Process for the Treatment of Soot Particles and the Cleaning of Exhaust Gases of an Internal Combustion Engine and Apparatus for Its Practice

The invention relates to a process for the treatment of soot particles and the cleaning of exhaust gases of an internal combustion engine and an apparatus for its practice.

West German Laid-open Application 3,502,448 discloses an apparatus for the removal of soot particles and other solid particles from the exhaust gas of motor vehicles, which apparatus contains a soot collector that must be freed of soot through a disposal nozzle. This apparatus has the disadvantage that it is not operative if the soot collector has become completely filled with soot. The soot collector must be cleaned out periodically and results in downtimes for the vehicle concerned.

The object of the invention is to provide a process and an apparatus of the type mentioned in the introduction, with which it is possible continuously to remove soot particles from the exhaust gas of an internal combustion engine and to clean the exhaust gas without the necessity of periodically cleaning a filter.

The invention has the advantage over the prior art in that, during operation of the internal combustion engine concerned, its exhaust gases are continuously freed of soot particles, whereby a filter for residual soot particles becomes filled with soot only after long operating periods. The process brings about and the apparatus permits the elimination of the soot particles and thereafter the destructive oxidation of the residual hydrocarbon groups and combustion of the carbon monoxide into carbon dioxide, so that only water vapor, H.sub.2 O, and carbon dioxide, CO.sub.2, are left as exhaust-gas constituents.

Further advantageous modifications of the invention will become apparent from the claims and the ensuing description.

The invention will be explained with reference to practical embodiments in conjunction with the drawings, in which

FIG. 1 is a perspective view of the apparatus in assembled condition;

FIG. 2 is a perspective exploded diagram of the apparatus;

FIG. 3 is a section through the apparatus in assembled condition;

FIG. 4 is a top plan view of a heating ring associated with the apparatus;

FIG. 5 is a view of a stay for a heating wire.

The apparatus contains, first, a casing 1 (FIG. 1), which consists of two casing halves 3, 5 held together by means of flanges 15, 16 and bolts 17. Here, bores with a diameter somewhat larger than that of the bolts are provided in one of the flanges 15. The bolts 17 sit loosely, i.e., with play, in the bores. In the other flange 16, threaded holes are provided into which the bolts 17 are screwed.

Before the two casing halves 3, 5 are brought together, a heating ring 9 (FIG. 2) and a flow cone 6 are inserted in the casing 1.

The first casing half 3 (FIG. 3) has an inlet 2 and the second casing half 5 has an outlet 22 for the exhaust gases. The flow cone 6 of the apparatus is inserted in the casing 1 such that its tip points toward the exhaust gases flowing in through the inlet 2 of the apparatus. Gas deflector plates 7 are provided at one edge 18 (FIG. 2) of the flow cone 6. Exhaust gases arriving in the direction of arrow 20 (FIG. 3) along a streamline 19 pass the inlet 2, the space formed between the flow cone 6 and the wall of the upper casing half 3, and the gas deflector plates 7 (FIG. 3). The gas deflector plates 7 cause the exhaust gases to be swirled in a circular path along the outer wall of the casing 1. The exhaust gases then pass through the electrically heated heating wires 10, 11, (FIGS. 2, 3, 4), clamped in the heating ring 9, at an angle to the gap between the heating wires 10 and the heating wires 11, after which they arrive in a first deflection chamber 4 in the second casing half 5. There, they impinge upon the outer wall of the second casing half 5 and, still swirling in a circular path corresponding to the outer wall of the second casing half 5, are deflected in the first deflection chamber 4. The exhaust gases are also directed toward the outer wall of the second casing half 5, since they are deflected beforehand toward the outer wall of the second casing half 5 by an edge 24 spread gradually outward on the flow cone 6 .

After deflection of the exhaust gases in the deflection chamber 4, they are passed for the second time -- again at an angle -- through the heating wires 10, 11 clamped and heated in the heating ring 9, and arrive at the inner surface 23 of the flow cone 6, where they are deflected -- while still being swirled in a circular ring -- and passed from here for the third time -- again at an angle -- through the heated heating wires 10, 11.

Because the exhaust gases and especially the soot particles pass through the heated heating wires 10, 11 three times and in the process sweep past the heating wires at an angle, intensive heating of the soot particles, which burn well as a result (pyrolysis), is achieved.

A line 12 leads from the inside of the flow cone 6 out of the first casing half 3. The area in which the line 12 discharges into the deflection chamber 8 in the flow cone 6 constitutes a quiescent zone for the exhaust gases. From here, residues that remain after the three-stage combustion can be sucked out of the casing 1. This is accomplished through a line 21 (FIGS. 1, 3), which is connected to a duct 14 in a space 31 (FIG. 3) disposed downstream from the outlet of the casing 1. A soot filter 30, preferably in the form of a replaceable filter cartridge, is interposed in the line 21.

During operation of the apparatus, an overpressure develops in the duct 14, so that combustion residues, i.e., soot particles, still present at the outlet 22 are conveyed through the line 21 to the soot filter 30 and deposited thereat. It can be replaced if the soot filter 30 is saturated with soot particles and other combustion residues. A sensor 32 connected, for example, to an electronic system (not shown in the drawings), can monitor the degree of saturation of the soot filter 30.

A duct 13 is used to supply fresh air, which is necessary when the engine adjustment is too rich. The supply of air into the deflection chamber 4 promotes the second and third combustion of the soot particles by the heating wires 10, 11. The control of the air supply to the duct 13, and thus to the deflection chamber 4, is provided by means known in themselves. Through another line 25 (FIGS. 1, 2), which also opens into the deflection chamber 4, a sample of the exhaust-gas stream can be taken directly from the deflection chamber 4 and its condition checked by means of a sensor.

Gas deflector plates 27 are also provided in the area of the casing half 5 (FIG. 3) for the purpose of swirling well the exhaust gases, which also entrain soot particles. Other gas deflector plates 37 are installed centrally upstream from the outlet.

The heating ring 9 bearing the heating wires 10, 11 consists of refractory ceramic material. In the practical embodiment, the heating wires 10, 11 are clamped between spring-loaded stays 26 (FIG. 5). The spring-loaded stays 26 compensate for changes in length of the heating wires 10, 11 due to varying temperatures.

In one practical embodiment, the heating wires 10, 11 have developed temperatures of between 700 and 800.degree. C.

The gas deflector plates 7 in one practical embodiment are inclined with an angle of attack of approximately 22.degree. C. with respect to the planes in which the heating wires are located.

In another practical embodiment, the inclination of all gas deflector plates 7, 27, 37 can be changed if necessary, e.g., by bending the gas deflector plates.

The exhaust gases emerge from the casing 1 through its outlet 22 and arrive at an exhaust-gas filter 28 which is known in itself, for example, a catalyst in the form of a monolithic element.

The operation of an internal combustion engine in conjunction with the described apparatus can be achieved, first, by supplying the ignition electrodes, i.e., the heating wires 10, 11, with current, thereby heating them up to high temperature. Only then will the internal combustion engine be started, thus ensuring excellent treatment and filtering-out of the soot particles as well as thorough cleaning of the exhaust gases.

The process for the treatment of soot particles and cleaning of exhaust gases of an internal combustion engine consists in moving exhaust gases containing soot particles past one or more ignition electrodes heated up to high temperature in order to burn said soot particles, feeding remaining soot particles to a soot filter, and passing the exhaust gases through an exhaust-gas filter. The exhaust gases which first entrain the soot particles are given a rotary motion so as to remove the same, and the soot particles are concentrated three-dimensionally by the action of centrifugal forces and, optionally, of a quiescent in-flowing zone or zones disposed in the flow path, and are passed from there to a soot filter. To initiate the combustion of newly arriving soot particles which are to be burned, one uses, instead of ignition electrodes, the heat of reaction of the already-burning soot particles and/or of the apparatus for carrying out the process, which has been heated up to high temperature.