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| Research on Stabilization of Free CaO in Basic Oxygen Furnace Slag with |
| Acidifier at High Temperature SiO2Bearing, , , ,
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YIN Xiao, ZHANG Chongmin, YANG Ji, LI Boyang, WANG Guocheng
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Published: 25 January 2018
Online: 2018-01-25
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| FeO | Fe2O3 | CaO | SiO2 | MgO | | 14.68 | 0.70 | 49.38 | 10.56 | 12.00 | | MnO | Al2O3 | P2O5 | Others | | | 5.25 | 2.02 | 2.61 | 2.80 | |
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Chemical compositions (mass fraction/%) of BOFS
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Images of experimental materials: (a)BOFS, (b)quartz sand
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| Content | S1 | S2 | S3 | S4 | S5 | | w(SiO2)/w(CaO) | 0.37 | 0.42 | 0.48 | 0.56 | 0.67 | | w(f-CaO)/% | 2.98 | 2.68 | 2.02 | 1.24 | 0.70 |
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Free CaO content of BOF slag modified at conditions of different w(SiO2)/w(CaO)
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Relation curve between η and w(SiO2)/w(CaO)
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XRD pattern for BOFS
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| Mineralogical phase | S1 | S2 | S3 | S4 | S5 | | MgO·Fe2O3 | √ | √ | √ | √ | √ | | CaO·MgO·2SiO2 | √ | — | — | — | — | | 2CaO·MgO·2SiO2 | — | √ | √ | √ | √ | | 2CaO·SiO2 | √ | √ | √ | √ | √ | | 2CaO·Fe2O3 | — | — | — | — | √ | | Ca2(Al,Fe)2O5 | √ | √ | √ | √ | √ | | Fe3O4 | √ | √ | √ | √ | √ | | Fe2O3 | — | — | — | — | √ |
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Mineralogical phases of BOF slag after modification
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| Sample | CaO | MgO | FeO | MnO | Al2O3 | SiO2 | | BOFS | 81.90 | 5.12 | 8.01 | 4.97 | — | — | | S2 | 79.55 | 5.57 | 6.44 | — | 5.98 | 2.47 |
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EDS results (mass fraction/%) of f-CaO in BOFS and S2
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XRD patterns of BOF slag before and after modification
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FESEM images of BOF slag before and after modification
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| Number | Reaction | Δf/(J·mol-1) | | 1 | SiO2(s)+CaO(s)=
CaO·SiO2(s) | -92 500+2.5T | | 2 | SiO2(s)+2CaO(s)=
2CaO·SiO2(s) | -118 800-11.3T | | 3 | 2SiO2(s)+3CaO(s)=
3CaO·2SiO2(s) | -236 800+9.6T | | 4 | SiO2(s)+3CaO(s)=
3CaO·SiO2(s) | -118 800-6.7T |
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Δf of the main silicates
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| Content | S1 | S2 | S3 | BOFS | | w(C3S)/w(C2S) | 11.06 | 1.77 | 0.44 | — | | w(CaO)/w(C2S) | 0.29 | 0.19 | 0.08 | 0.98 |
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Theoretical values of w(C3S)/w(C2S) and w(CaO)/w(C2S)
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CaO-SiO2 phase diagram[23]
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| No. | Source | Form | Size/μm | Characteristics | | 1 | H Suito et al[25] | Undissolved particles | 3—30 | Spongy, grainy | | 2 | F Wachsmuth et al[26] | Precipitate from melt | <4 | Grainy | | 3 | J Waligora et al[5] | Decomposition from C3S | 1—3 | Micro-inclusion | | This work | Before stabilization | Undissolved particles+
Precipitate from melt | 2—20 | Ellipsoid-like | | This work | After stabilization | Precipitate from melt+
Decomposition from C3S | 0.5—2 | Clustered ball-like |
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Classification and characteristics of f-CaO in steel slag
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2018, Vol. 32 
