FR2866061A1 - EXHAUST GAS PURIFYING DEVICE OF AN INTERNAL COMBUSTION ENGINE AND METHOD OF REGENERATING SUCH A DEVICE - Google Patents

Abstract

In a method of regenerating an exhaust device (3) of an internal combustion engine (1) - the exhaust gas device comprising a NOx accumulation catalyst (4) followed, in the direction of flow of the exhaust gas, a particulate filter (5) - the particulate filter (5) is supplied with additional air during desulphurization of the NOx accumulation catalyst (4) with exhaust gas sub-stoichiometric regime. For this purpose, the exhaust gas purification device comprises a complementary air supply device (6) which, during a regeneration, blows complementary air between the NOx accumulation catalyst (4) and the particulate filter (5).

Description

The invention relates to a method for regenerating a device

  for cleaning the exhaust gases of an internal combustion engine and an exhaust gas purification device of an internal combustion engine, said engine

  purification device comprising a NOx storage catalyst and a downstream particulate filter.

  Modern exhaust gas cleaning devices for an internal combustion engine, in particular for a spark ignition engine that can operate in a lean regime or for a diesel-type internal combustion engine, comprise a NOx accumulation catalyst and a fuel filter. particles disposed downstream. The "NOx accumulation catalyst" and "particulate filter" systems must be regenerated at specified intervals which depend on the load of the system concerned. In addition, because of the sulfur content of the fuels used, it is necessary to desulfurize, from time to time, the reservoir material of the NOx accumulation catalyst to ensure the reliability of the accumulator.

  It is in the context of complete desulfurization, which occurs when the engine is operating steadily in substoichiometric mode that the thiorégénération of a NOx accumulation catalyst is the most efficient. But there is undesirable emissions of H2S that must absolutely be avoided because of their toxicity and nauseating odor. In current direct fuel injection engines (FSI engines), in order to prevent and avoid unwanted secondary emissions of substances such as hydrogen sulphide, the air / fuel ratio is adjusted alternately around the stoichiometric value. which is also called vobulation in technical jargon. However, in the case of a spark ignition engine that can operate in a lean regime, this procedure is less efficient than a complete desulphurisation and, in the case of a diesel-type internal combustion engine, it is only possible to limited way.

  For example, DE 100 23 439 discloses a regeneration process in which an exhaust gas cleaning device consisting of a NOx tank and a downstream particle filter is regenerated. in two cycles. The NOx accumulation catalyst is denitrated by enrichment during a first cycle and, during a second cycle, the particulate filter is cleaned by the fire by increasing the temperature of the poor exhaust gas to a value greater than the ignition temperature of the soot, then the NOx accumulation catalyst is desulfurized by enrichment.

  The object of the invention is, therefore, to create a method and a device which ensure a better regeneration of an exhaust gas purification device of an internal combustion engine - said purification device being consisting of a NOx storage catalyst and a downstream particulate filter - without any H2S being released.

  This objective is solved by a method and a device which make it possible to bring air complementary to the particulate filter. Preferred embodiments of the invention will be described later in the document.

  In the process according to the invention for regenerating an exhaust gas purification device of an internal combustion engine - said exhaust gas purification device comprising a NOx accumulation catalyst followed, in the flow direction 3C) of the exhaust gas, of a particle filter -, the particulate filter is supplied with additional air during desulphurization of the NOx accumulation catalyst with exhaust gas in the sub-stoichiometric state .

  The supply of the particulate filter with complementary air preferably takes place with the start of the desulphurization of the NOx accumulation catalyst and, in particular, the supply of the complementary air particulate filter is completed at the end of the desulfurization of the NOx accumulation catalyst. Desulphurization of the simultaneous and synchronous NOx accumulation catalyst and filter regeneration is therefore preferably carried out. The desulphurization of the NOx accumulation catalyst takes place, in particular, by operating the internal combustion engine in a substoichiometric mode.

  In particular, the particulate filter may also be supplied with additional air during denitration of the NOx particulate filter with sub-stoichiometric exhaust gas, preferably feeding the complementary particulate air filter. with the beginning of denitration of the NOx accumulation catalyst and the supply of the complementary air particulate filter ending at the end of the denitration of the NOx accumulation catalyst. The denitration of the NOx storage catalyst preferably takes place by operating the internal combustion engine under a sub-stoichiometric regime.

  Feeding of the complementary air particulate filter is preferably accomplished by additional air blowing downstream of the NOx storage catalyst and upstream of the particulate filter.

  The device according to the invention for purifying the exhaust gas of an internal combustion engine comprises a NOx accumulation catalyst followed, in the direction of flow of the exhaust gas, of a particulate filter, the device further comprising a complementary air supply device for supplying additional air to the particulate filter. In particular, the complementary air supply device insufflates the complementary air after the NOx accumulation catalyst and before the particulate filter, and this, to bring the complementary air to the particulate filter on the inlet side of the exhaust gases of the this last. Preferably, the complementary air supply device comprises a complementary air pump.

  The particle filter comprises in particular a layer of precious metal and the device preferably comprises a control device which controls the regeneration of the NOx accumulation catalyst and the particulate filter, as well as the supply of additional air.

  Due to the complete desulphurization of the NOx accumulation catalyst by means of the sub-stoichiometric exhaust gas, it is true that undesirable secondary emission occurs, i.e. hydrogen sulfide H2S, but this secondary emission is then re-oxidized by the additional air blowing downstream of the NOx accumulation catalyst and upstream of the particulate filter. In other words, the sub-stoichiometric exhaust gas passing through the NOx accumulation catalyst during the desulfurization together with the additional air produce in the particulate filter, i.e. on the filter, a highly exothermic reaction, whereby HC, CO, H2S and soot components are oxidized and the particulate filter is regenerated.

  It follows therefore from the above-mentioned method the following general advantages.

  The desulphurization of the NOx storage catalyst and the regeneration of the particulate filter take place simultaneously and synchronously and the synchronous regeneration makes it possible to reduce the overconsumption of fuel since the two processes take place simultaneously.

  The functions "NOx storage" and "particle filtering" are structurally separated from one another so that it is possible to combine any NOx accumulation catalyst with any particulate filter.

  With respect to the regeneration of the particulate filter, the fact that said particulate filter can be regenerated without additional additives is an advantage. No additional fuel or additional tanks are needed. Therefore, even an ash intake in the particulate filter due to an additive can be completely ruled out, as is the case in conventional systems.

  In addition, the characteristic field area available for the regeneration of the internal combustion engine can be significantly enlarged and a particulate filter regeneration required in the partial load range is also possible at low exhaust temperatures since the necessary exotherm is produced directly on the filter. A reduction in the extra energy required to regenerate the particulate filter, i.e., the energy required to reach the flash point of the soot, is obtained since the temperature is produced directly on the filter and that, therefore, no unnecessary wall heat loss occurs upstream of the filter.

  The complete desulfurization advantageously makes it possible to completely prevent the emission of H2S. Complete desulfurization is more efficient, faster and more reliable than other methods such as, for example, the lambda swallowing mentioned above. In addition, any reduction of reducing agent during desulfurization can be oxidized downstream of the storage catalyst, resulting in further reduction of the HC and CO emission components.

  In addition, the additional air can also be used during the denitration to oxidize any irruptions of reducing agent, which in this case also leads to a further reduction of the HC and CO emission components.

  A preferred embodiment of the invention will be explained in detail hereinafter with the aid of the one and only drawing.

  Figure 1 shows schematically an exhaust gas cleaning device 2866061 6 according to the invention.

  An internal combustion engine 1, for example a spark-ignition engine that can operate at low speed or a diesel-type internal combustion engine, emits in a manifold 2 which is connected to an exhaust gas purification device. 3, exhaust gases to be purified. The exhaust gas purification device 3 comprises a NOx accumulation catalyst 4 and a particulate filter 5 which, in the flow direction of the exhaust gas, is disposed downstream. The NOx storage catalyst is connected to the manifold 2 via a front exhaust pipe 7 and the NOx storage catalyst is connected to the particulate filter 5 via a median exhaust pipe . The purified exhaust gas is discharged through a final pipe 9 connected to the particle filter 5 at the outlet side of the latter. In addition, the exhaust gas purification device comprises a complementary air supply device 6 which, if necessary, blows complementary air, via an insufflation hose 12, in the median exhaust pipe 8, that is to say between the NOx accumulation catalyst 4 and the particulate filter 5. The complementary air supply device 6 further comprises a complementary air pump 11 which draws additional air through a suction pipe 10 and which pumps it into the blowing pipe 12 in the direction of the arrows. Due to the introduction of the additional air, a strongly exothermic oxidation reaction takes place in the particulate filter 5 during a complete desulphurization, ie in the presence of exhaust gas in steady state. substoichiometric, which produces exhaust gas components to achieve the ignition temperature of the soot accumulated in the particle filter 5, that is to say about 500 to 700 C, and to regenerate the particulate filter 5.

  Although the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be readily understood by those skilled in the art that changes in shape and detail may be required. performed without departing from the spirit or scope of the invention.

  LIST OF REFERENCES 1 internal combustion engine 2 manifold 3 exhaust gas cleaning system 4 NOx accumulation catalyst particle filter 6 supplementary air supply device 7 front exhaust pipe 8 middle exhaust pipe 9 final hose suction hose 11 additional air pump 12 insufflation hose 2866061 9

Claims (14)

  A method of regenerating an exhaust gas cleaning device (3) of an internal combustion engine (1), the exhaust gas cleaning device (3) comprising a catalyst for accumulating exhaust gas NOx (4) followed, in the flow direction of the exhaust gas (5), with a particulate filter, characterized in that, during desulphurization of the NOx (4) accumulation catalyst with gases exhaust under substoichiometric conditions, the particulate filter (5) is supplied with additional air.   2. Method according to claim 1, characterized in that the supply of the particulate filter (5) with additional air takes place with the start of the desulfurization of the NOx accumulation catalyst (4).   3. Method according to claim 1 or 2, characterized in that the supply of the particulate filter (5) with additional air at the end of the desulfurization of the NOx accumulation catalyst (4) is stopped.   4. Method according to one of the preceding claims, characterized in that the desulfurization of the NOx accumulation catalyst (4) takes place by operating the internal combustion engine (1) sub-stoichiometric manner.   5. Process, especially according to one of the preceding claims, characterized in that the particulate filter (5) is supplied with additional air during denitration of the NOx accumulation catalyst (4) under sub-stoichiometric conditions of exhaust gas.   6. Method according to claim 5, characterized in that the supply of the particulate filter (5) in complementary air takes place with the beginning of the denitration of the NOx accumulation catalyst (4).   7. A method according to claim 5 or 6, characterized in that the supply of the particulate filter (5) with additional air is stopped at the end of the denitration of the NOx accumulation catalyst (4).   8. Method according to one of the preceding claims, characterized in that the denitration of the NOx accumulation catalyst (4) takes place by operating the internal combustion engine substoichiometric manner.   9. Method according to claim 1, characterized in that the supply of the particulate filter (5) in complementary air takes place by blowing the complementary air downstream of the NOx accumulation catalyst (4) and upstream of the filter with particles (5).   10. Exhaust gas purification device of an internal combustion engine, the exhaust gas purification device (3) comprising a NOx accumulation catalyst (4) followed in the flow direction exhaust gas, of a particulate filter (5), characterized in that the device (3) comprises a complementary air supply device (6) for supplying additional air to the particulate filter ( 5).   11. Device according to claim 10, characterized in that the complementary air supply device (6) blows the additional air downstream of the NOx accumulation catalyst (4) and upstream of the particulate filter (5). for supplying the additional air to the particulate filter (5) via the inlet side of the exhaust gas of the latter.   12. Device according to claim 10 or 11, characterized in that the complementary air supply device (6) comprises a complementary air pump (11).   13. Device according to one of claims 10 to   12, characterized in that the particulate filter (5) has a layer of precious metal.   14. Device according to one of claims 10 to   13, characterized in that the device (3) comprises a control device which controls the regeneration of the NOx accumulation catalyst (4) and the particulate filter (5), as well as the complementary air supply device (6). ).