WO1980000926A1

WO1980000926A1 - Flat panel electrode for electrostatic precipitators

Info

Publication number: WO1980000926A1
Application number: PCT/GB1979/000180
Authority: WO
Inventors: T Cottrell; B Tate; G Davies
Original assignee: Lodge Cottrell Ltd; T Cottrell; B Tate; G Davies
Priority date: 1978-11-09
Filing date: 1979-11-06
Publication date: 1980-05-15
Also published as: GB2044636B; JPS55501091A; DK294980A; NL7920112A; IT1124926B; GB2044636A; BE879891A; FR2440780A1; IT7927104A0

Abstract

An electrostatic precipitator electrode is an array of horizontally-extending double-skinned rectangular sub-panels (15) fabricated from sheet metal; adjacent panels interlock along their contiguous edges by integral hooked flanges (24, 25) forming male and female connector elements, the latter being provided by in-turning the panel skins (16, 17) into upwardly-open spaced-apart hooks located inside the sub-panels (15). The male elements are formed as oppositely-directed, downwardly-open hooks along conjoined edge portions of the skins (16, 17). A capping channel (30) clamped to the sub-panels along each vertical edge of the electrode (10) prevents electrode flexing. A modification is distinguished from the preferred embodiment essentially only in that the subpanels are single-skinned. Primary use of the electrode is as the collector in the final precipitation stage of a precipitator.

Description

"FLAT PANEL ELECTRODE FOR ELECTROSTATIC PRECIPITATORS".

TECHNICAL FIELD

This invention relates to flat panel electrodes for electrostatic precipitators for removing particulate matter from gas streams. BACKGROUND

In the electro-precipitation process, gasborne particles enter a chamber and are exposed therein to an electric field between discharge and collector electrodes. Negative corona discharge occurs at the discharge electrodes while the collector electrodes are normally maintained at earth potential. Particles are charged in the vicinity of the discharge electrodes and they then move towards the collector electrodes under the influence of the field. The particles reaching the collector electrodes give up their charge and accumulate thereon. From time to time the particles are dislodged from the collector electrodes using devices which rap the electrodes, and the dislodged particles are collected in a pit for periodic, removal from the chamber.

Electrostatic precipitators of single and plural stage type are known, but irrespective of their type all commercial electrostatic precipitators feature arrays of parallel electrodes located adjacent one another. In practical precipitators, the electrodes are large and when in the form of plates can be very awkward to handle in confined spaces when erecting the precipitators. Once assembled, large electrode plates can create such problems as to be barely practical. For instance, they can flex, warp or buckle in service even though measures may be taken to stiffen them. Such deformations can perturb the electrical conditions within a precipitator and lead to inefficient working. Moreover, variations in critical dimensions may occur and encourage flashover and this could create a fire or explosion risk. THE INVENTION

An object of the present invention is to provide an electrode structure which is rigid and capable of assembly within close tolerances.

It is another object to provide a rigid electrode structure susceptible of assembly from a plurality of interlocking modular panel elements.

According to the present invention, there is provided a flat panel electrode for an electrostatic precipitator, comprising an array of abutting sub-panels which incorporate means for interlocking adjacent sub-panels together edge-to-edge, and means which engage contiguous ends of the sub-panels at two opposite sides of the electrode to prevent flexure of the electrode parallel to the interlocked edges of the sub-panels.

The invention also provides a flat panel electrode for an electrostatic precipitator, comprising an array of abutting, double-skinned hollow sub-panels which incorporate means interlocking adjacent sub-panels together edge-to-edge, the interlocking means holding the sub-panels together being positioned within the thickness of the electrode, and means which engage contiguous ends of the sub-panels at two opposite sides of the electrode to prevent flexure of the electrode parallel to the interlocked edges of the sub-panel.

The invention comprehends an electrostatic precipitator incorporating one or more electrodes in accordance with either of the preceding two paragraphs. The invention will now be described in more detail by way of example only with reference to the accompanying drawings. IN THE DRAWINGS;

Fig. 1 is a fragmentary front elevational view of an electrostatic precipitator electrode according to the invention:

Fig. 2 is an enlarged sectional view on the line II-II of Fig. 1;

Fig. 3 is an enlarged sectional view on the line III-III of Fig. 1;

Fig. 4 is an enlarged sectional view on the line IV-IV of Fig. 1; and

Fig. 5 is an enlarged sectional view on the line V-V of Fig. 1. PREFERRED EMBODIMENT

The illustrated electrode 10 may be one of a group of parallel, adjacently-disposed identical collector electrodes in the precipitator. The electrode 10 is in the form of a substantially flat, rigid panel and is adapted to be suspended from a support (not shown) at the top of the precipitator chamber. For this purpose, the electrode 10 has a pair of suspending attachments or bolts 11 upstanding from its top edge 12.

The electrode 10 can be of substantial dimensions, e.g. 30 feet high by 6 or 9 feet wide, and can be about

1 inch thick. (9.15m x 1.83cm or 2.75m x 2.5 cm). It will be appreciated that the introduction of an electrode of such a size into the narrow confines of an erected precipitator could present considerable difficulties, and to mitigate them the electrode 10 is of modular, easy-assembly construction. On site assembly is straightforward and the construction affords great rigidity and stability on the finished fabrication.

The electrode 10 is composed of a multiplicity of modules, viz. sub-panels 15 each having opposed, spaced-apart sheet metal skins 16, 17. There can be ten such sub-panels 15 arranged one below another and forming the electrode 10. Neighbouring sub-panels 15 are joined together during assembly along their meeting top and bottom edges by means 20 which interlock the edges. The interlocking means 20 can take numerous forms including interlocking strip elements fastened along the top and bottom edges of the sub-panels 15. Preferably, the said means are contained wholly within the thickness of the electrode 10, as shown in Fig, 2. The illustrate structure has the means 20 integral with the skins 16, 17. Along the afore-mentioned edges, the skins are provided with interengaging flanges that hook together. For convenience, the interengaging flanges will hereafter be referred to as hook formations.

All the sub-panels but the top-most sub-panel 15 have their skins 16, 17 converging inwards towards one another adjacent their top edges. The skins 16, 17 of each sub-panel 15 meet at a central plane lying in the panel, and a transverse line 21 of spot welds 22 hold the skins face-to-face. Outwardly of the line of spot welds 22, the free top edges of skins 16, 17 are bent into the hook formations 24. As shown, the said free top edges are bent away from one another in opposite directions, and each is down-turned. The hook formations 24 when viewed end-on or in section as shown in Fig. 2 are of inverted, downwardly open U or V shape.

At their bottom edges, the skins of the sub-panels 15 also converge, but here they are not spot welded together. The skins are bent inwardly and upwardly to form upwardly-open U or V-shaped hook formations 25. The bottom edges of the skins are disposed inside the thickness of the sub-panels 15. It will be seen that there is a gap between hook formations 25 to admit hook formations 24.

Hook formations 24 can be regarded as part of a male connector element, and hook formations 25 as a corresponding female connector element. During assembly, the male connector element of each sub-panel 15 is insertable into the female element at the bottom of the next adjacent sub-panel by opening the gap between hook formations 25 sufficiently to pass the hook formations 24. The skins 16, 17 are adequately flexible for the hook formations 25 to be prised apart. Once the hook formations 24 have been disposed in the space 28 above hook formations 25, movement of the adjacent sub-panels in opposite directions causes interengagement of the hook formations 24 and 25, as shown in Fig. 2.

The assembled sub-sections 15 are further fastened together to form a rigid whole by means of lateral capping elements 30. Capping elements 30 extend vertically the length of electrode 10 along the two opposite sides thereof.

The capping elements 30 are of channel section ahd have opposite limbs 31, 32 which bear resiliently against the opposite skins 16, 17 of the sub-panels 15. The limbs 31, 32 are interconnected by a web 33 apertured at intervals to pass clamping bolts 34 of cavity fastenings 36. In the assembled electrode 10, the bolts 34 are located approximately at the mid heights of the sub-panels 15. In addition to the bolts 34, the cavity fastenings 36 comprise short bars 37 having screw-threaded apertures receiving the bolts 34. The bars 37 are longer but narrower than the spacing between the skins 16, 17. When the bolts are tightened, the bars 37 are drawn against internally-facing abutments at the opposite edges of the skins. The said abutments could be formed in various ways, e.g. by inturned lips at the said opposite edges. In the illustrated example, the abutments are formed by short lengths of angle 38 fastened to the skins for instance by welding. In use, the bars 37 serve to hold the skins 16, 17 apart in addition to securing the cappings 30 in place.

Member 40 seen in Fig. 3 between the edges of the skins and the web 33 is a reinforcing metal bar which extends the length of the electrode 10. Its purpose is safely to transmit rapping forces along the electrode to prevent damage to the electrode. Member 40 is apertured or slotted at intervals to pass the bolts 34. Unlike the other sub-panels 15, the top one does not terminate in a male connector element. Instead, top sub-panel 15 has its skins 16, 17 in-turned and reinforced by transversely extending plates 42 forming part of a welded structure including a bushing 43 which mounts the suspending bolts 11. The welded structure is designed to allow one or other or both of the bolts to rock sufficiently to assist adjustment of the electrode for exact verticality during installation. One or other or both bolts may be screw-threaded into bushing 43, again to assist adjustment during installation.

The lowermost sub-panel 15 is internally reinforced adjacent its bottom edge. Reinforcement may take numerous forms and by way of example is represented by a box section girder 44 welded to the skins 16, 17. The absence will be noted from Fig. 2, particularly, of upwardly-facing dust-catching ledges at the joints between adjacent sub-panels 15. Thanks to the inwardly and upwardly-convergent portions of the skins, the likelihood of dust collecting thereon is minimal and any accumulated dust is easily dislodged by rapping.

In the illustrated embodiment, the sub-panels 15 are of rectangular shape and their longer dimensions are arranged transversely of the electrode 10. The sub-panels could extend longitudinally of the panel instead, the joints between the sub-panels being vertical. The side-by-side sub-panels would then be interconnected by cappings along the top and bottom of the electrode.

If need be, the .individual sub-panels could embody internal bracing to help maintain the skins parallel and uniformly spaced apart. For some precipitators, a double-skinned electrode construction may be unnecessary. A single-skinned electrode can be fabricated along the lines of the illustrated embodiment from single-skinned sub-panels. These can be interlocked e.g. by interengaging hook formations and rendered rigid by means of capping elements clamped along opposite edges of the electrode. APPLICATIONS:

A collector array in a plural-stage precipitator can be assembled from electrodes constructed as above disclosed. If the flat panel electrode construction were used in an upstream collector stage, e.g. in the first stage, then the precipitator would ordinarily require a pre-ionizer. Preferably, however, the present electrode construction is employed only in the final cleaning stage of a precipitator, for when so employed gas cleaning efficiency is enhanced overall. A final stage equipped with the present electrode construction, instead of a more conventional wire electrode construction, is better able to remove smaller particles or fines from the lightlyladen gas entering the final stage.

The electrode structure disclosed above has substantial rigidity and hence changes in precipitator operating parameters caused by electrode flexing are minimised. Being of modular construction, on-site assembly of large electrodes within the confined spaces in electrostatic precipitators is possible, and electrodes of different sizes can be erected conveniently from a small number of standard components ex. stock. The design is simple to erect by relatively un-skilled labour. This, is an important practical advantage, because precipitators have frequently to be erected in remote areas using local, untrained workers.

Claims

Claims:

1. An electrode for an electrostatic precipitator, the electrode being in the form of a flat panel which is characterised by comprising an array of abutting sub-panels (15) which incorporate means (20) for interlocking adjacent sub-panels together edge-to-edge, and means (30) which engage contiguous ends of the sub-panels (15) at two opposite sides of the electrode (10) to prevent flexure of the electrode parallel to the interlocked edges of the sub-panels (15).

2. An electrode according to claim 1, characterised in that the sub-panels (15) are double-skinned hollow components, and the interlocking means holding the sub-panels (15) together are positioned within the thickness of the electrode (10).

3. An electrode according to claim 1 or claim 2, characterised in that the interlocking means (20) comprises hook formations (24, 25) along the edges of the adjacent sub-panels (15.). 4. An electrode according to claim 3, characterised in that the hook formations (24, 25) are integral with the sub-panels (15) and are bent-over flanges forming U or V-shaped interlockable channels along the abutting edges of the adjacent sub-panels (15). 5. An electrode according to claim 1 or claim 2, characterised in that the means (30) which engage the contiguous ends of the sub-panels (15) comprise channel-section cappings which extend the length of the two opposite sides of the electrode (10), the cappings including clamping means (36) engageable with each of the sub-panels (15).

6. An electrode according to claim 5, when dependent on claim 2, characterised in that the clamping means, comprise screw-threaded cavity fixings (36) which coaet with internal abutments (38) at the ends of the hollow sub-panels (15).

7. An electrode according to claim 6, characterised in that the abutments (38) are internal flanged elements at adjacent end edges of two skins (16, 17) forming the double-skinned sub-panels (15). 8. An electrode according to claim 2, characterised in that the means interlocking each pair of sub-panels (15) together comprises a male connector element on the edge of one sub-panel, and a female connector element on the edge of the other sub-panel into which the male element is insertable.

9. An electrode according to claim 8, characterised in that the two skins (16, 17) of the said one sub-panel converge and are spot welded together, and outwardly beyond the spot welding (22) the skins (16, 17) are formed into a pair of oppositely-directed hooked flanges (24), the structure constituting the male element.

10. An electrode according to claim 9, characterised in that the two skins (16, 17) of the said other sub-panel converge and terminate in in-turned hooked flanges (25) located in the interior of the sub-panel, the in-turned hooked flanges (25) being spaced apart and the structure constituting the female element. 11. An electrostatic precipitator including an array of electrodes each as claimed in any one of the preceding claims 1, 2, 8, 9 and 10.

12. A plural-stage electrostatic precipitator having as its final-stage collector the electrode as claimed in any one of the preceding claims 1, 2, 8, 9 and 10. AMENDED CLAIMS

(received by the International Bureau on 6 March 1980 (06.03.80)

2. An electrode according to claim 1, characterised in that the sub-panels (15) are double-skinned hollow components, and the interlocking means holding the sub-panels (15) together are positioned within the thickness of the electrode (10). 3. An electrode according to claim 1 or claim 2, characterised in that the interlocking means (20) comprises hook formations (24, 25) along the edges of the adjacent sub-panels (15).

4. An electrode according to claim 3, characterised in that the hook formations (24, 25) are integral with the sub-panels (15) and are bent-over flanges forming U or V-shaped interlockable channels along the abutting edges of the adjacent sub-panels (15).

5. An electrode according to claim 1 or claim 2, characterised in that the means (30) which engage the contiguous ends of the sub-panels (15) comprise channel-section cappings which extend the length of the two opposite sides of the electrode (10), the cappings including clamping means (36) engageable with each of the sub-panels (15).

7. An electrode according to claim 6, characterised in that .the abutments (38) are internal flanged elements at adjacent end edges of two skins (16, 17) forming the double-skinned sub-panels (15).

8. An electrode according to claim 2, characterised in that the means interlocking each pair of sub-panels (15) together comprises a male connector element on the edge of one sub-panel, and a female connector element on the edge of the other sub-panel into which the male element is intertable.

10. An electrode according to claim 9, characterised in that the two skins (16, 17) of the said other .sub-panel converge and terminate in in-turned hooked flanges (25) located in the interior of the sub-panel, the in-turned hooked flanges (25) being spaced apart and the structure constituting the female element.

11. An electrostatic precipitator including an array of electrodes each as claimed in any one of the preceding claims 1, 2, 8, 9 and 10.

12. A plural-stage electrostatic precipitator having as its final-stage collector the electrode as claimed in any one of the preceding claims 1, 2, 8, 9 and 10.

13. A hollow panel electrode for an electrostatic precipitator which is composed of an array of abutting, double-skinned sub-panels incorporating means interlocking adjoining sub-panels together edge to edge and two cappings which engage opposite ends of the electrode to prevent flexure thereof parallel to the interlocked edges of the adjoining sub-panels, the electrode being characterised by an absence of dust-trapping or flashover-promoting protrusions and by parallel-sided sub-panels (15) for which the interlocking means (20) are disposed wholly inside the sub-panels (15), the interlocking means being inter-fitting hooked formations (24, 25) along the edges of the adjoining sub-panels, one of the hooked formations (25) at each joint between sub-panels (15) being directed towards the interior of its respective sub-panel, generally parallel to the panel sides formed by skins (16, 17), and the other companion hooked formation being oppositely directed.

14. An electrode according to claim 13 characterised in that the hook formations (24, 25) are integral with the sub-panels (15) and are bent-over flanges forming U or V-shaped interlockable channels along the abutting edges of the adjacent sub-panels (15).

15. An electrode according to claim 13 or claim 14, characterised in that the interlocking means each constitute a male connector element on the edge of one sub-panel, and a female connector element on the edge of the adjoining sub-panel into which the male element is inserted.

16. An electrode according to claim 15 characterised in that the two skins (16, 17) of thesaid one sub-panel converge and are spot welded together, and outwardly beyond the spot welding (22) the skins (16, 17) are bent in opposite directions to form the hooked flanges (24), the structure constituting the male element.

17. An electrode according to claim 16 characterised in that the two skins (16, 17) of the said adjoining sub-panel converge and terminate in in-turned hooked flanges (25) located in the interior of the sub-panel, the in-turned hooked flanges (25) being spaced apart and the structure constituting the .female element.

18. An electrode according to any of claims 13 to 17 characterised in that the cappings (30) are of channel-section and extend the length of the two opposite sides of the electrode (10), the cappings including clamping means (36) entering the interior of the sub-panels (15).

19. An electrode according to claim 18 characterised in that the clamping means comprise screw-threaded cavity fixings (36) which coact with internal abutments (38) at the ends of the hollow sub-panels (15).

20. An electrode according to claim 7, characterised in that the abutments (38) are internal flanged elements at adjacent end edges of two skins (16, 17) forming the double-skinned sub-panels (15).

21. An electrostatic precipitator including an array of electrodes each as claimed in any one of the preceding claims 13 to 17.

22. A plural-stage electrostatic precipitator having as its final-stage collector the electrode as claimed in any one of the preceding claims13 to 17. STATEMENT UNDER ARTICLE 19

Original claims 1 to 12 are cancelled and new claims 13 to 22 are substituted therefor.

New claim 13 consolidates originally filed claims 1 to 3 and incorporates a more specific definition of the interlocking means referred to in original claim 1 and replacement claim 13.

The new dependent claims 14 to 22 are a rearrangement of the originally-filed dependent claims 4 to 12 after amendment consequential upon the drafting of replacement claim 13.

Replacement claim 13 is restricted to a double-skinned electrode and hence does not cover an alternative, single-skinned, construction described in the first paragraph of page 7 of the specification.

In those designated Contracting States the national laws of which permit voluntary amendment, the Applicants will request the deletion of the said passage on page 7.