| 1. |
- Chen, YuHong, et al.
(författare)
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Identification of Fe-containing phase in oxidation process of BOF slag
- 2017
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Ingår i: Key Engineering Materials. - Zürich : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 726, s. 564-568
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the Fe-containing phases in BOF slag were identified before and after oxidized with atmospheric air. XRD and SEM with EDS results showed that The element Fe existed in slag in the form of calcium ferrite, wustite solid solution and hematite. Mg solid solute in wustite. After oxidized, magnetite became the major mineral phase in slag and Mg+ replace the Fe2+ of magnetite crystal to form spinel
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| 2. |
- Engström, Fredrik, et al.
(författare)
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Crystallization behaviour of some steelmaking slags
- 2010
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 81:5, s. 362-371
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Tidskriftsartikel (refereegranskat)abstract
- The present study was aimed at highlighting the final properties of two different steelmaking slags which undergo different cooling rates. The experiments were conducted in laboratory scale using an induction furnace. One of the slags originates from an electric arc furnace (EAF) (high-alloyed) and the second slag from a basic oxygen furnace (BOF). The treatment of the slag included re-melting along with different cooling rates. The material collected from the tests was characterized through X-ray diffraction, scanning electron microscopy as well as thermodynamic calculations which were compared with experimental results, for confirmation. The results indicate that both the EAF and BOF slags show increased reactivity with water, as well as a decrease in crystal size when rapid cooling is applied. The wüstite-type solid solution (Mg,Fe,Mn)O varies in composition depending on the cooling conditions. Metastable Ca3SiO5 was found in the rapidly- cooled BOF slag.
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| 3. |
- Feng, Yan, et al.
(författare)
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Characterization and evaluation of the pozzolanic activity of granulated copper slag modified with CaO
- 2019
-
Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 232, s. 1112-1120
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Tidskriftsartikel (refereegranskat)abstract
- GCS, granulated copper slag, is currently utilized in cement and concrete with a low rate, due mainly to its low pozzolanic activity. The present study was thus performed by first mixing the GCS with CaO, and then melting and water-granulating the GCS-CaO mixtures, as to enhance the reactivity of GCS. Blended cements were formulated by replacing 30 wt. % of the cement, PC, with the modified GCS. The addition of CaO in GCS increased the release rates of heat from the early-age hydration of the blended cement pastes. The pastes with CSC20, the GCS of the highest CaO content (19.5%), acquired higher compressive strengths than those for the PC and other PC-GCS pastes at both 28 and 90 days of curing. The GCS richer in CaO consumed more calcium hydroxide for the formation of calcium silicate hydrates, with SEM micrographs showing a microstructure of more gel phases and less pores in PC-GCS paste. These results indicate that the modification by addition of CaO is an effective way to achieve a high reactivity for the GCS. It may then be possible to utilize the modified GCS as a high-quality supplementary cementitious material to enhance the sustainability for both copper and cement industries.
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| 4. |
- Feng, Yan, et al.
(författare)
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Mechanical Activation of Granulated Copper Slag and Its Influence on Hydration Heat and Compressive Strength of Blended Cement
- 2019
-
Ingår i: Materials. - Basel, Switzerland : MDPI. - 1996-1944. ; 12:5
-
Tidskriftsartikel (refereegranskat)abstract
- Mechanical activation of granulated copper slag (GCS) is carried out in the present study for the purposes of enhancing pozzolanic activity for the GCS. A vibration mill mills the GCS for 1, 2, and 3 h to produce samples with specific surface area of 0.67, 1.03 and 1.37 m²/g, respectively. The samples are used to replace 30% cement (PC) to get 3 PC-GCS binders. The hydration heat and compressive strength are measured for the binders and derivative thermogravimetric /thermogravimetric analysis (DTG/TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are used to characterize the paste samples. It is shown that cumulative heat and compressive strength at different ages of hydration and curing, respectively, are higher for the binders blending the GCS milled for a longer time. The compressive strength after 90 d of curing for the binder with the longest milling time reaches 35.7 MPa, which is higher than the strength of other binders and close to the strength value of 39.3 MPa obtained by the PC pastes. The percentage of fixed lime by the binder pastes at 28 days is correlated with the degree of pozzolanic reaction and strength development. The percentage is higher for the binder blending the GCS with longer milling time and higher specific surface area. The pastes with binders blending the GCS of specific surface area of 0.67 and 1.37 m²/g fix lime of 15.20 and 21.15%, respectively. These results together with results from X-ray diffraction (XRD), FTIR, and SEM investigations demonstrate that the mechanical activation via vibratory milling is an effective method to enhance the pozzolanic activity and the extent for cement substitution by the GCS as a suitable supplementary cementitious material (SCM).
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| 5. |
- Han, Fenglan, et al.
(författare)
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Environmental performance of fluorite used to catalyze MgO reduction in pidgeon process
- 2012
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Ingår i: Advanced Materials Research. - 1022-6680 .- 1662-8985. ; 577, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- Environmental performances of fluorite used as catalyzer for chemical reaction between MgO and Si were investigated by performing pilot scale experiments of Mg production. F amounts of 0.012-0.116 kg were added in the charged briquettes and Mg slag generated from the chemical reaction in most of the tests weighted 4.26-4.96 kg with F contents ranging 0.21-2.52%. Based on high recoveries of F, 83-100%, in the slag after the reaction, it is estimated that there are little or no F compounds leaving the retorts during the pilot tests. However, high amount of F, 72.9 mg/kg, was leached out from an Mg slag sample obtained from an Mg plant, making it necessary to decrease amount of fluorite used as catalyzer for the reaction or to improve operation conditions, thus, enhancing rate for chemical reaction between MgO and Si in Pidgeon process
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| 6. |
- Han, Fenglan, et al.
(författare)
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Fluoride evaporation during thermal treatment of waste slag from Mg production using pidgeon process
- 2012
-
Ingår i: Advanced Materials Research. - 1022-6680 .- 1662-8985. ; 581-582, s. 1044-1049
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Tidskriftsartikel (refereegranskat)abstract
- Fluoride evaporation from Mg slag samples was investigated. F content in the original slag sample from an Mg factory was 1.65%, which decreases to 0.98-1.54% in the samples heated at 1000-1400°C for 3 hours. The values of F evaporation from the test samples were 6.7-40.6%. The fluorides may evaporate in the atmosphere, causing air pollution. Some suggestions were presented based on study results obtained to minimize fluoride emissions and improve environmental performances of the Mg production by using Pidgeon process
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| 7. |
- Han, Fenglan, et al.
(författare)
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Innovative utilization of a borate additive in magnesium production to decrease environmental impact of fluorides from pidgeon process
- 2013
-
Ingår i: Advanced Materials Research. - 1022-6680 .- 1662-8985. ; 690-693, s. 378-389
-
Tidskriftsartikel (refereegranskat)abstract
- The present authors have utilized, for the first time, H3BO3 as an additive in pilot scale experiments of Mg production using Pidgeon process. The results from the experiments revealed positive effects of H3BO3 on both quantity and quality of the Mg metal crowns. Besides acting as a catalyzer for MgO reduction, H3BO3 stabilized also β-Ca2SiO4 in the Mg slag. Based on these results, H3BO3 may be adopted as an innovative additive replacing fluorite in the Mg production, to enhance sustainability and environmental soundness for the Pidgeon process in China.
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| 8. |
- Han, F.L., et al.
(författare)
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Fluorine vaporization and leaching from Mg slag treated at high temperature
- 2013
-
Ingår i: Advanced Materials Research. - 1022-6680 .- 1662-8985. ; 726-731, s. 2898-2907
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Tidskriftsartikel (refereegranskat)abstract
- Pidgeon process is used by more than 300 plants in China to produce magnesium (Mg) metal. Fluorite, ranging 2-3%, is often mixed in raw materials to catalyze the Mg production. The Mg slag from the production then contains F of several mass percent. When the Mg slag is used in construction or treated for recycling, possible F pollutions are of concerns. The present study used slag samples containing F of 0.98-2.15% from an Mg factory in northwest China. Both treatments at 1000-1400°C and leaching tests before and after the treatments were conducted for the slag samples. The study results show influences of the treatments on mineral compositions of the samples, which controlled F contents in both the slag samples and leachates. The results are reported and discussed. Some suggestions are also presented to minimize fluorine pollutions and to improve environmental performances of the Pidgeon process
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| 9. |
- Han, Fenglan, et al.
(författare)
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Treatments of magnesium slag to recycle waste from Pidgeon process
- 2012
-
Ingår i: Advanced Materials Research. - 1022-6680 .- 1662-8985. ; , s. 1657-1667
-
Tidskriftsartikel (refereegranskat)abstract
- Magnesium slag powder from a local magnesium plant was treated to improve the volume stability for its application as building materials. The slag was mixed with borates, pressed into briquettes, and then sintered at high temperature. SEM studies show that at the higher temperature Ca 2SiO4 polymorphs were stabilized by Na and B ions in the added borates. The free MgO content in the slag was also decreased by the sintering treatment. The slag powder, after mixing with 0.4-0.6% of borates and sintered at 1200°C in 5-6 hours, has become volume stable aggregates. It is then possible to use the treated slag in constructions, saving valuable natural resources and decreasing the global warming impact from magnesium production via Pidgeon process
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| 10. |
- Hu, Xianfeng, et al.
(författare)
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Carbothermic reduction of synthetic chromite with/without the addition of iron powder
- 2016
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 56:12, s. 2147-2155
-
Tidskriftsartikel (refereegranskat)abstract
- Carbothermic reduction of chromite is an important industrial process for extracting chromium from the chromite. To have a better understanding of the effect of iron on the carbothermic reduction of chromite, the reduction of synthetic chromite (FeCr2O4) by graphite with/without the addition of iron powder was investigated in this paper by Thermogravimetric Analysis (TGA) in argon atmosphere. The fractional reduced samples were examined by SEM/EDS and XRD analysis, and the reduction process was thermodynamically and kinetically evaluated. The experimental results show that the iron powder addition enhances the reduction of FeCr2O4 and this effect increases when increased amounts of iron powder are added. This phenomenon is attributed to the in situ dissolution of chromium into the iron and mixed carbide (Cr,Fe)7C3, which can decrease the activity of the nascent chromium formed by the reduction of the FeCr2O4. The experimental results indicate that the reduction of FeCr2O4 with up to 80 wt.% iron powder addition is likely to be a single-step process and the kinetic analysis suggests that the reduction reaction is likely to be either (a) chemical reaction at the surface of FeCr2O4 or (b) diffusional dissolution of the product (FeCr2) into the iron/alloy particles or the mixed control of (a) and (b).
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| 11. |
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| 12. |
- Hu, Xianfeng, et al.
(författare)
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Direct Alloying Steel with Chromium by Briquettes Made from Chromite Ore, Mill Scale, and Petroleum Coke
- 2017
-
Ingår i: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X. ; 88:5
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, the effectiveness of using briquettes made from chromite ore, mill scale, and petroleum coke for direct chromium alloying is tested by induction furnace trials carried out in three different scales. The experimental results show that steel scrap can be alloyed with chromium by the chromite ore in the briquettes and the Cr yield from the chromite ore increases with the increase in mill scale addition to the briquettes: the more mill scale is added to the briquettes, the lower the mass ratio of Cr to (Cr + Fe) would be, leading to a higher Cr yield from the chromite ore. Specifically, the maximum Cr yield from the chromite ore is 99.9% when the mass ratio of Cr to (Cr + Fe) in the briquettes is 0.05, and being 93.0% when the ratio is 0.10. However, when the ratio of Cr to (Cr + Fe) in the briquettes reaches 0.20, the maximum Cr yield is only 67.1%. The reduction of chromite ore under the present experimental conditions is promoted by a solid-state reduction mechanism.
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| 13. |
- Hu, Xianfeng, et al.
(författare)
-
Thermal Analysis Study on the Carbothermic Reduction of Chromite Ore with the Addition of Mill Scale
- 2016
-
Ingår i: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X. ; 87:5, s. 562-570
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a fundamental study on the carbothermic reduction of chromite ore with the addition of mill scale, which forms the basis for designing an alloying precursor, "chromite ore + mill scale + carbon," for direct chromium alloying. The reduction of chromite ore by petroleum coke with or without the addition of mill scale is investigated by Thermogravimetric Analysis (TGA) under non-isothermal conditions (from room temperature to 1823 K) in the argon atmosphere; the fractional reduced samples were characterized by SEM/EDS and XRD analyses. The experimental results show that the mill scale in the alloying mixture is reduced to high active iron first and disseminated around the chromite ore particles; the reduction of chromite ore is enhanced with the addition of mill scale especially at temperatures higher than 1623 K, and the enhancing effect increased with increasing mill scale addition. The enhancing effect is attributed to the presence of molten Fe-C alloy in the vicinity of chromite ore, which can decrease the thermodynamic activity of chromium by having chromium in situ dissolve into the melt. In this paper, the effect of mill scale addition on the reduction of chromite ore is investigated on the samples with three different amounts of mill scale addition (78 wt%, 38 wt%, and 0 for the samples #1b, #2b, and #3b, respectively) by thermogravimetric technique. The fractional reduced samples are characterized by SEM/EDS and XRD analyses. The mechanism of mill scale addition on the reduction of chromite ore is discussed and the industrial implications of the experimental results are also presented.
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| 14. |
- Hu, Xianfeng, et al.
(författare)
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Thermogravimetric study on carbothermic reduction of chromite ore under non-isothermal conditions
- 2015
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:6, s. 409-416
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the reduction of chromite ore by coke was investigated by means of thermogravimetric analysis under non-isothermal conditions (from room temperature to 1823 K). The fractional reduced samples were examined by SEM/EDS and X-ray diffraction analyses. The experimental results showed that the reduction of iron in the chromite ore started before that of chromium in the ore, and the reduction of chromium and iron in the ore overlapped to some degree. Chromium iron carbide (Cr,Fe)7C3, was found to be the intermediate phase during the reduction, and a chromium gradient was found in the spinel phase of the fractional reduced sample at 1673 K. A four-stage reduction process was proposed: one stage involving the reduction of iron in the chromite ore and three stages involving the reduction of chromium in the ore. The activity aspects of component FeCr2O4 and component MgCr2O4 in the chromite ore were considered. The difficulty in the reduction of the chromite ore is attributed to the fact that, as the reduction proceeds, the activity of the component MgCr2O4 in the fractional reduced ore will decrease to a very low level, which makes further reduction very difficult.
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| 15. |
- Jia, Qi, et al.
(författare)
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Effects of Fine Content, Binder Type and Porosity on Mechanical Properties of Cemented Paste Backfill with Co-Deposition of Tailings Sand and Smelter Slag
- 2016
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Ingår i: Electronic Journal of Geotechnical Engineering. - : Mete Öner. - 1089-3032. ; 21:20, s. 6971-6988
-
Tidskriftsartikel (refereegranskat)abstract
- Mine backfilling is a process where the underground voids resulted from mining are filled with waste materials. The potential of co-depositing iron sand produced from smelting process with tailings sand was investigated in the present study. Different amounts of iron sand were mixed with the tailings sand to prepare cemented paste backfill (CPB) samples. Two types of binders were used. Uniaxial compression tests were performed for the CPB samples after 28 days of curing. The porosities of the samplers after curing were calculated to correlate the porosity with the uniaxial compression strength, UCS. Results from uniaxial compression tests showed that the amount of iron sand and the type of the binder influences the UCS, as well as content values of fines and porosity. These results demonstrated the possibility for a part of Fe-sand to be deposited together with the tailings sand to increase UCS values for the CPB samples, which will be beneficial for both mining operation and environmental protection.
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| 16. |
- Jiang, L., et al.
(författare)
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Experimental investigation on BOF slag oxidation in air
- 2019
-
Ingår i: Ironmaking & steelmaking. - : Taylor and Francis Ltd.. - 0301-9233 .- 1743-2812. ; 46:8, s. 747-754
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Tidskriftsartikel (refereegranskat)abstract
- Basic oxygen furnace (BOF) slag contains a significant amount of iron-containing species, which is considered to be iron resources and therefore need to be recovered. In this work, the oxidation behaviour of BOF slag under air (at selected oxidation temperatures and holding time) was investigated to explore the potential of transforming non-magnetic wustite in the BOF slag into magnetic spinel, which may subsequently be recovered by magnetic separation. The experimental results show that the iron-containing spices in the BOF slag can be oxidised into magnetic spinel phases in the investigated temperature range of 1000–1150°C and thereafter be recovered by magnetic separation. The formation of these phases is closely related to the oxidation temperatures and holding time: a higher oxidation temperature and longer holding time lead to a larger amount of formed magnetic species; however, the amount of formed magnetic species decreases at elevated temperature (>1050°C) and with extended holding time (>40 min).
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| 17. |
- Jiang, Liang, et al.
(författare)
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Formation of Spinel Phases in Oxidized BOF Slag under Different Cooling Conditions
- 2017
-
Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 88:11
-
Tidskriftsartikel (refereegranskat)abstract
- To enhance utilization of wastes generated from steelmaking, a BOF slag sample from Ning Steel group in China is treated by oxidizing at 1500 °C for 30 min and then cooled by different methods. The treated samples are characterized, in combination with calculations using FactSage 6.4. XRD results show that iron oxides in BOF slag are converted largely by the oxidation to spinel phases, Fe3O4 and MgFe2O4, which also eliminates free CaO and MgO. EDS analyses show Fe element existing in di-calcium silicate and glass phase, which are Fe3+ ions formed by oxidation. An incorporation of Fe3+ ions into crystal structures has stabilized high temperature polymorph of C2S, β-C2S, and α’-C2S, in the treated slag samples. Fe3+ ions may also act as a network former to facilitate glass formation. This may make it possible for the glass and α’-C2S phase to complement each other, leading to a higher hydraulicity, while the BOF slag, after the spinel separation, is blended in cements. Some suggestions are proposed, based on the present and early studies, to enhance hydraulicity for the BOF slag, as well as grain sizes of spinel phases, which may result in economic and environmental benefits for steel and cement industries.
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| 18. |
- Jiang, L., et al.
(författare)
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Kinetics of the Oxidation Modification Process of CaO-SiO2-FeO-MgO Slag : [CaO-SiO2-FeO-MgO体系钢渣的氧化改质动力学研究]
- 2018
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Ingår i: Cailiao Daobao/Materials Review. - : Cailiao Daobaoshe/ Materials Review. - 1005-023X. ; 32:2, s. 650-656, 671
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of mineralogical phases in industrial slag transferred from non-magnetic to magnetic substances was carried out in this study, aiming at extraction of superfluous wustite and stabilization of free lime and free periclase. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to investigate the mineralogy and phase distribution. Wet magnetic separation was conducted to determine the recovery rate of iron. The thermodynamic and kine-tic calculations for the oxidation of steel slag in a CaO-SiO2-FeO-MgO system were also performed, and the results were compared with a CaO-SiO2-FeO system. XRD analysis and SEM-EDS observation confirmed the conversion from non-magnetic wustite to magnetite spinel (magnetite/magnesioferrite) after oxidation. Magnetic separation experiment indicated that the optimal oxidation temperature is 1 100℃, which coincided well with the thermodynamic calculations. The addition of periclase had a significant influence on the formation of spinel and leaded to the presence of spinel under a partial pressure of oxygen range log10(PO2)=4.3 (correspon-ding to air). The oxidation process of steel slag could be divided into three steps: initial incubation, chemical reaction and diffusion.
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| 19. |
- Jiang, Liang, et al.
(författare)
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Structural Characteristics and Hydration Kinetics of Oxidized Steel Slag in a CaO-FeO-SiO2-MgO System
- 2019
-
Ingår i: High Temperature Materials and Processes. - : Walter de Gruyter. - 0334-6455 .- 2191-0324. ; 38:1, s. 290-300
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Tidskriftsartikel (refereegranskat)abstract
- Although steel slag exhibits cementitious properties, the addition of steel slag in cement is still limited due to both the presence of excess iron oxides and instability of free lime and periclase. This paper proposes a method for oxidizing molten slag in air, aiming at extraction of superfluous wustite and stabilization of free lime and periclase. Mineralogical characteristics of raw slag and modified products were examined using X-ray diffraction (XRD), scanning electron microscopy equipped with backscattered electron imaging (SEM-BEI), energy dispersive spectrometry (EDS) and thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC). Thermodynamic calculations were performed to aid to discuss the experimental results. The results indicate that non-magnetic wustite and periclase are transformed into magnetic spinel (magnetite/magnesioferrite) after oxidation. Temperature has a significant effect on the formation of spinel. The mass fraction of free lime decreases from 3.54 wt.% to 0.96 wt.% as a result of the conversion from free lime to calcium ferrite.
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| 20. |
- Li, Jian-Li, et al.
(författare)
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Effect of FeO on the formation of spinel phases and chromium distribution in the CaO-SiO2-MgO-Al2O3-Cr2O3 system
- 2013
-
Ingår i: International Journal of Minerals, Metallurgy and Materials. - : Springer Science and Business Media LLC. - 1674-4799 .- 1869-103X. ; 20:3, s. 253-258
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Tidskriftsartikel (refereegranskat)abstract
- Synthetic slag samples of the CaO-SiO2-MgO-Al2O3-Cr2O3 system were obtained to clarify the effect of FeO on the formation of spinel phases and Cr distribution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), as well as the thermodynamic software FactSage 6.2, were used for sample characterization. The results show that the addition of FeO can decrease the viscosity of molten slag and the precipitation temperatures of melilite and merwinite. The solidus temperature significantly decreases from 1400 to 1250 degrees C with the increase of FeO content from 0wt% to 6wt%. The addition of FeO could enhance the content of Cr in spinel phases and reduce the content of Cr in soluble minerals, such as merwinite, melilite, and dicalcium silicate. Hence, the addition of FeO is conducive to decreasing Cr leaching.
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| 21. |
- Liu, G.Q., et al.
(författare)
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Naphthenic acid corrosion characteristic and corrosion product film resistance of carbon steel and Cr5Mo low alloy steel in secondary vacuum gas oil
- 2016
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Ingår i: Corrosion Engineering, Science and Technology. - 1478-422X .- 1743-2782. ; 51:6, s. 445-454
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Tidskriftsartikel (refereegranskat)abstract
- Although naphthenic acid corrosion (NAC) has been studied for many years, the mechanism of NAC is not fully understood. The objective of this paper is to study high-temperature NAC in secondary vacuum gas oil of an industrial crude oil vacuum distillation tower. A high-temperature autoclave was applied to conduct high-temperature corrosion test to investigate NAC behaviour of carbon steel and Cr5Mo low alloy steel at different sulphur contents and total acid numbers (TAN). The result shows that the corrosion rate of carbon steel and low alloy steel is high at low TAN and high TAN while it keeps at a low value at medium TAN. Corrosion product film on Cr5Mo low alloy steel surface is denser and more compact than that of carbon steel at high TAN. The chromium present in Cr5Mo low alloy steel plays an important role in NAC resistance by the formation of Cr7S8 film in the inner layer of the scale. Corrosion rates of the two steels in secondary vacuum gas oil are high at low TAN and high TAN, but low at medium TAN which are strange and different from previous experimental results conducted in non-industrial oil solution. A tentative explanation for this new phenomenon is also put forward.
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| 22. |
- Lui, Gui Qun, et al.
(författare)
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Sintering characteristics of BCSAF cement clinker with added wastes from production of manganese and magnesium metals
- 2017
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Ingår i: Advances in Cement Research. - : Institution of Civil Engineers (ICE). - 0951-7197 .- 1751-7605. ; 29:6, s. 227-235
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Tidskriftsartikel (refereegranskat)abstract
- The production of belite-calcium sulfoaluminate-ferrite (BCSAF) cement with the addition of industrial wastes as feedstock has been studied for many years. The preparation of clinkers is essential in cement production, in which all raw materials react with each other to generate key phases in cement under some specified conditions. The objective of this study was to investigate the sintering characteristics of BCSAF cement clinkers. Four BCSAF clinkers with different compositions were examined. High-temperature microscopy, quantitative x-ray powder diffraction analysis and scanning electron microscopy were used to analyse sintering features and phase composition. The results show that the use of wastes from the production of manganese and magnesium metals, which were added to the raw materials to make clinker pellets, can significantly reduce the firing temperature of BCSAF clinker. The firing temperatures of clinkers with added wastes were below 1300°C, much lower than the temperature used for conventional Portland cement (1450°C). The ferrite phase was always found to inter-grow with the C4A3S¯">C 4 A 3 S ¯ C4A3S¯ phase or C2AS phase, just like the interstitial phase. The ferrite phase acted as a solid solution during cement sintering. A small quantity of iron oxide can make the clinker more porous, leading to energy savings in subsequent grinding processes.
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| 23. |
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| 24. |
- Menad, Nourreddine, et al.
(författare)
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Thermal reduction of EAF dusts by using BF dusts as a reducing agent
- 2005
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Ingår i: Proceedings of the REWAS '04. - : Minerals, Metals & Materials Society. - 8495520060 ; , s. 2751-2760
-
Konferensbidrag (refereegranskat)abstract
- The investigation of the thermal reduction of Electric Arc Furnace Dust (EAFD) by Blast Furnace Dust (BFD) was carried out using simultaneous thermogravimetric analysis (STA) coupled with Quadrupole Mass Spectroscopy (QMS). Chemical and mineralogical analyses were also employed. EAF Dust, which mainly consists of higher zinc compounds as Zincite (ZnO) and Franklinite (ZnFe2O4), is produced in electric arc furnaces (EAF). Blast furnace dust (BFD) with a carbon-iron rich, flue by-product released in the iron-making process was used as a reductant agent. Both raw materials were examined individually in different controlled atmospheres of Ar, air and CO 2 between 20° and 1400°C. Different parameters such as effect of reaction atmosphere, temperature and quantity of the reductant agent were explored. The products of reaction were examined by x-ray diffraction (XRD) as well as the gaseous substances evolved in the reactions. The results indicated that, at 1300°C in Ar atmosphere, a complete reduction of oxide compounds contained in both samples is achieved with a 33 % reductant mixture
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| 25. |
- Mostaghel, Sina, et al.
(författare)
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Recycling of cathode ray tube in metallurgical processes : Influence on environmental properties of the slag
- 2011
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Ingår i: Global Journal of Environmental Science and Technology. - 2248-9630. ; 1:Artikelnr: 19
-
Tidskriftsartikel (refereegranskat)abstract
- A potential recycling rout for the end-of-life cathode ray tubes (CRT) is its application as a fluxing material in lead and copper smelting processes. Therefore, a thorough study on possible effects of the additional CRT on products and by-products of the metallurgical operation is required. In this paper, influences of CRT addition on mineralogy and leaching behaviour of a fayalite-type slag from a Swedish copper producer are investigated. Mixtures of slag/CRT, in different fractions, were prepared and re-melted in a Tamman furnace. Materials characterization using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and standard leaching tests were done for all samples. Results depict that the main crystalline phase of the slag does not change due to CRT addition. By 10 wt-% CRT addition, leachability of major elements decreases; whereas, that of some minor elements increases. With 35 wt-% CRT addition, leaching of some environmentally detrimental elements make the material unacceptable for construction purposes according to the regulations.
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| 26. |
- Mostaghel, Sina, et al.
(författare)
-
The effects of cooling rate on leaching behavior of some ferrous and non-ferrous slag systems
- 2012
-
Ingår i: Model Concept and Experiments.
-
Konferensbidrag (refereegranskat)abstract
- It has been proven that pyrometallurgical slags can be given favorable physico-mechanical characteristics which make them suitable for use in civil engineering applications providing fulfillment of various technical and environmental criteria, of which slag leaching behavior is one of the main concerns. Numerous investigations have been carried out over the last several decades to clarify the influence of cooling rate on microstructure and properties of the slag systems; however, there is controversy in the literature as to the effect of rapid cooling, e.g. water granulation, on release of potentially toxic elements. In the current work, a ladle slag, a basic oxygen furnace (BOF) slag, two different electric arc furnace (EAF) slags, from low-alloyed and high-alloyed steel production, and three different “fayalite-type” slags, from zinc-copper smelting processes with different Fe/SiO2 ratios, are investigated. Semi-rapidly solidified (in crucible system) and water granulated samples for each composition were prepared. The solidified materials were characterized using commonly applied characterization techniques. The experimental work is compared with thermodynamic calculations using the FactSageTM thermodynamic package. Standard European leaching tests were carried out for all samples to investigate the slag leaching behaviors. Results show that rapid solidification and generated amorphous structure do not necessarily immobilize environmentally concerned elements in the glassy network. Instead, due to several factors, a higher reactivity is observed and trace elements dissolve more readily in the aqueous solution. The main reasons behind such a behavior including higher contents of metastable phases, different surface structures, oxidation and increased amount of grain boundaries are thoroughly discussed.
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| 27. |
- Sandström, Åke, et al.
(författare)
-
EAF dust processing with a combination of hydro- and pyrometallurgical techniques
- 2003
-
Ingår i: EPD Congress 2003. - : Minerals, Metals & Materials Society. - 873395328 ; , s. 377-388
-
Konferensbidrag (refereegranskat)abstract
- An EAF dust sample generated in a scrap based steel mill was treated by a combination of hydro- and pyrometallurgical techniques. The EAF dust contained mainly ferritic spinels forming solid solution phases according to the general chemical formula (MnxZnyFe1-x-y)Fe2O4 and other oxide phases such as ZnO, CaO and Ca2Fe2O5. The EAF dust was first treated by hydrochloric acid leaching at pH = 3 which dissolved 63% of the zinc. The pyrometallurgical treatment of the leaching residue was studied using an induction heating system to simulate some important operations of EAF smelting of the residue in combination with steelmaking. The leaching residue was mixed with carbon powder to obtain a mixture with 52.1% ZnFe2O4 and 17.8% carbon. The mixture, scrap, and slag former were charged together in a crucible and heated to attain a melt temperature around 1650DGC. The effects of different amounts of mixture on the zinc balance and iron recovery were examined. Based on the test results, suggestions are made for the EAF recycling procedure of the leaching residue.
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| 28. |
- Tossavainen, Mia, et al.
(författare)
-
Characteristics of steel slag under different cooling conditions
- 2007
-
Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 27:10, s. 1335-1344
-
Tidskriftsartikel (refereegranskat)abstract
- Four types of steel slags, a ladle slag, a BOF (basic oxygen furnace) slag and two different EAF (electric arc furnace) slags, were characterized and modified by semi-rapid cooling in crucibles and rapid cooling by water granulation. The aim of this work was to investigate the effect of different cooling conditions on the properties of glassy slags with respect to their leaching and volume stability. Optical microscopy, X-ray diffraction, scanning electron microscope and a standard test leaching (prEN 12457-2/3) have been used for the investigation. The results show that the disintegrated ladle slag was made volume stable by water granulation, which consisted of 98% glass. However EAF slag 1, EAF slag 2 and the BOF slag formed 17%, 1% and 1% glass, respectively. The leaching test showed that the glass-containing matrix did not prevent leaching of minor elements from the modified slags. The solubility of chromium, molybdenum and vanadium varied in the different modifications, probably due to their presence in different minerals and their different distributions.
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| 29. |
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| 30. |
- Wang, Feng, et al.
(författare)
-
Influence of Mn oxides on chemical state and leaching of chromium in EAF slag
- 2013
-
Ingår i: Metalugia International. - 1582-2214. ; 18:8
-
Tidskriftsartikel (refereegranskat)abstract
- In order to study the influences of Mn oxides on Cr in Electronic Arc Furnace (EAF) slag produced in a stainless steelmaking plant. To simulate EAF slags, two synthetic slags (slag A and slag B) were prepared through melting the two groups of reagent-grade compounds, respectively. The phase composition of samples was characterized by means of XRD. In addition, the slags with different particle size and some mixture were leached following Europe standard procedure. There was only one main compound MgCr2O4 found in spinel phase in slag A. While there were two compounds MgCr2O4 and Mn2AlO4 co-existed in spinel phase in slag B, in which Mn and Cr occupy the octahehral sites. For leaching tests, the influence of different factors, such as slag types, slag particles size, mixed manganese oxides, were studied in detail. The leaching result shows that MnO2 melted in slag is the most important factor for improving Cr leaching. But Mn oxides mixed in Mn-free slag have a little influence on Cr leaching.
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| 31. |
- Wu, Laner, et al.
(författare)
-
Dusting control of magnesium slag produced by Pidgeon process
- 2013
-
Ingår i: Powders and grains 2013. - Melville, NY : American Institute of Physics (AIP). - 9780735411661 ; , s. 1282-1285
-
Konferensbidrag (refereegranskat)abstract
- Magnesium production by Pidgeon process has been developed very fast in China since 1990's. The waste slag from magnesium production has attracted broad attention because the huge amounts of the slag. For each ton of magnesium produced, there will be 6-8 tons of the slag generated. A big part of the Mg slag exists as fine dust with particle size of D95 < 0.1mm, which may pollute air, soil and water surrounding the Mg industry. The fine particles are generated by phase transformations of dicalcium silicate C2S (2CaOṡSiO 2) during the slag cooling. There is a volume expansion of more than 10% with the transformation of β-C2S to γ-C2S phase, causing a disintegration or dusting of the Mg slag. In the present study, several chemical stabilizers were used to treat the dusting Mg slag at 1200°C, including borates, phosphates and rare earth oxides, in order to obtain volume stable slag aggregates for environmental protection and recycling of the Mg slag. The volume expanding rates of the samples were measured. XRD and SEM studies were carried out to confirm effects of the stabilizers. The results show that all of the stabilizers were effective for the stabilization of Mg slag. Some differences between the stabilizers were also described and discussed
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| 32. |
- Wu, Laner, et al.
(författare)
-
Fluoride emissions from Pidgeon process for magnesium production
- 2012
-
Konferensbidrag (refereegranskat)abstract
- Primary magnesium is nowadays produced in China via Pidgeon process. An important reaction in the process is silicothermic reduction of MgO from dolime near 1200ºC under pressure of 2-10 Pa to generate Mg vapor. Fluorite, ranging 2-3% (mass fraction), is usually mixed with the raw materials to catalyze the reaction. Under the process conditions, CaF2 in the fluorite may form some fluorides to vaporize, thus polluting air. The fluorides remaining in the solid process waste, the Mg slag, may be dissolved to cause water pollution.In the present study, experiments were performed by using retorts of pilot scale in a maffle furnace to simulate the Pidgeon process for primary Mg production. The test materials, briquettes of 5.6-10 kg made of dolime, ferrosilicon and fluorite, were charged in the retorts and heated under conditions similar to the industry operation. Fluoride minerals in the Mg slag from the simulation experiments were identified by XRD and SEM-EDS techniques. Quantities of some F-containing phases formed in the process under equilibrium condition were calculated by FactSage 6.2 thermodynamic package. Fluoride distributions were determined to establish an F-balance among the input and output materials. Besides, slag samples from a magnesium plant were also characterized, including leaching test according to EN 12457-2.Based on these results, fluoride impacts on the environment were evaluated and discussed. Suggestions were also presented to minimize the environmental impacts from primary Mg production using the Pidgeon process.
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| 33. |
- Wu, L.N., et al.
(författare)
-
Fluorine vaporization and leaching from Mg slag treated at different conditions
- 2013
-
Ingår i: Advanced Materials Research. - 1022-6680 .- 1662-8985. ; 753-755, s. 88-94
-
Tidskriftsartikel (refereegranskat)abstract
- Both treatments and leaching tests of an Mg slag sample containing F of 2.15% from an Mg factory in northwest China were conducted in the present study, focusing on problems of F pollutions. By treating at 1000-1200°C in a muffle furnace, F leaching was decreased to a minimum level of 0.49-2.85 mg/l from the Mg slag with an original F leaching of 13.9 mg/l. The F leaching values increased to 4.83-95.5 mg/l, while treating the slag samples in a vacuum furnace. The treatments of Mg slag may thus be carried out in oxidizing atmosphere and under 1200°C to minimize fluorine pollutions and to improve environmental performances of the Pidgeon process.
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| 34. |
- Xu, An.Jun, et al.
(författare)
-
Recycling of EAF dust by smelting in the electric arc furnace and its influences on the EAF operation and dust generation
- 2010
-
Ingår i: Journal of Iron and Steel Research International. - 1006-706X .- 2210-3988. ; 17:Suppl. 2, s. 132-141
-
Tidskriftsartikel (refereegranskat)abstract
- The 2(nd) campaign for recycling electric arc furnace dust (EAFD) has been carried out at Uddeholms AB (early as Uddeholm Tooling AB). Studies examining the effects of EAFD smelting on parameters related to EAF products, energy consumption and EAFD generation have been performed jointly by Uddeholms AB and MiMeR, Minerals and Metals Recycling Research Center, at Lulea University of Technology. 114 tonnes of EAFD were smelted in 121 EAF heats during the campaign. Dust samples were taken isokinetically from the exhaust gas system during the charger processing. Data of Zn contents in the dust samples were combined with other results to examine the influence of EAF operating conditions and EAFD recycling on Zn evaporation. Via EAFD recycling, Zn content in dust increased from 21.5% to 29.7% and the quantity of dust decreased by more than 40%. There were hardly any negative impact noted during the campaign on the furnace energy consumption and properties of steel and slag tapped from the EAF, while the recycled EAFD was amounted to around 2% of the steel weight
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| 35. |
- Xue, Peng, et al.
(författare)
-
Air Quenching of Steel slag to Enhance its Hydraulic Activity for Recycling the Slag as Meterials in Cement and Concrete Applications
- 2017
-
Ingår i: Key Engineering Materials. - : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 737, s. 488-493
-
Tidskriftsartikel (refereegranskat)abstract
- A steel slag has been treated by air granulation, in order to enhance cementitious properties of the slag. Two samples with sizes ranged 1.68-2.38mm and 212-297μm and coded as Slag A and Slag B, respectively, were chosen from the granulated slag for investigations. A sample of the original steel slag was also studied. XRD analyses indicated the formations of α-C2S, β-C2S, C2F, C2MS2, f-MgO and α-C2S, C2F, f-MgO in Slag A and Slag B, respectively. The phases in the two slag samples were quite different from the phases found in steel slag. The SEM results show a reduction of C2S sizes from 10-20μm for the steel slag to nano-scales by air quenching for Slag B. This treatment of air quenching has increased the cumulative heat of hydration to 105.35J/g measured for Slag B, almost two times greater than that of the steel slag. The study results demonstrate a high potential for utilizations of the steel slag in cement and concrete applications after the slag treatment by air quenching. The treatment may thus lead to an environmental friendly and cost-effective recycling for the steel slag. This can also contribute to the sustainable developments in the steel and cement/concrete industries.
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| 36. |
- Xue, Peng, et al.
(författare)
-
Formation of MgFe2O4 and recycling of iron from modified BOF slag by magnetic separation
- 2017
-
Ingår i: Kang T'Ieh / Iron and Steel. - : Chinese Society for Metals. - 0449-749X. ; 52:7, s. 104-110
-
Tidskriftsartikel (refereegranskat)abstract
- Recycling of iron oxide from BOF slagshas always been a difficult issue in metallurgy. The core of this study was transforming the iron oxide into ferromagnetic phase MgFe2O4 by modifying industrial BOF slag appropriately first, and then recycling the iron resources by magnetic separation. The effect of basicity and calcination temperature on the formation of MgFe2O4 in synthetic BOF slags was investigated first, and then the industrial BOF slag was modified. Various experiments and analyses such as XRD, SEM-EDS, Factsage thermodynamic simulation and chemical analyses were conducted.The results show that the optimal basicity was 2, and the optimal calcination temperatures were 1 250 and 1 300℃. Moreover, MgFe2O4 was formed in modified BOF slag by mixing the industrial BOF slag with 6% SiO2 first, and then cooling the modified BOF slag from 1 400 to 1 270℃ at a rate of 1℃/min. After magnetic separation, the total Fe content in magnetic slag increased by 15.80%, to 37.00%, compared with that in the industrial BOF slag. This is better than the direct magnetic separation of iron oxide without any treatment
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| 37. |
- Xue, Peng, et al.
(författare)
-
Modification of industrial BOF slag : Formation of MgFe2O4 and recycling of iron
- 2017
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 712, s. 640-648
-
Tidskriftsartikel (refereegranskat)abstract
- Efficient recycling of iron oxide from industrial BOF (basic oxygen furnace) slags has always been an issue in metallurgy. In this study, a new method was developed for the efficient recycling of iron oxide: It was transformed into magnesioferrite spinel (MgFe2O4) by mixing the industrial BOF slag with 6.00% SiO2 first, and then the modified slag got cooled down from 1400 °C to 1270 °C at a rate of 1 °C/min. Finally, the Fe resources were recycled by magnetic separation. Various experiments and analyses such as XRD, SEM–EDS analyses, Factsage thermodynamic simulation, magnetization characterization, dry magnetic separation, and chemical analysis were carried out. The results show that the obtained MgFe2O4 has a high melting point (1716.76 °C in theory) and ferromagnetism (specific magnetic susceptibility of (8.03–206.84) × 10−5 m3/kg). Therefore, it could be separated from the weakly magnetic industrial BOF slag (specific magnetic susceptibility of (0.024–0.136) × 10−5 m3/kg). Furthermore, this new method could be applied to different BOF slags. The yield of MgFe2O4 increased to above 80% when the content of Fe2O3 was in the range 25.81–46.90%. After the modification and magnetic separation, the total Fe content increased by 15.80%, from 21.20% in the industrial BOF slag to 37.00% in the magnetic slag. This is better than the direct magnetic separation of iron oxide without any treatment. The magnetic slag could be reused as either a sintering or slag splashing material. The nonmagnetic slag can be used to produce high value-added building materials. Hence, this new method can be used to recycle the iron oxide from industrial BOF slags, achieving the sustainable development of the iron and steel industry.
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| 38. |
- Xue, Peng, et al.
(författare)
-
Research on the sintering process and characteristics of belite sulphoaluminate cement produced by BOF slag
- 2016
-
Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 122, s. 567-576
-
Tidskriftsartikel (refereegranskat)abstract
- The sintering process of belite sulphoaluminate cement (CSA1) clinker is still not clear to date. Besides, there are few reports concerning producing CSA by recycled BOF slag. Therefore, the sintering process of CSA was investigated from this perspective and the results can be a reference for BOF slag disposal. Four kinds of CSA clinkers with different additions of BOF slag were sintered at 1300 °C for 30 min. The sintering process was traced by heating microscope and the characteristics were analyzed by XRD, SEM-EDS and TAM Air. The results showed that the sintering degree of CSA clinker could be predicted by analyzing its sintering process. Furthermore, BOF slag could improve the melting state of CSA clinkers due to its composition containing iron oxide, manganese oxide and magnesium oxide. However, expansion was detected when the temperature reached 420 °C, which was arose by combined factors, namely volatilization of CO2 decomposed from MgCO3 and the thermal expansion of raw materials itself. The rational ratios of C2S, C4A3View the MathML sourceS¯, C4AF in CSA clinker with 14% BOF slag as raw material stood at 50%, 30%, 20% and its early hydration behavior was better than that of ordinary Portland cement (OPC) at the initial 16 h.
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| 39. |
- Yang, Qixing, et al.
(författare)
-
A fundamental study on recycling of wastes from stainless steel plants via the electric arc furnace
- 2000
-
Ingår i: 58th Electric Furnace Conference and 17th Process Technology Conference. - : Iron and Steel Society. - 1886362467 ; , s. 195-207
-
Konferensbidrag (refereegranskat)abstract
- Waste briquettes of high carbon contents have been smelted using an induction furnace in tests to gain fundamental information for EAF operations of the briquette smelting. The briquettes amounted to 5-15% of the weights of the metal charges, stainless steel scrap and alloys.
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| 40. |
- Yang, Qixing, et al.
(författare)
-
A laboratory study on smelt-reduction of briquettes made of wastes from stainless steel production
- 1999
-
Ingår i: REWAS '99. ; , s. 1061-1072
-
Konferensbidrag (refereegranskat)abstract
- Wastes from stainless steel production were briquetted together with carbon for smelt-reduction in the electric arc furnace, EAF, to achieve an internal recycling. A laboratory induction furnace was used to simulate the EAF to study the disintegration of the briquettes under heating and recovery of metals from briquettes melted together with stainless steel and slag-former. The influences of test conditions on carbon reduction of oxides in the briquettes were also examined. The briquettes endured heating at 1186°C under load and could be charged to the melt in small quantity without causing serious splashing. For a high metal recovery, it was necessary to charge the briquettes together with slag-former. Small local zones of smelt-reduction with high carbon concentration could thus be formed during heating. Silicon content in the metal near to the briquettes should be minimised to achieve a high degree of carbon reduction. Based on results obtained from this study, suggestions were made on smooth operations of smelt-reduction of the briquettes by using electric arc furnaces of large scale
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| 41. |
|
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| 42. |
- Yang, Qixing, et al.
(författare)
-
Briquette Smelting in Electric Arc Furnace to Recycle Wastes from Stainless Steel Production
- 2015
-
Ingår i: Journal of Iron and Steel Research International. - 1006-706X .- 2210-3988. ; 22:Suppl. 1, s. 10-16
-
Tidskriftsartikel (refereegranskat)abstract
- Wastes from stainless steel production were briquetted together with carbon for smelt-reduction in the electric arc furnace, EAF, to achieve an internal recycling. A laboratory induction furnace was used to simulate the EAF. With a close simulation of the smelting, disintegration of the briquettes heated under load and recovery of metals from briquettes melted together with stainless steel and slag former were investigated. The influences of test conditions on carbon reduction of oxides in the briquettes were also examined. The briquettes endured heating at 1 186 °C under load of 3.5 kg and could be charged to the melt in small quantity without causing serious splashing. For a high metal recovery, it was necessary to charge the briquettes together with slag former. Small local zones of smelt-reduction with high carbon concentration could thus be formed during the charger heating. Silicon content in the metal near to the briquettes should be minimised to achieve a high degree of carbon reduction. Based on results obtained from this study, suggestions were made on smooth operations of smelt-reduction of the briquettes by using EAF or induction furnace with large scales.
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| 43. |
- Yang, Qixing, et al.
(författare)
-
Dissolution behavior of fluorine from AOD slag after treatments for volume stabilization
- 2014
-
Ingår i: Applied Mechanics and Materials. - 1660-9336 .- 1662-7482. ; 587-589, s. 849-855
-
Tidskriftsartikel (refereegranskat)abstract
- AOD slag samples from steel works of Outokumpu Stainless Company were used to study F-dissolution relating to treatments for volume stabilization. Results from the slag tests and sample characterizations indicate that the slag re-melting with or without reduction and granulation with either water or gas have rather small effects on F leaching, as well as formation of different C2S polymorphs. The chemical composition and cooling condition are the two important parameters to control F leaching from slag samples. These two parameters should be combined together in an optimum way by the steel industry to treat slags for F-immobilization.
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| 44. |
- Yang, Qixing, et al.
(författare)
-
Dissolution behavior of fluorine in AOD slag from the production of stainless steel after treatment for volume stabilization
- 2012
-
Ingår i: Scanmet IV. - Luleå : MEFOS. - 9789163708596 ; , s. 517-526
-
Konferensbidrag (refereegranskat)abstract
- The slag tapped from AOD (Argon Oxygen Decarburization) converter disintegrates, sometimes, during cooling. Slag fines from the disintegration are difficult to handle and to use as materials for construction purposes. In our early research work, AOD slag samples were modified by agents containing B or P elements. Different slag cooling procedures were also used, including cooling inside crucibles after re-melting and granulation by water and gas. By the modification, the slag samples gained the volume stability and mechanical properties required for its utilization as construction materials.Different types of stainless steel slag from Outokumpu Stainless Company have been used to manufacture environmentally sound and ce-marked construction products. Fluorine leaching from some of the AOD slag samples were investigated. In some other steelmaking processes, such as hot metal pretreatment, secondary steel refining and the production of high alloyed steels, fluorite can be charged as a slag forming agent, with some F and CaF2 existing in the slag. When these slags are reused as road construction or landfill materials, a potential fluorine contamination to the ground water may occur.The present research work is carried out regarding both the volume stability and F-immobilization for AOD slag samples. The studied slag samples consist of new ones from plant gas granulation tests and some old ones from our early studies. Compositions and cooling conditions are selected as main parameters for slag tests using laboratory equipment. Samples from the plant and laboratory slag tests are characterized by XRD, SEM and leaching with EN12457-2/3. Formations of mineral phases for F-immobilization in the slag samples are also predict using FACTSAGE program.Results from the present study indicate that the chemical composition and cooling condition for a slag are the two important parameters to control F leaching. These two parameters should be considered together in an optimum way to treat the slag for fluorine immobilization.It may be possible, based on the results obtained, to develop some environmental friendly and cost effective methods for the stainless steel industry to treat the AOD slag. Some slag products with high volume stability and minimum F-dissolution may thus be obtained to use as construction materials for saving valuable natural resources.
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| 45. |
- Yang, Qixing, et al.
(författare)
-
EAF smelting trials of briquettes at Avesta works of Outokumpu Stainless Steel AB for recycling oily mill scale sludge from stainless steel production
- 2008
-
Ingår i: SCANMET III. - Luleå : MEFOS. - 9789163322693 ; , s. 561-570
-
Konferensbidrag (refereegranskat)abstract
- The production EAF of Avesta Works, Outokumpu Stainless AB, has been used to perform smelting reduction trials of briquettes consisting of oily mill scale sludge, carbon and other wastes. The trials were among several important activities in studies on waste recycling by EAF smelting carried out jointly by Avesta Works and MiMeR, the Minerals and Metals Recycling Research Centre, at Luleå University of Technology. A total of 7 briquette smelting trials were performed. The heats were processed smoothly smelting 3 tonnes of briquettes or 3,4% of the weight for metal charges. Quantities of FeSi powder and O2 gas injected and electric energy supplied were increased while the briquette weight was increased to 6 tonnes. No impacts were found on analyses of the crude stainless steel tapped from the EAF during the trials. Results of the briquette smelting have been evaluated by referring to the data from the reference heats and results from early laboratory tests. The recovery of Cr, Ni and Fe elements from the briquettes was nearly complete and was found to occur mainly through carbon reduction. Positive effects of briquette smelting on protecting metallic charges against gaseous oxidation have also been identified. This protection was through CO gas, generated from solid state C-O reaction in the briquettes, reacting with oxygen in the intruding air. The protection reduced losses of Cr, Ni and Fe elements from metallic charges to the slag. The slag weights were not increased in three trials as compared with the reference heats. There were moderate increases in the slag weights in four trial heats. The increases were, nevertheless, lower by 52-69% than the slag weights generated by a Si-reduction of the briquette oxides. By smelting 6-tonnes of briquettes in the trials, reliable information and results on C-O reactions in the briquettes for recovery of metal elements in the production EAF were obtained. After the trials, carbon-waste briquettes amounting to 1-3 tonnes were smelted very smoothly in many of the EAF heats at Avesta Works to recycle the oily mill scale sludge and other wastes from stainless steel production. The metal recoveries from the briquettes were then estimated based on the information and results of the C-O reaction and metal recovery obtained from the present trial heats.
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| 46. |
- Yang, Qixing, et al.
(författare)
-
EAF smelting trials of waste-carbon briquettes at Avesta works of Outokumpu Stainless AB for recycling oily mill scale sludge from stainless steel production
- 2009
-
Ingår i: Steel Research International. - 1611-3683 .- 1869-344X. ; 80:6, s. 422-428
-
Tidskriftsartikel (refereegranskat)abstract
- The EAF steel plant of Avesta Works, Outokumpu Stainless AB, has been used to perform smelting reduction trials of briquettes consisting of oily mill scale sludge, carbon and other wastes. A total of 7 briquette smelting trials were performed. The heats were processed smoothly smelting 3 t of briquettes or 3.4 mass-% of metal charges. The quantities of FeSi powder and 02 gas injected and electric energy supplied were increased to smelt briquettes of 6 t. No impacts were found on the analyses of the crude stainless steel tapped from the EAF during the trials. The results of the briquette smelting have been evaluated by referring to the data from the reference heats and results from earlier laboratory tests. The recovery of Cr, Ni and Fe elements from the briquettes was nearly complete and was found to occur mainly through carbon reduction. The slag masses were not increased in three trials as compared with the reference heats. There were moderate increases in the slag masses in four trial heats. The increases were, nevertheless, lower by 52-69% than the slag masses generated by Si-reduction of the briquette oxides. Afterwards, by referring results from the present trials, waste-carbon briquettes amounting to 1-3 t were smelted very smoothly in many of the EAF heats at Avesta Works to recycle the oily mill scale sludge and other wastes from stainless steel production.
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| 47. |
- Yang, Qixing, et al.
(författare)
-
Effects of bubble expansion on wear of refractory for BOF stirring plugs embedding tuyères
- 1997
-
Ingår i: Steel research. - : Wiley. - 0177-4832. ; 68:3, s. 107-114
-
Tidskriftsartikel (refereegranskat)abstract
- Single tuyere wear tests of MgO-C and burnt magnesia bricks were performed to study relations between tuyere characteristics and refractory wear parameters, with emphasis on the wear zone geometry. Either Ar or N2 was used as injected gas and the test temperature for liquid metal was 1400, 1550 and 1700 °C. A bubble expansion wear mechanism was proposed for the mechanical wear of tuyere refractory by comparison of bubble radii and the wear zone geometry of refractory bricks and H3BO3 disks. Equations are derived to predict the deep and shear wear zone radii and the refractory wear rate at values of the nominal Mach number up to one. These equations can be used for an optimum design of single- and multiple-tuyere plugs for combined blowing BOF, as well as for optimization of gas stirring operation to reduce the wear of MgO-C refractory around the tuyere and for the plugs.
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| 48. |
- Yang, Qixing, et al.
(författare)
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Effects of gas jet instability on refractory wear. A study by high-speed photography
- 1992
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Ingår i: Scandinavian journal of metallurgy. - 0371-0459 .- 1600-0692. ; 21:1, s. 15-26
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Tidskriftsartikel (refereegranskat)abstract
- To study influences of gas jet instability on tuyere refractory wear, gas injection was performed in an air-water system with a tuyere of 2 mm inner diameter. High-speed photography was used, with a framing rate of 8000 pictures per second, to film the tip region of a free and a half free tuyere. Characteristics of the cavity formed as a result of the jet instability were measured from the films, and the results were used in equations of bubble dynamics to calculate the pressure generated by the cavity motion. The film sequences show that as a result of the distortion of the gas-liquid interface, a throat in the gas jet is formed about 1.5D (tuyere i.d.) downstream of the tuyere tip. Radially moving gas starts to form an expanding cavity. The radius of the throat increases as it is pushed forward by the cavity expansion. With its radius reaching the maximum, the cavity stops growing. When the cavity collapses, bubble swarms are generated in the region near the tuyere. The cavity expands to 2D-4D (tuyere i.d.) within 1-15 ms. The maximum velocity of the expansion is about 10 m/s and acceleration ranges from 20 to 80 m/s2. The pressure calculated by using the cavity expansion data is in good agreement with the pressure measured at back-attack, which is around one half of the absolute pressure for the gas injection. This implies that the back-attack and cavity expansion are the same phenomenon. Passing the transition point of flow regimes the pressure increases very slowly as the injection rate increases. Occassionally, the cavity does not collapse immediately and it contracts after reaching the maximum radius. The cavity contraction generally takes longer than the expansion, with a velocity of about 2 m/s. The pressure reduction from the contraction is less than 0.1 bar which can not cause the formation of vapour bubbles in the liquid. By the cavity expansion, a liquid flow is set up which deforms and disintegrates gas bubbles nearby. At the moment of disintegration, liquid penetrates the concave side of the deformed bubble. The liquid flow may lead to an impact pressure of 30-90 bar in water and 210-630 bar in liquid steel. This pressure may cause refractory erosion with a pattern similar to that previously observed on H3BO3 disk surface. Besides the pitting erosion of the tuyere refractory, the influences of the jet instability on other factors of the refractory wear are also discussed.
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| 49. |
- Yang, Qixing, et al.
(författare)
-
Erosion of referactory during gas injection : a cavitation based model
- 1989
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Ingår i: Scaninject V. - : MEFOS. ; , s. 259-289
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Konferensbidrag (refereegranskat)abstract
- The problem of tuyere refractory wear has been studied in an air--water model using a 4 mm diamter tuyere. Erosion tests, with boric acid (H sub 3 BO sub 3 ) disks as refactory simulators, and measurements of back-attack frequency were carried out. The erosion pattern shows two distinct features: isolated elliptical pits and a continuous irregular shear wear pattern. The influence on these features of the surface hardness and gas flow rate was investigated. 24 ref.--
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| 50. |
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