US20110047991A1 - Exhaust gas purification apparatus - Google Patents

Exhaust gas purification apparatus Download PDF

Info

Publication number
US20110047991A1
US20110047991A1 US12/871,064 US87106410A US2011047991A1 US 20110047991 A1 US20110047991 A1 US 20110047991A1 US 87106410 A US87106410 A US 87106410A US 2011047991 A1 US2011047991 A1 US 2011047991A1
Authority
US
United States
Prior art keywords
exhaust gas
oxidation catalyst
catalyst
purification apparatus
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US12/871,064
Other languages
English (en)
Inventor
Yoshifumi Kato
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyota Industries Corp
Original Assignee
Toyota Industries Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyota Industries Corp filed Critical Toyota Industries Corp
Assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI reassignment KABUSHIKI KAISHA TOYOTA JIDOSHOKKI ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KATO, YOSHIFUMI
Publication of US20110047991A1 publication Critical patent/US20110047991A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0093—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are of the same type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0097—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/06—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a temperature sensor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/10—Carbon or carbon oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/14—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1602—Temperature of exhaust gas apparatus
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the present invention relates to an exhaust gas purification apparatus and, more specifically, to an exhaust gas purification apparatus having a urea SCR (selective catalytic reduction) system for reducing nitrogen oxides (NOx) in exhaust gas emitted from a diesel engine.
  • a urea SCR selective catalytic reduction
  • the urea SCR system has been developed for reducing NOx in exhaust gas emitted from a diesel engine.
  • the urea SCR system employs an SCR catalyst for converting NOx into nitrogen (N2) and water (H2O) by chemical reaction between NOx and ammonia (NH3) generated by hydrolysis of urea water.
  • the SCR catalyst is provided in the exhaust passage between the engine and the muffler. Furthermore, an oxidation catalyst and an injection valve for injecting urea water into exhaust gas are provided upstream of the SCR catalyst.
  • the oxidation catalyst oxidizes hydrocarbons (HC) and carbon monoxide (CO) in exhaust gas into water (H2O) and carbon dioxide (CO2) and also promotes the oxidation of nitrogen oxide (NO) into nitrogen dioxide (NO2).
  • a DPF diesel particulate filter
  • PM particulate matter
  • the exhaust gas purification apparatus including the urea SCR system and the DPF has many components provided between the engine and the muffler and requires a large space for mounting of such components to a vehicle. Therefore, the urea SCR system is required to be downsized and also to accomplish the NOx reduction efficiently for the usage of urea water.
  • an exhaust gas purification apparatus that includes a platinum-containing precatalyst having a function of filtering PM in exhaust gas, an SCR catalyst provided downstream of the platinum-containing precatalyst, a first supply device provided upstream of the platinum-containing precatalyst for supplying ammonia or urea and a second supply device provided between the platinum-containing precatalyst and the SCR catalyst for supplying ammonia or urea.
  • the platinum-containing precatalyst functions as a reduction catalyst under a temperature that is below about 250° C. and also as an oxidation catalyst under a temperature that is about 250° C. or higher.
  • the SCR catalyst is activated as a reduction catalyst under a temperature that is about 250° C. or higher.
  • the time for which the supplied urea stays upstream of the platinum-containing precatalyst or the SCR catalyst before reaching the precatalyst or the catalyst should be long for ensuring the time that is long enough for urea to be hydrolyzed into ammonia.
  • the distances between the first supply device and the platinum-containing precatalyst and between the second supply device and the SCR catalyst, respectively, should be long enough for the hydrolysis of urea. Therefore, there has been problems in that the apparatus increases its length and it is difficult to make it small.
  • the present invention is directed to providing an exhaust gas purification apparatus that improves the efficiency of NOx reduction relative to the urea water usage and makes possible downsizing of the apparatus.
  • An exhaust gas purification apparatus includes a first oxidation catalyst provided in a passage through which exhaust gas flows, a particulate matter collecting device provided downstream of the first oxidation catalyst, a SCR catalyst integrally formed with the particulate matter collecting device and having ammonia adsorption property, a second oxidation catalyst integrally formed with the particulate matter collecting device and oxidizing ammonia at a predetermined temperature or higher and a urea water supply device provided upstream of the SCR catalyst for supplying urea water.
  • the urea water supply device supplies urea water only when a temperature of the second oxidation catalyst is below the predetermined temperature.
  • FIG. 1 is a schematic view of an exhaust gas purification apparatus according to an embodiment of the present invention and its associated components;
  • FIG. 2 is a schematic cross sectional view of the exhaust gas purification apparatus of FIG. 1 .
  • the exhaust gas purification apparatus 101 is employed in a vehicle equipped with a diesel engine.
  • an engine assembly including an engine 1 and the exhaust gas purification apparatus 101 is designated generally by reference numeral 10 .
  • the engine 1 has a plurality of cylinders 1 A each having an intake port 1 B to which an intake manifold 4 is connected for distributing intake air to the respective cylinders 1 A.
  • the intake manifold 4 has an inlet 4 A to which an engine intake pipe 3 is connected and the engine intake pipe 3 is further connected to a compressor housing 8 A of a turbocharger 8 .
  • the compressor housing 8 A is connected to an intake pipe 2 through which outside air is introduced.
  • an exhaust manifold 5 is connected to a plurality of exhaust ports 1 C of the engine 1 for collecting exhaust gas emitted from the respective exhaust ports 1 C.
  • An outlet 5 A of the exhaust manifold 5 is connected to a turbine housing 8 B of the turbocharger 8 , to which the exhaust gas purification apparatus 101 having a substantially cylindrical shape is connected and disposed adjacent to a lateral side of the engine 1 .
  • the exhaust gas purification apparatus 101 is connected to an exhaust pipe 6 , the downstream end of which is further connected to a muffler 7 .
  • the intake pipe 2 , the turbocharger 8 , the engine intake pipe 3 and the intake manifold 4 cooperate to form an intake system of the vehicle, while the exhaust manifold 5 , the turbocharger 8 , the exhaust gas purification apparatus 101 , the exhaust pipe 6 and the muffler 7 cooperates to form an exhaust system of the vehicle.
  • the engine 1 , the engine intake pipe 3 , the intake manifold 4 , the exhaust manifold 5 and the turbocharger 8 cooperate to form the aforementioned engine assembly 10 .
  • the exhaust gas purification apparatus 101 includes a casing 11 having a substantially cylindrical shape.
  • the casing 11 has an upstream end face 11 A to which the outlet 8 B 2 of the turbine housing 8 B of the turbocharger 8 is connected and a downstream end face 11 B to which the upstream end 6 A of the exhaust pipe 6 is connected.
  • the casing 11 communicates internally with the turbine housing 8 B and the exhaust pipe 6 .
  • the cylindrical casing 11 houses therein a first oxidation catalyst layer 12 supporting a first oxidation catalyst and a diesel particulate filter (DPF) 13 D forming a particulate matter collecting device disposed downstream of the first oxidation catalyst layer 12 with respect to the flow of exhaust gas in the casing 11 .
  • the first oxidation catalyst layer 12 and the DPF 13 D are made in the form of a layer extending perpendicular to the axis of a cylindrical portion 11 C of the casing 11 over the entire radial dimension of the interior of the cylindrical portion 11 C.
  • the first oxidation catalyst layer 12 and the DPF 13 D are disposed spaced apart from each other thereby to form therebetween a space 16 .
  • the first oxidation catalyst layer 12 supports thereon the first oxidation catalyst for oxidizing hydrocarbons (HC) and carbon monoxide (CO) into water (H2O) and carbon dioxide (CO2) and also promoting the oxidation of nitrogen monoxide (NO) into nitrogen dioxide (NO2).
  • the first oxidation catalyst of the first oxidation catalyst layer 12 uses material such as platinum (Pt), palladium (Pd), rhodium (Rh), silver (Ag), iron (Fe), cupper (Cu), nickel (Ni), gold (Au) or a mixture of two or more of these materials.
  • the DPF 13 D is made of a porous material such as ceramic for capturing particulate matter (PM) contained in exhaust gas. For preventing the deterioration of the DPF 13 D caused by the accumulation of PM, PM accumulated in the DPF 13 D needs to be burned.
  • the DPF 13 D has an (urea) SCR catalyst 14 as a selective catalytic reduction catalyst supported thereon, e.g., by coating.
  • the DPF 13 D and the SCR catalyst 14 cooperate to integrally form a DPF 13 with catalyst.
  • the selective catalytic reduction catalyst serves to promote the chemical reaction selectively among specific chemical substances.
  • the urea SCR catalyst (hereinafter referred to as SCR catalyst) catalyzes the reaction between nitrogen oxide (NOx) and ammonia (NH3) thereby to reduce NOx into nitrogen (N2) and water (H2O).
  • NOx nitrogen oxide
  • NH3 ammonia
  • the SCR catalyst 14 has the above-described function and preferably has high ammonia adsorption property and also catalytic property under a low temperature.
  • the ammonia adsorption property of the SCR catalyst 14 should preferably be over 20 mg/l, i.e.
  • the SCR catalyst 14 should preferably be activated catalytically at 150° C. or higher.
  • the SCR catalyst 14 should preferably be made of a zeolite replaced by a metal such as iron and the like.
  • the SCR catalyst 14 being activated means rapid increase of the reduction rate of NOx by ammonia.
  • the DPF 13 D supporting the SCR catalyst 14 also has a second oxidation catalyst 15 supported thereon, e.g., by coating, for decreasing the combustion temperature of PM captured by the DPF 13 D.
  • the DPF 13 D and the second oxidation catalyst 15 cooperate to integrally form the DPF 13 with catalyst.
  • the DPF 13 with catalyst is formed by the DPF 13 D, the SCR catalyst 14 and the second oxidation catalyst 15 .
  • the second oxidation catalyst 15 should preferably decrease the PM combustion temperature to a temperature between 400 and 650° C.
  • the second oxidation catalyst 15 functions not only to decrease the PM combustion temperature but also to oxidize and decompose ammonia under a predetermined temperature Tp° C. or higher. However, the second oxidation catalyst 15 neither oxidizes nor decomposes ammonia at a temperature below the predetermined temperature Tp° C.
  • the predetermined temperature Tp° C. corresponds to a temperature at which the second oxidation catalyst 15 is activated.
  • the oxidation catalyst being activated means that 50% of object substance for oxidation is oxidized to a predetermined level. Since the temperature at which the catalyst is activated depends on the proportion of component materials of the catalyst and the concentration of the catalyst in the region of the DPF where the catalyst is supported thereon, the temperature Tp° C. at which the second oxidation catalyst 15 is activated may be between 150 and 250° C.
  • the second oxidation catalyst 15 may be Ag/CeO2 catalyst, i.e., silver (Ag) supported on ceria (CeO2).
  • the SCR catalyst 14 and the second oxidation catalyst 15 may be applied in either order to the DPF 13 D to be supported thereon, firstly the SCR catalyst 14 and then the second oxidation catalyst 15 or in the reverse order. Alternatively, a mixture of the SCR catalyst 14 and the second oxidation catalyst 15 may be supported on the DPF 13 D.
  • the DPF 13 D and the SCR catalyst 14 may be formed integrally in a manner that the SCR catalyst 14 is disposed in rear of the DPF 13 D and the DPF 13 D supports thereon the second oxidation catalyst 15 .
  • An injection valve 18 that is an electromagnetic valve is provided upstream of the first oxidation catalyst layer 12 in the cylindrical portion 11 C of the casing 11 .
  • the injection valve 18 forms the urea water supply device of the present invention.
  • the injection valve 18 is connected to a urea water tank 19 provided in a vehicle (not shown) and operable to inject urea water upstream of the first oxidation catalyst layer 12 (SCR catalyst 14 ) in the casing 11 .
  • the injection valve 18 is electrically connected to a dosing control unit (DCU) 20 that controls the opening and closing operation of the injection valve 18 .
  • the urea water tank 19 has an electric pump for supplying urea water to the injection valve 18 .
  • the electric pump is electrically connected to the DCU 20 and the pump operation is controlled by the DCU 20 .
  • the DCU 20 may be provided separately or formed integrally with an ECU for the vehicle.
  • a cylindrically-shaped mixer 17 is provided on the upstream end face 13 A of the DPF 13 with catalyst for distributing substances in exhaust gas uniformly over the end face 13 A.
  • the mixer 17 has a structure that is similar to that disclosed in Published Japanese Translation H06-509020 of PCT international publication or Japanese Patent Application Publication 2006-9608.
  • the mixer disclosed in Published Japanese Translation H06-509020 is made in the form of a lattice that divides the gas passage into plural cells so as to cause the gas flowing through each cell to flow spirally and also to flow toward the adjacent cell. This helps the substances in exhaust gas to be dispersed uniformly in the whole passage.
  • the mixer disclosed in Japanese Patent Application Publication 2006-9608 has plural plates each extending perpendicularly to the direction of gas flow, which provides serpentine gas passage serving to distribute the substances in the gas uniformly.
  • An exhaust gas temperature sensor 31 is provided downstream of the upstream end face 11 A of the casing 11 for detecting the temperature of exhaust gas.
  • the exhaust gas temperature sensor 31 is electrically connected to the DCU 20 and sends detected temperature information to the DCU 20 .
  • the exhaust gas purification apparatus 101 includes the SCR catalyst 14 and the DPF 13 D in a manner that they are integrally formed and is fixed to the engine assembly 10 and disposed adjacent to the engine 1 (refer to FIG. 1 ).
  • FIG. 1 while the engine 1 is running, outside air is flowed into the compressor housing 8 A of the turbocharger 8 through the intake pipe 2 .
  • the air is pumped by a compressor wheel (not shown) in the compressor housing 8 A and flowed to the engine intake pipe 3 under an increased pressure.
  • the air is flowed into a cylinder 1 A in the engine 1 through the engine intake pipe 3 and the intake manifold 4 .
  • the air in the cylinder 1 A is mixed with fuel (light oil) supplied into the cylinder 1 A and the fuel is ignited spontaneously for combustion.
  • Exhaust gas produced by the combustion is discharged into the exhaust manifold 5 through a plurality of exhaust ports 1 C to be collected by the exhaust manifold 5 and then flows into the turbine housing 8 B of the turbocharger 8 .
  • the exhaust gas flowing through the turbine housing 8 B increases the rotation speed of the turbine wheel (not shown) in the turbine housing 8 B and the compressor wheel connected to the turbine wheel and then is discharged into the exhaust gas purification apparatus 101 .
  • the exhaust gas flows through the exhaust pipe 6 and the muffler 7 and then is discharged outside the vehicle (not shown).
  • all the exhaust gas flowed into the exhaust gas purification apparatus 101 flows firstly through the first oxidation catalyst layer 12 . While the exhaust gas passes through the first oxidation catalyst layer 12 , hydrocarbons and carbon monoxide in the exhaust gas are oxidized into carbon dioxide and water, and part of NO is oxidized into NO2 that can be reduced easily. After flowing through the first oxidation catalyst layer 12 , the exhaust gas flows through the mixer 17 and then into the DPF 13 with catalyst. PM in the exhaust gas is captured by the DPF 13 D of the DPF 13 with catalyst.
  • the DCU 20 performs either one of the following two operations described under (1) and (2) based on the temperature information sent by the exhaust gas temperature sensor 31 .
  • the temperature T of exhaust gas detected by the exhaust gas temperature sensor 31 may be regarded as the temperature of the second oxidation catalyst 15 of the DPF 13 with catalyst. Therefore, when the temperature T of exhaust gas detected by the exhaust gas temperature sensor 31 shows Tp ° C. or higher, it may be considered that the second oxidation catalyst 15 is under a temperature environment where the second oxidation catalyst 15 can oxidize and decompose ammonia.
  • the DCU 20 When the temperature of exhaust gas is below 250° C., the DCU 20 operates the electric pump in the urea water tank 19 and also opens the injection valve 18 . Then, urea water is injected from the injection valve 18 upstream of the first oxidation catalyst layer 12 in the casing 11 .
  • the injected urea water is carried by the exhaust gas and flows through the first oxidation catalyst layer 12 .
  • the first oxidation catalyst layer 12 has therein the heat due to the exhaust gas flowing therethrough and also the reaction heat due to the oxidation of NO and other substances in exhaust gas. Therefore, most of the urea water flowing through the first oxidation catalyst layer 12 is hydrolyzed into ammonia and carbon dioxide by the heat that the first oxidation catalyst layer 12 has and the heat of the exhaust gas flowing through the first oxidation catalyst layer 12 .
  • the exhaust gas containing urea water and ammonia flows through the space 16 and then to the mixer 17 .
  • Urea water and ammonia are flowed through the mixer 17 while being dispersed and then into the DPF 13 with catalyst.
  • urea water in the exhaust gas that is not hydrolyzed in the first oxidation catalyst layer 12 is hydrolyzed into ammonia due to the heat of the exhaust gas before reaching the DPF 13 with catalyst that is integrally formed with the SCR catalyst 14 .
  • the time during which the urea water stays in the first oxidation catalyst layer 12 , the space 16 and the mixer 17 while flowing therethrough before reaching the SCR catalyst 14 satisfies the reaction time required for the hydrolysis of urea water.
  • the hydrolysis of urea water is accomplished with a high efficiency.
  • urea water injected from the injection valve 18 is hydrolyzed not only in the first oxidation catalyst layer 12 but also in the space 16 through which urea water flows before reaching the DPF 13 with catalyst, urea water is hydrolyzed into ammonia with a high efficiency. Therefore, the distance between the first oxidation catalyst layer 12 and the DPF 13 with catalyst in the exhaust gas purification apparatus 101 , i.e., the distance of the space 16 can be shortened, thus making it possible to construct the exhaust gas purification apparatus 101 small.
  • Ammonia contained in exhaust gas flowing into the DPF 13 with catalyst performs either one of the following two operations (1A) and (1B) depending on the temperature condition of the SCR catalyst 14 of the DPF 13 with catalyst.
  • the temperature of the SCR catalyst 14 is equivalent to the temperature of the second oxidation catalyst 15 and, therefore, the temperature T of the exhaust gas detected by the exhaust gas temperature sensor 31 is regarded as the temperature of the SCR catalyst 14 .
  • the predetermined temperature Ts° C. is 150° C. at which catalyst is generally activated.
  • the SCR catalyst 14 is not activated and, therefore, ammonia contained in the exhaust gas flowing into the DPF 13 with catalyst does not reduce NOx (including NO and NO2) contained in the exhaust gas by the catalytic reaction of the SCR catalyst 14 but is adsorbed on the SCR catalyst 14 .
  • the exhaust gas from which harmful ammonia is removed is discharged from the exhaust gas purification apparatus 101 . Therefore, the use of an SCR catalyst with high ammonia adsorption property is preferable for preventing harmful ammonia from being discharged outside the vehicle (not shown).
  • Ammonia that is contained in exhaust gas flowing into the DPF 13 with catalyst reduces NOx in the exhaust gas into N2 by the catalytic reaction of the SCR catalyst 14 . Residual ammonia that is not used in the reduction of NOx is adsorbed on the SCR catalyst 14 . Thus, the exhaust gas having reduced its NOx content and removed harmful ammonia therefrom while flowing through the DPF 13 with catalyst is discharged from the exhaust gas purification apparatus 101 .
  • the lower the temperature Ts° C. at which the SCR catalyst 14 is activated the larger the temperature range in which the SCR catalyst 14 can reduce NOx in exhaust gas. Therefore, the temperature Ts° C. at which the SCR catalyst 14 is activated should preferably be low.
  • the catalytic temperature of the second oxidation catalyst 15 of the DPF 13 with catalyst is substantially equivalent to the temperature of the exhaust gas detected by the exhaust gas temperature sensor 31 , which is below 250° C. that does not cause catalyst to oxidize and decompose ammonia. Therefore, the second oxidation catalyst 15 neither oxidizes nor decomposes ammonia in exhaust gas flowing through the DPF 13 with catalyst.
  • ammonia generated on the hydrolysis of urea water injected by the injection valve 18 is neither oxidized nor decomposed by the second oxidation catalyst 15 , but used for reducing NOx in exhaust gas or adsorbed on the SCR catalyst 14 with a high efficiency.
  • the DCU 20 stops the operation of the electric pump in the urea water tank 19 and also closes the injection valve 18 thereby to stop the injection of urea water from the injection valve 18 . Therefore, exhaust gas introduced into the casing 11 containing neither urea water nor ammonia generated by the hydrolysis of urea water flows through the first oxidation catalyst layer 12 and the mixer 17 and then into the DPF 13 with catalyst.
  • the SCR catalyst 14 of the DPF 13 with catalyst has a lot of ammonia that is generated and adsorbed on the SCR catalyst 14 when the temperature T of the exhaust gas is below 250° C.
  • the SCR catalyst 14 is activated when the temperature T of the exhaust gas is 250° C. or higher. Therefore, NOx in exhaust gas flowing into the DPF 13 with catalyst is reduced by ammonia that is adsorbed on the SCR catalyst 14 under the catalytic reaction of the SCR catalyst 14 .
  • the exhaust gas having reduced its NOx content and removed harmful ammonia therefrom while flowing through the DPF 13 with catalyst is discharged from the exhaust gas purification apparatus 101 .
  • the temperature at which the second oxidation catalyst 15 of the DPF 13 with catalyst is activated is 250° C. at which the second oxidation catalyst 15 can oxidize and decompose ammonia, or higher.
  • exhaust gas flowing through the DPF 13 with catalyst contains no ammonia, but ammonia is only adsorbed on the SCR catalyst 14 . Since the ammonia that is adsorbed on the SCR catalyst 14 is used for reducing NOx as described before, the ammonia is neither oxidized nor decomposed by the second oxidation catalyst 15 .
  • the exhaust gas temperature is 250° C. or higher, ammonia generated by the hydrolysis of urea water is used for reducing NOx in the exhaust gas without being oxidized and decomposed by the second oxidation catalyst 15 .
  • the exhaust gas purification apparatus 101 is disposed adjacent to the engine 1 and, therefore, hot exhaust gas immediately after being emitted from the engine 1 flows into the exhaust gas purification apparatus 101 through the turbocharger 8 . Furthermore, the heat generated by the engine 1 is imparted to the exhaust gas purification apparatus 101 located adjacent to the engine 1 and transmitted inward through outer wall of the casing 11 .
  • the first oxidation catalyst layer 12 and the DPF 13 with catalyst both disposed inside the casing 11 are subject to the heat of the hot exhaust gas and the heat imparted from the engine 1 and, therefore, the temperature of the respective components tends to increase.
  • the temperature increasing rate of the respective components, i.e., the oxidation catalyst of the first oxidation catalyst layer 12 and the SCR catalyst 14 of the DPF 13 with catalyst, in the exhaust gas purification apparatus 101 during a cold start of the engine 1 is improved and the time required for activating each catalyst during such cold start of the engine 1 is shortened. Eventually, the performance of NOx reduction is improved.
  • the exhaust gas purification apparatus 101 includes the first oxidation catalyst layer 12 provided in exhaust gas passage, the DPF 13 D provided downstream of the first oxidation catalyst layer 12 , the SCR catalyst 14 that is integrally formed with the DPF 13 D and can adsorb ammonia, the second oxidation catalyst 15 that is integrally formed with the DPF 13 D and oxidizes ammonia at a predetermined temperature or higher and the injection valve 18 provided upstream of the SCR catalyst 14 for supplying urea water only when the temperature of the second oxidation catalyst 15 is below a predetermined temperature.
  • the exhaust gas purification apparatus 101 in which the SCR catalyst 14 and the second oxidation catalyst 15 are integrally formed with the DPF 13 D, can be made small. Ammonia is generated on the hydrolysis of urea water supplied by the injection valve 18 with the aid of the first oxidation catalyst layer 12 and the like. However, since urea water is supplied below a predetermined temperature at which the second oxidation catalyst 15 is not activated for the oxidation, no generated ammonia is oxidized and decomposed by the second oxidation catalyst 15 .
  • the exhaust gas temperature sensor 31 is provided in the exhaust gas purification apparatus 101 for detecting the temperature of exhaust gas flowing through the second oxidation catalyst 15 . Regarding the temperature detected by the exhaust gas temperature sensor 31 as the temperature of the second oxidation catalyst 15 , controlling of the urea water supply from the injection valve 18 can be made easily by using the temperature of the second oxidation catalyst 15 .
  • urea water flowing through the first oxidation catalyst layer 12 can make use of the heat that the first oxidation catalyst layer 12 has therein such as the reaction heat due to the oxidation of nitrogen monoxide in exhaust gas into nitrogen dioxide and the heat that the exhaust gas has therein. Therefore, urea water flowing through the first oxidation catalyst layer 12 can be hydrolyzed at a high efficiency. Furthermore, by supplying urea water upstream of the first oxidation catalyst layer 12 , the time during which the supplied urea water stays upstream of the SCR catalyst 14 before reaching the SCR catalyst 14 is lengthened and.
  • urea water can be hydrolyzed efficiently before reaching the SCR catalyst 14 , with the result that NOx reduction performance of the exhaust gas purification apparatus 101 is improved. Accordingly, the distance between the first oxidation catalyst layer 12 and the DPF 13 with catalyst including the SCR catalyst 14 can be shortened, thereby making the exhaust gas purification apparatus 101 small.
  • the second oxidation catalyst 15 reduces the combustion temperature of the DPF 13 with catalyst during burning of PM captured by the DPF 13 D, the influence of the heat caused by burning PM for regenerating the DPF 13 D on the SCR catalyst 14 can be reduced. Therefore, the catalytic function of the SCR catalyst 14 for reducing NOx in the exhaust gas purification apparatus 101 , i.e., the durability of the SCR catalyst 14 , can be improved.
  • the exhaust gas purification apparatus 101 can be made still smaller.
  • the exhaust gas purification apparatus 101 is mounted to the engine assembly 10 and the hot exhaust gas emitted from the engine assembly 10 is introduced into the exhaust gas purification apparatus 101 .
  • the heat generated by the engine assembly 10 in operation is transmitted inside the casing 11 of the exhaust gas purification apparatus 101 . Therefore, the time for the temperature of the exhaust gas purification apparatus 101 to be increased to the level required for the hydrolysis of urea water and also for the temperature of the SCR catalyst 14 to the level required for activating the SCR catalyst 14 during a cold start of the engine can be shortened, with the result that the NOx reduction performance can be improved.
  • the exhaust gas purification apparatus 101 in the embodiment is provided in the engine assembly 10 having the turbocharger 8 , but the present invention is not limited to this structure.
  • the exhaust gas purification apparatus 101 may be directly connected to the outlet 5 A of the exhaust manifold 5 .
  • the exhaust gas purification apparatus 101 may be provided spaced apart from the engine assembly 10 .
  • the injection valve 18 is provided upstream of the first oxidation catalyst layer 12 so as to supply urea water upstream of the first oxidation catalyst layer 12 in the exhaust gas purification apparatus 101 according to the embodiment, but the present invention is not limited to this structure.
  • the injection valve 18 may be so arranged that urea water is supplied toward the downstream side of the first oxidation catalyst layer 12 .
  • This structure prevents ammonia generated on the hydrolysis of urea water from being oxidized and decomposed by the first oxidation catalyst layer 12 .
  • the casing 11 of the exhaust gas purification apparatuses 101 is cylindrically-shaped, but the casing 11 is not limited to this shape.
  • the casing 11 may be formed with a cross-section including a prism such as quadratic prism, a sphere or an ellipsoid.
  • the exhaust gas purification apparatus 101 includes the exhaust gas temperature sensor 31 provided upstream of the end face 11 A of the casing 11 , but the structure is not limited to this structure.
  • the exhaust gas temperature sensor 31 may be provided at a position that is adjacent to and immediately upstream or downstream of the second oxidation catalyst 15 .
  • the mixer 17 of the exhaust gas purification apparatus 101 may be dispensed with in the embodiment.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Filtering Of Dispersed Particles In Gases (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
US12/871,064 2009-09-02 2010-08-30 Exhaust gas purification apparatus Abandoned US20110047991A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2009202823A JP2011052610A (ja) 2009-09-02 2009-09-02 排気ガス浄化装置
JPP2009-202823 2009-09-02

Publications (1)

Publication Number Publication Date
US20110047991A1 true US20110047991A1 (en) 2011-03-03

Family

ID=43067043

Family Applications (1)

Application Number Title Priority Date Filing Date
US12/871,064 Abandoned US20110047991A1 (en) 2009-09-02 2010-08-30 Exhaust gas purification apparatus

Country Status (5)

Country Link
US (1) US20110047991A1 (ja)
EP (1) EP2299080B1 (ja)
JP (1) JP2011052610A (ja)
KR (1) KR20110025133A (ja)
AT (1) ATE551510T1 (ja)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130283770A1 (en) * 2010-12-22 2013-10-31 Mahindra & Mahindra Limited Integrated Exhaust Gas After-Treatment System for Diesel Fuel Engines
US20140090374A1 (en) * 2012-10-03 2014-04-03 Caterpollar Inc. Exhaust aftertreatment system and method
US20140116034A1 (en) * 2011-07-01 2014-05-01 Toyota Jidosha Kabushiki Kaisha Exhaust purification system for internal combustion engine
US20140182269A1 (en) * 2012-12-31 2014-07-03 Kia Motors Corporation Method and apparatus for controlling urea injection amount of vehicle
US10279313B2 (en) 2015-05-19 2019-05-07 Umicore Ag & Co. Kg Method, multifunctional filter and system for the removal of particulate matter and noxious compounds from engine exhaust gas
CN113882933A (zh) * 2021-11-12 2022-01-04 昆明理工大学 一种用于发电机组的通用型箱式集成尾气净化系统

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5869464B2 (ja) * 2012-11-28 2016-02-24 本田技研工業株式会社 内燃機関の排気浄化システム
CN104295350B (zh) * 2014-09-29 2017-02-01 日立汽车系统(苏州）有限公司 发动机系统和发动机系统的控制方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003004438A2 (en) * 2001-07-06 2003-01-16 3M Innovative Properties Company Inorganic fiber substrates for exhaust systems and methods of making same
EP1617051A1 (fr) * 2004-07-15 2006-01-18 Peugeot Citroen Automobiles SA Ligne d'echappement d'un moteur a combustion interne, et systeme d'epuration des gaz d'echappement la comprenant
US20070051096A1 (en) * 2003-02-26 2007-03-08 Umicore Ag Co. Kg Method of removing nitrogen oxides from the exhaust gas of a lean-burn internal combustion engine and exhaust-gas purification system therefor
JP2009121413A (ja) * 2007-11-16 2009-06-04 Toyota Motor Corp 排気浄化システムの異常診断装置
US20100058746A1 (en) * 2007-02-23 2010-03-11 Marcus Pfeifer Catalytic activated diesel particle filter with ammonia trap effect

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4123161A1 (de) 1991-07-12 1993-01-14 Siemens Ag Statischer mischer
DE10308287B4 (de) * 2003-02-26 2006-11-30 Umicore Ag & Co. Kg Verfahren zur Abgasreinigung
JP4347120B2 (ja) * 2004-04-12 2009-10-21 トヨタ自動車株式会社 排ガス浄化装置
JP2006009608A (ja) 2004-06-23 2006-01-12 Hino Motors Ltd 排気浄化装置
JP2006274986A (ja) * 2005-03-30 2006-10-12 Mitsubishi Fuso Truck & Bus Corp 排気後処理装置
JP2007239752A (ja) * 2007-03-30 2007-09-20 Toyota Motor Corp 内燃機関の排気浄化装置

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003004438A2 (en) * 2001-07-06 2003-01-16 3M Innovative Properties Company Inorganic fiber substrates for exhaust systems and methods of making same
US20070051096A1 (en) * 2003-02-26 2007-03-08 Umicore Ag Co. Kg Method of removing nitrogen oxides from the exhaust gas of a lean-burn internal combustion engine and exhaust-gas purification system therefor
EP1617051A1 (fr) * 2004-07-15 2006-01-18 Peugeot Citroen Automobiles SA Ligne d'echappement d'un moteur a combustion interne, et systeme d'epuration des gaz d'echappement la comprenant
US20100058746A1 (en) * 2007-02-23 2010-03-11 Marcus Pfeifer Catalytic activated diesel particle filter with ammonia trap effect
JP2009121413A (ja) * 2007-11-16 2009-06-04 Toyota Motor Corp 排気浄化システムの異常診断装置
US20100115918A1 (en) * 2007-11-16 2010-05-13 Hiroshi Sawada Abnormality diagnosis apparatus for exhaust purification system

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8950173B2 (en) * 2010-12-22 2015-02-10 Mahindra & Mahindra Limited Integrated exhaust gas after-treatment system for diesel fuel engines
US20130283770A1 (en) * 2010-12-22 2013-10-31 Mahindra & Mahindra Limited Integrated Exhaust Gas After-Treatment System for Diesel Fuel Engines
US9057298B2 (en) 2011-07-01 2015-06-16 Toyota Jidosha Kabushiki Kaisha Exhaust purification system for internal combustion engine
US20140216016A1 (en) * 2011-07-01 2014-08-07 Toyota Jidosha Kabushiki Kaisha Exhaust purification system for internal combustion engine
US20140116034A1 (en) * 2011-07-01 2014-05-01 Toyota Jidosha Kabushiki Kaisha Exhaust purification system for internal combustion engine
US9011569B2 (en) 2011-07-01 2015-04-21 Toyota Jidosha Kabushiki Kaisha Particulate filter
US9057299B2 (en) * 2011-07-01 2015-06-16 Toyota Jidosha Kabushiki Kaisha Exhaust purification system for internal combustion engine
US9080480B2 (en) * 2011-07-01 2015-07-14 Toyota Jidosha Kabushiki Kaisha Exhaust purification system for internal combustion engine
US20140090374A1 (en) * 2012-10-03 2014-04-03 Caterpollar Inc. Exhaust aftertreatment system and method
US20140182269A1 (en) * 2012-12-31 2014-07-03 Kia Motors Corporation Method and apparatus for controlling urea injection amount of vehicle
US9010092B2 (en) * 2012-12-31 2015-04-21 Hyundai Motor Company Method and apparatus for controlling urea injection amount of vehicle
US10279313B2 (en) 2015-05-19 2019-05-07 Umicore Ag & Co. Kg Method, multifunctional filter and system for the removal of particulate matter and noxious compounds from engine exhaust gas
CN113882933A (zh) * 2021-11-12 2022-01-04 昆明理工大学 一种用于发电机组的通用型箱式集成尾气净化系统

Also Published As

Publication number Publication date
EP2299080A1 (en) 2011-03-23
KR20110025133A (ko) 2011-03-09
ATE551510T1 (de) 2012-04-15
JP2011052610A (ja) 2011-03-17
EP2299080B1 (en) 2012-03-28

Similar Documents

Publication Publication Date Title
US20110052454A1 (en) Exhaust gas purification apparatus
EP2295754B1 (en) Exhaust gas purifing apparatus
EP2299080B1 (en) Exhaust gas purification apparatus
US20110047994A1 (en) Exhaust gas purification apparatus
EP2284371B1 (en) Exhaust gas purification apparatus
US8555617B2 (en) Exhaust gas treatment system including a four-way catalyst and urea SCR catalyst and method of using the same
US20070214777A1 (en) Methods Of Controlling Reductant Addition
US20120060471A1 (en) Exhaust gas aftertreatement system and method of operation
EP2278132A1 (en) Exhaust gas purification system
US8128880B2 (en) NOx reduction catalyst and exhaust system using the same
JP4450257B2 (ja) 排気浄化装置
JP4784761B2 (ja) 排気浄化装置
US9945278B2 (en) Exhaust gas mixer
US9145818B2 (en) Exhaust gas sampling device
JP2008128046A (ja) 排気浄化装置
JP2011047395A (ja) 排気システム
CN108060961B (zh) 还原剂喷雾和废气流引导及导流器
US20110030358A1 (en) Exhaust gas purification apparatus
JP4844766B2 (ja) 排気浄化装置

Legal Events

Date Code Title Description
AS Assignment

Owner name: KABUSHIKI KAISHA TOYOTA JIDOSHOKKI, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KATO, YOSHIFUMI;REEL/FRAME:024905/0381

Effective date: 20100826

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION