DE29825250U1 - Reducing emissions of nitrogen oxide(s) from lean-burn engine with associated exhaust system - by feeding aqueous urea solution from storage vessel through line to injector, returning solution to storage vessel, injecting solution into exhaust gases and passing gas to selective catalytic reduction reactor - Google Patents

Abstract

A method for reducing the emissions of NOx from a lean-burn engine with an associated exhaust system, including an exhaust passage linked to a reactor effective for selective catalytic NOx reduction, comprises feeding an aqueous urea solution from a storage vessel through a line to an injector; returning the urea solution from the injector to the storage vessel, the rates of feed and return being sufficient to supply urea as needed to the exhaust gases and maintain the temperature of the urea solution sufficiently low that it is not permitted sufficient time at elevated pressure to hydrolyse the urea to such an extent that solids precipitate; injecting the urea solution into the exhaust gases at a temperature sufficient for selective catalytic reaction (SCR); and passing the exhaust gas through the SCR reactor. Also claimed are: (i) a method in which a heat exchange fluid is passed in heat exchange contact with the line and/or injector, but otherwise the same as above; and (ii ) an apparatus for reducing the emissions of NOx from a lean-burn engine with an associated exhaust system, including an exhaust passage linked to a reactor effective for selective catalytic NOx reduction, comprising means for feeding an aqueous urea solution form a storage vessel through a line to an injector; means for returning the solution to the storage vessel, means for injecting the solution into the exhaust gas and exhaust passage means leading from the injector to an SCR reactor. Preferably the urea solution contains at least 25 wt.% urea. The temperature of the exhaust gases is 180-650 [deg]C. The urea solution is maintained at less than 140 [deg]C. The urea solution is injected into the exhaust gases at at least 30 psi. The urea solution is heated in whole or in part by an auxiliary heating means or by heat transfer from the exhaust. The urea solution is introduced into the exhaust between exhaust valves of the engine and a turbocharger exhaust turbine. The urea is introduced into the exhaust close-coupled relation with the SCR catalyst. Introduction of the urea solution into the exhaust is controlled by a controller integrated with an engine management system. The temperature of the urea solution is allowed to rise above 100 [deg]C and the solution is maintained at a pressure above the saturation vapour pressure of the temperature of the solution.

Description

The invention relates to devices that enable the safe and reliable reduction of nitrogen oxides (NO _x ) emissions while allowing a diesel or other lean burn engine to operate effectively.

Diesel and lean burn gasoline engines provide fuel economy benefits, but produce both NO _x and particulates during normal operation. When primary measures (operations that affect the combustion process itself, eg exhaust gas recirculation and engine control settings) are taken to reduce one, the other is normally increased. Consequently, the combustion conditions selected to reduce particulate contamination and obtain good fuel economy tend to increase NO _x .

The current and proposed regulations challenge the manufacturers to achieve good fuel economy and reduce particulates and NO _x . Lean combustion engines are required to accomplish the task of fuel economy, but the high levels of oxygen in the exhaust make typical exhaust catalyst systems ineffective to reduce NO _x .

SCR (Selective Catalytic Reduction) _x is available in some contexts for reducing NO for years. However, to date, SCR is dependent on the use of ammonia, resulting in safety issues associated with its storage and transportation. Urea is safer, but is not useful for many SCR applications - particularly mobile NO _x sources - because of the difficulty in converting it from a solid or an aqueous form to its active gaseous species, typically NH _i and HNCO radicals.

It currently available Need for a safe, economical and effective response to the problems with SCR, especially for mobile Diesel and other lean-burn engines.

When SCR catalysts are used to limit NO _x emissions from diesel engines, one must either deal with the dangers of ammonia or deal with the risk of catalyst fouling under most conditions. In this regard, see RJ Hulterman; A Selective Catalytic Reduction Of NO _x from Diesel Engines Using Injection Of Urea; Ph.D. thesis, September 1995. Hulterman describes several technical challenges, including nebulizer clogging, decomposition problems, and system dynamics. Similarly, SAE paper # 970185 entitled "Transient Performance of a Urea DeNO _x Catalyst for Low Emission Heavy Duty Diesel Engines" indicates that the injectors must be protected from excessive heat.

The limited Trials, urea SCR for To use diesel engines have the use of large pyrolysis chambers or other devices after the site of urea introduction into the exhaust gas required, as described in U.S. Patent No. 5,431,893 to Hug et al. disclosed. equipment This species highlights the known problems with urea. once introduced in diesel exhaust, needed the urea time to split, and can clog the Cause nozzle, if he is conventional, and as suggested in this disclosure. To protect the catalyst from fouling, Hug et al. extensive equipment in front. Furthermore This disclosure raises the necessity of holding the urea solution a temperature of less than 100 ° C to prevent decomposition before passing through the nozzle. They suggest the use of moderate urea pressures, if they deliver the urea, and find it necessary to have an alternative device to introduce high pressure air into the supply line when it becomes clogged. The nozzles, those of Hug et al. are obviously used in the Able, moderately-fine To produce sprays whose dispersion is assisted by additional air, but the droplets are still big enough to a big Pyrolysetunnel to require (see also WO 97/01387 and European Patent Application 487,886 A1.

Everyone the points of warning through these references about the difficulties of Use of urea with SCR systems, especially for mobile Sources, points to the effort who has had the subject and continues to do so.

The Specialty expects the development of a device that uses of urea in an SCR process simple, reliable, economical and safely enable would.

It is an object of the invention to provide a safe and reliable SCR system for reducing NO _x emissions from an internal combustion engine.

It It is an object of the invention to provide security problems with the storage and handling of ammonia for mobile uses are to be eliminated.

It is another object of the invention to allow the use of urea for SCR NO _x reduction, without clogging the feed lines due to the hydrolysis of the urea.

It Yet another object of the invention is the use of urea to enable the SCR the wetting of the or the solid deposit on the catalyst avoids.

It is another, more specific object of one aspect of the invention, to provide a simple, robust SCR system that is one of a kind fast response time is able to transient Conditions that prevail in diesel engines.

It is yet another and more specific object of the invention, the To allow use of urea in an SCR system, which allows the treatment of exhaust gas at temperatures between 180 and 650 ° C.

It is yet another and more specific object of the invention, the To allow use of urea in an SCR system, which allows integration with an engine management system (EMS), thus reducing the need for a extra tax or Control device is avoided.

It Another specific object of the invention is a simple one mechanical device for achieving the aforementioned objects and in particular, for tightly coupling the reagent injector and the SCR catalyst.

These and other objects are achieved by the present invention, which provides an improved NO _x reduction device.

The Invention is in the claims specified.

The method of the present invention reduces emissions of NO _x from a lean burn engine having an exhaust system associated therewith with an exhaust passage for carrying NO _x -containing exhaust gases to a reactor effective for selective catalytic NO _x reduction and in one embodiment:
Feeding an aqueous urea solution from a reservoir through a conduit to an injection valve; Returning an aqueous urea solution from the injection valve to the reservoir, wherein the supply and return rates are sufficient to supply the required urea to the exhaust gases for NO _x reduction and to keep the temperature of the urea solution sufficiently low to avoid sufficient time at elevated temperatures have to hydrolyze the urea to the extent that solid particles or solids are eliminated (for example, below about 140 ° C), injecting the urea solution into the exhaust gas at an exhaust gas temperature suitable for SCR and passing the exhaust gas through an SCR reactor ,

at a further embodiment will the reflux not realized or not the only measure Preservation of the temperature of the urea solution. In this embodiment may be a heat exchange fluid, such as air or an engine coolant, for heat exchange be brought into contact with the injection valve. In this embodiment The temperature of the urea solution may rise to above 100 ° C for as long be allowed as the urea solution at a pressure above the Saturation vapor pressure is held at this temperature.

Under the preferred embodiments of Process are the use of concentrated urea solutions, the e.g. at least about 25 weight percent (wt%) urea. Preferably Urea is injected when the temperature of the exhaust gases within of the range of about 180 to about 650 ° C.

The device in one embodiment comprises: means for delivering an aqueous urea solution from a storage container through a conduit to an injector; Means for returning the urea solution from the injector to the storage vessel, wherein the rates of charge and return are sufficient to supply the urea, as needed, to the exhaust gases for NO _x reduction and to keep the temperature of the urea solution low enough to assist it insufficient time is allowed to hydrolyze the urea to such an extent that the solids precipitate (eg, below 140 ° C); Injector means for injecting urea solution into the exhaust gases at an exhaust gas temperature effective for the SCR; and exhaust passage means leading from the injector means to an SCR reactor.

A preferred embodiment of the device further includes: means for measuring the temperature with the exhaust gas; Means for generating a signal corresponding to the measured exhaust gas temperature; Means for measuring the engine load; Means for generating a signal representative of the measured engine load; Means for measuring the temperature in the urea solution; Means for generating a signal corresponding to the measured temperature of the urea solution; and means for comparing the generated signals with reference values and generating control signals for regulating urea feed, injection and back guide.

The invention will be better understood and its advantages will be more apparent from the following detailed description, especially when read in light of the accompanying drawings, wherein:
The figure is a flow chart showing major components of an embodiment of the invention.

In In this description, the term "lean-burn engine" is intended to include engines equipped with an inlet oxygen concentration can be operated, the is larger as the amount for stoichiometric (or chemically correct) combustion of a hydrocarbon fuel is required, e.g. at least 1 wt% oxygen excess.

The term "engine" is intended to include, in a broad sense, all combustors that burn hydrocarbon fuels to provide heat, for example, for direct or indirect conversion to mechanical or electrical energy can benefit from the invention. However, the diesel engine is because the problems and advantages of the successful execution of reliable NO _x reduction are highlighted in diesel engines as used throughout this description for purposes of example. Stationary and mobile engines are contemplated.

Of the Term "diesel engine" is intended to all compression ignition engines as well as mobile (including Marine) and stationary Include power plants and the two-stroke, four-stroke and Kreiskolbentyps.

Of the Term "hydrocarbon fuel" is intended to all such Include fuels, made from "distillate fuel" or "petroleum". Gasoline, jet fuel, diesel fuel and various others distillate oils are included. The term "distillate fuel" means all such Products made by the distillation of petroleum or petroleum fractions and residues become. The term "petroleum" is intended in its usual Meaning all such materials, regardless of source, which is usually included in the meaning of the term, including Hydrocarbon materials, regardless of viscosity, which be recovered from fossil fuels.

The The term "diesel fuel" means "distillate fuel", including diesel fuel, the ASTM definition for Diesel fuels or others meet, although they are not made entirely of distillates and alcohols, ethers, Organonitroverbindungen and the like (e.g., methanol, ethanol, diethyl ether, methyl ethyl ether, nitromethane) may include. Also within the scope of this invention are emulsions and liquid fuels, derived from vegetable or mineral sources, such as corn, alfalfa, Slate and coal, derive. These fuels can too contain other additives known to those skilled in the art, including dyes, Cetane improvers, antioxidants, such as 2,6-di-tert-butyl-4-methylphenol, Corrosion inhibitors, rust inhibitors, such as alkylated succinic acids and anhydrides, bacteriostatic agents, antioxidants, metal deactivators, top cylinder lubricants, anti-icing agents and the like.

Of the Term "urea" is said to be urea in all its forms of trading, including: Ammelid; ammeline; ammonium carbonate; ammonium bicarbonate; ammonium carbamate; ammonium cyanate; ammonium salts inorganic acids, including sulfuric acid and phosphoric acid; Ammonium salts of organic acids, including formic acid and Acetic acid; biuret; cyanuric acid; isocyanic; melamine and tricyanourea. Typically, the trade form of Urea consisting essentially of urea, with 95% or more urea contained, or from a urea containing in this purity aqueous Solution.

Aqueous solutions of Urea can up to their solubility limits be used. Typically, the aqueous solution contains from about 2 to about 65% reagent, based on the weight of the solution. It is an advantage of the invention that they concentrate the use of Urea solutions possible. The prior art teaches that dilute solutions of urea are required are to avoid problems with the precipitation of degradation products. The invention allows using urea to the maximum advantage without the usual Worry with ammonia or the worry of clogging pipe and nozzle. Concentrated solutions are preferred because they restrict the amount of water that stored, transported, evaporated and frozen in winter protected must become. Typical concentrations of urea are within the range of about 25 to about 50%, e.g. about 35%.

The urea can be stored as a solution or dry in a canister. When stored dry, water is contacted with the urea when needed to make a solution. In this way, the solution concentration can be varied from near saturation (to minimize the storage and use of water) or to any possible concentration suitable for a vehicle or stationary installation. It is desirable in some circumstances to provide heaters for storing water and / or urea solution to prevent freezing or reduce gasification time. It may also be useful to use antifreeze materials.

Reference is made to the 1 which illustrates in diagrammatic form an embodiment of the invention. In short, the diesel engine becomes 10 via lines 12 and injectors 13 Fuel supplied. The engine produces exhaust gases containing NO _x passing through the exhaust pipe 20 be guided. The urea solution is removed from the container 30 through one or more injectors, like 32 , the exhaust pipe 12 fed. The exhaust gases are then passed through the SCR reactor unit 34 guided. The method is preferably by means of a control device 40 , which is integrated in an engine management system (EMS), regulated, whereby the need for an extra control device is avoided. In an embodiment not shown, the urea solution is introduced between the exhaust valves of the engine and a turbocharger exhaust gas turbine in the exhaust gas.

The invention enables the use of aqueous solutions of urea instead of ammonia for SCR NO _x reduction in a manner which avoids clogging of the solution feed and injector system with deposits of urea hydrolysis products or wetting or generation of solid deposits on the catalyst ,

The Advantages of preventing deposits in the reagent delivery system This will be achieved by ensuring that the Hydrolysis does not take place in the feed system. The advantage of Preventing deposits on the catalyst is by much promising rapid decomposition of the urea after the solution in the exhaust gases has been introduced reached. The fact that the invention is not based on a low urea concentration, To avoid decomposition in the feed lines increases the speed the decomposition of urea in the exhaust gas. In addition, the invention requires Do not use air to dilute urea solution to below 100 ° C too cool - such low temperatures, especially when using huge Volumes cooler Air can be achieved, which was introduced into the exhaust gases, the Decomposition of urea by the exhaust gases delay.

The figure shows a reagent injector system comprising a feed line, eg a common web 31 , with a return to the supply via the overflow line 33 used. This system retains a continuous flow of reagent between the storage tank 30 and the injector 32 at. The term injector is used herein to describe a device that is capable of controlling the flow of urea solution from the web 31 to regulate to the exhaust gases. The injector may be either a high pressure or low pressure device.

Under the low pressure devices are one of the available low pressure liquid distribution means, like a mechanical atomizer of the type for spraying used by paints, a sonic sprayer, a simple valve, which extends to a hose with a dispersion device, the a plurality of openings includes, to provide a fine spray, a pin-regulated Nozzle (resp. Spigot valve), which is capable of adjustable pattern to spray, or similar. Pressurized air nozzles can be used, it is but prefers to operate them with a minimum of air to the Cost of the equipment and to reduce the effect that air has on the cooling of the exhaust gas. In circumstances when neither the air supply still their cooling effect unacceptable closes The design compromises, air can be used to the To cool the injector and / or to assist in the injection of the urea solution.

Under The high-pressure injectors are injectors of the type which used for fuel injection, which at 68 to 680 atm (1000 to 10,000 psig) open abruptly and peak dynamic injection pressures of up to about 3400 atm (about 50,000 psig). Injectors of the Pin type work within the above-mentioned pressure ranges and can the additional Provide an advantage of a scratching, self-cleaning feature, around the injector deposits at the nozzle outlet to minimize. Other injectors can also be used regardless of the operating pressure, e.g. some work on pressing in the order of magnitude of 2 atm (30 psig).

Series mixers are preferably used to ensure good distribution of urea solution within the exhaust gases, especially when low pressure injectors are used. Distribution is important because high concentrations of urea solution can cause localized cooling, and this can result in droplets of water or particles of urea or pyrolysis products that survive and then affect the SCR catalyst. A suitable device is as a propeller 46 shown. In another embodiment, a perforated body, mist eliminator, static mixer, particulate trap, or other similar device having mixing capability may be used. The figure also shows the elbow 21 in exhaust pipe 20 which act as protection against contact of liquid or solid urea or urea residues with the catalyst in the SCR reactor 34 serves.

The embodiment illustrated in the figure includes a web pressure sensor 35 and a pressure control valve 36 one. Pressure within the web and the return lines through valve 36 and pump 37 in response to the control signals generated by the control device 40 to be provided. It is found that the pressurized lines 31 . 31 ' and 31 '' darker in the figure than the non-pressurized return lines 33 and 33 ' are shown. Optionally, a heat exchanger 50 in line 33 used to cool the urea solution in case of overheating. The wires 38 and 38 ' between the pump 37 and the container 30 move the urea solution when needed.

The control device 40 is preferably with an EMS for the engine 10 integrated to avoid the need for multiple different controllers and to use existing cabling wiring and sensors as much as possible. Various sensors are shown and are used to measure various operating parameters and generate operating signals that correspond to the measured parameters. The operating signals are then sent to the controller, which compares them with reference values, calculates one or more control signals, and sends the control signals to one or more devices that are being regulated.

The figure shows the sensor 41 for the engine, sensor 42 for the exhaust gas temperature, sensor 43 for the amount of urea in the container 30 and sensor 44 for the temperature of the urea solution in the return line 33 , The motor load, as represented by one or more suitable parameters, such as fuel flow, engine speed, throttle position or settings of the injection system, is a key parameters, and one of these or similar factors can be monitored to determine the amount of NO _x which is generated, and determine the need for the reagent feed to the heating unit or its hydrolysis products fed to the exhaust gases. Optional sensors, like sensor 45 for the NO _x residual concentrations, can be used for the feedback control to the extent that it is practical. The figure also shows in dotted lines operating signals sent to the controller and control signals sent to regulated devices.

The temperature of the urea solution throughout the system is maintained at a value low enough that at elevated temperature there is insufficient time to hydrolyze the urea to the extent that solids precipitate (eg, below about 140 ° C). The injector 32 tends to heat when the temperature of the exhaust gases after starting increases within the range of about 300 ° to about 650 ° C under high load for some engines. Unless precautions are taken, the high temperature causes hydrolysis of the urea prior to injection - causing the hydrolysis products to precipitate because of their lower solubility than urea. The invention continuously circulates the urea solution from the container 30 through the pipes 31 and 33 (and connected lines as regulated) to provide cooling to the injector. It is possible with appropriate controls to raise the temperature of the solution between 105 ° C and 130 ° C when the system is pressurized to the saturated vapor pressure for the temperatures in question. Because the residence time on the overflow line is short, the urea solution can be allowed to reach higher temperatures without reaching the solubility limit for the hydrolysis products. An auxiliary heater (not shown) may be in the container 30 or elsewhere in the feed or in the recycle system to achieve a desired temperature.

It is a clear advantage of the invention that no air is required to achieve temperature control - saving on equipment costs and preventing reduced efficiency due to the cooling effect of the air on the exhaust gases. It is also an advantage of the invention that the high pressure injector equipment can be configured with a return line for operating pressures high enough to cause atomization, preferably with at least some gasification, of the urea solution as the pressure is reduced. This feature allows close coupling of the injector with the SCR reactor 34 better.

In another embodiment, however, the return lines 33 and 33 ' not used or are not the sole means of maintaining the temperature. In this embodiment, heat exchange fluid, such as air or engine coolant, may be passed in heat exchange contact with the injector. Admittedly, in this embodiment, the temperature of the urea solution may be allowed to rise to over 100 ° C, as long as the urea solution is kept at the temperature at a pressure above the saturation vapor pressure.

It is possible to provide a catalyst for promoting hydrolysis and / or pyrolysis of the urea on one or more of the exhaust system component parts as a coating or as a separate element. For example, he could be on the exhaust pipe 20 , especially at the elbow 21 be upset. Also could be at the mixing device 46 be used. Coatings of this type have a double advantage, namely that the operating system is kept clean and the gasification of urea is increased. Suitable hydrolysis catalysts include those comprising 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 carbonate, potassium carbonate, 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 Harpe et al., U.S. Patent No. 5,139,754 to Hofmann, Sun and Luftglass, U.S. Patent No. 5,281,403 to Jones and JP HEI 2-191,528 to Ebina for another list of catalysts and methods See also EP 615 777 , Which discloses a mixed oxide catalyst composed of Al ₂ O ₃ -TiO ₂ -SiO ₂ -ZrO _2, which is able to break down urea in diesel exhaust gas).

Of the used SCR catalyst is one that is capable of concentration the outflowing To reduce nitrogen oxides in the presence of ammonia. These close to Example activated carbon, charcoal or coke, zeolites, vanadium oxide, tungsten oxide, titanium oxide, Iron oxide, copper oxide, manganese oxide, chromium oxide, precious metals, such as platinum group metals, such as platinum, palladium, rhodium and iridium, or mixtures of these one. Other SCR catalyst materials conventional in the art and are familiar to the expert can also be used. These SCR catalyst materials are typical on a carrier, such as a metal, ceramic, zeolite or homogeneous monolith, attached, although other carriers known in the art are also used can be.

Among the useful SCR catalysts are those which are the prior art processes described below. Selective catalytic reduction processes for reducing NO _x are known and use various catalytic agents. For example, in European Patent Application WO 210,392 Eichholtz and Weiler discuss the catalytic removal of nitrogen oxides using activated charcoal or activated coke with the addition of ammonia as the catalyst. Kato et al. in US Pat. No. 4,138,469 and Henke in U.S. Pat. No. 4,393,031, the catalytic reduction of NO _x using platinum group metals and / or other metals such as titanium, copper, molybdenum, vanadium, tungsten, or oxides disclose thereof with the addition of of ammonia to achieve the desired catalytic reduction (see also EP 487,886 which specifies a V ₂ O ₅ / WO ₃ / TiO ₂ catalyst with a working range of 220 to 280 ° C). Other platinum-based catalysts may have operating temperatures that are even lower, eg, down to about 180 ° C.

Another catalytic reduction process is disclosed in Canadian Patent 1,100,292 to Knight which relates to the use of a platinum group metal, gold and / or silver catalyst supported on a refractory oxide. Mori et al. discuss in U.S. Pat. No. 4,107,272, the catalytic reduction of NO _x using Oxyschwefel, sulfate, or sulfite compounds of vanadium, chromium, manganese, iron, copper and nickel with the addition of ammonia gas.

In a multiphase catalyst system disclosed by Ginger in the US patent No. 4,268,488 the action of a first catalyst, the one Copper compound, such as copper sulfate, and a second catalyst, the metal combinations, such as sulfates of vanadium and iron or Tungsten and iron, on a support comprises, on exhaust gas containing nitrogen oxides in the presence of ammonia.

The Exhaust into which the urea has been introduced is preferably via the SCR catalyst passed while the exhaust gas is at a suitably high temperature, typically between about 180 ° C and about 650 ° C, e.g. at least about 300 ° C. In this way, the active species facilitates because of the hydrolysis and gasification of the urea solution in the exhaust gas is present, the catalytic reduction of nitrogen oxides most effective. The Contains exhaust gas a surplus of oxygen. The use of the present invention with a the above SCR catalysts (their disclosure by reference particularly included) reduces or eliminates the requirement transport, storage and handling of large quantities of ammonia or ammonium water.

Because the invention is compatible with other emission reducing and fuel economy technologies, several hybrid methods become available to the engine designer, vehicle manufacturer and aftermarket market. For example, the fuel may be catalyzed with a suitable platinum group metal additive and / or catalyst adjuvant 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 described, for example, in U.S. Patent Nos. 4,892,562 and 4,891,050 to Bowers and Sprague, 5,034,020 to Epperly and Sprague, 5,215,652 to Epperly, Sprague, Kelso and Bowers, and 5,266,083 to Peter-Hoblyn, Epperly , Kelso and Sprague, WO 90/07561 by Epperly, Sprague, Kelso and Bowers, and U.S. Patent Application Serial No. No. 08 / 597,517, filed January 31, 1996 by Peter-Hoblyn, Valentine and Sprague, which are hereby incorporated by reference. If permitted by the application, a mixture of these compounds may be used with one or more other platinum group metal compounds, such as soaps, acetylacetonates, alcoholates, β-diketonates, and sulfonates, for example, of the type described in more detail below.

Of the Catalyst of the platinum group metal and / or another catalyst can be added in a manner appropriate for their intended purpose are effective, such as by adding fuel to bulk tanks, to the fuel in a tank connected to the engine, or by continuous or temporary addition, as by a suitable Dosing device, in: the fuel line leading to the engine, or in the form of a vapor, gas or aerosol into the air inlet, the exhaust gases in front of the filter, the exhaust gases after the filter but before Return to the Engine or a mixing chamber or equivalent devices, wherein the exhaust gases with inflowing Air are mixed.

If used, especially in conjunction with particulate filters, are preferred Catalyst compositions of a platinum group metal at concentrations less than 2 parts by weight of platinum group metal per million Parts per volume of fuel (ppm) used. For the purposes of this Description are all "parts per million "numbers based on weight to volume, i. Grams / million cubic centimeters (which can also be expressed as milligrams / liter), and the percentages are Weight percent, unless otherwise specified. auxiliary catalysts are used in amounts effective for their intended purpose are, preferably in quantities of 1 to 100 ppm of the fuel used, e.g. 10 to 60 ppm.

The Description before should show the average expert, such as the The present invention is implemented and is not intended to be all obvious deviations and embodiments in detail describe that to the experienced professional while reading this Description open up. It is intended, however, that all such obvious modifications and embodiments from the scope of the present invention, which is defined by the following claims is defined. The claims write the said Elements and process steps in all possible different arrangements and sequences that perform the tasks for effectively solve the present invention as far as this in context not expressly mentioned differently is.

Claims (42)

Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using a NO _x reducing reagent and a catalytic reactor ( 34 ) with: an injection valve ( 32 ) located in the exhaust duct ( 20 ) is positioned; a management device ( 31 ) for feeding reagent from a storage container ( 30 ) to the injection valve ( 32 ) to inject reagent into the exhaust passage and to cool the injection valve; a return device ( 33 ) for returning a portion of the reagent from the injection valve ( 32 ); a facility ( 43 . 44 ) for detecting the temperature of the reagent; and a facility ( 42 ) for detecting the temperature of exhaust gases in the exhaust passage. Apparatus for reducing the NO _x emissions (from a lean burn engine 10 ) with an associated exhaust system with an exhaust passage ( 20 ) for feeding NO _x -containing exhaust gases to a reactor ( 34 ) which is effective for selective catalytic NO _x reduction, the apparatus comprising: a supply means ( 37 ) for feeding a reagent from a container ( 30 ) through a line ( 31 ) to an injection valve ( 32 ); An institution ( 33 ) for returning reagent from the injector ( 32 ) to a container ( 30 ); An institution ( 40 . 41 . 42 . 43 . 44 ) for controlling the rates of reagent feed and return to supply reagent to the exhaust gases for NO _x reduction as needed and to cool the reagent; An institution ( 32 ) for injecting reagent into the exhaust gases in front of the reactor ( 34 ). Device for reducing the NO _x emissions from a diesel engine with an associated exhaust system with an exhaust duct ( 20 ) resulting in a selective catalytic reduction (SCR) reactor ( 34 ) which is effective for selective catalytic NO _x reduction with urea reagent in the exhaust gases, comprising: means ( 37 ) for passing an aqueous urea solution from a storage container through a conduit ( 31 ) to an injection valve ( 32 ); a facility ( 33 ) for returning urea solution from the injection valve to a storage container ( 30 ) having sufficient feed and recycle rates to deliver urea to the exhaust gases as necessary for NO _x reduction and to keep the temperature of the urea solution sufficiently low so that it can not have sufficient time at elevated temperatures to hydrolyze the urea to precipitate solids ; an injection valve device ( 32 ) for injecting urea solution into the exhaust gases at selective catalytic reduction (SCR) the exhaust gas temperature; and an exhaust channel device ( 20 ) supplied by the injection valve device ( 32 ) to the SCR reactor ( 34 ) leads. Device for the metered delivery of a reducing agent into the exhaust gas flow ( 20 ) of an internal combustion engine ( 10 ) with the aid of a dosing unit ( 32 ) with a container ( 30 ) through an inlet conduit ( 31 ) and an outlet conduit ( 33 ) is connected in a closed circuit, via which a reducing agent of the dosing unit ( 32 ) Heat, characterized in that the reducing agent passing through the dosing unit ( 32 ) is to be injected, at a transition from the outlet ( 33 ) is deducted. Device according to one of claims 1 to 4, in particular comprising: a device ( 42 ) to detect the temperature of the exhaust gas; a facility ( 40 ) to generate a signal representative of the detected exhaust gas temperature; a facility ( 41 ) to detect engine load; a facility ( 40 ) to generate a signal representing the detected engine load; a facility ( 43 and or 44 ) to detect the temperature of the urea solution; a facility ( 40 ) to generate a signal representing the detected urea solution temperature; and a facility ( 40 ) to compare the generated signals with reference values and to generate control signals for controlling the urea supply, injection and return. Device according to one of claims 1 to 5, further comprising a Device for passing heat exchange fluid in heat exchange contact with the injector. Device according to one of claims 1 to 6, which is a heater for the Reagent. Device according to one of claims 1 to 7, comprising a heat exchanger ( 50 ) in the return device ( 33 ) having. Device according to one of claims 1 to 8, comprising a pressure sensor ( 35 ) having. Device according to one of claims 1 to 9, which is a pressure regulating valve ( 36 ) to maintain the reagent pressure. Device according to one of claims 1 to 10, wherein the injection valve ( 32 ) is a pin injection valve. Device according to one of claims 1 to 11, further comprising a Particulate filter. Device according to one of claims 1 to 12, further comprising a Dosing device for introducing fuel additive with a catalyst metal into the fuel or the combustion air. Device according to one of claims 1 to 13, wherein the system is controlled by a controller ( 40 ) is controlled. Device according to one of claims 1 to 14, wherein the plant is controlled by a controller operating in an engine management system (EMS) is integrated. A lean NO _x emission apparatus according to any one of claims 1 to 15, wherein a reagent return is not the sole cooling source for the reagent. Apparatus for reducing NO _x emissions from a lean-burn engine according to any one of claims 1 to 16, wherein a return is not the only means for maintaining the temperature of the reagent and the apparatus further comprises means for passing a heat exchange fluid, eg air or engine coolant Having heat exchange contact with the injection valve. Device according to one of claims 1 to 17, comprising a device ( 43 ) for detecting the temperature of the reagent in the storage container. Device according to one of claims 1 to 18, comprising a device ( 44 ) for detecting the temperature of the reagent in the outlet conduit. Device according to one of claims 1 to 19, further comprising a device ( 42 ) for detecting the temperature of exhaust gases in the exhaust passage ( 33 ) having. Apparatus according to any one of claims 1 to 20, further comprising Device for conducting a heat exchange fluid in heat exchange contact with the injector. Apparatus according to any one of claims 1 to 21, wherein further the injection valve has a pin. Device according to one of claims 1 to 22, wherein the dosing unit ( 32 ) has a low pressure or high pressure fuel injection valve. Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing urea reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) is positioned; a management device ( 31 ) for feeding reagent from a storage container ( 30 ) to the injection valve ( 31 ) to inject reagent into the exhaust passage and to cool the injection valve; a return device ( 33 ) for returning a portion of the reagent from the injection valve ( 32 ); a facility ( 42 ) to detect the temperature of the exhaust gas; a facility ( 40 ) to generate a signal representative of the detected exhaust gas temperature; a facility ( 41 ) to detect engine load; a facility ( 40 ) to generate a signal representing the detected engine load; a facility ( 43 . 44 ) to detect the temperature of the urea solution; a facility ( 40 ) to generate a signal representing the detected urea solution temperature; and a facility ( 40 ) to compare the generated signals with reference values and to generate control signals for controlling urea supply, injection and return; and a facility ( 42 ) for detecting the temperature of exhaust gases in the exhaust passage. Apparatus for reducing the NO _x emissions from a lean burn engine according to claim 24, wherein a return flow is not the only means for maintaining the temperature of the reagent and the apparatus further comprises means for passing a heat exchange fluid in heat exchange contact with the injector. Device according to one of claims 24 to 25, comprising a pressure sensor ( 35 ) having. Device according to one of claims 24 to 26, which is a pressure regulating valve ( 36 ) to maintain the reagent pressure. Apparatus according to any one of claims 24 to 27, further comprising Particulate filter. Apparatus according to any of claims 24 to 28, further comprising Dosing device for introducing fuel additive with a catalyst metal into the fuel or the combustion air. Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing urea reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) is positioned; a management device ( 31 ) for feeding reagent from a storage container ( 30 ) to the injection valve ( 31 ) to inject reagent into the exhaust passage and to cool the injection valve; a return device ( 33 ) for returning a portion of the reagent from the injection valve ( 32 ); a facility ( 42 ) to detect the temperature of the exhaust gas; a facility ( 40 ) to generate a signal representative of the detected exhaust gas temperature; a facility ( 41 ) to detect engine load; a facility ( 40 ) to generate a signal representing the detected engine load; a facility ( 43 . 44 ) to detect the temperature of the urea solution; a facility ( 40 ) to generate a signal representing the detected urea solution temperature; and a facility ( 40 ) to compare the generated signals with reference values and to generate control signals for controlling urea supply, injection and return; a facility ( 42 ) for detecting the temperature of exhaust gases in the exhaust passage; means for passing a heat exchange fluid in heat exchange contact with the injection valve; a particulate filter; a metering device for introducing fuel additive with a catalyst metal in the fuel or the combustion air; a pressure sensor ( 35 ); and a pressure control valve ( 36 ) to maintain the reagent pressure. Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to detect the temperature of the exhaust gas; a facility ( 40 ) to generate a signal representative of the detected exhaust gas temperature; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to detect engine load; a facility ( 40 ) to a signal as a representation to generate the detected engine load; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to detect the temperature of the NO _x reducing reagent; a facility ( 40 ) to generate a signal representing the detected NO _x reducing reagent; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to detect the temperature of the exhaust gas; a facility ( 40 ) to generate a signal representative of the detected exhaust gas temperature; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to reduce the temperature of the NO _x reducing reagent in a return device ( 33 ) capture; a facility ( 40 ) to provide a signal representative of the detected NO _x reducing reagent in the recirculation means (FIG. 33 ) to create; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to detect the temperature of the exhaust gas; a facility ( 40 ) to generate a signal representative of the detected exhaust gas temperature; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 43 ) to reduce the level of urea in a storage container ( 30 ) capture; a facility ( 40 ) to display a signal representing the captured storage container ( 30 ) to create; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to detect the temperature of the exhaust gas; a facility ( 40 ) to generate a signal representative of the detected exhaust gas temperature; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to detect fuel flow to the engine; a facility ( 40 ) to generate a signal representing fuel flow; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to detect the throttle position; a facility ( 40 ) to generate a signal representative of the detected throttle position; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; a facility ( 42 ) to detect injector settings; a facility ( 40 ) to generate a signal representing the detected injector settings; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS). Device for reducing NO _x emissions in an exhaust gas duct ( 20 ) from a lean-burn engine ( 10 ) using NO _x reducing reagent and a catalytic reactor ( 34 ) comprising: an injection valve having a low pressure or high pressure fuel injection valve ( 32 ), which in the exhaust duct ( 20 ) and cooled by the NO _x reducing reagent; means for detecting NO _x residual concentrations in the exhaust gas; a facility ( 40 ) to generate a signal representing the detected NO _x residual concentrations in the exhaust gas; whereby the plant is controlled by means of a control system ( 40 ), which is integrated in an engine management system (EMS).