Patent Publication Number: US-4652310-A

Title: Process for making a hardening agent for weak soil or sludge from steel making slag

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                                 
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          Chemical Analytical Values (wt. %)                              
          Ig.                           Collapse Values                   
Material  Loss                                                            
              SiO.sub.2                                                   
                 Al.sub.2 O.sub.3                                         
                     T.Fe                                                 
                        CaO                                               
                           MgO                                            
                              MnO                                         
                                 Na.sub.2 O                               
                                     K.sub.2 O                            
                                        (%)     Remarks                   
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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                                
                                        0.2                               
Granite   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                                  
                                        --                                
sand                                                                      
Coal 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                                  
                                        --                                
slag                                                                      
Iron ore (A)                                                              
          --  1.5                                                         
                 1.2 63.5                                                 
                        -- -- -- --  -- --                                
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     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                                 
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          Sample                                                          
Material  1  2  3 4 5 6 7 8 9 10                                          
                                11 12                                     
                                     13                                   
                                       14                                 
                                         15 16                            
                                              17                          
                                                18 19                     
                                                     20                   
                                                       21                 
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Steelmaking slag (A)                                                      
          100   95                                                        
                  90                                                      
                    80                                                    
                      80                                                  
                        85                                                
                          90                                              
                            80                                            
                              80                                          
                                85                                        
Steelmaking slag (B)                                                      
             100                   90                                     
                                     80                                   
                                       90                                 
                                         85 80                            
                                              80                          
Steel making slag (C)                           100     95                
                                                90      90                
Granite          5                                                        
                  10                                                      
                    20                                                    
                       5                                 5                
Sandstone              5           10                                     
                                     20       10        10                
Slate                 10      20                                          
                                5                                         
Sand                    10             10                                 
Coal ash                 5               5                                
Dequartzite slag          10                 5                            
                                               5                          
Iron ore (A)                    5            5                            
Glass waste                  5  5                                         
Calamine                     5                 5                          
Foundry waste sand          10           5  10                            
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                                           TABLE 3                                 
__________________________________________________________________________
Sample No.                                                                
         1  2  3  4  5  6  7  8  9  10 11                                 
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Melting- 1520                                                             
            1505                                                          
               1315                                                       
                  1295                                                    
                     1290                                                 
                        1290                                              
                           1300                                           
                              1295                                        
                                 1230                                     
                                    1290                                  
                                       1235                               
temperature (°C.)                                                  
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Sample No.                                                                
         12 13 14  15 16 17  18 19 20  21                                 
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Melting- 1290                                                             
            1285                                                          
               1290                                                       
                   1285                                                   
                      1280                                                
                         1270                                             
                             1550                                         
                                1320                                      
                                   1295                                   
                                       1290                               
temperature (°C.)                                                  
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     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                                 
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                                                        Blast furnace     
                                                        cooled by         
                                                        water             
                                                raw material              
                                                        (products on      
Sample 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)           
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Hardening                                                                 
State                                                                     
1 day Δ                                                             
        Δ                                                           
          ○                                                        
            ○                                                      
              ○                                                    
                ○                                                  
                  ○                                                
                    ○                                              
                      ○                                            
                        ○                                          
                          ○                                        
                            ○                                      
                              ○                                    
                                ○                                  
                                  ○                                
                                    ○                              
                                      ○                            
                                        Δ ○                  
                                                ○                  
                                                ○                  
                                                x   x   Δ           
later                                                                     
3 days                                                                    
      ○                                                            
        ○                                                          
          ⊚                                                
            ⊚                                              
              ⊚                                            
                ⊚                                          
                  ⊚                                        
                    ⊚                                      
                      ⊚                                    
                        ⊚                                  
                          ⊚                                
                            ⊚                              
                              ⊚                            
                                ⊚                          
                                  ⊚                        
                                    ⊚                      
                                      ⊚                    
                                        ⊚                  
                                                ⊚          
                                                ⊚          
                                                ⊚          
                                                x   x   ○          
later                                                                     
7 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                                 
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Specimen No.    1  2 3  4  5  6  7  8  9  10 11                           
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Sludge          100                                                       
                   95                                                     
                     90 92 87 92 87 92 87 77 87                           
Cement              5                                                     
                     10                                                   
Quick lime              3     3   3 3   3  3 1.5                          
Plaster                     3                1.5                          
Sample No.              1   1 2   2 4   4  4 10                           
Amount of addition      5  10 5  10 5  10 20 10                           
Hardening-                                                                
      Touching                                                            
            1 day                                                         
                x  ○                                               
                     ○                                             
                        Δ                                           
                           ○                                       
                              ○                                    
                                 ○                                 
                                    ○                              
                                       ○                           
                                          ○                        
                                             ○                     
state inspection                                                          
            later                                                         
            3 days                                                        
                x  ○                                               
                     ○                                             
                        ○                                          
                           ○                                       
                              ○                                    
                                 ○                                 
                                    ○                              
                                       ○                           
                                          ○                        
                                             ○                     
            later                                                         
Crushing 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)                                                                   
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Specimen No.    12  13 14  15 16 17 18 19 20 21                           
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Sludge          92  77 87  77 87 87 92 87 92 87                           
Cement                              2   3  3  3                           
Quick lime      1.5 1.5                                                   
                        3   2  3  3                                       
Plaster         1.5 1.5     1                                             
Sample No.      12  12 13  13 BF 4 BF                                     
                                    4   4 12 12                           
Amount of addition                                                        
                 5  20 10  20 10 5 5                                      
                                    5  10  5 10                           
Hardening-                                                                
      Touching                                                            
            1 day                                                         
                ○                                                  
                    ○                                              
                       ○                                           
                           ○                                       
                              Δ                                     
                                 ○                                 
                                    ○                              
                                       ○                           
                                          ○                        
                                             ○                     
state inspection                                                          
            later                                                         
            3 days                                                        
                ○                                                  
                    ○                                              
                       ○                                           
                           ○                                       
                              ○                                    
                                 ○                                 
                                    ○                              
                                       ○                           
                                          ○                        
                                             ○                     
            later                                                         
Crushing 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)                                                                   
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     `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.