Electrostatic precipitator plate spacer and method of installing same

ELECTROSTATIC PRECIPITATOR PLATE SPACER AND METHOD OF INSTALLING SAME

BACKGROUND OF THE INVENTION 5

1. Field of the Invention

The present invention relates to plate type dust collecting electrostatic precipitators and in particular to a spacer for maintaining proper spacing between the electrode collector plates within the electrostatic precipita- 10 tor. More particularly, the invention relates to an electrode collector plate spacer which can be installed from the sides or from the top of the electrode collector plates and mounted in the desired position within the precipitator without dismantling the plates and their 15 supporting structure and without permanently attaching the spacer to the plates.

2. Description of the Prior Art

In the generation of electrical energy by burning coal, oil and other fuels to produce steam for power 20 generation, a certain amount of waste material in the form of dust, dirt particles, fly ash and other particulates are produced during combustion. In the past, these waste products have simply been discharged into the atmosphere. However in recent years, more stringent 25 environmental protection laws and regulations governing the discharge of pollutants into the atmosphere have been enacted, requiring that a larger percentage of these waste particles be collected before discharge into the atmosphere. One type of apparatus for collecting partic- 30 ulates from combustion product gases is the electrostatic precipitator.

Electrostatic precipitators typically have a plurality of collector electrode plates which are spaced apart from, and oriented parallel to, one another. A plurality 35 of corona electrode wires are disposed between the spaced plates. The collector plates consist of a series of joined metal panels. The plates are suspended from a support structure and are located a fixed horizontal distance from one another. The plurality of corona 40 electrode wires located between the spaced plates are oriented vertically. The corona electrode wires impart a charge to the dust particles as they move through the spaces between the plates. The dust and other particles become charged at a different polarity than the elec- 45 trode plates, whereby the charged particles are attracted to and collected on the electrode plates. Periodically the plates are cleaned, for example by shaking the plates, and the collected particulates are removed from the bottom of the precipitator. 50

One form of plate construction illustrated in FIG. 1 consists of a plurality of individual panels, the edges of which are bent into flanges which are interlocked with the flanges at the edges of adjacent panels. These interlocking flanges form outwardly projecting ribs 22 55 which extend vertically along the length of the collector plates. In addition to joining the individual panels into an electrode plate, the ribs 22 provide rigidity to the assembled plates enabling the plates to better maintain a flat parallel relationship with respect to the hori- 60 zontally spaced adjacent plates.

It is desirable that as high a voltage as possible be applied across the electrode plates and corona electrode wires to collect particles passing between the plates more efficiently. It is therefore critical to maintain a 65 constant horizontal spacing between neighboring plates, and in particular a constant spacing between the plates and the corona electrode wires extending there

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between, in order to prevent arcing between the wires and the plates and the subsequent destruction of the electrostatic field produced for collecting the dust particles. If a constant spacing cannot be maintained, the operating voltage must be reduced in order to prevent arcing with an attendant reduction in precipitation efficiency.

Precipitators having the particular collector electrode plate and corona electrode wire configuration described above, sometimes experience a serious problem of plate warping or bowing. Plate warping can occur during the life of the precipitator for a variety of reasons including cleaning (i.e., shaking) of the plates and the high temperature of the combustion gases passing over the plates. Plate warping seriously distorts the spacing between the electrode plates and the electrode wires and increases the danger of arcing, thereby necessitating a lower applied voltage and consequently resulting in a lower precipitation efficiency.

In order to eliminate or at least reduce plate warpage, various plate spacers and methods have been developed. A number of references disclose the use of spacer bars and/or cross braces which extend between adjacent plates in order to maintain interplate spacing. The great majority of these spacers are attached to one or more of the electrode plates, usually by welding. These braces extend horizontally between adjacent plates and provide sufficient strength and rigidity to maintain the plates in their spaced parallel relationship. Various types of these plate spacers are shown in U.S. Pat. Nos. 4,007,023; 4,239,514; 4,519,818; 4,478,614; and 4,479,813. Unfortunately, the installation of these kinds of spacers on existing electrostatic precipitators is extremely expensive and time consuming. A workman must enter between the spaced plates to mechanically attach the spacer to the plates, typically by welding, bolting or similar attachment procedure. This procedure can only be performed after the precipitator has been completely shut down and cooled since much of the supporting hardware for the plates and the corona wires must be removed in order to allow a workman sufficient space in which to work. This increases considerably the "down time" of the precipitator as well as the labor costs associated with the plate straightening procedure.

In response to these difficulties. Ahern in U.S. Pat. No. 4,559,064 developed a spacer comprising a rigid frame which slidably engages the vertically extending ribs on adjacent electrostatic precipitator plates. When a precipitator is new, the Ahern spacers can be installed without the necessity of a workman entering into the restricted space between adjacent plates. The frames are mounted over the ribs adjacent electrode plates, either at the top or the bottom of the precipitator, and slide along the ribs until reaching the desired vertical location within the precipitator. The frames clamp onto the ribs thereby enabling a workman standing outside the precipitator, using a long-handled tool, to slide the spacers into position between the plates purportedly without dismantling the precipitator.

Unfortunately, the Ahern spacers cannot be so easily installed on certain precipitators. For example on many precipitators of the above-described type, dimples are formed along the ribs in order to provide better interlocking between adjacent panels in a plate assembly. The Adhern spacers will not easily slide over these dimples. It is also not uncommon to encounter precipi

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place on the collecting electrode plate ribs as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of two adjacent and parallel 5 collector electrode plates in an electrostatic precipitator, the plates having installed therebetween a spacer of the kind shown in FIGS. 2 and 3, the spacer compressively engaging the plate ribs.

FIG. 2 is a side view of an electrostatic precipitator 10 plate spacer according to one embodiment of the present invention.

FIG. 3 is a bottom view of the spacer shown in FIG.

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FIG. 4 is a side view of an electrostatic precipitator 15 plate spacer according to another embodiment of the present invention.

FIG. S is a side view of an electrostatic precipitator plate spacer according to another embodiment of the present invention. 20

FIG. 6 is a bottom view of the spacer illustrated in FIG. 5.

FIG. 7 is a side view of an electrostatic precipitator plate spacer according to another embodiment of the present invention. 25

FIG. 8 is a bottom view of the precipitator plate spacer shown in FIG. 7.

FIG. 9 is a side view of an electrostatic precipitator plate spacer according to another embodiment of the present invention. 30

FIG. 10 is a side view of an electrostatic precipitator plate spacer according to another embodiment of the present invention.

FIG. 11 is a side view of an electrostatic precipitator plate spacer according to another embodiment of the 35 present invention.

FIG. 12 is a partial sectional view of the plate spacer illustrated in FIG. 11 and taken along line 12—12.

FIG. 13 is a partial sectional view of the plate spacer illustrated in FIG. 11 and taken along line 13—13. 40

FIG. 14 is a side view, with parts shown in section and other parts shown in phantom, showing the positioned and mounting of a spacer between adjacent parallel plates.

DETAILED DESCRIPTION OF THE 45
INVENTION

Referring to the drawings wherein like reference numerals refer to like elements in the several drawings, and especially referring to FIG. 1, there is shown a top 50 view of an adjacent set of electrostatic precipitator plates 20, each plate 20 being formed by a plurality of individual collector plate panels 21 which are joined together along their edges by interlocking flanges which form outwardly extending ribs 22. Typically, ribs 55 22 have a thickness of about & to 3/16 inch and project out from the plate 20 surface a distance of about 1£ inches. Accordingly, the inter-rib spacing ir is about 3 inches less than the interplate spacing ip.

A plurality of corona electrode wires 23 are sus- 60 pended from a suitable support means (not shown) so that the wires 23 extend downwardly between plates 20 equidistance between adjacent plates 20. As is known to those skilled in the art, the distance between a wire 23 and a plate 20 (i.e., distance Jip) must be less than the 65 distance between a wire 23 and a spacer 30. Otherwise, arcing will occur between the wire 23 and the spacer 30, reducing precipitator efficiency.

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Referring now to FIGS. 2 and 3, one form of the improved plate spacer is indicated generally at 30 and includes a pair of parallelogram-shaped braces 31 and 32. Both braces 31 and 32 are preferably formed by bending steel bars having a circular cross-section and a typical diameter of about \ inch into the illustrated parallelogram shape. Those skilled in the art will appreciate that bars having other than a circular cross section may also be used. Braces 31 and 32 are substantially the same size and shape. The ends of the bar forming brace 31 (as well as the ends of the bar forming brace 32) may be spliced together to form a splice joint 33, e.g. by welding. Braces 31 and 32 each have a geometric center which falls on a rotational axis 44 which is oriented perpendicularly to the plane of the drawing.

Braces 31 and 32 are attached to one another in a spaced apart relationship by welding a plurality of spacing bars 38 between the braces 31 and 32. The thickness of bars 38 should be substantially equal to slightly less than the thickness of ribs 22 on plates 20. In this way, braces 31 and 32 are maintained in a spaced relationship, the spacing S between braces 31 and 32 being substantially equal to slightly less than the thickness of ribs 22. Typically, spacing S is on the order of about J inch. Spacing bars 38 are positioned a distance inwardly from the outer ends of spacer 30 thereby leaving an open space or groove 39 between the pair of plate engaging edges 34 and 36 and an open space or groove 42 between the pair of plate engaging edges 35 and 37. When the spacer 30 is installed between electrostatic precipitator plates 20, ribs 22 extend into open spaces or grooves 39 and 42 as is best shown in FIG. 1. The spacer 30 is held in place between the adjacent pair of ribs 22 by compressing the projecting ribs 22 between the ends of braces 31,32, i.e. by a compressive frictional fit. Preferably, the thickness of the spacing bars 38 is slightly less than the thickness of ribs 22 in order to ensure a tight compressive frictional fit of the ribs 22 between braces 31,32.

An important advantage of the plate spacers of the present invention over the prior art spacers concerns the ease with which they are installed between a pair of adjacent electrostatic precipitator plates. To facilitate the mounting of spacer 30 between a pair of adjacent ribs 22, and angled mounting edge 40 is provided on one side of spacer 30, the angled edge 40 being contiguous with plate engaging edge 35. In order to satisfy the objectives of the present invention, the diagonal distance dd between axis 44 and the corner formed between edges 35 and 40 must be not more than about 3% greater than the distance hd along a horizontal plane between axis 44 and edge 35 (which distance is about one-half the horizontal interplate spacing, i.e., hdssjip.). In order to satisfy this relationship with the parallelogram-shaped spacer 30, the internal angle alpha between edge 35 and edge 40 must be greater than about 110°. Brace 32 has a size and shape identical to brace 31, and accordingly has the same angles and spacing relationships discussed above. On the opposite end of spacer 30, brace 31 has a second angled edge 41 which is contiguous with edge 34. Contiguous edges 34 and 41 form a corner of brace 31 that is diagonally opposite the corner formed by contiguous edges 35 and 40. The interior angle beta between edges 34 and 41 is also greater than about 110° and the diagonal distance between axis 44 and the corner formed between edges 34 and 41 is at most only about 3% greater than the horizontal distance between axis 44 and edge 34. Accord

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