JP2007278194A - Exhaust gas treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously reduce material such as PM and NOx by making use of electrostatic separation action. <P>SOLUTION: An electrostatic separation device 3 and an exhaust gas post-treatment device 4 are installed in an exhaust gas passage 2 of an internal combustion engine 1. The electrostatic separation device 3 is provided with a dust collection function charging electricity on PM in exhaust gas flowing in the exhaust gas passage 2 by corona discharge and collecting the same. PM collected by the electrostatic separation device 3 is returned to the intake passage of the internal combustion engine 1, eventually to a combustion chamber via a communication path 5, and is re-burned. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust treatment device for treating a gas (exhaust gas) discharged from a combustion device and containing various exhaust substances.

  Purifying the exhaust from the combustion device to suppress the expansion of air pollution is an important issue. For example, regarding diesel combustion engines, PM (particulate matter: particulate matter = mainly black smoke) in the exhaust (Soot), unburned fuel called SOF, components of lubricating oil, and components generated from sulfur in light oil fuel called sulfate) and NOx (nitrogen oxide) emissions are so-called trade Up to now, it has been necessary to install exhaust aftertreatment devices for both PM and NOx to suppress the emission of these regulated substances.

  For example, a diesel particulate filter (Diesel Particulate Filter) is installed in the exhaust passage as an exhaust aftertreatment device to reduce the amount of PM released into the atmosphere, and the exhaust gas is exhausted by passing through the diesel particulate filter. Some collect PM. However, since this is collected by a filter, there is a risk that exhaust pressure will increase and combustion efficiency will be lowered.

  Therefore, there is a need for an apparatus that can simultaneously reduce both PM and NOx emissions without adverse effects such as such an increase in exhaust pressure.

Here, Patent Document 1 discloses a technique of disposing a metal rod or the like in the center of a metal pipe and applying a high voltage between both electrodes of the metal pipe and the metal bar as an electrostatic collection and electrostatic separation technique. ing. This collects PM in the vicinity of the inner wall of the metal pipe by the action of electrostatic dust collection, and enables separation of the PM near the inner wall of the metal pipe and the vicinity of the center of the metal pipe. And it can separate into the gas flow which concentrated PM, and the gas flow which hardly contains PM by arranging piping of the double pipe structure in the latter part of such PM collection and separation part. it can.
Japanese Patent Laying-Open No. 2005-076497

  The present invention has been made in view of the above-described circumstances, and an exhaust capable of simultaneously reducing both substances such as PM and NOx while suppressing adverse effects such as an increase in exhaust pressure using an electrostatic separation action. An object is to provide a processing apparatus.

Therefore, the exhaust treatment device according to the present invention is
An exhaust treatment apparatus for a combustion apparatus for causing combustion and discharging a gas containing a substance that can be electrostatically separated,
An electrostatic separation means for introducing at least part of a gas containing an electrostatically separable substance discharged from the combustion apparatus and electrostatically separating the substance from the gas;
Recirculation means for recirculating at least part of the gas containing the substance electrostatically separated by the electrostatic separation means to the combustion chamber of the combustion device;
It is comprised including.

  The electrostatic separation means is a diversion means for diverting the gas containing the electrostatically separated substance and the remaining gas among the gas containing the electrostatic separable substance introduced into the electrostatic separation apparatus. Can be configured.

  An exhaust post-treatment device that performs a predetermined treatment on the remaining gas or a substance contained in the remaining gas can be disposed downstream of the electrostatic separation means in the remaining gas flow.

  The reflux means includes a communication passage that communicates the electrostatic separation means and a passage for introducing air to be used for combustion of the combustion device, and the communication passage includes the communication passage. A reformer that reforms a gas containing an electrostatically separated substance flowing in a passage, a heat exchange device that exchanges heat for a gas containing an electrostatically separated substance flowing in the communication path, and the communication At least one fuel addition device for adding fuel to the gas containing the electrostatically separated substance flowing through the passage may be provided.

  In the case where all of the reforming device, the heat exchange device, and the fuel addition device are disposed, the reforming device and the heat exchange device are configured to supply gas containing an electrostatically separated substance that flows through the communication path. The fuel addition device may be arranged in this order toward the downstream side in the flow direction, and the fuel addition device may be arranged to add fuel on the upstream side of the flow of the reformer.

  According to the present invention, both substances such as PM and NOx can be simultaneously reduced while suppressing adverse effects such as an increase in exhaust pressure by utilizing electrostatic separation.

  Hereinafter, a first embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

  The internal combustion engine 1 according to the first embodiment shown in FIG. 1 can be, for example, a diesel engine that performs diesel combustion. However, the present invention is not limited to this, and if it is a combustion apparatus with exhaust, In addition to gasoline engines and other internal combustion engines, any mobile or stationary combustion device can be used regardless of the combustion method.

  As shown in FIG. 1, an exhaust passage 2 is connected to the internal combustion engine 1, and an electrostatic separation device 3 is interposed in the exhaust passage 2, and an exhaust aftertreatment device 4 is disposed downstream of the exhaust. Is intervening.

  As shown in FIG. 2, the electrostatic separation device 3 is, for example, a cylindrical low voltage electrode (which can be a hollow shape having a desired longitudinal cross-sectional shape such as an ellipse or a rectangle in addition to a cylinder). The portion 3A includes a high-voltage electrode portion 3B that extends in the longitudinal direction in the vicinity of the central axis in the longitudinal direction, and an inner cylinder portion 3C. Here, the electrostatic separation device 3 corresponds to the electrostatic separation means according to the present invention.

  The low voltage electrode unit 3A is made of a conductor such as a metal such as stainless steel. The electrostatic separation device 3 according to the first embodiment includes a high voltage electrode unit 3B and a low voltage electrode unit 3A described later. And a dust collecting function for charging and capturing PM (particulate matter) 10 in the exhaust gas 6 flowing in the exhaust passage 2 by corona discharge generated by a high voltage applied between them.

  The high voltage electrode portion 3B is a discharge electrode (corona discharge electrode) that generates a corona discharge with the low voltage electrode portion 3A, and is composed of, for example, a stainless wire, a piano wire, a fine wire, a stranded wire, a rod-like member, or the like. be able to. The cross section of the high voltage electrode portion 3B in a direction substantially orthogonal to the longitudinal direction of the low voltage electrode portion 3A can be formed in a desired shape such as a round shape, an oval shape, or a square shape. A material having conductivity can be used. For example, a material having excellent corrosion resistance such as SUS (stainless steel), tungsten, nickel, titanium, and Inconel can be used.

  The inner cylinder portion 3C is an exhaust shunt member having a cylindrical shape (the cross-sectional shape in the longitudinal direction can be a desired shape in addition to a round shape, an oval shape, and a square shape). High concentration exhaust gas 6A containing a large amount of PM10 collected near the inner wall of the low voltage electrode portion 3A by corona discharge between the electrode portion 3B and low concentration exhaust gas 6B having a low concentration of PM10 inside can be separated. In addition, as shown in FIG. 2, the low voltage electrode portion 3B is disposed substantially concentrically with the low voltage electrode portion 3B on the exhaust downstream side of the low voltage electrode portion 3B. The inner cylinder portion 3C does not need to be a conductive member, and can be formed of an appropriate material such as metal, ceramic, or resin. Here, the inner cylinder portion 3 </ b> C corresponds to the flow dividing means according to the present invention.

  In the first embodiment, the inner cylinder portion 3C is connected to an exhaust passage 2 communicating with an exhaust aftertreatment device 4 described later in the exhaust gas downstream portion. For example, as shown in FIG. In addition, an opening 3 </ b> D configured by cutting out a part of the circumference that can return the excessive high-concentration exhaust 6 </ b> A to the exhaust passage 2 may be provided.

  The exhaust aftertreatment device 4 is, for example, a NOx occlusion reduction type three-way catalyst, a DPNR catalyst (a combination of a porous ceramic structure and a NOx occlusion reduction type three way catalyst. Catalysts that can significantly reduce PM and NOx by oxidation and reduction with NO), catalysts for HC-SCR (selective reduction-type NOx catalyst that purifies NOx using hydrocarbons as a reducing agent), urea SCR ( A catalyst for UREA-SCR (a selective reduction type NOx catalyst that purifies NOx using urea as a reducing agent), a diesel particulate filter, or the like can be used as required.

  Note that the exhaust aftertreatment device 4 has, for example, characteristics of exhaust gas flowing out to the exhaust downstream side through the inner cylinder portion 3C of the electrostatic separation device 3 (NOx, CO, HC, PM contained in the exhaust gas). It is possible to decide which of the above-mentioned various catalysts or filters to be used, or a combination of a plurality of them regardless of the same type or different types, etc. it can.

  Here, in the first embodiment, a communication path 5 that connects the electrostatic separation device 3 and an intake path (not shown) of the internal combustion engine 1 is provided. The communication path 5 functions as a reflux means according to the present invention, and a large amount of PM 10 collected near the inner wall of the low voltage electrode part 3A due to corona discharge between the low voltage electrode part 3A and the high voltage electrode part 3B. At least a part of the high-concentration exhaust 6A that is included is disposed as a recirculated gas so that it can be returned to the intake passage of the internal combustion engine 1 and to the combustion chamber (not shown). The connection portion with the low voltage electrode portion 3A and the connection portion with the intake passage of the internal combustion engine 1 can be at a position where at least a part of the high concentration exhaust 6A can be returned to the intake passage of the internal combustion engine 1. .

  The internal combustion engine 1 according to the first embodiment having such a configuration uses a gas in which reflux gas and intake air (fresh air) introduced from the outside through the intake passage of the internal combustion engine 1 are mixed. Since it can be led to the combustion chamber, PM10 contained in the reflux gas can be recombusted in the combustion chamber.

  That is, according to the first embodiment, the PM 10 contained in the exhaust gas is effectively collected by the electrostatic separation device 3, and the collected PM 10 is burned by the internal combustion engine 1 through the communication path 5. By returning to the chamber and recombusting, exhaust of the exhaust gas aftertreatment device 4 on the exhaust gas downstream side of the electrostatic separation device 3 and the exhaust of PM10 to the outside air can be effectively reduced.

  For this reason, for example, when the combustion temperature is lowered in order to reduce the NOx emission amount, the combustion deteriorates and the unburned residue increases and the PM emission amount increases (that is, the NOx emission amount and the PM emission amount). From the standpoint of preventing the spread of air pollution, conventionally, the exhaust aftertreatment device 4 has been adapted to collect a large amount of PM, for example, because there is a trade-off relationship with the emission amount). Although it was necessary to provide a diesel particulate filter, etc., according to the first embodiment, it is possible to effectively collect and re-burn PM, thus reducing NOx emissions from the combustion surface Even so, the amount of PM emission can be reduced.

  That is, according to the first embodiment, PM and NOx emissions can be simultaneously reduced. Therefore, for example, it is possible to reduce the burden on the exhaust aftertreatment device compared to the conventional one (such as reducing the capacity or extending the regeneration cycle), and further omitting the exhaust aftertreatment device depending on the situation. It becomes possible. If an exhaust aftertreatment device is provided, NOx, PM, etc. can be more effectively and reliably applied to exhaust in which both PM and NOx emissions are simultaneously reduced by the electrostatic separation device 3 and the communication passage 5. The amount of discharge to the outside air can be reduced.

  By the way, the first embodiment is configured to return the high-concentration exhaust 6A to the combustion chamber. Therefore, not only can PM be reburned to reduce the amount of PM discharged, but it also functions as an EGR at the same time. As an effect of EGR, the combustion temperature can be lowered while maintaining the fuel consumption to some extent, so that the NOx emission amount can be effectively reduced while maintaining the fuel consumption at a predetermined level.

  The recirculation gas flowing through the communication passage 5 is configured to be cooled so as to function as a so-called cool EGR (Cool Exhaust Gas Recirculation) system, and the combustion temperature is further lowered to further effectively reduce the NOx emission amount. It can also be reduced. In addition, a flow rate control valve that controls the flow rate of the recirculated gas so as to obtain a desired flow rate of the recirculated gas according to the operating state of the internal combustion engine 1 can be interposed in the communication path 5.

  Thus, in 1st Embodiment, it becomes possible to reduce both PM and NOx discharge | emission amount simultaneously by providing the electrostatic separation apparatus 3 and the communicating path 5. FIG. As a result, the burden on the exhaust aftertreatment device 4 can be reduced, so that the capacity of the exhaust aftertreatment device 4 can be reduced or omitted, and the configuration can be simplified and the weight can be reduced. It can also contribute to the reduction of manufacturing cost.

  Next, a second embodiment according to the present invention will be described in detail below with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the element similar to the element demonstrated in 1st embodiment mentioned above, and the detailed description shall be abbreviate | omitted.

  As shown in FIG. 4, in the second embodiment, as in the first embodiment, an internal combustion engine 1, an exhaust passage 2, an electrostatic separation device 3, an exhaust aftertreatment device 4, and a communication passage 5 are provided. On the other hand, a reformer 7 and a heat exchanger 8 are interposed in this order in the communication path 5 toward the downstream side of the flow of the reflux gas flowing through the communication path 5.

  Further, on the upstream side of the recirculation gas flow of the reformer 7, the fuel addition means of the fuel addition device 9 that supplies and supplies fuel for increasing the temperature of the recirculation gas flowing into the reformer 7 through the communication path 5. 8A is connected.

  In the second embodiment having such a configuration, the exhaust from the internal combustion engine 1 is disposed in the middle of the exhaust passage 2 in the electrostatic separator 3 as in the first embodiment. The high-concentration exhaust gas 6A containing a large amount of PM10 and the low-concentration exhaust gas 6B having a low PM10 concentration are separated, and at least a part of the high-concentration exhaust gas 6A is passed through the communication path 5 to the reformer 7 (for example, No. 2005-098226, etc.).

The reforming device 7 is supplied with fuel via the fuel addition means 8A of the fuel addition device 9 and acts on the reflux gas containing PM10, so that it has a highly ignitable gas or a highly combustible gas (including radicals). ) Efficiently. Specifically, since the reformer 7 according to the second embodiment acts on the high concentration exhaust 6A enriched with PM10, for example, the following reaction can be expected.
HC → CO, H ₂ , R—CHO, R—OH

  The recirculated gas reformed to a highly ignitable gas or a highly combustible gas in the reforming device 7 is controlled to a predetermined temperature by the heat exchanging device 8, and the intake passage of the internal combustion engine 1 through the communication passage 5. As a result, it is led to the combustion chamber and recombusted. Gases with high ignitability or flammability shorten the so-called ignition delay period, so that the initial combustion ratio is reduced and the increase in combustion temperature is suppressed, so that the thermal efficiency is suppressed while suppressing the increase in NOx emissions. As a result, the fuel consumption can be maintained at a high level.

  As described above, in the second embodiment, the high-concentration exhaust gas 6A containing a large amount of PM10 can be led to the intake passage of the internal combustion engine 1 through the communication passage 5 and then to the combustion chamber so that the PM10 can be reburned. In addition to effectively suppressing the discharge of PM10 to the outside air, the reformer 7 is provided to reform a part of the high concentration exhaust 6A into a highly ignitable gas or a highly combustible gas. In addition, since the combustion is performed again, the NOx emission amount can be effectively suppressed and the thermal efficiency can be extended and the fuel efficiency can be maintained at a high level.

  Regarding the reaction in the reformer 7, the generation of oxidizing species and the generation of reducing species are controlled by controlling the amount of fuel added from the fuel adding device 9 or adjusting the components of the fuel addition. be able to. In addition, any reforming device 7 that can perform reforming by acting on a reflux gas containing PM 10 so as to obtain a desired reforming can be used. For example, a plasma device, a catalyst device, a burner ( Combustion device) can be employed.

  As in the first embodiment, the second embodiment also includes the electrostatic separation device 3, the communication path 5, and the reforming device 7, so that both PM and NOx emissions can be reduced simultaneously. Therefore, the burden on the exhaust aftertreatment device 4 can be reduced, so that the capacity of the exhaust aftertreatment device 4 can be reduced or the exhaust aftertreatment device 4 can be omitted, and the configuration can be simplified. Therefore, the weight can be reduced and the manufacturing cost can be reduced.

  In the second embodiment, the reformer 7, the heat exchange device 8, and the fuel addition device 9 are described as an example. However, the present invention is not limited to this, and among these devices, The case where any one of them or any combination thereof is used is also included.

  In other words, when a desired reforming can be obtained by providing only the reforming device 7, it is possible to provide only the reforming device 7. In addition, when only the heat exchange device 8 is provided and desired combustion characteristics and exhaust characteristics are obtained only by adjusting the temperature of the reflux gas to a desired temperature, only the heat exchange device 8 can be provided. Furthermore, in the case where only the fuel addition device 9 is provided and the recirculated gas is burned as desired only by fuel addition to obtain desired combustion characteristics and exhaust characteristics, only the fuel addition device 9 can be provided. And it is also possible to use any of these or a combination of them so that desired combustion characteristics and exhaust characteristics can be obtained.

It is a figure explaining the structure of 1st embodiment which concerns on this invention. It is sectional drawing explaining the electrostatic separation apparatus which concerns on embodiment same as the above. It is a XX direction arrow line view in FIG. It is a figure explaining the structure of 2nd embodiment which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust passage 3 Electrostatic separation device 3A Low voltage electrode part 3B High voltage electrode part 3C Inner cylinder part 4 Exhaust treatment device 5 Communication path 6 Exhaust 6A High concentration exhaust gas 6B Low concentration exhaust gas 7 Reformer device 8 Heat exchange device 9 Fuel Adder 10 PM (Particulate Matter)

Claims (5)

An exhaust treatment apparatus for a combustion apparatus for causing combustion and discharging a gas containing a substance that can be electrostatically separated,
An electrostatic separation means for introducing at least a part of a gas containing an electrostatically separable substance discharged from the combustion apparatus and electrostatically separating the substance contained in the gas;
Recirculation means for recirculating at least part of the gas containing the substance electrostatically separated by the electrostatic separation means to the combustion chamber of the combustion device;
An exhaust treatment apparatus comprising:   The diverting means for diverting the electrostatic separation means into the gas containing the electrostatically separated substance and the remaining gas among the gas containing the electrostatic separable substance introduced into the electrostatic separation apparatus. The exhaust treatment device according to claim 1, comprising:   An exhaust post-treatment device that performs a predetermined process on the remaining gas or a substance contained in the remaining gas is disposed downstream of the electrostatic separation means in the remaining gas flow. The exhaust treatment device according to claim 1 or 2. The recirculation means includes a communication passage that communicates the electrostatic separation means and a passage for introducing air to be used for combustion of the combustion device;
A reforming device for reforming the gas containing the electrostatically separated substance flowing through the communication path in the communication path, and heat exchange for the gas containing the electrostatically separated substance flowing through the communication path. 4. The apparatus according to claim 1, wherein at least one of a heat exchange device to perform and a fuel addition device for adding fuel to a gas containing an electrostatically separated substance flowing through the communication path is disposed. The exhaust treatment apparatus according to one. When all of the reforming device, the heat exchange device, and the fuel addition device are disposed, the reforming device and the heat exchange device are configured to supply a gas containing electrostatically separated substances flowing through the communication path. The fuel addition device is arranged in this order toward the downstream side in the flow direction, and the fuel addition device is arranged to add fuel on the upstream side of the flow of the reformer. 5. An exhaust treatment apparatus according to 4.

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