JP2006200520A - Purifying device, purifying method and exhaust emission control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a purifying device enabling removal of diesel particulates included in exhaust gas and capable of efficiently performing such purification. <P>SOLUTION: A solid electrode 1 having oxygen ion electrical conductivity and an impressing means 2 impressing voltage between both faces of the solid electrode 1 are provided. The impressing means 2 impresses voltage such that one face 10 side of the solid electrode 1 on which diesel particulates are accumulated is an anode side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a purification device, a purification method for purifying unburned fine particles (diesel fine particles) and nitrogen oxides discharged from a combustor, and an exhaust gas purification system for purifying exhaust gas containing diesel fine particles and nitrogen oxides. About.

  Currently, the main role of logistics that supports people's lives and corporate activities is transported by truck, which is indispensable for economic activities. The diesel engine that powers the truck has higher thermal efficiency than other heat engines, and is effective for energy saving and global warming. However, diesel engines emit large amounts of air pollutants such as nitrogen oxides (NOx) and particulate matter (PM), and trucks have a considerable impact on environmental issues. Therefore, there is a need for efforts to disseminate diesel engines with low environmental impact and peripheral equipment, maintain economic activities, and further develop them.

Currently, there are a PM purification method using a filter and a NOx purification method using a catalyst as known purification methods for purifying NOx and PM discharged from a diesel engine.
Also, as an exhaust gas purification system using a solid electrolyte, an electrode containing a catalyst is laminated on both sides of the solid electrolyte, and combustion gas containing nitrogen oxide is supplied to the cathode side of the solid electrolyte, so that the decomposition process of nitrogen oxide There is a method in which the nitrogen oxides can be decomposed and removed by forcibly removing the active oxygen generated in step 1 through the solid electrolyte. However, this does not purify PM.

The conventional PM purification method has a problem of how to remove and regenerate the fine particles accumulated on the filter. There is a continuous regeneration type trap that is one of the continuous regeneration type systems that oxidizes NO in exhaust gas to NO ₂ and oxidizes fine particles collected on the filter by this NO ₂ . However, when the exhaust gas temperature does not reach 250 ° C., fine particles are not oxidized, and a separate NO purifier is required. DPNR (Diesel Particulate-NOx Reduction System) is a porous ceramic filter that supports a NOx occlusion reduction catalyst, which oxidizes PM by oxygen radicals generated during NOx occlusion and periodically and instantaneously injects fuel. There is a method of increasing the amount and reducing NOx adsorbed by CO and HC discharged at that time. However, this method requires delicate and accurate fuel injection control, and has problems such as deterioration of durability, high cost, and deterioration of fuel consumption.
Furthermore, conventionally known purification methods are insufficient to meet the exhaust gas standards of diesel engines that will be established in the future.

  The present invention has been made in view of the above problems, and provides a purification device and a purification method that can purify particulate matter and nitrogen oxides contained in exhaust gas, and perform purification efficiently. Furthermore, it aims at providing the exhaust gas purification system which enables purification | cleaning of both the particulate matter and nitrogen oxide in exhaust gas.

  In order to achieve the above object, the purification apparatus of the present invention comprises a solid electrolyte having oxygen ion conductivity and a voltage between both surfaces of the solid electrolyte so that one side of the solid electrolyte on which diesel particulates are deposited is the anode side. And an applying means for applying. According to the purification apparatus having such a configuration, by applying a voltage between both surfaces of the solid electrolyte by an application means, oxygen ions can be supplied from the cathode side to the anode side through the solid electrolyte and deposited on the anode side. The solid carbonaceous fine particles in the diesel fine particles can be oxidized to form carbon oxides. For example, it is possible to purify the exhaust gas by setting the cathode side surface of the solid electrolyte to the atmosphere side (atmosphere release side) and the anode side solid electrolyte surface to the exhaust gas side containing diesel particulates.

  Further, the solid electrolyte is provided with an electrode on the other side of the cathode, and when diesel particulates are deposited on one side of the solid electrolyte, the diesel particulates are energized by the application means, and the solid particles in the diesel particulates are energized. The carbonaceous fine particles themselves are preferably used as the anode. According to this configuration, when a certain amount of diesel particulates accumulates on one side of the solid electrolyte, the solid carbonaceous particulates in the diesel particulates are conductive, so energization is started and oxygen ion supply starts from the cathode side. Is done. Thereby, purification of diesel particulates including solid carbonaceous particulates on one side of the solid electrolyte is automatically started. Therefore, no electrode is required on the surface of the solid electrolyte that is on the anode side, and the cost can be reduced. Furthermore, since a certain amount of diesel particulates is deposited and is automatically energized when purification is required, the running cost can be reduced.

Further, the purifying device of the present invention comprises a solid electrolyte having oxygen ion conductivity, and an application means for applying a voltage between both surfaces of the solid electrolyte so that one side of the solid electrolyte on which diesel particulates are deposited is the anode side. And an adsorbent provided on one side of the solid electrolyte for adsorbing nitrogen oxides and an oxidation catalyst provided on the one side of the solid electrolyte.
According to the purification apparatus having such a configuration, by applying a voltage between both surfaces of the solid electrolyte by an application means, oxygen ions can be supplied from the cathode side to the anode side through the solid electrolyte and deposited on the anode side. The solid carbonaceous fine particles in the diesel fine particles can be oxidized to form carbon oxides containing carbon monoxide. Furthermore, the nitric oxide contained in the exhaust gas can be oxidized into nitrogen dioxide by the oxidation catalyst, and this nitrogen dioxide can be adsorbed by the adsorbent. The nitrogen dioxide adsorbed on the adsorbent can be reduced with carbon monoxide obtained by oxidizing the solid carbonaceous fine particles in the diesel fine particles to form nitrogen gas, and the carbon monoxide can be converted to carbon dioxide. Accordingly, it is possible to simultaneously purify both the solid carbonaceous fine particles and the nitrogen oxide in the diesel fine particles. For example, it is possible to purify the exhaust gas by setting the cathode side surface of the solid electrolyte to the atmosphere side (atmosphere release side) and the anode side solid electrolyte surface to the exhaust gas side containing diesel particulates.

  Furthermore, in this case, it is preferable that the applying means has switching means for periodically inverting the polarity of the applied voltage. According to this configuration, by reversing the polarity so that the other surface side (atmosphere side) of the solid electrolyte is the anode side, among the active oxygen generated when the nitrogen monoxide contained in the exhaust gas is adsorbed by the adsorbent Excess active oxygen can be moved to the cathode side. As a result, it is possible to prevent the nitrogen gas obtained by reducing the nitrogen dioxide adsorbed on the adsorbent on the one side of the solid electrolyte that is intended for purification from being again converted into nitrogen oxides by active oxygen. It becomes possible.

Further, the purification apparatus of the present invention comprises a solid electrolyte having oxygen ion conductivity and both sides of the solid electrolyte such that one side of the solid electrolyte on which unburned fine particles discharged from the combustor are deposited is the anode side. And an applying means for applying a voltage between them.
According to the purification apparatus having such a configuration, by applying a voltage between both surfaces of the solid electrolyte by an application means, oxygen ions can be supplied from the cathode side to the anode side through the solid electrolyte and deposited on the anode side. The solid carbonaceous fine particles in the fine particles can be oxidized to form carbon oxides. For example, the exhaust gas can be purified by setting the cathode side surface of the solid electrolyte to the atmosphere side (atmosphere release side) and the anode side solid electrolyte surface to the exhaust gas side containing fine particles. The unburned fine particles discharged from the combustor include, for example, those discharged from a diesel engine, a gasoline engine (direct injection type gasoline engine), a boiler or an industrial furnace.

Moreover, the purification apparatus of the present invention includes a solid electrolyte having ionic conductivity and capable of supplying oxygen ions to one side, and a first electrode and a second electrode provided on one side and the other side of the solid electrolyte, respectively. The purification structure has a structure in which exhaust gas containing unburned fine particles discharged from a combustor is passed from the first electrode side to the second electrode side to pass the fine particles to the first electrode. The first electrode side is an oxidation part that oxidizes the collected fine particles with oxygen ions given to the first electrode side by the solid electrolyte. It is characterized by having.
According to this configuration, since the purification structure is made porous, the fine particles can be collected on the first electrode side by passing the exhaust gas containing unburned fine particles through the purification structure ( Can be filtered). Then, on the first electrode side, the solid carbonaceous fine particles in the collected fine particles can be oxidized with oxygen ions provided by the solid electrolyte to form a carbon oxide.

  Moreover, in this purification apparatus, the second electrode side of the purification structure is a reducing unit that reduces nitrogen oxides contained in the exhaust gas that has permeated the purification structure. Thereby, by moving ions in the solid electrolyte, in the oxidation part on the first electrode side, the solid carbonaceous fine particles in the unburned fine particles can be oxidized into carbon oxides, In this reducing section, nitrogen oxides contained in the exhaust gas can be reduced to nitrogen gas. Thus, simultaneous purification (simultaneous decomposition) of solid carbonaceous fine particles and nitrogen oxides in the exhaust gas becomes possible.

  Furthermore, it is preferable that an adsorbent for adsorbing the nitrogen oxide is provided on the second electrode side of the purification structure. Thereby, the nitrogen oxide contained in the exhaust gas that has passed through the purification structure is adsorbed on the second electrode side. And this nitrogen oxide can be reduce | restored by moving ion from the 2nd electrode side to the 1st electrode side with a solid electrolyte.

  Alternatively, it is preferable that ceria or ceria oxide is provided on the second electrode side of the purification structure. Thereby, the nitrogen oxide contained in the exhaust gas that has passed through the purification structure can be reduced on the second electrode side.

The purification structure is switched between a state in which a voltage is applied between both electrodes so that the first electrode side is the anode side, and a state in which the application is stopped between both electrodes to form a closed circuit. It is preferably connected to possible control means.
According to this configuration, when the temperature of the exhaust gas is high, the purification structure (solid electrolyte) can be operated as a fuel cell by burning the solid carbonaceous fine particles collected on the first electrode side. . For this reason, by stopping application between the two electrodes to form a closed circuit, ions can be transferred without supplying electric energy to the purification structure, and solid carbonaceous fine particles and nitrogen oxides A purification process can be performed. When the temperature of the exhaust gas is low, a voltage is applied between the electrodes to move the ions, so that oxygen ions are given on the first electrode side to oxidize the solid carbonaceous fine particles, and the second electrode On the side, nitrogen oxides are reduced.

  Further, in the purification method of the present invention, a voltage is applied between both surfaces of a solid electrolyte having oxygen ion conductivity, oxygen ions are supplied from the cathode side to the anode side, and the oxygen ions are present on the anode side of the solid electrolyte. It is characterized by oxidizing diesel particulates. According to the purification method having such a configuration, by applying a voltage between both surfaces of the solid electrolyte, the solid carbonaceous fine particles in the diesel fine particles deposited on the anode side can be oxidized to form a carbon oxide. For example, it is possible to purify the exhaust gas by setting the cathode side surface of the solid electrolyte to the atmosphere side (atmosphere release side) and the anode side solid electrolyte surface to the exhaust gas side containing diesel particulates.

  Further, in the purification method of the present invention, a voltage is applied between both surfaces of a solid electrolyte having oxygen ion conductivity, oxygen ions are supplied from the cathode side to the anode side, and the oxide ions exist on the anode side of the solid electrolyte. The diesel particulates are oxidized to form carbon oxides containing carbon monoxide, and the nitric oxide present in the exhaust gas together with the diesel particulates is oxidized on the anode side of the solid electrolyte using an oxidation catalyst to form nitrogen dioxide. The nitrogen dioxide is adsorbed on the anode side, and the adsorbed nitrogen dioxide is reduced by the carbon monoxide.

  According to the purification method having such a configuration, by applying a voltage across the solid electrolyte, the solid carbonaceous fine particles in the diesel fine particles deposited on the anode side can be oxidized into carbon oxides. That is, for example, carbon monoxide can be used. Furthermore, the oxidation catalyst can promote the oxidation of the nitric oxide by nitrogen monoxide and oxygen contained in the exhaust gas, and the obtained nitrogen dioxide can be adsorbed. The adsorbed nitrogen oxide can be reduced to nitrogen gas by the carbon monoxide obtained by oxidizing the solid carbonaceous fine particles in the diesel fine particles. Therefore, it is possible to simultaneously purify both diesel particulates and nitrogen oxides.

Further, the purification method of the present invention allows the exhaust gas containing unburned fine particles to pass from the one side to the other side of the porous solid electrolyte having ionic conductivity and capable of supplying oxygen ions to one side. The fine particles are collected on the one surface side, and the collected fine particles are oxidized by the oxygen ions given to the one surface side by the solid electrolyte.
According to this method, the exhaust gas containing unburned fine particles is passed through the porous solid electrolyte so that the fine particles can be collected on the one surface side. Then, the solid carbonaceous fine particles in the collected fine particles can be oxidized on one side to form a carbon oxide.

  Moreover, in this case, nitrogen oxides contained in the exhaust gas that has permeated to the other surface side of the solid electrolyte can be reduced on the other surface side. Therefore, by moving ions in the solid electrolyte, the solid carbonaceous fine particles in the unburned fine particles can be oxidized on one side of the solid electrolyte to form carbon oxides, and at the same time, the exhaust gas is emitted on the other side. The nitrogen oxides contained in can be reduced to nitrogen gas. That is, simultaneous purification of solid carbonaceous fine particles and nitrogen oxides in the exhaust gas is performed.

  Furthermore, an exhaust gas purification system of the present invention includes an exhaust passage that allows exhaust gas containing diesel particulates and nitrogen oxides to pass through, and an exhaust gas purification device that is provided in a part of the exhaust passage. In the purification system, the exhaust gas purification device is provided with a solid electrolyte having one surface side in contact with the exhaust gas from the exhaust passage and the other surface side in the atmosphere and having oxygen ion conductivity, An adsorbent provided on the one surface side of the fixed electrolyte to adsorb nitrogen oxides, an oxidation catalyst provided on one surface side of the solid electrolyte, and the one surface side of the solid electrolyte as an anode side and the other surface side And an applying means for applying a voltage between both surfaces of the solid electrolyte so that the cathode is on the cathode side.

  According to the exhaust gas purification system having such a configuration, it is possible to simultaneously purify both diesel particulates and nitrogen oxides contained in the exhaust gas flowing through the exhaust passage, and to reduce them. In other words, in the exhaust gas purifying device, by applying a voltage across the solid electrolyte, the solid carbonaceous fine particles contained in the diesel fine particles deposited on the anode side are oxidized to form a carbon oxide containing carbon monoxide. be able to. Furthermore, the oxidation catalyst can promote the oxidation of nitric oxide by nitrogen monoxide and oxygen contained in the exhaust gas, and the obtained nitrogen dioxide can be adsorbed. The adsorbed nitrogen oxide can be reduced to nitrogen gas by the carbon monoxide obtained by oxidizing the solid carbonaceous fine particles in the diesel fine particles.

  Further, the exhaust gas purification system of the present invention includes an exhaust passage through which exhaust gas containing unburned particulates and nitrogen oxides discharged from a combustor passes, and an exhaust gas provided in a part of the exhaust passage. An exhaust gas purification system comprising a purification device, the exhaust gas purification device comprising: a solid electrolyte having ionic conductivity and capable of supplying oxygen ions to one side; and one side and the other side of the solid electrolyte And a purification structure having a first electrode and a second electrode respectively provided on the side, wherein the purification structure allows exhaust gas from the exhaust flow path to flow from the first electrode side to the second electrode side. The fine particles can be collected on the first electrode side by passing through, and the collected fine particles are applied to the first electrode side by the solid electrolyte on the first electrode side. Acid by oxygen ions It is an oxidized portion for, and the second electrode side is characterized in that there is a reduced section for reducing nitrogen oxides contained in the exhaust gas having passed through the purifier structure.

  According to this configuration, both unburned particulates and nitrogen oxides contained in the exhaust gas flowing through the exhaust passage can be simultaneously purified on one side and the other side of the purification structure, respectively. Reduction is possible. By passing the exhaust gas flowing into the exhaust gas purification device through the porous purification structure, unburned particulates can be automatically collected on the first electrode side of the purification structure. That is, since unburned fine particles can be collected by filtering the flowing exhaust gas in the purification structure, a separate energy source for collecting the fine particles can be eliminated. Then, on the first electrode side of the purification structure, the solid carbonaceous fine particles contained in the collected unburned fine particles can be oxidized to carbon dioxide. Furthermore, on the second electrode side, nitrogen oxides contained in the exhaust gas that has passed through the purification structure can be reduced to nitrogen gas.

  According to the present invention, it is possible to efficiently perform oxidation of diesel particulates, reduction of nitrogen oxides, and simultaneous treatment of these by injection of extremely minute energy, and it is possible to achieve purification of exhaust gas at a high level. . Therefore, if this purification device, purification method, and exhaust gas purification system are applied to purification of exhaust gas from a diesel engine, exhaust gas can be purified while maintaining high thermal efficiency of the diesel engine, which can be useful for environmental protection. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a model diagram showing a purification device according to an embodiment of the present invention. This purification device is for purifying diesel particulates contained in, for example, exhaust gas, and can purify solid carbonaceous particulates (particulate matter) M in diesel particulates, and solid carbonaceous particulates. It is an apparatus for purifying by oxidizing carbon contained in M. Furthermore, this apparatus can also process hydrocarbon fine particles in the diesel fine particles.
The apparatus shown in FIG. 1 includes a solid electrolyte 1 having oxygen ion conductivity and application means 2 for applying a voltage between both surfaces of the solid electrolyte 1.

  The solid electrolyte 1 shown in FIG. 1 has a panel shape, and the first electrode 3 is laminated on one surface 10 and the second electrode 4 is laminated on the other surface 11. As the solid electrolyte 1, for example, one used in a fuel cell can be applied, and oxygen ions can be moved by applying a potential difference to both ends of the solid electrolyte 1. In addition, the first electrode 3 and the second electrode 4 are formed into a plate shape by a material used as a normal electrode, but both the first electrode 3 and the second electrode 4 are porous so as to have oxygen permeability. It is an electrode.

  The applying means 2 can be a commonly used DC power supply, and preferably has a variable voltage. The applying means 2 applies a voltage between both surfaces of the solid electrolyte 1 so that the first electrode 3 provided on the one surface 10 side of the solid electrolyte 1 serves as an anode and the second electrode 4 provided on the other surface 11 side serves as a cathode. . The voltage applied by the applying means 2 depends on the electrical characteristics of the solid electrolyte 1 and the ambient temperature. For example, in the case of yttrium-stabilized zirconia, it is 10 volts or less at an atmospheric temperature of 350 ° C.

This purification device can be provided in an exhaust passage (not shown) for flowing exhaust gas discharged from a diesel engine, for example, and is provided so that one surface 10 side of the solid electrolyte 1 faces the exhaust passage. The one surface 10 side is an exhaust gas side G. The solid electrolyte 1 is provided so that the other surface 11 side of the solid electrolyte 1 faces the atmosphere side (atmosphere release side) A.
A deposition surface 12 on which diesel particulates are deposited is formed on the one surface 10 side which is the anode side of the solid electrolyte 1, and the outer surface of the first electrode 3 is a deposition surface 12 in FIG. 1. The outer surface of the first electrode 3 is the surface opposite to the contact surface with the solid electrolyte 1.

In the purification method using this purification device, diesel particulates are deposited on the deposition surface 12 on the one surface 10 side of the solid electrolyte 1, and a predetermined voltage is applied between both surfaces of the solid electrolyte 1 by the applying means 2, whereby the cathode side Oxygen ions are supplied from the anode to the anode side. The oxygen ions are used to oxidize diesel particulates present on the deposition surface 12 on the anode side. That is, oxygen contained in the atmosphere side A that is the cathode side is supplied as oxygen ions to the exhaust gas side G that is the anode side. Thereby, carbon contained in the solid carbonaceous fine particles M in the diesel fine particles is continuously oxidized to carbon monoxide and carbon dioxide (C + O ₂ → CO ₂ , 2C + O ₂ → 2CO), and the solid carbonaceous fine particles M are purified ( Disassembled). In addition, the arrow in the solid electrolyte 1 has shown the moving direction of oxygen ion.

  The purification device shown in FIG. 2 is obtained by omitting the first electrode 3 of the purification device of FIG. 1, and the other configurations are the same. That is, the electrode 4 that is the cathode side is provided only on the other surface 11 side of the solid electrolyte 1. This purification device utilizes the fact that the solid carbonaceous fine particles M in the diesel fine particles have conductivity, and the surface 10 of the solid electrolyte 1 is directly attached to the deposition surface 12 of the solid carbonaceous fine particles M contained in the diesel fine particles. When a certain amount of diesel particulates (solid carbonaceous particulates M) are deposited on one surface 10 of the solid electrolyte 1 and energization is started by the applying means 2, the cathode side of the atmosphere side A to the exhaust gas side G Oxygen ions are supplied to the anode side.

  That is, in this purification device, the lead wire 13 connected to the applying means 2 is connected to the one surface 10 side of the solid electrolyte 1. When diesel particulates are deposited on the surface 10 side of the solid electrolyte 1 and the solid carbonaceous particulates M in the deposited diesel particulates come into contact with the lead wires 13, voltage application is started by the applying means 2 and energization is performed. The solid carbonaceous fine particles M themselves are used as anodes. As a result, a predetermined potential difference is generated between both surfaces of the solid electrolyte 1 to supply oxygen ions. That is, when a certain amount of diesel particulate is deposited on the deposition surface 12, the purification is automatically started. The lead wire 13 is provided in a ring shape or a mesh shape on the one surface 10 side of the solid electrolyte 1, thereby solid carbonaceous matter in the diesel particulates partially deposited on the deposition surface 12 on the one surface 10 side of the solid electrolyte 1. Purification can be performed by bringing the fine particles M into contact with the lead wires 13.

  The purifying apparatus shown in FIG. 3 performs the treatment of diesel particulates by the purifying apparatus shown in FIG. 1 (FIG. 2) and the treatment of nitrogen oxides using an oxidation catalyst simultaneously and continuously. The nitrogen oxide to be treated is contained in the exhaust gas together with diesel particulates. In this purification device, an adsorbent 5 and an oxidation catalyst 6 are provided on one surface 10 side of the solid electrolyte 1 of the purification device shown in FIG. That is, this apparatus is provided with a solid electrolyte 1 having oxygen ion conductivity, an application means 2 for applying a voltage between both surfaces of the solid electrolyte 1, and one surface 10 side of the solid electrolyte 1 to adsorb nitrogen oxides. An adsorbent 5 and an oxidation catalyst 6 provided on the one surface 10 side of the solid electrolyte 1 are provided.

  The solid electrolyte 1 is the same as that shown in FIG. 1, and the applying means 2 applies a voltage so that the surface 10 side on which diesel particulates are deposited of the solid electrolyte 1 is the anode side. In this apparatus, the first electrode 3 provided on the one surface 10 side of the solid electrolyte 1 is preferably composed of a porous electrode including the oxidation catalyst 6. For example, the first electrode 3 can be porous platinum. That is, the first electrode 3 is used in combination as the oxidation catalyst 6. In FIG. 3, a nitrogen compound adsorbent 5 is laminated on the first electrode 3 (oxidation catalyst 6) in a net shape. Note that the adsorbent 5 can include barium. The adsorbent 5 shown in FIG. 3 is formed in layers.

The purification method by this purification apparatus shown in FIG. 3 is as follows. First, similarly to FIG. 1 (FIG. 2), a voltage is applied between both surfaces of the solid electrolyte 1 by the applying means 2 to supply oxygen ions from the cathode side to the anode side. Then, the solid carbonaceous fine particles M in the diesel fine particles present on the anode-side deposition surface 12 of the solid electrolyte 1 are oxidized (2C + O ₂ → 2CO) by the oxidized ions to form carbon oxides containing carbon monoxide (arrows). a). The diesel particulates having the solid carbonaceous particulates M are contained in the exhaust gas, and are deposited on the deposition surface 12 on the one surface 10 side of the solid electrolyte 1. The deposition surface 12 becomes the outer surface of the first electrode 3 having the oxidation catalyst 6 and the outer surface of the adsorbent 5.

The nitric oxide contained in the exhaust gas together with the diesel particulates is oxidized (NO + O ₂ → NO ₂ + O ^* ) by the oxidation catalyst 6 on the anode side of the solid electrolyte 1 to form nitrogen dioxide (arrows b-1 and b). -2). The oxygen used in the oxidation is mainly oxygen contained in the exhaust gas. The nitrogen dioxide is adsorbed on the adsorbent 5. Further, the adsorbed nitrogen dioxide is reduced (2NO ₂ + 4CO → N ₂ + 4CO ₂ ) with carbon monoxide obtained by oxidizing the solid carbonaceous fine particles M, so that nitrogen dioxide is nitrogen and carbon monoxide is carbon dioxide. (Arrow c). As described above, diesel particulates (solid carbonaceous particulates M) and nitrogen oxides (nitrogen monoxide) contained in the exhaust gas are continuously purified into nitrogen and carbon dioxide.

Further, oxidation of the solid carbonaceous fine particles M in the diesel fine particles is promoted by the oxidation catalyst 6 present on the deposition surface 12 of the diesel fine particles. Further, oxidation of solid carbonaceous fine particles M is promoted by active oxygen (O ^* ) generated when nitrogen monoxide is oxidized to nitrogen dioxide (NO + O ₂ → NO ₂ + O ^* ) (arrow b-1). .

Furthermore, the application means 2 of this purification device has switching means for periodically inverting the polarity of the applied voltage. That is, the first electrode 3 on the anode side is set as the cathode side, and the second electrode 4 on the cathode side is switched to the anode side, and this switching is performed continuously. FIG. 4 shows a state in which the first electrode 3 is on the cathode side and the second electrode 4 is on the anode side. As a result, the active oxygen (O ^*) generated on the one surface 10 side of the solid electrolyte 1 that is the exhaust gas side G is shown ^. ) Is forcibly returned to the other surface 11 side of the solid electrolyte 1 which is the atmosphere side A.

This is to suppress the recombination of nitrogen and nitric oxide (N ₂ + 2O ^* → 2NO, NO + O ^* → NO ₂ ) by active oxygen, thereby simultaneously purifying diesel particulates and nitric oxide. It can be done in a balanced manner. That is, the produced nitrogen is produced by reducing carbon dioxide adsorbed on the adsorbent 5 into nitrogen by carbon monoxide obtained by oxidizing solid carbonaceous fine particles M in diesel fine particles with oxygen ions. Is again oxidized with active oxygen to form nitrogen oxides. The switching means of the application means 2 can be constituted by electrical means, and the frequency and switching time can be changed according to the amount of active oxygen on the exhaust gas side G.

  Next, FIG. 5 is a schematic diagram showing a purification system for purifying exhaust gas from a diesel engine. This exhaust gas contains diesel particulates (solid carbonaceous particulates M) and nitrogen oxides (nitrogen monoxide). It is. This purification system includes an exhaust passage 7 that is connected to an exhaust port of a diesel engine (diesel engine) 15 and exhausts exhaust gas, and an exhaust gas purification device 8 that is provided in a part of the exhaust passage 7. Yes. Moreover, the exhaust flow path 7 shown in FIG. 5 is comprised by the exhaust pipe, and the exhaust gas purification chamber 16 which the exhaust gas purification apparatus 8 has in the middle of this exhaust pipe is provided. A plurality of solid electrolytes 1 are provided inside the exhaust gas purification chamber 16. The solid electrolyte 1 is the same as that shown in FIG.

  The exhaust gas purification device 8 is connected to the control device 17, and the control device 17 is provided with the switching means for periodically inverting the polarity of the applied voltage of the application means 2 and the application means 2, and the operation of the purification device 8 is controlled. I have control. Furthermore, the purification device 8 has a charging device 18 that charges diesel particulates contained in the exhaust gas and deposits the diesel particulates on the deposition surface 12 of the solid electrolyte 1 (see FIG. 3).

  This exhaust gas purification device 8 includes a plurality of solid electrolytes 1, and each solid electrolyte 1 is provided on one surface 10 side of the fixed electrolyte 1 and adsorbs nitrogen oxides, similarly to the purification device shown in FIG. 3. An adsorbent 5 to be applied, an oxidation catalyst 6 provided on one surface 10 side of the solid electrolyte 1, and an applying means 2 for applying a voltage between both surfaces of the solid electrolyte 1. The application means 2 is shared by a plurality of solid electrolytes 1. Each solid electrolyte 1 has oxygen ion conductivity, and is provided so that one surface 10 side is in contact with exhaust gas from the exhaust flow path 7 and the other surface 11 side is in contact with oxygen in the atmosphere. The applying means 2 applies a voltage between both surfaces of the solid electrolyte 1 so that the first electrode 3 provided on the one surface 10 side of the solid electrolyte 1 is the anode side and the second electrode 4 provided on the other surface 11 side is the cathode side. Applied. The exhaust gas purification device 8 has the solid electrolyte 1, the adsorbent 5, the oxidation catalyst 6, and the applying means 2 that are the same as those described with reference to FIGS. 1 to 4. For example, the applying means 2 has the polarity of the applied voltage. Switching means for periodically inverting is provided.

  FIG. 6 is a configuration diagram of a main part of an exhaust gas purification device 8 provided in the purification system of FIG. 5, and the purification device 8 has a plurality of solid electrolytes 1. 5 and 6, a plurality of (seven in FIG. 6) flat panel-shaped solid electrolytes 1 face each other with a mutual gap in the exhaust gas purification chamber 16 connected to the exhaust flow path 7. Are arranged so as to overlap each other. In addition, the solid electrolyte 1 is turned over alternately to form a laminated shape, and is disposed so that the one surfaces 10 and 10 of the adjacent solid electrolytes 1 and 1 or the other surfaces 11 and 11 face each other. A bar-shaped spacer member 19 is provided in each gap, and a solid electrolyte layer 20 is formed by the plurality of solid electrolytes 1. The solid electrolyte layer 20 is provided in the exhaust gas purification chamber 16.

An exhaust gas passage 21 or an air passage 22 is formed between the spacer members 19 and 19 in the gaps between the plurality of solid electrolytes 20. That is, the exhaust gas flow paths 21 and the air flow paths 22 are alternately formed in this order from the one side in the stacking direction of the solid electrolyte layer 20 (lower part in FIG. 6). In addition, between the one surfaces 10 and 10 of the adjacent solid electrolytes 1 and 1 is the exhaust gas flow path 21, and between the other surfaces 11 and 11 of the adjacent solid electrolytes 1 and 1 is the air flow path 22.
In addition, the direction of the spacer member 19 in the gap constituting the exhaust gas passage 21 and the direction of the spacer member 19 in the gap constituting the air passage 22 may be the same direction (not shown) or a predetermined direction. In FIG. 6, the spacer member 19 in the gap constituting the air flow path 22 is provided with a 90 ° direction changed with respect to the spacer member 19 of the exhaust gas flow path 21. The exhaust gas flow passage 21 penetrating in the exhaust gas flow direction (arrow g direction) and the air flow passage 22 penetrating in the direction orthogonal to the exhaust gas flow direction (arrow a direction) are alternately formed. Has been. The exhaust gas flowing from the exhaust flow path 7 is directly sent to the exhaust gas flow path 21 as it is, and the air flow path 22 is communicated with the atmosphere side A outside the exhaust gas purification chamber 16 so that the air flows. It is sent to the air flow path 22. As a result, when the exhaust gas passes through the exhaust gas passage 21, diesel particulates contained in the exhaust gas are deposited on the deposition surface 12 on the one surface 10 side of the solid electrolyte 1 facing the exhaust gas passage 21. It is oxidized and nitrogen oxides in the exhaust gas are reduced.

FIG. 7 shows a modified example of the exhaust gas purification device 8. In the exhaust gas purification chamber 16 having a rectangular cross section penetrating in the flow direction of the exhaust gas flowing in the exhaust flow path 7 (arrow g direction), A plurality of cylindrical solid electrolytes 1 are provided. The solid electrolyte 1 is configured as a cylinder so that the other surface 11 side that is the atmosphere side A is the inner surface, the outer peripheral surface of the cylindrical solid electrolyte 1 is the one surface 10 side that is the exhaust gas side G, and It becomes the deposition surface 12. The axial direction of the cylindrical solid electrolyte 1 is set to a direction (arrow a direction) perpendicular to the flow direction of the exhaust gas (arrow g direction), and the solid electrolyte 1 has a gap between each other in the exhaust gas purification chamber 16. Is provided.
Thereby, the inside of the cylindrical solid electrolyte 1 communicates with the atmosphere side A, and air can pass through the inside of the cylindrical solid electrolyte 1. The exhaust gas flowing from the exhaust passage 7 flows through the gap between the cylindrical solid electrolytes 1, 1, and the diesel particulates contained in the exhaust gas passing through the gap pass through the outer peripheral surface of the cylindrical solid electrolyte 1. It is deposited on the side deposition surface 12 and oxidized, and nitrogen oxides in the exhaust gas are reduced.

  6 and 7, diesel particulates in the exhaust gas introduced into the exhaust gas purification chamber 16 are charged by the charging device 18 (see FIG. 5), and the deposition surface 12 of the solid electrolyte 1 is charged. Is actively collecting diesel particulates. In other words, an electric field is formed by providing a charging electrode in the upstream portion where the exhaust gas flows into the exhaust gas purification device 8 and setting the electrode 3 (see FIG. 3) on the deposition surface 12 side of the solid electrolyte 1 to the ground level. The fine particles are charged, and the charged diesel fine particles are efficiently collected on the deposition surface 12 of the solid electrolyte 1.

Further, the exhaust gas purifying device 8 shown in FIG. 7 is disposed so that the outer peripheral surface that becomes the deposition surface 12 of the cylindrical solid electrolyte 1 partially blocks the exhaust gas, so Since it is sprayed directly, diesel particulates in the exhaust gas are efficiently collected on the outer peripheral surface of the solid electrolyte 1 due to its inertial force. Furthermore, since there is only the solid electrolyte 1 that makes it possible to purify the exhaust gas in the exhaust gas purification chamber 16, there is no possibility that diesel particulates accumulate on other parts and block the flow path, and the concentration of diesel particulates in the exhaust gas It is effective when is high.

  8 and 9 show still another modified example of the exhaust gas purification device 8. The solid electrolyte 1 of the purification device 8 is formed in a U-shaped cross section, and the solid electrolyte 1 has a side wall 23 extending from the opening to the back. It is comprised from the back wall 24 of the abutting end shape. The side wall 23 is set in a direction parallel to the flow direction (arrow g direction) of the exhaust gas flowing from the exhaust flow path 7, and the back wall 24 has a surface orthogonal to the flow direction of the exhaust gas. The solid electrolyte 1 is provided in the exhaust gas purification chamber 16. The inner surface of the solid electrolyte 1 having a U-shaped cross section is the deposition surface 12 on the side 10 shown in FIG. 3, and the outer surface of the solid electrolyte 1 is the atmosphere side A. The solid electrolyte 1 having a U-shaped cross section can be formed in a bottomed cylindrical shape having a circumferential side wall 23 and a back wall 24. Further, the solid electrolyte 1 having a U-shaped cross section is connected to the adjacent solid electrolyte 1 by a connecting wall member 25, and the exhaust gas purification chamber 16 is connected to the space on the exhaust gas side G and the atmosphere side by the connected solid electrolyte 1. It is partitioned into A space.

  Further, a pipe-like exhaust conduit 26 is inserted inside the solid electrolyte 1 having a U-shaped cross section with a gap from the inner surface of the solid electrolyte 1, and the exhaust gas flowing from the exhaust passage 7 is exhausted by the exhaust conduit 26. 1 to the back wall 24 side. The induced exhaust gas collides with the back wall 24 of the solid electrolyte 1, and then flows between the outer peripheral surface of the exhaust conduit 26 and the inner surface of the side wall 23 of the solid electrolyte 1, and the exhaust gas purified by the solid electrolyte 1 is discharged. It is discharged to the outside of the gas purification chamber 16. Note that an air inlet 27 and its outlet 28 are provided in the portion on the atmosphere side A of the exhaust gas purification chamber 16 partitioned by a plurality of connected solid electrolytes 1.

  Further, also in the exhaust gas purification device 8, as shown in FIG. 8, the diesel particulates are charged by the charging device 18, and the diesel particulates are collected on the deposition surface 12 of the solid electrolyte 1. In this case, the exhaust conduit 26 is used as a charging electrode, and the electrode 3 (see FIG. 3) on the deposition surface 12 side of the solid electrolyte 1 is set to the ground level, so that the outer peripheral surface of the exhaust conduit 26 and the inner surface of the solid electrolyte 1 are connected. Electrolysis is formed between them, and when the exhaust gas passes between them, the diesel particulates in the exhaust gas are charged, and the charged diesel particulates are efficiently collected on the deposition surface 12 of the solid electrolyte 1. And the diesel particulate deposited on the deposition surface 12 is purified.

  Explaining the purification method by the exhaust gas purification device 8 shown in FIG. 9, the exhaust gas flowing from the exhaust passage 7 first flows in the exhaust conduit 26. Diesel particulates in the exhaust gas that has passed through the exhaust conduit 26 are trapped on the deposition surface 12 of the back wall 24 of the solid electrolyte 1 due to its inertial force. The exhaust gas further flows between the discharge conduit 26 and the solid electrolyte 1, and diesel particulates charged by the charging device 18 between them are also generated on the side wall 23 of the solid electrolyte 1 by the electric field formed by the charging device 18. It is collected on the deposition surface 12. That is, the exhaust gas purifying device 8 has an inertia collecting action on the back wall 24 of the solid electrolyte 1 due to an inertia force of the exhaust gas and an electric collecting action by the charging device 18. In addition, diesel particulates with large particle diameters are effective for inertia collection, and those with small particle diameters are effective for electric collection. These two actions effectively convert diesel particulates with various particle diameters efficiently. Can be collected.

Next, still another embodiment of the purification apparatus according to the present invention will be described with reference to FIG. This purification device is a modification of the purification device shown in FIGS.
FIG. 10 is a model diagram showing a purification device, which is also capable of purifying exhaust gas discharged from a diesel engine. Solid carbonaceous fine particles M in diesel particulates contained in the exhaust gas, and Nitrogen oxide can be purified.
This purification apparatus has a solid electrolyte 1 having ionic conductivity and capable of supplying oxygen ions to one surface side, and a first electrode 3 and a second electrode provided on the one surface 10 side and the other surface 11 side, respectively, of the solid electrolyte 1. A purification structure 30 having an electrode 4 is provided.

  The solid electrolyte 1 has a panel shape, and the purification structure 30 is configured by laminating the first electrode 3 on one surface 10 and laminating the second electrode 4 on the other surface 11. As the solid electrolyte 1, for example, one used in a fuel cell can be applied, and ions can be moved by generating a potential difference between both ends of the solid electrolyte 1. In addition, as long as this solid electrolyte 1 can give an oxygen ion to the 1st electrode 3 side as a result, the ion which moves in the solid electrolyte 1 is not restricted to an oxygen ion.

  And this purification | cleaning structure 30 is made porous so that the gas containing nitrogen oxides can be permeate | transmitted except the diesel particulates (solid carbonaceous particulate M) among the exhaust gas which performs purification | cleaning. That is, the solid electrolyte 1 in the purification structure 30 is porous, and the first electrode 3 and the second electrode 4 are porous electrodes. By making the purification structure 30 porous, exhaust gas containing diesel particulates is passed from the first electrode 3 side to the second electrode 4 side (arrow F), thereby collecting the diesel particulates on the first electrode 3 side. Can be filtered.

Then, similarly to the purification device shown in FIG. 1, the solid carbonaceous fine particles M of the collected diesel fine particles are oxidized by oxygen ions given to the first electrode 3 side by the solid electrolyte 1 having a potential difference. be able to.
Further, the exhaust gas that has passed through the purification structure 30 contains nitrogen oxides, which will be reduced on the second electrode 4 side, as will be described later. That is, in the purification structure 30, the first electrode 3 side is an oxidation portion that oxidizes the solid carbonaceous fine particles M, and the second electrode 4 side that is the opposite side (back side) across the solid electrolyte 1 is The reducing part reduces nitrogen oxides. In other words, this purification device can purify the solid carbonaceous fine particles M on one surface side of the purification structure 30 and simultaneously purify nitrogen oxides on the other surface side.

The purifying structure 30 is connected with a control means 31 provided for performing such a purifying process, and the control means 31 is the same as that shown in the purifying apparatus of FIG. 2 has. More specifically, the control means 31 is provided as a closed circuit as a whole with the application means 2 capable of applying a voltage so that the first electrode 3 side becomes the anode side and a resistor provided in parallel with the application means 2. The bypass circuit unit 34 can be configured. Further, the control means 31 switches between the state in which the voltage is applied between the electrodes 3 and 4 by the applying means 2 and the state in which the application is stopped between the electrodes 3 and 4 to form the closed circuit. The switching control unit 35 is provided.
That is, although the temperature of the exhaust gas varies depending on the operating conditions of the diesel engine, when the exhaust gas temperature is low, the voltage is applied between the electrodes 3 and 4 by the applying means 2 so that the first electrode 3 side becomes the anode side. The ions can move in the solid electrolyte 1, and the simultaneous purification is possible.
However, when the engine load increases and the exhaust gas temperature increases, the solid carbonaceous fine particles M are easily oxidized on the first electrode 3 side of the purification structure 30 and the solid electrolyte 1 operates as a fuel cell. Can be made. Thus, the ions can be moved in the solid electrolyte 1 without supplying electric energy from the outside (by the applying means 2), and the simultaneous purification is performed. In other words, when the exhaust gas temperature becomes high and the ionic conductivity in the solid electrolyte 1 is high, the switching control unit 35 includes the solid electrolyte 1 in the state where the electrodes 3 and 4 are connected by the bypass circuit unit 34. By configuring a closed circuit in which no voltage is applied, ions can be moved in the solid electrolyte 1.

  The control means 31 is connected to a temperature sensor (not shown) that measures the temperature of the exhaust gas, and the switching control unit 35 is configured to perform a switching operation according to the output of the temperature sensor. In other words, the voltage is applied between the electrodes 3 and 4 when the temperature of the exhaust gas is low, and is automatically switched so as to form a closed circuit when the temperature is high. Thereby, power consumption can be suppressed and energy efficiency can be improved. Further, the switching of these states may be other than by means for detecting the temperature of the exhaust gas by a temperature sensor, and the fuel cell having an ion conductive function to such an extent that the solid electrolyte 1 can perform the simultaneous purification. It may be performed by detecting whether or not it can be operated.

And the purification method of the exhaust gas performed by this purification apparatus is made to pass diesel particulates on the one side 10 side by letting exhaust gas containing diesel particulates pass from the one side 10 side to the other side 11 side of the porous solid electrolyte 1. To collect. Then, when a predetermined potential difference is generated between both surfaces of the solid electrolyte 1, ions are moved from the other surface 11 side of the solid electrolyte 1 to the one surface 10 side so as to give oxygen ions to the one surface 10 side, and captured on the one surface 10 side. The collected diesel particulates are oxidized by oxygen ions. In FIG. 10, oxygen present in the other surface 11 side of the solid electrolyte 1 or oxygen atoms in the nitrogen oxide is moved as oxygen ions in the solid electrolyte 1, and the oxygen ions are moved to the first electrode 10 on the first surface 10 side. 3 side is supplied. Thereby, the carbon contained in the solid carbonaceous fine particles M in the collected diesel fine particles is continuously oxidized (C + O ₂ → CO ₂ ) into carbon dioxide, and the solid carbonaceous fine particles M are purified (decomposed). Then, the obtained carbon dioxide permeates through the purification structure 30 together with the exhaust gas flowing from the upstream side, flows to the second electrode 4 side which is the downstream side, and further downstream from the purification structure 30. Discharged.

Further, the nitrogen oxides contained in the exhaust gas that has passed through the purification structure 30 are purified on the second electrode 4 side (reduction part).
FIG. 11 is a diagram for explaining a mechanism for purifying nitrogen oxides on the second electrode 4 side, and ceria or ceria oxide is supported on the second electrode 4 side (cathode side) of the purifying structure 30. .
The purification method performed in this reduction unit is as follows. Ceria (ceria oxide) becomes a stable state of CeO _{2 in a} lean operation state (Ce ₂ O ₃ + 1 / 2O ₂ → 2CeO ₂ : oxygen storage effect by ceria). However, by applying a voltage by the applying means 2, oxygen is released on the second electrode 4 side, and Ce ₂ O ₃ can be kept in a stable state in a lean operation state (2CeO ₂ + 2e ⁻ → Ce ₂ O ₃ + O). ^2- ). At this time, oxygen ions are generated, and the oxygen ions are moved to the first electrode 3 side by the solid electrolyte 1, and the oxygen ions are used for oxidation of the solid carbonaceous fine particles M. Ceria can reduce nitrogen oxide (NO) in this state (Ce ₂ O ₃ + NO → 2CeO ₂ + 1 / 2N ₂ ).

FIG. 12 is a diagram for explaining another mechanism for purifying nitrogen oxides on the second electrode 4 side, and an adsorbent for adsorbing nitrogen oxides on the second electrode 4 (cathode side) of the purifying structure 30. 5 is carried. The adsorbent 5 is the same as that in the purification apparatus of FIG. 3 and is made of an alkali metal, such as potassium or barium. Further, the oxidation catalyst 6 is supported on the second electrode 4 as in FIG. As the oxidation catalyst 6, there is platinum, and the porous second electrode 4 itself can be used as the oxidation catalyst 6.
The barium oxide as the adsorbent 5 is in a stable state (barium carbonate) by reaction with carbon dioxide on the second electrode 4 side (BaO + CO ₂ → BaCO ₃ ).

The purification method performed in this reduction unit is as follows. The exhaust gas that has passed through the purification structure 30 contains nitrogen monoxide and oxygen. On the second electrode 4 side, the nitric oxide is oxidized (NO + O ₂ → NO ₂ + O ²⁻ ) by the oxidation catalyst 6. Nitrogen dioxide. At this time, oxygen ions are generated, and the oxygen ions are moved to the first electrode 3 side by the solid electrolyte 1, and the oxygen ions are used for oxidation of the solid carbonaceous fine particles M.
The nitrogen dioxide and nitrogen dioxide contained in the exhaust gas are adsorbed on the adsorbent 5 (BaCO ₃ + 2NO ₂ + O → Ba (NO ₃ ) ₂ + CO ₂ ), and voltage is applied by the applying means 2. Nitrogen dioxide is reduced (Ba (NO ₃ ) ₂ + 2e ⁻ → BaO + N ₂ + 2O ₂ + O ²⁻ ).
11 and 12, the oxygen ions generated on the second electrode 4 side can be forcibly moved to the first electrode 3 side by the solid electrolyte 1, so that the nitrogen obtained by reduction is nitrogen. It can be suppressed from being re-synthesized into an oxide.
This purification method is not a method using a reducing substance such as carbon monoxide but an electrochemical reduction method.

  In each embodiment, the voltage application by the application unit 2 may be always applied as a constant voltage. However, the application state of the voltage may be periodically changed or changed by the operation of the control unit 31. For example, it can be changed periodically between a state where a voltage is applied and a state where a voltage is not applied. That is, after a certain amount of solid carbonaceous fine particles M is deposited on the first electrode side 3 of the purification structure 30, the voltage may be applied for a predetermined time to perform the purification process intermittently. .

According to the purification apparatus of the present invention as described above, the exhaust gas is forced to flow in from the first electrode 3 side and discharged to the second electrode 4 side by the pressure of the exhaust gas. Since the purification structure 30 is porous, particulate matter (solid carbonaceous fine particles M) such as diesel particulates in the exhaust gas is collected on the first electrode 3 side. That is, the particulates in the exhaust gas are automatically collected on the first electrode 3 side by the filtering effect of the purification structure 30. Thereby, it is not necessary to collect diesel particulates on the electrode surface using an electric dust collector, and the cost and size of the apparatus can be reduced. The exhaust gas from which the fine particles have been collected and removed on the first electrode 3 side passes through the purification structure 30 and flows out to the second electrode 4 side. For example, as shown in FIG. Oxygen occlusion and nitrogen oxide reduction by the reaction at the second electrode 4 cause the nitrogen oxide contained in the exhaust gas to be occluded and decomposed.
Oxygen ions (active oxygen) generated at this time are forcibly excluded to the first electrode 3 side through the solid electrolyte 1 to which a voltage is applied. This suppresses NOx resynthesis on the second electrode 4 side, promotes oxidation of fine particles collected on the first electrode 3 side, and enables simultaneous purification of nitrogen oxides and solid carbonaceous fine particles M. It becomes.

  The DPNR known as a conventional purification device is a ceramic filter carrying a NOx occlusion reduction catalyst, but the discharge amount of the solid carbonaceous fine particles M is usually larger than the discharge amount of NOx. Therefore, it is necessary to add the reducing agent to the exhaust gas, and a configuration such as providing the addition device in the exhaust system is required separately. However, according to the purification apparatus of the present invention, the purification of the solid carbonaceous fine particles M and NOx is performed independently on each of the one side and the other side of the purification structure 30, so the solid carbonaceous fine particles M in the exhaust gas. It is possible to treat both independently without depending on the balance of NOx and NOx, and it is not necessary to add a reducing agent. Therefore, since the purification apparatus of the present invention can be simplified and compact in configuration, it can be retrofitted to an existing automobile.

  Furthermore, although sulfur is contained in the exhaust gas, this sulfur may adversely affect the reduction treatment of nitrogen oxides. However, when this sulfur is contained in the diesel particulates, the purification device of the present invention collects the diesel particulates containing sulfur on the first electrode 3 side of the purification structure 30, and the first side which is the back side thereof. Since the nitrogen oxide is reduced on the two electrode 4 side, fine particles containing sulfur are not deposited on the nitrogen oxide reducing electrode, and the influence of sulfur can be suppressed.

The solid electrolyte 1 used in the purification apparatus shown in FIGS. 1 to 4 and the porous purification structure 30 used in the purification apparatus shown in FIG. 10 will be described further. Examples of the solid electrolyte 1 include conventionally known yttrium-stabilized zirconia, ceria-based solid electrolyte, or molten carbonate type. In the case of zirconia, sufficient oxygen ions are supplied at a high exhaust temperature of 350 ° C. or higher. Is possible. And not only when the exhaust temperature is high (for example, 350 ° C.), but also when it is low (for example, 250 ° C. to 300 ° C.), or when the exhaust temperature is 250 ° C. or less, oxidation (combustion) of diesel particulates is effectively performed by supplying oxygen ions In order to make it perform, the ion conductivity can be improved by changing the shape and thickness of the solid electrolyte 1.
The above-described solid electrolyte 1 having oxygen ion conductivity generally has high oxygen ion conductivity at high temperatures and facilitates movement of oxygen ions, but conversely becomes difficult at low temperatures. If a high applied voltage is forcibly applied to the low-temperature solid electrolyte 1, the oxygen constituting the solid electrolyte 1 is forced to move, resulting in deterioration of the electrolyte 1.
Therefore, the solid electrolyte 1 may be heated to keep the temperature of the solid electrolyte 1 at about 330 ° C. to 370 ° C., or the gas temperature on the exhaust gas side G may be kept at about 330 ° C. to 370 ° C. Good. In the present invention, the applied voltage by the applying means 2 is lowered to 1 to 10 volts to prevent the solid electrolyte 1 from deteriorating, and oxygen ions are efficiently supplied at a sufficient rate.

Next, the specific specifications of the purification structure 30 shown in FIG. 10 will be described. As a whole, the purification structure 30 collects diesel particulates (solid carbonaceous particulates M) on one side thereof without passing through the particulates (solid carbonaceous particulates M) ( And a porous network having a myriad of continuous pores so that the exhaust gas excluding this can be permeated from one side to the other side.
The thickness of the first electrode 3 serving as a decomposition electrode for diesel particulates is preferably 1 μm or more and 5 mm or less, and preferably 5 μm or more and 50 μm. If this thickness is too thin, the diesel particulate collection rate may decrease, and if it is too thick, pressure loss may increase. The average pore diameter of the pores (cavities) in the porous first electrode 3 is 0.5 μm or more and 100 μm or less, preferably 1 μm or more and 10 μm, and the porosity is 10% or more and 80%. It is preferable to set the content to 40% or less and preferably 60% or less. If these values are too small, the pressure loss may increase, and if they are too large, the diesel particulate collection rate may decrease.
The solid electrolyte 1 has a thickness of 1 μm or more and 5 mm or less, preferably 10 μm or more and 500 μm. If this thickness is too thick, the pressure loss may increase. The average pore diameter of the pores (cavities) in the solid electrolyte 1 that is made porous is preferably 0.5 μm or more and 100 μm or less, preferably 1 μm or more and 30 μm, and the porosity is 10% or more and 80% or less. Preferably, it is 40% or more and 60% or less. If these values are too small, the pressure loss may increase, and if it is too large, the ionic conductivity per unit area may decrease.
The thickness of the second electrode 4 serving as a nitrogen oxide decomposition electrode is preferably 1 μm or more and 5 mm or less, and preferably 5 μm or more and 50 μm. If this thickness is too thick, the pressure loss may increase. The average pore diameter of the pores (cavities) in the second electrode 4 that is made porous is preferably 0.5 μm or more and 100 μm or less, preferably 1 μm or more and 30 μm, and the porosity is 10% or more and 80%. It is preferable to set the content to 40% or less and preferably 60% or less. If these values are too small, the pressure loss may increase.
Further, both or one of the average pore diameter and the porosity of the first electrode 3 may be smaller than that of the solid electrolyte 1 and the second electrode 4. That is, the pressure loss of the exhaust gas flowing in the solid electrolyte 1 and the second electrode 2 is reduced while maintaining the diesel particulate collection rate in the first electrode 3.

  In the purification structure 30, it is preferable to reduce the pressure loss in the purification structure 30 in order to efficiently transmit the exhaust gas in which diesel particulates are collected on the first electrode 3 side. This is because a large pressure loss causes a decrease in engine output and fuel consumption. The appropriate value of the pressure loss in the purification structure 30 according to the present invention depends on the thickness, average pore diameter, and porosity, and differs depending on the deposition state of diesel particulates and the flow rate of exhaust gas, but the diesel particulates are deposited. It is preferable that it is 20 kPa or less in a state where it is not (new state). Further, in order to reduce the pressure loss, it is necessary to make the porosity and the like so large that the porosity and the like do not decrease the collection rate of diesel particulates on the first electrode 3 side. The collection rate of diesel particulates on the third side is preferably porous which can be 90% or more.

  A method for producing the porous purification structure 30 will be described below. As a method for making the solid electrolyte 1 and the electrode porous, a conventionally known method can be applied. For example, a minute melt that has been contained during firing is used. There are a method of scattering materials (pellets) and a method of using a foaming agent. The porous material thus obtained is formed by countless holes (cavities) that are continuous from one surface side to the other surface side so as to be permeable to exhaust gas excluding diesel particulates.

  FIG. 13 is a schematic diagram showing a purification system for purifying exhaust gas from a diesel engine. Like the purification system shown in FIG. 5, this purification system includes an exhaust port of a diesel engine (diesel engine) 15 and An exhaust passage 7 that is connected and exhausts exhaust gas, and an exhaust gas purification device 8 provided in a part of the exhaust passage 7 are provided. The exhaust passage 7 is constituted by an exhaust pipe, and a cylindrical exhaust gas purification chamber 16 provided in the exhaust gas purification device 8 is provided in the middle of the exhaust pipe. The purification structure 30 is provided inside the exhaust gas purification chamber 16.

The exhaust gas purifying device 8 is the purifying device shown in FIG. 10, and the purifying structure 30 provided in the device 8 has a solid electrolyte that has ionic conductivity and can supply oxygen ions to the surface 10 side. 1 and a first electrode 3 and a second electrode 4 provided on the one surface 10 side and the other surface 11 side of the solid electrolyte 1, respectively. The purification structure 30 can collect the diesel particulates in the exhaust gas on the first electrode 3 side by passing the exhaust gas from the exhaust passage 7 from the first electrode 3 side to the second electrode 4 side. It is assumed to be porous. The control means 31 is connected to the purification structure 30.
Then, as described above, the diesel particulates collected on the first electrode 3 side are oxidized, and the nitrogen oxides contained in the exhaust gas that has permeated the purification structure 30 on the second electrode 4 side are reduced. .

  As shown in FIG. 14, the purification structure 30 includes a plurality of cylindrical portions 32 formed in a bottomed cylindrical shape, and plate-like portions interconnecting openings of the cylindrical portions 32. 33. The plate-like portion 33 is attached as a wall shape to the inner peripheral surface of the exhaust gas purification chamber 16 so as to face the exhaust gas flowing through the exhaust passage 7. The axial direction (exhaust gas flow direction) of the exhaust gas purification chamber 16 is an axial direction. The inner surface (inner peripheral surface and bottom surface) of the cylindrical portion 32 and the surface of the plate-shaped portion 33 continuous with the inner surface are the first electrode 3 side, and the cylinder is the opposite surface. The outer surface (outer peripheral surface and end surface) of the shaped portion 32 and the back surface of the plate-like portion 33 that is continuous with the outer surface are the second electrode 4 side. As a result, the exhaust gas flowing into the exhaust gas purification chamber 16 permeates from the surface of the plate-like portion 33 and the inner surface of the cylindrical portion 32 to the opposite surface, and diesel particulates are collected on the first electrode 3 side. Thus, the solid carbonaceous fine particles M are oxidized, nitrogen oxides are reduced on the second electrode 4 side, and the treated exhaust gas is discharged downstream of the exhaust gas purification chamber 16.

Further, according to the above purification apparatus, the diesel particulates in the exhaust gas also contain hydrocarbon (HC), and this hydrocarbon is oxidized into water and carbon dioxide (CmHn + ( m + n / 4) O ₂ → mCO ₂ + n / 2H ₂ O).
Furthermore, the purification device, the purification method, and the purification system according to the present invention can be applied not only to purification of exhaust gas discharged from a diesel engine but also to a wide range such as chemical synthesis and combustion systems. Further, the present invention is not limited to the illustrated form, and may be other forms within the scope of the present invention. Besides the solid electrolyte 1 having a panel shape, a cylindrical shape or a corrugated shape may be used depending on the site to be installed Etc.

The purification apparatus shown in FIGS. 1 to 4 and 10 can be made to function alone, or can be additionally provided to a conventionally known nitrogen oxide purification apparatus or particulate purification apparatus. That is, since the purification system of the present invention has a simple structure and can make the apparatus compact, it can be added as an auxiliary oxidation system when oxidation of diesel particulates is insufficient with the conventional apparatus.
Furthermore, in the said purification apparatus shown in FIGS. 1-4, the said charging device used as an electrostatic precipitator by corona discharge etc. is provided, and the diesel particulate contained in exhaust gas is efficiently deposited on the deposition surface 12 of the solid electrolyte 1 You may do it.

  Although the above purification apparatus, purification method, and exhaust gas purification system have been described as purifying exhaust gas discharged from a diesel engine, the exhaust gas is not limited to that exhausted from a diesel engine, The present invention can also be applied to those discharged from a direct-injection gasoline engine), a boiler or an industrial furnace.

It is a model figure which shows the purification apparatus which concerns on one Embodiment of this invention. It is a model figure which shows other embodiment of the purification apparatus. It is a model figure which shows another embodiment of the purification apparatus. It is a model figure explaining the effect | action of the switching means which reverses the polarity of the applied voltage which an application means has. It is a mimetic diagram showing the outline of the exhaust gas purification system concerning one embodiment of the present invention. It is a principal part block diagram of an exhaust-gas purification apparatus. It is a principal part block diagram which shows the modification of an exhaust-gas purification apparatus. It is a schematic diagram which shows the outline of the exhaust gas purification system which concerns on other embodiment of this invention. It is a principal part block diagram which shows the exhaust-gas purification apparatus which the purification system of FIG. 8 has. It is a model figure which shows another embodiment of the purification apparatus. It is explanatory drawing explaining the reduction mechanism of a nitrogen oxide. It is explanatory drawing explaining the other mechanism of a reduction | restoration of nitrogen oxides. It is a schematic diagram which shows the outline of other embodiment of an exhaust gas purification system. It is a principal part block diagram which shows the exhaust-gas purification apparatus which the purification system of FIG. 13 has.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solid electrolyte 2 Application means 3 1st electrode 4 2nd electrode 5 Adsorbent 6 Oxidation catalyst 7 Exhaust flow path 8 Exhaust gas purification apparatus 10 One side 11 Other side 30 Purification structure 31 Control means A Atmosphere side G Exhaust gas side M Solid Carbonaceous fine particles

Claims (16)

  And a solid electrolyte having oxygen ion conductivity, and an application means for applying a voltage between both surfaces of the solid electrolyte so that one side of the solid electrolyte on which diesel particulates are deposited is the anode side. Purification device to do.   The solid electrolyte is provided with an electrode on the other side of the cathode, and when diesel particulates are deposited on one side of the solid electrolyte, the diesel particulates are energized by the application means, and the solid carbonaceous matter in the diesel particulates The purification apparatus according to claim 1, wherein the fine particles themselves are used as anodes.   A solid electrolyte having oxygen ion conductivity, application means for applying a voltage between both surfaces of the solid electrolyte so that one side of the solid electrolyte on which diesel particulates are deposited is an anode side, and one side of the solid electrolyte A purification apparatus comprising: an adsorbent provided to adsorb nitrogen oxides; and an oxidation catalyst provided on one side of the solid electrolyte.   The purification device according to claim 3, wherein the applying unit includes a switching unit that periodically reverses the polarity of the applied voltage.   A solid electrolyte having oxygen ion conductivity, and an application means for applying a voltage between both surfaces of the solid electrolyte so that one side of the solid electrolyte on which unburned fine particles discharged from the combustor are deposited is the anode side A purification device comprising:   A solid electrolyte having ionic conductivity and capable of supplying oxygen ions to one side, and a purification structure having a first electrode and a second electrode provided on one side and the other side of the solid electrolyte, respectively. The purification structure can collect the fine particles on the first electrode side by passing exhaust gas containing unburned fine particles discharged from the combustor from the first electrode side to the second electrode side. The purification is characterized in that the first electrode side is an oxidizing portion that oxidizes the collected fine particles by oxygen ions applied to the first electrode side by the solid electrolyte. apparatus.   The purification device according to claim 6, wherein the second electrode side of the purification structure is a reduction unit that reduces nitrogen oxides contained in the exhaust gas that has permeated the purification structure.   The purification apparatus according to claim 7, wherein an adsorbent that adsorbs the nitrogen oxides is provided on the second electrode side of the purification structure.   The purification apparatus according to claim 7, wherein ceria or ceria oxide is provided on the second electrode side of the purification structure.   The purification structure can be switched between a state in which a voltage is applied between both electrodes so that the first electrode side is the anode side, and a state in which the application is stopped between both electrodes to form a closed circuit. The purification apparatus as described in any one of Claims 6-9 connected with the control means.   A voltage is applied between both surfaces of a solid electrolyte having oxygen ion conductivity, oxygen ions are supplied from the cathode side to the anode side, and diesel particulates present on the anode side of the solid electrolyte are oxidized by the oxygen ions. Purification method.   A voltage is applied across both surfaces of the solid electrolyte having oxygen ion conductivity, oxygen ions are supplied from the cathode side to the anode side, and the oxidized particulates oxidize the diesel particulates present on the anode side of the solid electrolyte to make a single oxidation. Carbon oxide containing carbon is used to oxidize nitrogen monoxide present in the exhaust gas together with the diesel particulates using an oxidation catalyst on the anode side of the solid electrolyte to form nitrogen dioxide. A purification method characterized in that the nitrogen dioxide adsorbed in the step is reduced by the carbon monoxide.   By passing an exhaust gas containing unburned fine particles from one surface side to the other surface side of a porous solid electrolyte having ionic conductivity and capable of supplying oxygen ions to one surface side, the fine particles are captured on the one surface side. A purification method characterized in that the collected and collected fine particles are oxidized by the oxygen ions given to the one surface side by the solid electrolyte.   The purification method according to claim 13, wherein nitrogen oxides contained in the exhaust gas permeated to the other surface side of the solid electrolyte are reduced on the other surface side.   An exhaust gas purification system comprising an exhaust passage for passing exhaust gas containing diesel particulates and nitrogen oxides, and an exhaust gas purification device provided in a part of the exhaust passage, wherein the exhaust gas The purification device is provided on one surface side of the fixed electrolyte, and a solid electrolyte having one surface side in contact with the exhaust gas from the exhaust passage and the other surface in the atmosphere and having oxygen ion conductivity. An adsorbent that adsorbs nitrogen oxides, an oxidation catalyst provided on one side of the solid electrolyte, and the solid electrolyte so that the one side of the solid electrolyte is the anode side and the other side is the cathode side And an application means for applying a voltage between both surfaces of the exhaust gas purification system.   An exhaust gas purification system comprising an exhaust passage for passing exhaust gas containing unburned particulates and nitrogen oxides discharged from a combustor, and an exhaust gas purification device provided in a part of the exhaust passage The exhaust gas purification device includes a solid electrolyte having ionic conductivity and capable of supplying oxygen ions to one side, a first electrode provided on each side and the other side of the solid electrolyte, and a first electrode A purification structure having two electrodes, and the purification structure passes the exhaust gas from the exhaust passage from the first electrode side to the second electrode side, thereby passing the particulates to the first electrode side. The first electrode side is an oxidation part that oxidizes the collected fine particles with oxygen ions given to the first electrode side by the solid electrolyte, And the second electrode It is the exhaust gas purification system, characterized in that there is a reduced section for reducing nitrogen oxides contained in the exhaust gas having passed through the purifier structure.

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