JP2014077371A - Exhaust gas emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently reduce NOx in an exhaust gas of an engine and prevent corrosion or the like in the engine by supplying a nitrogen-enriched gas dried in a dryer and separated in an air separator to an EGR pipe.SOLUTION: An EGR pipe 19 for allowing part of an exhaust gas of an engine 11 as an EGR gas to flow back from an exhaust passage 13 to an intake passage 12 connects the exhaust passage and the intake passage of an engine by bypassing the engine, and an EGR valve 20 provided in the EGR pipe adjusts an airflow of EGR gas flowing in the EGR pipe. In addition, an air compressor 23 compresses air, and a drier 24 collects moisture contained in the air compressed by the air compressor to dry the air. Furthermore, an air separator 26 separates the air dried in the dryer into an oxygen-enriched gas having high oxygen concentration and a nitrogen-enriched gas having high nitrogen concentration, and a nitrogen-enriched gas supply means 36 supplies the nitrogen-enriched gas separated in the air separator to the EGR pipe.

Description

  The present invention relates to an apparatus for purifying exhaust gas by reducing nitrogen oxide (NOx) contained in the exhaust gas of the engine.

  Conventionally, an apparatus for supplying enriched air to an engine that operates by internal combustion of a mixture of fuel and combustion air has been disclosed (see, for example, Patent Document 1). The enriched air supply device comprises a casing, a non-porous membrane contained in the casing, a non-permeate cavity on one side of the membrane in the casing, and a permeation on the other side of the membrane in the casing. A selective gas permeable membrane unit including a material cavity, a pressure change means for generating a negative pressure gradient from the non-permeate cavity pressure to the permeate cavity pressure between the membranes, oxygen enriched air or nitrogen rich And a supply selection valve for guiding either of the converted air to the engine. And the mixture which does not contain the air from air | atmosphere is provided by operation of this apparatus. The non-porous membrane has an oxygen / nitrogen selectivity of at least 1.4 by weight, an oxygen permeability of 50 barrels, and perfluoro-2,2-dimethyl-1,3-dioxole. It is formed of an amorphous copolymer and is at a temperature below the glass transition temperature of the amorphous copolymer. The impermeate cavity also selectively allows permeation of oxygen from the atmospheric feed stream entering one side of the membrane in the casing through the membrane, and the nitrogen-enriched air stream generated there is a source for the impermeate. become. Further, the permeate cavity is a permeate stream source of oxygen-enriched air, and the permeate stream feed flow ratio determines the step cut.

  The operation of the enriched air supply apparatus configured as described above will be described. The process of supplying enriched air to the engine can be used to improve various engine performance parameters. Improvements include reducing various nitrogen oxide concentrations in engine exhaust, increasing engine power, increasing engine lean burn limits, and reducing cold start emissions. NOx emissions reduction can occur due to supplying nitrogen-enriched air to the engine. Also, to reduce cold start emissions and improve lean burn limits and engine power, the air supplied to the engine should be enriched oxygen. In this case, it can be easily converted into an oxygen-enriched air supply by simply switching the position of the valve. Thus, the operation can be easily switched between the supply of the nitrogen-enriched non-permeate component and the supply of the oxygen-enriched permeate component simply by operating the valve. Thus, this apparatus can be used to obtain optimal engine performance that requires either enriched oxygen air or nitrogen enriched air depending on the criteria programmed into the central processor unit.

  For example, when the engine starts from cold conditions, it is desirable to supply oxygen-enriched air to minimize cold start emissions. The central processor unit detects a low engine temperature (eg from sensing means). The programmed algorithm instructs the processor to turn the switch three-way switching vent valve to vent the unpermeate component (divergence, release) and to turn the three-way switching supply valve to supply the permeate component. The program sends a signal to the flow control valve to make a step cut to achieve optimal cold start emissions. A reduction in NOx emissions may be desirable when the engine achieves a steady operating temperature condition as detected by the sensing means. The processor may instruct the device to switch the position of the valve to supply the non-permeate component to the engine while the permeate component is vented. Thereafter, the processor sends the output to the flow control valve to reach the optimum stage cut for NOx emission reduction according to the programmed algorithm. Many criteria used to switch between permeate and non-permeate feed modes can be programmed into the processor algorithm.

JP-T-2002-504643 (Claim 17, paragraphs [0043], [0043], [0054], [0055], FIG. 4)

  However, in the conventional apparatus for supplying enriched air shown in Patent Document 1, when nitrogen-enriched air separated by the selective gas permeable membrane unit contains a relatively large amount of water, When the enriched air is supplied to the engine in order to reduce NOx emissions, there is a possibility that corrosion due to the moisture or the like may occur inside the engine.

A first object of the present invention is to efficiently supply NOx in exhaust gas discharged from an engine by supplying nitrogen-enriched gas obtained by separating air dried by a dryer with an air separator to an EGR pipe. An object of the present invention is to provide an exhaust gas purification device that can reduce the corrosion and prevent corrosion inside the engine. The second object of the present invention is to make it possible to efficiently reduce NOx even when the exhaust gas temperature is low by reacting part of NO in the exhaust gas with ozone to make it highly reactive NO _2. It is to provide a purification device. The third object of the present invention is to supply a part of the oxygen-enriched gas or nitrogen-enriched gas separated by the air separator to the dryer by the purge means, and discharge it together with the water vapor (moisture) separated by this dryer. Thus, an object of the present invention is to provide an exhaust gas purifying apparatus capable of efficiently regenerating a dryer.

  As shown in FIGS. 1 and 2, the first aspect of the present invention connects the exhaust passage 13 and the intake passage 12 of the engine 11 by bypassing the engine 11, and exhausts a part of the exhaust gas of the engine 11 as EGR gas. In an exhaust gas purifying apparatus comprising an EGR pipe 19 that recirculates from the passage 13 to the intake passage 12 and an EGR valve 20 that is provided in the EGR pipe 19 and adjusts the flow rate of the EGR gas that flows through the EGR pipe 19. The compressor 23, a dryer 24 that collects moisture contained in the air compressed by the air compressor 23 and dries the air, and the air dried by the dryer 24 is converted into an oxygen-enriched gas and a nitrogen concentration with a high oxygen concentration. Air separator 26 that separates into high nitrogen enriched gas, and nitrogen enriched gas that supplies the nitrogen enriched gas separated by air separator 26 to EGR pipe 19 Characterized in that a gas supply means 36.

The second aspect of the present invention is an invention based on the first aspect, and is further provided in the exhaust passage 13 downstream of the exhaust gas from the connection portion of the EGR pipe 19 to the exhaust passage 13 as shown in FIG. A selective reduction catalyst 43 capable of reducing NOx in the exhaust gas to N ₂ , an ozone generator 86 for converting oxygen in the oxygen-enriched gas separated by the air separator 26 into ozone 90, and exhaust gas from the EGR pipe 19 An ozone injection nozzle 81 that is provided facing the exhaust passage 13 between the connection portion to the passage 13 and the selective catalytic reduction catalyst 43 and injects ozone 90 generated by the ozone generator 86 into the exhaust passage 13, and an ozone generator The ozone supply means 87 for supplying the ozone 90 generated at 86 to the ozone injection nozzle 81 and the exhaust passage 13 between the connection portion of the EGR pipe 19 to the exhaust passage 13 and the selective reduction catalyst 43 are provided. Reducing agent 4 The reducing agent injection nozzle 47 for injecting into the exhaust passage 13, and further comprising a reducing agent 45 further a reducing agent supply means 46 for supplying the reducing agent injection nozzle 47.

  A third aspect of the present invention is an invention based on the first aspect, and further, as shown in FIG. 4, the air separator 26 has an oxygen-enriched film 26 a, and the oxygen-enriched gas is supplied by a dryer 24. The dried air is generated by passing through the oxygen-enriched film 26a, and the nitrogen-enriched gas is generated by passing the air dried by the dryer 24 without passing through the oxygen-enriched film 26a. Features.

  A fourth aspect of the present invention is an invention based on the first or second aspect, and further, as shown in FIG. 1, is an oxygen-enriched gas or a nitrogen-enriched gas separated by an air separator 26. The apparatus further includes a purge means 40 for removing moisture in the dryer 24 using the unit.

  A fifth aspect of the present invention is an invention based on the second aspect, and is further characterized in that the reducing agent 45 is fuel or urea water as shown in FIG.

  In the exhaust gas purifying apparatus according to the first aspect of the present invention, after the air compressed by the air compressor is dried by a dryer, it is separated into nitrogen-enriched gas and oxygen-enriched gas by an air separator. Since gas is supplied to the EGR pipe, NOx in the exhaust gas discharged from the engine can be efficiently reduced. Also, if the nitrogen-enriched air separated by the selective gas permeable membrane unit contains a relatively large amount of water, when the nitrogen-enriched air is supplied to the engine to reduce NOx emissions, Compared with the conventional enriched air supply device that may cause corrosion due to moisture inside the engine, in the present invention, as described above, after the air compressed by the air compressor is dried by the dryer The air separator separates the nitrogen-enriched gas and the oxygen-enriched gas, and the separated nitrogen-enriched gas is supplied to the EGR pipe, so that corrosion inside the engine can be prevented.

In the exhaust gas purifying apparatus of the second aspect of the present invention, the ozone generated by the ozone generator is injected into the exhaust pipe from the ozone injection nozzle, a high portion of the NO in the exhaust gas is reactive reacts with ozone NO ₂ When this highly reactive NO ₂ flows into the selective catalytic reduction catalyst together with the reducing agent injected into the exhaust pipe from the reducing agent injection nozzle, even when the exhaust gas temperature is low, the highly reactive NO ₂ Is reduced to N ₂ by the progress of the selective reduction reaction with the reducing agent in the selective reduction catalyst. As a result, NOx can be efficiently reduced even when the exhaust gas temperature is low.

  In the exhaust gas purifying apparatus according to the third aspect of the present invention, the air separator is constituted by an oxygen-enriched membrane, and air dried by the dryer passes through the oxygen-enriched membrane to generate an oxygen-enriched gas. Since the air dried by (1) passes through the oxygen-enriched membrane without passing through it, a nitrogen-enriched gas is generated, so that the oxygen-enriched gas and the nitrogen-enriched gas are reliably separated by the oxygen-enriched membrane. As a result, with an air separator having a relatively simple structure, an oxygen-enriched gas and a nitrogen-enriched gas can be efficiently generated by the oxygen-enriched membrane of the air separator.

  In the exhaust gas purifying apparatus of the fourth aspect of the present invention, a part of the oxygen-enriched gas or nitrogen-enriched gas separated by the air separator is supplied to the dryer by the purge means, and the water vapor ( It is discharged together with moisture. When the ozone generator is not used, the dryer is regenerated by unnecessary oxygen-enriched gas separated by the air separator. On the other hand, when the ozone generator is used, the dryer is regenerated by a part of the nitrogen-enriched gas that is not supplied to the EGR pipe. As a result, the dryer can be efficiently regenerated.

In the exhaust gas purification apparatus of the fifth aspect of the present invention, when ozone is injected from the ozone injection nozzle into the exhaust pipe when the reducing agent is fuel or urea water, a part of NO in the exhaust gas reacts with ozone and reacts. sex of becomes higher NO _2, high NO ₂ of this reactivity, when flowing into the selective reduction catalyst with the fuel or urea water is injected into the exhaust pipe from the reducing agent injection nozzle, even when the exhaust gas temperature is low The highly reactive NO ₂ is reduced to N ₂ by the progress of the selective reduction reaction with the fuel or urea water in the selective reduction catalyst. On the other hand, when the reducing agent is a fuel, the fuel is partially oxidized by ozone into an active reducing agent made of an oxygen-containing hydrocarbon such as an aldehyde and supplied to the selective catalytic reduction catalyst. Since the active reducing agent comprising oxygen-containing hydrocarbons such as aldehyde is higher in reactivity than the gasified fuel as the NOx reducing agent in the selective catalytic reduction catalyst, NOx in the exhaust gas within a relatively wide exhaust gas temperature range. Can be efficiently reduced.

It is a lineblock diagram of an exhaust gas purification device of a 1st embodiment of the present invention. It is a figure which is the state which fractured | ruptured the case which accommodated the air compressor, dryer, air separator, etc. which are used for the exhaust gas purification apparatus, and shows the connection state by piping of each member. It is a principal part expanded sectional view of the hollow fiber which comprises the water vapor separation membrane of the dryer. It is a principal part expanded sectional view of the hollow fiber which comprises the oxygen enrichment film | membrane of the air separator. It is a figure which shows each change of the reduction rate of the EGR gas flow rate with respect to the change of the flow rate of the nitrogen enriched gas isolate | separated with the air separator, and the fall rate of a moisture content. It is a block diagram of the exhaust gas purification apparatus of 2nd Embodiment of this invention. It is a figure which is the state which fractured | ruptured the case which accommodated the air compressor, dryer, air separator, ozone generator etc. which are used for the exhaust gas purification apparatus, and shows the connection state by piping of each member.

  Next, an embodiment for carrying out the present invention will be described with reference to the drawings.

<First Embodiment>
As shown in FIG. 1, an intake pipe 12b is connected to an intake port of a diesel engine 11 via an intake manifold 12a, and an exhaust pipe 13b is connected to an exhaust port via an exhaust manifold 13a. The intake manifold 12a and the intake pipe 12b constitute an intake passage 12, and the exhaust manifold 13a and the exhaust pipe 13b constitute an exhaust passage 13. The intake pipe 12b is provided with a compressor housing 17a of the turbocharger 17 and an intercooler 18 for cooling the intake air compressed by the turbocharger 17, and the exhaust pipe 13b is provided with a turbine of the turbocharger 17. A housing 17b is provided. Compressor rotor blades (not shown) are rotatably accommodated in the compressor housing 17a, and turbine rotor blades (not shown) are rotatably accommodated in the turbine housing 17b. The compressor rotor blades and the turbine rotor blades are connected by a shaft (not shown), and the compressor rotor blades are rotated via the turbine rotor blades and the shaft by the energy of the exhaust gas discharged from the engine 11, and the compressor rotor blades are rotated. Thus, the intake air in the intake pipe is compressed. Further, the exhaust manifold 13a and the intake pipe 12b are connected by bypassing the engine 11 by the EGR pipe 19. The EGR pipe 19 branches from the exhaust manifold 13 a and joins to the intake pipe 12 b on the intake downstream side of the intercooler 18. As a result, part of the exhaust gas from the engine 11 flows through the EGR pipe 19 as EGR gas from the exhaust manifold 13a toward the intake pipe 12b. Further, the EGR pipe 19 is provided with an EGR valve 20 that adjusts the flow rate of EGR gas recirculated from the exhaust manifold 13a to the intake pipe 12b. In addition, the code | symbol 21 in FIG. 1 is an EGR cooler which cools the EGR gas which passes the EGR pipe | tube 19. As shown in FIG.

  In addition to the EGR gas, the EGR pipe 19 is supplied with a nitrogen-enriched gas having a high nitrogen concentration generated by the enriched gas generator 22. The enriched gas generator 22 includes an air compressor 23 that compresses air in the atmosphere, a dryer 24 that collects moisture contained in the air compressed by the air compressor 23 and dries the air, and a dryer 24. The air separator 26 separates the air dried by the above step into an oxygen-enriched gas having a high oxygen concentration and a nitrogen-enriched gas having a high nitrogen concentration. In this embodiment, the air compressor 41 is configured to be driven by a battery having a DC voltage of 24V. In this embodiment, the air compressor is driven by a battery having a DC voltage of 24V. However, the air compressor is driven by a crankshaft of an engine, or in the case of a hybrid vehicle, a battery having a DC voltage of 200 to 300V. It may be driven.

  The dryer 24 includes a water vapor separation membrane 24a (FIG. 3) that is easily permeable to water vapor (water) and hardly permeable to air, and a cylindrical housing 24d (FIG. 2) that accommodates the water vapor separation membrane 24a. The water vapor separation membrane 24a is formed by bundling, for example, an aromatic polyimide asymmetric hollow fiber 24b having a film thickness of 100 μm, an outer diameter of 500 μm, and a length of 450 mm, and is housed in a housing 24d extending in the longitudinal direction thereof (see FIG. 2). The hollow fiber 24b has a through hole 24c at the center and has an asymmetrical dense structure in the film thickness direction. The inner diameter of the through hole 24c is, for example, 300 μm. An air inlet 24e for introducing air compressed by the air compressor 23 is formed on the lower surface of the housing 24d, and an air outlet 24f for discharging air dried by the dryer 24 is formed on the upper surface of the housing 24d. It is formed. The air introduction port 24e is connected to the lower end of each hollow fiber 24b of the water vapor separation membrane 24a, and the air discharge port 24f is connected to the upper end of each hollow fiber 24b of the water vapor separation membrane 24a, whereby the air introduction port 24e and the air discharge port 24f is connected in communication with the through hole 24c of each hollow fiber 24b (FIGS. 2 and 3). Further, a purge gas introduction port 24g for introducing a nitrogen-enriched gas, which will be described later, as a purge gas is formed in the upper portion of the side wall of the housing 24d. A purge gas discharge port 24h is formed (FIG. 2). The nitrogen-enriched gas introduced from the purge gas inlet 24g passes through the outer peripheral surface of the hollow fiber 24b of the water vapor separation membrane 24a and is discharged from the purge gas outlet 24h.

  Here, when air containing water vapor (water) flows through the through holes 24c of the hollow fibers 24b of the water vapor separation membrane 24a, the difference in water vapor partial pressure existing on the inner surface side and the outer surface side of the hollow fiber 24b membrane is determined. As driving force, water vapor in the air flowing through the through-hole 24c permeates from the inner surface side of the membrane of the hollow fiber 24b having a high water vapor partial pressure to the outer surface side of the membrane of the hollow fiber 24b having a low water vapor partial pressure. The water vapor in the air flowing through the through hole 24c is reduced, and the dried air is discharged from the air discharge port 24f (FIG. 3).

  On the other hand, the air separator 26 includes an oxygen-enriched film 26a (FIG. 4) having a property of allowing oxygen gas to permeate more easily than nitrogen gas in the atmosphere, and a cylindrical housing 26d (FIG. 4) that accommodates the oxygen-enriched film 26a. 2). The oxygen-enriched film 26a is configured to separate the air dried by the dryer 24 into an oxygen-enriched gas having a high oxygen concentration and a nitrogen-enriched gas having a high nitrogen concentration. Specifically, the oxygen-enriched membrane 26a is formed by bundling hollow fibers 26b made of a polymer that selectively transmits oxygen gas compared to nitrogen gas and having a through hole 26c formed in the center (FIG. 4). ), And is accommodated in the housing 26d extending in the longitudinal direction thereof (FIG. 2). Further, the hollow fiber 26b constituting the oxygen-enriched membrane 26a is preferably formed of a glassy polymer having a high degree of separation between oxygen gas and nitrogen gas, and the degree of separation between oxygen gas and nitrogen gas is particularly large and mechanical. More preferably, it is formed of polyimide having excellent strength, heat resistance and durability. The membrane of the hollow fiber 26b constituting the oxygen-enriched membrane 26a may be a homogeneous membrane having a uniform density in the film thickness direction, or a plurality of hollow fibers having different inner diameters, outer diameters, and densities are inserted. A composite film having a non-uniform density in the film thickness direction may be used, but it is preferable to use an asymmetric film having a high transmission rate by having an asymmetrical dense structure in the film thickness direction. Furthermore, it is preferable that the film thickness of the hollow fiber 26b is set in a range of 10 μm to 500 μm, and the outer diameter of the hollow fiber 26b is set in a range of 50 μm to 2000 μm.

  A dry air inlet 26e for introducing air dried by the dryer 24 is formed on the upper surface of the housing 26d that accommodates the oxygen-enriched film 26a, and nitrogen separated by the air separator 26 is formed on the lower surface of the housing 26d. A nitrogen-enriched gas discharge port 26f for discharging the enriched gas is formed (FIG. 2). The dry air inlet 26e is connected to the upper end of each hollow fiber 26b of the oxygen-enriched membrane 26a, and the nitrogen-enriched gas outlet 26f is connected to the lower end of each hollow fiber 26b of the oxygen-enriched membrane 26a. The inlet 26e and the nitrogen-enriched gas outlet 26f are connected in communication with the through hole 26c of each hollow fiber 26b. An oxygen-enriched gas discharge port 26g for discharging oxygen-enriched gas is formed in the lower portion of the side wall of the housing 26d that accommodates the oxygen-enriched film 26a. By passing through the membrane of the hollow fiber 26b of the oxygen-enriched membrane 26a, the oxygen-enriched gas having an increased oxygen concentration is discharged from the oxygen-enriched gas discharge port 26g.

  Here, the principle of separation into an oxygen-enriched gas having a high oxygen concentration and a nitrogen-enriched gas having a high nitrogen concentration by the oxygen-enriched film 26a will be described. When dry air flows through the through holes 26c of the hollow fibers 26b of the oxygen-enriched membrane 26a, the membrane of the hollow fibers 26b is thermally vibrated to form a gap through which gas passes. Oxygen molecules and nitrogen molecules are taken into the gaps. At this time, the oxygen-enriched membrane 26a is formed to be relatively thin, and the rate at which oxygen molecules permeate through the hollow fiber 26b membrane is about 2.5 times greater than the rate at which nitrogen molecules permeate through the hollow fiber 26b membrane. Oxygen molecules quickly permeate from the inner surface side of the membrane of the hollow fiber 26b having a high partial pressure to the outer surface side of the hollow fiber 26b having a low partial pressure. Thereby, the oxygen concentration on the outer surface side of the membrane of the hollow fiber 26b is increased, and the oxygen concentration on the inner surface side of the membrane of the hollow fiber 26b is decreased. As a result, the oxygen-enriched gas is generated when air passes through the oxygen-enriched film 26a, and the nitrogen-enriched gas is generated when air passes through the oxygen-enriched film 26a without passing through it. The gap formed in the membrane of the hollow fiber 26b by the thermal vibration is about 5 nm.

  On the other hand, the discharge port of the air compressor 23 is connected to the air introduction port 24e of the dryer 24 by the first supply pipe 31, and the air discharge port 24f of the dryer 24 is connected to the dry air introduction port of the air separator 26 by the second supply pipe 32. 26e (FIGS. 1 and 2). Further, the nitrogen-enriched gas discharge port 26f of the air separator 26 is connected to the EGR pipe 19 between the EGR valve 20 and the connection part to the intake pipe 12b by the third supply pipe 33. The third supply pipe 33 includes a nitrogen-enriched gas compressor 34 that supplies nitrogen-enriched gas to the intake pipe 12b, and a nitrogen-enriched gas flow rate adjustment that adjusts the supply amount of the nitrogen-enriched gas to the intake pipe 12b. A valve 35 is provided. In this embodiment, the nitrogen-enriched gas compressor 34 is configured to be driven by a battery having a DC voltage of 24V. The third supply pipe 33, the nitrogen-enriched gas compressor 34, and the nitrogen-enriched gas flow rate adjusting valve 35 constitute a nitrogen-enriched gas supply means 36. The oxygen-enriched gas outlet 26g of the air separator 26 is connected to the purge gas inlet 24g of the dryer 24 by a purge pipe 37, and one end of a drain pipe 38 is connected to the purge gas outlet 24h of the dryer 24. Is provided with a purge flow rate adjusting valve 39 for adjusting the flow rate of the oxygen-enriched gas passing through the purge pipe 37. The purge means 37 is constituted by the purge pipe 37, the drain pipe 38 and the purge flow rate adjusting valve 39. The other end of the drain pipe 38 is connected to the exhaust pipe 16b on the exhaust gas downstream side of the selective reduction catalyst 43 described later. Further, the first supply pipe 31 is provided with an air tank 41 for storing the air compressed by the air compressor 23. The air tank 41 is provided to supply a sufficient amount of air to the air separator 26 and relieve air pressure fluctuations even when the flow rates of the oxygen-enriched gas and the nitrogen-enriched gas are suddenly changed. . In addition, the code | symbol 42 in FIG. 2 is a housing | casing which accommodates each member of the enriched gas production | generation apparatus 22. FIG.

  On the other hand, a selective reduction catalyst 43 made of a silver catalyst is provided in the middle of the exhaust pipe 16b (FIG. 1). The selective reduction catalyst 43 is accommodated in a case 44 having a larger diameter than the exhaust pipe 16b. The selective reduction catalyst 43 is a monolithic catalyst, and is configured by coating a cordierite honeycomb carrier with silver zeolite or silver alumina. Specifically, the selective reduction catalyst 43 made of silver zeolite is configured by coating a honeycomb carrier with a slurry containing zeolite powder obtained by ion exchange of silver. The selective reduction catalyst 43 made of silver alumina is configured by coating a honeycomb carrier with a slurry containing γ-alumina powder or θ-alumina powder supporting silver. In this embodiment, a silver-based catalyst is used as the selective reduction catalyst, but a silver-based catalyst to which palladium is added may be used. That is, the selective catalytic reduction catalyst composed of a palladium-added silver-based catalyst is a monolithic catalyst, and is configured by coating a honeycomb carrier made of cordierite with silver zeolite or silver alumina added with palladium. Specifically, the selective catalytic reduction catalyst made of silver zeolite to which palladium is added is configured by coating a honeycomb carrier with a slurry containing zeolite powder obtained by ion exchange of silver and palladium. The selective reduction catalyst made of silver alumina to which palladium is added is configured by coating a honeycomb carrier with a slurry containing γ-alumina powder or θ-alumina powder supporting silver and palladium. By using a silver-based catalyst to which palladium is added as the selective reduction catalyst, the NOx reduction performance in the exhaust gas at a relatively low exhaust gas temperature can be improved as compared with the case where a silver-based catalyst to which palladium is not added is used.

  On the other hand, a reducing agent supply means 46 for injecting (supplying) the reducing agent 45 to the exhaust pipe 16b is connected to the exhaust pipe 16b upstream of the selective reduction catalyst 43 (FIG. 1). The reducing agent supply means 46 includes a reducing agent injection nozzle 47 that faces the exhaust pipe 16b upstream of the selective reduction catalyst 43, a reducing agent supply pipe 48 having a tip connected to the reducing agent injection nozzle 47, and the reduction agent. A reducing agent tank 49 connected to the proximal end of the reducing agent supply pipe 48 and storing the reducing agent 45; a reducing agent pump 51 that pumps the reducing agent 45 in the reducing agent tank 49 to the reducing agent injection nozzle 47; and a reducing agent. And a reducing agent supply amount adjusting valve 52 that adjusts the supply amount (injection amount) of the reducing agent 45 injected from the injection nozzle 47. As the reducing agent 45, in this embodiment, diesel oil that is the fuel of the diesel engine 11 is used. Accordingly, the reducing agent tank 49 that stores the reducing agent 45 can also be used as the fuel tank of the engine 11. The reducing agent pump 51 is provided in the reducing agent supply pipe 46 between the reducing agent injection nozzle 47 and the reducing agent tank 49, and the reducing agent supply amount adjusting valve 52 is connected between the reducing agent injection nozzle 47 and the reducing agent pump 51. It is provided in the reducing agent supply pipe 48 in between. Further, the reducing agent supply amount adjusting valve 52 is provided in the reducing agent supply pipe 48 and adjusts the supply pressure of the reducing agent 45 to the reducing agent injection nozzle 47, and the base end of the reducing agent injection nozzle 47. And a reducing agent on-off valve 54 that opens and closes the base end of the reducing agent injection nozzle 47.

  The reducing agent pressure regulating valve 53 is a three-way valve having first to third ports 53a to 53c, the first port 53a is connected to the discharge port of the reducing agent pump 51, and the second port 53b is a reducing agent opening / closing valve 54. The third port 53c is connected to the reducing agent tank 49 via the return pipe 56 (FIG. 1). When the reducing agent pressure adjusting valve 53 is turned on, the reducing agent 45 pumped by the reducing agent pump 51 flows into the reducing agent pressure adjusting valve 53 from the first port 53a, and is adjusted to a predetermined pressure by the reducing agent pressure adjusting valve 53. After that, the pressure is fed from the second port 53b to the reducing agent on-off valve 54. When the reducing agent pressure adjusting valve 53 is turned off, the reducing agent 45 pumped by the reducing agent pump 51 flows from the first port 53a into the reducing agent pressure adjusting valve 53 and then passes through the return pipe 56 from the third port 53c. It is returned to the reducing agent tank 49.

  On the other hand, the exhaust pipe 16b between the reducing agent injection nozzle 47 and the selective reduction catalyst 43 flows into the selective reduction catalyst 43, specifically, into the case 44 on the exhaust gas upstream side of the selective reduction catalyst 43. A temperature sensor 57 for detecting the temperature of the immediately preceding exhaust gas is provided (FIG. 1). An NOx sensor 58 that detects the concentration of NOx in the exhaust gas is provided in the exhaust pipe 16b between the turbine housing 17b of the turbocharger 17 and the reducing agent injection nozzle 47. Further, a boost pressure sensor 59 for detecting the boost pressure of the intake turbocharger 17 is provided in the intake pipe 12b between the intercooler 18 and the connection portion to the intake manifold 12a. Furthermore, an air cleaner 61 provided in the vicinity of the air intake of the intake pipe 12b is provided with an intake air amount sensor 62 for detecting the amount of air flowing into the intake pipe 12b (intake air amount). The detection outputs of the temperature sensor 57, the NOx sensor 58, the boost pressure sensor 59, and the intake air amount sensor 62 are connected to the control input of the controller 63. The control output of the controller 63 is the EGR valve 20, the air compressor 23, and the nitrogen enrichment. The gas compressor 34, the nitrogen-enriched gas flow rate adjustment valve 35, the purge flow rate adjustment valve 39, the reducing agent pump 51, the reducing agent pressure adjusting valve 53, and the reducing agent opening / closing valve 54 are connected to each other. The controller 63 is provided with a memory 64. The memory 64 stores the opening of the EGR valve 20 and the operation of the nitrogen-enriched gas compressor 34 according to the exhaust gas temperature at the inlet of the selective catalytic reduction catalyst 43, the NOx concentration in the exhaust gas, and the amount of air flowing into the intake pipe 12b. Presence / absence of the nitrogen-enriched gas flow rate adjustment valve 35, presence / absence of the operation of the reducing agent pump 51, presence / absence of the operation of the reducing agent pressure adjustment valve 53, Stored as a map. Further, the rotational speed of the nitrogen-enriched gas compressor 34 corresponding to the boost pressure of the intake air supercharged by the turbocharger 17 is stored in advance in the memory 64 as a map.

  The operation of the exhaust gas purification apparatus configured as described above will be described. When the engine 11 is started, the controller 63 takes in the detection outputs of the temperature sensor 57, the NOx sensor 58, the boost pressure sensor 59, and the intake air amount sensor 62, and compares these detection outputs with the map stored in the memory 64. The EGR valve 20 is opened at a predetermined opening, the air compressor 23 of the enriched gas generator 22 is operated, the purge flow rate adjusting valve 39 is opened at a predetermined opening, and the nitrogen-enriched gas compressor 34 is opened. And the nitrogen-enriched gas flow rate adjustment valve 35 is opened at a predetermined opening degree. When the air compressor 23 is operated, air in the atmosphere is compressed and stored in the air tank 41. The air is dried after removing water vapor (water) by the dryer 24, and the dried air is separated by the air separator 26 into an oxygen-enriched gas having a high oxygen concentration and a nitrogen-enriched gas having a high nitrogen concentration. The nitrogen-enriched gas separated by the air separator 26 is supplied to the EGR pipe 19 through the third supply pipe 33 by the nitrogen-enriched gas compressor 34. The nitrogen-enriched gas is mixed with the exhaust gas flowing through the EGR pipe 19 to become EGR gas. Since the oxygen concentration and the amount of water contained in the EGR gas are extremely low, when the EGR gas is supplied to the engine 11, NOx in the exhaust gas discharged from the engine 11 can be efficiently reduced. Further, since the oxygen concentration and the amount of water contained in the EGR gas are extremely low, the EGR cooler 21 can be miniaturized and corrosion inside the engine 11 can be prevented. For example, when a part of exhaust gas (EGR gas) is flowing through the EGR pipe 19 at 1200 liters / minute (20 liters / second), a nitrogen-enriched gas having a nitrogen concentration of 99% is supplied from the third supply pipe 33 to the EGR pipe. FIG. 5 shows the calculation results of the rate of reduction of the EGR gas flow rate and the rate of reduction of the moisture content when supplied to 19. As is clear from FIG. 5, for example, when a nitrogen-enriched gas of 100 liters / min is supplied to the EGR pipe 19, the EGR gas flow rate can be reduced by about 13%, and the water content is reduced by about 21%. Thus, the reduction of the EGR gas flow rate leads to the miniaturization of the EGR cooler 21, and the reduction of the moisture content leads to the reduction of the dew condensation water.

  On the other hand, the oxygen-enriched gas separated by the air separator 26 is supplied to the dryer 24 from the purge gas inlet 24g through the purge pipe 37. By supplying this oxygen-enriched gas to the dryer 24, drain water that is water separated by the dryer 24 is extruded and passes through the drain pipe 38 into the exhaust pipe 13 b on the exhaust gas downstream side from the selective reduction catalyst 43. Discharged. Thus, since the dryer 24 is regenerated using an unnecessary oxygen-enriched gas as the EGR gas without using the nitrogen-enriched gas necessary as the EGR gas, the dryer 24 can be efficiently regenerated. Further, since it is not necessary to directly use the air compressed by the air compressor 23 to regenerate the dryer 24, the consumption of the air compressed by the air compressor 23 can be suppressed. As a result, since the discharge capacity of the air compressor 23 can be reduced, the size of the air compressor 23 can be reduced. Note that the oxygen-enriched gas discharged through the drain pipe 38 into the exhaust pipe 13b on the downstream side of the exhaust gas from the selective reduction catalyst 43 is oxidized (combusted) by the relatively high temperature exhaust gas. Disappear.

  When the exhaust gas temperature becomes relatively high (for example, 180 ° C. or more), the controller 63 operates the reducing agent pump 51 of the reducing agent supply means 46 based on the detection output of the temperature sensor 57 to reduce the reducing agent pressure adjustment valve. 53 is turned on, and the reducing agent on-off valve 54 is opened and closed. The reducing agent 45 (fuel) is intermittently injected from the reducing agent injection nozzle 47 by opening and closing the reducing agent opening / closing valve 54. When the mist-like reducing agent 45 injected from the reducing agent injection nozzle 47 is quickly gasified by the relatively high temperature exhaust gas and flows into the selective reduction catalyst 43 together with the exhaust gas, the reducing agent 45 is placed on the selective reduction catalyst 43. As a result, NOx in the exhaust gas is reduced, that is, the reducing agent 45 reacts with NOx in the exhaust gas on the selective catalytic reduction catalyst 43, so that NOx is quickly rendered harmless. As a result, NOx in the exhaust gas can be further reduced.

<Second Embodiment>
6 and 7 show a second embodiment of the present invention. 6 and 7, the same reference numerals as those in FIGS. 1 and 2 denote the same components. In this embodiment, an ozone injection nozzle 81 is provided in the exhaust pipe 16 b between the NOx sensor 58 and the reducing agent injection nozzle 47. The ozone injection nozzle 81 is connected to the enriched gas generator and ozone generator 82. The enriched gas generation and ozone generator 82 includes an air compressor 23 that compresses air in the atmosphere, a dryer 24 that dries the air compressed by the air compressor 23, and air that is dried by the dryer 24. Is separated into an oxygen-enriched gas having a high oxygen concentration and a nitrogen-enriched gas having a high nitrogen concentration, and a part of the nitrogen-enriched gas separated by the air separator 26 is supplied to the EGR pipe 19. A nitrogen-enriched gas supply means 36, a purge means 83 for removing moisture in the dryer using the remainder of the nitrogen-enriched gas separated by the air separator 26, and an oxygen separated by the air separator 26. An ozone generator 86 that converts oxygen in the enriched gas into ozone 90, and ozone supply means 8 that supplies the ozone 90 generated by the ozone generator 86 to the ozone injection nozzle 81. With the door. The air compressor 23, dryer 24, air separator 26 and nitrogen-enriched gas supply means 36 are the same as the air compressor, dryer, air separator and nitrogen-enriched gas supply means of the first embodiment. Composed.

  The purge means 83 is branched from a third supply pipe 33 (to be described later) and connected to a purge gas inlet 24g of the dryer 24, one end connected to the purge gas outlet 24h of the dryer 24, and the other end in the atmosphere. And a purge flow rate adjusting valve 39 which is provided in the purge pipe 84 and adjusts the flow rate of the nitrogen-enriched gas passing through the purge pipe 84. The ozone generator 86 is a silent discharge type in this embodiment. Specifically, although not shown, the ozone generator 86 applies a high-frequency high voltage between a pair of electrodes that are arranged in parallel to each other at a predetermined interval and one or both of which are covered with a dielectric material. A discharge is generated, and a part of oxygen contained in the air is converted into ozone 90 by the plasma discharge. Further, the ozone supply means 87 includes an ozone supply pipe 88 having a base end connected to the ozone discharge port of the ozone generator 86 and a tip connected to the ozone injection nozzle 81, and a check valve 89 provided on the ozone supply pipe 88. It consists of. The check valve 89 is configured to allow the ozone 90 to flow from the ozone generator 86 to the ozone injection nozzle 81 and prevent the ozone 90 or the exhaust gas from flowing from the ozone injection nozzle 81 to the ozone generator 86. The

  On the other hand, the discharge port of the air compressor 23 is connected to the air introduction port 24e of the dryer 24 by the first supply pipe 31, and the air discharge port 24f of the dryer 24 is connected to the dry air introduction port of the air separator 26 by the second supply pipe 32. 26e (FIG. 7). Further, the nitrogen-enriched gas discharge port 26f of the air separator 26 is connected to the EGR pipe 19 between the EGR valve 20 and the connection part to the intake pipe 12b by the third supply pipe 33. The oxygen-enriched gas outlet 26g of the air separator 26 is connected to the oxygen-enriched gas inlet 86a of the ozone generator 86 by a fourth supply pipe 94, and an ozone supply pipe is connected to the ozone outlet 86b of the ozone generator 86. The base ends of 88 are connected. Further, the distal end of the purge pipe 84 whose proximal end branches off from the middle of the third supply pipe 33 is connected to the purge gas inlet 24g of the dryer 24, and one end of the drain pipe 85 is connected to the purge gas outlet 24h of the dryer 24. Reference numeral 96 in FIG. 7 is a housing that houses the enriched gas generation and ozone generator 82, and reference numerals 97 and 98 in FIG. 7 are fans that cool the ozone generator 86. Further, an air tank 41 is provided in the first supply pipe 31 between the air compressor 23 and the dryer 24 as in the first embodiment.

  Returning to FIG. 6, the detection outputs of the temperature sensor 57, NOx sensor 58, boost pressure sensor 59 and intake air amount sensor 62 are connected to the control input of the controller 63, and the control output of the controller 63 is the EGR valve 20, for air Compressor 23, nitrogen enriched gas compressor 34, nitrogen enriched gas flow rate adjustment valve 35, purge flow rate adjustment valve 39, reducing agent pump 51, reducing agent pressure adjustment valve 53, reducing agent opening / closing valve 54, and ozone generator 86, respectively. Connected. The controller 63 is provided with a memory 64. The memory 64 stores the opening degree of the EGR valve 20 and the operation of the nitrogen-enriched gas compressor 34 according to the exhaust gas temperature at the inlet of the selective catalytic reduction catalyst 43, the NOx concentration in the exhaust gas, and the amount of air flowing into the intake pipe. Presence / absence, opening degree of the nitrogen-enriched gas flow rate adjustment valve 35, presence / absence of operation of the reducing agent pump 51, presence / absence of operation of the reducing agent pressure adjustment valve 53, number of opening / closing of the reducing agent on / off valve 54 per unit time The presence or absence of operation of the device 86 is stored in advance as a map. Further, the rotational speed of the nitrogen-enriched gas compressor 34 corresponding to the boost pressure of the intake air supercharged by the turbocharger 17 is stored in advance in the memory 64 as a map. The configuration other than the above is the same as that of the first embodiment.

  The operation of the exhaust gas purification apparatus configured as described above will be described. When the engine 11 is started, the controller 63 takes in the detection outputs of the temperature sensor 57, the NOx sensor 58, the boost pressure sensor 59, and the intake air amount sensor 62, and compares these detection outputs with the map stored in the memory 64. The EGR valve 20 is opened at a predetermined opening, the air compressor 23 of the enriched gas generator 22 is operated, the purge flow rate adjusting valve 39 is opened at a predetermined opening, and the nitrogen-enriched gas compressor 34 is opened. The nitrogen-enriched gas flow rate adjustment valve 35 is opened at a predetermined opening and the ozone generator is operated. When the air compressor 23 is operated, air in the atmosphere is compressed and stored in the air tank 41. The air is dried after removing water vapor (water) by the dryer 24, and the dried air is separated by the air separator 26 into an oxygen-enriched gas having a high oxygen concentration and a nitrogen-enriched gas having a high nitrogen concentration. A part of the nitrogen-enriched gas separated by the air separator 26 is supplied to the EGR pipe 19 through the third supply pipe 33 by the nitrogen-enriched gas compressor 34. A part of the nitrogen-enriched gas is mixed with the exhaust gas flowing through the EGR pipe 19 to become EGR gas. Since the oxygen concentration and the amount of water contained in the EGR gas are extremely low, when the EGR gas is supplied to the engine 11, NOx in the exhaust gas discharged from the engine 11 can be efficiently reduced. Further, since the oxygen concentration and the amount of water contained in the EGR gas are extremely low, corrosion inside the engine 11 and the like can be prevented, and the EGR cooler 21 can be downsized.

  The remainder of the nitrogen-enriched gas separated by the air separator 26 is supplied to the dryer 24 from the purge gas inlet 24g through the purge pipe 84. By supplying the remainder of the nitrogen-enriched gas to the dryer 24, drain water that is water separated by the dryer 24 is extruded and discharged to the atmosphere through the drain pipe 85. As described above, since the dryer 24 is regenerated using the excess nitrogen-enriched gas that is not used as the EGR gas among the nitrogen-enriched gas, the dryer 24 can be efficiently regenerated. Further, since it is not necessary to directly use the air compressed by the air compressor 23 to regenerate the dryer 24, the consumption of the air compressed by the air compressor 23 can be suppressed. As a result, since the discharge capacity of the air compressor 23 can be reduced, the size of the air compressor 23 can be reduced. The reason why the nitrogen-enriched gas that has passed through the drain pipe 85 is directly discharged to the atmosphere is that the nitrogen-enriched gas is not flammable.

On the other hand, the oxygen-enriched gas separated by the air separator 26 is supplied to the ozone generator 86, and a part of the oxygen in the oxygen-enriched gas is converted to ozone by the ozone generator 86, and this ozone is supplied to the ozone supply means. The ozone is supplied to the ozone injection nozzle 81 through the ozone supply pipe 88 of 87. The ozone supplied to the ozone injection nozzle 81 is injected from the ozone injection nozzle 81 into the exhaust pipe 13b. And by this ozone, a part of NO in the exhaust gas is oxidized to NO _{2 as shown} in the following formula (1). When the exhaust gas temperature is in the range of 200 to 250 ° C., the NO ₂ contains a reducing agent 45 (gas containing fuel, oxygenated containing either or both of aldehyde and alcohol described later) in the selective catalytic reduction catalyst 43. And an active reducing agent made of a hydrocarbon-based hydrocarbon).
O ₃ + NO → O ₂ + NO ₂ (1)

Further, when the reducing agent pump 51 is driven, the reducing agent pressure adjusting valve 53 is turned on, and the reducing agent opening / closing valve 54 is opened / closed, the reducing agent 45 intermittently passes through the reducing agent supply pipe 48 to the exhaust pipe 13b. Is injected into. The reducing agent 45 supplied to the exhaust pipe 13b is generated by an ozone generator 86 and supplied to the exhaust pipe 13b by an ozone supply means 87, so that an oxygen-containing carbonization containing either one or both of aldehyde and alcohol is used. Partially oxidized to an active reducing agent consisting of hydrogen. This active reducing agent has reactivity as a NOx reducing agent that reduces NOx (NO and NO ₂ ) in the exhaust gas to N ₂ in the selective catalytic reduction catalyst 43 when the exhaust gas temperature is in the range of 250 to 500 ° C. Has a function to enhance. Here, examples of the aldehyde include acetaldehyde and formaldehyde, and examples of the alcohol include methyl alcohol and ethyl alcohol. Oxygen atoms in ozone are highly reactive, and thus generate oxygen-containing hydrocarbons such as hydrocarbon partial oxides (aldehyde, alcohol, etc.) when reacted with fuels such as light oil.

When the exhaust gas temperature is in the range of 200 to 250 ° C., the controller 63 controls the air compressor 23 and the ozone generator 86 to supply a relatively small amount of ozone to the exhaust pipe 13b. The controller 63 controls the opening / closing interval or opening / closing time of the reducing agent on / off valve 54 and supplies a relatively small amount of the reducing agent 45 to the exhaust pipe 13b. NOx in which part of NO is oxidized to NO ₂ by ozone, a relatively small amount of gasified fuel, and an active reducing agent comprising a relatively small amount of oxygen-containing hydrocarbon such as aldehyde partially oxidized by ozone; However, when supplied to the selective catalytic reduction catalyst 43, NO ₂ in NOx reacts relatively actively with the reducing agent 45 (active reducing agent comprising gasified fuel or oxygen-containing hydrocarbon such as aldehyde). Reduced to N ₂ .

When the exhaust gas temperature rises within a range of 200 to 250 ° C., the controller 63 controls the air compressor 23 and the ozone generator 86 to increase the supply amount of ozone to the exhaust pipe 13b. Further, the controller 63 controls the opening / closing interval or opening / closing time of the reducing agent opening / closing valve 54 to increase the supply amount of the reducing agent 45 to the exhaust pipe 13b. NOx containing NO ₂ increased by an increase in the ozone supply amount, a relatively small amount of gasified fuel, and an active reducing agent comprising an oxygen-containing hydrocarbon such as an aldehyde increased by an increase in the ozone supply amount When supplied to the selective catalytic reduction catalyst 43, NO ₂ in NOx reacts actively with the reducing agent 45 (active reducing agent comprising gasified fuel or oxygen-containing hydrocarbon such as aldehyde) and N _2. As the exhaust gas temperature rises, the NOx reduction rate in the exhaust gas rapidly increases.

When the exhaust gas temperature falls within the range of 250 to 500 ° C., the controller 63 controls the air compressor 23 and the ozone generator 86 to control the supply amount of ozone to the exhaust pipe 13b when the exhaust gas temperature is 200 to 250 ° C. Decrease slightly more. Further, the controller 63 controls the opening / closing interval or opening / closing time of the reducing agent on / off valve 54 so that the supply amount of the reducing agent 45 to the exhaust pipe 13b is approximately the same as when the exhaust gas temperature is 200 to 250 ° C. (however, Change according to the exhaust gas flow rate.) Here, the amount of ozone supplied to the exhaust pipe 13b is slightly reduced because ozone is easily decomposed when the exhaust gas temperature is increased to 250 to 500 ° C., so that ozone is supplied to the high temperature exhaust pipe 13b. This is because part of NO in the exhaust gas is hardly oxidized to NO ₂ by ozone, and the reducing agent 45 is hardly partially oxidized by ozone to an active reducing agent made of an oxygen-containing hydrocarbon such as aldehyde. NOx slightly containing NO ₂ obtained by partial oxidation of NO by ozone, an active reducing agent consisting of oxygen-containing hydrocarbons such as aldehydes, and activity consisting of oxygen-containing hydrocarbons such as aldehydes by ozone When a relatively large amount of fuel gasified without being partially oxidized by the reducing agent is supplied to the selective catalytic reduction catalyst 43, NO ₂ in the NOx is reduced to contain the reducing agent 45 (gasified fuel, aldehyde, etc.). Although it is reduced to N ₂ by reacting with an active reducing agent comprising an oxygen-based hydrocarbon), the NOx reduction rate in the exhaust gas gradually decreases as the exhaust gas temperature rises. As a result, the NOx in the exhaust gas can be reduced relatively efficiently over a wide temperature range where the exhaust gas temperature is 200 to 500 ° C.

  In the first and second embodiments, the exhaust gas purifying apparatus of the present invention is applied to a diesel engine. However, the exhaust gas purifying apparatus of the present invention may be applied to a gasoline engine. In the first and second embodiments, the exhaust gas purification apparatus of the present invention is applied to a turbocharged diesel engine. However, the exhaust gas purification apparatus of the present invention is applied to a naturally aspirated diesel engine or a naturally aspirated gasoline. It may be applied to the engine. In the first and second embodiments, the exhaust manifold and the intake pipe are connected by the EGR pipe. However, the exhaust pipe and the intake pipe or the intake manifold are connected by the EGR pipe, or the exhaust pipe is exhausted by the EGR pipe. A manifold and an intake manifold may be connected. In the first and second embodiments, the air tank is provided between the compressor and the dryer. However, when the flow rates of the oxygen-enriched gas and the nitrogen-enriched gas do not change suddenly, the air tank is provided. It does not have to be. In the first and second embodiments, a mist separator may be provided between the air tank and the dryer. The mist separator collects dust and water droplets contained in the air. In the first and second embodiments, the reducing agent pressure is adjusted by the reducing agent pressure adjusting valve which is a three-way valve. However, the reducing agent on / off valve is not used without using the reducing agent pressure adjusting valve. You may carry out by adjustment of opening / closing time and the presence or absence of the action | operation of a reducing agent pump. In the second embodiment, the ozone injection nozzle is provided in the exhaust pipe between the NOx sensor and the reducing agent injection nozzle. However, the ozone injection nozzle is provided between the reducing agent injection nozzle and the selective reduction catalyst. You may provide in an exhaust pipe. Furthermore, in the second embodiment, the silent discharge type is used as the ozone generator, but the creeping discharge type is used as the ozone generator, the ozone generator is generated by emitting ultraviolet rays to the air, A system that generates ozone by electrolyzing water may be used.

  Furthermore, in the first and second embodiments, light oil (fuel) is used as the reducing agent, but urea water may be used as the reducing agent. In this case, the selective catalytic reduction catalyst is a monolith catalyst, and is configured by coating a cordierite honeycomb carrier with zeolite or zirconia. Examples of zeolite include copper zeolite, iron zeolite, zinc zeolite, and cobalt zeolite. The selective reduction catalyst made of copper zeolite is configured by coating a honeycomb carrier with a slurry containing zeolite powder obtained by ion-exchange of copper. In addition, the selective reduction catalyst made of iron zeolite, zinc zeolite or cobalt zeolite is configured by coating a honeycomb carrier with a slurry containing zeolite powder obtained by ion exchange of iron, zinc or cobalt. Further, the selective reduction catalyst made of zirconia is configured by coating a honeycomb carrier with a slurry containing γ-alumina powder or θ-alumina powder supporting zirconia.

11 Diesel engine (engine)
DESCRIPTION OF SYMBOLS 12 Intake passage 13 Exhaust passage 19 EGR pipe 20 EGR valve 23 Air compressor 24 Dryer 26 Air separator 26a Oxygen-enriched film 36 Nitrogen-enriched gas supply means 40, 83 Purge means 43 Selective reduction catalyst 45 Reductant 46 Reductant Supply means 47 Reducing agent injection nozzle 81 Ozone injection nozzle 86 Ozone generator 87 Ozone supply means 90 Ozone

Claims (5)

An exhaust passage (13) of the engine (11) and an intake passage (12) are connected by bypassing the engine (11), and a part of the exhaust gas of the engine (11) is taken as EGR gas from the exhaust passage (13). An exhaust gas comprising an EGR pipe (19) that recirculates to the intake passage (12), and an EGR valve (20) that is provided in the EGR pipe (19) and adjusts the flow rate of the EGR gas that flows through the EGR pipe (19). In the purification device,
An air compressor (23) for compressing air;
A dryer (24) for collecting moisture contained in the air compressed by the air compressor (23) and drying the air;
An air separator (26) for separating the air dried by the dryer (24) into an oxygen-enriched gas having a high oxygen concentration and a nitrogen-enriched gas having a high nitrogen concentration;
An exhaust gas purification apparatus comprising: a nitrogen-enriched gas supply means (36) for supplying the nitrogen-enriched gas separated by the air separator (26) to the EGR pipe (19). A selective reduction catalyst (43) provided in the exhaust passage (13) downstream of the exhaust gas from the connection portion of the EGR pipe (19) to the exhaust passage (13) and capable of reducing NOx in the exhaust gas to N ₂ ;
An ozone generator (86) for converting oxygen in the oxygen-enriched gas separated by the air separator (26) into ozone (90);
It is provided facing the exhaust passage (13) between the connection portion of the EGR pipe (19) to the exhaust passage (13) and the selective catalytic reduction catalyst (43) and is generated by the ozone generator (86). Ozone injection nozzle (81) for injecting ozone into the exhaust passage (13),
Ozone supply means (87) for supplying ozone generated by the ozone generator (86) to the ozone injection nozzle (81);
A reducing agent (45) provided facing the exhaust passage (13) between the connection portion of the EGR pipe (19) to the exhaust passage (13) and the selective catalytic reduction catalyst (43) is disposed in the exhaust passage. A reducing agent injection nozzle (47) for injecting into (13);
The exhaust gas purifying apparatus according to claim 1, further comprising a reducing agent supply means (46) for supplying the reducing agent (45) to the reducing agent injection nozzle (47).   The air separator (26) has an oxygen-enriched membrane (26a), and the oxygen-enriched gas is generated when the air dried by the dryer (24) passes through the oxygen-enriched membrane (26a). The exhaust gas purifying apparatus according to claim 1, wherein the nitrogen-enriched gas is generated by passing air dried by the dryer (24) without passing through the oxygen-enriched membrane (26a).   The apparatus further comprises purge means (40, 83) for removing moisture in the dryer (24) using a part of the oxygen-enriched gas or the nitrogen-enriched gas separated by the air separator (26). The exhaust gas purification apparatus according to claim 1 or 2.   The exhaust gas purifying apparatus according to claim 2, wherein the reducing agent (45) is fuel or urea water.

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