Process for using steelmaking slag

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

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.sub.2, F.CaO, F.MgO, 2CaO.Fe.sub.2 O.sub.3, 4CaO.Al.sub.2 O.sub.3 Fe.sub.2 O.sub.3, Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4 and FeO, etc. The steelmaking slag is received by a cinder plate and is discharged. 2CaO.SiO.sub.2 causes expansion and collapse at the time of converting .beta..fwdarw..gamma. 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 .alpha.'-.beta.-2CaO.SiO.sub.2 to 2CaO.SiO.sub.2 -2CaO.MgO.2SiO.sub.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.sup.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.sup.2, 200.degree. 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 (.degree.C.)__________________________________________________________________________ Sample No. 12 13 14 15 16 17 18 19 20 21__________________________________________________________________________Melting- 1290 1285 1290 1285 1280 1270 1550 1320 1295 1290temperature (.degree.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.degree.-110.degree. C. for more than 24 hours, the dried mixture was dissolved in a Sliconit electric furnace at 1500.degree. 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 .DELTA. .DELTA. .circle. .circle. .circle. .circle. .circle. .circle. .circle. .circle. .circle. .circle. .circle. .circle. .circle. .circle. .circle. .DELTA. .circle. .circle. .circle. x x .DELTA.later3 days .circle. .circle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. x x .circle.later7 days .circle. .circle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. .circleincircle. x x .circleincircle.later__________________________________________________________________________

In Table 4, symbol .circleincircle. means `very hard` pushing with a hand, symbol .circle. means `hard`, symbol .DELTA. 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 .beta. and .alpha.'-2Ca.SiO.sub.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 (32.phi..times.35 mm, molding pressure 1t/cm.sup.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.times.50.times.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.sup.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 .circle. 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 `'` of the test numbers in Table 10 means the same mixing proportions as the same test numbers in Table 7 without the symbol `'`.

______________________________________Particlesize 1000- 500- 250- 125-(.mu.) +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' impossible -- -- 7' impossible -- -- 3' impossible -- -- 6' good 29 86 9' good 30 9511' good 37 9914' good 31 9317' good 41 12020' good 32 9921' 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' or Test No. 7' 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' 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.

Claims

1. A process for making a binder from steelmaking slag, comprising:

adding a reforming agent selected from the group consisting of silicate rock, calamine, glass waste, foundry waste sand, waste brick, red mud, volcanic spouting matter, blast furnace slag, desilica slag, iron oxide and mixtures thereof to a molten steelmaking slag in an amount ranging from about 5 to about 30% by weight of the molten steelmaking slag to lower the melting point and viscosity of the steelmaking slag and to produce a molten reaction forming a reacted steelmaking slag;

rapidly cooling the reacted steelmaking slag to form a powder composed mainly of glass comprising 2CaO.SiO.sub.2 and 2CaO.MgO.2SiO.sub.2,

removing iron from the powder;

finely grinding the powder to a brain value greater than 3200 cm.sup.2 /g; and then

mixing the finely-ground powder with from about 3 to about 5% by weight of the powder of an agent selected from the group consisting of lime, plaster, cement and mixtures thereof as a binder to form pellets or briquettes.

2. A process according to claim 1, further comprising mixing cement clinker with the powder in the mixing step.

3. A process according to claim 1, wherein the moletn reaction is initiated by the heat of the molten steelmaking slag.

4. A process according to claim 1, wherein the reforming agent is added to the molten steelmaking slag as a granular powder.

5. A process according to claim 1, wherein the binder agent is mixed with the powder as a powder.

6. A process according to claim 1, wherein iron is removed from the powder by magnetic dressing.

7. A process according to claim 1, wherein the reacted steelmaking slag is rapidly cooled in water.

8. A process according to claim 1 further comprising forming the binder to pellets.

9. A process according to claim 1 further comprising forming the binder into briquettes.

10. A binder composition for pellets or briquettes, comprising

a powder ground to a brain value of greater than 3200 cm.sup.2 /g, said powder comprising glass formed by rapidly cooling the reaction product of molten steelmaking slag and about 5 to about 30% by weight of the steelmaking slag of a reforming agent selected from the group consisting of silicate rock, calamine, glass waste, foundry waste sand, waste brick, red mud, volcanic spouting matter, blast furnace slag, desilica slag, iron oxide and mixtures thereof, from which iron has been removed, said reaction product comprising 2CaO.SiO.sub.2 and 2CaO.MgO.2SiO.sub.2, and about 3 to about 5% by weight of the powder of an agent selected from the group consisting of lime, plaster, cement and mixtures thereof.

11. A binder composition according to claim 10, wherein the reforming agent comprises from about 5 to about 30% by weight of the molten steelmaking slag.

12. A binder composition according to claim 10 further comprising cement clinker.

13. A binder composition according to claim 10, formed into pellets.

14. A binder composition according to claim 10, formed into briquettes.