Classifications

• • 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
  • F02D41/008—Controlling each cylinder individually
  • F02D41/0082—Controlling each cylinder individually per groups or banks
• • 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
  • 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
• • 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

Definitions

• the invention relates to the regeneration of a NOx storage catalytic converter of an internal combustion engine, for example a lean-mix engine, a DI engine or a diesel engine, according to the preamble of claim 1.
• NOx storage catalysts are more promising than the zeolite catalysts just discussed, since they use both the hydrocarbons in the exhaust gas and the hydrogen and CO as reducing agents. Basically, they are 3-way catalysts with a component for storing NOx. However, the NOx accumulator clogs with NOx, especially after longer lean phases of the engine, and is therefore no longer effective.
• EP 0540280 describes the exhaust gas treatment with the aid of an exhaust gas treatment system which contains a means for storing and releasing the NOx, the nitrogen oxides being temporarily stored in the lean operation of the engine and being released thermally by heating the introduced exhaust gas. The nitrogen oxides released are then decomposed again under oxidizing conditions by means of a NOx-decomposing catalyst.
• the NOx-decomposing catalyst can consist of a 3-way catalyst and / or a zeolite catalyst which is operated at ⁇ less than or equal to one.
• the temperature range in which the 3-way catalytic converters start up is particularly problematic here because nitrous oxide is increasingly formed in this phase by partial reduction of the motorized nitrogen oxides. If periodic cooling of the 3-way catalytic converter is to be passed through this area again and again, an excessive production of nitrous oxide is to be expected, which is undesirable because of the greenhouse gas relevance of this gas.
• EP 0562 805 describes an exhaust gas aftertreatment of an internal combustion engine, in which the exhaust system has two lean NOx catalysts which are alternately flowed and arranged parallel to one another. Furthermore, the known device comprises a device for changing the space velocity of the exhaust gas in order to be able to set an optimal space velocity of the exhaust gas. In addition, the exhaust system has a means for injecting HC directly into the exhaust duct.
• the suitability for long-term use is questionable, since zeolite catalysts are not thermally stable, in particular they cannot tolerate a rich or stoichiometric exhaust gas.
• the durability of the device for changing the space velocity of the exhaust gas circuit is also problematic.
• the catalyst according to EP 0 562 805 does not reach the order of magnitude of over 90% required to comply with the newer exhaust gas limit values. Furthermore, the problem of nitrous oxide formation and the insufficient HC and CO conversion of these catalysts is unsolved.
• EP 0580 389 discloses a method for exhaust gas aftertreatment of lean-burn engines which are equipped with a NOx absorber based on alkali, alkaline earth or rare earth metals, a 3-way catalytic converter arranged downstream, and with sensors for detecting the load and the exhaust gas temperature .
• the information from the sensors limits the area within which the NOx absorber is able to store nitrogen oxides.
• Regeneration of the catalyst is achieved by greasing for a predetermined period.
• a disadvantage of this known device is the separation between the absorber and the 3-way catalytic converter, since the predominantly engine-generated nitrogen oxides must first be oxidized to NO2 in order to be stored in the absorber.
• EP 0560991 describes a system for treating an exhaust gas of an internal combustion engine, in which the absorber and the catalyst are contained in a housing.
• the nitrogen oxides are stored when the engine is operated lean, i.e. H. the exhaust gas is lean, and released when the oxygen concentration in the exhaust gas is reduced to rich or stoichiometric ⁇ values, so that the released NOx is reduced with the unburned hydrocarbons and the CO of the exhaust gas.
• the switchover from the lean to the rich or stoichiometric operation is accompanied by torque jumps which the driver of the vehicle perceives as only desirable if they occur during an acceleration phase. If these torque jumps occur during a constant operating phase, they are perceived as extremely undesirable. Since the NOx store is normally emptied during constant operating phases, attempts are made to reduce these torque jumps by shifting the ignition timing simultaneously with the enrichment.
• the currently known NOx storage catalytic converters are deactivated by sulfur-containing fuel.
• the NOx-absorbing material of the NOx storage catalyst in particular BaO or BaC ⁇ 3 ⁇ forms with the SO2 present in the exhaust gas, which oxidized to SO3 on the platinum present in the catalyst, thermally stable sulfates which can be decomposed at a temperature which is above the temperature at which the nitrates formed from the storage material and the NO2 are decomposed.
• a sulfate regeneration program is therefore carried out from time to time, increasing the temperature to approx. 600 - 700 ° C by enriching the
• Exhaust gas is caused to decompose the sulfates.
• a disadvantage of the enrichment is that this is normally correlated with an increase in engine power, so that ultimately the vehicle accelerates unintentionally when the desulfation is carried out.
• the invention is therefore based on the object of providing a device for treating exhaust gas from an internal combustion engine which brings about a reduction in the NOx content of the exhaust gas and / or in the sulfate content of the NOx accumulator without the occurrence of a torque jump or an increased power output.
• the invention is used in the detoxification of exhaust gases from an internal combustion engine, the detoxification being in particular a reduction of the nitrogen oxides.
• the invention can also be used for the intermediate storage of SOx, as can be the case depending on the sulfur content of the fuel in exhaust gas cleaning devices of lean-burn internal combustion engines.
• NOx is usually stored by storing NO 2 (for example as nitrate), alkaline earth oxides and / or carbonates (for example BaO) being particularly suitable.
• Such substances are also able to store SOx, in particular in the form of SO 3 as sulfates.
• a SOx storage can be placed in front of a NOx storage if desired, which means that the SOx storage has higher temperatures than the NOx storage and the NOx storage is not poisoned by SOx.
• the SOx is either as such or after reaction with CO and / or HC in the most varied Released compounds, whereby no SOx is stored in the subsequent NOx storage under the present regeneration conditions.
• NOx storage will be used, unless otherwise noted, these explanations also apply equally to SOx storage or a combination of these storage facilities.
• the ⁇ value is preferably> 1.01 during the release phase of the NOx. It is possible to switch back and forth between lean engine operation and slightly above the stoichiometric exhaust gas value, the timing of the switchover depending on the duration of the lean operation.
• part of the cylinders is selectively enriched individually, while the other part of the cylinders continues to be operated lean.
• the selective cylinder-specific ⁇ detuning is preferably carried out during a constant operating phase without load changes.
• the cylinder-specific enrichment is advantageously carried out with half or a number of cylinders close to half.
• the selective cylinder-specific ⁇ detuning can be carried out with a control unit.
• this is achieved by selectively greasing the engine with one part of the cylinders and producing the other part of the cylinders lean to generate the almost stoichiometric exhaust gas. Only slight torque fluctuations occur and the engine power is not increased. Therefore one can do without further measures such as an excessive adjustment of the ignition timing.
• nitrous oxide in the process according to the invention is advantageously not above that of known 3-way catalysts. Furthermore, the device according to the invention brings about a desulfation of the NOx store through the corresponding selective cylinder-specific ⁇ detuning.
• the following table shows measured values of the gross nitrogen oxide conversion ⁇ isjOx of an engine with lean and regeneration operation in a continuous sequence of lean operation and subsequent regeneration operation once with a rich ⁇ value of 0.85 and once with a ⁇ slightly above the stoichiometric value Values of 1.01. It can be seen from the table that even slightly above of the stoichiometric ⁇ value working according to the invention
• FIG. 1 schematically shows the arrangement of the exhaust system on an internal combustion engine.
• reference numeral 1 represents a machine with more than one cylinder, such as a lean-mix gasoline engine, a diesel gasoline engine or a diesel engine, which is subsequently arranged an exhaust gas purification system 2 that has a NOx storage catalytic converter 3 having.
• a gross ⁇ value ie. H. an averaged ⁇ value of all cylinders, set from slightly above the stoichiometric value of the exhaust gas for the regeneration of the NOx storage 3 and thus causes regeneration and desulfation of the NOx storage.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Exhaust Gas After Treatment (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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ID=7853466

Family Applications (1)

Country Status (6)

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Citations (2)

Family Cites Families (14)

• 1997
  • 1997-12-29 DE DE19758018A patent/DE19758018A1/de not_active Withdrawn
• 1998
  • 1998-12-10 US US09/582,681 patent/US6823657B1/en not_active Expired - Fee Related
  • 1998-12-10 JP JP2000526286A patent/JP4299457B2/ja not_active Expired - Fee Related
  • 1998-12-10 WO PCT/EP1998/008061 patent/WO1999033548A1/de not_active Ceased
  • 1998-12-10 EP EP98965807A patent/EP1058578B1/de not_active Expired - Lifetime
  • 1998-12-10 DE DE59808396T patent/DE59808396D1/de not_active Expired - Lifetime
  • 1998-12-10 CN CNB988127342A patent/CN1262336C/zh not_active Expired - Fee Related

Patent Citations (2)

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