US 2881857 A
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April 14, 1959 w. 'r. cosBY ETAL 2,881,857
' ELECTROSTATIC PRECIPITATORS Filed May 26, 1955 Anse lam! le ss 6:16am! J's/$2136 7! Daw n In venlona States Patent 2,881,857 ELECTROSTATIC PRECIPITATORS Application May 26, 1955, Serial No. 511,334 Claims priority, application Great Britain June 3, 1954 1 Claim. 01. 183- 7) The present invention concerns electrostatic precipitators, and more particularly relates to an improved electrode for use in such arrangements.v
Electrostatic precipitators are used extensively for the removal of solid particles, such as fly ash, from gases before they are discharged to atmosphere. Usually in such precipitators a series of negatively charged electrodes are arranged vertically or horizontally within a tower which also contains a plurality of earthed plates constituting positive electrodes, and the gases are led through the tower before being discharged.
The negative electrodes are usually formed by wires, rods, bars, tubes or the like mounted in a frame, and as such they suffer from two inherent disadvantages.
Firstly, it is known that an accumulation of dust on the wires, rods, bars or tubes or the like reduces the operating efiiciency, and it is necessary to remove the dust at frequent intervals by rapping the negative electrodes with mechanically driven hammers or the like. It has been observed that a visible corona discharge, even from freshly cleaned electrodes, in an electrostatic precipitator does not take place uniformly, but rather at more or less fixed locations at intervals along the lengths of the electrodes. This indicates that discharge takes place from locally sharp or pointed parts of the electrodes; and one of the objects of the present invention is to provide a negative electrode having sharp points protruding therefrom at spaced intervals along its length so that the smothering or suppressing eifect, resulting from particles being deposited on the electrode after having been precipitated from the gas, is minimised. Furthermore, such sharp points ensure that an adequate discharge is maintained, and that a strong depositing field surrounds the electrode.
Secondly, difliculty is often experienced, particularly in the case of wire or thin rod electrodes, in arranging the negative electrodes under correct tension in the supporting framework. Thus it is diflicult to arrange for each individual wire or rod to be tensioned to the same extent, owing to the tendency of the framework to distort, and yet if this is not achieved, the electrode may sag or sway and the spacing, which is usually critical, will be upset. It is another object of the present invention therefore, to provide a negative electrode having a certain amount of inherent elasticity to allow for its tensioning within a supporting framework. Yet another object is the provision of an electrode which is readily fixed in such a framework.
According to the present invention, an electrode for electrostatic precipitators is formed from barbed wire having a plurality of line or parent strands.
In this specification and in the claiming clauses hereof the term barbed wire is used to describe the manufactured article in which the line or parent strands are twisted together with a fairly long lay or pitch, and cross wires are tightly interwoven and clinched at right- 2,881,857 Patented Apr. 14, 1959 angles thereto to formmulti-point barbs at intervals of 1" to 6" along the completed product.
Preferably the electrode is formed from two-ply barbed wire, that is the wire has twin line or parent strands, but the advantage of inherent elasticity is still obtained if a wire having more strands is used. Commercial barbed wire normally has two or three strands and is therefore suitable for use in the present invention.
. The electrode may embody fixing means, enabling the electrode to be fastened into a supporting framework of the precipitator. For instance, the fixing means may be constituted by ferrules mounted on the wire and arranged to co-operate with the framework. Preferably at least one of the ferrules is adapted to enable the tensioning force on the wire of the electrode to be adjusted when it is mounted in the framework of the precipitator.
The invention. will now be further described by way of example with reference tolthe accompanying drawings, the only figure of whichsh ows the end regions of an electrode constructed according to the present invention for use in an electrostatic precipitator.
The electrode illustrated is formed from two-ply barbed wire having line or parent strands a, b and barbs c. Although the cross wires which have been formed into the barbs have, in the example shown, been wrapped between and around both line or parent strands, Glidden type barbed wire, in which the cross wires are fastened to only one line or parent strand of a multi-ply wire, is equally suitable. Similarly, although four barbs are shown per cluster, this is not to be in any way considered restrictive, and two, six or even more barbs may be provided.
The electrode includes fixing means, constituted by ferrules d and e mounted on each end of the wire. Each of the ferrules is formed with a central bore, and after it has been slipped on to a plain portion of a piece of barbed wire cut to the approximate length of the electrode required, the protruding ends of the parent or line strands are splayed as shown in the figure.
Ferrule d is plain apart from a flange d which abuts against the framework i (shown dotted) of the electrode mounting when the ferrule is inserted in a bore therein. The other ferrule is threaded on its outer surface so that it can have nuts g and h run thereon when it has been fitted through another bore in the opposite side of the framework 1'. A Washer f is placed on the ferrule before nuts 3 and h are threaded thereon, so that nut g does not bear directly on the framework i. It will be readily appreciated that adjustment of nut g will deter mine the tensioning force applied to the wire of the electrode whilst nut h locks the arrangement after adjustment.
As previously stated, barbed wire having more than two line or parent strands may be employed. It is difficult to arrange for the wire of each electrode to be tensioned to exactly the same extent, but with multi-ply Wire, when the wire has been tightened to such an extent that it is horizontal, or vertical as the case may be, there is still a margin of extension available due to the additional length of the parent or line strands taken up in their marriage. As a result of this the wire, considered as a whole, has an inherent elasticity, and it is not until this has been completely overcome by further tightening that actual extension of the strands is involved. The elasticity is most pronounced with two-ply wire and understandably tends to decrease with the increase of the number of parent or line strands.
Fixing of the electrode in the framework is a simple matter as has been described and as may be seen from the drawing. Each of the strands of the wire projecting 3 through each ferrule is splayed and provides an anchor against which the tensioning force may act.
The barbs form convenient points along the electrode from which discharge can take place, and they do. not tend to become covered or smothered with dust precipitated from the gases being treated.
The barbed wire used for the electrode of the invention is preferably galvanised mild steel and may be subjected to any other treatment normally employed in the manufacture of that product.
In an electrostatic precipitator having a pair" of spaced frame elements, an electrostatic prccipitator electrode comprising a pair of spaced, opposed ferrules each having a bore extending longitudinally therethrough, one of said ferrules extending through and bearing against one of said frame elements, the other of said ferrules extendingthrough the other of said frame elements and having a threaded exterior surface, a barbed wire element having a plurality of line strands with splayed' ends, said elements extending between said ferrules and through the longitudinal bore of each ferrule with the splayed ends of said line strands engaging the. outermost end of 4, each ferrule, and an adjusting nut engaging the threaded exterior surface of said other ferrule and bearing against said other frame element, said other ferrule being movable with respect to said first ferrule in response to adjustment of said nut. to cause the outermost end of each ferrule to bear against the splayed ends of said line strands to tension said barbed wire element to a predetermined extent.
References Cited in the file of this patent UNITED STATES PATENT 1,325,136 Bradley n..- Dad, is, 1 919 2,362,716 Phillips Nov. 14, 1944 2,631,687 Dohrer 17. 1953 FOREIGN PATENTS 6,837 Great Britain Mar. 21, 1898 231,378: Great r New. r42 1905 of 190'sv v 517,262 Germany 2, 19?!