A suspension device and a rapping mechanism for electrodes in an electrostatic precipitator

Abstract: A suspension device and a rapping mechanism for electrodes (1), preferably collecting electrodes in a high voltage supplied electrostatic precipitator, where the suspension device comprises at least one horizontally located supporting element (2) from which a number of electrodes (1) are suspended, said supporting element (2) being connected to the inner of a precipitator housing, and where the rapping mechanism is of the type which transmits a rapping influence to the uppermost ends of the electrodes, is characterized in that the electrodes (1) are pivotably suspended, preferably excentrically, that means (10) are provided for stabilizing the electrodes (1) with a substantially vertical axis, and that the supporting element (2) is provided with means (4) for receiving impact or vibrating influences supplied by an impact hammer (5) or vibrator in the longitudinal direction of the element (2), that the supporting element is suspended resiliently in its longitudinal direction.

Description: The invention relates to an assembly of electrodes and a suspension device and a rapping mechanism for said electrodes, preferably collecting electrodes, in an electrostatic precipitator for cleaning the snoke gases from industrial plants, power supply plants and the like, and wherein the suspension device comprises the elements set forth in the preamble of claim 1. Due to the way in which such an electrostatic precipitator works, dust is deposited on its electrodes during operation and therefore they should be relieved of this dust which is effected by transmitting impact energy to the electrodes thus exposing them to intensive vibration whereby the deposited dust is released. The impact energy required for rapping or vibrating the electrodes is usually produced by a number of hammers being lifted off their vertically suspended position by a rotating shaft which extends transversally across the precipitator width and subsequently being released so as to revert to their vertical position. For each hammer an impact rod or an impact beam is provided which is hit by the hammer when the latter reverts to its vertical position and from the impact rod/beam the supplied impact energy is then transmitted to a section of precipitator electrodes. Rapping mechanisms of this type are known, e.g. from Duda: "Cement Data Book", 3rd edition, pp. 596-598 (Bauverlag GmbH - Wiesbaden und Berlin 1985) and patent disclosures Nos. US 3,844,742 and EP-A-0398476. Usually the collecting electrodes consist of vertically suspended narrow substantially rectangular plates which at their uppermost ends are fastened to a suspension arrangement in a precipitator housing. The collecting electrodes may be mounted in mutually parallel rows forming precipitator sections and the rapping is preferably effected sectionwise by means of drop hammers and impact rods. The collecting electrodes may be fastened to the suspension arrangement, e.g. using bolts yielding a stiff connection. Alternatively an excentrical one-point suspension arrangement of the electrode may be employed. Such suspension arrangement is known e.g. from US patent No. 5,051,119. In electrostatic precipitators of the so-called European type drop hammers and impact rods are usually used which are connected to the lowermost ends of the collecting electrodes and thereby they present the disadvantage that the hammers and their supporting elements occupy comparatively much space at the end of and below the precipitator sections which, in turn, presupposes an increased length and height of the precipitator housing containing the sections. In the so-called American-type electrostatic precipitators, the rapping of the electrodes is often effected from the top of the precipitator, the rapping mechanism then being mounted externally on top of the precipitator housing and the rapping being effected by means of vertically mounted impact rods which hit the electrode suspension arrangement vertically. In this case each impact rod is provided with slide sealings around the passage through the precipitator housing roof. Certain types of "American" precipitators may alternatively be provided with a vertically acting rapping mechanism mounted inside the precipitator housing which actuates the electrodes axially. Moreover, when American-type precipitators are used having the rapping mechanism mounted on top of the precipitator housing roof, the volume occupied by the aggregate precipitator in the relevant plant is substantially increased. From FR 787 043 and US 3 892 545 it is known to supply a rapping impact directly to the electrodes at the lower end of these. In this case the energy is transmitted effectively to the electrode, however, a rapping mechanism of significant proportions is required. The suspension of the electrodes at their upper ends is of minor importance since no rapping energy is transmitted through the connection between the suspension and the electrode. A suspension device and a rapping mechanism of the type described in the introductory part of the description is known from DE 3 539 205. The electrodes described in this prior art publication are supported at both their lower and their upper ends. This means that the possibility of an individual thermal expansion of the electrodes is limited. It is therefore the object of the present invention to provide an assembly of electrodes and a suspension device and a rapping mechanism for said electrodes in an electrostatic precipitator and of the type described above which permit a reduction of the volume occupied compared to known structures and which moreover allow for an improved transmission of the impact energy to the electrode and at the same time allow for an individual thermal expansion of the electrodes. This object is achieved by a device comprising the features set forth in the characterising portion of claim 1. Hereby a suspension device and a rapping mechanism are provided wherein it is no longer necessary to mount the rapping mechanism on the outside of the precipitator housing as it is customary, e.g. in case of American type precipitators, whereby the aggregate precipitator volume is reduced. Due to the suspension free of play the electrode(s) is/are unable to perform translation movements relative to the supporting element and a proper transmission of the impact or vibrating influence can take place from the supporting element to the electrode(s). The vertical part allows for a better transmission of the vibrating or impact influence from the support to the electrode. In a preferred embodiment the individual electrode relative to its vertical center line is suspended excentrically from the support and means for stabilizing the electrode(s) with a substantially vertical axis are provided at the lowermost end of the electrode(s). This improves the possibility of controlling the position of the electrodes. In a further preferred embodiment of the invention the means for stabilizing the electrode(s) with a substantially vertical axis is constituted of a rod element which supports the electrode(s) from that side relative to the vertical center line where the excentrical suspension means on the individual electrode is provided. Due to the pivotable suspension of the electrode(s) it is possible to supply a rapping influence to both the top and the bottom of the electrodes. This is particularly advantageous in connection with long electrodes, which may be difficult to clean by supplying a rapping influence to the one end only. The suspension means of the electrode comprises preferably an open area for receiving a part of the supporting element whereby this open area is wedge-shaped so that due to gravity influence on the electrode, the received part of the supporting element rests at two points of the electrode suspension means. The supporting element is preferably suspended resiliently in its longitudinal direction and due to the resilient suspension arrangement of the supporting element in the longitudinal direction of the latter, a subtantially improved energy transmission to the electrodes is provided since substantially less energy is absorbed in the precipitator housing The supporting element may advantageously be suspended in carrier beams which serve as flexing springs thereby rendering the structure very simple. The result of rapping/vibrating at both ends of the electrodes is substantially superior to rapping/vibrating at only one end. In addition to the advantages previously mentioned regarding a reduction of the volume occupied at the top of the precipitator housing and an improved energy transmission, the further advantage is obtained with this particularly convenient embodiment of the invention that the cleaning of the electrodes is further improved as the suspension device according to the invention allows for the combination of rapping at the uppermost end of the electrodes with rapping at the lowermost end of the electrodes. An embodiment of the invention will now be explained in further detail with reference to the drawings, wherein Fig. 1 shows a section of collecting electrodes suspended in a suspension device according to the invention, Fig. 2 is a more detailed view of a portion of the suspension device and a rapping mechanism connected thereto, Fig. 3 is a side view of portions of the suspension device in its dismounted state, Fig. 4 is a top plane view of portions of the suspension device in its dismounted state, Fig. 5 is a sectional view of portions of the suspension device in its dismounted state, and Fig. 6 is second sectional view of portions of the suspension device in its dismounted state. Fig. 1 shows a section of plate-shaped collecting electrodes 1 which are suspended excentrically from a supporting element 2. The supporting element 2 is suspended in a not shown precipitator housing, e.g. in the roof thereof, by means of communication rods 3, which have the capacity to be resilient in the longitudinal direction of the supporting element 2. At the one end of the supporting element 2 an anvil 4 is arranged for receiving impact influences from a hammer 5. At the bottom, the electrode section is provided with a rapping mechanism known per se where the impact rod constitutes a stabilizing device 10 for the electrodes and where a hammer 11 is provided at the end of the impact rod. The use of a lower impact system concurrently with an upper impact system is rendered possible by the excentrical suspension of the uppermost electrode ends and the free movement of the electrodes partly in the axial direction of the electrodes partly in the direction away from the stabilization device. Furthermore, the free movement of the electrodes in their axial direction means that the expansion of the electrodes in their axial direction will not cause the electrode to flex as would be the case with known systems where rapping is effected at the uppermost ends of the electrodes and where the lowermost ends of the electrodes are usually fastened. Fig. 2 shows more in detail how each plate electrode 1 is designed with a suspension hook 6 at its uppermost end. This hook 6 is caused to cooperate with carrier devices 7 on the supporting element 2. The fastening of the communication rod 3 on the supporting element 2 will also appear clearly. When exposed to impact influence with the hammer 5 on the anvil 4, the communication rod 3 will move resiliently in the impact orientation. Fig. 3 which is a side view of the supporting element 2, fig. 4 which is a top plane view of the supporting element, and figs 5 and 6 which are sectional views through the supporting element along the lines I-I and II-II, respectively, in fig. 4 show how the supporting element may be designed by use of two angular elements where carrier elements for the electrodes 1 are arranged between two opposite and mutually spaced surfaces and where additional transversal angular elements are welded onto the transversal and substantially parallel top surfaces, said angular elements serving as fastening points for the communication rods 3 in addition to forming the link between the two longitudinal angular elements. As depicted herein the anvil 4 is bolted onto the two longitudinal angular elements. Although a drop hammer and an anvil has been described in connection with this embodiment, a vibrator could as well be used.

Claims: An assembly of electrodes and a suspension device and a rapping mechanism for said electrodes, preferably collecting electrodes (1) , in an electrostatic precipitator for cleaning the smoke gases from industrial plants, power supply plants and the like, and wherein the suspension device comprises at least one substantially horizontally arranged elongated supporting element (2) from which a number of electrodes are suspended, said supporting element (2) being connected to the inner of a precipitator housing, and wherein the rapping mechanism (4,5) is of the type which transmits an impact or vibrating influence to the individual electrode (1) at its uppermost ends where the rapping mechanism (4,5) is adapted to supply an impact or vibrating influence to the supporting element (2) in the longitudinal direction of this, the individual electrode (1) is provided with means (6) for cooperating with the supporting element (2) and each electrode (1) is suspended pivotably about a horizontal axis on the supporting element (2) characterized in that the suspension means comprises a hook-shaped part (6) which in a mounted state comprises a substantially vertical part and in connection to this an inclined part, and in that the supporting element is provided with means to cooperate with this hook-shaped part (6) in such a way that due to gravity influence the electrode (1) is in contact with the supporting element (2) at two in the longitudinal direction of the supporting element (2) mutually distanced points, whereby each electrode is free of play relative to the supporting element (2) in the longitudinal direction of this. An assembly according to claim 1, characterized in that the individual electrode (1) is suspended excentrically relative to its vertical center line and that means for stabilizing the electrode(s) (1) with a substantially vertical axis are provided at the lowermost end of the electrode(s). An assembly according to claim 2, characterized in that the means for stabilizing the electrode(s) with a substantially vertical axis is constituted of a rod element (10) which supports the electrode(s) (1) from that side relative to the vertical center line where the excentrical suspension means (6) on the individual electrode (1) is provided. An assembly according to claim 3, characterized in that the rod element (10) comprises means for receiving impact or vibrating influences and that a means (11) for supplying an impact or vibrating influence to the rod element (10) is provided. An assembly according to one of claims 1-4, characterized in that the electrode (1) comprises preferably an open area for receiving a part of the supporting element whereby this open area is wedge-shaped so that due to gravity influence on the electrode, the received part of the supporting element (2) rests at two points of the electrode suspension means. An assembly according to one of claims 1-5, characterized in that the supporting element (2) is made of elongated elements (8) which are mutually connected by shaft elements (9) which cooperates with suspension means (6) at the upper end of the individual electrode. An assembly according to one of claims 1-6, characterized in that the supporting element (2) is suspended resiliently inits longitudinal direction. An assembly according to one of claims 1-7, characterized in that the supporting element (2) is suspended resiliently by means of carrier beams (3) acting as flexing springs.

Inventors: ANDERSEN TORBEN PAULLI, ANDERSEN, TORBEN PAULLI
Applicants: COMPANIA SEVILLANA DE ELECTRIC, FLS MILJO AS, COMPANIA SEVILLANA DE ELECTRICIDAD, FLS MILJO A/S
Application year: 1995
Main classification: B03C3
IPC codes: B03C3