Abstract:
A slow setting resin-bonded taphole mix consisting essentially of a uniform admixture of a refractory grog and a bonding composition consisting essentially of a low volatile high softening point phenolic resin, a high boiling point for said resin, and a clay, and the method of using said mix to seal tapholes.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to taphole mixes for use in metal-making furnaces and particularly large production blast furnaces. 
     At the present time variety of refractory materials are utilized to seal tapholes in such furnaces but have not been found to be satisfactory, particularly for high temperature extrusion. Most satisfactory to date have been those refractory grogs wherein the grog is bonded by a combination of clay and either pitch or creosote. While pitch and creosote bonded grogs for use as taphole mixes are operable, they are not entirely satisfactory in that they give off toxic fumes and accordingly are hazardous to use. Moreover, the pitch and/or creosote bonded refractory grogs are more difficult to remove from the taphole; as by drilling, after use. 
     Attempts to overcome this problem by using resin-bonded refractory grogs have not proven successful for a variety of reasons. Amongst other reasons, they are more costly than the pitch and creosote, set too rapidly, and have insufficient hot strength after the taphole mix is put into place, thus effectively precluding their use in large production blast furnaces in which high temperatures are attained. 
     SUMMARY OF THE INVENTION 
     The resin-bonded taphole mix of the present invention overcomes the problems of the prior art to provide a low cost, effective, non-toxic, high temperature extrudable mix suitable for use in metal-making furnaces, including high temperature blast furnaces. 
     Briefly, the present invention comprises a slow setting resin-bonded taphole mix consisting essentially of a substantially uniform admixture of a refractory grog and a bonding composition consisting essentially of a clay, a low volatile high softening point phenolic resin, and a high boiling point solvent. The invention also comprises the method of closing a taphole comprising applying to said taphole the foregoing mix and curing said mix. 
     DETAILED DESCRIPTION 
     The two essential components of the present invention are the refractory grog and the bonding composition. As to the refractory grog, it can be any alumina, grog, silica grog, calcined fire clay grog, pyropholite grog, fused alumina grog, fused mullite grog, sintered alumina grog, or mixture thereof presently used in taphole mixes. Conventionally, these grogs also contain materials to give increased slag resistance such as silicon carbide, graphite, or other carbon forms or mixtures thereof. 
     In the present invention, it is preferred to use a grog consisting essentially of alumina-silica calcines, fused alumina with silicon carbide and graphite. 
     The proportions by weight of the various components in the grog in the present invention are not critical so long as the components are present in amounts sufficient to give the strength and other properties required for the particular conditions of the metalmaking furnace in which the taphole mix is to be utilized. For high temperature use; such as blast furnaces, it is also in some cases advisable to add silicon in an amount sufficient to increase the mix&#39;s hot strength after cure; although this does add to cost. The amount of silicon added will vary dependent upon the particular grog used, but is suitably about 1.5 to 3 parts by weight for each 100 parts by weight of the refractory grog and clay in the mix. 
     With respect to the bonding composition, clay has been utilized in the past together with the creosote or pitch for bonding purposes and it is again utilized for this same purpose. The novelty of the present invention is to utilize a low volatile high softening point phenolic resin and a high boiling point solvent for said resin which is compatible therewith. As previously noted, resins have not been satisfactory before since resin bonds and systems set up so much faster than pitch-creosote systems that it precluded their use from large production blast furnaces where high temperatures are utilized. 
     As to the clay used in the bonding composition, it can be any conventionally used for that purpose such as ball clays, bentonites, and the like and mixtures thereof. 
     The two critical elements in the bonding composition are the phenolic resin and the high boiling point solvent therefor. It is preferred to use a solid rein; most suitably a powdered one, although predissolved resins can also be used. The powdered phenolic resin must have, as noted, low volatiles and high softening point. Suitable for this purpose are the novolac resins with softening points above about 220° F.; such as RD 2477 from BORDEN INC. 
     With respect to the solvent, it must not only be compatible with the resin, but have a boiling point above about 550° F., particularly when being utilized in high temperature blast furnaces. Most suitable for this purpose is triethylene glycol; although other solvents such as tetraethylene glycol and the like, or mixtures thereof can be utilized. 
     As to proportions, while large amounts of resin, such as 12% by weight based on 100 percent by weight of the mix (refractory grog, clay, and silicon (if any)) can be utilized, from a cost viewpoint, as well as effectiveness, it has been found that amounts as low as 4% can be utilized, although it is preferred to utilize from about 6% to 8% by weight. Correspondingly, larger amounts of the solvent would be required with the larger amounts of resin, but solvent also can be utilized in an amount preferably from 8% to 11% by weight, although amounts from about 7% to 15% can be utilized. 
    
    
     The invention will be further illustrated in connection with the following examples which are set forth for purposes of illustration only. In these examples, the workability index, green bulk density, cold and hot crush strength, drip slag test and extrusion pressure testing are determined utilizing the conventional apparatus and procedures for that purpose in testing taphole mixes. Also, the proportions of materials in the mix is in percent by weight, with the plus additions; resin and solvent, being based on 100% by weight of the mix. 
     EXAMPLES 1-4 
     A series of mixes was prepared by admixing in the conventional manner various refractory grogs and utilizing a typical pitch bonding in one mix and a phenolic resin and solvent therefor as the bonding agent for the other mixes. The various components of the mixes and the results of the tests thereon are shown in Table I below. 
     
                                           TABLE I__________________________________________________________________________              EXAMPLESMix Designation:   1    2    3     4__________________________________________________________________________Mix:Calcined Fire Clay Grain -(Mo. Flint Grain)3/10 mesh           18%10/28              1628/65               6Ball Mill Fines (BMF)              32   32   29.5  27Crude Kyanite (-100 mesh)              10P-Carb              3Amorphous Graphite (MEXALOY)               5Ball Clay (GLEASON)              10   10   12.5  15Plus Additions:Powdered Pitch     10.5 --   --    --Methyl Napthaline  10.5 --   --    --Powdered Phenolic Resin              --   8    8     8(BORDEN RD 2477)Triethylene Glycol --   9.5  9.5   10Mix Temperature, °F.:              117  104  107   116Workability Index: 47   25   24    28Extrusion Pressure at 300° F.To initiate flow:  50   30   50    40To maintain flow:  90   40   60    50Cold Crushing Strength, kPa              6330 8530 12110 10600After drying at500° F. (Av 3):Weight Loss, %     6.9  4.5  4.8   5.4After Heating at 500° F. (Av 3):Reheat Change after 30 min at 2000° F., ReducingLinear Change, Ht, %:              +1.5 +0.1 +2.4  +1.7Linear Change, Dia., %:              +3.6 +5.5 +4.8  +4.3Weight Loss, %:    14.2 14.5 14.3  14.5Hot Crushing Strength at 2000° F.,              760  750  820   660psi: (load rate was 400 lbs/min)Drip Slag Test at 2900° F. using              50   59   --    --500 g of Duquesne BF Slag (Reducing)Volume loss, cc:__________________________________________________________________________ 
    
     EXAMPLES 5-11 
     The procedures of Examples 1 to 4 were followed but using different grogs and different proportions of resin and solvent. The results are set forth in Table II below. 
     
                                           TABLE II__________________________________________________________________________         EXAMPLESMix Designation:         5    6     7     8     9     10    11__________________________________________________________________________Mix:Calcined Alumina-silica(Ucal 60)3/10 mesh           12%10/28 mesh         1128/65 mesh          5BMF           25   27    30    32    29.5  32    27Silicon Carbide (DCF)         15   15    10    10    10    10    15Crude Kyanite (-100 m)              10Amorphous Graphite         7.5  7.5   7.5   7.5   10    7.5   7.5(MEXALOY)Silicon (-100 m)         2    --    2     --    --    --    --Ball Clay (GLEASON)                12.5Plus Additions:Phenolic Resin (BORDEN         8    8     8     8     8     6     6RD 2477)Triethylene Glycol         10.25              10.25 10.25 10.01 10.0  10.25 10.25Mixing Time, min:         8    8     7     6     6     10    8Mix Temperature, °F.:         110  114   119   117   122   111   115Workability Index         25   27    29    31    25    22    21(14 lb weight):Green Bulk Density, pcf         143  143   143   144   142   145   145(Av 3):Cold Crushing Strength, psi         2200 18200 19400 17800 17300 14000 14100After Curing 6 hours at500° F. (Av 3):Hot Crushing Strength, psi         1200 800   1000  570   790   980   --At 2000° F.:Drip Slag Testing at 2800° F.         11   --    --    --    --    21    --Using 1000 gms Duquesne BFslag, ReducingVolume Eroded, cu cm:Extrusion Pressure, psi300° F., 2 hour holdInitial:      50   --    --    --    --    120   --Hold:         380  --    --    --    --    520   --Raw Stock Cost, $/ton:         396  366   369   339   344   314   342__________________________________________________________________________ 
    
     In all instances with the resin-bonded products of the present invention there was lower fuming, none of the toxicity that is present with pitch and creosote, as well as the ability to have high temperature extrusion. Also the mix of the present invention extrudes easier and more quickly at all temperature levels thus resulting in lower strain in the mud gun used to apply the mix to the taphole. 
     Moreover, the resin-bonded mixes were softer and acted to plug up any cracks appearing in the taphole. Moreover, the resin was easier to clean out and drill out than with the pitch or creosote bonded resins. 
     While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but, on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.