JP4581130B2 - Exhaust gas treatment method and exhaust gas treatment apparatus - Google Patents

Description

  The present invention relates to an exhaust gas treatment method and an exhaust gas treatment device that purify exhaust gas of an internal combustion engine mounted on an automobile or the like by using a corona discharge provided with a charge aggregation portion and a filter portion.

  Electrostatic agglomeration devices, electrostatic dust collectors, and the like are used as exhaust gas treatment devices for factory gas, power plant gas, automobile gas, etc., and as gas treatment devices for various manufacturing factories and medical sites. In these gas treatment devices, a high voltage is applied between the corona electrode and the dust collecting electrode to generate a corona discharge in the gas, and this corona discharge charges floating fine particles in the gas, and the charged particles are electrostatically charged. It is attracted to the dust collecting electrode by force to enlarge or capture.

  In the electrostatic precipitator using these discharges, the gas to be treated is passed through a cylindrical body, and a dust collecting electrode formed by the cylindrical body or a cylindrical dust collecting electrode provided separately from the cylindrical body is used. A corona electrode is arranged at substantially the center (axial center), and a high voltage is applied between the corona electrode and the dust collecting electrode, thereby generating a corona discharge in the gas and charging suspended fine particles in the gas.

  The charged particles are moved to the surface of the dust collecting electrode by an electrostatic force by an electric field formed between the corona electrode and the dust collecting electrode, and are captured on the surface of the dust collecting electrode. The trapped particles are separated from the dust collecting electrode and collected by shaking or the like as in the electric dust collector or the like, or burned and removed by heating with a heater or the like provided adjacent to the dust collecting electrode.

  When exhaust gas from an internal combustion engine such as a diesel engine mounted on an automobile is targeted, PM (Particulate Matter) contained in the exhaust gas is treated as a component to be treated. However, this PM contains soot (soot), which is said to be particularly difficult to burn, and SOF (Soluble Organic Fraction), which is steam at high temperatures. This Soot is an engine exhaust material mainly composed of carbon, and SOF is a component dissolved in an organic solvent such as benzene and toluene, which is generated due to unburned fuel and oil, and burns on the surface of the oxidation catalyst. it can.

  In this electrostatic precipitating method, the part that performs the electrostatic precipitating action becomes an electrostatic collecting part when paying attention to the collecting function, and becomes an electrostatic collecting part when paying attention to the aggregating function. Electrostatic collection on the dust electrode. The soot trapped and deposited on the dust collecting electrode is eventually peeled off by the flow of exhaust gas and re-scatters.

  In other words, electrostatic dust collection creates a bond between the particles captured on the surface of the dust collection electrode, causing the fine particles to agglomerate and swell. It peels off from the surface and re-scatters. The re-scattered particles gradually increase in particle size while being repeatedly charged, trapped, and peeled off in the gas processing apparatus, but are eventually discharged from the electrostatic precipitator by re-scattering. These re-scattered particles are agglomerated and enlarged, and by utilizing this characteristic, it is possible to effectively collect soot even if a coarse filter is disposed in the subsequent stage.

  On the other hand, the gasified SOF in the exhaust gas becomes sticky mist when cooled and condensed and liquefied, and this mist-like SOF captures ultra-fine particles and agglomerates and enlarges according to the principle of bird's-eye. To do. That is, this SOF is useful as a binder for collecting Soot and agglomerating. In order to utilize this SOF coagulation enlargement function when collecting ultrafine particles, it is effective to provide a dust collecting device such as a filter on the downstream side of the electrocoagulation device.

  In the configuration in which the filter is arranged on the downstream side, the ultrafine particles in the exhaust gas agglomerate and enlarge due to the synergistic effect of the electrostatic action and the adhesion function of the liquefied SOF, and the particles discharged from the electrocoagulation apparatus Since the particle size becomes large, these particles can be easily captured even with a coarse filter.

  However, since the entire amount of this SOF cannot be used, if it is necessary to remove this SOF at a high removal rate, it is necessary to use an oxidation catalyst in combination. This gasified SOF can be oxidized with an oxidation catalyst, and the higher the temperature, the higher the catalytic activity of this oxidation catalyst. Also, the electrocoagulation device becomes unstable when the corona discharge exceeds 500 ° C. and has sufficient power. Since it cannot be charged and the electrostatic precipitating action decreases, it is usually necessary to install an oxidation catalyst in front of the exhaust pipe where the gas temperature is high and install an electrostatic precipitator behind the exhaust pipe where the gas temperature decreases. Conceivable.

  However, when the oxidation catalyst is disposed upstream of the electrocoagulation device, SOF is oxidized by the oxidation catalyst, so that the effect of capturing ultrafine particles in the electrocoagulation device is reduced, and the capture is performed. Collection efficiency will not increase. In addition, when the aggregate composed of SOF and Soot flows into the oxidation catalyst, the oxidation catalyst is clogged.

  Therefore, it is better to treat the remaining SOF used for the capture of Soot and the agglomeration with an oxidation catalyst, and the position of the oxidation catalyst is lower than the upstream (upstream side) of the charged aggregation part. It is better to place it on the side. That is, considering the functions of the electrocoagulation device, the filter, and the oxidation catalyst, the exhaust gas can be purified most effectively by arranging the electrocoagulation device, the coarse filter, and the oxidation catalyst in this order from the upstream side.

However, the exhaust gas purifying apparatus using this electrocoagulation apparatus has a problem of deterioration in purification performance due to PM accumulation and a problem of deterioration in fuel consumption.
That is, since electrostatic force is always supplied when the charged agglomeration portion is energized for corona discharge, the charged PM is electrically attracted and attached to the surface of the dust collecting electrode. For this reason, it does not easily peel off in the flow of exhaust gas, but accumulates and accumulates sequentially until it becomes sufficiently large. Then, the PM is enlarged and easily peeled off, or the flow rate of the exhaust gas is increased, and the enlarged PM is flowed downstream only after the force larger than the force adhering to the wall surface by the electrostatic force acts.

  For this reason, in the charged and agglomerated portion using the electric dust collection effect by the turbulent flow promoting means in the vicinity of the surface of the dust collecting electrode, the irregularities for promoting turbulent flow are buried by the PM deposition during the deposition of PM, thereby promoting the turbulent flow There arises a problem that the effect is lowered and the dust collecting performance is lowered.

  The operating state of the internal combustion engine changes in various operating states from an idling state to a high rotation / high load state according to the use / running conditions of the automobile, and accordingly, the exhaust gas flow rate, temperature, PM amount, etc. The state of the exhaust gas changes. Therefore, an exhaust gas treatment device mounted on a vehicle is required to have a performance for efficiently purifying PM under all these conditions. At the same time, by controlling the input power according to the state of the exhaust gas, it is considered that the input power for corona discharge to the charging and aggregating portion can be minimized and the deterioration of fuel consumption can be suppressed.

  Therefore, in the exhaust gas purifying apparatus having a charging aggregation unit that charges and aggregates the components to be collected in the exhaust gas by corona discharge, in order to reduce power consumption as much as possible while maintaining the purification performance, the charging aggregation unit The power input to the engine increases when the internal combustion engine is in a high rotation and high load condition, that is, when the exhaust gas amount and the PM amount are large, and when the internal combustion engine is in a low rotation and low load condition, that is, It is desirable to reduce the amount of exhaust gas and PM when the amount is small. Furthermore, since PM does not exist in the exhaust gas under the condition where the fuel injection is stopped, it is desirable to turn off the input power to the charging and aggregating portion.

Several proposals have been made regarding the control of the input power.
As one of them, a target energization current value to be supplied between the discharge electrode pair and the collection electrode pair is calculated based on the operating conditions of the vehicle diesel engine, and is applied between the electrode pair based on the calculated target current value. An exhaust gas purifying device for a vehicle diesel engine that controls a voltage value to be applied has been proposed (see, for example, Patent Document 1).

  In this exhaust gas purifying device, the operating conditions of the engine, in particular, the operating conditions linked to the diesel particulate emissions include the cooling water temperature, the fuel injection amount, the speed (load), etc., and the diesel engine when these conditions are changed The particulate discharge amount is stored in advance in the storage unit of the microcomputer device as a map, and the minimum energization current value capable of processing the predicted discharge amount with a predetermined purification rate is obtained based on this map.

  In addition, a plasma generator for generating active oxygen or the like having high oxidation removal capability for PM by corona discharge is provided on the upstream side of the particulate filter, and the six conditions for the PM oxidation removal capability of the particulate filter are insufficient. Has been proposed (see, for example, Patent Document 2).

  On the other hand, the inventors have the following relationship that the fuel injection amount into the cylinder of the internal combustion engine is closely related to the state of the exhaust gas, and the fuel injection is stopped at the time of engine braking. The following knowledge was obtained.

Since fuel injection is stopped during the engine braking operation, PM in the exhaust gas is eliminated, so there is no problem even if the purification performance of the charge aggregation portion temporarily decreases. Further, when the input power to the charging and aggregating part is turned OFF, the electrostatic force between the PM and the dust collecting electrode disappears at that moment, so the accumulated PM is easily peeled off by the flow of exhaust gas, and the enlarged PM Flows out to the downstream filter section. This re-scattering of the PM recovers the turbulent flow promoting action such as irregularities in the vicinity of the surface of the dust collecting electrode. Therefore, it is preferable to positively remove the PM from the dust collecting electrode when the input power is turned off.
Japanese Patent No. 3070621 ([0049], [0050], FIG. 21) JP 2002-349240 A ([0089], [0090], FIG. 34)

  The present invention has been made in order to obtain the above knowledge and solve the above problems, and its purpose is to use an agglomeration function and a dust collection function by corona discharge and a filter dust collection function, thereby In a vehicle-mounted exhaust gas treatment device that collects and collects fine particles by agglomeration, the agglomeration function by corona discharge is achieved with very simple input power control that stops energization of the charged agglomeration part during engine braking. It is an object of the present invention to provide an exhaust gas processing method and an exhaust gas processing device that can recover the power consumption and save power consumption.

  An exhaust gas treatment method for achieving the above-described object is achieved by providing, on the upstream side, a charge agglomeration part that aggregates by charging a component to be collected in exhaust gas of an internal combustion engine mounted on a vehicle by corona discharge. In the exhaust gas processing method of the exhaust gas processing device provided with a filter part for collecting the component that has been made downstream, controlling the discharge power input to the charging and aggregating part based on the operating conditions of the internal combustion engine, and When the fuel injection amount becomes zero by the engine brake operation of the internal combustion engine, the energization to the charging aggregation unit is stopped, and the energization to the charging aggregation unit is stopped while the engine braking operation is detected. .

  With this configuration, fuel injection is made zero during engine braking operation, so PM is not generated in the exhaust gas, and the accumulated PM is scattered by losing electrostatic force by stopping energization to the charge aggregation part. Therefore, the aggregation ability of the charged aggregation portion can be recovered without deteriorating the exhaust gas purification performance.

  Further, in the above exhaust gas treatment method, when the energization to the charged aggregation portion is stopped, an impact is given to the charged aggregation portion. This impact is applied using a hammering device for an electrostatic precipitator, an impact applying device for a bag filter, an impact applying device used in a powder device, a sliding hammer using a linear solenoid, or an electromagnetic solenoid. Can be used.

With this configuration, PM that has lost its electrostatic force due to the stop of energization to the charge aggregation portion can be efficiently removed from the charge aggregation portion.
And, the exhaust gas treatment device for achieving the above-mentioned object is, on the upstream side, a charged aggregation portion that aggregates by charging the collection target component in the exhaust gas of the internal combustion engine mounted on the vehicle by corona discharge, An exhaust gas processing apparatus provided with a filter unit for collecting the agglomerated components on the downstream side, controlling discharge electric power supplied to the charging and aggregating unit based on operating conditions of the internal combustion engine, and the internal combustion engine The engine stops energization when the fuel injection amount becomes zero due to the engine braking operation, and continues to stop energizing the charging aggregation unit while detecting the engine braking operation. A gas processing control device is provided.

Further, the exhaust gas processing apparatus is configured to give an impact to the charging aggregation portion when the energization to the charging aggregation portion is stopped.
Furthermore, in the above exhaust gas processing apparatus, an oxidation catalyst is provided on the downstream side of the filter unit. With this configuration, the remaining SOF used for soot capture and coagulation enlargement can be processed, and the exhaust gas purification performance can be further improved.

  According to the exhaust gas processing method and the exhaust gas processing apparatus of the present invention, the recovery of the coagulation function by corona discharge and the power consumption can be achieved with a very simple input power control that stops energization to the charged aggregation unit during engine braking. Savings.

  Hereinafter, an exhaust gas processing method and an exhaust gas processing apparatus according to embodiments of the present invention will be described with reference to the drawings, taking an exhaust gas processing apparatus using exhaust gas from a diesel engine mounted on a vehicle as a processing target gas as an example. To do.

  As shown in FIG. 1, in the exhaust gas processing apparatus 1 of the first embodiment, a charging aggregation unit 10 that aggregates by charging a soot component, which is a collection target component in exhaust gas, by corona discharge is disposed upstream. In addition, the filter unit 20 for collecting the aggregated components is provided on the downstream side, an oxidation catalyst 30 is further provided on the downstream side of the filter unit 20, and an impact applying device (impact applying unit) is further provided on the charging aggregation unit 10. 40.

  In other words, the charged agglomeration portion 10 that coarsens and aggregates and temporarily collects soot by corona discharge is disposed in the front stage, and the filter portion 20 that collects the enlarged soot re-scattered from the charged agglomeration portion 10 is disposed in the middle stage. An oxidation catalyst 30 for purifying the vaporized component such as SOF that has been converted into a gas is disposed in the subsequent stage.

  Further, a differential pressure sensor 51 for detecting the differential pressure across the filter unit 20 is provided, and an oxygen concentration sensor 52 and an exhaust gas temperature sensor 53 are further provided on the downstream side of the filter unit 20. The outputs of these sensors 51, 52, 53 are input to the control device 50 of the exhaust gas processing device 1. The control device 50 is configured to be incorporated in an engine control device that is usually called an engine control unit, and controls corona discharge of the charge aggregation unit 10 and regeneration means of the filter unit 20.

  The charging aggregation unit 10 is configured by arranging a plurality of, for example, six charging aggregation units 11 in parallel. As shown in FIGS. 3 to 5, the charging and aggregating unit 11 includes a dust collecting electrode 11 a formed of a low voltage electrode and a corona electrode 11 b formed of a high voltage electrode.

  In particular, the charging aggregation unit 10 preferably has a multi-tube structure in which the charging aggregation units 11 are arranged in parallel. Since the electric power that can be input to the charging aggregation unit 10 has a large relationship with the PM collecting ability, if the function of the charging aggregation unit 10 is sufficiently exerted in a wide operating range from idling to the maximum rotation speed of the engine, Either a long tube or a short tube will be used. However, in an automobile, the installation space is limited, and considering that the long one to keep the insulation state is disadvantageous in terms of strength and vibration. This is because a multi-tube structure is advantageous.

  The dust collecting electrode 11a is made of a conductive material such as SUS304, and is formed in a cylindrical body such as a cylindrical body. The upstream side is connected to the gas inlet chamber 11c and the downstream side is connected to the gas outlet chamber 11d. The The cylindrical body 11a as the dust collecting electrode also serves as a passage wall of the gas passage. The cross-sectional shape of the cylindrical body 11a is not particularly limited. Considering the stability of the corona discharge, a circular shape is preferable, but it may be a square or the like. In particular, when a plurality of corona electrodes 11b are provided, an elliptical shape, a triangular shape, a rectangular shape, or other polygonal shapes may be used.

  The corona electrode 11b may be an electrode having a high electric field concentration coefficient, and may be a linear body (wire shape) such as a thin wire electrode, a square electrode, or a projection-structured electrode, or a linear body such as a rod, such as a hollow wire made of SUS304. Etc. are formed. And it arrange | positions inside the cylindrical body 11b, for example, the center, such as an axial center part of a cylindrical body. Further, as shown in FIG. 5, a plurality of corona electrodes 11b may be provided inside the cylindrical body 11b.

  The dust collection electrode 11a and the corona electrode 11b are configured to be electrically insulated from each other by an insulator or the like. The dust collecting electrode 11a is electrically grounded (grounded) and maintained at the ground potential, but is maintained at another potential as necessary. On the other hand, the corona electrode 11b is connected to a high voltage power source. The high voltage generated by this high-voltage power source and applied to the corona electrode 11b is generally preferably a negative direct-current voltage, but may be any of direct current, alternating current, pulsed, The polarity may be negative or positive. Moreover, the voltage should just be a voltage which can generate | occur | produce a corona discharge in the exhaust gas G which passes between this cylindrical body 11a and the corona electrode 11b.

  The impact applying device 40 is a device for applying impact, vibration, etc. to the dust collecting electrode 11a in order to promote the peeling of the PM accumulated on the dust collecting electrode 11a. An impact applying device for a filter, an impact applying device used in a powder device, or the like can be used. More specifically, a pneumatic hammering device (air hammer / air knocker) that generates an impact force by releasing a piston fixed with a strong magnetic force at high speed by supplying compressed air, or a piston rod using the energy of an electromagnet These are an electromagnetic hammering device (electromagnetic maghammer) that generates an impact force by moving at a high speed, a sliding hammer that uses a linear solenoid, an impact generator that uses an electromagnetic solenoid, and the like.

  The passage wall of the cylindrical body 11a of the charging aggregation portion 10 is used as a cooling wall (gas cooling portion) so that the exhaust gas G can be cooled by the charging aggregation portion 10. That is, the outer surface side of the cylindrical body 11a is configured to be naturally air-cooled or forcedly cooled.

  In this natural air cooling, the outer surface of the cylindrical body 11a is kept warm, or the cylindrical body 11a is not sealed with another cylindrical body (not shown) such as a case of the exhaust gas treatment device 1, and is in an open air state. For example, it is easy to make contact with the outside air, such as providing a ventilation hole for another cylindrical body serving as a case, so that natural convection heat transfer is easily performed. Moreover, in order to promote the cooling effect by heat radiation, the temperature of surrounding members is lowered, or in order to increase the cooling effect by heat conduction, it is brought into contact with a low-temperature heat conductor. Furthermore, cooling fins that promote heat dissipation to the outside of the cylindrical body 11a can be provided on the outer surface of the cylindrical body 11a. Examples of the cooling fins include smooth annular fins, slot fins, tent fins, strip fins, and wire loop fins that are generally used in heat exchangers.

  Further, in forced cooling, a fan or the like blows air to the outer surface of the cylindrical body 11a to perform forced cooling by convective heat transfer, or the cylindrical body 11a has a double tube structure through which a coolant such as cooling water passes. The structure 11a is configured to be forcibly cooled with a refrigerant. Not limited to these cooling means, general cooling means can be applied.

  In the exhaust gas treatment device 1 mounted on the vehicle, a strong wind is applied to a portion of the cylindrical body 11 exposed to the outside air of the charging and aggregating unit 10 due to traveling of the vehicle. The exhaust gas G is cooled. Therefore, even if no special or active cooling means is provided, a cooling effect can be obtained unless an active heat retaining means is provided.

  This gas cooling is particularly effective when the processing target gas G is at a temperature of 200 ° C. or higher. In other words, when the gas to be processed is 200 ° C. or higher, most of the components such as SOF are evaporated and gasified, but by this gas cooling, the exhaust gas G is brought to a temperature lower than that and the evaporated components such as SOF are changed. It can be condensed and liquefied, and the stickiness of this liquefied component can exert an effect similar to that of a sticky bird, so that microparticles such as Soot can be aggregated very efficiently. That is, the presence of the liquefied SOF component exerts the adhesive action of soot aggregation.

  Further, in the charging aggregation unit 11 of the charging aggregation unit 10, as shown in FIGS. 6 to 8, turbulence is promoted with respect to the flow of the exhaust gas G in the vicinity of the inner surface of the cylindrical body 11 a of the charging aggregation unit 10. The turbulent flow promoting means 11e can be provided on or near the surface of the cylindrical body 11a. The turbulent flow promoting means 11e may be provided by processing the surface of the cylindrical body 11a, or a structure separate from the cylindrical body 11a may be disposed in contact with or floating on the surface of the cylindrical body 11a. Good.

  The turbulent flow promoting means 11e may have an uneven structure, and this uneven structure is formed by inserting one or more linear bodies (round bars or square bars) in a spiral shape into the cylindrical body 11a. It is also possible to provide an internally grooved tube structure by wrapping around the inner surface of 11a, or providing regular irregularities such as trapezoidal convex portions, lattice grooves, and spiral grooves by grooving on the inner surface of the cylindrical body 11a. In addition, ring-shaped convex portions are formed on the inner surface of the cylindrical body 11a at intervals in the axial direction of the cylindrical body 11a, formed with fins having a three-dimensional structure, or blasted and rough irregularities. Can also be formed. These irregularities may be formed uniformly or may be distributed.

  Furthermore, not only the cylindrical body 11a is processed, but also a plate material provided with irregularities by processing, or a plate material that is already formed with irregularities is shaped and inserted so as to be insertable into the cylindrical body 11a. The cylindrical body 11a may be inserted into a planar body that is already commercially available with irregularities. Sheet-like projections such as wire mesh, punching metal, and expander metal are useful as this planar body, and slit grills, diamond screens, dimple screens (without holes), dimple screens (with holes), slit bay screens, A punching screen such as a bridge bay screen, a triangular bay screen, a semi-circular bay screen, etc. can be used.

  The turbulent flow promotion by the turbulent flow promoting means 11e can increase the agitating action in the cross-sectional direction of the flow path, thereby shortening the time required for charging the components in the exhaust gas in the entire flow path space and collecting charged particles. It is possible to facilitate the contact of the dust electrode with the opposing surface, increase the residence time associated with the reduction of the main flow velocity in the vicinity of the exhaust gas opposing surface, and further promote the capture of charged particles by electrostatic force. it can.

  Further, the charging aggregation unit 11 of the charging aggregation unit 10 can also be configured as follows. As shown in FIGS. 9 to 13, the gas passage wall of the charging and aggregating unit 11, that is, the gas passage wall of the charging and aggregating unit 10 is formed of a cylindrical body 11 f, and the dust collecting electrode 11 a serving as a low-voltage electrode is gas. It is formed of a conductive cylindrical body disposed near the surface of the passage wall 11f. Further, the corona electrode 11b is formed of a linear high-voltage electrode arranged inside the cylindrical body 11f. Both the cylindrical body 11f and the dust collecting electrode 11a may be formed of a conductive material. However, if the cylindrical body 11f is formed of an insulating material and the dust collecting electrode 11a is formed of a conductive material, the surface of the charge aggregation unit 11 is formed. Is electrically insulated by the cylindrical body 11f, the safety against leakage etc. is increased.

  Further, when the turbulent flow promoting means 11e is provided on or near the surface of the dust collecting electrode 11a as shown in FIGS. 9 to 12, or when the dust collecting electrode 11a is formed with the turbulent flow promoting means 11e as shown in FIG. The effect by the turbulent flow promoting means 11e can be obtained.

  In this configuration, since the dust collecting electrode 11a is formed separately from the cylindrical body 11f, the dust collecting electrode 11a does not need the function of the gas passage wall. Therefore, the dust collection electrode 11a may have gas permeability and can increase the surface area, so that the effect of cohesive enlargement can be further increased. Further, when the cylindrical body 11f is formed of an insulator, the surface of the charging and aggregating unit 11 can be electrically insulated, and the safety against leakage etc. can be increased.

  The filter unit 20 is configured to have a filter for collecting and removing aggregates that are coarsened and re-scattered from the charge aggregation unit 10. This filter may be made of ceramics such as SiC and cordierite having excellent heat resistance. However, if the filter is made of a metal filter such as stainless steel, the collected PM may be heated at a high temperature. Since it is difficult to melt, it can be easily regenerated by flaming combustion.

  Since the filter unit 20 collects the soot that is a collection target component in the upstream charging aggregation unit 10 after aggregation and enlargement, the filter unit 20 can be formed with a relatively coarse filter having a small pressure loss. . The filter unit 20 may be a non-continuous regeneration filter that does not carry a catalyst, or a continuous regeneration filter that carries a catalyst.

  When the amount of soot collected increases and the filter portion 20 becomes clogged, the filter portion 20 needs to be regenerated in order to burn and remove the soot, and a heating means for that purpose is required.

As the heating means, a heater, a burner, a short-circuit electrode, or the like can be considered.
In the heater for heating, a heater such as a metal wire is embedded in the surface of the filter member or in the surface and inside, and the heater is heated by energizing the heater to raise the temperature of the filter unit 20. In the case of this heater method, the temperature rise and maintenance temperature of the filter unit 20 are controlled by the electric resistance value of the heater and the input power.

  The burner supplies combustion gas immediately before the filter unit 20 and heats the filter unit 20 to raise the temperature. The burner is supplied with external fuel (which can be shared with vehicle fuel). Burns and generates hot gases. Although the temperature of the filter unit 20 is increased by the high temperature gas, since the high temperature gas is injected into the exhaust gas, PM in the exhaust gas can be ignited to contribute to the temperature increase of the filter unit 20.

  The shorting electrode is formed between electrodes provided adjacent to each other when the soot accumulates, or an electrode provided adjacent to the conductive portion of the filter member, and between the electrodes or between the conductive portion of the filter member and the electrode. When the gap is filled with the collected soot, it is electrically short-circuited, and the soot is self-burned by the spark generated by this short-circuit.

  In the case of ceramic filters, local heating by heating means makes it difficult to make the temperature of the filter uniform, and heat cracking due to uneven reproduction and temperature difference is likely to occur, but in the case of metal filters, the temperature is uniform. Is easy. In the case of a metal filter, a method using a short-circuit electrode can be used in addition to an external heating method using a heater or a burner.

  The oxidation catalyst 30 is formed by supporting an oxidation catalyst such as platinum on a support such as a ceramic honeycomb structure, and is not liquefied even by gas cooling, but an evaporation component such as SOF that passes through the filter unit 20 in a gas phase state. To purify.

  And in this exhaust gas processing apparatus 1, the exhaust gas G is purified as follows. In the most upstream charging aggregation section 10, the exhaust gas G is allowed to pass from the gas inlet chamber 11 c into the cylindrical body (dust collection electrode) 11 a of each charging aggregation unit 11. At the same time, a high voltage is applied between the corona electrode 11b and the dust collecting electrode 11a to form a corona discharge inside the dust collecting electrode 11a, and the soot of PM in the exhaust gas G passing through the inside of the dust collecting electrode 11a. : Charge the target component such as 煤) and agglomerate the charged particles.

  In the charging aggregation unit 10, solid components such as soot in the exhaust gas are charged using charging by corona discharge. At the same time, the exhaust gas G is cooled, and a liquid component such as a mist-like SOF (soluble organic component) condensed by this cooling serves as a binder. Therefore, in this exhaust gas processing apparatus 1, since the binder function of the liquid component condensed by cooling can be used, fine soot particles can be aggregated more efficiently. That is, in the charging condensing unit 10, in addition to the electrostatic dust collecting function of corona discharge, the floating fine particles in the exhaust gas G can be efficiently agglomerated and enlarged using the adhesion function of liquid components such as SOF condensed by gas cooling. .

  The aggregate is moved to the dust collecting electrode 11a by the clonal force by the electric field between the corona electrode 11b and the dust collecting electrode 11a, and is temporarily collected on the surface of the dust collecting electrode 11a. The electric charge is gradually lost by touching 11a, and further becomes coarse on the wall surface. As a result, it peels off from the surface of the dust collecting electrode 11a by the flow of the exhaust gas G and re-scatters.

  Then, the re-scattered aggregates and the components to be collected that directly flow in are collected by the filter unit 20, but the aggregates that are re-scattered or aggregated around the SOF are coarsened and enlarged. Therefore, even if the filter has a relatively coarse mesh, it can be collected efficiently. Therefore, finer soot particles can be efficiently collected as compared with a case where mechanical trapping is performed only with a normal physical filter. In addition, since the filter part 20 can use a coarse filter with a small pressure loss, a pressure loss can be made small, and it can operate continuously for a considerable long time until clogging.

  Further, in the most downstream oxidation catalyst 30, components such as SOF that have passed through the charge aggregation unit 10 and the filter unit 20 while being gasified are oxidized and removed. Thereby, evaporation components such as SOF that have not been condensed can also be removed, so that the PM removal capability can be further enhanced.

As a result, the exhaust gas G flowing into the exhaust gas processing device 1 is discharged from the exhaust gas processing device 1 as purified exhaust gas Gc.
Then, when the collection target component such as Soot is accumulated and clogging progresses and exceeds a predetermined limit value (threshold value), the filter is heated by a heating means (not shown) provided in the filter. Then, the temperature of the filter is raised to a temperature at which the soot can be ignited (about 500 ° C.) or more to burn and remove the soot. Even if the temperature rise of the filter is localized, once the combustion of the soot is started, combustion heat is generated and the propagation of the combustion occurs. Therefore, the soot of the entire filter can be burned and removed to regenerate the entire filter. In this case, when the filter unit 20 is formed of a metal filter, the soot is hardly melted even at a high temperature when the soot is burned and removed, so that the soot can be easily regenerated by flaming combustion.

  In the present invention, the energization of the charging and aggregating unit 10 is stopped during the engine braking operation of the vehicle. In the ON / OFF control of the input power to the charging and aggregating unit 10, as shown by A in FIG. 2, it is basically set to ON when the engine brake is not operating and OFF when the engine brake is operating. However, it is necessary to consider the time from when the fuel injection is stopped during the operation of the engine brake to when the exhaust gas (fresh air as it is) reaches the charging and aggregating portion 10 from the inside of the cylinder. In other words, in order to save the input power, it is preferable to delay the time when the input power is OFF by a little time Δt1 as compared with the time when the operation of the engine brake is ON, as indicated by B in FIG. Further, as shown by B and C in FIG. 2, when the input power is turned on, it is preferable from the viewpoint of improving fuel efficiency that the engine brake operation is delayed by a little time Δt2 than when the operation of the engine brake is turned off.

  During this engine braking, the fuel injection into the cylinder of the internal combustion engine is stopped and the fuel injection amount becomes zero, so PM is not generated in the exhaust gas, so that the exhaust gas purification performance is not degraded. The aggregation ability of the charged aggregation portion 10 can be recovered.

  Further, by stopping energization to the charging and aggregating unit 10, the electrostatic force of the PM which has been enlarged and accumulated can be lost and re-scattered and collected by the filter unit 20, thereby reducing the exhaust gas purification performance. The aggregation ability of the charged aggregation part 10 can be recovered without any problem.

  Further, during the engine braking operation, the impact applying device 40 applies an impact to the charging aggregation portion 10. As a result, it is possible to promote the removal of the PM that has lost its electrostatic force due to the stop of energization of the charge aggregation portion 10.

  The removal of the PM accumulated on the charged aggregation portion 10 exposes the turbulence promoting means 11e from the burial of the turbulence promoting means 11e due to the accumulated PM, so that the turbulence promoting means 11e is particularly provided. This has a great effect on the recovery of the aggregation ability of the charged aggregation portion 10.

It is a figure which shows typically the structure of the gas processing apparatus which concerns on this invention. It is a figure which shows the timing of ON / OFF of an engine brake and ON / OFF of input electric power. It is a sectional side view of a charge aggregation unit. It is sectional drawing which shows the charging aggregation unit whose cross-sectional shape of a cylindrical body is circular. FIG. 3 is a cross-sectional view showing a charging and aggregating unit in which a cylindrical body is a flat body having a circular end and a plurality of corona electrodes. It is a sectional side view of the charging aggregation unit provided with the turbulent flow promoting means. It is sectional drawing which shows the charging aggregation unit with a circular cross-sectional shape of the cylindrical body which provided the turbulent flow promotion means. FIG. 5 is a cross-sectional view showing a charging and aggregating unit in which a tubular body provided with turbulent flow promoting means is a flat body having a circular end and a plurality of corona electrodes. It is a sectional side view of the charge aggregation unit which formed the dust collection electrode and the cylindrical body separately. It is sectional drawing which shows the charging aggregation unit with a circular cross-sectional shape of the cylindrical body formed separately from the dust collection electrode which provided the turbulent flow promotion means. FIG. 4 is a cross-sectional view showing a charging and aggregating unit in which a cylindrical body formed separately from a dust collecting electrode provided with turbulent flow promoting means is a flat body having a circular end and a plurality of corona electrodes. It is sectional drawing which shows the charging aggregation unit whose cross-sectional shape of the cylindrical body formed separately from the dust collection electrode which provided the turbulent flow promotion means is a rectangle. FIG. 5 is a cross-sectional view showing a charging and aggregating unit in which a cylindrical body formed separately from a dust collecting electrode serving also as a turbulent flow promoting means is rectangular and has a plurality of corona electrodes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust-gas processing apparatus 10 Charge aggregation part 20 Filter part 30 Oxidation catalyst 40 Impact application apparatus 50 Control apparatus

Claims (5)

Exhaust gas equipped with a charge aggregation part that collects and aggregates the components to be collected in the exhaust gas of the internal combustion engine mounted on the vehicle by corona discharge, and a filter part that collects the aggregated components on the downstream side In the exhaust gas treatment method of a gas treatment device,
Based on the operating conditions of the internal combustion engine, the discharge power supplied to the charging aggregation unit is controlled, and when the fuel injection amount becomes zero due to the engine braking operation of the internal combustion engine, the energization to the charging aggregation unit is stopped. The exhaust gas processing method is characterized by continuing to stop energization of the charging and aggregating portion while detecting the engine braking operation.   2. The exhaust gas processing method according to claim 1, wherein when the energization to the charging aggregation portion is stopped, an impact is applied to the charging aggregation portion. Exhaust gas equipped with a charge aggregation part that collects and aggregates the components to be collected in the exhaust gas of the internal combustion engine mounted on the vehicle by corona discharge, and a filter part that collects the aggregated components on the downstream side A gas treatment device,
Based on the operating conditions of the internal combustion engine, the discharge power supplied to the charging aggregation unit is controlled, and when the fuel injection amount becomes zero due to the engine braking operation of the internal combustion engine, the energization to the charging aggregation unit is stopped. An exhaust gas processing apparatus comprising an exhaust gas processing control device that continues to stop energization of the charging and aggregating unit while detecting an engine brake operation.   4. The exhaust gas processing apparatus according to claim 3, wherein when the energization to the charging aggregation portion is stopped, an impact is applied to the charging aggregation portion.   The exhaust gas processing apparatus according to claim 3 or 4, wherein an oxidation catalyst is provided on a downstream side of the filter unit.

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