Abstract:
A monolithic refractory composition having relatively high thermal conductivity and a relatively high degree of water insolubility consisting essentially of, by weight, 50-75% coarse grain flake graphite; 5-30% fine grain flake graphite; and the remainder crude clay; and the addition based upon the total weight of said mix of 10-25% liquid phenolic resin in combination with an alcoholic solvent, and a resin curing agent.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to compositions particularly suited for the formation of refractory monoliths, and in particular to such a composition for forming a ramming mix for use as a cooler plate packing material in blast furnaces. 
     Monolithic or monolith forming refractories are special mixes or blends of dry granular or stiffly plastic refractory materials, with which virtually joint free linings are formed. They embrace a wide range of mineral compositions and vary greatly in their physical and chemical properties. In various types of furnaces, monolithic refractories are used to advantage over brick construction. The use of monolithic refractories enables the installation to be made in a relatively short period of time whereby any delays resulting from a required manufacture of special brick shapes may be avoided. Further, the use of monolithic refractories frequently eliminate difficult brick laying tasks. The use of monolithic refractories is of particularly importance in the maintenance of furnaces. Substantial repairs may be made with a minimum loss of time, and in some instances, even during continued operation of the furnace. 
     A ramming mix is one type of composition typically used to create a monolith. One application of a ramming mix involves the use thereof as a cooler plate packing material in blast furnaces. Requirements for the ramming mix to satisfy the needs of this particular application include relatively high thermal conductivity, a dried cold crushing strength of at least 1000 psi, reheat stability at 1000° F., ramming mix or platic consistency, a relatively high degree of water insolubility, and a curing temperature not exceeding 250° F. Although some ramming mixes satisfy one or more of the required properties, the ramming mix of the present invention satisfies all of the properties. Further, the present ramming mix is sold as a single component and has a four-month shelf life. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of this invention to provide a ramming mix particularly suitable for use as a cooler plate packing material in blast furnaces and having the following properties: 
     (1) relatively high thermal conductivity; 
     (2) dried cold crushing strength of at least 1000 psi; 
     (3) reheat stability at 1000° F. (linear shrinkage not exceeding 1.5%); 
     (4) ramming mix or plastic consistency; 
     (5) a relatively high degree of water insolubility; and 
     (6) a curing temperature not exceeding 250° F. 
     The above objective is attained in a monolithic refractory batch composition comprising, by weight, 50-75% relatively large grain flake graphite; 5-30% relatively micronized flake graphite; approximately 20% ball clay, said batch further containing, based on its total weight, 10-25% liquid phenolic resin in combination with an alcoholic solvent, and 0.5-2% resin curing agent. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A commercial need was identified for a refractory to be used as a packing material for a blast furnace shell and cooler plate, having the following properties: 
     (1) thermal conductivity of 75 Btu/ft 2  --Hr.°F/in. at 1500° F. (in the &#34;fast&#34; direction); 
     (2) dried cold crushing strength of at least 1000 psi; 
     (3) reheat stability at 1000° F.; and 
     (4) ramming mix or plastic consistency. 
     As used herein, the term &#34;fast&#34; direction is the measurement of conductivity in a direction taken perpendicular to that in which the material is pressed in applying the same, while the &#34;slow&#34; direction corresponds to measurement of the thermal conductivity in the direction taken parallel to that in which the material is pressed or rammed. 
     Initially, it is presupposed that a monolith refractory based on silicon carbide and/or flake graphite could be produced to meet the above requirements. Initial work included evaluation of a series of bench scale mixes consisting of silicon carbide, graphite and clay. This was done to determine the effect, if any, that the addition or elimination of graphite to a commercial ramming mix would have on the Mix&#39;s plastic consistency. Referring to Tables I and II, poor plastic properties and reduced crushing strength in Mixes E, E-1 and F corresponded to the inclusion of flake graphite in amounts exceeding 12.5%. Mix A had the highest cold crushing strength (900 psi) after drying. The thermal conductivity of a ramming mix containing 10% flake graphite, was 45.8 Btu/ft 2  --Hr.°/in. at 1500° F. in the &#34;fast&#34; direction. Consequently, it was assumed that the thermal conductivity of Mixes D through G would not meet the desired goal of at least 75 Btu/ft 2  --Hr.°F./in. 
     
                                           TABLE I__________________________________________________________________________            Mix Designation:            A    A-1 A-2 B    B-1  C   C-1 D__________________________________________________________________________Mix:Silicon Carbide -8/+16 mesh     40%-16/+30 mesh      5%-30/+50 mesh     10%-50/+100 mesh     5%Silicon Carbide DCF            30   30  35  25   25   20  20  151631 Flake Graphite            --   --  --  --   --   --  --  10Mexaloy Graphite --   --  --  --   --   --  --  --M &amp; D Ball Clay  10   --  --  15   --   20  --  15Jackson Ball Clay            --   10  --  --   15   --  20  --SPV Volclay      --   --   5  --   --   --  --  --Plus Additions:Silicanit         2%Water (for pressing)             7.3 6.8 8.8  7.7  7.8 8.1 8.0  8.6Water (for storage)            10.3 7.9 9.8 12.7 10.8 9.6 9.0 10.6Bulk Density, pcf (Av. 3)After Heating 18 Hrs. at 250° F.:            156  158 150 155  155  154 152 147After Heating 5 Hrs. at 2000° F.:*            156  156 149 152  152  150 148 144Apparent Porosity, % (Av. 3)            20.1 19.4                     23.0                         20.9 20.7 21.6                                       22.7                                           22.6After Heating 5 Hrs. at 2000° F.:*Reheat 2000° F. (Av. 3)*Linear Change:   -0.3.                 -0.2                     +0.2                         ±0.2                              ±0.3                                   ±0.3                                       -0.3                                           -0.3Volume Change:   -0.8 -0.2                     -0.2                         -0.4 -0.3 -0.3                                       -0.7                                           -0.8Cold Crushing Strength, psi            900  890 740 730  740  640 600 630After Heating 18 Hrs. at 250° F.Workability (Storage Data)            40   40  35  37   43   37  39  3314# wt. as Made for PressingTempered for Storage            43   50  50  50   45   43  44  46            (5# wt.)     (5# wt.)                              (5# wt.)After One Week   29   26  32  56   31   31  30  33            (5# wt.)          (5# wt.)After One Month  42   21  24  55   50   24  23  33After Two Months 33   22  25  49   39   21  19  33After Three Months            37   16  24  44   35   18  15  38__________________________________________________________________________ *Reducing conditions. 
    
     
                                           TABLE II__________________________________________________________________________            Mix Designation:            D-1 D-2 E   E-1 E-2 F   G__________________________________________________________________________Silicon Carbide -8/+16 mesh     40%-16/+30 mesh      5%-30/+50 mesh     10%-50/+100 mesh     5%Silicon Carbide DCF            15  20  12.5                        12.5                            15  15  151631 Flake Graphite            10  --  12.5                        12.5                            --  15  --Mexaloy Graphite --  10  --  --  15  --  15M &amp; D Ball Clay  --  --  15  --  --  10  10Jackson Ball Clay            15  --  --  15  --  --  --SPV Volclay      --  10  --  --  10  --  --Plus Additions:Silicanit         12%Carboxymethyl Cellulose            --  --  --  --  --   0.75                                     0.75Water (for pressing)             8.5                 9.7                     8.5                         8.6                            10.0                                12.6                                    13.5Water (for storage)            10.0                11.2                    10.0                        10.1                            11.1                                14.6                                    15.5Bulk Density, pcf (Av. 3)After Heating 18 Hrs. at 250° F.:            146 144 145 144 140 131 125After Heating 5 Hrs. at 2000° F.:*            143 142 142 141 137 129 124Apparent Porosity, % (Av. 3)            22.8                23.8                    23.2                        23.1                            25.1                                30.1                                    32.1After Heating 5 Hrs. at 2000° F.:*Reheat 2000° F. (Av. 3)*Linear Change:   -0.2                -0.4                    ±0.2                        -0.2                            -0.2                                -0.1                                    ±0.4Volume Change:   -0.5                -0.5                    -0.4                        -0.7                            -0.4                                -0.5                                    -0.4Cold Crushing Strength, psi            600 750 540 510 600 560 280After Heating 18 Hrs. at 250° F.Workability (Storage Data)            35  30  32  39  32  35  3514 # wt. as Made for PressingTempered for Storage            50  43  43  50  46  46  46After One Week   43  36  26  36  38  36  38After One Month  34  33  29  39  38  52  50After Two Months 31  32  28  34  35   60+                                     60+After Three Months            30  32  28  35  37  --  --__________________________________________________________________________ *Reducing conditions. 
    
     Referring to Table III, there is shown the results of the testing of a second series of mixes. The second series of mixes, labeled H through L, were made from a batch including silicon carbide, clay and increased amounts of either Mexaloy, micronized amorphous, or micronized flake graphite. These mixes also contained a powdered pitch addition to improve crushing strength after drying. Mixes I, K and L included micronized flake graphite. These mixes required additional quantities of water for forming the monolith and consequently, the density of the monolith was significantly reduced. The thermal conductivity of Mix H and J was determined to be 30 Btu/ft 2  --Hr.°F./in. in the &#34;slow&#34; direction. None of these mixes proved commercially acceptable. 
     
                                           TABLE III__________________________________________________________________________             Mix Designation:             H    I   J    K   L__________________________________________________________________________Mix:Silicon Caribde -8/+16 mesh       40%  40%                       40%  40%                                28%-16/+30 mesh       5    5  10    5  10-30/+50 mesh      10   10   5   10   4-50/+100 mesh     --    5  --    5  --Silicon Carbide, DCF             --    5  --   --  --Ashbury Micronized Graphite #505             30   --  --   --  30Ashbury Micronized Graphite #FG             --   20  --   27  10Mexaloy Graphite  --   --  40   --  --Powdered Pitch    10   10  10   10   8M &amp; D Ball Clay    5    5   5   --SPV Volclay       --   --  --    3  --Plus Additions:Silicanit         2%Water (for pressing)             10   12  12   14  14Water (for storage)             13   21  16   23  23Bulk Density, pcf (Av. 3) As Made:             134  127 134  120 124After Heating 18 Hrs. at 250° F.:             124  116 120  107 110After Heating 5 Hrs. at 2000° F.:*             118  112 114  --  --Method of Forming:             21/8&#34; × 2 1/2&#34; Cylinders Pressed at 1000 psiCold Crusing Strength, psi (Av. 3)After Heating 18 Hrs. at 250° F.             930  650 950  370 690After heating 18 Hrs. at 400° F.             1380 1190                      1120 670 1090Workability (Storage Data)             29   35  42   25  295# wt. as Made:After One Week    25   30  41   24  23After One Month   49   62  27   19  20             (14# wt.)After Two Months  40   20  60   17  50             (14# wt.)                      (14# wt.)                               (14# wt.)__________________________________________________________________________ *Reducing conditions. 
    
     Additional mixes were prepared (M, N, O, P and R) as indicated in Table IV. These mixes were prepared as resin bonded, flake graphite plastics. These mixes contained 80 to 100% flake graphite (Asbury 3166A and Asbury micronized FG) with additions of alumina (M) or ball clay (N, O and P). The resin required to bring these mixes to a plastic consistency ranged from 35 to 50%. These mixes were pressable, but laminations and severe cracking occurred after drying of the pressed specimen. 
     
                       TABLE IV______________________________________      Mix Designation:      M     N       O       P     R______________________________________Mix:Asbury 3166A  50%     55%     60%   55%   60%GraphiteAsbury Micronized        30      30      30    30    410Flake Graphite, FGM &amp; D Ball Clay        --      15      10    15    --A-17 Alumina 20      --      --    --    --Plus Additions:ML-53 Resin  35      35      --    --    --RL-2302 Resin        --      --      --    50    50RM 441 Resin --      --      35    --    --Stadex       4.0     4.0     4.0   4.0   4.0Darvon C     0.10    0.10    0.10  0.10  0.10Method of Forming:        Six inch bars were pressed at 1000 psiObservation: None of these mixes had good compaction        properties and laminations resulted        after pressing.Bulk Density, pcf        100     93      102   100   93After Drying 18Hrs. at 500° F.______________________________________ 
    
     Additional mixes (X, Y and Z) were prepared as ramming mixes having reduced binder additions. These mixes are described in detail in Table V. Mixes Y and Z (100% flake graphite) contained reduced amounts of liquid resin, while Mix X contained water. Mix Y, having the 20% addition of ball clay, provided a mix with the best rammability. The thermal conductivity of Mix Y in the &#34;slow&#34; direction was 55.0 Btu/ft 2  --Hr.°F./in. at 1500° F. In contrast, Mix X had a thermal conductivity value of 35.0 Btu/Ft 2  --Hr.°F./in. at 1500° F. in the &#34;slow&#34; direction. The thermal conductivity for Mix Y was also determined in the &#34;fast&#34; direction. This was done by continuously ramming a large block of material and then cutting nine-inch straights from the block. The thermal conductivity was measured perpendicular to the direction of ramming. The thermal conductivity value for Mix Y in the &#34;fast&#34; direction was 82.6 Btu/Ft. 2  --Hr.°F./in. at 1500° F. This represents a difference of 27.5 Btu/Ft. 2  --Hr.°F./in. over the thermal conductivity value of the same mix in the &#34;slow&#34; direction. 
     
                       TABLE V______________________________________       Mix Designation:       X        Y         Z______________________________________Mix:Asbury 3166A   40%        50%       50%Flake GraphiteAsbury Micronized         30         30        50Flake Graphite FGM &amp; D Ball Clay         20         20        --Powdered Pitch         10         --        --Plus Additions:RM441 Liquid Resin         --         21        30Water         18         --        --Stadex         4          4         4Darvon C      0.10         0.10    0.10Bulk Density, pcf(Av. 3) As Made:After Heating 18 Hrs.         110        117       102at 500° F.After Heating 5 Hrs.         90         108       86at 1500° F.*Forming Pressure, psi: 1000         2000       1000Appearance After         Some lamina-                    Good com- SevereForming:      tions oc-  paction   laminations         curred in  properties                              occurred in         shape                pressed 9&#34;                              straightsCold Crushing Strength         650        1310      440psi (Av. 3) After Heat-ing 18 Hrs. at 500° F.:Linear Change, %After Heating 18 Hrs.         -0.8       -0.4      --at 500° F.After Heating 5 Hrs.         --         -1.2      --at 1500° F.:*Observed StorageBehavior:After 1 week  Good       Good      --After 1 month Good       Good      --After 2 months         --         Good      --Bulk Density, pcf (Av. 3)         --         103       --After RammingContinuously:After Ramming and         --         93        --Heating 18 Hrs.at 500° F.Appearance afterRamming And Drying at500° F. (Mix Y only)         Cut samples from large rammed         blocks were essentially lamination         free. The brick were submitted for         Thermal Conductivity Determination         in the &#34;Fast Direction&#34;.______________________________________ *Reducing conditions. 
    
     After heating at 1500° F., Mix Y had a linear change of -1.2% and a volume change of -3.8%. Table VI illustrates a comparison of the thermal conductivity between mixes H, J, X and Y. 
     Based upon the test work, it was determined that Mix Y would represent the best candidate for a graphite based high conductivity ramming mix. A sample of the mix was tested, with the evaluation of the test indicating that the mix was commercially satisfactory in all respects, except that it had a relatively high degree of water solubility and required a higher than desired resin curing temperature of 500° F. It was decided to conduct additional testing to develop a high thermal conductivity mix having a high degree of water insolubility and a curing temperature of about 250° F. Mix Y was used as the starting basis for the additional test work. 
     
                                           TABLE VI__________________________________________________________________________Thermal Conductivity on Selected Mixes*Mix Designation:H         J         X         Y         YSlow Direction     Slow Direction               Slow Direction                         Slow Direction                                   Fast DirectionMean Thermal     Mean Thermal               Mean Thermal                         Mean Thermal                                   Mean ThermalTempera-Conduc-     Tempera-          Conduc-               Tempera-                    Conduc-                         Tempera-                              Conduc-                                   Tempera-                                        Conduc-ture (°F.)tivity     ture (°F.)          tivity               ture (°F.)                    tivity                         ture (°F.)                              tivity                                   ture (°F.)                                        tivity__________________________________________________________________________ 323 23.73      323 25.40                311 24.59                          306 50.16                                   311  84.891065 26.03     1050 27.51               1146 26.74                         1154 46.0 1165 82.581805 33.98     1792 33.30               1781 38.94                         1838 56.66                                   689  85.941455 31.56     1445 32.07               1426 36.59                         1471 56.44                                   225  88.961089 28.86     1089 30.07               1044 35.05                         1088 55.04 720 26.88      717 27.96                660 36.00                          699 54.19 243 24.48      249 25.96                224 34.94                          236 56.23__________________________________________________________________________ *Argon Atmosphere Btu/Ft.sup.2 -Hr. °F./in. 
    
     Table VII illustrates the test work conducted on additional mixes AA-EE. A resorcinol type resin and various powdered phenolic resins were added to the mixes in an attempt to achieve the best water insoluble cure. Water solubility was measured by determining the weight loss of cured samples that were exposed to boiling water for six hours. Initial tests indicated that Mix EE, which contained RL-2302 resin manufactured by Borden Chemical Company (RL-2302 resin was formerly sold as ML-25R resin), showed the best water insolubility (lowest weight loss). RL-2302 resin is a phenolic resin which can be thermoset by the addition of a curing agent. As curing agent either hexamethylenetetramine (&#34;hexa&#34;) or stadex were used. The curing agents caused the resin to thermoset at relatively low temperatures at about 250° F. An alcoholic solvent such as ethylene glycol was also used in some instances. 
     
                       TABLE VII______________________________________          Mix Designation:          AA   BB     CC      DD   EE______________________________________Mix:Asbury 3166A     50      50    50    50    50Flake GraphiteAsbury FG110     30      30    30    30    30Micronized Flake GraphiteM &amp; D Ball Clay  20      20    20    20    20Plus Additions:RM441 Resin (65% solids)            25     --     --    --   --RL-2304 Resin    --      22    --    --   --SD 5132 Powdered Resin            --     --     10    --   --SD 5144 Powdered Resin            --     --     --    15   --RL-2302 Resin    --     --     --    --    22Ethylene Glycol  --       8    --    --    12Water            --     --     20    20   --Hexa             1.6    1.4    1.0   --   1.8Stadex           --     --     --    4.0  --Method of Forming:            1.5&#34; × 1.5&#34; Dia Cylinders Were            Pressed at 1000 psiBulk Density, pcf After            117      116  107   106   115Pressing at 1000 psi:After Drying 18  109     108   --    --    108Hrs. at 180° F.After Drying 12  --      107   --    --    108Hrs. at 250° F.*Cold Crushing Strength psiAfter Drying18 Hrs. at 180° F.:            --     1190   --    --   1050After Drying18 Hrs. at 250° F.:            --     1420   --    --   1370Water Solubility Test, %Weight LossAfter Drying at 180° F. and            6.3    4.2    Dissolved                                   2.4Boiling 6 Hrs.After Drying at 250° F. and            4.5    2.8    2.5   3.5  2.3Boiling 6 Hrs.______________________________________ 
    
     Additional tests were conducted as illustrated in Table VIII with newly prepared mixes FF-JJ. These mixes were all made with RL-2302 resin. In these mixes, the amount of Asbury FG micronized graphite was varied in the mix to determine the effect on rammability, pore size, and ultimately, thermal conductivity. A Mercury porosimetry test, conducted on Mixes GG, II and JJ, determined that Mix II had the smallest average pore diameter (5 microns). The thermal conductivity of Mix II was determined perpendicular to the direction of ramming (high thermal conductivity value or &#34;fast&#34; direction) and parallel to the direction of ramming (low thermal conductivity value or &#34;slow&#34; direction). 
     
                       TABLE VIII______________________________________      Mix Designation:      FF    GG      HH      II    JJ______________________________________Mix:Asbury 3166A 55      60      65    70     80Flake GraphiteAsbury FG110 25      20      15    10    --Micronized FlakeGraphiteM &amp; D Ball Clay        20      20      20    20     20Plus Additions:RL-2302 Resin        22      22      18    16     14Ethylene Glycol         7      2.5      3     3    2.5Hexa         1.8     1.8     1.8   1.5   1.2Method of Forming:        1.5&#34; × 1.5&#34; Dia Cylinders Were        Pressed at 100 psiBulk Density, pcfAfter Ramming and        --      --      --    112    98Drying at 250° F.After Pressing at        112     114     116   117   121100 psi:After Drying 18        108     111     112   113   116Hrs. at 180° F.After Drying 18        108     110     112   112   111Hrs. at 250° F.*After Heating        --      --      --    109   --5 Hrs. at 1000° F.Apparent Porosity, %        --      15.6    15.6  17.1  17.0After Ramming andDrying 18 Hrs.at 250° F.Average Pore Dia.,        --      8.5     --    5.0   6.3Microns (MercuryPorosimetry)After Ramming andDrying 18 Hrs. at250° F.Cold CrushingStrength psiAfter Drying 1070    1850    1840  1740  1930at 180° F.After Drying 1550    1920    2160  1800  2720250° F.Linear Change, %After Drying at        --      -0.7    -0.2  -0.3  -0.6250° F.After Heating        --      --      --    -1.0  --5 Hrs. at 1000° F.,ReducingVolume Change, %After Drying at        --      -0.7    -0.2  -0.2  -0.3250° F.After Heating 5 Hrs.        --      --      --    -3.0  --at 1000° F., ReducingWater Solubility% Weight LossAfter Drying at        2.1     3.8     4.8   4.9   4.6180° F., andBoiling 6 Hrs.After Drying at        1.3     0.7     0.7   0.6   0.4250° F., andBoiling 6 Hrs.______________________________________ 
    
     Table IX illustrates the comparative testing conducted on these mixes. 
     Mix II had the best ramming and compaction properties compared to other mixes. Its degree of water insolubility after curing at 180° F. and 250° F. was improved compared to previously developed mixes. The thermal conductivity of this material was 168.3 Btu/Ft 2  --Hr.°F./in. compared to 84.9 Btu/Ft 2  --Hr.°F./in. for previously developed Mix Y (&#34;fast&#34; direction). Mix JJ had a thermal conductivity of 69.4 Btu/Ft 2  --Hr.°F./in. Mix II had improved thermal conductivity compared to mixes Y and JJ due to better ramming properties, increased rammed density, and smaller average pore size. Mix II therefore achieved the best overall commercial characteristics as a ramming mix for packing around blast furnace cooler plates. Mix II has high conductivity, high cold crushing strength (in excess of 1500 psi after heating at 250° F.), a high degree of water insolubility and good ramming properties. 
     
                                           TABLE IX__________________________________________________________________________Thermal Conductivity (Argon Atmosphere)Mix Designation:Y*        Y*        II**      II**      JJ**Fast Direction     Slow Direction               Fast Direction                         Slow Direction                                   Fast DirectionMean Thermal     Mean Thermal               Mean Thermal                         Mean Thermal                                   Mean ThermalTempera-Conduc-     Tempera-          Conduc-               Tempera-                    Conduc-                         Tempera-                              Conduc-                                   Tempera-                                        Conduc-ture (°F.)tivity     ture (°F.)          tivity               ture (°F.)                    tivity                         ture (°F.)                              tivity                                   ture (°F.)                                        tivity__________________________________________________________________________311  84.9 306  50.2 312  168.3                         309  54.2 310  69.41165 82.6 1154 46.0 1201 139.6                         1180 50.5 1226 65.5689  85.9 699  54.2 709  143.0                         709  53.7 733  69.3225  89.0 236  56.2 258  152.0                         244  55.6 242  76.7__________________________________________________________________________ *Test Samples were cured at 500° F. **Test Samples were coked at 1000° F. ***Test Samples were cured at 250° F. 
    
     Table X illustrates the Taylor Standard Series screen analysis of Mix II. 
     
                       TABLE X______________________________________Mix Designation:       II______________________________________Screen Analysis% Held on8             mesh10            mesh14                         --20                         --28                          2     235                          848                         2865                         22    58100                        10150                        --    10200                         2270                        --325                        --     2Minus 325     mesh         28    28______________________________________ 
    
     While the preferred embodiment of the present invention has been described and illustrated, the invention should not be limited thereto, but may be otherwise embodied within the scope of the following claims.