JP2008051037A - Exhaust gas treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment apparatus efficiently flocculating fine particles contained in exhaust gas. <P>SOLUTION: The exhaust gas treatment apparatus 1 comprises: a pipe body 4 functioning as a flow passage flowing exhaust gas therethrough; an electrostatic flocculation device 2 flocculating the fine particles 5 contained in the exhaust gas 6; and a honeycomb filter 3 collecting the fine particles 5 flocculated by the electrostatic flocculation device 2. The electrostatic flocculation device 2 has: a first discharge electrode part 7 generating first discharge 17 for making one fine particles 5 have positive electric charge or negative electric charge; and a second discharge electrode part 8 generating second discharge 18 for making other fine particles 5 have electric charge with polarity different from that of the first discharge 17. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas treatment device. More specifically, the present invention relates to an exhaust gas processing apparatus that efficiently aggregates particulates contained in exhaust gas and collects them with a filter.

  Particulates and harmful substances in exhaust gas emitted from internal combustion engines such as automobile engines, construction machinery engines, and stationary engines for industrial machinery, and other combustion equipment, are taken into the exhaust gas in consideration of environmental impact. There is a growing need for removal. In particular, regulations regarding the removal of particulates (hereinafter sometimes referred to as “PM”) emitted from diesel engines tend to be strengthened worldwide, and a collection filter (diesel particulate filter: hereinafter referred to as “PM”) is removed. The use of a honeycomb filter has attracted attention as a "DPF"), and various systems have been proposed.

  The DPF is usually provided with a predetermined partition (predetermined cell) having a porous partition wall that partitions and forms a plurality of cells serving as fluid flow paths, one end of which is open and the other end is plugged. Cell) and the remaining cells (residual cells) with one end plugged and the other end opened alternately, and flow from one end where a given cell opens The trapped fluid (exhaust gas) permeates through the partition walls and flows out into the remaining cells as permeated fluid, and the permeated fluid flows out from the other end where the remaining cells open, thereby trapping PM in the exhaust gas. Collect and remove.

  Further, as an exhaust gas processing apparatus for processing exhaust gas containing PM as described above, for example, after colliding with a collision guide member provided inside a flow path through which exhaust gas passes, the negative charge is obtained by a charged body. A device that is electrically charged and then attracted to a positively charged body to be electrically collected is disclosed (see Patent Document 1). PM that has passed through the positively charged body is collected by a downstream filter, and is incinerated and removed by energizing the positively charged body to function as a heater.

  Such an exhaust gas treatment device has a drawback that the pressure loss increases because the flow path configuration is complicated, and the manufacture thereof is not easy. In addition, a sufficient aggregation effect cannot be obtained, and the fine particles are released through the apparatus without being aggregated.

  For this reason, a high voltage is applied between the two as an agglomerator that aggregates exhaust particulates in the exhaust gas in an exhaust passage formed by the exhaust pipe of the internal combustion engine and through which the exhaust gas flows in the axial direction of the exhaust pipe. An electrode composed of two types of charge release and charge recovery for transferring and receiving charges due to corona discharge is disposed so that the charge transfer section of the first type electrode is located at a substantially central portion in the radial direction of the exhaust passage. In addition, there has been disclosed an exhaust treatment apparatus provided with an aggregator that charges exhaust particulates by the electric charge generated by the corona discharge and aggregates the exhaust particulates at an electrode for collecting the electric charge (see Patent Document 2).

  Further, as an agglomerator for an exhaust treatment device that is used in an exhaust treatment device as described above and agglomerates the exhaust particulate charged by corona discharge by the agglomeration unit, the agglomeration unit has a downstream of the exhaust gas flow of the charging unit. An exhaust treatment apparatus agglomerator is disclosed in which a first conductive body is disposed, and the first conductive body is applied to a positive potential (see Patent Document 3).

  Furthermore, a PM aggregating means that is disposed in the exhaust path of the engine and agglomerates the particulate matter contained in the exhaust gas of the engine to generate a particulate matter having a large particle size (aggregated PM), and the exhaust from the PM aggregating means. An exhaust purification device is disclosed that includes a PM collection unit that is disposed downstream of the gas flow direction and collects the aggregated PM aggregated by the PM aggregation unit (see Patent Document 4).

Japanese Patent Laid-Open No. 2001-41024 JP 2005-320955 A JP 2005-324094 A JP 2006-29267 A

  However, the exhaust treatment apparatus disclosed in Patent Document 2 is charged because particles charged by electric charges are moved by an electric field and aggregated at an electrode (downstream electrode) for collecting electric charges. A residence time for the fine particles to move to the electrode must be secured. For this reason, in order to obtain a sufficient aggregation effect of fine particles, it is necessary to increase the distance between the electrodes, and there is a problem that the apparatus becomes large. When the exhaust treatment apparatus becomes large in this way, it becomes extremely difficult to install the exhaust treatment apparatus in an automobile or the like to treat the exhaust gas.

  Further, in the exhaust treatment device disclosed in Patent Document 2, the area of the electrode (downstream electrode) for collecting electric charge is extremely small, so that many fine particles are not captured by the electrode and pass through the electrode. Therefore, there is a problem that the effect of aggregating the fine particles is small, and the fine particles can hardly be agglomerated in practice.

  Further, the aggregator for an exhaust treatment device described in Patent Document 3 is configured to draw a charged fine particle by applying a high voltage to the first conductive body constituting the aggregation part. Compared with the exhaust treatment apparatus disclosed in Patent Document 2, the moving distance of the charged fine particles can be shortened, and the agglomeration effect is also enhanced. However, the configuration of the electrodes (charging portion and aggregation portion) is extremely complicated, and there is a problem that it is difficult to use in an automobile or the like to which large vibrations are applied. The exhaust treatment apparatus aggregator is configured to apply a high voltage to the first conductive body constituting the agglomeration portion to attract the charged fine particles, but includes carbon. In other words, the insulating structure is extremely difficult to attach due to adhesion of fine particles with low resistivity, which is not practical.

  In addition, the fine particles contained in the exhaust gas normally collide with each other by the free diffusion of Brownian motion, in addition to the aggregation by the above-described method (aggregation by applying an electric charge and attracting the electrode). By combining, enlargement (aggregation) is performed.

  In the above-described exhaust treatment apparatuses of Patent Documents 2 and 3, since the fine particles are charged with a negative charge, the fine particles moving between the electrodes are fine particles having a single charge (specifically, a negative charge). It will only exist. The fine particles having a single charge inhibit the collision described above by the electric repulsive force, and the aggregation due to the Brownian motion is hardly performed.

  Further, the PM aggregating means used in the exhaust gas purification device described in Patent Document 4 moves the fine particles charged by electric charges by an electric field as shown in Patent Documents 2 and 3 above, thereby forming electrodes (downstream electrodes). ), The size of the apparatus is increased, the structure is extremely complicated, and it is difficult to use the apparatus for automobiles to which large vibrations or the like are applied.

  The present invention has been made in order to solve the above-described problems of the prior art, and provides an exhaust gas processing apparatus that efficiently aggregates particulates contained in exhaust gas and collects them with a filter.

  As a result of intensive studies to solve the above-described problems of the prior art, the present inventors have found that the fine particles contained in the exhaust gas are divided into fine particles given positive charge and fine particles given negative charge. It was conceived that the above problems could be solved by agglomerating the fine particles generated in one exhaust system and given the respective charges, and collecting the agglomerated fine particles by the honeycomb filter, and completed the present invention. It was. Specifically, the following exhaust gas treatment apparatus is provided by the present invention.

[1] A tubular body serving as a flow path through which exhaust gas passes, an electrostatic aggregator disposed inside the tubular body for agglomerating fine particles contained in the exhaust gas, and the electrostatic aggregator An exhaust gas treatment device comprising: a honeycomb filter for collecting fine particles agglomerated by the electrostatic filter, wherein the electrostatic aggregator performs a first discharge for applying a positive or negative charge to the fine particles. An exhaust gas treatment apparatus, comprising: a first discharge electrode portion to be generated; and a second discharge electrode portion for generating a second discharge for applying a charge having a polarity different from that of the first discharge to the fine particles.

[2] The exhaust gas treatment according to [1], wherein the fine particles charged to charges having different polarities by the first discharge and the second discharge are attracted to each other by a Coulomb force and aggregated at least in a space. apparatus.

[3] A part of the tube body is divided into two so that the inner space is parallel to the flow direction of the exhaust gas, and a first flow path and a second flow path are formed. The exhaust gas processing apparatus according to [1] or [2], wherein the first discharge electrode part is disposed in the first flow path and the second discharge electrode part is disposed in the second flow path.

[4] At least one of the first discharge electrode portion and the second discharge electrode portion is configured to perform corona discharge using the inner surface of the tubular body as a counter electrode. ] The exhaust-gas processing apparatus in any one of.

[5] At least one of the first discharge electrode portion and the second discharge electrode portion includes a dielectric, and is configured to perform creeping discharge on the surface of the dielectric. [3] The exhaust gas treatment device according to any one of [3].

[6] The charge amount of the first discharge generated by the first discharge electrode part and the charge amount of the second discharge generated by the second discharge electrode part can be independently controlled. The exhaust gas processing apparatus according to any one of [1] to [5].

[7] The electrostatic aggregator includes at least one of the first discharge electrode part and the second discharge electrode part, and the two or more first discharge electrode parts and / or the first discharge electrode part. The exhaust gas processing apparatus according to any one of [1] to [6], wherein two discharge electrode portions are arranged in series in the pipe body in the flow direction of the exhaust gas.

[8] The honeycomb filter includes a porous partition wall that defines a plurality of cells serving as a flow path through which the exhaust gas passes, and has one end (filter inlet end) opened and the other end. A predetermined cell (inlet opening cell) in which the (filter outlet end) is sealed, and a remaining cell (outlet opening cell) in which the filter inlet end is sealed and the filter outlet end is opened. The exhaust gas treatment device according to any one of [1] to [7], which is arranged alternately.

[9] The exhaust gas treatment device according to [8], wherein the honeycomb filter has a catalyst supported on a surface of the partition wall and / or inside the partition wall.

[10] The exhaust gas treatment device according to [8] or [9], wherein the honeycomb filter has a cell density of 50 to 300 cells / cm ² .

[11] The exhaust gas treatment device according to any one of [8] to [10], wherein the honeycomb filter has an average pore diameter of 20 to 150 μm.

[12] The exhaust gas treatment device according to any one of [8] to [11], wherein the honeycomb filter has a porosity of 30 to 80%.

  The exhaust gas treatment apparatus according to the present invention is a fine particle contained in exhaust gas, which is charged to a charge having a different polarity by the first discharge and the second discharge, that is, a fine particle given a positive charge. And negatively charged fine particles are generated in one exhaust system, and the fine particles charged to the respective charges are agglomerated so that the fine particles can be efficiently agglomerated. Can be collected well. In addition, since the collision of the fine particles due to the free diffusion of the Brownian motion is not hindered, the effect of the fine particle aggregation due to the Brownian motion can be expected. In particular, the exhaust gas treatment apparatus of the present embodiment is capable of aggregating particles that are charged with different polarities by means of Coulomb force and aggregating the particles at least in a space simply and efficiently. Can do.

  Further, since the fine particles charged to the respective charges are aggregated not only in the upstream space of the honeycomb filter but also in the internal space after flowing into the honeycomb filter, the fine particles can be efficiently aggregated. .

  In addition, the exhaust gas treatment apparatus of the present invention attracts fine particles, as in the conventional case, in order to agglomerate the charged fine particles in the flow path formed by the tube or the space in the honeycomb filter. Therefore, the number of parts can be greatly reduced as compared with a conventional exhaust gas processing apparatus. Since it has such a simple configuration and is not easily damaged by vibration or the like, it can be suitably used as an exhaust gas treatment apparatus for automobiles to which large vibration or the like is applied.

  Embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments and is based on the knowledge of those skilled in the art without departing from the scope of the present invention. It goes without saying that various changes, modifications, and improvements can be added.

[Exhaust gas treatment equipment]
FIG. 1 is an explanatory view schematically illustrating an embodiment of an exhaust gas treatment apparatus of the present invention, and is a cross-sectional view cut along a plane parallel to the flow direction of a flow path through which exhaust gas passes. 2 is an explanatory view schematically showing the configuration of the electrostatic aggregator constituting the exhaust gas treatment device of FIG. 1, and FIG. 3 is a flow direction of the flow path of the electrostatic aggregator shown in FIG. It is sectional drawing cut | disconnected by the surface perpendicular | vertical to.

  As shown in FIGS. 1 to 3, the exhaust gas treatment device 1 of the present embodiment includes a tubular body 4 serving as a flow path through which the exhaust gas 6 passes, and an exhaust gas 6 disposed inside the tubular body 4. An electrostatic aggregator 2 for aggregating the fine particles 5 contained in the filter, and a honeycomb filter 3 for collecting the fine particles 15 (hereinafter also referred to as “aggregated fine particles”) aggregated by the electrostatic aggregator 2; A first discharge electrode unit 7 in which an electrostatic aggregator 2 generates a first discharge 17 for applying a positive or negative charge to one fine particle 5; This is an exhaust gas treatment apparatus 1 having a second discharge electrode portion 8 for generating a second discharge 18 for applying a charge having a polarity different from that of the first discharge 17 to the other fine particles 5.

  The electrostatic aggregator 2 constituting the exhaust gas treatment device 1 shown in FIGS. 1 to 3 has a positive discharge electrode portion (first discharge) for generating a first discharge 17 for giving a positive charge to one fine particle 5. It has an electrode part 7) and a negative discharge electrode part (second discharge electrode part 8) for generating a second discharge 18 for giving a negative charge to the other fine particles 5.

  According to the exhaust gas treatment apparatus 1 of this embodiment, the first discharge 17 and the second discharge 18 are charged with the fine particles 5 charged with different charges, that is, the fine particles 5a given positive charges. The fine particles 5b having a negative charge are generated and the charged fine particles 5a and 5b are agglomerated, so that the fine particles 5 can be efficiently agglomerated. Can be collected well. In particular, the fine particles 5a and 5b charged to the respective charges are attracted by Coulomb force and aggregated at least in a space, specifically, in a space downstream of the positive discharge electrode portion 7 and the negative discharge electrode portion 8. Therefore, even with an apparatus having a simple configuration, the fine particles can be aggregated extremely efficiently. The exhaust gas 6 containing such aggregated fine particles 15 is purified by the honeycomb filter 3, and the purified purified gas 9 is discharged from the downstream side of the honeycomb filter 3. In particular, in the exhaust gas treatment device 1 of the present embodiment, the enlarged aggregated fine particles 15 are collected by the honeycomb filter 3, so that the cell density and the partition wall are larger than those of the honeycomb filter used in the conventional exhaust gas treatment device. Even when a honeycomb filter having a large average pore size or the like is used, fine particles can be collected well without reducing the collection efficiency. Such a honeycomb filter has a small pressure loss in an initial state, and can reduce a burden on an internal combustion engine such as an engine.

  Further, the exhaust gas treatment device 1 of the present embodiment does not charge all the fine particles to a single charge unlike the conventional exhaust gas treatment device, and therefore, the collision of the fine particles 5 due to Brownian motion free diffusion is inhibited. The cohesive effect due to Brownian motion can also be expected.

  In addition, the fine particles 5a and 5b charged to the respective charges flow into the honeycomb filter 3 after flowing into the honeycomb filter 3 as well as the space upstream of the honeycomb filter 3 (the internal space of the tubular body 4 forming the flow path). Since the agglomeration is also performed in the space in the space 3, the fine particles 5a and 5b can be favorably agglomerated even if the electrostatic aggregator 2 and the honeycomb filter 3 are arranged close to each other. Furthermore, such fine particles 5a and 5b can be aggregated not only in the above-described space but also by adhering to the surface of the tubular body 4 forming the flow path, for example.

  In addition, the exhaust gas treatment apparatus 1 of the present embodiment is configured so that the particulates 5a and 5b charged to charges having different polarities are attracted to each other by Coulomb force, and the internal space of the tubular body 4 and the honeycomb filter forming the flow path 3 is agglomerated in the space of the conventional exhaust gas processing apparatus (see, for example, Patent Document 2), it is not necessary to use an electrode for attracting fine particles, and has a very simple configuration. Compared with the processing apparatus, the number of parts can be greatly reduced. For this reason, it can be suitably used as an exhaust gas treatment apparatus for automobiles and the like to which large vibrations are applied.

[Electrostatic aggregator]
Here, the electrostatic aggregator used in the exhaust gas treatment apparatus of the present embodiment will be described more specifically. The electrostatic aggregator 2 includes a first discharge electrode portion 7 for generating a first discharge 17 for applying a positive or negative charge (positive charge in FIG. The first discharge 7 has two electrode portions, a second discharge electrode portion 8 for generating a second discharge 18 for giving a charge of a different polarity (negative charge in FIG. 1), A part of the fine particles contained in the exhaust gas 6 can be charged to a positive charge, and the remaining fine particles can be charged to a negative charge.

  The 1st discharge electrode part 7 and the 2nd discharge electrode part 8 are arrange | positioned in the position which does not interfere with generation | occurrence | production of each discharge (1st discharge 17 and 2nd discharge 18). In the exhaust gas treatment device 1 shown in FIGS. 1 to 3, the tip of each electrode portion is arranged at the center in the flow direction of the tube body 4 so as to face the opposite side of the inner surface of the tube body 4. .

  In the exhaust gas treatment device 1 shown in FIGS. 1 to 3, the first discharge electrode portion 7 and the second discharge electrode portion 8 perform corona discharge using the inner side surfaces of the tubular body 4 forming the flow path as respective counter electrodes. An example in the case of being configured to perform is shown. For example, in the exhaust gas treatment apparatus 1 of the present embodiment, as shown in FIGS. 4 and 5, the first discharge electrode portion 7 and the second discharge electrode portion 8 each have a dielectric 19, and the dielectric The surface of the body 19 may be configured to perform creeping discharges having different polarities. Here, FIG. 4 is an explanatory view schematically showing a configuration of an electrostatic aggregator used in another embodiment of the exhaust gas treatment apparatus of the present invention, and FIG. 5 is an electrostatic aggregator shown in FIG. It is sectional drawing which cut | disconnected by the surface perpendicular | vertical to the flow direction of the flow path. Furthermore, in the exhaust gas treatment apparatus of the present embodiment, although not shown, the first discharge electrode portion and the second discharge electrode portion may have different configurations, for example, different shapes or different discharge methods. Specifically, even if one electrode part is configured to perform corona discharge as shown in FIG. 2 and the other electrode part is configured to perform creeping discharge as shown in FIG. Good.

  The electrode portions (first discharge electrode portion 7 and second discharge electrode portion 8) configured to perform corona discharge as shown in FIGS. 1 to 3 have a simple electrode structure and a direct current power source (DC power source). ), AC power supply (AC power supply), pulse power supply, and all other high-voltage power supplies. In particular, the DC power supply can be downsized by increasing the switching frequency, and can greatly contribute to downsizing of the entire exhaust gas treatment apparatus. On the other hand, the electrode portions (first discharge electrode portion 7 and second discharge electrode portion 8) configured to perform creeping discharge on the surface of the dielectric 19 as shown in FIGS. 4 and 5 are low resistivity fine particles. Therefore, there is no influence of insulation degradation, gas temperature, gas properties, and the like due to adhesion of the gas, and stable discharge can be performed.

  The electrode parts (the first discharge electrode part 7 and the second discharge electrode part 8) configured to perform corona discharge as shown in FIGS. 1 to 3 are formed at the tips of the respective electrode parts formed at acute angles. The corona discharge is performed by applying a high voltage between the inner surface of the tube body 4. There are no particular restrictions on the shape or the like of such an electrode portion, but it is preferable that the tip has a sharp shape such as a needle shape, a rod shape, or a plate shape and the electric field concentrates.

  When corona discharge is performed using the inner side surface of the tube body 4 as each counter electrode, the tip of each electrode part (the first discharge electrode part 7 and the second discharge electrode part 8), the inner side surface of the tube body 4, Is preferably 5 to 40 mm, and more preferably 15 to 30 mm. If the distance between the tip of the electrode section and the inner surface of the tube is less than 5 mm, the distance between the tip of the needle-shaped electrode section and the inner surface of the tube (the distance between the discharge electrodes) is too small. The movement of the main part is mainly the movement to the tube and the aggregation on the tube, and the entire exhaust gas may not be charged and aggregated efficiently. In addition, the electric field concentration at the tip of the needle-like electrode portion is reduced, and stable discharge may be difficult. On the other hand, if it exceeds 40 mm, the gap between the tip of the needle-like electrode part and the inner surface of the tube body becomes too wide, and it becomes difficult to generate a discharge, or a very large voltage is required to cause a discharge. is there.

  4 and 5, the electrode portions (the first discharge electrode portion 7 and the second discharge electrode portion 8) configured to perform creeping discharge are connected to the high voltage portion 22 of the power source 20. In addition, a high-voltage conductor 28 is wound around the surface of the dielectric 19 in a coil shape, and a ground electrode 24 is disposed inside the dielectric 19. A high positive or negative voltage is applied to the conductor 28 to cause creeping discharge on the surface of the dielectric 19.

  In addition, when the electrode part (the 1st discharge electrode part 7 and the 2nd discharge electrode part 8) comprised so that such a creeping discharge is used is used, it is possible to perform a creeping discharge only by this electrode part. However, for example, the inner surface of the tube 4 may be a ground electrode of each electrode portion, and an electric field may be further generated between the electrode portion and the tube 4.

  The dielectric used for the electrode portion configured to perform creeping discharge as shown in FIGS. 4 and 5 is not particularly limited as long as it can be suitably used as a dielectric. For example, aluminum oxide, magnesium oxide, silicon oxide, silicon nitride, aluminum nitride, mullite, spinel, cordierite, magnesium-calcium-titanium oxide, barium-titanium-zinc oxide, and barium-titanium oxide It is preferable to contain at least one compound selected from the group consisting of A dielectric containing such a compound is difficult to break even if temperature fluctuation occurs, and has excellent thermal shock resistance.

  Here, the process of agglomerating fine particles in the exhaust gas treatment apparatus shown in FIGS. The exhaust gas treatment apparatus 1 shown in FIGS. 1 to 3 includes a DC type electrostatic aggregator 2 that uses an AC power source 20 as a power source by rectifying an AC power source 20 into a direct current. As a specific power source configuration, as shown in FIG. 2, a transformer 21 is connected to an AC power source 20, energy is stored in the transformer 21, and the high voltage unit 22 is formed by discharging the energy. Yes. And the high voltage part 22 is converted into direct current | flow by the rectification | straightening effect | action of the diode 23, and is connected to the 1st discharge electrode part 7 (positive electrode side) via resistance 27 (high resistance, for example, 500k-20M (ohm)). . The first discharge electrode portion 7 to which the high voltage is applied performs corona discharge (first discharge) using the inner surface of the tube body 4 as a counter electrode (negative electrode side). The resistor 27 is used as a limiting resistor for limiting the current that flows when the impedance between the electrode portion and the tube body decreases, and suppressing the discharge from arcing.

  On the other hand, for the second discharge electrode portion 8, in order to use the inner surface of the tube body 4 as a counter electrode, a high voltage obtained by rectifying the AC power supply 20 into direct current is applied to the inner surface of the tube body 4. Corona discharge (second discharge) is performed from the inner surface toward the second discharge electrode portion 8. That is, the inner surface of the tube body 4 is on the positive electrode side, and the second discharge electrode portion 8 is on the negative electrode side.

  In the corona discharge (first discharge 17) by the first discharge electrode part 7, when a positive high voltage is applied to the tip of the needle-like electrode part (first discharge electrode part 7), the tip of the needle-like electrode part Corona discharge occurs in the vicinity and a weakly ionized plasma is formed. Although positive ions and electrons are generated in the plasma, the generated electrons flow from the needle-shaped tip to the first discharge electrode portion 7, and the positive ions generated by the first discharge 17 are opposed to the opposing electrodes (inside the tube 4). To the side). The fine particles 5a in the exhaust gas 6 collide with the positive ions, thereby charging the fine particles 5a to a positive charge.

  On the other hand, in the corona discharge (second discharge 18) by the second discharge electrode part 8, when a negative high voltage is applied to the tip of the needle-like electrode part (second discharge electrode part 8), the needle-like electrode part Corona discharge is generated in the vicinity of the tip of the electrode to form weakly ionized plasma. Although positive ions and electrons are generated in the plasma, the generated positive ions are immediately neutralized by being combined with electrons at the tip of the needle-like electrode portion. The remaining electrons are ionized by attaching to oxygen or the like having particularly good electron adhesion, and the fine particles 5b in the exhaust gas 6 are charged to a negative charge by the oxygen ions.

  In this way, the fine particles 5a and 5b charged to a positive or negative charge are attracted to fine particles having different polarities by the Coulomb force, and are agglomerated as they are combined with each other. Further, since the fine particles 5a and 5b repeat collisions also by free diffusion of Brownian motion, aggregation is further promoted.

  The exhaust gas treatment apparatus shown in FIGS. 1 to 3 uses a rectification type circuit that utilizes the rectification action of the diode 23. For the DC power supply, for example, a flyback system, a forward A circuit using a method, a resonance method, or the like may be used.

  Further, in the exhaust gas treatment apparatus of the present embodiment, for example, as shown in FIG. 6, a transformer 21 is connected to an AC power supply 20, and energy is stored in and discharged from the transformer 21, so The voltage waveform to be applied to the first discharge electrode portion 7 and the second discharge electrode portion 8 is formed so that the polarity of the applied voltage is different while the high voltage in the high voltage portion 22 remains alternating. A voltage may be applied to each electrode part so as to be shifted by a half cycle, and corona discharges having different polarities may be generated.

  The voltage supplied from the AC power supply 20 is not limited to a sine wave voltage as shown in FIG. 6, and is, for example, a power supply that supplies a pulse voltage or a power supply that supplies a square wave voltage. May be. When such a voltage is applied, the polarity of the charged charges in the first discharge electrode portion 7 and the second discharge electrode portion 8 changes every time the voltage polarity is reversed.

  Note that when a power source that supplies a pulse voltage is used, rectification by a diode or the like is not necessary, so that the configuration of the power source can be simplified and the power source can be manufactured at low cost. In addition, when a power source that supplies a pulse voltage is used, the transformer of the power source can be reduced in size.

  In the case of using a power source that applies a positive and negative alternating voltage to a transformer such as a sine wave, a square wave, or a pulse, there is no particular limitation on the period, but the charge time constant τ represented by the following formula (1) It is preferable to make it longer. If the period of the AC voltage to be used is shorter than the charging time constant τ, the fine particles are not sufficiently charged, and the desired aggregation performance may not be obtained.

Charge time constant τ = 4 · ε ₀ · E / J (1)
(Where ε ₀ is the dielectric constant of vacuum, E is the electric field, and J is the ion current density)

  In addition, when the voltage supplied from the power source is a pulse voltage, it is preferable because the flashover voltage can be increased and the corona current density can be increased. In particular, when the pulse width of the pulse voltage is shortened, the flashover voltage can be further increased. Specifically, the pulse width is preferably 50 ns to 100 μs, and more preferably 100 ns to 20 μs. In this specification, the pulse width refers to the time width at the 50% position (rising edge, falling edge) of the peak value.

  Further, when the voltage supplied from the power source is a pulse voltage, the value of the electric field E can be increased. Since the amount of charge given to the fine particles is proportional to the electric field E, the saturation charge amount can be increased.

  Further, in the exhaust gas treatment device of the present embodiment, as shown in FIG. 7, two power sources 20a and 20b for applying a voltage to each of the first discharge electrode portion 7 and the second discharge electrode portion 8 are provided. It may be used. Thus, when two power supplies 20a and 20b are used, the power supplies 20a and 20b are controlled so that the polarities applied to the first discharge electrode portion 7 and the second discharge electrode portion 8 are different, and the polarities are different. Two discharges are generated.

  As shown in FIGS. 4 and 5, the first discharge electrode portion 7 and the second discharge electrode portion 8 are configured to perform creeping discharges having different polarities on the surface of the dielectric 19. The power source 20 is a power source (in FIG. 4, a sine wave AC power source) that applies a positive and negative alternating voltage to a transformer such as a sine wave, a square wave, and a pulse. By discharging this, the high voltage part 22 is formed, and high voltages having different polarities are applied to the first discharge electrode part 7 and the second discharge electrode part 8.

  Regarding the specific values of the voltage and power applied to the first discharge electrode part and the second discharge electrode part, the size of the tube serving as the flow path, the flow rate and flow rate of the exhaust gas passing through the flow path, and further the exhaust gas Depending on the amount and size of the fine particles contained in the gas, it is appropriately selected so that an appropriate discharge can be generated. For example, when processing exhaust gas discharged from a diesel engine, the voltage is Is preferably 2 to 25 kV, and more preferably 5 to 25 kV. Moreover, it is preferable that electric power is 1-50W, and it is still more preferable that it is 5-25W. By comprising in this way, the exhaust gas discharged | emitted from a diesel engine can be processed favorably.

  Further, in the exhaust gas treatment apparatus of the present embodiment, as shown in FIG. 1, the inner space is partitioned into two so that a part of the tube body 4 is parallel to the flow direction of the exhaust gas 6. The first flow path 25 and the second flow path 26 are formed, and one electrode portion (first discharge electrode portion 7) is disposed in the first flow path 25, and the other electrode is disposed in the second flow path 26. Part (second discharge electrode part 8) may be arranged. With such a configuration, the first flow channel 25 and the second flow channel 26 can satisfactorily generate the fine particles 5a and 5b charged with different charges. Of course, in the exhaust gas treatment device of the present embodiment, the ends of the first discharge electrode part and the second discharge electrode part are simply formed in the tube body without dividing the internal space of the tube body into two in this way. You may arrange | position so that it may face the other side of an inner surface.

  Further, in the exhaust gas treatment device 1 of the present embodiment, for example, the charge amount of the first discharge 17 generated by the first discharge electrode portion 7 and the charge amount of the second discharge 18 generated by the second discharge electrode portion 8. May be configured to be independently controllable. By configuring in this way, for example, the charge amount can be made different between the fine particle 5a given a positive charge and the fine particle 5b given a negative charge.

  When such fine particles 5a and 5b are aggregated, the aggregated fine particles 15 are in a state in which either positive or negative charge remains, and other fine particles 5a and 5b that have not yet aggregated or other aggregated fine particles. 15 can easily occur in a continuous manner, thereby improving the aggregation efficiency and increasing the particle diameter of the aggregated fine particles 15. Thereby, the collection efficiency of the honeycomb filter can be further improved. In particular, agglomerated fine particles in which one charge remains is more likely to agglomerate with fine particles having a relatively small particle size (for example, other fine particles that have not yet been agglomerated). The amount of fine particles that flow in can be reduced, and even if a honeycomb filter with a large cell density, average pore size of partition walls, or the like is used, fine particles can be collected well without reducing the collection efficiency. it can.

  Further, in the exhaust gas treatment apparatus of the present embodiment described so far, the first discharge electrode part and the second discharge electrode part of the electrostatic aggregator are arranged one by one inside the tube body. For example, although not shown, the electrostatic aggregator has at least one of the first discharge electrode part and the second discharge electrode part, and the two or more first discharge electrode parts and / Or the 2nd discharge electrode part may be arrange | positioned in the inside of a tubular body in series with the flow direction of exhaust gas, respectively. By comprising in this way, an electric charge is again given to the aggregated fine particles once aggregated, aggregation of the aggregated fine particles can be further promoted, and aggregated fine particles having a larger particle diameter can be generated.

  For example, the electrostatic aggregator has two first discharge electrode portions and two second discharge electrode portions, and each electrode portion is arranged in series in the exhaust gas flow direction inside the tube body. In the case of being, first, positive or negative charges are given to the fine particles by the discharge generated in the first discharge electrode portion and the second discharge electrode portion on the upstream side, and these fine particles are attracted by Coulomb force, After agglomerating at least in space, a positive or negative charge is further given to the obtained aggregated fine particles by the discharge generated at the first discharge electrode part and the second discharge electrode part on the downstream side, and these aggregated fine particles are subjected to Coulomb force. And can be further aggregated.

  As described above, when two or more first discharge electrode portions and / or second discharge electrode portions are arranged in series in the flow direction of the exhaust gas inside the tube body, they are charged. The fine particles are preferably arranged in series at a predetermined interval so that the fine particles can be well aggregated between the electrode parts arranged in series. In addition, the number of the 1st discharge electrode part arrange | positioned inside a tubular body and the 2nd discharge electrode part may be the same, and may differ.

  Further, in the exhaust gas treatment device of the present embodiment, instead of the above-described configuration in which the electrostatic aggregator has two or more first discharge electrode portions and / or second discharge electrode portions, for example, the electrostatic aggregator itself 2 or more, and two or more electrostatic aggregators may be arranged in series in the exhaust gas flow direction inside the tube body. By configuring in this way, the same effect, that is, the aggregated fine particles once aggregated can be recharged to further promote the aggregation of the aggregated fine particles, and the aggregated fine particles having a larger particle diameter are generated. be able to.

[Tube]
Tubes constituting the exhaust gas treatment device of the present embodiment are flow paths through which exhaust gas discharged from internal combustion engines such as automobile engines, construction machine engines, industrial machine stationary engines, and other combustion equipment passes. Thus, an electrostatic aggregator is arranged inside. Furthermore, this tubular body is a counter electrode of the first discharge electrode portion and the second discharge electrode portion when the first discharge and the second discharge are corona discharges.

  Although there is no restriction | limiting in particular about the material of a pipe body, The electroconductive material, for example, the stainless steel material used for the exhaust pipe of a motor vehicle, can be used suitably. Such a conductive material can be suitably used as a counter electrode of an electrode portion for performing corona discharge, and of course, an electrode portion for performing creeping discharge on a tube body thus configured. It can also be used as a ground electrode for generating an electric field between the electrode portion for performing creeping discharge and the tube.

[Honeycomb filter]
As shown in FIG. 1, the honeycomb filter 3 used in the exhaust gas treatment device 1 of the present embodiment is a filter for collecting the fine particles 15 aggregated by the electrostatic aggregator 2. As such a honey-comb filter 3, what is used as a conventionally well-known diesel particulate filter (DPF) for collecting the fine particles contained in exhaust gas, such as an engine, can be used suitably.

  For example, such a honeycomb filter 3 includes a porous partition wall 11 that partitions and forms a plurality of cells 12 serving as flow paths through which exhaust gas passes, and one end (filter inlet end) is opened and A predetermined cell (inlet open cell) with the other end (filter outlet end) sealed, and a remaining cell (outlet open cell) with the filter inlet end sealed and the filter outlet end opened Are preferably arranged alternately. Reference numeral 13 denotes a plugged portion that plugs the end of the cell 12.

  The material of the partition walls constituting the honeycomb filter is not particularly limited. From the viewpoint of strength and heat resistance, silicon carbide, silicon-silicon carbide based composite material, cordierite, silicon nitride, mullite, alumina, spinel, silicon carbide-cordierite based composite material, silicon-silicon carbide composite material, lithium aluminum silicate It is preferable to use at least one selected from the group consisting of aluminum titanate and Fe—Cr—Al-based metals.

  In such a honeycomb filter, when the collected fine particles are deposited on the partition wall, the pressure loss increases, so that the engine is burdened, and the fuel consumption and drivability are lowered. For this reason, regeneration is performed periodically using heating means such as a heater, or post-injection is performed under engine control to oxidize unburned fuel and raise the exhaust gas temperature, burning fine particles deposited on the partition walls It is preferable to reproduce the filter function by performing the reproduction.

  For this reason, in order to promote the combustion at the time of regeneration as described above, the honeycomb filter is preferably one in which a catalyst is supported on the surface of the partition wall and / or inside the partition wall. Such a catalyst is not particularly limited as long as fine particles can be combusted by the heat of exhaust gas. For example, a noble metal element, an element of group VIa of an element periodic table, and an element of group VIII of an element periodic table An element selected from the above can be supported. Specifically, platinum (Pt), palladium (Pd), rhodium (Rh), nickel (Ni), cobalt (Co), molybdenum (Mo), tungsten (W), cerium (Ce), copper (Cu), Examples thereof include vanadium (V), iron (Fe), gold (Au), silver (Ag), and the like, and at least one simple substance or compound selected from these can be used. Moreover, you may carry | support a NOx selective reduction type catalyst component and a NOx occlusion type catalyst component.

  Further, as described above, in the exhaust gas treatment device of the present embodiment, the enlarged aggregated fine particles are collected by the honeycomb filter, so that the cell density or the density of the exhaust gas treatment device is larger than that of the honeycomb filter used in the conventional exhaust gas treatment device. Even when a honeycomb filter having a large average pore diameter of partition walls is used, fine particles can be collected well without reducing the collection efficiency. Such a honeycomb filter has a small pressure loss in an initial state, and can reduce a burden on an internal combustion engine such as an engine.

Specifically, the honeycomb filter used in the exhaust gas treatment apparatus of the present embodiment preferably has a cell density of 50 to 300 cells / cm ² , and 100 to 200 cells / cm ² . More preferably it is. In addition, the honeycomb filter preferably has an average pore diameter of 20 to 150 μm, and more preferably 40 to 100 μm. The average pore diameter is a value measured by the method of “JASO Automobile Standard Automobile Exhaust Gas Purification Catalyst Ceramic Monolith Carrier Test Method M505-87, 6.3 Total Pore Volume, Median Pore Diameter”. is there.

  Although not particularly limited, the honeycomb filter used in the exhaust gas treatment device of the present embodiment preferably has a partition wall porosity of 30 to 80%, and preferably 40 to 60%. Is more preferable. The porosity described above is a value measured by a calculation method from the pore volume. By using such a honeycomb filter, the pressure loss of the exhaust gas treatment device can be reduced.

  INDUSTRIAL APPLICABILITY The exhaust gas treatment apparatus of the present invention is used to remove particulates and harmful substances in exhaust gas discharged from internal combustion engines such as automobile engines, construction machine engines, stationary engines for industrial machines, and other combustion equipment. be able to. In particular, it can be suitably used as an exhaust gas treatment device for efficiently removing fine particles in the exhaust gas.

It is explanatory drawing which illustrates typically one Embodiment of the exhaust gas processing apparatus of this invention, and is sectional drawing cut | disconnected by the surface parallel to the flow direction of the flow path through which exhaust gas passes. It is explanatory drawing which shows typically the structure of the electrostatic aggregator which comprises the exhaust-gas processing apparatus of FIG. It is sectional drawing which cut | disconnected the electrostatic aggregator shown in FIG. 2 by the surface perpendicular | vertical to the flow direction of a flow path. It is explanatory drawing which shows typically the structure of the electrostatic aggregator used for other embodiment of the exhaust-gas processing apparatus of this invention. It is sectional drawing which cut | disconnected the electrostatic aggregator shown in FIG. 4 by the surface perpendicular | vertical to the flow direction of a flow path. It is explanatory drawing which shows typically the structure of the electrostatic aggregator used for other embodiment of the exhaust-gas processing apparatus of this invention. It is explanatory drawing which shows typically the structure of the electrostatic aggregator used for other embodiment of the exhaust-gas processing apparatus of this invention.

Explanation of symbols

1: exhaust gas treatment device, 2: electrostatic aggregator, 3: honeycomb filter, 4: flow path, 5, 5a, 5b: fine particles, 6: exhaust gas, 7: first discharge electrode section, 8: second discharge Electrode part, 9: Purified gas, 11: Partition, 12: Cell, 13: Sealing part, 15: Aggregated fine particles (aggregated fine particles), 17: First discharge, 18: Second discharge, 19: Dielectric 20, 20a, 20b: power supply, 21: transformer, 22: high voltage section, 23: diode, 24: ground electrode, 25: first flow path, 26: second flow path, 27: resistance, 28: conductor .

Claims (12)

A tube serving as a flow path through which the exhaust gas passes, an electrostatic aggregator disposed inside the tube for agglomerating fine particles contained in the exhaust gas, and agglomerated by the electrostatic aggregator An exhaust gas treatment device comprising a honeycomb filter for collecting fine particles,
The electrostatic aggregator provides a first discharge electrode section for generating a first discharge for giving a positive or negative charge to the fine particles, and a charge having a polarity different from that of the first discharge to the fine particles. An exhaust gas treatment device having a second discharge electrode portion for generating the second discharge.   2. The exhaust gas treatment apparatus according to claim 1, wherein the fine particles charged to charges having different polarities by the first discharge and the second discharge are attracted by a Coulomb force and aggregated at least in a space. A part of the tubular body is divided into two internal spaces so as to be parallel to the flow direction of the exhaust gas, and a first flow path and a second flow path are formed,
3. The exhaust gas processing apparatus according to claim 1, wherein the first discharge electrode part is disposed in the first flow path, and the second discharge electrode part is disposed in the second flow path.   At least one of said 1st discharge electrode part and said 2nd discharge electrode part is comprised so that corona discharge may be performed by making the inner surface of the said tubular body into a counter electrode. The exhaust gas treatment device according to 1.   4. At least one of said 1st discharge electrode part and said 2nd discharge electrode part has a dielectric material, It is comprised so that creeping discharge may be performed on the surface of the said dielectric material. The exhaust gas treatment apparatus according to one item.   The charge amount of the first discharge generated by the first discharge electrode portion and the charge amount of the second discharge generated by the second discharge electrode portion can be independently controlled. The exhaust gas processing apparatus according to any one of?   The electrostatic aggregator has at least one of the first discharge electrode part and the second discharge electrode part, and the two or more first discharge electrode parts and / or the second discharge electrode. The exhaust gas processing apparatus according to any one of claims 1 to 6, wherein a portion is arranged in series in the flow direction of the exhaust gas inside the tubular body.   The honeycomb filter includes a porous partition wall that defines a plurality of cells serving as flow paths through which the exhaust gas passes, and one end (filter inlet end) is opened and the other end (filter outlet) Predetermined cells (inlet open cells) whose end portions are sealed and residual cells (outlet open cells) whose filter inlet end portions are sealed and whose filter outlet end portions are open are alternately arranged. The exhaust gas treatment device according to any one of claims 1 to 7, wherein the exhaust gas treatment device is provided.   The exhaust gas treatment apparatus according to claim 8, wherein the honeycomb filter has a catalyst supported on a surface of the partition wall and / or inside the partition wall. The honeycomb filter, the cell density, the exhaust gas processing device according to claim 8 or 9 is of 50 to 300 cells / cm ^2.   The exhaust gas treatment apparatus according to any one of claims 8 to 10, wherein the honeycomb filter has an average pore diameter of 20 to 150 µm.   The exhaust gas treatment device according to any one of claims 8 to 11, wherein the honeycomb filter has a porosity of 30 to 80%.

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