JP2009127585A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of efficiently purifying noxious component in exhaust gas. <P>SOLUTION: A heat exchanger 5 is disposed in a first exhaust gas channel 31 which exhaust gas from an engine 1 pass through. The heat exchanger 5 is divided into a high temperature side channel 5a and a low temperature side channel 5b by a bulkhead 5c. Heat is exchanged between the high temperature side channel 5a and the low temperature side channel 5b. Fluid passing through the high temperature side channel 5a is cooled and fluid passing through the low temperature side channel 5b is re-heated. A first exhaust gas channel 31 includes a plasma processing part 4 as a first reaction part. A first catalyst part 6 containing catalyst purifying NOx is disposed at a downstream side of the plasma processing part 4 as a second reaction part inducing next step reaction following the reaction in the first reaction part based on it. An upstream side of the plasma processing part 4 and the high temperature side channel 5a of the heat exchanger 5 are connected to keep flow, and a downstream side of the plasma processing part 4 and an upstream side of the first catalyst part 6 are connected via the low temperature side channel 5b of the heat exchanger 5 to keep flow. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device that purifies harmful components in combustion exhaust gas discharged from an internal combustion engine or the like.

The exhaust gas discharged from the automobile engine contains nitrogen oxides (NO _x ), carbon monoxide (CO), and hydrocarbons (HC) as harmful components. There is an automobile exhaust gas treatment device in which a catalytic purification device that purifies these harmful gases by catalytic action is incorporated in an exhaust passage of an engine, and a plasma processing device is connected upstream of the catalytic purification device. In this plasma processing apparatus of an automobile exhaust gas processing apparatus, a part of NO _x is separated into N ₂ and O _2, and a part of CO and hydrocarbon reacts with oxygen to become CO ₂ and H ₂ O. Detoxified. The harmful components that have not been rendered harmless in the plasma processing apparatus flow into the catalytic purification device connected to the downstream side of the plasma processing apparatus. The harmful component flows into the catalytic purification device in an excited state given a large amount of energy from the plasma, and the energy is activated by the energy, and the oxidation or reduction is promoted to improve the efficiency of the exhaust gas purification treatment (for example, Patent Document 1).
In addition, a heat exchanger and an adsorbent are disposed in an exhaust passage through which exhaust gas of the internal combustion engine passes, and a catalyst is disposed downstream of the adsorbent, and the heat exchanger is disposed upstream of the adsorbent, and the adsorbent. There is an exhaust gas purification device that can exchange heat with the upstream side of the catalyst and the upstream side of the catalyst. In this exhaust gas purification device, immediately after the engine is started, exhaust gas containing harmful components discharged from the engine passes through the heat exchanger and flows out at a low temperature, and the harmful components are adsorbed by the adsorbent. . The exhaust gas from which harmful components have been removed by the adsorbent is reheated by the heat exchanger and introduced into the catalyst, and the catalyst is efficiently heated to reach the activation temperature early. As a result, when the exhaust gas temperature rises immediately after starting the engine, the adsorbent can once adsorb the harmful component until the catalyst reaches an activation temperature that can purify the harmful component in the exhaust gas. Is prevented from being released into the atmosphere (see, for example, Patent Document 2).

JP-A-6-335621 (first page) Japanese Patent Laid-Open No. 2001-295543 (first page)

In the exhaust gas treatment apparatus for automobiles of Patent Document 1, harmful components that have not been rendered harmless by the plasma treatment apparatus are caused to flow into the catalytic purification apparatus in an excited state given a large energy from the plasma. It is necessary to provide in the upstream of a type purification device. However, the temperature of the exhaust gas from the engine decreases according to the exhaust gas flowing direction due to the influence of heat release to the outside, and the temperature of the downstream catalytic purification device becomes lower than that of the upstream plasma processing device. Therefore, there is a problem that it is difficult to use the catalytic purification device at a high temperature at which the purification treatment can be performed efficiently and a high purification rate cannot be obtained.
In the exhaust gas purifying apparatus of Patent Document 2, the adsorbent is usable until the adsorbent is saturated, and when the adsorbent becomes higher than the desorption temperature, the adsorbing ability is lost. Therefore, the adsorbent acts only for a certain time after the engine is started, and there is a problem that the harmful components are not sufficiently purified because the harmful components in the exhaust gas are purified only by the catalyst during the steady operation.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an exhaust gas purification device capable of efficiently purifying harmful components in exhaust gas.

  The exhaust gas purifying apparatus according to the present invention is provided in a first exhaust gas flow path through which exhaust gas discharged from an engine passes, and the first reaction part with which the exhaust gas reacts, the first exhaust gas flow A high-temperature channel provided on the upstream side of the first reaction unit in the channel and a low-temperature channel provided on the downstream side of the first reaction unit in the first exhaust gas channel And a second reaction that is provided on the downstream side of the low-temperature side passage in the first exhaust gas passage and causes the next-stage reaction based on the reaction in the first reaction section. And the temperature of the first reaction part is lower than the temperature of the second reaction part.

In the exhaust gas flow path, the exhaust gas discharged from the engine is introduced into the second reaction part after passing through the first reaction part, and the role of the second reaction part in the next stage in the first reaction part. Therefore, the exhaust gas purification function is improved.
Further, the exhaust gas discharged from the engine by the heat exchanger is lowered in temperature and introduced into the first reaction part, and then reheated by the heat exchanger and heated to be introduced into the second reaction part. Therefore, the exhaust gas flowing through the second reaction section downstream from the first reaction section on the upstream side in the exhaust flow path can be made high temperature, and the first reaction section and the second reaction section can be easily heated. Reactivity can be efficiently expressed.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram of an exhaust gas processing apparatus according to Embodiment 1 of the present invention, and shows a state connected to an engine 1.
As shown in FIG. 1, several cylinders (not shown) are provided in the engine 1, and the exhaust gas burned in the cylinder is sent from a plurality of exhaust manifolds 2 to one exhaust pipe. It is introduced into the first exhaust gas passage 31.
A plasma processing unit 4 is provided as a first reaction unit in the first exhaust gas flow path 31, and a subsequent reaction following this is performed on the downstream side of the plasma processing unit 4 based on the reaction in the first reaction unit. second first catalyst unit 6 containing _the NO _x purification catalyst for purifying NO _x is arranged as a reaction unit, further heat exchanger 5, the high-temperature side flow passage 5a is upstream of the plasma processing unit 4 caused In addition, the low-temperature channel 5 b is provided on the downstream side of the plasma processing unit 4 and on the upstream side of the first catalyst unit 6. In the exhaust gas treatment device of the present embodiment, the exhaust gas discharged from the engine 1 flows into the high temperature side flow path 5a, passes through the plasma processing unit 4 and then flows into the low temperature side flow path 5b, and in the heat exchanger 5, Heat is exchanged through the partition wall 5c separating the high temperature side flow path 5a and the low temperature side flow path 5b, and the exhaust gas passing through the high temperature side flow path 5a is cooled and introduced into the plasma processing unit 4, After passing, it is reheated in the low temperature side channel 5 b and introduced into the first catalyst unit 6.

The plasma processing unit 4 according to the present embodiment includes a discharge electrode, and exhaust gas passes between the discharge electrodes. A plasma control device 7 and a high voltage power source 8 are connected to each other. The plasma control device 7 controls the operation of the plasma processing unit 4 by controlling the high voltage power supply 8 and the like based on the information on the monitored plasma generation status, the information on the rotational speed of the engine 1 and the exhaust gas temperature, and the like. This ultimately controls the amount of plasma generation.
In the present embodiment, the plasma processing unit 4 is provided as a first reaction unit responsible for a pre-reaction for purifying harmful components in the exhaust gas, and is a reaction performed in the plasma processing unit 4. The conversion treatment means that at least a part of hydrocarbons contained in the exhaust gas is converted into highly reactive hydrocarbons such as aldehydes, alcohols or unsaturated hydrocarbons, or NO is converted to NO ₂ . To do.
That is, when the exhaust gas passes between the discharge electrodes, discharge plasma is generated, and first, dissociation occurs in the oxygen molecules and water molecules in the exhaust gas as shown in the following equation. In the formula, * indicates that an atom or molecule is in an excited state.
O ₂ → 2O ^*
H ₂ O → H ^* + OH ^*
As shown in the following reaction formula, O ^* and OH ^* react with HC and NO, which are harmful gases, to finally formaldehyde, acetaldehyde, NO _{2 and the} like.
HC + O ^* (or OH ^* ) → aldehyde, etc. NO + O ^* → NO ₂

Exhaust gas emitted from automobile engines contains nitrogen oxides (NO _x ), carbon monoxide (CO), and hydrocarbons (HC) as harmful components, and is contained in exhaust gases from gasoline lean burn engines and diesel engines. Contains a large amount of oxygen, and NO _x purification is particularly problematic.
On the other hand, in the plasma processing unit 4 according to the present embodiment, exhaust gas containing oxygen is subjected to discharge plasma treatment, thereby generating aldehyde and NO ₂ by the discharge chemical reaction shown in the above formula, thereby exhaust gas. Hazardous gas inside can be made into highly reactive reducing gas or oxidizing gas, and the exhaust gas purification function is improved, especially in exhaust gas such as gasoline lean burn engine and diesel engine. It is effective for purifying engine exhaust gas.

FIG. 2 is a characteristic diagram showing a change in the conversion rate to NO ₂ depending on the plasma electrode temperature of the plasma processing unit 4 according to the exhaust gas purification apparatus of the present embodiment, and the conversion rate to NO ₂ is expressed by the following equation. Value.
NO ₂ conversion rate = plasma processing unit outlet NO ₂ concentration / plasma processing unit inlet NO _x concentration As shown in FIG. 2, when the plasma electrode temperature of the plasma processing unit 4 is about 350 ° C., it is converted to NO ₂ by plasma processing. It can be seen that the conversion is most efficiently applied and there is an optimum temperature for the plasma treatment.

The NO _x purification catalyst used for the first catalyst unit 6 according to the present embodiment is a catalyst in which a catalyst is supported on a honeycomb-shaped honeycomb ceramic substrate. For example, a purification reaction of aldehyde and NO _{2 on} the ceramic substrate. There are silver catalysts supported on alumina and zeolite-based catalysts which are effective for the above.
An exhaust gas containing aldehydes or NO ₂ obtained by a discharge chemical reaction in the plasma processing unit 4 is introduced into the first catalyst unit 6 according to the present embodiment, and further subjected to a cleaning process. The cleaning treatment in the first catalyst unit 6 is a next-stage reaction based on the reaction in the plasma processing unit 4, and aldehydes and NO ₂ contained in the exhaust gas are converted into N ₂ , CO ₂ , H ₂ O. It is to convert to.
FIG. 3 is a characteristic diagram showing the relationship between the catalyst temperature and the NO _x purification rate in the first catalyst unit 6 according to the exhaust gas purification apparatus of the present embodiment, and the NO _x purification rate is expressed by the following equation. Value.
_The NO _x purification rate = - as shown in (catalyst unit inlet concentration of NO _x catalyst unit outlet concentration of NO _x) / catalyst unit inlet concentration of NO _x Figure 3, the catalyst temperature of the first catalyst portion 6 is at about 420 ° C. , purification rate of the NO _x by the catalyst is the highest, it can be seen that the optimum temperature is present in the purification of the NO _x.

As described above, the present inventors have found that the purification rate is increased by providing the plasma processing unit 4 on the upstream side of the first catalyst unit 6 in the exhaust gas passage of the present embodiment. Furthermore, it has been found that the optimum temperature (420 ° C.) of the downstream first catalyst unit 6 is higher than the optimum temperature (350 ° C.) of the upstream plasma processing unit 4.
Therefore, in the present embodiment, the exhaust gas discharged from the engine 1 is lowered in temperature by the heat exchanger 5 and introduced into the plasma processing unit 4, and then reheated by the heat exchanger 5 to be first catalyst unit 6. As a result, the temperatures of the plasma processing unit 4 and the first catalyst unit 6 can be optimized, and a high exhaust gas purification rate can be realized.

That is, in the present embodiment, by generating aldehyde and NO ₂ in the plasma discharge processing unit 4, a part of the role of the first catalyst unit 6 in the next stage is performed, so that the exhaust gas purification function is improved. To do. In this way, the exhaust gas containing oxygen is subjected to discharge plasma treatment, and the harmful gas in the exhaust gas is reformed into a highly reactive reducing gas and oxidizing gas, and then passed through the first catalyst unit 6. Thus, the exhaust gas is efficiently cleaned.
Further, the exhaust gas discharged from the engine 1 is introduced into the high temperature side flow path 5a of the heat exchanger 5, and the high temperature exhaust gas passes through the plasma processing unit 4 to the low temperature side flow path 5b of the heat exchanger 5. The introduced exhaust gas is heated through the partition wall 5 c and is introduced into the first catalyst unit 6 at an optimum temperature for the first catalyst unit 6. On the other hand, the temperature of the exhaust gas discharged from the engine 1 and introduced into the high temperature side flow path 5a of the heat exchanger 5 is lowered by heat exchange with the exhaust gas passing through the low temperature side flow path 5b of the heat exchanger 5. The temperature becomes optimum for the plasma processing unit 4 and is introduced into the plasma processing unit 4. In this way, since the optimum temperature for each of the plasma processing unit 4 and the first catalyst unit 6 can be realized, the functions of the plasma processing unit 4 and the first catalyst unit 6 can be efficiently expressed and the exhaust gas can be exhausted. Gas purification rate is improved.
This will be specifically described below.

FIG. 4 is a partially broken perspective view of the plasma processing unit 4 according to the present embodiment.
The plasma processing unit 4 includes an outer tube 41 through which exhaust gas can pass from the left to the right in FIG. Flange 48 is provided at both ends of the outer pipe 41, and it can be connected to the exhaust gas flow path by the flange 48 and incorporated into the exhaust gas purification device. The material of the outer tube 41 may be an insulating material and is not limited to one. For example, ceramic such as aluminum oxide can be used.
Inside the outer tube 41, a high voltage electrode 42 fixed by a mesh 43 is provided coaxially with the outer tube 41. The high voltage electrode 42 is connected to a high voltage electrode terminal 42 a and a power supply terminal 42 b by a high voltage cable 46 in order to supply a voltage. The power supply terminal 42b is connected to the plasma control device 7 by a cable (not shown). The ground electrode 44 is attached to the outer tube 41 in surface contact with the outer tube 41 by tightening a fixing screw 47. Further, a cable (not shown) for connecting to the plasma control device 7 is also attached by tightening the fixing screw 47.
In addition, the material of the mesh 43 should just be an insulator, for example, ceramics, such as aluminum oxide, can be used. The material of the high voltage electrode 42 and the ground electrode 44 may be a conductor, and for example, stainless steel can be used.

  In the plasma processing unit 4 configured as described above, an AC high voltage or a pulsed high voltage is applied between the high voltage electrode 42 and the ground electrode 44, so that the voltage between the high voltage electrode 42 and the outer tube 41 is increased. Silent discharge occurs in the space. The length of the space where silent discharge occurs in the gas flow direction is the same as the length of the ground electrode 44 in the exhaust gas flow direction. That is, silent discharge occurs in the space surrounded by the ground electrode 44. The exhaust gas introduced into the plasma processing unit 4 passes through the mesh 43 and the silent discharge space. The exhaust gas chemically reacts as described above by the discharge plasma in this passage process.

FIG. 5 is a configuration diagram of the heat exchanger 5 according to the present embodiment. A part of the outer wall of the first pipe 51 is surrounded by the heat exchange container 53, two holes are provided in the wall surface of the heat exchange container 53, and the second pipe 52 is fitted into each hole, and one second Exhaust gas is introduced into the heat exchange container 53 through the pipe 52, and exhaust gas is discharged from the heat exchange container 53 through the other second pipe 52. At both ends of the first and second pipes, flanges 54 are provided for incorporating the heat exchanger 5 into the exhaust gas flow path of the exhaust gas purification apparatus in the present embodiment.
In the present embodiment, the heat exchanger 5 is in the first exhaust gas flow path 31, the upstream side of the second pipe 52 is on the engine 1 side, the downstream side is on the plasma processing unit 4 side, and the first The pipe 51 is assembled so that the upstream side is the plasma processing unit 4 side and the downstream side is the first catalyst unit 6 side. When incorporated in this way, in the heat exchanger 5, the inside of the first pipe 51 in the heat exchanger 53 through which the exhaust gas emitted from the plasma processing unit 4 flows becomes the low temperature side flow path 5 b, The region other than the first pipe 51 in the heat exchange vessel 53 through which the exhaust gas flows becomes the high temperature side flow path 5a, and the tube wall of the first pipe 51 becomes the partition wall 5c, so that the high temperature side flow path 5a and the low temperature side Heat is exchanged with the flow path 5b, the fluid passing through the high temperature side flow path 5a is cooled, and the fluid passing through the low temperature side flow path 5b is reheated.
That is, since the exhaust gas from the engine 1 is introduced into the high temperature side channel 5a and exchanges heat while flowing through the high temperature side channel 5a, the outlet temperature of the high temperature side channel 5a is the amount of heat exchanged. The exhaust gas that is supplied to the plasma processing apparatus 4 at an optimal temperature and flows out of the plasma processing unit 4 flows through the first pipe 51 in the heat exchange vessel 53 while the pipe wall of the first pipe 51 is As a result of the heat exchange by contacting the partition wall 5c, the temperature rises and can be supplied to the first catalyst unit 6 at the optimum temperature.

It should be noted that the exhaust gas purifying apparatus of the present embodiment is practically used by appropriately designing as follows.
That is, the exhaust gas collected by the exhaust manifold 2 is introduced into the heat exchanger 5 via the first exhaust gas flow path 31, and the temperature is reduced due to heat radiation to the outside when the exhaust gas flows. Since the amount of heat released to the outside varies depending on the length of the first exhaust gas passage 31, the length of the first exhaust gas passage 31 is set to a temperature at which the inlet of the heat exchanger 5 is determined in advance. Set as follows.
In addition, it is preferable that the temperature of the exhaust gas exiting the heat exchanger 5 is the optimum temperature of the plasma processing unit 4, but when the temperature is higher than the optimum temperature, the heat exchanger 5 and the plasma treatment are performed. The interval between the portions 4 is lengthened, and the exhaust gas is cooled by heat radiation to the outside and supplied to the plasma processing portion 4 as an optimum temperature.
Further, the heat exchange amount of the heat exchanger 5 is designed so that the temperature of the exhaust gas emitted from the heat exchanger 5 does not fall below the optimum temperature of the plasma processing unit 4, and the temperature of the gas emitted from the plasma processing unit 4 decreases. In order to prevent this, the flow path to the heat exchanger 5 is shortened or a heat insulating material is installed.

  FIG. 6 is a configuration diagram of another heat exchanger according to the present embodiment, in which heat exchange fins 55 are welded to the outer wall of the first pipe 51 to increase the contact area with the exhaust gas. The heat exchange efficiency inside the heat exchange vessel 53 can be increased, and the heat exchange amount is also increased from the structure of FIG.

FIG. 7 is a configuration diagram of a double-pipe heat exchanger that is another heat exchanger according to the present embodiment, and the plasma processing unit 4 is disposed inside an outer external flow path 61 through which exhaust gas from the engine 1 flows. An internal flow path 62 through which exhaust gas emitted from the air flows is installed.
As shown in FIG. 7, the exhaust gas from the engine 1 is first introduced from the inlet 63 into the internal flow path 61 that is the external flow path that is the high temperature side flow path and is taken out from the outlet 64. The exhaust gas that has exited from the plasma processing unit 4 exits from the inlet 65 through the internal flow path 62 and through the outlet 66. Since the exhaust gas exchanges heat while flowing through the external flow path 61 and the internal flow path 62, the temperature of the exhaust gas that has exited from the outlet 64 decreases, reaching the optimum temperature of the plasma processing unit 4. Since the temperature is increased by performing heat exchange, the optimum temperature of the first catalyst unit 6 can be achieved.

FIG. 8 is a configuration diagram of a multi-tube heat exchanger that is another heat exchanger according to the present embodiment, and plasma is generated in an external flow path 71 that is a high-temperature side flow path through which exhaust gas from the engine 1 flows. A large number of internal flow paths 72 that are low-temperature flow paths through which exhaust gas discharged from the processing unit 4 flows are installed.
As shown in FIG. 8, exhaust gas from the engine 1 is first introduced from the inlet 73 into the external flow path 71 and taken out from the outlet 74. Exhaust gas emitted from the plasma processing unit 4 exits from the outlet 76 through the internal flow path 72 provided in large numbers from the inlet 75. The exhaust gas exchanges heat while flowing through the external flow path 71 and the internal flow path 72. In this case, since a large number of internal flow paths 72, which are low-temperature flow paths, are installed so that the surface area with which the exhaust gas contacts is larger than that of the heat exchanger shown in FIG. 7, the heat exchange amount is also shown in FIG. More than the heat exchanger.

Embodiment 2. FIG.
FIG. 9 is a conceptual diagram of the exhaust gas processing apparatus according to the second embodiment of the present invention, and shows a state connected to the engine 1.
As shown in FIG. 9, the exhaust gas processing apparatus of the present embodiment is the first exhaust gas flow path that is the main flow path in which the exhaust gas from the engine 1 flows mainly in the exhaust gas processing apparatus of the first embodiment. A second exhaust gas flow path 32 from 31 branches on the upstream side of the high temperature side flow path 5a of the heat exchanger 5 and is directly connected to the plasma processing unit 4 to branch portions of the first and second exhaust gas flow paths. Is provided with a flow rate switching device 30.
The first exhaust gas flow channel 31 is a flow channel for introducing exhaust gas to the plasma processing unit 4 via the heat exchanger 5, and the second exhaust gas flow channel 32 is not allowed to pass through the heat exchanger 5. This is a flow path for introducing exhaust gas directly into the plasma processing unit 4. The flow rate switching device 30 is a flow rate ratio of the exhaust gas flowing from the first exhaust gas flow channel 31 to the high temperature side flow channel 5a of the heat exchanger 5 and the exhaust gas flowing directly to the plasma processing device 4 without passing through the heat exchanger 5. The flow rate ratio is controlled by a flow rate control device 33 connected to the flow rate switching device 30.

As described in the first embodiment, the plasma processing unit 4 has an optimum temperature of about 350 ° C., and the NO _x purification catalyst that purifies NO _x in the first catalyst unit 6 has an optimum temperature of about 420 ° C. For example, when the size of the heat exchanger 5 and the length of the exhaust gas flow path are set so that the plasma processing unit 4 is 350 ° C. and the first catalyst unit 6 is 420 ° C. under the high rotational speed condition of the engine 1, When the rotational speed of the engine 1 decreases, the flow rate of the exhaust gas decreases and the exhaust gas temperature also decreases. Therefore, in the exhaust gas purifying apparatus in a state set based on the high engine speed condition of the engine 1, the temperatures of the plasma processing unit 4 and the first catalyst unit 6 are lower than originally intended temperatures.

  On the other hand, since the exhaust gas purification apparatus of the present embodiment includes the flow rate control device 33, the flow rate control device 33 controls the flow rate switching device 30 in accordance with the conditions of the engine 1, so that the first The flow rate ratio between the exhaust gas flowing through the heat exchanger 5 through the exhaust gas passage 31 and the exhaust gas that has not been cooled down without passing through the heat exchanger 5 through the second exhaust gas passage 32 can be changed. As a result, when the rotational speed of the engine 1 decreases, a part of the exhaust gas is directly introduced into the plasma processing unit 4 via the second exhaust gas passage 32 without passing through the heat exchanger 5. Then, by mixing with the exhaust gas that has passed through the heat exchanger 5, the temperature of the exhaust gas flowing into the plasma processing unit 4 can be raised and adjusted to an optimum temperature.

  The flow rate switching device 30 can be realized by a device in which valves are provided in the first exhaust gas flow path 31 and the second exhaust gas flow path 32 and the respective opening areas are changed. Further, an opening / closing valve is provided only in the second exhaust gas passage 32, and the opening area of the first exhaust gas passage 31 and the second exhaust gas passage 32 can be changed by changing the opening of the valve. Since the ratio changes, both exhaust gas flow rates can be changed.

  As described above, according to the exhaust gas purifying apparatus of the present embodiment, the flow rate switching device 30 and the flow rate control device 33 are installed, and the exhaust gas flowing through the heat exchanger 5 and the exhaust gas not passing through the heat exchanger 5 are installed. Therefore, the temperature of the plasma processing unit 4 and the first catalyst unit 6 can be kept at the optimum temperature, and the exhaust gas purification rate can be easily improved. can do.

Embodiment 3 FIG.
FIG. 10 is a conceptual diagram of the exhaust gas treatment device according to Embodiment 3 of the present invention, and shows a state connected to the engine 1.
In the present embodiment, instead of the plasma processing unit 4 used as the first reaction unit in the first embodiment, at least a part of hydrocarbons contained in the exhaust gas is converted into aldehydes or the like by the action of a catalyst. The second catalyst unit 9 containing the hydrocarbon reforming catalyst is provided.
As the hydrocarbon reforming catalyst according to the present embodiment, a honeycomb-shaped honeycomb ceramic base material in which various catalysts effective for hydrocarbon reforming are supported on a carrier such as alumina, silica, or zeolite is used. It is done. In the case of using a silver catalyst supported on alumina, it was confirmed that aldehyde was generated from alcohol.

As the hydrocarbon reforming catalyst of the second catalyst unit 9 according to the present embodiment, a honeycomb ceramic base material coated with alumina, and a silver catalyst loaded in an amount of 2 g per liter of honeycomb volume, nitrogen is used. A fluid that is oxide (NO _x ) 150 ppm, ethanol 300 ppm, oxygen 10% (all concentrations are volume ratios), and the remaining nitrogen is introduced into the exhaust gas purification apparatus of the present embodiment and generated from ethanol. The amount of acetaldehyde produced was measured.
FIG. 11 is a characteristic diagram showing a change in the amount of acetaldehyde produced by the catalyst temperature of the hydrocarbon reforming catalyst of the second catalyst unit 9 according to the present embodiment. As shown in FIG. 11, it can be seen that the amount of acetaldehyde produced increases at a temperature of about 300 to 350 ° C.

In the exhaust gas purification apparatus of the present embodiment, the first catalyst unit 6 containing the NO _x purification catalyst provided on the downstream side of the second catalyst unit 9 is about 420 ° C. as described in the first embodiment. Is the optimum temperature. For this reason, in order to set the second catalyst unit 9 to 300 to 350 ° C. and the first catalyst unit 6 to 420 ° C., the heat exchanger 5 is incorporated in the same manner as in the first embodiment. The same effect can be obtained.

As another example of the hydrocarbon reforming catalyst, there is a catalyst in which alumina is applied to a honeycomb ceramic base material and ruthenium is supported, and it was confirmed that formaldehyde is generated from methane. The amount of ruthenium catalyst supported is 0.5 g per liter of honeycomb volume.
In this case, with the ruthenium catalyst, the amount of formaldehyde generated becomes maximum at about 250 ° C., and the ruthenium catalyst is operated at a lower temperature than the silver catalyst. Therefore, in order to set the second catalyst portion 9 to 250 ° C. and the first catalyst portion 6 to 420 ° C., the heat exchanger 5 has a specification in which the heat exchange amount is increased as compared with the case where a silver catalyst is used. By doing so, the same effect as in the first embodiment can be obtained.

The hydrocarbon reforming catalyst is not limited to a silver catalyst or a ruthenium catalyst, and at least a part of the hydrocarbons contained in the exhaust gas has high reactivity such as aldehydes, alcohols and unsaturated hydrocarbons. Any catalyst that can be converted into hydrocarbons at a temperature lower than that of the NO _x purification catalyst unit 6 is applicable.
As described above, according to the exhaust gas purification apparatus of the present embodiment, the second catalyst unit 9 having the hydrocarbon reforming catalyst is installed as the first reaction unit, and the second catalyst is installed in the heat exchanger 5. since part 9 and can optimize the temperature of the first catalyst unit 6, the purification rate of exhaust gas can be efficiently expressed functional hydrocarbon reforming catalyst and _the NO _x purification catalyst can be improved.

Embodiment 4 FIG.
FIG. 12 is a conceptual diagram of an exhaust gas treatment apparatus according to Embodiment 4 of the present invention, and shows a state connected to the engine 1.
The exhaust gas processing apparatus of the present embodiment is the hydrocarbon supply means for supplying fuel from the fuel tank 10 before the exhaust gas from the engine 1 flows into the plasma processing unit 4 in the exhaust gas processing apparatus of the first embodiment. 11 is connected.
Under the operating conditions of the engine 1, the hydrocarbon concentration in the exhaust gas may be low. In this case, in the exhaust gas purification apparatus of the present embodiment, hydrocarbons can be added from the external fuel tank 10. The amount of hydrocarbons to be supplied is an amount necessary for purifying NO _x in the exhaust gas. If the operating conditions of the engine 1 are determined, a constant amount may be supplied, and the operating conditions of the engine 1 are changed. In such a case, it is sufficient to supply a hydrocarbon amount corresponding to that. In the case of supplying liquid fuel, if a spray device such as an injector is used as the hydrocarbon supply means 11, mixing into the exhaust gas is promoted.
In the case of a gasoline engine, the gasoline to be used for the engine 1 can be used as the fuel to be supplied. Further, hydrocarbons different from the fuel of the engine 1 may be supplied from the fuel tank 10.

In the present embodiment, first, the engine 1 is adjusted so that hydrocarbons contained in the exhaust gas are reduced. Further, acetic acid or propylene is further added by the hydrocarbon supply means 11 according to the present embodiment under the condition that a predetermined NO _x purification rate is indicated by the hydrocarbons contained in the exhaust gas, thereby improving the NO _x purification. The rate was measured.
FIG. 13 shows a constant NO _x purification rate for hydrocarbons contained in exhaust gas, and further NO _x purification for the amount of acetic acid or propylene added by the hydrocarbon supply means according to the present embodiment. In the characteristic diagram showing the rate of improvement, the horizontal axis is the ratio of the molar amount of hydrocarbon added by the hydrocarbon supply means 11 according to the present embodiment and the molar amount of NO _x at the time of addition, and the vertical axis is the hydrocarbon content. It shows the percentage of the NO _x purification rate was increased by the addition, in the figure a case where acetic acid was added, b is the characteristic of the case of adding propylene.
As shown in FIG. 13, since _the NO _x purification rate is increased more with increasing the addition amount of the hydrocarbon, the effect by the addition of hydrocarbons was confirmed. The more the hydrocarbon is added, the greater the effect is. However, it is preferable to add the minimum amount required for each condition of the engine 1 from the viewpoint of fuel cost.

Further, when acetic acid was added, the temperature of the first catalyst portion 6 was about 420 ° C., and when propylene was added, about 450 ° C. showed a good NO _x purification rate. Since the optimum temperature of the first catalyst unit 6 differs depending on the type of hydrocarbon added in this way, the first heat exchange amount of the heat exchanger 5 is set optimally according to the added hydrocarbon. The characteristics of the NO _x purification catalyst of the catalyst unit 6 can be utilized to the maximum extent.
The optimum temperature of the first catalyst unit 6 can be set by changing the specifications of the heat exchanger 5 depending on the type of hydrocarbon. However, the exhaust gas purifying apparatus of the second embodiment is the same as the present embodiment. The temperature can be easily adjusted by providing the hydrocarbon supply means 11 in the.
As described above, according to the exhaust gas purification apparatus of the present embodiment, when the hydrocarbons in the exhaust gas from the engine 1 are small, fuel containing an appropriate amount of hydrocarbons is supplied from the hydrocarbon supply means 11, it is possible to optimize the temperature of the first catalyst unit 6 in the heat exchanger 5, the catalytic function of the NO _x purifying catalyst of the plasma processing unit 4 first catalyst portion 6 is improved, NO _X purification rate improves.

Embodiment 5 FIG.
FIG. 14 is a conceptual diagram of an exhaust gas treatment apparatus according to Embodiment 5 of the present invention, and shows a state connected to the engine 1.
The exhaust gas treatment device of the present embodiment contains the hydrocarbon reforming catalyst used in the third embodiment as the first reaction unit in place of the plasma treatment device 4 in the exhaust gas treatment device of the fourth embodiment. A hydrocarbon supplying means 11 for supplying fuel from the fuel tank 10 before the exhaust gas from the engine 1 flows into the second catalyst portion 9 is connected to the second catalyst portion 9.
With the exhaust gas processing apparatus configured as described above, the same effects as those of the fourth embodiment can be obtained.

In addition, the exhaust gas purification apparatus of Embodiment 1-5 is not limited to what cleans the harmful | toxic component of the exhaust gas exhausted from the lean burn engine for gasoline, It can apply also to a diesel engine.
Moreover, although the case where the NO _x purification catalyst is used as the first catalyst unit 6 as the second reaction unit has been described, the present invention is not limited thereto, and the reaction is affected by the temperature, and is higher than the temperature of the first reaction unit. As long as the reaction is activated, the same effect can be obtained.
Moreover, the present invention can be applied not only to automobiles but also to purifying harmful components of exhaust gas exhausted from a ship engine, for example.

1 is a conceptual diagram of an exhaust gas treatment apparatus according to Embodiment 1 of the present invention. It is a characteristic diagram showing the change of conversion to NO ₂ by the plasma electrode temperature of the plasma processing unit according to the exhaust gas purifying apparatus of the first embodiment of the present invention. It is a characteristic diagram showing the relationship between the purification rate of the catalyst temperature and the NO _x in _the NO _x purification catalyst unit according to an exhaust gas purifying apparatus of the first embodiment of the present invention. It is a partially broken perspective view of the plasma processing unit according to the exhaust gas purification apparatus of Embodiment 1 of the present invention. It is a block diagram of the heat exchanger which concerns on the exhaust gas purification apparatus of Embodiment 1 of this invention. It is a block diagram of another heat exchanger which concerns on the exhaust gas purification apparatus of Embodiment 1 of this invention. It is a block diagram of another heat exchanger which concerns on the exhaust gas purification apparatus of Embodiment 1 of this invention. It is a block diagram of another heat exchanger which concerns on the exhaust gas purification apparatus of Embodiment 1 of this invention. It is a conceptual diagram of the exhaust gas processing apparatus of Embodiment 2 of this invention. It is a conceptual diagram of the exhaust gas processing apparatus of Embodiment 3 of this invention. It is a characteristic view which shows the change of the production amount of acetaldehyde by the catalyst temperature of the 2nd catalyst part which concerns on the exhaust gas processing apparatus of Embodiment 3 of this invention. It is a conceptual diagram of the exhaust gas processing apparatus of Embodiment 4 of this invention. It is a characteristic diagram showing the _the NO _x purification rate improvement rate relative to the addition amount of acetic acid and propylene by the hydrocarbon feed means according to the exhaust gas treatment apparatus of a fourth embodiment of the present invention. It is a conceptual diagram of the exhaust gas processing apparatus of Embodiment 5 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Engine, 31 1st exhaust gas flow path, 4 Plasma processing part (1st reaction part), 5 Heat exchanger, 5a: High temperature side flow path, 5b Low temperature side flow path, 5c Partition, 6 1st catalyst Part (first reaction part), 30 flow rate switching device, 32 second exhaust gas flow path, 9 second catalyst part (first reaction part).

Claims (5)

  Provided in a first exhaust gas flow path through which exhaust gas discharged from the engine passes, the first reaction section in which the exhaust gas reacts, upstream of the first reaction section in the first exhaust gas flow path A heat exchanger in which a high temperature side channel provided on the side and a low temperature side channel provided on the downstream side of the first reaction section in the first exhaust gas channel are separated by a partition, and the first A second reaction section that is provided downstream of the low-temperature side flow path in the one exhaust gas flow path and that generates a next-stage reaction based on a reaction in the first reaction section; An exhaust gas purifier having a temperature lower than that of the second reaction section.   A second exhaust gas passage branched from the first exhaust gas passage upstream of the high temperature side passage of the heat exchanger and directly connected to the first reaction section; and the first and second exhaust gases. The exhaust gas purification device according to claim 1, further comprising a flow rate switching device provided at a branch portion of the flow path. Plasma processing unit first reaction section, the second reaction section of claim 1 or claim 2, characterized in that the first catalyst portion containing _the NO _x purification catalyst for purifying NO _x Exhaust gas purification device. Is the first catalyst portion containing _the NO _x purification catalyst second catalyst part containing a hydrocarbon reforming catalyst which first reaction unit to convert the hydrocarbons and a second reaction unit for purifying the NO _x The exhaust gas purifying device according to claim 1 or 2, wherein the exhaust gas purifying device according to claim 1 or 2 is provided.   The exhaust gas purification apparatus according to any one of claims 1 to 4, further comprising a hydrocarbon supply means for supplying hydrocarbons upstream of the first reaction section.

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