Synthetic Slag Research Articles

Microstructural Characterisation of Ti and V-containing Synthetic Slags Mimicking the Chemical Composition of the Slag Inclusions of Ferrous Artefacts Produced in the Iron Factory of São João de Ipanema (XIX century, Brazil)

Microstructural Characterisation of Ti and V-containing Synthetic Slags Mimicking the Chemical Composition of the Slag Inclusions of Ferrous Artefacts Produced in the Iron Factory of São João de Ipanema (XIX century, Brazil)

Effects of the Chemical Composition of Synthetic Slags Compared to an Average Blast Furnace Slag

AbstractTo study the effect of the main oxides and the minor components in slags on their reactivity as SCM, various glasses were synthesized to stepwise imitate a commercial slag of average chemical composition. First, a glass was produced from the main oxides CaO, Al2O3 and SiO2. In a second step, the minor components MgO, Fe2O3, Na2O and K2O were added separately to the main oxide mix. A selection of two synthetic glasses was tested for their compressive strength contribution (up to 90 days) by substituting 20 wt.% of cement. After all testing times, the synthetic slags achieved a strength similar to that of the commercial product. The reactivities determined by heat flow calorimetry (R3 test) correlate with the calculation of NBO/T and the results of 29Si MAS NMR showing that a decreased degree of polymerization enhances the reactivity. Apart from that, FTIR spectroscopy and 27Al MAS NMR indicate a similar structure of the original and the synthetic slags.

Use of residues as fillers in alkali‐activated binders

AbstractThe demand for resource saving and recycling of waste materials to achieve a circular economy is increasing. In Europe, nearly all blast furnace slag and fly ash are used as supplementary cementitious material. Furthermore, there is urgent need to reduce the CO2 emissions of building materials industry. Like in OPC‐based concretes, the reduction in the binder content by the use of fillers can be a way to reduce the CO2 emissions of alkali‐activated binders even further. Therefore, this study aims at the use of industrial residues as a filler in alkali‐activated materials to reduce the CO2 emissions of alkali‐activated binders. In this study, three industrial residues including municipal solid waste incineration ash (MSWIA), steel slag (SS) and ash formed by the thermal treatment of tar‐containing asphalt (EcoF) are used as fillers for alkali‐activated binders and are compared with fine quartz powder as an inert reference filler. The binder is ground granulated synthetic slag, which is replaced with the four filler materials at a 32 vol.% replacement level. The samples are reacted with 15 and 25 wt.% NaOH solution. The results show a potential advantage of using SS and EcoF as a filler in concrete as they exhibited a slightly higher compressive strength at all tested ages compared to quartz powder.

Formation Mechanism of High‐MnO‐Content SiO2/SiO2–MnO–(CaO–Al2O3) Dual‐Phase Inclusions in Si–Mn‐Killed Steel

This study investigates the deformation characteristics of SiO2–MnO–(CaO–Al2O3)‐type inclusions in silicon manganese deoxidized steel from continuous casting to rolling. The results reveal that the inclusions contain 60–80% SiO2, 10–35% MnO, and a combined CaO and Al2O3 content of <20%. SiO2 precipitates inside the inclusions during the continuous casting and rolling processes, which results in the formation of pure SiO2/SiO2–MnO–(CaO–Al2O3) dual‐phase inclusions in the remaining components owing to the increase in the MnO content to 15–40%. According to the experimental results of melting rate measurement and thermodynamic calculation using FactSage8.1, the SiO2–MnO–(CaO–Al2O3) phase has a high proportion of liquid components at 1100–1360 °C and exhibits good deformation properties during the breaking down and rolling processes. When the total content of CaO, Al2O3, and MgO in the SiO2–CaO–Al2O3–MgO–MnO inclusions reaches 30–50%, SiO2 precipitation is inhibited during the continuous casting to rolling process. Through the addition of metal manganese and carbon powder during the pre‐deoxidation process, followed by alloying with ferrosilicon and metal manganese, and then the addition of acidic synthetic slag for slag formation, the proportion of SiO2/SiO2–MnO–(CaO–Al2O3) dual‐phase inclusions in the casting billet is increased from 12% to >60%.

CaO solubility in the FeOt-SiO2-CaO-Al2O3-(ZnO, Cr2O3) system at 1200 and 1250°C under pO2 of 10−10 atm

CaO solubility in the FeOt-SiO2-CaO-Al2O3-(ZnO, Cr2O3) system has been experimentally investigated at 1200 and 1250 °C under pO2 of 10−10 atm. Synthetic slags rich in CaO were equilibrated at desired temperatures, followed by water quenching, and analyzed using electron probe X-ray microanalysis (EPMA). In the quaternary FeOt-SiO2-CaO-(6 to 10 wt%) Al2O3 system, CaO solubility exhibits a linear increase from 27.5 to 36.9 wt% with decreasing the FeO/SiO2 (F/S) ratio from 1.66 to 0.62 at 1250 °C. Similarly, at 1200 °C, the CaO solubility increases from 24.9 to 30.8 wt% as the F/S ratio drops from 1.25 to 0.56. Excessive CaO addition to the slags results in the precipitation of melilite phase. Wustite is observed in the F/S ratio range of 1.66 to 1.0, and the size of wustite particles decreases as the F/S ratio decreases. At both 1200 and 1250 °C, the liquid phase with an F/S ratio below 0.42 is in equilibrium with wollastonite (CaSiO3) in the FeOt-SiO2-CaO-Al2O3 system. The addition of a small amount of ZnO (0.4–1.1 wt%) in the slags leads to a slight decrease in CaO solubility by 1–3 wt%, while the presence of 3.3–8.1 wt% of ZnO in the slags results in a decrease of 5–11 wt% in CaO solubility. Similar to the FeOt-SiO2-CaO-Al2O3 system, the equilibrated CaO-containing solid phase is also melilite in the FeOt-SiO2-CaO-Al2O3-ZnO system. With the addition of a small amount of Cr2O3 (1.0 wt%) to the FeOt-SiO2-CaO-Al2O3-ZnO system, spinel and dicalcium silicate (Ca2SiO4) precipitate from the liquid slag, and the dissolved CaO concentration in liquid slag increases by 1–3.6 wt% in the F/S ratio range of 1.58 to 0.84, compared to the Cr2O3-free system.

Industrial utilization of complex, multicomponent technogenic formations and their safe movement

The description of slags produced by LLC «Klyuchevskaya concentrating factory» is given. Samples of metallic chromium, ferrochrome and ferrotitane slag are presented. The chemical composition of high-alumina refractory cements used for the production and the physico-mechanical properties of cements obtained by remelting metallic chromium slags are given. The chemical composition of the alumina intermediate obtained during the remelting of metallic chromium slags for the smelting of synthetic slags. Charge compositions during remelting of metallic chromium slags. The scheme of covering the bottom of the dump truck body is given. Ill. 5. Ref. 10. Tab. 3.

Investigations on Single Minerals and Synthetic Ash Components for the Enrichment of Copper from Waste Incineration Bottom Ashes by Flotation

Currently, MSWI (municipal solid waste incineration) ashes are predominantly landfilled, although they can have copper contents comparable to those of low-grade ores. Based on a previously published characterization of MSWI-BA, this paper presents investigations on the identification of potential collectors for copper recovery from MSWI-BA by flotation. The studies were conducted with single minerals (mainly copper oxide and sulfide) and synthetic slag components. Collector screening included thiourea-, thiophosphate-, and thiocarbamate-based collectors. In addition to commercial collector mixtures, pure ureas were also examined. At least one representative from each collector group was selected for the more in-depth studies: the thiourea S-n-dodecyle-iso-thiourea hydrochloride, the thiophosphate Danaflot 245, AERO 3473, and AERO MX-5160 as a mixture of a thiocarbamate and thiophosphates. Studies of the influence of collector concentration and pH were carried out with these. In addition, the contact angles of various metal oxides and the matrix composition with and without collector treatment were determined. Subsequently, flotation tests were carried out with mixtures of copper oxide and the individual matrix components (quartz, glass, cement, gypsum). AERO MX-5160 proved to be the most suitable collector, although alginic acid was added as a depressant due to a lack of selectivity towards gypsum.

Effect of B2O3 on viscosity of high-magnesia blast furnace slag

Metallurgical companies in the Urals account for 50 – 60 % of local raw materials. Its deficit is compensated by the use of materials imported from Central Russia, the Kola Peninsula and Kazakhstan. Replacing them with the local raw materials would increase the competitiveness of metal produced in the Urals, so the question of assessing the possibility of replacing imported raw materials with local ones is very relevant. Such raw materials could be siderite ores from the Bakal deposit. They are not in demand by metallurgists because of their low iron content and high magnesium content. With growth of siderites in a charge the magnesium oxide content in slag increases that influences its viscosity and makes it difficult or impossible to smelt using more than 20 % of siderites. The use of boron oxide has been suggested to liquefy the slag. The synthetic slag containing 26.8 % CaO, 38.1 % SiO2 , 11.8 % Al2O3 , 23.6 % MgO, simulating composition of slag from MMK blast-furnace smelting with the addition of 30 % of burnt siderites is short and unstable. The temperature corresponding to the slag viscosity at the blast furnace outlet (0.5 Pa·s) is 1390 °C and the temperature corresponding to the melting point (viscosity 2.5 Pa·s) is 1367 °C. If boric anhydride is added to such a slag, it becomes long and stable. In the melts, when the proportion of B2O3 is increased from 0 to 12 %, the temperature at which the slag viscosity is 0.5 Pa·s and 2.5 Pa·s decreases to 1260 °C, and 1100 °C, respectively. This makes it possible to significantly increase the siderite content in blast furnace charge.

Exploring influence of MgO/CaO on crystallization characteristics to understand fluidity of synthetic coal slags

The crystallization has significant influence on fluidity of slag and slag discharge of entrained-flow-bed (EFB) gasifier. The crystallization characteristics and fluidity of five synthetic slags with different MgO/CaO ratios prepared on the basis of the range of oxide contents of Zhundong coal ash were investigated in this study. The results show that with the MgO/CaO ratio increase, the initial crystallization temperature increases, and the main temperature range of crystallization ratio growth moves to higher temperature range gradually which causes Tp25 (Tp25 is the temperature corresponding to the viscosity of 25 Pa·s) to increase. Mg-rich crystals are formed preferentially than Ca-rich crystals when adding the same amount of MgO and CaO during cooling. The effective slagging operating temperature range decrease from 217 °C for the slag with a 0:4 MgO/CaO ratio to 44 °C for the slag with a 4:0 MgO/CaO ratio with the MgO/CaO ratio increase. The slags with 2:2 and 1:3 MgO/CaO ratios show similar effective slagging operating temperature range, Tp25 and the temperature corresponding to the viscosity of 2 Pa·s. However, compared with the slag with a 1:3 MgO/CaO ratio, the crystallization ratio and rate of slag with a 2:2 MgO/CaO ratio are lower within lower temperature range (1300–1200 °C), causing its lower critical viscosity temperature and wider actual operating temperature range. Of the five slags, the widest effective slagging operating temperature range and the lowest Tp25 of the slag with a 0:4 MgO/CaO ratio due to its low crystallization ratio, and wider actual operating temperature range of the slag with a 2:2 MgO/CaO ratio make the two slags suitable for slag discharge of EFB gasifier.

Effect of temperature on oxidation behavior and occurrence state of sulfur in KR slag

The main component (CaO) in KR (Kambara reaction) desulfurization slag is a high value slag raw material for converter smelting, and attempts to utilize KR desulfurization slag in converter smelting are conducive to reducing the buildup of KR desulfurization slag and improving the economic efficiency of converter smelting. However, the removal of sulfur in the slag is a key issue. The influence of temperature on the sulfur oxidation behavior in KR slag in the form of synthetic slag was investigated. SEM-EDS, XRD, and an infrared carbon and sulfur analyzer were used to analyze and detect the oxidized slag samples at different temperatures. The results show that the desulfurization rate increases gradually with the increase in temperature at a flow rate of Ar-50%O2 of 2 L/min. Under the condition of low temperature (T ? 1220?), the desulfurization rate of slag is less affected by temperature. When T > is 1220?, the desulfurization rate of slag is greatly affected by temperature. When the reaction temperature reaches 1420?, the desulfurization rate reaches 93.5%. Furthermore, the types of sulfur-containing phases in the oxidized slag samples gradually decrease with the increase of temperature, and the sulfur in the oxidized slag samples is mainly present in the silicate phase when the temperature is less than or equal to 1220?.

Utilization of White Aluminium Dross Based Briquetted Synthetic Slag during Secondary Steelmaking Process

Utilization of White Aluminium Dross Based Briquetted Synthetic Slag during Secondary Steelmaking Process

Utilisation of white aluminium dross-based briquetted synthetic slag during secondary steelmaking process

Utilisation of white aluminium dross-based briquetted synthetic slag during secondary steelmaking process

Influence of CaO and Fe2O on the surface tension and structure of SiO2-Al2O3-CaO-Fe2O3-MgO synthetic slags

The surface tension of coal slags influences the adhesion between the slag and furnace walls in slagging gasifiers, which further influences the efficiency, maintenance cost and reliability of the gasifier. The influence of CaO and Fe2O3 on the surface tension and structure of synthetic slags were investigated. The results indicate that the surface tension linearly increases with the increase of CaO content in the synthetic slag. When Fe2O3 exceeds 3.8 mole%, the surface tension of synthetic slag increases slowly with the increase of Fe2O3, which is related to Fe2O3 acting as an intermediate oxide. The degree of polymerization and the electrostatic potential of ions are related to a variation in surface tension, and the number of unsatisfied bonds increases because the Si-O-Si network structure was depolymerized. Here, NBO/T cannot reflect the degree of depolymerization of slag due to the variation in intermediate Fe2O3 contents.

Influence of composition and cooling rate of alumocalcium slag on its crumblability

The main components of metallurgical slags are iron compounds, which are extracted by reduction smelting. There are several types of this process with obtaining various products based on iron and slags of various compositions (aluminum-calcium self-disintegrating), etc. The mode of smelting and cooling of alumocalcium slag, formed during melting in the furnace, should ensure the most complete spontaneous crumbling of it, as well as high rates of extraction of REM from it. Synthetic slags similar in phase composition to industrial samples after smelting of iron-containing ores were selected for the experiments. The simulated samples correspond to the region of primary crystallization of bicalcium silicate on the triple state diagram of CaO – SiO2 – Al2O3 system. The slag after crumbling was subjected to a sieve analysis using a mechanical sieve. In the experiments, slags with a silicon module k = 2.0 were used, which actively crumbled during their cooling. With an increase in the silicon module, the crumbling deteriorates. It was established that it is impossible to precisely limit the areas of compositions of crumbling slags at certain cooling rates. The conducted studies showed that the crumblability of slags improves as it approaches the center of the bicalcium silicate region. The composition of slags close to composition of the intersection points of the lines 2CaO·SiO2 – 2CaO·Al2O3 and 2CaO·SiO2 – 12CaO·7Al2O3 with the lines of the permanent silicon module granulometric composition almost does not depend on the cooling rate. The temperature mode from smelting to cooling affects the slags crumblability. The most promising are slags with a silicon module in the range of 2.85 – 3.00, close to the phase triangle 12CaO·7Al2O3 – 2CaO·SiO2 – 2CaO·Al2O3 .

Performance of minerals and crystallization properties of synthetic slags with various CaO/MgO in slagging gasifiers

AbstractThe fluidity of coal ash slag at high temperatures is an important factor that determines its applicability and operating conditions in entrained flow gasification. In this study, six synthetic slags with different CaO/MgO rations were prepared to study their effect on slag fluidity. The results showed that the flow temperature of slags decreased first and then increased with the decrease of CaO/MgO ratio. When the slag had a high or low CaO/MgO ratio, or when the contents of CaO and MgO in the slag were similar, the homogeneous slag showed a lower viscosity. The crystallization tendency of Ca was stronger than that of Mg. During cooling, slags with high or low CaO/MgO ratio showed obvious crystallization tendency, and formation of crystals would lead to a sharp increase in slag viscosity, so that the temperature of critical viscosity of slags decreased first and then increased with the decrease of CaO/MgO ratio.

Leaching characteristics of Sc-enriched, Fe-depleted acidic slags

Scandium is currently classified as a critical raw material for the European Union, and several research projects focus on the search for new sources to supply to its expected increasing demand. The Kiviniemi mafic intrusion in Finland is a potential primary source for Sc; at Kiviniemi, Sc occurs mainly within the lattices of ferrous silicates, clinopyroxene and amphibole. Some of the main challenges in leaching of Kiviniemi-type feed material are related to either the complexity of Fe and Ti separation from Sc-containing solutions or a possible gelation problem when leaching a material with a high SiO2 content. According to preliminary beneficiation tests, direct acid leaching of the Kiviniemi feed material was not successful mainly due to extensive leaching of Fe from the ferrous concentrate. Therefore, a processing scenario with conventional magnetic separation followed by pyrometallurgical reduction of the FeO component to tackle the Fe issue prior hydrometallurgical stage was studied in the previous parts of our project. Leaching experiments in this study focus on the possibilities to extract Sc from low-FeO, Sc2O3-enriched amorphous slag. Both a synthetic slag and slags produced from Kiviniemi concentrates were submitted to H2SO4-based leaching experiments applying dry digestion, H2O2-assisted leaching, and high-pressure acid leaching (HPAL). The formation of silicic acid (gelation) under acidic conditions was avoided with all these methods. With H2O2-assisted leaching, efficiencies reached 40–50%, whereas leaching with dry digestion was very limited. With HPAL, the leaching efficiency remained at 30–45% under experimental conditions of 2.5 M H2SO4, 60 bar, and 150 °C. These levels of leaching efficiencies are due to an amorphous structure and high SiO2 content of the slag. Future options for hydrometallurgical processing of Kiviniemi-type slags could include controlled cooling of the slag to produce crystalline structures, combined potentially with further chemical modification to enable selectivity for leaching.

Iron Removal from Metallurgical Grade Silicon Melts Using Synthetic Slags and Oxygen Injection.

Novel SiO2-CaO-CaF2-R2O-MgO based synthetic slags (R2O represents alkali metal oxides) with varied binary basicity values were used with oxygen injection to refine silicon melts and remove Fe from metallurgical-grade silicon. Silicon samples and slags at the silicon-slag interfaces were obtained during refinement. The compositions of the silicon samples were analyzed, and the quenched slag samples and mild cooling slags from the final crucible were inspected using scanning electron microscopy and energy dispersive X-ray spectroscopy. After 15 min of refinement, the Fe removal rate ranged from 52.3 to 60.1 wt%. During the refining process, the Fe-concentrated phase formed within the silicon droplets and was then transferred to the silicon-slag interfaces and wetted with slags. The Fe-concentrated phase at the silicon-slag interface can dissolve directly in the slags. It can also be transferred into the slag phase in the form of droplets, which can be affected by the binary basicity of the slags. Ti removal demonstrated a similar mechanism. Fe-bearing crystals were not detected in the quenched slag samples obtained during refinement, while complex Fe-bearing phases were detected in the final slag. This study demonstrates Fe removal from metallurgical-grade Si using slag refining methods and reveals the removal mechanism during the refinement.

Effect of recycling ladle furnace slag as flux on steel desulphurization during secondary steel making

ABSTRACT Recycling ladle furnace (LF) slag helps in sustainable steel making and reduces steel production costs. This paper focuses on recycling Si/Mn/Al-killed LF slag as a replacement for CaO–Al2O3-based synthetic slag for treating high carbon Si/Mn-killed steels. Characterization of different types of LF slag was carried out to identify chemical composition and mineralogical phases. Industrial trials were carried out by recycling LF slag along with lime and calcined bauxite as additives. The effect of recycled LF slag on the kinetics of desulphurization and other process parameters was studied and compared with regular practice. It was observed that LF slag can be recycled successfully as a replacement for CaO–Al2O3-based synthetic slag at an industrial scale.

Thermophysical properties of synthetic slags of the FeO – MnO – CaO – Al2O3 –– SiO2 system

In the electrometallurgy of manganese alloys, viscosity has an important effect on the production indicators from the physicochemical properties of slag. During the smelting of manganese alloys, the main amount of heat spent on reduction reactions is released due to the current passing through the liquid slag phase, since the resistance of the latter, depending on the composition, affects the completeness of the reduction of manganese from melts. In the case of refined ferromanganese by the silicothermic method, the vast majority of silicon of silicomanganese is refined with higher manganese oxides or it is burned out due to oxygen in the air. The paper presents the results of thermophysical properties of slags representing the FeO - MnO - CaO - Al2O3 - SiO2 system. Laboratory experiments were carried out on synthetic slags by varying the slag basicity CaO / SiО2 = 1.5 - 1.9 and the concentration of Al2O3 = 5 - 15%. As a result, graphs of the dependence of these properties on temperature values are constructed, the activation energies of the viscous flow are calculated and the phase compositions of the experimental slags are determined using a mathematical model of the diagram of the FeO - MnO - CaO - Al2O3 - SiO2 system. Thus, an increase in the concentration of aluminum oxide against its usual level, changing the basicity of the slag, significantly affected the physicochemical properties of the slag and thereby contributes to the adjustment of the parameters of the electric melting process. At the same time, it is advisable to study the interaction of some Physical chemical properties of slags on the melting conditions of manganese ferroalloys in relation to the composition of slags.

The Role of Slag Carryover on the Non-metallic Inclusion Evolution and Magnetic Behavior in Electrical Steel

In the present investigation, a set of high-temperature experimentations were carried out to improve the understanding of the influence of slag carryover (SCO) on non-metallic inclusion evolution during the production of high silicon electrical steels for functional applications. It was observed that the liquid steel treated with synthetic slag and lime resulted in the formation of CaO-based complex oxide, sulfide, and nitride inclusions in the matrix. Whereas the top slag (synthetic slag and lime) contaminated with carryover slag transforms the complex oxide inclusions to Mn free oxy-sulfide inclusions in the high Si steel. Further, the high-silicon steel evaluated for magnetic property confirms the detrimental magnetic behavior of the steel treated using the top slag with the excess amount of SCO (10 kg/t). The increase in coercivity is due to a higher fraction of sub-micron inclusions in the steel matrix. The industry implications of the present findings are highlighted in the light of the evolution of Goss texture in high silicon steel during downstream processing. The evolution of detrimental inclusions in functional grade (electrical) steels due to the presence of SCO call for stringent process control during the upstream processing of liquid steel to maintain the desired magnetic properties.