CN101006252A - Reductant addition in exhaust system comprising nox-absorbent - Google Patents

Reductant addition in exhaust system comprising nox-absorbent Download PDF

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Publication number
CN101006252A
CN101006252A CNA2005800279733A CN200580027973A CN101006252A CN 101006252 A CN101006252 A CN 101006252A CN A2005800279733 A CNA2005800279733 A CN A2005800279733A CN 200580027973 A CN200580027973 A CN 200580027973A CN 101006252 A CN101006252 A CN 101006252A
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CN
China
Prior art keywords
vent systems
absorbing agent
reducing agent
systems according
catcher
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Pending
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CNA2005800279733A
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Chinese (zh)
Inventor
J·T·吉尼
M·V·特维格
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Johnson Matthey PLC
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Johnson Matthey PLC
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Priority claimed from PCT/GB2004/002643 external-priority patent/WO2004113691A2/en
Application filed by Johnson Matthey PLC filed Critical Johnson Matthey PLC
Publication of CN101006252A publication Critical patent/CN101006252A/en
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Abstract

An exhaust system for a vehicular lean-burn internal combustion engine comprises a NOX-absorbent, a reductant injector (78) disposed upstream of the NOX-absorbent and means (50), when in use, for controlling reductant addition, wherein the reductant addition control means supplies reductant to the NOX-absorbent at all vehicle speeds in a duty cycle at a rate which is predetermined to correlate with a desired NOX conversion at the average duty cycle speed of the vehicle.

Description

Comprise NO xThe interpolation of the reducing agent in the vent systems of absorbing agent
Technical field
The present invention relates to a kind of NO of comprising xThe vent systems that is used for lean-burn internal combustion engine of absorbing agent, and relate in particular to a kind of for the N that regenerates OxAbsorbing agent and with NO xBe reduced to N 2Purpose and control the method for the interpolation of the reducing agent in this vent systems.
Background technique
For example, learn a kind of vent systems that is used for such as the lean-burn internal combustion engine of diesel engine or gasoline engine from EP 0560991, this vent systems comprises NO xAbsorbing agent.
As used in this, " NO xCatcher " be to comprise NO xThe catalyzer of absorbing agent and be used for NO is oxidized to NO 2Catalyzer.NO xCatcher is also referred to as " thin NO xCatcher " or " LNC ".
Typical NO xTrap formulation comprises: oxide catalyst composition, as platinum (Pt); NO xAbsorbing agent is as the compound of alkali metal (for example potassium and/or caesium); Alkaline earth metal compounds such as barium or strontium; Or typically, such as the compound of the rare earth metal of lanthanum and/or yttrium; And reducing catalyst, for example rhodium.Be generally used for NO for this prescription in lean-combustion engine operation period xA kind of mechanism of storage is that in the first step, NO reacts to form NO with the locational oxygen of the active oxidation on platinum 2Second step comprised the storage medium absorption of N O by the inorganic nitrate form 2
Though inorganic NO xStorage component typically exists as oxide, and should be understood that is having air or comprising CO 2And H 2Under the situation of the exhaust of O, it also can be the form of carbonite or hydroxide.
When motor under the enriching condition or when at high temperature moving discontinuously, that the nitrate material becomes thermodynamic instability and decompose, produce NO or NO 2Under denseer condition, these NO xMaterial is reduced to N by carbon monoxide, hydrogen and hydrocarbon 2, this can take place on reducing catalyst.
Comprise NO xThe purpose of the vent systems of catcher is to improve the Economy of motor, satisfies relevant emission standards simultaneously, for example Europe IV.
For the NO that regenerates xThe NO that catcher and reduction discharge xPurpose and the system that controls the interpolation of reducing agent is known, but often require very complicated controlling mechanism (regimes), this controlling mechanism comprises the processor of a plurality of sensors inputs and operation complicated algorithm.As a result, this system is very expensive.
EP-B-0341832 (by with reference to being contained in this) has illustrated a kind of method that is used for the particulate (PM) of burning diesel oil machine exhaust, and this method is included on the catalyzer NO in the exhaust is oxidized to NO 2, from exhaust gas filter PM with at NO 2In at the following PM that filters of burning up to 400 ℃.This system can buy from Johnson Matthey, and as CRT On market, sell.
We have investigated regeneration NO xThe method of absorbing agent, and we find that use comprises NO xThe vent systems of absorbing agent and need just can not satisfy relevant emission standards such as the complex equipment the network of the processor of algorithm programming and sensor input is as Europe IV.This discovery is particularly useful for the market of retrofiting.
Summary of the invention
According to a first aspect of the invention, provide a kind of vent systems that is used for automobile-used lean-burn internal combustion engine, this vent systems comprises NO xAbsorbing agent, be arranged in NO xThe reducing agent injector of absorbing agent upstream and being used to is in use controlled the device of the interpolation of reducing agent, and wherein reducing agent adds under control gear all speed of a motor vehicle in work cycle and with a speed reducing agent supplied to NO xAbsorbing agent, this speed are predetermined to be and the NO that wishes under the average duty cycle speed of vehicle xConversion is associated.
A first aspect of the present invention is particularly useful for the remodeling market such as the limited operation circuit vehicle of bus and refuse collection vehicle.Thought is to determine under average duty cycle speed at NO xNeed what kind of reducing agent injection rate in the absorbing agent, with the NO of reduction selected amount x, for example 90%.For example, work as NO xAbsorbing agent is NO xDuring the composition of catcher, hydrocarbon (HC) fuel that SC system controller can be arranged to produce in use continuous beat and amount sprays, and for example per minute sprayed 2 seconds.SC system controller also can be arranged to provide long dense HC fuel impulse once in a while, to guarantee NO xThe basic holomorphosis of catcher has more frequent shorter enriching pulse sequence subsequently to keep NO xThe storage capacity of catcher.The detail of injection strategy depends on vehicle and work cycle thereof.
Under the speed that is higher than average duty cycle speed, more NO will be arranged xBigger mass air flow, and because the reducing agent deficiency, so NO xOverall conversion will descend.Yet because fair speed will be unlikely, for example in the bus of down town, so system can satisfy NO in whole driving circulation xEmission standard and the fuel consumption that do not increase; Equally, when the speed of a motor vehicle drops to when being lower than average duty cycle speed, HC can be discharged from, but on work cycle on average, system can satisfy the emission standard for HC.The correlation of HC injection rate and average duty cycle speed can be designed to be suitable for application-specific, for example will expect the intown bus in Manchester (Britain) and meet with and London (Britain) intown different work cycle.
In an embodiment of first aspect, at reducing agent injector and NO xBe furnished with oxidation catalyst between the absorbing agent, be used for increasing NO for regeneration xThe temperature of catcher and/or remove deoxidation to guarantee to be used for NO from exhaust xThe dense exhaust of the regeneration of absorbing agent.
In specific layout, described NO xThe downstream of the layout that the EP-B-0341832 that catcher and being used for carries the system layout of reducing agent to mention in the above illustrates.That is to say, be used for NO is oxidized to NO 2Catalyzer follow the filter of selectively catalysis, reducing agent injector has been followed NO then xAbsorbing agent.
In one embodiment, the NO that uses among the present invention xAbsorbing agent is NO xThe composition of catcher.
If otherwise explanation, the catalyst coated of using among the present invention is on high surface area carrier monomer, and this carrier monomer is made by metal or pottery or carbofrax material, for example steinheilite.A kind of common layout is a honeycomb ceramics, per square inch 100-600 unit (cpsi) run through monomer structure, as 300-400 cpsi (15.5-93.0 unit cm -2, 46.5-62.0 unit cm for example -2).
Internal-combustion engine can be diesel engine or gasoline engine, as gasoline direct injection engine.Diesel engine can be light duty engine or the heavy-duty engine that limits as by relevant laws and regulations.
Reduce NO in the exhaust of automobile-used lean-burn internal combustion engine according to a second aspect of the invention xMethod be included in NO xIn the absorbing agent from exhaust absorption of N O x, make NO under all speed of a motor vehicle in work cycle xAbsorbing agent contacts with reducing agent with regeneration NO xAbsorbing agent and with NO xBe reduced to N 2, reducing agent speed of spraying and the NO that under average duty cycle speed, wishes wherein xConversion is associated.
Description of drawings
In order more fully to understand the present invention, embodiments of the invention are described with reference to the accompanying drawings, in the accompanying drawings:
Fig. 1 illustrates schematic system according to a first aspect of the invention;
Fig. 2 draws fuel quantity to the schematic graph of time, is illustrated in the fuel injection strategy that uses in the system of Fig. 1;
Fig. 3 is a work embodiment's of the present invention schematic representation;
Fig. 4 be illustrate among the embodiment of Fig. 3 as the upstream air/fuel of the function of road speeds plotted curve than (AFR);
Fig. 5 is the embodiment NO under idling operation that illustrates for Fig. 3 xThe plotted curve of measurement result;
Fig. 6 is the plotted curve that illustrates for the corresponding system temperature under idling operation of the track among Fig. 5;
Fig. 7 is the NO of embodiment under 40mph that illustrates for Fig. 3 xThe plotted curve of measurement result;
Fig. 8 is the plotted curve that illustrates for track shown in Figure 7 corresponding temperature measurement result under 40mph; With
Fig. 9 illustrates the NO as the function of road speeds for the system of Fig. 3 xThe plotted curve that transforms.
Embodiment
In system shown in Figure 1 50, the 52nd, regulating system controller (CSC), the 54th, main switch, the 56th, alternator, the 58th, blocking capacitor, the 60th, thermocouple, the 62nd, injection controller (ICU), the 64th, petrolift, the 66th, valve, the 68th, fuel injector, the 70th, positive line of electric force.CSC 52 provides the switch of electric power for ICU 62 if main power switch 54 is connected, motor is as moving by definite from the interchange pulsation (ripple) of the alternator 56 after the blocking capacitor 58, and the output of suitably locating with the thermocouple 60 that detects vent systems is higher than the NO that is used for suitable xNO on the catcher xThe minimum predetermined temperature of reduction.Main switch 54 does not need to be connected to the key on positi.
CSC 52 is designed to produce continuous beat and amount when meeting all three features (detection of main switch position, alternator pulsation and be higher than the delivery temperature of predetermined minimum value) HC sprays.When CSC 52 connected, electric power supplied to jet pump 64 and ICU 62, and ICU 62 operation solenoid valves 66 are to produce a series of pulses to pass through NO in exhaust xEnriching waste gas before the oxidation catalyst of absorption composition upstream.Typically, injection controller will provide long enriching pulse once in a while, to guarantee NO xCatcher is emptied completely substantially, and follows more frequent shorter enriching pulse sequence after this, and for example per minute sprayed 2 seconds, to keep NO xThe storage capacity (see figure 2) of catcher.
This fuel injection rate and the NO that under average duty cycle speed, selects xConversion is associated, and for example 90%.The detail of injection strategy depends on vehicle and work cycle thereof.
Though adopt NO described herein xThe system of catcher very usually is developed to provides simple controlling mechanism should when carry out NO with prediction xTrap regeneration especially is applied under the remodeling situation, and many vehicles have comprised that multiple sensors is to enter data into the ECU of the others that are used to control vehicle operating.By the suitable programming again of ECU, in order to predict residue NO xThe purpose of catcher ability can adopt one or more this existing sensor inputs.This connects including, but not limited to: the state by detecting suitable clock apparatus from key or time of the predetermined or prediction of the process of regenerating last time; Air-flow on the TWC or mainfold vacuum; Ignition timing; Engine speed; Throttle position; Exhaust redox composition for example uses lambda sensor (lambda sensor), preferably linear oxygen sensors; Fuel injection amount in the motor; Comprise under the situation in exhaust gas recirculation (EGR) loop the position of EGR valve and detected thus EGR amount at vehicle; Engine coolant temperature; With comprise NO in vent systems xUnder the situation of sensor, NO xThe NO that catcher upstream and/or detected downstream arrive xAmount.When using clock embodiment, can regulate the time of estimating subsequently in response to the data input.
Only provide following detailed example by illustration.
Example
The vent systems (10) (being shown in Fig. 3) that coupling has 6 liters of turbosupercharged engines and comprises the single-deck bus of engine turbine (12) is modified to comprise and is used for No. three shunts (14) among of three parallel arms (16) are transferred in exhaust, blast air in each arm is a uniform flow, and the type of described single-deck bus has been passed through European stage (European Stage) 1 emission limit set.Each arm (16) comprises the chamber (18) that comprises oxidation catalyst (20), and this oxidation catalyst has been followed NO xCatcher (22).Air-flow is then at NO xThe combined downstream of catcher, and all blast air is discharged NO through " purification " oxidation catalyst (24) to remove before being directly delivered to atmosphere in exhaust xAny unburned hydrocarbon (HC) of catcher.Be positioned with the fuel injector (26) that comprises fuel solenoid (28) in each oxidation catalyst (20) front, NO arranged in bypassing exhaust device (14) front xSensor (29), NO xThere is the NO of combination the catcher back x/ air-fuel ratio sensor (30), and have in the outlet port of oxidation catalyst (20) front and back and reactor the thermocouple of measuring temperature (T1, T2, T3, T4).Oxidation catalyst (20) and NO xEach all is coated in catcher (22) pottery and runs through on the monomer, and this monomer is 400 unit in -2(62 unit cm -2) and 0.06 in (0.15mm) wall thickness.Oxidation catalyst (20) is that 5.66in (144mm) diameter * 3in (76mm) and volume are 75.5in 3(1.24 liters), NO xCatcher (22) be same diameter but long for 6in (152mm), and " purifications " catalyzer (24) is that 10.5in (267mm) diameter * 3in (76mm) grows, and volume is 260in 3(4.26 liters).
Described test only uses an arm of multiple exhaust to carry out.Vehicle uses the diesel oil operation that comprises 50ppm sulphur, and moves a plurality of time periods under the stabilized speed of idling, 10,20,30 and 40 mph; Fuel sprays at each place of these points, and the air fuel ratio between injection period is definite as among Fig. 4.Experience ground select time and the combination of endurance (sprayed in 2 seconds, each arm per minute once) are because it provides delivery temperature (with NO xCatcher maintains in the effective temperature window) and NO xThe best of breed that transforms.
Fig. 5 illustrates for idling operation from motor and at NO xNO after the catcher xEffulent (ppm) and at NO xThe air fuel ratio of measuring after the catcher.Fig. 6 illustrates for temperature curve mutually of the same period.From Fig. 5 as seen, when the beginning burner oil in the idling phase, air fuel ratio is as decline from rare to dense from the prediction Fig. 3 is desired, and at NO originally xAfter breaking through (breakthrough), visible good NO xTransform.Pass by in time, air fuel ratio remains thin at whole injection events, but still keeps good NO xTransform.The exotherm that produces on oxidation catalyst (T2) helps to keep NO xThe temperature of catcher is within its 220-250 ℃ action pane.Exotherm (T3) also is positioned at and crosses NO xCatcher, the burning of the unreacted gaseous reducing agent of its part origin spontaneous oxidation catalyzer produces.We are interpreted as meaning that with this result the part of this exotherm comes under comfortable this engine idling condition along with the time is increased in NO xThe burning of the unburned fuel drop that reacts on the surface of catcher.Thereby this is because the fuel that the system entry temperature descends and to be not enough to vaporize and to enter, and the air/fuel that detects of rear sensor become than peak value more not obvious and round, a series of depositions, vaporization and the oxidation subsequently of hint fuel droplet.The part that is caused by this incident thickens and also is used to keep observed NO xThe catcher operating efficiency.
Remain on the bus under the stabilized speed of 40mph test the results are shown in Fig. 7 and Fig. 8.Here exhaust flow rate is much higher, but uses and injection flow rate identical under idling, and exhaust is expected to remain thin (Fig. 3) between injection period.Yet, except that the breakthrough peak value when the burner oil first,, on all the other operating times, reduced NO though be unlike under the idling so efficiently x(T2) exotherm on (T3) is lower than sometimes under idling, but because the thermal capacity of the flow rate of the increase of exhaust, so exotherm (T3) also is an obvious results.Therefore exothermic reaction still takes place, and we believe that also this is by the band oxidation catalyst and at NO because of some unburned fuel drop xBurned on the catcher.Though the inlet temperature that oxidation catalyst is higher, but still reckon with retaining of fuel droplet can be taken place is because bigger exhaust flow rate may be carried drop by oxidation catalyst, as by crossing NO xShown the same of the significant exotherm that catcher is measured and observed trap regeneration under tangible thin condition.
Fig. 9 illustrates the calculating average N O as function of speed for system xTrend in the transformation efficiency.Fig. 3 shows dense exhaust conditions do not take place more than about 6mph, but obtained good NO crossing under the thin condition of broad velocity range xTransform.This is especially significant in the scope from the idling to 30mph, and this scope is the most frequently used operating range for the urban district urban transit bus.

Claims (21)

1. a vent systems that is used for automobile-used lean-burn internal combustion engine comprises NO xAbsorbing agent, be arranged in this NO xThe reducing agent injector of absorbing agent upstream (68) and be used to control the device (50) that reducing agent adds when using, wherein said reducing agent add under control gear all speed of a motor vehicle in work cycle and with a speed reducing agent are supplied to described NO xAbsorbing agent, described speed pre-determine into desirable NO under the average duty cycle speed of described vehicle xConversion is associated.
2. vent systems according to claim 1 is characterized in that, described NO xAbsorbing agent is from selecting by alkaline earth metal compound, alkali metal compound, rare earth compound with the group that wherein two or more mixture is formed arbitrarily.
3. vent systems according to claim 2 is characterized in that, described or every kind of alkaline-earth metal is to select from the group of being made up of barium, magnesium, strontium and calcium.
4. vent systems according to claim 2 is characterized in that, described or every kind of alkali metal is to select from the group of being made up of potassium and caesium.
5. vent systems according to claim 2 is characterized in that, described or every kind of rare earth metal is to select from the group of being made up of cerium, yttrium, lanthanum and praseodymium.
6. according to claim 2,3,4 or 5 described vent systems, it is characterized in that described or every kind of alkaline earth metal compound, described or every kind of alkali metal compound is described or every kind of rare earth compound is bearing on the supporting material.
7. vent systems according to claim 6 is characterized in that, described or every kind of supporting is from by selecting aluminium oxide, silica, titanium oxide, zirconium oxide, cerium dioxide and the group that wherein two or more synthesis oxide or mixture are formed arbitrarily.
8. vent systems according to claim 6 is characterized in that, described NO xAbsorbing agent comprises described supporting.
9. require described vent systems according to any one aforesaid right, it is characterized in that, described NO xAbsorbing agent is the NO that comprises the catalyzer that is used for oxidation NO xThe composition of catcher.
10. vent systems according to claim 9 is characterized in that, described NO oxidation catalyst comprises the platinum group metal, is platinum and/or palladium alternatively.
11., it is characterized in that described NO according to claim 9 or 10 described vent systems xCatcher comprises NO xReducing catalyst is preferably rhodium.
12. require described vent systems according to any one aforesaid right, comprise being arranged in described reducing agent injector (68) and described NO xOxidation catalyst between the absorbing agent.
13. require described vent systems according to any one aforesaid right, comprise that the upstream that is arranged in described reducing agent injector is used for NO is oxidized to NO 2Catalyzer.
14. vent systems according to claim 13 is characterized in that, described NO oxidation catalyst is the platinum in the aluminium oxide supporting.
15., comprise the particulate filter that is arranged in the catalysis alternatively between described oxidation catalyst and the described reducing agent injector according to claim 13 or 14 described vent systems.
16., it is characterized in that described NO according to claim 9,10 or 11 described vent systems xCatcher comprises particulate filter.
17. require described vent systems according to any one aforesaid right, comprise control gear, described control gear is the described exhaust gas composition of enriching discontinuously in use, and described NO is used to regenerate xAbsorbing agent.
18. according to being subordinated to claim 9,10 or 11 o'clock the described vent systems of claim 17, it is characterized in that, described control gear in use only when described catalyzer to NO xWhen having activity, reduction just reducing agent is supplied to described NO xCatcher.
19. one kind comprises the diesel engine according to the described vent systems of any one aforesaid right requirement.
20. LD-diesel according to claim 19.
21. the NO in the exhaust of the automobile-used lean-burn internal combustion engine of reduction xMethod, this method is included in NO xAbsorb NO in the absorbing agent from described exhaust x, make described NO under all speed of a motor vehicle in work cycle xAbsorbing agent contacts with the described NO that regenerates with reducing agent xAbsorbing agent and with NO xBe reduced into N 2, reducing agent speed of spraying and the NO that under average duty cycle speed, wishes wherein xConversion is associated.
CNA2005800279733A 2004-06-18 2005-06-16 Reductant addition in exhaust system comprising nox-absorbent Pending CN101006252A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
PCT/GB2004/002643 WO2004113691A2 (en) 2003-06-18 2004-06-18 System and method of controlling reductant addition
GBPCT/GB2004/002643 2004-06-18
GB0428289.3 2004-12-24

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US20110041482A1 (en) * 2009-08-20 2011-02-24 Gm Global Technology Operations, Inc. Method and apparatus for exhaust aftertreatment of an internal combustion engine
JP5862868B2 (en) * 2011-11-18 2016-02-16 三菱自動車工業株式会社 Engine exhaust purification system
CN106807186A (en) * 2015-11-30 2017-06-09 中国国际海运集装箱(集团)股份有限公司 The standby main frame smoke processing system of extra large frock

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