WO2012008948A1 - PACKAGING OF DOC+DFP/NH3(g) MIXER/NOx SLIP CATALYST IN EXHAUST SYSTEM - Google Patents
PACKAGING OF DOC+DFP/NH3(g) MIXER/NOx SLIP CATALYST IN EXHAUST SYSTEM Download PDFInfo
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- WO2012008948A1 WO2012008948A1 PCT/US2010/041770 US2010041770W WO2012008948A1 WO 2012008948 A1 WO2012008948 A1 WO 2012008948A1 US 2010041770 W US2010041770 W US 2010041770W WO 2012008948 A1 WO2012008948 A1 WO 2012008948A1
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- mixing chamber
- exhaust gas
- diesel
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- exhaust
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Classifications
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- 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]
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- 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
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- 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
- F01N3/103—Oxidation catalysts for HC and CO only
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- 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
- F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
- F01N2240/20—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being a flow director or deflector
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- 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
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- 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 apparatus and method for treating and mixing diesel exhaust in a diesel exhaust system.
- the present invention provides methods for injecting reagent into a diesel exhaust stream to reduce nitrogen oxides (NO x ) while reducing packaging space, lowering the starting reaction temperature, facilitating certification and preventing clogging of the exhaust gas system.
- NO x nitrogen oxides
- Diesel engines are efficient, durable and economical. Diesel exhaust, however, can harm both the environment and people. To reduce this harm, governments, such as the United States and the European Union, have proposed stricter diesel exhaust emission regulations. These environmental regulations require diesel engines to meet the same pollution emission standards as gasoline engines.
- a lean burning engine provides improved fuel efficiency by operating with an amount of oxygen in excess of the amount necessary for complete combustion of the fuel. Such engines are said to run “lean” or on a “lean mixture.”
- the increase in fuel efficiency is offset by the creation of undesirable pollution emissions in the form of nitrogen oxides (NO x ).
- NO x nitrogen oxides
- Nitrogen oxide emissions are regulated through regular emission testing requirements.
- One method used to reduce NO x emissions from lean burn internal combustion engines is known as selective catalytic reduction. When used to reduce ⁇ emissions from a diesel engine, selective catalytic reduction involves injecting atomized urea into the exhaust stream of the engine in relation to one or more selected engine operational parameters and running the stream through a reactor containing a catalyst.
- urea must first be reacted to form ammonia (N3 ⁇ 4) before it can reduce the NO x emissions. Accordingly, packaging length and weight must be great enough to accommodate the intermediate reaction. Further, while 3 ⁇ 4 reacts at a temperature of about 150° C, urea needs to achieve about 180° C to begin reaction.
- the exhaust gas treatment system package is fluidly coupled to an exhaust pipe, for example, of a diesel-engine.
- a mixing chamber is sized to have a minimum volume necessary to allow injected gaseous ammonia to react with exhaust gas to reduce NO x level therein below a predetermined threshold and then the mixing chamber is positioned within the exhaust gas treatment system package.
- Providing a gaseous ammonia source coupled to the mixing chamber completes an embodiment of the system.
- the gaseous ammonia source comprises a tank of solid ammonium, preferably contained within a cartridge of, for example, strontium chloride.
- the mixing chamber volume is smaller than a volume required for reacting liquid urea with exhaust gas to reduce NO x and the predetermined threshold is a federal emission standard for acceptable emissions for a specific vehicle.
- the exhaust gas treatment system package of the method preferably comprises a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a NO x slip catalyst (NSC) canister, wherein the DOC, DPF and NSC are all fluidly coupled together and to the mixing chamber.
- DOC diesel oxidation catalyst
- DPF diesel particulate filter
- NSC NO x slip catalyst
- FIG. 1 is a schematic illustrating a typical aqueous urea mixer/injector device for a diesel exhaust system
- FIG. 2 is a schematic illustrating an embodiment of a mixer/NE injection device of the present invention for a diesel exhaust system
- FIG. 3 is a schematic illustrating another embodiment of a mixer/NE injection device of the present invention in a diesel exhaust system.
- FIG. 1 there is illustrated a typical exhaust gas treatment system package 110.
- Exhaust gas is discharged from the diesel engine 100, through conduit such as exhaust piping to the exhaust gas treatment system 1 10.
- the exhaust gas treatment system 1 10 typically consists of, in order of exhaust gas flow, a diesel oxidation catalyst (DOC) 112, a diesel particulate filter (DPF) 114, a mixing chamber 116, and a NO x slip catalyst (NSC) 118.
- DOC 112, DPF 1 14 and NSC 1 18 are additional exhaust gas treatment structures present in most diesel exhaust gas treatment systems and which form no part of the present system 10. Such structures will be generally referenced herein and identified in the drawing figures but, as each of these additional exhaust treatment structures is commonly understood by those skilled in the art, a detailed discussion of each is avoided for the purpose of focusing discussion on the system 10 as set forth in the appended claims.
- the mixing chamber 1 16 is shown to include a connection pipe 120 with an injector 122 at the upstream end where aqueous urea is injected into a laminar diesel exhaust flow as it is discharged from the DOC 1 12 and DPF 114.
- the urea/exhaust stream proceeds through the mixing chamber 116 where the urea is converted to a gaseous ammonia which is capable of reacting with the NO x of the exhaust gas.
- a substantial length of pipe 120 is needed to allow for adequate mixing of the two components before the flow enters the NSC 1 18.
- the mixing chamber 1 16 adds packaging length and weight to the diesel exhaust system 100 which might otherwise be used for other after-treatment substrates.
- FIGS. 2 - 3 there is illustrated a diesel engine exhaust gas treatment system, generally designated by the numeral 10.
- the system 10 is shown in two distinct exhaust gas treatment configurations.
- FIG. 2 illustrates an exhaust gas configuration similar to that of FIG. 1 where the downstream order of components is DOC 12, then DPF 14 and NSC 18 sandwiched about a mixing chamber 216.
- FIG. 3 illustrates a configuration where the NSC 18 is on the DPF 14— i.e., NO x slip catalyst on diesel particulate filter (NPF) 19— sandwiching the mixing chamber 216 with the DOC 12.
- NPF diesel particulate filter
- Other configurations may exist in which the mixing chamber 216 is moved up or downstream in the exhaust flow.
- the packaging space required for the mixing chamber 216 is substantially reduced from that required for a typical mixing chamber 116 illustrated in FIG. 1.
- the reduced packaging length is made possible by the injection of gaseous ammonia (NH 3 ) into the mixing chamber, as opposed to injecting aqueous urea which must then react for a length of the mixing chamber 216 to convert to NH 3 .
- the gaseous ammonia reacts with the exhaust gas to reduce NO x at a lower temperature than is required to convert the urea to gaseous ammonia. Accordingly, particularly after a cold start, the reduction of NO x in the exhaust stream begins much sooner with the present system.
- FTP Federal Test Procedure
- FTP certifications are typically cumulative and often have a "cold cycle" component as part of the test procedure.
- the "cold cycle” component accounts for one-seventh of the overall test while the "hot cycle” component results make up the remaining six-sevenths.
- the improved lower temperature reaction time in ⁇ emission control as a result of injecting gaseous ammonia into the exhaust stream, results in improved "cold cycle” test results over prior urea systems.
- the improvements in the "cold cycle” component provide greater flexibility in the more harsh "hot cycle” component of the test procedure.
- Successful certification of diesel engine vehicles using the present NO x emission control system 10 is increased as a result.
- the present mixing chamber 216 is comprised of a housing 20 defining a volume 25, an injection tube 22 fed by an exterior injector boss 30 coupled to a supply (not shown), and a mixer 24.
- FIGS. 2 and 3 illustrate the diameter of the housing 20 (approx. 12 inches (30.5 cm)) is substantially equal to that of the surrounding exhaust gas treatment structures— e.g., DPF 14 and NSC 18.
- the need for reducers 123 (FIG. 1) is eliminated, further reducing the packaging size of the entire diesel exhaust treatment system.
- Reagent e.g., gaseous NH 3
- injection points 23 immediately enters the turbulent diesel exhaust stream as it moves toward the chamber exit 35 (FIGS. 2 and 3).
- a relatively short distance is needed to provide the necessary mixing time to create a homogonous reagent/diesel exhaust.
- the homogenous mixture is then exited from the mixing chamber 25 into one of either the NSC 18 (FIG. 2) or the NPF 19 (FIG. 3) for further treatment.
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
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- Exhaust Gas After Treatment (AREA)
Abstract
An exhaust gas treatment system package fluidly coupled to an exhaust pipe of a diesel-engine is disclosed. A mixing chamber is sized to have a minimum volume necessary to allow injected gaseous ammonia to react with exhaust gas to reduce NOx level therein below a threshold and then the mixing chamber is positioned within the package. A gaseous ammonia source coupled to the mixing chamber is included. The gaseous ammonia source comprises a tank of solid ammonium, preferably contained within a cartridge of strontium chloride. The mixing chamber volume is smaller than a volume required for reacting liquid urea with exhaust gas to reduce NOx and the threshold is an emission standard for a vehicle. The package comprises a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a NOx slip catalyst (NSC) canister. The DOC, DPF and NSC are fluidly coupled together and to the mixing chamber.
Description
PACKAGING OF DOC+DFP/NH3(g)MIXER/NOx SLIP CATALYST IN EXHAUST
SYSTEM
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to an apparatus and method for treating and mixing diesel exhaust in a diesel exhaust system. Particularly, the present invention provides methods for injecting reagent into a diesel exhaust stream to reduce nitrogen oxides (NOx) while reducing packaging space, lowering the starting reaction temperature, facilitating certification and preventing clogging of the exhaust gas system.
BACKGROUND OF THE INVENTION
[0002] Diesel engines are efficient, durable and economical. Diesel exhaust, however, can harm both the environment and people. To reduce this harm, governments, such as the United States and the European Union, have proposed stricter diesel exhaust emission regulations. These environmental regulations require diesel engines to meet the same pollution emission standards as gasoline engines.
[0003] Typically, to meet such regulations and standards, diesel engine systems require equipment additions and modifications. Additional equipment can often lead to additional weight and/or additional packaging length.
[0004] For example, a lean burning engine provides improved fuel efficiency by operating with an amount of oxygen in excess of the amount necessary for complete combustion of the fuel. Such engines are said to run "lean" or on a "lean mixture." However, the increase in fuel efficiency is offset by the creation of undesirable pollution emissions in the form of nitrogen oxides (NOx). Nitrogen oxide emissions are regulated through regular emission testing requirements. One method used to reduce NOx emissions from lean burn internal combustion engines is known as selective catalytic reduction. When used to reduce Οχ emissions from a diesel engine, selective catalytic reduction involves injecting atomized urea into the exhaust stream of the engine in relation to one or more selected engine operational parameters and running the stream through a reactor containing a catalyst.
[0005] However, selective catalytic reduction and the use of aqueous urea involve many disadvantages. For example, the urea must first be reacted to form ammonia (N¾) before it can reduce the NOx emissions. Accordingly, packaging length and weight must be great enough to accommodate the intermediate reaction. Further, while ¾ reacts at a
temperature of about 150° C, urea needs to achieve about 180° C to begin reaction.
Accordingly, reduction of NOx is unnecessarily delayed by the intermediate reaction converting urea to ammonia. The higher required reaction temperature of a urea system may also lead to more difficult engine certification under any Federal Test Procedure (FTP) having a cold cycle component.
[0006] Still another disadvantage of aqueous urea exhaust treatment is the propensity for clogging of the exhaust stream, causing pressure drops which can foul system sensors. When combined with soot prevalent in an exhaust gas stream, the gas/liquid urea will form blockages and add excess weight in the treatment canisters. Finally, the highly corrosiveness and poor lubricity of aqueous urea make it an unsuitable exhaust gas treatment component.
[0007] It would be advantageous to provide methods and apparatus for addressing the regulations and standards without adding weight or length to an already complex diesel exhaust system. Accordingly, it would be advantageous to provide methods and apparatus for injecting a NOx reducing reagent into the diesel exhaust stream of a lean burn engine where little or no added weight or packaging length is required. Further, it would be advantageous to provide an exhaust gas treatment system which improves emission certification and facilitates the reduction of clogging.
[0008] The methods and apparatus of the present invention provide the foregoing and other advantages.
SUMMARY OF THE INVENTION
[0009] There is disclosed herein an improved method for reducing space requirements for an exhaust gas treatment system package on a diesel-engine vehicle which avoids the disadvantages of prior devices while affording additional structural and operating advantages.
[0010] Generally speaking, the exhaust gas treatment system package is fluidly coupled to an exhaust pipe, for example, of a diesel-engine. A mixing chamber is sized to have a minimum volume necessary to allow injected gaseous ammonia to react with exhaust gas to reduce NOx level therein below a predetermined threshold and then the mixing chamber is positioned within the exhaust gas treatment system package. Providing a gaseous ammonia source coupled to the mixing chamber completes an embodiment of the system.
[0011] In an embodiment of the invention, the gaseous ammonia source comprises a tank of solid ammonium, preferably contained within a cartridge of, for example, strontium chloride.
[0012] Preferably, the mixing chamber volume is smaller than a volume required for reacting liquid urea with exhaust gas to reduce NOx and the predetermined threshold is a federal emission standard for acceptable emissions for a specific vehicle. The exhaust gas treatment system package of the method preferably comprises a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a NOx slip catalyst (NSC) canister, wherein the DOC, DPF and NSC are all fluidly coupled together and to the mixing chamber.
[0013] These and other aspects of the invention may be understood more readily from the following description and the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated.
[0015] FIG. 1 is a schematic illustrating a typical aqueous urea mixer/injector device for a diesel exhaust system;
[0016] FIG. 2 is a schematic illustrating an embodiment of a mixer/NE injection device of the present invention for a diesel exhaust system; and
[0017] FIG. 3 is a schematic illustrating another embodiment of a mixer/NE injection device of the present invention in a diesel exhaust system.
DETAILED DESCRIPTION OF THE INVENTION
[0018] While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to embodiments illustrated.
[0019] Referring to FIG. 1, there is illustrated a typical exhaust gas treatment system package 110. Exhaust gas is discharged from the diesel engine 100, through conduit such as exhaust piping to the exhaust gas treatment system 1 10. The exhaust gas treatment system 1 10 typically consists of, in order of exhaust gas flow, a diesel oxidation catalyst (DOC) 112, a diesel particulate filter (DPF) 114, a mixing chamber 116, and a NOx slip catalyst (NSC)
118. The DOC 112, DPF 1 14 and NSC 1 18 are additional exhaust gas treatment structures present in most diesel exhaust gas treatment systems and which form no part of the present system 10. Such structures will be generally referenced herein and identified in the drawing figures but, as each of these additional exhaust treatment structures is commonly understood by those skilled in the art, a detailed discussion of each is avoided for the purpose of focusing discussion on the system 10 as set forth in the appended claims.
[0020] The mixing chamber 1 16 is shown to include a connection pipe 120 with an injector 122 at the upstream end where aqueous urea is injected into a laminar diesel exhaust flow as it is discharged from the DOC 1 12 and DPF 114. The urea/exhaust stream proceeds through the mixing chamber 116 where the urea is converted to a gaseous ammonia which is capable of reacting with the NOx of the exhaust gas. A substantial length of pipe 120 is needed to allow for adequate mixing of the two components before the flow enters the NSC 1 18. As such, the mixing chamber 1 16 adds packaging length and weight to the diesel exhaust system 100 which might otherwise be used for other after-treatment substrates.
[0021] Referring to FIGS. 2 - 3, there is illustrated a diesel engine exhaust gas treatment system, generally designated by the numeral 10. The system 10 is shown in two distinct exhaust gas treatment configurations. FIG. 2 illustrates an exhaust gas configuration similar to that of FIG. 1 where the downstream order of components is DOC 12, then DPF 14 and NSC 18 sandwiched about a mixing chamber 216. Alternatively, FIG. 3 illustrates a configuration where the NSC 18 is on the DPF 14— i.e., NOx slip catalyst on diesel particulate filter (NPF) 19— sandwiching the mixing chamber 216 with the DOC 12. Other configurations may exist in which the mixing chamber 216 is moved up or downstream in the exhaust flow.
[0022] Regardless of the specific configuration, it is clear from examination of FIGS. 2 and 3 that the packaging space required for the mixing chamber 216 is substantially reduced from that required for a typical mixing chamber 116 illustrated in FIG. 1. The reduced packaging length is made possible by the injection of gaseous ammonia (NH3) into the mixing chamber, as opposed to injecting aqueous urea which must then react for a length of the mixing chamber 216 to convert to NH3. Further, the gaseous ammonia reacts with the exhaust gas to reduce NOx at a lower temperature than is required to convert the urea to gaseous ammonia. Accordingly, particularly after a cold start, the reduction of NOx in the exhaust stream begins much sooner with the present system.
[0023] Another benefit of the lower temperature NOx reduction relates to Federal Test Procedure (FTP) for emissions on diesel-engine vehicles. FTP certifications are typically
cumulative and often have a "cold cycle" component as part of the test procedure. For example, in one such FTP engine emission certification process, the "cold cycle" component accounts for one-seventh of the overall test while the "hot cycle" component results make up the remaining six-sevenths. As noted above, the improved lower temperature reaction time in Οχ emission control as a result of injecting gaseous ammonia into the exhaust stream, results in improved "cold cycle" test results over prior urea systems. As the test results are cumulative, the improvements in the "cold cycle" component provide greater flexibility in the more harsh "hot cycle" component of the test procedure. Successful certification of diesel engine vehicles using the present NOx emission control system 10 is increased as a result.
[0024] In fact, improved "cold cycle" testing results provide the ability to use less NOx washcoat in exhaust after-treatment canisters. The use of less washcoat is a cost savings over prior art systems.
[0025] Clogging/blockage and pressure drops in urea systems are also a problem overcome by the present exhaust treatment system 10. The very nature of an exhaust system results in a considerable amount of soot being deposited in various nooks, recesses, corners and other such areas of the system. The injection of liquid urea can mix with the
accumulated soot and cake in passages to cause clogging/blockage and critical pressure drops which may result in backflow of exhaust. If not cleaned from the exhaust system, such accumulated caking can increase weight within the exhaust system.
[0026] However, with the injection of gaseous ammonia there is no increased risk of caking with the accumulated soot. Instead it is just the contrary, as the ammonia gas entrains the soot and carries it from the present exhaust system 10. Decreased pressure drops, decreased clogging, and decreased weight are the positive result of the ammonia gas injection.
[0027] Structurally speaking, the present mixing chamber 216 is comprised of a housing 20 defining a volume 25, an injection tube 22 fed by an exterior injector boss 30 coupled to a supply (not shown), and a mixer 24. FIGS. 2 and 3 illustrate the diameter of the housing 20 (approx. 12 inches (30.5 cm)) is substantially equal to that of the surrounding exhaust gas treatment structures— e.g., DPF 14 and NSC 18. By providing the larger diameter system housing 20 (vs. narrow connecting pipe 120), the need for reducers 123 (FIG. 1) is eliminated, further reducing the packaging size of the entire diesel exhaust treatment system.
[0028] Reagent (e.g., gaseous NH3) discharged from injection points 23 immediately enters the turbulent diesel exhaust stream as it moves toward the chamber exit 35 (FIGS. 2
and 3). As stated above, a relatively short distance is needed to provide the necessary mixing time to create a homogonous reagent/diesel exhaust.
[0029] The homogenous mixture is then exited from the mixing chamber 25 into one of either the NSC 18 (FIG. 2) or the NPF 19 (FIG. 3) for further treatment.
[0030] The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants' contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.
Claims
1. A method for reducing space requirement for an exhaust gas treatment system package on a diesel-engine vehicle, the method comprising the steps of:
fluidly coupling components of an exhaust gas treatment system package to an engine exhaust system of the diesel-engine vehicle;
sizing a mixing chamber to have a minimum volume necessary to allow injected gaseous ammonia to react with exhaust gas to reduce NOx level therein below a
predetermined threshold;
positioning the mixing chamber within the exhaust gas treatment system package; and providing a gaseous ammonia source coupled to the mixing chamber.
2. The method of Claim 1, wherein the gaseous ammonia source comprises a tank of solid ammonium.
3. The method of Claim 1, wherein the mixing chamber volume is smaller than a volume required for reacting liquid urea with exhaust gas to reduce NOx.
4. The method of Claim 1, wherein the predetermined threshold is a federal emission standard.
5. The method of Claim 1, wherein the exhaust gas treatment system package comprises: a diesel oxidation catalyst (DOC);
a diesel particulate filter (DPF); and
a NOx slip catalyst (NSC) canister, wherein the DOC, DPF and NSC are all fluidly coupled together and to the mixing chamber.
6. The method of Claim 5, wherein the mixing chamber is positioned between the diesel particulate filter (DPF) and the NOx slip catalyst canister.
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PCT/US2010/041770 WO2012008948A1 (en) | 2010-07-13 | 2010-07-13 | PACKAGING OF DOC+DFP/NH3(g) MIXER/NOx SLIP CATALYST IN EXHAUST SYSTEM |
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PCT/US2010/041770 WO2012008948A1 (en) | 2010-07-13 | 2010-07-13 | PACKAGING OF DOC+DFP/NH3(g) MIXER/NOx SLIP CATALYST IN EXHAUST SYSTEM |
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CN113294224A (en) * | 2021-04-22 | 2021-08-24 | 南京朗森自动化设备有限公司 | Tail gas double-reduction treatment method for on-vehicle |
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CN106030063A (en) * | 2013-11-15 | 2016-10-12 | 罗伯特·博世有限公司 | Exhaust gas post treatment system |
CN113250788A (en) * | 2021-04-22 | 2021-08-13 | 南京朗森自动化设备有限公司 | Tail gas dual-drop treatment system for in-use vehicle |
CN113294224A (en) * | 2021-04-22 | 2021-08-24 | 南京朗森自动化设备有限公司 | Tail gas double-reduction treatment method for on-vehicle |
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