JP2016200149A - Method for running an engine fed with a fuel containing a catalyst for reproducing a particulate filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a method for reproducing a particulate filter by using a fuel-added catalyst, which method is not so complicated as the known method so that it does not cost like the known one.SOLUTION: The present invention relates to a method for running the internal combustion engine of a vehicle equipped with an exhaust system having a catalyst particulate filter, the internal combustion engine to be fed with a fuel containing a catalyst for reproducing the particulate filter. The method is characterized in that the concentration of the catalyst in the fuel is discontinuously changed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for operating an internal combustion engine, in particular a diesel engine, supplied with a fuel containing a catalyst for regenerating a particulate filter. This method is applied to an automobile equipped with a catalyst particulate filter that removes black smoke from engine exhaust gas.

  In order to meet the new emission regulations for vehicles, in particular diesel vehicles, these vehicles are gradually equipped with a particulate filter (PF). This is already the case in Europe since the Euro 5 emission standards were established. In most cases, a catalyst is used to help periodically remove soot trapped in the filter by combustion, thereby regenerating PF.

  The PF is regenerated by periodically raising the temperature upstream of the PF to a temperature sufficiently high to remove the soot by combustion and thereby regenerate the PF.

  This temperature is usually above 650 ° C., so to reach this level of heat, fuel is either generally burned in the engine (post-injection) or in an oxidation catalytic converter upstream of the PF. This is because the temperature of exhaust gas for diesel engines is generally significantly lower, usually below 400 ° C. The temperature of the exhaust gas also tends to decrease due to new combustion technologies such as HCCI (premixed compression ignition) type homogenous charge combustion. When the vehicle is used under certain conditions, such as during use in an urban area, the temperature is also very low, often below 250 ° C.

  The second important parameter is the duration of PF regeneration, ie the length of time that the temperature upstream of the PF needs to be maintained at a high level. In addition to the greater economic and environmental impact of additional fuel consumption, in some cases, such as when traveling around urban areas where the duration is often short, it may be long enough to regenerate the PF. It is impossible to maintain this state.

It will be appreciated that there are several advantages when the frequency of these regenerations can be reduced and the duration can be shortened, and when regeneration can be performed at lower temperatures. This is because it has the effect of reducing the fuel consumption of the vehicle since the amount of fuel used for post-injection is reduced. As a result, greenhouse gas (CO ₂ ) vehicle emissions are reduced.

  This also makes it possible to use a material that does not have to be heat-resistant, such as silicon carbide, and therefore a less expensive material, PF. In addition, reducing the duration of post-injection has also been found to be beneficial with respect to other criteria such as engine life and life of some components such as high pressure fuel injectors, or even engine refueling intervals .

To meet these objectives, this regeneration promoting catalyst is generally used in two important ways.
-An oxidation catalyst is introduced into the pores of the PF wall. Therefore, PF is said to be a catalyst particulate filter, or is called a catalyst soot filter (CSF). Catalysts are generally noble metals such as platinum and transition metal oxides such as alumina, or even reducing oxides such as cerium, cerium and zirconium, or more generally rare earth oxides. Consists of. This technology is currently widely used in modern vehicles that meet European Euro 5 emission standards.
-On the other hand, the use of a PF regeneration additive supported by the fuel supplied to the engine, known as Fuel Borne Catalyst (FBC). Various FBC additives are known, particularly cerium-based and / or iron-based additives. This technology is currently installed in diesel vehicles as well.

  The second method is generally more effective and allows the PF to be regenerated in a more economical and environmentally friendly manner under all driving conditions, especially during urban driving.

  However, the main drawback of FBC technology is that it has the complexity to implement it, in particular the fuel has the most constant possible additive concentration as currently implemented in vehicles equipped with this technology. In the complexity when doing so. Typically, this objective will be to maintain additive concentrations that do not change significantly in the fuel, i.e., additive concentrations that typically exhibit concentration fluctuations of less than 20% or even less than 10%.

  A system that allows the introduction of FBC catalyst additive into the fuel to help regenerate the PF generally contains a reserve of additive and has a minimum volume that needs to be installed in an area near the fuel tank. Depends on 2 to 3 liter large reservoir.

  Current methods of metering additives also require high precision metering pumps that must be controlled using additional and dedicated electronic units. This electronic unit generally relies on a vehicle electronic central control unit or ECU. The additive content in the fuel is high enough to allow excellent regeneration of PF, but not so high as to cause premature fouling of PF due to inorganic residues from PF regeneration that remain trapped in the PF In order to ensure this, it is necessary to manage the weighing device very accurately. In general, when the level of fuel in the tank increases as a result of the addition of fuel, the ECU communicates this information to the computer, and the computer determines how much the additive concentration in the fuel remains constant at all times. Inform the pump whether the additive should be injected into the tank.

  These metering pumps are very accurate and very expensive. The use of such a method also requires that the metering system be operated exactly as a slave device and that its operating condition be checked. Thus, the system becomes complex and consequently expensive.

  The object of the present invention is to propose a method that is not as complex as the known method and is therefore less expensive to implement.

  For this purpose, the method according to the invention is a method for operating an internal combustion engine of a vehicle equipped with an exhaust system comprising a catalytic particulate filter (CSF), the engine containing a catalyst for regenerating the particulate filter. This is a method of supplying fuel, which is characterized in that the catalyst concentration in the fuel changes discontinuously.

  The method of the present invention allows the CSF to be regenerated effectively, especially at low temperatures, without the need for complex systems of the prior art to maintain the fuel concentration at a constant value.

  Other features, details and advantages of the invention will become even more fully apparent from reading the following description given with reference to the accompanying drawings.

It is a figure which shows the catalyst concentration of a fuel with time and according to the filling level of a fuel tank.

  An essential feature of the method of the present invention is that the catalyst concentration in the fuel changes discontinuously. What it means is that, unlike the known methods, this concentration is not constant and can change over time, and furthermore it changes discontinuously. Thus, in a very short time or instantly, the concentration can take on different values. Its concentration is zero and can vary within a range that can vary, for example, by a factor of 0 to 30, more particularly 0 to 20. Even more particularly, these ranges can vary from 0 to 15, in particular from 0 to 5. Thus, this concentration remains constant for a certain length of time for a certain length of time, then changes to another value in a very short time or instantly and then for a certain period of time. It is possible to remain.

  The method of the present invention can be implemented by various selective methods.

According to a first option, the method is carried out under conditions such that the catalyst concentration in the fuel changes only once during the CSF charging period. The concentration therefore varies from a value V ₀ that can be _zero to a value V _n such that V _n > V ₀ .

  The filter filling period is a period in which exhaust gas flows through the CSF, and means a period in which the CSF is gradually filled with smoke. These are all engine operating periods outside the filter regeneration period.

According to the second option of the method of the present invention, the catalyst concentration in the fuel still changes several times during the particulate filter filling period. Thus, the concentration moves from a value V ₀ that can be _zero to a value V _n and then to another value V _{n + 1} , where these values are V _{n + 1} > V _n > V ₀ .

According to another option, the method is carried out such that the catalyst concentration in the fuel changes once or several times during the particulate filter filling period. Thus, the concentration can move from a non-zero value V ₀ to a value V _n and then possibly to another value V _{n + 1} , where these values are V _{n + 1} <V _n <V ₀ .

  In the case of the second choice or the third selection value, the number of times the change occurs can be unlimited.

  Finally, according to yet another option, the catalyst concentration in the fuel can be varied to rise or fall several times during the CSF filling period, and this concentration can be zero over a period of time. .

  The present invention can be used with any type of CSF regeneration catalyst. These catalysts are well known. More specifically, and by way of example only, the catalyst can take the form of a colloidal dispersion. The colloids of this colloidal dispersion are based on rare earth and / or compounds of metals selected from Group IIA, Group IVA, Group VIIA, Group VIII, Group IB, Group IIB, Group IIIB and Group IVB of the Periodic Table can do.

  These colloids can more particularly be based on cerium and / or iron compounds.

  It is also possible to use a colloidal dispersion containing the cleaning composition.

  The periodic table of elements referred to in this specification is French Chemical Society Bulletin No. 1 (January 1966).

  Examples of colloidal dispersions include those described in patent applications such as EP 671205, WO 97/19022, 01/10545 and 03/053560. The last two describe, in particular, cerium compound-based and iron compound-based dispersions, respectively, which also contain amphiphiles.

  The application of WO 2010/150040 can also be mentioned, which describes a colloidal dispersion based on a detergent composition containing an iron compound, an amphiphile and a quaternary ammonium salt. doing.

The quaternary ammonium salt can be the following reaction product.
(I) at least one compound that can comprise (a) a condensation product of a hydrocarbyl-substituted acylating agent and a compound having an oxygen or nitrogen atom that can condense the acylating agent, A condensation product having one tertiary amino group,
(B) a polyalkene-substituted amine having at least one tertiary amino group, and (c) a Mannich reaction product having at least one tertiary amino group, the hydrocarbyl substitution A Mannich reaction product derived from phenol, an aldehyde and an amine, and (ii) a quaternizing agent suitable for converting the tertiary amino group of compound (i) to a quaternary nitrogen.

  The quaternizing agent can include dialkyl sulfate, benzyl halide, hydrocarbyl substituted carbonate, hydrocarbyl substituted epoxy in combination with an acid or mixtures thereof.

  Catalyst PF is also well known. They generally comprise at least one metal-based catalyst selected from platinum or a platinum group metal such as palladium. Of course, combinations of platinum with these metals or even combinations of these metals with each other are possible.

  The catalytic metal can be incorporated into the filter or applied to the filter in a known manner. It can be included, for example, in a coating (washcoat), which itself is applied to the filter. This washcoat can be selected from alumina, titanium oxide, silica, spinel, zeolite, silicate, crystalline aluminum phosphate or mixtures thereof. More specifically, alumina can be used. The washcoat can also contain a reducing substance that can directly or indirectly serve for the burning of soot. By way of example, mention may be made of materials based on cerium oxide-based substances such as olivine, optionally doped cerium- and zirconium-based mixed oxides, or even manganese oxides.

Thus, if the PF catalyst is a catalyst that helps remove soot by combustion, it is present on the filter in a relatively low amount, ie generally in an amount of at most 70 g / ft ³ (2.5 g / dm ³ ). . This amount is expressed in terms of the mass of elemental metal, for example the mass of platinum, relative to the volume of PF. This amount can be more particularly at most 60 g / ft ³ (2.1 g / dm ³ ) and even more particularly at most 50 g / ft ³ (1.8 g / dm ³ ).

  The mass concentration of the regenerated catalyst in the fuel is advantageously comprised between 0 ppm and 30 ppm, especially when it is in the form of a colloidal dispersion, the content of which, for example, iron in the case of iron-based colloidal dispersions, Expressed in terms of elemental metals. The catalyst content of soot emitted by the engine, expressed in terms of elemental metal mass, is between 0% and 8%, depending on the fuel regeneration catalyst content, the vehicle fuel consumption and the soot production. Can be included in between.

  When practicing the method of the present invention, the vehicle will run with fuel containing a variable content of regenerated catalyst, which may be zero over a certain period of time. The soot produced by the engine will be richer or less rich in elements that play an active role in regenerating CSF, depending on the level of additive in the fuel.

  Therefore, the CSF is alternately filled with smoke containing no regenerated catalyst additive or smoke containing a variable concentration. The fuel used during periodic regeneration of the CSF may or may not contain additives.

  Then, regeneration is performed by a conventional method under the control of the vehicle ECU using the technology selected by the manufacturer.

  An advantage of the present invention is that the additive can be introduced into the fuel by a simple system that is cheaper than known systems, the metering strategy of which is simple and can be quickly installed in the vehicle. That is. A system that does not require an interface with the central control system ECU of the vehicle is particularly preferred because it makes the installation of the system in the vehicle simpler.

  A simple embodiment is shown below in which the additives can be introduced in different and varying amounts over time.

  The first embodiment involves manually adding a volume of additive, typically a liquid, which is poured into the vehicle fuel tank. The amount of additive is calculated so that the content of the material that is effective to regenerate the CSF is high enough to promote the combustion of soot trapped in the CSF. As an example, in the case of an additive of a colloidal dispersion system of iron particles, such as dispersion C in Example 3 of the patent application, WO 2010/150040 pamphlet, the elemental iron content of the fuel immediately after the additive is manually added May advantageously be comprised between 2 and 30 ppm with respect to the mass of metallic iron, and more particularly between 5 and 20 ppm with respect to the mass of metallic iron.

  By this simple means, additives can be added to the fuel when needed, especially at regular intervals, especially when the vehicle is used mainly in urban areas, for example every 1000 to 3000 km. Can do. This means can also be used when the indicator lamp on the vehicle instrument panel reports a failure of the pollution reduction means.

  FIG. 1 shows a graph of the regenerated catalyst concentration in the fuel that can be obtained when a certain amount of additive is added manually to the tank periodically, in this case every 2200 km (or 44 hours of travel). An example is shown. This example takes into account a constant fuel consumption of 6 l / 100 km, a constant speed of 50 km / h and hence a constant fuel consumption of 3 l / h. Normally as soon as a certain amount of additive is added (event 1 shown in the figure as Ev1: a certain volume of regenerated catalyst achieves 15 ppm metallic iron content in 40 liters of fuel present in the tank) The iron content increases rapidly from 0 ppm to 15 ppm in this case. This iron content is constant over a period of time until the fuel is added to the tank, thereby adding the remaining volume of additive-containing fuel and the volume of fuel added (and thus not containing additives) The concentration of iron in each ratio is diluted (event 2 shown as Ev2: 40 L of fuel (without additives) is added to the 20 L of fuel remaining in the tank). This event is repeated four times in this example. With each addition, the iron concentration decreases proportionally.

  The figure also shows the duration of CSF regeneration, ie regenerations (identified with stars in the figure) that occur at regular 700 km intervals, ie every 14 hours of driving. For example, a CSF soot loading corresponding to the first regeneration would cause the vehicle to have a 50% chance of adding no additives and a 50% chance of adding 15 ppm by weight of iron. It will be noted that this occurred by operating with fuel. Example 1 below shows the benefits obtained through CSF regeneration engine testing conducted under these filling conditions.

  Therefore, soot filling into the CSF occurs with fuels whose additive concentration can vary, and an amount of additive can be manually poured into the tank every 2200 km (44 hours) in this case. It will be noted that benefits can be gained by using the very simple system required.

  Another embodiment can be used by equipping the vehicle with simple and autonomous means of introducing the regenerated catalyst, ie not connected to the central ECU of the vehicle. This means can include adding a small FBC tank, typically 1 l or less, and a metering pump that can inject a given amount of additive into the fuel tank at regular intervals. Compared to existing systems, the pumped volume is constant, so the pump can be less complex and therefore less expensive. The pump can be programmed, for example, to be injected at regular intervals (time intervals such as every 5 to 10 hours and / or intervals relating to distances such as every 1000 to 3000 km), thus eliminating the need for an interface with the ECU It is. A local device located in the pump, such as an application of power or a GPS chip, can inform the pump that the vehicle is traveling or provide the distance the vehicle has traveled it can.

  An example will now be described.

Example 1
A diesel engine (4 cylinders, 2 liters, air-cooled, turbocharged, 81 kW) provided by the Volkswagen group was used on the engine test bench. The exhaust line installed downstream is composed of an oxidation catalytic converter including platinum-based and alumina-based washcoats, followed by a commercial CSF (total filter capacity 3 L) including platinum-based and alumina-based washcoats. This is a commercial line.

  The fuel used is a commercial fuel according to standard EN590 DIN 51628, containing less than 10 ppm sulfur and containing 7% by volume of FAME or fatty acid methyl ester. When an FBC regenerative catalyst is used, the fuel is loaded with an amount of FBC additive that allows the fuel to achieve various metallic iron contents expressed in ppm by mass relative to the mass of the fuel. Added. The FBC additive used is an additive in a colloidal dispersion system of iron particles such as dispersion C in Example 3 of the patent application, WO 2010/150040 pamphlet, and the elemental iron content of this additive is It was 4.3% by mass of metallic iron.

  The iron content of the additive-containing fuel is monitored directly with an organic liquid using X-ray fluorescence techniques.

  The test is performed in two consecutive steps: a CSF soot filling step and a subsequent CSF regeneration step. The conditions for these two steps are exactly the same for the various tests, with the exception being the type of fuel used (whether it contains additives).

  The filling phase is performed by running the engine at a speed of 3000 revolutions per minute (rpm) and using a torque of 45 Nm for approximately 6 hours. This filling phase is stopped when the CSF is filled with 12 g of fine particles (or soot). During this phase, the temperature of the gas upstream of the CSF is 230 ° C to 235 ° C. Under these conditions, particulate discharge is about 2 g / hour.

  After this filling phase, the CSF is removed and weighed to inspect the mass of particulates that filled the CSF during this phase.

  Then, the CSF is reattached to the test bench and heated by the engine returned to the supercharging operation state (3000 rpm / 45 Nm) for 30 minutes. Then, the engine state is changed (torque 80 Nm / 2200 rpm), and the engine central control unit (ECU) monitors the post-injection, enables the temperature upstream of the CSF to rise to 500 ° C., and starts the regeneration of the CSF. to enable. These states are maintained for 60 minutes, and this time is measured from the start of post injection.

  In all cases, the fuel used for regeneration corresponds to the last fuel used in the CSF filling phase.

The effectiveness of CSF regeneration is measured with the following two parameters.
The mass of soot removed by combustion during regeneration, calculated from the weight before CSF filling (Mo), the weight after filling (Mc) and the weight at the end of regeneration (Mr). The percentage of soot removed by combustion after 60 minutes of regeneration is expressed as:
Total% of burnt smoke = (Mc-Mr) / (Mc-Mo) x 100
The mass of burnt soot at any instant t in regeneration, from the change in pressure drop DPt before and after CSF at each instant, the pressure drop at the start of regeneration (DPc) of the CSF filled with soot mass Considering the pressure drop (Mc-Mo), the pressure drop after 60 minutes (DPr) corresponds to the pressure drop (Mr-Mo) of CSF filled with unburned soot, Calculated mass.
% Of burnt soot (t) = ((DPc−DPt) / (Dpc−Dpr)) × total% of burnt soot

  In general, the higher these parameters, the more effective the playback.

  Various tests were conducted with different fuels during CSF filling.

  Three reference tests (not according to the invention) were carried out using fuels containing no additives (test 1) or using fuels with additives added through CSF filling and regeneration (containing fuel additives) Test 10 in which the amount was 15 ppm of iron and test 11) in which the fuel additive content was 3 ppm of iron were performed.

  Eight tests (according to the present invention) using a fuel containing no additive (fuel number 1) at the start of CSF filling, and then a fuel containing additive at the end of filling (fuel number 2) (Tests 2-5 and 8-9) or in reverse order, i.e. using fuel containing additives at the start of filling and then using fuel containing no additives ( Tests 6-7) were performed.

  Each of the tests represents the respective fill time with and without the additive containing fuel or the variation in the amount of FBC additive contained in the fuel.

  Table 1 compares the results obtained during CSF regeneration, i.e. at the end of the regeneration period (1 hour) or at the start of regeneration (20 minutes), which represents the percent of the soot burned as a whole.

  At each time point, it is obtained by calculating the average of the CSF effectiveness with the fuel containing no additive (Test 1) and the average of the effectiveness of the CSF filled with the additive-containing fuel (Test 10). Compare against theoretical effectiveness.

  First, the effectiveness of regeneration can be greatly improved by adding FBC to the fuel throughout the CSF filling period (Test 10 and Test 11), which is almost complete after 20 minutes at 500 ° C. (88 Note that% to 90% soot is burning) and iron concentration (3 to 15 ppm) has little effect on regeneration.

  Conversely, when fuel containing no additive is used (Test 1), regeneration is incomplete (60% after 1 hour) and occurs much slower (39% regeneration after 20 minutes). .

  By filling the CSF by alternately using the fuel containing no additive and the fuel containing the additive thereafter (or vice versa), the effectiveness of CSF generation can be greatly improved.

  Filling with fuel containing 15 ppm iron additive with 50% probability (test 2 or 6), so that after complete regeneration (85% to 87%) at the end of the test and after 20 minutes of regeneration Very advanced regeneration (72% to 80%) can be achieved.

  Unexpectedly, it was found that the experimentally observed values were significantly higher than the theoretical values when considering the contribution from the introduced FBC and the fuel without additives.

  Test 2 represents the CSF filling state described for the CSF filling at the time of the first regeneration of the CSF of FIG.

  These conclusions are that the fuel in which the CSF contains an additive (15% to 50%) and the order in which the fuel containing the additive is used (whether it is used at the start or end of the filling period) ) Regardless of the ratio of filling time, it is effective.

  Furthermore, it can be seen that beneficial synergistic effects can be observed with very little amount of FBC in the fuel, as illustrated in Test 8 and Test 9.

Example 2
Another series of CSF regeneration engine tests were performed using the same protocol and the same equipment as described in Example 1.

  Here, CSF was filled while changing the FBC concentration in the fuel (same as in Example 1) more frequently.

  Therefore, CSF filling was performed using a series of fuels as described in Table 2.

  Table 3 compares the results obtained during CSF regeneration, which represent the percent of soot burned overall, ie at the end of the regeneration period (1 hour) or at the start of regeneration (20 minutes).

  Adding FBC additives to the fuel (Tests 10, 12, and 13) can improve effectiveness compared to regeneration of CSF filled with fuel that does not contain additives (Test 1). It should be noted that it is possible (substantially complete playback and improved playback dynamics). Use of fuel in which the additive content is fully controlled over time by addition in different quantities over time (Tests 12 and 13), including incorporating periods of no additive added to the fuel ( The result is the same as test 10).

Claims (10)

  A method for operating an internal combustion engine of a vehicle equipped with an exhaust system comprising a catalyst particulate filter, wherein the engine is supplied with a fuel containing a catalyst for regenerating the particulate filter. A method characterized in that the concentration of the catalyst changes discontinuously.   The method according to claim 1, wherein the concentration of the catalyst in the fuel changes only once during the filling period of the particulate filter.   The method according to claim 1, wherein the concentration of the catalyst in the fuel changes several times during the filling period of the particulate filter.   The method according to claim 1, wherein the concentration of the catalyst in the fuel changes so as to decrease once or several times during the filling period of the particulate filter.   The method according to claim 1, wherein the concentration of the catalyst in the fuel changes so as to increase or decrease several times during the filling period of the particulate filter.   6. The method according to any one of claims 1 to 5, characterized in that the catalyst for regenerating the particulate filter takes the form of a colloidal dispersion.   The colloid of the colloidal dispersion is based on a rare earth and / or a compound of a metal selected from Group IIA, Group IVA, Group VIIA, Group VIII, Group IB, Group IIB, Group IIIB and Group IVB of the Periodic Table The method according to claim 6, wherein:   8. A method according to claim 7, characterized in that the colloid of the colloidal dispersion is based on a compound of cerium and / or iron.   The method according to claim 6, wherein the colloidal dispersion contains a cleaning composition.   10. A method according to claim 8 or 9, characterized in that the colloidal dispersion is based on a detergent composition comprising an iron compound, an amphiphile and a quaternary ammonium salt.

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