KR102357036B1 - Selective catalytic reuction system and operating the same - Google Patents

Abstract

The present invention relates to a selective catalytic reduction system for reducing nitrogen oxides contained in exhaust gas discharged from a diesel engine and a method for operating the same, and the selective catalytic reduction system according to an embodiment of the present invention is a nitrogen oxide contained in exhaust gas. A reactor having a catalyst provided therein for reducing , a plurality of pressure sensors for measuring the differential pressure between the front and rear ends of the reactor with the catalyst interposed therebetween, and a plurality of for measuring the nitrogen oxide reduction efficiency of the exhaust gas that has passed through the catalyst of nitrogen oxide concentration sensor.

Description

Selective catalytic reduction system and its operating method

An embodiment of the present invention relates to a selective catalytic reduction system and an operating method thereof, and more particularly, to a selective catalytic reduction system for reducing nitrogen oxides in exhaust gas discharged from a diesel engine and an operating method thereof.

In general, a selective catalytic reduction (SCR) system is a system for reducing nitrogen oxides contained in exhaust gas by purifying exhaust gas generated from diesel engines, boilers, incinerators, and the like.

Among them, the diesel engine contains a large amount of nitrogen oxides (NOx) in the exhaust gas due to the compression ignition combustion method. Also, unlike gasoline engines, diesel engines cannot use a three-way catalyst because of their lean burn. In order to satisfy the stricter exhaust gas regulations, the introduction of a selective catalytic reduction (SCR) system to diesel engines is becoming common.

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.

However, in the case of a diesel engine mainly operated at a low load, such as a diesel engine used in a ship, urea is deposited in the urea water used as a reducing agent, so that a deposit is easily generated.

For example, when urea is injected into an exhaust gas having a temperature of less than 250 degrees Celsius, biuret, cyanuric acid, melamine, and ammeline, which are produced while decomposing urea It may be formed in sediments such as When the diesel engine is operated at low load, the temperature of the exhaust gas is lowered, and thus the formation of deposits is increased.

In addition, since diesel engines used in ships mainly use low-quality fuel with a high sulfur content, in this case, urea and soot used as a reducing agent block the inlet of the reactor in which the catalyst is installed. The phenomenon occurs frequently. This phenomenon may increase the pressure of the exhaust gas of the diesel engine and cause deterioration of performance or fuel consumption efficiency, and in the long term, may cause the entire engine to stop.

An embodiment of the present invention provides a selective catalytic reduction system capable of effective maintenance by measuring and monitoring the pressure difference between the front and rear ends of the reactor in which the catalyst is installed and the nitrogen oxide reduction efficiency, and a method for operating the same.

According to an embodiment of the present invention, a selective catalytic reduction (SCR) system for reducing nitrogen oxides contained in exhaust gas discharged from a diesel engine includes a catalyst for reducing nitrogen oxides contained in exhaust gas inside. A reactor provided in the, a plurality of pressure sensors for measuring the differential pressure between the front and rear ends of the reactor with the catalyst interposed therebetween, and a plurality of nitrogen oxide concentration sensors for measuring the nitrogen oxide reduction efficiency of the exhaust gas that has passed through the catalyst do. In addition, if the pressure difference between the front and rear ends of the reactor measured by the plurality of pressure sensors is equal to or greater than the reference value or the nitrogen oxide reduction efficiency measured by the plurality of nitrogen oxide concentration sensors is less than the reference value, the diesel engine is set to the maximum load for a preset time. drive

The selective catalytic reduction (SCR) system includes a cleaning warning light that lights up when the pressure difference between the front and rear ends of the reactor measured by the plurality of pressure sensors is equal to or greater than a reference value even after the diesel engine is operated at maximum load; Even after the diesel engine is operated at the maximum load, when the nitrogen oxide reduction efficiency measured by the plurality of nitrogen oxide concentration sensors is less than the reference value, a catalyst replacement warning lamp may be further included.

The diesel engine is equipped with a supercharger, and when the catalyst replacement warning light is turned on while the cleaning warning light is turned off, the diesel engine equipped with the supercharger can be checked for abnormality along with the replacement of the catalyst. .

The selective catalytic reduction (SCR) system further includes a control device that receives information from the plurality of pressure sensors and the plurality of nitrogen oxide concentration sensors and transmits signals to the cleaning warning lamp and the catalyst replacement warning lamp can do.

In addition, according to an embodiment of the present invention, the selective catalytic reduction system operating method for reducing nitrogen oxides contained in exhaust gas discharged from a diesel engine using a reactor having a catalyst installed therein is provided before and after the reactor with the catalyst interposed therebetween. Measuring the exhaust gas differential pressure of the stage, measuring the nitrogen oxide reduction efficiency of the exhaust gas that has passed through the catalyst, and when the differential pressure of the exhaust gas is greater than or equal to the reference value or the nitrogen oxide reduction efficiency is less than the reference value, the diesel engine is set operating at full load for a period of time.

In addition, the selective catalytic reduction system operating method includes the steps of again measuring the exhaust gas differential pressure and nitrogen oxide reduction efficiency after the maximum load operation of the diesel engine, and the differential pressure of the exhaust gas after the maximum load operation of the diesel engine is greater than or equal to the reference value The method may further include removing a deposit or plugging, and if the nitrogen oxide reduction efficiency is less than a reference value, removing the deposit or plugging and replacing the catalyst.

In addition, in the selective catalytic reduction system operating method, if the differential pressure of the exhaust gas is less than the reference value after the maximum load operation of the diesel engine and the nitrogen oxide reduction efficiency is less than the reference value, the diesel engine is replaced with the replacement of the catalyst. It may further include the step of

According to an embodiment of the present invention, the selective catalytic reduction system and its operating method can be effectively maintained by measuring and monitoring the pressure difference between the front and rear ends of the reactor in which the catalyst is installed and the nitrogen oxide reduction efficiency.

1 is a configuration diagram in which a selective catalytic reduction system according to an embodiment of the present invention is used.
FIG. 2 is a perspective view showing a reactor used in the selective catalytic reduction system of FIG. 1 .
3 is a flowchart illustrating a method of operating a selective catalytic reduction system according to an embodiment of the present invention.

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.

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 an embodiment of the present invention will be described with reference to FIGS. 1 and 2 .

1 and 2, the selective catalytic reduction system 101 according to an embodiment of the present invention may be used to reduce nitrogen oxides contained in the exhaust gas discharged from the diesel engine 200, In particular, it can be used to reduce nitrogen oxides contained in exhaust gas discharged from a diesel engine 200 that uses high sulfur oil as a fuel, such as a ship.

In addition, the diesel engine 200 to which the selective catalytic reduction system 101 according to an embodiment of the present invention is applied may be equipped with a supercharger (250, turbo charger). In FIG. 1, reference numeral 280 denotes an air cooler.

Selective catalytic reduction system 101 according to an embodiment of the present invention includes a reactor 300, a plurality of pressure sensors (410, 420), and a plurality of nitrogen oxide concentration sensors (460, 470).

In addition, the selective catalytic reduction system 101 according to an embodiment of the present invention may further include a cleaning warning light 453 , a catalyst replacement warning light 458 , and a control device 450 .

In addition, the selective catalytic reduction system 101 according to an embodiment of the present invention may further include an exhaust flow path 610 in which the exhaust gas discharged from the diesel engine 200 moves. That is, the exhaust flow path 610 moves so that the exhaust gas containing nitrogen oxide (NOx) discharged from the diesel engine is discharged.

The reactor 300 is installed on the exhaust passage 610 . The reactor 300 includes a catalyst 350 for reducing nitrogen oxides (NOx) contained in the exhaust gas. The catalyst 350 promotes a reaction between nitrogen oxides (NOx) and a reducing agent contained in exhaust gas to reduce nitrogen oxides (NOx) into nitrogen and water vapor. At this time, an aqueous solution of urea is used as a reducing agent to react with and reduce nitrogen oxides (NOx). Urea (urea, CO(NH ₂ ) ₂ ) in aqueous urea solution is hydrolyzed or pyrolyzed to produce ammonia (NH ₃ ) and isocyanic acid (HNCO). And isocyanic acid (HNCO) is again decomposed into _{ammonia (NH 3} ) and carbon dioxide (CO _{2 ).} That is, when urea is decomposed, ammonia is finally produced. And ammonia (NH ₃ ) serves as a final reducing agent that directly reacts with nitrogen oxides.

For example, the reducing agent may be injected into the exhaust passage 600 through a reducing agent injection device (not shown). The sprayed reducing agent is mixed with the exhaust gas and passes through the catalyst 350 of the reactor 300 to reduce nitrogen oxides (NOx) contained in the exhaust gas.

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 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 stably reduce nitrogen oxides without being poisoned. When the catalyst 350 reacts outside the active temperature range, the catalyst is poisoned and the efficiency is lowered. Specifically, the poisoning material that poisons 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 reduce the activity of the catalyst 350 . When the catalyst 350 is poisoned, it can be replaced or regenerated and used. Since the catalyst poisoning material is decomposed at a relatively high temperature, the poisoned catalyst may be regenerated by increasing the temperature of the catalyst 350 .

A plurality of pressure sensors 410 and 420 are provided. A plurality of pressure sensors 410 and 420 measure the differential pressure between the front and rear ends of the reactor 300 with the catalyst 350 interposed therebetween. That is, the plurality of pressure sensors 410 and 420 include a first pressure sensor 410 installed at a front end of the reactor 300 and a second pressure sensor 420 installed at a rear end of the reactor 300 .

When the difference between the pressures measured by the first pressure sensor 410 and the second pressure sensor 420 is equal to or greater than the reference value, it is determined that the normal operation state is out. Here, the reference value may be set according to the type of the diesel engine 200 , the size of the reactor 300 , and the type and shape of the catalyst 350 installed inside the reactor 300 .

A plurality of nitrogen oxide concentration sensors 460 and 470 are also provided to measure the nitrogen oxide reduction efficiency of the exhaust gas that has passed through the catalyst 350 . That is, the plurality of nitrogen oxide concentration sensors 460 and 470 include a first nitrogen oxide concentration sensor 460 installed at the front end of the reactor 300 and a second nitrogen oxide concentration sensor 470 installed at the rear end of the reactor 300 . . The first nitrogen oxide concentration sensor 460 and the second nitrogen oxide concentration sensor 470 measure the nitrogen oxide concentration at the front and rear ends of the reactor 300 with the catalyst 350 interposed therebetween to calculate nitrogen oxide reduction efficiency.

Specifically, the nitrogen oxide reduction efficiency is calculated by comparing the nitrogen oxide concentration measured by the first nitrogen oxide concentration sensor 460 with the nitrogen oxide concentration measured by the second nitrogen oxide concentration sensor 470 .

If the NOx reduction efficiency is less than the reference value, it is judged that the normal operation state is out. Here, the reference value may also be set according to the type of the diesel engine 200 , the size of the reactor 300 , and the type and shape of the catalyst 350 installed inside the reactor 300 .

The control device 450 may receive information from the plurality of pressure sensors 410 and 420 and the plurality of nitrogen oxide concentration sensors 460 and 470 to control the operation of the diesel engine 200 .

Also, the control device 450 may transmit signals to the cleaning warning light 453 and the catalyst replacement warning light 458 .

Also, the control device 450 may have the form of a control panel, and a cleaning warning light 453 and a catalyst replacement warning light 458 may be provided in the control device 450 .

However, an embodiment of the present invention is not limited to the above, and the control device 450 may be omitted.

When the control device 450 is omitted, the cleaning warning light 453 receives signals from the plurality of pressure sensors 410 and 420, and the catalyst replacement warning light 458 receives signals from the plurality of nitrogen oxide concentration sensors 460 and 470. can receive

In addition, the operator may determine the lighting status of the cleaning warning lamp 453 and the catalyst replacement warning lamp 458 , and directly take measures to control the operation of the diesel engine 200 on behalf of the control device 450 .

In one embodiment of the present invention, the control device 450 is the pressure difference between the front and rear ends of the reactor 300 measured by the plurality of pressure sensors 410 and 420 is equal to or greater than the reference value or the plurality of nitrogen oxide concentration sensors 460 and 470 If the measured nitrogen oxide reduction efficiency is less than the reference value, the diesel engine 200 is operated at the maximum load for a preset time.

For example, the preset time may be one hour. However, one embodiment of the present invention is not limited thereto, and various settings are made according to the type of the diesel engine 200 , the temperature of exhaust gas, the size of the reactor 300 , and the type of catalyst installed inside the reactor 300 . can be

Even after the diesel engine 200 is operated at the maximum load, if the pressure difference between the front and rear ends of the reactor 300 measured by the plurality of pressure sensors 410 and 420 is equal to or greater than the reference value, the control device 450 turns on the cleaning warning light 452 make it

When the cleaning warning lamp 453 is turned on, the operator performs a cleaning operation of removing deposits or plugging generated in the reactor 300 or the exhaust passage 610 .

In addition, if the nitrogen oxide reduction efficiency measured by the plurality of nitrogen oxide concentration sensors 460 and 470 is less than the reference value even after the diesel engine 200 is operated at the maximum load, the control device 450 turns on the catalyst replacement warning lamp 458 . make it

When the catalyst replacement warning light 458 is turned on, the operator performs the replacement operation of the catalyst 350 .

In particular, when the catalyst replacement warning lamp 458 is turned on while the cleaning warning lamp 453 is turned off, it instructs to check whether the diesel engine 200 is abnormal along with the replacement of the catalyst 350 .

On the other hand, when the cleaning warning lamp 453 is turned on while the catalyst replacement warning lamp 458 is turned off, it is determined that the occlusion by the generation of deposits or plugging is simply the cause, and the cleaning operation is performed.

With such a configuration, the selective catalytic reduction system 101 according to an embodiment of the present invention is effectively maintained by measuring and monitoring the pressure difference and nitrogen oxide reduction efficiency between the front and rear ends of the reactor 300 in which the catalyst 350 is installed. can do.

In particular, effective inspection is performed by monitoring whether or not cleaning work is required for the reactor 300 and the exhaust flow path 610 and whether the catalyst 350 is replaced, as well as the presence or absence of abnormalities in the diesel engine 200 equipped with the supercharger 250 . can do.

Hereinafter, an operating method of the selective catalytic reduction system 101 according to an embodiment of the present invention will be described in detail with reference to FIG. 3 .

The operating method of the selective catalytic reduction system 101 according to an embodiment of the present invention reduces nitrogen oxides contained in the exhaust gas discharged from the diesel engine 200 using the reactor 300 in which the catalyst 350 is installed. In the process, the pressure difference between the front and rear ends of the reactor 300 and the nitrogen oxide reduction efficiency are measured to determine whether cleaning work is required for the reactor 300 and the exhaust passage 610, whether the catalyst 350 is replaced, and the supercharger 250. It is possible to monitor the possibility of abnormality of the diesel engine 200 equipped with.

First, the selective catalytic reduction system 101 is operated to reduce nitrogen oxides contained in the exhaust gas discharged from the diesel engine 200 .

When the selective catalytic reduction system 101 according to an embodiment of the present invention is operated, a plurality of pressure sensors 410 and 420 measure the differential pressure of exhaust gas at the front and rear ends of the reactor 300 with the catalyst 350 interposed therebetween, A plurality of nitrogen oxide concentration sensors 460 and 470 measure and monitor the nitrogen oxide reduction efficiency of the exhaust gas that has passed through the catalyst 350 .

During monitoring, if the differential pressure of the exhaust gas is greater than or equal to the reference value or the nitrogen oxide reduction efficiency is less than the reference value, the diesel engine 200 is operated at the maximum load for a preset time. For example, the preset time may be one hour. In addition, the reference value may be set according to the type and shape of the diesel engine 200 , the size of the reactor 300 , and the type and shape of the catalyst 350 installed inside the reactor 300 .

When the diesel engine 200 is operated at the maximum load, the temperature of the exhaust gas rises, and the catalyst 350 poisoned by the thermal energy of the exhaust gas having the elevated temperature may be regenerated, or deposits or plugging may be removed.

Next, after the maximum load operation of the diesel engine 200 , the exhaust gas differential pressure and nitrogen oxide reduction efficiency are measured again. And if the differential pressure of exhaust gas after the maximum load operation of the diesel engine 200 is equal to or greater than the reference value, deposits or plugging are removed.

In this case, although there is no problem in the activity of the catalyst 350, it is determined that a deposit is generated at the front end of the reactor 300, or plugging by soot or urea is generated. will perform

In addition, if the nitrogen oxide reduction efficiency is also less than the reference value, a deposit or plugging is removed and the catalyst 350 is replaced. In this case, it is determined that there is a problem in the activity of the catalyst 350 in addition to the formation of deposits and plugging, and the catalyst replacement is also performed.

On the other hand, if the differential pressure of exhaust gas is less than the reference value and the nitrogen oxide reduction efficiency is less than the reference value after the maximum load operation of the diesel engine 200 , the catalyst 350 is replaced and the diesel engine 200 is checked for abnormalities.

In this case, in a state in which the activity of the catalyst 350 is reduced and not recovered, the cause of the decrease in the activity of the catalyst 350 is an abnormality in the supercharger 250 of the diesel engine 200 and the catalyst 350 is It can be seen as poisoning by oil or sulfur poisoning due to the use of low-quality fuel, or abnormal heat generation due to malfunction of the injector. Accordingly, not only the catalyst 350 is replaced, but also the overall abnormality of the diesel engine 200 is checked.

On the other hand, when the differential pressure of exhaust gas is greater than or equal to the reference value and the nitrogen oxide reduction efficiency is greater than or equal to the reference value after maximum load operation of the diesel engine 9200, it is determined that the cause is simply due to blockage by the generation of deposits or plugging. will do the job.

By operating the selective catalytic reduction system 101 according to an embodiment of the present invention according to this method, it is effective by measuring and monitoring the pressure difference between the front and rear ends of the reactor 300 in which the catalyst 350 is installed and the nitrogen oxide reduction efficiency. Maintenance is possible.

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 will 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.

101: selective catalytic reduction system
200: diesel engine
250: supercharger
300: reactor
350: catalyst
410: first pressure sensor
420: second pressure sensor
450: control device
453: cleaning warning light
458: catalyst replacement warning light
460: first nitrogen oxide concentration sensor
470: second nitrogen oxide concentration sensor
610: exhaust flow path

Claims (7)

In a selective catalytic reduction (SCR) system for reducing nitrogen oxides contained in exhaust gas discharged from a diesel engine,
a reactor provided therein with a catalyst for reducing nitrogen oxides contained in exhaust gas;
a plurality of pressure sensors for measuring the differential pressure between the front and rear ends of the reactor with the catalyst interposed therebetween;
a plurality of nitrogen oxide concentration sensors for measuring the nitrogen oxide reduction efficiency of the exhaust gas that has passed through the catalyst;
a cleaning warning light that is turned on when the pressure difference between the front and rear ends of the reactor measured by the plurality of pressure sensors is equal to or greater than a reference value even after the diesel engine is operated at the maximum load; and
Catalyst replacement warning light that is turned on when the nitrogen oxide reduction efficiency measured by the plurality of nitrogen oxide concentration sensors is less than the reference value even after the diesel engine is operated at the maximum load
includes,
If the pressure difference between the front and rear ends of the reactor measured by the plurality of pressure sensors is equal to or greater than the reference value or the nitrogen oxide reduction efficiency measured by the plurality of nitrogen oxide concentration sensors is less than the reference value, the diesel engine is operated at maximum load for a preset time Selective Catalytic Reduction System. delete According to claim 1,
The diesel engine is equipped with a supercharger, and when the catalyst replacement warning light is turned on while the cleaning warning light is turned off, the diesel engine equipped with the supercharger is replaced with the catalyst and checked for abnormalities. Selective catalyst reduction system. According to claim 1,
Selective catalytic reduction system further comprising a control device for receiving information from the plurality of pressure sensors and the plurality of nitrogen oxide concentration sensors and transmitting signals to the cleaning warning light and the catalyst replacement warning light. In the method of operating a selective catalytic reduction system for reducing nitrogen oxides contained in exhaust gas discharged from a diesel engine using a reactor having a catalyst installed therein,
measuring the differential pressure of exhaust gas between front and rear ends of the reactor with the catalyst interposed therebetween;
measuring the nitrogen oxide reduction efficiency of the exhaust gas that has passed through the catalyst;
operating the diesel engine at maximum load for a preset time when the differential pressure of the exhaust gas is greater than or equal to the reference value or the nitrogen oxide reduction efficiency is less than the reference value;
Measuring the exhaust gas differential pressure and nitrogen oxide reduction efficiency again after the maximum load operation of the diesel engine;
removing deposits or plugging when the differential pressure of exhaust gas is greater than or equal to a reference value after the maximum load operation of the diesel engine; and
If the nitrogen oxide reduction efficiency is less than the reference value, removing the deposit or plugging and replacing the catalyst
A method of operating a selective catalytic reduction system comprising a. delete 6. The method of claim 5,
After the maximum load operation of the diesel engine, if the differential pressure of the exhaust gas is less than the reference value and the nitrogen oxide reduction efficiency is less than the reference value, the selective catalytic reduction system operation further comprising the step of checking whether the diesel engine is abnormal with replacement of the catalyst Way.

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