the reducing agent supply line between the reducing agent supply pump and the injection nozzle.

The selective catalytic reduction system includes a reducing agent supply control valve installed in the reducing agent supply line between the connection point with the washing water supply line and the reducing agent storage unit, and installed on the reducing agent supply line to measure the supply pressure of the reducing agent A reducing agent pressure detection device, a reducing agent flow rate detection device installed on the reducing agent supply line to detect the supply flow rate of the reducing agent, and installed in the reducing agent supply line between the reducing agent flow rate detection device and the injection nozzle to control whether the reducing agent is injected It may further include a reducing agent injection valve.

In addition, the selective catalytic reduction system may further include a reducing agent filter installed in the reducing agent supply line between the reducing agent supply control valve and the reducing agent supply pump. And the washing water supply line may be connected to the reducing agent supply line between the reducing agent supply control valve and the reducing agent filter.

The reducing agent supply pump may be a volumetric metering control pump.

The selective catalytic reduction system includes a dampener for pulsation damping installed in the reducing agent supply line downstream of the reducing agent supply pump, and installed in the reducing agent supply line downstream of the reducing agent supply pump to maintain a constant back pressure It may further include a back pressure valve.

In addition, the selective catalytic reduction system includes a reducing agent recovery line branched from the reducing agent supply line between the reducing agent supply pump and the pulsation damping damper and connected to the reducing agent storage unit, and a relief valve installed on the reducing agent recovery line. may include

The outlet of the reducing agent storage unit may be formed at the same height as the reducing agent supply pump or at a higher position.

The selective catalytic reduction system may further include a washing water supply valve installed on the washing water supply line, and a washing water supply pressure detecting device installed on the washing water supply line.

In addition, the selective catalytic reduction system includes an air supply valve installed on the air supply line, a first air supply pressure detection device installed on the air supply line downstream of the air supply valve, and the first air supply pressure an air pressure regulating valve installed on the air supply line downstream of the detection device, a second air supply pressure detection device installed on the air supply line downstream of the air pressure regulating valve, and the first air supply pressure detection device And it may further include an air injection valve installed in the air supply line between the injection nozzle.

The selective catalytic reduction system may further include an air filter installed in the air supply line between the first air supply pressure detection device and the air pressure control valve.

The purge line may be branched from the air supply line upstream or downstream of the air pressure regulating valve.

The selective catalytic reduction system may further include a control device for controlling the operation of the reducing agent supply pump and whether the washing water and the compressed air are supplied. And when the supply of the reducing agent to the spray nozzle is stopped, the control device performs a primary cleaning operation using the washing water supplied by the washing water supply unit, and then using the compressed air supplied by the air supply unit 2 Car washing can be done.

The washing water supplied by the washing water supply unit is supplied to the injection nozzle by the operation of the reducing agent supply pump, and the control device sets the supply amount of the washing water supplied by the reducing agent supply pump to the maximum supply flow rate of the reducing agent supply pump. It is possible to control the operation of the reducing agent supply pump so as to be less than 60%.

After the secondary cleaning operation is finished, the washing water may remain in the reducing agent supply line between the point connected to the washing water supply line and the point connected to the purge line.

In addition, in the selective catalytic reduction system, exhaust gas containing nitrogen oxides (NOx) is discharged and the exhaust passage in which the reducing agent decomposition chamber is installed, and a reactor installed on the exhaust passage and provided with a catalyst therein; It may further include a recirculation passage branched from the downstream exhaust passage and joining the exhaust passage upstream of the reactor, a blower installed on the recirculation passage, and a heating device installed on the recirculation passage.

And the reducing agent decomposition chamber may be installed in the recirculation passage downstream than the heating device.

The selective catalytic reduction system may further include a reducing agent injection unit installed at the junction of the recirculation passage and the exhaust passage.

The selective catalytic reduction system includes a bypass passage branching from the exhaust passage upstream of the reactor and joining the exhaust passage downstream of the reactor, and a bypass installed in the bypass passage to open and close the bypass passage It may further include a valve.

In addition, a plurality of the exhaust passage, the reactor, the recirculation passage, the blower, the heating device, and the reducing agent decomposition chamber may be provided. And a plurality of the injection nozzles may be respectively installed for each of the plurality of reducing agent decomposition chambers. In addition, one end of the reducing agent supply line and the air supply line may be respectively branched and connected to a plurality of injection nozzles.

The selective catalytic reduction system may further include a control device for controlling the amount of the reducing agent injected from the injection nozzle according to the content of nitrogen oxides contained in the exhaust gas. And the control device may calculate the total amount of the reducing agent to be supplied to each of the plurality of injection nozzles, and control the operation of the reducing agent supply pump to supply the calculated total amount of the reducing agent.

According to an embodiment of the present invention, the selective catalytic reduction system can not only stably clean the residual reducing agent even with a simple configuration, but also effectively suppress the occurrence of malfunction.

1 is a block diagram of a selective catalytic reduction system according to a first embodiment of the present invention.
FIG. 2 is a detailed configuration diagram of an integrated reducing agent supply device used in the selective catalytic reduction system of FIG. 1 .
3 is a detailed configuration diagram of the integrated reducing agent supply device used in the selective catalytic reduction system according to a modification of the first embodiment of the present invention.
4 shows a form in which the selective catalytic reduction system of FIG. 1 is applied to a ship.
5 and 6 are graphs showing a control method of the reducing agent supply pump used in the selective catalytic reduction system of FIG.
7 is a block diagram of a selective catalytic reduction system according to a second embodiment of the present invention.
8 is a detailed configuration diagram of the integrated reducing agent supply device used in the selective catalytic reduction system of FIG.

Hereinafter, with reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In addition, in various embodiments, components having the same configuration are typically described in the first embodiment using the same reference numerals, and only configurations different from those of the first embodiment will be described in the second embodiment. do.

It is noted that the drawings are schematic and not drawn to scale. Relative dimensions and proportions of parts in the drawings are shown exaggerated or reduced in size for clarity and convenience in the drawings, and any dimensions are illustrative only and not limiting. And the same reference numerals are used to denote like features to the same structure, element, or part appearing in two or more drawings.

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

Hereinafter, a selective catalytic reduction (SCR) system 101 according to a first embodiment of the present invention will be described with reference to FIG. 1 .

The selective catalytic reduction (SCR) system 101 according to the first embodiment of the present invention is used to reduce nitrogen oxides (NOx) contained in exhaust gas discharged from a power plant. For example, the power unit may be a diesel engine used as a main power source for supplying propulsion to a ship or used for power generation. That is, the diesel engine may be a marine 2-stroke low-speed diesel engine or a 4-stroke medium-speed diesel engine. However, the first embodiment of the present invention is not limited thereto. The power unit may be an internal combustion engine for a plant or an engine for a vehicle. That is, various types of engines known to those of ordinary skill in the art may be used as the power device.

1 and 2, the selective catalytic reduction system 101 according to the first embodiment of the present invention is an exhaust passage 610, a reactor 300, a recirculation passage 680, a blower 450, Heating device 400, reducing agent injection unit 470, bypass flow path 630, bypass valve 730, reducing agent decomposition chamber 500, spray nozzle 270, reducing agent storage unit 250, reducing agent supply line 621 , a reducing agent supply pump 280 , a washing water supply line 625 , a washing water supply unit 250 , an air supply unit 230 , an air supply line 623 , a purge line 627 , a purge valve 727 ) , reducing agent supply control valve 721, reducing agent pressure detecting device 821, reducing agent flow rate detecting device 831, reducing agent injection valve 722, reducing agent filter 841, pulsation damping dampener 861, back pressure valve ( 862 , a reducing agent recovery line 628 , a relief valve 728 , a washing water supply valve 725 , a washing water supply pressure detection device 825 , an air supply valve 726 , a first air supply pressure detection device 823 . ), an air pressure control valve 723 , a second air supply pressure detection device 824 , an air injection valve 724 , an air filter 842 , and a control device 700 .

Here, the injection nozzle 270, the reducing agent supply line 621, the reducing agent supply pump 280, the washing water supply line 625, the air supply line 623, the purge line 627, the purge valve 727, the reducing agent Supply control valve 721 , reducing agent pressure detecting device 821 , reducing agent flow rate detecting device 831 , reducing agent injection valve 722 , reducing agent filter 841 , pulsation damping damper 861 , back pressure valve 862 ) , reducing agent recovery line 628, relief valve 728, washing water supply valve 725, washing water supply pressure detection device 825, air supply valve 726, first air supply pressure detection device 823, The air pressure control valve 723 , the second air supply pressure detection device 824 , the air injection valve 724 , and the air filter 842 may constitute the integrated reducing agent supply device 201 .

The exhaust flow path 610 moves the exhaust gas containing nitrogen oxide (NOx) discharged from the power unit. For example, the exhaust flow path 610 may connect an exhaust port of an engine, which is a power device, and a reactor 300 to be described later.

The reactor 300 is installed on the exhaust passage 610 . The reactor 300 includes a catalyst 350 that causes a selective catalytic reduction reaction to reduce nitrogen oxides (NOx) contained in the exhaust gas. The catalyst 350 may promote a reaction between nitrogen oxides (NOx) and a reducing agent contained in the exhaust gas to reduce nitrogen oxides (NOx) into nitrogen and water vapor. In this case, ammonia (NH ₃ ) may be used as a final reducing agent to be reduced by reacting with nitrogen oxide (NOx).

In addition, the catalyst 350 may be disposed in the form of a module, and a plurality of catalyst modules may be loaded in a direction crossing the direction in which the exhaust gas moves in the reactor 300 to form a plurality of catalyst layers. The plurality of catalyst layers may be arranged to be spaced apart from each other based on the direction in which the exhaust gas moves in the reactor 300 .

In addition, the plurality of catalyst modules may be formed in a hexahedron. For example, the plurality of catalyst modules may be a cuboid or a cube. When the catalyst module is formed in a rectangular parallelepiped or cube as described above, it is easy to load the catalyst module, and it is easy to replace and transport the catalyst module, and it is possible to maximize the efficiency of the catalyst 350 included in the catalyst module.

In addition, the catalyst 350 may be made of various materials known to those skilled in the art, such as zeolite, vanadium, and platinum. For example, the catalyst 350 may have an activation temperature within the range of 200 degrees Celsius to 500 degrees Celsius. Here, the activation temperature refers to a temperature at which the catalyst 350 can stably reduce nitrogen oxides without being poisoned. When the catalyst 350 reacts outside the active temperature range, the catalyst 350 is poisoned and the efficiency is lowered.

For example, when a reduction reaction to reduce nitrogen oxides contained in exhaust gas occurs at a relatively low temperature of 150 degrees Celsius or more and less than 250 degrees Celsius, sulfur oxides (SOx) of exhaust gas and ammonia (NH ₃ ) as a reducing agent may react to form a catalyst poisoning substance. Specifically, the poisoning material poisoning the catalyst 350 may include at least one of ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) and ammonium bisulfate (NH ₄ HSO ₄ ). This catalyst poisoning material is adsorbed to the catalyst 350 to decrease the activity of the selective reduction catalyst 350 . Since the catalyst poisoning material 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 may be heated to regenerate the poisoned catalyst 350 .

The bypass flow path 630 may branch from the exhaust flow path 610 upstream of the reactor 300 and join the exhaust flow path 610 downstream of the reactor 300 . That is, the bypass flow path 630 may bypass the reactor 300 . Accordingly, when the operation of the selective catalytic reduction system 101 is stopped and the exhaust gas does not need to pass through the reactor 300 , it is possible to move the exhaust gas through the bypass flow path 630 .

Meanwhile, in the present specification, the term downstream means the rear with respect to the moving direction of the fluid, and the upstream refers to the front with respect to the moving direction of the fluid.

The bypass valve 730 may be installed in the bypass flow path 630 to open and close the bypass flow path 630 .

The recirculation flow path 680 may branch from the exhaust flow path 610 downstream from the reactor 300 and join the exhaust flow path 610 upstream of the reactor 300 .

The blower 450 may be installed on the recirculation passage 680 . The blower 450 may suck a portion of the exhaust gas moving along the exhaust passage 610 into the recirculation passage 680 .

The heating device 400 may be installed on the recirculation passage 680 . The heating device 400 heats the exhaust gas moving along the recirculation flow path 680 to increase the temperature.

The reducing agent decomposition chamber 500 may be installed in the recirculation flow path 680 downstream of the heating device 400 . The reducing agent decomposition chamber 500 may decompose the reducing agent to reduce nitrogen oxides. In the selective catalytic reduction system 101, ammonia (NH ₃ ) is reacted with nitrogen oxides to reduce nitrogen oxides, but since ammonia itself is not easy to store and transport as a pollutant, a stable aqueous urea solution is used rather than directly using ammonia It is common to do That is, after injecting an aqueous solution of urea (CO(NH ₂ ) ₂ ) into the reducing agent decomposition chamber 500 and hydrolyzing or pyrolyzing it to generate ammonia (NH ₃ ), the catalyst 350 is built-in reactor ( 300) is supplied.

The reducing agent injection unit 470 may be installed at the junction of the recirculation flow path 680 and the exhaust flow path 610 . The reducing agent injection unit 470 injects ammonia (NH ₃ ) generated by decomposing the reducing agent in the reducing agent decomposition chamber 500 into the exhaust gas moving toward the reactor 300 .

The injection nozzle 270 may inject the reducing agent into the reducing agent decomposition chamber 500 . Here, the reducing agent may be an aqueous urea solution.

The reducing agent storage unit 210 may store an aqueous solution of urea as a reducing agent to be sprayed by the spray nozzle 270 . In addition, the outlet of the reducing agent storage unit 210, as shown in FIG. 4, may be formed at the same height or high position (h) as the reducing agent supply pump 280 to be described later. 4 exemplarily shows the positions of the reducing agent storage unit 210, the reducing agent supply pump 280, and the injection nozzle 270 when the selective catalytic reduction system 101 is installed on the ship 100.

When the outlet of the reducing agent storage unit 210 is installed at a higher position than the reducing agent supply pump 280, the reducing agent is naturally higher than atmospheric pressure by the level of the reducing agent stored in the reducing agent storage unit 210 to the reducing agent supply pump 280. is supplied, it is possible to fully utilize the performance of the reducing agent supply pump 280 . On the other hand, if the reducing agent supply pump 280 is installed higher than the outlet of the reducing agent storage unit 210, the reducing agent supply pump 280 becomes an operating condition to suck the reducing agent, and the discharge performance of the reducing agent supply pump 280 is lowered. and if it exceeds the limit suction range, the operation of the reducing agent supply pump 280 may become impossible, and the fluid and air are sucked together to cause cavitation in the reducing agent supply pump 280, and damage to the reducing agent supply pump 280 may occur. can

The reducing agent supply line 621 may connect the reducing agent storage unit 210 and the spray nozzle 270 .

The reducing agent supply pump 280 may be installed on the reducing agent supply line 621 . As an example, the reducing agent supply pump 280 may be a volumetric quantitative control pump. That is, a pump capable of controlling the supply flow rate of the reducing agent required by the pump itself as the reducing agent supply pump 280 may be used. As the volumetric quantitative control pump, a diaphragm or cylinder type volumetric pump for supplying a fluid in the form of reciprocating a predetermined volume may be used. Such a volumetric quantitative control pump controls the supply flow rate by adjusting the number of reciprocations of the volume by controlling the number of rotations of the motor driving the pump as a method of controlling the flow rate, or fixing the number of reciprocations and adjusting the reciprocating length, that is, adjusting the reciprocation length. It can be changed to control the feed flow rate. In addition, it is possible to control the supply flow rate in a wider flow rate range by combining the above two methods.

The flow control of such a volumetric quantitative control pump is a closed loop in which a device capable of detecting the flow rate is installed at the pump outlet end, and the rotation speed or reciprocating length of the pump motor is adjusted to match the flow rate to be supplied at the pump outlet. method is applied, or the open-loop method can be applied by inputting data on the supply flow rate for each motor revolution of the pump or the supply flow rate for each reciprocating length of the pump to the control device, and adjusting the pump motor revolution number or reciprocating length for each flow to be supplied. there is.

5 and 6 are graphs illustrating a process of controlling a volumetric quantitative control pump in an open-loop manner.

As shown in FIG. 5 , the amount of reducing agent injection is adjusted by controlling the rotation speed of the motor driving the volumetric quantitative control pump according to the engine load, or the volumetric quantitative control pump according to the engine load as shown in FIG. 6 . By controlling the reciprocating length, the injection amount of the reducing agent can be adjusted.

In addition, by mixing the above-described open-loop method and the closed-loop method, the target flow rate is controlled in the open-loop method at the beginning of the control, and then the supply flow rate is detected through the flow rate detecting means installed at the pump outlet, thereby correcting the pump control. may be applied.

In addition, in order to control the rotation speed of the motor that drives the pump, a frequency control device of the supply current may be separately provided, or an inverter may be provided in the form of a built-in motor, in which case the user inputs an analog current or voltage signal, It can be controlled by matching it with the frequency. In addition, in the case of a flow control method through reciprocating length adjustment, it may include a reciprocating length adjusting device inside the pump or may be mounted in a form that is separately added from the outside, and matches the analog current or voltage signal input from the user with the reciprocating length. can be controlled In addition, the available range of the supply flow rate of the pump can be expanded by controlling the motor rotation speed and the reciprocating length by mixing the two flow control methods described above.

Meanwhile, the first embodiment of the present invention is not limited to the above, and a pump other than the volumetric quantitative control pump may be used as the reducing agent supply pump 280 . However, it is important that the reducing agent supply flow range is wide even when a volumetric quantitative control pump is not used, and in the case of flow control using a centrifugal pump and a flow control valve, the By controlling the supply pressure of the centrifugal pump, it is possible to further expand the supply flow range.

A damper for pulsation damping 861 is installed in the reducing agent supply line 621 downstream of the reducing agent supply pump 280 to reduce the pulsation of the fluid discharged from the reducing agent supply pump 280 . Here, the fluid may be, for example, a reducing agent or washing water.

The back pressure valve 862 is installed in the reducing agent supply line 621 downstream of the reducing agent supply pump 280 to constantly maintain the back pressure of the reducing agent supply line 621 downstream of the reducing agent supply pump 280 .

The reducing agent recovery line 628 may be branched from the reducing agent supply line 261 between the reducing agent supply pump 280 and the pulsation damping damper 861 and connected to the reducing agent storage unit 210 . The reducing agent recovery line 628 recovers the reducing agent that is not sprayed by the spray nozzle 270 after being discharged from the reducing agent supply pump 280 to the reducing agent storage unit 210 .

The relief valve 728 may be installed in the reducing agent recovery line 628 . That is, when the reducing agent supply line 621 downstream of the reducing agent supply pump 280 exceeds a preset pressure, the relief valve 728 is opened and the reducing agent is recovered through the reducing agent recovery line 628 to the reducing agent storage unit 210 . will do

On the other hand, for example, if the concentration of nitrogen oxide contained in the exhaust gas changes according to the operating conditions or environment of the marine engine, the supply of the reducing agent may be temporarily stopped. Responsiveness may deteriorate when resuming supply of reducing agent. In addition, when the reducing agent supply pump 280 is operated and the reducing agent is sprayed from the spray nozzle 270 at the same time, the reducing agent is not evenly sprayed from the spray nozzle 270 at the initial stage of spraying the reducing agent.

Therefore, in the first embodiment of the present invention, the reducing agent is injected at a constant pressure from the injection nozzle 270 and in order to improve the responsiveness to the reducing agent injection, the reducing agent supply pump 280 is earlier than the time when the reducing agent supply is required. It can be operated and the reducing agent supply line 621 that supplies the reducing agent to the spray nozzle 270 through the reducing agent recovery line 628 and the relief valve 728 is maintained at a constant pressure to inject the reducing agent from the spray nozzle 270 Not only can the responsiveness be improved at the time of starting, but also the reducing agent can be sprayed evenly.

The washing water supply line 625 may be connected to the reducing agent supply line 621 between the reducing agent supply pump 280 and the reducing agent storage unit 210 .

The washing water supply unit 250 may supply washing water to the washing water supply line 625 . The washing water supplied by the washing water supply unit 250 may be used to remove the reducing agent remaining in the reducing agent supply line 621 or the spray nozzle 270 after the supply of the reducing agent to the spray nozzle 270 is stopped.

The washing water supply valve 725 may be installed on the washing water supply line 625 to open and close the washing water supply line 625 .

The washing water supply pressure detecting device 825 may be installed on the washing water supply line 625 . The control device 700 to be described later may generate a warning when the pressure of the washing water detected by the washing water supply pressure detecting device 825 is lower or higher than the washing water allowable pressure. Here, the allowable pressure of the washing water may vary according to the detailed specifications of the selective catalytic reduction system 101 .

The air supply unit 230 may supply compressed air to be sprayed by the spray nozzle 270 . The compressed air supplied by the air supply unit 230 may be used for atomization of the reducing agent sprayed from the injection nozzle 270 or used for cleaning the reducing agent supply line 621 . In addition, the air supply unit 230 may be configured in various methods known to those of ordinary skill in the art.

The air supply line 623 may connect the air supply unit 230 and the spray nozzle 270 .

The air supply valve 726 may be installed on the air supply line 623 to open and close the air supply line 623 .

The first air supply pressure detecting device 823 may be installed on the air supply line 623 downstream of the air supply valve 726 . The first air supply pressure detection device 823 may detect the pressure of the compressed air supplied by the air supply unit 230 . When the compressed air pressure detected by the first air supply pressure detection device 823 is lower than or higher than the allowable air pressure, the control device 700 to be described later may generate a warning. Here, the allowable air pressure may vary according to the detailed specifications of the selective catalytic reduction system 101 .

The air pressure control valve 723 may be installed on the air supply line 623 downstream of the first air supply pressure detection device 823 . The air pressure control valve 723 may adjust the pressure of the compressed air so that the compressed air supplied from the air supply line 623 is an appropriate pressure according to the purpose for which it is used.

The second air supply pressure detection device 824 may be installed on the air supply line 623 downstream of the air pressure control valve 723 . The second air supply pressure detection device 824 cooperates with the air pressure control valve 723 to help the air pressure control valve 723 regulate the pressure of the compressed air.

The air injection valve 724 may be installed in the air supply line 623 between the first air supply pressure detection device 824 and the injection nozzle 270 . That is, the air injection valve 724 may control whether compressed air is injected by the injection nozzle 270 .

The air filter 842 may be installed in the air supply line 623 between the first air supply pressure detection device 823 and the air pressure control valve 723 . The air filter 842 may remove foreign substances contained in the compressed air supplied by the air supply unit 230 .

The purge line 627 may branch from the air supply line 623 and join the reducing agent supply line 621 between the reducing agent supply pump 280 and the injection nozzle 270 . The reducing agent and washing water remaining in the spray nozzle 270 can be removed by using the compressed air supplied from the air supply unit 230 by the purge line 627 .

For example, the purge line 627 may be branched from the air supply line 623 downstream of the air pressure control valve 723 . In addition, the purge line 627 may be joined to the reducing agent supply line 621 downstream than the reducing agent supply pump 280 .

However, the first embodiment of the present invention is not limited to the above, and as shown in FIG. 3 , the purge line 627 is branched from the air supply line 623 upstream of the air pressure control valve 723 . can

The purge valve 727 may be installed on the purge line 627 to open and close the purge line 627 .

The reducing agent supply control valve 721 may be installed in the reducing agent supply line 621 between the connection point to the washing water supply line 625 and the reducing agent storage unit 210 . The reducing agent supply control valve 721 may control the supply and blocking of the reducing agent.

The reducing agent pressure detection device 821 may be installed on the reducing agent supply line 621 to measure the supply pressure of the reducing agent. A plurality of reducing agent pressure detection device 821 may be installed as needed.

On the other hand, the control device 700 to be described later may generate a warning when the pressure detected by the reducing agent pressure detection device 821 exceeds or is less than the reducing agent allowable pressure. Here, the allowable pressure of the reducing agent may vary according to the detailed specifications of the selective catalytic reduction system 101 .

The reducing agent flow rate detection device 831 may be installed on the reducing agent supply line 621 to detect the supply flow rate of the reducing agent. The control device 700 to be described later can determine the amount of the reducing agent currently being supplied based on the information provided by the reducing agent flow rate detection device 831 and the reducing agent pressure detection device 821 .

The reducing agent injection valve 722 may be installed in the reducing agent supply line 621 between the reducing agent flow rate detection device 831 and the injection nozzle 270 to control whether or not the reducing agent is injected.

The reducing agent filter 841 may be installed in the reducing agent supply line 621 between the reducing agent supply control valve 721 and the reducing agent supply pump 280 . The reducing agent filter 841 may remove foreign substances contained in the reducing agent. In addition, the washing water supply line 625 may be connected to the reducing agent supply line 621 between the reducing agent supply control valve 721 and the reducing agent filter 841 . Accordingly, the washing water supplied to the reducing agent supply line 621 through the washing water supply line 625 also passes through the reducing agent filter 841 .

The control device 700 may control various valves used in the selective catalytic reduction system 101 , the reducing agent supply pump 280 , the heating device 400 , and the blower 450 .

In particular, in the first embodiment of the present invention, the control device 700 can control the operation of the reducing agent supply pump 270 and the supply of washing water and compressed air, the control device 700 is the injection nozzle 270 ), when the supply of the reducing agent is stopped, the primary cleaning operation is performed using the cleaning water supplied by the cleaning water supply unit 250, and then the secondary cleaning operation is performed using the compressed air supplied by the air supply unit 230. can do.

At this time, the washing water supplied by the washing water supply unit 250 may be supplied to the spray nozzle 270 by the operation of the reducing agent supply pump 280 .

According to the first embodiment of the present invention, since the washing water supply line 625 is connected to the reducing agent supply line 621 between the reducing agent supply pump 280 and the reducing agent storage unit 210, the reducing agent supply pump 280 By using the washing water can be supplied toward the injection nozzle 270 at the same pressure as the reducing agent supply pressure.

If, as in the first embodiment of the present invention, the washing water cannot be supplied using the reducing agent supply pump 280, a separate washing water supply pump for supplying the washing water to the selective catalytic reduction system 101 is required At this time, the separate washing water supply pump must be able to supply the washing water at a pressure higher than the pressure required when the reducing agent is injected from the injection nozzle 270 when the injection nozzle 270 is a single fluid type nozzle, and the injection nozzle ( If the 270) is a liquid-type nozzle, the washing water can be smoothly supplied only when the washing water can be supplied to the spray nozzle 270 at a pressure higher than the pressure of the compressed air supplied together for atomization. When cleaning water is used for cleaning the reducing agent supply line 621 and the spray nozzle 270, when the cleaning water is supplied while the spray nozzle 270 is spraying compressed air, the reducing agent is compressed by the pressure of the compressed air. This is because the reverse pressure to the supply line 621 acts, and therefore, the supply pressure of the washing water must be higher than the air reverse working pressure to prevent the reverse flow of the washing water and perform the washing smoothly. However, providing a separate washing water supply pump to satisfy the above-described performance may cause a significant increase in the initial installation cost and maintenance cost of the selective catalytic reduction system 101 .

In addition, according to the first embodiment of the present invention, the control device 700 supplies the reducing agent so that the supply amount of the washing water supplied by the reducing agent supply pump 280 is 60% or less of the maximum supply flow rate of the reducing agent supply pump 280 . The operation of the pump 280 may be controlled.

In addition, according to the first embodiment of the present invention, after the secondary cleaning operation is finished, there is a washing water in the reducing agent supply line 621 between the point connected to the washing water supply line 625 and the point connected to the purge line 627 . will remain Therefore, the reducing agent supply line 621 in which the reducing agent flow rate detection device 831 is installed is emptied, and it is possible to prevent the reducing agent flow rate detection device 831 from malfunctioning.

By such a configuration, the selective catalytic reduction system 101 according to the first embodiment of the present invention can not only stably clean the residual reducing agent even with a simple configuration, but also effectively suppress the occurrence of malfunction.

Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 7 and 8 .

7 and 8, in the selective catalytic reduction system 102 according to the second embodiment of the present invention, the exhaust passages 611 and 612, the catalysts 351 and 352 are built-in reactors 301 and 302 ), bypass flow path (631, 632), bypass valve (731, 732), recirculation flow path (681, 682), blower (451, 452), heating device (401, 402), reducing agent injection unit (471, 472) ), and a plurality of reducing agent decomposition chambers 501 and 502 may be provided. And a plurality of injection nozzles 271 and 272 may be installed for each of the plurality of reducing agent decomposition chambers 501 and 502, respectively. In addition, a plurality of control devices 701 and 702 may be provided as needed.

In addition, one end of the reducing agent supply line 621 and the air supply line 623 may be respectively branched and connected to the plurality of spray nozzles 271 and 272 .

In addition, in the second embodiment of the present invention, one integrated reducing agent supply device 202 is a plurality of injection nozzles 271 and 272 are used, and one end of the reducing agent supply line 621 and the air supply line 623 is branched. , The basic structure is the same as that of the first embodiment, except that a plurality of valves and sensors are installed according to the branching of the reducing agent supply line 621 and the air supply line 623 .

In addition, the control device 700 may control the amount of the reducing agent to be injected from the plurality of injection nozzles 271 and 272, respectively, according to the content of nitrogen oxides contained in the exhaust gas.

Specifically, the control device 700 calculates the total amount of the reducing agent to be supplied to the plurality of injection nozzles 271 and 272, respectively, and controls the operation of the reducing agent supply pump 280 to supply the calculated total amount of the reducing agent. can

By such a configuration, the selective catalytic reduction system 102 according to the second embodiment of the present invention can also stably clean the residual reducing agent even with a simple configuration, as well as effectively suppress the occurrence of malfunction.

In particular, by using one integrated reducing agent supply device 202 to reduce nitrogen oxides contained in exhaust gas discharged from a plurality of power units, the overall configuration of the selective catalytic reduction system 102 can be simplified.

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

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

100: ship
101, 102: selective catalytic reduction system
201, 202: integrated reducing agent supply unit
210: reducing agent storage unit
230: air supply
250: washing water supply unit
270, 271, 272: spray nozzle
280: reducing agent supply pump
300, 301, 302: reactor
350, 351, 352: catalyst
400, 401, 402: heating device
450, 451, 452: blower
470, 471, 472: reducing agent injection unit
500, 501, 502: reducing agent decomposition chamber
610, 611, 612: exhaust flow path
621: reducing agent supply line
623: air supply line
625: washing water supply line
627: purge line
628: reducing agent recovery line
630, 631, 632: Bypass Euro
680, 681, 682: recirculation flow path
700, 701, 702: control unit
721: reducing agent supply control valve
722: reducing agent injection valve
723: air pressure regulating valve
724: air injection valve
725: flushing water supply valve
726: air supply valve
727: purge valve
728: relief valve
730, 731, 732: bypass valve
821: reducing agent pressure detection device
823: first air pressure detection device
824: second air pressure detection device
825: washing water pressure detection device
831: reducing agent flow rate detection device
841: reducing agent filter
842: air filter
861: dampener for pulsation damping
862: back pressure valve

Claims (20)

a reducing agent decomposition chamber for decomposing the reducing agent to reduce nitrogen oxides;
a spray nozzle for spraying a reducing agent into the reducing agent decomposition chamber;
a reducing agent storage unit for storing the reducing agent to be sprayed by the injection nozzle;
a reducing agent supply line connecting the reducing agent storage unit and the spray nozzle;
a reducing agent supply pump installed on the reducing agent supply line;
a washing water supply line connected to the reducing agent supply line between the reducing agent supply pump and the reducing agent storage unit;
a washing water supply unit supplying washing water to the washing water supply line;
an air supply unit for supplying compressed air to be sprayed by the spray nozzle;
an air supply line connecting the air supply unit and the spray nozzle; and
A purge line branching from the air supply line and joining the reducing agent supply line between the reducing agent supply pump and the injection nozzle
A selective catalytic reduction system comprising a. According to claim 1,
a reducing agent supply control valve installed in the reducing agent supply line between the connection point to the washing water supply line and the reducing agent storage unit;
a reducing agent pressure detection device installed on the reducing agent supply line to measure the supply pressure of the reducing agent;
a reducing agent flow rate detection device installed on the reducing agent supply line to detect the supply flow rate of the reducing agent; and
A reducing agent injection valve installed in the reducing agent supply line between the reducing agent flow rate detection device and the injection nozzle to control whether or not the reducing agent is injected
Selective catalytic reduction system, characterized in that it further comprises. 3. The method of claim 2,
Further comprising a reducing agent filter installed in the reducing agent supply line between the reducing agent supply control valve and the reducing agent supply pump,
The washing water supply line is a selective catalytic reduction system, characterized in that connected to the reducing agent supply line between the reducing agent supply control valve and the reducing agent filter. According to claim 1,
The selective catalytic reduction system, characterized in that the reducing agent supply pump is a volumetric quantitative control pump. 5. The method of claim 4,
a dampener for pulsation damping installed in the reducing agent supply line downstream from the reducing agent supply pump;
A back pressure valve installed in the reducing agent supply line downstream of the reducing agent supply pump to maintain a constant back pressure
Selective catalytic reduction system, characterized in that it further comprises. 6. The method of claim 5,
a reducing agent recovery line branched from the reducing agent supply line between the reducing agent supply pump and the pulsation damping damper and connected to the reducing agent storage unit;
Relief valve installed in the reducing agent return line
Selective catalytic reduction system further comprising a. According to claim 1,
The outlet of the reducing agent storage unit is a selective catalytic reduction system, characterized in that formed at the same height or high position as the reducing agent supply pump. According to claim 1,
a washing water supply valve installed on the washing water supply line;
Washing water supply pressure detection device installed on the washing water supply line
Selective catalytic reduction system, characterized in that it further comprises. According to claim 1,
an air supply valve installed on the air supply line;
a first air supply pressure detecting device installed on the air supply line downstream of the air supply valve;
an air pressure regulating valve installed on the air supply line downstream of the first air supply pressure detecting device;
a second air supply pressure detecting device installed on the air supply line downstream of the air pressure regulating valve; and
an air injection valve installed in the air supply line between the first air supply pressure detection device and the injection nozzle
Selective catalytic reduction system, characterized in that it further comprises. 10. The method of claim 9,
Selective catalytic reduction system, characterized in that it further comprises an air filter installed in the air supply line between the first air supply pressure detection device and the air pressure control valve. 10. The method of claim 9,
The purge line is a selective catalytic reduction system, characterized in that branching from the air supply line upstream or downstream of the air pressure control valve. According to claim 1,
Further comprising a control device for controlling the operation of the reducing agent supply pump and the supply of the washing water and the compressed air,
When the supply of the reducing agent to the spray nozzle is stopped, the control device performs a primary cleaning operation using the washing water supplied by the washing water supply unit, and then performs a secondary cleaning operation using the compressed air supplied by the air supply unit. A selective catalytic reduction system, characterized in that performing a cleaning operation. 13. The method of claim 12,
The washing water supplied by the washing water supply unit is supplied to the spray nozzle by the operation of the reducing agent supply pump,
The control device is a selective catalytic reduction system, characterized in that for controlling the operation of the reducing agent supply pump so that the supply amount of the washing water supplied by the reducing agent supply pump is 60% or less of the maximum supply flow rate of the reducing agent supply pump. 13. The method of claim 12,
Selective catalytic reduction system, characterized in that the washing water remains in the reducing agent supply line between the point connected to the washing water supply line and the point connected to the purge line after the secondary washing operation is finished. 15. The method according to any one of claims 1 to 14,
an exhaust passage through which exhaust gas containing nitrogen oxide (NOx) is discharged and the reducing agent decomposition chamber is installed;
a reactor installed on the exhaust passage and provided with a catalyst therein;
a recirculation passage branching from the exhaust passage downstream of the reactor and joining the exhaust passage upstream of the reactor;
a blower installed on the recirculation passage; and
a heating device installed on the recirculation passage
Selective catalytic reduction system, characterized in that it further comprises. 16. The method of claim 15,
The reducing agent decomposition chamber is a selective catalytic reduction system, characterized in that installed in the recirculation passage downstream than the heating device. 16. The method of claim 15,
Selective catalytic reduction system, characterized in that it further comprises a reducing agent injection unit installed at the junction of the recirculation passage and the exhaust passage. 16. The method of claim 15,
a bypass passage branching from the exhaust passage upstream of the reactor and joining the exhaust passage downstream of the reactor;
A bypass valve installed in the bypass flow path to open and close the bypass flow path
Selective catalytic reduction system, characterized in that it further comprises. 16. The method of claim 15,
A plurality of the exhaust passage, the reactor, the recirculation passage, the blower, the heating device, and the reducing agent decomposition chamber are provided,
A plurality of the injection nozzles are installed for each of the plurality of reducing agent decomposition chambers,
Selective catalytic reduction system, characterized in that one end of the reducing agent supply line and the air supply line is respectively branched and connected to a plurality of injection nozzles. 20. The method of claim 19,
Further comprising a control device for controlling the amount of the reducing agent injected from the injection nozzle according to the content of nitrogen oxides contained in the exhaust gas,
Selective catalytic reduction system, characterized in that the control device calculates the total amount of the reducing agent to be supplied to each of the plurality of injection nozzles, and controls the operation of the reducing agent supply pump to supply the calculated total amount of the reducing agent.

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