DE102004039124B4 - Electric filter for a firing system - Google Patents

Abstract

electrostatic precipitator for one Furnace, with a filter electrode (8), with an electrode holder (7), above which the filter electrode (8) in a flue gas pipe (1) of the furnace is held and can be supplied with voltage, and with an insulator (5) surrounding the electrode holder (7), characterized that the electrode holder (7) via holding webs (18) with a they surround, conically in the direction of the flue gas tube (1) expanding housing (4) is connected so that purge air openings (16) are formed between the retaining webs (18), between which Purge air (SL) in the direction of the flue gas tube (1) can be guided, wherein the electrode holder (7) baffle plates (6.1) perpendicular to their direction of travel 6.2), which except for an air gap (x), which is dimensioned so that he bigger as the voltage caused by the breakdown gap, the Interior of the conical housing (4) complete, and / or the wide end of the conical housing (4) with a perpendicular to the housing axis extending ring electrode (20) is completed.

Description

The The invention relates to an electrostatic filter according to the preamble of the claim 1. The invention also relates to a method for operating the Electrostatic precipitator.

conventional Small combustion plants, as a rule, these are plants with up to maximum 70 KW output, dismissed, measured by the total smoke emission volume, disproportionately many Pollutants in the atmosphere. In addition, small combustion plants, albeit irregularly, often used to burn plastic, cardboard, paper and waste wood. this leads to an additional one considerable dust emission. With the help of an electrostatic filter, which arranged in the exhaust pipe of a furnace, can in Flue gas particles also with an aerodynamic diameter retained by less than 10 microns and thus the air hygiene be improved.

With Aid of the electrostatic precipitator becomes electrically charged solid and liquid particles, which are located in the flue gas, in a generated by the electrostatic precipitator deflected and held back electric field. The particles need to first be electrostatically charged by means of an electrode. Subsequently become the unipolar charged particles as a result of the effect of Electrostatic field deposited on separation plates. With help Such an electrostatic filter can be dust particles and aerosols with grain sizes from 0.01 to 60 microns deposit.

electrostatic precipitator for combustion plants, which are also called electrostatic particle filters, are for Furnaces from the prior art WO 00/33945 known. There is an electrostatic precipitator for a firing system described, for example, on a fireplace can be put on. The electrostatic precipitator consists of a frame, which is placed on the chimney, an insulator, from the frame interior out into the middle of the frame and at the end of one with a weight provided electrode hangs and reaches into the fireplace. When the firing system in operation is and flows through the chimney with particulate flue gas is with the help of the electrostatic filter for it ensured that the particles contained in the flue gas retained become. For this purpose, a high voltage is applied to the electrode, which As a result, the particles are electrostatically charged and knock down by the fireplace and the frame. This can, however at a longer Operation of the electrostatic precipitator cause the particles that accumulate on the insulator, due to their electrical conductivity form an electrically conductive bridge between the insulator and the frame and thereby degrade the effect of the insulator.

From the DE 44 07 152 C1 a device for the isolation of electrostatic precipitators has become known. The separator is held by a support tube which runs coaxially inside a protective tube and carries a rotationally symmetrical body. Along the support tube flushing air is blown to the separator inside the protective tube, which is accelerated outside the rotationally symmetrical body. The distance of the outermost points of the body to the inner wall of the protective tube is in a certain ratio to the inner radius of the protective tube. The rotationally symmetrical body is also set back from the mouth of the protective tube. The mouth of the protective tube has a beaded edge, that is an outwardly curved edge. Experiments have shown that in a single flow body, which is set back from the mouth, a fogging of the front is unavoidable. However, the particle efficiency of the filter drops rapidly and electrical breakdowns threaten.

outgoing From the above prior art, the invention is the object to propose an electrostatic precipitator that is low maintenance, trouble-free and reliable works and prevents it from being in the flue gas Deposit particles on the electrode holder of the electrostatic precipitator and affect the effect of the electrode insulator, as well as a method to indicate the operation of such an electrostatic precipitator.

These The object is achieved by an electric filter according to claim 1 and by a method according to claim 10 solved

advantageous Further developments of the invention will become apparent from the specified in the dependent claims Features.

Of the invention Electrostatic precipitator for a furnace has a filter electrode, an electrode support over which the filter electrode is held in an exhaust pipe of the furnace and can be supplied with voltage, and an insulator, which the Surrounds electrode holder. In addition, in the electrostatic precipitator Plate, which is arranged on the insulator, and a scavenging air opening provided over the purge air guided in the direction of the plate can be.

at the inventive Method for operating the electrostatic precipitator for a firing system is about the Purge air opening purge air along the Insulator blown in the direction of the plate.

In one embodiment of the inventive electrostatic filter another plate is provided see, which is attached to the insulator. As a result, the susceptibility of the electrostatic precipitator to further reduce by the number of particles that can get into the critical area is further reduced.

at a further embodiment of the inventive Electrostatic precipitator is provided that the diameter of a plate greater as the diameter of the other plate is, with the plate with the bigger one Diameter closer located on the exhaust pipe, as the other plate. This can be done the number of particles coming from the exhaust pipe in the critical Stream area, reduce considerably.

Of the Plate can be designed as a separate component or together with form a molded part of the insulator. In training as a separate component the plate can be made of metal, which has the advantage of a easy to produce and higher heat resistance offers.

Favorable Way is in the inventive Electrostatic precipitator a housing provided, which surrounds the insulator and the plate and that itself to the purge air outlet rejuvenated. That way you can the main flow direction the purge air pretend.

Furthermore can the inventive Electrostatic precipitator be designed so that between the plate and the housing an air gap is provided which is dimensioned so that he greater as the voltage caused by the breakdown gap. Thereby It is ensured that between the plate and the housing no Significant voltage drop arises.

Furthermore can the inventive Electrostatic precipitator may also be provided with a ring electrode, which in is arranged some distance around the insulator around by means of electrostatic forces The penetration of particles in the critical area continues to increase to reduce.

to solution the object is also proposed by means of an ionizer the purge air electrostatically similar to how the particles in the flue gas charge. Thus, by the scavenging air generates a charge cloud around the iso lator around, which is an electrostatic Repulsion of the flue gas particles causes and thus to cleanliness of the insulator contributes.

Of the invention Electrostatic precipitator can according to a further feature of the invention in Isolator have scavenging air outlets, the above a scavenging air channel arranged in the insulator can be supplied with purging air are.

at a development of the inventive electrostatic precipitator are the Purge air outlets in a star shape the long side of the insulator arranged. This allows the particle deposition around to reduce the insulator.

To A further embodiment of the invention may be in the electrostatic precipitator the plate protrude into the exhaust pipe, resulting in larger distances between the plate or the plates on the one hand and the housing or the exhaust pipe on the other hand, to ensure the safety electrical breakdowns to increase.

Of There is also the possibility to equip the electrostatic filter with a means for heating the scavenging air. By heating the purge air is ensures that in the exhaust pipe, especially downstream, no undesirable Form air currents can.

After all can the inventive electrostatic precipitator be equipped with a means for generating a purge air flow. The means for generating the purge air stream For example, it can be a fan or a fan. Alternatively or also additionally For this purpose, a negative pressure prevailing in the suction tube can be used, to suck in air from the environment and as purge air on the insulator and pass the plates allow.

One embodiment The invention is shown schematically in the drawing and will in the following explained. Show it:

1 a first possible embodiment of the inventive electrostatic filter in cross section,

2 a second possible embodiment of the inventive electrostatic precipitator in cross section, and

3 the inventive electrostatic filter in a sectional view along the section AA.

Of the invention Electrostatic precipitator is basically for all Firing systems suitable. Preferably, however, it finds application in small combustion plants. The electrostatic precipitator is in the exhaust channel, So the suction pipe or the chimney of the firing system, installed. So that the electrostatically charged flue gas particles on the flue gas channel This will be in the area where the particles separate to leave, conductive formed by the tube electrode surrounding the filter electrode, for example is made of sheet steel, chrome steel or aluminum or a such sheet or perforated plate or wire mesh in the exhaust duct is used.

At the in 1 shown first embodiment of the electrostatic precipitator for a firing system is in the flue gas duct or exhaust duct 1 a filter electrode 8th , which is also referred to as a spray electrode, preferably arranged parallel to the flue gas stream RG. The filter electrode 8th is using an electrode holder 7 in the flue gas channel 1 held and supplied with a high voltage. The electrode holder 7 is via an electrical connection 9 , which may be formed for example as a plug connection, with a high voltage cable 10 , which became an in 1 not shown high voltage generator leads, connected. The opposite pole to the spray electrode 8th forms the housing 2 the electrostatic filter in conjunction with the metallic trained portion of the flue gas duct 1 , The housing 2 is for this purpose via the grounding line 13 connected to ground. The electrical and mechanical connection between the housing 2 and the electrically conductive region of the flue gas duct 1 is about screw connections 3 accomplished. To prevent there is a short circuit between the electrode holder 7 and the housing 2 of the electrostatic precipitator is the electrode holder 7 from an insulator 5 surround. It is not necessary that the insulator 5 over the entire length of the electrode holder 7 extends. To the filter electrode 8th , the electrode holder 7 and the insulator 5 to fasten, the insulator becomes 5 in a preferably formed of metal sleeve 17 pushed, which with the help of retaining bars 18 (please refer 3 ) on a cylindrical holder 4.1 is attached. The cylindrical holder 4.1 is part of a conical housing section 4 , which in turn is part of the housing 2 is. The housing 2 may preferably be made of metal. At that the flue gas channel 1 facing the end of the insulator 5 are a first plate 6.1 and a second plate 6.2 attached. The insulator 5 is together with the sleeve 17 such with the cylindrical holder 4.1 connected that between the bracket 4.1 and the sleeve 17 an air gap 16 arises, through which purging air SL can flow. The air gap 16 is also referred to below as purge air outlet or purge air.

The front area 19.1 and rear area 19.2 inside the conical housing section 4 are protected from excessive particulate separation by ensuring that the purge air SL passes through the purge air outlet 16 in the direction of the exhaust duct 1 is blown. They take care of the two plates 6.1 and 6.2 resulting air vortex that the particles located in the flue gas RG, if at all, then only to a very small extent in the rear area 19.2 can penetrate. The two plates 6.1 and 6.2 together with the purge air flow form a two-stage particle barrier. The air gap x between the plate 6.1 respectively. 6.2 and the conical housing portion 4 is chosen so that the smallest possible gap results in order to achieve the highest possible flow velocity for the purging air SL in this area. On the other hand, in the dimensioning of the air gap x, however, care is also taken that between the plate 6.1 or the plate 6.2 and the conical portion of the housing 4 no voltage breakdown occurs. The positions of the first plate 6.1 and the second plate 6.2 arise from the technical boundary conditions. If necessary, the plate can 6.1 also in the flue gas duct 1 protrude.

The number of plates required is also dependent on the technical conditions. So it may also be sufficient on the insulator 5 just to provide a plate. Preferably, the first plate 6.1 made of metal, because metal is both robust and heat resistant. Optionally, both plates can 6.1 and 6.2 and optionally further plates made of metal.

The purge air SL can either be from a fan or blower 21 be generated. Alternatively, however, the scavenging air flow can also be generated by one in the flue gas duct 1 existing negative pressure is exploited to the purge air SL from the environment through the purge air inlet 25 , the pipe 15 and the purge air outlet 16 past the two plates 6.2 and 6.1 in the flue gas duct 1 to suck. If necessary, the purging air flow can be controlled by means of the blower or the fan 21 be additionally reinforced. If desired, the purge air SL can additionally with the help of an ionizer 22 be ionized to keep particles away from the insulator by electrostatic repulsion. By a corresponding structural design and the connector 9 act as an ionizer. The connector may for example have peaks, edges and ridges to produce a local corona.

Finally, there is also the possibility of using a heating element 23 Preheat the purge air SL to a desired temperature, so that the purge air SL in the flue gas duct 1 does not lead to an undesirable air flow, which counteracts the flue gas flow RG.

The in 1 The electrostatic filter shown can also be equipped with a temperature sensor 11 be equipped. That of the temperature sensor 11 Temperature measurement signal generated at the end of the line 12 tapped and one in 1 not shown control are supplied, via which then the fan 21 and controlling the high voltage source for high voltage generation.

In 2 is an alternative embodiment represented the inventive electrostatic precipitator. In the 2 The embodiment shown differs from that in FIG 1 shown embodiment in that on the insulator 5 no plates are provided, but instead the insulator 5 from a ring electrode 20 surrounded by the line 24 is supplied with voltage and ensures that the particles located in the flue gas RG not in the areas 19.1 and 19.2 can penetrate.

If necessary, the two in the 1 and 2 shown embodiments are also combined. So it is conceivable, for example, on the insulator 5 only a plate 6.1 and additionally the ring electrode 20 or on the insulator 5 two plates and in addition the ring electrode 20 to use.

In 3 the electrostatic filter is shown in cross-section along the section line AA.

If necessary, the rear side of the housing 2 via a reducer 14 with a flexible hose or pipe 15 get connected. Depending on the application, can over the pipe 15 then sucked the purge air SL and / or additionally via the fan 21 be blown.

Additionally or alternatively to the described embodiments, it may be provided in the inventive electrostatic filter that the insulator 5 inside one or more air ducts that end in several air outlets, but what in the 1 to 3 not shown. The scavenging air SL flows out via the air outlets, which are preferably arranged radially on the longitudinal side of the insulator, in order to ensure that the insulator remains essentially free of particles in the flue gas.

As a high voltage generator, for example, a high voltage transformer with downstream rectifier can be used. Typically, the high voltage transformer has a power between 20 and 200 VA and can be operated with 220 V / 50 Hz or even with 110 V / 60 Hz alternating current. Charging the spray electrode 8th can be either negative or positive with respect to the ground reference potential.

The cleaning of the collector, so the exhaust duct 1 , can be done after removal of the electrostatic precipitator, for example by hand with the aid of water or special cleaning agents. In the usual operation of a small combustion plant as the main heat generator, a cycle of one to two months has proven to be advantageous as a cleaning cycle. Sporadic operation of the firing system results in correspondingly longer cleaning cycles.

The previous description of the embodiments according to the present invention This invention is for illustrative purposes only and not for purpose the restriction the invention. In the context of the invention are various changes and Modifications possible, without departing from the scope of the invention and its equivalents.

1

suction tube

2

filter housing

3

screw

4

cone

4.1

cylindrical holder

5

insulator

6.1

first Plate

6.2

second Plate

7

electrode holder

8th

electrode

9

electrical connection

10

High voltage cables

11

temperature sensor

12

Leads

13

ground wire

14

reducer

15

flexible pipe

16

purge air outlet

17

shell

18

holding web

19.1

front funnel area

19.2

rear funnel area

20

ring electrode

21

fan

22

ionizer

23

heating element

24

electric wire

25

Purging air / purge air inlet

RG

flue gas

SL

purge air

x

Distance / air gap

Claims (10)

Electrostatic precipitator for a firing plant, with a filter electrode ( 8th ), with an electrode holder ( 7 ) over which the filter electrode ( 8th ) in a flue gas tube ( 1 ) is maintained and can be supplied with voltage, and with an insulator ( 5 ) holding the electrode holder ( 7 ), characterized in that the electrode holder ( 7 ) via retaining webs ( 18 ) with an enclosing them, in the direction of the flue gas tube ( 1 ) conically expanding housing ( 4 ), so that purge air openings ( 16 ) between the retaining webs ( 18 ) are formed, between which purging air (SL) in the direction of the flue gas tube ( 1 ) is feasible, wherein the electrode holder ( 7 ) perpendicular to their direction of impact baffle plate ( 6.1 . 6.2 ), which except for an air gap (x), which is dimensioned so is that it is larger than the voltage caused by the breakdown gap, the interior of the conical housing ( 4 ), and / or the wide end of the conical housing ( 4 ) having a perpendicular to the housing axis extending ring electrode ( 20 ) is completed. Electrostatic precipitator according to claim 1, characterized in that the ring electrode ( 20 ) is formed as a ring diaphragm, by the inner ring edge with the inside of the conical housing ( 4 ) At its mouth overhanging in the radial direction to the center. Electrostatic precipitator according to one of the preceding claims, characterized in that an ionizer ( 22 ) and fan ( 21 ) are present for ionizing the purging air (SL) and then conveying the same through the flushing openings ( 16 ) in the flue gas tube ( 1 ). Electrostatic precipitator according to one of the preceding claims, characterized in that a plug connection ( 9 ) present as an ionizer ( 22 ) is formed, and via which the electrode holder ( 7 ) is connectable to a high voltage source. Electrofilter according to one of the preceding claims, in which the insulator ( 5 ) Has scavenging air outlets, which via a in the insulator ( 5 ) arranged scavenging air duct with purge air (SL) can be supplied. Electrofilter according to claim 5, wherein the scavenging air outlets are star-shaped on the longitudinal side of the insulator ( 5 ) are arranged. Electrofilter according to one of the preceding claims, wherein the baffle plate ( 6.1 ) into the exhaust pipe ( 1 protrudes. Electrofilter according to one of the preceding claims, with a means for heating the purging air ( 23 ). Electrofilter according to one of the preceding claims, having a means for generating a purging air stream ( 21 ). Method for operating an electrostatic filter according to one of Claims 1 to 9, in which purging air (SL) is used to prevent particle accumulation via purging air openings (US Pat. 16 ) around the electrode holder ( 7 ) along the insulator ( 5 ) in the direction of the flue gas tube ( 1 ) around the baffle plates ( 6.1 . 6.2 ) around and / or through the annular aperture ( 20 ) to be led.