Abstract:
A removable, reusable, pleated woven wire filter comprising: (a) a stainless steel perforated core having one-half-inch stainless steel round bar reinforcement rings welded to one-half-inch stainless steel round bar cross bars to create bar-ring junctures, and having 11-gauge stainless steel attachment clips welded to each end of the perforated core; (b) a three-layer stainless steel pleated woven wire filter media wrapped around the perforated core, the filter media having spaced apart pleats with external peaks, and an external filter media surface comprising the external peaks of the pleats; (c) a stainless steel flattened expanded metal shroud adjacent to and encircling the external peaks, and (d) a stainless steel top end cap base and a stainless steel bottom end cap base connected to the metal shroud, both cap bases sealed against top and bottom ends of the filter media with a stainless steel adhesive sealant rated at 2,000 degrees Fahrenheit.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This patent application is a continuation-in-part of patent application Ser. No. 12/197,840, filed Aug. 25, 2008, entitled “Pleated Woven Wire Filter”, and listing as the inventor Frank Lynn Bridges. This continuation-in-part patent application also claims the benefit of provisional patent application Ser. No. 60/968,532, filed Aug. 28, 2007, entitled “Pleated Woven Wire Filter”, and listing as the inventor Frank Lynn Bridges. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     None. 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     None. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The invention relates to a back-washable filter for use in petrochemical processes involving corrosive high temperature liquid or gas streams with high concentrations of solids wherein the filter requires frequent backwashing. 
     (2) Description of the Related Art 
     U.S. Pat. No. 6,986,842 (“the Bortnik patent”), which is incorporated herein by this reference, discloses a fluid filter element having a pleated filter media with spaced apart pleats, an external filter media surface comprising the external peaks of the pleats, and a flexible foam filter media sleeve in contact with and extending between the pleats of the peaks of the external filter media surface. The filter media sleeve maintains the spacing between the external peaks of the pleats of the pleated filter media. The pleated filter media is for fluid applications and includes fragile material media layers between wire meshes, but the patent states that the number of media layers is “typically from 1-10 layers” (Column 3, lines 64-65). The Bortnik patent does not disclose means for preventing the expansion of the pleated filter media radially against the filter media sleeve during a backwash cycle, does not disclose means for sealing between the pleats and the ends of the filter, does not disclose using only a single layer of pleated woven-wire as a filter media, and discloses no a) optimal number of pleats to the circumference of the cylinder, b) optimal radial depth of each pleat, and c) optimal axial length of the pleats. 
     U.S. Pat. No. 4,786,670 (the “Tracey” patent), which is incorporated herein by this reference, discloses a compressible non-asbestos high-temperature sheet material usable for gaskets. U.S. Pat. No. 5,376,278 (the “Salem” patent), which is incorporated herein by this reference, discloses a filter used in a process vessel in a nuclear power generating plant; that is, a filter and a method for separating charged particles from a liquid stream. U.S. Pat. No. 5,795,369 (the “Taub” patent), which is incorporated herein by this reference, discloses a fluted filter media for a fiber bed mist eliminator, including “a layer of fluted filter media  48  and a support structure. The support structure preferably includes an inner cage  50 , and an outer cage  52 .” U.S. Pat. No. 6,962,256 (the “Nguyen” patent), which is incorporated herein by this reference, discloses a plastic molded center tube assembly. 
     Most of the existing reusable back-washable filters are offered in small diameters with limited surface areas. Thus a user must install large quantities of such filters in a single pressure vessel, in order to accommodate the high flow rates and heavy contaminant loadings associated with industrial process streams. Due to the material composition and design structure of most of such filters, the flow rates of known liquids and gases through those filters are low in relation to their surface area. Available gasket materials for sealing the filters are limited because the gaskets must survive high temperatures and corrosive chemicals. Most back-washable filters contain multiple filter elements, as in the Bortnik patent. Such multi-filter element filters suffer from at least two major deficiencies: 1) a limited surface area of the cylindrical designs which restrict flow in both the filtrate and backwash cycles, and 2) the backwash cycle is less efficient because the close proximity of filter elements in a multi-element filter results in the back-flushed contaminant collecting on the adjacent filter elements, and thereby increasing the backwash cycle time. 
     In light of the foregoing, a need remains for a reusable back-washable filter for use in petrochemical processes involving corrosive high temperature liquid or gas streams with high concentrations of solids wherein the filter requires frequent backwashing. More particularly, a need still remains for a reusable back-washable filter having a) means to keep the filter from radially expanding during a backwash cycle, b) means for sealing between the pleats and the ends of the cylinder containing the pleated woven-wire, c) optimized number of pleats to the circumference of the cylinder, d) optimized radial depth of each pleat, and e) optimized axial length of the pleats. 
     BRIEF SUMMARY OF THE INVENTION 
     A removable, reusable, pleated woven wire filter, configured for removing particulate material from a heavy coker gas oil process stream, the process stream containing any of asphaltenes, heavy catalytic-cracked petroleum distillates, catalytic-cracked petroleum clarified oils, residual heavy petroleum coker gas oil, vacuum gas oil, naptha, coke fines, H 2 S. Sulphur. Butane, Butene, and Chrysene, the filter comprising: (a) a reinforced 11-gauge stainless steel perforated core having one-half-inch stainless steel round bar reinforcement rings welded to one-half-inch stainless steel round bar cross bars to create bar-ring junctures, and having 11-gauge stainless steel attachment clips welded to each end of the perforated core; (b) a three-layer stainless steel pleated woven wire filter media wrapped around the perforated core, attached to the perforated core by 18-gauge stainless steel tie wires at each of the bar-ring junctures; and further attached at each end of the perforated core by attachment clips welded to each open end of the perforated core; the filter media having spaced apart pleats with external peaks, and an external filter media surface comprising the external peaks of the pleats; (c) a stainless steel flattened expanded metal shroud adjacent to and encircling the external peaks, and (d) a one-inch-thick stainless steel top end cap base and a three-quarter-inch-thick stainless steel bottom end cap base connected to the metal shroud, both cap bases sealed against top and bottom ends of the filter media with a stainless steel adhesive sealant rated at 2,000 degrees Fahrenheit, wherein the wire filter is further adapted for filtering a process stream operating between 300 and 800 degrees Fahrenheit, and between 150 psig and 500 psig, and is further adapted for being backwashed with a backwash purge pressure that can vary from 100 psig to 200 psig. 
     In another feature of the invention, a required square footage of filter media, determined by flow rate calculations for the given process, is divided by a number between 33 and 34 to determine the inside diameter of the perforated core. 
     In still another feature of the invention, the filter media consists of: a) an inner layer of woven wire metal mesh; b) a middle layer of stainless steel micronic filter cloth; and c) an outer layer of woven wire metal mesh, wherein the inner and outer layers support the filter cloth. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a side view of the filter of the present invention in typical process vessel. 
         FIG. 2  is a perspective view of the filter. 
         FIG. 3A  is a perspective view of a first outer support structure for the filter. 
         FIG. 3B  shows a first outer support structure as a stainless steel flattened expanded metal shroud. 
         FIG. 3C  shows one of the diamond configurations that comprise the first outer support structure. 
         FIG. 4  is a side view of part of a second outer support structure for the filter. 
         FIG. 5  is a perspective view of an inner support structure for the filter. 
         FIG. 6  is a side view of the filter showing its second outer support structure and its inner core. 
         FIG. 7A  shows the top end cap of the filter, and a plan view of the top of the outer support structure for the filter. 
         FIG. 7B  shows one of the lifting lugs of the filter. 
         FIG. 8  shows both plan and elevation views of the two ends of the outer and inner support structures for the filter. 
         FIG. 9A  is a plan view of the bottom of the outer support structure for the filter. 
         FIG. 9B  shows a round bar inserted through a tubular member, which is welded to the horizontal surface of the top end cap of the filter. 
         FIG. 9C  shows a round bar inserted through a tubular member, which is welded to the horizontal surface of the bottom end cap of the filter. 
         FIG. 10  shows the filter media attached to the perforated core of the filter. 
         FIG. 11  shows the top end cap of the filter. 
         FIG. 12  shows the bottom end cap of the filter. 
         FIG. 13  shows the top end cap connected to the round bar tie rods that connect the bottom end cap to the top end cap. 
         FIG. 14  shows the bottom end cap attached by the round bar tie rods to the top end cap. 
         FIG. 15  shows the perforated core of the filter, welded to reinforcement rings and cross brace supports, and having tie wires inserted through the bottom of the first layer of the pleated wire media. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1 , a process vessel  10  contains an inlet nozzle  12 , an outlet nozzle  14 , a backwash nozzle  16 , and a filter  18 , built according to the present invention. Dirty fluid enters the process vessel  10  through the inlet nozzle  12 , and flows from outside of the filter  18 , through a filter media  19 . The filter media  19  is made of a three layer stainless steel pleated woven wire. After the dirty fluid flows through the filter media  19 , it then flows through a stainless steel top end cap  20 , and through a 1½ inch thick stainless steel top flange plate  22 , exiting through the outlet nozzle  14 . During backwashing, liquid flows into the outlet nozzle  14 , through the filter media  19 , out through a stainless steel bottom end cap  23 , and out through the backwash nozzle  16 . In the preferred embodiment, the filter media  19  comprises three layers of stainless steel pleated wire with a minimum pleat depth of four inches and a minimum pleat length of forty-eight inches, providing 2.67 square feet of surface area per pleat, consisting of an inner layer of 8-mesh, 0.025 inch wire diameter stainless steel woven wire metal mesh, a middle layer of stainless steel micronic filter cloth, and an outer layer of 20-mesh, 0.014 inch wire diameter stainless steel woven wire metal mesh. In the preferred embodiment, the stainless steel micronic filter cloth is the twilled dutch weave manufactured by Southwestern Wire Cloth, having a mesh count per inch of 165×1400 with wire diameters of 0.0028 inch in the warp direction, and 0.0016 inch diameter in the shute direction. This micronic layer of wire has an absolute rating of 16 microns, and a nominal rating of 10 microns. The inner and outer layers of stainless steel woven wire function as a support structure for the stainless steel micronic filter cloth. A stainless steel adhesive sealant  21 , rated at 2,000 F, functions as a fluid containment barrier and structural reinforcement bond connecting a reinforced 11-gauge stainless steel perforated core  62  (shown in  FIG. 7A ), the filter media  19 , a stainless steel 21-gauge tie wire  83  (shown in  FIG. 17 ), the end caps  20 ,  23 , and eight cap tie rods  24 . The adhesive sealant  21  seals the ends of the filter media  19  against the top end cap  20  and the bottom end cap  23 . The adhesive sealant  21  can endure temperatures up to 2,000 F, and has the flexibility and compressibility to accept the rigid wire members of the filter media  19 , and provides a positive seal against fluid by-pass, while offering a high operating temperature of 2,000 degrees Fahrenheit. In the preferred embodiment, the adhesive sealant  21  is the DURABOND brand, sold by Cotronics Corp., Brooklyn, N.Y. 
     The eight cap tie rods  24  are ½ inch O.D. stainless steel vertical round bar rods with threaded ends which attach to the top end cap  20  and the bottom end cap  23  in pre-drilled and threaded holes, and thus keep pressure against the ends of the filter media  19 . Each cap  20  and  23  has a two-inch wide×11-gauge thick stainless steel lip. Angle iron legs  25 , which are 2 inch×2 inch×¼ inch thick carbon steel, are welded to the top flange plate  22 , to a ½ inch thick carbon steel bottom ring  26 , and to a 2 inch×2 inch×¼ inch carbon steel angle iron horizontal support  27 . The top flange plate  22  is sized to fit the particular process vessel  10 . Sixteen SA-193-B7 stud bolts  28  connect the top flange plate  22  to the top end cap  20 . Once the filter assembly is attached to the top flange plate  22 , the horizontal support  27  is welded into position immediately adjacent to the underside of the bottom end cap  23  to provide additional seal support pressure for the wire fins of the filter media  19  during operation, when vibration and movement could occur during the filter and backwash cycles. 
     Referring now to  FIG. 2 , the filter  18  is ideally mounted on a shipping skid  30  for transportation to the location of a process vessel  10 . The shipping skid  30  includes insert points  32  for a forklift. The filter media  19  has two separate outer support structures connected to it, a first outer support structure  40 , shown in more detail in  FIG. 3 , and a second outer support structure  50 , shown in more detail in  FIG. 4 . In one embodiment a stainless steel first outer support structure  40  supports the filter media  19  during backwashing. The first outer support structure  40  includes a series of 1 inch wide×11-gauge thick stainless steel horizontal bands  42  that are welded to four 1 inch wide×11-gauge thick stainless steel metal flat bar vertical supports  44 . Ideally, the horizontal bands  42  are spaced about a foot apart. The first outer support structure  40  minimizes the chances of pleat deformation and woven wire deterioration of the filter media  19  from abrasion during pleat movement. 
     Referring now to  FIG. 3 , the first outer support structure  40  does not connect to the top and bottom end caps  20 ,  23 , which are shown in dotted lines merely to show their locations with respect to the first outer support structure  40 . 
     Referring now to  FIG. 3B , in the preferred embodiment, a first outer support structure  41  is a stainless steel flattened expanded metal shroud with 80% open area. The first outer support structure  41  includes the angle iron legs  25 . The first outer support structure  41  provides backwash support for the filter media  19 . 
     Referring now to  FIG. 3C , the first outer support structure  41  further comprises a series of diamond configurations  46  made of strands  45 . Each diamond configuration  46  has a height  47  and a width  48 . In the preferred embodiment, the height  47  is 1.33 inches, and the width  48  is 3.15 inches. This results in an opening for each diamond configuration having a height of 1.062 inches, and a width of 2.75 inches. The thickness of each strand  45  is 0.050 inches. 
     Referring now to  FIG. 4 , a second outer support structure  50  includes the top flange plate  22 , with two 3 inch×3 inch×½ inch thick stainless steel lifting lugs  52  welded to it. The two lifting lugs  52  aid in lifting the heavy filter  18  into and out of the process vessel  10 . The second outer support structure  50  also includes the bottom ring  26 , which has four carbon steel 1 inch O.D.×1 inch long round bar risers  54  welded to it, to keep the entire filter assembly off the ground during manufacturing. The second outer support structure  50  includes the eight cap tie rods  24  threaded into a top end cap base  56  of the top end cap  20 . The top end cap base  56  is made of one-inch-thick stainless steel. The eight cap tie rods  24  are also threaded into a bottom end cap base  58  of the bottom end cap  23 . The bottom end cap base  58  is made of ¾ inch thick stainless steel. The second outer support structure  50  also includes the angle iron legs  25  welded to the top flange plate  22 , to the bottom ring  26 , and to the horizontal support  27 . 
     Referring now to  FIG. 5 , an inner support structure  60  includes a reinforced 11-gauge stainless steel perforated core  62  that contains one-half-inch O.D. stainless steel round bar rings  64  with ½ inch O.D. stainless steel round bar cross-braces  66 . At the top of the perforated core  62  are 11-gauge stainless steel clips  68  that are bent over to hold in place the filter media  19 . In the preferred embodiment the perforated core  62  has a minimum I.D. of ten inches and a minimum length of forty-eight inches, the perforated holes are ⅛ inch in diameter, and spaced 3/16 inch on staggered centers, and there are a minimum of four rings  64 , having the cross-braces  66 , equally spaced at a maximum of 10 inches apart on the perforated core  62 . 
     Referring now to  FIG. 6 , the second outer support structure  50  of  FIG. 4  is shown together with the filter media  19  and a Flexitallic® brand spiral-wound gasket  29  located between the top flange plate  22  and the top end cap  20 . 
     Referring now to  FIG. 7A , a top plan view of the filter  18  shows the perforated core  62  surrounded by the filter media  19  surrounded by the horizontal bands  42 . In the preferred embodiment the first outer support structure  41 , shown in  FIGS. 15 and 16 , replaces the first outer support structure  40 . Also shown in  FIG. 7A  is the top end cap  20 , the top flange plate  22 , and the lifting lugs  52 . One of the lifting lugs  52  is shown in a separate side view in  FIG. 7B . 
     Referring now to  FIG. 8 , the top end cap  20  includes an 11-gauge by two inch wide stainless steel inner perimeter lip ring  70 , an 11-gauge by two inch wide stainless steel outer perimeter lip ring  72 , and a one-inch thick stainless steel metal plate, which is a top end cap base  80 . The bottom end cap  23  includes an 11-gauge×2 inch wide stainless steel inner perimeter lip ring  74 , an 11-gauge×2 inch wide stainless steel outer perimeter lip ring  76 , and a three-quarter-inch thick stainless steel metal plate, which is a bottom end cap base  82 . 
     Referring now to  FIG. 9A , threaded bolt holes  78  are machined into the top flange plate  22  to fasten the top end cap base  80  to the top flange plate  22  with the bolts  28 . 
     Referring to  FIG. 9B , a ⅝ inch O.D. stainless steel tubular fixture  84  is seal welded at its lower perimeter by a weld  86  to the top end cap base  80  on the interior of the top end cap  20  adjacent to the outer perimeter lip ring  72  and centered over the threaded bolt holes  78  in the top end cap base  80  in a pattern that will align with the lay-out of the cap tie rods  24 . The adhesive sealant  21  is then poured into the top end cap  20  encircling the tubular fixture  84 , encapsulating it to a depth equivalent to the height of the outer perimeter lip ring  72  with the encapsulation extending to and rising level with the inner perimeter lip ring  70 . 
     Referring to  FIG. 9C , a ⅝ inch O.D. stainless steel tubular fixture  85  is seal welded at its lower perimeter by a weld  87  to the bottom end cap base  82  on the interior of the bottom end cap  23 , adjacent to the bottom end cap outer perimeter lip ring  76 , and centered over the threaded bolt holes  78  in the bottom end cap base  82  in a pattern that will align with the lay-out of the tie rods  24 . The adhesive sealant  21  is then poured into the end cap  23 , encircling the tubular fixture  85 , encapsulating it to a depth equivalent to the height of the bottom end cap outer perimeter lip ring  76 , with the encapsulation extending to and rising level with the bottom end cap inner perimeter lip ring  74 . 
     Referring to  FIG. 10 , the filter media  19  is shown attached to the perforated core  62 , which contains the rings  64  with the cross-braces  66  welded to the rings  64  in cross configuration, as also shown in  FIG. 5 . 
     Referring to  FIG. 11 , the top end cap  20  includes the inner perimeter lip ring  70  for aligning the perforated core  62 , the outer perimeter lip ring  72 , and the stud bolts  28  that fasten the top end cap base  80  to the top flange plate  22 . 
     Referring to  FIG. 12 , the bottom end cap  23  includes the inner perimeter lip ring  74 , for aligning the perforated core  62 , and the outer perimeter lip ring  76 , and is shown connected to the tie rods  24  that connect the bottom end cap base  82  to the top end cap base  80  (not shown in  FIG. 12 ). 
     Referring to  FIG. 13 , the top end cap  20 , including the inner perimeter lip ring  70 , the outer perimeter lip ring  72 , and the bolts  28 , is shown connected to the tie rods  24  that connect the bottom end cap base  82  to the top end cap base  80  (not shown in  FIG. 13 ). 
     Referring to  FIG. 14 , the bottom end cap base  82 , with the inner perimeter lip ring  74  and the outer perimeter lip ring  76 , is shown attached by the tie rods  24  to the top end cap  20 . 
     Referring to  FIG. 15 , the perforated core  62  is shown welded to the rings  64  and the cross-braces  66  are welded to the rings  64 . The first layer  90  of the three layer filter media  19 , is shown attached to the perforated core  62  by inserting the tie wire  83  through the bottom of the pleat depth of the first layer  90  adjacent to the perforated core  62 , where the cross-braces  66  intersect and are welded to the rings  64 . The tie wire  83  has a minimum tensile strength of 267 KSI. The tie wire  83  is shown inserted and manually twisted around the ring  64  and the cross-brace  66  with a minimum of four twists per inch, and a maximum of nine twists per inch. The tie wire  83  is applied at every intersection of the cross-braces  66  with the rings  64 . In the preferred embodiment the rings  64  and the cross-braces  66  are equally spaced at a maximum of 10 inches on the perforated core  62 . In addition, the cross-braces  66  are shown welded to the rings  64 , welded inside the perforated core  62  with the tie wire  83  tied to the first layer  90 . A middle layer of stainless steel micronic filter cloth  92  has a mesh count of 165×1400 with wire diameters of 0.0028 inch in the warp direction and 0.0016 inch diameter in the shute direction. The filter cloth  92  has an absolute rating of 16 microns and a nominal rating of 10 microns. A 20 mesh 0.014 inch wire diameter stainless steel woven wire metal mesh  94  is the outer layer of the filter media  19 . 
     According to the manufacturing process of the present invention, the process has been optimized to calculate the proper size of a filter needed for a given process. With a known process stream fluid specification (including but not limited to specific gravity, viscosity, required micron retention, allowable pressure drop, line size, operating pressure, and operating temperature) and a required flow rate, the required surface area of the filter media  19  can be obtained based on manufacturers efficiency ratings for the specific micron rated metal woven wire media that will satisfy process conditions. 
     The following definitions apply for the three equations listed below: 
     D is the inside diameter of the perforated core  62 . On a retrofit application, D must not exceed thirteen inches less than the inside diameter of the existing process vessel. This maximum D allows a four-inch pleat depth, plus five inches for end cap outside diameter allowance and vessel wall spacing factors. 
     C is the circumference in inches of the perforated core  62 . 
     P is the pleat depth in inches of the filter media  19 . The maximum pleat depth for micron rated metal woven wire is four inches. In the preferred embodiment the minimum pleat depth is four inches. 
     N is the number of pleats per inch of the circumference of the perforated core  62 . The maximum number of pleats for micron rated metal woven wire is four pleats per inch of circumference. In the preferred embodiment the minimum pleats per inch is 3.5. 
     H is the pleat height. The maximum industry standard pleat height for micron rated metal woven wire is forty-eight inches. In the preferred embodiment the minimum pleat height is sixty inches. 
     S is the surface area of the filter media  19 .
         C=πD   4C=N   (2 P ) NH=S          

     D affects C by a factor of pi (3.14159), which in the next step affects N by a factor of 4. When this factor (now 12.5664) is applied to P, which by limitation is a maximum of 8, then the figure of 100.53 becomes a constant against H, which (again by limitation) is 48. The new formula constant is now 4,825.4976. This figure represents square inches, so when divided by 144, the number 33.51 (in square feet) is obtained as the surface area constant. In the preferred embodiment the H factor changes to 60 and the formula constant is 6,031.872. When divided by 144, the number 41.88 (in square feet) is obtained as the surface area constant. 
     Thus, the selection of the size of the inside diameter of a process vessel  10  depends on the inside diameter of the perforated core  62 . As an example, if flow rate calculations dictate a required square footage of filter cloth to be 1,000 square feet, then 1,000 sq. ft. divided by 33.51 yields a 29.84 inch inside diameter for the perforated core  62 . When this figure is added to the thirteen-inch minimum clearance requirement for the process vessel  10 , the minimum inside diameter of the process vessel  10  is 42.84 inches. In the preferred embodiment the 1,000 square feet is divided by 41.88, which yields a minimum inside diameter of the process vessel  10  as 23.88 inches. 
     Conversely, for a known size of a process vessel  10 , one deducts thirteen inches from the inside diameter of the process vessel  10 , and then multiplies that figure by 33.51. As an example, if the process vessel  10  has an inside diameter of thirty-six inches, this would factor as a twenty-three inch inside diameter of the perforated core  62 , which when multiplied by 33.51 would equal 770.73 square feet of surface area available, assuming that the vertical clearance in the process vessel  10  will accommodate the height of the filter media  19 . When the available surface area is known, then a maximum flow rate can be established for the vessel with inlet and outlet nozzle limitations being the only other factors. In the preferred embodiment for a process vessel with an inside diameter of thirty-six inches and a deduction of thirteen inches, yielding a twenty-three inch inside diameter of the perforated core  62 , is then multiplied by 41.88, which equals 963.24 square feet of surface area.