EP0969915A1 - Procede de reduction d'oxyde d'azote contenus dans des gaz d'evacuation contenant de l'oxygene, en particulier dans des gaz d'echappement de moteurs a combustion interne - Google Patents

Procede de reduction d'oxyde d'azote contenus dans des gaz d'evacuation contenant de l'oxygene, en particulier dans des gaz d'echappement de moteurs a combustion interne

Info

Publication number
EP0969915A1
EP0969915A1 EP98965777A EP98965777A EP0969915A1 EP 0969915 A1 EP0969915 A1 EP 0969915A1 EP 98965777 A EP98965777 A EP 98965777A EP 98965777 A EP98965777 A EP 98965777A EP 0969915 A1 EP0969915 A1 EP 0969915A1
Authority
EP
European Patent Office
Prior art keywords
reducing agent
exhaust gas
gas
metering
solid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP98965777A
Other languages
German (de)
English (en)
Inventor
Gunter GÜRICH
Bernhard LÜERS
Manuel Hernier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
FEV Europe GmbH
Original Assignee
FEV Motorentechnik GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE19845944A external-priority patent/DE19845944A1/de
Application filed by FEV Motorentechnik GmbH and Co KG filed Critical FEV Motorentechnik GmbH and Co KG
Publication of EP0969915A1 publication Critical patent/EP0969915A1/fr
Ceased legal-status Critical Current

Links

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
    • B01D53/46—Removing components of defined structure
    • B01D53/54—Nitrogen compounds
    • B01D53/56—Nitrogen oxides
    • B01D53/565—Nitrogen oxides by treating the gases with solids
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/20—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being a flow director or deflector
    • 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
    • F01N2610/06—Adding substances to exhaust gases the substance being in the gaseous form
    • 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
    • F01N2610/08—Adding substances to exhaust gases with prior mixing of the substances with a gas, e.g. air
    • 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
    • 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 a method for reducing nitrogen oxides in an oxygen-containing exhaust gas stream, in particular in exhaust gases from internal combustion engines, which are subjected to a catalytic exhaust gas aftertreatment in a catalytic converter.
  • the catalytic aftertreatment of oxygen-containing exhaust gases from internal combustion engines to reduce the NO x emission requires a so-called selective catalytic reduction, which makes it possible to in the exhaust gas with the nitrogen oxides, ie NO and N0 2 molecular nitrogen (N 2 ), carbon dioxide (C0 2 ) and Form water, in diesel engines, but also in gasoline engines with direct fuel injection. This takes place through the supply of reducing agents, which is difficult, however, with regard to the metering in the required small amounts in highly dynamically operated internal combustion engines in mobile use with fluctuating nitrogen emissions.
  • the reducing agent in powder form on the exhaust side of the internal combustion engine.
  • the powdery reducing agent is supplied by gravity and is introduced into the exhaust pipe with the aid of a mechanical distributor device with blower air support. Dosing the smallest amounts of reducing agents is very difficult in this technique.
  • the use of hygroscopic reducing agents causes considerable problems here, since the flowability is a prerequisite for the proper functioning of such a system.
  • the reducing agent is pumped into the exhaust gas.
  • the reducing agent is broken down into reductive components, so-called fission products, outside the exhaust gas flow.
  • the aim of this procedure is to reduce the reaction speed of the actual reduction step in the reducing agent nitrogen oxide system and to increase it
  • the system can only be used in the case of stationary or almost stationary nitrogen oxide generation because there is a risk of ammonia breakthrough.
  • the solid, nitrogenous reducing agent is converted to ammonia in a pressure-resistant converter.
  • An intermediate storage for ammonia is filled and emptied at intervals.
  • the adaptation of the reducing agent flow to a highly dynamic exhaust gas volume is provided.
  • This system requires a pressure-resistant pressure vessel arrangement for the temporary storage of the problem substance ammonia.
  • the invention has for its object to provide a method of the type mentioned, which does not have the disadvantages discussed above.
  • a reducing agent present as a solid is converted into gas under the action of heat and the gas is broken down thermally and / or catalytically into reductive products in a reaction chamber, which are then admixed with the exhaust gas to be reduced before the catalyst.
  • gas or “gasification” in the sense of the present invention includes both
  • the method according to the invention has the advantage in particular for vehicles that the reducing agent to be used in solid form, ie. H. can be carried with the least amount of inventory.
  • the further advantage is that the gas generated and required for the catalytic reaction in the exhaust gas catalytic converter can be admixed to the exhaust gas to be reduced in a much simpler manner, with corresponding additions in the course of gasification of the solid also making it possible to meter in the smallest quantities.
  • reducing agents can also be used in the liquid or gaseous phase, which are in a storage container and / or in a Do not disintegrate into dosing products. Problem substances, such as ammonia, are then not stored, but only generated when they are converted into reductive products in the course of the process. When it is stored, the reducing agent does not break down into fission products which are ineffective for the reduction of NO x .
  • the decomposition of the reducing agent converted into gas form into reductive products can now be carried out according to the invention either by a pyrolysis reaction under further heat or by the supply of water, in particular water vapor, by a catalytically supported hydrolysis reaction.
  • the hydrolysis reaction has the advantage that, on the one hand, the exhaust gas temperatures are sufficient or at least only a slight increase in temperature is necessary. On the other hand, there is the advantage that the water vapor content in combustion exhaust gases is usually sufficient, so that no or only a small amount of additional water has to be added in order to be able to carry out the hydrolysis reaction.
  • the amount of gas required is regulated by changing the heating power acting on the solid.
  • the gas volume flow can be changed, for example, via a controllable metering valve.
  • the amount of gas required is regulated by changing the solids supply.
  • a combination of the two measures is particularly advantageous, so that the minimum heating power required for gasification of the solid is applied and then the amount of gas required can be increased accordingly by increasing the heating power and / or increasing the supply of solids, and vice versa, so as a function of the regulate the supply of the reductive products present in gaseous form in each case as a result of the operational exhaust gas quantity.
  • the amount of exhaust gas components, in particular NO x and / or reductive products of the reducing agent, in particular amide ions and / or isocyanic acid and / or ammonia is recorded behind the catalyst.
  • the reducing agent is only introduced into the exhaust gas in the amount required in each case.
  • the amount of reductive products behind the catalyst should be "zero" if possible. If increased values are found, the supply of reducing agent must be reduced. If the proportions of NO x are recorded , regulation of the supply of reducing agent is also possible. In an embodiment, it is expedient if the reducing agent is metered in via a control device as a function of the NO x values detected.
  • the reducing agent is metered in via a control unit as a function of engine-specific characteristic maps via the No x contents and / or the HC contents in the exhaust gas. If such empirically determined maps are "stored" in the engine control system, then it is possible to carry out the metering depending on the operation even without complex exhaust gas sensors, since these maps are in operation in the
  • Control device read” and metered in for the respective operating point in the map "stored" amount of reducing agent.
  • a time-variable clock frequency or a varying opening cross section of a metering valve can also be determined as a map and stored in the control device.
  • the specific gasification rate of the reducing agent as a function of the heating output and / or heating temperature can be set up as a map and stored in the control device and used for metering in the gasified reducing agent.
  • a control signal for metering can be generated in the control device, which leads to an optimal supply of the reducing agent gas quantity, in which an optimal exhaust gas aftertreatment is achieved.
  • the gas is premixed in a carrier gas in the form of exhaust gas and / or air and the premixing is mixed into the exhaust gas stream.
  • the gas generated by the action of heat from the reducing agent present as a solid is thermodynamically adjusted so that it has a slight overpressure compared to the exhaust gas pressure, so that here a "natural", given the heating power and / or given amount of solid in the simplest way dependent pressure drop is generated.
  • This pressure drop generated by the heating power enables the gas to be metered precisely over time.
  • the volume of gas generated by the effect of heating builds up a correspondingly low overpressure in the container, for example 0.5 bar above the exhaust gas counterpressure, which then allows the gas to flow off.
  • the heating effect can be applied to the reducing agent by supplying heat via the container wall and / or at least one heating element inside the container.
  • the differential pressure between the heating chamber in which the gasification takes place and the exhaust pipe can be measured and regulated via the heating power. It is then possible to measure precisely metered quantities of reducing agents via the metering valve, which operates in an advantageously clocked manner.
  • the admixture to the exhaust gas is carried out with the aid of a pressure gradient between the gasification region and the exhaust gas flow.
  • This can be done in a simple manner by designing the exhaust duct at the admixing point in the manner of a Venturi tube, so that the reduction in static pressure due to the increase in velocity in the exhaust gas stream generates the corresponding pressure drop with respect to the gasification device and the outflow of the generated gas is promoted.
  • the reducing agent gas can be mixed in with the aid of a partial flow of exhaust gas or air, which is generated by a corresponding fan.
  • Reducing agent takes place via a controllable metering device, in particular a metering valve, which is controlled via the control device. direction is controlled.
  • the metering can take place, for example, by opening the metering valve in cycles.
  • the container can be provided as a refill container or in a particularly advantageous manner as a replacement cartridge. This results in a unit that is easy to handle and only has to be plugged on, the closure being opened and, at the same time, an outwardly tight connection to the treatment device being created.
  • corresponding fittings can also be introduced into the container filling, such as level sensors, mechanical discharge devices, heating devices, possibly in connection with gas extraction devices.
  • Replacement cartridges can also be used as a cartridge battery in order to cover the longest possible operating periods.
  • solid reducing agent cyanuric acid and / or melamine and / or urea and / or biuret and / or trioret and / or other nitrogenous reducing agents are used individually or in mixtures which, after a phase change from solid to gaseous, are used can be broken down into reductive products if more energy is supplied or several of these components can be used.
  • cyanuric acid has proven particularly expedient here.
  • the solid reducing agent can be used in a free-flowing state.
  • the free-flowing reducing agent can be conveyed from a storage container directly via mechanical systems into a heating device and / or can be located overall in the heating device.
  • the solid reducing agent is used in the form of a compact.
  • Such compacts can be made up, for example, as a stack of tablets or as rods or the like which are then advanced accordingly against the heating device and / or are located in the heating device as a whole.
  • FIG. 1 schematically shows the implementation of a reducing agent in a pyrolysis reaction to produce reductive products
  • Fig. 2 is a flow diagram for a first embodiment of a method for generating and supplying gaseous reductive products according to the process flow according to.
  • Fig. 1
  • Fig. 5 shows a practical arrangement for installation on a vehicle to carry out the method acc. Fig. 4.
  • Fig. 1 the basic reaction of the conversion of a solid reducing agent, here cyanuric acid, into the gas form and then the decomposition into a reductive product and its admixture to the reducing exhaust gas and the subsequent exhaust gas aftertreatment in a catalyst is shown schematically.
  • cyanuric acid heat with a temperature level of 300 to 450 ° C is required for the conversion from a solid form into the gas form.
  • the gaseous cyanuric acid is converted into 3 (HNCO) by a further supply of heat,
  • Isocyanic acid A further heat supply with a temperature level of more than 400 ° C is required here. Isocyanic acid is then again heated with a temperature level of 450 to 750 ° C in a possibly catalytically supported pyrolysis reaction converted into the required reductive products, which is formed in the reaction of isocyanic acid essentially by the NH (amide ion), which is then mixed into the exhaust gas.
  • the subsequent catalytically supported reaction between NH and NO x in the exhaust gas catalytic converter here requires a temperature level of the exhaust gas of more than 400 ° C. Such a temperature level is given, for example, in stationary systems, in particular combustion engines operated in a steady state at full load.
  • the flow diagram according to FIG. 2 shows an exhaust pipe 1 of an internal combustion engine, for example a diesel engine, which is provided with a catalytic converter device 2 which has a selective reduction catalytic converter. Exhaust gas flows through exhaust gas line 1 in the direction of arrow 3.
  • an internal combustion engine for example a diesel engine
  • a catalytic converter device 2 which has a selective reduction catalytic converter. Exhaust gas flows through exhaust gas line 1 in the direction of arrow 3.
  • a device 4 for supplying a reducing agent present as a solid is assigned to the exhaust gas line 1.
  • the device 4 essentially consists of a storage container 5 for a reducing agent 6 present as a solid.
  • the reducing agent 6 can be in free-flowing form or as a solid.
  • the storage container 5 can be provided with a conveying device 7, with which the solid 6 is conveyed in the direction of an outlet opening 8.
  • the conveyor 7 is schematically represented by a press plate 7.1 with a loading spring 7.2.
  • the pressure plate 7.1 can also be provided with a seal, so that pressure is exerted on the rear space, for example, via a
  • Branch duct with exhaust gas can be made.
  • the reservoir 5 must be designed in its transition area to the outlet opening 8 so that no "bridges" can form.
  • a mechanical dosing device 8.1 can be provided in the area of the outlet opening 8, which doses volumetrically in the case of free-flowing reducing agent or scrapes off corresponding particle quantities in the case of a solid body via a drive.
  • the reducing agent itself must not be used for gluing or tend to bake, but must keep its flowability even with changing external conditions, such as the change of season. If the arrangement is not connected to the motor and vibrations are thereby introduced into the container 5, the arrangement of a corresponding vibrator can be expedient, which is controlled periodically and prevents bridging.
  • the dosing device 8.1 opens into a chamber-shaped heating device 9 which has a porous, heatable wall which comes into direct contact with the supplied reducing agent, here represented only by a schematic heating coil 9.1, so that the gasification process can take place here.
  • the mechanical dosing device is not required.
  • the allocation of the storage container and the heating device must then be designed in such a way that the reducing agent is pressed onto the heating device via a corresponding conveying device.
  • the gasification of the reducing agent can be effected or supported by heating the container walls, which are then thermally insulated from the outside, or by means of heating elements immersed in the container filling, as indicated in FIG. 4 with the heating coil 12.1.
  • the gaseous reducing agent now enters from the heating device 9 into a metering chamber 10, the walls of which are provided with thermal insulation 11 and the wall area is provided with a further heating device 12, so that a condensation of the gaseous reducing agent on the walls is avoided.
  • the metering chamber 10 is followed by a reaction chamber 13 which is provided with a further heating device 14 and which makes it possible to thermally break down the reducing agent gas entering the reaction chamber 13 from the metering chamber 10 into its reductive components.
  • cyanuric acid ie (HNCO) 3
  • the reaction mer 13 according to the diagram acc. Fig. 1 with the help of the additional heat supply by the heating device 14 via the decomposition into HNCO and into the faster reducing NH generated the reductive product.
  • the supply of the gas to the reaction chamber 13 can be regulated via a metering valve 10.1 (FIG. 2), which operates in an analog or clocked manner.
  • the gas can be discharged directly from the reaction chamber 13 via a mixing pipe 15.
  • the mouth of the admixing pipe 15 can be provided with a mechanical distribution device 16 in order to bring about a distribution that is as uniform as possible over the entire flow cross section before entering the catalytic converter 2.
  • the distribution device can be formed, for example, by a baffle plate at the outlet opening. It is appropriate for a swirl body 16.1 to be arranged in the exhaust pipe 1 at least in front of the mouth of the admixing pipe.
  • reaction chamber 13 is one
  • premixing chamber 17 which is connected via a feed pipe 18 for a carrier gas.
  • Hot air and a partial exhaust gas stream can be used as carrier gases, which are provided via appropriate sources and with the appropriate pre-pressure.
  • Exhaust gas as a carrier gas can be removed upstream from the exhaust pipe 1.
  • part of the oxygen-containing carrier gas can thus be premixed with the gaseous reducing agent flowing in from the reaction chamber 13 and the premixing can then be introduced into the exhaust pipe as described above due to the pressure difference between the mouth 16 of the supply pipe 15 and the (higher) pressure in the premixing chamber 17 can be initiated.
  • An controllable valve 19 in front of the premixing chamber 17 can prevent an uncontrolled outflow of the reducing agent, for example in the event of a vehicle fire.
  • All "hot” chambers and the connecting channels are expediently surrounded by the insulating jacket 11.
  • the overall arrangement is connected to a control device 20, which in turn can be connected to the engine control.
  • the heating power of the heating device 9 is controlled via the control device 20, the supply of heating energy being controlled via a corresponding temperature sensor 21. 2, the heating energy can be optimally controlled via a pressure sensor 26.
  • Engine-specific and / or specific maps of the aftertreatment device, NO x indicators and / or HC maps for all operating states can be "stored" in the control, so that the supply is on Reducing agent can be regulated according to the specifications of the maps.
  • both the heating power of the heating device 12 of the metering chamber 10 and the heating power of the heating device 14 of the reaction chamber 13 are each controlled and regulated accordingly by temperature sensors 22 and 23, and the valve 19 is controlled.
  • a further metering valve 10.1 can be arranged, which can also be designed as a check valve that opens only when needed, so that the heating of the reaction chamber 13 is only switched on when needed, while via the heater in the Heating chamber 9 a basic temperature level is maintained.
  • a basic pressure level can be maintained via a pressure sensor 26.
  • the regulation of the supply quantities of solid reducing agent from the storage container 5 is always expedient when a lower and an upper limit temperature is reached for the heating device 9 and a change in the quantity of gas to be generated is only possible by changing the supply of solids.
  • Another way to reduce the amount heating capacity is a subdivision of the storage container into individual segments filled with reducing agent, which can be charged separately with heating power, so that not all of the reducing agent in the storage container has to be brought to a higher temperature level.
  • the decay products of the reducing agent used in the exhaust gas stream can be detected, in particular amide ions and / or isocyanic acid and / or ammonia or also nitrogen oxides and then via the control device 20 a regulation of the heating power of the heating device 9 and / or a regulation of the Quantity supply of reducing agent from the storage container 5 can be influenced and / or dosing by means of the metering valve 10.1.
  • the fill level in the storage container 5 can be checked via a sensor 25, so that when a minimum quantity is reached a corresponding signal is generated which indicates to the operator the need for refilling.
  • the heating output can also be monitored, for example via the duration or frequency of activation of the metering valve. If the output rises above a limit value, a signal to replace the cartridge can be given.
  • FIG. 3 schematically shows another basic reaction of the conversion of a solid reducing agent, here cyanuric acid, into the gas form and then the decomposition into a reductive product and its admixture with the reducing exhaust gas and the subsequent exhaust gas aftertreatment are shown in a catalytic converter.
  • cyanuric acid heat with a temperature level of 300 to 450 ° C is required for the conversion from a solid form into the gas form.
  • steam By supplying steam at 150 to 350 ° C, the gaseous cyanuric acid is converted to NH 3 (ammonia), which takes place as a possibly catalytically supported hydrolysis reaction.
  • the ammonia obtained as a reductive product is then mixed into the exhaust gas.
  • the subsequent catalytically supported reaction between NH 3 and NO x in the exhaust gas catalytic converter requires a temperature level of the exhaust gas of only more than 120 ° C. Such a temperature level is given, for example, in the case of non-stationary internal combustion engines in vehicles.
  • Fig. 4 shows in the form of a flow chart the process according to the process flow according. Fig. 3, as is particularly useful in vehicle engines with changing load requirements.
  • the process is based on the use of an exchangeable cartridge 5.1 with a reducing agent filling. It is expedient here if the heating and gasification device 9/10 is brought into direct contact with the reducing agent filling.
  • the closed cartridge 5.1 is connected to the device in a pressure-tight manner, the heating device 12.1 touching the interface or penetrating into the reducing agent filling 6.
  • the resulting reducing agent gas which is under a corresponding excess pressure, can then be fed into the.
  • Exceed reaction chamber 13 The arrangement of a throttle point 10.2 in the transition between the heating and gasification device 9/10 and the reaction chamber 13 is expedient for the precise metering.
  • all “hot” chambers and connecting channels, including the cartridge 5.1, are surrounded by an insulating jacket, which here is for simplification the drawing is not shown.
  • the reaction chamber 13, for example when using cyanuric acid essentially converts it into ammonia as a reductive product.
  • water-containing waste gas is fed to the reaction chamber 13 via a feed line 18.1, in order to bring about hydrolysis.
  • a hydrolysis catalytic converter 13.1 can further assist the decomposition, so that here the degree of conversion, the reaction temperature and the residence time of the gas can be optimized during the transformation into reductive components in the reaction chamber 13
  • FIG. 5 a practical arrangement of a device for carrying out the reaction method according to FIG. 3, working in accordance with the flow diagram according to FIG. 4, is shown schematically in its individual components.
  • a storage container 5 preferably in the form of an exchangeable cartridge for a reducing agent in solid form (free-flowing or solid)
  • the porous base designed as a heating device 9 is connected to the metering chamber 10, in which the additional heating device 12 is arranged, by means of which this space is heated in such a way that resublimation of the gas generated is avoided.
  • Via the controlled metering valve 10.1 Via the controlled metering valve 10.1, a correspondingly measured amount of gas is converted into a hydrolysis
  • Reaction chamber 13.1 trained catalyst which is heated via the heating device 14 in order to bring about the decomposition of the gas here.
  • a partial exhaust gas stream as indicated in FIG. 4 as partial exhaust gas stream 18.1, can be introduced in front of the reaction chamber 13 through a discharge pipe 1.1 from the exhaust pipe 1.
  • the water content in the exhaust gas is usually sufficient for the hydrolysis reaction of the gas with the water to bring about the desired formation of reductive products, as shown in FIG. 3 for cyanuric acid as a reducing agent. If necessary, small amounts of water vapor can be injected.
  • the gaseous reducing agent present in the form of reductive products exits the reaction chamber 13 via the feed pipe 15 into the exhaust gas nal 1 on.
  • the exhaust gas is swirled in the feed area in such a way that a practically uniform distribution over the entire flow cross section in the exhaust gas line 1 is achieved.
  • a second cartridge 5.3 which is connected to the metering chamber 10 of the first cartridge 5 by means of a feed line 28 and in which a check valve 29 is arranged, a correspondingly larger amount of reducing agent can be made available.
  • the second cartridge 5.3 is also equipped with a heating device 9 for generating a reducing agent gas and a metering chamber 10 with an additional heating device 12.
  • the arrangement acc. Fig. 5 can also be modified so that in addition to an "active" cartridge 5 for normal operation, a second cartridge for the cold start phase is arranged, which is only switched on in the start phase. This second
  • the heating capacity of the cartridge can be designed so that corresponding amounts of reducing agent gas are available very quickly.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Combustion & Propulsion (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Toxicology (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Catalysts (AREA)

Abstract

L'invention concerne un procédé de réduction d'oxydes d'azote contenus dans un courant de gaz évacués contenant de l'oxygène, en particulier dans des gaz d'échappement de moteur à combustion interne qui sont soumis à un traitement catalytique dans un catalyseur. Ledit procédé se caractérise en ce qu'un agent de réduction, présent sous la forme d'une matière solide, est converti en gaz sous l'effet de la chaleur, le gaz ainsi formé étant décomposé dans une chambre de réaction, thermiquement et/ou catalytiquement, en produits réducteurs qui sont alors mélangés aux gaz d'échappement devant subir la réduction.
EP98965777A 1997-12-12 1998-12-07 Procede de reduction d'oxyde d'azote contenus dans des gaz d'evacuation contenant de l'oxygene, en particulier dans des gaz d'echappement de moteurs a combustion interne Ceased EP0969915A1 (fr)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
DE19755376 1997-12-12
DE19755376 1997-12-12
DE19821494 1998-05-13
DE19821494 1998-05-13
DE19845944 1998-10-06
DE19845944A DE19845944A1 (de) 1997-12-12 1998-10-06 Verfahren zur Reduktion von Stickoxiden in sauerstoffhaltigen Abgasen, insbesondere Abgasen von Verbrennungsmotoren
PCT/EP1998/007937 WO1999030811A1 (fr) 1997-12-12 1998-12-07 Procede de reduction d'oxyde d'azote contenus dans des gaz d'evacuation contenant de l'oxygene, en particulier dans des gaz d'echappement de moteurs a combustion interne

Publications (1)

Publication Number Publication Date
EP0969915A1 true EP0969915A1 (fr) 2000-01-12

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EP98965777A Ceased EP0969915A1 (fr) 1997-12-12 1998-12-07 Procede de reduction d'oxyde d'azote contenus dans des gaz d'evacuation contenant de l'oxygene, en particulier dans des gaz d'echappement de moteurs a combustion interne

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Country Link
EP (1) EP0969915A1 (fr)
JP (1) JP2001523165A (fr)
WO (1) WO1999030811A1 (fr)

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JP4854122B2 (ja) * 2001-03-16 2012-01-18 東京瓦斯株式会社 還元剤添加量制御方法
US7849674B2 (en) 2003-09-19 2010-12-14 Nissan Diesel Motor Co., Ltd. Exhaust emission purifying apparatus for engine
US7614213B2 (en) 2003-09-19 2009-11-10 Nissan Diesel Motor Co., Ltd. Engine exhaust emission purification apparatus
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EP1712754A4 (fr) 2004-02-02 2010-09-29 Nissan Diesel Motor Co Dispositif de purification des gaz d'echappement d'un moteur à combustion interne
WO2005073529A1 (fr) 2004-02-02 2005-08-11 Nissan Diesel Motor Co., Ltd. Dispositif de purification des gaz d’echappement d’un moteur
JP3715985B1 (ja) 2004-10-29 2005-11-16 日産ディーゼル工業株式会社 液体還元剤噴射ノズル構造
JP4290110B2 (ja) * 2004-11-04 2009-07-01 日産ディーゼル工業株式会社 排気浄化装置
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JP5020028B2 (ja) * 2007-11-09 2012-09-05 三菱ふそうトラック・バス株式会社 排気浄化装置
JP5232613B2 (ja) 2008-12-08 2013-07-10 三菱重工業株式会社 排ガス浄化装置
JP5276460B2 (ja) * 2009-01-30 2013-08-28 三菱重工業株式会社 排ガス浄化装置
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JP5846487B2 (ja) * 2011-12-13 2016-01-20 三菱自動車工業株式会社 排ガス浄化装置
KR101989111B1 (ko) * 2017-05-23 2019-06-13 엘지전자 주식회사 질소산화물 저감장치
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WO1999030811A8 (fr) 1999-08-12
JP2001523165A (ja) 2001-11-20

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