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
• • 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
  • B01D53/9495—Controlling the catalytic process
• • 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
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/021—Introducing corrections for particular conditions exterior to the engine
  • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
  • F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
  • F02D41/0275—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
  • F02D41/028—Desulfurisation of NOx traps or adsorbent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/30—Sulfur compounds
  • B01D2257/302—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
  • 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
  • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
  • F01N2570/24—Hydrogen sulfide (H2S)
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
  • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• the subject of the invention is a process for the desulfation of an exhaust gas purification catalyst of an internal combustion engine, in particular a diesel engine for an automobile.
• the exhaust gas purification system has a catalyst comprising a means of accumulation of nitrogen oxides, generally called "NO x -trap", which is integrated in the process. exhaust line and in which are trapped nitrogen oxides emitted during normal operation of the engine lean mixture.
• a catalyst comprising a product for storing nitrogen oxides in the form of nitrates, for example alumina on which alkali and / or alkaline earth elements, rare earths and metals are deposited. precious.
• a nitrogen oxide storage catalyst is described in detail, for example, in EP-A-0580389.
• NO x -trap type catalysts are sensitive to sulfur which is present in the lubricant and the fuel and is found in the exhaust gas, after passing through the combustion chamber, mainly in the form of SO 2 .
• SO 2 is readily oxidized to SO 3 which reacts with the basic catalyst sites in competition with NO 2 .
• sulfuric acid is stronger than nitric acid, the sulphates thus formed have a greater thermodynamic stability than the corresponding nitrates.
• the nitrogen oxide trap will accumulate sulfur in the form of sulphates which will gradually occupy the adsorption sites. nitrogen oxides, until saturation of the accumulation product.
• Such a catalyst must be periodically regenerated by exploiting the engine in a rich regime for a certain time in order to decompose the nitrates by releasing NO x, which is then reduced to nitrogen by the reducing agents such as H 2 , HC and CO contained in the gases. escape, as written in EP-A-0 580 389.
• Desulfation that is to say the removal of sulphates occupying the NO x adsorption sites is the same type of mechanisms as that of nitrates, but with the constraint of greater stability.
• the reduction of the sulphates requires a rich medium and much higher temperatures than the NO x reduction.
• WO2002053885 proposes a different desulfation process of the invention, because it uses an electric heating means.
• Document DE10153901 proposes a method of switching of richness consisting of rapidly alternating poor phases and rich phases. However, the phases are not precisely adjusted to reduce the emission of smelly species.
• the object of the invention is to remedy such drawbacks.
• the desulfation is carried out during operation of a lean-burn engine, at separate time intervals, by heating the catalyst to a minimum regeneration temperature of at least 550 ° for example and regulating for a short time the composition of the gaseous mixture which can be overall reducing.
• the emission during desulfation of malodorous sulfur species is avoided or at least reduced by a precise adjustment of the composition of the mixture to a richness very little greater than 1, that is to say less than 1, 05.
• the richness of the mixture is adjusted so as not to exceed 1, 03 and, preferably, to be of the order of 1.01.
• FIG. 1 shows three diagrams indicating, for three tests carried out at different richnesses, the variations in the proportions of the species sulfur emitted in the exhaust gas;
• Figure 2 is a diagram indicating, for different wealth, the relative proportions of sulfur species emitted in desulfation;
• Figure 3 is a diagram showing the proportions of reducers emitted to the exhaust.
• the following table groups together all the gaseous compositions that have been tested for different kinds of richness, indicating, for each composition, the relative proportions of oxygen, water and the main reducing agents.
• the changeover to rich mixture takes place at the same moment, after a time of about 250 seconds corresponding to the heating of the catalyst tested to the desired temperature.
• Figure 1 has a richness of 1, 10. It is observed that the released proportion of H 2 S increases sharply from the tilting to a concentration greater than 120 ppm and then decreases gradually. The concentration of COS follows a similar but more moderate evolution, the peak reached being 40 ppm. On the other hand, the concentration of SO 2 remains very low.
• Figure 1c which corresponds to a richness of 1.01, shows a complete change in the relative proportions of the sulfur species.
• the gases emitted mainly comprise sulfur dioxide, the concentration of which increases abruptly as soon as it tilts, to a peak of the order of 170 ppm.
• the concentration of H 2 S is very low at tilting and then increases only moderately. COS concentration is still very low.
• This diagram shows the selectivity in each of the sulfur species emitted in desulphatation and also indicates that a very slight excess of reducing agents, that is to say a richness slightly greater than 1, makes it possible to considerably limit the sulphide formation. hydrogen and, consequently, the emission of unpleasant odors.
• FIG. 3 shows, according to the richness of the mixture, the evolution, from the tilting, of the concentrations of reducers, respectively CO on the scale of left and HC on the scale of right. It appears that the use, according to the invention, of a low desulfation richness, of the order of 1.01, makes it possible to considerably reduce the amount of reducing agents and, in particular, carbon monoxide, emitted at the exhaust.
• pollution control systems such as nitrogen oxides traps and particulate filters must be regenerated and, for this purpose, it is known to develop "multi-injection" strategies introducing a post -injection in the relaxation phase in order to raise the temperature of the gases.
• the regeneration of NO x traps being made lean, it is possible for the desulfation, to carry out a fractionation richness around the stoichiometric setting by adjusting the composition of the mixture to a richness slightly higher than 1 for a few seconds each operating cycle in lean mixture for NO x reduction.
• the invention thus makes it possible to optimize the desulphation both with respect to the depollution for the regeneration of the purification system and also with respect to the environment by suppressing or, at least, reducing the unpleasant odor and toxicity of sulfur species emitted during desulfation.
• the invention is not limited to the details of the embodiment which has just been described, but covers all the variants remaining in the same protective frame.
• it is particularly advantageous to carry out desulphation at a richness of 1.01, but a significant reduction in the emission of smelly sulfur species is obtained by not exceeding a richness of 1.05, and preferably 1. , 03.

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

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• 2006
  • 2006-02-01 FR FR0600941A patent/FR2896704B1/fr not_active Expired - Fee Related
• 2007
  • 2007-02-01 WO PCT/FR2007/050729 patent/WO2007090977A2/fr not_active Ceased
  • 2007-02-01 EP EP07731557A patent/EP1979587A2/de not_active Withdrawn

Non-Patent Citations (1)

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