WO2003002854A1 - Procede de desulfuration d'absorbeurs de nox - Google Patents

Procede de desulfuration d'absorbeurs de nox Download PDF

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Publication number
WO2003002854A1
WO2003002854A1 PCT/EP2002/006249 EP0206249W WO03002854A1 WO 2003002854 A1 WO2003002854 A1 WO 2003002854A1 EP 0206249 W EP0206249 W EP 0206249W WO 03002854 A1 WO03002854 A1 WO 03002854A1
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WO
WIPO (PCT)
Prior art keywords
nox
adsorbing
electrically conductive
conductive substrate
compounds
Prior art date
Application number
PCT/EP2002/006249
Other languages
English (en)
Inventor
Steven Brillant
Willy Marrecau
Original Assignee
N.V. Bekaert S.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from EP01202456A external-priority patent/EP1270886A1/fr
Application filed by N.V. Bekaert S.A. filed Critical N.V. Bekaert S.A.
Priority to JP2003508810A priority Critical patent/JP2004521256A/ja
Priority to EP02740693A priority patent/EP1399652A1/fr
Priority to US10/482,135 priority patent/US20040216448A1/en
Publication of WO2003002854A1 publication Critical patent/WO2003002854A1/fr

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    • 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
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/085—Sulfur or sulfur oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9431—Processes characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/96—Regeneration, reactivation or recycling of reactants
    • 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
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0097—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
    • 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
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/011—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more purifying devices arranged in parallel
    • F01N13/017—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more purifying devices arranged in parallel the purifying devices are arranged in a single housing
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F01N3/0226—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being fibrous
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/027—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using electric or magnetic heating means
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/031—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters having means for by-passing filters, e.g. when clogged or during cold engine start
    • F01N3/032—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters having means for by-passing filters, e.g. when clogged or during cold engine start during filter regeneration only
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • 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
    • F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
    • 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
    • F01N3/0821—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with particulate filters
    • 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
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • 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—Regulation of absorbents or adsorbents, e.g. purging
    • 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
    • F01N2250/00—Combinations of different methods of purification
    • F01N2250/14—Combinations of different methods of purification absorption or adsorption, and filtering
    • 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
    • F01N2260/00—Exhaust treating devices having provisions not otherwise provided for
    • F01N2260/04—Exhaust treating devices having provisions not otherwise provided for for regeneration or reactivation, e.g. of catalyst
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/10—Fibrous material, e.g. mineral or metallic wool
    • 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
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/14—Sintered material
    • 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
    • F01N2410/00—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device
    • F01N2410/04—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device during regeneration period, e.g. of particle filter
    • 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
    • F01N2410/00—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device
    • F01N2410/12—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device in case of absorption, adsorption or desorption of exhaust gas constituents
    • 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
    • F01N2510/00—Surface coverings
    • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
    • 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

Definitions

  • the present invention relates to a method of desulfation of NOx- adsorbers in a diesel exhaust system.
  • the invention further relates to a NOx-adsorbing element able to perform this method, and an NOx- adsorbing unit, comprising such NOx-adsorbing elements.
  • deNOx-catalysts In the selective catalytic reduction with hydrocarbons (deNOx-catalysts), the urea or ammonia of the SCR system is replaced by hydrocarbons.
  • the developed deNOx catalysts have specific drawbacks, related primarily to narrow temperature windows, insufficient thermal durability and/or sulfur tolerance. More importantly 10-20% NOx conversions of the system on regulated test cycles have been reported. deNOx catalysts are not currently seen as technology capable of coping with the stringent future emission targets.
  • NOx adsorbing compounds were incorporated. These compounds were supposed to adsorb NOx during periods of low exhaust gas temperature, when de deNOx catalyst activity was low, and to release it at temperatures which could favor the selective reaction with hydrocarbons.
  • NOx adsorber addition of NOx adsorbing compounds, coupled with the three-way catalyst result is the NOx adsorber.
  • NOx adsorbers are materials which store NOx under lean combustion conditions (low air to fuel ratio) and release and catalytically reduce the stored NOx under rich combustion conditions. The NOx adsorber can achieve 90% NOx reduction efficiency over relative wide temperature window.
  • the catalyst washcoat combines three active components:
  • an oxidation catalyst eg Pt
  • the system cycles through two stages of operation, including
  • the two stages of operation, storage and regeneration, essentially comprises in total 3 steps:
  • NOx emissions from the diesel engine are typically composed of 90-95% nirtric oxide, NO.
  • the NO is oxidised as much as possible to NO2 over an appropriate oxidising catalyst, eg Pt
  • the adsorbing compound eg BaO
  • NO 2 is to be provided as much as possible, since NO2 is adsorbed best by the NOx-adsorbing compounds.
  • Regeneration of the NOx adsorber involves reaction mechanisms virtually identical to those found in the gasoline three-way catalyst.
  • a reductant, presumable carbon monoxide or hydrocarbons reacts with NOx in the absences of oxygen to form elementary nitrogen. Therefore periodic "rich" conditions, a rich air to fuel mixture, are necessary.
  • such enrichment of the exhaust gases with additional HC could be realized by two methods: (1) Injection of hydrocarbons, preferable diesel fuel, into the exhaust system upstream of the catalyst or (2) Late-in-cylinder injection in a common rail fuel system (or merely late injection timing in conventional fuel systems).
  • the adsorber/catalyst performance gradually declines as fewer sites are available for NOx adsorption.
  • the S-comprising compounds stay present on the NOx adsorber. Higher levels of sulfur in fuel results in faster and more severe deactivation.
  • the present invention relates to a method of desulfation of NOx- adsorbers in combustion systems , comprising the steps of
  • ⁇ executing a loading step by passing the exhaust gasses from the diesel exhaust system through the electrically conductive substrate, at least partially oxidizing S-comprising compounds and at least ⁇ partially adsorbing oxidized S-comprising compounds as adsorbed
  • combustion system is meant a system which burns or combusts fuels, e.g. diesel, such as diesel burners or diesel engines, stationary or integrated in cars, trucks, boats or other transport means.
  • fuels e.g. diesel, such as diesel burners or diesel engines, stationary or integrated in cars, trucks, boats or other transport means.
  • the electrically conductive substrate comprising metal fibers, an oxidizing catalyst, a reducing catalyst and a NOx-adsorbing compound is hereafter referred to as "NOx-adsorber".
  • NOx-adsorber The electrically conductive substrate comprising metal fibers, an oxidizing catalyst, a reducing catalyst and a NOx-adsorbing compound is hereafter referred to as "NOx-adsorber".
  • the S-comprising compounds are oxidated and adsorbed .
  • the adsorbed S-comprising compound is a sulfate.
  • NOx from the combustion reaction is oxidized, essentially to NO 2 . This NO 2 , and possibly also the remaining NOx, is adsorbed by the NOx-adsorbing compound as inorganic nitrates.
  • the adsorbed S- comprising compounds usually sulfates will become unstable and decompose into SO 3 and the NOx-adsorbing compound.
  • These NOx- adsorbing compounds may then retake their function of adsorbing compound for either NOx or S-comprising compounds, usually SO 3 .
  • this temperature increase is obtained by providing electrical current to the electrical conductive substrate, which is heated due to the Joule-effect.
  • the temperature of the substrate is increased above the decomposition temperature of the adsorbed S-comprising components.
  • An advantage is that the temperature may be increased to more than 700°C, which decomposes the S-comprising components, being trapped on the NOx- adsorber, independent of the combustion process. So the "S-poisoning" of the NOx-adsorber is limited or reversed when the substrate is heated above the decomposing temperature of the S-comprising components.
  • S-rich diesel may be tolerated by a process comprising an NOx-adsorber as subject of the invention, being able to execute the process as subject of the invention.
  • the desulfation step of the process may be done while exhaust gasses pass through the substrate (hereafter referred to as "on-line”), or the exhaust gasses are prevented to pass through the electrically conductive substrate (hereafter referred to as "off-line”).
  • the latter off- line situation is to be preferred.
  • the desulfatation step is preferably done when the capacity or efficiency of the NOx-adsorber becomes too small.
  • Additional desadsorbtion and reducing steps may be done periodically in order to release the N-comprising compounds, usually nitrates, on the NOx- adsober.
  • the desadsorbtion and reducing steps of the adsorbed nitrates to N 2 may be done on-line or off-line.
  • the desadsorbtion and reducing steps of the N-comprising compounds are done periodically, preferably when the NOx-adsorber is near its saturation point.
  • the time and frequency of executing a loading step, a desulfation step or a desadsorbtion and reducing step of the N-comprising compounds may be preset or calculated, taking the combustion conditions into account, or may depend on appropriate measurement e.g. downstream the electrically conductive substrate. Also the time of electrically heating the electrically conductive substrate may be preset or calculated, taking the S-load of the NOx-adsorber into account.
  • the storage capacity and frequency of regeneration must be optimized during the design of the NOx-adsorber. Typically capacity of Barium adsorbers in the fresh state amounts to around 2g NOx per liter of catalyst volume. Depending on the engine emissions, catalyst size and condition, and the desired NOx reduction, regeneration must be performed every 30-120 seconds. The duration of
  • the desadsorbtion and reducing step may be done by appropriate motor management, providing hydrocarbons and/or CO to the NOx-adsober.
  • the initiation of the desadsorbtion and reducing step may be provided by a diesel combustion under rich combustion circumstances. These rich combustion circumstances provide the necessary hydrocarbons and/or CO for the reduction of the adsobed N-comprising compounds, and increasing the temperature of the exhaust gasses, and so of the N- comprising compounds, above the desadsorbtion temperature of the N- comprising compounds adsorbed on the NOx-adsorber. More diesel is provided to the combustion reaction.
  • electrical current is provided to the electrically conductive substrate of the NOx-adsorber, in order to increase the temperature of the NOx-adsorber, so assisting the desadsorbtion of the N-comprising compounds. Since the temperature is not to be as high as necessary to release the adsorbed S-comprising compounds, less current is necessary.
  • CO and hydrocarbons may be provided by partially combusting soot, trapped by a soot trap which is installed upstream of the NOx-adsorber.
  • a soot trap which is installed upstream of the NOx-adsorber.
  • an electrically regeneratable metal fiber soot filter being part of the combustion system, is installed upstream the NOx-adsorber.
  • this electrically regeneratable metal fiber soot filter is installed close to the electrically conductive substrate of the NOx- adsorber, e.g. both the electrically regeneratable metal fiber soot filter and the electrically conductive substrate facing one to the other.
  • the electrically regeneratable metal fiber soot filter will be loaded with soot after a certain period of time, this is during the loading step.
  • electrical current is provided to the electrically regeneratable metal fiber soot filter, which, due to the Joule effect, will be heated above the ignition temperature of the soot.
  • Hydrocarbons and CO may be obtained by combustion of the soot and SOF are vaporized.
  • the hydrocarbons, CO and SOF are used as reductans during the reduction reaction of the decomposed N-comprising compounds adsorbed on the off-stream NOx-adsorber, providing N2.
  • the NOx-adsorber positioned in the direct vicinity of the electrically regeneratable metal fiber soot filter will be heated to a certain extend by heated exhaust gasses passing through the electrically conductive substrate or via radiation from the electrically regeneratable metal fiber soot filter.
  • the electrical conductive substrate may additionally be heated, if necessary, using electric current passing through the substrate during desadsorption and reduction of the adsorbed N-comprising compound. Since the temperature is not to be as high as necessary to release the adsorbed S-comprising compounds, less current is necessary.
  • additional desadsorbing and reducing steps may be executed, using combustion under rich combustion circumstances.
  • the management e.g. duration and frequency of steps, and if necessary additional motor management
  • these steps of the process being the desadsorbtion and reduction of the N-comprising components, desulfation step, and possibly the regeneration step of the soot filter
  • the NOx-adsorber comprises an oxidizing catalyst, e.g. Pt or Pd.
  • the NOx-adsorber further comprises a reducing catalyst, e.g. Rh.
  • the NOx-adsorber also comprises an NOx-adsorbing compound, comprising alkali-earth metals, such as Mg, Ca, Sr or Ba, alkali metals such as Li, Na, K, or Cs or rare earth metals such as Y, La or other lanthanides.
  • Those NOx-adsorbing compounds are preferably present as salt such as oxides.
  • BaO is used.
  • active elements may be present homogeneously over the depth of the substrate, through which the exhaust gasses are to flow.
  • each active element may be present at preferred depth of the substrate.
  • They may be provided on the substrate using presently known coating techniques, such as CVD- techniques, sol-gel techniques or by using wash coats.
  • the catalyst support and the active elements can be provided on the substrate using precipitation and coprecipitation techniques, e.g. using washcoats.
  • the washcoats can be applied as an aqueous slurry, by a continuous or non- continuous dipping process, washcoats can also be applied using a spray process.
  • the catalyst support and active elements can also be provided on the substrate using a sol-gel preparation. If the above techniques only where used to ad a support on the substrate, CVD techniques or other know coating techniques can be used to provide the substrate/support with the active elements.
  • Some metal fleece surface treatments may be used prior to the application of the above described techniques, and some heat treatments can be applied afterwards.
  • the electrically conductive substrate preferably comprises metal fibers.
  • the substrate may differ in alloy, length and diameter according to the required properties of the substrate.
  • the substrate consists of a metal fiber fleece.
  • a sintered metal fiber fleece is most preferred.
  • the weight, air permeability, thickness, electrical surface resistance, surface density and/or porosity may be varied to provide the required substrate properties.
  • the electrically conductive substrate may further comprise other heat resistant materials and fibers, such as ceramic fibers.
  • the invention further relates to a NOx-adsorbing element able to perform this process as subject of the invention.
  • An NOx-adsorbing element as subject of the invention comprises an electrically conductive substrate, which comprises metal fibers.
  • metal fibers are to be understood as all kinds of metal fibers, preferably stainless steel fibers.
  • the alloy of metal or steel may be chosen depending on the temperature range which is to be withstand by the metal fibers.
  • Stainless steel fibers of AISI alloys of the 300- or 400 series, or alloys such as Inconel® are to be preferred.
  • alloys comprising Fe, Al and Cr are preferred, such as Fecralloy®.
  • the fibers may be obtained by any presently known production method, such as bundle drawing or shaving.
  • Fiber equivalent diameters between land 100 ⁇ m are to be used, preferably between 2 and 50 ⁇ m, e.g. between 12 and 35 ⁇ m such as 12, 17 and 22 ⁇ m.
  • the metal fiber fleece is sintered using appropriate sintering circumstances, according to the alloy used.
  • the metal fibers are obtainable by bundle drawing or coil shaving. The latter is described more in detail in WO97/04152.
  • Equivalent diameter is to be understood as the diameter of a radial cut of an imaginary round fiber, having an identical surface as the radial cut of the fiber under consideration.
  • the substrate comprises or preferably even consists of metal fibers.
  • a 100% metal fiber fleece is preferably, possibly sintered.
  • Such electrically conductive substrate may further comprise thermally resistant e.g. ceramic particles or thermally resistant e.g. ceramic fibers.
  • the electrical resistance can be varied over the surface of the substrate, although preferably, this electrical resistance is identical over the surface of the substrate and not directionally dependent.
  • the electrically regeneratable metal fiber soot filter preferably comprises or even consists of metal fibers.
  • a 100% metal fiber fleece is preferably, possibly sintered.
  • Such electrically regeneratable metal fiber soot filter may further comprise thermally resistant e.g. ceramic particles or thermally resistant e.g. ceramic fibers.
  • the electrical resistance can be varied over the surface of the electrically regeneratable metal fiber soot filter, although preferably, this electrical resistance is identical over the surface of the electrically regeneratable metal fiber soot filter and not directionally dependent.
  • Metal fibers used to provide electrically regeneratable metal fiber soot filter may be of the same of a different type as the metal fibers used to provide the electrically conductive substrate of the NOx-adsorber.
  • the weight, air permeability, thickness, electrical surface resistance, surface density and/or porosity of the electrically conductive substrate may be varied to provide the required substrate properties.
  • the electrically conductive substrate is provided with at least two contact bodies, via which the electrically conductive substrate may be connected by means of current supply cables with an electrical power system, e.g. a battery and/or an integrated circuit, periodically switching the electrical current in order to execute the decomposition step of the S-comprising compounds of the NOx- adsorber.
  • an electrical power system e.g. a battery and/or an integrated circuit
  • This contact body divides in a proper way the electric current over the electrically conductive substrate.
  • these contact bodies are metal foils, e.g. Ni-foil or metal woven meshes, preferably sintered at two ends of the electrically conductive substrate.
  • the contact bodies are thermally spayed on the electrically conductive substrate.
  • the current supply cables are connected to the contact bodies by welding (e.g. spot-welding), thermally spraying, sintering or by means of bolts and nuts.
  • Identical or similar contact bodies may be provided to the electrically regeneratable metal fiber soot filter, if one is installed upstream of the electrically conductive substrate.
  • An NOx-adsorbing element further comprises a fixing means, which is to keep the electrically conductive substrate in place.
  • the electrically conductive substrate is electrically insulated from the fixing means, or the fixing means itself is provided out of electrically insulating material.
  • this electrically regeneratable metal fiber soot filter may be fixed by the same fixing means as the one keeping the electrically conductive substrate in place.
  • a number of NOx- adsorbing elements may be assembled to a NOx- adsorbing unit, in order to provide sufficient electrically conductive substrate to the combustion system.
  • Each NOx- adsorbing element separately, or a group of NOx- adsorbing elements together are located in a housing.
  • the electrically regeneratable metal fiber soot filter or filters are located in the same housing.
  • the electrically regeneratable metal fiber soot filter or filters are positioned near the electrically conductive substrate or substrates and are fixed by the same fixing means.
  • a NOx- adsorbing unit further comprises an appropriate valve system, which shut of the NOx- adsorbing element or elements during the execution of the different steps.
  • This valve system may be controlled by the same integrated circuit as the one which controls the provision of electric current tot he NOx-adsorbing element.
  • NOx-adsorbing unit possibly with integrated electrically regeneratable metal fiber soot filter
  • appropriate electrical equipment and components such as integrated circuits, connected to the electrically conductive substrates, the valve system and possibly to the electrically regeneratable metal fiber soot filters or measurement equipment controlling the process parameters in the NOx-adsorbing unit (e.g. pressures, temperatures, NOx-concentrations, ).
  • the NOx-adsorbing unit is then a part of the combustion system as subject of the invention, which further comprises a combustion unit and an exhaust system, of which the NOx-adsorbing unit, and so the NOx- adsorbing elements, are part of.
  • FIGURE 1 , and FIGURE 2 show a detail of NOx-adsorbing elements as subject of the invention.
  • - FIGURE 3 is a section of an NOx-adsorbing element as subject of the invention.
  • FIGURE 4 and FIGURE 5 show contact bodies of an NOx-adsorbing element as subject of the invention.
  • FIGURE 6 shows an alternative cross section of an NOx-adsorbing element as subject of the invention.
  • FIGURE 7 shows schematically a NOx-adsorbing element comprising additionally an electrically regeneratable metal fiber soot filter
  • FIGURE 8 shows schematically anNOx-adsorbing unit as subject of the invention.
  • FIGURE 1 Preferred NOx-adsorbing elements as subject of the invention are shown in FIGURE 1 , 2 and 3.
  • a number of NOx-adsorbing elements 11 are stacked one on top of the other. They all have a ring-like shape.
  • a perforated metal tube 12 is positioned inside the inner opening 13 of the NOx-adsorbing element. Between each NOx-adsorbing element, a disc-like Si0 2 felt material 14 is positioned to thermally insulate the different NOx-adsorbing elements from each other.
  • a metal plate 15 is fixed against the upper and lower NOx-adsorbing element e.g. as shown in FIGURE 1 by means of a screw 16, which pushes the plate towards the NOx-adsorbing element.
  • a spring may be introduced between the plate 15 and the crew 16 to absorb thermal expansions of the stack of NOx- adsorbing elements 11.
  • the exhaust gas flows in from the outer side of the NOx-adsorbing elements (indicated with arrow 17), through the electrically conductive substrate 18 through the perforations of the metal tube 12, to the further elements of the combustion system, of which it is part, as indicated with arrow 19.
  • the gas flow may be directed in the other direction, being an "inside-out" flow.
  • a metal fiber fleece is used as electrically conductive substrate 18.
  • the NOx-loaded gas flows in via the inflow side 20, through the metal fiber fleece, via the outflow side 21 of the metal fiber fleece to the further combustion system.
  • the metal fiber fleece is connected via two contact bodies 22 and 23 to an electric circuit 24, providing electrical current to the metal fiber fleece in order to heat the electrically conductive substrate.
  • the metal fiber fleece is preferably pleated in such a way that the thermal radiation heat, generated by the pleats 25, radiates to the adjacent pleats, as indicated by arrows 26.
  • a sintered metal fiber fleece comprising three layers of stainless steel fibers is used as electrically conductive substrate.
  • a first layer comprises 600 g/m 2 of Fecralloy® fibers with equivalent diameter of 17 ⁇ m.
  • a second layer of Fecralloy® fibers is applied on top of the first layer. This layer comprises 250 g/m 2 of fibers with equivalent diameter of 22 ⁇ m.
  • a third layer of Fecralloy® fibers is applied on top of the second layer, having fibers with equivalent diameter of 35 ⁇ m. This third layer comprises 600 g/m 2 fibers.
  • An oxidizing catalyst Pt, and a reducing catalyst Rh is provided.
  • BaO is preferably used as NOx-adsorbing compound.
  • FIGURE 2 The set-up of a preferred embodiment of the NOx-adsorbing element is shown in FIGURE 2.
  • a fixing means being a flank 28 of the NOx- adsorbing element comprises a metal rim 29, to which a wire mesh 30 is spot welded on several spots 31.
  • a fine layer of ceramic material 32 was sprayed on the electrical and thermal insulating side 33 of the flank.
  • a relatively thick layer of ceramic adhesive 34 was applied on this mesh and the electrical and thermal insulating side 33, before the metal fiber fleece 18, loaded with an oxidizing catalyst, a reducing catalyst and an
  • this ceramic adhesive 34 which comprises more than 10% of weight of short metal fibers.
  • a fine Ni-sheet 36 was sintered to the ends of the metal fiber fleece. Both contact bodies were brought together and fixed to an insulating plate 37, e.g. a mica- plate by means of two bolts 38 and 39. In order to avoid electrical contact between contact body 22 and bolt 38, and between contact body 23 and bolt 39, two mica sheets were inserted between the insulating plate 37 and the contact bodies 22 and 23.
  • an insulating plate 37 e.g. a mica- plate
  • FIGURE 5 An alternative set-up is shown in FIGURE 5.
  • An identical set-up as in FIGURE 4 is used, but the contact body 22 is shaped in such a way that no material of this contact body 22 is present at behind bolt 38, fixing the contact body 23 to the insulating plate 37.
  • the contact body 23 is shaped in such a way that no material of this contact body 23 is present at behind bolt 39, fixing the contact body 22 to the insulating plate 37.
  • the use of two mica plates 40 may be avoided, which may simplify the construction of the NOx-adsorbing element.
  • the electric connection of the contact bodies to the power supply or an integrated circuit may be done by a current supply cable, connected to e.g. the used bolts and nuts.
  • FIGURE 6 An alternative cut according to BB' is shown in FIGURE 6.
  • the perforated tube in this embodiment has an elliptic section.
  • the metal fiber fleece is pleated according to pleating lines, which enables radiation from one pleat to another during the increasing of the temperature for the desulfatation steps of the adsorbed S-comprising compounds as subject of the invention.
  • the NOx- and S-loaded exhaust gasses are supplied to the NOx-adsorbing element.
  • the oxidizing catalyst oxidizes the NOx and the oxidated products are trapped or adsorbed by the NOx-adsorber, forming N-comprising compounds.
  • Pt is used as an oxidizing catalyst.
  • NOx is oxidized to a large extend to NO 2 .
  • NO 2 and the remaining NOx is than adsorbed on by the NOx-adsorbing compound as N-comprising compounds.
  • the NOx-adsorbing compound is BaO, so Ba(NO 3 ) 2 is provided.
  • these compounds become unstable and are released again as NO 2 and possibly NOx. This may be obtained by running the combustion process for a short period in time under rich combustion circumstances. Hydrocarbons and CO is than provided to the NOx-adsorber. Possibly, some electric current may be provided to the electrically conductive substrate to increase its temperature (e.g. above 200°C) due to Joule- effects. This helps to proceed the desadsorbtion and reduction step.
  • N-comprising compounds usually NO and NO 2
  • the reducing catalyst preferably Rh, providing N 2 , and making use of the hydrocarbons and/or CO as reductance.
  • the exhaust gasses comprise also amounts of S-comprising elements, which are at least partially oxidized by the oxidizing catalyst to oxidized S-comprising compounds, usually S0 3 , when the exhaust gasses pass trough the electrically conductive subsstrate.
  • This oxidized S-comprising compound is than at least partially adsorbed by the NOx-adsorbing compound as adsorbed S-comprising components, usually sulfates.
  • the temperature of the electrically conductive substrate is preferably increased above 700 °C.
  • the desulfation of NOx adsorbers requires temperatures between 500-700°C.
  • a desulfation of Barium-based NOx-adsorbers is achieved at at least 650°C.
  • SO 3 has been adsorbed as BaSO 4 .
  • the temperature is to increase preferably to more than 700°C to release SO 3 again. This may be realized since the substrate is electrically conductive, and electric current is provided to the substrate to heat this substrate due to its Joule effect.
  • a NOx-adsorbing unit as subject of the invention comprises appropriate valve systems to shut down one or more NOx-adsorbing elements during desadsorbtion and reduction of the N-comprising components and/or decomposition of the adsorbed S-comprising compounds, in case one of the steps is done off-line.
  • FIGURE 7 shows a preferred embodiment of NOx-adsorbing element as subject of the invention, comprising a NOx-adsorber and an electrically regeneratable metal fiber soot filter.
  • the NOx-adsorbing element has a ring-like structure.
  • FIGURE 7 shows a section of the NOx-adsorbing element, perpendicular to its axis 71.
  • An electrically regeneratable metal fiber soot filter 72 is provided, being a sintered metal fiber fleece, having an essentially rectangular shape. This rectangle is pleated parallel to one pair of edges of the rectangle, so providing the other pair of edges a waves shape. The two edges parallel to the pleating lines are brought together at each edge, a contact body 73 and 74 is provided.
  • An electrically conductive substrate 75 is provided, being a sintered metal fiber fleece, having an essentially identical shape as the electrically regeneratable metal fiber soot filter 72.
  • This electrically conductive substrate 75 is pleated to an essentially identical shape as the electrically regeneratable metal fiber soot filter filter 72.
  • the electrically conductive substrate 75 is positioned downstream of the electrically regeneratable metal fiber soot filter 72. To both edges of the electrically conductive substrate, two contact bodies 76 and 77 may be provided.
  • the metal fiber fleeces are preferably pleated in such a way that the thermal radiation heat, generated by the pleats 78, radiates to the adjacent pleats, as indicated by arrows 79.
  • An important reduction of electrical power is obtained using this radiation heat to increase the temperature of the electrically regeneratable metal fiber soot filter and electrically conductive substrate during execution of the regenerating, respectively desulftation step and/or releasing and reducing steps of the process as subject of the invention. Since the electrically regeneratable metal fiber soot filter 72 is situated close to the electrically conductive substrate 75, thermal energy will radiate from the electrically regeneratable metal fiber soot filter 72 to the electrically conductive substrate 75, so partially increasing the temperature of the electrically conductive substrate during regeneration of the filter.
  • a sintered metal fiber fleece comprising three layers of stainless steel fibers is used.
  • a first layer comprises 600 g/m 2 of Fecralloy® fibers with equivalent diameter of
  • An oxidizing catalyst Pt, and a reducing catalyst Rh is provided.
  • BaO is preferably used as NOx-adsorbing compound.
  • a second metal fiber fleece is used as an electrically regeneratable metal fiber soot filter, which traps the soot particulate and SOF before the exhaust gas is to flow though the electrically conductive substrate.
  • the soot and SOF, retained by this metal fiber fleece will be released, e.g; vaporized as far as SOF is concerned, or combusts, as far as soot is concerned, and provide hydrocarbons and CO to the part of the combustion system downstream of this metal fiber fleece, being an electrically regeneratable metal fiber soot filter.
  • a sintered metal fiber fleece comprising three layers of stainless steel fibers is preferably used.
  • a first layer comprises 600 g/m 2 of Fecralloy® fibers with equivalent diameter of 17 ⁇ m.
  • a second layer of Fecralloy® fibers is applied on top of the first layer. This layer comprises 250 g/m 2 of fibers with equivalent diameter of 22 ⁇ m.
  • a third layer of Fecralloy® fibers is applied on top of the second layer, having fibers with equivalent diameter of 35 ⁇ m. This third layer comprises 600 g/m 2 fibers.
  • a soot retention of 91% was obtained, using a stainless steel fleece, having a porosity of 85%.
  • the soot was so-called depth filtered. This is to be understood as the fact that soot particles were trapped through the whole depth of the filter. SOF is present in its liquid phase on the soot particulates.
  • the contact bodies 73, 74, 76 and 77 used to provide electric current to the electrically regeneratable metal fiber soot filter 72, and the electrically conductive substrate 75, are identical to the one as indicates 22 and 23 in FIGURE 3.
  • the contact bodies 73, 74, 76 and 77 are connected to a power supply and/or an appropriate integrated circuit 70.
  • Both the electrically regeneratable metal fiber soot filter 72 and the electrically conductive substrate 75 are integrated in a NOx-adsobring element in a similar way as shown in FIGURE 2.
  • this NOx-converting unit preferably the exhaust gas flows in from the outer side of the NOx-adsorbing element, through the electrically regeneratable metal fiber soot filter 72, through the electrically conductive substrate 75, out of the NOx-adsorbing element.
  • soot and SOF are retained by the electrically regeneratable metal fiber soot filter 72.
  • the exhaust gasses, still loaded with NOx is than provided to the electrically conductive substrate 75.
  • the oxidizing catalyst oxidizes the NOx and the oxidated products are trapped or adsorbed by the NOx-adsorber, forming N-comprising compounds, usually nitrides. S-comprising compounds are adsorbed as well.
  • Pt is used as an oxidizing catalyst.
  • NOx is oxidized to a large extend to NO 2 .
  • NO 2 and the remaining NOx is than adsorbed on by the NOx-adsorbing compound as N-comprising compounds.
  • the NOx-adsorbing compound is BaO, so Ba(NO3)2 is provided.
  • the exhaust gas is preferably prevented to flow through the electrically regeneratable metal fiber soot filter 72 and the electrically conductive substrate 75.
  • Electrical current is provided to the electrically regeneratable metal fiber soot filter via current supply cables and the contact bodies 76 and 77.
  • the electrically regeneratable metal fiber soot filter 72 is heated unto a temperature up to 1000°C, but preferably in the range of 500°C to 600°C.
  • the soot and the SOF, which was retained by the electrically regeneratable metal fiber soot filter 72, is combusted or vaporized, providing CO 2 , CO and hydrocarbon compounds.
  • the electrically conductive substrate 75 Due to the increased temperature of the electrically regeneratable metal fiber soot filter 72, the electrically conductive substrate 75 is also heated, up to a temperature of more than 250°C.
  • the N-comprising compounds become unstable and are released again as NO 2 and possibly NOx. Thermal energy, radiated by this electrically regeneratable filer during regeneration is used. In case this temperature is not reached due to radiation of the electrically regeneratable metal fiber soot filter 72 during regeneration, additional electrical current may be supplied to the electrically conductive substrate 75.
  • the electrically conductive substrate 75 comprise significantly amounts of S-comprising elements (e.g. due to combustion of S-rich diesel), periodically the temperature of the substrate is preferably increased above 700 °C.
  • electrical current is provided to the electrically conductive substrate 75.
  • BaO is used, SO 3 has been adsorbed as BaSO 4 .
  • the temperature is to increase to more than 700°C to release SO 3 again. This may be realized when the substrate being electrically conductive, and electric current is provided to the substrate to heat this substrate due to its Joule effect.
  • this desulfation step is executed simultaneously with a regeneration of the electrically regeneratable metal fiber soot filter 72.
  • An NOx-adsorbing unit 88 is shown in FIGURE 8. As shown, several NOx-adsorbing elements 80 are stacked into stacks 87, which are in their turn located in a housing 86.
  • All NOx-adsorbing elements 80 have a ring-like shape.
  • a perforated metal tube 81 is positioned inside the inner opening 82 of the NOx- adsorbing elements.
  • a disc-like SiO 2 felt material 83 is positioned between each NOx-adsorbing element to thermally insulate the different NOx- adsorbing elements from each other.
  • Several stacks are positioned in NOx-adsorbing unit 88.
  • a valve system 84 is installed comprising one or several valves 85, which can shut off periodically one or more stacks, while other stacks are kept inline.
  • one or several NOx-adsorbing elements are to execute the desadsorption and reducing step, the desulfation step and possibly the regeneration step of a soot filter.
  • the electric current supply to the different NOx-adsorbing elements 80 and the control of the valve system 84 may be done by one integrated circuit 86.
  • This NOx-adsorbing unit 88 may be used as a part of the exhaust system being part of a combustion system, e.g. a diesel engine.

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Abstract

L'invention concerne un procédé de désulfuration d'absorbeurs de NOx (11) dans un système d'échappement de moteurs diesel. Ce procédé consiste à augmenter périodiquement la température du substrat électroconducteur (18) de l'absorbeur de NOx (11), au-delà de la température de décomposition des composés sulfurés absorbés, en alimentant ce substrat électroconducteur (18) en courant électrique.
PCT/EP2002/006249 2001-06-26 2002-06-21 Procede de desulfuration d'absorbeurs de nox WO2003002854A1 (fr)

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JP2003508810A JP2004521256A (ja) 2001-06-26 2002-06-21 ＮＯｘ吸着体を脱硫する方法
EP02740693A EP1399652A1 (fr) 2001-06-26 2002-06-21 Procede de desulfuration d'absorbeurs de nox
US10/482,135 US20040216448A1 (en) 2001-06-26 2002-06-21 Method of desulfation of nox-adsorbers

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US30045601P 2001-06-26 2001-06-26
US30043201P 2001-06-26 2001-06-26
US60/300,456 2001-06-26
EP01202456A EP1270886A1 (fr) 2001-06-26 2001-06-26 Procédé et dispositif pour diminuer le taux de NOx dans un système d'échappement Diesel
EP01202457.6 2001-06-26
US60/300,432 2001-06-26
EP01202456.8 2001-06-26
EP01202457 2001-06-26

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JP2004521256A (ja) 2004-07-15
EP1399652A1 (fr) 2004-03-24
CN1513082A (zh) 2004-07-14
US20040216448A1 (en) 2004-11-04

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