JP2005337042A - Exhaust gas purification muffler for diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas purification muffler for a diesel engine in which an inflammable substance is burned/removed and a nitrogen oxide is decomposed/removed. <P>SOLUTION: The exhaust gas purification muffler for the diesel engine is constituted of first and second purification mufflers (1, 30) connected in series. The first muffler (1) comprises a decomposition combustion unit (20). The decomposition combustion unit (20) is constituted of donut-like organic fibrous carriers (22, 22, ...) in which goethite or hematite is deposited and carried on a carrier obtained by forming a non-woven fabric-like material of inorganic fiber to a donut-like shape. The second purification muffler is constituted of a ceramic ball (39) carried with nitrogen oxide adsorbent and a nitrogen oxide decomposition catalyst and the ceramic ball (39) is stored in a reticulate vessel (38). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification muffler for a diesel engine, and more specifically, an exhaust gas purification muffler that burns combustibles such as solid carbon particles in exhaust gas discharged from a diesel engine, and an exhaust gas purification muffler that decomposes nitrogen oxides Further, the present invention relates to an exhaust gas purification muffler that burns combustible materials and decomposes nitrogen oxides.

As is well known, exhaust gas discharged from diesel engines contains carbon monoxide, carbon dioxide, hydrocarbons, solid carbon particles, nitrogen oxides, etc., which are one of the causes of air pollution. . In particular, solid carbon fine particles are discharged into the atmosphere as black smoke, which is a cause of environmental pollution. Nitrogen oxides also cause photochemical smocks. Therefore, various exhaust gas purifying apparatuses for removing these pollutants have been proposed. For example, a purification method in which solid carbon particles are burned in a muffler and discharged as carbon dioxide has been proposed.
Patent Document 1 also proposes a cyclone type black smoke removal muffler. This black smoke removal muffler swirls exhaust gas flowing into the casing in the circumferential direction, and the centrifugal force causes the solid carbon particles to be biased and separated in the circumferential direction, thereby purifying the purified gas from which the solid carbon particles have been separated. It discharges from the center to the outside of the housing. In addition, a filter for capturing solid carbon particles separated by centrifugal force is provided on the circumferential portion on the downstream side of the housing.

Japanese Patent Laid-Open No. 9-177541

According to the conventional black smoke removal muffler described above, the solid carbon particles burn in the muffler, so that there is an advantage that there is no emission of black smoke into the atmosphere. However, there is a drawback in that nitrogen oxides that cause other air pollution are discharged. In other words, when solid carbon particles burn in the black smoke removal muffler, the temperature becomes high, so nitrogen in the air and a large amount of oxygen exhausted from the diesel engine cause a chemical reaction to become nitrogen oxides. is there. Such nitrogen oxides can be supplemented by spraying ammonia liquid or the like in the exhaust pipe for stationary large diesel engines, but the ammonia liquid is not recyclable because it is not recyclable. , Become bigger. As a result, it cannot be applied to a diesel engine for vehicles, a diesel engine for small power generation, or the like.
According to the invention described in Patent Document 1, it is recognized that solid carbon particles can be removed to some extent, and a moderate effect is recognized as a muffler for mounting on a vehicle. However, since the solid carbon particles clogged in the filter are removed by energizing the heater provided in the filter and burning it, the removal operation is troublesome, and there are some practical problems. is there.
The present invention has been made in view of the circumstances as described above, and an object thereof is to provide an exhaust gas purification muffler for a diesel engine in which combustibles such as solid carbon particles are burned and removed. Further, another invention provides an exhaust gas purification muffler in which harmful nitrogen oxides are decomposed, and still another invention is a diesel in which both combustibles such as solid carbon particles and nitrogen oxides are removed. It aims at providing the exhaust gas purification muffler for engines.

  In order to achieve the above object, the present invention is applied with a combustion catalyst made of goethite or hematite for burning combustibles such as solid carbon particles and hydrocarbons. Such a combustion catalyst is attached to or carried on a material knitted from inorganic fibers such as ceramic fibers and silica fibers, or a non-woven material three-dimensionally interlaced into a donut shape. A donut-like inorganic fiber carrier carrying a combustion catalyst is packed into a net-like cylinder to constitute a decomposition combustion unit. In another aspect of the invention, a nitrogen decomposition catalyst that adsorbs nitrogen oxides or decomposes them into harmless nitrogen oxides and water and a nitrogen adsorbent are applied to achieve the above object.

Thus, according to the first aspect of the present invention, in order to achieve the above object, the exhaust gas entering from one upstream end is purified inside and exhausted from the other downstream end. A purification muffler comprising a casing and a cracking combustion unit disposed in the casing in the axial direction, wherein the cracking combustion unit is made of a metal having an upstream opening and a downstream end closed by a bottom plate. A net-like cylindrical body, and a donut-like inorganic fiber carrier on which inorganic fibers are three-dimensionally interlaced to form a nonwoven fabric and to which goethite or hematite is attached or supported. The doughnut-shaped inorganic fibrous carrier is packed in the cylindrical body from the bottom plate to the opening. According to a second aspect of the present invention, in the purification muffler according to the first aspect, a positioning projection having a predetermined length is provided in the axial direction from the bottom plate and the opening of the net-like cylindrical body. In the purification muffler according to claim 1 or 2, the outer periphery of the housing is covered with a heat insulating material.
The invention according to claim 4 includes a box body in which the exhaust gas entering from one upstream end is purified inside and exhausted from the other downstream end, A ceramic ball carrying a nitrogen oxide adsorbent and a nitrogen oxide decomposition catalyst is accommodated. The invention according to claim 5 is a box body in which exhaust gas entering from one upstream end is purified inside and discharged from the other downstream end, and a net-like shape in the box And a ceramic ball carrying a nitrogen oxide decomposition catalyst, a baffle plate for preventing an exhaust gas short circuit is provided in the box, and the exhaust gas is in the form of a net. It is comprised so that it may flow in the said ceramic ball accommodated in the container. In the invention described in claim 6, the purification muffler according to any one of claims 1 to 3 and the purification muffler according to claim 4 or 5 are connected in series.

As described above, according to the invention described in claim 1, goethite or hematite is supported on the doughnut-shaped inorganic fibrous support, and packed in the net-shaped cylindrical body to constitute the decomposition combustion unit. And since the decomposition combustion unit comprised in this way is provided in the housing | casing, the carbon monoxide in waste gas is burned and becomes harmless carbon dioxide gas. The oily hydrocarbon flows into the doughnut-shaped inorganic fiber carrier while adhering to the surface of the solid carbon particles, and adheres to and accumulates on the surface and gaps of the inorganic fiber. When deposited, the internal pressure of the doughnut-shaped inorganic fiber carrier increases, and the internal temperature is increased by the exhaust gas, so that the hydrocarbons ignite by the synergistic action of the pressure and temperature. The hydrocarbons and solid carbon particles burn instantly. As a result, a combustible substance in the exhaust gas discharged from the diesel engine is combusted and becomes a harmless gas.
According to another invention, since the ceramic ball carrying the nitrogen oxide adsorbent and the nitrogen oxide decomposition catalyst is housed in the box, the nitrogen oxide is decomposed into nitrogen gas and water, and the nitrogen gas is Adsorbed.
According to the invention in which the purification muffler according to any one of claims 1 to 3 and the purification muffler according to claim 4 or 5 are connected in series, the purification muffler is included in the exhaust gas discharged from the diesel engine. Both harmful combustibles and nitrogen oxides can be removed and purified.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. The purification muffler according to the present embodiment shown in FIG. 1 includes a first purification muffler 1 for decomposing and burning mainly combustibles such as solid carbon particles located on the left side in FIG. The second purification muffler 30 is disposed mainly in order to decompose and remove nitrogen oxides. These first and second purification mufflers 1 and 30 can be used alone, but are usually connected in series and used.

  The first purification muffler 1 for solid carbon particle decomposition combustion comprises a casing 2 having a predetermined diameter and a plurality of solid carbon particle decomposition combustion units 20, 20,... Provided in the casing 2. ing. The casing 2 has a tubular shape as a whole, and a first side plate 3 is detachably attached to an opening on the upstream side, and a second side plate 7 is similarly detachably attached to an opening on the downstream side. It has been. An exhaust gas supply pipe 6 with a flange 5 is provided at a substantially central portion of the first side plate 3, and an exhaust gas exhaust pipe 9 with a flange 8 is provided on the second side plate 7 in the same manner. A heat insulating material 10 is provided on the outer periphery of the housing 2. Thereby, the temperature of the exhaust gas discharged from the diesel engine is maintained at 150 to 20, 20,... 0 ° C., and the oxidation reaction of the chemical substance in the exhaust gas is maintained. Inside the housing 2 configured in this manner, the plate-like first mounting member 11 is spaced from the first side plate 3 by a predetermined distance, and the second side plate 7 is spaced by a predetermined distance. Similarly, a second mounting member 14 having a plate shape is detachably mounted. Between the first side plate 3 and the first mounting member 11 is an exhaust gas distribution chamber 12, and between the second side plate 7 and the second mounting member 14 is an exhaust gas collecting chamber 15. The first mounting member 11 has exhaust gas passage through holes 13, 13,... That have substantially the same diameter as the cracked combustion units 20, 20,. Is opened. The first mounting member 11 is also provided with a plurality of through holes into which a plurality of projections for positioning the decomposition combustion units 20, 20,... Are inserted. Is not shown. The second attachment member 14 is opened except for portions corresponding to the decomposition combustion units 20, 20,. The exhaust gas purified through these openings 16, 16... Flows into the exhaust gas collecting chamber 15. Also, the second mounting member 14 is provided with relatively large-diameter through holes 17, 17,... Into which the positioning projections for the decomposition combustion units 20, 20,.

  As shown in the enlarged view of FIG. 2A, the decomposition combustion unit 20 includes a net-like cylindrical body 21 ′ and a plurality of net-like cylindrical bodies 21 ′ packed therein. It consists of doughnut-shaped inorganic fibrous supports 22, 22,. The net-like cylindrical body 21 ′ is formed in a net shape from a metal wire, preferably a non-rust steel wire or thin rod-like members 21, 21. A donut-shaped lid 25 is attached to the opening on the upstream side. The lid 25 is provided with a plurality of positioning projections 26, 26,... Inserted into the through holes of the first mounting member 11. On the other hand, the downstream end is closed by the bottom plate 27. The bottom plate 27 is provided with a single protrusion 28 for positioning that is inserted into the through hole 17 of the second mounting member 14.

As shown in FIG. 2B, the doughnut-shaped inorganic fiber carrier 22 is made of a material in which inorganic fibers such as silica fibers and ceramic fibers are knitted, or three-dimensionally interlaced. The non-woven fabric material has a through hole 23 with a predetermined diameter inside, and is formed in a donut shape as a whole so as to have a predetermined length, that is, a thickness T, radially outward from the through hole 23. . The donut-shaped inorganic fiber carrier 22 thus configured is subjected to a combustion catalyst treatment. Specifically, goethite (—FeOOH) or hematite (Fe ₂ O ₃ ) obtained by dehydration reaction of goethite is immersed in water and pulled up and dried. As a result, a doughnut-shaped inorganic fiber carrier 22 in which goethite or hematite is attached or supported on the surface of the nonwoven fabric of inorganic fibers, gaps between the inorganic fibers, or the like is obtained. The doughnut-shaped inorganic fiber carriers 22, 22,... Configured in this way are sequentially packed into the net-like cylindrical body 21 ′ from the bottom plate 27. Then, the lid body 25 is attached. The cracked combustion unit 20 thus obtained is shown in FIG.

  The decomposition combustion units 20, 20,... Configured as described above are mounted in the housing 2 as follows, for example. That is, the protrusion 28 of the bottom plate 27 of the decomposition combustion unit 20 is inserted into the through hole 13 of the second mounting member 14. As a result, one end of the decomposition combustion unit 20 is positioned and attached to the second attachment member 14. Similarly, the required number of cracked combustion units 20, 20,... Are attached. Next, the plurality of protrusions 26, 26,... Of the lid body 25 of the decomposition combustion unit 20 are inserted into the through holes of the first mounting member 11. Thereby, the both ends of the decomposition combustion units 20, 20,... Are held by the first and second mounting members 11, 14. The first and second attachment members 11 and 14 are fixed in the housing 2. The assembled state is shown in FIG.

  Next, the operation of the first purification muffler 1 for removing the solid carbon particles will be described. Although not shown in FIG. 1, the casing 2 is attached to the exhaust port of the diesel engine via a flange 5. The exhaust gas discharged from the diesel engine is appropriately supplied from the exhaust gas distribution chamber 12 into the plurality of cracked combustion units 20, 20,. The exhaust gas contains carbon monoxide CO, hydrocarbon HC, solid carbon particles, nitrogen oxides NOx and the like. On the other hand, the temperature of the exhaust gas is 150 to 200 ° C., and the inside of the housing 2 is kept at substantially the same temperature.

The goethite (-FeOOH) supported on the doughnut-shaped inorganic fiber support 22 of the cracking combustion unit 20 is transformed into hematite (Fe ₂ O ₃ ), that is, iron oxide by a dehydration reaction in a heated state of about 220 ° C. Oxygen is released during the process of transition from hematite to magnetite (Fe ₃ O ₄ ) at about 300 ° C. This oxygen oxidizes or burns organic matter. Magnetite adsorbs oxygen and returns to hematite. In the doughnut-shaped inorganic fibrous carrier 22, a cycle is formed between the hematite and the magnetite as described above, and carbon monoxide in the exhaust gas is
It is oxidized to carbon dioxide gas by CO + O ₂ = CO ₂ and flows to the downstream exhaust gas collecting chamber 15. Nitrogen oxide NOx flows through the doughnut-shaped inorganic fiber carriers 22, 22,... To the exhaust gas collecting chamber 15.

The hydrocarbon HC is an oil, flows into the doughnut-shaped inorganic fiber carriers 22, 22,... While adhering to the surface of the solid carbon particles, and the donut-shaped inorganic fiber carriers 22, 22,. It adheres and accumulates on the surface of inorganic fibers, gaps, and the like. The internal pressure of the accumulated doughnut-shaped inorganic fiber carriers 22, 22, ... rises due to the pressure of exhaust gas discharged from the diesel engine. Then, since the inside of the donut-shaped inorganic fiber carriers 22, 22,... Is at a high temperature such as 150 to 200 ° C., the hydrocarbon HC is ignited by a synergistic action with the pressure. Since the inside of the doughnut-shaped inorganic fiber carriers 22, 22,... Is rich in oxygen, the adhering hydrocarbon HC and solid carbon particles are
2HC + O ₂ = H ₂ C + CO ₂
By C + O ₂ = CO ₂ , the fuel burns instantaneously, becomes dihydrocarbon and carbon dioxide, and flows into the exhaust gas collecting chamber 15. By this combustion, the doughnut-shaped inorganic fiber carriers 22, 22,... Return to the state before adhesion. Thereafter, carbon monoxide, hydrocarbons, solid carbon particles and the like are combusted and purified in the same manner. Then, it is discharged from the exhaust gas collecting chamber 15 to the outside together with nitrogen oxide from the exhaust gas discharge pipe 9.

  Next, returning to FIG. 1 again, an embodiment of the second purification muffler 30 will be described. The second purification muffler 30 according to the present embodiment decomposes nitrogen oxide into nitrogen gas and water, and discharges the outside. As shown in FIG. The outer box 41 has a larger diameter than the inner box 31. A ceramic ball carrying a nitrogen oxide adsorbent and a nitrogen oxide decomposition catalyst is accommodated in the inner box 31. The upstream side of the inner box 31 is open, and the opening is sealed with a lid 33 with a supply pipe 32. Further, the downstream side is throttled to form an exhaust pipe 34. The first to third baffle plates 35 to 37 for preventing the exhaust gas from being short-circuited are provided in the inner box 31 thus configured in a vertical direction at a predetermined interval. More specifically, the first and third baffle plates 35 and 37 extend from the bottom to a predetermined height, and the second baffle plate 36 extends from the top to a predetermined position. As a result, the exhaust gas flows detoured as indicated by the arrow. A net-like container 38 is attached between the baffle plates 35 and 37, and a ceramic ball 39 carrying a nitrogen oxide adsorbent and a nitrogen oxide decomposition catalyst is accommodated in the net-like container 38. . An outside air passage 42 is provided between the inner box 31 and the outer box 41, and the outside air that has entered from the upstream intake port 43 is guided toward the exhaust pipe 34.

  The ceramic balls 39 carrying the nitrogen oxide adsorbent and the nitrogen oxide decomposition catalyst 39 are produced as follows. That is, a granulated product having a diameter of 5 to 7 mm is made from clay containing zeolite, and a mixed portion composed of rhodium Rh, cerium Ce, magnesium Mg, and manganese dioxide is supported on the surface, and then fired at about 800 ° C. To do. Palladium Pb can be used instead of rhodium.

The second purification muffler 30 operates as follows. That is, it has been confirmed that cerium oxide CeO ₃ stably adsorbs nitrogen oxides. Manganese dioxide has been recognized to oxidize nitric oxide NO. Therefore, when the exhaust gas containing nitrogen oxide enters the inner box 31 of the second purification muffler 30 and comes into contact with the ceramic ball 39, the nitrogen oxide is efficiently adsorbed. The mixture of cerium oxide and manganese dioxide exhibits a catalytic effect even at a relatively low temperature such as 150 ° C. On the other hand, palladium has a high hydrogen activity, hydrogen activated by palladium is released onto the mixture of cerium oxide and manganese dioxide, and the nitrogen oxides adsorbed on the cerium oxide are converted into nitrogen gas N ₂ and water H ₂ O. Disassembled. The harmless exhaust gas is discharged from the inner box 31 to the outside through the exhaust pipe 34. At this time, it is diluted or lowered in temperature by the outside air introduced from the outside air passage 42 and discharged to the outside.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the embodiment shown in FIG. 1, a plurality of decomposition combustion units 20 are provided, but it is obvious that even a single decomposition unit can be implemented. It is also clear that the net-like cylindrical body 21 'is not limited to the illustrated embodiment, and can be implemented in a polygonal shape. Furthermore, the shape and structure of the first and second purification mufflers 1 and 30 are not limited to the illustrated embodiment. In the embodiment shown in FIG. Although the diameters of the two purification mufflers 1 and 30 are different, it is also clear that they can be carried out with the same diameter. Furthermore, it can be carried out without a heat insulating material.

  As described above, the first purification muffler 1 according to the present embodiment burns combustible materials such as solid carbon particles and hydrocarbons, and the second purification muffler 30 adsorbs nitrogen oxides or nitrogen gas. Since these are decomposed into water, if they are connected in series, the exhaust gas discharged from the diesel engine can be purified or rendered harmless. At this time, by connecting so that the outside air passage 42 is secured, outside air is sucked by the ejector effect, and the temperature of the inner box 31 is lowered.

1 is a cross-sectional view schematically showing an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which expands and shows the decomposition | disassembly combustion unit concerning embodiment of this invention, The (a) is a perspective view which shows the whole, The (b) is a perspective view which shows the element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st purification muffler 2 Case 10 Heat insulating material 20 Decomposition combustion unit 21 'Net-like cylindrical body 22 Donut-shaped inorganic fibrous carrier 26 Positioning projection 28 Positioning projection 30 Second purification muffler 39 Nitrogen oxide adsorbent and Nitrogen oxide decomposition Ceramic ball with catalyst

Claims (6)

From a casing in which exhaust gas entering from one upstream end is purified inside and discharged from the other downstream end, and a cracking combustion unit disposed in the casing in the axial direction A purifying muffler,
The cracking combustion unit is formed into a non-woven fabric by three-dimensionally intermingling inorganic fibers with a metal net-like cylindrical body that is open on the upstream side and closed on the bottom end with a bottom plate. It consists of a donut-shaped inorganic fibrous carrier to which site or hematite is attached or supported,
An exhaust gas purification muffler for a diesel engine, characterized in that the doughnut-shaped inorganic fiber carrier is packed in the net-like cylindrical body from its bottom plate to an opening.   The exhaust muffler for a diesel engine according to claim 1, wherein a positioning projection having a predetermined length is provided in the axial direction from the bottom plate and the opening of the net-like cylindrical body.   The exhaust muffler for a diesel engine according to claim 1 or 2, wherein the outer peripheral portion of the casing is covered with a heat insulating material.   An exhaust gas entering from one upstream end is purified inside and exhausted from the other downstream end, and the nitrogen oxide adsorbent and nitrogen oxide are contained in the box An exhaust gas purification muffler for a diesel engine, characterized in that a ceramic ball carrying a cracking catalyst is accommodated. The exhaust gas entering from one upstream end is purified inside and exhausted from the other downstream end, and the nitrogen oxidation stored in a net-like container inside the box Consisting of ceramic adsorbent and ceramic ball carrying nitrogen oxide decomposition catalyst,
A baffle plate for preventing an exhaust gas short circuit is provided in the box, and the exhaust gas is configured to flow through the ceramic balls housed in the net-like container. Purification muffler.   An exhaust gas purification muffler for a diesel engine, wherein the purification muffler according to any one of claims 1 to 3 and the purification muffler according to claim 4 or 5 are connected in series.

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