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
  • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
  • F01N3/0871—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents using means for controlling, e.g. purging, the absorbents or adsorbents
  • F01N3/0885—Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
• • 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
  • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus
  • F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
  • F01N11/005—Monitoring or diagnostic devices for exhaust-gas treatment apparatus the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus the temperature or pressure being estimated, e.g. by means of a theoretical model
• • 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
  • F01N9/00—Electrical control of exhaust gas treating apparatus
  • F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration
• • 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
  • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
  • F01N2570/04—Sulfur or sulfur 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
  • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
  • F01N2900/06—Parameters used for exhaust control or diagnosing
  • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
  • F01N2900/1612—SOx amount trapped in catalyst
• • 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
• • 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

Definitions

• the present invention relates to a method for treatment of exhaust -gas streams resulting from a combustion process by using an aftertreatment system.
• the invention also relates to a system and a vehicle, and also to a computer program and a computer program product .
• Such emission standards often include requirements which define acceptable limits for exhaust gas emissions from vehicles equipped with internal combustion engines. For example, emission levels of nitrous oxides (NO x ) , hydrocarbons (HC) , carbon monoxide (CO) and particles are often regulated for most types of vehicles in these standards.
• NO x nitrous oxides
• HC hydrocarbons
• CO carbon monoxide
• the exhaust gases caused by the combustion in the internal combustion engine are aftertreated (cleaned) .
• a so-called catalytic cleaning process can be used, for which reason aftertreatment systems, for example in vehicles and other craft, also usually comprise at least one catalyst.
• aftertreatment systems for example in vehicles and other craft, also usually comprise at least one catalyst.
• aftertreatment systems optionally in combination with one or more catalysts, can comprise other components, for example particle filters.
• soot particles are formed.
• Particle filters are used to trap these soot particles and function in such a way that the exhaust-gas stream is conveyed through a filter structure where soot particles are captured from the passing exhaust-gas stream and are collected in the particle filter.
• the particle filter fills with soot as the vehicle is being driven and, sooner or later, the filter has to be emptied of soot, which is usually achieved with the aid of so-called regeneration .
• Regeneration means that the soot particles, which mainly consist of carbon particles, are converted to carbon dioxide and/or carbon monoxide in one or more chemical processes, and regeneration can take place in different ways.
• Regeneration can take place, for example, with the aid of so-called N0 2 -based regeneration, often also called passive regeneration.
• N0 2 -based regeneration nitrogen monoxide and carbon monoxide are formed by a reaction between carbon and nitrogen dioxide.
• the N0 2 -based regeneration has the advantage that desired reaction speeds, and thus the rate at which the filter is emptied, can be achieved at relatively low
• the N0 2 -based regeneration is strongly dependent on the availability of nitrogen dioxide. If the availability of nitrogen dioxide is reduced, the speed of regeneration is also reduced.
• nitrogen dioxide can be reduced, for example, if the formation of nitrogen dioxide is inhibited, which can happen, for example, if one or more components in the aftertreatment system are "poisoned" by sulfur, where said sulfur normally occurs in at least certain types of fuel, e.g. diesel .
• the present invention relates to a method for estimating an accumulation of sulfur in an aftertreatment system, wherein said aftertreatment system is designed for treatment of an exhaust-gas stream resulting from a combustion in an internal combustion engine, and wherein said aftertreatment system includes at least one first component.
• the method includes determining a representation of a first temperature
• the sulfur that fuel e.g. diesel
• the active coating often consisting of noble metals or other metals, with which components in the aftertreatment system are usually provided.
• sulfur molecules e.g. in the form of sulfates or other SO x compounds such as sulfur monoxide, sulfur dioxide, sulfur trioxide, etc., bind to metal
• sulfur is used below, in connection with accumulation in the
• the aftertreatment system can comprise an SCR catalyst, e.g.
• the present invention reduces problems with sulfur poisoning of components in the aftertreatment system by estimating an accumulation of sulfur as a function of the prevailing
• This estimation can then be used to determine, for example, when desulfurization should be carried out, e.g. when a first quantity of sulfur has become accumulated, in order thereby to reduce problems with accumulated sulfur.
• the accumulation of sulfur is strongly temperature -dependent and, according to one embodiment, only a representation of a temperature for the aftertreatment system is used in order, based on this temperature, to estimate an accumulated quantity of sulfur.
• This representation can, for example, consist of signals from one or more temperature sensors arranged in the aftertreatment system, or of a temperature representation calculated with the aid of a suitable computation model, e.g. based on a temperature sensor arranged upstream of the
• an even more accurate estimation of the accumulated sulfur quantity can be made.
• the estimation can also be based on the fuel or type of fuel that is used. Depending on the degree of purity of the fuel, it will contain different amounts of sulfur and, by also taking account of the sulfur content, a more accurate estimation can be obtained.
• the sulfur content of the fuel can, for example, be a maximum sulfur content that is legally allowed in the fuel in the region in question, or specific information for the specific fuel which is used, where this sulfur content can be stored in a suitable way in the control system of the vehicle. According to one
• the sulfur content is assessed on the basis of a previously estimated accumulation.
• the sulfur accumulation rate is also dependent on the sulfur flow through the aftertreatment system. The higher the flow, the sooner active coatings in the aftertreatment system, e.g. in an oxidation catalyst and/or a particle filter, become coated with sulfur.
• the sulfur flow i.e. the quantity of sulfur supplied to the aftertreatment system, can be
• the sulfur accumulation rate is also dependent on the quantity of already accumulated sulfur, and, the greater the quantity of sulfur that has already been accumulated, the slower further accumulation will take place.
• the estimation of the accumulated quantity of sulfur can thus depend only on a temperature or alternatively also be based on one or more of the sulfur content of the fuel, the quantity of fuel supplied and the actual sulfur accumulation. Other parameters can also be used for determining the accumulation.
• the lower the temperature in the aftertreatment system the quicker sulfur accumulation will take place.
• This sulfur accumulation will take place mainly in the component in the aftertreatment system which is first impacted by the exhaust - gas stream, e.g. an oxidation catalyst or a particle filter.
• Said temperature of said aftertreatment system can therefore consist, for example, of a representation of a temperature for this first component, either measured directly with a sensor or calculated with the aid of a suitable computation model .
• said first measure includes carrying out desulfurizat ion .
• the desulfurization can be carried out in any suitable way, and, according to one embodiment, desulfurization is carried out by cyclically increasing the temperature of the aftertreatment system, e.g. controlled for the component where sulfur
• the temperature of components in the aftertreatment system is "pulsed" .
• the component which is mainly exposed to the poisoning is, as seen from the internal combustion engine, the first (noble) metal-coated component that the exhaust -gas stream meets, for example an oxidation catalyst.
• the cyclical increase of the temperature has the advantage that, since the desulfurization is strongly
• a high temperature gives good desulfurization
• a high temperature can be achieved in the component that has mainly been poisoned, and, by then allowing the temperature to drop to a lower level before the
• the temperature in downstream components in the aftertreatment system will not be increased to the same extent, on account of the thermal inertia of the components.
• the temperature of a sulfur-poisoned component can be increased with the aid of such a method to a substantially higher temperature compared with what downstream components have as tolerance, which means that good
• Fig. 1A shows schematically a vehicle in which the present
• Fig. IB shows a control unit in the control system for the
• Fig. 2 shows the aftertreatment system in more detail for the vehicle shown in Fig. 1.
• Fig. 3 shows an example of the regeneration (soot burn-out) speed as a function of the soot quantity in the particle filter, and the temperature dependence thereof .
• Fig. 4 shows the temperature dependence for oxidation of
• Fig. 5 shows a method according to one illustrative embodiment of the present invention.
• Fig. 6 shows a diagram of sulfur accumulation over time.
• Fig. 7 shows a method according to an illustrative embodiment of the present invention.
• Fig. 1A shows schematically a drive train in a vehicle 100 according to one embodiment of the present invention.
• the vehicle 100 shown schematically in Fig. 1A comprises only one axle with driving wheels 113, 114, but the invention is also applicable to vehicles where more than one axle is provided with driving wheels, and also to vehicles with one or more additional axles, for example one or more support axles.
• the drive train comprises an internal combustion engine 101, which in a conventional way, via an output shaft on the internal combustion engine 101, usually via a flywheel 102, is
• the internal combustion engine 101 is controlled by the control system of the vehicle via a control unit 115.
• the clutch 106 which can be an automatically controlled clutch for example, and the gearbox 103 are
• the drive train of the vehicle can also be of another type, such as a type with a conventional automatic gearbox, etc.
• a shaft 107 leading from the gearbox 103 drives the driving wheels 113, 114 via a final gear 108, for example a
• the vehicle 100 also comprises an aftertreatment system
• exhaust-gas cleaning system 200 for treatment (cleaning) of exhaust-gas emissions resulting from combustion in the
• combustion chamber (s) e.g. cylinders
• the aftertreatment system is shown in more detail in Fig. 2.
• the figure shows the internal combustion engine 101 of the vehicle 100, where the exhaust gases (exhaust-gas stream) generated in the combustion are conveyed via a turbo unit 220.
• the exhaust-gas stream resulting from the combustion often drives a turbo unit, which in turn compresses the incoming air for combustion in the cylinders.
• turbo unit can be of the compound type, for example.
• the function of different types of turbo units is well known and is therefore not described in any more detail herein.
• the exhaust-gas stream is then conveyed via a pipe 204 (indicated by arrows) to a diesel particle filter (DPF) 202 via a diesel oxidation catalyst (DOC) 205.
• DPF diesel particle filter
• DOC diesel oxidation catalyst
• the oxidation catalyst DOC 205 has several functions and is normally used primarily, in the aftertreatment , to oxidize remaining hydrocarbons and carbon monoxide in the exhaust-gas stream to carbon dioxide and water. In the oxidation of hydrocarbons (i.e. oxidation of fuel), heat is also formed, which can be used to increase the temperature of the particle filter during emptying, so-called regeneration, of the
• the oxidation catalyst 205 can also oxidize a large fraction of the nitrogen monoxides (NO) occurring in the exhaust-gas stream to nitrogen dioxide (N0 2 ) .
• This nitrogen dioxide is used, for example, in N0 2 -based regeneration. Other reactions can also occur in the oxidation catalyst.
• the aftertreatment system also comprises an SCR (Selective Catalytic Reduction) catalyst 201 arranged downstream of the particle filter 202.
• SCR catalysts use ammonia (NH 3 ) , or a compound from which ammonia can be generated/formed, as an additive for reducing the quantity of nitrous oxides NO x in the exhaust-gas stream.
• NH 3 ammonia
• the efficiency of this reduction is dependent on the ratio between NO and N0 2 in the exhaust-gas stream, for which reason this reaction is also negatively affected at reduced N0 2 conversion.
• DOC 205, DPF 202 and SCR catalyst 201 are integrated in one and the same exhaust- gas cleaning unit.
• these components do not need to be integrated in one and the same exhaust-gas cleaning unit, and instead the components can be arranged in another way when deemed suitable, and one or more of said components can, for example, consist of separate units.
• Fig. 2 also shows temperature sensors 210-212 and a differential pressure sensor 209.
• control systems in modern vehicles consist of a communications bus system consisting of one or more communications buses for interconnecting a number of
• ECU electronice control units
• control units such as the control units, or controllers, 115, 208, and various components arranged on the vehicle.
• ECU electronice control units
• Such a control system can comprise a large number of control units, and the responsibility for a specific function can be divided amongst more than one control unit.
• Figs 1A-1B show only the control units 115, 208.
• control unit 208 which, in the embodiment shown, is responsible according to the above for other functions in the aftertreatment system 200, for example regeneration (emptying) of the particle filter 202, but the invention can also be implemented in a control unit dedicated to the present
• control unit 208 in addition to being dependent on sensor signals from one or more of temperature sensors 210-212, will probably also be dependent, for example, on information that is received, for example, from the one or more control units that control the engine functions, i.e. in the present case the control unit 115.
• Control units of the type shown are normally arranged to receive sensor signals from different parts of the vehicle.
• the control unit 208 can, for example, receive sensor signals according to the above, and also from control units other than the control unit 115.
• Such control units are also usually- arranged to output control signals to different vehicle parts and vehicle components.
• the control unit 208 can output signals to the engine control unit 115, for example.
• control is often controlled by programmed instructions.
• programmed instructions typically consist of a computer program which, when it is executed in a computer or control unit, causes the computer/control unit to perform the desired control, such as method steps according to the present
• the computer program is usually part of a computer program product, where the computer program product comprises a suitable storage medium 121 (see Fig. IB) with the computer program 109 stored on said storage medium 121.
• Said digital storage medium 121 can be, for example, one from the following group: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory) , EPROM (Erasable PROM) , Flash memory, EEPROM
• control unit 208 An example of a control unit (the control unit 208) is shown schematically in Fig. IB, wherein the control unit in turn can comprise a computing unit 120, which can be in the form, for example, of any suitable type of processor or microcomputer, for example a circuit for digital signal processing (Digital Signal Processor, DSP) , or a circuit having a predetermined specific function (Application Specific Integrated Circuit, ASIC) .
• the computing unit 120 is connected to a memory unit
• the computing unit 120 which provides the computing unit 120 with, for example, the stored program code 109 and/or the stored data that the computing unit 120 requires in order to be able to perform computations.
• the computing unit 120 is also arranged to store partial or final results of computations in the memory unit 121.
• control unit is provided with devices
• the devices 123, 124 for the transmission of output signals are arranged to convert computation results from the computing unit 120 to output signals for transmission to other parts of the control system of the vehicle and/or the one or more components for which the signals are intended.
• Each of the connections to the devices for receiving and transmitting input and output signals can be in the form of one or more of a cable; a data bus, such as a CAN bus (Controller Area
• Network bus a MOST bus (Media Oriented Systems Transport bus) , or some other bus configuration; or by a wireless connection .
• MOST bus Media Oriented Systems Transport bus
• soot particles are formed during the combustion in the internal combustion engine 101. These soot particles should not, and in many cases must not, be emitted into the surroundings of the vehicle. Diesel particles consist of hydrocarbons, carbon (soot) and inorganic substances such as sulfur and ash. As has been mentioned above, these soot particles are trapped by the particle filter 202, which functions in such a way that the exhaust-gas stream is conveyed through a filter structure in which soot particles are captured from the passing exhaust -gas stream in order thereafter to be collected in the particle filter 202. With the aid of the particle filter 202, a very large proportion of the particles can be separated from the exhaust-gas stream.
• the separated particles are thus collected in the particle filter 202, wherein the latter fills up with soot over time, and, if the filter is filled to a certain level, the filter has to be "emptied” . If the filter is filled to too high a level, the vehicle performance may be affected, and at the same time there may also be a risk of fire on account of soot accumulation in combination with high temperatures.
• the particle filter 202 is regenerated at more or less regular intervals, and a
• a suitable time for regeneration of the particle filter can be carried out, for example, with the aid of the control unit 208 which, for example, can determine a suitable time/suitable times at least partially with the aid of signals from the differential pressure sensor 209.
• the temperature tolerance of the components in the exhaust-gas system is often limited, which means that the active regeneration can have a maximum permissible temperature which is low in relation to the temperatures that are required if the desired reaction speed is to be achieved.
• the temperatures required in this type of regeneration for a desired reaction speed may thus be too high in relation to temperature tolerances of the components in the aftertreatment system.
• the particle filter 202 and/or (if present) the downstream SCR catalyst 201 often have design-related limits as regards the maximum temperature to which they can be exposed.
• N0 2 -based regeneration is often applied in such systems.
• the N0 2 -based regeneration has the advantage that desired reaction speeds, and therefore the rate at which the filter is emptied, can be achieved at
• N0 2 -based regeneration the regeneration of the particle filters typically takes place at temperatures in the range of 200°C - 500°C, although
• Fig. 3 shows an example of the regeneration (soot burn-out) speed in N0 2 -based regeneration as a function of the soot quantity in the particle filter 202, and for operating
• the regeneration speed is also illustrated for low and high concentrations of nitrogen dioxide.
• the burn-out rate is low at a low temperature (350 °C) and a low concentration of nitrogen dioxide.
• the temperature dependence of the regeneration speed is clear from the fact that the burn-out rate is relatively low even at a high concentration of nitrogen dioxide as long as the filter temperature is low.
• the burn-out rate is considerably higher at 450°C, even if there is a low concentration of nitrogen dioxide, but a high temperature in combination with high contents of N0 2 is preferred.
• the passive regeneration is also dependent on the availability of nitrogen dioxide. Normally, however, the nitrogen dioxide N0 2 content of the total quantity of nitrous oxides NO x generated during combustion in the internal
• the combustion engine is only 0 - 10% of the total quantity of nitrous oxides N0 X in the exhaust-gas stream.
• the N0 2 content can be even as low as 2 - 4%.
• the nitrogen dioxide content in the exhaust -gas stream is as high as possible when the exhaust -gas stream enters the particle filter 202. It is therefore also desirable to increase the quantity of nitrogen dioxide N0 2 in the exhaust-gas stream resulting from the combustion in the internal combustion engine.
• conversion can be carried out in several different ways and, in accordance with the above, can be achieved with the aid of the oxidation catalyst 205, where nitrogen monoxide can be oxidized to nitrogen dioxide.
• oxidation of nitrogen monoxide to nitrogen dioxide in the oxidation catalyst is also a strongly temperature-dependent process, which is illustrated in Fig. 4.
• the nitrogen dioxide content of the total quantity of nitrous oxides in the exhaust-gas stream can be increased to almost 60% at favorable temperatures.
• a strongly temperature-dependent process which is illustrated in Fig. 4.
• temperature of the order of 250°C - 350°C would be optimal in passive regeneration for achieving the highest possible degree of oxidation of nitrogen monoxide to nitrogen dioxide.
• temperature of 200-250° (the temperature data shown are only illustrative examples, and actual values may differ from these.
• the way in which the temperatures are determined/calculated can influence the temperature limits. A number of ways of determining the temperature of the filter are illustrated below) .
• the burn-out speed (the regeneration speed) thus increases with the quantity of NO x in the exhaust -gas stream, the temperature of the exhaust-gas stream (of the particle filter) and the current quantity of soot in the particle filter. Consequently, the N0 2 -based regeneration requires good
• the N0 2 content of the total quantity of NO x in the exhaust-gas stream can be markedly increased with the aid of the oxidation catalyst 205, where the resulting N0 2 content after the oxidation catalyst 205 is strongly dependent on the temperature.
• the conversion of NO to N0 2 with the aid of the oxidation catalyst is not only dependent on the temperature of the oxidation catalyst, but also dependent on whether the performance of the oxidation catalyst 205 is affected by undesired coating.
• the temperature of the exhaust-gas stream resulting from the combustion will vary. If the internal combustion engine works hard, the exhaust-gas stream will keep a higher temperature, whereas, conversely, if the vehicle is driven with a relatively low load on the internal combustion engine, the temperature of the exhaust-gas stream will be substantially lower. If the vehicle is driven for a long period in such a way that the temperature of the exhaust-gas stream maintains relatively low temperatures, e.g. temperatures below 150-300°C, the function of the oxidation catalyst 205 will degrade on account of the fact that the sulfur usually present in various forms in the fuel reacts with the active coating of the oxidation catalyst 205, which usually comprises one or more noble metals or other suitable metals such as aluminum, for example. This in turn has a negative effect on the properties of the oxidation catalyst 205 as regards the N0 2 conversion, since the active surface of the active coating is reduced on account of sulfur
• the sulfur can react with the active coating and, for example, form sulfates such as aluminum sulfate, platinum sulfate and palladium sulfate, e.g.
• N0 2 conversion in an oxidation catalyst with sulfur accumulation will thus provide a lower content of N0 2 under otherwise identical conditions.
• This reduction in N0 2 conversion of the oxidation catalyst therefore means that a smaller quantity of N0 2 is available in the N0 2 -based regeneration of the particle filter, thereby reducing the conversion of soot and thus the regeneration speed .
• the aftertreatment system 200 can comprise an SCR catalyst, which is usually placed downstream of the oxidation catalyst and the particle filter.
• the SCR catalyst is dependent, for its function, on good availability of N0 2 in order for the overall N0 2 conversion in the
• a method for estimating an accumulated sulfur quantity in an after- treatment system.
• suitable measures can then be taken, for example when the accumulated sulfur quantity amounts to a first sulfur quantity, for the purpose of effectively reducing problems that arise with sulfur coating in the oxidation catalyst, without the risk of damaging more temperature- sensitive components arranged downstream .
• Fig. 5 shows a method 500 according to the present invention for estimating an accumulated sulfur quantity.
• the method begins at step 501, where it is determined whether accumulation of sulfur is to be estimated, and, when an estimation is to be carried out, the method continues to step 502.
• the transition from step 501 to step 502 can be
• a parameter representing an aggregated estimated sulfur accumulation S est is set at a suitable value.
• step 502 an accumulation term Si n i and a desulfurization term S avs , which are described below, can also be set to zero.
• the method continues to step 503 in order to determine a
• the estimation of the sulfur coating in the aftertreatment system 200 can be carried out for the aftertreatment system 200 as a whole, i.e. the aftertreatment system can be considered as an entity. In practice, most of the accumulated sulfur will have been collected in the component that comes first in the after- treatment system 200, since this component is the first that will be coated when the exhaust-gas stream first passes it. The estimation of collected sulfur in the aftertreatment system can thus also be seen as constituting an estimation of the component coming first in the aftertreatment system 200, i.e. in the above example the oxidation catalyst. In
• said temperature T of the aftertreatment system 200 can be determined in different ways. For example, it can be determined with the aid of one or more temperature sensors arranged in the aftertreatment system 200, e.g. one or more of the temperature sensors 210-212, where the value T can be based on one sensor or, for example, on a weighted value based on values from several sensors.
• the temperature T can thus be, for example, the temperature of the oxidation catalyst or the temperature of the particle filter.
• some other suitable temperature sensor can be used, e.g.
• the temperature ⁇ can also be arranged to be determined with the aid of a suitable calculation model based on existing conditions such as the current engine control parameters, etc.
• the time period i is any suitable time period and can, for example, depend on the inertia in the aftertreatment system 200, i.e. how quickly the temperature T can be changed. If the temperature ⁇ is changed slowly, the time period i can be quite a long time period. The length of the time period i should be such that the temperature T can be regarded as constant during the time period.
• the time period i can, for example, be 10 ms, 100 ms, 1 second, 5 seconds, or another suitable time period, such as a shorter or considerably longer time period.
• the time period ti can also be arranged to vary from one time period t ⁇ to a following time period t ⁇ +1 , e.g. depending on the existing operating conditions. If the operating conditions are
• the time period t ⁇ can also be kept constant, whereas the time period t ⁇ can, for example, be arranged to vary with varying operating conditions.
• the length of the time period can thus be arranged to be changed at each new time period ti. According to what is described below, not only the temperature ⁇ but also other parameters can be used for determination of the sulfur
• time period ti can be set to a suitable value also on the basis of these one or more
• an estimation is made of the accumulated sulfur quantity Si n i.
• the accumulation of sulfur is strongly temperature-dependent, where the rate of accumulation decreases with increasing temperature T. If the temperature T exceeds some suitable temperature, accumulation of sulfur will no longer take place, and instead the high temperature will bring about a
• desulfurization i.e. the binding between accumulated sulfur molecules and the metals of the coating present in the
• the temperature T should reach relatively high temperatures in order for the accumulated sulfur to react to the intended extent with the passing exhaust-gas stream.
• the binding of the sulfur to the metals of the coating can thus be broken, which means that some of the accumulated sulfur can disappear, and the poisoning is thus reduced.
• the dependence of ⁇ can be regarded as such that accumulation takes place with constant speed as long as T is below a temperature limit ⁇ .
• the desulfurization in its simplest form can be such that the dependence of T can be such that desulfurization takes place with constant speed as long as T is above a temperature limit T 2 , which can be equal to or above or below the temperature limit Ti .
• T 2 is below Ti , accumulation and desulfurization will therefore take place simultaneously.
• the total estimated accumulated quantity S est can then be estimated as S est — S es t + Si n i — Sa s i step 505 .
• S est has thus been estimated in step 505
• the method continues to step 506 in order to determine whether S est has reached a quantity Sn m according to what is described below. Since the temperature varies, S est can either be increased or decreased after each time period, depending on the effect of the
• Sj .n i and S avs are thus estimated as a function of a temperature T only.
• other parameters are also taken into account. For example, an existing accumulation can be
• Fig. 6 shows a highly schematic example of how accumulation and desulfurization vary as a function of the time t for any given temperature T, where the actual appearance of the curves may vary greatly from the case illustrated. Moreover, T is different for the accumulation curve and the illustrated desulfurization curves, since the figure simultaneously indicates both high accumulation and high desulfurization, which is normally not the case. For any given temperature T, the combined result will generally be either a net
• the shown level S max can, for example, represent the maximum quantity that can be accumulated in the oxidation catalyst, for example.
• the level S max is normally higher than the level Sii m , which can, for example, represent the level that entails the maximum decrease in the performance of the aftertreatment system that can be accepted.
• the solid line represents
• the already estimated quantity 5 est should also be taken into account for determination of accumulation for a certain time period ti, since accumulation will take place substantially more slowly when a large quantity of sulfur is already accumulated.
• a calculation model for calculation of S avs can advantageously take account of the strong temperature dependence of the desulfurization .
• different calculation models can be used for different temperatures ⁇ .
• one and the same calculation model can take account of the temperature T.
• a mapping method is used in which accumulation/desulfurization is estimated by looking up a table for example, where the table values can be empirically determined values, for
• accumulation can also be
• the accumulation profile can often be considered to be substantially constant up to at least some temperature, wherein, for example, accumulation up to some suitable temperature, for example, can be approximated with one and the same curve of the type shown in Fig. 6.
• account is also taken of the sulfur flow.
• the sulfur coating speed is also dependent on the sulfur flow, and the higher the flow, i.e. the more sulfur molecules that are supplied to the aftertreatment system, the quicker the active surfaces of the oxidation catalyst are coated with sulfur.
• the sulfur flow depends mainly on the sulfur content of the fuel and on the amount of fuel supplied to the internal combustion engine. That is to say, the higher the fuel consumption of the vehicle, the greater the sulfur flow will be.
• oxidation catalyst can also be determined in other suitable ways .
• a counting-up term Sj . ni and a counting-down term S avs are both determined, wherein the estimated
• step 506 it is then determined whether S est has reached a limit value Si im . As long as this is not the case, the method returns to step 503 for new temperature determination, wherein the time t is counted with a further interval t ⁇ according to the above, and wherein the method again continues to step 504 for determining a change of Sj . ni and S avs , and thereby S est , during the subsequent time interval j + i . This lasts for as long as the limit value S llm has not been reached. Under favorable conditions, where the vehicle is driven with high load for a long time, the accumulation of sulfur may be low or even more or less non-existent, by virtue of high temperatures in the aftertreatment system being maintained. In such
• step 506 If it is determined in step 506 that the accumulated estimated sulfur quantity S est is equal to or exceeds the limit value Siim, the method continues to step 507.
• the limit value Sum can be set to any suitable level, such as a certain number of grams of accumulated sulfur, and can, for example, represent an accumulation at which it is judged that, for example, the performance of the aftertreatment system and/or of the
• oxidation catalyst for example has in some respect, such as e.g. the conversion of N0 X to N0 2 , dropped to some level, e.g. a level at which performance is considered to have dropped by half or another suitable level, for example in the range of 0- 90% of the maximum performance.
• S est can be set to some suitable quantity of sulfur, e.g., but absolutely not limited to, an arbitrary number of grams of fuel in the range of 1-50 grams.
• the sulfur quantity can be set on the basis of the existing configuration of the aftertreatment system in question, e.g. the size of the oxidation catalyst, etc., and it can also be arranged to vary with the existing operating parameters of the vehicle.
• only an accumulation of sulfur is determined, i.e. only an estimation of the accumulated sulfur quantity S es t is made, wherein this estimation can then be used, when so required, by other methods present in the vehicle.
• a measure is also taken when the sulfur accumulation reaches some suitable level, e.g. the level Sn m .
• a measure to reduce problems with accumulation of sulfur is taken directly in step 507 according to what is described below in connection with step 510.
• a measure to reduce problems with accumulation of sulfur is taken directly in step 507 according to what is described below in connection with step 510.
• step 507 a further determination is first carried out before any measure is taken.
• step 507 a degree of filling of the particle filter is estimated.
• particles are separated from the exhaust-gas stream with the aid of the particle filter 202, wherein the latter has to be regenerated with time.
• the degree of filling can be determined, for example, with the aid of signals from the differential pressure sensor 209 according to the above. The more the particle filter 202 is filled up, the greater the pressure difference across the particle filter 202 will be.
• the degree of filling of the particle filter is thus estimated in step 507, e.g. with the aid of said differential pressure sensor 209. If the degree of filling Pfii te r exceeds some suitable level Pum, i.e. if the differential pressure exceeds some suitable level for example, step 508, it can be judged that the sulfur accumulation is as serious as the estimation S est indicates, wherein the method continues to step 510 for measures to be taken to reduce the sulfur accumulation.
• the method can continue to step 509 for another type of measure to be taken. For example, the method can wait for a period of time, after which a new determination of the soot content is carried out, and, if the difference in soot content indicates rapid filling, the sulfur accumulation can be considered to be high after all, and measures can be taken.
• the method can be ended, e.g. to wait for regeneration to take place.
• a regeneration method can be activated in step 509, wherein the regeneration speed can be determined. This determination can be carried out, for example, with the aid of the differential pressure sensor 209.
• the differential pressure across the particle filter will decrease as the filter is emptied of soot particles and as the flow resistance thus drops. If this reduction in differential pressure takes place more slowly than expected in the
• regeneration which can be determined for example by comparing the speed at which the differential pressure decreases in relation to existing regeneration conditions, it can be determined that the regeneration speed is unexpectedly slow, which after all indicates sulfur coating in the oxidation catalyst, which should be dealt with in order to avoid later problems .
• step 509 for various reasons, it may be considered that a measure for reducing problems with accumulated sulfur needs to be taken after all.
• This measure can consist of a desulfurization method for the purpose of reducing the
• At least one measure is taken in step 510 in order to reduce problems with accumulated sulfur.
• the measure can, for example, also be taken if it is determined that a certain time has elapsed since a preceding desulfurization was carried out, wherein new desulfurization may be considered desirable even if, for example, the degree of filling of the particle filter does not exceed said first level, e.g. in order to avoid the risk of problems occurring at a later stage.
• said measure thus includes carrying out desulfurization, which desulfurization can be carried out in any suitable way.
• desulfurization can be carried out in any suitable way.
• the desulfurization can be carried out in any suitable way.
• the component which is mainly exposed to the poisoning is, as seen from the internal combustion engine, the first (noble) metal-coated component that the exhaust -gas stream meets, for example oxidation catalyst 205.
• the cyclical increase of the temperature has the advantage that, since the desulfurization is strongly
• a high temperature can be achieved in the component that has mainly been poisoned, and, by then allowing the temperature to drop to a lower level before the temperature is increased again, the temperature in downstream components in the aftertreatment system will not be increased to the same extent, on account of the thermal inertia of the components.
• the temperature is increased cyclically for the component in which sulfur accumulation has been confirmed, without supplying fuel for oxidation to said exhaust-gas stream in said aftertreatment system, i.e. the temperature is instead increased cyclically by controlling the internal combustion engine so that it provides an exhaust -gas stream of higher temperature when increasing the temperature of the component in which sulfur accumulation has been
• the temperature of the components in the aftertreatment system is "pulsed" without uncombusted fuel being supplied to the exhaust-gas stream.
• the desulfurization has the effect that, for example, the oxidation catalyst can be detoxified, and its original
• step 701 to step 702 can, for example, be controlled by step 509 in Fig. 5.
• steps 702-705 estimation of S es t is carried out in a manner corresponding to the one that was carried out above with reference to steps 502-505 in Fig. 5. However, since a
• S ⁇ n i will probably have a low or only minimal value, while the term S avSl which according to the above counts down S est , will be higher.
• the term S in i can be completely ignored and thus not determined at all in the desulfurization .
• S est will consequently be continuously counted down, and in step 706 it is therefore determined whether S est has dropped to a level Siim2 / which respresents any suitable level, e.g. zero for complete desulfurization, or some suitable amount, such as a suitable number of grams.
• the level is preferably set to a level above zero, since the desulfurization can otherwise take an unreasonably long time.
• the method returns to step 703.
• S egt has dropped to the level Sii m2
• the method continues to step 508 in order to conclude the desulfurization .
• the invention has been explained above in connection with the system shown in Fig. 2.
• the aftertreatment system shown in Fig. 2 is one that is commonly found in heavy vehicles, at least in jurisdictions where there are strict emission standards .
• the particle filter instead comprises noble-metal coatings, so that the chemical processes occurring in the oxidation catalyst instead occur in the particle filter, wherein the aftertreatment system therefore does not comprise any DOC.
• the invention is also applicable here, since sulfur accumulation will in this case mainly take place in the particle filter.
• the aftertreatment system 200 can also comprise more components than have been illustrated above.
• the aftertreatment system 200 can also comprise more components than have been illustrated above.
• the aftertreatment system can comprise an ASC (ammonia slip catalyst) (not shown) .
• ASC ammonia slip catalyst
• the present invention has been explained above in connection with vehicles.
• the invention is also applicable to any kind of craft/process in which after- treatment systems according to the above can be used, for example watercraft or aircraft with combustion processes according to the above.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Exhaust Gas After Treatment (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=49882360

Family Applications (1)

Country Status (2)

Cited By (2)

Citations (9)

• 2013
  • 2013-07-04 DE DE201311003036 patent/DE112013003036T5/de not_active Withdrawn
  • 2013-07-04 WO PCT/SE2013/050866 patent/WO2014007749A1/fr not_active Ceased

Patent Citations (9)

Also Published As

Similar Documents

Legal Events