KR101316867B1 - System for purifying exhaust gas and method thereof - Google Patents

Abstract

The present invention discloses an exhaust gas purification system and method thereof. Exhaust gas purification system according to an embodiment of the present invention is the redox reduction of the exhaust gas containing a hydrocarbon adsorption catalyst and the hydrocarbon desorbed from the hydrocarbon adsorption catalyst in which the hydrocarbon contained in the exhaust gas is occluded and desorbed according to the temperature And a selective reduction catalyst for storing and desorbing ammonia discharged from the three-way catalyst device according to the temperature, and reducing nitrogen oxide using the desorbed ammonia.

Description

Exhaust gas purification system and its method {SYSTEM FOR PURIFYING EXHAUST GAS AND METHOD THEREOF}

The present invention relates to an exhaust gas purification system and a method thereof, and to an exhaust gas purification system and a method including a selective reduction catalyst for reducing nitrogen oxides to nitrogen gas.

Exhaust gas purification systems using three-way catalysts are generally used to convert harmful substances (CO, HC, NO _X ) from the engine into harmless substances (CO _2, H ₂ O, N ₂ ). The three-way catalyst converts the harmful substances into harmless materials at the same time when the ratio of fuel to air supplied to the engine attains a theoretical air-fuel ratio.

However, in the case of a lean engine in which the air-fuel ratio is lean, the removal rate of nitrogen oxides (NO _X ), that is, the reduction rate of nitrogen oxides (NO _X ) is lowered.

If in order to solve this problem, generally air-fuel ratio is lean, the three-way catalyst generates ammonia as a nitrogen oxide (NO _X) in the exhaust gas (NH _3), and the generated ammonia (NH ₃₎ to react with the nitrogen oxide (NO _X) Reduced to nitrogen gas.

In particular, an exhaust gas purification apparatus having a three-way catalyst, a nitrogen oxide absorption reduction catalyst, and an ammonia adsorption denitrification catalyst in an exhaust gas passage controls fuel injection to remove nitrogen oxides in the exhaust gas. Specifically, the exhaust gas of the lean air-fuel ratio is discharged from the cylinder during normal operation, and the nitrogen oxides in the exhaust gas are absorbed by the nitrogen oxide absorption reduction catalyst. If the amount of nitrogen oxide absorbed by the nitrogen oxide absorption reduction catalyst exceeds a predetermined level, the control circuit performs additional fuel injection during the explosion stroke or the exhaust stroke of the cylinder to enrich the air-fuel ratio of the exhaust gas discharged from the cylinder. Adjust to the air-fuel ratio. The rich air-fuel ratio exhausted from the cylinder flows into the three-way catalyst and the nitrogen oxides in the exhaust gas are converted from the three-way catalyst to ammonia. When the rich air-fuel ratio exhaust gas flows through the nitrogen oxide absorption reduction catalyst, the nitrogen oxide is released from the nitrogen oxide absorption reduction catalyst and reduced to nitrogen gas by ammonia in the exhaust gas.

However, the exhaust gas purification device additionally introduces fuel into the cylinder of the engine rather than using the exhaust gas itself to remove nitrogen oxides in the exhaust gas.

The present invention provides an exhaust gas purification system and method for effectively removing nitrogen oxides (NO _X ) in exhaust gas.

The present invention provides an exhaust gas purification system and method for producing ammonia (NH ₃ ) using the hydrocarbon (HC) of exhaust gas and removing nitrogen oxides (NO _X ) in the exhaust gas.

The present invention provides an exhaust gas purification system and method for effectively removing hydrocarbon (HC) and nitrogen oxides (NO _X ) in exhaust gas.

In order to solve the above problems, the exhaust gas purifying apparatus according to the embodiment of the present invention is a hydrocarbon adsorption catalyst and the hydrocarbon desorbed from the hydrocarbon adsorption catalyst and the hydrocarbon adsorption and desorption according to the temperature of the hydrocarbon contained in the exhaust gas And a three-way catalyst device for oxidatively reducing exhaust gas including a and an ammonia discharged from the three-way catalyst device according to a temperature, and a selective reduction catalyst for reducing nitrogen oxide using the desorbed ammonia.

The apparatus may further include a first adjusting member configured to adjust the temperature of the hydrocarbon adsorption catalyst to occlude and desorb the hydrocarbon.

In addition, the first adjusting member may include a first cooling member for lowering the temperature of the hydrocarbon adsorption catalyst so that the hydrocarbon is occluded.

In addition, the cooling medium of the first cooling member may be oil or cooling water.

In addition, the first control member may include a first heating member for raising the temperature of the hydrocarbon adsorption catalyst so that the hydrocarbon is desorbed.

The method may further include a second control member for adjusting the temperature of the selective reduction catalyst to occlude and desorb the ammonia.

In addition, the second control member may include a second heating member for raising the temperature of the selective reduction catalyst such that the ammonia is desorbed.

In addition, the hydrocarbon adsorption catalyst may further include a three-way catalyst layer.

The apparatus may further include a three-way catalyst device provided in front of the hydrocarbon adsorption catalyst and configured to redox the exhaust gas discharged from the engine.

The exhaust gas purification system according to another embodiment of the present invention oxidizes an exhaust gas including a hydrocarbon adsorption catalyst in which hydrocarbons contained in exhaust gas are occluded and desorbed according to temperature, and hydrocarbons desorbed from the hydrocarbon adsorption catalyst. The three-way catalytic device for reducing and the ammonia discharged from the three-way catalyst device are occluded and desorbed according to the temperature, and the temperature of the selective reduction catalyst and the hydrocarbon adsorption catalyst for reducing nitrogen oxides by using the desorbed ammonia is adjusted. And a first regulating member that occludes and desorbs hydrocarbons, a second regulating member that absorbs and desorbs ammonia by controlling a temperature of the selective reduction catalyst, and a control part controlling the first regulating member and the second regulating member. do.

In addition, when the nitrogen oxide is detected at the front end of the selective reduction catalyst, the controller may adjust the second control member to increase the temperature of the selective reduction catalyst above the active temperature of the selective reduction catalyst.

In addition, when it is determined that ammonia to be occluded in the selective reduction catalyst is required, the controller adjusts the first regulating member to maintain the hydrocarbon adsorption catalyst at a temperature at which the hydrocarbon can be occluded for a predetermined time. The first adjusting member may be readjusted to raise the hydrocarbon adsorption catalyst to a temperature at which the hydrocarbon can be desorbed.

The apparatus may further include a three-way catalyst device provided in front of the hydrocarbon adsorption catalyst and configured to redox the exhaust gas discharged from the engine.

Hydrocarbon adsorption catalyst in which the hydrocarbon contained in the exhaust gas according to another embodiment of the present invention is occluded and desorbed according to the temperature, Three-way catalyst for redoxing the exhaust gas containing the hydrocarbon desorbed from the hydrocarbon adsorption catalyst, In the exhaust gas purification method using an exhaust gas device comprising a selective reduction catalyst for the ammonia discharged from the three-way catalyst is occluded and desorbed in accordance with the temperature, the nitrogen oxide is reduced by using the desorbed ammonia, the selective reduction catalyst Determining whether ammonia is required in the step and if it is determined that the ammonia is necessary, by adjusting the hydrocarbon adsorption catalyst to the storage possible temperature to set the hydrocarbon contained in the exhaust gas to the hydrocarbon adsorption catalyst Occlusion and the temperature of the hydrocarbon adsorption catalyst Desorbing the occluded hydrocarbon by increasing the desorbed hydrocarbon, reducing the desorbed hydrocarbon to ammonia through the three-way catalyst, occluding the ammonia in the selective reduction catalyst, and nitrogen oxide at the front end of the selective reduction catalyst. Determining whether it is detected, and when the nitrogen oxide is detected, increasing the temperature of the selective reduction catalyst to desorb the occluded ammonia, and reducing the nitrogen oxide using the desorbed ammonia. do.

Hydrocarbon adsorption catalyst in which the hydrocarbon contained in the exhaust gas according to another embodiment of the present invention is occluded and desorbed according to the temperature, Three-way catalyst for redoxing the exhaust gas containing the hydrocarbon desorbed from the hydrocarbon adsorption catalyst, In the exhaust gas purification method using an exhaust gas device comprising a selective reduction catalyst for the ammonia discharged from the three-way catalyst is occluded and desorbed in accordance with the temperature, the nitrogen oxide is reduced by using the desorbed ammonia, the selective reduction catalyst When ammonia is needed to reduce the nitrogen oxides in the gas, the temperature of the hydrocarbon adsorption catalyst is adjusted to occlude and desorb hydrocarbons, and the ammonia generated by the desorbed hydrocarbons is occluded in the selective reduction catalysts, and When oxides are generated, the temperature of the selective reduction catalyst To remove the occluded ammonia is raised to the activation temperature is reduced to nitrogen oxides.

The present invention can effectively remove nitrogen oxides (NO _X ) in the exhaust gas.

The present invention can use a hydrocarbon (HC) in the exhaust gas to generate ammonia (NH ₃ ) and to remove nitrogen oxides (NO _X ) in the exhaust gas.

The present invention can effectively remove hydrocarbons (HC) and nitrogen oxides (NO _X ) in the exhaust gas.

1 and 2 are views showing an exhaust gas purification system according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention, and are not intended to limit the scope of the inventions. I will do it.

1 and 2 are views showing an exhaust gas purification system according to an embodiment of the present invention.

1 and 2, an exhaust gas purification system according to an exemplary embodiment of the present invention includes an engine 10, a first three-way catalyst device 20, a hydrocarbon adsorption catalyst 30, and a second three-way catalyst device 40. ), A selective reduction catalyst 50, a first regulating member 60, a second regulating member 70, and a controller 80.

The engine 10 burns fuel and air to convert chemical energy into mechanical energy. The engine 10 includes a plurality of cylinders 11 into which fuel and air are introduced, and an ignition device for igniting the fuel and air introduced into the cylinder 11. [ The engine 10 is connected to the intake manifold 15 to receive air into the cylinder 11 and to exhaust the exhaust gas generated in the combustion process to the exhaust manifold 17, .

The first three-way catalyst device 20 is installed in the exhaust pipe 19 connected to the engine 10 to redox the exhaust gas discharged from the engine 10. In general, the first three-way catalytic device 20 changes three harmful substances (CO, HC, NO _X ) contained in the exhaust gas into harmless gases (CO _2, H ₂ O, N ₂ ) by oxidation / reduction reactions. Let's do it.

The first three-way catalyst device 20 mainly uses platinum (Pt), palladium (Pd) and rhodium (Rh) as catalysts for promoting redox reactions. Platinum or palladium catalysts mainly promote oxidation reactions to reduce carbon monoxide (CO) and hydrocarbons (HC), and rhodium catalysts are mainly responsible for reduction reactions to reduce nitrogen oxides (NO _X ). When the air-fuel ratio is lean, that is, when the air is excessive, the first three-way catalytic device 20 actively undergoes an oxidation reaction to reduce carbon monoxide (CO) and hydrocarbons (HC), thereby providing water (H ₂ O) and carbon dioxide (CO). ₂ ) the production rate is increased, when the air-fuel ratio is rich, that is, when the fuel is excessive, a reduction reaction to reduce the nitrogen oxides (NO _X ) occurs actively to increase the production rate of nitrogen (N ₂ ).

The hydrocarbon adsorption catalyst 30 is provided in the exhaust pipe behind the first three-way catalyst device 20. The hydrocarbon adsorption catalyst 30 forms a layer that adsorbs hydrocarbons (HC) including zeolite, and occludes and desorbs hydrocarbons. Specifically, the hydrocarbon HC is occluded in the hydrocarbon adsorption layer 32 in the normal temperature region, and the hydrocarbon HC occluded in the high temperature region, for example, about 210 ° C, is desorbed.

As shown in FIG. 2, the hydrocarbon adsorption catalyst 30 may include a three-way catalyst layer 34 for oxidizing and reducing exhaust gases, that is, hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO _X ). have. The three-way catalyst layer 34 mainly uses platinum (Pt), palladium (Pd) and rhodium (Rh) like the first three-way catalyst device 20. The hydrocarbon adsorption layer 32 and the three-way catalyst layer 34 may be provided up and down. In particular, the hydrocarbon adsorption layer 32 may be provided below the three-way catalyst layer 34, but is not limited thereto.

The second three-way catalyst device 40 is provided at the rear of the hydrocarbon adsorption catalyst 30 and oxidizes and reduces the exhaust gas containing the hydrocarbon desorbed from the hydrocarbon adsorption catalyst 30. Like the three-way catalyst layer 34 and the first three-way catalyst device 20, the second three-way catalyst device 40 mainly uses platinum (Pt), palladium (Pd), and rhodium (Rh).

In the three-way catalyst layer 34 and the second three-way catalyst device 40 of the hydrocarbon adsorption catalyst 30, the fuel is excessively supplied due to the hydrocarbon desorbed from the hydrocarbon adsorption catalyst 30, that is, the air-fuel ratio is lean. It becomes a state. Thus, in the three-way catalyst layer 34 and the second three-way catalyst device 40, nitrogen oxides (NO _X ) are reduced to generate ammonia (NH ₃ ).

The selective reduction catalyst 50 is provided in the exhaust pipe 19 behind the second three way catalytic apparatus 40. The selective reduction catalyst 50 reduces nitrogen oxides (NO _X ) to nitrogen gas using ammonia (NH ₃ ). The selective reduction catalyst 50 includes an ammonia adsorption layer 52 that occludes and desorbs ammonia (NH ₃ ), and the ammonia adsorption layer 52 is ammonia (NH ₃ ) adsorption material including zeolite and the like. It is composed. The ammonia adsorption layer 52 is occluded and desorbed ammonia (NH ₃ ) in accordance with the temperature.

As mentioned above, the hydrocarbon HC is occluded and desorbed according to the temperature of the hydrocarbon adsorption catalyst 30. Accordingly, the first control member 60 is directly attached to the hydrocarbon adsorption catalyst 30 to transfer or absorb heat thereto to directly control its temperature to adsorb and desorb hydrocarbon HC.
The first adjustment member 60 includes a first cooling member 62 and a first heating member 64. The first cooling member 62 absorbs heat from the hydrocarbon adsorption catalyst 30 to lower the temperature thereof so that hydrocarbon HC is occluded, and is provided adjacent to the hydrocarbon adsorption catalyst 30.
The first cooling member 62 may use various materials as the cooling medium. In one example, the cooling medium may be oil or cooling water. The first heating member 64 raises the temperature of the hydrocarbon adsorption catalyst 30 to desorb the hydrocarbon HC, and is provided adjacent to the hydrocarbon adsorption catalyst 30.

In addition, ammonia (NH ₃ ) is also occluded and desorbed in accordance with the temperature of the selective reduction catalyst (50). Thus, the second control member 70 controls the temperature of the selective reduction catalyst 50 to occlude and desorb ammonia (NH ₃ ). The second regulating member 70 includes a second heating member 74, and the second heating member 74 transfers heat directly to the selective reduction catalyst 50 so that ammonia (NH ₃ ) can be desorbed to adjust its temperature. Is raised and provided adjacent to the ammonia adsorption layer 52.

The controller 80 controls the first adjusting member 60 and the second adjusting member 70.

Specifically, the controller 80 controls the temperature of the hydrocarbon adsorption catalyst 30 by controlling the first adjusting member 60 to generate ammonia (NH ₃ ). When ammonia (NH ₃ ) to be stored in the selective reduction catalyst 50 is required, the controller 80 controls the first adjusting member 60 so that the hydrocarbon adsorption catalyst 30 can store the hydrocarbon HC. Is maintained for a predetermined time, and the first control member 60 is controlled to allow the hydrocarbon adsorption catalyst 30 to rise to the detachable temperature of the hydrocarbon (HC). Accordingly, the hydrocarbon (HC) occluded for a predetermined time is desorbed to the hydrocarbon (HC) adsorption layer, and the nitrogen oxide (H) is excessively supplied from the three-way catalyst layer 34 or the second three-way catalyst device 40. NO _X ) is reduced to ammonia (NH ₃ ). At this time, the hydrocarbon adsorption catalyst 30 maintains the occlusion temperature of the hydrocarbon (HC) for a predetermined time, to provide an air-fuel ratio state for the production of ammonia (NH ₃ ). According to one example, the predetermined time may be about 100 seconds. The controller 80 may set the predetermined time in advance.

In addition, the control unit 80 receives a detection state of the nitrogen oxide (NO _X ) from the detection unit provided in front of the selective reduction catalyst 50. When nitrogen oxide NO _x is detected or when the amount of detection of the nitrogen oxide NO _x exceeds a predetermined amount, the controller 80 adjusts the second adjusting member 70 to adjust the temperature of the selective reduction catalyst 50. Raise above the active temperature of the selective reduction catalyst 50. When the selective reduction catalyst 50 is active, the ammonia (NH ₃₎ the ammonia is being desorbed, the desorption of ammonia (NH ₃₎ (NH ₃₎ are nitrogen oxides (NO _X) occluded in the adsorbent bed is reduced to nitrogen gas.

It will be described in detail the regeneration method using the soot exhaust gas purification system described above.

The exhaust gas purification system 1 is performed during operation of the engine 10. Since the temperature of the engine 10 is low at the time of initial start-up, the hydrocarbon HC contained in the exhaust gas discharged from the engine 10 or the exhaust gas discharged through the first three-way catalyst device 20 is a hydrocarbon adsorption catalyst. It is occluded in 30. When the hydrocarbon adsorption catalyst 30 rises to the desorption temperature of the hydrocarbon HC due to the temperature rise of the exhaust gas, the hydrocarbon HC stored in the hydrocarbon storage layer is desorbed. The desorbed hydrocarbon (HC) is supplied to the three-way catalyst layer 34 and / or the second three-way catalyst device 40, and the air-fuel ratio becomes thin due to the desorbed hydrocarbon (HC). Thus, the nitrogen oxides (NO _X ) are reduced to ammonia (NH ₃ ). Ammonia (NH ₃ ) is occluded in the ammonia storage layer (52) of the selective reduction catalyst (50) device, and when the stored ammonia (NH ₃ ) is desorbed to reduce the nitrogen oxides (NOX).

When the temperature of the engine rises while the vehicle is running, that is, after the initial start of the engine and the temperature rises in the exhaust gas, the temperature of the hydrocarbon adsorption catalyst 30 also rises. As a result, the hydrocarbon HC cannot be occluded in the hydrocarbon adsorption catalyst 30. At this time, when it is determined that ammonia (NH ₃ ) to be used in the selective reduction catalyst 50 device is necessary, the controller 80 controls the first refrigeration member of the first regulating member 60 so as to adsorb the hydrocarbon adsorption catalyst 30. ) Is reduced to the temperature at which the hydrocarbon (HC) can occlude. When a certain amount of hydrocarbon HC is occluded, the controller 80 controls the first heating member 64 of the first regulating member 60 to adjust the temperature of the hydrocarbon adsorption catalyst 30 to the hydrocarbon HC. Increase to a removable temperature. At this time, a certain amount of hydrocarbon (HC) is desorbed, thereby reducing nitrogen oxide (NO _X ) to ammonia (NH ₃ ).

When the selective reduction catalyst 50 is not activated or when nitrogen oxides (NOX) are not detected, ammonia (NH ₃ ) is occluded in the ammonia (NH ₃ ) adsorption layer of the selective reduction catalyst 50. When nitrogen oxide NO _x is detected, the controller 80 increases the temperature of the selective reduction catalyst 50 by using the second heating device of the second regulating member 70 to activate it. At this time, the occluded ammonia (NH ₃ ) is desorbed, thereby reducing the nitrogen oxide (NO _X ) to nitrogen gas.

Hydrocarbon (HC) occlusion and desorption process in the hydrocarbon adsorption catalyst 30 and ammonia (NH ₃ ) occlusion and desorption process in the selective reduction catalyst 50 may occur in time series. However, the present invention is not limited thereto, and the hydrocarbon (HC) storage and desorption process and the ammonia (NH 3) storage and desorption process may occur at the same time with each catalyst.
In an embodiment of the present invention, HC trap (hydrocarbon occlusion catalyst) in a vehicle adsorbs hydrocarbon at all times, and a large amount of nitrogen oxide is generated after fuel cut or in an air-fuel ratio (15.5) of 15.5 or more, thereby reducing SCR (selective reduction). Since ammonia is consumed in the catalyst), the time required for ammonia is after the fuel cut or under an air-fuel ratio of 15.5.
In addition, the oxygen sensor after the fuel cut or the front end of the catalyst indicates an air-fuel ratio of 15.5 or more so that a large amount of nitrogen oxides are generated.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And all changes to the scope that are deemed to be valid.

1 Exhaust gas purification system
10 engine
20 first three-way catalytic device
30 hydrocarbon storage catalyst
32 Hydrocarbon storage layer 34 Three-way catalyst layer
40 second ternary catalyst device
50 selective reduction catalyst
60 first adjusting member
62 First cooling member 64 First heating member
70 second adjusting member
74 second heating member
80 control unit

Claims (15)

A hydrocarbon adsorption catalyst in which hydrocarbons contained in the exhaust gas are occluded and desorbed according to temperature;
A three-way catalyst device for redoxing the exhaust gas containing hydrocarbons desorbed from the hydrocarbon adsorption catalyst;
A selective reduction catalyst which occludes and desorbs ammonia discharged from the three-way catalytic apparatus according to temperature, and reduces nitrogen oxides using the desorbed ammonia; And
A first regulating member attached directly to the hydrocarbon adsorption catalyst to transfer or cool heat thereto to occlude and desorb the hydrocarbon; Lt; / RTI >
The first regulating member includes a first cooling member attached directly to the hydrocarbon adsorption catalyst to absorb the hydrocarbon and absorbs heat to lower the temperature, wherein the cooling medium of the first cooling member is oil or cooling water. Exhaust gas filter. delete delete delete The method of claim 1,
The first adjusting member is
And a first heating member for raising the temperature of the hydrocarbon adsorption catalyst such that the hydrocarbon is desorbed. The method of claim 1,
And a second adjusting member attached directly to the selective reduction catalyst to adjust its temperature to occlude and desorb the ammonia. The method according to claim 6,
The second adjusting member is
And a second heating member for raising the temperature of the selective reduction catalyst to desorb the ammonia. The method according to any one of claims 1, 5, 6, and 7,
The hydrocarbon adsorption catalyst further comprises a three-way catalyst layer. The method according to any one of claims 1, 5, 6, and 7,
And a three-way catalyst device provided in front of the hydrocarbon adsorption catalyst and configured to redox the exhaust gas discharged from the engine. A hydrocarbon adsorption catalyst in which hydrocarbons contained in the exhaust gas are occluded and desorbed according to temperature;
A three-way catalyst device for redoxing the exhaust gas containing hydrocarbons desorbed from the hydrocarbon adsorption catalyst;
A selective reduction catalyst which occludes and desorbs ammonia discharged from the three-way catalytic apparatus according to temperature, and reduces nitrogen oxides using the desorbed ammonia;
A first regulating member attached directly to the hydrocarbon adsorption catalyst to adjust its temperature to occlude and desorb the hydrocarbon;
A second adjusting member attached directly to the selective reduction catalyst to adjust its temperature to occlude and desorb the ammonia; And
A control unit controlling the first adjusting member and the second adjusting member;
Exhaust gas purification system comprising a. 11. The method of claim 10,
The control unit
And when nitrogen oxide is detected in front of the selective reduction catalyst, adjusting the second regulating member to raise the temperature of the selective reduction catalyst to above the active temperature of the selective reduction catalyst. 11. The method of claim 10,
The control unit
When it is determined that ammonia to be occluded in the selective reduction catalyst is necessary,
Adjusting the first regulating member to maintain the hydrocarbon adsorption catalyst for a predetermined time at a temperature at which the hydrocarbon can occlude;
And regulating the first regulating member to raise the hydrocarbon adsorption catalyst to a temperature at which the hydrocarbon can be desorbed. 13. The method according to any one of claims 10 to 12,
And a three-way catalyst device provided in front of the hydrocarbon adsorption catalyst and configured to redox the exhaust gas discharged from the engine. A hydrocarbon adsorption catalyst in which hydrocarbons contained in the exhaust gas are occluded and desorbed according to temperature, a three-way catalyst for redox-reducing the exhaust gas containing hydrocarbons desorbed from the hydrocarbon adsorption catalyst, and ammonia discharged from the three-way catalyst In the exhaust gas purification method using an exhaust gas device comprising a selective reduction catalyst that is occluded and desorbed according to temperature and reduces nitrogen oxides using the desorbed ammonia,
Determining whether ammonia is required for the selective reduction catalyst;
When it is determined that the ammonia is necessary, the hydrocarbon is absorbed directly to the hydrocarbon adsorption catalyst and cooled to an occupable temperature to occlude hydrocarbons contained in the exhaust gas for a predetermined time in the hydrocarbon adsorption catalyst, and the carbonization Directly heating the hydrogen adsorption catalyst to increase the temperature to desorb the occluded hydrocarbon;
Reducing the desorbed hydrocarbon to ammonia via the three-way catalyst;
Occluding the ammonia in the selective reduction catalyst;
Determining whether nitrogen oxide is detected at the front end of the selective reduction catalyst;
When the nitrogen oxide is detected, directly transferring heat to the selective reduction catalyst to increase its temperature to desorb the occluded ammonia; And
Reducing the nitrogen oxides using the desorbed ammonia;
Exhaust gas purification method comprising a. A hydrocarbon adsorption catalyst in which hydrocarbons contained in the exhaust gas are occluded and desorbed according to temperature, a three-way catalyst for redox-reducing the exhaust gas containing hydrocarbons desorbed from the hydrocarbon adsorption catalyst, and ammonia discharged from the three-way catalyst In the exhaust gas purification method using an exhaust gas device comprising a selective reduction catalyst that is occluded and desorbed according to temperature and reduces nitrogen oxides using the desorbed ammonia,
When ammonia is required to reduce the nitrogen oxides in the selective reduction catalyst, the hydrocarbon adsorption catalyst is directly heated or cooled to adjust the temperature to occlude and desorb the hydrocarbon, and to remove the ammonia produced by the desorbed hydrocarbon. When nitrogen oxide is occluded in the selective reduction catalyst and the nitrogen oxide is detected at the front end of the selective reduction catalyst, the selective reduction catalyst is directly heated to raise the temperature to the active temperature to desorb the occluded ammonia to reduce the nitrogen oxide. Purification method.

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