Abstract:
A process for making a binder from steelmaking slag. About 5-30 wt. % of a reforming agent selected from the group consisting of silicate rock, mineral, calamine, glass waste, foundry waste sand, waste brick, red mud, volcanic spouting matter, blast furnace slag, desilica slag, iron oxide and mixtures thereof is added to a molten steelmaking slag, causing a molten reaction forming a reacted steelmaking slag. The reacted steelmaking slag is rapidly cooled to form a powder. Iron is removed from the powder and the powder is then mixed with from about 3-5 wt. % of a powder selected from the group consisting of lime, plaster, cement and mixtures thereof, which can then be used as a binder for pellets or briquettes.

Description:
This application is a continuation of application Ser. No. 892,876, filed July 28, 1986, said Ser. No. 892,876 being a continuation of application Ser. No. 800,016, filed Nov. 20, 1985, both now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a process for using steelmaking slag which is produced but not disposed of, wherein the steelmaking slag is used as a binder for pellets or briquettes. 
     Steelmaking slag usually contains 2CaO.SiO 2 , F.CaO, F.MgO, 2CaO.Fe 2  O 3 , 4CaO.Al 2  O 3  Fe 2  O 3 , Fe 2  O 3 , Fe 3  O 4  and FeO, etc. The steelmaking slag is received by a cinder plate and is discharged. 2CaO.SiO 2  causes expansion and collapse at the time of converting β→γ and F.CaO or F.MgO contained as components also cause expansion and collapse. Therefore, most steelmaking slags are disposed of without reclamation. 
     Cement or briquette are used as a binder for pellets or briquettes since powder ore having a lower viscosity is used in steel material. However, it takes a long time to harden with small amount of binder, the latter treatment is inconvenient, and the yield rate of products is low. Addition of a lot of binder causes a lowering of the quality of iron in the pellet or briquette. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to improve the steelmaking slag, which is an unused natural resource. The steelmaking slag is used as a binder which rapidly hardens just after adding and mixing at the time of producing pellets of briquettes. 
     Another object of the present invention is achieved by adding 5-30 wt.% of a reforming agent consisting of one or more groups of silicate rock, mineral, calamine, glass waste, foundry waste sand, waste brick, red mud, volcanic spouting matter, blast furnace slag, desilicate slag and iron oxide to molten steelmaking slag, to produce a molten reaction, then rapidly cooling the reacted molten steelmaking slag, treating the cooled product to remove iron and finally mixing the resulting steelmaking powder and 3-5 wt.% of powder consisting of one or more groups of lime, plaster and cement. A proper amount of cement clinker can also be added to the mixed powder. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First, the reforming agent consisting of silicate rock or minerals is added to a molten slag having a high sensitive heat, and the molten reaction takes place by virtue of the high sensitive heat of the molten steelmaking slag. Adding the reforming agent is not restricted if the mixed powder is mixed enough. Charging granular or powdery reforming agent with bubbling gas into the molten steelmaking slag by a lanspipe is especially preferable in improving the molten reaction. Addition of the reforming agent lowers the melting point and viscosity of the steelmaking slag, and facilitates a rapid and sufficient subsequent cooling. The mineral composition is changed from α&#39;-β-2CaO.SiO 2  to 2CaO.SiO 2  -2CaO.MgO.2SiO 2 , and is steadied after the rapid cooling because glass becomes the main composition. Less than 5 wt.% of the reforming agent does not result in any particular improvement in the above-mentioned mineral composition of the steelmaking slag, or lowering of the melting point and viscosity. It is preferable that the molten reaction only take place due to the sensitive heat of the steelmaking slag because of operation efficiency and economic considerations. Therefore, 30 wt.% maximum reforming agent is preferable for the abovementioned reasons. Rapid cooling by the water throwing system is usually used after the molten reaction with the reforming agent. Iron contained in the steelmaking slag is recovered by magnetic dressing or other proper processes. The treated steelmaking slag is thus obtained. Suitable grinding is carried out at the time of recovering iron because iron and other matter are separated. The resulting treated steelmaking slag can be finely ground before or after adding one or more of lime, plaster and cement. The particle size is preferably as small as possible. The brain value is more than 3200 cm 2  /g. 
     A three (3) wt.% minimum of lime, plaster and cement is required for mixing with the treated steelmaking slag. Otherwise, the hardening ability of the mixed powder becomes low, it takes a long time to harden, and the maximum hardening degree is low. However, over 5 wt. % does not adversely affect the hardening ability, but the quality of iron in the pellet or briquette becomes low. Therefore, between 3 and 5 wt.% lime, plaster, or cement is preferable. 
     Embodiments and results will now be shown. 
     Table 1 shows the chemical analytical values of the raw materials used in the embodiments. 
     
                                           TABLE 1__________________________________________________________________________    Chemical Analytical Values (wt. %)    Ig.                           Collapse ValuesMaterial Loss        SiO.sub.2           Al.sub.2 O.sub.3               T.Fe                  CaO                     MgO                        MnO                           Na.sub.2 O                               K.sub.2 O                                  (%)     Remarks__________________________________________________________________________Steelmaking slag    +2.5        9.9           1.0 21.5                  43.5                     6.7                        4.6                           0.2 0.0                                  35.0    Converter slag(A)Steelmaking slag    +0.9        19.4           4.3 27.5                  39.0                     4.2                        4.8                           0.2 0.0                                  6.5     Electric furnaces(B)                                            slag (oxidizing term)Steelmaking slag    0.7 27.4           3.9 0.6                  44.5                     6.3                        -- 0.1 0.0                                  100.0   (reducing term)(C)Blast furnace    2.0 29.5           14.1               0.6                  41.4                     6.4                        --  0.05                                0.01                                  0.2Granite  2.3 70.2           14.5               3.1                  0.9                     0.6                        -- 2.7 1.9                                  --Sandstone    1.9 71.5           14.2               2.5                  0.6                     0.5                        -- 2.9 0.9                                  --Slate    6.6 63.3           15.5               4.3                  1.7                     1.3                        -- 1.1 0.9                                  --Sand (river sand)    0.2 87.2           3.1 0.2                  0.2                     0.1                        -- 1.1 0.3                                  --Calamine +3.3        29.0           17.4               28.7                  12.1                     2.8                        -- --  -- --Glass waste    --  73.0           2.0 0.4                  5.8                     3.4                        -- 14.7                               0.5                                  --Foundry  5.3 86.1           3.0 0.2                  2.0                     0.1                        -- 1.0 1.1                                  --waste sandCoal ash --  55.9           26.0               3.6                  5.4                     2.0                        -- --  -- --Dequartzite    --  29.6           12.3               7.6                  32.5                     4.5                        -- 0.2 0.0                                  --slagIron ore (A)    --  1.5           1.2 63.5                  -- -- -- --  -- --__________________________________________________________________________ 
    
     Steelmaking slags (A), (B), and (C) in Table 1 above show the composition of steelmaking slags from which iron is recovered. The collapse values were calculated under the conditions of 20 Kg/cm 2 , 200° C., 3 hours and 10-25 mm based on the ASTM method, and the results show less than 10 mm of collapsed matter. 
     Table 3 shows the results in which the melting heat of each mixture shown in the following Table 2 was determined with materials shown in Table 1 by the Seger Cone method. 
     
                                           TABLE 2__________________________________________________________________________      SampleMaterial   1  2  3 4 5 6 7 8 9 10                            11                              12                                13                                  14                                    15                                      16                                        17                                          18 19                                                20                                                 21__________________________________________________________________________Steelmaking slag (A)      100   95              90                80                  80                    85                      90                        80                          80                            85Steelmaking slag (B)         100                  90                                80                                  90                                    85                                      80                                        80Steelmaking slag (C)                           100     95                                          90      90Granite          5 10                20                   5                               5Sandstone               5          10                                20      10        10Slate                  10      20                             5         5Sand                     10            10Coal ash                  5               5Dequartzite slag           10               5                                         5Iron ore (A)                      5Glass waste                   5   5Calamine                      5               5Foundry waste sand           10           5                                      10__________________________________________________________________________ 
    
     
                                           TABLE 3__________________________________________________________________________    Sample No.    1  2  3  4  5  6  7  8  9  10 11__________________________________________________________________________Melting- 1520       1505          1315             1295                1290                   1290                      1300                         1295                            1230                               1290                                  1235temperature (°C.)__________________________________________________________________________    Sample No.    12  13 14 15 16  17 18 19 20  21__________________________________________________________________________Melting- 1290        1285           1290              1285                 1280                     1270                        1550                           1320                              1295                                  1290temperature (°C.)__________________________________________________________________________ 
    
     The examples show that steelmaking slags No. 1, No. 2, and No. 18, which have high melting points by themselves, become mixtures having low melting points by adding the reforming agent as shown in Table 3. 
     Next, the mixtures in Table 2 were dried in an isothermal dryer furnace at 105°-110° C. for more than 24 hours, the dried mixture was dissolved in a Sliconit electric furnace at 1500° C., the dissolved mixture was taken out from the furnace and was cooled in water, and the cooled mixture was dried again. The dried mixture was then ground to under 200 mesh, 3 wt.% of lime was mixed to the ground mixture with water, and the mixture was then closed up in a vinyl sack. 
     Table 4 shows the harden-state of the mixtures. 
     
                                           TABLE 4__________________________________________________________________________                                                   Blast furnace                                                   cooled by                                                   waterSample No.                                      raw material                                                   (products on1       2 3 4 5 6 7 8 9 10                     11                       12                         13                           14                             15                               16                                 17                                   18                                     19                                       20                                         21                                           No. 1                                               No.                                                   market)__________________________________________________________________________HardeningState1 day Δ   Δ     ○       ○         ○           ○             ○               ○                 ○                   ○                     ○                       ○                         ○                           ○                             ○                               ○                                 ○                                   Δ ○                                           ○                                           ○                                           x   x   Δlater3 days ○   ○     ⊚       ⊚         ⊚           ⊚             ⊚               ⊚                 ⊚                   ⊚                     ⊚                       ⊚                         ⊚                           ⊚                             ⊚                               ⊚                                 ⊚                                   ⊚                                           ⊚                                           ⊚                                           ⊚                                           x   x   ○later7 days ○   ○     ⊚       ⊚         ⊚           ⊚             ⊚               ⊚                 ⊚                   ⊚                     ⊚                       ⊚                         ⊚                           ⊚                             ⊚                               ⊚                                 ⊚                                   ⊚                                           ⊚                                           ⊚                                           ⊚                                           x   x   ⊚later__________________________________________________________________________ 
    
     In Table 4, symbol  ⊚  means `very hard` pushing with a hand, symbol  ○  means `hard`, symbol Δ means `a little hard`, and symbol X means `non-harden`. 
     Samples No. 1 and No. 2, which were not rapidly cooled with water, were not completely hardened, as shown in Table 4. Other samples which were rapidly cooled with the reforming agent started to harden in the early steps. Most samples cooled with the reforming agent were made of glass, and β and α&#39;-2Ca.SiO 2  existed. 
     Embodiments of the present invention will now be described. 
    
    
     EMBODIMENT I 
     Non-viscous powder ore (particle size is shown in Table 5) was compressed and was used as a binder. 
     Mixing proportions for 19 specimens are shown in Table 6. 
     A concrete compression tester (100 t) was used for pretesting, and the mixture was molded by the tablet method (32φ×35 mm, molding pressure 1t/cm 2 , water for addition 4.5%). 
     Table 7 shows the crushing strength for various specimens with the passage of time from 3 minutes to 4 days. 
     Considerable mixture was produced by a briquette apparatus (50×50×32 mm, water for addition 5%, lineage pressure 3.3t/cm). 
     Table 8 shows the producing yield rate and the crushing strength required for breaking, etc. 
     
                                           TABLE 5__________________________________________________________________________Particlesize (mm) +10    10-7       7-5          5-3             3-2                2-1                   1-0.5                      0.5-0.25                           0.25-0.125                                 0.125-0.105                                       -0.105                                           Total__________________________________________________________________________wt. (%) 0.61    8.01       14.29          10.14             6.32                12.36                   7.88                      7.97 13.16 4.53  14.73                                           100.00__________________________________________________________________________ 
    
     
                       TABLE 6______________________________________Mixing proportion (wt. %)   Sample   Mixing No.             CementSpecimen   proportion             clinker  Lime  Plaster                                  Cement______________________________________ 1       1                 3   97 2       2                 3   97 3      18                 3   97 4       4                 3   97 5      12                 3   97 6      21                 3   97 7       4        92       0.5   2.5    5 8       4        87       3   10 9       4        67       0.5   2.5   3010      12        92       0.5   2.5    511      12        87       0.5   2.5   1012      21        92       0.5   2.5    513      21        87       0.5   2.5   1014      21        47       0.5   2.5   5015       4                              3   9716       4                             95    517      12                              3   9718      12                             90   1019      21                             95    5______________________________________ 
    
     Sample Numbers in Table 6 are the same numbers as in Table 2. 
     The mixtures in specimens No. 1-No. 14 shown in Table 6 were ground by a ballmill to 3100±50 cm 2  /g brain value, portland cement available on the market was added to the ground samples, and specimens No. 15-No. 19 were thus obtained. 
     
                                           TABLE 7__________________________________________________________________________Mixing proportion (wt. %)           Specimen    Crushing strength (Kg/peace)Test            (No.)       3  6  9  15 1  2  3   4No.   Powder ore    Plain cement           (Proportion)                  Bentonite                       mins                          mins                             mins                                mins                                   day                                      days                                         days                                             days__________________________________________________________________________ 1 95    5                  38 41 45 48 393                                      440                                         1117                                             1365 2 95           1           42 46 49 56 470                                      620                                         735  865           5 3 95           3           49 55 58 61 505                                      670                                         787  890           5 4 95           4           48 56 57 60 510                                      675                                         790  900           5 5 95           5           47 49 51 59 495                                      650                                         785  890           5 6 95           6           49 54 59 62 500                                      670                                         780  880           5 7 92    5             3    42 47 52 53 777                                      890                                         1013                                             1087 8 92           1      3    49 50 59 67 573                                      670                                         790  825           5 9 92           3      3    52 55 63 72 625                                      705                                         815  951           510 92           5      3    49 51 59 67 575                                      670                                         795  840           511 92           6      3    51 53 60 70 600                                      690                                         805  925           512 92           7      3    39 41 44 49 420                                      590                                         1150                                             1305           513 95           9           39 42 48 50 450                                      465                                         1050                                             1355           514 92           9      3    41 43 49 52 435                                      450                                         1010                                             1250           515 95           12          39 41 47 49 445                                      470                                         1040                                             1405           516 92           12     3    42 43 49 51 505                                      570                                         1070                                             1415           517 95           14          44 46 51 54 430                                      460                                         985 1100           518 92           14     3    43 44 51 53 440                                      470                                         1010                                             1260           519 92    3      1      2    47 49 54 60 610                                      705                                         740 1025           320 92    3      11     2    44 45 50 57 605                                      720                                         730 1020           321 92    4      14     2    46 47 52 60 620                                      715                                         745 1153           222 92           15     3    38 40 46 46 440                                      460                                         1020                                             1320           523 92           16     3    40 42 47 49 445                                      465                                         1015                                             1325           524 95           15          39 41 48 49 500                                      560                                         1065                                             1300           525 95           17          43 45 52 54 435                                      465                                         990 1100           526 92           17     3    42 43 50 52 445                                      475                                         1005                                             1255           527 95           18          44 46 50 51 610                                      715                                         735 1050           528 95           19          43 44 51 53 615                                      710                                         740 1150           5__________________________________________________________________________ 
    
     
                       TABLE 8______________________________________ Crushing    Dropping strength*.sup.1             strength*.sup.2                         Producing                                AdditionTest  (Kg/peace)  (No. of times)                         yield rate                                of waterNo.   2 days  5 days  3 days                       5 days                             (%)    (%)______________________________________1     --      --      --    --    30     53     75      290      9    17    55     56     85      320     16    22    75     512    90      385     17    26    76     515    85      370     16    26    80     516    90      330     17    27    85     519    90      400     17    27    93     522    87      340     17    24    75     524    84      365     17    25    78     526    90      325     17    27    86     527    90      385     17    27    89     5______________________________________ *.sup.1 Strength in which briquette  ○  is pressed to mark direction until briquette is broken down. *.sup.2 The number of times in which a briquette is dropped from a height onto an iron plate having a 10 mm thickness, until it is broken down to 1/2 its original size. 
    
     Left side test numbers in Table 8 are the same numbers as in Table 7, the same numbers show the same mixing proportions. 
     From the results of Embodiment I, it can be seen that it takes few days to have enough strength after mixing cement in Test No. 1 and cement and bentonite in Test No. 2 to produce a briquette with the powder ore. Test No. 3, using Sample 18, in which the reforming agent is not added, shows a weak dropping strength. In the present invention, considerably great strength is observed directly after the mixing, and is an advantage of the present invention. Therefore, it will be appreciated that enough durability is obtained directly after the mixing and the producing yield rate is a high percentage, as shown in Table 8. 
     EMBODIMENT II 
     Iron ore having the same mixing proportions of test numbers in Table 7 is produced to the particle sizes shown in Table 9. 
     Table 10 shows the pelletizing and the dropping strength of 10-5 mm pellets. The symbol `&#39;` of the test numbers in Table 10 means the same mixing proportions as the same test numbers in Table 7 without the symbol `&#39;`. 
     
         ______________________________________Particlesize           1000-   500- 250- 125-(μ) +1000   500     250  125  105   -105  Total______________________________________wt. (%)  0.07    .18     15.43                       20.49                            12.71 1.21  100.00______________________________________ 
    
     
                       TABLE 10______________________________________              Dropping    CrushingTest               strength    strengthNo.   Pelletizing  (No. of times)*.sup.1                          (Kg/peace)*.sup.2______________________________________ 1&#39;   impossible   --          -- 7&#39;   impossible   --          -- 3&#39;   impossible   --          -- 6&#39;   good         29          86 9&#39;   good         30          9511&#39;   good         37          9914&#39;   good         31          9317&#39;   good         41          12020&#39;   good         32          9921&#39;   good         36          105______________________________________ *.sup.1 The number of times in which, 3 days later, pellets are dropped from a 1 m height onto an iron plate having a 10 mm thickness, and are broken down to 1/2 their size. *.sup.2 Crushing strength, 3 days later. 
    
     The pelletizing of Test No. 1&#39; or Test No. 7&#39; using cement or cement and bentonite as a binder is impossible in Embodiment II. The pelletizing of Sample No. 18 in which the reforming agent is not added and a binder of Test No. 3&#39; in which lime is mixed are also impossible. The pelletizing of a binder consisting of a specimen contains a mixture of reforming agent, lime, plaster and cement, or a specimen mixing the above four components and cement clinker is possible, and it is also observed that dropping strength and crushing strength are satisfactory. 
     As mentioned above, in the present invention, steelmaking slag in the molton state is effectively reacted with silicate crag or a reforming agent consisting of minerals by using the sensitive heat of the slag, the reacted steelmaking slag is rapidly cooled, and considerably great strength is made possible by adding lime, plaster or cement, etc. It takes only 2-3 minutes to harden in producing a pellet or briquette, the quality of iron never become low because even a little amount of the binder has a considerable hardening ability, the producing yield rate is high, and the producing efficiency is also high. Cement clinker also has high hardenability, but it is preferred that cement clinker not be added, thereby producing a higher quality iron using steelmaking slag which is industrially discarded abolished matter.