FR2821116A1 - Regeneration of particle filter used with heat engine in a parallel hybrid motor vehicle, uses hydrogen, from fuel cell or reservoir, injected and burned in exhaust to ensure combustion of particles - Google Patents

Abstract

The filter is regenerated by injecting and burning hydrogen in the exhaust system (4) ahead of the filter (5), ensuring combustion of particles trapped by the filter. The hydrogen is obtained from the fuel cell (7) used to provide electrical power for the vehicle, or alternatively from a hydrogen reservoir (2).

Description

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 The invention relates to a method and a device for regenerating a particulate filter for separating soot particles from an exhaust gas from a heat engine, for example from a diesel engine and in particular from a particulate filter placed on an exhaust line of a motor vehicle comprising a heat engine and, preferably, a diesel engine.

 Heat engines and in particular diesel engines include combustion chambers in which a fuel, for example diesel, undergoes combustion and produces burnt gases which are evacuated by engine pipes and an exhaust line.

 In the case of diesel engines in particular, the improvement of the aerothermal power of the combustion chambers and the increase in the injection pressure have made it possible to make considerable progress in terms of fuel combustion, so that practically complete combustion is obtained, at least in certain engine operating phases. As a result, the discharge of pollutants into the exhaust gases is considerably reduced. However, in certain engine operating phases, combustion is incomplete, which results in the formation of soot particles which are entrained by the exhaust gases.

 To eliminate these particles entrained by the exhaust gases, in the case of motor vehicles of recent design, an exhaust gas filtration is carried out which is controlled according to the operating conditions of the engine. This eliminates a very large proportion of the particles, so that the gases discharged at the outlet of the exhaust line have a very low particle content. To carry out pilot filtration of exhaust gases, a particle filter (FAP) is used which is interposed on the exhaust line, generally in the high temperature part of the exhaust line close to the engine.

 Particulate filters have a filter body designed to stop soot particles, placed inside a filter casing connected to the exhaust line.

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 The major difficulty in the operation of particulate filters lies in the regeneration of the filter, when it is loaded with soot particles. Indeed, when the particulate filter has been used for a certain time, it is loaded with particles deposited in the porosities of the filtration body, so that it introduces an increased pressure drop on the circulation of the exhaust gases. and less effectively filters the particles contained in the exhaust gases.

 It is therefore necessary to regenerate the particle filter. This regeneration is carried out by burning the soot inside the particle filter, benefiting from the high temperature of the exhaust gases in the particle filter and the presence of atmospheric combustion air in the exhaust gases.

 However, the exhaust gases from diesel engines have a temperature which is not sufficient to ensure the combustion of the particles, at least in certain phases of use of the heat engine, for example in the case of a motor vehicle engine. , during a traffic phase in urban areas. The temperature of the exhaust gases is then not sufficient to initiate regeneration by combustion of the particles.

 To lower the combustion temperature of the particles, it is known to use catalyst products, generally in the form of metal oxides such as cerine. Additives containing catalysts or products intended to form catalysts during the combustion of fuel are injected into the fuel used to supply the engine.

 Catalyst products or products intended to form catalysts are expensive and must be introduced in metered amounts into the fuel of the motor vehicle. It is therefore necessary to provide for special maintenance of the vehicle to ensure the presence of soot combustion additives in the fuel, for example to fill up with a tank of cerine intended to be injected into the fuel, with a certain periodicity. , for example every 80,000 km. In addition, combustion additives such as cerine are prohibited by certain regulations.

 Motor vehicles include a source of electrical energy which can be constituted, for example, in a conventional manner, by an al-

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 ternator and a storage battery which are used for various functions on the motor vehicle.

 In vehicles of modern or future design, provision has been made to use an electrical source constituted by a fuel cell which can be used to replace the battery and / or the alternator of the motor vehicle, or even in certain types of modern vehicles for supplying current to an electric motor driving the motor vehicle.

 Motor vehicles with particularly flexible and adaptable conditions of use may comprise both a heat engine and an electric motor, the heat engine possibly being for example a diesel engine.

 Such vehicles called hybrid vehicles can be used in town, with purely electric propulsion and on the road, using the heat engine.

 In this case, or more generally in the case of any vehicle comprising a heat engine and in particular a diesel engine, it may be desirable to place a particle filter on the engine exhaust line to ensure non-polluting operation in all phases of vehicle use.

 Apart from the use of heat engines such as diesel engines for the propulsion of motor vehicles, it may also be necessary to use particle filters to purify the exhaust gases from the engines. Particulate filters can be useful on an exhaust pipe of naval propulsion engines or even on stationary heat engines, for example generator engines.

 In the general case of a heat engine with an exhaust line or pipe on which a particulate filter is placed, regeneration of the particulate filter (DPF) must be carried out periodically, to ensure satisfactory operation of the particulate filter on long periods of use.

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 It is desirable to carry out this regeneration of the FAP without introducing an additive such as cerine into the fuel used by the heat engine.

 The object of the invention is therefore to propose a method for regenerating a particulate filter for the filtration of soot particles from an exhaust gas of a heat engine disposed on an exhaust line of the heat engine, this process allows efficient regeneration of the particulate filter without using an additive introduced into the fuel of the heat engine.

 For this purpose, the particle filter is regenerated by injecting and burning hydrogen in the exhaust line, upstream from the particle filter, so as to raise the temperature in the particle filter to a level ensuring combustion of particles, regardless of engine operating cycles.

 The invention applies in particular to the case of a particulate filter placed on an exhaust line of a motor vehicle which comprises the heat engine as propulsion means and a source of electrical energy comprising a fuel cell; in this case, at least part of the hydrogen injected into the exhaust line, upstream of the particulate filter, comes from the fuel cell or from a means of supplying the fuel cell with hydrogen.

à une seconde extrémité opposée à la première, au moyen de fourniture d'hydrogène. The invention also relates to a device for regenerating a particulate filter for filtering the exhaust gases of a heat engine placed on an exhaust line of the heat engine and comprising a means of supplying hydrogen consisting by at least one of a storage means and a means for producing hydrogen and a pipe for injecting hydrogen into the exhaust line, connected at one end to the exhaust line, upstream of the particulate filter, and,

at a second end opposite the first, by means of supply of hydrogen.

In the case where the particulate filter is placed on the exhaust line of a motor vehicle comprising the heat engine as a means of propulsion and a source of electrical energy comprising a battery

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 fuel, the hydrogen supply means may include at least one of the fuel cell, a reformer supplying the fuel cell with hydrogen and a hydrogen storage buffer tank.

 In order to clearly understand the invention, a description will now be given, with reference to the appended figure, of a process for regenerating soot from a heat engine by a process according to the invention and the device used.

 The single figure is a diagram showing the various functional elements of a motor vehicle comprising a fuel cell, these elements being used for propulsion of the motor vehicle, the electrical supply of components or equipment of the motor vehicle, or the treatment of gases exhaust.

 In the figure, a heat engine 1 for propelling the motor vehicle is shown schematically by means of a transmission 3.

 The exhaust gases from the heat engine 1, which is a diesel engine in the example described, are discharged into an exhaust line 4 on which a particle filter 5 is inserted.

la charge peut être assurée par l'intermédiaire d'une pile à combustible 7. La pile à combustible 7 peut être également utilisée pour assurer directement l'alimentation électrique des composants et équipements du véhicule automobile.

The motor vehicle comprises components and equipment which are supplied with electric current by a storage battery 6, of which

the charge can be provided by means of a fuel cell 7. The fuel cell 7 can also be used to directly supply electrical power to the components and equipment of the motor vehicle.

The fuel cell 7 is supplied with hydrogen, either by means of a reformer 8 ensuring the production of hydrogen, from at least one hydrocarbon or other hydrogenated component, of the fuel stored in a fuel tank 9 supplying the reformer 8, or a hydrogen storage reserve 2 mounted on the vehicle.

 The fuel cell, which can be of the PEMFC (Proton Exchange Membrane Fuel Cell) or SOFC (Solid Oxide Fuel Cell) or AFC (Alkaline Fuel Cell) type, operates using hydrogen from the reforming of hydrocarbons.

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bures constituant le carburant, dans le réformeur 8, ou en utilisant l'hydrogène issu de la réserve de stockage 2 présente sur le véhicule.

bures constituting the fuel, in the reformer 8, or by using the hydrogen from the storage reserve 2 present on the vehicle.

 SOFC fuel cells use a simplified reforming station while PEMFC cells, which are more sensitive to impurities, use a hydrogenated gas or reformate containing high purity hydrogen.

 For the implementation of the method of the invention, a line 10 for injecting hydrogen into the exhaust line 4 is provided, upstream of the particle filter 5. The line 10 for injecting hydrogen is connected to the reformer, the fuel cell and the hydrogen storage tank 2, so as to be able to supply the exhaust line 4 with hydrogen coming either from the reformer 8, or from the fuel cell 7, or from both the fuel cell 7 and the reformer 8, or even from the hydrogen storage reserve 2 mounted on the motor vehicle.

 The hydrogen reserve 2 can be constituted, for example, by a cryogenic storage reserve of hydrogen in liquid form contained, for example, in an insulating tank; a reserve of hydrogen under pressure, for example inside a tube or a bottle or also a reserve of hydrogen stored in a material such as a metal hydride or consisting of carbon nanotubes, c that is to say carbon in the form of small tubes having a very small internal diameter in which is contained and stored hydrogen.

 A buffer tank 11 can be inserted on the injection line 10 and connected to at least one of the fuel cell and the reformer, the excess hydrogen produced by the fuel cell 7 or the reformer 8 in certain phases. of engine operation being stored inside the buffer tank 11 and used in phases requiring injection of hydrogen into the exhaust line.

 The hydrogen can be brought into the buffer tank 11 from the hydrogen reserve 2 which can be connected to the buffer tank 11 and through it to the hydrogen injection line 10. The hydrogen reserve 2 can alternatively be directly connected to the injection line 10.

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It may be advantageous to provide a connection pipe 12 between the hydrogen injection pipe 10 and a fuel supply pipe for the heat engine 7, in order to reduce the polluting emissions of the heat engine in certain phases of operation.

 The heat produced by the fuel cell can be transmitted to the heat engine via a gas line 13. This gives rise to a faster temperature rise during certain engine operating phases, such as for example the first starts. , which quickly increases the efficiency of the pollution control system.

 As shown by arrow 14, in certain engine operating phases, the fuel cell 7 can produce excess electrical energy which can be used, for example, for heating the engine or the particle filter 5, during the regeneration phases of the engine. filter by combustion of soot.

 An operation detector 15 of the particle filter 5 which can be constituted for example by a pressure sensor indicating the fouling state of the filter is associated with the particle filter 5 and connected to an electronic control unit or supervisor 16 to ensure controlling the injection of hydrogen into the exhaust line, when the regeneration of the particulate filter 5 has become necessary.

ou le réformeur 8, d'une phase hydrogène en excès pouvant être utilisée pour l'injection dans la ligne d'échappement. The supervisor 16 is connected by electrical conductors to respective detectors 17 and 18 associated with the fuel cell 7 and the reformer 8, making it possible to determine the presence in the fuel cell 7

or the reformer 8, of an excess hydrogen phase which can be used for injection into the exhaust line.

 The supervisor 16 can also be connected to means for injecting the storage tank 11 and the hydrogen reserve 2, such as solenoid valves which can be opened to inject hydrogen into the exhaust line 4 , upstream of the particle filter 5, when the filter is dirty, either from the storage tank 11, or directly from the hydrogen reserve 2.

 When the sensor 15 detects a fouling of the particle filter 5, the signal transmitted to the supervisor 16 makes it possible to carry out an injection of hy-

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 drogen in the injection line 10 and in the exhaust line 4 of the heat engine 1, either from the reserve 2, or from the buffer tank 11, or directly from the reformer 8 and / or the fuel cell 7 in the case where the supervisor 16 has detected the presence of excess hydrogen phases in the reformer 8 and / or the fuel cell 7. The hydrogen injection can be carried out simultaneously from several means of supply of hydrogen constituted by the means of storage or production of hydrogen on board the motor vehicle.

 In certain phases, for example when the fuel cell does not supply electric current, quantities of excess hydrogen phase may be available.

The reformer 8 can also be controlled by the supervisor 16 to produce hydrogen intended to be injected into the exhaust duct 4.

The excess hydrogen in the fuel cell 7 or produced by the reformer 8 can be stored in the buffer tank 11 and used in a deferred manner for injection into the exhaust duct 4, when fouling of the particle filter 5.

When hydrogen is introduced into the exhaust duct 4, the high temperature exhaust gases containing oxidizing gases and in particular atmospheric air cause the combustion of the hydrogen with very high heat generation. The high temperature combustion gases passing through the particulate filter 5 cause the combustion of the soot and therefore the regeneration of the particulate filter 5.

 The combustion of hydrogen does not produce carbon monoxide, hydrocarbons or particles.

 The process according to the invention therefore makes it possible to obtain a regeneration of the filter, without using catalysis additives which are usually necessary for carrying out the combustion of the particles deposited in the particulate filter, at the temperature of the engine exhaust gases. .

 The invention is not limited to the embodiment which has been described.

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 The hydrogen injection can be carried out only from a reserve of hydrogen, for example on board a vehicle with or without a fuel cell, the heat engine of which provides propulsion.

 It is possible to control the injection of hydrogen from a hydrogen reserve, the fuel cell, the reformer or a buffer tank by means different from those which have been described, comprising means electronic of any type controlled from measurement signals defining the state of the particle filter, the fuel cell, the reformer or a buffer tank.

 The invention applies mainly to motor vehicles comprising a diesel engine but it can also be applied in the case of motor vehicles comprising a petrol engine and in the case of heat engines used for naval propulsion or of heat engines of fixed or mobile installations but not directly linked to a propulsion system by means of a transmission, such as engines of generator sets.

 The invention also applies in the case of motor vehicles of the so-called "hybrid" type comprising a heat engine, for example a diesel engine, and an electric motor supplied with current by a battery and / or a fuel cell capable of ensuring the propulsion of the motor vehicle, by means of a transmission, controlled so that the heat engine or the electric motor is used for propulsion, according to the driving conditions of the motor vehicle.

Claims (13)

 1.-Method for regenerating a particulate filter (5) for the filtration of soot particles from the exhaust of a heat engine disposed on an exhaust line of the heat engine (1), characterized by the fact that the particle filter (5) is regenerated by injecting and burning hydrogen in the exhaust line (4), upstream from the particle filter, so as to raise the temperature in the particle filter up to a level ensuring combustion of the particles, regardless of the engine operating cycles.  2.-Method according to claim 1, characterized in that at least part of the hydrogen injected into the exhaust line comes from a hydrogen storage reserve (2).  3.-Method according to claim 2, characterized in that the hydrogen reserve (2) consists of one of the following storage means: cryogenic storage reserve of hydrogen in liquid form, storage reserve of hydrogen under pressure, reserve for storing hydrogen in a material such as a metal hydride or made up of carbon nanotubes.  4.- Method according to any one of claims 1 to 3, of regeneration of a particle filter (5) placed on an exhaust line (4) of a motor vehicle comprising the heat engine (1) as means propulsion system and a source of electrical energy comprising a fuel cell (7), characterized in that at least part of the hydrogen injected into the exhaust line (4) comes from the fuel cell (7 ) or a means (8,2) for supplying the fuel cell with hydrogen. SOFC, AFC.  5.-regeneration method according to claim 4, characterized in that the fuel cell is of one of the following types: PEMFC,  6.-regeneration method according to any one of claims 4 and 5, characterized in that the fuel cell (7) is supplied with hydrogen, either by a hydrogen storage reserve (2) on board the vehicle , or by a reformer (8) for producing hydrogen from at least one hydrogenated component of a fuel, and a part of the <Desc / Clms Page number 11>  less of the hydrogen injected into the exhaust pipe (4) comes from at least one of the hydrogen reserve (2) and the reformer (8).  7.-regeneration method according to any one of claims 4,5 and 6, characterized in that at least one of the fuel cell (7), the reformer (8) and the storage reserve d hydrogen (2) is connected to a buffer tank (11) for storing hydrogen and that the hydrogen injected into the exhaust duct (4) comes from the buffer tank (11).  8.- Regeneration device for a particulate filter (5) for the filtration of exhaust gas from a heat engine (1) arranged on an exhaust line (4) of the heat engine (1), characterized by the fact that it comprises a means for supplying hydrogen constituted by at least one of a storage reserve and a means for producing hydrogen and a pipe (10) for injecting hydrogen into the exhaust line (4) connected at one end to the exhaust line (4), upstream of the particulate filter (5) and at a second end opposite the first, by means of hydrogen supply (2 , 7, 8, 11).  9.- Device according to claim 8, characterized in that the means for supplying hydrogen comprises at least one reserve of stoc-

 kage of hydrogen (2) of one of the following types: cryogenic storage reserve of hydrogen in liquid form, hydrogen storage reserve under pressure, storage reserve of hydrogen in a material such as metallic hydride or made up of carbon nanotubes.  10.-regeneration device according to any one of claims 8 and 9 of a particulate filter (5) placed on the exhaust line (4) of a motor vehicle comprising the heat engine (1) as a means of propulsion and an electric power source (7,8) comprising a fuel cell (7), characterized in that the means for supplying hydrogen comprises at least one of the fuel cell (7), d 'a reformer (8) supplying the fuel cell (7) with hydrogen, a hydrogen storage reserve (2) and a hydrogen storage buffer tank (11).  11.-regeneration device according to claim 10, characterized in that it comprises a control unit (16) connected to a sensor <Desc / Clms Page number 12>  (15) the fouling state of the particulate filter (5) and at least one sensor (17, 18) for detecting an excess of hydrogen in the fuel cell (7,8), so controlling the injection of hydrogen through the injection line (10) into the exhaust line (4), upstream of the particulate filter (5).  12.- Device according to any one of claims 10 and 11, characterized in that the source of electrical energy (6,7, 8) comprising a fuel cell (7), comprises a reformer (8) for the production of hydrogen from fuel, a buffer tank (11) and means (16) for controlling a hydrogen injection from at least one of the fuel cell (7) of the reformer (8 ) the hydrogen storage reserve (2) and the buffer tank (11).  13.-regeneration device according to claim 12, characterized in that the control unit (16) is connected to at least one sensor (15) for detecting the level of fouling of the particulate filter (5) and to at least one sensor (17,18) for detecting an excess of hydrogen in the fuel cell (7,8)