Abstract:
A process for making a hardening agent for weak soil or sludge from steelmaking slag. About 5-30 wt. % of specified reforming agent selected from the group consisting of one or more of silicate rock, mineral, calamine, glass waste, foundry waste sand, waste brick, red mud, volcanic slag, iron oxide and mixtures thereof is added to a molten steelmaking slag, causing a reaction forming a reacted steelmaking slag. The reacted steelmaking slag is then rapidly cooled to form a powder. Iron is then removed from the powder and the powder is then mixed with from about 3-5% of a powder selected from the group consisting of one or more of lime, plaster and cement to form a hardening agent for weak soil or sludge.

Description:
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 reforming agent for weak soil or sludge. 
     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→α and F.CaO or F.MgO contained as components also cause expansion and collapse. Therefore, most of the steelmaking slag is disposed of without reclamation. 
     Cement is used for weak soil or sludge, but a great quantity of cement is required and is very expensive. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to improve steelmaking slags, which are unused natural resources. The steelmaking slag is used for the hardening of weak soil or sludge. 
     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, desilica slag and iron oxide to molten steelmaking slag to produce a molten reaction rapidly cooling the reacted molten steelmaking slag treating the cooled product to remove iron, and mixing the resulting steelmaking powder and 3-5 wt.% of a powder consisting of one or more groups of lime, plaster and cement. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First, the reforming agent consisting of silicate rock or mineral is added to a molten steelmaking slag having a high sensitive heat, and the molten reaction is 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 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 the molten reaction take place due only 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 above-mentioned 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 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 for weak soil or sludge becomes low, and it takes a long time to harden. However, over 5 wt.% does not adversely affect the hardening ability. Therefore, between 3 and 5 wt.% lime, plaster, or cement is preferable. 
    
    
     Embodiment and results will now be shown. 
     Table 1 shows the chemical analytical values of the raw materials used in the embodiment. 
     
                                           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 waste     5.3 86.1            3.0 0.2                    2.0                      0.1                         -- 1.0 1.1                                   --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 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                                         80Steel making slag (C)                           100     95                                           90      90Granite          5             10               20                  5                                 5Sandstone              5           10                                20       10        10Slate                 10      20                           5Sand                    10             10Coal ash                 5               5Dequartzite slag          10                 5                                          5Iron ore (A)                    5            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 115°-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                                                   water                                           raw material                                                   (products onSample No. 1 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 foregoing agent were mainly made of glass, and β and α&#39;-2Ca.SiO 2  existed. 
     An embodiment of the present invention will now be described 
     EMBODIMENT 
     Each sample in Table 2 ground to under 200 mesh was added to sludge containing 30.5 wt.% of water (kailinite, montmorillonite and α--quartz) by a morter pasting pot. The sludge was then divided into three layers by the soil treating mold lanner, and the divided sludge was cultivated wet for 1 month. 
     Table 5 shows the resulting crushing strength. 
     
                                           TABLE 5__________________________________________________________________________Specimen No.    1  2 3  4  5  6  7  8  9  10 11__________________________________________________________________________Sludge          100              95                90 92 87 92 87 92 87 77 87Cement              5                10Quick lime              3     3   3 3   3  3 1.5Plaster                     3                1.5Sample No.              1   1 2   2 4   4  4 10Amount of addition      5  10 5  10 5  10 20 10Hardening- Touching       1 day           x  ○                ○                   Δ                      ○                         ○                            ○                               ○                                  ○                                     ○                                        ○state inspection       later       3 days           x  ○                ○                   ○                      ○                         ○                            ○                               ○                                  ○                                     ○                                        ○       laterCrushing strength           0  5.5                12.9                   6.7                      10.5                         10.0                            10.5                               11.0                                  11.5                                     15.7                                        11.0(30 days)(Kg/cm)__________________________________________________________________________Specimen No.    12  13 14  15 16 17 18 19 20 21__________________________________________________________________________Sludge          92  77 87  77 87 87 92 87 92 87Cement                              2   3  3  3Quick lime      1.5 1.5                   3   2  3  3Plaster         1.5 1.5     1Sample No.      12  12 13  13 BF 4 BF                               4   4 12 12Amount of addition            5  20 10  20 10 5 5                               5  10  5 10Hardening- Touching       1 day           ○               ○                  ○                      ○                         Δ                            ○                               ○                                  ○                                     ○                                        ○state inspection       later       3 days           ○               ○                  ○                      ○                         ○                            ○                               ○                                  ○                                     ○                                        ○       laterCrushing strength           9.1 13.5                  12.0                      15.0                         6.1                            8.5                               8.8                                  11.8                                     9.4                                        12.4(30 days)(Kg/cm)__________________________________________________________________________ 
    
     `BF` for specimen No. 16 and No. 17 in Table 5 means Blast Furnace Slag which is rapidly cooled with water. 
     Symbol  ○  means `hard`, pushing with a hand, symbol Δ means `a little hard` and symbol X means `non-harden`. 
     The present invention shows the same effect when using cement, or more considerable effect in the hardening, and is enough used for the sludge hardening agent as shown in the Embodiment. 
     Sample No. 1, to which was not added the reforming agent, hardly hardened except after the addition of lots of sample No. 1, and the strength after hardening is low as shown in specimens No. 4 and No. 5. 
     As mentioned above, in the present invention, molten steelmaking slag is effectively reacted with silicate rock or a reforming agent consisting of minerals by using sensitive heat. The reacted steelmaking slag is rapidly cooled, and considerably high strength is achieved by adding lime, plaster or cement etc. A hardening agent for weak soil or sludge is obtained. 
     Furthermore, the steelmaking slag, which is industrial waste is mainly used as raw material in the process of the present invention, which is very economical.