CN105715345A

CN105715345A - Method for monitoring methane oxidation catalyst

Info

Publication number: CN105715345A
Application number: CN201510949767.3A
Authority: CN
Inventors: M.格勒克勒; W.克里斯特尔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-12-19
Filing date: 2015-12-18
Publication date: 2016-06-29
Anticipated expiration: 2035-12-18
Also published as: CN105715345B; FR3030622A1; FR3030622B1; DE102014226675A1

Abstract

In a method for monitoring a methane oxidation catalyst (13) in an exhaust gas after-treatment system for an internal combustion engine (10), at least one injection device (17) for liquid fuel is arranged at the upstream of the methane oxidation catalyst (13) in the exhaust gas after-treatment system. In the monitoring method, a first step is to injecting liquid fuel through the injection device (17). The characteristics of the methane oxidation catalyst (13) with respect to the liquid fuel are observed. Preferably, in the second step of the method, the characteristics of the methane oxidation catalyst with respect to methane conversion can be concluded from the characteristics of the methane oxidation catalyst with respect to the liquid fuel, and thus the activity variation possibly present in the methane oxidation catalyst can be inferred, for instance, from a comparison value.

Description

For the method monitoring methane oxidation catalyst

Technical field

A kind of method that the present invention relates to methane oxidation catalyst for monitoring in the exhausted gas post-processing system of internal combustion engine, wherein, at least one injection apparatus being used for fuel is disposed in the upstream of this methane oxidation catalyst.

Background technology

Known some internal combustion engines, it both can be with the gas containing methane, such as natural gas or methane, it is also possible to runs with the mixture being made up of combustion gas and other fuel, such as diesel fuel.

Gas engine purely usually derives from from gasoline engine or diesel engine, wherein, generally carries out by spark plug for lighting the external source igniting of air/gas mixture.In diesel engine/gas engine, electromotor is in principle based on diesel engine, and its diesel oil operation that both allow for purely also allow for diesel fuel and the hybrid operation of combustion gas.Here, a part for diesel oil calorific value is substituted by combustion gas.Total fuel, that is the igniting of diesel oil-air/gas mixture, completed by diesel fuel composition.Here, can be to 70% by the substitution rate of combustion gas diesel oil substitute fuel.

In all at least part of adnexaes based on the burning of the gas containing methane, occur in that higher, the problem of untreated electromotor discharge of methane thing.First, for reasons of climate protection, it is necessary to reduce discharge of methane thing in the framework of exhaust after-treatment.Known some methane oxidation catalysts (MOC), its methane comprised in oxidation gaseous effluent on the basis of rich in the formula of palladium.Such formula can be used for this, that these formula have palladium (Pd) and platinum (Pt) until the weight ratio of such as 7:1 or the biggest.Other methane oxidation catalyst then formula based on so-called only palladium, such as Pd/ aluminum oxide.But when higher than 400 ° of C, generally the most only just can observe that certain methane converts.For complete oxidation, it is often necessary to far surpass the temperature of 500 ° of C.

The characteristic of methane oxidation catalyst and universal for the characteristic of catalyst can be illustrated by so-called cranking temperature when in view of temperature, under cranking temperature, there occurs the conversion of the predetermined part of the harmful substance comprised in the offgas.Cranking temperature is also frequently referred to as initiation temperature.In showing the most aging catalyst that conversion ratio is deteriorated, required cranking temperature is generally enhanced.About methane oxidation catalyst, cranking temperature the most usually not demonstrates the change trend of fierceness in the new state of catalyst.Required minimum temperature the most usually extends in the range of 400 to 550 ° of C linearly.

Regulations based on legislative bodies, the parts that the waste gas of automobile is relevant must be monitored when in view of emission limit value to be observed.A kind of OBD (On-Board-Diagnose, OBD) is needed for this.The most known adnexa for monitoring catalyst (Ansatz) uses and is being on the position of the upstream and downstream of catalyst the temperature being determined.Typically can assess the integrated degree of exothermic reaction in the catalyst from these temperature values (heat release), thus this degree is applicable to the function of monitoring catalyst.But about methane oxidation catalyst, this monitoring is generally difficult to, because due to the most violent temperature characterisitic of methane oxidation catalyst, the change of heat release value when methane converts in methane oxidation catalyst less has feature.

Summary of the invention

Invention advantage

The method that the invention provides a kind of extremely advantageous monitoring methane oxidation catalyst in the exhausted gas post-processing system of internal combustion engine, the method is particularly suited for the monitoring during OBD (OBD).In the present inventive method at this based on a kind of exhausted gas post-processing system, in this exhausted gas post-processing system, set at least one injection apparatus for the fuel of liquid in methane oxidation catalyst upstream.In first step in the present inventive method, the fuel of liquid is injected in exhaust system by injection apparatus.Methane oxidation catalyst is observed about characteristic produced by the fuel of liquid.In a kind of preferably design in the present inventive method, in the second step of the method, infer, about the characteristic of the fuel of liquid, the characteristic that methane oxidation catalyst converts about methane from methane oxidation catalyst.In this way can be particularly by such as representing some fiducial values of a kind of new methane oxidation catalyst to infer the activity variation that there may exist of methane oxidation catalyst.Additionally can by methane oxidation catalyst by the present invention it is observed that characteristic and/or by the activity variation that can determine that by the present invention, identify methane oxidation catalyst the most normally work and may time whether be expanded (expansion identification).Generally can convert with the methane coming in the present inventive method indirectly to quantify in methane oxidation catalyst.

Make use of in the present inventive method, the characteristic that the characteristic of methane oxidation catalyst converts about methane than methane oxidation catalyst when converting from the fuel of liquid that is especially from diesel fuel or Fuel Petroleum or from the Hydrocarbon of their mixture is more clearly characterized.But because the activity of such as methane oxidation catalyst is deteriorated or aging can also be determined about the conversion of the Hydrocarbon of the fuel from liquid, so by methane oxidation catalyst about the characteristic obtained by the present invention of the fuel of liquid it is concluded that go out the characteristic that methane oxidation catalyst converts about methane, thus deterioration of efficiency can be indirectly confirmed when methane oxidation.

In first step in the present inventive method, particularly determining such a parameter, it characterizes the methane oxidation catalyst starting characteristic (light off characteristics) about temperature.For characterizing the methane oxidation catalyst parameter about the starting characteristic of temperature, particularly to cranking temperature or initiation temperature.Just obtained this parameter when the fuel of liquid is injected into exhaust system, say, that this parameter is obtained by the fuel about liquid, wherein, convert in methane oxidation catalyst from from the fuel of liquid directly to the Hydrocarbon sprayed into of exhaust system.In second step in the present inventive method, preferably methane oxidation catalyst about the characteristic of the fuel of liquid and methane oxidation catalyst about the relatedness between the characteristic of the fuel containing methane on the basis of infer the characteristic that methane oxidation catalyst converts about methane.Here, the fuel containing methane or in the corresponding waste gas component produced starting characteristic can be gone out from the parametric inference of the starting characteristic of the methane oxidation catalyst characterized for the fuel of liquid.Can such as determine the activity variation that there may exist that methane oxidation catalyst converts about methane by this way.

Relatedness between the characteristic of the characteristic of the methane oxidation catalyst in the fuel of liquid and the methane oxidation catalyst in the fuel containing methane, can such as obtain according to experiment.Relatedness can be to be such as stored in the controller of exhausted gas post-processing system with characteristic form or with characteristic field (Kennfeld) or similar form, it is thus possible to about the characteristic measured in the present inventive method of the fuel of liquid from methane oxidation catalyst can infer the methane oxidation catalyst characteristic when methane converts from this characteristic curve or this characteristic field in a straightforward manner and therefore can perform the monitoring to methane oxidation catalyst.

Thus observing the methane oxidation catalyst characteristic about the fuel of liquid in a kind of preferred design in the present inventive method, way is: determine the heat release in methane oxidation catalyst region.One or many temperature survey it preferably is carried out for this.Such as temperature probe (temperature sensor) can be set at the upstream and downstream of methane oxidation catalyst, thus it is observed that the variations in temperature relevant to methane oxidation catalyst is moved towards.Conversion in the catalyst can be assessed in a per se known way from this variations in temperature trend or this heat release, thus can particularly obtain cranking temperature.

As determining alternative or the additional aspects of heat release, diagnosis also carries out (lambda (Lambda)-air coefficient λ) on the basis of lambda probe signal.Need exhausted gas post-processing system to have at least one lambda probe for this.In first step in the present inventive method, the fuel in liquid is injected into exhaust system after or during the period in this case, and methane oxidation catalyst is obtained by lambda probe signal about the characteristic of the fuel of liquid.Here, preferably at least one lambda of the upstream arrangement probe at methane oxidation catalyst and arranged downstream at least another lambda at methane oxidation catalyst are popped one's head in.Spray into exhaust system by the signal of two lambdas probe at the fuel of liquid and can obtain the methane oxidation catalyst characteristic about the fuel of liquid after or during the period.In this design of described method, being injected in exhaust system a kind of the most micro-dense mixture preferably created in the offgas in the upstream of methane oxidation catalyst by the fuel of liquid, this mixture preferably produces under the λ value being slightly less than 1.Move or deviation by comparing the time of the λ value of the upstream at methane oxidation catalyst in the λ value in the downstream of methane oxidation catalyst, can be inferred that the function of methane oxidation catalyst and particularly infer the conversion of Hydrocarbon of the fuel from liquid in methane oxidation catalyst.The methane oxidation catalyst characteristic about the fuel of liquid can be obtained by this way.Therefore the methane oxidation catalyst cranking temperature about the fuel of liquid can such as be determined on the basis of lambda probe signal.

The basis of diagnosis based on lambda probe signal in particular, in that, the time of lambda probe signal moves and is additionally caused by the amount of adsorbed or stored oxygen on a catalyst, and this amount generally reduces when catalyst is aging.Until after methane oxidation catalyst, before methane oxidation catalyst micro-dense gas component fracture time or until being in the time of the signal response of the lambda probe in methane oxidation catalyst downstream, directly adsorbed on methane oxidation catalyst or the amount of stored oxygen is relevant and Hydrocarbon with the fuel from introduced liquid and the kinetics of the conversion of oxygen adsorbed on a catalyst or store relevant.Additionally, the signal of lambda probe is by incomplete or not have the amount of Hydrocarbon of conversion and type to be affected and therefore suffer from the affecting of light off characteristics of methane oxidation catalyst.Lambda probe signal generally moves towards bigger λ value in face of the Hydrocarbon of the long-chain of fracture, because Hydrocarbon does not reacts with remaining oxygen the most on a sensor.In general this be also especially suitable for the thinnest of methane oxidation catalyst downstream and micro-dense gas component.Thus, lambda probe signal is extremely suitable for analyzing the characteristic of methane oxidation catalyst during by the monitoring method of the present invention.

Therefore by the most especially can thus come indirectly to prove that the activity in methane oxidation catalyst is deteriorated or generally speaking performance change when methane converts, that is, the characteristic from the methane oxidation catalyst when the Hydrocarbon of the fuel from liquid converts and the relatedness from the characteristic of the methane oxidation catalyst when the fuel of liquid converts and the characteristic when methane converts infers the characteristic when methane converts.Thus can quantify the methane in methane oxidation catalyst to convert, thus can identify and assess the aging of methane oxidation catalyst.In addition, with can also directly prove in the present inventive method, the most whether methane oxidation catalyst exists, and can expand identification thus to realize methane oxidation catalyst by simple mode especially for this, that is, in fuel injection period or the most such as measure the heat release by methane oxidation catalyst.For this aspect of the present invention, the most forcibly need to infer, about the relatedness between the fuel of liquid and the characteristic converted about methane, the activity variation that the methane oxidation catalyst that there may exist converts about methane from methane oxidation catalyst before this.Generally observation methane oxidation catalyst is just sufficient to infer about the characteristic of the fuel of liquid, if there is methane oxidation catalyst.

In a kind of preferably design in the present inventive method, use the monitoring method for methane oxidation catalyst, methane oxidation catalyst includes at least the material storing oxygen, particularly zirconium oxide and/or lanthana and/or cerium oxide and/or praseodymium oxide and/or Dineodymium trioxide or their mixture.Therefore the material storing oxygen can be particularly based on zirconium oxide and/or lanthana and/or cerium oxide and/or praseodymium oxide and/or Dineodymium trioxide or their mixture.Stored by the oxygen relevant to these materials in methane oxidation catalyst, it is therefore prevented that or at least reduce the fracture of Hydrocarbon on methane oxidation catalyst.According to Yin in the present inventive method, form is that the additional Hydrocarbon of the fuel of liquid is injected in exhaust system, so using the material storing oxygen extremely advantageous when in view of minimizing discharge.It is referred to take into account the embodiment above when using lambda probe signal for the advantage of purpose in the present inventive method under this mutual relation, wherein, usual methane oxidation catalyst is for storing the ability of oxygen or oxygen absorbent along with the most aging and reduce.The most especially in the most aging methane oxidation catalyst, the risk of the Hydrocarbon of fracture is higher, thus extremely advantageous uses the material storing oxygen in methane oxidation catalyst.

Especially can use in a particularly advantageous manner in this exhausted gas post-processing system with methane oxidation catalyst by the monitoring method of the present invention, described exhausted gas post-processing system is equipped with the injection apparatus for injecting fuel directly into exhaust system for other reasons.When exhausted gas post-processing system is associated with internal combustion engine (electromotor only run) being provided only for fuel gas operation with combustion gas, it is likely to require the fuel for liquid, the such as injection of bavin Water Oil Or Gas arranges a single storage tank, and injection apparatus is supplied with the fuel of liquid by this storage tank.

The present invention additionally includes a kind of computer program, and it is for performing illustrated method.Additionally, present invention additionally comprises a kind of machine-readable storage medium, it storing illustrated computer program, and also include the controller of a kind of electronics, it is arranged for performing in the present inventive method.It is implemented as computer program in the present inventive method or is as the advantage controlling program, even existing system, such as automobile, can also be arranged for performing in the present inventive method in a straightforward manner, as long as exhausted gas post-processing system is equipped with methane oxidation catalyst and is equipped with at least one injection apparatus for the fuel of liquid in methane oxidation catalyst upstream.

The explanation of embodiment is drawn by other the feature of the present invention and advantage by next combining accompanying drawing.Can be realized individually or in combination with one another respectively in this feature.

Accompanying drawing explanation

Accompanying drawing is performed for the schematic diagram of the parts of exhausted gas post-processing system in the present inventive method.

Detailed description of the invention

Accompanying drawing schematically shows the layout of the parts by the exhausted gas post-processing system of the present invention, and these parts are arranged in the exhaust system of internal combustion engine 10.Internal combustion engine 10 particularly relates to gas engine that a kind of energy lean-burn runs, that can run or diesel oil/gas engine with the mixture of combustion gas and diesel oil.In order to improve the power of internal combustion engine 10, join for internal combustion engine 10 and be provided with turbocharger 11.The waste gas of internal combustion engine 10 was guided through sulfur adsorbent equipment 12 in exhaust system before this.Arranged downstream at sulfur adsorbent equipment 12 methane oxidation catalyst 13, wherein, carries out the oxidation comprising methane in the offgas in methane oxidation catalyst 13.Reached by the sulfur adsorbent equipment 12 front connect, the function of methane oxidation will not due in waste gas the composition of sulfur-bearing and suffer damage or be deteriorated.System also includes SCR catalyst 16, in order to reduce the mass fraction comprising nitrogen oxides in the offgas.The reactant needed for catalytic reaction in SCR catalyst 16, the aqueous solution of urea (such as AdBlue) of such as liquid, it is injected in exhaust system by being arranged in the metering position 15 of SCR catalyst 16 upstream.This example of exhausted gas post-processing system also has the particulate filter 14 of catalysis, and it is disposed in the upstream of SCR catalyst 16.

The upstream of methane oxidation catalyst 13 and simultaneously upstream arrangement at sulfur adsorbent equipment 12 fuel injector 17 injection apparatus as the fuel for liquid.Fuel injector 17 is not therefore spatially directly next to methane oxidation catalyst 13, but is arranged in being located slightly away from it in the upstream region of methane oxidation catalyst 13.By syringe 17 by the fuel of liquid, that is particularly bavin Water Oil Or Gas, during in the present inventive method, it is injected directly into exhaust system.By this directly to additional fuel injection (salvo) in exhaust system, carry out the most particularly monitoring to methane oxidation catalyst 13 during OBD.It is difficult to be quantized, so according to the present invention, the substitute is the conversion of the Hydrocarbon studying the fuel from liquid in methane oxidation catalyst 13 in methane oxidation catalyst 13 because methane converts this.Basis is, is converted into basis with the methane of the variation in methane oxidation catalyst equally when the conversion of the Hydrocarbon from liquid fuel is deteriorated.

In the preferred design of one, analyze the cranking temperature of methane oxidation catalyst 13 when with the addition of the exhaust gas conversion of fuel of liquid.Therefore pass through given the associating of the methane oxidation catalyst 13 characteristic when the Hydrocarbon of the fuel from liquid converts and the characteristic of methane oxidation catalyst 13 when methane converts, can infer, by the present invention, the characteristic that methane oxidation catalyst 13 converts about methane.Can conclude therefrom that the activity of the methane oxidation catalyst that there may exist is deteriorated and aging especially by fiducial value.Can such as use the parameter of the characteristic characterizing new methane oxidation catalyst as fiducial value.Fiducial value can the most also be the value of the past of the quantization from methane conversion, thus changes over observation methane and convert and therefore can determine its loss of activity slowly that there may exist during the service life of methane oxidation catalyst.

The research of characteristic when the additional Hydrocarbon of the methane oxidation catalyst 13 fuel from liquid in exhaust system is converted, however, it would be possible to carry out in a different manner.The temperature survey at methane oxidation catalyst 13 upstream and downstream is particularly preferably performed for this.Therefore, in the example of exhausted gas post-processing system shown in the drawings, temperature sensor 18 and 19 is set in the upstream of methane oxidation catalyst or downstream.The heat release on methane oxidation catalyst 13 can be observed in a per se known way for this and conclude therefrom that at the conversion within methane oxidation catalyst 13 or conversion ratio.As to thermometric additional aspects or replacement scheme, it is possible to use measurement based on lambda probe signal is for by the purpose of the present invention.On the position of temperature sensor 18 or 19, such as alternatively or additionally set some lambda sensor (Lmabda probe) for this, thus combustion air ratio (λ) can be obtained by lambda probe signal at the upstream and downstream of methane oxidation catalyst.Lambda probe generally indicates that the cross sensitivity of Hydrocarbon of specific degrees, thus is equally inferred the conversion of Hydrocarbon within methane oxidation catalyst by lambda probe signal.

It is not limited to this exhausted gas post-processing system by the monitoring method of the present invention.More precisely, described method can also be used for monitoring the methane oxidation catalyst in other exhausted gas post-processing system, if directly or be connected to methane oxidation catalyst upstream and arrange at least one if the injection apparatus of the fuel of liquid.

Claims

1. the method being used for monitoring the methane oxidation catalyst (13) in the exhausted gas post-processing system of internal combustion engine (10), wherein, methane oxidation catalyst (13) upstream arrangement at least one for the injection apparatus (17) of fuel of liquid, it is characterized in that, the fuel of liquid is observed by injected and methane oxidation catalyst (13) the characteristic about the fuel of liquid of injection apparatus (17).

2. the method as described in claim 1, it is characterised in that infer, about the characteristic of the fuel of liquid, the characteristic that methane oxidation catalyst converts about methane from methane oxidation catalyst (13) in the second step of the method.

3. the method as described in claim 1 or 2, it is characterised in that infer the activity variation that there may exist of methane oxidation catalyst especially by fiducial value.

4. the method as described in aforementioned any one of claim, it is characterised in that be deteriorated by the characteristic of methane oxidation catalyst (13) and/or the activity that be there may exist by methane oxidation catalyst and infer the expansion that there may exist of methane oxidation catalyst (13).

5. the method as described in aforementioned any one of claim, it is characterized in that, in the first step illustrated in claim 1 of the method, obtain the parameter of the starting characteristic about temperature of at least one sign methane oxidation catalyst (13) of the fuel about liquid.

6. the method as described in any one of claim 2 to 5, it is characterized in that, in the second step of the method, methane oxidation catalyst (13) about the characteristic of the fuel of liquid and methane oxidation catalyst about the relatedness between the characteristic of the fuel containing methane on the basis of, infer the characteristic that methane oxidation catalyst converts about methane.

7. the method as described in claim 6, it is characterised in that relatedness is determined according to experiment and/or relatedness is inferred by characteristic curve or characteristic field, wherein, characteristic curve or characteristic field are preferably stored in the control unit of exhausted gas post-processing system.

8. the method as described in aforementioned any one of claim, it is characterised in that observing the methane oxidation catalyst (13) characteristic about the fuel of liquid, way is: determine the heat release in methane oxidation catalyst (13) region by temperature survey.

9. the method as described in aforementioned any one of claim, it is characterised in that exhausted gas post-processing system includes that at least one lambda is popped one's head in, wherein, methane oxidation catalyst (13) is obtained by lambda probe signal about the characteristic of the fuel of liquid.

10. the method as described in claim 9, it is characterized in that, in exhausted gas post-processing system, at least one lambda of the upstream arrangement probe at methane oxidation catalyst (13) and at least one lambda of arranged downstream at methane oxidation catalyst are popped one's head in, wherein, the signal by two lambda probes obtains the methane oxidation catalyst characteristic about the fuel of liquid.

11. methods as described in claim 10, it is characterized in that, create micro-dense fuel mixture by the upstream being injected in methane oxidation catalyst (13) of the fuel of liquid, and compare by the lambda probe signal in the downstream at methane oxidation catalyst and move, in the time of the lambda probe signal of the upstream of methane oxidation catalyst, the characteristic obtaining methane oxidation catalyst about the fuel of liquid.

12. methods as described in aforementioned any one of claim, it is characterized in that, methane oxidation catalyst (13) comprises at least one material storing oxygen, particularly zirconium oxide and/or lanthana and/or cerium oxide and/or praseodymium oxide and/or Dineodymium trioxide or their mixture.

13. 1 kinds of computer programs, it is arranged for performing the method as described in any one of claim 1 to 12.

14. 1 kinds of storage mediums that can be read by machine, store on the storage medium according to the computer program described in claim 13.

The controller of 15. 1 kinds of electronics, its step being arranged for performing the method as described in any one of claim 1 to 12.