JP3894938B2 - Exhaust gas treatment device and exhaust gas treatment method - Google Patents

Description

  The present invention relates to an exhaust gas processing apparatus and an exhaust gas processing method for purifying exhaust gas of an internal combustion engine mounted on an automobile, etc., by using a corona discharge provided with a charge aggregation part and a filter part.

  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. The corona discharge charges the suspended 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.

  However, the conventional electric dust collection method has a problem that the solidified soot component can be removed, but the removal rate of the gasified SOF component is not high.

  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 ultrafine particles and agglomerates and enlarges in accordance with 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.

  In electrostatic dust collection, soot (solid particles) is electrostatically collected. However, the amount that can be collected by the dust collection electrode is limited, and when the limit amount is exceeded, the exhaust gas flows in the form of re-scattering. It will be released again. Therefore, the purification performance can be maintained for a long time if the Soot can be removed from the dust collection electrode by some means before the limit amount that can be collected is exceeded. Examples of this means include a scraping (scraping) collecting means and a combustion removing means by heating with a heater (see, for example, Patent Documents 1 to 3).

  However, with this drop-off collection means, particles trapped at the time of drop-off re-scatter into the main flow of exhaust gas, and the purification performance temporarily deteriorates at the time of drop-off. There is a problem that processing is also required separately.

  In order to avoid the deterioration of the purification performance, two charging agglomeration portions are provided, and an exhaust gas switching process is required. In addition, a mechanical mechanism for paying off is also required. Therefore, it is difficult to reduce the size especially when mounted on an automobile.

  In addition, although combustion removal means by heater heating is possible in principle, if the dust collection electrode exposed to the main stream of exhaust gas is heated, heat will escape to the exhaust gas, resulting in poor thermal efficiency. There's a problem. In particular, the combustion of Soot requires a high temperature of 500 ° C. or higher, and thus a great amount of electric power is required. In order to avoid this, two systems for charging and aggregating portions are provided and an exhaust gas switching process is required (see, for example, Patent Document 4).

  In addition, when the filter unit is provided after the charging aggregation unit, the same applies to the regeneration processing for burning and removing the soot collected by the filter unit, and the filter unit or the charging aggregation unit and the filter unit are combined. Two systems are provided and an exhaust gas switching process is required.

  That is, in the prior art, unless two systems of the charging aggregation section or the combination of the charging aggregation section and the filter are provided, an energy efficient system configuration cannot be realized and it is difficult to make the apparatus compact.

  Furthermore, when the exhaust gas of an engine mounted on a car is targeted, the operating condition of the car engine varies from idling to high load / high rotation. The apparatus is required to have the ability to efficiently purify PM under all these operating conditions.

  However, when the exhaust gas temperature is low and the state where the soot collected by the filter cannot be oxidized continues for a long time, the temperature of the filter is raised to the self-combustion start temperature of the soot and collected. It is necessary to regenerate the filter such as burning and removing the soot.

  In this regeneration operation, particularly in a continuous regeneration type filter, exhaust gas for filter regeneration by fuel injection control such as post injection into the cylinder of the internal combustion engine in order to raise the temperature of the filter during regeneration of the filter. However, in this case, there is a problem that the corona discharge becomes unstable because the temperature of the discharge part is increased by the high-temperature exhaust gas.

  In order to avoid this destabilization of the discharge, if the energization to the discharge part is stopped during the regeneration control, the purification action of the electrocoagulation device cannot be used. Therefore, when a coarse filter is used, PM is collected. There is a problem that PM cannot flow out to the downstream side of the exhaust gas treatment device.

  Moreover, since the exhaust gas amount increases and the flow rate increases due to the temperature rise of the exhaust gas, re-scattering in the electrostatic precipitator tends to occur, and PM tends to flow out.

  Therefore, it is necessary to stabilize the discharge and the exhaust gas flow rate (flow velocity) at the same time so that the PM does not flow downstream due to re-scattering, etc. Control is required.

  On the other hand, the inventors have found that the temporal degradation characteristic of the collection performance of the soot of the electrostatic collection section changes with the exhaust gas flow rate, and obtained the following knowledge.

  In other words, when the exhaust gas of an internal combustion engine of an automobile is targeted, the flow rate of the exhaust gas changes according to changes in the rotation speed and the load. Therefore, during actual operation, according to the dynamic change in the rotation speed and the load. The exhaust gas flow rate also changes dynamically. And, in a region where the exhaust gas flow rate is high at a high rotational speed and high load, the re-scattering phenomenon of the electrostatic collector is likely to occur, and the PM purification performance at the outlet of the electrostatic collector is deteriorated in a relatively short time. It is necessary to arrange a filter in the subsequent stage to capture the re-scattered particles.

On the other hand, in a region where the exhaust gas flow rate is low at a low rotational speed and low load, the re-scattering phenomenon of the electrostatic collector is unlikely to occur, and high purification performance can be achieved over a relatively long period of time without a filter being placed downstream. Can be maintained.
JP-A-11-165095 JP 2000-176313 A JP 59-85415 A JP 56-15852 A

  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 system that collects and collects fine particles by agglomeration, a compact, relatively simple configuration and relatively simple regeneration control reduce the purification rate and runaway PM during filter regeneration. It is an object of the present invention to provide an exhaust gas processing apparatus and an exhaust gas processing method capable of regenerating a filter efficiently while avoiding the above.

An exhaust gas treatment apparatus for achieving the above object has a dust collecting electrode and a corona electrode, and the components to be collected in the exhaust gas of the internal combustion engine are aggregated by being charged by corona discharge and temporarily aggregated. A charging and aggregating part that collects in the filter, a filter part that collects the agglomerated component, a bypass passage that bypasses the filter part, and a flow of at least most of the exhaust gas to the filter part and the bypass passage. A flow path switching means for switching, and when the rotational speed of the internal combustion engine is equal to or lower than a predetermined rotational speed and the load is equal to or lower than the predetermined load, the charging target component is charged by performing corona discharge in the charging aggregation section. It is configured to switch the flow of at least the most part of the exhaust gas to the bypass passage while temporarily collecting at the aggregating portion .

  In the exhaust gas purifying apparatus described above, while having a regenerating means for regenerating the filter part, while switching at least the most flow of the exhaust gas to the bypass passage, The regeneration unit performs the regeneration process of the filter unit.

  In the exhaust gas purifying apparatus described above, the filter unit is formed by a continuous regeneration type filter, and when the temperature of the exhaust gas is higher than a predetermined temperature at which the filter unit can be regenerated, at least most of the exhaust gas When the flow of the exhaust gas is lower than a predetermined temperature at which the filter unit can be regenerated and the load of the internal combustion engine is equal to or lower than the predetermined load without switching the flow to the bypass passage, at least most of the exhaust gas The flow is switched to the bypass passage.

  Alternatively, when the filter unit is formed of a filter other than a continuous regeneration type filter and the temperature of the exhaust gas is higher than the temperature at which the component to be collected collected by the filter unit can self-ignite, When at least most of the flow is not switched to the bypass passage, the temperature of the exhaust gas is lower than the temperature at which self-ignition is possible, and the load of the internal combustion engine is equal to or lower than a predetermined load, at least most of the exhaust gas The flow is switched to the bypass passage.

  Further, in the above exhaust gas processing apparatus, the filter unit is formed by a filter other than a continuous regeneration type filter, and when the flow of at least most of the exhaust gas is switched to the bypass passage, the regeneration is performed. The filter unit is configured to be heated by the regenerating unit.

  Further, in the above exhaust gas treatment device, when an oxidation catalyst is provided downstream from the joining portion where the flow path on the downstream side of the filter unit and the bypass passage are merged, gasification is performed by the oxidation catalyst. It is possible to decompose the evaporation component such as SOF that has passed through the charging and aggregating portion and the filter portion. Therefore, the gasified component can be purified by the oxidation catalyst disposed on the downstream side in the entire operation region of the engine including the regeneration.

  Further, the exhaust gas processing apparatus is configured such that the exhaust gas is cooled by the charging and aggregating unit. Thereby, evaporation components such as SOF in the exhaust gas can be condensed and liquefied, and fine particle components such as Soot can be aggregated very efficiently due to the adhesiveness of the liquefied components.

  The operating state of the internal combustion engine below the predetermined rotational speed and below the predetermined load is that the corona discharge is stabilized, and the collection target component such as PM in the exhaust gas is aggregated in the charging aggregation section, and the charging aggregation is performed. The operation state of the internal combustion engine is such that the exhaust gas flow rate is such that the collection target component collected in the portion hardly rescatters. Hereinafter, the operation region in this state is referred to as a “regeneration processing operation region”.

  The specific range of the regeneration processing operation region determined by the predetermined rotational speed and the predetermined load is different in the state of exhaust gas depending on the model of the internal combustion engine. Since the exhaust gas temperature at which regeneration is not required varies depending on the combustible temperature, it is difficult to determine it uniformly, but it is determined for each engine model or for each individual engine. Can be calculated and input from the input data before determination.

  Further, as the filter unit, not only a coarse filter but also a continuous regeneration type filter carrying a catalyst or a non-continuous regeneration type filter not carrying a catalyst can be used.

  In the case of a continuous regeneration type filter, if the exhaust gas temperature is equal to or higher than a predetermined temperature (for example, about 350 ° C.) at which the filter unit can be regenerated, catalytic components can oxidize collection target components such as PM soot. The temperature range in which the collection target component can self-combust is widened. Therefore, the regeneration area is widened, and the regeneration processing operation area can be set narrow.

  On the other hand, in the case of a non-continuous regeneration type filter, in the regeneration region at a temperature at which PM can self-combust, that is, a temperature at which self-ignition is possible (for example, about 500 ° C.) or higher, Although it does not occur, accumulation of the components to be collected occurs below this, and it is necessary to forcibly regenerate, so the operation region for regeneration processing becomes wider than when a continuous regeneration type filter is used. However, even if the operation area for regeneration treatment is wide, it does not carry a catalyst, so that it is not necessary to take measures against the deterioration of the catalyst due to the high temperature of the filter due to combustion of the components to be collected during regeneration treatment. There is.

  In this exhaust gas purification device, when the operation state of the internal combustion engine is a high-revolution operation state or a high-load operation state non-regeneration treatment operation region, switching so that most of the exhaust gas flows to the filter unit, The charging target part such as PM in the exhaust gas is collected by the charge aggregation part and the filter part that perform corona discharge. At this time, solid particles such as soot that are electrostatically collected while agglomerating and agglomerating in the charged agglomerated part are peeled off and re-scattered by the flow of the exhaust gas, but the re-scattered particles are collected in the subsequent filter part. The Therefore, a high purification rate can be maintained.

  On the other hand, when the operating state of the internal combustion engine is a low-revolution and low-load operating state for the regeneration process, the charging agglomeration unit that performs corona discharge by switching so that most of the exhaust gas flows to the bypass passage Only the components to be collected such as PM in the exhaust gas are collected. At this time, since the collection target component contained in the exhaust gas is small and the amount of the exhaust gas is small, the collection target component is not re-scattered while being collected in the charged aggregation portion. Therefore, even if most of the exhaust gas is bypassed through the filter portion, the purification rate does not decrease, so that a high purification rate can be maintained.

  When the operation state of the internal combustion engine is a high rotation operation state or a high load operation state, and the collection amount of the collection target component in the filter unit is not the predetermined collection limit amount (threshold value), Since it is not necessary to perform the regeneration process in particular, the operation is continued as it is. In addition, this collection amount can be estimated from the differential pressure before and after the filter section.

  The collection target component collected by the filter unit is burned and removed when the rotation speed and load increase and the temperature of the exhaust gas rises to about 500 ° C. However, the operation state of the internal combustion engine does not become the operation region for regeneration processing, and the temperature of the exhaust gas reaches the temperature (for example, about 500 ° C.) at which the collection target component collected by the filter unit starts combustion. When the high rotation operation state and the high load operation state continue without being performed and the collection amount of the collection target component in the filter unit reaches a predetermined collection limit amount (threshold), the operation of the internal combustion engine is performed. Until the state shifts to the operation region for regeneration processing or until the regeneration is performed by self-combustion when the exhaust gas reaches about 500 ° C. or more, the regeneration processing is waited for as long as possible, but the filter section can be collected. When the final limit is exceeded, the filter unit may be regenerated. In this regeneration process, the filter unit is heated by a regeneration means for regeneration and the components to be collected are burned and removed.

  In this regeneration process, since the temperature of the exhaust gas is relatively high, the regeneration process can be performed by adding a small amount of heat. Therefore, in the case of heater heating, less power is consumed. This regeneration process is performed while performing corona discharge in the charge aggregation portion, and the collection target component in the exhaust gas is collected in the charge aggregation portion and the filter portion.

  When the operating state of the internal combustion engine shifts to the regeneration processing operation region, the regeneration processing of the filter unit is performed as follows.

  First, when the operation state of the internal combustion engine is a high rotation operation state or a high load operation state and the operation state of the regeneration processing operation region is started after starting the regeneration processing of the filter unit, the exhaust gas is While at least most of the flow is switched to the bypass passage, the heating of the filter unit by the regeneration means for regeneration process is continued, the component to be collected is burned and removed, and the regeneration process of the filter unit is continued. This regeneration process is performed while performing corona discharge in the charge aggregation section, and the collection target component in the exhaust gas is collected in the charge aggregation section.

  In the regeneration process of the filter part in this regeneration process operation region, the heat of the filter part can be prevented from being taken away by the exhaust gas by bypassing the filter part of the flow of most of the exhaust gas. And power consumption can be reduced. Moreover, since the amount of oxygen supplied by the exhaust gas is small, thermal runaway can be prevented.

  Further, even when the regeneration process of the filter unit is performed not by heating but by removal by a mechanical mechanism, the collected component to be collected does not rescatter in the main flow of exhaust gas.

  Next, when the operation state of the internal combustion engine is changed from the high rotation operation state or the high load operation state to the operation state of the regeneration processing region without performing the regeneration processing of the filter unit, the flow path switching means Switch at least most of the flow of exhaust gas to the bypass passage.

  And even if the collection amount of the collection target component in the filter unit does not reach the predetermined collection limit amount (threshold value), the filter unit is heated by the regeneration means for the regeneration process, and the collection target component is burned and removed. Then, regeneration processing of the filter unit is performed. And this regeneration process is complete | finished when the collected collection target component is burned and removed.

  The timing for completing the regeneration of the filter unit is when the oxidation of the components to be collected is completed. Specifically, when the oxygen concentration of the exhaust gas downstream of the filter unit is increased, or A case where the exhaust gas temperature on the downstream side starts to decrease may be considered. This timing can be detected from an output value of an oxygen concentration sensor or an exhaust gas temperature sensor arranged on the downstream side of the filter unit.

  By carrying out this regeneration process, the collection target component collected in the filter unit is removed, and then the operation state of the internal combustion engine is a high rotation operation state or a high load operation state, that is, a non-regeneration process operation region. Then, it becomes possible to sufficiently collect the component to be collected, which is re-scattered from the charged aggregation portion, with the filter portion. In addition, the number and time of the regeneration processing of the filter unit in the non-regeneration processing operation region can be significantly reduced.

  Further, in this operation state for the regeneration process, since the charging aggregation unit performs corona discharge both during and after the regeneration process of the filter unit, the collection target component in the exhaust gas is collected in the charging aggregation unit. Is done.

  In addition, when the regeneration process of the filter unit is not performed and the operation state is shifted from the non-regeneration process operation state to the regeneration process operation region, in order to simplify the control, the filter unit captures the collection target component. Regardless of the amount of collection, the regeneration process may be performed without fail, but in order to reduce the heating power associated with the regeneration process, the operation state in the non-regeneration process operation region has changed from the previous regeneration process to a predetermined time. Is configured to perform the regeneration process only when the amount of collection of the collection target component in the filter unit exceeds the predetermined regeneration process start amount (threshold value) when exceeding the regeneration processing operation region May be. The predetermined regeneration processing start amount (threshold value) is set smaller than the predetermined collection limit amount (threshold value).

  In addition, as a regeneration means for regenerating the filter unit, an external heating method means such as an electric heater for directly heating the filter, a burner for supplying a high-temperature gas for heating the filter, or a component to be collected is accumulated. A gap between the electrodes provided adjacent to each other is filled, electricity is short-circuited between both electrodes, and an electric short-type means for starting self-combustion of the component to be collected by a spark generated by this short-circuit can be used. .

  This exhaust gas flow path switching means is constituted by switching of a switching valve or the like and several on-off valves. However, when the main flow of exhaust gas is switched to the bypass passage, the exhaust gas flows into the filter section. Without stopping completely, the exhaust gas flow path to the filter part is formed so that a gap is opened even when the switching valve or on-off valve is closed so that a small amount of exhaust gas flows to the filter part. In order to prevent the runaway combustion of the collection target component, supply of an appropriate amount of oxygen for oxidation of the collection target component to the filter unit and cooling of the filter unit are performed. This not only prevents burning and melting of the filter part, but also prevents thermal deterioration of the catalyst when it is supported.

The exhaust gas treatment method for achieving the above object, and a dust collecting electrode and the corona electrode, the collecting target component in the exhaust gas of an internal combustion engine as well as aggregate is charged by corona discharge A charging and aggregating part that temporarily collects, a filter part that collects the agglomerated component, a bypass passage that bypasses the filter part, and at least most of the flow of exhaust gas in the filter part and the bypass passage In the exhaust gas processing apparatus having the flow path switching means for switching to the above, when the rotational speed of the internal combustion engine is equal to or higher than the predetermined speed or the load is equal to or higher than the predetermined load, at least most of the flow of the exhaust gas flows to the filter unit. switched, the particulate collecting target component accumulated in the filter unit, when the rotation speed of the internal combustion engine and equal to or less than the predetermined rotation speed load is below a predetermined load, in the charging aggregation unit While temporarily collected by the charging aggregation unit collected target component by performing corona discharge, by switching the flow of at least a majority of the exhaust gas to the bypass passage, disconnecting the filter unit from the main flow of exhaust gas The reproduction processing of the filter unit is performed.

  In other words, according to the present invention, in the non-regeneration treatment operation region where the exhaust gas flow rate is high, most of the exhaust gas is allowed to flow through the filter unit downstream of the charge aggregation unit in accordance with the engine speed and load, In the regeneration operation area where the exhaust gas flow rate is low and the exhaust gas flow rate is low, the charged agglomeration part, which also has the function of electrostatic Most of the gas is passed through the bypass passage, and the filter unit is separated from the main flow of the exhaust gas so that the regeneration process of the filter unit is performed.

  With this configuration, the filter unit can be separated from the main flow of exhaust gas at the time of regeneration. Therefore, when regenerating by heater heating, heat is not lost to the exhaust gas, so that thermal efficiency is improved and power consumption is reduced. In addition, even when the filter part is regenerated by scraping off, there is almost no exhaust gas flow, so that the trapped component to be collected is hardly scattered again in the exhaust gas. Therefore, it is not necessary to provide two systems for charging and aggregating sections and filter sections, and high purification performance can be obtained with a compact apparatus.

  In addition, when the engine speed and load are low, the target components collected in the charging and aggregating part are scattered again and captured by the filter part when the engine speed and load are high, resulting in high engine speed and load. In the region where the exhaust gas temperature rises to about 500 ° C., it is removed by combustion.

  And the collection object component stored in the filter part of the downstream side can be effectively regenerated by the above heat regeneration process or the like when the engine speed and load are low. Further, when the engine speed and load are high, most of the exhaust gas circulates. Therefore, especially when the exhaust gas temperature rises to a temperature (about 500 ° C.) at which the components to be collected can self-ignite. Combustion removal is possible without heating. Further, when the temperature of the exhaust gas is relatively high, it is possible to perform additional heating to a temperature at which self-ignition can be performed with a slight heater power.

  In addition, the exhaust gas processing apparatus provided with the existing DPF is additionally provided with a regeneration means for raising the temperature of the charge aggregation part and, if necessary, the filter part and the control method of the present invention. It can be a processing device.

  According to the exhaust gas processing apparatus and the exhaust gas processing method of the present invention, the following effects can be obtained.

  When the operating state of the internal combustion engine is in the operating state of the regeneration processing operation region when the rotational speed of the internal combustion engine is equal to or lower than the predetermined rotational speed and the load is equal to or lower than the predetermined load, the filter unit is regenerated. Since at least most of this is performed by switching to the bypass passage, the heat for filter regeneration processing is not taken away by the exhaust gas, and the regeneration of the filter portion can be performed with high thermal efficiency. Can be reduced.

  In addition, since the temperature of the filter unit is raised by the regenerating unit without increasing the temperature of the exhaust gas flowing into the charging aggregation unit for the regeneration process of the filter unit, the exhaust gas flowing into the charging aggregation unit during the regeneration process The temperature is low, the corona discharge is stable, the agglomeration and collection efficiency is increased, the exhaust gas flow rate is low, the flow rate is slow, and re-scattering is difficult to occur. It is not necessary. Therefore, even when the exhaust gas after passing through the charging and aggregating part bypasses the filter part during the regeneration process of the filter part, the collection target component such as PM does not flow out to the downstream side of the exhaust gas processing apparatus. The purification rate does not deteriorate during the regeneration process.

  When the filter part is regenerated, at least most of the exhaust gas flows through the bypass passage, so that the amount of oxygen flowing into the filter part is reduced, and runaway combustion of the collection target component collected in the filter part is prevented. Can be suppressed. In addition, since a small amount of exhaust gas is allowed to flow through the filter unit, the filter unit can be cooled, and runaway combustion of the collection target component due to excessive temperature rise of the filter unit can also be suppressed by this cooling.

  Therefore, by adopting the above exhaust gas treatment device, it is possible to regenerate the filter part in an energy efficient manner, and with a compact and simple configuration, there is a problem of a reduction in the purification rate during the filter part regeneration process, burnout of the filter part, Problems of melting loss and deterioration of the supported catalyst can also be solved.

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

  As shown in FIG. 1, the exhaust gas treatment apparatus 1 is configured such that the aggregating component 10 is agglomerated by charging a soot component, which is a collection target component in the exhaust gas, by charging with corona discharge to agglomerate. Is provided on the downstream side, and a bypass passage 40 that bypasses the filter unit 20 is provided. Further, the oxidation catalyst 30 is provided on the downstream side of the filter unit 20 and on the downstream side of the joining portion 42 of the bypass passage 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 that purifies the evaporated component such as SOF that has been converted into a gas is disposed in the subsequent stage, and a bypass passage 40 that bypasses only the filter unit 20 is provided.

  The bypass passage 40 is branched from between the charging and aggregating unit 10 and the filter unit 20, and joins the joining unit 42 between the filter unit 20 and the oxidation catalyst 30. A switching valve 41 serving as a flow path switching unit is provided between the charging aggregation unit 10 and the filter unit 20. The switching valve 41 has a role of switching the flow of the exhaust gas between the flow to the filter unit 20 and the flow to the bypass passage 40, and is normally formed by one switching valve 41, but is constituted by a plurality of on-off valves. May be. Even when the flow of the exhaust gas is switched to the bypass passage 40 at the time of regeneration of the filter unit 20, the PM collected in the filter unit 20 without completely blocking the flow of the exhaust gas to the filter unit 20. A small amount of exhaust gas is introduced so that oxygen for combustion can be supplied.

  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. 2 to 4, 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, when the exhaust gas of an engine mounted on an automobile is targeted, it is preferable that the charging aggregation unit 10 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, but in consideration of the limited placement space in automobiles and the disadvantage of long and long to keep the insulation state 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 11a, for example, the center, such as an axial center part of a cylindrical body. In addition, as shown in FIG. 4, a plurality of corona electrodes 11b may be provided inside the cylindrical body 11a.

  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.

  And the passage wall of this cylindrical body 11a is used as a cooling wall (gas cooling part), and it is comprised so that the exhaust gas G can be cooled by the charge aggregation part 10. FIG. 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.

  When the exhaust gas treatment device 1 is mounted on a vehicle, a strong wind is applied to a portion such as 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 by natural heat dissipation. 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. 5 to 7, 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. 8 to 12, the gas passage wall of the charging and aggregating unit 11, that is, the gas passage wall of the charging and aggregating portion 10 is formed of a cylindrical body 11f, and the dust collecting electrode 11a 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 charged 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. 8 to 11, 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.

  The filter unit 20 needs to be regenerated in order to burn and remove the soot when the collection amount of the soot increases and becomes clogged, and a regenerating means for that purpose is necessary.

  As the regeneration 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 to generate heat 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 downstream of the branching portion of the bypass passage 40 to heat the filter unit 20 to raise the temperature. The burner is supplied with external fuel (with vehicle fuel). It can be shared) and burned to generate hot gas. 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 the regeneration means makes it difficult to make the temperature of the filter uniform and heat cracks due to uneven reproduction and temperature differences are likely to occur. However, in the case of a metal filter, 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. 11a is touched and loses electric charge, and is further coarsened on the wall surface. As a result, it is peeled off from the surface of the dust collecting electrode 11a by the flow of the exhaust gas G and scattered again.

  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 regenerating 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.

  In the present invention, the control for regenerating the filter unit 20 is performed when the engine is operating at a predetermined rotation speed or lower and a predetermined load or lower. Here, the operation region in this state is referred to as a “regeneration processing operation region”.

  The predetermined rotational speed and the predetermined load that define the regeneration processing operation region are different in the exhaust gas state depending on the model of the internal combustion engine, and the regeneration is not necessary depending on the temperature at which the PM in the filter unit 20 can self-combust. It is difficult to uniformly determine the range because the exhaust gas temperatures are different, but it can be determined in advance for each engine model or for each engine by experiments or the like.

  That is, in this regeneration processing operation region, the corona discharge of the charging aggregation unit 10 is stabilized, and the collection target component such as PM collected in the charging aggregation unit 10 is aggregated in the charging aggregation unit 10. Since the exhaust gas flow rate is such that it does not re-scatter, specific numerical values such as the rotational speed can be determined from the relationship between the exhaust gas state obtained experimentally and the engine operating state. These numerical values are input to the control device in advance, and are calculated from these input data by the time when it is determined whether or not the engine operating state is in the regeneration processing operating region.

  An example of the regeneration processing operation region is an experimental result of a specific model. The rotation speed and load are 50 to 60% or less of the rotation speed and load at the maximum output.

  Next, the purification of the exhaust gas G and the regeneration process of the filter unit 20 in the exhaust gas processing apparatus according to the embodiment of the present invention will be described.

  In the exhaust gas purification device 1, at least most of the exhaust gas G flows to the filter unit 20 when the operation state of the internal combustion engine is a high-revolution operation state or a high-load operation state non-regeneration treatment operation region. Then, the collection target component such as PM in the exhaust gas G is collected by the charging aggregation unit 10 and the filter unit 20 performing corona discharge.

  At this time, the solid particles of the soot are electrostatically collected while being agglomerated and enlarged on the dust collecting electrode in the charging and aggregating unit 10. However, since the amount of exhaust gas G is large and the flow velocity is large, the deposited solid particles are the exhaust gas G. It peels off by the flow and re-scatters. However, since the re-scattered particles are collected by the subsequent filter unit 20, a high purification rate can be maintained.

  The soot collected by the filter unit 20 is burned and removed when the rotational speed and load increase and the temperature of the exhaust gas G rises to a temperature at which self-ignition is possible (about 500 ° C.).

  When the operating state of the internal combustion engine is in the low-speed and low-load operating state for the regeneration process, the corona discharge is performed by switching so that at least most of the exhaust gas G flows to the bypass passage 40. The soot in the exhaust gas G is collected only by the charge aggregation part 10. At this time, since the soot contained in the exhaust gas G is small and the amount of the exhaust gas G is small and the flow speed is small, the soot is not collected again in the charged aggregation part 10 while being collected. Therefore, even if most of the exhaust gas G is bypassed through the filter unit 20, the purification rate of the exhaust gas G does not decrease, so that a high purification rate can be maintained.

  When the operation state of the internal combustion engine is a non-regeneration processing operation region in a high rotation operation state or a high load operation state, and the collection amount of soot in the filter unit 20 is not the predetermined collection limit amount (threshold value). Since it is not necessary to perform the regeneration process of the filter unit 20 in particular, the operation is continued as it is. Note that the collected amount can be estimated from the detection value of the differential pressure sensor 51 that detects the differential pressure across the filter unit 20.

  Further, the high rotation operation state and the high load operation state continue, the operation state of the internal combustion engine does not become the regeneration processing operation region, and the soot in which the temperature of the exhaust gas G is collected by the filter unit 20 is reduced. When the amount of collected Soot in the filter unit 20 reaches a predetermined collection limit (threshold) without reaching the temperature at which self-ignition can be started to start combustion, that is, detected by the differential pressure sensor 51. When the front-rear differential pressure exceeds a predetermined limit value (threshold value), the following processing is performed.

  Until the operation state of the internal combustion engine shifts to the operation region for regeneration processing, or until regeneration by self-combustion is performed after the exhaust gas G becomes higher than the temperature at which self-ignition occurs, When the final limit that can be collected is exceeded, regeneration processing of the filter unit 20 is performed.

  In this regeneration process, the filter unit 20 is heated by regeneration means for regeneration process, exhaust gas temperature rise or the like, and soot is burned and removed. In this regeneration process, since the temperature of the exhaust gas G is relatively high, the regeneration process can be performed by adding a small amount of heat. Therefore, in the case of heater heating, less power is consumed. This regeneration process is performed while performing corona discharge in the charging aggregation unit 10, and the soot content in the exhaust gas G is collected by the charging aggregation unit 10 and the filter unit 20.

  Then, the regeneration processing of the filter unit 20 is performed by operating the switching valve 41 when the engine operating state changes from the engine start state, the high rotation operation state, or the high load operation state to the regeneration processing operation region. In addition, at least most of the exhaust gas G that has passed through the charging aggregation unit 10 is switched to the bypass passage 40, and the regeneration processing of the filter unit 20 is performed while the charging aggregation unit 10 performs corona discharge.

  The regeneration process of the filter unit 20 continues the regeneration process when the engine operation state has shifted to the operation state of the regeneration processing operation region, and continues the regeneration process before the transition. If not, the regeneration process is started regardless of the amount of the target component to be collected in the filter unit 20.

  In this regeneration process, the temperature of the exhaust gas G flowing into the charging and aggregating unit 10 is not increased for the regeneration process of the filter unit 20, that is, the regeneration of the filter unit 20 regardless of the rotational speed and output required for the engine. Only for the processing, the regeneration of the filter unit 20 is performed by raising the temperature of the filter unit 20 by the regenerating unit without increasing the exhaust gas temperature by performing the post injection or the like by the fuel injection control into the cylinder of the engine. Do.

  The end of the regeneration process of the filter unit 20 is when the oxygen concentration of the exhaust gas G on the downstream side of the filter unit 20 is increased after the oxidation of the component to be collected is completed. This timing can be detected from the detection value of the oxygen concentration sensor 52 arranged on the downstream side of the filter unit 20. Alternatively, it may be the time when the temperature of the exhaust gas G on the downstream side of the filter unit 20 starts to decrease. In this case, the temperature is detected from the detection value of the exhaust gas temperature sensor 53 disposed on the downstream side of the filter unit 20. be able to.

  Since the soot collected by the filter unit 20 is removed by performing the regeneration process of the filter unit 20, the operation state of the internal combustion engine is next set to a high rotation operation state or a high load operation state, that is, a non-regeneration process. The soot that re-scatters from the charging and aggregating unit 10 when the operation region is reached can be sufficiently collected by the filter unit 20. Moreover, the frequency | count and time of the regeneration process of the filter part 20 in the driving | operation area | region for non-regeneration | regeneration processes can be decreased.

  Further, in this regeneration processing operation state, the charging aggregation unit 10 performs corona discharge both during and after the regeneration process of the filter unit 20, so that the soot in the exhaust gas G is captured by the charging aggregation unit 10. Be collected.

  In the case where the regeneration process of the filter unit 20 is not performed and the operation state of the regeneration process operation region is changed from the non-regeneration process operation state, as described above, in order to simplify the control, Regardless of the collection amount of the component to be collected in the filter unit 20, the regeneration process may be performed without fail. However, in order to reduce the heating power associated with the regeneration process, the regeneration process is not performed. When the operation state of the regeneration processing operation region exceeds a predetermined time or when the soot collection amount in the filter unit 20 is shifted to the regeneration processing operation region, the soot collection amount exceeds a predetermined regeneration processing start amount (threshold). The reproduction process may be performed only in the case of

  According to the exhaust gas processing apparatus 1 and the exhaust gas processing method described above, the following effects can be obtained.

  With this configuration, when the operating state of the internal combustion engine is a high-speed operating state or a high-load operating state, and when there are many components to be collected in the exhaust gas, both the charge aggregation unit 10 and the filter unit 20 capture. Since the collection target component is collected, the exhaust gas G can be purified with a high purification rate.

  Further, when the operating state of the internal combustion engine is a low rotation and low load operating state, that is, the regeneration processing operating state, at least most of the exhaust gas G is switched to the bypass passage 40 and collected only by the charging and aggregating unit 10. The target component is collected. In this state, the exhaust gas G can be purified at a high purification rate because the flow rate of the exhaust gas G and the collection target component in the exhaust gas G are small. The filter unit 20 can be separated from the main flow of the exhaust gas G during the regeneration process.

  The collection target component stored in the charging aggregation unit 10 in the operation state of the regeneration processing operation region is re-scattered when the engine speed and the load are increased by moving to the non-regeneration processing operation region. In the region where the engine speed and the load are high and the exhaust gas temperature rises to a temperature at which self-ignition is possible (about 500 ° C.), it is burned and removed without particularly performing a regeneration process.

  Then, the target components collected in the downstream filter unit 20 without being burned off can be self-ignited with a slight heating amount when the temperature of the exhaust gas G is relatively high in the non-regeneration treatment operation region. In the regeneration processing operating region where the engine speed and load can be reduced, regeneration processing can be performed in a state separated from the main flow of the exhaust gas G, so that regeneration can be performed efficiently.

  In other words, in the regeneration processing operation region where the rotational speed of the internal combustion engine is equal to or lower than the predetermined rotational speed and the load is equal to or lower than the predetermined load, at least most of the exhaust gas G is switched to the bypass passage 40 and the exhaust gas G Since the regeneration process of the filter unit 20 is performed when most of the filter unit 20 bypasses the filter unit 20, the filter unit 20 can be separated from the main flow of the exhaust gas G during the regeneration process.

  Therefore, when regenerating by heater heating, it can be avoided that a large amount of exhaust gas having a low temperature flows in and takes heat of the filter unit 20, and the regeneration process can be performed efficiently. Therefore, it is possible to reduce the power consumption associated with the reproduction process by the reproduction unit. Even when the filter unit 20 is regenerated by a mechanical mechanism, there is almost no flow of the exhaust gas G, so that the collected component to be collected hardly rescatters in the exhaust gas G.

  Accordingly, there is no need to provide two systems of the charge aggregation unit 10 and the filter unit 20, and high purification performance can be obtained with a compact device.

  Further, in the regeneration process of the filter unit 20 when in the regeneration processing operation region, the exhaust gas G flowing into the charging aggregation unit 10 is regenerated without increasing the temperature for the regeneration process of the filter unit 20. Since the temperature is raised by the means, the temperature of the exhaust gas G flowing into the charging and aggregating portion 10 can be kept low during the regeneration process.

  Therefore, in the charging and aggregating unit 10, the corona discharge is stable and the agglomeration and collection efficiency is increased, and the flow rate of the exhaust gas G is small, the flow rate is slow, and re-scattering is difficult to occur. It has become. That is, the collecting function by the filter unit 20 is not required.

  Therefore, when the filter unit 20 is regenerated, even if most of the exhaust gas G that has passed through the charge aggregation unit 10 bypasses the filter unit 20, the collection target component such as PM is downstream of the exhaust gas processing device 1. The purification rate does not deteriorate during the regeneration process.

  Furthermore, since the amount of exhaust gas G flowing into the filter unit 20 is limited during the regeneration process of the filter unit 20, the amount of oxygen supplied to the filter unit 20 can be limited, and runaway combustion of PM in the filter unit 20 can be suppressed. . In addition, since a part of the exhaust gas having a low temperature flows into the filter unit 20, local overheating of the filter unit 20 can be cooled, and the temperature of the filter unit 20 can be made uniform. Accordingly, it is possible to prevent the filter from being burned out or melted, and furthermore, when a catalyst is supported, thermal deterioration of the catalyst can be prevented.

  When the filter unit 20 is formed of a continuous regeneration type filter, when the exhaust gas temperature is equal to or higher than a predetermined temperature (for example, about 350 ° C.) at which the filter unit 20 can be regenerated, PM soot or the like is generated by catalytic action. Since the component to be collected can be oxidized, the temperature range in which the component to be collected can be self-combusted is widened. Therefore, the regeneration operation area is narrowed.

  Further, when the filter unit 20 is formed of a discontinuous regenerative filter, accumulation of PM in the filter unit 20 does not occur above the temperature at which PM can self-ignite (about 500 ° C.). Therefore, the regeneration processing operation area becomes wider than when a continuous regeneration type filter is used. However, since the catalyst is not carried even when the operation region for the regeneration process is widened, no countermeasure is required against deterioration of the catalyst even if the filter becomes hot due to combustion of the collection target component during the regeneration process. .

  In the above description, the exhaust gas of the diesel engine has been described as the gas to be processed. However, the present invention is not limited to the exhaust gas of an internal combustion engine mounted on an automobile, but the exhaust gas of various industrial machines and stationary internal combustion engines. It can also be used as an exhaust gas processing apparatus and an exhaust gas processing method.

It is a figure which shows typically the structure of the gas processing apparatus which concerns on this invention. 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 Bypass passage
41 switching valve 50 control device

Claims (8)

It has a dust collection electrode and a corona electrode, and charges and aggregates the collection target component in the exhaust gas of the internal combustion engine by corona discharge , and collects the aggregated component. A filter section that collects, a bypass passage that bypasses the filter section, and a flow path switching means that switches the flow of at least most of the exhaust gas to the filter section and the bypass passage, and the rotational speed of the internal combustion engine is predetermined When the load is equal to or less than a predetermined load and corona discharge is performed at the charged aggregation portion, the collection target component is temporarily collected at the charged aggregation portion, and at least a large amount of exhaust gas is collected. An exhaust gas processing apparatus, wherein the flow of the part is switched to the bypass passage.   The regeneration unit for regenerating the filter unit, and when the flow of at least most of the exhaust gas is switched to the bypass passage, the filter unit is used by the regeneration unit while performing corona discharge in the charging aggregation unit. The exhaust gas processing apparatus according to claim 1, wherein the regeneration process is performed. While forming the filter portion with a continuous regeneration type filter,
When the temperature of the exhaust gas is higher than a predetermined temperature at which the filter unit can be regenerated, the flow of at least most of the exhaust gas is not switched to the bypass passage,
When the temperature of the exhaust gas is lower than a predetermined temperature at which the filter unit can be regenerated and the load of the internal combustion engine is equal to or lower than the predetermined load, the flow of at least most of the exhaust gas is switched to the bypass passage. The exhaust gas treatment apparatus according to claim 1 or 2, characterized in that. While forming the filter portion with a filter other than a continuous regeneration type filter,
When the temperature of the exhaust gas is higher than the temperature capable of self-ignition of the collection target component collected in the filter unit, the flow of at least most of the exhaust gas is not switched to the bypass passage,
When the temperature of the exhaust gas is lower than the temperature at which self-ignition is possible and the load of the internal combustion engine is equal to or lower than a predetermined load, the flow of at least most of the exhaust gas is switched to the bypass passage. Item 3. The exhaust gas treatment apparatus according to Item 1 or 2. While forming the filter portion with a filter other than a continuous regeneration type filter,
5. The exhaust gas processing apparatus according to claim 4, wherein when the flow of at least most of the exhaust gas is switched to the bypass passage, the filter section is regenerated by the regeneration means for regeneration.   The exhaust gas processing apparatus according to any one of claims 1 to 5, wherein an oxidation catalyst is provided downstream of a joining portion where a flow path on the downstream side of the filter unit and the bypass passage are joined. .   The exhaust gas processing device according to any one of claims 1 to 6, wherein the exhaust gas is cooled by the charging and aggregating unit. It has a dust collection electrode and a corona electrode, and charges and aggregates the collection target component in the exhaust gas of the internal combustion engine by corona discharge , and collects the aggregated component. In an exhaust gas processing apparatus having a filter unit to be collected, a bypass passage that bypasses the filter unit, and a flow path switching unit that switches at least most of the flow of exhaust gas to the filter unit and the bypass passage,
When the rotational speed of the internal combustion engine is equal to or higher than the predetermined rotational speed or the load is equal to or higher than the predetermined load, the flow of at least most of the exhaust gas is switched to the filter portion, and the particulate collection target component is changed by the filter portion. Accumulate,
When the rotational speed of the internal combustion engine is equal to or lower than the predetermined rotational speed and the load is equal to or lower than the predetermined load, the collection target component is temporarily collected by the charged aggregation section by performing corona discharge in the charged aggregation section. while, by switching the flow of at least a majority of the exhaust gas to the bypass passage, disconnecting the filter unit from the main flow of the exhaust gas, the exhaust gas treatment method, which comprises carrying out the regeneration process of the filter unit.

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