DE102004039124A1 - Electric filter for a firing system - Google Patents

Abstract

The electric filter according to the invention for a firing system has a filter electrode (8), an electrode holder (7), via which the filter electrode (8) is held in an exhaust pipe (1) of the furnace and can be supplied with voltage, and an insulator (5), which surrounds the electrode holder (7). In addition, a plate (6.1), which is arranged on the insulator (5), and a scavenging air opening (16) are provided in the electrostatic filter, wherein scavenging air (SL) can be guided in the direction of the plate (6.1) via the scavenging air opening (16).

Description

technical area

The The invention relates to an electrostatic precipitator for combustion plants, as they For example, in private households or in commercial enterprises can be found. The invention is also particularly suitable for small combustion plants, such as fireplace stoves, tiled stoves, room stoves, cookers, ovens and Boilers fueled with wood, suitable. 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 one produced 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.

State of technology

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 Leitfä form an electrically conductive bridge between the insulator and the frame and thereby degrade the effect of the insulator.

presentation the invention

A The object of the invention is an electrostatic precipitator for a furnace which is low-maintenance and works trouble-free and reliable. In addition to be prevented in the electrostatic precipitator, that in Flue gas located particles on the electrode holder of the electrostatic precipitator deposit and affect the effect of the electrode insulator.

The Task is accompanied by an electric filter for a firing system the features according to claim 1 solved.

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.

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

at an embodiment of the inventive Electrostatic precipitator is another plate provided on the insulator is appropriate. This can be done the susceptibility of the electrostatic precipitator by reducing the number of particles, which can reach the critical area, is further reduced.

In a further embodiment of the inventive electrostatic filter is provided that the diameter of the one plate is greater than the diameter of the other plate, wherein the plate with the larger diameter is closer to the exhaust pipe than the other plate. As a result, the number of particles that flow from the exhaust pipe into the critical area can be significantly reduced.

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 insulator, 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.

Short description the drawings

in the Below, the invention with several embodiments with reference to explained three figures further.

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

2 shows a second possible embodiment of the inventive electrostatic precipitator in cross section.

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

Ways to execute the invention

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 duct, 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 are deposited should be 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 the 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 to provide only 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.

This 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 (15)

Electrostatic precipitator for a combustion plant, - with a filter electrode ( 8th ), - with an electrode holder ( 7 ) over which the filter electrode ( 8th ) in an exhaust pipe ( 1 ) of the furnace and can be supplied with voltage, - with an insulator ( 5 ) holding the electrode holder ( 7 ), - with a plate ( 6.1 ) on the insulator ( 5 ) is arranged, and - with a scavenging air opening ( 16 ) via the scavenging air (SL) in the direction of the plate ( 6.1 ) is feasible. Electric filter according to claim 1, with a further plate ( 6.2 ) on the insulator ( 5 ) is arranged. Electrostatic precipitator according to claim 2, - in which the two plates ( 6.1 . 6.2 ) have different diameters, and - wherein the plate with the larger diameter ( 6.1 ) closer to the exhaust pipe ( 1 ) is arranged as the plate with the smaller diameter ( 6.2 ). Electrofilter according to one of claims 1 to 3, in which the plate ( 6.1 ) is made of metal. Electrofilter according to one of claims 1 to 4, in which a plate ( 6.1 ) and the isolator ( 5 ) surrounding housing ( 2 ) is provided, which is to the scavenging air opening ( 16 ) tapers. Electrofilter according to claim 5, wherein between the plate ( 6.1 ) and the housing ( 4 ) An air gap (x) is provided, which is so dimensio ned that it is greater than the voltage caused by the breakdown gap. Electrofilter according to one of claims 1 to 6, having a ring electrode ( 20 ) around the insulator ( 5 ) is arranged around. Electrofilter according to one of claims 1 to 7, with an ionizer ( 22 ) for ionizing the purge air (SL). Electrofilter according to one of the claims 1 to 8, with a plug connection ( 9 ), which are used as ionizers ( 22 ) is formed, and via which the electrode holder ( 7 ) is connectable to a high voltage source. Electrofilter according to one of the claims 1 to 9, 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. An electrostatic precipitator according to claim 10, wherein the purge air outlets are star-shaped on the longitudinal side of the insulator ( 5 ) are arranged. Electrofilter according to one of the claims 1 to 11, in which the plate ( 6.1 ) into the exhaust pipe ( 1 protrudes. Electrofilter according to one of the claims 1 to 12, with a means for heating the purging air ( 23 ). Electrofilter according to one of the claims 1 to 13, having a means for generating a purging air stream ( 21 ). Method for operating an electrostatic filter according to one of the claims 1 to 14, in which via the scavenging air opening ( 16 ) Purge air (SL) along the insulator ( 5 ) in the direction of plate ( 6.1 . 6.2 ) to be led.