Abstract:
A removable, reusable, pleated woven wire filter for removing particulate material from a heavy coker gas oil process stream. The filter comprises: (a) a perforated core; (b) a pleated woven wire filter media wrapped around the perforated core, the filter media having spaced apart pleats 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) top and bottom end caps connected to the stainless steel flattened expanded metal shroud, and sealed against top and bottom ends of the filter media with a stainless steel adhesive sealant rated at 2,000 degrees Fahrenheit. The process stream operates between 300 and 800 degrees Fahrenheit, and between 150 psig and 500 psig. The filter can withstand a backwash purge pressure from 100 psig to 200 psig.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    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 
       [0002]    None. 
       THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    None. 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC. 
       [0004]    None. 
       BACKGROUND OF THE INVENTION 
       [0005]    (1) Field of the Invention 
         [0006]    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. 
         [0007]    (2) Description of the related art 
         [0008]    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. 
         [0009]    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. 
         [0010]    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. 
         [0011]    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 
       [0012]    A removable, reusable, pleated woven wire filter for removing particulate material from a heavy coker gas oil process stream, the filter capable of withstanding a backwash purge pressure, the process stream containing asphaltenes, heavy catalytic-cracked petroleum distillates, catalytic-cracked petroleum clarified oils, residual heavy petroleum coker gas oil, vacuum gas oil, naptha, coke fines, H2S, Sulphur, Butane, Butene, and Chrysene, the filter comprising: (a) a perforated core; (b) a pleated woven wire filter media wrapped around the perforated core, the filter media having spaced apart pleats 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) top and bottom end caps connected to the stainless steel flattened expanded metal shroud, and sealed against top and bottom ends of the filter media with a stainless steel adhesive sealant rated at 2,000 degrees Fahrenheit, wherein the process stream operates between 300 and 800 degrees Fahrenheit, and between 150 psig and 500 psig, and the backwash purge pressure varies from 100 psig to 200 psig. 
         [0013]    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. 
         [0014]    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 
         [0015]      FIG. 1  is a side view of the filter of the present invention in a typical process vessel. 
           [0016]      FIG. 2  is a perspective view of the filter. 
           [0017]      FIG. 3  is a perspective view of a first outer support structure for the filter. 
           [0018]      FIG. 4  is a side view of part of a second outer support structure for the filter. 
           [0019]      FIG. 5  is a perspective view of an inner support structure for the filter. 
           [0020]      FIG. 6  is a side view of the filter showing its supporting structures and its inner core. 
           [0021]      FIG. 7  is a plan view of the top of the outer support structure for the filter. 
           [0022]      FIG. 8  is a plan view of the bottom of the outer support structure for the. filter. 
           [0023]      FIG. 9  shows both plan and elevation views of the two ends of the outer and inner support structures for the filter. 
           [0024]      FIG. 10  shows the filter media, of the filter of the present invention, attached to the perforated core. 
           [0025]      FIG. 11  shows the top end cap of the filter. 
           [0026]      FIG. 12  shows the bottom end cap of the filter. 
           [0027]      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. 
           [0028]      FIG. 14  shows the bottom end cap attached by the round bar tie rods to the top end cap. 
           [0029]      FIG. 15  shows an outer support structure  41 , as a stainless steel flattened expanded metal shroud. 
           [0030]      FIG. 16  shows one of the diamond configurations that comprise the support structure  41 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    In  FIG. 1 , a typical 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 , through a top end cap  20 , and through a 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 the bottom end cap  23 , and out through the backwash nozzle  16 . The filter media  19  comprises three layers of pleated wire, consisting of an inner layer of woven wire metal mesh, a middle layer of stainless steel micronic filter cloth, and an outer layer of 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. The inner and outer layers function as a support structure for the 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 perforated core  62  (shown in  FIG. 7   a ), the filter media  19 , the end caps  20 ,  23 , and tie rods  24 . The sealant  21  seal the ends of the filter media  19  against the top end cap  20  and the bottom end cap  23 . The 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 sealant  21  is the DURABOND brand, sold by Cotronics Corp., Brooklyn, N.Y. 
         [0032]    Eight cap tie rods  24  are 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 lip. Angle iron legs  25  are welded to the top flange plate  22 , to a bottom ring  26 , and to an angle iron horizontal support  27 . The top flange plate  22  is sized to fit the particular process vessel  10 . Sixteen bolts  28  connect the top flange plate  22  to the top end cap  20 , with a Flexitallic® brand gasket  29  located between the top flange plate  22  and the top end cap  20 . Once the filter assembly is attached to the top flange plate  22 , the angle iron 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. 
         [0033]    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, shown in more detail in  FIG. 3  and  FIG. 4 , connected to it. 
         [0034]    Referring now to  FIG. 3 , in one embodiment an outer support structure  40  supports the filter media  19  during backwashing. It does not connect to the top and bottom end caps  20 ,  23 , which are shown in dotted lines merely to show the location of the outer support structure  40 . The outer support structure  40  includes a series of metal horizontal bands  42  that are welded to four vertical metal flat bar supports  44 . Ideally, the horizontal bands are spaced about a foot apart. The outer support structure  40  minimizes the chances of pleat deformation and woven wire deterioration of the filter media  19  from abrasion during pleat movement. 
         [0035]    Referring now to  FIG. 15 , in the preferred embodiment, an outer support structure  41  is a stainless steel flattened expanded metal shroud with 80% open area. This expanded metal outer shroud provides improved backwash support for the filter media  19 . The structure  41  includes the angle iron legs  25 . 
         [0036]    Referring now to  FIG. 16 , the 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  of the support structure  41  is 0.050 inches. 
         [0037]    Referring now to  FIG. 4 , a second outer support structure  50  includes the top flange plate  22 , with two 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 outer support structure  50  also includes the bottom ring  26 , which has four one-inch risers  54  welded to it, to keep the entire filter assembly off the ground during manufacturing. As noted with reference to  FIG. 1 , the outer support structure  50  includes eight cap tie rods  24  threaded into the top end cap  20  and the bottom end cap  23 , and angle iron legs  25  welded to the top flange plate  22 , to a bottom ring  26 , and to an angle iron horizontal support  27 . 
         [0038]    Referring now to  FIG. 5 , an inner support structure  60  includes a perforated core  62  that contains rings  64  with cross-braces  66 . At the top of the core  62  are clips  68  that are bent over to hold in place the filter media  19 . 
         [0039]    Referring now to  FIG. 6 , the second outer support structure  50  of  FIG. 4  is shown together with the pleated woven wire filter media  19 . 
         [0040]    Referring now to  FIG. 7A , a top plan view of the filter  18  shows the perforated core  62  surrounded by the pleated woven wire filter media  19  surrounded by the horizontal bands  42 . Also shown is the top end cap  20 , the top flange plate  22 , and the lifting lugs  52 , one of which is shown in a separate side view in  FIG. 7B . 
         [0041]    Referring now to  FIG. 8 , the top flange plate  22  includes threaded bolt holes  78  that are machined into the top flange plate  22  to fasten the top end cap  20  to the plate  22  with the B-7 stud bolts  28 . 
         [0042]    Referring now to  FIG. 9 , the top end cap  20  includes an inner perimeter lip ring  70 , an outer perimeter lip ring  72 , and a one-inch thick metal plate  80 . The bottom end cap  23  includes an inner perimeter lip ring  74 , an outer perimeter lip ring  76 , and a three-quarter-inch thick metal plate  82 . 
         [0043]    Referring to  FIG. 10 , the filter media  19  is shown attached to the perforated core  62 , which contains rings  64  with cross-braces  66 , as also shown in  FIG. 5 . 
         [0044]    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  20  to the top flange plate  22 . 
         [0045]    Referring to  FIG. 12 , the bottom end cap  23  includes the inner perimeter lip ring  74  for aligning the perforated core  62 , the outer perimeter lip ring  76 , and the round bar tie rods  24  that connect the bottom end cap  23  to the top end cap  20 . 
         [0046]    Referring to  FIG. 13 , the top end cap  20 , including the inner perimeter lip ring  70 , the outer perimeter lip ring  72 , and the stud bolts  28 , is shown connected to the round bar tie rods  24  that connect the bottom end cap  23  to the top end cap  20 . 
         [0047]    Referring to  FIG. 14 , the bottom end cap  23 , with the inner perimeter lip ring  74  and the outer perimeter lip ring  76 , is shown attached by the round bar tie rods  24  to the top end cap  20 . 
         [0048]    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&#39; efficiency ratings for the specific micron rated metal woven wire media that will satisfy process conditions. 
         [0049]    The following definitions apply for the three equations listed below: 
         [0050]    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. 
         [0051]    C is the circumference in inches of the perforated core  62 . 
         [0052]    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. 
         [0053]    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. 
         [0054]    H is the pleat height. The maximum pleat height for micron rated metal woven wire is forty-eight inches. 
         [0055]    S is the surface area of the filter media  19 . 
         [0000]    
       
      
       C=πD  
      
     
         [0000]      4 C=N    
         [0000]      (2 P ) NH=S    
         [0056]    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. 
         [0057]    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 stainless steel micronic 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. 
         [0058]    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.