Device for simultaneous removal of SO2 and NOx from flue gases by high frequency discharge

Abstract: Device for simultaneous removal of SO₂ and NO x from flue gases by means of high frequency discharge with Tesla coil, consisting of Tesla coil and chamber which are electrically connected with one another.

Description: Field of the Invention The invention belongs to the fields of filtering or removal of SO 2 and NO x from flue gases which are the result of fossil fuel combustion or metallurgical processes. In the general case, the invention is used for filtering gases containing SO 2 and NO x as well as for filtering other pollutants from air. Prior Art The existing methods for filtering SO 2 and NO x from flue gases are chemical methods based on dry or wet procedures. The result of filtering, or byproduct, is gypsum which has very limited commercial value. It practically means that one kind of pollutant is turned into another kind, but a less harmful one. In this case, land is sacrificed for the storage of filtering products and mostly subterranean water is being polluted. The rate of efficiency of such a technology is about 50% for SO 2 and the occasional regeneration of installation is indispensable due to saturation. One method is based on the electron beam irradiation of flue gas in the presence of ammonium (in stoichiometric amount). This method has a high efficiency rate. Almost 100% for SO 2 and about 80% - 90% for NO x and it does not result in saturation. Artificial fertilizer is obtained as an important byproduct (ammonium sulfate and ammonium nitrate) which also has commercial value. Since artificial fertilizer produced in such a way is used in agriculture, storage presents no problems. However, the inadequacies of this method are expensive accelerators that operate in the regime of high power, i.e. 100 kW and more. Pilot plants on the basis of this method work under real conditions in the USA, Japan and Germany and since 1991 in Poland, too. The DE-A-3 708 508 and the GB-A-1 009 331 provide an electronic excitation of flue gas by electric discharge, generated between two electrodes. To prevent arcing dielectric material is located between these electrodes. However, according to GB-A-1 009 331 only a conversion of sulfur trioxide of 75% is obtained even with voltages of several KV and frequencies of several hundred thousands per second. The FR-A-835 288 discloses the provision of electrical excitation by using magnetic fields with frequencies of up to 600 megacycles. This method is applicable to stimulate chemical reactions. This art is known since 1938 but apparently was never improved successfully for the efficient removal of SO 2 and NO x from flue gases. The next method for flue gas filtering is based on impulse corona discharge. Although the filter chamber is comparatively simple, the high power impulse supply of raising time ranging in ns and repetition rate up to 300 Hz is very expensive. The rate of efficiency of this method is about 50 - 60% and it is still in the experimental phase. Methods for removal of SO 2 and NO x from flue gases, which are based on the interaction of electrons with flue gas in the presence of ammonium, are, unlike chemical methods, electronic methods or so called electronic filtering. Filters which are based on these methods represent very promising devices for the removal of SO 2 and NO x from fuel gases. Technical Problem The technical problem of this invention is the removal of SO 2 and NO x from gases of various origin, as well as the removal of other air pollutants. The problem is solved by a device according to claim 1. Improvements of the device are present in related dependent claims. Description of the Invention The essence of the present invention is the utilization of a Tesla coil as a high voltage and high frequency generator connected to specially designed electrode (or electrodes), so that the electrons are excited to oscillate in the chamber filled with flue gas. These high energy electrons excite, ionize and dissociate in the chamber filled with flue gas which, in the presence of ammonium, leads to chemical reactions resulting finally in the removal of SO 2 and NO x from flue gases and their conversion into ammonium salts. To articulate it differently, this method enables a simple and significantly cheaper way of electronic filtering of flue gases to be achieved. Instead of Tesla coil, any high frequency generator can be used. Therefore, for the sake of concise and simple explanation, the expression "Tesla coil" will in the following text also imply any other type of high voltage and high frequency generator with continual or impulse operation regime. The device for simultaneous removal of SO 2 and NO x from flue gases by means of high frequency discharge from Tesla coil is schematically presented in Figure 1. It consists of Tesla coil 1 and filter chamber 2 where a specially designed electrode 3 is placed which is connected to the one side of Tesla coil through feed through 4. For simplicity sake, one or more electrodes are represented by electrode 3, in Fig. 1 and more details are available below. Flue gas enters filter chamber 2 from side 5. Ammonium, in stoichiometric amount, is added to flue gas through opening 6, so the mixture of flue gas and ammonium passes through the system of electrodes with high frequency field and exits through opening 7. Gas is further transported through a pipe to filter for the removal of electronic filtering products - artificial fertilizers - and then, it proceeds through the tube to, for example, bag filter for fertilizer collection, but devoid of SO 2 and NO x and into the atmosphere. Filter chamber 2 can be a tube of different cross sectional views: circular, square, rectangular, etc.. Electrode 3 can have different shapes. Some are schematically shown in Fig. 2: as a wire 31, a set of parallel wires 32, mesh with round edges 33, mesh with sharp tips 34, a number of tips 35, etc.. Also, each of these electrodes may be separate or the electrodes can be combined one with the other or with regard to chamber 2, or with differently shaped electrodes or chambers in order to obtain maximum efficiency of electronic filtering of flue gases. At the same time, the ammonium injection system is adjusted in such a way to maintain a (nearly) stoichiometric amount. When magnetic field is applied to the filter chamber, it increases efficiency and ionization of flue gas, and therefore the efficiency of the electronic filter. Figure 3a schematically shows a case where a parallel magnetic field B is applied to the chamber, whereas Figure 3b shows a perpendicular magnetic field B1. At the same time the way how a magnetic field is produced, whether by permanent magnet or electromagnet, is of no importance. In the second case, a suitable power supply is necessary. It is implied in the above description that the feed-throughs, i.e. electrode supports, are isolated from the chamber. The chamber is also grounded. This device can also be used for filtering gas from other harmful ingredients, such as, for example, CO, CO 2 , various hydrocarbonates, etc. - in that case no ammonium is added - by adjusting discharge parameters, frequency, and both electrical and magnetic field strength, as well as the geometry of electrodes.

Claims: Device suitable for simultaneous removal of SO 2 and NO x from a flue gas in the presence of ammonium by means of a corona discharge comprising a filter chamber (2) for introducing the flue; an electrode (3) placed in the filter chamber (2); a high voltage generator connected to the electrode (3) to supply voltage to the electrode (3), no dielectric screen being present in the path of the discharge, the device being characterised in that said high voltage generator is also a high frequency voltage generator with continual or impulse operating regime. Device of claim 1, characterised in that the high voltage generator is a Tesla coil (1). Device according to claims 1 or 2, characterised in that said chamber (2) is a tube of circular, square, rectangular or other arbitrary cross-sectional view, where one or more electrodes (3) are placed which are connected to the high voltage generator. Device according to anyone of claims 1 to 3, characterised in that the electrode (3) is made of wire (31), set of wires (32), mesh (33, 34, 35), several meshes (33, 34, 35), tips, set of tips or one or more electrodes (3) of arbitrary shape. Device according to anyone of claims 1 to 4, characterised by a parallel or perpendicular magnetic field (B) influencing the chamber (2).

Inventors: MILJEVIC VUJO DR, MILJEVIC, VUJO, DR.
Applicants: MILJEVIC VUJO, MILJEVIC, VUJO, DR.
Application year: 1993
Main classification: B01D53
IPC codes: B01D53, B01J19