JP6838384B2 - Exhaust gas purification system and poison control method for exhaust gas purification system - Google Patents

Description

The present invention relates to an exhaust gas purification system that purifies the exhaust gas of an internal combustion engine or the like mounted on a vehicle, and a method for suppressing poisoning of the exhaust gas purification system.

In the internal combustion engine mounted on the vehicle, an oxidation catalyst device for raising the temperature of exhaust gas and adjusting the NOx concentration, a fine particle collecting device for collecting fine particles (PM), and ammonia generated from urea water An exhaust gas purification system that combines a selective reduction catalyst device for purifying nitrogen oxides (NOx) using the following as a reducing agent, an ammonia slip catalyst device for oxidizing ammonia and avoiding the outflow of ammonia to the outside air, etc. Is used to purify the exhaust gas emitted from the internal combustion engine.

Further, although it is a NOx purification system for an internal combustion engine that does not have a DPF, an exhaust bypass passage provided with a heat capacitance body is provided between the pre-stage oxidation catalyst and the urea SCR catalyst to allow exhaust gas to pass through the exhaust heat capacitance body. Alternatively, a NOx purification system for an internal combustion engine has been proposed in which the temperature of the exhaust gas reaching the SCR catalyst is adjusted by bypassing the exhaust gas to the exhaust heat capacitance body to stabilize the NOx purification performance by the SCR catalyst. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-79861

By the way, toxic substances such as sulfur oxides (SOx) are generated by sulfur components contained in fuel, engine oil, etc., and these toxic substances are deposited on the catalyst of the oxidation catalyst device or the fine particle collection device. It may end up. These toxic substances are separated from the heated oxidation catalyst device and fine particle collecting device during forced regeneration in which the temperature of the exhaust gas is raised to burn and remove the PM accumulated in the fine particle collecting device. Since it adheres to the selective reduction type catalyst device and the ammonia slip catalyst device arranged on the downstream side (second stage), the adhesion of the toxic substance lowers the NOx purification performance of these devices.

Furthermore, when the noble metal (PGM), which is the active species of the catalyst of the oxidation catalyst device and the fine particle collection device, becomes high temperature, it becomes vapor and adheres to the selective reduction type catalyst device and the ammonia slip catalyst device on the downstream side. The selectivity of the ammonia oxidation performance in these devices is improved, and ammonia, which is a NOx reducing agent, is oxidized first, and the NOx purification performance is deteriorated.

An object of the present invention is an exhaust gas purification system provided with an oxidation catalyst device, a fine particle collection device, and a selective reduction catalyst device in the exhaust passage of an internal combustion engine in order from the upstream side, such as sulfur oxides and precious metals. It is possible to prevent toxic substances from adhering to the urea selective reduction type catalyst device on the downstream side, thereby suppressing the poisoning of the exhaust gas purification system and the exhaust gas purification system that can maintain high exhaust gas purification performance. To provide a method.

The exhaust gas purification system of the present invention for achieving the above object is an exhaust gas purification system in which an oxidation catalyst device, a fine particle collection device, and a selective reduction catalyst device are provided in the exhaust passage of the internal combustion engine in this order from the upstream side. in, the exhaust passage and the exhaust main passage between the particulate collection device and the selective reduction catalyst device, constituted by the exhaust gas bypass passage you parallel with the main exhaust passage, wherein the flow path of exhaust gas an exhaust switching mechanism for switching the exhaust bypass passage and the exhaust main path, communicating communicating with poisoning substance adsorber disposed in the exhaust bypass passage, the two compartments and compartments of both of these reactions compartment and water compartments A heat storage device having a passage and storing a part of the heat of the exhaust gas passing through the toxic substance adsorbing device by a chemical reaction, and a part of the exhaust gas passing through the exhaust main passage in the water compartment or comprising a heating passage heating in total, a first valve mechanism for introducing the exhaust gas before Symbol main exhaust passage to the heating passage, a control device for controlling the exhaust switching mechanism and the first valve mechanism It is composed of.

The method for suppressing poisoning of the exhaust gas purification system of the present invention for achieving the above object is an exhaust gas purification system that purifies the exhaust gas of an internal combustion engine by an oxidation catalyst device, a fine particle collection device, and a selective reduction type catalyst device. the method poisoning suppression, the exhaust passage between the particulate collection device and the selective reduction catalyst device, a main exhaust passage, parallel with the main exhaust passage, and includes a poisoning substance adsorber exhaust bypass passage and is composed of, when the forced regeneration of the particulate collection device, or when the temperature of the exhaust gas flowing into the above preset temperature of the particulate collection device, said exhaust flowing exhaust gas to the bypass passage, the it is the poisoning substance adsorbing device provided in the exhaust bypass passage, thereby adsorbing the poisoning substance of the particulate collection device the exhaust gas flowing out from the reaction zone and A part of the heat of the exhaust gas passing through the toxic substance adsorbing device is stored by a chemical reaction by a heat storage device having two compartments of the moisture compartment and a communication passage communicating both of these compartments, and the fine particles are captured. The heating passage was branched from the exhaust main passage at the preparatory stage before the forced regeneration of the collector, or when the temperature of the exhaust gas flowing into the fine particle collector was equal to or higher than the preset preparation temperature. A part or all of the exhaust gas passing through the exhaust main passage is introduced into the heating passage by the first valve mechanism provided in the branch portion, and the moisture section of the heat storage device is passed through the exhaust main passage. It is a method characterized by heating with.

According to the exhaust gas purification system of the present invention and the poisoning suppression method of the exhaust gas purification system, an oxidation catalyst device, a fine particle collection device, and a selective reduction type catalyst device are provided in the exhaust passage of the internal combustion engine in this order from the upstream side. In the exhaust gas purification system, it is possible to prevent toxic substances such as sulfur oxides and precious metals from adhering to the selective reduction type catalyst device and ammonia slip catalyst device on the downstream side, thereby improving the exhaust gas purification performance. Can be maintained as it is.

It is a figure which shows typically the structure of the exhaust gas purification system of 1st Embodiment which concerns on this invention, and is the figure which shows the flow of the exhaust gas in a normal state. It is a figure which shows the flow of the exhaust gas at the time of the forced regeneration of the fine particle collection apparatus in the exhaust gas purification system of FIG. It is a figure which shows typically the structure of the exhaust gas purification system of the 2nd Embodiment which concerns on this invention, and is the figure which shows the flow of the exhaust gas in a normal state. It is a figure which shows the flow of the exhaust gas and the flow of water vapor at the time of the preparatory stage just before the forced regeneration of the fine particle collector in the exhaust gas purification system of FIG. It is a figure which shows the flow of the exhaust gas at the time of the forced regeneration of the fine particle collection apparatus in the exhaust gas purification system of FIG. It is a figure which shows typically the XX cross section of the toxic substance adsorption device and the heat storage device of FIG. It is a figure which shows typically the structure of the exhaust gas purification system of the comparative example, and is the figure which shows the flow of the exhaust gas in a normal state. It is a figure which shows the flow of the exhaust gas at the time of the forced regeneration of the fine particle collection apparatus in the exhaust gas purification system of the comparative example of FIG.

Hereinafter, the exhaust gas purification system of the embodiment according to the present invention and the phosphorus poisoning suppression method of the exhaust gas purification system will be described with reference to the drawings.

As shown in FIGS. 1 and 2, the exhaust gas purification system 1 of the first embodiment of the present invention has an exhaust passage 11 through which the exhaust gas G discharged from the engine (internal combustion engine: E) 10 passes. From the upstream side, an oxidation catalyst device (DOC) 12, a fine particle collection device (F) 13, a selective reduction catalyst device (SCR) 14, and an ammonia slip catalyst device (ASC) 15 are provided.

In this oxidation catalyst device 12, noble metals such as platinum (Pt), palladium (Pd), and rhodium (Rh) are applied to a support having a flow-through type honeycomb structure made of ceramics made of cordierite or the like. Oxygen (O ₂ ) in the exhaust gas G is used as a catalyst to oxidize hydrocarbons (HC) and (carbon monoxide (CO)) contained in the exhaust gas G, or are contained in particulate matter (PM). It is a catalyst device that oxidizes the unburned combustion substance (SOF) and converts it into _{water (H 2} O) and carbon dioxide (CO _2).

Then, when the oxidation catalyst device 12 is forcibly regenerated by burning and removing the PM collected by the fine particle collecting device 13, the post injection of the fuel injection in the cylinder of the engine 10 or the exhaust passage 11 By direct injection in the exhaust pipe, which injects fuel directly into the exhaust pipe from a provided fuel injection nozzle (not shown), fuel is supplied into the exhaust gas G to increase the unburned fuel in the exhaust gas G, and this unburned fuel is increased. The fuel is oxidized by a catalytic reaction in the oxidation catalyst device 12, and the heat generated by this oxidation raises the temperature of the exhaust gas G, and the nitrogen monoxide (NO) in the exhaust gas G is nitrogen dioxide (NO ₂ ). The ratio of "NO: NO ₂ " in the exhaust gas G (ratio in molar ratio) is set to a value close to "1: 1" to promote the combustion of PM in the fine particle collecting device 13. Have a role.

Further, the fine particle collecting device 13 is for collecting particulate matter (PM) in the exhaust gas G. For example, the inlet and the outlet of the cells (channels) of the porous ceramic honeycomb are alternately looked at. Consists of a sealed monolith honeycomb type wall flow type filter.

In this fine particle collecting device 13, the exhaust gas G flows in from the inlet of the unsealed cell, and the adjacent outlet is formed on the boundary between the unsealed cell and the cell wall for collecting PM. It passes through and exits the adjacent exit from the exit of the unsealed cell. PM is collected by this wall for collecting PM, but since there is a limit to the amount of PM that can be collected, high-temperature exhaust gas is sent to the fine particle collecting device 13 before the amount of PM collected is saturated. Forced PM regeneration control is performed to burn and remove the collected PM by passing through G, and the PM collection ability is restored.

The selective reduction catalyst device 14 has a catalyst zeolite such as iron ion exchange aluminosilicate supported on a carrier such as a ceramic honeycomb, and is injected by a urea water supply device 16 provided in an exhaust passage 11 on the upstream side thereof. A device that purifies nitrogen oxides (NOx) contained in exhaust gas G into nitrogen (N _{2 ) using ammonia (NH 3} ) produced by hydrolysis of the urea water U by the heat of exhaust gas G as a reducing agent. Is.

The ammonia slip catalyst device 15 has almost the same configuration as the oxidation catalyst device 12, and has a flow-through type honeycomb structure carrier or the like made of ceramics made of cordierite or the like as a raw material, and platinum (Pt) or palladium. It is composed of a noble metal such as (Pd) and rhodium (Rh) as a catalyst. _{Then, by oxidizing ammonia (NH 3} ) in the exhaust gas G and converting it into nitrogen (N ₂ ) and water (H ₂ O), the ammonia flowing out from the selective reduction catalyst device 14 is purified. , Prevents ammonia from flowing out into the atmosphere from the exhaust gas purification system 1.

Further, a first temperature sensor 21 for detecting the temperature T1 of the exhaust gas G flowing into the oxidation catalyst device 12, and a second temperature sensor 22 for detecting the temperature T2 of the exhaust gas G flowing into the fine particle collecting device 13. , A differential pressure sensor 23 for detecting the front-rear differential pressure of the fine particle collecting device 13, a third temperature sensor 24 for detecting the temperature T3 of the exhaust gas G flowing out of the fine particle collecting device 13, and a selective reduction catalyst device. A first NOx concentration sensor 25 for detecting the NOx concentration of the exhaust gas G flowing into the 14, a second NOx concentration sensor 26 for detecting the NOx concentration of the exhaust gas G flowing out from the ammonia slip catalyst device (ASC) 15, and the like. Be prepared.

In addition, engine control that inputs the detection values of these various sensors 21 to 26, the detection data of the engine 10, and the data for control, and outputs the control data for controlling the engine 10 and the exhaust gas purification system 1. A control device 20 called a unit (ECU) is provided.

Further, the exhaust gas purification system 1 includes a urea water injection system including a urea water supply device 16 that supplies urea water U into the exhaust gas G for NOx purification in the selective reduction catalyst device 14, and an exhaust pipe. A fuel injection system for direct fuel injection and the like are arranged, but these configurations are not directly related to the present invention and are omitted here for the sake of brevity.

Then, in the exhaust gas purification system 1 and the poisoning suppression method in the exhaust gas purification system according to the first embodiment of the present invention, the exhaust passage 11 between the fine particle collection device 13 and the urea water injection valve 16 is provided. It is composed of an exhaust main passage 11a and an exhaust bypass passage 11b parallel to the exhaust main passage 11a and provided with a toxic substance adsorption device 17. At the same time, it is provided with exhaust switching mechanisms 18a and 18b for switching the flow path of the exhaust gas G between the exhaust main passage 11a and the exhaust bypass passage 11b, and a control device 20 for controlling the exhaust switching mechanisms 18a and 18b.

The toxic substance adsorbing device 17 has a sulfur oxide adsorbing section 17a holding a sulfur oxide adsorbent and a noble metal adsorbing section 17b holding a noble metal adsorbent. This sulfur oxide adsorbent is obtained by applying calcium carbonate to a honeycomb made of cordierite whose base material is a flow-through type, and adsorbs sulfur oxides by a chemical reaction. On the other hand, the noble metal adsorbent is a honeycomb made of cordierite having a flow-through base material coated with zeolite, and adsorbs the noble metal by physical adsorption.

When the exhaust switching mechanisms 18a and 18b are composed of two three-way valves, the exhaust switching mechanisms 18a and 18b are the first three-way valves 18a provided at a portion where the exhaust bypass passage 11b branches from the exhaust main passage 11a. And a second three-way valve 18b provided at a portion where the exhaust bypass passage 11b joins the exhaust main passage 11a, and both the first three-way valve 18a and the second three-way valve 18b are exhaust mains. Assuming that the flow path is on the passage 11a side, the exhaust gas G passes through the exhaust main passage 11a, and conversely, the flow paths of both the first three-way valve 18a and the second three-way valve 18b are on the exhaust bypass passage 11b side. The exhaust gas G passes through the exhaust bypass passage 11b.

When the exhaust switching mechanisms 18a and 18b are composed of two on-off valves, for example, the first opening / closing provided in the exhaust main passage 11a on the downstream side of the portion where the exhaust bypass passage 11b branches from the exhaust main passage 11a. It is composed of a valve (not shown) and a second on-off valve (not shown) provided on the upstream side of the portion where the exhaust bypass passage 11b joins the exhaust main passage 11a, and is composed of a first on-off valve and a second on-off valve. When both valves are opened, the exhaust gas G passes through the exhaust main passage 11a, and conversely, when both or one of the first on-off valve and the second on-off valve is closed, the exhaust gas is exhaust gas. G will pass through the exhaust bypass passage 11b.

The exhaust switching mechanisms 18a and 18b may have a configuration other than the above, and even if the exhaust gas G flow path is completely switched, the flow rate passing through the exhaust main passage 11a and the exhaust bypass passage 11b are passed. It may have a flow rate adjusting function capable of adjusting the flow rate to be performed.

With this configuration, the control device 20 switches the exhaust gas when the fine particle collecting device 13 is forcibly regenerated or when the temperature T2 of the exhaust gas G flowing into the fine particle collecting device 13 is equal to or higher than a preset set temperature Tc. When the mechanism 18a and 18b are controlled to control the adsorption of toxic substances to switch the flow path of the exhaust gas G to the exhaust bypass passage 11b, the exhaust gas G becomes forced to regenerate when the fine particle collecting device 13 is forcibly regenerated. Since the temperature T2 becomes high or becomes high before forced regeneration, the high-temperature exhaust gas G flows into the exhaust bypass passage 11b and passes through the toxic substance adsorption device 17.

When the exhaust gas G having a high temperature passes through the toxic substance adsorption device 17, the sulfur oxide in the exhaust gas G is adsorbed in the sulfur oxide adsorption section 17a, and the noble metal in the exhaust gas G is adsorbed in the noble metal adsorption section 17b. Adsorb with. As a result, toxic substances such as sulfur oxides and precious metals flowing out from the oxidation catalyst device 12 and the fine particle collection device 13 exposed to the high-temperature exhaust gas G are separated from the selective reduction catalyst device 14 on the downstream side. Since it can be prevented from flowing into the ammonia slip catalyst device 15, it is possible to suppress the deterioration of the purification performance due to the toxic substances in these devices 14 and 15.

Further, since the sulfur oxide adsorbent and the noble metal adsorbent are saturated when a certain amount of sulfur oxide and noble metal are adsorbed and no longer adsorbed, the control device 20 is attached to the toxic substance adsorbing device 17. The cumulative amount of the adsorbed poisonous substance is calculated, and when it is determined that the cumulative amount exceeds the preset alarm amount, an alarm is output. The output of this alarm promotes the exchange of the sulfur oxide adsorbent and the noble metal adsorbent of the toxic substance adsorbing device 17, and prevents the saturation of these adsorbents.

More specifically, with respect to sulfur oxides, since the sulfur component is derived from fuel and engine oil, the fuel and engine oil are derived from the operating state of the engine 10 (engine rotation speed Ne, load Q or fuel injection amount q). The amount of sulfur oxides that flow out into the exhaust gas G and the amount of sulfur oxides adsorbed by the sulfur oxide adsorbent are estimated from the amount of sulfur components contained in them. Therefore, when the integrated value of the adsorption amount of sulfur oxide exceeds the preset limit adsorption amount of sulfur oxide, an alarm is output. The alarm includes a visual alarm such as lighting and blinking of an alarm lamp and an auditory alarm such as a buzzer, a bell, and a voice message, and the alarm is generated by appropriately selecting the alarm.

Further, since the precious metal is derived from the catalyst supported on the oxidation catalyst device 12 and the fine particle collecting device 13, how much engine operation, especially forced regeneration and passage of high-temperature exhaust gas G, can be determined by experiments in advance. A database is created by grasping how much precious metal is detached and adsorbed by the toxic substance adsorbing device 17 in the elapsed state, and cumulative calculation is performed based on this database during control. The amount of precious metal adsorbed on the toxic substance adsorbing device 17 is estimated. When this estimated amount exceeds the preset limit adsorption amount of the precious metal, an alarm is output as in the case of sulfur oxides.

Then, in the method for suppressing poisoning of the exhaust gas purification system of the first embodiment, the exhaust gas G of the internal combustion engine 10 is purified by the oxidation catalyst device 12, the fine particle collection device 13, and the urea selective reduction catalyst device 14. This is a method for suppressing poisoning of the exhaust gas purification system 1. In this method, the exhaust passage 11 between the fine particle collecting device 13 and the selective reduction catalyst device 14 is provided in parallel with the exhaust main passage 11a and the exhaust main passage 11a, and is provided with a toxic substance adsorbing device 17. It is composed of an exhaust bypass passage 11b. At the same time, when the fine particle collecting device 13 is forcibly regenerated, or when the temperature T2 of the exhaust gas G flowing into the fine particle collecting device 13 is equal to or higher than the preset set temperature Tc, the exhaust gas enters the exhaust bypass passage 11b. This is a method in which G is flowed and the toxic substances (SOx, PGM) in the exhaust gas G flowing out from the fine particle collecting device 13 are adsorbed by the toxic substance adsorbing device 17 provided in the exhaust bypass passage 11b. ..

According to the above-mentioned exhaust gas purification system 1 and the exhaust gas purification system poisoning suppression method, the oxidation catalyst device 12, the fine particle collection device 13, and the selective reduction catalyst device are sequentially connected to the exhaust passage 11 of the engine 10 from the upstream side. In the exhaust gas purification system 1 provided with 14, it is possible to prevent toxic substances such as sulfur oxides and precious metals from adhering to the selective reduction type catalyst device 14 in the subsequent stage, whereby the selective reduction type catalyst device 14 of the selective reduction type catalyst device 14 can be prevented. Exhaust gas purification performance can be maintained at a high level. Further, when the ammonia slip catalyst device 15 is provided on the downstream side of the selective reduction type catalyst device 14, it is possible to prevent the ammonia slip catalyst device 15 from being poisoned, and the exhaust gas purification performance of the ammonia slip catalyst device 15 can be suppressed. Can be kept high.

Further, when the adsorption amount of the toxic substance in the toxic substance adsorption device 17 is calculated from the engine rotation speed Ne indicating the engine operating state, the load Q, and the like, and the adsorption amount of the toxic substance exceeds the limit adsorption amount. , Since an alarm or warning for urging the replacement of the adsorbent is generated, saturation of the adsorbent can be prevented.

Next, the exhaust gas purification system 1A and the method for suppressing poisoning of the exhaust gas purification system according to the second embodiment shown in FIGS. 3 to 6 will be described. In the exhaust gas purification system 1A of the second embodiment, the configuration of the exhaust gas purification system 1 of the first embodiment is further provided with the following configuration.

That is, a heat storage device 31 is provided to store a part of the heat of the exhaust gas G passing through the exhaust bypass passage 11b by a chemical reaction. The heat storage device 31 includes two compartments, a reaction compartment 31a and a moisture compartment 31b, and a communication passage 31c that communicates both compartments 31a and 31b.

Further, a heating passage 31e for heating the moisture compartment 31b of the heat storage device 31 with the exhaust gas G, a three-way valve (first valve mechanism) 31d for introducing the exhaust gas G into the heating passage 31e, and a reaction compartment 31a. A heat radiation passage 31g for heating at least one of the oxidation catalyst device 12 or the fine particle collection device 13 with water vapor from the water vapor and an on-off valve (second valve mechanism) 31f for introducing water vapor into the heat radiation passage are provided. ..

With this configuration, when the heat storage device 31 is heated to store heat, the heat can be absorbed and stored by the _{endothermic reaction "Ca (OH) 2} + 109 kJ / mol → CaO + H _{2 O" in the reaction compartment 31a.} it can. The endothermic reaction, calcium hydroxide and calcium oxide (CaO) water (H ₂ O) and is generated by a chemical reaction (Ca (OH) ₂₎ is a reaction that occurs when decomposing again. This water is moved from the reaction compartment 31a to the water compartment 31b and accumulated by the communication passage 31c. On the other hand, when taking out the heat from the heat storage device 31, is supplied to water moisture compartment 31b in the reaction zone 31a, and calcium oxide (CaO) water (H ₂ O) and to form calcium hydroxide and reaction Since heat is generated and dissipated by the exothermic reaction "CaO + H ₂ O → Ca (OH) ₂ + 109 kJ / mol", the heat chemically stored in the reaction compartment 31a can be taken out.

Then, the control device 20 is in the preparatory stage before the forced regeneration of the fine particle collecting device 13, or when the temperature T2 of the exhaust gas G flowing into the fine particle collecting device 13 is equal to or higher than the preset preparation temperature Ta. , The three-way valve (first valve mechanism) 31d is controlled to perform the first preheating control for introducing the exhaust gas G from the exhaust main passage 11a into the heating passage 31e. The preparation temperature Ta is set to a temperature slightly lower than the set temperature by an experiment or the like in advance so that a sufficient time can be obtained for the first preheating control or the second preheating control.

Alternatively, the control device 20 is in the preparatory stage before the forced regeneration of the fine particle collecting device 13, or when the temperature T2 of the exhaust gas G flowing into the fine particle collecting device 13 is equal to or higher than the preset preparation temperature Ta. , The three-way valve (first valve mechanism) 31d is controlled to introduce the exhaust gas G from the exhaust main passage 11a into the heating passage 31e, and the on-off valve (second valve mechanism) 31f is controlled to control the reaction compartment. The second preheating control is performed to introduce the water vapor H from 31a into the heat dissipation passage 31g.

By these controls, immediately before the forced regeneration of the fine particle collecting device 13, the three-way valve (first valve mechanism) 31d is controlled to introduce a part or all of the exhaust gas G into the heating passage 31e and chemically. The water in the moisture compartment 31b can be heated to steam by the heat of the exhaust gas G by flowing it around the heat storage device 31. That is, the heat of the exhaust gas G can be used to start the exothermic reaction of the heat storage device 31, and the heat generated by the exothermic reaction of the reaction compartment 31a can be used for raising the temperature and activating the toxic substance adsorption device 17. it can. Further, by opening the on-off valve (second valve mechanism) 31f, the heat obtained by the exothermic reaction can be sent to at least one or both of the oxidation catalyst awareness 12 and the fine particle collecting device 13 by steam H. For example, water vapor H is sent into the canning containing the oxidation catalyst device 12 and the fine particle collecting device 13. As a result, the amount of fuel injected during forced regeneration can be reduced by raising the temperature of the fine particle collecting device 13 with the heat obtained from the exothermic reaction, which improves fuel efficiency and injects excess hydrocarbon (HC). By suppressing injection), it becomes possible to prevent HC poisoning of the catalyst. Further, the calcium oxide (CaO) used in the heat storage device 31 is replaced at the time of periodic inspection or vehicle inspection.

Then, the method for suppressing the poisoning of the exhaust gas purification system according to the second embodiment is the following first preheating control or the second method in addition to the method for suppressing the poisoning of the exhaust gas purification system according to the first embodiment. This is a method of performing either preheating control.

In the first preheating control, the control device 20 sets a preset preparation temperature T2 of the exhaust gas G flowing into the fine particle collecting device 13 at the preparatory stage before the forced regeneration of the fine particle collecting device 13. When the temperature is Ta or higher, the three-way valve (first valve mechanism) 31d is controlled to introduce the exhaust gas G from the exhaust main passage 11a into the heating passage 31e.

In the second preheating control, the control device 20 sets a preset preparation temperature T2 of the exhaust gas G flowing into the fine particle collecting device 13 at the preparatory stage before the forced regeneration of the fine particle collecting device 13. When it is Ta or more, the three-way valve (first valve mechanism) 31d is controlled to introduce the exhaust gas G from the exhaust main passage 11a into the heating passage 31e, and the on-off valve (second valve mechanism) 31f is controlled. Then, the water vapor H from the reaction compartment 31a is introduced into the heat dissipation passage 31g.

In the detection of the preparatory stage before the forced regeneration of the fine particle collecting device 13, for example, a quasi-judgment value slightly smaller than the determination value of the PM deposition amount at which the forced regeneration is performed is provided, and the PM deposition amount becomes the quasi-determination value. When the preparation stage is reached, the above-mentioned first preheating control or second preheating control is performed, and when the PM accumulation amount reaches the judgment value, the forced regeneration is assumed and the forced regeneration is performed. To carry out.

When this forced regeneration is carried out, the first preheating control and the second preheating control are completed, the three-way valve (first valve mechanism) 31d is controlled to close the valve, and the heating passage 31e is closed. Further, the on-off valve (second valve mechanism) 31f is controlled to close the valve to close the heat dissipation passage 31g. The PM deposit amount can be substituted by, for example, the differential pressure measured by the differential pressure sensor 23. In this case, assuming that the preparatory stage is reached when the measured differential pressure reaches the quasi-judgment differential pressure, the first preheating control or the second preheating control is performed, and the measured differential pressure is the judgment difference. Forced playback starts when pressure is applied.

After entering the preparatory stage and performing the first preheating control or the second preheating control for a preset time, the forced regeneration is configured to enter as it is without determining the forced regeneration. Is also good. Alternatively, after the forced regeneration is determined, a preparatory stage is provided before the forced regeneration, and the first preheating control or the second preheating control is performed for a preset time, and then the forced regeneration is started. You may.

As a result, by implementing the first preheating control or the second preheating control, the toxic substance adsorbing device 17 is heated by the heat of the exhaust gas G and the heat stored in the heat storage device 31 to raise the temperature and activate it. Further, by implementing the second preheating control, the heat stored in the heat storage device 31 heats the oxidation catalyst device 12 or the fine particle collecting device 13 to raise the temperature. As a result, it is possible to save fuel for raising the temperature of the oxidation catalyst device 12 or the fine particle collecting device 13.

Since the forced regeneration is carried out after this preparatory step, the toxic substance adsorbing device 17 can efficiently adsorb the toxic substance, and the oxidation catalyst device 12 or the fine particles already heated in the preliminary step can be adsorbed. Since the temperature of the collection device 13 is raised, in the case of a configuration in which the temperature of the oxidation catalyst device 12 is raised, hydrocarbons and nitrogen monoxide in the exhaust gas G can be efficiently oxidized by activating the catalyst of the oxidation catalyst device 12. Further, in the case of the configuration in which the temperature of the fine particle collecting device 13 is raised, the amount of heat required for raising the temperature of the fine particle collecting device 13 can be reduced, so that forced regeneration can be performed with less fuel.

Therefore, according to the exhaust gas purification system 1S of the second embodiment and the poisoning suppression method of the exhaust gas purification system, the following effects are obtained by the first preheating control or the second preheating control. Can be obtained.

First, due to the first preheating control, when the temperature of the exhaust gas G is high, such as during forced regeneration of the fine particle collecting device 13, the flow path of the exhaust gas G is switched to the exhaust bypass passage 11b, so that the high temperature exhaust gas When G passes through the toxic substance adsorbing device 17, a part of the heat of the exhaust gas G can be stored in the heat storage device 31 by an endothermic reaction.

Further, in the preparatory stage before the forced regeneration of the fine particle collecting device 13, or when the temperature T2 of the exhaust gas G flowing into the fine particle collecting device 13 is equal to or higher than the preset preparation temperature Ta, the exhaust main passage 11a By introducing the exhaust gas G from the above into the heating passage 31e, the moisture compartment 31b of the heat storage device 31 is heated by the exhaust gas G from the outside to evaporate the moisture in the moisture compartment 31b and supply it to the reaction compartment 31a. be able to. As a result, an exothermic reaction is carried out in the reaction compartment 31a, and the generated heat is used to heat and activate the toxic substance adsorbent of the toxic substance adsorbing device 17 arranged inside the heat storage device 31. can do. As a result, when the fine particle collecting device 13 is forcibly regenerated, or when the temperature T2 of the exhaust gas G flowing into the fine particle collecting device 13 is equal to or higher than the preset set temperature Tc, the toxic substance adsorbing device 17 is used. , Sulfur oxides and precious metals can be adsorbed more efficiently.

Next, in addition to the effect of the first preheating control, the on-off valve (second valve mechanism) 31f is controlled by the second preheating control to introduce the water vapor H from the reaction compartment 31a into the heat dissipation passage 31g. Therefore, at least one of the oxidation catalyst device 12 and the fine particle collecting device 13 can be heated by the steam H, and the fuel required for raising the temperature of these oxidation catalyst device 12 or the fine particle collecting device 13 Will be able to save.

Then, in the exhaust gas purification system 1X as a comparative example as shown in FIGS. 7 and 8, the exhaust gas G discharged from the engine (internal combustion engine: E) 10 passes through the exhaust passage 11 in order from the upstream side. , Oxidation catalyst device (DOC) 12, Fine particle collection device (F) 13 for collecting particulate matter (PM), Selective reduction catalyst device for purifying nitrogen oxides (NOx) in exhaust gas G ( It is configured to include SCR) 14 and an ammonia slip catalyst device (ASC) 15.

In the case of this comparative example, when sulfur oxides (SOx) are generated by the sulfur content contained in fuel, engine oil, etc., these poisonous substances are collected in the oxidation catalyst device 12 and fine particles. As shown in FIG. 8, sulfur oxides (SOx) and noble metals (PGM) are heated to a high temperature during forced regeneration in which PM deposited on the catalyst of the device 13 is burned and removed by burning and removing PM deposited on the fine particle collecting device 13. It may separate from the oxide catalyst device 12 and the fine particle collection device 13 and adhere to the selective reduction type catalyst device 14 and the ammonia slip catalyst device 15 arranged on the downstream side, and the NOx purification performance of these devices may be deteriorated. There is a problem of poisoning due to sulfur oxides that it decreases.

Further, when the temperature of the catalyst becomes high, the noble metal (PGM), which is the active species of the catalyst of the oxidation catalyst device and the fine particle collecting device, becomes vapor and adheres to the selective reducing catalyst device 14 and the ammonia slip catalyst device 15 on the downstream side. As a result, the selectivity of the ammonia oxidation performance of these devices 14 and 15 is improved, and ammonia, which is a NOx reducing agent, is oxidized first, and the NOx purification performance is deteriorated. There is also a problem.

In contrast to this comparative example, in the exhaust gas purification systems 1, 1A and the exhaust gas purification system poisoning suppression method according to the first and second embodiments of the present invention, the poisoning by sulfur oxides is also covered by precious metals. Poison can also be suppressed, and further, in the exhaust gas purification system 1A of the second embodiment and the poisoning suppression method of the exhaust gas purification system, the exhaust gas G is provided by the heat storage device 31 that chemically stores heat. Effective use of heat can contribute to improving fuel efficiency.

1,1A, 1X Exhaust gas purification system 10 Engine (internal combustion engine)
11 Exhaust passage 11a Exhaust main passage 11b Exhaust bypass passage 12 Oxidation catalyst device (DOC)
13 Fine particle collector (F)
14 Selective reduction catalyst device (SCR)
15 Ammonia slip catalyst device (ASC)
16 Urea water injection valve 17 Toxic substance adsorption device 17a Sulfur oxide adsorption section 17b Precious metal adsorption section 18a First three-way valve (exhaust switching mechanism)
18b Second three-way valve (exhaust switching mechanism)
20 Control device 21 1st temperature sensor 22 2nd temperature sensor 24 3rd temperature sensor 23 Differential pressure sensor 25 1st NOx concentration sensor 26 2nd NOx concentration sensor 31 Heat storage device 31a Reaction compartment 31b Moisture compartment 31c Communication passage 31d Three-way valve (1st Valve mechanism)
31e Heating passage 31f On-off valve (second valve mechanism)
31g Heat dissipation passage G Exhaust gas H Water vapor T1 Temperature of exhaust gas flowing into the oxidation catalyst device T2 Temperature of exhaust gas flowing into the fine particle collecting device T3 Temperature of exhaust gas flowing out of the fine particle collecting device Ta Preparation temperature Tc Set temperature

Claims (9)

In an exhaust gas purification system equipped with an oxidation catalyst device, a fine particle collection device, and a selective reduction catalyst device in order from the upstream side in the exhaust passage of the internal combustion engine.
The exhaust passage and the exhaust main passage between the particulate collection device and the selective reduction catalyst device, constituted by the exhaust gas bypass passage you parallel with the main exhaust passage,
Both the exhaust switching mechanism, and the poisoning substances adsorbed device disposed in the exhaust bypass passage, the two compartments of the reaction zone and the water zone and their switching the flow path of the exhaust gas to the exhaust bypass passage and the exhaust main path a communication passage for communicating the compartments, the passage and the heat storage device storing heat by chemical reaction a portion of the exhaust gas passing through the poisoning substance adsorber heat, pre SL main exhaust passage the water compartments a heating passage heating in some or all of the exhaust gas, the first valve mechanism for introducing the exhaust gas in the main exhaust passage to the heating passage and the exhaust switching mechanism and the first valve An exhaust gas purification system characterized by being equipped with a control device that controls the mechanism. The heating passage when the control device is in the preparatory stage before the forced regeneration of the fine particle collecting device, or when the temperature of the exhaust gas flowing into the fine particle collecting device is equal to or higher than a preset preparation temperature. The first valve mechanism provided in the branch portion branched from the exhaust main passage is controlled to perform the first preheating control for introducing the exhaust gas from the exhaust main passage into the heating passage. The exhaust gas purification system according to claim 1. Wherein that it comprises a radiating passage for heating at least one of the oxidation catalyst device or the particle catch arrangement, the second valve mechanism for introducing steam into the heat-dissipating passage water vapor generated from the previous SL reaction zone The exhaust purification system according to claim 1. When the control device is in the preparatory stage before the forced regeneration of the fine particle collection device or when the temperature of the exhaust gas flowing into the fine particle collection device is equal to or higher than a preset preparation temperature, the heating passage is used as the exhaust main. The first valve mechanism provided in the branch portion branched from the passage is controlled to introduce the exhaust gas from the exhaust main passage into the heating passage, and the second valve mechanism is controlled to control the reaction. The exhaust gas purification system according to claim 3, further comprising performing a second preheating control for introducing water vapor generated from the compartment into the heat dissipation passage. The exhaust gas purification system according to any one of claims 1 to 4, wherein the toxic substance adsorbing device has a sulfur oxide adsorbent and a noble metal adsorbent. The control device controls the exhaust switching mechanism when the fine particle collecting device is forcibly regenerated or when the temperature of the exhaust gas flowing into the fine particle collecting device is equal to or higher than a preset set temperature. The exhaust gas purification system according to any one of claims 1 to 5, wherein the exhaust gas flow path is switched to the bypass passage to control the adsorption of toxic substances. The control device calculates the cumulative amount of the poisonous substance adsorbed on the poisonous substance adsorbing device, and outputs an alarm when it is determined that the cumulative amount exceeds a preset alarm amount. The exhaust gas purification system according to any one of claims 1 to 6, wherein the exhaust gas purification system is characterized. In the method of suppressing poisoning of an exhaust gas purification system that purifies the exhaust gas of an internal combustion engine by an oxidation catalyst device, a fine particle collecting device, and a selective reduction type catalyst device.
The exhaust passage between the fine particle collector and the selective reduction catalyst device.But, Exhaust main passage and exhaust bypass passage parallel to this exhaust main passage and equipped with a toxic substance adsorption device. Has been
At the time of forced regeneration of the fine particle collecting device, or when the temperature of the exhaust gas flowing into the fine particle collecting device is equal to or higher than a preset set temperature, the exhaust gas is flowed through the exhaust bypass passage to exhaust the exhaust gas. Provided in the bypass passageSaidThe toxic substance adsorbing device adsorbs the toxic substance in the exhaust gas flowing out from the fine particle collecting device.Along with the reaction compartment and moisture By a heat storage device having two compartments of the compartment and a communication passage communicating both of these compartments. A part of the heat of the exhaust gas passing through the toxic substance adsorbing device is stored by a chemical reaction.
At the preparatory stage before forced regeneration of the fine particle collecting device, or to the fine particle collecting device When the temperature of the inflowing exhaust gas is equal to or higher than the preset preparation temperature, the heating passage is exhausted. Exhaust gas from the exhaust main passage is provided by the first valve mechanism provided at the branch portion branched from the main passage. Is introduced into the heating passage to pass the moisture compartment of the heat storage device through the exhaust main passage. Heat with some or all of the gasA method for controlling poisoning of an exhaust gas purification system. At the preparatory stage before forced regeneration of the fine particle collecting device, or to the fine particle collecting device When the temperature of the inflowing exhaust gas is equal to or higher than the preset preparation temperature, the second valve mechanism causes the above. The water vapor generated from the reaction compartment is introduced into the heat radiating passage, and the anti-reverse introduced into the heat radiating passage. At least of the oxidation catalyst device or the fine particle collecting device with the steam generated from the response compartment. The method for suppressing poisoning of an exhaust gas purification system according to claim 8, wherein one of them is heated. ..

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