JP4225012B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control device for an internal combustion engine.
[0002]
[Prior art]
NO when the ambient atmosphere is lean_XWhen the stoichiometric or rich air-fuel ratio is absorbed, NO_XNO release_XPlacing the catalyst device carrying the catalyst in the engine exhaust system,_XNO is contained in the exhaust gas of diesel engines_XIt is known to sufficiently suppress atmospheric emissions. However, this catalytic device is infinitely NO_XCan not be absorbed, NO of the catalytic device_XBefore the absorption capacity saturates, the NO that was absorbed with a rich air-fuel ratio in the vicinity_XAnd NO released by the reducing substance when the rich air-fuel ratio is achieved._XRegeneration treatment to reduce and purify is necessary. For this reason, in Japanese Patent No. 2793415, fuel is directly supplied to the catalyst device, and the atmosphere in the vicinity of the catalyst device is set to a rich air-fuel ratio.
[0003]
By the way, the aforementioned NO_XThe catalyst is SO_XNO_XIt is absorbed by the same mechanism. SO absorbed in this way_XIs NO_XAs shown in FIG. 2, since it is not released only by setting the atmosphere near the rich air-fuel ratio,_XThe amount of absorption increases. SO_XWhen the amount of absorption increases (hereinafter referred to as S poisoning), the corresponding amount of NO_XAbsorption capacity is reduced.
[0004]
As a recovery process for recovering the S poisoning of the catalyst device, the ambient atmosphere may be set to a rich air-fuel ratio and the catalyst device may be heated to a high temperature. Especially SO in exhaust gas_XIs NO_XSince it is absorbed immediately upon contact with the catalyst, the entire catalytic device is not poisoned with S, but the exhaust upstream portion of the catalytic device is mainly poisoned with S. Thereby, for the recovery process, only the exhaust upstream portion of the catalyst device needs to be at a high temperature, and the recovery process can be carried out relatively easily.
[0005]
[Problems to be solved by the invention]
In the above-described conventional technology, the fuel supplied to the catalyst device for the regeneration process is distributed throughout the catalyst device while evaporating along with the exhaust gas flow, so that the regeneration process of the entire catalyst device becomes possible. However, on the other hand, the S component contained in the fuel is also distributed throughout the catalyst device and is oxidized by the noble metal catalyst or the like to be SO._XNO after_XThe catalyst is poisoned with sulfur, that is, the entire catalyst device is poisoned with sulfur by the fuel supplied for the regeneration process. When the entire catalyst device is poisoned in this way, the recovery process requires the entire catalyst device to be at a high temperature, which not only requires a large amount of energy consumption, but also NO._XIn the case where the catalyst and the catalyst are supported, the noble metal catalyst may be exposed to high temperature for a relatively long time and may be thermally deteriorated.
[0006]
Accordingly, the object of the present invention is to provide NO when the ambient atmosphere has a lean air-fuel ratio._XWhen the stoichiometric or rich air-fuel ratio is absorbed, NO_XNO release_XIn an exhaust gas purification apparatus for an internal combustion engine that includes a catalyst device that supports a catalyst, even if fuel is supplied to the catalyst device for regeneration, the overall sulfur poisoning of the catalyst device is prevented.
[0007]
[Means for Solving the Problems]
  The exhaust gas purification apparatus for an internal combustion engine according to claim 1 of the present invention is NO when the ambient atmosphere is a lean air-fuel ratio._XWhen the stoichiometric or rich air-fuel ratio is absorbed, NO_XNO release_XIn an exhaust gas purification apparatus for an internal combustion engine, comprising: a catalyst device that supports a catalyst; and a fuel supply device that supplies fuel to the catalyst device for regeneration processing of the catalyst device. Separation of low-sulfur component fuel from fuel and supply to the catalyst deviceThe remaining fuel from which the low sulfur component fuel is separated is burned in the cylinder.It is characterized by that.
[0008]
According to a second aspect of the present invention, there is provided the exhaust gas purification apparatus for an internal combustion engine according to the first aspect, wherein the fuel supply device is configured to increase the fuel in the fuel tank by a separation membrane. It separates into the aromatic compound as a sulfur component fuel, and the said low sulfur component fuel.
[0009]
An internal combustion engine exhaust gas purification apparatus according to a third aspect of the present invention is the internal combustion engine exhaust gas purification apparatus according to the first aspect, wherein the fuel supply device cools the fuel in the fuel tank and is It is characterized by separating into a low boiling point component fuel as a sulfur component fuel and a high boiling point normal paraffin as the low sulfur component fuel.
[0010]
According to a fourth aspect of the present invention, there is provided the exhaust gas purification apparatus for an internal combustion engine according to the third aspect, wherein the fuel supply device supplies the low sulfur component fuel that has been wax-deposited by cooling. Heating and separating into a low boiling point component and a high boiling point component and supplying only the low boiling point component of the low sulfur component fuel to the catalyst device.
[0011]
An exhaust gas purification apparatus for an internal combustion engine according to claim 5 according to the present invention is the exhaust gas purification apparatus for internal combustion engine according to claim 1, wherein the boiling point temperature of the normal fuel is changed to normal fuel as fuel in the fuel tank. A low sulfur component fuel having a boiling point higher than the range or the same boiling point as the high boiling point within the boiling temperature range is added, and the fuel supply device cools the fuel in the fuel tank to reduce the low sulfur component fuel. It is characterized by separating.
[0012]
An exhaust emission control device for an internal combustion engine according to claim 6 according to the present invention is the exhaust gas purification device for internal combustion engine according to claim 1, wherein the boiling point temperature of the normal fuel is changed to normal fuel as fuel in the fuel tank. A low sulfur component fuel having a boiling point lower than the range or the same boiling point as the low boiling point within the boiling temperature range is added, and the fuel supply device distills the fuel in the fuel tank to produce the low sulfur component fuel. It is characterized by separating.
[0013]
According to a seventh aspect of the present invention, there is provided an exhaust gas purification apparatus for an internal combustion engine according to the seventh aspect, wherein the fuel in the fuel tank is distilled using an electric heater in the exhaust gas purification apparatus for the internal combustion engine according to the sixth aspect. Features.
[0014]
An internal combustion engine exhaust gas purification apparatus according to an eighth aspect of the present invention is the internal combustion engine exhaust gas purification apparatus according to the sixth aspect, wherein an exhaust gas temperature or an in-cylinder combustion temperature is utilized in the fuel tank. It is characterized by distilling the fuel.
[0015]
An internal combustion engine exhaust gas purification apparatus according to claim 9 of the present invention is the exhaust gas purification apparatus for internal combustion engine according to claim 6, wherein the fuel in the fuel tank is distilled using the engine coolant temperature. It is characterized by that.
[0016]
An internal combustion engine exhaust gas purification apparatus according to a tenth aspect of the present invention is the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to ninth aspects, wherein the exhaust gas purification apparatus is disposed on the exhaust upstream side of the catalyst device. SO in gas_XSO to collect_XCollection device and the SO_XSO from the collector_XAnd a bypass means for allowing the exhaust gas to bypass the catalyst device when discharging the catalyst.
[0017]
An internal combustion engine exhaust gas purification apparatus according to an eleventh aspect of the present invention is the internal combustion engine exhaust gas purification apparatus according to the tenth aspect, wherein the catalytic device is a particulate filter, and the bypass means is the particulate filter. The present invention is characterized in that it is formed integrally with a reversing means capable of reversing the exhaust upstream side and the exhaust downstream side of the curate filter.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic longitudinal sectional view of a four-stroke diesel engine equipped with an exhaust emission control device according to the present invention. In the figure, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5a is a cavity formed on the top surface of the piston 4, 5 is a combustion chamber formed in the cavity 5a, 6 Is an electrically controlled fuel injection valve, 7 is a pair of intake valves, 8 is an intake port, 9 is a pair of exhaust valves, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to an air cleaner 14 via an intake duct 13. A throttle valve 16 driven by an electric motor 15 is disposed in the intake duct 13. On the other hand, the exhaust port 10 is connected to an exhaust pipe 18 via an exhaust manifold 17.
[0019]
As shown in FIG. 1, an air-fuel ratio sensor 21 is disposed in the exhaust manifold 17. The exhaust manifold 17 and the surge tank 12 are connected to each other via an EGR passage 22, and an electrically controlled EGR control valve 23 is disposed in the EGR passage 22. A cooling device 24 for cooling the EGR gas flowing in the EGR passage 22 is disposed around the EGR passage 22. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 24, and the EGR gas is cooled by the engine cooling water.
[0020]
On the other hand, each fuel injection valve 6 is connected to a fuel reservoir, so-called common rail 26, via a fuel supply pipe 25. Fuel is supplied into the common rail 26 from an electrically controlled fuel pump 27 with variable discharge amount, and the fuel supplied into the common rail 26 is supplied to the fuel injection valve 6 through each fuel supply pipe 25. A fuel pressure sensor 28 for detecting the fuel pressure in the common rail 26 is attached to the common rail 26, and a fuel pump 27 is set so that the fuel pressure in the common rail 26 becomes a target fuel pressure based on an output signal of the fuel pressure sensor 28. The discharge amount is controlled.
[0021]
An electronic control unit 30 receives an output signal from the air-fuel ratio sensor 21 and an output signal from the fuel pressure sensor 28. Further, a load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and an output signal of the load sensor 41 is also input to the electronic control unit 30. For example, an output signal of a crank angle sensor 42 that generates an output pulse every 30 ° rotation is also input. Thus, the electronic control unit 30 operates the fuel injection valve 6, the electric motor 15, the EGR control valve 23, and the fuel pump 27 based on various signals.
[0022]
FIG. 2 shows the catalyst device 70 connected to the downstream side of the exhaust manifold 17 via the exhaust pipe 18. A fuel supply device 100 for supplying fuel to the catalyst device 70 is provided immediately upstream of the catalyst device 70. The catalyst device 70 has a plurality of partition walls extending in the axial direction forming a honeycomb structure, and alumina or the like is used for the surfaces of these partition walls, which will be described below._XAn absorbent and a noble metal catalyst such as platinum Pt are supported.
[0023]
NO_XIn this embodiment, the absorbent is selected from an alkali metal such as potassium K, sodium Na, lithium Li, and cesium Cs, an alkaline earth such as barium Ba and calcium Ca, and a rare earth such as lanthanum La and yttrium Y. Is at least one. This NO_XThe absorbent is NO when the air-fuel ratio in the ambient atmosphere (the ratio of air to fuel, regardless of how much fuel is burned using oxygen in the air) is lean._XNO is absorbed when the air-fuel ratio becomes stoichiometric or rich._XNO release_XPerforms absorption and release action.
[0024]
NO_XThe mechanism of the absorption and release action of the absorbent will be described by taking as an example the case where platinum Pt and barium Ba are supported on the partition walls of the catalyst device 70, but other noble metals, alkali metals, alkaline earths, and rare earths may be used. The mechanism is similar.
[0025]
When combustion is performed with the air-fuel ratio being lean, the oxygen concentration in the exhaust gas is high.₂Is O₂ ^-Or O^2-It adheres to the surface of platinum Pt. On the other hand, NO in the exhaust gas is O on the surface of platinum Pt.₂ ^-Or O^2-Reacts with NO₂(2NO + O₂→ 2NO₂). Then the generated NO₂Part of the nitrate is absorbed on the absorbent while being oxidized on platinum Pt, and is combined with barium oxide BaO and nitrate ion NO._Three ^-Diffuses into the absorbent in the form of In this way NO_XIs NO_XAbsorbed in the absorbent. NO on the surface of platinum Pt as long as the oxygen concentration in the vicinity atmosphere is high₂Is produced and NO in the absorbent_XUnless the absorption capacity is saturated, NO₂Is absorbed into the absorbent and nitrate ion NO._Three ^-Is generated.
[0026]
On the other hand, when the air-fuel ratio of the nearby atmosphere is made rich, the oxygen concentration decreases, and as a result, NO on the surface of platinum Pt.₂The production amount of is reduced. NO₂When the production amount of NO decreases, the reaction proceeds in the reverse direction (NO_Three ^-→ NO₂) And thus nitrate ion NO in the absorbent_Three ^-Is NO₂Is released from the absorbent in the form of NO at this time_XNO released from the absorbent_XIs reduced by reacting with HC and CO contained in the nearby atmosphere. In this way, NO on the surface of platinum Pt.₂NO from the absorbent to the next when no longer exists₂Is released. Therefore, when the air-fuel ratio of the nearby atmosphere is made rich, NO is quickly reached._XNO from absorbent_XIs released, and this released NO_XNO in the atmosphere to be reduced and purified_XWill not be discharged.
[0027]
In this case, even if the air-fuel ratio of the nearby atmosphere is the stoichiometric air-fuel ratio, NO_XNO from absorbent_XIs released. However, in this case NO_XNO from absorbent_XNO is released only gradually_XTotal NO absorbed by the storage reduction catalyst device_XIt takes a little longer time to release.
[0028]
By the way NO_XAbsorbent NO_XAbsorption capacity is limited, NO_XAbsorbent NO_XNO before absorption capacity saturates_XNO from absorbent_XNeed to be released. That is, NO absorbed in the catalyst device 70_XAmount is NO_XBefore reaching storage capacity, NO_XNeeds to be regenerated and reduced and purified._XThe amount needs to be estimated. For example, NO per unit time_XThe amount of absorption is determined in advance in the form of a map as a function of the required load and engine speed, and the NO per unit time is obtained._XBy accumulating the amount of absorption, NO absorbed by the catalyst device 70_XThe amount can be estimated.
[0029]
In this embodiment, this NO_XIn order to regenerate the catalyst device when the amount of absorption exceeds a predetermined allowable value, fuel is supplied using the fuel supply device 100, so that the atmosphere in the vicinity of the catalyst device 70 is changed to the stoichiometric air-fuel ratio or rich air-fuel ratio. This state is maintained for at least the time until regeneration is completed (the shorter the air-fuel ratio in the vicinity atmosphere is, the shorter the state is). The liquid fuel supplied from the fuel supply device 100 flows into the catalyst device 70 together with the exhaust gas, and is distributed and vaporized throughout the catalyst device 70. Thereby, the atmosphere in the vicinity of the catalyst device 70 can be set to the stoichiometric air-fuel ratio or the rich air-fuel ratio, and the catalyst device 70 can be regenerated as a whole.
[0030]
By the way, the fuel of the internal combustion engine contains sulfur. Thus, when the fuel for the regeneration process is distributed throughout the catalyst device 70, the sulfur in the fuel is oxidized by the noble metal catalyst along with the fuel vaporization, and the SO._XIs generated. SO_XNO to the catalyst device 70_XIt is absorbed in the form of sulfate by the same mechanism. Since sulfate is a stable substance, it is difficult to be released from the catalyst device 70 even if the surrounding atmosphere has a rich air-fuel ratio, and the amount of occlusion increases gradually. The amount of nitrate or sulfate that can be stored in the catalyst device 70 is finite, and if the amount of sulfate stored in the catalyst device 70 increases (hereinafter referred to as SO)._X(Referred to as poisoning), the amount of nitrate that can be stored decreases, and finally, NO_XCannot absorb.
[0031]
Sulfate has a rich air-fuel ratio in the vicinity and a high temperature (about 600 ° C. or higher)._XCan be released as However, if the catalytic device 70 is totally poisoned with sulfur, the catalytic device 70 needs to be heated to a high temperature as a whole, which requires not only a large amount of energy but also a relatively long heating time. And this long heating time makes NO_XAbsorbents and precious metal catalysts can be thermally degraded.
[0032]
Accordingly, it is necessary to prevent the overall sulfur poisoning of the catalyst device 70. In this embodiment, the fuel supply device 100 removes sulfur components from the fuel in the same fuel tank that is injected into the cylinder. A low-sulfur component fuel that is contained at all or little is separated and supplied to the catalyst device 70. For this purpose, the fuel supply device 100 has a fuel separation device. In FIG. 2, reference numeral 109 denotes a low sulfur component fuel separated by the fuel separation device for injecting it directly upstream of the catalyst device 70 of the engine exhaust system. It is an injection valve that forms part of the fuel supply device 100.
[0033]
The fuel separation device may have any separation membrane that does not allow aromatic compounds such as benzothiophene and dibenzothiophene in the fuel to pass therethrough. The aromatic compound in the fuel is a high-sulfur component fuel that contains a large amount of sulfur components. If this is separated by the separation membrane and returned to the fuel tank, only the other low-sulfur component fuel that passes through the separation membrane is injected. 109 enables supply to the catalyst device 70.
[0034]
Moreover, the normal light oil which is a fuel of a diesel engine has the component content rate for every boiling point in the boiling point temperature range as shown by A in FIG. If a low sulfur component fuel B having a boiling point lower than its boiling temperature range and having the sulfur component removed is added to such a normal fuel as a fuel in the fuel tank, a heating means is used as a fuel separator. What is necessary is just to have.
[0035]
For example, the fuel separator can be configured as shown in FIG. In FIG. 4, reference numeral 101 denotes a liquid fuel passage for guiding the fuel in the fuel tank so as to pass through the heating means 104, and a fuel pump 102 is provided for this purpose. Reference numeral 103 denotes a gaseous fuel passage for taking out the fuel vaporized when passing through the heating means 104 from the liquid fuel passage 101. Reference numeral 105 denotes a cooling device for cooling and liquefying the gaseous fuel passing through the gaseous fuel passage 103. As this cooling device, the outside air temperature or vehicle running wind can be used. Reference numeral 106 denotes a reservoir for storing liquefied fuel. Reference numeral 107 denotes a fuel injection passage for guiding the fuel in the reservoir 106 to the aforementioned injection valve 109, and a pressurizing pump 108 is provided for this purpose.
[0036]
Here, the heating means 104 heats the fuel in the liquid fuel passage 101 so that only the low sulfur component fuel added into the fuel tank is vaporized. The heating temperature for that purpose may be, for example, the maximum temperature in the boiling point range of the low sulfur component fuel or a temperature between this maximum temperature and the minimum temperature (for example, 150 ° C.) in the boiling point range of the normal fuel.
[0037]
When the boiling point range of the added low-sulfur component fuel is relatively low and the heating temperature is set to a relatively low temperature of less than 100 ° C, the temperature of the engine coolant before flowing into the radiator is used. can do.
[0038]
On the other hand, when the heating temperature is set to 100 ° C. or higher, the exhaust gas temperature in the engine exhaust system can be used. FIG. 5 shows a case where engine combustion heat is used as the heating means. In FIG. 5, 4 is a piston, and the liquid fuel passage 101 is formed in the cylinder block 2. In this case, the liquid fuel passage 101 is branched into four passages 101a, 101b, 101c, and 101d having different distances along the cylinder bore. Each branch passage is provided with closing valves V1, V2, V3 and V4.
[0039]
When the combustion temperature is low, such as when the engine is under low load, only the closing valve V1 is opened. As a result, the fuel passes through the liquid fuel passage 101 and the branch passage 101a and extends along the cylinder bore in the cylinder block 2, so that the engine combustion heat can be received sufficiently and the combustion temperature is low. Also, the fuel can be heated to a set temperature.
[0040]
When the combustion temperature increases as the engine load increases, only the closing valve V2 is opened. As a result, the fuel passes through the liquid fuel passage 101 and the branch passage 101b, and is slightly shorter along the cylinder bore in the cylinder block 2 than when passing through the branch passage 101a. In this way, the heat received by the engine combustion heat becomes slightly insufficient as the combustion temperature increases, and the fuel can be heated to the set temperature.
[0041]
If the combustion temperature further increases as the engine load increases, only the shut-off valve V3 is opened, and the heat received by the engine combustion heat is further insufficient, and if the combustion temperature further increases as in the case of a high engine load, Only the shut-off valve V4 is opened to make the heat of engine combustion heat received further insufficient. Thus, the set temperature can heat the fuel in the fuel tank for any combustion temperature.
[0042]
FIG. 6 also shows a case where engine combustion heat is used as the heating means. In FIG. 6, 4 is a piston, and the liquid fuel passage 101 is formed in the cylinder block 2. Further, in the cylinder block 2, a cooling water passage 200 is provided adjacent to the liquid fuel passage 101, and the four passages 200 a, 200 b, 200 c, and 200 c have different distances along the liquid fuel passage 101. Branches to 200d. Each branch passage is provided with closing valves V4, V5, V6 and V7.
[0043]
When the combustion temperature is low, such as when the engine is under a low load, only the closing valve V8 is opened. Accordingly, the cooling water passes through the branch passage 200d and along the liquid fuel passage 101 in the cylinder block 2, so that the fuel passing through the liquid fuel passage 101 is slightly cooled, and the combustion temperature is low. Even if it is low, the fuel can be brought to the set temperature.
[0044]
When the combustion temperature increases as the engine load increases, only the closing valve V7 is opened. As a result, the cooling water passes through the branch passage 200c and extends along the liquid fuel passage 101 slightly longer in the cylinder block 2 than when passing through the branch passage 200d. In this way, the cooling power by the cooling water can be increased by an amount corresponding to the increase in the combustion temperature, and the fuel can be brought to the set temperature.
[0045]
If the combustion temperature further increases as the engine load increases, only the shut-off valve V6 is opened, and the cooling power by the cooling water is further increased. If the combustion temperature further increases as in the case of a high engine load, the valve is closed. Only the valve V5 is opened to further increase the cooling power by the cooling water. Thus, the set temperature can heat the fuel in the fuel tank for any combustion temperature.
[0046]
FIG. 7 shows a vacuum boiling device added when the fuel in the fuel tank cannot be heated to the set temperature at which the low-boiling point fuel vaporizes or is not heated by the heating means. In FIG. 7, 110 is a pressure reducing cylinder, and 110 a is a piston that reciprocates in the pressure reducing cylinder 110. Reference numeral 111 denotes a pump cylinder, and reference numeral 111 a denotes a piston that reciprocates in the pump cylinder 111. The decompression cylinder 110 and the pump cylinder 111 are communicated with each other through a communication passage 113, and a check valve that allows only a gaseous fuel flow into the pump cylinder 111 is disposed in the communication passage 113. Reference numeral 114 denotes a gaseous fuel passage corresponding to 103 in FIG.
[0047]
When fuel having a temperature lower than the set temperature is introduced into the pressure reducing cylinder 110 by the passage 112, the passage 112 is closed by the closing valve 112a. When the volume in the decompression cylinder 110 is expanded by the operation of the piston 110a, the fuel introduced into the decompression cylinder 110 boils under reduced pressure and vaporizes. Next, the volume in the pressure reducing cylinder 110 is decreased by the operation of the piston 110a, and at the same time the volume of the pump cylinder 111 is expanded by the operation of the piston 111a. Inhaled. Next, when the volume in the pump cylinder 111 is reduced by the operation of the piston 111a, the vaporized fuel and the fuel liquefied in the pump cylinder 111 are discharged through the gaseous fuel passage 114. The closing valve 112a of the passage 112 has a volume in the decompression cylinder 110 that is less than that when the piston 110a is closed so that liquid fuel that does not boil in the decompression cylinder 110 does not flow into the pump piston 111 through the communication passage 113. When it becomes slightly small, it is opened and the liquid fuel in the decompression cylinder 110 is discharged from the passage 112.
[0048]
The low-sulfur component fuel B added to the normal fuel has a boiling point temperature range lower than that of the normal fuel. However, the low sulfur component B added to the normal fuel as indicated by a one-dot chain line in FIG. The component fuel may be on the low boiling point side within the normal boiling point temperature range of the fuel. As a result, the set temperature for heating the fuel is increased, and the components on the low boiling point side of the normal fuel are also separated at the same time. However, as shown in FIG. In addition to the low rate and not so much normal fuel being separated, the normal fuel components separated here are mainly low-boiling normal paraffins and are essentially free of sulfur. As a result, even if the normal fuel component and the added low sulfur component fuel containing almost no sulfur are separated at the same time, the average sulfur content of the separated fuel is considerably low. Even when used in the regeneration process, the catalyst device 70 is hardly poisoned by S. In addition, the use of a fuel having a low boiling point for the regeneration treatment of the catalyst device 70 improves the fuel vaporization when the catalyst device 70 is supplied to the catalyst device 70, and the inside of the catalyst device 70 is reliably desired by supplying the minimum amount of fuel. The regenerative air-fuel ratio can be made.
[0049]
FIG. 8 shows a case where the boiling range of the low sulfur component fuel C added to the fuel tank is higher than the boiling range of the normal fuel A. In this case, the low sulfur component fuel C is separated by cooling the fuel in the fuel tank to solidify and deposit the low sulfur component fuel C. In such a separation device, a Peltier element or the like whose temperature is lowered by energization can be used. For example, the fuel in the fuel tank is led into a buffer tank that can be cooled by a Peltier element, and the low sulfur component fuel is deposited at the bottom of the buffer tank. Next, after the liquid fuel that does not solidify is discharged from the buffer tank, the buffer tank is heated to liquefy the low sulfur component fuel. In this way, the low sulfur component fuel can be separated.
[0050]
The low sulfur component fuel added to the normal fuel may be on the high boiling point side within the boiling point temperature range of the normal fuel, as indicated by C ′ shown by a one-dot chain line in FIG. 8. As a result, the high-boiling component of the normal fuel is also separated at the same time. However, as shown in FIG. 8, the content of the high-boiling component of the normal fuel is low, and so much normal fuel is not separated. In addition, the normal fuel component separated here is mainly a high-boiling normal paraffin indicated by A ′ in FIG. 8 and essentially does not contain sulfur. As a result, even if this normal fuel component is separated at the same time as the added low sulfur component fuel, the average sulfur content of the separated fuel is very low and is used for the regeneration treatment of the catalyst device 70. However, the catalytic device 70 is hardly poisoned by S.
[0051]
Moreover, since the high boiling normal paraffin A ′ contains almost no sulfur, in particular, only the high boiling normal paraffin is separated from the normal fuel by cooling without adding a low sulfur component fuel, and this is used as a catalyst. You may make it use for the reproduction | regeneration processing of the apparatus 70. FIG. In this case, since the high boiling normal paraffin A ′ may be insufficiently vaporized when supplied to the catalyst device 70, the buffer tank is gradually heated after being precipitated in the buffer tank. It is preferable to use only the high boiling normal paraffin on the low boiling point side liquefied relatively early in the regeneration treatment of the catalyst device 70.
[0052]
By the way, the exhaust gas of a diesel engine contains particulates mainly composed of soot, and it is desired that these particulates are not released into the atmosphere. For this reason, it has been proposed to arrange a particulate filter for collecting particulates in the engine exhaust system. The above-mentioned NO is added to this particulate filter._XWhen the absorbent and the noble metal catalyst are supported, NO is similarly applied as described above._XIn addition, the collected particulates can be oxidized and removed, and the increase in exhaust resistance of the particulate filter due to the collected particulates can be prevented.
[0053]
In this case, NO_XAs the absorbent, it is preferable to use an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, and strontium Sr.
[0054]
The mechanism of oxidation of the collected particulates will be briefly explained. NO in the exhaust gas_XWhen adhering to the absorbent surface, particulates and NO_XThe oxygen concentration decreases at the contact surface with the absorbent. NO with high oxygen concentration when oxygen concentration decreases_XThere is a concentration difference with the absorbent, so NO_XOxygen in the absorbent is particulate and NO_XAttempts to move toward the contact surface with the absorbent. As a result, NO_XOxygen O and NO are decomposed from the nitrate formed in the absorbent, and oxygen O becomes particulate and NO._XFacing the contact surface with the absorbent, NO is NO_XReleased from the absorbent to the outside. NO released to the outside is oxidized on the platinum Pt on the downstream side, and again NO._XAbsorbed in the absorbent 1.
[0055]
Particulate and NO_XThe oxygen O toward the contact surface with the absorbent is oxygen decomposed from a compound such as nitrate. Oxygen O decomposed from the compound has high energy and has extremely high activity. Therefore, particulates and NO_XOxygen toward the contact surface with the absorbent is active oxygen O. When these active oxygens O come into contact with the particulates, the particulates are oxidized without emitting a luminous flame in a few minutes to several tens of minutes. In addition, active oxygen O that oxidizes particulates is NO._XAlso released when NO is absorbed by the absorbent. NO_XNitrate ions NO in the active oxygen release agent 61 while repeatedly binding and separating oxygen atoms_Three ^-The active oxygen is generated during this period. Particulates are also oxidized by this active oxygen.
[0056]
FIG. 9 shows NO in a particulate filter as a catalyst device._XThe case where an absorbent is carried is shown. In FIG. 9, reference numeral 18 ′ denotes an exhaust pipe located on the downstream side of the exhaust manifold 17. Reference numeral 71 denotes a switching unit connected to the exhaust pipe 18 ', and 70' denotes a particulate filter as a catalyst device. One side of the particulate filter 70 ′ and the switching unit 71 are connected by a first connection part 72a, and the other side of the particulate filter 70 ′ and the switching part 71 are connected by a second connection part 72b. An exhaust passage 73 is connected to the downstream side of the switching unit 71. The switching unit 71 includes a valve body 71 a that can block the exhaust flow in the switching unit 71. The valve body 71a is driven by a negative pressure actuator or a step motor. In the first shut-off position of the valve body 71a shown in FIG. 9, the upstream side in the switching part 71 is communicated with the first connection part 72a and the downstream side in the switching part 71 is communicated with the second connection part 72b. 9 flows from one side of the particulate filter 70 ′ to the other side as indicated by arrows in FIG. 9.
[0057]
Moreover, FIG. 10 has shown the 2nd interruption | blocking position of the valve body 71a. At this shut-off position, the upstream side in the switching unit 71 communicates with the second connection part 72b and the downstream side in the switching unit 71 communicates with the first connection part 72a, and the exhaust gas is as shown by arrows in FIG. , Flows from the other side of the particulate filter 70 ′ to one side. Thus, by switching the valve body 71a from one of the first cutoff position and the second cutoff position to the other, the direction of the exhaust gas flowing into the particulate filter 70 ′ can be reversed, that is, the particulate filter 70 ′. It is possible to reverse the exhaust upstream side and the exhaust downstream side. Moreover, FIG. 11 has shown the open position of the valve body 71a between a 1st interruption | blocking position and a 2nd interruption | blocking position. In this open position, the inside of the switching unit 71 is not shut off, and the exhaust gas flows by bypassing the particulate filter 70 ′ as indicated by an arrow in FIG. 11.
[0058]
As described above, the exhaust purification device can reverse the exhaust upstream side and the exhaust downstream side of the particulate filter by switching the valve body 71a from one of the two shut-off positions to the other with a very simple configuration. In addition, if the valve body 71a is in the open position, the exhaust gas can bypass the particulate filter 70.
[0059]
Further, in the particulate filter, a large opening area is required for facilitating the inflow of exhaust gas. However, in the present exhaust purification device, as shown in FIG. A particulate filter having an open area can be used.
[0060]
By the way, platinum Pt and NO_XSince the absorbent becomes active as the temperature increases, NO per unit time_XThe amount of active oxygen O released from the absorbent increases as the temperature of the particulate filter increases. As a matter of course, the higher the temperature of the particulate itself, the easier it is to be removed by oxidation. Therefore, the amount of fine particles that can be removed by oxidation without emitting a luminous flame per unit time on the particulate filter increases as the temperature of the particulate filter increases.
[0061]
The solid line in FIG. 12 indicates the amount G of fine particles that can be removed by oxidation without emitting a bright flame per unit time. In FIG. 12, the horizontal axis indicates the temperature TF of the particulate filter. FIG. 12 shows the amount of fine particles G that can be removed by oxidation when the unit time is 1 second, that is, the amount of fine particles G that can be removed by oxidation per second. be able to. For example, when 10 minutes is used as the unit time, the oxidizable and removable fine particle amount G per unit time represents the oxidizable and removable fine particle amount G per 10 minutes. Even in this case, the unit time on the particulate filter As shown in FIG. 12, the amount G of fine particles that can be removed by oxidation without emitting a bright flame increases as the temperature of the particulate filter 70 ′ increases.
[0062]
Now, when the amount of particulate discharged from the combustion chamber per unit time is referred to as discharged particulate amount M, when this discharged particulate amount M is smaller than the oxidizable and removable particulate amount G, for example, the amount of particulate discharged per second. When M is smaller than the amount G of fine particles that can be removed by oxidation per second, or when the amount M of fine particles discharged per 10 minutes is smaller than the amount of fine particles G that can be removed by oxidation every 10 minutes, that is, in region I in FIG. All the particulates discharged from the chamber are sequentially oxidized and removed within a short time without emitting a bright flame on the particulate filter 70 '.
[0063]
On the other hand, when the amount M of discharged fine particles is larger than the amount G of fine particles that can be removed by oxidation, that is, in the region II in FIG. 12, the amount of active oxygen is insufficient to sequentially oxidize all the particulates. When particulates remain in the particulate filter 70 'in this way, such residual particulates gradually change into carbonaceous matter that is difficult to oxidize, and when the exhaust upstream surface is covered with residual particulates, oxidation of NO by platinum Pt. Action and NO_XThe action of releasing active oxygen by the absorbent is suppressed. As a result, the residual particulates can be gradually oxidized over time, but if the residual particulates are not removed at an early stage, other particulates will accumulate on the next. Thus, when the particulates are deposited in a laminated form, the particulates are platinum Pt or NO._XBecause of the distance from the absorbent, even particulates that are easily oxidized are not oxidized by active oxygen. Accordingly, if the state in which the amount M of discharged particulates is larger than the amount G of particulates that can be removed by oxidation continues, particulates accumulate on the particulate filter in a stacked manner.
[0064]
In the present embodiment, when oxidation removal is insufficient and particulates remain on the particulate filter or before that, the shutoff position of the valve body 71a is switched, and the exhaust upstream side of the particulate filter 70 ′ and the exhaust gas are exhausted. The downstream side is reversed.
[0065]
FIG. 13 is an enlarged cross-sectional view of the partition wall of the particulate filter 70 ′. The particulate filter is, for example, a wall flow type having a honeycomb structure formed of a porous material such as cordierite, and has a large number of axial spaces subdivided by a large number of partition walls extending in the axial direction. ing. In two adjacent axial spaces, the plug closes one on the exhaust downstream side and the other on the exhaust upstream side. Thus, one of the two adjacent axial spaces serves as an exhaust gas inflow passage, the other serves as an outflow passage, and the exhaust gas always passes through the partition wall. Particulates in the exhaust gas are very small compared to the pore size of the partition walls, but are collected by colliding with the exhaust upstream surface of the partition walls and the pore surfaces in the partition walls. Thus, each partition functions as a collection wall for collecting particulates. In the particulate filter 70 ′, NO or the like is used on both side surfaces of the partition walls, and preferably on the pore surfaces in the partition walls._XAn absorbent and a noble metal catalyst are supported.
[0066]
As shown by the lattice in FIG. 13A, the exhaust upstream surface of the partition wall where the exhaust gas mainly collides and the exhaust gas flow facing surface in the pores collide and collect particulates as one collection surface. The active oxygen release agent oxidizes and removes, but this oxidative removal becomes insufficient and particulates may remain. At this time, the exhaust resistance of the particulate filter 70 ′ does not adversely affect the running of the vehicle, but if particulates further accumulate, problems such as a significant decrease in engine output occur. Thereby, at this time, the exhaust upstream side and the exhaust downstream side of the particulate filter 70 'are reversed. As a result, no further particulate is deposited on the particulate remaining on one of the collection surfaces of the partition wall, and the residual particulate is gradually oxidized and removed by the active oxygen released from one of the collection surfaces. The Further, the particulates remaining in the pores of the partition walls are easily broken and fragmented by the exhaust gas flow in the opposite direction, and move downstream as shown in FIG.
[0067]
As a result, many of the finely divided particulates are dispersed in the pores of the partition walls, that is, the particulates flow, so that NO supported on the pore inner surfaces of the partition walls._XThere is an increased chance of oxidation removal in direct contact with the absorbent. Thus, NO also enters the pores of the partition walls._XBy supporting the absorbent, the residual particulates can be remarkably easily oxidized and removed. Further, in addition to this oxidation removal, the other collecting surface of the partition wall upstream due to the backflow of the exhaust gas, that is, the exhaust upstream surface of the partition wall where the exhaust gas mainly collides now and the exhaust in the pores On the gas flow facing surface (which is on the side opposite to the one collecting surface), new particulates in the exhaust gas adhere and NO._XIt is oxidized and removed by the active oxygen released from the absorbent. A part of the active oxygen released from the active oxygen release agent during the oxidation removal moves to the downstream side together with the exhaust gas, and the remaining particulates are oxidized and removed by the backflow of the exhaust gas.
[0068]
That is, the residual particulates on one collecting surface in the partition wall are not only for the active oxygen released from this collecting surface, but also for the oxidation removal of the particulates on the other collecting surface of the partition wall by the backflow of exhaust gas. The remaining active oxygen used comes from the exhaust gas. As a result, even if particulates are accumulated to some extent on one collecting surface of the partition wall at the time of switching of the valve body, if the exhaust gas flows backward, the particulates accumulated on the residual particulates In addition to the arrival of active oxygen, no further particulates are deposited, so the deposited particulates are gradually oxidized and removed. Oxidation removal is possible. In this way, when the first collection surface and the second collection surface are alternately used for collecting particulates, each collection is always compared to the case where particulates are collected on a single collection surface. Since the amount of particulates collected at the collecting surface can be reduced and it is advantageous for the removal of particulates by oxidation, particulates do not accumulate on the particulate filter 70 ′, and the particulate filter is clogged. Can be prevented.
[0069]
Thus, NO_XIf the catalyst device for purifying the catalyst is a particulate filter, the particulates in the exhaust gas can be removed without being released into the atmosphere. Of course, this particulate filter 70 'also has NO._XIn order to prevent sulfur poisoning, the low-sulfur component fuel is supplied to the particulate filter 70 ′ in the exhaust pipe 18 ′ located upstream of the switching unit 71. An injection valve 109 is provided. In this regeneration process, a large amount of NO_XWhen oxygen is released, active oxygen is released all at once, so that if there is residual particulate, it can be satisfactorily oxidized and removed. As a result, almost all engine operation is carried out in the region II of FIG. 12, and if the particulate filter 70 ′ is not accumulated in the particulate filter 70 ′ by combining the regeneration processing of the particulate filter 70 ′, as in this embodiment. Such reverse means can be omitted. The position of the injection valve 109 may be between the switching unit 71 and the particulate filter 70 ′, that is, the injection valve 109 may be arranged in both or one of the first connection part 72a and the second connection part 72b. . When the injection valve 109 is disposed on one side, it is necessary to control the position of the valve body 71a so that the fuel injected from the injection valve 109 is supplied to the particulate filter 70 'during the regeneration process.
[0070]
By the way, since the fuel burned in the cylinder still contains sulfur, the SO in the exhaust gas_XAs a result, the catalyst device 70 or the particulate filter 70 ′ as the catalyst device is poisoned by S. SO flowing into the catalyst device 70 or the particulate filter 70 '_XIs mainly located in the exhaust upstream part_XSO in exhaust gas to be absorbed by the absorbent_XS poisoning due to is only in the exhaust upstream side portion of the catalyst device 70 or the particulate filter 70 '. When the exhaust upstream side and the exhaust downstream side of the particulate filter 70 'are occasionally reversed as in the present embodiment, both ends of the particulate filter 70' are poisoned with S. The entire curative filter 70 'is not poisoned by S.
[0071]
In the case of such partial S poisoning, it is only necessary to raise the temperature of only the S poisoned part in the catalyst device 70 or the particulate filter 70 ′, and the energy required for the recovery process is not so much. In addition, the heating time can be shortened, NO._XThe absorbent and the noble metal catalyst are not thermally deteriorated. As a result, the recovery process can be carried out relatively easily, but the recovery process is still less preferred.
[0072]
In the present embodiment, upstream of the injection valve 109 in the exhaust pipe 18 ′, the SO in the exhaust gas is introduced before flowing into the particulate filter 70 ′._XSO to collect_XA collection device 74 is provided. SO_XThe collection device 74 is NO_XIt may be one carrying an absorbent, but NO_XSO more than absorbent_XIt is preferable to carry a substance that easily absorbs. Thus, the SO in the exhaust gas_XIs SO_XThe particulate filter 70 'is not poisoned by the sulfur collected by the collection device. Such SO_XThe collection device may be arranged upstream of the catalyst device 70 and the injection valve 109 in FIG. Thus SO in the exhaust gas_XSO to collect_XWhen the collection device is provided, in the regeneration process, the low sulfur component fuel is supplied to the catalyst device 70 or the particulate filter 70 ′ by the injection valve 109, so that the catalyst device 70 or the particulate filter 70 ′ is supplied. S poisoning can be almost completely prevented.
[0073]
However, what SO_XEven the collection device is infinitely SO_XCan not be collected, SO_XNeed to be released. SO released in this way_XIt is meaningless to flow into the particulate filter 70 ', and this SO_XAt the time of discharge, it is necessary to set the valve body 71a to the open position shown in FIG. 11 so that the exhaust gas does not flow into the particulate filter 70 '.
[0074]
Thus, the SO_XWhen the collection device 74 is provided, it is necessary to provide bypass means that allows the exhaust gas to bypass the particulate filter 70 ′ or the catalyst device 70. Since it is integrated with the reversing means for preventing the accumulation of particulates on the curate filter, it is advantageous in terms of vehicle mountability and cost reduction.
[0075]
The present invention provides a relatively large amount of NO in the exhaust gas._XThe present invention is also applicable to a gasoline engine that performs lean combustion that includes.
[0076]
【The invention's effect】
As described above, the exhaust gas purification apparatus for an internal combustion engine according to the present invention is NO when the ambient atmosphere has a lean air-fuel ratio._XWhen the stoichiometric or rich air-fuel ratio is absorbed, NO_XNO release_XIn an exhaust emission control device for an internal combustion engine, comprising: a catalyst device that supports a catalyst; and a fuel supply device that supplies fuel to the catalyst device for regeneration processing of the catalyst device. Since the low sulfur component fuel is separated and supplied to the catalyst device, the overall sulfur poisoning of the catalyst device can be prevented during the regeneration process.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of a diesel engine equipped with an exhaust emission control device according to the present invention.
FIG. 2 is a plan view showing an exhaust emission control device according to the present invention.
FIG. 3 is a graph showing the content of components at each boiling point in the fuel in the fuel tank.
FIG. 4 is a schematic view of a fuel separator.
FIG. 5 is a schematic view showing heating means in the fuel separator.
FIG. 6 is a schematic view showing another heating means of the fuel separator.
FIG. 7 is a schematic view showing a vacuum boiling apparatus used in combination with fuel heating means.
FIG. 8 is another graph showing the content of components at each boiling point in the fuel in the fuel tank.
FIG. 9 is a plan view showing another exhaust emission control device according to the present invention.
10 is a view showing another blocking position of the valve body different from FIG. 9. FIG.
FIG. 11 is a view showing an open position of the valve body.
FIG. 12 is a diagram showing the relationship between the amount of fine particles that can be removed by oxidation and the temperature of the particulate filter.
FIG. 13 is an enlarged cross-sectional view of a partition wall of a particulate filter.
[Explanation of symbols]
70 ... Catalyst device
70 '... Particulate filter
100 ... Fuel supply device

Claims (11)

A catalyst device carrying a NO _X catalyst that absorbs NO _X when the ambient atmosphere is a lean air-fuel ratio and releases NO _X when it is a stoichiometric or rich air-fuel ratio, and the catalyst device for regeneration processing of the catalyst device in the exhaust purification system of an internal combustion engine having a fuel supply device for supplying fuel to said fuel supply device, the fuel in the fuel tank to separate the low sulfur content fuels supplied to the catalytic converter, the low-sulfur An exhaust gas purification apparatus for an internal combustion engine, wherein the remaining fuel from which the component fuel is separated is burned in a cylinder . 2. The exhaust of the internal combustion engine according to claim 1, wherein the fuel supply device separates the fuel in the fuel tank into an aromatic compound as a high sulfur component fuel and the low sulfur component fuel by a separation membrane. Purification equipment. 2. The fuel supply device according to claim 1, wherein the fuel in the fuel tank is cooled and separated into a low boiling point component fuel as a high sulfur component fuel and a high boiling point normal paraffin as the low sulfur component fuel. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1. The fuel supply device heats the low-sulfur component fuel that has been wax-deposited by cooling and separates it into a low-boiling-side component and a high-boiling-side component so that only the low-boiling-side component of the low-sulfur component fuel is the catalytic device. The exhaust emission control device for an internal combustion engine according to claim 3, wherein the exhaust gas purification device is supplied to the internal combustion engine. As the fuel in the fuel tank, a low-sulfur component fuel having a boiling point higher than the boiling point temperature range of the normal fuel or the same boiling point as the high boiling point side in the boiling point temperature range is added to the normal fuel, and the fuel supply device The exhaust purification device for an internal combustion engine according to claim 1, wherein the fuel in the fuel tank is cooled to separate the low sulfur component fuel. As the fuel in the fuel tank, a low sulfur component fuel having a boiling point lower than the boiling point temperature range of the normal fuel or the same boiling point as the low boiling point side in the boiling point temperature range is added to the normal fuel, and the fuel supply device The exhaust purification device of an internal combustion engine according to claim 1, wherein the fuel in the fuel tank is distilled to separate the low sulfur component fuel. The exhaust purification device for an internal combustion engine according to claim 6, wherein the fuel in the fuel tank is distilled using an electric heater. The exhaust gas purification apparatus for an internal combustion engine according to claim 6, wherein the fuel in the fuel tank is distilled using an exhaust gas temperature or an in-cylinder combustion temperature. The exhaust gas purification apparatus for an internal combustion engine according to claim 6, wherein the fuel in the fuel tank is distilled using the engine coolant temperature. And SO _X trap for trapping SO _X in the exhaust gas is disposed in the exhaust upstream of the catalytic converter, the catalytic converter exhaust gas when releasing the SO _X from the SO _X trap An exhaust purification device for an internal combustion engine according to any one of claims 1 to 9, further comprising bypass means for bypassing. The catalyst device is a particulate filter, and the bypass unit is formed integrally with a reverse rotation unit that can reverse the exhaust upstream side and the exhaust downstream side of the particulate filter. The exhaust emission control device for an internal combustion engine according to claim 10.

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