The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Tao Jiang - One of the best experts on this subject based on the ideXlab platform.
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selective recovery of chromium from Ferronickel slag via alkaline roasting followed by water leaching
Journal of Hazardous Materials, 2019Co-Authors: Yuanbo Zhang, Huimin Tang, Weiguang Tian, Guoshen Liang, Zhiwei Peng, Joonho Lee, Mingjun Rao, Tao JiangAbstract:Chromium was selectively recovered from Ferronickel slag by roasting the slag with addition of Na2O2, followed by water leaching. The thermodynamic analysis revealed that in the presence of Na2O2 at appropriate temperatures, the Cr2O3 in the Ferronickel slag can be converted to NaCrO2, instead of Na2CrO4, which prevents the formation of highly toxic Cr (VI). The experimental results confirmed that under the optimal alkaline roasting and water leaching conditions of the mass ratio of Ferronickel slag to Na2O2 of 1, roasting temperature of 600 °C, roasting time of 1 h, leaching temperature of 50 °C, leaching time of 1 h, and liquid-to-solid ratio of 10 mL/g, 92.33% of Cr was leached with 64.28% of Na and 11.16% of Si and only 0.06 wt % Cr was left in the leaching residue. The high leaching percentage of Cr was a result of the transformation of Cr2O3 in the Ferronickel slag to NaCrO2 with a loose structure during alkaline roasting that was beneficial to water dissolution. Compared to the traditional alkaline roasting process, the proposed more environmentally friendly method did not produce toxic Cr (VI) during recovery of chromium and the resulting residue has potential to be used as a good construction material.
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valorization of Ferronickel slag into refractory materials effect of sintering temperature
JOM, 2019Co-Authors: Zhiwei Peng, Huimin Tang, Weiguang Tian, Guoshen Liang, Yuanbo Zhang, Joonho Lee, Mingjun Rao, Tao JiangAbstract:Preparation of refractory materials from Ferronickel slag by sintering over a broad temperature range (1200°C to 1500°C) with addition of sintered magnesia was explored. The thermodynamic calculations indicated that the amounts of newly generated high-melting-point forsterite and spinel phases increase with increasing temperature. The experimental analysis demonstrated that elevating the sintering temperature promoted conversion and crystallization of forsterite and spinel phases from the original phase of the slag, with simultaneous reduction of low-melting-point enstatite. There was also rapid growth of spinel grains from about 0.5 μm to 5 μm, which should be controlled by selecting an appropriate temperature. The results showed that, by sintering the slag at 1400°C for 3 h with addition of 20 wt.% sintered magnesia, a high-quality refractory material with refractoriness of 1680°C, bulk density of 2.93 g/cm3, apparent porosity of 1.81%, and compressive strength of 166.62 MPa was obtained.
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From Ferronickel slag to value-added refractory materials: A microwave sintering strategy
Resources Conservation and Recycling, 2019Co-Authors: Zhiwei Peng, Huimin Tang, Weiguang Tian, Yuanbo Zhang, Robin Augustine, Joonho Lee, Yanhu Chen, Tao JiangAbstract:Abstract The present study proposes a novel strategy for preparation of refractory materials from potentially hazardous Ferronickel slag by microwave sintering of the slag with addition of sintered magnesia in which a series of chemical reactions were involved. This strategy was developed based on examination of the phase transformations and microstructural changes of the slag during microwave sintering through X-ray diffraction (XRD) analysis and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis, which determined the properties of refractory materials derived from the slag. It was shown that under microwave irradiation there existed rapid transformation of the olivine phase in the slag to high-melting point phases, including forsterite and spinels (e.g., magnesium iron chromate spinel, magnesium chromate spinel, and magnesium iron aluminate spinel). As a result, a high-quality refractory material with refractoriness of 1730 °C, bulk density of 2.80 g/cm3, apparent porosity of 1.6%, and compressive strength of 206.62 MPa was obtained by microwave sintering of the slag at 1350 °C for only 20 min with addition of 25 wt % sintered magnesia. Because the microwave sintering strategy not only elevated the refractoriness by 70 °C, but also reduced the heating duration required by the conventional approach by 6 times, it demonstrated apparent technological superiority and wide application prospect in preparing superior-quality refractory materials from Ferronickel slag and relevant industrial waste, which contributed to conservation of resources and energy as well as environmental protection.
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chromium a double edged sword in preparation of refractory materials from Ferronickel slag
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Zhiwei Peng, Huimin Tang, Weiguang Tian, Guoshen Liang, Yuanbo Zhang, Mingjun Rao, Tao JiangAbstract:This study reports the role of chromium as a double-edged sword in the preparation of refractory materials from Ferronickel slag with the addition of sintered magnesia based on the thermodynamic analysis and experimental exploration of the phase transformation of Ferronickel slag during the sintering process. The results of thermodynamic calculation, X-ray diffraction, and electron probe microanalysis revealed that in the presence of sintered magnesia (20 wt %) and Cr2O3 (0–6 wt %), forsterite, donathite (instead of magnesium chromate spinel generated without addition of Cr2O3), magnesium aluminate spinel, and enstatite were formed. The forsterite and spinel phases contributed to high refractoriness of the prepared material by sintering. However, with excessive addition of Cr2O3 (>6 wt %), the quantity of enstatite increased obviously, which would lower the refractoriness of refractory material. For this reason, the addition of chromium or its content in the slag should be carefully controlled to fully ex...
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facile route for preparing refractory materials from Ferronickel slag with addition of magnesia
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Zhiwei Peng, Huimin Tang, Weiguang Tian, Guoshen Liang, Yuanbo Zhang, Mingjun Rao, Tao JiangAbstract:The feasibility of a facile technological route to preparation of refractory materials from a Ferronickel slag with the addition of sintered magnesia was verified in this study based on the thermodynamics analysis and the experimental exploration of the effect of the sintered magnesia addition on the phase transformation of Ferronickel slag during the sintering process. For the first time, the results of thermodynamics calculation, X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analyses revealed that the original phase of the slag can be transformed to high melting point phases by addition of MgO during the sintering process at high temperatures (e.g., 1350 °C). Specifically, the olivine in Ferronickel slag decomposed initially, generating a low-iron olivine phase and an enstatite phase. With increasing addition of sintered magnesia, the enstatite phase changed to forsterite, and the iron, aluminum, and chromium components in the Ferronickel slag c...
Konstantinos Komnitsas - One of the best experts on this subject based on the ideXlab platform.
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factors affecting co valorization of fayalitic and Ferronickel slags for the production of alkali activated materials
Science of The Total Environment, 2020Co-Authors: Konstantinos Komnitsas, Georgios Bartzas, Vasiliki Karmali, Lourdes Yurramendi, Evangelos PetrakisAbstract:Abstract The first objective of this experimental study is the assessment of the alkali activation potential of two types of fayalitic slags, an as-received one (FS) and the one obtained after plasma treatment (FSP) of the initial FS, for the production of alkali activated materials (AAMs). Furthermore, the second objective is the elucidation of the co-valorization potential of FS and FSP slags when mixed with Ferronickel (FeNi) slag (LS). The alkaline activating solution used was a mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The effect of various operating parameters, such as H2O/Na2O and SiO2/Na2O ratios present in the activating solution, curing temperature, curing period and ageing period on the compressive strength, density, water adsorption, porosity and toxicity of the produced AAMs was explored. The structural integrity of selected AAMs was investigated after firing specimens for 6 h at temperature up to 500 °C, immersion in distilled water and acidic solution or subjection to freeze-thaw cycles for a period of 7 or 30 days. The results of this study show that FS- and FSP-based AAMs acquire compressive strength of 44.8 MPa and 27.2 MPa, respectively. When FS and FSP were mixed with LS at 50:50%wt ratios the compressive strength of the produced specimens increased to 64.3 MPa and 45.8 MPa, respectively. Furthermore, selected AAMs produced after co-valorisation of slags retained sufficient compressive strength after firing at 500 °C, 45–68 MPa, and exhibited very low toxicity. These findings prove the alkali activation potential of fayalitic slags as well as their co-valorization with Ferronickel slag for the production of AAMs, an approach which is in line with the principles of zero-waste and circular economy.
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Assessment of Alkali Activation Potential of a Polish Ferronickel Slag
MDPI AG, 2019Co-Authors: Konstantinos Komnitsas, Georgios Bartzas, Vasiliki Karmali, Evangelos Petrakis, Witold Kurylak, Grzegorz Pietek, Jarosław KanasiewiczAbstract:In this study, the alkali activation potential of a Polish Ferronickel slag (PS), for the production of inorganic polymers (IPs), is investigated. The effect of the main synthesis parameters, i.e., strength of the activating solution, consisting of NaOH and Na2SiO3 solutions and affecting (SiO2 + Al2O3)/Na2O and other important molar ratios in the reactive paste, pre-curing period, curing temperature and time and ageing period was investigated. The structural integrity of the produced specimens was tested after their (i) immersion in distilled water and acidic solutions for a period of 7–30 days, and (ii) firing at temperatures between 200 °C and 1000 °C. Several analytical techniques including X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, Differential scanning analysis-Thermogravimetry and Scanning Electron Microscopy were used for the characterization of the produced IPs. Results show that under the optimum synthesis conditions the IPs obtain compressive strength that exceeds 65 MPa. An innovative aspect of this study is that after heating at 400 °C, the specimens acquire compressive strength of 115 MPa and this indicates that they can be also used as fire resistant materials. This study highlights the potential of alkali activation for the valorization of a Ferronickel slag and the production of IPs that can be used as binders or in several construction applications, thus improving the sustainability of the metallurgical sector
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valorization of construction and demolition c d and industrial wastes through alkali activation
Construction and Building Materials, 2016Co-Authors: Dimitra Zaharaki, Michalis Galetakis, Konstantinos KomnitsasAbstract:Abstract In the present experimental study, the valorization of construction and demolition (C&D) and industrial wastes, namely Ferronickel slag and red mud, through alkali activation is investigated. Specimens were produced by mixing various proportions of the raw materials with NaOH and sodium silicate solutions. The paste was cast in cubic metal moulds with an edge of 5 cm, cured at 80 °C for 24 h and then aged for 7 days at room temperature. The produced specimens were subjected to compressive strength testing. The effect of the molarity of the activating solution, the mineralogy of the raw materials and the ratios of SiO 2 /Al 2 O 3 and SiO 2 /(Al 2 O 3 + CaO) on the compressive strength of the final products was investigated. Also, the effect of high temperature heating (400–800 °C) on the structural integrity of the produced specimens was assessed. The use of analytical techniques, namely X-ray diffraction, Thermogravimetric Analysis, Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy provided insights on the morphology, structure and thermal resistance of the produced specimens.
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life cycle assessment of Ferronickel production in greece
Resources Conservation and Recycling, 2015Co-Authors: Georgios Bartzas, Konstantinos KomnitsasAbstract:Abstract Ferronickel (FeNi) is predominantly produced from nickeliferous laterite ores which are converted into a product with a nickel content of around 20%. With increasing emphasis being put on energy efficiency and global climate change, it is important for the nickel industry to further explore energy saving issues and to evaluate a number of potential opportunities for reducing the greenhouse gas footprint of primary FeNi production. The present study adopted a life cycle assessment (LCA) approach to assess energy consumption and greenhouse gas footprints of the main processing stages of a typical Greek nickel laterite ore for the production of Ferronickel. In this context, a detailed life cycle directory was created based on facility-specific data and used for a holistic cradle-to-gate LCA analysis (including mining and the main ore processing routes). The following energy and environmental indicators were assessed: global warming potential (GWP), acidification potential (AP) and primary energy demand (PED). Using current FeNi production as a baseline scenario (BL), two alternative scenarios, namely (i) the green energy (GE) scenario that involves 50% substitution of fossil fuels mix (lignite and coal) with biochar and 50% substitution of lignite with renewable resources for electricity production, and (ii) the waste utilization (WU) scenario that includes 65% utilization of slag in the construction sector, to improve energy and waste utilization, minimize the adverse environmental impacts and therefore achieve more sustainable FeNi production were investigated. Results showed that the best alternative scenario for energy savings and reduction of associated GHG emissions during FeNi production was the GE scenario. With this scenario energy savings and GHG emissions were about 17% and 35% lower compared to BL scenario, respectively. Lower reduction in energy consumption (7%) and GHG emissions (13%) compared to the BL scenario was attained when the WU scenario was considered.
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effect of sulphate and nitrate anions on heavy metal immobilisation in Ferronickel slag geopolymers
Applied Clay Science, 2013Co-Authors: Konstantinos Komnitsas, Dimitra Zaharaki, Georgios BartzasAbstract:article i nfo Industrial wastes need to be valorised and new techniques need to be developed for the production of secondary materials or immobilisation of hazardous elements in order to improve sustainability of the respective industrial sector. In the present experimental study the effect of monovalent and divalent anions, such as sulphate and nitrate, on heavy metal immobilisation in Ferronickel slag geopolymers was investigat- ed. Low calcium electric arc Ferronickel slag was geopolymerised using KOH and Na2SiO3 as activators, in the presence of limited quantities of sulphate and nitrate salts of Pb, Cu, Cr or Ni. Gel properties, final strength of the specimens produced and immobilisation of heavy metals were determined, in order to explore the poten- tial of geopolymerisation in developing a hazardous waste encapsulation matrix. In addition, the Toxicity Characteristics Leaching Procedure was used to assess the potential toxicity of the produced geopolymers. The experimental results indicate that even limited quantities of sulphates and nitrates in the starting mix- ture affect adversely geopolymerisation of Ferronickel slag. XRD (X-ray diffraction), SEM (scanning electron microscopy) and FTIR (Fourier transform infrared spectroscopy) studies were carried out to identify new phases, reactions taking place and thus elucidate the main mechanisms involved.
Ashish Kumer Saha - One of the best experts on this subject based on the ideXlab platform.
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effect of sulphate exposure on mortar consisting of Ferronickel slag aggregate and supplementary cementitious materials
Journal of building engineering, 2020Co-Authors: Ashish Kumer Saha, Prabir Kumar SarkerAbstract:Abstract The present study evaluates the effect of sulphate attack on mortar samples consisting of different proportions of Ferronickel slag (FNS) aggregate and supplementary cementitious materials (SCM) such as fly ash and ground FNS (GFNS). The physical and chemical changes occurred in mortar specimens after exposure to 5% sodium sulphate solution were investigated. The test results showed no significant effect of using different percentages of FNS aggregate on sulphate attack of the specimens. Higher expansion and strength loss with visible surface cracking were noticed in the specimens using no SCM. Specimens using fly ash or GFNS as SCM exhibited low expansion and only marginal strength losses. This improvement against sulphate resistance by fly ash and GFNS was due to their pozzolanic activity that improved the microstructure and prevention of ettringite formation, which was confirmed by scanning electron microscopic (SEM) images and energy dispersive spectroscopy (EDS). Therefore, the use of FNS aggregate did not have any negative effect on the sulphate resistance of mortar specimens. The use of GFNS improved sulphate resistance by pozzolanic reaction similar to that of fly ash.
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durability characteristics of concrete using Ferronickel slag fine aggregate and fly ash
Magazine of Concrete Research, 2018Co-Authors: Ashish Kumer Saha, Prabir Kumar SarkerAbstract:The production process of Ferronickel generates an enormous amount of slag (FNS) as a by-product, which has potential for use as a fine aggregate in concrete. However, information regarding the dur...
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durability of mortar incorporating Ferronickel slag aggregate and supplementary cementitious materials subjected to wet dry cycles
International Journal of Concrete Structures and Materials, 2018Co-Authors: Ashish Kumer Saha, Prabir Kumar SarkerAbstract:This paper presents the strength and durability of cement mortars using 0–100% Ferronickel slag (FNS) as replacement of natural sand and 30% fly ash or ground granulated blast furnace slag (GGBFS) as cement replacement. The maximum mortar compressive strength was achieved with 50% sand replacement by FNS. Durability was evaluated by the changes in compressive strength and mass of mortar specimens after 28 cycles of alternate wetting at 23 °C and drying at 110 °C. Strength loss increased by the increase of FNS content with marginal increases in the mass loss. Though a maximum strength loss of up to 26% was observed, the values were only 3–9% for 25–100% FNS contents in the mixtures containing 30% fly ash. The XRD data showed that the pozzolanic reaction of fly ash helped to reduce the strength loss caused by wet–dry cycles. Overall, the volume of permeable voids (VPV) and performance in wet–dry cycles for 50% FNS and 30% fly ash were better than those for 100% OPC and natural sand.
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soundness and compressive strength of portland cement blended with ground granulated Ferronickel slag
Construction and Building Materials, 2017Co-Authors: Muhammad Rahman, Prabir Kumar Sarker, Faiz Uddin Ahmed Shaikh, Ashish Kumer SahaAbstract:Abstract This paper evaluates the fresh and hardened properties of cement pastes and mortars blended with a ground granulated high-magnesium Ferronickel slag (FNS). The main elements of the slag are Silicon (Si), Magnesium (Mg) and Iron (Fe). Test results show that water demand and setting times were not significantly changed by use of the FNS as cement replacement up to 50%. Le-Chatelier soundness test, autoclave expansion test and accelerated curing at 80 °C for 120 days showed no increase of expansion by up to 65% FNS despite its high magnesium content. This is because the Mg was found to be in the form of stable forsterite ferroan that did not take part in the hydration and expansive Mg(OH)2 (Brucite) was not found in the scanning electron microscope (SEM) images of the microstructure and powder X-ray diffraction (XRD). The 28-day strength activity index of the FNS was 84%. The 90-day mortar compressive strengths were 93% and 68% of the control specimen for 20% and 50% FNS respectively. Thus the soundness and strength development of the ground FNS were found comparable to those of other commonly used supplementary cementitious materials such as class F fly ash.
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compressive strength of mortar containing Ferronickel slag as replacement of natural sand
Procedia Engineering, 2017Co-Authors: Ashish Kumer Saha, Prabir Kumar SarkerAbstract:Abstract Uses of various industrial by-products have been extensively studied in the past few decades in order to enhance the sustainability of construction industry. By-products can be used as alternatives to binders as well as aggregates in concrete. A large quantity of granulated Ferronickel slag (FNS) is produced as a by-product in the smelting of nickel ore. This paper presents the effects of using Ferronickel slag as a replacement of natural sand in cement mortar. The slag was produced by sea water-cooling of the by-product from the smelting of garnierite nickel ore. The grain size distribution of the slag was found suitable for using as fine aggregate in concrete. It was found that flow of fresh mortar increased with the increase of FNS up to 50% replacement of sand and then declined with further increase of FNS. The compressive strength of the hardened mortar specimens increased with the increase of FNS up to 50% and then declined with further increase of FNS. Use of fly ash as 30% cement replacement together with FNS as replacement of sand increased the flow of fresh mortar and decreased the strength of hardened specimens.
Zhonghui Chen - One of the best experts on this subject based on the ideXlab platform.
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effect of Ferronickel slag as fine aggregate on properties of concrete
Construction and Building Materials, 2019Co-Authors: Jianwei Sun, Jingjing Feng, Zhonghui ChenAbstract:Abstract This study investigated the influence of Ferronickel slag replacing sand as fine aggregate on the properties of concrete under the same superplasticizer content. The results indicate that the addition of two types of Ferronickel slag decrease the workability of fresh concrete. The addition of blast furnace slag (BS) obviously decreases the apparent density of concrete while the addition of electric furnace slag (ES) slightly increases the apparent density. Mechanical strengths increase with BS content increasing, but decrease with ES content increasing. High BS content can improve the resistance of concrete to chloride ion penetration while using ES as fine aggregate has little effect on the resistance to chloride ion penetration. Water absorption of concrete decreases with BS content increasing but increases with ES content increasing. BS has a positive impact on sulfate attack resistance and fire resistance. Using 25% ES also has an active effect on resisting sulfate attack. However, the addition of ES has little effect on improving the fire resistance of concrete. As a result, using 75% BS or 25% ES is the best choices in engineering application.
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Hydration mechanism of composite binders containing blast furnace Ferronickel slag at different curing temperatures
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Jianwei Sun, Zhe Wang, Zhonghui ChenAbstract:This study investigated hydration mechanism of composite binders containing blast furnace Ferronickel slag at different curing temperatures. Different levels of cement replacement (15, 30, and 45% by mass) and curing temperatures (25 and 60 °C) were set. In addition to pure cement, a composite binder containing quartz with a particle size distribution similar to Ferronickel slag was selected as the control sample. The results reveal that blast furnace Ferronickel slag can show the pozzolanic reactivity at an early stage at room temperature despite low activity, and an early high curing temperature can improve the activity significantly. The influence of high curing temperature on the pozzolanic reaction is greater than the influence of high curing temperature on cement hydration at an early stage, and as a result, the Ca(OH)2 content in the cementitious system is lowered. However, the influence on the pozzolanic reaction is not obvious in the later stage. The high curing temperature does not change the type of hydration product but increases the content of the C–S–H gel, resulting in a significantly higher Ca–Si ratio and a slightly lower Al–Si ratio. In addition, the high curing temperature improves the early compressive strength of the concrete containing blast furnace Ferronickel slag and reduces later compressive strength. A suitable dosage of blast furnace Ferronickel slag may improve the resistance to chloride ion penetration of concrete at a high curing temperature.
Yuanbo Zhang - One of the best experts on this subject based on the ideXlab platform.
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selective recovery of chromium from Ferronickel slag via alkaline roasting followed by water leaching
Journal of Hazardous Materials, 2019Co-Authors: Yuanbo Zhang, Huimin Tang, Weiguang Tian, Guoshen Liang, Zhiwei Peng, Joonho Lee, Mingjun Rao, Tao JiangAbstract:Chromium was selectively recovered from Ferronickel slag by roasting the slag with addition of Na2O2, followed by water leaching. The thermodynamic analysis revealed that in the presence of Na2O2 at appropriate temperatures, the Cr2O3 in the Ferronickel slag can be converted to NaCrO2, instead of Na2CrO4, which prevents the formation of highly toxic Cr (VI). The experimental results confirmed that under the optimal alkaline roasting and water leaching conditions of the mass ratio of Ferronickel slag to Na2O2 of 1, roasting temperature of 600 °C, roasting time of 1 h, leaching temperature of 50 °C, leaching time of 1 h, and liquid-to-solid ratio of 10 mL/g, 92.33% of Cr was leached with 64.28% of Na and 11.16% of Si and only 0.06 wt % Cr was left in the leaching residue. The high leaching percentage of Cr was a result of the transformation of Cr2O3 in the Ferronickel slag to NaCrO2 with a loose structure during alkaline roasting that was beneficial to water dissolution. Compared to the traditional alkaline roasting process, the proposed more environmentally friendly method did not produce toxic Cr (VI) during recovery of chromium and the resulting residue has potential to be used as a good construction material.
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valorization of Ferronickel slag into refractory materials effect of sintering temperature
JOM, 2019Co-Authors: Zhiwei Peng, Huimin Tang, Weiguang Tian, Guoshen Liang, Yuanbo Zhang, Joonho Lee, Mingjun Rao, Tao JiangAbstract:Preparation of refractory materials from Ferronickel slag by sintering over a broad temperature range (1200°C to 1500°C) with addition of sintered magnesia was explored. The thermodynamic calculations indicated that the amounts of newly generated high-melting-point forsterite and spinel phases increase with increasing temperature. The experimental analysis demonstrated that elevating the sintering temperature promoted conversion and crystallization of forsterite and spinel phases from the original phase of the slag, with simultaneous reduction of low-melting-point enstatite. There was also rapid growth of spinel grains from about 0.5 μm to 5 μm, which should be controlled by selecting an appropriate temperature. The results showed that, by sintering the slag at 1400°C for 3 h with addition of 20 wt.% sintered magnesia, a high-quality refractory material with refractoriness of 1680°C, bulk density of 2.93 g/cm3, apparent porosity of 1.81%, and compressive strength of 166.62 MPa was obtained.
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From Ferronickel slag to value-added refractory materials: A microwave sintering strategy
Resources Conservation and Recycling, 2019Co-Authors: Zhiwei Peng, Huimin Tang, Weiguang Tian, Yuanbo Zhang, Robin Augustine, Joonho Lee, Yanhu Chen, Tao JiangAbstract:Abstract The present study proposes a novel strategy for preparation of refractory materials from potentially hazardous Ferronickel slag by microwave sintering of the slag with addition of sintered magnesia in which a series of chemical reactions were involved. This strategy was developed based on examination of the phase transformations and microstructural changes of the slag during microwave sintering through X-ray diffraction (XRD) analysis and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis, which determined the properties of refractory materials derived from the slag. It was shown that under microwave irradiation there existed rapid transformation of the olivine phase in the slag to high-melting point phases, including forsterite and spinels (e.g., magnesium iron chromate spinel, magnesium chromate spinel, and magnesium iron aluminate spinel). As a result, a high-quality refractory material with refractoriness of 1730 °C, bulk density of 2.80 g/cm3, apparent porosity of 1.6%, and compressive strength of 206.62 MPa was obtained by microwave sintering of the slag at 1350 °C for only 20 min with addition of 25 wt % sintered magnesia. Because the microwave sintering strategy not only elevated the refractoriness by 70 °C, but also reduced the heating duration required by the conventional approach by 6 times, it demonstrated apparent technological superiority and wide application prospect in preparing superior-quality refractory materials from Ferronickel slag and relevant industrial waste, which contributed to conservation of resources and energy as well as environmental protection.
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chromium a double edged sword in preparation of refractory materials from Ferronickel slag
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Zhiwei Peng, Huimin Tang, Weiguang Tian, Guoshen Liang, Yuanbo Zhang, Mingjun Rao, Tao JiangAbstract:This study reports the role of chromium as a double-edged sword in the preparation of refractory materials from Ferronickel slag with the addition of sintered magnesia based on the thermodynamic analysis and experimental exploration of the phase transformation of Ferronickel slag during the sintering process. The results of thermodynamic calculation, X-ray diffraction, and electron probe microanalysis revealed that in the presence of sintered magnesia (20 wt %) and Cr2O3 (0–6 wt %), forsterite, donathite (instead of magnesium chromate spinel generated without addition of Cr2O3), magnesium aluminate spinel, and enstatite were formed. The forsterite and spinel phases contributed to high refractoriness of the prepared material by sintering. However, with excessive addition of Cr2O3 (>6 wt %), the quantity of enstatite increased obviously, which would lower the refractoriness of refractory material. For this reason, the addition of chromium or its content in the slag should be carefully controlled to fully ex...
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facile route for preparing refractory materials from Ferronickel slag with addition of magnesia
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Zhiwei Peng, Huimin Tang, Weiguang Tian, Guoshen Liang, Yuanbo Zhang, Mingjun Rao, Tao JiangAbstract:The feasibility of a facile technological route to preparation of refractory materials from a Ferronickel slag with the addition of sintered magnesia was verified in this study based on the thermodynamics analysis and the experimental exploration of the effect of the sintered magnesia addition on the phase transformation of Ferronickel slag during the sintering process. For the first time, the results of thermodynamics calculation, X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analyses revealed that the original phase of the slag can be transformed to high melting point phases by addition of MgO during the sintering process at high temperatures (e.g., 1350 °C). Specifically, the olivine in Ferronickel slag decomposed initially, generating a low-iron olivine phase and an enstatite phase. With increasing addition of sintered magnesia, the enstatite phase changed to forsterite, and the iron, aluminum, and chromium components in the Ferronickel slag c...