DE202016000886U1 - Automatic brush cleaning for precipitation electrodes of plate electrostatic precipitators - Google Patents

Abstract

Automatic brush cleaning for separation plates of electrostatic precipitators, characterized in that each active side of a separation plate per a strip brush is moved by means of a mechanical drive system for cleaning these on the plates.

Description

The state of the art in the combustion of biomass in small decentralized combustion plants is currently that lack of suitable filter systems polluting fine particulate matter are emitted. As of 2015, the legislator requires relatively strict dust limits for biomass boilers from a nominal heat output of 4 kW for new boilers in the context of the amended 1st Federal Immission Control Ordinance. The limit value for dust of 20 mg / m ^{3 can} be met in the vast majority of cases only with the help of additional filter systems.

State of the art are electrostatic precipitators, as they have already proven in large combustion plants (coal plants, biomass cogeneration plants). The dust separated from the flue gas collects on the plate-shaped precipitation electrodes (also deposition plates) and forms a more or less strongly adhering layer there. The growing layer reduces the efficiency of deposition as the thickness increases. Therefore, this must be removed regularly. For large industrial filter systems, the principle of mechanical knocking (strong hammer blow on the separator plates) has proven itself. The adhering dust is released by the vibration of the plate caused by the impact and falls into the dust collector of the electrostatic precipitator. The disadvantage of this principle is the very high noise emission. If small electrostatic precipitators are operated in or near residential or commercial buildings, knocking will cause severe noise pollution.

The task to be solved is the construction of an automated cleaning system for the separation plates, which works efficiently and avoids noise emissions as far as possible.

The present invention is based on the idea to clean the separation plates by mechanically driven brushes.

In the drawing of this Appendix, the functional scheme of brush cleaning is shown in a plate electrostatic precipitator. The flue gas from the biomass boiler occurs at the inlet nozzle ( 1 ) into the electrostatic precipitator. At the outlet nozzle ( 2 ), the dust-cleaned flue gas leaves the electrostatic precipitator and is fed to the chimney. The particles in the flue gas are charged negatively by the spray electrodes (not shown) and in the electric field between the spray electrodes and positively charged separation plates ( 3 ) and finally separated. On the separation plates ( 3 ) thus forms an adherent layer of dust.

The separation plates should be at defined time intervals by the strip brushes ( 11 ) are cleaned by pulling the elongated brushes at the switched off high voltage on the electrostatic precipitator at least once back and forth over the entire width of the separation plates. These are the total of 4 (per active plate side a brush) shown in the drawing strip brushes ( 11 ) at the upper and lower end on rotating roller chains ( 5 . 6 ) attached. The upper roller chain ( 5 ) and the lower roller chain ( 6 ) are driven by a common drive shaft ( 7 ) via a respective drive sprocket ( 12 ). The position and tension of the drive chain are determined by deflection sprockets ( 13 ) and tension sprockets ( 14 ) Are defined. The roller chains ( 5 . 6 ) guide the strip brush with a slow movement along the separation plates ( 3 ) back and forth. The mechanical drive is controlled by a geared motor ( 9 ) accomplished outside the flue gas space. For this purpose, the drive shafts by means of a shaft seal ( 10 ) led to the outside. For the illustrated compact electrostatic filter with left and right lanes, at least 2 brush cleaning systems are required. To save effort, the two drive shafts ( 7 ) via a roller chain and 2 sprockets ( 8th ) connected so that they can be driven together by a geared motor.

The dust removed from the plates falls into the dust collector ( 4 ).

For automation of the system at least 2 position sensors ( 15 ) required. In the drawing, the rest position is shown. When the geared motor is switched on, the brushes are pulled over the separating plates until the opposite position sensor ( 15 ) indicates the arrival of the strip brush. At that moment, the geared motor changes the direction of rotation and the brush is moved again in the direction of the rest position, which the position sensor indicates again. In case of heavy contamination of the separation plates, the process can be repeated several times. In order to avoid flashovers through the cleaning system, the high voltage at the electrostatic precipitator must be switched off during cleaning. Ideally, you can use for cleaning downtime of the biomass boiler.

As an alternative to the construction shown in the drawing with vertical strip brush, the strip brush can also be operated horizontally. The circulating roller chains would then be arranged left and right of the alley. The complete structure would then be rotated by 90 ° with respect to the drawn variant.

As an alternative to the variant shown in the drawing, the strip brush can also be operated in circulation (instead of back and forth). This could also be the lateral boundary surfaces ( 16 ) clean. One of the position detectors ( 15 ) would still need to detect the parking position of the brush.

Claims (8)

Automatic brush cleaning for separation plates of electrostatic precipitators, characterized in that each active side of a separation plate per a strip brush is moved by means of a mechanical drive system for cleaning these on the plates. Brush cleaning according to claim 1, characterized in that the strip brush between 2 rotating roller chains is fixed so that almost the entire separation plate can be cleaned. Brush cleaning according to one of the preceding claims, characterized in that the end positions of the brushes on the separation plates can be detected by position sensors. Brush cleaning according to one of the preceding claims, characterized in that in each case 2 Abreinigungssysteme can be driven by connecting the drive shafts with only one drive unit. Brush cleaning according to one of the preceding claims, characterized in that each lane of the electrostatic filter operates with 2 rotating roller chains, 2 strip brushes and a common drive shaft. Brush cleaning according to one of the preceding claims, characterized in that per circulating roller chain with a drive sprocket, 2 Umlenkkettenrädern and a Spannkettenrad works. Brush cleaning according to one of the preceding claims, characterized in that the arrangement can be operated both with vertically aligned strip brush (as shown) and with a horizontal strip brush. The entire brush cleaning has to be turned by 90 °. Brush cleaning according to one of the preceding claims, characterized in that the strip brush can also be operated circumferentially with additional cleaning of the side surfaces.

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