Abstract:
Cold-reduced flat-rolled low carbon steel strip is surface cleansed of ferromagnetic contaminants including iron fines, iron oxide particulate and associated debris which result from gauge-reduction operations. Such ferromagnetic contaminants are permanently removed from the strip steel hot-dip galvanizing system by dynamically concentrating such contaminant which are flushed to a magnetically-assisted particle separation container, formed from paramagnetic sheet material, which retains such contaminants, while cleansing solution at a desired purity level, is returned to the surface cleansing system; with sedimentation tank means providing for diminishing waste disposal concerns by separating sludge and recycling liquid.

Description:
RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part of co-owned and copending U.S. patent application Ser. No. 09/121,109, filed Jan. 23, 1998, which was a continuation-in-part of copending and co-owned application Ser. No. 08/794,783, filed Feb. 3, 1997, entitled CONTINUOUS PARTICLE SEPARATION OPERATIONS (now U.S. Pat. No. 5,830,282) which was a continuation-in-part of copending and co-owned application Ser. No. 08/445,530, filed May 23, 1995, entitled APPARATUS FOR CONTINUOUS FLAT-ROLLED STEEL STRIP CLEANSING AND FINISHING OPERATIONS (now U.S. Pat. No. 5,599,395). 
     
    
     
       INTRODUCTION  
         [0002]    This invention relates to finishing operations involving hot-dip zinc spelter coating strip steel. In its more specific aspects this invention is concerned with minimizing aqueous requirements for caustic cleansing solution supply purposes; and, with substantially-eliminating aqueous waste discharge from surface-cleansing operations.  
         OBJECTS OF THE INVENTION  
         [0003]    An important object is to provide for continuing uniform surface cleansing by maintaining uniform purity-level standards for the cleansing solution.  
           [0004]    Another object is to enable minimizing of waste disposal, in particular, substantially-eliminating contaminated waste water disposal. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0005]    [0005]FIG. 1 is a schematic general arrangement view for describing method and apparatus combinations of the invention;  
         [0006]    [0006]FIG. 2 is a more detailed view of the circulating system for surface cleansing solution of the invention;  
         [0007]    [0007]FIG. 3 is a more detailed view of a magnetically-assisted particle separator embodiment of the invention;  
         [0008]    [0008]FIG. 4 is side-elevational view of the sludge-separator sedimentation tank of the invention, and  
         [0009]    [0009]FIG. 5 is an end elevated view of the tank of FIG. 4. 
     
    
     DETAILED DESCRIPTION  
       [0010]    Contaminants, to be separated caustic surface cleansing solution during preparation of flat-rolled steel for finishing operations, comprise iron fines, particulate-iron oxide and associated debris. Priority levels for the cleansing solution are measured in parts per millions (ppm) of iron fines.  
         [0011]    In continuous strip finishing mills, large surface areas of strip are handled per unit time; and, the solid contaminant quantities of iron fines from thickness gauge cold reduction operations, iron-oxide largely resulting from hot rolling operations, and associated debris-resulting from the use of cold rolling oil, have in the past, required dumping large-capacities of contaminated surface cleansing solutions. Contaminated cleansing solution, from large capacity facilities have required periodic dumping of large amounts of contaminated solution; which must then be fully replenished so as to involve an interruption in operations. Dependent on production deadlines there can be a tendency to allow “purity levels” to rise significantly above a desired level.  
         [0012]    Also, any requirement to dump those large contaminated quantities, as taught herein, results in non-uniform surface cleansing during line operation; which adversely effects the hot dip coating operations, the hot-dip coating apparatus, and is also detrimental to continuously annealing equipment located in-line between the surface cleansing-operation and the hot dip coating apparatus.  
         [0013]    The present invention provide uniform surface cleansing solution and solves waste disposal problems now being experienced by mills in certain localities.  
         [0014]    In the embodiment of FIG. 1, leading and trailing edges of cold rolled strip, from coils  10  and  12 , are trimmed and directed, for joining of such trimmed edges, into strip welder  14 , so as to maintain continuous strip  15  during hot dip zinc-spelter coating finishing operations.  
         [0015]    For surface cleansing, continuous strip  15  is directed into a cleansing tank means  16  having a large capacity for surface cleansing solution.  
         [0016]    Surface brushing stations  18  and  19  can augment the action of the caustic cleansing solution  20 , in the cleansing tank means  16 .  
         [0017]    Strip  22  travels from cleansing tank  16  into continuous annealing furnace  24 , for heating to a temperature of about 1000° F. in a non-oxidizing, preferably mildly-reducing, atmosphere to prevent surface oxidation; that atmosphere continues for subsequent introduction of the strip, at about 900° F., into a hot-dip zinc-spelter coating bath (not shown).  
         [0018]    Combinations of apparatus for maintaining desired purity level surface-cleansing solution are shown, and the combinations of steps are described, in relation to FIG. 1.  
         [0019]    During the surface cleansing operation, solution  20  is continuously, and controllable, withdrawn from holding means  16 , and directed, for example, by conduit  25  of FIG. 1 into a dynamic action continuous filter, such as cyclone  26 . The centrifugal force of cyclone apparatus  26  directs contaminants toward the side walls for accumulation and continuous-flushing removal at outlet  27 , through conduit  28 .  
         [0020]    The filtrate, from which a significant percentages of contaminants are separated, is returned through conduit  29  to facility cleansing tank means  16 .  
         [0021]    To assist compliance with restrictive sewer-disposal provisions, flushed contaminants are directed, in accordance with the invention, through conduit  28  to magnetically-assisted separator unit  30  (FIG. 1). A more detailed view, of the circulating system arrangement is shown in FIG. 2; and, also of the magnetically-assisted separator embodiment of the invention is shown in FIG. 3.  
         [0022]    Referring to the schematic general-arrangement view of FIG. 1, magnetically-separated contaminants are retained in separator  30 ; and, the purified liquid portion of the material flushed disclosure from cyclone  26  are returned, through conduit  32 , to cleansing tank means  16 .  
         [0023]    Purity level, of the returning liquid is measured at the sampling station shown by means gauge  34 .  
         [0024]    Contaminated solution from separator unit  30  can be released promptly, including by washing the interior of that, unit. Drain valves  35 ,  36 , direct contaminated discharge from unit  30 , through conduits  37 ,  38  and  39 , for sludge separation.  
         [0025]    Capacities are selected such that the surface-cleansing operation need not be interrupted for removal of contaminants. Magnetically-assisted particle separator  30  has a capacity equal to about ten percent of the capacity of the surface-cleansing facility  16 ; and sludge-separating sedimentation tank  40  of FIG. 1 has about thirty percent more capacity than that of separator unit  30 .  
         [0026]    Semi-solid sludge is transferred from sedimentation tank  40 , by auger  42 , into drum containers, such as  44  of FIG. 1. Such sludge can be directed to a sintering plant for forming pellets for recycling in an iron-production unit and other recycling measures; or, can be directed for solid waste-site disposal.  
         [0027]    The solution in sedimentation tank  40  is decanted, from selected height-levels of tank  40 ; starting at the uppermost level, by use of valves  46 ,  47 ,  48  of each with associated conduits, as shown in FIG. 1.  
         [0028]    Sludge is concentrated for removal by auger  42 , with about eighty-five to about ninety-five percent of the liquid received from magnetically-assisted separator unit  30 , being sufficiently free of sludge for recycling through the magnetically assisted separator  30  and return to surface cleansing. Pump  50  (FIG. 1), by means of conduit  52  and control valve  53 , returns surface cleansing liquid, as shown, from selected levels designated by valves  46 ,  47 , and  48 . Separator unit  30  purifies decanted liquid for recycled use in the surface cleansing system.  
         [0029]    Also, caustic, and fresh caustic cleansing solution, to compensate for losses due to evaporation and/or product “drag-out”, are augmented from source  54  (FIG. 1) through conduit  56 . Valves  58 ,  59  are positioned to direct solution from source  54  and to return from purified liquid from separator unit  30 , and to return the filtrate from cyclone  26  to selected locations of the surface cleansing facility, along the elongated holding means  16 .  
         [0030]    In FIG. 2, like reference numbers are used, where possible, in describing the solution circulation system in more detail. Strip  15  is fed into the surface cleansing location, combines surface brushing components in portion  60  and added cleansing solution in wash portion  61 . Surface-cleansed strip  22  is then directed for further in-line processing. The combined cleansing solution capacity of solution  60 ,  61  is about five thousand gallons.  
         [0031]    Purity level of the surface cleansing liquid in ppm iron fines can be measured at gauge sampling locations  62 ,  63  and  64 . One method is to remove contaminated solution at strip entry ends of elongated tank portions  60 ,  61 ; and, to return desired purity-level solution to the strip exit area of portion  61 , for counterflow, in relation to the strip, in the surface cleansing system. Such counter-flow can significantly diminish particle quantities carried out, by the strip, into the annealing furnace.  
         [0032]    Valves  65  and  66  (FIG. 2), at the entry and exit of particle separator  30 , enable isolation of that particle separator for drainage into sedimented tank  40  (FIG. 1).  
         [0033]    The magnetically asserted particle separator  30  (shown in FIG. 1 and  2 ), utilizes paramagnetic polymer sheet material in forming the interior and exterior walls of FIG. 3 polypropylene which can be bonded together to provide the desired capacity and direction of flow of solution being decontaminated. Permanent magnets are supported on polymer coated plain carbon steel, or a paramagnetic stainless steel, frame so as to capable of being pivotally-rotated, as mounted on an exterior wall to terminate the magnetic flux action internally, for assisting in removal of contaminated contents.  
         [0034]    As shown in FIG. 3, permanent magnets are mounted in rows  66 ,  67 ,  68 ,  69  and  70  along the longitudinal end of separator unit  30  as shown in FIG. 3; and, can be mounted along side walls for higher separation capacity than that of the specific embodiment being disclosed.  
         [0035]    Pivotally-mounting the magnets externally, enables those magnets to be readily moved into an orientation at an angle to the wall surface, such that lines of magnetic flux are no longer acting internally of unit  30 .  
         [0036]    Permanent magnets can be housed internally between polymer sheets at centrally-located wall petitions; such internal mounted magnet would not be pivotally mounted; however, contaminants retained by such magnets can be washed from adjacent polymer surfaces using pressurized water supply available at mill sites. And, such pressurized water supply can be used to augment removal from the internal wall surfaces of which have externally mounted magnets.  
         [0037]    Floatation froth detainer  72  at the exit end of unit  30 , prevents floating debris from being pumped into the surface cleansing system. The capacity of unit  30  is about five hundred gallons; and, can be withdrawn simultaneously at both longitudinal end valves  35 ,  36 ; or from a single longitudinal end portion of unit  30  by using a single valve separately.  
         [0038]    Magnetically-assisted separator  30  can be drained and washed-down promptly, at any time, without interrupting surface cleansing operations. Typically, it would be drained when the return solution, at sampling gauge  32 , shown in both FIGS. 1 and 2, exceeded a desired purity level, such as about fifty ppm iron fines. However, unit  30  can be drained promptly at any time, and would ordinarily be drained, and circulation continued, during regular periodic maintenance periods for the processing line. Continuing the solution circulation system of FIG. 2 at such time decreases the level of contaminant fines well below a desired operating maximum of about fifty ppm.  
         [0039]    Contaminated cleansing solution drained, through valves  35 ,  36 , of magnetically-assisted separation unit  30 , is directed to inlet pipe  76 , got entering into a polypropylene sludge-separation sedimentation tank  40 , shown in more detail in FIGS. 4 and 5. A polypropylene auger  42  is located at the intersection of floor panels  78 ,  79  of sedimentation tank  40 , such panels are angled downwardly for semi-solid sludge to auger  42  for removal.  
         [0040]    Liquid decanting valve means  46 ,  47 ,  48  are each shown at its respective decanting level in FIGS. 4 and 5. Sedimentation tank  40  is covered by cover plates shown at  80 ,  81 ,  82  in FIG. 4; a vent port  84  is provided as shown in FIGS. 4 and 5.  
         [0041]    The magnetically-assisted particle separator  30 , sedimentation tank  40 , and auger  42  preferably fabricated from an engineered polymer, such as polypropylene.  
         [0042]    The cleansing caustic is available from Elf Autochem North America, Inc., 2375 State Road, Cornwall Heights, Pa. 19020; and separation equipment  26 , for dynamic flow separation of solids and liquids, is available from Lakos Separators USA, 1911 North Helm Avenue, Fresno, Calif. 93727; interval or continuous flushing of purged material is available on such units.  
         [0043]    For purposes of measuring iron fines in ppm, five thousand gallons of cleansing solution are equal to slightly more than six hundred thousand ounces of solution. The embodiment being disclosed can maintain a uniform low level of less than about thirty ppm iron fines, by using six hundred gauss magnets, supplied by Eriez Magnetics, of Erie, Pa., under the heading of “Extra Power 600”. Added strength magnets extending to about fifteen hundred gauss are available.  
         [0044]    Applicable data for continuous-strip zinc spelter cleansing operations, for a continuous hot-dip coating line, are set forth below:  
                           TABLE I                                       Surface Cleansing Solution   about 5,000 gals           Holding and Scrubbing Tank 16           Withdrawal Rate of Dynamic   about 2,700 gals/hr           Filter Apparatus 26           Rate of Filtrate Return from 26   about 2,300 gals/hr           Magnetically-Asserting   about 500 gals           Separator 30, Capacity           Rate Flushed Purged From 26   about 400 gals/hr           Magnet Field Strength   600 gauss per magnet           Number of Magnets Per Row   4           Total Magnets on Entrance Side Endwall   12            Total Magnets on Exit Side Endwall   8           Capacity of Sludge-Separation   about 650 gals.           Sedimentation Tank 40                      
 
         [0045]    While specific materials, capacities, flow rates and other data have been set forth for purposes of describing an embodiment of the invention, it should be recognized that in the light of the above teachings, those specifics can be changed without departing from the principles of the invention; therefore is determining the scope of patentable subject matter, references should be made to the appended claims, as well as the above description.