Device and method for purifying gases

0001The present invention relates to a device for purifying gases with a filter container, in which a flow space is formed for the gas to be cleaned, at least one arranged in the flow space and a discharge electrode arranged in the flow space deposition electrode, wherein by applying a voltage between the discharge electrode and the deposition electrode particles of the gas to be purified can be deposited on the deposition electrode, and a method therefor.

0002There are known electrostatic precipitators (<patcit id="pcit0001" dnum="US20090151568A1"><text>US 2009/0151568 A1</text></patcit>), in which in an electric field, a negative discharge electrode and a deposition electrode are provided. By applying a high voltage, particles are charged and deposited on the deposition electrode. In such electrostatic precipitators, there is the problem that, on the one hand, the degree of separation is limited and, on the other hand, the separating electrode is contaminated and, as a result, the filter performance is impaired. A mechanical cleaning is usually associated with considerable effort and is not possible in every case.

0003The <patcit id="pcit0002" dnum="EP0299197A2"><text>EP 0 299 197 A2</text></patcit> discloses an electrostatic filter for purifying gases in which particles are electrically charged and attracted by electrodes. The electrodes may have a porous structure and be made of a metal wool braid. A similar filter for the purification of combustion gases is in the<patcit id="pcit0003" dnum="EP1669562A1"><text>EP 1 669 562 A1</text></patcit> shown.

0004In the <patcit id="pcit0004" dnum="EP2614894A1"><text>EP 2 614 894 A1</text></patcit> discloses an electrostatic wet filter in which a plurality of vertically suspended tubular electrodes are arranged suspended. In the tubular electrodes discharge electrodes are provided along its vertical axis. The tubular electrodes are wetted with water.

0005It is therefore an object of the present invention to provide an apparatus and a method for purifying gases, which has a high filter performance and is easy to clean.

0006This object is achieved with a device having the features of claim 1 and a method with the features of claim 17.

0007According to the invention, the deposition electrode is formed as a flow-through conductive filter material for the mechanical filtering of particles. This ensures that the gas to be purified flows through the filter material which can be flowed through, and thus the distance between the particles and the separation electrode is extremely small, so that the cleaning performance is increased. The combination of a mechanical filtering and filtering according to the principle of the electrostatic filter can thus improve the filtering. For cleaning only the through-flowable filter material of the separation electrode must be cleaned.

0008In contrast to the known electrostatic precipitators, the separation electrodes made of conductive materials are flowed through by the gas to be purified in the novel electrostatic precipitators and in particular cleaned by means of pneumatic backwashing. The deposition electrodes or filter elements can consist of multilayer fabrics, fleeces, porous materials or fillings. Preferably, the deposition electrodes or filter elements are made of stainless steels

0009Preferably, the deposition electrode has a conductive filter fabric and / or a conductive filter fleece, and other porous / durchström bare conductive materials made from granules or chips are conceivable The deposition / filter elements can be made of metal, especially stainless steel. As a result, the deposition electrode can also be used at high temperatures, in particular for the purification of combustion gases. The filter material may be made of fibers, granules or chips, which have a thickness of less than 2mm or 0.5 mm, in particular less than 0.3 mm. Such fibers, wires, granules or chips can be processed into a filter material whose mesh size or pore size is less than 2 mm, in particular less than 0.6 mm, for example less than 0.3 mm,

0010The filter material may comprise a plurality of layers with a conductive filter fabric and / or a conductive filter fleece. The layers may have different or equal permeability to gases. The permeability can be reduced from outside to inside. The layers may for example consist of wire mesh with the same or different mesh size.

0011The filter material preferably has a thickness of more than 2 mm, in particular between 5 mm and 30 mm. As a result, the gas to be purified is passed through a thick filter material, at which a deposition of the particles takes place.

0012According to a further embodiment of the invention, the filter material may be formed tubular, bag-shaped or hood-shaped. For this purpose, the filter material of the deposition electrode can be held on dimensionally stable support bodies, such as baskets, in order to assume a defined position within the flow space. The production of self-supporting filter elements is conceivable, for example, a self-rigid wire mesh. As a result, both the function of the electrostatic precipitator and the cleaning can be optimized.

0013For cleaning a blowing in of a cleaning gas is used in countercurrent operation. The flow space is traversed in the region of the filter material by the gas to be cleaned in a first direction, wherein the filter material can be flowed through by a cleaning gas against this flow direction in a second direction, so that detached and collected on the filter material deposited particles in a pneumatic cleaning can be. This leads to the advantage that the once deposited particles are not passed through the flow space to the clean gas side during the cleaning process, but again into the space in which the raw gas is present. Such a pneumatic cleaning can be done at regular intervals, with an automatic cleaning is possible.

0014The tubular, pocket or hood-shaped filter elements can be kept vertically suspended or horizontally lying or cantilevered or even arranged at an angle between vertically and horizontally in the flow space. Preferably, the filter elements are arranged at an angle between 15 ° and 45 °, in particular about 30 ° deflected from the vertical. The flow through the raw gas is designed so that a falling flow is realized in the filter housing (down flow principle).

0015Furthermore, a plurality of spray electrodes in the form of spray wires are arranged in the flow space at a distance from the tubular deposition electrodes. The spray electrodes can be stretched between insulators in the flow space and provided at a defined distance, for example between 3 cm and 30 cm, spaced from the deposition electrodes. The spray electrodes may be aligned parallel to the longitudinal axis of the filter elements or at an angle thereto, in particular also at right angles.

0016The device according to the invention for purifying gases is particularly suitable for the purification of hot gases, especially combustion gases, especially when the filter material is made of a filter fabric or a filter fabric of metal. The gases may have a temperature greater than 100 ° C, in particular greater than 200 ° C, if necessary, but also temperatures of over 300 or above 400 ° C. Also, the use at ambient temperature is possible.

0017The invention will be explained in more detail below with reference to an embodiment with reference to the accompanying drawings. Show it:<dl id="dl0001"><dt>FIG. 1</dt><dd>a schematic view of a device according to the invention for purifying gases, and</dd><dt>FIG. 2</dt><dd>a sectional view through the device of <figref idref="f0001">FIG. 1</figref>,</dd></dl>

0018A device 1 for purifying gases comprises a filter container 2, on which an inlet 3 for a gas to be cleaned is formed. In the filter container 2, a flow space 4 is formed, in which a plurality of discharge electrodes 20 and deposition electrodes 5 is arranged. The deposition electrodes 5 are formed as a filter material through which flow is possible, in particular of a filter fabric and / or a filter fabric, granules or chips made of an electrically conductive material. Preferably, metallic materials are used for the filter material, for example stainless steel. The filter material can be made of fibers, wires, granules or chips, which have a thickness of 0.1 to 2 mm, in particular between 0.1 mm and 0.2 mm. The thickness of the filter material is preferably in a range between 2 mm and 30 mm, wherein the filter material can be arranged in one or more layers, in particular also 2 to 15 layers of filter material can be used. If a grid-shaped filter material, for example a filter fabric, is used, the mesh size can be in a range between 0.2 mm and 10 mm, in particular 1 mm to 5 mm.

0019The deposition electrodes 5 made of the filter material are tubular, pocket-shaped or hood-shaped and are flowed through from outside to inside by the gas to be cleaned. In this case, the deposition electrodes 5 are formed closed on their underside, while they are mounted at its upper side to an intermediate wall 7 in the filter container 2 to a tubular holder 8 hanging. The tubular separating electrodes 5 are thus flowed through from the outside to the inside, wherein the purified gas flows through the tubular holder 8 to an outlet 6 on the filter container 2.

0020Spaced apart from the deposition electrodes 5, a plurality of spray electrodes 20 in the form of spray wires are provided, each stretched between the insulator 21 and the insulator 22 and spaced from the deposition electrodes 5, for example at a distance of between 1 cm and 30 cm, in particular 3 cm to 10 cm. The insulator 21 may be fixed to the intermediate wall 7 via a holder 24, while the insulator 22 is fixed to a holder 23 fixed to the filter container 2.

0021So that the deposition electrodes 5 remain arranged in the flow-through state in a predetermined position in the flow space 4, the separation electrodes 5 are held with the filter material to dimensionally stable support bodies, for example on baskets on which the filter material is fixed. As a result, movements relative to the spray electrodes 20 are largely avoided.

0022In order to clean the separation electrodes 5, a cleaning tube 9 is provided above the tubular holder 8, are provided in the nozzle 10, whose opening is directed to the tubular holders 8. Through the nozzles 10, a cleaning gas thus be blown into the individual tubular -, pocket or hood-shaped deposition electrodes 5, wherein the cleaning gas is blown against the flow direction of the gas to be cleaned by the filter material. By the cleaning process, the deposited particles are collected at the deposition electrodes 5 at a hopper 11 at the bottom of the filter container 2 and disposed of via a rotary valve 12 or other means.

0023The cleaning gas is fed into the cleaning pipe 9 by a pressure vessel 13, which can be charged via a compressor 14. As a cleaning gas, for example, air can be used, wherein a controller 15 is provided to repeat the cleaning operation at certain intervals. For this purpose, pressure measurements can be carried out via lines 16 and 17 to determine the pressure in the filter tank 2 on the clean gas side and the raw gas side and thereby detect a possible degree of clogging. Other parameters can be used for the controller 15 for cleaning. As a result of the sudden injection of a cleaning gas through the cleaning tube and the nozzles 10, particles adhering to the separating electrode 5 can be blown away counter to the direction of flow, so that they are collected in the hopper 11. The pressure and the volume of the blown cleaning gas can be selected depending on the size of the deposition electrodes 5 and the filter container 2.

0024In <figref idref="f0002">FIG. 2</figref> is a horizontal section through the filter container 2 is shown having on one side of the inlet 3 with the gas to be cleaned. In the flow space of the filter container 2, a plurality of tubular, pocket or hood-shaped deposition electrodes 5 are arranged suspended from filter material, which are surrounded by a plurality of spray electrodes 20 in the form of spray wires. Between the spray electrodes 20 and the deposition electrodes 5, a voltage source 25 is arranged, which is connected via a line 26 to the individual spray electrodes 2 and with a line 27 to the deposition electrodes 5, which is shown only schematically. As a result, an electrical potential is formed between the discharge electrodes 20 and the deposition electrodes 5, which may be in a range between 6 kV and 80 kV, for example.

0025The device 1 according to the invention is particularly suitable for the purification of hot gases, especially combustion gases, which may have temperatures between 250 ° C and over 500 ° C, for example in biomass incinerators, Syntesegasreaktoren or internal combustion engines, for example marine or large diesel engines. Other applications in the field of gas cleaning are possible.

LIST OF REFERENCE NUMBERS

0026<dl id="dl0002" compact="compact"><dt>1</dt><dd>device</dd><dt>2</dt><dd>filter container</dd><dt>3</dt><dd>inlet</dd><dt>4</dt><dd>flow chamber</dd><dt>5</dt><dd>deposition electrode</dd><dt>6</dt><dd>outlet</dd><dt>7</dt><dd>partition</dd><dt>8th</dt><dd>holder</dd><dt>9</dt><dd>cleaning pipe</dd><dt>10</dt><dd>jet</dd><dt>11</dt><dd>funnel</dd><dt>12</dt><dd>rotary</dd><dt>13</dt><dd>pressure vessel</dd><dt>14</dt><dd>compressor</dd><dt>15</dt><dd>control</dd><dt>16</dt><dd>management</dd><dt>17</dt><dd>management</dd><dt>20</dt><dd>spray electrode</dd><dt>21</dt><dd>insulator</dd><dt>22</dt><dd>insulator</dd><dt>23</dt><dd>holder</dd><dt>24</dt><dd>holder</dd><dt>25</dt><dd>voltage source</dd><dt>26</dt><dd>management</dd><dt>27</dt><dd>management</dd></dl>