Abstract:
A thimble assembly for a cyclone separator comprising a plurality of carrier brackets separately mountable on a shelf of the separator along the perimeter of a circular exhaust opening, a plurality of segments vertically successively suspended from the brackets, the segments of an upper row being joined to the brackets, the segments of each successive lower row being joined to the segments of a row immediately above, each bracket exclusively serving a chord of an arc concentric with the circular opening that is substantially the same in length as the chord of an arc that a segment spans, a center-to-center chordal spacing of adjacent brackets being the same as a center-to-center distance of an adjacent pair of segments.

Description:
[0001]    The present invention relates to a thimble assembly for a cyclone separator particularly useful in high temperature, corrosive atmospheres. 
       BACKGROUND OF THE INVENTION 
       [0002]    Cyclone separators are used in different applications where solid particulates suspended in a gas phase are to be separated from the gas phase. A separator typically comprises a cyclone housing having an upper substantially cylindrical part with an upwardly extending circular discharge for the gas phase, a lower conical part having an outlet at its narrow bottom for discharging particulate matter, a tangential inlet in the upper part for introducing the suspension which is to be separated, and a central circular structure called a thimble depending from a shelf at an upper wall of the housing. The thimble (which can also be referred to as a central tube, a vortex finder or a dip tube) is adjacent the outlet and extends from the shelf axially in the cyclone housing to a distal free open end. The thimble forces the incoming suspension to rotate around the outside of the cyclone creating rotation and a vortex in the center of the cyclone allowing gas to exit upwardly through the discharge duct and obstructs particulate matter from exiting upwardly so that the particulate matter exits through the outlet at the bottom of the conical part. 
         [0003]    U.S. Pat. Nos. 4,505,051 and 7,841,477 describe cyclone separators; the contents of these patents and the contents of the patents cited in these patents are incorporated herein by reference. 
         [0004]    Cyclone separators such as used in cement making plants operate at very high temperature, approaching 1000 degrees C. for example, and are exposed to corrosive materials. These harsh environments can degrade the thimble to a condition requiring its replacement long before the end of the working life of the cyclone separator. 
         [0005]    Replacement of a thimble has been an expensive proposition in part because a new premium thimble will typically be custom built for a specific installation. Experienced suppliers, to reduce costly manufacturing mistakes, will often visit the prospective site of a repair or upgrade to closely verify the geometry of the separator to assure that the replacement thimble to be manufactured will fit the separator unit when it is delivered. This field study adds to basic costs and extends the delivery time of a replacement thimble. 
         [0006]    Heretofore, premium replacement thimbles have been custom built, often on a rush basis, after a failure or the detection of an insipient failure. The aftermarket industry has generally not found it practical to build and inventory complete thimble units because of the variety of separator sizes in installed plants. 
         [0007]    Cyclone separators operating at high temperature and subjected to corrosive materials have been susceptible to early thimble degradation in part, because of relatively large exposed metal areas. Prior thimble designs have been relatively expensive to manufacture, for example, because segments making up the circular thimbles were made with arcuate shapes that complicated their tooling, molding, and assembly. 
       SUMMARY OF THE INVENTION 
       [0008]    The invention provides a thimble assembly for a cyclone separator that, using common parts, can be installed on cyclone units of a wide size range. The inventive technology allows a manufacturer to produce thimble parts with an economy of scale and to inventory the parts prior to receiving an order for a particular installation. The technology effectively eliminates lead times, is flexible enough to eliminate the need to confirm the size of the required unit by dispatching an agent of the manufacturer to the perspective installation site and eliminates engineering time to design custom parts. 
         [0009]    Segments used to construct the inventive thimble are less expensive to manufacture and are longer lasting than prior art parts. The foregoing improvements and advantages as well as others will become apparent from the following description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is an exploded perspective view of a cyclone separator showing the thimble of the invention; 
           [0011]      FIG. 2  is a fragmentary enlarged perspective view of a mounting area of the thimble; 
           [0012]      FIG. 3  is a perspective view of a top row segment of the inventive thimble; 
           [0013]      FIG. 3A  is an elevational view of the top row segment of  FIG. 3  with a right hand part of a refractory covering removed; 
           [0014]      FIG. 3B  is a cross-sectional view of the top row segment taken in a plane indicated at  3 B- 3 B in  FIG. 3A ; 
           [0015]      FIG. 3C  is a top view of the top segment as modified in  FIG. 3A ; 
           [0016]      FIG. 4  is a perspective view of a middle row segment of the inventive thimble; 
           [0017]      FIG. 4A  is an elevational view of the middle row segment of  FIG. 4  with a right hand part of a refractory covering removed; 
           [0018]      FIG. 4B  is a cross-sectional view of the middle row segment taken in a plane indicated at  4 B- 4 B in  FIG. 4A ; 
           [0019]      FIG. 4C  is a top view of the middle segment as modified in  FIG. 4A ; 
           [0020]      FIG. 5  is a perspective view of a bottom row segment of the inventive thimble; 
           [0021]      FIG. 5A  is an elevational view of the bottom row segment of  FIG. 5  with a right hand part of a refractory covering removed; 
           [0022]      FIG. 5B  is a cross-sectional view of the bottom row segment taken in a plane indicated at  5 B- 5 B in  FIG. 5A ; 
           [0023]      FIG. 5C  is a top view of the bottom row segment as modified in  FIG. 5A ; 
           [0024]      FIG. 6  is a perspective view of a segment mounting bracket; 
           [0025]      FIG. 7  is a perspective view of a placement link; 
           [0026]      FIG. 8  is a perspective view of a bottom segment row link assembly; and 
           [0027]      FIG. 9  is a somewhat diagrammatic view of an installed mounting bracket and part of a top row segment suspended by the mounting bracket. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0028]      FIG. 1  illustrates a cyclone separator  10  of a type that is used, for example, in a lower hot stage of a cement manufacturing plant. A mixed phase of gases and solid particulate matter enters an inlet  11  of a housing  12 . In the housing  12 , the mixture swirls around a central thimble  13 . Gases enter a lower open end  14  of the thimble  13 , pass vertically upwardly through the interior of the thimble and exit the housing  12 . Particulate matter descends in the housing  12  and exits through an outlet  16  in a conical bottom part  17  of the housing  12 . 
         [0029]    The thimble  13  is concentric with an opening  19  defining an inside diameter bounded by a shelf  21  formed by an upper wall  22  of the housing  12 . 
         [0030]    The shelf opening diameter of existing cyclone separators of the type under consideration here is generally in the range of 3 to 5 meters. The thimble  13  will have a nominal diameter corresponding to (technically smaller than) the diameter of the opening  19  formed by the shelf  21 . It is customary to construct a thimble of loosely joined segments organized in axially draped circumferential rows. 
         [0031]    In the illustrated thimble construction, all of the segments  26  of a particular row are identical and the segments of one row are different from another row, although the middle two rows have identical segments. Various segments  26   x ,  26   y  and  26   z  are shown in  FIGS. 3, 4 and 5 , respectively. Herein, when a number designation has no suffix letter x, y or z, the designation is intended to mean any one of the segments  26 . This convention will be used with certain other elements of the segments  26 . All of the segments  26  have a steel plate core  27   x ,  27   y  and  27   z  encased in a refractory  28   x ,  28   y  and  28   z . The segments  26  are plate-like, being longer than they are wide. Each segment  26  has two pairs of tabs  29  projecting from an upper edge or face of the refractory  28 . Pairs of the tabs  29  have aligned 1 1/16 inch holes  31  allowing the tab pairs to serve as a clevis. The upper segments  26   x  ( FIGS. 3, 3A -C) and the middle segments  26   y  ( FIGS. 4, 4A -C) have plate areas with 1 1/16 inch holes  32  that are adapted to be received in the clevises formed by tabs  29  of an underlying segment  26 . The plate cores  27  are rectangular steel plates of, for example, 3/16 inch thickness, 21 5/16 inch length and 8 15/16 inch width. The plate cores  27  are bent on a longitudinal center line so that half of the core plate is in a plane 4.5 degrees from the plane of the other half. The clevis tabs  29 , made of 3/16 inch steel plate, are welded flat against opposite sides of a respective plate core  27  so that each tab pair diverges at the 4.5 degree angle from the other pair. A cantilevered upper part of a tab  29  is offset away from the opposite tab to provide a space of 7/16 inch, for example, therebetween. 
         [0032]    Top edges of all of the plate cores  27  and bottom edges of the top and middle plate cores  27   x ,  27   y  are notched in a central zone thereby saving weight of material that would otherwise be unstressed and, therefore, a non-functional area. 
         [0033]    The plate cores  27  including their ends are encased in the refractory  28  except for pockets  36 , that receive clevis tabs  29  of the middle or bottom segments  26   y ,  26   z  or pockets  37  on the bottom segments  26   z  that receive link assemblies described below. The pockets  36  have a reverse draft or undercut of, for example, 20 degrees. 
         [0034]      FIGS. 3C, 4C and 5C  show that the steel plate cores  27  are oriented so that an imaginary chord-like line between their respective longitudinal edges is parallel to opposite main faces  38   x ,  38   y ,  38   z  and  39   x ,  39   y  and  39   z  of their respective refractory  28   x ,  28   y  and  28   z . The main faces or sides  38 ,  39  of each refractory  28  are parallel while narrow vertical sides  40   x ,  40   y  and  40   z  of each refractory  28   x ,  28   y  and  28   z  symmetrically diverge from one another at a shallow angle of, for example 9 degrees. Refractory with flat main faces is more efficient to production cast than prior art refractory with curved faces. By way of example, the refractories  28  can be 21⅝ inch long, 12 1/16 inch wide at the major or main face  39  and 1 15/16 inch thick (the exception being the bottom row segment  26   z  having a refractory length of 23⅝ inch). The minor main face  38  of a segment  26  when assembled in a thimble  13  faces the thimble interior. 
         [0035]    The steel plate core  27   x  of the upper segments  26   x  has a pair of oval circular anchors  30  welded perpendicular to the planes of the core at the top and bottom notched central zone  33 ,  34 . The anchors  30  can be the drops or slugs from punching 1 1/16 inch slots in brackets described below. The upper and lower cross hatched areas on the plate core  27   x , depicted in  FIG. 3A  can be protected with a rubberized coating and the inner cross hatched area can be covered with an adhesion promoting coating. 
         [0036]    The steel plate core  27   y  of the second and third middle row segments  26   y  and the steel plate core  27   z  of the bottom row segments  26   z  have D-shaped holes  45  punched in their mid-sections. Anchor discs  35 , made from 1 1/16 inch hole drops are welded in the D-shaped holes  45  perpendicular to and centered across the plane of the plate cores  27   y ,  27   z . The cross hatched area of the plate core  27   y  and anchors  35  shown cross hatched in  FIG. 4A  can be coated with a rubberized coating. 
         [0037]    The bottom row segment plate core  27   z  is distinguished from the top and middle plate cores  27   x  and  27   y  by having its lower pin holes  32  with a greater center-to-center distance so that they are closer to the longitudinal edges of the plate core  27   z.    
         [0038]      FIG. 6  illustrates a mounting bracket  41  for suspending the thimble segments  26  by coupling with the top row of segments  26   x . The bracket  41  is a weldment of shaped steel plates. A base  42  of the bracket can be made of ¼ inch steel plate with the remaining bracket parts being made of 3/16 inch steel plate. The base  42  has a generally rectangular shape in plan view with a pair of tabs  43 ,  44  and  46 ,  47  at each end. A rear tab  43  on the right in  FIGS. 6 and 2  is raised above a flat plane of the base proper a distance corresponding to the thickness of the base plate  42 . Similarly, a front tab  47  on the left in  FIGS. 6 and 2  is raised above the base plane. Left and right hand U-shaped members  48 ,  49  are welded to opposite end areas of the base  42 . A plate  51  welded flush with a front edge  52  of the base  42  is also welded to side legs of the members  48 ,  49  for reinforcement purposes. A center web  53 ,  54  of each of the members  48 ,  49  lies in a vertical plane and has a 1 1/16 inch wide oval hole  56 . The stamped drops from the holes  56  can be used for the anchors  30  of the top segment plate cores  27   x . The center webs  53 ,  54  are suspended a distance from the base plate front edge  52  a distance considerably greater than the thickness of the segment tabs  29 . The planes of the center webs  53 ,  54  are out of parallelism by a small angle of 4.5 degrees, the same angle as the divergence of the pairs of segment tabs  29 . In such a manner that they are symmetrical with a line perpendicular to the front edge  52  of the base  42 . The oval holes  56  are centered, for example, at 6 3/16 inch so that they correspond with the spacing between pairs of tab holes  31  of a segment  26 . Gusset plates  58 ,  59  ( FIG. 2 ) reinforce the elevated tabs  43 ,  47 . Upper edges of the webs  53 ,  54  are shaped to provide small upstanding tabs  61 . 
         [0039]    A thimble  13  is installed piecemeal circumferentially along the perimeter of the shelf opening  19 . The brackets  41  are arranged around the shelf ID with the tabs  43 - 47  overlying or underlying the tabs of adjacent brackets. This process is assisted by use of placement links  71  illustrated in  FIG. 7 . A link  71  bridging each adjacent pair of brackets  41  has rectangular holes  72  that fit over the bracket tabs  61  of adjacent brackets to properly space the adjacent brackets. When all of the brackets  41  are properly positioned, the overlying and underlying tabs  43 - 47  can be welded together and the base  42  of the brackets can be welded on the shelf. Thereafter, the rows of segments  26  are suspended from the brackets  41 . The upper segments  26   x  are individually raised with their tab  29  straddling the webs  53 ,  54  of adjacent brackets. When the tab holes  31  and bracket web holes  56  are aligned, a short steel pin of, for example 1 inch diameter is installed in these holes. The pins can have steel washers pre-welded on one end and be secured after the pins are in place by steel washers welded on the opposite end. For economy, the pin washers can be formed from material blanked out of the plate cores  27  to form the central notches at the top and bottom of the segments  26 . 
         [0040]    Successive rows of segments  26   y ,  26   z  are similarly installed by raising a segment so that its tabs  29  straddle exposed lower holes  32  in two adjacent segments of the preceding segment row. One inch pins, as just described, are installed in the aligned tab and segment core holes  31 ,  32 . The segments  26   z  of the bottom row of segments are stabilized by coupling adjacent segments together with a link assembly  76  illustrated in  FIG. 8 . Steel pins  77 , again 1 inch in diameter, are pre-welded to a steel link  78 . The pre-welded pins  77  are inserted in lower holes  32  of adjacent plate cores  27   z  and another steel link  79  of the assembly  76  at opposite faces of the segments is installed and welded on the inserted pin ends. 
         [0041]    Areas of the refractory  28  excluded from a segment  26  for clearance of the tabs  29  or link assembly  76  can be filled with refractory after the connecting pins are in place and the retainer washers and links  78  are welded on. The undercut or reverse taper of the clearance formations or pockets  36  assist in holding the filled in refractory. 
         [0042]    In accordance with the invention, the number of mounting brackets  41  to be used is determined by the inside diameter of the shelf  18 . Study has revealed that a large majority of existing cyclone separators of the type under consideration here have a nominal diameter between 3 meters and 5 meters. The geometry of the disclosed mounting bracket  41  and segments  26  is based on use of 4 meters as an average or mean of these diameter dimensions and with sufficient clearance in their joints to allow them to conform to 3 meter to 5 meter shelf inside diameters. The disclosed inventive brackets  41  are configured to be practically located radially in relation to a shelf edge  19  ( FIG. 9 ) in a range of 2 inches (51 mm.). This allows the brackets  41  to cover any shelf inside diameter (ID) in the 3 meter to 5 meter range since the addition or removal of one bracket  41  (and the corresponding addition or removal of one staggered column of segments  26 ) will change the diameter nominally by 4 inches. This relationship comes from the essential equality of the arc length and the effective chord length of a bracket  41  or segment  26 , on a circle at a shelf ID spanned by a bracket or a segment. This arcuate/chordal span or length is the center to center spacing of adjacent brackets  41  or segments  26 , 12⅜ inches, which is twice the center to center distance of the bracket holes  56 , 6 3/16 inches. A change in circumference of 12⅜ inches effects a change in diameter of 4 inches (12⅜÷π) or a radius change at the shelf ID of 2 inches. 
         [0043]    For the bracket  41  to have adequate footing on the shelf  21 , the bracket should have a radial width more than twice the difference between a minimum and a maximum shelf ID, this difference in the illustrated case is 2 inches shown in  FIG. 9 . As a rule, based on the foregoing, the base should preferably have a radial width dimension that is at least ⅓ the effective chord length of the bracket. 
         [0044]    Clearance of the 1 inch diameter pins in the 1 1/16 inch holes and the 7/16 inch gap between pairs of tabs  29  receiving 3/16 inch plate core material, assures that the parts can be easily field assembled regardless of the shelf ID and corresponding number of brackets  41  and segments  26  being used. 
         [0045]    It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. For example, the dimensions referenced in this disclosure are only exemplary and may be varied to suit the circumstances. It is expected that a thimble can be constructed of only three rows of segments or more than four rows of segments. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.