WO2018091987A2

WO2018091987A2 - Method and apparatus for regenerating diesel particulate filters and catalytic converters

Info

Publication number: WO2018091987A2
Application number: PCT/IB2017/056285
Authority: WO
Inventors: Mario LISANTI
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-11-15
Filing date: 2017-10-11
Publication date: 2018-05-24
Anticipated expiration: 2019-05-15
Also published as: IT201600115059A1; WO2018091987A3

Abstract

A method for regenerating diesel particulate filters (F) and catalytic converters of motor vehicles is described, the method comprising the steps of: a. placing either the diesel particulate filter (F) or the catalytic converters inside a washing chamber (3); b. depressurizing, or at most making vacuum in, the diesel particulate filter (F) or catalytic converter; c. feeding at least one washing fluid into the diesel particulate filter (F) or catalytic converter. An apparatus (1) is also described in which this method is carried out.

Description

Method and apparatus for regenerating diesel particulate filters

and catalytic converters

_***

DESCRIPTION

Field of the Invention

The present invention relates to a method and apparatus for regenerating diesel particulate filters and catalytic converters of vehicles.

In particular, the present invention relates to a method and apparatus for regenerating used diesel particulate filters and used catalytic converters.

State of the art

The use of devices adapted to intercept exhaust gases of motor vehicles, in order to reduce as far as possible pollutants contained in the exhaust gases themselves, has been known for years now. In particular catalytic devices, or catalytic mufflers, or simply catalytic converters are widely used in petrol vehicles, while in diesel vehicles catalytic converters are used in combination with diesel particulate filters. In fact, while pollutants produced by petrol vehicles are mostly carbon monoxide (CO), unburned hydrocarbons (HC) and nitrogen oxides (NO_x), diesel vehicles produce not only these gaseous substances but also fine particles generated by incomplete combustion of diesel fuel. These particles, which are harmful to humans and environment, are generally referred to as "particulate matter" and are virtually invisible because they have dimensions smaller than 10 pm, falling within the category known as PM10. These are solid particles essentially formed by a carbon core on which hydrocarbons, metals, water, and sulfur compounds are deposited.

Catalytic converters are devices in which chemical reactions able to convert highly harmful substances into less harmful substances take place. They usually contain a plurality of small-size channels obtained either by furrowing a ceramic structure or rolling a plurality of thin corrugated metal sheets. These channels are impregnated with elements capable of catalyzing the reactions of interest, i.e. capable of transforming carbon monoxide (CO), unburned hydrocarbons (HC) and nitrogen oxides (NO_x) into nitrogen (N2), water (H2O) and carbon dioxide (CO2). Such substances, which are the true catalysts of the mentioned chemical reactions, are usually platinum, palladium and rhodium. The exhaust gases are forced to pass through the channels so as to react with such elements and come out of the catalytic converter with less toxic composition which is anyway tolerated by current regulations.

By contrast, diesel particulate filters are real mechanical filters able to trap the particulate matter. Generally, such filters comprise a monolithic structure of porous silicon carbide. The porosity of the silicon creates a plurality of small channels able to trap particulate matter therein. Therefore, filters are structurally very similar to catalytic converters.

The catalytic converter and the diesel particulate filter are arranged in series along the exhaust-gas path of the diesel vehicle and can be physically separate or incorporated in a single box-shaped case.

The present invention mainly relates both to diesel particulate filters and box-shaped cases comprising filter and catalytic converter, as well as to catalytic converters.

The diesel particulate filters currently available on the market are basically of two types: FAP (Filtres a particules) and DPF (Diesel Particulate Filter). These are two types of filters having very similar structure and operation and differing from one another only in the regeneration method. In fact, diesel particulate filters require a periodic regenerative process able to clear them from the particles accumulated inside them. This process is automatically carried out by the vehicle on which the filter is mounted, usually every 400 to 1000 km, while the vehicle is running.

Substantially, the filter is regenerated by periodically burning particles trapped in its channels. However, particulate combustion takes place at a temperature of about 550 - 650°C but, while driving in the city, exhaust gases reach the filter at a temperature of 150 - 200°C. In order to reach the particulate combustion temperature, the control unit of modern diesel engines works post- injections of diesel fuel which, by burning, raises the temperature.

The difference between FAP filters and DPF filters is that while cerium oxide is introduced in the former in order to lower the combustion starting temperature of the particulate matter to 450°C, such additive is not added in DPF types. In both cases, when the filter has to be regenerated, the vehicle driver is warned by means of a suitable warning light. Therefore, he will have to cover a non-urban journey, i.e. to drive the vehicle at speeds above 70 Km / h, in order to obtain the desired temperatures and cause combustion of the particulate matter deposited in the filter. In this way the filter is partially regenerated.

However, when diesel vehicles have traveled high distances (above 15,000 km), the mentioned regenerating process may be ineffective and cause large amounts of particulate matter to accumulate in the filter. This not only adversely affects the engine operation, fuel consumption and generated pollution but also causes the filter itself to be irreversibly damaged.

Since the replacing operation of a diesel particulate filter is expensive, many processes and apparatuses have been proposed for regenerating the filter of diesel vehicles covering long distances, in order to overcome this drawback without having to replace the filter. These processes are carried out in garages and involve removing the filter from the vehicle so that it can be washed with water or other washing liquids.

The processes and apparatus described in patents EP 1302232, EP 1252919, US 7,326,265 and patent applications WO 02/094415, EP 1060780, WO 03/093659 are some examples. All the described processes provide that the filter is washed with a washing liquid and/or a washing gas, which are pressurized or at atmospheric pressure, by means of generally long-lasting washing cycles. Some of them provide that the filter is preheated in special ovens or by hot air flows, so as to facilitate particulate combustion and thus filter cleaning. Others provide a step of drying the filter in special ovens or by means of hot flows. All known methods require long running times to be effective. In fact, a complete regenerative cycle lasts at least 30 minutes.

A further drawback of the prior art processes lies in that they require high energy consumption thus resulting expensive. In fact, known methods, in order to be effective, require high flow rates of washing fluids and/or high pressures, otherwise the particulate material can not be separated from the filter.

In addition to this, those processes and devices that require the filters to be pretreated or dried in special ovens, are particularly expensive.

Another drawback of known regenerating processes is that they involve the risk of breakage of the filters. In fact, high pressures and pulses transmitted to the filter body by washing fluids can jeopardize the structural integrity of the filter, i.e. damage the thin walls which separate the channels of the filter body, obviously resulting in adverse effects on both the operation and useful life of the filter.

This problem is particularly relevant in the regeneration methods involving the injection of the washing fluid under pressure through the outlet of a box-shaped case containing the filter. In fact, when diesel particulate filters are enclosed in metal cases, these are generally provided with small-diameter inlet sections and large-diameter outlet sections, whereby the pressurized washing fluid injected through the outlet cannot flow out of the narrow inlet section through which it is forced, and the pressure inside the body suddenly increases, causing the filter to be irreversibly damaged.

European Patent Application EP 2500078 describes a method and apparatus for regenerating filters in which a flow of washing liquid together with a flow of washing gas pass through the filter at the same time throughout the washing cycle. With this method and apparatus, a sufficiently high regeneration is obtained in 20-30 minutes.

The Applicant has now developed a method and apparatus able to obtain better regeneration in the same time, or the same regeneration in a shorter time. US 2010/307339 describes a method for regenerating DPF filters by using compressed air pulses alternating at regular intervals on either sides of the filter (paragraphs 31 , 34 and 35 and claim 1 ), by using a pop-up valve fed by a compressed-air tank or a blower. In some cases, different pressures are used for the inlet air at one side of the filter with respect to the pressure of the inlet air at the opposite side of the filter (par. 36 and 37). If required, the filter is alternatively heated and cooled (par. 32) so that the effect of thermal expansions and contractions can be exploited in order to detach residues from the filter surfaces. Expected pressures are averagely high (par.37): 90-125 PSI which correspond to 6.20-8.61 bar, and 60-80 PSI which correspond to 0.07- 5.52 bar. A blower (par. 39) can be used to direct air to a filter side, the air having a pressure between 0.5 - 20 PSI, which correspond to 0.03-1 .38 bar, and 1 -5 PSI which correspond to 0.03-0.34 bar, for 2-10 seconds. Other fluids, including water or steam, can be used (par. 55). Suction of the ashes and residues removed from the filter is provided. Suction is provided between the DPF and the catalytic converter during the cleaning cycle (tables and examples).

WO 2016/029926 describes a method for regenerating DPF filters while the latter are still installed on vehicles and connected to the engine. The method involves heating the DPF filter: the DPF filter is kept warm by the vehicle control unit. At this point, air pulses are directed to the DPF in the opposite direction with respect to the normal flow of exhaust gases, and the residues expelled from the DPF are suctioned from the opposite side and collected in a container (page 6). Air pulses are obtained by using compressed air contained in a vehicle tank at 4-10 bar, preferably 6.5 bar abs (page 7, lines 20-24). In a case (described on page 7), the normal pressure drop inside the DPF filter is used to obtain the suctioning flow to suction residues.

US 2006/0070359 describes a method for regenerating DPF filters without disassembling DPF filters from the vehicles (par. 32). Compressed air at 70-1 10 PSI is used (par. 40). No washing liquid is passed through the DPF filter being regenerated.

Summary of the invention

The object of the present invention is therefore to provide a method and apparatus for regenerating diesel particulate filters which are free from the aforesaid drawbacks.

In particular, a first object of the present invention is to provide a method for regenerating diesel particulate filters disassembled from the vehicles, i.e. not connected to the corresponding engine, the method being at the same time rapid and effective.

It is a further object of the present invention to provide a regenerating method which is not only cost-effective, but also able to guarantee high regeneration of the filter separate from its engine.

Another object of the present invention is to provide a regeneration method that safeguards the integrity of the filter, i.e. a method which, although rapid and effective, does not jeopardize the structural characteristics of the filter.

A further object of the present invention is to provide an apparatus for regenerating isolated diesel particulate filters, i.e. filters separate from respective engines and vehicles, which is simple, effective and involving low production, operation and maintenance costs.

Another object of the present invention is to provide a method and apparatus for regenerating diesel particulate filters both able to be applied also to catalytic converters possibly combined with the diesel particulate filters themselves.

These and other objects are achieved by means of a method and apparatus as claimed in claims 1 and 9, respectively.

In particular, in its first aspect, the present invention relates to a method for regenerating diesel particulate filters and catalytic devices separate from their respective motor vehicles, comprising the following steps:

a. depressurizing, or at most making vacuum in, the diesel particulate filter or catalytic converter; b. feeding at least one washing fluid into the filter or catalytic converter.

For the sake of simplicity, the term filter will be used hereinafter to indistinctly denote diesel particulate filters, catalytic converters or an assembly thereof.

The expression "washing fluid" denotes a liquid passing through the filter to be regenerated so as to remove residues, encrustations, etc.

This method, by providing depressurization within the filter, i.e. obtaining pressures lower than atmospheric pressure or at least vacuum, provides extremely high efficiency in a short time. In fact, the air normally present in the filter channels, which would prevent the washing liquid from reaching all the cavities, can be removed by generating depression in the filter, thereby obtaining rapid and deep cleaning. The liquid can quickly penetrate the filter, seeping into all of its interstices, and clean it deeply thus achieving a high level of regeneration of the same.

Neither high pressures nor pretreatments are required for this method which is therefore cost-effective.

Preferably, in order to obtain the most inexpensiveness, a washing cycle lasts 5-10 minutes and this is sufficient to achieve a good regeneration of the filter, above 95%. The easiest way to measure the effectiveness of regeneration is through a differential pressure transmitter that, on equal input conditions of the filter, detects the output pressure before and after the cleaning.

The method of the present invention, not requiring high pressures, also ensures the integrity of the treated filter, i.e. it overcomes the risk of damaging the filter structure.

This method can be further applied also to catalytic converters.

Before regenerating the DPE filter or catalytic converter, they are disassembled from the respective engines. Once regenerated, they are reassembled on the vehicles.

Preferably, step a comprises the obtainment of a pressure lower than atmospheric pressure in the filter, for example equal to 10 ÷ 700 mbar (absolute pressure). This depression allows the narrow channels of the filter to be cleared of air and any exhaust gas trapped therein, without damaging the filter.

Preferably, the depression is obtained by using a blower so that high flow rates are available. Preferably, the blower cooperates with a flow-reversing valve so that the direction of the air flow can be reversed. These are simple and inexpensive devices easy to be found on the market.

According to a preferred embodiment of the method of the invention, step b of feeding at least one washing fluid inside the filter comprises feeding a washing liquid, or a washing gas or a mixture of washing liquid and washing gas. The Applicant found that a better filter regeneration can be obtained quickly, by feeding a mixture of liquid and gas.

This step b can be carried out either continuously or discontinuously, with or without pressure pulses. The Applicant verified that by continuously carrying out the step b and by imparting pressure pulses to the washing fluid passing through the filter, a high percentage of particulate trapped within the filter can be expelled from the filter.

Preferably, the method involves applying a plurality of pressure pulses in the washing liquid or in the mixture of washing liquid and gas. Preferably, each pulse is caused by a pressure peak p between 1 and 10 bar and lasts a time t between 1 and 10 seconds. These pressure and durability values allow effective cleaning of the filter to be obtained without damaging the latter and without excessive energy consumption.

Preferably, the method of the invention provides a step c of drying the filter, after step b. If the step c is provided, it is preferably carried out by the same blower carrying out the step a. In fact, thanks to the flow reversing valve, it is possible to reverse the air flow generated by the blower. This flow, which during the step a acts to suction from the filter outlet, is reversed so that the air is pushed inside the filter, thus drying the filter.

According to the second aspect of the invention, the latter relates to an apparatus for regenerating diesel particulate filters and catalytic converters of motor vehicles, comprising:

at least one turbomachine adapted to depressurize, or at most making vacuum in, the filter during the regenerating process;

- at least one feeding line to feed a washing fluid to the filter.

An apparatus of this type is simple, quick and effective, as the presence of a turbomachine able to generate a depression in the filter causes the filter regeneration to be high and occur quickly without damaging the filter, for the reasons previously described.

Advantageously, the turbomachine is a blower that suctions air from the filter in "depression" mode and blows air into the filter in "drying" mode. In fact, neither high operation costs nor high maintenance costs are required by the blower.

Preferably, the blower cooperates with a flow reversing valve, so that the former has its mode changed from "drying" to "depression" and vice versa.

An apparatus of this type, equipped with blower and flow reversing valve, is simple, effective and economical. In fact, the desired depression can be generated thanks to the blower and flow reversing valve, with low investment and operation costs. In addition, the blower in combination with the flow reversing valve allow the same blower to be used with reversed flow with respect to the step of generating depression, and also to inject air into the filter for drying after washing. Therefore, multiple operations are carried out by the apparatus with a single device, resulting in several advantages as regard investment costs. In addition, a blower of about 4÷5 KW can generate a flow of 10O700 m³/h, i.e. a flow having high flow rates and therefore high efficiency. Thanks to this feature, the apparatus for regenerating diesel particulate filters according to the present invention is even more efficient.

Preferably, the apparatus comprises a filter washing chamber and sleeves able to fluidically connect:

- the turbomachine with the filter, and - the washing liquid feeding line with the filter.

The sleeves can be handled by the operator to be easily and sealingly coupled to each filter to be regenerated, and to be separated from any regenerated filter just as easily.

Preferably, the apparatus of the present invention comprises at least one containing tank to contain the at least one washing fluid. Even more preferably, there are two fluids, a liquid and a gas, as well as two tanks, one for liquid and the other for gas.

According to a preferred embodiment, the apparatus of the present invention also comprises at least one turbomachine adapted to feed a washing fluid (which in turn may be a mixture) into the at least one feeding line and thus into the filter. Preferably, there are two turbomachines: a submersible-type pump for washing liquids and a compressor for washing gases, for example an air compressor.

Preferably, the apparatus of the present invention further comprises a mixing valve adapted to mix a washing gas, preferably air, with a washing liquid, preferably water with detergent.

Herein, with "diesel particulate filter" is meant both the actual filter and the box-shaped case containing the same, together with the catalytic converter or else without catalytic converter.

Furthermore, herein, speaking about "regeneration" of the filter, the latter should be considered as at least partially regenerated.

In this description and in the following claims, when speaking about "vacuum" reference is made to pressures below the atmospheric pressure, not necessarily hard vacuum, although it may be at most hard vacuum, and when speaking about pressures, reference is made to absolute pressures, i.e. pressures measured by taking the vacuum as reference instead of the atmospheric pressure.

Finally, herein, the term "vehicle" comprises cars, buses, lorries, vans, and any means of transport with internal-combustion engine. Brief list of figures

More features and advantages of the method and apparatus of the invention will be more evident by considering the following specification of some, but not exclusive, preferred embodiments, which are illustrated by way of example only and without limitations, with the aid of the accompanying drawings, in which:

- figure 1 shows a schematic front view of the apparatus of the present invention, wherein the method of the present invention is carried out according to a preferred embodiment;

- figure 2 shows a partial view, partially showing through figure 1 ;

- figure 3 shows some details of the apparatus of figure 1 , during the method of the present invention; and

- figure 4 shows an operating scheme of the apparatus according to a possible embodiment;

- figure 5 shows an operating scheme of the apparatus according to another embodiment.

Detailed description of the invention

The following detailed description refers to a method and apparatus for regenerating diesel particulate filters and catalytic converters of motor vehicles.

In figure 1 , reference numeral 1 generally shows an apparatus for regenerating diesel particulate filters according to a preferred embodiment.

In particular, the apparatus 1 comprises a first housing 2 accommodating a washing chamber 3 adapted to receive a filter F during the regenerating process, and a second housing 4 accommodating a control panel 5 and other components described hereafter.

The first housing 2 comprises an opening provided with a closable door 6 delimiting the washing chamber 3. The door 6 is adapted to allow the filter F to be inserted and removed from the washing chamber 3 and, at the same time, to protect the operator against any leakage of washing liquid. The door 6 is further provided with a transparent portion allowing the operator to monitor the regenerating process.

Referring to figure 3, it can be seen that the washing chamber 3 comprises a support 9 for the filter F, which is preferably provided with a horizontal arm adapted to vertically support the filter F during the regenerating process. The filter F is positioned vertically when the longitudinal axis of its channels is vertical. The dimensions of this support 9, preferably the height thereof, can be adjusted so as to conform to different types of commercially available filters F and catalytic converters. According to preferred embodiments, the apparatus 1 is provided with a connector adapted to connect the filter F to the arm of the support 9 and to hold the same filter in position during the regenerating process.

Advantageously, in the washing chamber 3, the filter F is arranged so that its inlet section 10 of exhaust gases faces downwards and its outlet section 1 1 faces upwards, so that the washing fluids, preferably fed by the top portion, enter the filter F from its outlet section 1 1 (countercurrently with respect to the direction of exhaust gases passing through the filter being used on the respective vehicle).

The apparatus 1 also includes a supporting base 12 of the filter F, able to prevent the filter F from being displaced during regeneration, and a washing liquid collecting receptacle not shown in the figures, which is positioned below the washing chamber 3.

The apparatus 1 for regenerating filters F according to the present invention further comprises at least one turbomachine adapted to depressurize, or at most make vacuum in, the filter F, i.e. during the regenerating process. Said turbomachine is preferably a blower 7, but it may also be a vacuum pump or other suitable means.

The blower 7 can work in two different modes. In particular, when in the "depression" mode, it is adapted to suction gas, typically air, from the filter F and when in the "drying" mode it is adapted to blow gas, typically air, into filter F. The blower 7 is preferably a side-channel type blower having power of 4 ÷ 7 KW and flow rate of 100 ÷ 700 m³ / h.

The advantage of providing a blower 7 is that it can be used to carry out two functions, namely to create a depression and, by reversing its flow, to create a drying flow in the filter F. The other advantage associated with the use of a blower 7 is that it generates higher flow rates with respect to those of a compressor having the same power.

Flow reversal is made possible by a gas-flow reversing valve 8 which cooperates with the blower 7 in order to change its mode, or to switch from the "depression" function in which air is suctioned from the filter F , to the "drying" one in which air is pushed into filter F, and vice versa. These valves are easily available on the market and can be equipped with an electric or pneumatic actuator.

According to the present invention, the apparatus 1 further comprises at least one feeding line 13, 14 to feed at least one washing fluid. According to the preferred embodiment shown in the figures, there are two feeding lines 13, 14, a first feeding line 13 intended to feed a washing liquid and a second feeding line 14 intended to feed a washing gas.

Preferably, the apparatus 1 comprises at least one containing tank 15, 16 to contain the at least one washing fluid. As shown in figure 4, there are two tanks 15, 16: a first tank 15 adapted to contain a washing liquid, preferably water to which detergent is added, and a second tank 16 adapted to contain a washing gas, preferably air.

The apparatus 1 further comprises a turbomachine adapted to feed the washing liquid to the first feeding line 13 and then inside the washing chamber 3 in the filter F. This turbomachine is preferably a pump 17. The pump is preferably of submersible type and has flow rate of 50÷300 l/min.

The apparatus 1 additionally comprises a further turbomachine adapted to push the washing liquid to the second feeding line 14 and then inside the washing chamber 3 in the filter F. This turbomachine is preferably a compressor 18, but it could also be a further blower. Alternatively, the same blower 7 may be used to introduce the washing gas into the washing chamber 3 in the filter F.

The apparatus 1 further comprises a mixing valve 19 adapted to mix a washing gas with a washing liquid. In the preferred embodiment, it is a four-way valve, as shown in Figure 4. Two of these four ways are designed to input liquid and gas respectively, one way is to output the gas, liquid or mixture obtained therefrom, and the remaining way is designed for discharging what results from the drying of the filter F, as explained below.

The apparatus 1 comprises a feeding pipe 23, through which the washing fluids are conveyed to the filter F, and a discharging pipe 20 used for the step of drying the filter F, step which will be described below. The feeding pipe 23 can contain washing liquid, washing gas or a mixture thereof, depending on the adjustment of the valve 19.

The first feeding line 13, the second feeding line 14 and the outlet pipe 20 are provided with respective non-return valves 21 in order to prevent backflows.

Advantageously, the apparatus 1 is further provided with a filtering device to filter the washing liquid, not shown in figures. It is preferably arranged in the second housing 4 and is able to intercept particulate matter and further residues removed from filter F.

As shown in figures 1 and 2, the second housing 4 comprises a control panel 5 including operator controls and flow-rate and/or pressure indicators.

Preferably, the apparatus 1 of the present invention not only comprises a silencer 22 for the operator comfort but also has wheels in order to be easily moved.

A preferred embodiment of the method for regenerating diesel particulate filters and catalytic converters of the present invention will now be described, the method being carried out by the apparatus 1 above described.

The filter F is initially placed inside the washing chamber 3. Preferably, the filter F is vertically positioned with its outlet section 1 1 of the exhaust gas upward and its inlet section 10 of the exhaust gas downward, so that the washing fluids, preferably fed from above, enter the filter F through its outlet section 1 1 generally having diameter smaller than the inlet section 10.

The operator first has to introduce the filter F into the washing chamber 3 through the opening of the first housing 2 by opening the appropriate door 6, then secure the filter F to the support 9 by means of an appropriate connector, next fluidically connect the filter F to the line 23 and to a discharging line by means of appropriate sealing sleeves 24, then hermetically close the door 6 and finally start the apparatus 1 by means of the control panel 5.

The sleeves 24 can be coupled to the filter F substantially in fluid-tight manner, except for minimal negligible leakages, so that the inlet and outlet flows to/from the washing chamber 3 are substantially conveyed inside and outside the filter F. For example, the sleeves 24 are cone-shaped.

Subsequently, the method of the present invention provides for a step a of depressurizing, or making vacuum in, the filter F. Preferably, the depressurization corresponds to an absolute pressure inside the filter F in the range of 10÷700 mbar.

Preferably, said step a is carried out by means of at least one blower 7, but it may be carried out by any turbomachine or other suitable vacuum tool. Since, as mentioned, the method according to the preferred embodiment does not require hard vacuum, a blower 7 is used for economic reasons and in order to ensure high flow rate, as well as because its flow can be reversed allowing it to be used as a compressor.

Advantageously, the blower 7 is preferably of side-channel type having power of 4 ÷ 7 KW and flow rate of 100 ÷ 700 m³ / h.

Preferably, the blower 7 cooperates with a gas-flow reversing valve 8, as described above.

Subsequently, according to a step b, the method of the present invention provides that at least one washing fluid is fed into the filter F.

Preferably, there are two washing fluids fed to the apparatus 1 : a washing liquid, preferably comprising water to which at least one detergent of degreasing type is added, and a washing gas, preferably air. In this way, by means of appropriate valves, only washing liquid, only washing gas or a mixture of washing liquid and gas can be fed to the washing chamber 3, and then to the filter F.

The washing fluids can be fed in different ways. In fact liquid, air or a mixture thereof can be fed in series, i.e. one fluid after the other according to predetermined orders, sequences and timings, or else two or three of them (of air, liquid and mixture) can be fed at the same time. Moreover, the washing fluids can be fed either continuously or discontinuously. In all cases, pressure pulses can be provided with air, liquid or mixture during feeding.

A preferred embodiment of the invention provides a mixture of air and washing liquid to be continuously fed to the filter F by delivering pressure pulses with air.

Preferably, each pressure pulse is a pressure peak p between 1 and 10 bar and lasts a time t between 2 and 6 seconds.

The washing liquid is fed by means of a turbomachine, preferably a submersible pump 17 and preferably having a flow rate of 50÷300 l/min.

The washing liquid is preferably taken from a first tank 15 and then injected into a first feeding line 13 by means of the pump 17 preferably placed inside the tank 15. Such liquid is preferably fed at a temperature in the range of 10÷60°C, for example 50°C.

On the contrary, the washing gas is fed by means of a compressor 18 or an additional blower or another turbomachine, or by means of the same blower 7 making vacuum in the washing chamber 3, as explained above.

The washing gas is preferably taken from a second tank 16 and then injected into a second feeding line 14 by means of the compressor 18.

In other words, once the depression is created in the filter F, a control unit drives the pump 17 and the compressor 18 in order to simultaneously feed washing liquid and gas, which are conveyed into a mixing valve 19 which then delivers a mixture of the two fluids to the washing chamber 3 through a feeding pipe 23. The mixture is substantially biphasic because air is not soluble in water but dissolved in the form of small bubbles.

The mixture then enters the filter F through a connector and can penetrate everywhere in short time, as it finds the channels of the filter F substantially free of air. Pressure pulses are imparted to the filter F, preferably by air, while the mixture flows in the filter F. Such pulses can be generated by varying the speed of the compressor 18 and/or by intermittently releasing predetermined amounts of air stored in the second tank 16.

Preferably, the air pulses are 1 to 20 and each of them has pressure between 1 and 10 bar and lasts a time between 1 and 10 seconds.

This allows the particulate matter deposited in filter F to be removed so that a good regeneration level of 95% can be obtained with a washing cycle lasting 5-10 minutes.

The washing cycle can be extended up to 20 minutes in order to achieve even better regeneration.

Figure 5 shows an alternative scheme of the apparatus according to the present invention.

The washing liquid is drawn from a collecting tank 15 by a submersible pump 17 so as to be delivered to the filter F while the filter F itself, already constrained to the sleeves 24, is regenerated.

The liquid is taken from the tank 15 by the pump 17 and delivered to a liquid tank 28 after having been filtered at 29.

The blower 7 is connected to the submersible pump 17 and a non-return valve 25 is interposed between them, in order to prevent the washing liquid from entering the blower 7. Depending on the position of the reversing valve 8, the blower 7:

- suctions only air from the filter F through the "vacuum" line 26, the reversing valve 8 and the pump 17, when the on-off valve 27 is closed, or

- suctions both air and washing liquid from the filter F through the "vacuum" line 26, the reversing valve 8 and the pump 17, when the on-off valve 27 is open and the liquid flows out of the tank 28, or else

- blows drying air into filter F, in the opposite way along the just- described elements.

During the drying, the filter F can be disconnected from the upper sleeve 24.

The on-off valves 27 are preferably IN/OUT type solenoid valves.

A compressor 18, or the blower 7 itself (variation not shown), pressurizes a compressed-air tank 16, which in turn is connected to a tank 28 of water or washing liquid. The reference numeral 25 denotes non-return valves.

The method of the present invention, according to a preferred embodiment, further comprises a step c of drying the filter F.

This step c can be carried out either by means of the compressor 18 or by the same blower 7 carrying out the step b of making vacuum. In this case, first, a reversing step must be carried out to reverse the air flow by means of an appropriate electric or pneumatic reversing valve 8, by which the blower 7 changes its mode from "depression" to "drying", i.e. from the configuration in which air is suctioned into the one in which air is blown. In this way, by injecting air into filter F, it is possible to dry it. This drying phase is carried out for 10÷30 minutes.

A discharge pipe 20 allows air and residues resulting from the drying to flow out of the washing chamber 3. This pipe 20 is connected to the washing chamber 3 by means of the afore said mixing valve 19 which, in this case, is a four-way valve.

Pre-washing steps, carried out before the step b of feeding the washing fluids, can be provided although they are not required by the method of the present invention, which achieves a rapid and effective regeneration of the filter only with the aforementioned steps a and b.

Obviously, further modifications and variations, anyway all falling within the protection scope of the present invention, can be applied to the regenerating method and apparatus according to the present invention by the field technician, in order to satisfy contingent and specific requirements. For example, a plurality of feeding pipes 23, each intended for feeding one or more washing fluids within the washing chamber 3, could be provided. In addition, a previously-prepared mixture of washing fluids could be delivered to the washing chamber 3, in which case the mixing valve 19 could be omitted and only one feeding line 13, 14 could be provided.

Claims

1. A method for regenerating diesel particulate filters (F) and catalytic converters of motor vehicles, comprising the following steps:

a. depressurizing, or at most making vacuum in, the filter (F) or catalytic converter, which are separate from the respective vehicle/engine;

b. feeding at least one washing fluid into the filter (F) or catalytic converter.

2. Method according to claim 1 , wherein during step a, the absolute pressure inside the filter (F) or the catalytic converter is in the range from 10 to 700 mbar.

3. Method according to claim 1 or 2, wherein step a is carried out by at least one blower (7).

4. Method according to one of the preceding claims, wherein step b comprises feeding a washing liquid, a washing gas or a mixture of washing liquid and washing gas.

5. Method according to one of the preceding claims, wherein step b is carried out continuously and/or with pressure pulses imparted to the washing fluid.

6. Method according to claim 5, wherein each pressure pulse corresponds to a pressure peak p between 1 and 10 bar and lasts a time t between 1 and 10 seconds.

7. Method according to any one of preceding claims, further comprising a step c of drying the filter (F).

8. Method according to claim 7 when depending from claim 3, wherein said drying step c is carried out by the same blower (7) carrying out the step a of making vacuum.

9. An apparatus (1 ) for regenerating diesel particulate filters (F) and catalytic converters of motor vehicles, comprising:

at least one turbomachine adapted to depressurize, or at most keeping vacuum inside, the filter (F) and/or the catalytic converter, during the regenerating process, the diesel particulate filter (F) and the catalytic converter being functionally separate from the respective vehicle/engine;

at least one feeding line (13, 14) to feed at least one washing fluid into the filter (F) and/or the catalytic converter.

10. Apparatus (1 ) according to claim 9, wherein said turbomachine is a blower (7) adapted to suction air or gas from the filter (F) in "depression" mode and to blow air or gas into the filter (F) in "drying" mode.

11. Apparatus (1 ) according to claim 10, wherein said blower (7) cooperates with a reversing valve (8) to reverse the gas flow, so that its mode is switched from "pressure" to "drying" mode and vice versa.

12. Apparatus (1 ) according to one of claims 9 - 1 1 , comprising at least one containing tank (15, 16) to contain the at least one washing fluid.

13. Apparatus (1 ) according to one of claims 9 - 12, further comprising at least one turbomachine adapted to feed the at least one washing fluid into the at least one feeding line (13, 14) and then the filter (F).

14. Apparatus (1 ) according to one of claims 9 - 13, further comprising a mixing valve (19) adapted to mix a washing gas with a washing liquid.