Abstract:
A bow-reduced precipitator collector plate assembly and an appertaining method include a precipitator collector plate that contacts a spring-like stiffening element configured to be attached to a fixed anchor or an adjacent anchoring collector plate. The stiffening element is configured to apply a force in a direction normal to a primary plane, which is generally co-linear but opposite in direction of a direction of bowing, of the precipitator collecting plate.

Description:
BACKGROUND OF THE INVENTION 
   The invention is directed to a system and appertaining method for minimizing a bowing of collector plates in an electrostatic precipitator utilizing a clip configuration that permits movement of the collector plate. 
   In an electrostatic precipitator, discharge electrodes and collector plates are disposed in a flue in which particle-containing gases flow. The particles in the flowing gas are ionized by the discharge electrode, and migrate toward the collector plates as a result of electrostatic attraction, where they are held. Periodically, the collector plates are rapped to shake the accumulated particles from them to a collection bin for disposal. In order for the rapping to be effective in removing accumulated particles, the collector plates must have some degree of freedom for movement. 
   Over time, the collector plates, which have an extremely large surface area, become bowed or warped. Since the difference in potential between the discharge electrode and the collector plate is dependent on the spacing between them, bowing of the collector plates changes this distance and reduces the efficiency of the precipitator, and in extreme cases may result in arcing if the spacing becomes too small. 
   U.S. Pat. No. 4,516,992 addresses the problem of bowing or warping of the plate electrodes in a precipitator collecting plate  90  ( FIG. 9 , present application) by providing a connector  94  that is fixedly mounted to a bar  92  to one end of the collecting plate  90 . The plate may be straightened by applying a torque moment to the elongated bar  92  to which the other end of the connector is attached. 
     FIG. 2  of the &#39;992 patent illustrates the location of exemplary discharge wires  38  and a bowing that changes the distance of the plates to these wires. 
   The design of the &#39;992 patent may work adequately when a limited symmetrical bow occurs in a precipitator plate, but does little to address complex forms of bowing in multiple dimensions or twisting deformations of the plates which is very common. 
   SUMMARY OF THE INVENTION 
   The present invention provides an inexpensive way to assist in the straightening of a collecting plate (or preventing bowing in the collecting plate), utilizing one or more clamps or clips, each having a stiffening element attached to it. The clamp is affixed at the edge of an collector plate or at an anchor point, and the stiffening element extends over a portion of the surface of the collector plate. The stiffening element provides a spring force that opposes the bowing or warping, and either straightens an already-bowed plate, or minimizes the bowing of a fresh plate. 
   The clamp itself may be an “off the shelf” item, and the stiffening element fastened to the clamp may be constructed from a number of known sources, such as a commercially available conduit strut clamp. 
   In operation, the precipitator gets energized with high voltage direct current (DC). As the flue gas flows through fields of the precipitator, the particulate get negatively charged from the high voltage. These charged particles are collected on the positively charged plates, and, over the years of operation, the plates (that may be as long as 48 feet in length) have a tendency of bowing. As noted previously, when a bow occurs, it reduces the clearance between the energized electrode and the plate surface. This reduced clearance affects the performance of charging the particles and the over-all performance of the precipitator. 
   When installing the clips, the plates are retained in a straight line while at the same time are allowed to move freely (as designed), and the clips do not affect the rapping operation of the removing the particulate from the plates. 
   Advantageously, multiple clips may be used on a single plate so that very complex forms of bending, warping, twisting, and deformation can be addressed. As many or as few clips needed can be added to adapt to whatever bending problems arise. 
   Furthermore, the clips are extremely easy to manufacture (a trained technician can manufacture over 100 in a couple of hours), require little in the way of installation (no holes, welding, etc.), and are very inexpensive. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a top view of a first embodiment of the precipitator plate clip; 
       FIG. 2  is a side view of the embodiment of the precipitator plate clip shown in  FIG. 1 ; 
       FIG. 3  is an end view of the embodiment of the precipitator plate clip shown in  FIG. 1 ; 
       FIG. 4  is a top view of a second embodiment of the precipitator plate clip; 
       FIG. 5  is a side view of the embodiment of the precipitator plate clip shown in  FIG. 4 ; 
       FIG. 6  is an end view of the embodiment of the precipitator plate clip shown in  FIG. 4 ; 
       FIG. 7  is a side view of the first embodiment of the precipitator clip holding a first variant of a precipitator plate; 
       FIG. 8  is a side view of the second embodiment of the precipitator clip holding a first variant of a precipitator plate; 
       FIG. 9  is a side view of the second embodiment of the precipitator clip holding a second variant of a precipitator plate; 
       FIG. 10  is an isometric view of a precipitator collector plate with straightening elements according to the prior art; 
       FIG. 11  is a top view of a known conduit strut clamp that can be disassembled so that its constituent parts can be used in the clip; 
       FIG. 12  is a side view of the conduit strut clamp shown in  FIG. 11 ; 
       FIG. 13  is a top view of a known conduit strut clamp having shorter members than that shown in  FIG. 11 ; and 
       FIG. 14  is a side view of the conduit strut clamp shown in  FIG. 13 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The descriptions below refer to embodiments of the invention and should not be construed as limiting the invention in any way. 
     FIGS. 1–3  illustrate a first embodiment of a precipitator collecting plate clip  10  used for straightening or maintaining the straightness of a precipitator collecting plate  60  ( FIG. 7 );  FIG. 1  is a top view,  FIG. 2  is a side view, and  FIG. 3  is an end view of this embodiment. 
   According to the embodiment, the clip  10  comprises a beam clamp  20  (generically, a fastening mechanism) that serves to affix the clip  10  to another element. According to this embodiment, the clamp  20  comprises an anchoring bolt  22  that is used to affix the clip  10  by pinning a portion of the other element between an end of the bolt  26  and a beam clamp mating surface  28 , as will be described in greater detail below. 
   The clamp  20  has a spring-like sheet or plate stiffening element  30  connected to it that is made of a material capable of providing at least some force in a direction perpendicular to a plane defined by a primary surface of the stiffening element  30 . The stiffening element  30  is affixed to the clamp  20  by, e.g., a fastening screw  24 . By providing a spring-like force with the stiffening element  30 , the force on the plate  60  is minimized in contrast to the use of a rigid stiffening element, such as a bar, which permits maximum motion for the plate  60  during the rapping operation. 
   According to the embodiment shown in  FIGS. 1–3 , the stiffening element  30  is constructed as being generally flat in one dimension, having slight deviations to accommodate the clamp  20  itself and a point of fastening. 
   Exemplary dimensions of the stiffening element  30  are 4.25″ in a maximum length dimension, 1.25″ in a width dimension, and approximately 0.1875″ in a thickness dimension. One of skill in the art, however, would recognize that other dimensions could easily be used to achieve the same effect. The precise composition and dimensions are not critical to the invention. The stiffening element  30  may be made from sheet or plate stock so that it is inexpensive and simple to construct, and is capable of providing the necessary spring-like force to straighten or prevent from bowing, the plates  60 .  FIGS. 11–14  illustrate conduit strut clamps whose arms  30 ,  30 ′ can be directly used as the stiffening elements  30 ,  30 ′ with some slight bending alterations. Advantageously, these strut clamp arms  30 ,  30 ′ have an acceptable amount of stiffness in them and already have holes drilled in them, so that further drilling is not necessary. 
   Similarly, the dimensions of the clamp  20  are not crucial. In the embodiment shown, the clamp may have a height of approximately 1.625″ and a width of 1″, however, any clamp  20  that could attach to a stiffening element  30  and to an anchor or adjacent precipitating plate  50  could be used. 
     FIG. 7  illustrates the plate clip  10  being utilized with a fixed anchor  50 , which may be rigidly mounted to a frame or may possibly be another adjacent collector plate  60  (the collector plate  60  being shown in an end view such that the view line is parallel with a plane defining the primary surface of the plate  60 ). As can be seen in  FIG. 7 , the clamp  20  is affixed to the anchor  50  by sandwiching a portion of the anchor  50  between an end  26  of the bolt  22  and a mating surface  28  of the clamp  20 , the bolt end  26  applying sufficient pressure to an anchor bolt surface  52  of the anchor  50  to ensure that the clamp  20  is securely fastened to the anchor  50 . 
   In this embodiment, the bolt may be easily accessed for tightening based on a gap between the anchor/adjacent plate  50  and the bottom of the clamp  20  without requiring any changes to be anchor/adjacent plate  50 . Note that the figures are not necessarily drawn precisely to scale. 
   In this embodiment, a bottom surface of the stiffening element  30  serves as the contacting surface  32  for the plate  60  via its mating surface  62 .  FIG. 7  illustrates how the presence of the stiffening element  30  serves to impart a force to the collector plate  60  in a direction opposite that of a direction of bow, i.e., the force applied to the collector plate  60  is normal to a primary plane of the plate  60 . This force can serve to straighten out a plate  60  that is already bowed, or can prevent a plate  60  from becoming bowed. One or more clips  10  can be utilized along the length of a collector plate  60 . The clips  10  provide the necessary force to reduce/prevent bowing while at the same time permit movement of the plate  60  during the rapping operation. Thus, as illustrated in  FIG. 7 , the stiffening element  30  is designed to contact an outer surface of the plate  60 . 
   The plate clip  10  can be constructed and installed very inexpensively and does not require any significant modification of an existing precipitator system in order to be utilized. 
     FIGS. 4–6  illustrate a second embodiment of a precipitator collecting plate clip  10  used for straightening or maintaining the straightness of a precipitator collecting plate  60 ′ ( FIG. 8 );  FIG. 4  is a top view,  FIG. 6  is a side view, and  FIG. 5  is an end view of this embodiment. 
   According to the second embodiment, the clip  10  comprises a beam clamp  20  similar to that of the first embodiment that serves to affix the clip  10  to another element. According to this embodiment, the clamp  20  comprises an anchoring bolt  22  that is used to affix the clip  10  by pinning a portion of the other element between an end of the bolt  26  and a beam clamp mating surface  28 . 
   The clamp  20  has a spring-like sheet or plate stiffening element  30 ′ connected to it that is made of a material capable of providing at least some force in a direction perpendicular to a plane defined by a primary surface of the stiffening element  30 . The stiffening element  30 ′ is affixed to the clamp  20  by, e.g., a fastening screw  24 . 
   According to the embodiment shown in  FIGS. 4–6 , the stiffening element  30 ′ is constructed as having a z-shaped cross section when viewed edgewise. Ideally, the angles of the z-shape are constructed as close to 90° as possible. 
   Exemplary dimensions and construction of the stiffening element  30 ′ are similar to those of the previously described for stiffening element  30 , with the exception that the overall length could be, e.g., 6.25″ before bending. After bending, the two end portions that are parallel may be 2″ each, with the central portion at approximately a right angle to the end portions could be approximately 2.25″. This dimension must be great enough so that the stiffening portion can accommodate a plate edge width on a plate for which it might be used. 
     FIG. 8  illustrates the plate clip  10  being utilized with a fixed anchor  50 , which may be rigidly mounted to a frame or may possibly be another adjacent collector plate  60  (the collector plate  60  being shown in an end view such that the view line is parallel with a plane defining the primary surface of the plate  60 ). As can be seen in  FIG. 8 , the clamp  20  is affixed to the anchor  50  by sandwiching a portion of the anchor  50  between an end  26  of the bolt  22  and a mating surface  28  of the clamp  20 , the bolt end  26  applying sufficient pressure to an anchor bolt surface  52  of the anchor  50  to ensure that the clamp  20  is securely fastened to the anchor  50 . 
   In this embodiment, a top surface of the stiffening element  30  serves as the contacting surface  32 ′ for the plate  60  via its mating surface  62 .  FIG. 8  illustrates how the presence of the stiffening element  30 ′ serves to impart a force to the collector plate  60  in a direction opposite that of a direction of bow, i.e., the force applied to the collector plate  60  is normal to a primary plane of the plate  60 . This force can serve to straighten out a plate  60  that is already bowed, or can prevent a plate  60  from becoming bowed. As indicated in the description of the first embodiment, one or more clips  10  can be utilized along the length of a collector plate  60 . The clips  10  provide the necessary force to reduce/prevent bowing while at the same time permit movement of the plate  60  during the rapping operation. Thus, as illustrated in  FIG. 8 , the stiffening element  30 ′ is designed to contact an outer surface of the plate  60 . 
   It should be noted that the use of clips using multiple variants of the stiffening element  30 ,  30 ′ can be added to a single plate  60  to address a particular type of bowing problem, which may be compound in nature. 
     FIG. 9  shows an embodiment of the invention utilizing the plate clip illustrated in  FIG. 8  where the plate  60 ′ has ends that are shaped differently. This illustrates that the invention is not limited solely to the configurations shown, but can be construed as comprising any variety of shapes have any number of features. 
   Similar to the first embodiment, the plate clip  10  can be constructed and installed very inexpensively and does not require any significant modification of an existing precipitator system in order to be utilized. 
   For the purposes of promoting an understanding of the principles of the invention, reference has been made to the preferred embodiments illustrated in the drawings, and specific language has been used to describe these embodiments. However, no limitation of the scope of the invention is intended by this specific language, and the invention should be construed to encompass all embodiments that would normally occur to one of ordinary skill in the art. The particular implementations shown and described herein are illustrative examples of the invention and are not intended to otherwise limit the scope of the invention in any way. Furthermore, the connecting lines, or connectors shown in the various figures presented are intended to represent exemplary functional relationships and/or physical or logical couplings between the various elements. It should be noted that many alternative or additional functional relationships, physical connections or logical connections may be present in a practical device. Moreover, no item or component is essential to the practice of the invention unless the element is specifically described as “essential” or “critical”. Numerous modifications and adaptations will be readily apparent to those skilled in this art without departing from the spirit and scope of the present invention. 
   
     
       
             
           
             
             
             
           
         
             
                 
             
             
               REFERENCE CHARACTERS 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               10 
               precipitator collecting plate clip 
             
             
                 
               20 
               beam clamp (fastening mechanism) 
             
             
                 
               22 
               anchoring bolt 
             
             
                 
               24 
               fastening screw 
             
             
                 
               26 
               bolt end 
             
             
                 
               28 
               beam clamp mating surface 
             
             
                 
               30, 30′ 
               spring-like sheet or plate stiffening element 
             
             
                 
               32, 32 
               stiffening element contacting surface 
             
             
                 
               50, 50′ 
               fixed anchor or possibly another anchoring collector plate 
             
             
                 
               52 
               anchor bolt surface 
             
             
                 
               60, 60′ 
               precipitator collecting plate 
             
             
                 
               62, 62′ 
               precipitator plate mating surface