JP6193734B2 - Particle charged exhaust purification system - Google Patents

Description

  The present invention relates to a particle charged exhaust purification device.

  Conventionally, exhaust purification is carried out by installing an aftertreatment device in the middle of the exhaust pipe of a diesel engine. As this type of aftertreatment device, particulate matter (particulate matter) discharged from the diesel engine is used. A particulate filter that collects (a particulate material) is known.

  The particulate filter mainly comprises a filter body having a porous honeycomb structure made of ceramic such as cordierite, and the inlets of the respective flow paths partitioned in a lattice shape in the filter body are alternately plugged by plugs. In addition, for the flow channel whose inlet is not sealed, its outlet is sealed with a plug, and only the exhaust gas that has permeated through the porous thin wall partitioning each flow channel is discharged downstream. Thus, the particulates are collected on the inner surface of the porous thin wall.

  Then, corona discharge is generated in the exhaust pipe, the particulates are charged by the corona discharge, and collected by the particulate filter, thereby improving the collection rate of the particulate filter and charging. It has been proposed to suppress an increase in pressure loss compared to when no particulates are collected.

  As described above, for example, Patent Document 1 shows a general technical level related to an exhaust purification device using corona discharge.

  In the apparatus disclosed in Patent Document 1, when a negative high voltage is applied to the tip of the needle-like electrode part, corona discharge occurs near the tip of the needle-like electrode part, and weakly ionized plasma is formed. The 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 adhering to oxygen or the like that has particularly good electron adhesion, and the particulates in the exhaust gas are charged with negative charges by the oxygen ions. In this way, the particulates charged with a positive or negative charge are attracted to the particulates having different polarities by the Coulomb force, and are aggregated by bonding to each other.

JP 2008-51037 A

  However, in the case of the device disclosed in Patent Document 1, the shape of the electrode portion that performs corona discharge is a needle shape, the tip is sharp, and the electric field concentrates, so a wide range of particulates that are floating particles can be obtained. It was difficult to charge uniformly over the period.

  Further, in order to uniformly charge the particulates over a wide range, it is necessary to dispose a large number of the needle-like electrode portions in the exhaust pipe, and the structure becomes complicated and practical application is difficult.

  The present invention has been made in view of the above-described conventional problems, and can uniformly charge the particulates over a wide range without complicating the structure, and can improve the collection rate of the particulate filter. In addition, an object of the present invention is to provide a particle charged exhaust gas purification device that can suppress an increase in pressure loss.

The present invention is a particle charged exhaust gas purification apparatus in which a particulate filter is disposed in the middle of an exhaust pipe of an engine,
A creeping discharge electrode disposed upstream of the particulate filter in the exhaust gas flow direction, having a dielectric interposed between a ground electrode and an AC electrode, and having a exhaust gas flow hole formed therein;
A DC electrode disposed on the upstream side in the exhaust gas flow direction from the particulate filter on the downstream side in the exhaust gas flow direction from the creeping discharge electrode, and provided with a flow hole for the exhaust gas .
A pre-stage oxidation catalyst is disposed between the creeping discharge electrode and the DC electrode,
The creeping discharge electrode is disposed so that the AC electrode faces the upstream end surface of the pre-stage oxidation catalyst, and an AC high voltage is applied to the AC electrode from an AC power source,
The direct current electrode is disposed so as to face the downstream end face of the pre-stage oxidation catalyst, and a positive direct current high voltage is applied from a direct current power source to the direct current electrode . Is.

  According to the particle charged exhaust gas purification apparatus of the present invention, the particulates can be uniformly charged over a wide range without complicating the structure, the collection rate of the particulate filter can be improved, and the pressure loss can be reduced. An excellent effect that the increase can be suppressed can be achieved.

  Further, in the particle charged exhaust gas purification apparatus, it is very effective in assisting the function of the front-stage oxidation catalyst to arrange a front-stage oxidation catalyst between the creeping discharge electrode and the DC electrode. Become.

1 is an overall schematic configuration diagram showing an embodiment of a particle charged exhaust gas purification apparatus of the present invention. It is a principal part expanded sectional view which shows the creeping discharge electrode and DC electrode in the Example of the particle | grain charge exhaust gas purification apparatus of this invention, Comprising: It is the II section enlarged view of FIG. It is a diagram which compares and shows the change of the particulate filter differential pressure | voltage with respect to time with the case where it does not perform and the case where particle charge is performed. It is a diagram which compares and shows the relationship between the particle diameter and particle concentration in the downstream of a particulate filter by the case where particle charging is performed and the case where particle charging is not performed.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 and 2 show an embodiment of a particle charged exhaust gas purification apparatus of the present invention, wherein 1 is a diesel engine, 2 is a turbocharger, and in a diesel engine 1 equipped with the turbocharger 2, an air cleaner 3 From the intercooler 6 is sent to the intercooler 6 to be cooled, and the intake air 4 pressurized by the compressor 2a is cooled. The intake air 4 is guided to the intake manifold 7 and distributed to the cylinders 8 of the diesel engine 1 (in FIG. 1 exemplifies the case of inline 6 cylinders). The exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 10, and is sent to the exhaust pipe 11 after driving the turbine 2b. Yes.

  In the middle of the exhaust pipe 11, a front-stage oxidation catalyst 12 having a honeycomb structure and a particulate filter 13 that integrally supports the oxidation catalyst are disposed sequentially from the upstream side in the exhaust gas flow direction. A fuel addition device 15 for adding and supplying fuel such as light oil to the exhaust gas 9 is equipped on the exhaust inlet side of the catalyst 12.

  The fuel addition device 15 includes a fuel tank 16 in which fuel such as light oil is stored, a fuel pressurizing pump 17 that pumps fuel such as light oil stored in the fuel tank 16, and a pumping by the fuel pressurizing pump 17. And a fuel addition nozzle 18 for spraying fuel such as light oil to the exhaust inlet side of the upstream oxidation catalyst 12, and fuel such as light oil stored in the fuel tank 16 by a fuel pressurizing pump 17. The fuel addition nozzle 18 sprays fuel such as light oil onto the exhaust gas 9 flowing through the exhaust pipe 11, causes an oxidation reaction in the pre-stage oxidation catalyst 12, and puts the exhaust gas 9 heated by the reaction heat into the particulates. The catalyst is introduced into the curative filter 13 to raise the catalyst bed temperature, whereby the particulate is burned to regenerate the particulate filter 13.

  In the case of this embodiment, as shown in FIG. 2, a dielectric 19c is interposed between the ground electrode 19a and the AC electrode 19b on the upstream side of the particulate filter 13 in the exhaust gas flow direction, and the exhaust hole 9 flow hole 19d. A surface discharge electrode 19 having a perforated gas is disposed, and a flow hole 20a for the exhaust gas 9 is formed upstream of the particulate filter 13 in the exhaust gas distribution direction on the downstream side of the surface discharge electrode 19 in the exhaust gas distribution direction. A direct current electrode 20 is disposed, and the pre-stage oxidation catalyst 12 is disposed between the creeping discharge electrode 19 and the direct current electrode 20.

  The ground electrode 19a is grounded, the AC power source 21 is connected to the AC electrode 19b and an AC high voltage (3 to 4 kV) is applied, and the DC power source 22 is connected to the DC electrode 20 and a DC high voltage. (5 to 10 kV) is applied.

  Next, the operation of the above embodiment will be described.

  When an AC high voltage is applied from the AC power source 21 to the AC electrode 19b of the creeping discharge electrode 19, a barrier discharge (creeping discharge) is performed, and a plasma in which positive ions and negative ions are mixed with the ground electrode 19a is generated. In this state, when a positive DC high voltage is applied to the DC electrode 20 from the DC power source 22, negative ions having the opposite polarity move so as to be attracted to the DC electrode 20 through the honeycomb in the pre-stage oxidation catalyst 12.

Here, the condition that the particulates that are floating particles are strongly charged is:
1. High electric field 2. High charge (ion) density There are three points that the contact time between ions and particles is long. In this example, all of these conditions are satisfied.

  Thereby, when the exhaust gas 9 passes through the preceding oxidation catalyst 12, the particulates contained in the exhaust gas 9 are charged and guided to the inside of the particulate filter 13.

  The charged particulates aggregate on the surface layer inside the particulate filter 13, thereby increasing the collection rate and suppressing the pressure loss increase of the particulate filter 13 during deposition.

  When the particle charging is performed as in the present embodiment, the change in the differential pressure of the particulate filter 13 with respect to time is suppressed to be lower than that in the case where the particle charging is not performed, as shown in FIG. The reason for this is that when the particulates having a small particle diameter without being aggregated are collected by the particulate filter 13, the gap between the particulates is small and clogging is likely to occur, whereas the particles are aggregated to have a particle diameter. This is because when the particulates having increased in size are collected by the particulate filter 13, a gap is generated between the collected particulates, and the particulates themselves function as a filter and clogging is less likely to occur.

  Further, when particle charging is performed as in the present embodiment, the relationship between the particle diameter and particle concentration on the downstream side of the particulate filter 13 is compared with the case where particle charging is not performed, as shown in FIG. In particular, the larger the particle diameter, the lower the particle concentration. This is because the particulates having a larger particle size due to aggregation are collected by the particulate filter 13, so that the concentration of the particulates having a larger particle size is lowered on the downstream side of the particulate filter 13. . Incidentally, the particle concentration is represented by the number of particles per unit volume.

  As a result, unlike the device disclosed in Patent Document 1, the shape of the electrode portion that performs corona discharge is needle-like and the shape in which the electric field concentrates. Creeping discharge) occurs on the surface from the creeping discharge electrode 19, and furthermore, by using the in-honeycomb discharge in the pre-stage oxidation catalyst 12, the charge spreads uniformly in the gas flow cross section, so that the particulates that are floating particles are spread over a wide range. It is possible to charge uniformly over the entire area.

  Further, in order to uniformly charge the particulates over a wide range, it is not necessary to arrange a large number of needle-like electrode portions in the exhaust pipe 11 as shown in Patent Document 1, so that the structure is complicated. Without commercialization.

  In this way, the particulates can be uniformly charged over a wide range without complicating the structure, the collection rate of the particulate filter 13 can be improved, and an increase in pressure loss can be suppressed.

  Moreover, when the activity of the pre-stage oxidation catalyst 12 is low at a low temperature, an AC high voltage is applied from the AC power source 21 to the AC electrode 19b of the creeping discharge electrode 19, and a barrier discharge (creeping discharge) is performed. When a plasma in which positive ions and negative ions are mixed with each other is generated, highly reactive ozone is generated, so that it is possible to efficiently oxidize HC and NO with the ozone, and the creeping discharge electrode 19 and the DC The arrangement of the preceding oxidation catalyst 12 between the electrode 20 is very effective in assisting the function of the preceding oxidation catalyst 12.

  In addition, the particle | grain charge exhaust gas purification apparatus of this invention is not limited only to the above-mentioned Example, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

1 Diesel engine (engine)
9 Exhaust gas 11 Exhaust pipe 12 Pre-stage oxidation catalyst 13 Particulate filter 19 Creeping discharge electrode 19a Ground electrode 19b AC electrode 19c Dielectric 19d Flow hole 20 DC electrode 20a Flow hole

Claims (1)

A particle charged exhaust gas purification device in which a particulate filter is disposed in the middle of an engine exhaust pipe,
A creeping discharge electrode disposed upstream of the particulate filter in the exhaust gas flow direction, having a dielectric interposed between a ground electrode and an AC electrode, and having a exhaust gas flow hole formed therein;
A DC electrode disposed on the upstream side in the exhaust gas flow direction from the particulate filter on the downstream side in the exhaust gas flow direction from the creeping discharge electrode, and provided with a flow hole for the exhaust gas .
A pre-stage oxidation catalyst is disposed between the creeping discharge electrode and the DC electrode,
The creeping discharge electrode is disposed so that the AC electrode faces the upstream end surface of the pre-stage oxidation catalyst, and an AC high voltage is applied to the AC electrode from an AC power source,
The particle-charged exhaust gas purification apparatus , wherein the DC electrode is disposed so as to face a downstream end face of the pre-stage oxidation catalyst, and a positive DC high voltage is applied to the DC electrode from a DC power source .

Images