KR102364271B1 - Exhaust gas purification device including combined catalyst filter and a control method of the same - Google Patents

Abstract

The present invention relates to an exhaust gas purification device including a combined catalyst filter and a control method thereof and, more specifically, to a reductant supply control method for an exhaust gas purification device comprising: a diesel oxidation catalyst (DOC) installed at a rear end of a diesel engine to oxidize hydrocarbon (HC) and carbon monoxide (CO) contained in exhaust gas; and a composite catalyst filter installed at a rear end of the DOC to collect particulate matter contained in the exhaust gas, and including a catalyst coating layer in which a NH_3-SCR catalyst and H_2-SCR catalyst are composite-applied on the wall surface of a diesel particulate filter (DPF). Therefore, the exhaust gas purification device effectively removes nitrogen oxide (NOx) emitted from the diesel engine according to the operating conditions of the diesel engine and minimizes the generation of unreacted ammonia slip (NH_3 slip).

Description

Exhaust gas purification device including composite catalyst filter and control method thereof

The present invention relates to an exhaust gas purification device, and more particularly, to an exhaust gas purification device including a composite catalyst filter made of a composite denitration catalyst and a control method thereof.

The emission concentration of air pollutants such as nitrogen oxide (NOx) and particulate matter (PM) contained in exhaust gas emitted from automobiles and power plants is high. In order to minimize the generation of air pollutants and satisfy environmental regulations, an exhaust gas purification system, which is a post-processing device such as a nitrogen oxide removal catalyst (DeNOx Catalyst) and a diesel particulate filter (DPF), is essential. Such an exhaust gas purification device uses a complex configuration of pollutant reduction processes such as filters and catalysts to remove pollutants such as nitrogen oxides (NOx) and particulate matter (PM).

Diesel Oxidation Catalyst (DOC), Lean NOx Trap (LNT, Lean NOx Trap), Diesel Particulate Filter (DPF), Selective Catalytic Reduction (SCR) for exhaust gas purification of diesel engines ) or an exhaust gas purification system in which a selective reduction catalyst (SCR) is coated on a diesel particulate filter (DPF), such as a catalytic filter (SCR coated on DPF, sDPF), etc., is applied in the industry to simplify the exhaust gas purification system. there is. Among them, selective reduction catalyst (SCR) and sDPF are the most commonly used methods using NH ₃ -SCR reaction using ammonia (NH ₃ ) as a reducing agent to remove nitrogen oxides (NOx).

As a reducing agent for the NH ₃ -SCR reaction in selective reduction catalyst (SCR) and sDPF, ammonia (NH ₃ ) is a toxic gas and due to problems such as stability, it is directly injected into the exhaust gas pipe in the form of urea, and the exhaust pipe The urea water (urea) injected into the ammonia (NH ₃ ) converted by the exhaust heat of the engine is used for the reaction.

However, the method of using urea as a reducing agent in the existing exhaust gas purification system can effectively remove nitrogen oxides (NOx) in the temperature range of 250 ° C to 400 ° C, but the efficiency is lowered in the low temperature region below that there is In addition, since a temperature of 300° C. or higher is required for smooth conversion of urea, which is a reducing agent, into ammonia (NH ₃ ), the injection of the reducing agent is limited at a low temperature below that.

As regulations on air pollutant emission are tightened around the world, the average exhaust temperature of diesel engines is decreasing. Existing exhaust gas purification devices reduce nitrogen oxide (NOx) It is difficult to remove effectively, and in the case of diesel engines for power generation, the use time in low-temperature conditions is increasing due to the increase in load fluctuations, start-stops and restarts due to the connection of power sources such as renewable energy and ESS (Energy Storage System). However, the issue of air pollutant emission during restart and shutdown is being raised.

In addition, the amount of urea injected is increasing to improve the NH ₃ /NOx ratio required for the system in order to satisfy the stricter air pollutant emission standards, but exhaust with a high NH ₃ /NOx ratio in a low-temperature environment The operation of the gas purifier increases the occurrence of unreacted ammonia slip (NH ₃ slip), which causes problems such as clogging of catalysts and filters of the exhaust gas purifier due to the formation of ammonium salts, and the action of fine dust precursors in the atmosphere.

Korean Patent Application No. 10-2018-0020215

In consideration of the above, the present invention provides ammonia (NH 3 ) and hydrogen (H 2 ) as a denitration catalyst to minimize unreacted ammonia slip (NH ₃ slip) generation in the exhaust gas purification device so that ammonia (NH ₃ ) and hydrogen (H ₂ ) reducing agents are applied to NH ₃ -SCR catalyst An object of the present invention is to provide an exhaust gas purification device including a composite catalyst filter (NH ₃ ·H ₂ -sDPF) in which a H ₂ -SCR catalyst is coated on a diesel particulate filter (DPF).

In addition, the present invention relates to an exhaust gas purification device including the composite catalyst filter, which is discharged from a diesel engine according to the operating conditions of the diesel engine from a low temperature operating condition of less than 250° C. An object of the present invention is to provide a method for controlling supply of a reducing agent to an exhaust gas purifier to effectively remove nitrogen oxides (NOx).

The exhaust gas purification apparatus of the present invention for achieving the above object is a composite catalyst formed by applying another denitration catalyst to the filter wall along the passage direction of the exhaust gas introduced into a diesel particulate filter (DPF) installed at the rear end of a diesel engine. It is made with a filter.

Specifically, the exhaust gas purifier is installed at the rear end of a diesel engine to oxidize hydrocarbons (HC) and carbon monoxide (CO) contained in exhaust gas, a diesel oxidation catalyst (DOC), and a diesel oxidation catalyst (DOC) installed at the rear end of the exhaust gas The particulate matter contained in the gas is collected, and the NH ₃ -SCR catalyst and the H ₂ -SCR catalyst may include a complex catalyst filter including a catalyst coating layer coated on the wall surface of the diesel particulate filter (DPF).

In the composite catalyst filter, the NH ₃ -SCR catalyst composition is on the wall at the front end of the diesel particulate filter (DPF) through which exhaust gas flows from the diesel particulate filter (DPF) having a wall-flow filter structure. A first catalyst coating layer formed to be coated, and a second catalyst coating layer coated with H ₂ -SCR catalyst composition on the rear end wall of the diesel particulate filter (DPF) through which exhaust gas is discharged through the first catalyst coating layer. can

The H ₂ -SCR catalyst composition is a H ₂ -SCR catalyst or a mixture of H ₂ -SCR catalyst and NH ₃ -SCR catalyst, and the second catalyst coating layer is as follows according to the H ₂ -SCR catalyst composition It can be applied in the form of a coating layer.

The second catalyst coating layer is a coating layer in which the H ₂ -SCR catalyst composition is a single component of the H ₂ -SCR catalyst, the H ₂ -SCR catalyst composition is a coating layer in which the H ₂ -SCR catalyst and the NH ₃ -SCR catalyst are mixed; And the H ₂ -SCR catalyst composition is coated as a single component H ₂ -SCR catalyst layer and the H ₂ -SCR catalyst layer is formed above or below the NH ₃ -SCR catalyst composition is coated as a single component NH ₃ -SCR catalyst layer It may be made of any one selected from the coating layer consisting of.

As the NH ₃ -SCR catalyst, which is a main component of the NH ₃ -SCR catalyst composition, any one or more selected from a vanadia-based catalyst and a zeolite-based catalyst may be used.

The H ₂ -SCR catalyst may be a platinum (Pt)-based catalyst.

In order to achieve another object, the control method of the exhaust gas purification apparatus of the present invention relates to a method of controlling the supply of a reducing agent in the exhaust gas purification apparatus including the above-described composite catalyst filter.

Specifically, the control method of the exhaust gas purification apparatus of the present invention includes (a) the exhaust gas is introduced from the diesel particulate filter (DPF) installed at the rear end of the diesel oxidation catalyst (DOC) to collect particulate matter contained in the exhaust gas. A first catalyst coating layer coated with NH ₃ -SCR catalyst composition on the front end wall of the diesel particulate filter (DPF), and the rear end wall of the diesel particulate filter (DPF) through which exhaust gas is discharged through the first catalyst coating layer Measuring the temperature of the rear end of the composite catalyst filter in an exhaust gas purification device including a composite catalyst filter comprising a second catalyst coating layer coated with H ₂ -SCR catalyst composition, (b) measured in step (a) If the temperature at the rear end of the complex catalyst filter is equal to or higher than the set temperature, supplying an ammonia (NH ₃ )-based reducing agent through the reducing agent supply unit, (c) the temperature of the rear end of the complex catalyst filter measured in step (a) is the set temperature If it is less than, the step of supplying a hydrogen (H ₂ ) reducing agent through the reducing agent supply unit, (d) measuring the ammonia (NH ₃ ) concentration and the nitrogen oxide (NOx) concentration in front of the composite catalyst filter to calculate the NH ₃ /NOx ratio step, (e) if the NH ₃ /NOx ratio is less than a set concentration ratio, purifying nitrogen oxides (NOx) in the composite catalyst filter without supplying a reducing agent, and (f) if the NH ₃ /NOx ratio is greater than the set concentration ratio , by additionally supplying a hydrogen (H ₂ ) reducing agent through the reducing agent supply unit to purify nitrogen oxides (NOx) in the composite catalyst filter.

The set temperature is preferably 250 °C to 400 °C.

As the set concentration of the NH ₃ /NOx ratio, the set concentration ratio is preferably 0.8 to 0.9.

The exhaust gas purification device including the composite catalyst filter of the present invention and its control method have low efficiency of NH ₃ -SCR, and hydrogen (H ₂ ) ) to effectively remove nitrogen oxides (NOx) in exhaust gas by controlling the supply as a reducing agent.

In addition, when the normal operating conditions of a diesel engine of about 300°C to 400°C are reached above 250°C, the supply of hydrogen (H ₂ ) reducing agent is stopped in the exhaust gas purification device of the present invention and ammonia (NH ₃ )-based reducing agent is injected. Effectively removes nitrogen oxides (NOx).

In addition, under operating conditions where the NH ₃ /NOx ratio is as high as 0.8 to 0.9 or nitrogen oxides (NOx) do not satisfy the emission conditions, ammonia (NH ₃ )-based reducing agent and hydrogen (H ₂ ) reducing agent are injected together, and NH ₃ / There is an effect of purifying nitrogen oxides (NOx) while minimizing the occurrence of unreacted ammonia slip (NH ₃ slip) on the composite catalyst filter by avoiding operation with a high NOx ratio.

Accordingly, if exhaust gas is purified through the exhaust gas purification apparatus including the composite catalyst filter and the control method thereof according to the present invention, air pollutants are discharged under low-temperature diesel engine operating conditions such as during cold start, restart and stop of the diesel engine. There is an effect that can minimize problems such as filter clogging of the exhaust gas purification device due to the generation of ammonium-based solid salt caused by the generation of unreacted ammonia slip (NH ₃ slip), and the action of fine dust precursors.

1 is a cross-sectional view of a composite catalyst filter according to an embodiment of the present invention.
2 and 3 are flowcharts illustrating a control method according to operating conditions of a diesel engine using an exhaust gas purification apparatus according to an embodiment of the present invention.
4 to 6 are block diagrams of an exhaust gas purification apparatus according to an embodiment of the present invention.
7 is a graph showing the conversion rate of nitrogen oxide (NOx) according to the reducing agent injection conditions in the exhaust gas purification apparatus according to Comparative Example 1 and Example 1 of the present invention.

Hereinafter, the composite catalyst filter of the present invention, an exhaust gas purification apparatus including the same, and a control method of the exhaust gas purification apparatus will be described in more detail with reference to the accompanying drawings.

1 is a cross-sectional view of a composite catalyst filter applied to an exhaust gas purification apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the composite catalyst filter of the present invention is a honeycomb diaphragm-flow filter in the form of a honeycomb wall-flow filter for collecting particulates. It is a composite catalyst filter (NH ₃ ·H ₂ -sDPF) made by applying two types of denitration catalysts.

In one embodiment, in the composite catalyst filter, a first catalyst coating layer coated with an NH ₃ -SCR catalyst composition is formed on the front wall of the diesel particulate filter through which exhaust gas flows, and the first catalyst coating layer is passed through the filter. A second catalyst coating layer coated with an H ₂ -SCR catalyst composition is formed on a wall at the rear end of which exhaust gas is emitted.

Particulate matter in the exhaust gas of the engine is removed from the front part of the composite catalyst filter in which the first catalyst coating layer having a wall-flow filter structure is formed, and nitrogen oxides (NOx) is removed by being converted into nitrogen (N ₂ ) and water (H ₂ O) through a reaction with the reducing agent injected from the front end of the composite catalyst filter.

The NH ₃ -SCR catalyst composition may use a vanadia-based catalyst and a zeolite-based catalyst.

The vanadia catalyst is preferably vanadium pentoxide (V ₂ O ₅ ) as an active material and tungsten trioxide (WO ₃ ) and titanium dioxide (TiO ₂ ). A transition metal such as cerium (CeO ₂ ) may be used. In addition, as the zeolite-based catalyst, a zeolite-based ceramic catalyst substituted with an element such as copper (Cu) or iron (Fe) may be preferably used.

The H ₂ -SCR catalyst composition is composed of a single component of the H ₂ -SCR catalyst with the H ₂ -SCR catalyst as a main component, or a second catalyst coating layer in a mixed configuration in which the NH ₃ -SCR catalyst and the H ₂ -SCR catalyst are mixed. can be formed

The H ₂ -SCR catalyst composition may use a platinum (Pt)-based catalyst including platinum (Pt) as an active material.

The second catalyst coating layer of the rear part of the composite catalyst filter is a coating layer coated with an H ₂ -SCR catalyst composition consisting of a single component of the H ₂ -SCR catalyst, and the H ₂ -SCR catalyst and the NH ₃ -SCR catalyst are uniformly coated. A coating layer comprising a mixed H ₂ -SCR catalyst composition coated thereon, and a single component coated H ₂ -SCR catalyst layer and the H ₂ -SCR catalyst layer formed above or below the NH ₃ -SCR catalyst NH coated with a single component The ₃ -SCR catalyst layer may be formed of any one selected from among the layered coating layers.

The cell density of the composite catalyst filter and the amounts of the NH ₃ -SCR catalyst and the H ₂ -SCR catalyst to be coated may be adjusted according to conditions such as an allowable back pressure of the engine and a target nitrogen oxide conversion rate.

In the composite catalyst filter of the present invention configured as described above, the ammonia (NH ₃ ) reducing agent or hydrogen (H ₂ ) reducing agent injected from the front end of the composite catalyst filter according to the operating conditions of the engine includes the first catalyst coating layer and the second agent formed inside the composite catalyst filter. 2 Purify nitrogen oxides (NOx) through a reduction reaction on the catalyst coating layer.

A control method according to a diesel engine operating condition using the exhaust gas purification apparatus according to an embodiment of the present invention is as shown in FIGS. 2 and 3 .

As shown in FIG. 2 , the control method according to the diesel engine operating conditions by using the exhaust gas purification device including the composite catalyst filter includes (a) measuring the temperature at the rear end of the composite catalyst filter (S100), ( b) if the temperature at the rear end of the complex catalyst filter is above the set temperature, supplying an ammonia (NH ₃ )-based reducing agent through the reducing agent supply unit (S200), (c) if the temperature at the rear end of the complex catalyst filter is less than the set temperature, Supplying a hydrogen (H ₂ ) reducing agent through the reducing agent supply unit (S300), (d) measuring the ammonia (NH ₃ ) concentration and the nitrogen oxide (NOx) concentration in front of the composite catalyst filter to calculate the NH ₃ /NOx ratio (S400), (e) if the NH ₃ /NOx ratio is less than a set concentration ratio, purifying nitrogen oxides (NOx) in the composite catalyst filter without supplying a reducing agent (S500), and (f) the NH ₃ /NOx If the ratio is greater than or equal to the set concentration ratio, by additionally supplying a hydrogen (H ₂ ) reducing agent through the reducing agent supply unit, including the step (S600) of purifying nitrogen oxides (NOx) in the composite catalyst filter by controlling the supply of the reducing agent to exhaust gas can purify

Specifically, as shown in FIG. 3 , the temperature (T) of the rear end of the composite catalyst filter is measured as a variable for the exhaust gas purifier among the variables related to the injection of the reducing agent after the engine is started (S100). In this case, the temperature T at the rear end of the complex catalyst filter may be measured by a temperature sensor installed at the rear end of the complex catalyst filter among the sensor units installed on the exhaust gas flow path.

It is determined whether the measured temperature (T) of the rear end of the composite catalyst filter is above the set temperature (T1) range, where the set temperature (T1) is 250°C to 400°C above the normal operating temperature range of the diesel engine of 250°C desirable.

If the measured temperature (T) at the rear end of the complex catalyst filter is above the set temperature, ammonia (NH ₃ )-based reducing agent is supplied through the reducing agent supply unit at the front end of the complex catalyst filter to remove nitrogen oxides (NOx) (S200) ).

The set temperature of the rear end of the complex catalyst filter for the injection of the reducing agent in the step S200 may vary depending on the type of the ammonia (NH ₃ )-based reducing agent, and in the case of the reducing agent of NH ₃ (g), it is 250 ℃ or more and less than 300 ℃, When using urea water (aq), it is particularly preferable to set it to 300°C or higher.

If the measured temperature (T1) at the rear end of the complex catalyst filter is less than the set temperature and is less than 250 ° C, which is the low-temperature operation condition of the diesel engine, hydrogen (H ₂ ) reducing agent is supplied through the reducing agent supply unit in front of the complex catalyst filter to supply nitrogen oxide ( NOx) is removed (S300). Here, the low-temperature operation condition means an operation condition during cold start and restart/stop of the diesel engine.

When the hydrogen (H ₂ ) reducing agent is supplied in step S300 and the temperature at the rear end of the composite catalyst filter measured again is equal to or higher than the set temperature (T1), ammonia ( NH ₃ )-based reducing agent may be supplied to remove nitrogen oxides (NOx).

After the step S300, it is possible to control the injection amount of the hydrogen reducing agent in order to satisfy the emission standard of nitrogen oxides (NOx) of the engine.

Specifically, as another reducing agent injection-related variable, the NH ₃ /NOx ratio (R) is calculated by measuring the concentrations of ammonia (NH ₃ ) and nitrogen oxide (NOx) in the exhaust gas as a variable for exhaust gas (S400).

It is determined whether the calculated NH ₃ /NOx ratio (R) is less than a set concentration ratio (R1) range that satisfies the emission standard of nitrogen oxides (NOx), where the set concentration ratio (R1) is NH ₃ /NOx ratio 0.8 to 0.9, and more preferably 0.8.

If the calculated NH ₃ /NOx ratio is less than 0.8, nitrogen oxides (NOx) are purified in the composite catalyst filter without additional reducing agent supply (S500).

If the calculated NH ₃ /NOx ratio is 0.8 or higher or the nitrogen oxide (NOx) concentration in the exhaust gas does not meet the emission standards, additional hydrogen (H ₂ ) reducing agent is supplied through the reducing agent supply unit in front of the composite catalyst filter. , when the calculated NH ₃ /NOx ratio is less than 0.8 and satisfies the nitrogen oxide (NOx) emission concentration, nitrogen oxide (NOx) is removed from the composite catalyst filter (S600).

The supply of the reducing agent in step S600 may be injected together with the hydrogen (H ₂ ) reducing agent without additional ammonia (NH ₃ )-based reducing agent supply.

When the operating temperature of the exhaust gas purification device is lower than the proper operating temperature of the exhaust gas purification device through the control of the supply of reducing agent in the exhaust gas purification device as described above, ammonia (NH ₃ )-based reducing agent is additionally supplied to satisfy the high NH ₃ /NOx ratio to slip unreacted ammonia ( NH ₃ slip) does not occur, but by supplying a hydrogen (H ₂ ) reducing agent, it is possible to effectively purify nitrogen oxides (NOx).

The exhaust gas purification apparatus including the composite catalyst filter of the present invention is a diesel oxidation catalyst (DOC, 20), a reducing agent supply unit 40, and a composite catalyst filter in the exhaust gas flow path through which the exhaust gas discharged to the diesel engine 10 moves. (30) The device is configured in the order.

In the exhaust gas purification device, the diesel oxidation catalyst 20 is installed at the rear end of the diesel engine to oxidize and remove unburned hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas, and a part of nitrogen monoxide (NO) to nitrogen dioxide (NO) ₂ ) to perform the conversion.

The exhaust gas passing through the diesel oxidation catalyst 20 flows into the composite catalyst filter 30 installed at the rear end of the diesel oxidation catalyst 20 to physically collect particulate matter (PM) in the exhaust gas, and the collected particulate matter (PM) is continuously removed through a chemical reaction with nitrogen dioxide (NO ₂ ) generated in the diesel oxidation catalyst 20 previously.

Although not shown separately in the drawings, the exhaust gas purifying device of the present invention is installed on the exhaust gas flow path to control the supply of reducing agent according to the diesel engine operating conditions, and a sensor unit for monitoring variables related to the reducing agent injection, delivered from the sensor unit A control unit for controlling the reducing agent supply unit by determining the type and reducing agent injection amount to be supplied based on the received information may be configured.

The sensor unit is a temperature sensor for measuring the temperature of the exhaust gas to monitor the load of the engine, the flow rate of the exhaust gas, the concentration of air pollutants, the temperature of the exhaust gas, the temperature and back pressure of the reducing agent injection, etc. A nitrogen oxide (NOx) concentration sensor for measuring the nitrogen oxide concentration of the gas, an ammonia concentration sensor for measuring the ammonia (NH ₃ ) concentration of the exhaust gas, and an exhaust gas back pressure sensor may be included.

In the exhaust gas purification apparatus including the composite catalyst filter of the present invention, the supply of the reducing agent is controlled as shown in FIGS. 4 to 6 according to the diesel engine operating conditions.

Ammonia (NH ₃ ) reducing agent and hydrogen (H ₂ ) reducing agent are individually or simultaneously injected through the reducing agent supply unit 40 according to the operating conditions of the diesel engine, and particulate matter and nitrogen oxides (NOx) in the composite catalyst filter 30 ) is removed and the exhaust gas is purified.

4 is a view showing the control state of the supply of the reducing agent in a low-temperature operating condition in which the temperature of the exhaust gas purification device, such as the initial start and restart of the engine is less than 250 ℃. Under the low temperature temperature condition of the diesel engine 10, the hydrogen (H ₂ ) reducing agent is supplied alone through the reducing agent supply unit 40 of the front end 30 of the composite catalyst filter, and the H ₂ -SCR catalyst coated in the composite catalyst filter is mixed with the The reaction is used to remove nitrogen oxides (NOx).

5 is a view showing the control state of the supply of the reducing agent under the normal operating conditions of the temperature range of 300 °C to 400 °C when the temperature of the exhaust gas purification device is 300 °C or higher. Under the normal operating temperature condition of the diesel engine 10, urea water is exclusively supplied as an ammonia (NH ₃ )-based reducing agent through the reducing agent supply unit 40 of the front end 30 of the composite catalyst filter, and NH ₃ - Nitrogen oxide (NOx) is removed by reaction with the SCR catalyst.

6 is a view showing the control state of the supply of the reducing agent under the operating conditions NH ₃ /NOx ratio is 0.8 or more or the nitrogen oxide (NOx) concentration in the exhaust gas does not satisfy the emission standard. In this case, in order to control the NH ₃ /NOx ratio to be less than 0.8, the supply amount of urea water supplied through the reducing agent supply unit 40 of the front stage 30 of the composite catalyst filter is maintained, and additionally hydrogen (H ₂ ) A reducing agent is supplied Thus, nitrogen oxide (NOx) is additionally removed without ammonia slip (NH ₃ slip), and the NH ₃ /NOx ratio can be controlled to be less than 0.8.

As a reducing agent required to remove nitrogen oxides (NOx) from exhaust gas, ammonia (NH ₃ )-based reducing agent and hydrogen (H ₂ ) reducing agent are supplied into the exhaust gas purification device through the reducing agent supply unit 40 installed in front of the composite catalyst filter 30 The reducing agent supplied in this way is detoxified into carbon dioxide (CO ₂ ) and water (H ₂ O) through a reduction reaction with nitrogen oxides (NOx) on the catalyst of the composite catalyst filter 30 .

The removal efficiency of nitrogen oxides (NOx) according to the injection temperature conditions of the catalyst and the reducing agent coated on the diesel particulate filter (DPF) in the exhaust gas purification system was evaluated as follows.

Comparative Example 1 is an exhaust gas purification device comprising a diesel particulate filter (DPF) coated with only a vanadium pentoxide (V ₂ O ₅ ) catalyst, which is a vanadia-based catalyst as an NH ₃ -SCR catalyst.

As described above, in Example 1, a vanadium pentoxide (V ₂ O ₅ ) catalyst, which is a vanadia-based catalyst, is coated with an NH ₃ -SCR catalyst on the front wall surface of the diesel particulate filter, and exhaust gas is It is an exhaust gas purification device composed of a composite catalyst filter (NH ₃ ·H ₂ -sDPF) coated with a platinum (Pt) catalyst with H ₂ -SCR catalyst on the rear wall of the diesel particulate filter coming out.

In Comparative Example 1 and Example 1, a cordierite-based diesel particulate filter (DPF) of 100 cells/in ² was used. As the NH ₃ -SCR catalyst, a vanadium pentoxide (V ₂ O ₅ ) catalyst, which is a vanadia-based catalyst, is coated on a diesel particulate filter (DPF) in an amount of 90 g/L, and platinum is used as the H ₂ -SCR catalyst (Pt) 30 g/ft ³ was coated on a diesel particulate filter (DPF).

Nitrogen oxide (NOx) removal performance evaluation uses a simulated gas having a composition of nitrogen oxide (NOx) 500 ppm, oxygen (O ₂ ) 13%, H ₂ O 5%, and gas space velocity (GHSV) = 24,000 h ^-1 and evaluated. The reducing agent required for the reaction was used by supplying NH ₃ (g) and H ₂ (g) separately or simultaneously, and each Comparative Example 1 and Example 1 was evaluated under the reducing agent injection conditions as shown in Table 1 below, and the results are shown in Fig. 7 is shown.

division catalyst Reductant injection conditions 150℃ 200℃ 250℃ 300℃ 350℃ 400℃ Comparative Example 1 V ₂ O ₅ series NH ₃ /NOx = 0.9 Example 1 V ₂ O ₅ +Pt series H ₂ /NOx = 10.0 NH ₃ /NOx=0.8, H ₂ /NOx = 5.0

7 is a graph showing the conversion rate of nitrogen oxide (NOx) according to the reducing agent injection conditions in the exhaust gas purification apparatus according to Comparative Example 1 and Example 1. Referring to FIG.

As shown in FIG. 7, at a temperature of 200° C. or less, Example 1 showed a nitrogen oxide (NOx) conversion more than twice that of Comparative Example 1, and NH ₃ of Example 1 even at 250° C. or higher, which is a normal operating temperature condition. A conversion of over 90% was achieved while maintaining the /NOx ratio at 0.8. Therefore, it has a higher nitrogen oxide (NOx) purification rate than in the low temperature region and the normal operation region through the composite catalyst filter.

As described above, in the exhaust gas purification device including the composite catalyst filter according to the embodiment of the present invention, the efficiency of NH ₃ -SCR is low, and hydrogen ( H ₂ ) is supplied as a reducing agent to remove nitrogen oxides (NOx). And when the normal operation condition of the temperature of 250 ℃ or more is reached, the supply of hydrogen (H ₂ ) reducing agent is stopped and urea water (urea) is injected to remove nitrogen oxides (NOx). Furthermore, under operating conditions that exhibit a high NH ₃ /NOx ratio of 0.8 to 0.9 or more or the nitrogen oxide (NOx) concentration in the exhaust gas does not satisfy the emission standards, hydrogen (H ₂ ) reducing agent is added without additional urea supply. By injecting, it is possible to avoid the operation of an engine that requires a high NH ₃ /NOx ratio of 0.8 or more to minimize the slip generation of unreacted ammonia (NH ₃ ) and to effectively remove nitrogen oxides (NOx). It is possible to control the supply of the reducing agent in the exhaust gas purification system including.

The above-described embodiment is only a preferred embodiment that allows those of ordinary skill in the art to which the present invention pertains (hereinafter referred to as 'person of ordinary skill in the art') to easily practice the present invention, and the above-described embodiment and accompanying drawings Since it is not limited to, the scope of the present invention is not limited thereto. Accordingly, it will be apparent to those skilled in the art that various substitutions, modifications, and changes are possible within the scope of the present invention, and it is apparent that parts easily changeable by those skilled in the art are also included in the scope of the present invention. .

10: diesel engine
20: diesel oxidation catalyst
30: composite catalyst filter
40: reducing agent supply unit

Claims (12)

a diesel oxidation catalyst (DOC) installed at the rear end of a diesel engine to oxidize hydrocarbons (HC) and carbon monoxide (CO) contained in exhaust gas; and
It is installed at the rear end of the diesel oxidation catalyst (DOC) to collect particulate matter contained in exhaust gas, and the NH ₃ -SCR catalyst and H ₂ -SCR catalyst are compositely coated on the wall surface of the diesel particulate filter (DPF) as a catalyst coating layer. A composite catalyst filter consisting of;
The composite catalyst filter includes: a first catalyst coating layer coated with an NH ₃ -SCR catalyst composition on the front end wall of the diesel particulate filter (DPF) through which exhaust gas flows from the diesel particulate filter (DPF); and
and a second catalyst coating layer coated with an H ₂ -SCR catalyst composition on the rear end wall of the diesel particulate filter (DPF) through which exhaust gas is discharged through the first catalyst coating layer. delete The method of claim 1,
The second catalyst coating layer,
The H ₂ -SCR catalyst composition is a coating layer comprising a single component of the H ₂ -SCR catalyst;
a coating layer in which the H ₂ -SCR catalyst composition is a mixture of an H ₂ -SCR catalyst and a NH ₃ -SCR catalyst; and
The H ₂ -SCR catalyst composition is formed on the upper or lower portion of the H _{2 -SCR catalyst layer and the H 2 -SCR} catalyst layer coated as a single component, the NH ₃ -SCR catalyst composition is coated as a single component NH ₃ -SCR catalyst layer made of a coating layer; Exhaust gas purification device, characterized in that made of any one selected from. The method of claim 1,
The NH ₃ -SCR catalyst is an exhaust gas purification apparatus, characterized in that at least one selected from a vanadia-based catalyst and a zeolite-based catalyst. The method of claim 1,
The H ₂ -SCR catalyst is an exhaust gas purification device, characterized in that the platinum (Pt)-based catalyst. (a) NH ₃ on the front end wall of the diesel particulate filter (DPF) through which exhaust gas flows from the diesel particulate filter (DPF) installed at the rear end of the diesel oxidation catalyst (DOC) to collect particulate matter contained in the exhaust gas -SCR catalyst composition coated first catalyst coating layer, and H ₂ -SCR catalyst composition coated second catalyst coating layer on the rear end wall of the diesel particulate filter (DPF) through which exhaust gas is discharged through the first catalyst coating layer Measuring the temperature of the rear end of the composite catalyst filter in the exhaust gas purification apparatus including the composite catalyst filter consisting of;
(b) supplying an ammonia (NH ₃ )-based reducing agent through a reducing agent supply unit when the temperature of the rear end of the composite catalyst filter measured in step (a) is equal to or higher than a set temperature;
(c) if the temperature of the rear end of the composite catalyst filter measured in step (a) is less than a set temperature, supplying a hydrogen (H ₂ ) reducing agent through a reducing agent supply unit;
(d) calculating the NH ₃ /NOx ratio by measuring the ammonia (NH ₃ ) concentration and the nitrogen oxide (NOx) concentration in front of the composite catalyst filter;
(e) if the NH ₃ /NOx ratio is less than a set concentration ratio, purifying nitrogen oxides (NOx) in the composite catalyst filter without supplying a reducing agent; and
(f) purifying nitrogen oxides (NOx) in the composite catalyst filter by additionally supplying hydrogen (H ₂ ) reducing agent through the reducing agent supply unit when the NH ₃ /NOx ratio is greater than or equal to a set concentration ratio; A control method of an exhaust gas purification system. 7. The method of claim 6,
The set temperature is a control method of an exhaust gas purification device, characterized in that 250 ℃ to 400 ℃. 7. The method of claim 6,
The set concentration ratio is a control method of an exhaust gas purification apparatus, characterized in that 0.8 to 0.9. delete 7. The method of claim 6,
The second catalyst coating layer,
The H ₂ -SCR catalyst composition is a coating layer comprising a single component of the H ₂ -SCR catalyst;
a coating layer in which the H ₂ -SCR catalyst composition is a mixture of an H ₂ -SCR catalyst and a NH ₃ -SCR catalyst; and
The H ₂ -SCR catalyst composition is formed on the upper or lower portion of the H _{2 -SCR catalyst layer and the H 2 -SCR} catalyst layer coated as a single component, the NH ₃ -SCR catalyst composition is coated as a single component NH ₃ -SCR catalyst layer made of a coating layer; Control method of an exhaust gas purification device, characterized in that made of any one selected from. 7. The method of claim 6,
The NH ₃ -SCR catalyst is a control method of an exhaust gas purification apparatus, characterized in that at least one selected from a vanadia-based catalyst and a zeolite-based catalyst. 7. The method of claim 6,
The H ₂ -SCR catalyst is a control method of an exhaust gas purification device, characterized in that the platinum (Pt)-based catalyst.

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