Process and device for purifying exhaust gases.

p0001The invention relates to a process for the purification of exhaust gases according to the preamble of claim 1 and to an apparatus for performing the method.

p0002Such a process is for purification of NO_x-, S0₂-and- dusty flue gases of all kind, whether they come from an internal combustion engine or an incinerator.

p0003already known is a method in which the exhaust gases can be purified from power plants by means of electron beams. In this electron-beam-dry scrubber method, the electrons in a vacuum at 10-⁶ Torr created and accelerated to high energies. They are then shot into the reactor through a cooled film, through which the exhaust gas to be purified is passed. A portion of the energy supplied is lost as waste heat in the film. A disadvantage of this process is that it is energy-intensive and therefore costly.

p0004The invention is therefore based on the object to provide a method with the NO_x-, S0₂- And dusty flue gases of any kind can be cleaned very cheap.

p0005This object is achieved by the characterizing features of claim 1.

p0006Two devices for performing the method are disclosed in the claims 4 and 7. FIG.

p0007With the inventive method it is possible the shares contained in the exhaust to NO_X and S0₂ chemically implement. Depending on the process and associated design of apparatus the cleaning equipment can especially NO reduced and S0₂- Oxidized or both gases are oxidized. The intermediates formed in this reaction, for example H₂SO₄ or HN0₃ can be condensed or converted by adding ammonia in Awmoniumsulfat or ammonium nitrate. Other additives with oxidizing or reducing nature are also possible. The dust contained in the exhaust gas is deposited by means of the electric field formed from the exhaust gas.

p0008For carrying out the process a reactor is used which has two flat electrodes, which are arranged at a defined distance parallel to each other. One of the two electrodes is the second electrode on its side facing with a dielectric material coated preferably glass. To the two electrodes a DC or pulsed AC voltage is applied such that it results in the formation of several of spaced, localized discharge zones, in particular for the formation of small plasma zones. This discharge zones to be cleaned exhaust gas is at least partially through ball. According to the invention the dielectric layer of the first electrode is provided opposite the second electrode with holes through which the exhaust gas between the two electrodes can be initiated. There is a possibility, the second electrode also closed form and introduce the exhaust gas to be cleaned parallel to the longitudinal axis of the two electrodes in the area between these. According to both the reactor forming electrodes are rectangular. Via one or more lines, additives in the form of ammonia or other oxidizing or reducing chemical compounds in the reactor, in particular in the region between the electrodes, or before or after these are introduced.

p0009According to the invention, the second dielectric layer is formed opposite electrode as a movable endless belt having a brush-like surface. When applying a DC voltage between the two electrodes, especially when applying a negative voltage to this movable electrode the dust contained in the exhaust gas to the electrode is moved toward, and received by its brush-like surface. The dust can be washed out of the brush-like surface, sucked or scraped from her.

p0010Besides the described arrangement for generating a plasma or many micro plasmas, other plasma sources such as microwaves, radio waves, arc or corona discharges can be used to generate such discharge zones.

p0011The inventive method can also be used for the selective removal of nitrogen from previously desulfurized exhaust gases. In this case, the reactor is connected after the desulfurization.

p0012The electrons used for the purification of exhaust gas in the reactor of the invention do not require high acceleration energy. The use of vacuum electron guns for generating high-energy electrons are therefore not required, so that the cleaning of the exhaust gas can be carried out very economically. The discharge between the electrodes of the reactor takes place with a very low power density per unit area. For purification of large amounts of flue gas space are required, which have the dimension of the cross section of the flue gas pipe.

p0013The invention will be explained with reference to drawings.

p0014Show it:<ul><li>Figure 1: a vertical section through a reactor for purifying exhaust gases,</li><li>2 shows a variant of the reactor shown in Figure 1,</li><li>3: a further embodiment of the inventive reactor.</li><li>4 shows a third variant of a reactor</li></ul>

p0015In Figure 1 of the reactor 1 of the invention is shown schematically. In the embodiment shown here, it is formed by two electrodes 2 and 3, which are arranged at a distance of a few millimeters vertically and coverage of each other. The two electrodes 2 and 3 are preferably rectangular and made of sheet-metal plates. The first electrode 2 is provided on its second electrode 2 side facing with a dielectric layer 4, which is in the embodiment Example shown here is made from glass. The two electrodes 2 and 3 are connected to a positive DC power source, wherein one of the two electrodes 2 and 3 is connected to ground. Instead of a DC voltage or direct current source can be connected to the two electrodes and to a pulsed voltage. In both cases, it comes between the two electrodes 2 and 3, in particular between the dielectric layer 4 and the second electrode 3 to form a plurality of small, localized, of separate discharge areas 6. The cleaned exhaust gas 10 is introduced between the electrodes 2 and 3 and the discharge zone 6 supplied. The introduction of the exhaust gas to be cleaned 10 is preferably carried out in parallel to the longitudinal axis of the two electrodes 3 and 4. On the Leitungen.15,16 and 17 can chemical additives are introduced into the reactor. According to the invention, such substances are introduced into the reactor, have the oxidizing or reducing properties and by supporting the plasma exhaust gas components NO_x and / or S0₂ implement into usable end products. A suitable additive is, for example, ammonia. This can be formed from the exhaust gas components, ammonium sulfate or ammonium nitrate.

p0016Instead of the two electrodes 2 and 3, the reactor 1, if necessary with more than two electrodes are upgraded out, particularly when large quantities are to be cleaned in the exhaust gas. According to the invention there is the possibility a plurality of such electrodes 2 and 3 alternately with each other to be arranged so that following an electrode 2 upward and untenhin an electrode 3, and at this another electrode 2 adjoins, etc. When using a plurality of such electrodes 2 and 3 to formation of a reactor 1, the electrodes 2,3 all turn at the same distance from each other. The electrodes 2 are also in this case provided on their surfaces facing the electrodes 3 with a dielectric layer 4th then a certain amount of exhaust gas can be hindurchieleitet for cleaning between each two electrodes 2 and 3. FIG. The length of the electrodes used 2 and 3 is, whether the reactor 1 consists of only two such electrodes or more, preferably selected between 0.1 and 1 m. If necessary, a plurality of such reactors may be connected in series for the purification of the exhaust gas, wherein the exhaust gas to be purified is passed through the entire series connection of the reactors first

p0017The purified exhaust gas emerging from the reactor 1 is referred to herein and in all other representations with 11th

p0018The embodiment illustrated in Figure 2 of the reactor has the same components as those shown in Figure 1 and in the associated description illustrated embodiment. The same components are therefore provided with the same reference numerals. The difference consists in the formation of the electrode 3 and the supply of the exhaust gas. As Figure 2 shows, the Elek is electrode 3 regionally with holes. 7 These openings are arranged perpendicular to the longitudinal axis of the second electrode 3rd They allow the supply of the exhaust gas to be cleaned in den.Bereich between the two electrodes 2 and 3, perpendicular to the longitudinal axis of these two electrodes. Thereby, the possibility is provided to introduce in parallel to the longitudinal axis of the electrodes 2 and 3, nitrogen gas 8 in the area between the electrodes 2 and 3. FIG. By this measure, from the introduced nitrogen gas 8 atomic nitrogen is created which is then used for the reduction of the nitrogen oxide contained in exhaust gas. 6 By the additional use of atomic nitrogen for reduction of the nitrogen oxide, the operation of reactor 1 is further improved. In particular hereby the exhaust gas can be purified, which is loaded with large amounts of nitric oxide. By use of this reactor is ensured that a solches.Abgas after cleaning of completely_`is liberated nitric oxide.

p0019The reactor 1 shown in Figure 3 is particularly suitable for the purification of exhaust gases, which are loaded next to sulfur dioxide, nitrogen oxide in addition to dust. The illustrated reactor 1 in turn comprises two electrodes 2 and 3. FIG. The first electrode is formed by a metallic surface having the same dimensions as the electrode illustrated in Figures 1 and Fingur second The electrode 2 is coated on its side facing the second electrode 3 side with a dielectric layer 4, in particular a glass layer. In addition, the electrode 2 is connected to a power source. 5 At a defined distance from that electrode 2, preferably at a distance of a few millimeters, the second electrode 3 is arranged such that it is disposed parallel and comprehensively to the first electrode of the second

p0020The second electrode 3 is, as Figure 3 shows, as an end 'untied formed. This endless belt has the same width as the electrode second The endless belt is movably supported and guided for this purpose over two rollers 3W. One of the two rollers is connected to ground. The two rollers are positioned 3W and the dimensions of the electrode 3 is selected so that the first electrode 2 facing surface of the electrode 3 having the same length as this. The surface of the electrode 3 is formed like a brush. In particular, thin wires 3 are so arranged that they project perpendicularly from the surface on the entire surface of the electrode.

p0021The cleaned exhaust gas 10 is introduced parallel to the longitudinal axis of the two electrodes 2 and 3 between them. a plurality of localized, separate discharge zones 6 · are formed by the connection of the current source 5 between the two electrodes 2 and 3, the effects of the exhaust gas to be cleaned 10 exposed. The dust contained in the exhaust gas 10 is transported to the second electrode 3 negatively charged due to the electric field and the forming inclusion therein of the brush-like surface. The endless belt-shaped electrode 3, with the aid of the two rollers 3W continuously moved, so that the accumulating on the surface of the electrode 3, dust is continuously transported away from the area of ​​Entlandungszonen 6th On the rear side of the dust is then removed by washing or blowing of the surface, and a dust hopper 18 are fed, so that the surface is then again available for further use.

p0022Figure 4 schematically shows a reactor 1, in particular its reaction zone 21. This reaction zone 21 may for example be designed as a tube and sized so that it can be, (not shown) as a portion of an exhaust passage used. The plasma generating device is in this case arranged within the reaction zone 21 in which the exhaust gas is purified. It is formed by a microwave or a high frequency source, through an arc, spark or a so-called silent discharge arrangement. Via the lines 31,32 and 33 are additives in the reaction zone initiated which support the effect of the plasma generated.