WO1998028070A1 - Procede et dispositif pour reduire les emissions toxiques d'un moteur a gaz pauvre par reduction catalytique selective a injection d'uree - Google Patents

Procede et dispositif pour reduire les emissions toxiques d'un moteur a gaz pauvre par reduction catalytique selective a injection d'uree Download PDF

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Publication number
WO1998028070A1
WO1998028070A1 PCT/US1997/023796 US9723796W WO9828070A1 WO 1998028070 A1 WO1998028070 A1 WO 1998028070A1 US 9723796 W US9723796 W US 9723796W WO 9828070 A1 WO9828070 A1 WO 9828070A1
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WIPO (PCT)
Prior art keywords
urea
exhaust
reagent
catalyst
nitrogenous
Prior art date
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PCT/US1997/023796
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English (en)
Inventor
Jeremy D. Peter-Hoblyn
Eric Balles
John E. Hofmann
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Clean Diesel Technologies, Inc.
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Publication date
Application filed by Clean Diesel Technologies, Inc. filed Critical Clean Diesel Technologies, Inc.
Priority to AU56185/98A priority Critical patent/AU5618598A/en
Publication of WO1998028070A1 publication Critical patent/WO1998028070A1/fr

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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]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9431—Processes characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9495—Controlling the catalytic process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/20—Mixing gases with liquids
    • B01F23/21—Mixing gases with liquids by introducing liquids into gaseous media
    • B01F23/213—Mixing gases with liquids by introducing liquids into gaseous media by spraying or atomising of the liquids
    • B01F23/2132—Mixing gases with liquids by introducing liquids into gaseous media by spraying or atomising of the liquids using nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/10—Mixing by creating a vortex flow, e.g. by tangential introduction of flow components
    • B01F25/103—Mixing by creating a vortex flow, e.g. by tangential introduction of flow components with additional mixing means other than vortex mixers, e.g. the vortex chamber being positioned in another mixing chamber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/40—Static mixers
    • B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
    • B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
    • B01F25/431—Straight mixing tubes with baffles or obstructions that do not cause substantial pressure drop; Baffles therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2067—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
    • 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
    • F01N2240/40—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 hydrolysis catalyst
    • 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/10—Adding substances to exhaust gases the substance being heated, e.g. by heating tank or supply line of the added substance
    • 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
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1453—Sprayers or atomisers; Arrangement thereof in the exhaust 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
    • 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 invention relates to means and methods which enable the safe and reliabie reduction of nitrogen oxiaes (NO x ) emissions while permitting a diesei or other lean-bum engine to operate efficiently with low particulate emissions.
  • NO x nitrogen oxiaes
  • the need for fuel efficiency is a long-term environmental (carbon dioxide) as well as economic issue.
  • NO x has short term environmental consequences. While there is known to be ⁇ tradeoff between NO x and complete combustion, diesei and other lean-bum engines produce both NO x and particulates during normal operation. However, when primary measures (actions which affect the combustion process itself, e.g., exhaust gas recirculation and engine timing adjustments) are taken to reduce one, the other is usually increased. Thus, combustion conditions selected to reduce pollution from particulates and obtain good fuel economy tend to increase NO x .
  • Current and proposed regulations challenge manufacturers to achieve good fuel economy and reduce particulates and NO x .
  • Lean-bu engines will be necessary to achieve The fuel economy objective
  • catalyst systems typically used for treating exhaust from spark ignition engines (which run with close to stoichiomet ⁇ c balance of air and fuel) are not effective in reducing NO x generated by diesei and other lean-burn engines.
  • Selective catalytic reduction utilizing ammonia has haa some degree of success as a secondary measure for stationary sources of NO x , but would be too aangerous for mooile use.
  • Urea hydrolysates nave been identified as alternatives to urea in several contexts. See for example, U.S Patent No. 4,997,631 to Hofmann, et al., PCT application WO 92/02291 to von Harpe, et al , and U. S Patent No 5,139 754, Hofmann, Sun and Heilglass Also see U S Patent No 5,281 ,403 to Jones and JP HEI 2-191 ,528 to Ebma Each of these requires the use or added hydrolysis equipment and ends up producing ammonia to some extent The disclosures of these documents are incorporated by reference. On-board storage of hydrolysates would also be undesirable.
  • the process in one of its aspecTs, comprises: heating and pressurizing an aqueous solution of nitrogenous NO x -reduc ⁇ ng reagent, and injecting heated and pressurized NO x -reduc ⁇ ng reagent into exhaust gas at an exhaust gas temperature of from 200 to 650°C, upstream of an SCR reactor.
  • Injectors of the pintle type are preferred.
  • a plurality of injectors are operated to inject the solution and are positioned in radial, skewed and/or longitudinally-spaced orientation on the exhaust pipe.
  • a catalyst can be provided in the conduit for the heated reagent to facilitate hydrolysis.
  • the heat can be supplied by heat exchange with the exhausT and/or by an auxiliary means.
  • a mixing device is provided to assure mixing and/or prevent contact of any ungasified reagent with the SCR reactor.
  • an oxidation catalyst can be provided downstream of the SCR reactor for the purpose of el ⁇ m ⁇ n ⁇ ng ammonia or other gaseous byproducTs which might otherwise pass through the system.
  • Figure 1 is a schematic representation of one emboaiment of the invention
  • Figure 2 is a representation of one arrangement of injectors on an exhaust conduit in close-coupled relation to an SCR catalyst, partially cut away to show a the spray pattern of the injectors;
  • Figure 3 is a schematic representation, similar to that of Figure 1 , but with the provision of a control system and an oxidation catalyst in the exhaust system to prevent inaavertent release of large amounts of ammonia or other by-product gases, and
  • Figure 4 is a cross-section taken along line 4-4 in Figure 2 showing a spray pattern achieved by a sKewed injector arrangement.
  • the term “lean-bum engine” is meant to include engines that can be operated with at least a 1% excess of,
  • engine is meant in the broad sense to include all combustors which combust fuel to provide heat, e.g., for direct or indirect conversion TO mechanical or electrical energy.
  • Internal combustion engines of the Otto, Diesel and turbine types, as well as burners and furnaces, are included and can benefit from the invention.
  • the diesei engine is used throughout this description for purposes of example. Stationary and mobile engines are contemplated
  • 'Diesel engine' is meant to include all compression-ignition engines, for both mobile (including marine) and stationary power plants and of the two-stroke per cycle, four-s + roke per cycle and rotary types
  • hydrocarbon fuel is meant to include all of those fuels which form emulsions with aqueous NO x -reduc ⁇ ng reagents such as urea, either with or without an added emulsifier.
  • aqueous NO x -reduc ⁇ ng reagents such as urea
  • Gasoline, jet fuel, diesei fuel, and various other distillate fuels are included.
  • distillate fuel means all of those products prepared by the distillation of petroleum or petroleum fractions and residues.
  • petroleum in its usual sense to include all of those materials regardless o ⁇ source normally included within the meaning of the term, including hydrocarbon ma ⁇ e ⁇ als, regardless of viscosity, that are recovered from fossil fuels.
  • diesei fuel means distillate fuels" including diesei fuels meeting the ASTM definition for aiesel fuels or others even though they are not wholly comprised of distillates and can comprise alcohols, ethers, organo-nitro compounds and the like (e.g., methanol, ethanol, diethyl ether methyl ethyl ether, nitromethane)
  • emulsions and liquid fuels derived from vegetable or mineral sources such as com ⁇ lf ⁇ lf ⁇ , shale, and coal
  • These fuels may also contain other additives known to those skilled in the art, including dyes, cetane improvers, anti-oxidants such as 2,6-d ⁇ -tert ⁇ ary-butyl-4-methylphenol, corrosion inhibitors, rust inhibitors such as alkylated succinic acids and anhydrides bacte ⁇ ostatic agents, gum inhibitors, metal deactivators, upper cylinder lubricants, antncing agents and the like
  • nitrogenous NO x -reduc ⁇ ng reagent is broad enough to include all of those nitrogenous materials known to reduce NO x in the presence or a NO y reducing catalyst
  • suitable NO - reducing reagents are those that are normally liquid or solid at temperatures up to 50°C and do not readily hydrolyze to ammonia or other gaseous species under the conditions of storage, but can be broken down (with a catalyst if necessary) into the effective gaseous species (e.g , NH, and HCNO radicals) at temperatures practical for diesei engines, e g , from about 200 to about 650°C, including the following urea, ammonium carbamate and the alkali metal and alkaline earth carbamaTe salts, urea hydrolysis products, including ammonium carbonate and ammonium b ⁇ caroona ⁇ e urea dimers and polymers, sucn as biuret, urea adducts and urea condensation products, amine
  • nitrogenous NO x -reduc ⁇ ng reagent applies to not only a reagent to which heat and pressure are applied according to the invention, but to the breakdown products of that reagent It is desired that the NO x - reducing reagent not readily hydrolyze to ammonia or other gases under the conditions of storage, e g , temperatures of -30 to 50°C, because the presence of gaseous species requires pressure storage, and it is not desirable to store fuel under pressure See U. S Patents No.
  • aqueous solutions of these reagents can be employed up to the solubility limits of the particular reagent.
  • the aqueous soluTion of nitrogenous NO x -reduc ⁇ ng reagent will contain rrom about 5 to about 65% reagent based on the weight of the solution
  • a narrower range is from about 25 to about 40%, e.g. about 35%. It is an advantage of the invention that hydrolysis of the reagent can begin under pressure, but the pressure can maintain the reagent in aqueous solution (liquid form) for errective metering by the iniectors
  • FIG. 1 which ⁇ llustra ⁇ es in schematic form, one embodiment of the invention wherein the exhaust from a diesei engine 10 is treated to reduce NO x
  • the engine is equipped with an exhaust system having an exhaust passage, such as 20, leading to a catalytic reactor, such as SCR unit 30, effective for selective catalytic NO x reauction
  • the invention enables utilization of aqueous solutions of urea and like nitrogenous NO x - reducing reagents in place of ammonia for SCR NO x reduction in a manner which avoids wetting or forming solid deposits on the catalyst
  • These advantages are achieved by pressurizing and heating the reagent such that the aqueous solution is flashed off substantially immediately upon injection and the urea in the reagent has been at least partially hydrolyzed prior to injecting the solution, which will then comprise the products of the at least partial hydrolysis, into the exhaust system.
  • the invention enables the gasification of the reagent with no significant residence time in the exhaust gases and permits close-coupling of a reagent injector and an SCR catalyst (e.g., less than 1 meter, and pre ⁇ erably from about 0.05 to about 0.5 meters).
  • the invention also provides the ability to inject the reagent in a ⁇ scre ⁇ e charges to ⁇ ac ⁇ l ⁇ tate high energy mixing and accurate dosage. Because the inje ⁇ on is done in a manner effective for causing immediate gasification of the fluid fed to the injector, and mixing of it with the exhaust gases.
  • Figure 1 shows a diesei engine 10 having an exhaust manifold/passage 12 directing the exhaust from the engine to an exhaust system 20 including a NO x -reduc ⁇ ng SCR catalyst 30 before discharge of the combustion gases to the atmosphere.
  • the diesei engine is supplied with fuel from tank 40 via line 42 and fuel injectors 44, 44', 44", and 44"
  • the fuel tank includes diesei fuel and can be emulsified with water and/or an oxygena ⁇ ed hydrocarbon and/or contain a platinum group metal catalyst composition and/or an auxiliary catalyst composition as will be explained later.
  • Combustion air from line 14 enters turbine 16, and is introduced into the cylinders of the diesei engine and compressed in normal fashion for a diesei engine within each cylinder.
  • Turbine 16 is driven by turbine 17 positioned in exhaust line 12.
  • the diesel fuel is injected into the cylinders where it ignites in the presence of the air which nas been heated due to compression within the cylinders.
  • Figure 1 enables reducing the emissions of NO x from a diesei engine by causing essentially immediate gasification of the reagent upon injection. This facilitates a rapid response time necessary for good control and permits feeding reagent on an as-needed basis.
  • An aqueous urea solution is introduced from tank 50, through line 52 into exhaust passage 12 by pump 54.
  • Line 52 is shown to include a heater 56. Heating can also oe achieved by providing good neat exchange contact (either direct or indirect) with the exhaust system or the engine.
  • the line 52 can be wrapped around the exhaust conduit 30.
  • the heating means 54 can be used as the sole or a supplementary heater, It is desired to heat the solution to at least 100°C, and preferably to within the range of from about 200 to about 500°C, Diesel exhaust can be employed as the source of heat where the exhaust gas temperatures are more than 300°C,
  • the pressure required for the aqueous solution of reagent in line 52 can be proviaed by a separate pump.
  • the pressure will be sufficient, at least, to maintain the reagent solution in the liquid phase for accurate metering.
  • pressures of 200 to 2000 psi can be utilized and are well within the capabilities of the type of lines, pumps and injectors utilized for fuel injection.
  • the use of pressure along with the heat has the added advantage of facilitating the hydrolysis of the urea or other reagent in a single phase system without requiring storage means because it can be done on an as needed basis.
  • a catalyst can be employed in line 52 for aiding the hydrolysis of the urea.
  • Injection of discrete charges of reagent facilitates accurate dosing and the use of injectors that resist fouling. It is preferred, but not absolutely essential that the aqueous solution be maintained as a single phase and that bubbles be prevented from forming in the line 52. Exceptions can be made depending on the type of pump and injectors employed Constant-pressure, solenoid-operated injectors can be operated at rates as high as 50 and even 100 cycles per second and the frequency or the mark space ratio (on-off pulse width ratio) can be varied to control the injection rate, Injectors that lift to begin injection at a particular threshold pressure can be fed by a positive displacement pump or via solenoid actuated valves
  • a static mixer 32 (or an uncatalyzed support or a diesei particulate trap) can be positionea between the gasification chamber and the NO x -reduct ⁇ on catalyst. It is, however, an advantage of the invention that the immediate gasification of the reagent solution and the high energy of introduction, permit close coupling of the injectors and the catalyst. It is also an advantage of the invention that engine designers can focus on fuel economy and low particulate emissions while relying on the SCR of the invention to control NO x
  • FIG. 1 shows injector 60 to be located just upstream of the outlet vanes 17 of a turbocharger. This is one of the preferred orientations, another being centrally wrthin exhaust passage 12 (not shown).
  • Figure 3 shows injection following the turbocharger,
  • the injector means or the line 52 may contain one or more catalysts capable of aiding hydrolysis of the urea,
  • Figure 2 shows, partially cut away, one arrangement of a plurality of injectors, Injectors of the pintle type are preferred. These are well known for use in diesei engines to supply, A pintle-type injector has a plunger with a projection at the terminal end which extends into a single injecTor opening in the closed position. This has advantages for control and to help maintain the injector hole free and open.
  • Figure 2 shows a plurality of injectors 60 being fed aqueous reagent solution from a ring-shaped manifold 62, which in turn is fed from line 52 and heater 56. The individual injectors are shown threaded into mounting ring 64 and can be operated to simultaneously or sequentially inject the solution.
  • Figure 4 is a cross-secTion Taken along line 4-4 in Figure 2 showing a spray pattern achieved by a skewed injecTor arrangement.
  • the skewed orientation can enhance mixing which, due to the high energy introduction offered by the invention without the use of air or other propellant, is already very good, They can also be in longitudinally-spacea orientation on the exhaust pipe.
  • Figure 3 illustrates a control system of a type useful to maintain the proper level of reagent ⁇ n ⁇ roduction (i.e., dosage).
  • the controller can also time the injections to occur at staggered times in a predetermined sequence designed to smooth out the rate of introduction despite the use of pulsed injectors.
  • the introduction of the reagent in discrete charges by injection facilitates control of dosage in response to feed-forward control, with trim as to feedback parameters if desired.
  • the ability to closely control reagent dosing facilitates the use of controllers with adaptive learning capabilities.
  • the usually-occurring spikes or discontinuities in NO x levels can be better tracked with injection of reagent in the proper concentrations.
  • the aqueous reagent solution can be fed into the exhaust in response to a feed-forward controller in response to a number of measured parameters, including fuel flow, throttle setting, engine speed, rack setting, intake air temperature, barometric pressure, intake air humidity, exhaust gas temperature and/or other parameters effective for particular engines.
  • trim or feed back control can be provided based on residual gas species following the catalyst, e.g., the level of NO x , HC or CO.
  • reference to Figure 3 shows a control system including flow meter 72 which can sense the fuel flow and generaTe an operation signal representative of fuel flow. Sensors are also shown to determine gas species in the exhaust (76) and the temperature of the exhaust (78) prior to the catalyst 30.
  • the operation signal representative of fuel flow, exhaust gas temperature and residual gas species are received by a controller 74 and compared to stored values.
  • the controller can then generate one or more control signals based on the comparisons.
  • the control s ⁇ gnal(s) is then sent to metering pump 54 or other suitable device for metering the correct amount of urea to line 52 or alternatively to injector nozzle controllers. If desired, feedback control can be employed to trim the system in response to residual levels of ammonia, other gas species, or any other measurable engine or exhaust gas property.
  • Figure 3 also shows a catalyst 34 downstream of the SCR catalyst 30 for the purpose of eliminating ammonia which might otherwise pass through the system and provide an objectionable odor.
  • the catalysts suitable for this purpose are oxidation catalysts, which can have the added advantage of reducing hydrocarbons or particulate species which might remain in the exhaust.
  • the SCR catalyst can be preceded by an in-line mixing device 32, or an uncatalyzed support material or other trap to pick up any ungasified water or reagent or particulate materials.
  • the uncatalyzed support material if employed, can have a volume of from about 5 to about 50% of that of the SCR catalyst.
  • the system of the invention is fully compatible with other emission control and fuel economy technologies such as particulate traps, pass-through exhaust catalysts for reducing hydrocarbons, particulates and carbon monoxide, fuel catalysts for improving the operation of these devices and/or improving fuel economy, fuel emulsions, exhaust gas recirculation, engine timing modifications, and the like.
  • the active species formed by the hydrolysis and gasification of the urea or other reagent are introduced into the exhaust gases in an amount sufficient to provide the degree of NO x reduction desired.
  • the desired amount can be dictated by regulation, engine design requirements or other criteria.
  • a molar ratio of the active species to the baseline nitrogen oxides level (by which is meant the pre-treatment level of NO x in the effluent) of at least about 0.3: 1 will be employed, More narrowly, the reagent is supplied to provide a molar ratio of active species to baseline nitrogen oxides of about 0.5: 1 to about 1 : 1.
  • the reagent levels or target NO x concentrations in the exhaust can be preprogrammed into the controller 74 based on tested values for given fuel flows and related parameters, or sensors and related controls can be provided to provide real-time readouts.
  • a sensor means might be provided to correct preprogrammed values by feedback control.
  • the fuel and the aqueous reagent are supplied to the fuel storage tank associated with the engine as an emulsion.
  • the fuel and aqueous solution Prior to introduction into the engine, the fuel and aqueous solution can be separated into their component parts by fuel water separators of the type known in the art for separating small amounts of water from diesei fuel. It will simply be necessary to use a suitable device, e.g., a filter or centrifuge, sized for the volumes of water employed. See copending, co monly assigned U S Patent Appl ⁇ ca ⁇ on No. (attorney s docket number 2937-P1020A) filed November 19, 1996 by J D Peter-Hoblyn, J. M. Valentine and Theodore Tarabulski, the disclosure of which is incorporated by reference.
  • the hydrolysis catalysts are ones which comprise a material selected from the group consisting of phosphoric acid and acid phosphates, alkali metal hydroxides and carbonates, such as sodium hydroxide, potassium hydroxide, sodium carbona ⁇ e, po ⁇ ass ⁇ um caroona ⁇ e, alkali metal silicates, alkaline earth metal hydroxides and oxides, aluminum hydroxide and oxides, and mixtures of two or more of these. See also U. S. Patent No. 4,997,631 to Hofmann, et al., PCT application WO 92/02291 to von Harpe, et al., U. S. Patent No.
  • Catalysts which comprise water-soluble materials can be added to or blended with the urea in tank 50 or otherwise o ⁇ or to being introduced into the line 52 or other suitable conduit
  • An imporrant effect of injecting heated aqueous reagent solutions under high pressure gasification is an essentially immediate gasification and breakdown of any remaining urea hydrolysis products and remaining urea as active species such that there is a greatly-reduced risk of catalyst wetting, fouling or inactivation
  • the evaporation of the water and the gasification of the reagent solution upon introduction into the gasification chamber have the advantage that no atomizing air is required and no droplets of water will contact the catalyst - thereby greatly diminishing the threat of reagent deposition and/or catalyst deactivation,
  • ⁇ device 32 can be provided to catch and, if desired, break down the residues with a pyrolysis catalyst, such as in the form of a coating in the device 32, so that they do not enter the SCR catalyst.
  • the urea is typically supplied as an aqueous solution containing from 25 to 50% urea by weight It can be stored in tank 50 in this form or the urea can be stored dry in a canister, with water passed through as needed to prepare a solution which is near saturation (to minimize water storage and use) or to any concentration suitable for the vehicle It will be desired in many circumstances to provide heaters tor the water and/or urea solution storage to prevent freezing or to reduce reaction time in the gasification chamber. Likewise, it may be useful to employ antifreeze materials,
  • the SCR catalyst used is one capable of reducing the effluent nitrogen oxides concentration in the presence of ammonia
  • These include, for instance, activated carbon, charcoal or coke, zeolites, vanadium oxide, tungsten oxide, titanium oxide, iron oxide, copper oxide, manganese oxide, chromium oxide, noble metals such as platinum grouo metals like platinum, palladium, rhodium, and indium, or mixtures of these
  • Other SCR catalyst materials conventional in the art and familiar to the skilled artisan can also be utilized.
  • These SCR catalyst materials are typically mounted on a support such as a metal, ceramic, zeolite, or homogeneous monolith, although other art-known supports can also be used.
  • Patent 4,393,031 disclose the catalytic reduction of NO x using platinum grouo metals and/or other metals such as titanium, copper, molybdenum, vanadium, tungsten, or oxides thereof with the addition of ammonia to achieve the desired catalytic reduction.
  • Ginger in U.S. Patent 4,268,488, discloses exposing a nitrogen oxides containing effluent to a first catalyst comprising a copper compound such as copper sulfate and a second catalyst comprising metal combinations such as sulfates of vanadium and iron or tungsten and iron on a carrier in the presence of ammonia.
  • a first catalyst comprising a copper compound such as copper sulfate and a second catalyst comprising metal combinations such as sulfates of vanadium and iron or tungsten and iron on a carrier in the presence of ammonia.
  • the effluent containing the gasified reagent is most preferably passed over the SCR catalyst while the effluent is at a temperature between about 100°C and about 500°C, preferably at least 300°C.
  • the active species present in the effluent due to hydrolysis and gasification of the reagent solution most effectively facilitates the catalytic reduction of nitrogen oxides
  • the effluent will preferably contain an excess of oxygen.
  • the fuel can be catalyzed with a suitable platinum group metal additive and/or auxiliary catalyst composition selected from the group consisting of compounds of sodium, lithium, potassium, calcium magnesium, cerium, iron, copper, manganese, and mixtures Among the compounds are any of those disclosed for example in prior U.S.
  • a blend of these compounds can be used with one or more other platinum group metal compounds such as soaps, acetyl acetonates, aicoholates, ⁇ -diketonates, and sulfonates, e.g., of the type which will be described in more detail below.
  • platinum group metal compounds such as soaps, acetyl acetonates, aicoholates, ⁇ -diketonates, and sulfonates, e.g., of the type which will be described in more detail below.
  • the platinum group metal catalyst and/or other catalyst can be added in any manner effective for its intended purpose, such as by adding it to the fuel in bulk storage, to the fuel in a tank associated with the engine, or by continuous or intermittent addition, such as by a suitable metering device, into: the fuel line leading to the engine, or in the form of a vapor, gas or aerosol into the air intake, the exhaust gases before the trap, exhaust gases after the trap but before recirculation to the engine, or a mixing chamber or equivalent means wherein the exhaust gases are mixed with incoming air.
  • platinum group metal catalyst compositions are preferably employed at concentrations of less than 1 part by weight of platinum group metal per million parts by volume fuel (ppm),
  • ppm platinum group metal per million parts by volume fuel
  • all "parts per million” figures are on a weight to volume basis, i.e., grams/million cubic centimeters (which can also be expressed as milligrams/liter), and percentages are given by weight, unless otherwise indicated.
  • Auxiliary catalysts are employed at levels effective for their intended purpose, preferably at levels of from 1 to 100 ppm of the fuel utilized, e.g., 10 to 60 ppm.

Abstract

L'émission d'oxydes d'azotes par les moteurs à gaz pauvre (diesel par exemple) est réduite si l'on vaporise rapidement de l'urée ou un équivalent après l'avoir injectée dans les gaz d'échappement en fonction des besoins. De préférence, une solution aqueuse d'urée chauffée et sous pression (au moins partiellement hydrolysée) est injectée dans les gaz d'échappement, de façon à passer rapidement, avec la libération rapide d'énergie, de la phase liquide à la phase gazeuse. Les produits de dégradation gazeux de l'urée sont ensuite introduits avec les gaz d'échappement dans un catalyseur de réduction catalytique sélective (SCR) (30). Les injecteurs (60) de type aiguille sont préférés. De préférence, on utilise, pour injecter la solution, une pluralité d'injecteurs (50) qui sont positionnés sur le tuyau d'échappement (20) selon une orientation radiale, en biais ou longitudinale. La chaleur peut être fournie par échange thermique avec l'échappement et/ou par un système auxiliaire (56).
PCT/US1997/023796 1996-12-20 1997-12-22 Procede et dispositif pour reduire les emissions toxiques d'un moteur a gaz pauvre par reduction catalytique selective a injection d'uree WO1998028070A1 (fr)

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US08/772,275 1996-12-20

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GB2383548A (en) * 2001-10-17 2003-07-02 Fleetguard Inc A selective catalytic reduction device and methods for use therein
EP1378560A2 (fr) * 2002-06-07 2004-01-07 Ethyl Corporation Additifs aqueux utilisés dans des systèmes de combustion de fuels hydrocarbonés
WO2005025725A1 (fr) * 2003-09-05 2005-03-24 Robert Bosch Gmbh Dispositif de traitement d'une solution produit semi-fini d'agent reducteur pour traitement posterieur de gaz d'echappement
WO2005033480A1 (fr) 2003-09-30 2005-04-14 Nissan Diesel Motor Co., Ltd. Dispositif et procede de purification des gaz d'echappement pour un moteur
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WO2006087555A1 (fr) * 2005-02-16 2006-08-24 Imi Vision Limited Traitement de gaz d'echappement
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WO2006122561A1 (fr) * 2005-05-20 2006-11-23 Grundfos Nonox A/S Atomisation de fluides par collision mutuelle de flux fluidiques
EP1956206A2 (fr) 2007-02-09 2008-08-13 Sulzer Chemtech AG Système de nettoyage des gaz d'échappement
US7485272B2 (en) 2005-11-30 2009-02-03 Caterpillar Inc. Multi-stage system for selective catalytic reduction
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EP2837784A4 (fr) * 2012-04-09 2015-05-06 Toyota Motor Co Ltd Dispositif d'épuration d'échappement pour moteur à combustion interne
US9475005B2 (en) 2014-06-06 2016-10-25 Clean Diesel Technologies, Inc. Three-way catalyst systems including Fe-activated Rh and Ba-Pd material compositions
US9511358B2 (en) 2013-11-26 2016-12-06 Clean Diesel Technologies, Inc. Spinel compositions and applications thereof
US9511353B2 (en) 2013-03-15 2016-12-06 Clean Diesel Technologies, Inc. (Cdti) Firing (calcination) process and method related to metallic substrates coated with ZPGM catalyst
US9511350B2 (en) 2013-05-10 2016-12-06 Clean Diesel Technologies, Inc. (Cdti) ZPGM Diesel Oxidation Catalysts and methods of making and using same
US9545626B2 (en) 2013-07-12 2017-01-17 Clean Diesel Technologies, Inc. Optimization of Zero-PGM washcoat and overcoat loadings on metallic substrate
US9555400B2 (en) 2013-11-26 2017-01-31 Clean Diesel Technologies, Inc. Synergized PGM catalyst systems including platinum for TWC application
RU2617396C2 (ru) * 2015-07-01 2017-04-24 Государственное научное учреждение Всероссийский научно-исследовательский институт ветеринарной вирусологии и микробиологии Россельхозакадемии Устройство для получения высокодисперсных аэрозолей
RU2623396C1 (ru) * 2015-12-22 2017-06-26 Государственное научное учреждение Всероссийский научно-исследовательский институт ветеринарной вирусологии и микробиологии Российской академии сельскохозяйственных наук Генератор высокодисперсных аэрозолей
US9700841B2 (en) 2015-03-13 2017-07-11 Byd Company Limited Synergized PGM close-coupled catalysts for TWC applications
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US9759113B2 (en) 2012-05-10 2017-09-12 Tenneco Automotive Operating Company Inc. Coaxial flow injector
US9771534B2 (en) 2013-06-06 2017-09-26 Clean Diesel Technologies, Inc. (Cdti) Diesel exhaust treatment systems and methods
US9861964B1 (en) 2016-12-13 2018-01-09 Clean Diesel Technologies, Inc. Enhanced catalytic activity at the stoichiometric condition of zero-PGM catalysts for TWC applications
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CN108005762A (zh) * 2017-11-17 2018-05-08 国网山东省电力公司荣成市供电公司 一种电力工程车的scr系统
US10265684B2 (en) 2017-05-04 2019-04-23 Cdti Advanced Materials, Inc. Highly active and thermally stable coated gasoline particulate filters
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EP0900923A3 (fr) * 1997-09-05 1999-09-29 Robert Bosch Gmbh Dispositif de distribution d'un mélange
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GB2383548A (en) * 2001-10-17 2003-07-02 Fleetguard Inc A selective catalytic reduction device and methods for use therein
EP1378560A2 (fr) * 2002-06-07 2004-01-07 Ethyl Corporation Additifs aqueux utilisés dans des systèmes de combustion de fuels hydrocarbonés
EP1378560A3 (fr) * 2002-06-07 2004-01-14 Ethyl Corporation Additifs aqueux utilisés dans des systèmes de combustion de fuels hydrocarbonés
WO2005025725A1 (fr) * 2003-09-05 2005-03-24 Robert Bosch Gmbh Dispositif de traitement d'une solution produit semi-fini d'agent reducteur pour traitement posterieur de gaz d'echappement
EP1676986A4 (fr) * 2003-09-30 2010-02-10 Nissan Diesel Motor Co Dispositif et procede de purification des gaz d'echappement pour un moteur
WO2005033480A1 (fr) 2003-09-30 2005-04-14 Nissan Diesel Motor Co., Ltd. Dispositif et procede de purification des gaz d'echappement pour un moteur
EP1676986A1 (fr) * 2003-09-30 2006-07-05 Nissan Diesel Motor Co., Ltd. Dispositif et procede de purification des gaz d'echappement pour un moteur
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WO2006052168A1 (fr) * 2004-10-11 2006-05-18 Volvo Lastvagnar Ab Systeme et procede de reduction des oxydes d'azote des gaz d'echappement generes par un moteur a combustion interne a melange pauvre
WO2006087541A1 (fr) * 2005-02-16 2006-08-24 Imi Vision Limited Traitement des gaz d'echappement
WO2006087553A1 (fr) * 2005-02-16 2006-08-24 Imi Vision Limited Traitement des gaz d'echappement
WO2006087555A1 (fr) * 2005-02-16 2006-08-24 Imi Vision Limited Traitement de gaz d'echappement
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EP1956206A2 (fr) 2007-02-09 2008-08-13 Sulzer Chemtech AG Système de nettoyage des gaz d'échappement
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EP2214808A4 (fr) * 2007-10-30 2010-11-24 Babcock Power Environmental In Système de contrôle adaptatif pour le contrôle de distribution de réactif dans les réacteurs scr
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US10316739B2 (en) 2008-06-27 2019-06-11 Umicore Ag & Co. Kg Method and device for the purification of diesel exhaust gases
EP3473825A1 (fr) * 2008-06-27 2019-04-24 Umicore Ag & Co. Kg Procédé et dispositif de nettoyage de gaz d'échappement de moteurs diesel
EP2138681A1 (fr) * 2008-06-27 2009-12-30 Umicore AG & Co. KG Procédé et dispositif de nettoyage de gaz d'échappement diesel
US10001053B2 (en) 2008-06-27 2018-06-19 Umicore Ag & Co. Kg Method and device for the purification of diesel exhaust gases
US8171722B2 (en) 2008-12-05 2012-05-08 Caterpillar Inc. Fluid delivery system
WO2011147556A1 (fr) * 2010-05-25 2011-12-01 Mtu Friedrichshafen Gmbh Dispositif de retraitement des gaz d'échappement
FR2963058A1 (fr) * 2010-07-22 2012-01-27 Bosch Gmbh Robert Procede de gestion d'un systeme de dosage regule en pression d'un catalyseur scr
US8943808B2 (en) 2010-09-27 2015-02-03 Caterpillar Inc. Reductant dosing system
EP2551009A1 (fr) * 2011-07-29 2013-01-30 Deere & Company Formulation de fluide d'échappement diesel ayant une haute teneur en ammonium et point de congélation bas
US8518354B2 (en) 2011-07-29 2013-08-27 Deere & Company Diesel exhaust fluid formulation having a high ammonium content and a low freezing point
EP2837784A4 (fr) * 2012-04-09 2015-05-06 Toyota Motor Co Ltd Dispositif d'épuration d'échappement pour moteur à combustion interne
US10465582B2 (en) 2012-05-07 2019-11-05 Tenneco Automotive Operating Company Inc. Reagent injector
US9759113B2 (en) 2012-05-10 2017-09-12 Tenneco Automotive Operating Company Inc. Coaxial flow injector
US9511353B2 (en) 2013-03-15 2016-12-06 Clean Diesel Technologies, Inc. (Cdti) Firing (calcination) process and method related to metallic substrates coated with ZPGM catalyst
WO2014154936A1 (fr) * 2013-03-26 2014-10-02 Aalto University Foundation Système rcs pour le post-traitement de gaz d'échappement de moteurs diesels et procédé correspondant utilisant la technologie rcs
US9511350B2 (en) 2013-05-10 2016-12-06 Clean Diesel Technologies, Inc. (Cdti) ZPGM Diesel Oxidation Catalysts and methods of making and using same
US9771534B2 (en) 2013-06-06 2017-09-26 Clean Diesel Technologies, Inc. (Cdti) Diesel exhaust treatment systems and methods
US9545626B2 (en) 2013-07-12 2017-01-17 Clean Diesel Technologies, Inc. Optimization of Zero-PGM washcoat and overcoat loadings on metallic substrate
US9511358B2 (en) 2013-11-26 2016-12-06 Clean Diesel Technologies, Inc. Spinel compositions and applications thereof
US9555400B2 (en) 2013-11-26 2017-01-31 Clean Diesel Technologies, Inc. Synergized PGM catalyst systems including platinum for TWC application
US9579604B2 (en) 2014-06-06 2017-02-28 Clean Diesel Technologies, Inc. Base metal activated rhodium coatings for catalysts in three-way catalyst (TWC) applications
US9475005B2 (en) 2014-06-06 2016-10-25 Clean Diesel Technologies, Inc. Three-way catalyst systems including Fe-activated Rh and Ba-Pd material compositions
US9475004B2 (en) 2014-06-06 2016-10-25 Clean Diesel Technologies, Inc. Rhodium-iron catalysts
US9731279B2 (en) 2014-10-30 2017-08-15 Clean Diesel Technologies, Inc. Thermal stability of copper-manganese spinel as Zero PGM catalyst for TWC application
US9700841B2 (en) 2015-03-13 2017-07-11 Byd Company Limited Synergized PGM close-coupled catalysts for TWC applications
US9951706B2 (en) 2015-04-21 2018-04-24 Clean Diesel Technologies, Inc. Calibration strategies to improve spinel mixed metal oxides catalytic converters
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RU2623396C1 (ru) * 2015-12-22 2017-06-26 Государственное научное учреждение Всероссийский научно-исследовательский институт ветеринарной вирусологии и микробиологии Российской академии сельскохозяйственных наук Генератор высокодисперсных аэрозолей
US10533472B2 (en) 2016-05-12 2020-01-14 Cdti Advanced Materials, Inc. Application of synergized-PGM with ultra-low PGM loadings as close-coupled three-way catalysts for internal combustion engines
US9861964B1 (en) 2016-12-13 2018-01-09 Clean Diesel Technologies, Inc. Enhanced catalytic activity at the stoichiometric condition of zero-PGM catalysts for TWC applications
US10265684B2 (en) 2017-05-04 2019-04-23 Cdti Advanced Materials, Inc. Highly active and thermally stable coated gasoline particulate filters
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