KR20200054400A - Method for improving durability of selective reduction catalyst, selective reduction catalyst system including the method, and internal combustion engine - Google Patents

Abstract

According to an advisable embodiment of the present invention, a method of improving the durability of a selective reduction catalyst is capable of measuring the NO_X conversion rate of a selective reduction catalyst, and then, making a conversion to a performance promotion SCR reaction through the addition of an enhancer if the NO_X conversion rate is less than a preset value, while performing a general SCR reaction by stopping the addition of the enhancer when the NO_X conversion rate reaches the preset value. According to the present invention, through the method of improving the durability of an SCR system catalyst, a conversion route for nitrogen oxides is changed by adding ammonia (NH_3) or urea (NH_2CONH_2) along with an enhancer when a deterioration in the activity of a selective reduction catalyst is found. Therefore, the lifespan of the selective reduction catalyst can be increased and the activity can be considerably improved.

Description

Method for improving durability of selective reduction catalyst, selective reduction catalyst system to which the method has been applied, and internal combustion engine {Method for improving durability of selective reduction catalyst, selective reduction catalyst system including the method, and internal combustion engine}

The present invention relates to a method for improving the durability of a selective reduction catalyst, a selective reduction catalyst system to which the method is applied, and an internal combustion engine, and specifically, to improve the durability of a selective reduction catalyst (SCR catalyst) for treating diesel engine exhaust gas of a ship. It's about how.

When burning fossil fuels such as coal, petroleum, natural steam, or waste, exhaust gas contains nitrogen oxides or sulfur oxides. These oxides are pollutants that are the main causes of air pollution and must be removed before discharge into the atmosphere.

2. Description of the Related Art In general, a main engine that drives a propeller to propel a ship and an auxiliary engine that is an auxiliary power system for supplying power to various equipment or equipment mounted on the ship are installed and operated.

The exhaust gas discharged after combustion in such a ship engine contains a number of suspended particulates and harmful substances such as nitrogen oxides NO _X and sulfur oxides SO _X.

Here, NO _X as an important air pollutant is nitrous oxide (N ₂ O), nitrogen monoxide (NO), dinitrogen trioxide (N ₂ O ₃ ), nitrogen dioxide (NO ₂ ), dinitrogen pentoxide (N ₂ O ₅ ), and Although it is a term including nitrogen oxides such as nitrogen trioxide (NO ₃ ), NO and NO ₂ , which are the most problematic causes of air pollution among these nitrogen oxides, are generally referred to as NO _X.

In general, an exhaust line of an engine is installed with a diesel particulate filter (DPF), a selective catalytic reduction (SCR) device, a scrubber (SOx removal), and the like to remove harmful components in the exhaust gas.

Among them, the selective reduction catalyst (SCR catalyst) system is a device that decomposes nitrogen oxides (NO _X ) in exhaust gas into water and nitrogen, which are harmless to the environment, through chemical reaction with urea in the catalyst layer, and then discharges them.

Here, the selective reduction catalyst (SCR: Selective Catalytic Reduction) consists of a porous catalyst filter formed with an extrusion or metallic coating, and one or two are continuously installed in a denitrification reactor installed in an exhaust line to remove harmful components in the exhaust gas. .

According to the selective reduction catalyst ( (SCR: Selective Catalytic Reduction) method, ammonia or urea is injected to the front end of the catalyst to cause a chemical reaction such as the following Chemical Formula 1.

(1) 4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O

That is, nitrogen oxides contained in the exhaust gas can be changed to non-polluting water (H ₂ O) and nitrogen (N ₂ ) by reacting with ammonia.

On the other hand, when combustion of coal or heavy oil in a boiler, sulfur substances such as sulfur dioxide (SO ₂ ) and sulfur trioxide (SO ₃ ) are generated. Among them, sulfur dioxide (SO ₂ ) is partially selected by a selective reduction catalyst as shown in Chemical Formula 2 below. the sulfur trioxide is oxidized (SO _3), thereby increasing the concentration of sulfur trioxide (SO ₃₎ in the entire exhaust gas.

Since the increase of sulfur trioxide (SO ₃ ) may damage the equipment at the back of the SCR, the conversion rate of sulfur trioxide (SO ₃ ) to sulfur dioxide (SO ₂ ) is limited to within 1%. Recently, the concentration of sulfur (S) in fuel In the high case, the conversion rate of sulfur trioxide (SO ₃ ) is limited to within 0.7%.

(2) 2SO ₂ + O ₂ → 2SO ₃

And, in general, moisture is present in the exhaust gas, and a part of ammonia (NH ₃ ), sulfur trioxide (SO ₃ ), and moisture (H ₂ O) input to convert NO to N ₂ are as shown in Chemical Formula 3 below. Reaction may form an ammonium sulfate salt.

(3) NH ₃ + SO ₃ + H ₂ O → NH ₄ HSO ₄ , (NH ₄ ) ₂ SO ₄

Here, the ammonium sulfate salt is adsorbed on the surface of the catalyst, the gap, and the pores to degrade the activity of the catalyst.

Since the pores formed in the catalyst serve to increase the surface area where nitrogen oxide and ammonia can react, there is a problem in that when the pores of the catalyst are clogged, the surface area that can be reacted decreases to decrease the catalyst activity or shorten the life of the catalyst.

Substances that adsorb the surface of the catalyst and reduce the activity of the catalyst, such as ammonium sulfate, are called poisons. When the catalyst surface is poisoned with a substance such as ammonium sulfate, the poisoned catalyst is withdrawn from the denitrification reactor and poisoned through chemical treatment. If the catalyst cannot be regenerated or regenerated by removing material, the catalyst must be discarded.

That is, the poisonous substance generated when nitrogen oxide (NO _X ) in the exhaust gas is removed through the selective reduction catalyst (SCR catalyst) system is in a gaseous state above a certain temperature (for example, 340 ° C), but below this specific temperature It exists in a liquid state and adheres to the surface of the selective reduction catalyst, thereby covering the active point of the selective reduction catalyst surface, thereby lowering the activity of the selective reduction catalyst.

In particular, in the case of a ship, when a ship is anchored in a port or is operating on the open sea, the selective reduction catalyst (SCR catalyst) system stops operation, and the piping before and after the SCR system is closed, and the temperature inside the SCR system goes down to room temperature. .

When the internal temperature of the SCR system was lowered to room temperature, there was a problem in that moisture remaining inside the SCR system reacted and condensed with the sulfur component during operation of the ECA (Emission Control Area) area, leading to corrosion of the system and deterioration of catalyst performance. .

KR -10-2013-0013134 A1 KR -10-1057342 B KR -10-2014-0079485 A1

The present invention has been proposed to solve the above problems, and the present invention provides an enhancer simultaneously with the addition of ammonia (NH ₃ ) or urea (NH ₂ CONH ₂ ) when the activity of the selective reduction catalyst (SCR catalyst) decreases. It is an object of the present invention to provide a method for improving catalyst durability of a selective reduction catalyst (SCR catalyst) capable of effectively removing nitrogen oxides by increasing the life of the catalyst and improving activity by introducing it.

In addition, the present invention has an object to provide a selective reduction catalyst (SCR catalyst) system, and an internal combustion engine to which the method for improving the durability of the selective reduction catalyst is applied.

The problem to be solved by the present invention is not limited to the problem (s) mentioned above, and another problem (s) not mentioned will be clearly understood by those skilled in the art from the following description.

In order to solve the above problems, the method for improving the durability of a selective reduction catalyst according to an exemplary embodiment of the present invention measures the NO _X conversion rate of the selective reduction catalyst, and when the NO _X conversion rate is less than a predetermined value, an enhancer is added together. It is characterized by performing a general SCR reaction by switching to a performance-promoting SCR reaction by injecting and stopping the addition of an enhancer when the NO _X conversion rate reaches a predetermined value or more.

In one embodiment, it is preferable to calculate the poisoning rate of a selective reduction catalyst (SCR catalyst) using the NO _X conversion rate.

In one embodiment, the enhancer, it is preferable to convert the general SCR reaction to a performance promoting SCR reaction.

In one embodiment, the enhancer is preferably one or more selected from the group consisting of nitrogen dioxide (NO ₂ ), ozone (O ₃ ), and ammonium nitrate (NH ₄ NO ₃ ).

In one embodiment, the preset value of the NO _X conversion rate is preferably 50 to 60%.

According to another preferred embodiment of the present invention, the selective reduction catalyst system to which the method for improving the durability of the selective reduction catalyst is applied, is provided with a selective reduction catalyst (SCR catalyst), and ammonia (NH ₃ ) or urea (NH ₂ CONH ₂ ) on one side. ) To convert NO _X to N ₂ ; A sensor unit disposed at the rear end of the one side of the reactor and measuring a NO _X conversion rate; When the NO _X conversion rate measured by the sensor unit is less than or equal to a preset value, a control unit is added to the reactor to switch to a performance-promoting SCR reaction, and when the NO _X conversion rate reaches a predetermined value or more, a control unit for stopping the input of the promoter; It characterized in that it comprises.

In one embodiment, the preset value of the NO _X conversion rate is preferably 50 to 60%.

In one embodiment, the enhancer, it is preferable to convert the general SCR reaction to a performance promoting SCR reaction.

In one embodiment, the enhancer is preferably one or more selected from the group consisting of nitrogen dioxide (NO ₂ ), ozone (O ₃ ), and ammonium nitrate (NH ₄ NO ₃ ).

An internal combustion engine according to another preferred embodiment of the present invention is characterized by comprising the selective reduction catalyst system described above.

When the durability improvement method of the SCR system catalyst according to the present invention is used, when the durability improvement method of the SCR system catalyst according to the present invention is used, when the activity of the selective reduction catalyst is lowered, ammonia (NH ₃ ) or urea (NH ₂ CONH) _{In the case of 2} ), by adding the enhancer together, the conversion path of nitrogen oxide is changed, thereby increasing the life of the selective reduction catalyst and dramatically improving the activity.

In addition, the present invention has the effect of providing a selective reduction catalyst system and an internal combustion engine capable of exhibiting catalyst performance equivalent to that of the initial catalyst, and exhibiting excellent denitrification performance.

1 is a schematic diagram of a method for improving the durability of an SCR system catalyst according to an embodiment of the present invention.
2 shows an image of an apparatus for treating exhaust gas and a poisoned catalyst.
3 is a graph showing the NO _X conversion rate when SO ₂ gas is injected under general SCR conditions.
4 (a) to 4 (c) are images of the front-rear end of the reactor after reacting with SO ₂ added under general SCR conditions.
5 is an image of a comparison of the general SCR and NO _X conversion rate for performance promotion SCR.
Figure 6 shows the results of a comparison of the general SCR and performance-promoting SCR reaction.
7 compares the difference in NO _X reduction performance between a general SCR and a performance-promoting SCR.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

It should be understood that all numerical values representing the amount of ingredients, process conditions, and the like used in the present specification and claims are modified in the term "about" in all cases. Accordingly, unless indicated otherwise, the numerical parameters set forth in the following specification and appended claims are approximate and may vary depending on the nature desired. At least, it is not intended to limit the application of uniformity to the claims, and each numerical parameter should be interpreted by taking into account the reported significant digits and applying the usual rounding method.

Although the numerical ranges and parameters presenting the broad scope of the present invention are approximate, the numerical values given in the specific examples are described as accurately as possible. However, any numerical value can contain certain errors that inevitably arise from the standard deviation that appears in each test measurement, for example, device and / or operator errors.

In addition, any numerical range described in this specification is assumed to include all sub-ranges. For example, a range of “1 to 10” includes all sub-ranges between the minimum value 1 described and the maximum value 10 described (including 1 and 10), ie, the minimum value of 1 or more and the maximum value of 10 or less.

All patents, publications, or other disclosures cited herein are incorporated by reference in whole or in part, but the inclusions thereof are only to the extent that they do not conflict with the definitions, statements, or other disclosures disclosed herein. Is applicable. The disclosures explicitly set forth in this specification take precedence over any conflicting content contained herein, by reference, to itself and to the extent necessary. Although incorporated herein by reference, any content or portion thereof that conflicts with the definitions, statements, or other disclosures provided herein is to be included only to the extent that there is no conflict between the inclusion and the content already disclosed. will be.

This specification describes various different features and aspects of the invention with reference to various exemplary non-limiting embodiments.

However, it is understood that the present invention includes a number of alternative embodiments, which can be achieved by combining the various features, aspects and examples described herein in any combination, which will be useful to those skilled in the art. .

The term "SCR" herein refers to a selective catalytic reduction method designed to remove NO _X from flue gas generated during the incineration of household wastes and combustion processes that produce electricity in power plants using fossil fuels, biofuels and / or biomass. it means. SCR uses a reducing agent such as ammonia injected into the flue gas stream, and is moved to the catalytic reaction chamber, where the catalytic material promotes the reduction of various NOx components using a reducing agent in the flue gas to promote elemental nitrogen and water. Produces The SCR catalyst may also be referred to as a “DeNOx catalyst”.

SCR catalysts typically have a structure that includes a honeycomb catalyst batch, a pleated catalyst batch and a plate catalyst batch that maximizes the catalyst surface area. The catalyst structures mentioned are the most common in the art, but other catalyst structures and arrangements are possible, and are included in the scope of the present invention and the definition of “SCR catalyst”.

The term “SCR catalyst” herein refers to catalyst materials, catalyst substrates (non-limiting examples, titanium oxide), catalyst support materials (non-limiting examples, metal mesh, eg plate-type catalysts), catalyst support structures, and catalysts. Includes all frameworks that secure the support structure for forming the module.

The selective reduction catalyst (SCR catalyst) provided in a conventional ship has problems in that poisonous substances such as ammonium sulfate are adsorbed on the surface, crevices, pores, etc. of the catalyst due to the sulfur component contained in the exhaust gas, thereby reducing the activity of the catalyst.

When poisoned with a substance such as ammonium sulfate on the surface of the catalyst, the poisoned catalyst is withdrawn from the denitrification reactor to perform a chemical treatment process capable of removing the poisonous substance of the catalyst or to discard the catalyst. When the catalyst is regenerated (chemical treatment process) or disposed, the operation of the boiler or the engine must be stopped, and thus there is a problem that enormous economic loss occurs.

The present invention has been proposed to solve the above problems, and the present invention provides an enhancer simultaneously with the addition of ammonia (NH ₃ ) or urea (NH ₂ CONH ₂ ) when the activity of the selective reduction catalyst (SCR catalyst) decreases. It is an object of the present invention to provide a method for improving catalyst durability of a selective reduction catalyst (SCR catalyst) capable of effectively removing nitrogen oxides by increasing the life of the catalyst and improving activity by introducing it.

In addition, the present invention has an object to provide a selective reduction catalyst (SCR catalyst) system, and an internal combustion engine to which the method for improving the durability of the selective reduction catalyst is applied.

Using the method for improving the durability of the SCR system catalyst according to the present invention, when the activity of the selective reduction catalyst is lowered, the conversion path of nitrogen oxides by adding an enhancer when adding ammonia (NH ₃ ) or urea (NH ₂ CONH ₂ ) By changing the, there is an advantage that can increase the life of the selective reduction catalyst and dramatically improve the activity.

In addition, the present invention has the effect of providing a selective reduction catalyst system and an internal combustion engine capable of exhibiting catalyst performance equivalent to that of the initial catalyst, and exhibiting excellent denitrification performance.

Prior to the present invention will be described the main components constituting the general selective reduction catalyst (SCR catalyst) system.

The main components include a guide vane allowing the exhaust gas containing NO _X to flow into the denitrification reactor while maintaining uniform hydrodynamic properties, a reducing agent injection system for smooth mixing between ammonia or urea supplied as a reducing agent and exhaust gas, and urea -It can be classified into denitrification catalyst where SCR denitrification reaction occurs, and online measurement system that can measure and transmit ppm concentrations of NO _X , NH ₃ , and SO _X in real time.

Among these components, in order to not only exert the desired denitrification performance but also not adversely affect other processes of the engine, the most important thing is a denitration catalyst, that is, a selective reduction catalyst (SCR catalyst).

When the selective reduction catalyst (SCR catalyst) as described above is poisoned by ammonium sulfate, there is an economical disadvantage because the engine must be stopped and the catalyst must be cleaned or the catalyst needs to be replaced.

The present invention is to make the most of the non-poisoned portion of the selective reduction catalyst (SCR catalyst) to exhibit the same or similar activity as that of the initial catalyst.

1 is a schematic diagram of a method for improving the durability of an SCR system catalyst according to an embodiment of the present invention.

The method for improving the durability of a selective reduction catalyst according to an embodiment of the present invention measures a selective reduction catalyst (SCR catalyst) NO _X conversion rate (S100), and if the NO _X conversion rate is less than a predetermined value, an enhancer is added together. It is characterized in that it converts to a performance-promoting SCR reaction (S300), and when the NO _X conversion rate reaches a predetermined value or more, the input of the enhancer is stopped (S200) to perform a general SCR reaction.

First, before measuring the NO _X conversion rate of the selective reduction catalyst (S100), NO _x is converted into water and nitrogen by supplying ammonia (NH ₃ ) or urea (NH ₂ CONH ₂ ) to the denitrification reactor with exhaust gas input (S50). ).

That is, the NO _X conversion rate measurement (S100) may be performed after a process of converting NO _X to N ₂ by reacting exhaust gas with ammonia or urea in a denitrification reactor (S50).

Figure 2 shows the image of the exhaust gas treatment apparatus and poisoned catalyst, Figure 3 shows the NO _X conversion rate when SO ₂ gas is injected under general SCR conditions, Figures 4 (a) to 4 (c) are This is an image of the front and rear of the reactor after reacting with SO ₂ added under normal SCR conditions in the laboratory.

In general, the exhaust gas emitted from the engine does not contain only nitrogen monoxide (NO) generated by combustion, but contains NO ₂ , N ₂ O, etc. generated by combining with residual oxygen, and other nitrogen oxides In comparison, the concentration of NO is the highest, and the concentration of NO ₂ is low.

Since the concentration of NO ₂ is low, in the process of reducing NO _X to N ₂ by reacting the exhaust gas with ammonia or urea, nitrogen monoxide (NO) is converted into nitrogen (N ₂ ) in the reaction path as shown in Reaction Scheme 1 below. do.

NO _X in the exhaust gas can be converted into N ₂ by the above process alone, and when ammonia (NH ₃ ), which is a reducing agent, is used in the above process, nitrogen (N ₂ ) and water (H ₂ O) according to the reaction route of Reaction Scheme 1 below. ) Is generated.

[Scheme 1]

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O

In addition, when urea is used as a reducing agent in the above process, ammonia is produced according to the reaction route of Reaction Scheme 2 below, and finally nitrogen (N ₂ ) and water (H ₂ O) are generated according to the route of Reaction Scheme 1. .

[Scheme 2]

(1) NH ₂ CONH ₂ → NH ₃ + HNCO

(2) HNCO + H ₂ O → NH ₃ + CO ₂

(3) NH ₂ CONH ₂ + H ₂ O → 2NH ₃ + CO ₂

That is, when urea is used as a reducing agent, NH ₃ and HNCO are generated from the thermal decomposition of the urea, and HNCO is converted back to NH ₃ according to hydrolysis.

Therefore, even if urea is used as a reducing agent, since NH ₃ finally functions as a reducing agent, nitrogen (N ₂ ) and water (H ₂ O) are generated according to the route of Reaction Scheme 1 above.

The ammonia (NH ₃ ) is a gas phase, and the urea may be liquid.

However, when the selective reduction catalyst system is formed by the above process, some ammonia contained in the exhaust gas as shown in Reaction Scheme 3 below reacts with sulfur trioxide (SO ₃ ) and moisture (H ₂ 0) to form an ammonium sulfate salt. Can be.

[Scheme 3]

NH ₃ + SO ₃ + H ₂ O → NH ₄ HSO ₄ , (NH ₄ ) ₂ SO ₄

Since the ammonium sulfate is present as a liquid at a certain temperature or lower, it is adsorbed on the surface and pores of the selective reduction catalyst, resulting in a problem of deteriorating the life and activity of the catalyst.

The present invention can measure the NO _X conversion rate of the selective reduction catalyst (S100), and invert the reaction according to the result to increase the activity of the catalyst and improve durability.

The NO _X conversion rate can be used to calculate the poisoning rate of a selective reduction catalyst (SCR catalyst).

In addition, when the NO _X conversion rate is measured (S100), and when the NO _X conversion rate is less than a preset value, an enhancement agent is added (S300) to convert to a performance-promoting SCR reaction, and the NO _X conversion rate reaches a predetermined value or more. When the input of the enhancer is stopped (S200), the general SCR reaction may be performed.

The NO _X conversion rate may be calculated by the NO / N ₂ concentration ratio of the exhaust gas discharged, and may be measured by a chemi-luminum detector (CLD) detection method.

Assuming that the concentration of NO in the exhaust gas is 100% and the concentration of N ₂ is 0%, the first catalyst provided in the denitrification reactor can reduce NO to 100% with N ₂ , wherein NO / N ₂ The concentration ratio is 0, and when the NO / N ₂ concentration ratio is 1, it can be confirmed that the activity of the catalyst was lowered.

The chemical luminescence (CLD) detection method uses nitrogen monoxide contained in the exhaust gas by using the chemical emission intensity generated when NO ₂ is generated by the reaction of nitrogen monoxide and ozone in the exhaust gas with nitrogen monoxide. It is the principle of measuring concentration.

In addition, when measuring nitrogen oxides (NO + NO ₂ ), nitrogen dioxide in exhaust gas is converted to nitrogen monoxide through a converter, and then measured in the same manner as when measuring nitrogen monoxide to obtain the total nitrogen oxide value. .

In one embodiment of the present invention, if the NO _X conversion rate is less than a predetermined value, an enhancer may be added when converting NO _{X in} exhaust gas.

The preset value of the NO _X conversion rate may be 50 to 60%.

That is, when the measured NO _X conversion rate is measured to be 50 to 60%, an enhancement agent may be added to convert into a performance-promoting SCR reaction as shown in Reaction Scheme 4 below (S300).

[Reaction Scheme 4]

2NH ₃ + NO + NO ₂ → 2N ₂ + 3H ₂ O

The reaction scheme 4 has a merit that can exhibit a high NO _X reduction rate even if the catalyst has a reduced activity because the reaction rate is faster than that of the general SCR reaction scheme 1.

The enhancer can convert a general SCR reaction into a performance promoting SCR reaction.

The NO ₂ which is an enhancer may be directly introduced into the denitrification reactor, and if the NO can be converted into NO ₂ in the denitrification reactor to perform a performance-promoting SCR reaction, the type is not limited. May be one or more selected from the group consisting of nitrogen dioxide (NO ₂ ), ozone (O ₃ ), and ammonium nitrate (NH ₄ NO ₃ ), and more specifically, nitrogen dioxide (NO ₂ ).

5 is an image of a comparison of the general SCR and NO _X conversion rate for performance promotion SCR.

In one embodiment of the present invention, when the NO _X conversion rate reaches a predetermined value or more, the input of the enhancer may be stopped (S200).

When the measured NO _X conversion rate is 60% or more, the input of the enhancer may be stopped (S200) and NO _X may be converted by a general SCR reaction as shown in Reaction Scheme 1 above.

That is, the present invention has an advantage of improving the activity and life of the catalyst by periodically changing the general SCR reaction and the performance promoting SCR reaction according to the measured NO _X conversion.

Here, the periodic can be set in consideration of the general activity level and life, such as a power source, a driving device, and a catalyst.

A selective reduction catalyst (SCR catalyst) system to which a method for improving durability of a selective reduction catalyst according to another embodiment of the present invention is applied includes a denitration reactor for converting NO _X in exhaust gas to N ₂ ; A sensor unit disposed at a rear end of the denitrification reactor and measuring NO _X conversion rate; When the NO _X conversion rate measured by the sensor unit is equal to or less than a preset value, a control unit is added to the denitrification reactor to switch to a performance-promoting SCR reaction, and when the NO _X conversion rate reaches a predetermined value or more, a control unit for stopping the input of the promoter It characterized in that it contains a.

The denitrification reactor is not limited in its kind.

A supply line capable of supplying ammonia (NH ₃ ), urea (NH ₂ CONH ₂ ), and an enhancer may be further provided on one side of the denitrification reactor.

The denitrification reactor may further be provided with a discharge line for converting NO _X to N ₂ for discharge.

So long as the NO _X conversion rate of the exhaust gas sensor to measure the NO _X conversion portion can be measured, it does not limit the type.

The control unit may control the input and stop by calculating the amount of the enhancer according to the NO _X conversion rate measured by the NO _X sensor unit.

When the NO _X conversion rate measured by the sensor unit is less than 50 to 60%, the control unit may switch to a performance-promoting SCR reaction by introducing an enhancer, and when the NO _X conversion rate is 50 to 60% or more, the input of the enhancer is stopped. It can be made to proceed with a general SCR reaction.

By determining whether or not the enhancer is added by the control unit, there is an advantage of maintaining the initial performance of the catalyst even if the selective reduction catalyst is poisoned with ammonium sulfate.

The enhancer may convert the general SCR reaction into a performance promoting SCR reaction.

It is also possible to directly inject the NO ₂ as an enhancer to the reactor, and if the NO can be converted to NO ₂ in the denitrification reactor, the type is not limited, specifically, nitrogen dioxide (NO ₂ ), ozone (O ₃ ) , And ammonium nitrate (NH ₄ NO ₃ ), and may be one or more selected from the group consisting of nitrogen nitrate (NO ₂ ).

An internal combustion engine according to another embodiment of the present invention is provided, including the selective reduction catalyst system described above.

Hereinafter, it will be described in more detail through production examples and experimental examples of the present invention.

Preparation Example: Preparation of poisoned selective reduction catalyst

We built a bench flow system and simulated the exhaust gas emitted from the actual engine.

The selective reduction catalyst is made of 3 Inch, 0.9 cm in diameter, and 13 g in weight, and then, after mounting the selective reduction catalyst in a glass tube of a furnace, a bench flow system, NO for 25 minutes at a temperature of 400 ° C. Gas was added and SO ₂ gas was added for 80 minutes to prepare a sulfur poisoned selective reduction catalyst.

Experimental Example: NO _X reduction performance of poisoned selective reduction catalyst

After the sulfur poisoned selective reduction catalyst prepared according to the manufacturing example was installed in the glass tube of the system furnace, NO gas was continuously flowed, NO ₂ gas was added for 25 minutes, and an experiment was stopped for 25 minutes. 5 times.

FIG. 6 shows the results of a comparison experiment of a general SCR and a performance promoting SCR reaction, and FIG. 7 compares a difference between the general SCR and the performance promoting SCR NO _X reduction performance.

Referring to FIGS. 6 and 7, when the sulfur poisoning selective reduction catalyst was supplied only with NO gas, NO was converted to N ₂ as shown in Reaction Formula 1 according to a general SCR reaction route, and performance was promoted when supplied with NO ₂ gas. It was confirmed that the NO _X conversion rate was increased according to the SCR reaction path.

In addition, by repeatedly performing the supply and interruption of the NO ₂ gas as an enhancer, the performance of the sulfur poisoned selective reduction catalyst was partially recovered, thereby confirming that the NO _X conversion was increased.

The present invention has been proposed to solve the above problems, and the present invention provides an enhancer simultaneously with the addition of ammonia (NH ₃ ) or urea (NH ₂ CONH ₂ ) when the activity of the selective reduction catalyst (SCR catalyst) decreases. It is an object of the present invention to provide a method for improving catalyst durability of a selective reduction catalyst (SCR catalyst) capable of effectively removing nitrogen oxides by increasing the life of the catalyst and improving activity by introducing it.

In addition, the present invention has an object to provide a selective reduction catalyst (SCR catalyst) system, and an internal combustion engine to which the method for improving the durability of the selective reduction catalyst is applied.

When the durability improvement method of the SCR system catalyst according to the present invention is used, when the activity of the selective reduction catalyst is lowered, a reduction reaction of nitrogen oxides is performed by adding an ammonia (NH ₃ ) or urea (NH ₂ CONH ₂ ) and simultaneously with an enhancer. By changing the route, there is an advantage that the life of the selective reduction catalyst can be increased and the activity can be dramatically improved.

In addition, the present invention has the effect of providing a selective reduction catalyst system and an internal combustion engine capable of exhibiting catalyst performance equivalent to that of the initial catalyst, and exhibiting excellent denitrification performance.

So far, a method for improving the durability of a selective reduction catalyst according to an embodiment of the present invention has been described with reference to specific embodiments of a selective reduction catalyst system and an internal combustion engine including the same, but within the limits that do not depart from the scope of the invention It is obvious that implementation modifications are possible.

Therefore, it should not be limited to the embodiments described in the scope of the present invention, and should be determined not only by the claims to be described later, but also by the claims and equivalents.

That is, the above-described embodiments are illustrative in all respects, and should be understood as not limiting, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims and It should be construed that any altered or modified form derived from the equivalent concept is included in the scope of the present invention.

S50: NO _X conversion
S100: NO _X conversion rate measurement
S200: Stop the enhancer
S300: Enhancement agent input

Claims (10)

When measuring the NO _X conversion rate of the selective reduction catalyst, and the NO _X conversion rate less than the predetermined value, when the input the promoter with by switching to the performance promotes SCR reaction, the NO _X conversion rate reaches a predetermined value or more the enhancer added Method for improving the durability of a selective reduction catalyst, characterized in that to perform a normal SCR reaction by stopping.
According to claim 1,
Method for improving the durability of a selective reduction catalyst, characterized by calculating the poisoning rate of a selective reduction catalyst (SCR catalyst) using the NO _X conversion rate.
According to claim 1,
The enhancer,
A method for improving durability of a selective reduction catalyst, characterized in that the general SCR reaction is converted into a performance-promoting SCR reaction.
According to claim 3,
The enhancer,
Method for improving the durability of a selective reduction catalyst, characterized in that at least one member selected from the group consisting of nitrogen dioxide (NO ₂ ), ozone (O ₃ ), and ammonium nitrate (NH ₄ NO ₃ ).
According to claim 1,
Method for improving the durability of the selective reduction catalyst, characterized in that the predetermined value of the NO _X conversion rate is 50 to 60%.
A denitrification reactor for converting NO _X in exhaust gas to N ₂ ;
A sensor unit disposed at a rear end of the denitrification reactor and measuring NO _X conversion rate;
When the NO _X conversion rate measured by the sensor unit is equal to or less than a preset value, a control unit is added to the denitrification reactor to switch to a performance-promoting SCR reaction, and when the NO _X conversion rate reaches a predetermined value or more, a control unit for stopping the input of the promoter ; Selective reduction catalyst system comprising a.
The method of claim 6,
Selective reduction catalyst system, characterized in that the predetermined value of the NO _X conversion is 50 ~ 60%.
The method of claim 6,
The enhancer,
A selective reduction catalyst system characterized by converting a general SCR reaction into a performance promoting SCR reaction.
The method of claim 8,
The enhancer,
Selective reduction catalyst system, characterized in that at least one member selected from the group consisting of nitrogen dioxide (NO ₂ ), ozone (O ₃ ), and ammonium nitrate (NH ₄ NO ₃ ).
An internal combustion engine comprising the selective reduction catalyst system of claim 6.

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